2003Detection of seven Candida species using the Light-Cycler system

Journal of Medical Microbiology (2003),52,229–238DOI 10.1099/jmm.0.05049-0

05049&2003SGM Printed in Great Britain

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Correspondence P.Lewis White

lewis.white@https://www.wendangku.net/doc/d5678327.html,

Received 16August 2002Accepted 12November 2002

Detection of seven Candida species using the Light-Cycler system

P.Lewis White,Anjali Shetty and Rosemary A.Barnes

Department of Medical Microbiology and PHLS,University Hospital Wales,Heath Park,Cardiff CF144XN,UK

Due to the limitations of classical methods for the detection of systemic fungal infections and the high mortality rates associated with these infections,it has become essential to develop a quick,sensitive and speci?c detection assay.By using the Idaho Technologies Light-Cycler system,a qualitative real-time PCR system has been developed for the detection of the leading causes of systemic infection within the genus Candida .The sensitivity of the assay was comparable to

previously described PCR methods (1–5c.f.u.ml à1)and,by the use of a single Candida probe,it was able to detect,but not differentiate between,seven species of Candida (Candida albicans ,Candida dubliniensis ,Candida glabrata ,Candida kefyr ,Candida krusei ,Candida parapsilosis and Candida tropicalis ).Single-round ampli?cation on the Light-Cycler allowed rapid turn-around of clinical samples (within one working day)and it was shown to be more sensitive than classical procedures,exposing 39possible systemic infections that were not detected by blood culture.

INTRODUCTION

It has been widely published and accepted that invasive fungal infections are a major cause of morbidity and mortality in the immunocompromised patient (Whimbey et al .,1987;Denning,1998;Wright &Wenzel,1997),and Candida species have become the fourth most-frequent cause of nosocomial blood-stream infection in critically ill patients (Nishikawa et al .,1999).With further advances in medical intervention and the increasing population of immunocom-promised patients,the list of human fungal pathogens continues to grow (Chen et al .,2000);within the genus Candida ,there has been an increase in the incidence of infection with species other than Candida albicans (Reiss &Morrison,1993;Gleason et al .,1997).

Early initiation of antifungal therapy is paramount in reducing the high mortality rates associated with fungaemia (Morace et al .,1997)and is dependent on early detection of the fungal infection.The current ‘gold standard’for detec-tion of systemic infection is blood culture,but this is believed to lack sensitivity and has been shown to be positive in less than 50%of patients with chronic disseminated candidiasis and is rarely positive for patients with invasive aspergillosis (Einsele et al .,1997).Culture techniques are also time-consuming,taking up to 3weeks,an unacceptable period for the treatment of fungaemia.Conversely,the lack of a reliable early diagnostic marker may lead to the unnecessary empiri-cal treatment of patients who do not have fungal infections.The end result is unacceptable toxicity in many patients and massive expense;it is estimated that the UK National Health Service spends ￡30million per annum on systemic antifun-gals,and this is set to rise.

It is essential to overcome the limitations of the traditional culture-based fungal detection methods and replace them with rapid and sensitive procedures that are capable of detecting non-culturable/non-viable cells or circulating free fungal DNA (i.e.molecular methods).Recently,many groups have developed molecular-based assays for the detection of fungal DNA.Examples of this include more traditional molecular techniques such as comparison of DNA sequence and polymorphism (Chen et al .,2000),restriction fragment length polymorphisms (RFLP)(Morace orace et al .,1997),Southern blotting (Einsele et al .,1997),nested PCR (Jaeger et al .,2000;Mathis et al .,1997)and typing methods such as random ampli?cation of poly-morphic DNA (RAPD)(Metzgar et al .,1998;Lehmann et al .,1992).The major drawback with these techniques is that they require post-ampli?cation handling and,as such,in-crease the time to result and,more importantly,the chance of contamination.These limitations have led to the develop-ment of ‘real-time’molecular assays that dispense with the need for post-ampli?cation handling and are therefore leading the diagnostic molecular ?eld forward.

Detection of candidal and Aspergillus RNA from clinical samples has been developed using nucleic acid sequence-based ampli?cation (NASBA)(Widjojoatmodjo et al .,1999;Loef?er et al .,2001).NASBA is an isothermal nucleic acid

Abbreviations:FRET,?uorescence resonance energy transfer;NASBA,nucleic acid sequence-based ampli?cation;RFLP,restriction fragment length polymorphism.

ampli?cation process using avian myeloblastosis virus re-verse transcriptase(AMV-RT),RNase H and T7RNA polymerase.Detection is determined by enhanced chemi-luminescence(ECL,‘end-point’detection)or by molecular beacon(‘real-time’detection).Both the ampli?cation and ‘end-point’detection procedures have been described pre-viously(Widjojoatmodjo et al.,1999;Loef?er et al.,2001) and so will not be included here.Like all molecular assays, NASBA has high sensitivity and speci?city,but,unlike DNA-based assays,it requires less starting material and has a quicker nucleic acid extraction procedure.A drawback with NASBA is that the ampli?cation/end-point detection process takes considerably longer than when using a Light-Cycler and the difference in the overall time to result is therefore negligible.Furthermore,NASBA RNA targets are less stable than their DNA counterparts and this,coupled with the ubiquitous nature of RNases,may be problematic in a diagnostic setting.

Detection of fungal DNA from clinical Candida species has been developed on the TaqMan PCR system,but this has only been used for rapid identi?cation of cultured Candida species and,as yet,nothing has been published describing the detection of non-culturable/non-viable cells(Guiver et al.,2001).

Alternative DNA-detection methods have been developed utilizing the Roche Diagnostics Light-Cycler(Loef?er et al., 2000a,b),but these are not suitable for use on the Idaho Technologies Light-Cycler system.Loef?er et al.(2000b) described their procedure for the detection of C.albicans and Aspergillus fumigatus using the Roche Diagnostics Light-Cycler.Despite the principles of both the Roche and the Idaho Light-Cycler systems being the same(use of small volume,rapid thermocycling and real-time,in-tube?uores-cence detection of the PCR product),it was not possible to transfer the procedure of Loef?er et al.(2000b)on to the Idaho Light-Cycler.The problems appeared to be due to the production of primer dimers and primer–probe dimers which,in turn,led to the production of dimer melting curves that interfered when determining results.In addition,the probe designed by Loef?er et al.(2000b)was speci?c for C. albicans,but with the increasing incidence of infection with non-C.albicans Candida species,it was decided that it would be bene?cial to have a probe that could detect the major infectious Candida species.

The Candida probe is based on a system different from that of Loef?er et al.(2000b),who developed a hybridization probe. In their assay,a?uorescence resonance energy transfer (FRET)system relies on two?uorescently labelled probes, a donor and an acceptor,which bind in a head-to-tail orientation.When together,there is an energy transfer between the?uorescent dyes,leading to an emission of red ?uorescent light from the acceptor probe,which is measured by the photohybrids in the Light-Cycler.Our system uses a single biprobe that is labelled with the?uorescent dye Cy5; the?uorescent dye SYBR green is used to detect the PCR amplicon.The probe will only emit?uorescence when bound to the PCR amplicon;when bound,it accepts energy from the ?uorescent dye SYBR green,which binds to the minor groove on double-stranded DNA.The advantage of this system is the simplicity of a single probe,although a setback is the generation of a SYBR green signal due to non-speci?c ampli?cation or the production of primer–probe dimers. Following each ampli?cation cycle,the?uorescence of both the probe and amplicon is monitored and,provided the target DNA template is present,the?uorescence increases with every cycle.The cycle at which the?uorescence rises above background is known as the crossing-point.This represents the start of detectable ampli?cation/probe bind-ing and is dependent on the initial template concentration. After the ampli?cation process,the amplicons are gradually exposed to an increasing temperature and the?uorescence of both the probe and amplicon is monitored continually during this process.As the temperature passes through the denaturation point(the melting temperature)of?rstly the probe and then the amplicon,a dramatic fall in?uorescence is observed and a melting curve is generated.The data are then converted into melting peaks by the Light-Cycler software,which?lters out background?uorescence and plots the negative derivative of?uorescence with respect to temperature(àdF/dT vs T).

We report a‘real-time’PCR assay for the detection of clinically relevant Candida.Unlike previous publications, the assay was suitable for use on the Idaho Technologies Light-Cycler and was able to detect the seven main patho-genic species of Candida.The assay was as sensitive as previously described methods and this could be improved by the use of a nested system.

METHODS

Fungal cultures.Ten strains of C.albicans,one strain of Candida dubliniensis,one strain of Candida famata,10strains of Candida glabrata,four strains of Candida guillermondii,?ve strains of Candida kefyr,?ve strains of Candida krusei,one strain of Candida lipolytica, eight strains of Candida parapsilosis,six strains of Candida tropicalis,10 strains of Aspergillus fumigatus,?ve strains of Aspergillus niger,one strain of Cryptococcus neoformans and two strains of Saccharomyces cerevisiae were obtained from our clinical culture collection and grown on Sabauraud’s glucose agar for3–4days at308C.Yeast species were originally identi?ed by colorimetric sugar-utilization tests(Auxacolour; Bio-Rad),chlamydaspore production and microscopy,while the moulds were identi?ed by microscopy.To con?rm their identity, DNA was extracted from the species and part of the18S rRNA gene(a region spanning positions550–760in the18S rRNA gene of C.albicans, accession no.M60302.1)was ampli?ed by PCR and sequenced.All identities were con?rmed.The night before extractions were to be carried out,glucose broth was inoculated with the fungi and incubated overnight at308C.If whole EDTA-blood specimens were spiked with fungi,serial dilutions were carried out using sterile saline solutions until the desired fungal load was achieved.This was checked by plate counts and by using Fuchs–Rosenthal counting chambers.

Controls.Blood from healthy individuals and water were included as negative extraction controls.In addition to the negative controls,when extractions were carried out from clinical samples,blood from a healthy individual was spiked with the desired fungal load(,10c.f.u.mlà1)

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and the sample was included as a positive extraction control.For each Light-Cycler experiment,the extraction controls plus a positive PCR control(DNA from a cultured Candida strain)and two negative PCR controls(DNA from a cultured Aspergillus strain and water)were included.

Clinical samples.Clinical samples were requested from patients thought to be at risk from fungal infection(pyrexia,neutropenia and no response to antibacterial antibiotics).In an on-going pilot study,472 whole EDTA-blood samples from113patients were tested by both the single-round Light-Cycler assay and by the nested PCR method.Of these patients,35were receiving treatment for leukaemia,27were bone-marrow-transplant patients,19were suffering various types of lymph-oma,six were receiving treatment for myeloma and four were suffering from pneumonia.The remaining22patients had a variety of disorders including premature birth,aplastic anaemia,oesophageal rupture, AIDS,respiratory failure and liver cirrhosis,but all were pyrexic and not responding to antibacterial antibiotics and were considered at high risk for fungal infection.

Twice weekly,5ml EDTA-whole blood from each patient was sent to the laboratory,where it was transferred to a sterile universal tube and frozen (à808C)until the day of the DNA extraction.At the request of the clinician or if the specimen was positive,further samples were sent and analysed.Only patients with more than one sample have been included in this study.

In addition to the blood samples sent for fungal PCR and blood culture, a variety of super?cial samples were sent for culture.These included a range of swabs(mouth,throat,skin,genital and wound swabs),sputum, urine and faecal samples.

DNA extraction.DNA was extracted as described by Loef?er et al. (1997)using recombinant lyticase(Sigma-Aldrich)and the Qiamp tissue kit(Qiagen)with two minor modi?cations.Firstly,when precipitating DNA with ethanol,the solution was incubated on ice for 30min;this was found to increase the yield of DNA.Secondly,after the elution of the DNA,YM-100microconcentrators(Millipore)were used to increase the DNA concentration.All reagents were?lter-sterilized through0·2ìm?lters before use.

Primer and probe design.When designing the pan-fungal primers, over10018S rRNA sequences from pathogenic fungi were downloaded from the NCBI database.These included10different genera and40 different species and,when the primers were entered into a BLAST search (Altschul et al.,1997),the top500matches were all fungal.In designing the Candida probe,50sequences from the seven most prevalent species of Candida were compared using DNASIS 2.5(Hitachi Software Engineering Co.).

PCR

Light-Cycler assay.The Light-Cycler used was designed and manu-factured by Idaho Technologies(Bio/gene)and all primers and probes were purchased from Oswel Research Products.The primers(L18F,59-CTCGTAGTTGAACCTTGG;L18R,59-GCCTGCTTTGAACACTCT) were pan-fungal and were designed to bind to two conserved regions encompassing a variable region within the18S rRNA gene.PCR ampli?cation produced a140bp amplicon that corresponded to the region spanning positions620–760in the18S rRNA gene of C.albicans. The ampli?ed product was detected by the presence of a SYBR green ?uorescent signal and a Cy5-labelled probe(Candida probe,59-TTTTGATGCGTACTGGACCCTGT)was used to bind to a Candida-speci?c sequence within the PCR amplicon.

The PCR mixture consisted of5ìl Light-Cycler master-mix(Biogene), which contained the dNTPs,exo-Taq DNA polymerase,3mM magne-sium chloride,Taq Start antibody(Sigma),0·5ìl of each primer(?nal concentration600nM),0·5ìl SYBR green(diluted1:1000,as recommended by Biogene),1ìl Candida probe(?nal concentration 300nM)and1ìl template DNA and the mixture was made up to10ìl with molecular-grade water.

The PCR program was one cycle of denaturation at958C for15s followed by60cycles of958C for0s,annealing at628C for2s and extension at748C for2s.The Light-Cycler was then programmed to carry out a melting cycle to determine the melting temperature of the amplicon and probe.This consisted of a denaturing step at958C for15 s,after which the Light-Cycler cooled to508C and then increased the temperature at a rate of0·28C sà1until the temperature reached958C. During this stage,the Light-Cycler was continuously measuring the ?uorescence.

Nested PCR assay.To improve the sensitivity of the assay,a nested PCR was developed combining both a block-based PCR machine (Crocodile III,Appligene)and the Light-Cycler system.The?rst round (block-based)PCR used pan-fungal primers(182F,59-GAGGG CAAGTCTGGTG;18R2,59-CCTGCTTTGAACACTCTAA)targeting the18S rRNA gene and spanned the PCR amplicon described above. Ampli?cation by PCR produced a210bp amplicon that corresponded to the region spanning positions550–760in the18S rRNA gene of C. albicans.

The PCR mixture consisted of5ìl103PCR buffer,5ìl dNTPs(?nal concentration200nM),2ìl of each primer(?nal concentration500 nM),0·5ìl(2·5U)of Taq DNA polymerase(Sigma)and5ìl DNA template,made up to50ìl with molecular-grade water.The PCR program consisted of one cycle of denaturation at948C for5min followed by35cycles of948C for1min,598C for1min and728C for 1·5min and,?nally,one cycle at728C for7min.Aliquots of5ìl of the PCR amplicons were then electrophoresed on a TAE/2%agarose gel and visualized under UV light after staining with ethidium bromide.Of the remaining45ìl of amplicon,10ìl was diluted(1:50)before the second-round PCR was carried out on the Light-Cycler as described above.

Contamination control.Before any stage of the experiment[DNA extraction,PCR master-mix preparation(?rst and second round), addition of template to master-mix(?rst and second round),PCR ampli?cation(?rst and second round)]was performed,all work-surfaces including cabinets,pipettes,racks and microcentrifuges, including rotors and adaptors,were wiped down with Microsol (Anachem)and DNAzap(Ambion).

Each stage,including the?rst and second rounds of ampli?cation,was carried out in separate laboratories that were independently equipped, including laboratory coats.To prevent DNA carry-over,personnel performing the DNA extraction were not allowed to carry out the PCR set-up on the same day.

All PCR reagents were aliquotted into single-use sterile tubes in a UV-treated clean cupboard that was also used for PCR master-mix set-up. The aliquotted master-mix was transferred to another room for addition of the template.After addition of the DNA,the PCR mixture was transferred to the correct ampli?cation room,dependent on whether it was a single-round PCR assay or the?rst round of the nested-PCR assay.

After the?rst round of the nested PCR,the products were diluted using diethyl pyrocarbonate-treated water(Ambion)that had been dispensed in a clean cabinet.The diluted products were transferred to the second ampli?cation room,where they were added to the second PCR master-mix(prepared in a clean cabinet)in another cabinet to prevent contamination with previously aerosolized amplicons.

Before any transfer racks were returned to their original rooms,they were soaked in Microsol and wiped down with DNAzap.

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RFLP detection of Aspergillus.In addition to the Candida PCR,each sample was tested by RFLP for the presence of Aspergillus DNA.After the second round of the nested PCR,each amplicon was puri?ed using Qiaquick columns(Qiagen)and then,to determine the amplicon concentration,the product was analysed by1%agarose gel electro-phoresis.RFLP digestion was performed by using up to17ìl of the puri?ed amplicon mixed with1ìl(10U)of the restriction enzyme Sca I (Amersham Pharmacia Biotech)and2ìl of the buffer supplied.This was incubated for3h at378C.The digested product was then analysed by4%Metaphor agarose(Flowgen)gel electrophoresis.The undigested amplicons were140–160bp in size,depending on the species and genus of the fungus.After the digestion,DNA from Aspergillus species was cut into two fragments,of100and50–60bp.All fragment sizes were determined against a molecular mass marker(PCR marker50–2000bp; Sigma)(see Fig.1).

RESULTS

PCR ampli?cation

Using the pan-fungal primers,the14species(four genera) tested all provided the expected size of PCR amplicon (140bp for yeast,150–160bp for moulds).Sequencing

revealed the amplicons to be the expected targets(results not shown).

Detection of Aspergillus by RFLP

A Sca I digest differentiated the seven Aspergillus species(A. fumigatus,Aspergillus?avus,A.niger,Aspergillus nidulans, Aspergillus candidus,Aspergillus terreus and Aspergillus or-yzae)from the12yeast species tested(C.albicans, C. dubliniensis,C.glabrata,C.guillermondii,C.kefyr,C.krusei, C.lipolytica,C.parapsilosis,C.tropicalis,Cryptococcus neofor-mans and S.cerevisiae)(Fig.1).Digestion with Sca I cut the Aspergillus amplicon(150–160bp)into two fragments,of 100and50bp,although some undigested amplicon was apparent.None of the yeast amplicons possessed the correct recognition sequence for Sca I and so the PCR amplicon remained undigested(Fig.1).

Speci?city of the Candida probe

Using DNA extracted from the cultured fungi,the Candida probe was tested for its speci?city.The Candida probe hybridized with C.albicans,C.kefyr,C.krusei,C.dubliniensis, C.tropicalis,C.parapsilosis and C.glabrata but would not hybridize to DNA from C.guillermondii,C.lipolytica,C. famata,A.fumigatus,A.niger,S.cerevisiae or Cryptococcus neoformans.All the species tested produced an amplicon,as represented by the SYBR green peak on the melting pro?les, but only the afore-mentioned seven Candida species pro-duced a Cy5(probe)signal,giving rise to the representative double-peaked melting pro?le(Fig.2).The melting tem-perature of the Candida probe was between59and628C and the PCR amplicon melted at between87and898C;both melting temperatures were dependent on the species being used in the experiment.

When tested with DNA extracted from blood donated from healthy individuals,although some non-speci?c ampli?ca-tion occurred,no probe hybridization was seen.This was also true for blood spiked with0c.f.u.C.albicans mlà1(Fig.3).It was noted in all tests that,even when no fungal cells/DNA were present,some non-speci?c ampli?cation occurred.The absence of any probe signal con?rmed that it was not one of the medically important Candida species tested for.Multiple attempts to sequence the ampli?ed products resulted in incoherent data,indicating that ampli?cation was non-speci?c.

Sensitivity of the single-round Candida PCR assay

In order to?nd the lower limit of sensitivity,blood from healthy individuals spiked with C.albicans cells in the range 2·53102to0c.f.u.mlà1was https://www.wendangku.net/doc/d5678327.html,ing this technique,we were able to detect Candida down to a reproducible limit of5 c.f.u.mlà1(Fig.3),a sensitivity that corresponded to the reproducible detection limit using the Roche Light-Cycler/ FRET-based system(Loef?er et al.,2000b).It was found that, if the extraction modi?cations noted earlier in this publica-tion were not applied,the reproducible detection limit increased to20–30c.f.u.mlà1whole blood. Reproducibility of the assay

In total,spiked whole blood(103to0c.f.u.mlà1)from healthy individuals was extracted on?ve separate occasions and,for each extraction,the Candida PCR was repeated three times.Each time,the same results were achieved,with the lower sensitivity always being5 c.f.u.mlà1.Since the development of the assay,100clinical experiments have been carried out and only twice have the positive extraction controls(,10c.f.u.mlà1)failed to work and,on both occasions,this could be attributed to errors during the extraction

procedure.

Fig.1.TAE/4%Metaphor agarose gels showing Sca I digestion of L18F/L18R https://www.wendangku.net/doc/d5678327.html,nes:M,markers;1,C.albicans;2,A.oryzae; 3,C.dubliniensis;4,C.glabrata;5,C.guillermondii;6,C.kefyr;7,C. krusei;8, C.lipolytica;9, C.parapsilosis;10, C.tropicalis;11, Cryptococcus neoformans;12,Saccharomyces cerevisiae;13,A. fumigatus;14,A.?avus;15,A.niger;16,A.nidulans;17,A.candidus; 18,A.terreus.Molecular mass marker sizes:2000,1500,1000,750, 500,300,150and50bp.

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Sensitivity of the nested Candida PCR assay In order to determine the lower sensitivity limit,blood from healthy individuals was spiked with C.albicans cells in the range 103to 0c.f.u.ml à1and DNA was extracted as described above.The ?rst-round PCR gave an amplicon of around 200bp,although this was not always visible,depending on the size of the initial spike.This extra ampli?cation step improved the detection of Candida to 1c.f.u.ml à1(Fig.4),a ?gure that is comparable with results published for NASBA and PCR-ELISA detection of Candida .

When comparing the single-round PCR assay with the nested PCR assay,the crossing-points were as follows:for 250c.f.u.ml à1,26cycles for the single-round versus 7cycles for the nested;for 30c.f.u.ml à1,30cycles for the single-round versus 15cycles for the nested;and,for 5c.f.u.ml à1,32cycles for the single-round versus 19cycles for the nested PCR (Fig.

5).As the crossing-point is dependent on the initial template concentration,the results indicate that the nested PCR assay has greatly increased the template concentration and has therefore improved the sensitivity of the overall assay.The results for the single-round PCR assay are consistent with results published for experiments on both the Roche Light-Cycler system and block-based assays (Einsele et al .,1997;Loef?er et al .,2000b).

Analysis of clinical samples

In interpreting the results from the 472EDTA-whole blood samples tested,a number of factors need to be considered.Due to the increased chances of contamination involved with a nested PCR,only samples that were positive by both the single-round Light-Cycler assay and the nested PCR assay could initially be regarded as PCR-positive;any samples that were only positive by the nested PCR method were repeated before they were considered PCR-positive.All of the PCR-positive samples tested were positive by both assays.To con?rm the results,samples that were considered PCR-positive were also tested by RFLP.All of the samples that were positive by PCR were also positive by RFLP (results not shown).To rule out contamination during the ?rst DNA extraction,any patient that was initially considered PCR-positive for Candida had a follow-up sample taken and only if this second sample gave a PCR-positive result was the patient considered to have possible candidiasis.

The PCR method detected candidal DNA in 27of the 113(23·9%)patients tested (42of 472samples tested),but only 11(9·7%)of these patients had multiple samples that were PCR-positive,the other 16(14·2%)had only a single PCR-positive sample.Concurrent with the PCR,all the patients were tested for fungal infection by blood culture.Of the 113patients investigated,only 3(2·7%)had Candida -positive

?d F /d T

Temperature (oC)

(e)

(d)

(c)

(b)

(a)

PCR amplicon melt

Candida probe melt

Fig.2.Representative melting pro?les of (a)a species detected by the Candida probe (C.albicans ),(b)–(d)three species not detected by the Candida probe (b,C.famata ;c,Cryptococcus neoformans ;d,Aspergillus fumigatus )and (e)a negative control

(water).

Fig.3.Determination of the sensitivity of the single-round Candida PCR assay.Whole blood from healthy individuals was spiked with serial dilutions of C.albicans cells (250,30,5or 0c.f.u.ml à1)and then extracted.

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blood cultures,compared with 27(23·9%)positive by PCR.Two of the blood culture Candida -positive patients were also positive for Candida by PCR,although one of the blood culture Candida -positive patients was not detected by the Candida PCR;however,this patient had received 5days of antifungal treatment before a sample was sent for fungal PCR

analysis.The sample was positive for Aspergillus by RFLP (Table 1).None of the samples that were PCR-negative for both Candida and Aspergillus were positive by blood culture.On the basis of Aspergillus RFLP analysis,a further 15(13·3%)patients were positive for Aspergillus DNA (results

1

2

(a)

(b)

(c)

(d)

(e)

(f)

(g)

(h)

Temperature (oC)Temperature (oC)

?d F /d T

Fig.4.Determination of the sensitivity of the single-round Candida PCR assay (column 1)and the nested Candida PCR assay (column 2)using serially diluted C.albicans cells extracted from spiked whole blood from healthy individuals.(a)C.albicans positive control.(b)–(g)Dilutions containing 5(b),2(c),1(d),0·5(1c.f.u.in 2ml)(e),0·25(1c.f.u.in 4ml)(f)or 0c.f.u.ml à1(g).(h)Water control.

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not shown),but only 5(4·4%)of these had multiple PCR/RFLP-positive https://www.wendangku.net/doc/d5678327.html,puted tomography (CT)scans and chest X-rays indicated that nine of these patients were suspected of having an opportunistic lung infection and one of these patients also had positive Aspergillus histopathology results,including A.niger colonization of lung,brain,heart

and discs of the lumbar region.On extracting DNA from the heart and lung tissue,RFLP analysis con?rmed the presence of Aspergillus .Sequencing of the Aspergillus PCR product identi?ed the species as A.niger ,thus con?rming the histo-pathology results.None of the patients had Aspergillus -positive blood cultures.

Microbiological data revealed that the patients that were PCR-positive for Candida or Aspergillus tended to have higher levels of fungal colonization at super?cial sites.Of the 27patients who were Candida PCR-positive,59·3%had super?cial fungal colonization [predominantly (81·3%)Candida species;Table 1].Eight of the 15patients who were Aspergillus RFLP-positive were also colonized,mainly by Candida species (75%).Only 16of the 71(22·5%)patients who were consistently PCR-negative showed any signs of super?cial colonization (Table 1).

In total,37·2%(14·1%using multiple-sample PCR-posi-tives only)of the suspected cases were positive for Candida (23·9/9·7%)and Aspergillus (13·3/4·4%)as determined by the PCR/RFLP method,whereas blood culture only detected Candida in 3of 113(2·7%)cases,and no Aspergillus was cultured.One patient was Candida PCR-negative but posi-tive for Candida by blood culture,although this patient had received antifungal treatment before being tested by PCR.

DISCUSSION

With the development of real-time PCR,progress has been made in the development of techniques for the detection of infectious organisms.Most of this research has been directed at detecting viruses (Schroter et al .,2001;Kawai et al .,1999;Funato et al .,2001;Whalley et al .,2001;van Elden et al .,2001;Schutten et al .,2000)and bacteria (Corless et al .,

2001;

Fig.5.Crossing-points of ?uorescence of serially diluted C.albicans cells extracted from spiked whole blood from healthy individuals.Curves show dilutions containing 250(curves A),30(B)or 5(C)c.f.u.ml à1.(a)Serial dilutions already ampli?ed by the ?rst round of the nested PCR.(b)Serial dilutions ampli?ed by the Light-Cycler system only.

Table 1.Colonization of patients tested by PCR/RFLP

*One of these patients had super?cial and deep-seated Candida (blood culture)infection.This patient was not positive for Candida by PCR.

?These patients had super?cial and deep-seated Candida (blood culture)colonization.Detection of Candida species using the Light-Cycler

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Rantakokko-Jalava&Jalava,2001;Qi et al.,2001;Mygind et al.,2001),with less work focused on the detection of fungi (Loef?er et al.,2000a,b;Palladino et al.,2001).With the number and range of opportunistic fungal infections in-creasing and the necessity for early diagnosis,the develop-ment of a real-time method for fungal detection is imperative (Chen et al.,2000;Reiss&Morrison,1993;Gleason et al., 1997).

Approximately80%of systemic fungal infections are caused by Candida species,with60%of these infections caused by C. albicans,although there are an increasing number of cases of infection caused by non-C.albicans species such as C. tropicalis,C.parapsilosis,C.glabrata and C.krusei.It was therefore crucial to design a system that would be able to detect all these species without the need for time-consuming post-ampli?cation handling,e.g.RFLP analysis.By develop-ing a?uorescently labelled probe for use on the Light-Cycler system,we were able to detect C.albicans,C.parapsilosis,C. tropicalis,C.krusei and C.glabrata as well as C.kefyr and C. dubliniensis,with no cross-hybridization with other major fungal pathogens(Fig.2).In terms of epidemiology,it would have been bene?cial to design species-speci?c probes that could have been used for samples that were positive with the pan-candidal probe,and this may be pursued in the future, although this would increase the work-load.It is also bene?cial to distinguish between azole-sensitive and azole-resistant Candida strains and so provide information on the appropriate antifungal therapy;Loef?er et al.(2000a)have developed a Light-Cycler-based method for this.

It has been suggested that the fungal load in blood samples is frequently lower than10c.f.u.mlà1of blood,with25%of cases having a fungal load of1c.f.u.mlà1or below.As such a very small amount of fungal DNA would be present(Loef?er et al.,2000b),the sensitivity of the assay is critical.By targeting the multicopy(.100copies;Einsele et al.,1997) 18S rRNA gene,the sensitivity of the assay is enhanced. Without the nested PCR,the Light-Cycler/probe system was able to detect as little as to5c.f.u.mlà1reproducibly,thus detecting most cases of candidal infection.To enhance the sensitivity further,a nested PCR was developed and this allowed reproducible detection down to1c.f.u.mlà1,a level comparable with other published techniques.To keep the assay within1working day,the single-round assay should be employed,but it should be noted that,if the?rst round of the nested PCR is performed overnight,the nested PCR assay can be completed in less than1·5working days.

The use of PCR-ELISA has been shown to be100%speci?c at a sensitivity level of5c.f.u.mlà1of blood(Loef?er et al., 1998),but this technique costs more per sample and takes considerably longer than a Light-Cycler reaction.The same is true for the use of Southern blotting;Einsele et al.(1997), using a variety of probes to detect Candida species,reported a sensitivity of10to50fg DNA,which was equivalent to1c.f.u. mlà1of blood.Although species-level identi?cation was achieved,the sample handling time was considerable,de-pending on the fungal species causing the infection.The most promising alternative to the Light-Cycler system is the use of NASBA.Research has been carried out for the detection of both Candida and Aspergillus species(Widjojoatmodjo et al., 1999;Loef?er et al.,2001)and indicated a comparable sensitivity limit of1c.f.u.mlà1blood,with few drawbacks. The rapid sample turn-around and high sensitivity of NASBA make it a good alternative for the detection of infection.

Contamination is accepted as a major problem in detecting fungal infection,especially in ampli?cation techniques based on the use of pan-fungal primers.As yeasts and moulds are ubiquitous in the environment,controlling contamination of extraction and PCR reagents is essential.When using a nested PCR system,it is imperative that every precaution is taken to minimize the chance of cross-contamination and that all positive results need repeat con?rmation.The presence of fungal DNA in the enzyme Zymolyase has been reported previously(Rimek et al.,1999;Loef?er et al.,1999) and,on testing three batches of the enzyme,we discovered DNA from S.cerevisiae(results not shown).On testing DNA extracted from S.cerevisiae on the Light-Cycler,there was ampli?cation by PCR but no cross-reactivity with the Candida probe and,on comparing S.cerevisiae18S rRNA sequence data,it was decided that no cross-reactivity was likely to occur.

Occasionally,batches of103PCR buffer have been found to contain fungal DNA(Loef?er et al.,1999),and this highlights the problems in detecting fungal infections con?dently using commercial reagents.It has been predicted that only a?nite number of airborne fungal species contaminate samples during the extraction procedure and that the rate of contamination is no greater than any other PCR technique (Loef?er et al.,1999).Nevertheless,with the development of new procedures with improved sensitivities,the problem may become more apparent.It is therefore essential that the speci?cities of assays be vigorously con?rmed.

The actual source of fungal nucleotides in the blood of patients suffering from fungaemia is still unknown.Whether they are extracted from intact cells(including non-viable/ non-culturable cells)circulating in the bloodstream or from fungal cells that have been engulfed by white blood cells,or from free nucleic acid,remains unclear.This and other research con?rms that it is possible to extract and detect DNA/RNA from intact fungal cells spiked into whole blood, although it is undecided whether this is the case in the clinical scenario.It has also been hypothesized that candidal cells or nucleic acids may pass into the bloodstream by absorption through the gut lining and give rise to one-off(false)positive results(as is the case with galactomannan/mannan and the ELISA assays).In this study,over80clinical DNA extractions were performed and,each time,a negative extraction control (EDTA blood from a healthy individual)was included.In total,15healthy volunteers donated blood on at least three separate occasions and not once did the negative control give a positive result.Although this evidence suggests that false positives due to adsorption of fungal cells/nucleic acid

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236Journal of Medical Microbiology52

through the gut is unlikely,it cannot be excluded in the clinical scenario,where the cytotoxic effects of many anti-biotics may damage the gut lining.

The use of18S rRNA genes for the detection and identi?ca-tion of many fungi has been described extensively(Einsele et al.,1997;Jaeger et al.,2000;Mathis et al.,1997; Widjojoatmodjo et al.,1999;Loef?er et al.,2000b,2001), as has the possibility of using the internal transcribed spacer (ITS)regions between the actual rRNA genes(Chen et al., 2000;Williams et al.,1995;White et al.,1990).Being less highly conserved than the rRNA genes,targeting the ITS regions would allow easier species-level identi?cation and this could be applied to the Light-Cycler system.For example,within the genus Candida,the ITS2region varies in size from251bp for Candida lustianiae up to428bp for C. kefyr(Chen et al.,2000),and this variation could be exploited.One of the bene?ts of the Light-Cycler system is its ability to differentiate PCR amplicons by analysis of their melting curves.The melting temperature of the amplicon is dependent on the G+C content,length and sequence,and Ririe et al.(1997)predict that a1kb amplicon would melt at a temperature128C higher than would a40bp primer dimer of similar G+C content.The actual melting temperature of the PCR product is also a function of the rate of temperature transition,with a slower rate of temperature transition providing greater melting temperature precision(Ririe et al.,1997).By carefully designing a pan-Candida probe, we may be able to achieve species-level identi?cation for a range of Candida species within a single Light-Cycler reaction and so provide a much higher standard of differ-entiation but within a much shorter time-scale.

In conclusion,the single-round Light-Cycler system devel-oped provides a rapid,accurate and reproducible method that combines the enhanced sensitivity and increased speci-?city of probe hybridization for the detection of the most common forms of systemic candidal infection.The sensitiv-ity of the assay can be improved by utilizing the nested Light-Cycler,but this will increase the time to detection and increase the complexity of the assay.As primers are pan-fungal,the assay can be easily modi?ed for the detection of other pathogenic and/or opportunistic fungal infections by the design of speci?c probes.

The clinical relevance of the PCR results in most cases still remains uncertain.Only two of the PCR positives were con?rmed by a positive blood culture,although the con-?rmation of a PCR result by a technique known to be much less sensitive does seem unwise.Of the11patients with multiple Candida PCR-positive results,seven were treated with liposomal amphotericin B;all seven responded to treatment and all became Candida PCR negative.Of the four remaining patients,two were treated with?uconazole but did not respond,whilst the other two were not treated and the symptoms in one of these patients did resolve.However, under the current consensus criteria for the diagnosis of fungaemia(Ascioglu et al.,2002),a case with multiple PCR positives does not provide enough evidence to prove a case of invasive Candida or Aspergillus infection and,at most,it can be used as one criterion in de?ning a probable case of fungaemia.The PCR result must,at all times,be collated with other clinical evidence:radiology(CT scans and chest X-rays),culture(both super?cial and deep-seated colon-ization),histopathology(if available),patient history [underlying illness,current therapy(including antifungal treatment),previous fungal infections,other opportunistic infections(e.g.cytomegalovirus)]and other lab-based assays (ELISA or latex agglutination for the detection of mannan or galactomannan).Using the above information,only three cases in this study could be classi?ed as proven candidaemias; the cases with multiple PCR-positive results were considered as probable fungaemias,while the cases with single PCR positives were considered as possible or suspected fungae-mias.

At the present time,it is still not possible to prove a case of fungaemia without a positive blood culture combined with the compatible clinical symptoms,but it is hoped that further research into fungal PCR will provide a credible method to overcome the sensitivity limitations of blood culture. REFERENCES

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模具弹簧规格及参数

模具彈簧规格及参数 一.彈簧功能 彈簧是模具中廣泛應用的彈性零件,主要用于卸料、壓料、推件和頂出等工作.根據荷重不同,共分五種不同顏色加以區分,易於判別和選用. 二.規格系列 1.彈簧外徑系列: Φ6Φ8,Φ10,Φ12,Φ14,Φ16,Φ18,Φ20,Φ22,Φ25,Φ 30,Φ35,Φ40,Φ50等. 2.種類 3.彈簧長度：15<=L<=80MM時,每5MM為一個階; 80==100MM時,每25MM為一個階.

4.扁线彈簧最小直径6mm 5.彈簧內徑等于彈簧外徑的二分之一. 6.相同直径颜色的弹簧，不管自由长度是多长，压40％产生的力一样 结论：相同直径颜色的弹簧，自由长度越短，压缩1mm产生的力越大 7.通常使用的最大壓縮比是彈簧使用30萬次的最大壓縮比. 汽车模具使用50萬次的最大壓縮比.. 8.弹簧能压缩的长度=弹簧的自由长度x弹簧的压缩比 例：Φ20绿色弹簧长度50mm，弹簧要求寿命30万次，弹簧能压缩多 长？ 50x24％=12(mm) 9.弹簧的长度=弹簧要压缩的长度÷弹簧的压缩比 例：弹簧要压缩20mm, 弹簧颜色为红色，弹簧要求寿命50万次 要用多长的弹簧？ 长弹簧 10. 11.

预压3mm,預壓縮量隨實際情況而定.);閉模狀態彈簧壓縮量小於或等於最大壓縮量(最大壓縮量LA=彈簧自由長L*最大壓縮比取值%). 2.模板压料，脱料板压料優先選用綠色或棕色（茶色，咖啡色) 彈簧;如果向上成形的下模压料，折弯脱料所需的頂料力不很大時,可選用紅色,绿色彈簧，浮料用黄色，圆线弹簧. 3.復合模外脫料板用紅色彈簧,內脫料板用綠色或棕色彈簧.

模具弹簧规格及参数

模具弹簧规格及参数 一.弹簧功能 弹簧是模具中广泛应用的弹性零件,主要用于卸料、压料、推件和顶出等工作.根据荷重不同,共分五种不同颜色加以区分,易於判别和选用. 二.规格系列 1.弹簧外径系列:Φ6Φ8,Φ10,Φ12,Φ14,Φ16,Φ18,Φ20,Φ22,Φ25,Φ30,Φ35,Φ40,Φ50等. 2.种类 3.弹簧长度：15<=L<=80MM时,每5MM为一个阶; 80==100MM时,每25MM为一个阶. 4.扁线弹簧最小直径6mm 5.弹簧内径等于弹簧外径的二分之一. 6.相同直径颜色的弹簧，不管自由长度是多长，压40％产生的力一样 结论：相同直径颜色的弹簧，自由长度越短，压缩1mm产生的力越大 7.通常使用的最大压缩比是弹簧使用30万次的最大压缩比. 汽车模具使用50万次的最大压缩比.. 8.弹簧能压缩的长度=弹簧的自由长度x弹簧的压缩比 例：Φ20绿色弹簧长度50mm，弹簧要求寿命30万次，弹簧能压缩多长？

50x24％=12(mm) 9.弹簧的长度=弹簧要压缩的长度÷弹簧的压缩比 例：弹簧要压缩20mm,弹簧颜色为红色，弹簧要求寿命50万次 要用多长的弹簧？ 弹簧的长度=20÷28.8％+5MM=74.4 查表选用75MM长弹簧 一般选弹簧长度会加5mm的安全余量 10.弹簧要压缩的长度=活动板行程+3~5mm预压(常规预压3mm) 11.弹簧模板孔的大小直径<20模板孔=D+1 直径>=20模板孔=D+2 三.选用原则 1.长度选择一般保证:在开模状态弹簧的预压缩量等於3~5(常规预压3mm,预压缩量随 实际情况而定.);闭模状态弹簧压缩量小於或等於最大压缩量(最大压缩量LA=弹簧 自由长L*最大压缩比取值%). 2.模板压料，脱料板压料优先选用绿色或棕色（茶色，咖啡色)弹簧;如果向上成形的 下模压料，折弯脱料所需的顶料力不很大时,可选用红色,绿色弹簧，浮料用黄色，圆线弹簧. 3.复合模外脱料板用红色弹簧,内脱料板用绿色或棕色弹簧. 4.活动定位销一般选用Φ6顶料销,配Φ10黄色弹簧和M12止付螺丝. Φ8顶料销,配Φ12黄色弹簧和M14止付螺丝. 5.冲孔模和成形模用绿色或棕色（茶色，咖啡色)弹簧,如有特殊需求时,由专案主管确 定. 6.弹簧规格优先选用Φ30.在空间较小区域可考虑选用其它规格(如Φ25,Φ20,Φ18,Φ 16…...等).Φ25的内导柱用Φ30的弹簧脱料 Φ20的内导柱用Φ25的弹簧脱料 四.排配原则 1.弹簧过孔中心到模板边缘距离大於外径D,与其他孔距离保持实体壁厚大於5MM, 空间不足时最少留2MM. 2.弹簧排列首先考虑受力重点部位,然後再考虑整个模具受力均衡平稳.受力重点部 位是指:复合模的内脱料板外形和冲头的周围;冲孔模的冲头周围;成形模的折弯边 及有抽成形的地方. 3.成形模采用气垫结构时,下打板排配2~6个弹簧.下模座上不沉孔,弹簧选用黄色或 蓝色即可.

模具弹簧规格及参数

模具弹簧规格及参数 Document serial number【KKGB-LBS98YT-BS8CB-BSUT-BST108】

模具弹簧规格及参数 一. 弹簧功能 弹簧是模具中广泛应用的弹性零件,主要用于卸料、压料、推件和顶出等工作.根据荷重不同,共分五种不同颜色加以区分,易於判别和选用. 二. 规格系列 1.弹簧外径系列: Φ6Φ8,Φ10,Φ12,Φ14,Φ16,Φ18,Φ20,Φ22,Φ25,Φ30,Φ 35,Φ40,Φ50等. 2.种类 3.弹簧长度：15<=L<=80MM时,每5MM为一个阶; 80==100MM时,每25MM为一个阶. 4.扁线弹簧最小直径6mm 5.弹簧内径等于弹簧外径的二分之一. 6.相同直径颜色的弹簧，不管自由长度是多长，压40％产生的力一样 结论：相同直径颜色的弹簧，自由长度越短，压缩1mm产生的力越大 7.通常使用的最大压缩比是弹簧使用30万次的最大压缩比. 汽车模具使用50万次的最大压缩比..

8.弹簧能压缩的长度=弹簧的自由长度x弹簧的压缩比 例：Φ20绿色弹簧长度50mm，弹簧要求寿命30万次，弹簧能压缩多长 50x24％=12(mm) 9.弹簧的长度=弹簧要压缩的长度÷弹簧的压缩比 例：弹簧要压缩20mm, 弹簧颜色为红色，弹簧要求寿命50万次 要用多长的弹簧 弹簧的长度=20÷％+5MM= 查表选用75MM长弹簧 一般选弹簧长度会加5mm的安全余量 10.弹簧要压缩的长度=活动板行程+3~5mm预压 (常规预压3mm) 11.弹簧模板孔的大小直径<20模板孔=D+1 直径>=20模板孔=D+2 三. 选用原则 1.长度选择一般保证:在开模状态弹簧的预压缩量等於3~5(常规预压3mm,预 压缩量随实际情况而定.);闭模状态弹簧压缩量小於或等於最大压缩量 (最大压缩量LA=弹簧自由长L*最大压缩比取值%). 2.模板压料，脱料板压料优先选用绿色或棕色（茶色，咖啡色)弹簧;如果 向上成形的下模压料，折弯脱料所需的顶料力不很大时,可选用红色,绿色弹簧，浮料用黄色，圆线弹簧. 3.复合模外脱料板用红色弹簧,内脱料板用绿色或棕色弹簧. 4.活动定位销一般选用Φ6顶料销,配Φ10黄色弹簧和M12止付螺丝. Φ8顶料销,配Φ12黄色弹簧和M14止付螺丝. 5.冲孔模和成形模用绿色或棕色（茶色，咖啡色)弹簧,如有特殊需求时,由 专案主管确定. 6.弹簧规格优先选用Φ30.在空间较小区域可考虑选用其它规格(如Φ25,Φ 20,Φ18,Φ16…...等).Φ25的内导柱用Φ30的弹簧脱料 Φ20的内导柱用Φ25的弹簧脱料 四. 排配原则 1.弹簧过孔中心到模板边缘距离大於外径D,与其他孔距离保持实体壁厚大 於5MM,空间不足时最少留2MM. 2.弹簧排列首先考虑受力重点部位,然後再考虑整个模具受力均衡平稳.受 力重点部位是指:复合模的内脱料板外形和冲头的周围;冲孔模的冲头周 围;成形模的折弯边及有抽成形的地方.

天津大学2020硕士研究生初试考试自命题科目大纲807工程光学与光电子学基础

一、考试模块划分方式： 考试内容分为A、B 两个模块，考生可任选其中一个模块。A 模块为工程光学，B 模块为光电子学基础。 二、各模块初试大纲： A模块：工程光学 （一）考试的总体要求 本门课程的考试旨在考核学生有关应用光学和物理光学方面的基本概念、基本理论和实际解决光学问题的能力。 考生应独立完成考试内容，在回答试卷问题时，要求概念准确，逻辑清楚，必要的解题步骤不能省略，光路图应清晰正确。 （二）考试的内容及比例 考试内容包括应用光学和物理光学两部分。 “应用光学”应掌握的重点知识包括：几何光学的基本理论和成像概念、理想光学系统理论、光学系统中的光束限制、平面和平面系统对成像的影响、像差的基本概念和典型光学系统的性质、成像关系及光束限制等。具体知识点如下： 1、掌握几何光学基本定律与成像基本概念，包括：四大基本定律及全反射的内容与现象解释；完善成像条件的概念和相关表述；几何光学符号规则以及单个折射球面、反射球面的成像公式、放大率公式等。 2、掌握理想光学系统的基本理论和典型应用，包括：基点、基面的主要类型及其特点；图解法求像的方法；解析法求像方法（牛顿公式、高斯公式）；理想光学系统三个放大率的定义、计算公式及物理意义；理想光学系统两焦距之间的关系；正切计算法以及几种典型组合光组的结构特点、成像关系等。 3、掌握平面系统的主要种类及应用，包括：平面镜的成像特点及光学杠杆原理和应用；反射棱镜的种类、基本用途及成像方向判别；光楔的偏向角公式及其应用等。 4、掌握典型光学系统的光束限制分析，包括：孔径光阑、入瞳、出瞳、孔径角的定义及它们的关系；视场光阑、入窗、出窗、视场角的定义及它们的关系；渐晕、渐晕光阑、渐晕系数的定义；物方远心光路的工作原理；光瞳衔接原则及其作用；场镜的定义、作用和成像关系等。 5、了解像差基本概念，包括：像差的定义、种类和消像差的基本原则；7 种几何像差的定义、影响因素、性质和消像差方法等。 6、掌握几种典型光学系统的基本原理和特点，包括：正常眼、近视眼和远视眼的定义和特征，校正非正常眼的方法；视觉放大率的概念、表达式及其意义；显微镜系统的结构特点、成像特点、光束限制特点及主要参数的计算公式；临界照明和坷拉照明系统的组成、优缺点；望远系统的结构特点、成像特点、光束限制特点及主要参数的计算公式；摄影系统的结构特点、成像特点、光束限制特点及主要参数的计算公式；投影系统的概念、计算公式以及其照明系统的衔接条件等。 “物理光学”应掌握的重点知识包括：光的电磁理论基础、光的干涉和干涉系统、光的衍射、光的偏振和晶体光学基础等。具体知识点如下：

光电子技术第三版安毓英刘继芳等著习题答案完整版

第一章 1. 设在半径为R c 的圆盘中心法线上，距盘圆中心为l 0处有一个辐射强度为I e 的点源S ，如图所示。试计算该点源发射到盘圆的辐射功率。 解：因为 ΩΦd d e e I = ， 且 ()??? ? ??+- =-===Ω?22000212cos 12sin c R R l l d d r dS d c πθπ?θθ 所以??? ? ??+-=Ω=Φ220012c e e e R l l I d I π 2. 如图所示，设小面源的面积为?A s ，辐射亮度为L e ，面源法线 与l 0的夹角为θs ；被照面的面积为?A c ，到面源?A s 的距离为l 0。若θc 为辐射在被照面?A c 的入射角，试计算小面源在?A c 上产生的辐射照度。 解：亮度定义: r r e e A dI L θ?cos = 强度定义:Ω Φ =d d I e e 可得辐射通量：Ω?=Φd A L d s s e e θcos 在给定方向上立体角为：2 0cos l A d c c θ?= Ω 则在小面源在?A c 上辐射照度为：20 cos cos l A L dA d E c s s e e e θθ?=Φ= 3.假如有一个按朗伯余弦定律发射辐射的大扩展源（如红外装置面对的天空背景），其各处的辐亮度L e 均相同，试计算该扩展源在面积为A d 的探测器表面上产生的辐照度。 答：由θ cos dA d d L e ΩΦ = 得θcos dA d L d e Ω=Φ，且()2 2cos r l A d d +=Ωθ 则辐照度：()e e e L d r l rdr l L E πθπ =+=? ?∞ 20 0222 2 4. 霓虹灯发的光是热辐射吗？ l 0 S R c 第1.1题图 L e ?A s ?A c l 0 θs θc 第1.2题图

模具弹簧规格及参数

模具彈簧规格及参数 一. 令狐采学 二.彈簧功能 彈簧是模具中廣泛應用的彈性零件,主要用于卸料、壓料、推件和頂出等工作.根據荷重不同,共分五種不同顏色加以區分,易於判別和選用. 三.規格系列 1.彈簧外徑系 列:Φ6Φ8,Φ10,Φ12,Φ14,Φ16,Φ18,Φ20,Φ22,Φ25,Φ30,Φ35, Φ40,Φ50等. 2.種類

3.彈簧長度：15<=L<=80MM時,每5MM為一個階; 80==100MM時,每25MM為一個階. 4.扁线彈簧最小直径6mm 5.彈簧內徑等于彈簧外徑的二分之一. 6.相同直径颜色的弹簧，不管自由长度是多长，压40％产生的力一样 结论：相同直径颜色的弹簧，自由长度越短，压缩1mm 产生的力越大 7.通常使用的最大壓縮比是彈簧使用30萬次的最大壓縮比. 汽车模具使用50萬次的最大壓縮比.. 8.弹簧能压缩的长度=弹簧的自由长度x弹簧的压缩比例：Φ20绿色弹簧长度50mm，弹簧要求寿命30万次，弹簧能压缩多长？ 50x24％=12(mm) 9.弹簧的长度=弹簧要压缩的长度÷弹簧的压缩比 例：弹簧要压缩20mm, 弹簧颜色为红色，弹簧要求寿

命50万次 要用多长的弹簧？ 弹簧的长度=20÷28.8％+5MM=74.4 查表选用75MM长弹簧 一般选弹簧长度会加5mm的安全余量 10.弹簧要压缩的长度=活动板行程+3~5mm预压(常规 预压3mm) 11.弹簧模板孔的大小直径<20模板孔=D+1 直径>=20模板孔=D+2 四.選用原則 1.長度選擇一般保証:在開模狀態彈簧的預壓縮量等於 3~5(常规预压3mm,預壓縮量隨實際情況而定.);閉模狀態 彈簧壓縮量小於或等於最大壓縮量(最大壓縮量LA=彈 簧自由長L*最大壓縮比取值%). 2.模板压料，脱料板压料優先選用綠色或棕色（茶色，咖 啡色)彈簧;如果向上成形的下模压料，折弯脱料所需的 頂料力不很大時,可選用紅色,绿色彈簧，浮料用黄色， 圆线弹簧. 3.復合模外脫料板用紅色彈簧,內脫料板用綠色或棕色彈 簧. 4.活動定位銷一般選用Φ6頂料銷,配Φ10黃色彈簧和

电子信息类论文模板

(空一行) 基于ＲS４85通信的51单片机恒温控制系统设计（黑体小二） (空一行） 潘雄（宋体四号) (吉首大学物理科学与信息工程学院，湖南吉首416000）(宋体五号) （空一行) 摘要(黑体四号) 由于现代工艺越来越多的需要对实时温度进行监测和控制，而且需要的精度越来越高。所以温度控制系统国内外许多有关人员的重视,得到了十分广泛的应用。本恒温控制系统是利用单片机键盘设置恒温系统的温度值,并实时对温度进行采集,并传输到控制器，控制器采用ＰID控制算法来对温度进行控制;并且把实时温度在LCD 上显示出来。在温度的控制过程中,经过PID控制算法后可以得到的一个PID返回值，控制器通过这个ＰID返回值，来控制加温与降温的快慢。(摘要正文宋体小四) 关键词(黑体四号):MＣS5１单片机;温度采集；单片机键盘;LCD显示;温度控制;ＰＩD算法(宋体小四,词与词之间用分号） （空一行） Tｈｅ５1 ＳCM TemperaturｅControl Sｙsｔem Design Based oｎRS4８5 Cｏmmuniｃａtiｏn (标题字体TimeｓＮｅw Roman三号字加粗）(空一行) ＰaｎXiong(字体Tiｍes NｅｗRoｍaｎ小四) (Ｃollege oｆＰｈysics Science anｄInfｏrmａtｉｏnＥngineerｉnｇ,Ｊｉｓhou Uｎ iversiｔy,Ｊｉshou,Ｈunan41６0０0) （单位字体Tｉｍes New Roman五号） (空一行) Ａbｓtracｔ(TimｅｓNew Romaｎ小四，加粗) As more ａnd mｏｒe ｍodeｒn techｎology to tｈe neeｄs of ｒｅal－ｔime ｍonitoringａnd coｎtroｌｏf tempeｒaｔure, ｂｕt ａlso thｅｉncreasｉnglｙhｉgｈprecisｉon．Ｔheｒｅｆore, teｍpeｒature controｌsｙstｅｍon tｈe m ａｎｙｄｏmestｉｃanｄfｏrｅign aｔｔentioｎhaｓbｅｅn veｒｙwide ｒaｎge of ａpplicａtions. Ｔhe temperaｔｕre ｃｏｎｔroｌsystem iｓto ｕse ＳCＭｋｅyboaｒd setｔingｓof the temｐerａtuｒe ｔhermｏｓtaｔsysｔem and reaｌ-tｉｍe ｔｅｍｐｅrａtｕre on ｔhe acqｕisition anｄtranｓｍissiｏn to ｔhe contｒｏlｌｅr, coｎtrollｅr PIDａlgoritｈm usｅd toｃoｎtｒol tｈe tｅｍperaｔure,and the real-time ｔemperａtｕｒe on tｈｅLCD dispｌayＯut. Iｎt

模具弹簧规格及参数

模具弹簧规格及参数 弹簧功能 弹簧是模具中广泛应用的弹性零件，主要用于卸料、压料、推件和顶出等工作?根据荷重不同,共分五种不同颜色加以区分,易於判别和选用? 规格系列 1. 弹簧外径系列:①6①8,①10,①12，①14，①16,①18,①20,①22， ①25,①30,①35,①40,①50等. 2. 种类 3. 弹簧长度：15<=L<=80MM 时,每5MM 为一个阶; 80=V L V=100MM时，每10MM 为一个阶; L>=100MM 时，每25MM 为一个阶. 4. 扁线弹簧最小直径6mm

5?弹簧内径等于弹簧外径的二分之 6?相同直径颜色的弹簧，不管自由长度是多长，压40%产生的力一样 结论：相同直径颜色的弹簧，自由长度越短，压缩1mm产生的力越大 7.通常使用的最大压缩比是弹簧使用30万次的最大压缩比. 汽车模具使用50万次的最大压缩比.. 8?弹簧能压缩的长度=弹簧的自由长度x弹簧的压缩比 例：①20绿色弹簧长度50mm,弹簧要求寿命30万次，弹簧能压缩多长？ 50x24% =12（mm） 9?弹簧的长度=弹簧要压缩的长度-弹簧的压缩比 例：弹簧要压缩20mm,弹簧颜色为红色，弹簧要求寿命50万次 要用多长的弹簧？ 弹簧的长度=20 - 28.8 % +5MM=74.4 查表选用75MM长弹簧 一般选弹簧长度会加5mm的安全余量 10. 弹簧要压缩的长度=活动板行程+3~5mm预压（常规预压3mm） 11. 弹簧模板孔的大小直径＜20模板孔=D+1 直径＞=20模板孔=D+2 三.选用原则 1. 长度选择一般保证:在开模状态弹簧的预压缩量等於3~5（常规预压3mm, 预压缩量随实 际情况而定.）;闭模状态弹簧压缩量小於或等於最大压缩量（最大压缩量LA=弹簧自由 长L*最大压缩比取值%）.

模具弹簧规格及参数

模具弹簧规格及参数 一. 弹簧功能 弹簧是模具中广泛应用的弹性零件,主要用于卸料、压料、推件和顶出等工作.根据荷重不同,共分五种不同颜色加以区分,易於判别和选用. 二. 规格系列 1.弹簧外径系列:Φ6Φ8,Φ10,Φ12,Φ14,Φ16,Φ18,Φ20,Φ22,Φ25,Φ 30,Φ35,Φ40,Φ50等. 2.种类 3.弹簧长度：15<=L<=80MM时,每5MM为一个阶; 80==100MM时,每25MM为一个阶.

4.扁线弹簧最小直径6mm 5.弹簧内径等于弹簧外径的二分之一. 6.相同直径颜色的弹簧，不管自由长度是多长，压40％产生的力一样 结论：相同直径颜色的弹簧，自由长度越短，压缩1mm产生的力越大 7.通常使用的最大压缩比是弹簧使用30万次的最大压缩比. 汽车模具使用50万次的最大压缩比.. 8.弹簧能压缩的长度=弹簧的自由长度x弹簧的压缩比 例：Φ20绿色弹簧长度50mm，弹簧要求寿命30万次，弹簧能压缩多长？ 50x24％=12(mm) 9.弹簧的长度=弹簧要压缩的长度÷弹簧的压缩比 例：弹簧要压缩20mm, 弹簧颜色为红色，弹簧要求寿命50万次 要用多长的弹簧？ 弹簧的长度=20÷28.8％+5MM=74.4 查表选用75MM长弹簧一般选弹簧长度会加5mm的安全余量 10.弹簧要压缩的长度=活动板行程+3~5mm预压 (常规预压3mm) 11.弹簧模板孔的大小直径<20模板孔=D+1 直径>=20模板孔=D+2 三. 选用原则 1.长度选择一般保证:在开模状态弹簧的预压缩量等於3~5(常规预

模具弹簧规格及参数

模具弹簧规格及参数 Last updated at 10:00 am on 25th December 2020

模具弹簧规格及参数 一.弹簧功能 弹簧是模具中广泛应用的弹性零件,主要用于卸料、压料、推件和顶出等工作. 根据荷重不同,共分五种不同颜色加以区分,易於判别和选用. 二.规格系列 1.弹簧外径系列: Φ6Φ8,Φ10,Φ12,Φ14,Φ16,Φ18,Φ20,Φ22,Φ25,Φ30,Φ35,Φ40,Φ50等.

2.种类 3.弹簧长度：15<=L<=80MM时,每5MM为一个阶; 80==100MM时,每25MM为一个阶. 4.扁线弹簧最小直径6mm 5.弹簧内径等于弹簧外径的二分之一.

6.相同直径颜色的弹簧，不管自由长度是多长，压40％产生的力一样 结论：相同直径颜色的弹簧，自由长度越短，压缩1mm产生的力越大 7.通常使用的最大压缩比是弹簧使用30万次的最大压缩比. 汽车模具使用50万次的最大压缩比.. 8.弹簧能压缩的长度=弹簧的自由长度x弹簧的压缩比 例：Φ20绿色弹簧长度50mm，弹簧要求寿命30万次，弹簧能压缩多长？ 50x24％=12(mm) 9.弹簧的长度=弹簧要压缩的长度÷弹簧的压缩比 例：弹簧要压缩20mm, 弹簧颜色为红色，弹簧要求寿命50万次 要用多长的弹簧？ 弹簧的长度=20÷％+5MM= 查表选用75MM长弹簧 一般选弹簧长度会加5mm的安全余量 10.弹簧要压缩的长度=活动板行程+3~5mm预压 (常规预压3mm) 11.弹簧模板孔的大小直径<20模板孔=D+1 直径>=20模板孔=D+2

电子广告屏策划方案

策划书 班级：电信10813班 组长：曾佳 组员：黄金 杨树林

LED电子广告屏的设计与制作 摘要 本设计使用AT89C51系列单片机作为主控制模块，利用简单的外围电路来驱动16*32的点阵LED显示屏。点阵显示屏广泛应用于医院、机场、银行等公共场所，所以本设计具有很强的现实应用性。 本LED显示屏能够以动态扫描的方式同时显示八个8×8点阵汉字。设计中采用了SPI接口的GB2312标准字库，支持所有的国标字符和ASCII标准字符的显示。因为采用串行传输方式，使本系统的可扩展性得到提升，便于多个显示单元的级联。 本文从LED显示屏的数学模型入手，详细阐述了LED硬件电路的设计、计算和软件系统的流程。 关键词发光二极管LED 单片机MCU 串行传输Serial Data Transfer 显示屏Display

第1章课题背景 1.1LED显示屏的发展史 随着社会文化的不断发展，人们的消费标准不断改变，户外灯箱广告更是扮演着越来越重要的宣传角色，不论是汽车站，火车站，股市交易市场，还是学校都离不开它，然而传统的霓虹灯广告牌不论是在显示效果、耗电量还是可修改性上都无法满足当前社会的需求，传统的霓虹灯广告亟待改进。 由于单片机技术的不断发展和高亮度LED发光管的出现使得大屏幕高亮度LED电子广告屏成为可能，与传统的霓虹灯广告在显示效果以及可修改性上都有着无法比拟的优势，而且单片机的日益平民化以及LED技术的不断创新，使得高亮度高清晰的LED点阵广告牌与传统霓虹灯广告牌的成本日益接近。另外，SMT 技术的飞速发展，开关电源的大规模使用，使其无论在体积上还是在可靠性上都比传统的霓虹灯广告有明显的优势，为其在特殊领域的应用奠定了基础。 这种新兴的大屏幕显示技术成为众人目光的焦点。与传统的显示设备相比，首先，LED 显示屏色彩丰富，3基色的发光管的可以显示全彩色，显示显示方式变化多样（文字、图形、动画、视频、电视画面等）、亮度高，是集光电子技术、微电子技术、计算机技术、信息处理技术于一体的高技术产品，可用来显示文字、计算机屏幕同步的图形。其次，LED 显示屏的象素采用LED发光二极管，将多个发光二极管以序列的形式构成LED显示阵列，这种显示屏具有耗电省、成本低、亮度清晰度高、寿命长等优点，而且 LED 显示屏以其受空间限制较小，并可以根据用户要求设计屏的大小，具有全彩色效果，视角大，是信息传播设施划时代的产品。再次，LED 显示屏应用广泛，金融证券、银行利率、商业广告、文化娱乐等方面，显示效果清晰稳定，越来越多的地方开始使用LED电子显示屏，有巨大的社会效益和经济效益。它以其超大画面、超宽视觉、灵活多变的显示方式等独居一格的优势，是目前国际上使用广泛的显示系统。 1.2LED电子显示屏的分类 1.2.1 按颜色分类 单基色显示屏:单一颜色（红色或绿色）。 双基色显示屏：红和绿双基色，256级灰度、可以显示65536 种颜色。 全彩色显示屏：红、绿、蓝三基色，256级灰度的全彩色显示屏可以显 示一千六百多万种颜色。

光电子技术课后答案第三版

习 题1 1. 设在半径为R c 的圆盘中心法线上，距盘圆中心为l 0处有一个辐射强度为I e 的点源S ，如图所示。试计算该点源发射到盘圆的辐射功率。 Ω Φd d e e I = ， 2 2 πd l R c = Ω 20 2 e πd d l R I I c e e ==ΩΦ 2. 如图所示，设小面源的面积为?A s ，辐射亮度为L e ，面源法线与l 0的夹角为θs ；被照面的面积为?A c ，到面源?A s 的距离为l 0。若θc 为辐射在被照面?A c 的入射角，试计算小面源在?A c 上产生的辐射照度。 用定义r r e e A dI L θ?cos = 和A E e e d d Φ= 求解。 4. 霓虹灯发的光是热辐射吗？ 不是热辐射。 6. 从黑体辐射曲线图可以看出，不同温度下的黑体辐射曲线的极大值处的波长λm 随温度T 的升高而减小。试由普朗克热辐射公式导出 常数=T m λ。 这一关系式称为维恩位移定律，其中常数为2.898?10-3m ?K 。 普朗克热辐射公式求一阶导数，令其等于0，即可求的。 9. 常用的彩色胶卷一般分为日光型和灯光型。你知道这是按什么区分的吗？ 按色温区分。 习 题2 1. 何为大气窗口，试分析光谱位于大气窗口内的光辐射的大气衰减因素。 对某些特定的波长，大气呈现出极为强烈的吸收。光波几乎无法通过。根据大气的这种选择吸收特性，一般把近红外区分成八个区段，将透过率较高的波段称为大气窗口。 l 0 S R c 第1题图 L e ?A s ?A c l 0 θs θc 第2题图

2. 何为大气湍流效应，大气湍流对光束的传播产生哪些影响？ 是一种无规则的漩涡流动，流体质点的运动轨迹十分复杂，既有横向运动，又有纵向运动，空间每一点的运动速度围绕某一平均值随机起伏。这种湍流状态将使激光辐射在传播过程中随机地改变其光波参量，使光束质量受到严重影响，出现所谓光束截面内的强度闪烁、光束的弯曲和漂移（亦称方向抖动）、光束弥散畸变以及空间相干性退化等现象，统称为大气湍流效应。 5. 何为电光晶体的半波电压？半波电压由晶体的那些参数决定？ 当光波的两个垂直分量E x '，E y '的光程差为半个波长（相应的相位差为π）时所需要加的电压，称为半波电压。 7. 若取v s =616m/s ，n =2.35， f s =10MHz ，λ0=0.6328μm ，试估算发生拉曼-纳斯衍射所允许的最大晶体长度L max =? 由公式0 2 20 2 044λλλs s s f nv n L L = ≈ <计算，得到 6 12 2 2 2 max 10 6328.0410 10061635.24-?????= = λs s f nv L 。 10. 一束线偏振光经过长L =25cm ，直径D =1cm 的实心玻璃，玻璃外绕N =250匝导线，通有电流I =5A 。取韦尔德常数为V =0.25?10-5（'）/cm ?T ，试计算光的旋转角θ。 由公式L αθ=、VH =α和L NI H =计算，得到VNI =θ。 11. 概括光纤弱导条件的意义。 从理论上讲，光纤的弱导特性是光纤与微波圆波导之间的重要差别之一。实际使用的光纤，特别是单模光纤，其掺杂浓度都很小，使纤芯和包层只有很小的折射率差。所以弱导的基本含义是指很小的折射率差就能构成良好的光纤波导结构，而且为制造提供了很大的方便。 15. 光波水下传输有那些特殊问题？ 主要是设法克服这种后向散射的影响。措施如下： ⑴适当地选择滤光片和检偏器，以分辨无规则偏振的后向散射和有规则偏振的目标反射。 ⑵尽可能的分开发射光源和接收器。 ⑶采用如图2-28所示的距离选通技术。当光源发射的光脉冲朝向目标传播时，接收器

光电子技术第三版安毓英刘继芳等著习题答案完整版

第一章 1. 设在半径为F C 的圆盘中心法线上，距盘圆中心为l o 处有一个 辐射强度为I e 的点源S,如图所示。试计算该点源发射到盘圆的辐射 功率 2. 如图所示，设小面源的面积为 A,辐 射亮度为L e ,面源法线 与10的夹角为s ；被照面的面积为 A ，到面源 A 的距离为丨0。若 c 为辐射在被照面 Ac 的入射角，试计算小面源在 A 上产生的辐射 强度定义:l e d 可得辐射通量 : d e L e A s cos s d 在给定方向上立体角为： A c cos 3. 假如有一个按朗伯余弦定律发射辐射的大扩展源（如红外装置 面对的天空背景），其各处的辐亮度L e 均相同，试计算该扩展源在面 积为A d 的探测器表面上 产生的辐照度。 答：由 L e d 得 d L e d dAcos ，且 d A ； cos 2 d dAcos l r 则辐照度：E e L e l 2 也p 2 d L e e e ° I 2 r 2 2 0 e 4. 霓虹灯发的光是热辐射吗？ 解：因为， dS ~2~ r sin d d 2 1 cos 10 所以 l e d 2 I e 1 1 R 2 照度。 解：亮度定义： 则在小面源在 A 上辐射照度为: E e L e A s cos s cos —c dA S

不是热辐射。霓虹灯发的光是电致发光，在两端放置有电极的真空充入氖或氩等惰性气体，当两极间的电压增加到一定数值时，气体中的原子或离子受到被电场加速的电子的轰击，使原子中的电子受到激发。当它由激发状态回复到正常状态会发光，这一过程称为电致发光过程。 6.从黑体辐射曲线图可以看出，不同温度下的黑体辐射曲线的极大值处的波长m随温度T的升高而减小。试由普朗克热辐射公式导出 。 答：这一关系式称为维恩位移定律，其中常数为10-3m K。 普朗克热辐射公式求一阶导数，令其等于0,即可求的。 7.黑体辐射曲线下的面积等于等于在相应温度下黑体的辐射出射度M试有普朗克的辐射公式导出M与温度T的四次方成正比，即 M 常数T4 这一关系式称斯特藩-波耳兹曼定律，其中常数为i0-8w/mk 解答：教材P9,并参见大学物理相关内容。 9.常用的彩色胶卷一般分为日光型和灯光型。你知道这是按什么区分的吗？ 按色温区分。 10 v dv为频率在v~v dv间黑体辐射能量密度，d为波长在 ~ d间黑体辐射能量密度。已知v BhvFexphvk B T 1 ， 试求。 解答： 由 C ,通过全微分进行计算。 11如果激光器和微波器分别在入=10卩m入=500nn和v =3000MHz 输出一瓦的连续功率，问每秒钟从激光上能级向下能级跃迁的粒子数分别是多少？ 解答: hC P Nhv

模具弹簧规格及参数

模具弹簧规格及参数 Company number：【0089WT-8898YT-W8CCB-BUUT-202108】

模具弹簧规格及参数 一.弹簧功能 弹簧是模具中广泛应用的弹性零件,主要用于卸料、压料、推件和顶出等工作.根据荷重不同,共分五种不同颜色加以区分,易於判别和选用. 二.规格系列 1.弹簧外径系列:Φ6Φ8,Φ10,Φ12,Φ14,Φ16,Φ18,Φ20,Φ22,Φ25,Φ30,Φ35,Φ40,Φ50等. 2.种类 3.弹簧长度：15<=L<=80MM时,每5MM为一个阶; 80==100MM时,每25MM为一个阶. 4.扁线弹簧最小直径6mm

5.弹簧内径等于弹簧外径的二分之一. 6.相同直径颜色的弹簧，不管自由长度是多长，压40％产生的力一样 结论：相同直径颜色的弹簧，自由长度越短，压缩1mm产生的力越大 7.通常使用的最大压缩比是弹簧使用30万次的最大压缩比. 汽车模具使用50万次的最大压缩比.. 8.弹簧能压缩的长度=弹簧的自由长度x弹簧的压缩比 例：Φ20绿色弹簧长度50mm，弹簧要求寿命30万次，弹簧能压缩多长 50x24％=12(mm) 9.弹簧的长度=弹簧要压缩的长度÷弹簧的压缩比 例：弹簧要压缩20mm, 弹簧颜色为红色，弹簧要求寿命50万次要用多长的弹簧 弹簧的长度=20÷％+5MM= 查表选用75MM长弹簧 一般选弹簧长度会加5mm的安全余量 10.弹簧要压缩的长度=活动板行程+3~5mm预压 (常规预压3mm) 11.弹簧模板孔的大小直径<20模板孔=D+1 直径>=20模板孔=D+2 三.选用原则 1.长度选择一般保证:在开模状态弹簧的预压缩量等於3~5(常规预压3mm,预 压缩量随实际情况而定.);闭模状态弹簧压缩量小於或等於最大压缩量(最大压缩量LA=弹簧自由长L*最大压缩比取值%). 2.模板压料，脱料板压料优先选用绿色或棕色（茶色，咖啡色)弹簧;如果向 上成形的下模压料，折弯脱料所需的顶料力不很大时,可选用红色,绿色弹簧，浮料用黄色，圆线弹簧. 3.复合模外脱料板用红色弹簧,内脱料板用绿色或棕色弹簧. 4.活动定位销一般选用Φ6顶料销,配Φ10黄色弹簧和M12止付螺丝.

光电子技术的发展历程和展望.huangsheng

光电子技术的发展历程和展望 摘要 光电子作为信息科学的一个分支，它是将传统光学技术，现在微电子技术，精密机械及计算机有机结合起来，孕育而生的新技术，成为获取光信息或借助光提取其他信息的重要手段。随着社会科学的加速发展，光电子技术的应用越来越深入到社会生活的各个方面。今天，各种电子高科技产品太多源于光电子技术，相信在以后的生活中，光电子技术会得到更普遍的应用，得到更多的人重视。自1960年世界第一台红宝石激光器的诞生起，光电技术的发展步伐明显加速，仪器、技术等更新频繁。激光器作为一种有效的工具，极大地推动了光电子技术的发展！本文讨论了光电子技术的前世今生、发展历程、在各个时期的重要发明,光电子技术今后的发展方向和展望。熟悉光电子技术的发展历史和所研究的方向、领域，为将来打算从事该方面的研究工作打下基础。 关键词：光电子技术；激光器；展望

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