Ripples in 488nm channel
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Dear List
Whenever i am imaging any channel through 488nm laser i am getting circular ripples in the background (of green colour, concentric green and black rings) which are very prominent. I do not see any background when i check my sample in epifluorescence illumination. These ripples are coming whenever i am imaging through 488nm laser at all objectives (10x, 20x, 40x and 60x oil).The ripples also get magnified with higher mag lens and zoomed up when we do optical zooming so appear less prominent when using high mag lens. Ours is a central facility and our system gets started from 10.00AM till the evening.It is very strange to write that these ripples start coming in the afternoon and become more and more prominent when we continue (even start appearing in the DIC image with concentric black and white rings). When we shut down the system and restart it (this is advised from the company people) after a while say 1hour or something we still get the same ripples but somehow when we shut down the system till the next morning, we do not see such problem the very next day. Company rep says that this is a problem they have not encountered with before with any customer. They are suspecting if the laser is dying (which i think is not the case, however i may be wrong). This has been experienced with different samples (not a problem with one particular kind of sample). Any kind of possible explanations are welcome which will enable us to understand at least the cause of this. Thanks in advance Charu Charu Tanwar Imaging Specialist Advanced Instrumentation Research Facility Jawaharlal Nehru University New Delhi India |
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Dear Charu,
I agree, this is weird. Sometimes it happens that one sees circular ripples in the background when some of the excitation laser light manages to pass through dichroics and fluorescence light filters to the photo detectors. Or, in case of, e.g., the Leica when the selected detection band is too close to the excitation wavelength. But these ripples, at least in the systems I know, are un-altered when changing the objective. However, as you write, the ripples you observe get magnified with the objective. Might it be that you see a reflection / interference from any condenser optics? Question: Do you see theses ripples even in an image detected by means of a transmitted light detector? Best wishes, Johannes > Dear List > > Whenever i am imaging any channel through 488nm laser i am getting > circular > ripples in the background (of green colour, concentric green and black > rings) which are very prominent. I do not see any background when i check > my > sample in epifluorescence illumination. These ripples are coming whenever > i > am imaging through 488nm laser at all objectives (10x, 20x, 40x and 60x > oil).The ripples also get magnified with higher mag lens and zoomed up > when > we do optical zooming so appear less prominent when using high mag lens. > > Ours is a central facility and our system gets started from 10.00AM till > the > evening.It is very strange to write that these ripples start coming in the > afternoon and become more and more prominent when we continue (even start > appearing in the DIC image with concentric black and white rings). When we > shut down the system and restart it (this is advised from the company > people) after a while say 1hour or something we still get the same ripples > but somehow when we shut down the system till the next morning, we do not > see such problem the very next day. > Company rep says that this is a problem they have not encountered with > before with any customer. They are suspecting if the laser is dying (which > i > think is not the case, however i may be wrong). > > This has been experienced with different samples (not a problem with one > particular kind of sample). > Any kind of possible explanations are welcome which will enable us to > understand at least the cause of this. > > Thanks in advance > Charu > > > Charu Tanwar > Imaging Specialist > Advanced Instrumentation Research Facility > Jawaharlal Nehru University > New Delhi > India > -- P. Johannes Helm Voice: (+47) 228 51159 (office) Fax: (+47) 228 51499 (office) |
 
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Peter Gabriel Pitrone |
Re: Ripples in 488nm channel
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In reply to this post by Charu Tanwar
Hello Charu,
Could it be a old optical filter that has seen it's better days? If the scope is older than 5-10 years, it could be that the soft coated filters that were used have been burned through. Which would reek havoc on your PMT's... Pete On May 14, 2010, at 10:16 AM, Charu Tanwar wrote: > Dear List > > Whenever i am imaging any channel through 488nm laser i am getting circular > ripples in the background (of green colour, concentric green and black > rings) which are very prominent. I do not see any background when i check my > sample in epifluorescence illumination. These ripples are coming whenever i > am imaging through 488nm laser at all objectives (10x, 20x, 40x and 60x > oil).The ripples also get magnified with higher mag lens and zoomed up when > we do optical zooming so appear less prominent when using high mag lens. > > Ours is a central facility and our system gets started from 10.00AM till the > evening.It is very strange to write that these ripples start coming in the > afternoon and become more and more prominent when we continue (even start > appearing in the DIC image with concentric black and white rings). When we > shut down the system and restart it (this is advised from the company > people) after a while say 1hour or something we still get the same ripples > but somehow when we shut down the system till the next morning, we do not > see such problem the very next day. > Company rep says that this is a problem they have not encountered with > before with any customer. They are suspecting if the laser is dying (which i > think is not the case, however i may be wrong). > > This has been experienced with different samples (not a problem with one > particular kind of sample). > Any kind of possible explanations are welcome which will enable us to > understand at least the cause of this. > > Thanks in advance > Charu > > > Charu Tanwar > Imaging Specialist > Advanced Instrumentation Research Facility > Jawaharlal Nehru University > New Delhi > India |
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In reply to this post by Charu Tanwar
Dear Johannes
I chose dichroic such that no laser reflection should come and selected detection band was not close to that of excitation wavelength. When i continue scanning with this problem for long period (30min or long) then these appear in DIC image also with concentric black and white rings but not so prominent. Thanks Charu CHARU TANWAR Imaging Specialist Advanced Instrumentation Research Facility Jawaharlal Nehru University New Delhi 110067 India. |
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I had this very same problem years ago with a Leica TCS 4D confocal. Had to send images of the problem to Leica home office in Germany. If I remember correctly it was the PMT that needed to be worked on ( It was Dr. Charles Hemphill from Leica who fixed the problem for me). If you have a Leica you should contact your service rep because it is a hardware issue.
Chere Petty M.S. Manager of UMBC Keith R. Porter Core Imaging Facility Department of Biological Sciences University of Maryland Baltimore County (UMBC) 1000 Hilltop Circle Baltimore Maryland 21250 301-367-8408 [hidden email] emumbc.com On May 14, 2010, at 6:04 AM, Charu Tanwar wrote: > Dear Johannes > I chose dichroic such that no laser reflection should come and selected > detection band was not close to that of excitation wavelength. > When i continue scanning with this problem for long period (30min or long) > then these appear in DIC image also with concentric black and white rings > but not so prominent. > Thanks > Charu > > CHARU TANWAR > Imaging Specialist > Advanced Instrumentation Research Facility > Jawaharlal Nehru University > New Delhi 110067 > India. > |
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Evangelos Gatzogiannis |
Re: Ripples in 488nm channel
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Dear Charu, I see ripples (like a stone falling into a mill pond) in images from time to time, but from a different source - hopefully this may be a little illuminating. I send in two external laser beams, overlap them, and then do CARS microscopy - a unique feature of our facility. If the two beams aren't well overlapped and are clipping an internal dichroic, or there is an inappropriate dichroic in place you will get these interference-like fringes. The answer for me is usually better alignment, but since you have an FV1000 I don't know what you can do with alignment. My gut instinct with your fringes is 1) some kind of misalignment of 488 laser 2) inappropriate dichroic. Hope this was of any help. Best, Evangelos Gatzogiannis Advanced Biological Imaging Scientist Harvard University Center for Nanoscale Systems Cambridge, MA 02138 On May 14, 2010, at 7:47 AM, charu tanwar wrote:
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In reply to this post by Charu Tanwar
Charu, one further question:
Is there possibly anywhere an aperture in your raypath before the beam scanner which would be slightly smaller than the beam diameter? This would, of course, induce interferences. Best, Johannes > We have Olympus FV1000 system and i have sent images to the > representatives.Thank you for the help. > > CHARU TANWAR > Imaging Specialist > Advanced Instrumentation Research Facility > Jawaharlal Nehru University > New Delhi 110067 > India. > > --- On Fri, 14/5/10, Chere Petty <[hidden email]> wrote: > > > From: Chere Petty <[hidden email]> > Subject: Re: Ripples in 488nm channel > To: [hidden email] > Date: Friday, 14 May, 2010, 4:14 PM > > > I had this very same problem years ago with a Leica TCS 4D confocal. Had > to send images of the problem to Leica home office in Germany. If I > remember correctly it was the PMT that needed to be worked on ( It was Dr. > Charles Hemphill from Leica who fixed the problem for me). If you have a > Leica you should contact your service rep because it is a hardware issue. > Chere Petty M.S. > Manager of UMBC Keith R. Porter Core Imaging Facility > Department of Biological Sciences > University of Maryland Baltimore County > (UMBC) > 1000 Hilltop Circle > Baltimore Maryland 21250 > 301-367-8408 > [hidden email] > emumbc.com > > > > On May 14, 2010, at 6:04 AM, Charu Tanwar wrote: > >> Dear Johannes >> I chose dichroic such that no laser reflection should come and selected >> detection band was not close to that of excitation wavelength. >> When i continue scanning with this problem for long period (30min or >> long) >> then these appear in DIC image also with concentric black and white >> rings >> but not so prominent. >> Thanks >> Charu >> >> CHARU TANWAR >> Imaging Specialist >> Advanced Instrumentation Research Facility >> Jawaharlal Nehru University >> New Delhi 110067 >> India. >> > > > -- P. Johannes Helm Voice: (+47) 228 51159 (office) Fax: (+47) 228 51499 (office) |
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Evangelos Gatzogiannis |
Re: Ripples in 488nm channel
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In reply to this post by Charu Tanwar
I agree, aperatures and Irises also induce these "ripples" in the beam. On May 14, 2010, at 7:47 AM, charu tanwar wrote:
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In reply to this post by Charu Tanwar
It's been my experience, believe it or not, that this pattern has been the result of dirty coverslips. If buffer salts dry on the top surface of the coverslip and you try to image through the salts, they can cause this phenomenon. We have a Leica system here and have seen this problem. With clean coverslips we have not seen the problem. Check the top side of the coverslip and see if it is clean and dry. If it has dirt on it (dried culture medium or salts from your immuno labeling run), it could be the source of the rings.
Edward Haller, Lab Manager University of South Florida Integrative Biology Department Electron Microscopy Core SCA 110 4202 East Fowler Avenue Tampa, FL 33620 813-974-2676 [hidden email] ________________________________________ From: Confocal Microscopy List [[hidden email]] On Behalf Of Charu Tanwar [[hidden email]] Sent: Friday, May 14, 2010 4:16 AM To: [hidden email] Subject: Ripples in 488nm channel Dear List Whenever i am imaging any channel through 488nm laser i am getting circular ripples in the background (of green colour, concentric green and black rings) which are very prominent. I do not see any background when i check my sample in epifluorescence illumination. These ripples are coming whenever i am imaging through 488nm laser at all objectives (10x, 20x, 40x and 60x oil).The ripples also get magnified with higher mag lens and zoomed up when we do optical zooming so appear less prominent when using high mag lens. Ours is a central facility and our system gets started from 10.00AM till the evening.It is very strange to write that these ripples start coming in the afternoon and become more and more prominent when we continue (even start appearing in the DIC image with concentric black and white rings). When we shut down the system and restart it (this is advised from the company people) after a while say 1hour or something we still get the same ripples but somehow when we shut down the system till the next morning, we do not see such problem the very next day. Company rep says that this is a problem they have not encountered with before with any customer. They are suspecting if the laser is dying (which i think is not the case, however i may be wrong). This has been experienced with different samples (not a problem with one particular kind of sample). Any kind of possible explanations are welcome which will enable us to understand at least the cause of this. Thanks in advance Charu Charu Tanwar Imaging Specialist Advanced Instrumentation Research Facility Jawaharlal Nehru University New Delhi India |
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Oshel, Philip Eugene |
Re: Ripples in 488nm channel
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In reply to this post by Charu Tanwar
I have seen ripples like these in our FV300. It usually is from one
of 2 sources: the image is being taken too close to either the coverslip or the slide (too shallow or too deep into the sample [a thin one if too deep]) and we're getting reflected light from the glass, or we have on both the 488 Ar laser and the 543 HeNe laser. In this latter case, light from the HeNe is bouncing around inside the scan head and getting into the Channel 1 (=488) PMT, because the barrier filter for Channel 1 is a long-pass filter that passes the light from the HeNe. This happens even when imaging only Channel 1. The solution is to either "turn off" the HeNe (set the ND filter at the source to 0% trans) or to put in the 2nd Channel 1 barrier filter to create a band-pass filter that blocks the reflected HeNe light. Phil We have Olympus FV1000 system and i have sent images to the representatives.Thank you for the help. CHARU TANWAR Imaging Specialist Advanced Instrumentation Research Facility Jawaharlal Nehru University New Delhi 110067 India. --- On Fri, 14/5/10, Chere Petty <[hidden email]> wrote: From: Chere Petty <[hidden email]> Subject: Re: Ripples in 488nm channel To: [hidden email] Date: Friday, 14 May, 2010, 4:14 PM I had this very same problem years ago with a Leica TCS 4D confocal. Had to send images of the problem to Leica home office in Germany. If I remember correctly it was the PMT that needed to be worked on ( It was Dr. Charles Hemphill from Leica who fixed the problem for me). If you have a Leica you should contact your service rep because it is a hardware issue. Chere Petty M.S. Manager of UMBC Keith R. Porter Core Imaging Facility Department of Biological Sciences University of Maryland Baltimore County (UMBC) 1000 Hilltop Circle Baltimore Maryland 21250 301-367-8408 <http://in.mc83.mail.yahoo.com/mc/compose?to=cpetty1@...>[hidden email] emumbc.com On May 14, 2010, at 6:04 AM, Charu Tanwar wrote: > Dear Johannes > I chose dichroic such that no laser reflection should come and selected > detection band was not close to that of excitation wavelength. > When i continue scanning with this problem for long period (30min or long) > then these appear in DIC image also with concentric black and white rings > but not so prominent. > Thanks > Charu > > CHARU TANWAR > Imaging Specialist > Advanced Instrumentation Research Facility > Jawaharlal Nehru University > New Delhi 110067 > India. > -- Philip Oshel Microscopy Facility Supervisor Biology Department 024C Brooks Hall Central Michigan University Mt. Pleasant, MI 48859 (989) 774-3576 |
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Martin Wessendorf-2 |
Re: Ripples in 488nm channel
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In reply to this post by Charu Tanwar
Dear Charu--
Try decreasing the laser power and correspondingly increasing the PMT voltage. Then try the reverse: increase the laser and decrease the PMT voltage. Do the ripples become more prominent with increased PMT voltage? --Given that they get worse later in the day, when the system would've warmed up and the PMTs would be running hot, I wonder if it has something to do with the PMTs. Another thing to test would be to see if there is a way to increase the ventilation to the PMTs. Good luck-- Martin Wessendorf Charu Tanwar wrote: > Dear List > > Whenever i am imaging any channel through 488nm laser i am getting circular > ripples in the background (of green colour, concentric green and black > rings) which are very prominent. I do not see any background when i check my > sample in epifluorescence illumination. These ripples are coming whenever i > am imaging through 488nm laser at all objectives (10x, 20x, 40x and 60x > oil).The ripples also get magnified with higher mag lens and zoomed up when > we do optical zooming so appear less prominent when using high mag lens. > > Ours is a central facility and our system gets started from 10.00AM till the > evening.It is very strange to write that these ripples start coming in the > afternoon and become more and more prominent when we continue (even start > appearing in the DIC image with concentric black and white rings). When we > shut down the system and restart it (this is advised from the company > people) after a while say 1hour or something we still get the same ripples > but somehow when we shut down the system till the next morning, we do not > see such problem the very next day. > Company rep says that this is a problem they have not encountered with > before with any customer. They are suspecting if the laser is dying (which i > think is not the case, however i may be wrong). > > This has been experienced with different samples (not a problem with one > particular kind of sample). > Any kind of possible explanations are welcome which will enable us to > understand at least the cause of this. > > Thanks in advance > Charu > > > Charu Tanwar > Imaging Specialist > Advanced Instrumentation Research Facility > Jawaharlal Nehru University > New Delhi > India -- Martin Wessendorf, Ph.D. office: (612) 626-0145 Assoc Prof, Dept Neuroscience lab: (612) 624-2991 University of Minnesota Preferred FAX: (612) 624-8118 6-145 Jackson Hall, 321 Church St. SE Dept Fax: (612) 626-5009 Minneapolis, MN 55455 e-mail: [hidden email] |
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In reply to this post by Oshel, Philip Eugene
Charu,
Just to add to the many good suggestions so far... my first guess would have been that you have either the wrong dichroic or emission filter in place, or maybe the emission filter is not there at all. Are you absolutely sure that the correct filters are in place? And are you sure these filters have the transmission/reflection characteristics you think they have? Maybe as some have suggested some of your excitation light is getting through to the detector with the dichroic or the emission filter. I stress that point because I've run into this problem before on our confocal system, inadvertently creating a "backscatter" image of the sample when forgetting to insert the emission filter (it's a Olympus FV300 as well, which requires inserting filters by hand so this is a common mistake). Backscatter images will often have these concentric rings or interference fringes. Next, I would check to see if you have any bubbles in your immersion fluid, but you mentioned that you use this microscope with low magnification objectives which probably don't need water or oil, so that is likely not the problem. Make sure the substrates you're using are clean (various glass cleaning procedures are available on the web; try wiping the the outer sides of your glass with ethanol and a kimwipe before putting it down on the microscope. Do you see the same effect when you change the pinhole size? Do the rings change shape or size when you do that? This could be an indication that the pinhole has gone out of alignment, and that can be fixed. It occurs to me that you need some kind of "negative control" for this effect. Do other users see the same effect with different filter settings / fluorophores / samples? If so, then it's definitely an instrument related issue. Do you see the same problem in other PMT channels? Since it's an FV300, you could physically swap the emission filters to the opposite channel and see if the same effect occurs in that channel. If you end up producing rings in the other channel and the problem goes away in the first channel, then it's a filter related problem. If you find out what the source of the error was, please do share with all of us so we can avoid it as well! John Oreopoulos On 2010-05-14, at 8:41 AM, Philip Oshel wrote: > I have seen ripples like these in our FV300. It usually is from one of 2 sources: the image is being taken too close to either the coverslip or the slide (too shallow or too deep into the sample [a thin one if too deep]) and we're getting reflected light from the glass, or we have on both the 488 Ar laser and the 543 HeNe laser. In this latter case, light from the HeNe is bouncing around inside the scan head and getting into the Channel 1 (=488) PMT, because the barrier filter for Channel 1 is a long-pass filter that passes the light from the HeNe. This happens even when imaging only Channel 1. The solution is to either "turn off" the HeNe (set the ND filter at the source to 0% trans) or to put in the 2nd Channel 1 barrier filter to create a band-pass filter that blocks the reflected HeNe light. > > Phil > > We have Olympus FV1000 system and i have sent images to the representatives.Thank you for the help. > > CHARU TANWAR > Imaging Specialist > Advanced Instrumentation Research Facility > Jawaharlal Nehru University > New Delhi 110067 > India. > > --- On Fri, 14/5/10, Chere Petty <[hidden email]> wrote: > > > From: Chere Petty <[hidden email]> > Subject: Re: Ripples in 488nm channel > To: [hidden email] > Date: Friday, 14 May, 2010, 4:14 PM > > I had this very same problem years ago with a Leica TCS 4D confocal. Had to send images of the problem to Leica home office in Germany. If I remember correctly it was the PMT that needed to be worked on ( It was Dr. Charles Hemphill from Leica who fixed the problem for me). If you have a Leica you should contact your service rep because it is a hardware issue. > Chere Petty M.S. > Manager of UMBC Keith R. Porter Core Imaging Facility > Department of Biological Sciences > University of Maryland Baltimore County > (UMBC) > 1000 Hilltop Circle > Baltimore Maryland 21250 > 301-367-8408 > <http://in.mc83.mail.yahoo.com/mc/compose?to=cpetty1@...>[hidden email] > emumbc.com > > > > On May 14, 2010, at 6:04 AM, Charu Tanwar wrote: > >> Dear Johannes >> I chose dichroic such that no laser reflection should come and selected >> detection band was not close to that of excitation wavelength. >> When i continue scanning with this problem for long period (30min or long) >> then these appear in DIC image also with concentric black and white rings >> but not so prominent. >> Thanks >> Charu >> >> CHARU TANWAR >> Imaging Specialist >> Advanced Instrumentation Research Facility >> Jawaharlal Nehru University >> New Delhi 110067 >> India. >> > > > -- > Philip Oshel > Microscopy Facility Supervisor > Biology Department > 024C Brooks Hall > Central Michigan University > Mt. Pleasant, MI 48859 > (989) 774-3576 |
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Larson Jeffrey M. |
Re: Ripples in 488nm channel
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In reply to this post by Charu Tanwar
Charu,
You do not identify the microscope you are using so my comments will be generalized and broadly applicable. Concentric rings that may even be off center in the field and not associated with structure in the specimen are likely to be interference fringes. Such fringes respond exactly as you describe to changes in objective lens and scan zoom settings. You can identify interference fringes by their sinusoidal brightening and darkening between fringes. You will be able to see the fringes clearly if you image a uniform fluorescence slide like the Chroma slides or a slide made from a dilute FITC or TRITC solution. The source of the fringes can be almost anywhere that there are plane parallel glass surfaced in the illumination path. The ring pattern you see most likely comes from the interference of backscattered photons from two plane parallel surfaces. You can check to see if the fringes are associated with a particular dichroic mirror. Emission filters and second dichroic mirrors are unlikely to be the source of the problem because light reaching them is no longer coherent. If you have an inverted microscope, it is likely to have a thin glass protective plate somewhere beneath the nosepiece intended to prevent media and other liquids from dripping inside the microscope. Removing that plate will solve your problem if the plate is the offending component but be sure to replace it with a new one as soon as possible to prevent damage to your microscope. You might think that the confocal pinhole would remove the fringes, but in my experience, where the source is located in the infinity space of the microscope, it does not. Depending upon the microscope, you may need a service technician to help you with this. Good luck. Jeff Larson Jeffrey M Larson Confocal Systems Product Manager Nikon Instruments Inc. 1300 Walt Whitman Road Melville NY 11747-3064 Office: 631-547-8540 Fax: 631-547-4033 Mobile: 516-617-2228 [hidden email] www.nikoninstruments.com -----Original Message----- From: Confocal Microscopy List [mailto:[hidden email]] On Behalf Of Charu Tanwar Sent: Friday, May 14, 2010 4:17 AM To: [hidden email] Subject: Ripples in 488nm channel Dear List Whenever i am imaging any channel through 488nm laser i am getting circular ripples in the background (of green colour, concentric green and black rings) which are very prominent. I do not see any background when i check my sample in epifluorescence illumination. These ripples are coming whenever i am imaging through 488nm laser at all objectives (10x, 20x, 40x and 60x oil).The ripples also get magnified with higher mag lens and zoomed up when we do optical zooming so appear less prominent when using high mag lens. Ours is a central facility and our system gets started from 10.00AM till the evening.It is very strange to write that these ripples start coming in the afternoon and become more and more prominent when we continue (even start appearing in the DIC image with concentric black and white rings). When we shut down the system and restart it (this is advised from the company people) after a while say 1hour or something we still get the same ripples but somehow when we shut down the system till the next morning, we do not see such problem the very next day. Company rep says that this is a problem they have not encountered with before with any customer. They are suspecting if the laser is dying (which i think is not the case, however i may be wrong). This has been experienced with different samples (not a problem with one particular kind of sample). Any kind of possible explanations are welcome which will enable us to understand at least the cause of this. Thanks in advance Charu Charu Tanwar Imaging Specialist Advanced Instrumentation Research Facility Jawaharlal Nehru University New Delhi India CONFIDENTIAL: This e-mail including any attachments is intended only for the party or parties to whom it is addressed and may contain information which is privileged and/or confidential. If you are not the intended recipient, you are hereby notified that any use, disclosure, dissemination, distribution, copying, or printing of any information contained in or attached to this e-mail is STRICTLY PROHIBITED and may constitute a breach of confidentiality and/or privilege. If you have received this e-mail in error, please notify immediately the sender by reply e-mail and then delete this e-mail and any attachments in their entirety from your system. Thank you. This e-mail message including any attachments is believed to be free of any viruses; however, it is the sole responsibility of the recipient to ensure that it is virus free, and Nikon does not accept any responsibility for any loss, disruption or damage to your data or computer system which may occur in connection with this e-mail including any attachments. |
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In reply to this post by Haller, Edward
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In reply to this post by John Oreopoulos
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Hi Charu, It’s very puzzling that you are able to image in the
morning without the “ripples” but then later on experience this
problem again. We had a faulty beam splitter on our Leica system that caused
reflection artefacts a while ago. It was our DD488/568, which we used a lot. I’m
not sure why it had degraded but we had it replaced and everything was fine
again. Do you have a range of different beam splitters that you can
compare? My apologies if someone has already suggested this. There have
been a lot of emails on this subject but I thought it might be worth suggesting
having the condition of your beam splitter checked. Kind regards, Jacqui Jacqueline
Ross Biomedical Imaging Microscopist From: Confocal Microscopy List
[mailto:[hidden email]] On Behalf Of charu tanwar
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In reply to this post by Charu Tanwar
Hi, again, Charu,
the weird thing is that you don't have the ripples in the morning, when starting, but get them later on. In order to make the haystack with the hidden needle a little bit smaller, is it possible that you do the following things (unless you've already done them): a) Switch off the laser for quite some time so that it can coold down but keep the rest of the setup switched on. Then scan. Are the ripples there at once or not? b) If the ripples are there straight away in a), keep the laser on and switch off the rest and keep the rest switched off for quite some time to cool down. Switch on again and scan. Ripples there at once? c) Possibly the ripples aren't there straight away in neither a) nor b). Then, keep everything on for quite some time but do not scan. Like that, any fibers, fibercouplings, apertures a.s.o. in the ray path of the laser beam could cool down. Then scan again. Are the ripples there at once? This might help to nail down the culprit. Good success and best wishes, Johannes -- P. Johannes Helm Voice: (+47) 228 51159 (office) Fax: (+47) 228 51499 (office) |
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Hi,
here's another hint: Check activity in other labs next to you. I once had an issue with laser fluctuations that were caused by a machine next door. Okay, no definite proof for this, but plugging the laser to a different power circuit solved the issue. Sorry for the double post if this has been suggested already... -Martin -- Dr.rer.nat. Martin Vogel Max-Planck-Institute of Biophysics Frankfurt, Germany Johannes Helm <[hidden email]> hat am 17. Mai 2010 um 12:22 geschrieben: > Hi, again, Charu, > > > the weird thing is that you don't have the ripples in the morning, when > starting, but get them later on. > > In order to make the haystack with the hidden needle a little bit smaller, > is it possible that you do the following things (unless you've already > done them): > > a) > Switch off the laser for quite some time so that it can coold down but > keep the rest of the setup switched on. Then scan. Are the ripples there > at once or not? > > b) > If the ripples are there straight away in a), keep the laser on and switch > off the rest and keep the rest switched off for quite some time to cool > down. Switch on again and scan. Ripples there at once? > > c) > Possibly the ripples aren't there straight away in neither a) nor b). > Then, keep everything on for quite some time but do not scan. Like that, > any fibers, fibercouplings, apertures a.s.o. in the ray path of the laser > beam could cool down. Then scan again. Are the ripples there at once? > > This might help to nail down the culprit. > > Good success and best wishes, > > Johannes > > > -- > P. Johannes Helm > > Voice: (+47) 228 51159 (office) > Fax: (+47) 228 51499 (office) |
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