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[DIY] Astro CCD 16-bit Color 6Mpx Camera

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#1076 N_DD

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Posted 03 October 2016 - 11:11 AM

Hi!

thanks to hippieua  :bow:  I have completed a Cam86 board, and I am now working on the cooling of the sensor and the sealing of the enclosure: I have a TEC-12704 and would need some suggestion about which heatsink and fan to use, as well as which UV-IR filter to seal the camera. I have found this and according to the transmission graph should be ok and not so pricey... any ideas?

 

Nico



#1077 archimede

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Posted 03 October 2016 - 02:42 PM

Light emission from the output amplifier??

hello BGRE, thank you for having responded to me, I do not understand your question, in what sense you ask me if the amplifier emits light ?? which component you say ?? these days I made the most detailed evidence, and I found that bias out well only if it does not cool the CCD chip, cool it when you come out, that vertical stripes on the left side, and if you increase the transmission rate also increasing stric, c ' is a way to get off even more data rates, because the minimum is 80, maybe it takes a veocità of even more low transmission, but what I can not understand is why when I cool the CCD deteriorates much more, I tried even with a 'other cam84 equal I spare in case it breaks, but does the same thing also that,, really strange



#1078 archimede

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Posted 03 October 2016 - 04:10 PM

B_2016-10-03_22-27-55.jpg

  

 here is a bias to 10 degrees below zero, with gain and offset at 38 to 4, increasing offsets the lines come across the picture surface,



#1079 BGRE

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Posted 03 October 2016 - 11:51 PM

The on chip output MOSFET in some CCDs actually emits light when biased.
This light is only detected by a small area of pixels close to the on chip amplifier.
There was a NATO conference on CCD image sensors in the 1980's.
I may still have a copy somewhere.
You can get interference fringes with CCDs but its usually only a problem for longer wavelengths and thinned chips.
Variations in chip substrate doping etc can also lead to striations in the image.

#1080 archimede

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Posted 04 October 2016 - 12:42 AM

hello BGRE, thank you for answering, so as to tell me if the MOSFET chip emits light, there soono ways to solve this problem ?, or do I try to make some changes ?? because with this disorder of vertical lines it is impossible to obtain uniform image .. also because when I go to pull the signal processing come out and you see a lot



#1081 archimede

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Posted 04 October 2016 - 01:11 AM

Single__2016-10-04_08-05-42_Bin1x1_0.0001s__na.jpg

 

I enclose a photo of bias made without cooling the CCD sensor to +18 degrees ambient temperature

 

 

 

 

The on chip output MOSFET in some CCDs actually emits light when biased.
This light is only detected by a small area of pixels close to the on chip amplifier.
There was a NATO conference on CCD image sensors in the 1980's.
I may still have a copy somewhere.
You can get interference fringes with CCDs but its usually only a problem for longer wavelengths and thinned chips.
Variations in chip substrate doping etc can also lead to striations in the image.

 



#1082 BGRE

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Posted 04 October 2016 - 03:07 AM

The usual solution to light emission from the output amplifier is to turn it off during exposure and only turn it on during readout.

#1083 archimede

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Posted 04 October 2016 - 11:50 AM

The usual solution to light emission from the output amplifier is to turn it off during exposure and only turn it on during readout.

then turning off the mosfet you should solve this problem ?? how can I turn this off mosfet during the exposure and turn it back on in the reading ??



#1084 vakulenko_sergiy

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Posted 04 October 2016 - 12:04 PM

Cam84 turns off amplifier during exposure if exposure duration more than 1sec.


Edited by vakulenko_sergiy, 04 October 2016 - 12:17 PM.


#1085 archimede

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Posted 04 October 2016 - 12:41 PM

and bias the duration of exposure is 0.001 seconds, but whatever the vertical lines on the left are also in the 300 second exposure photos or even more, I can not understand why the lines are there only when the sensor is cooled , bias in the photos that I posted the first is with cooled ccd and the second is with ccd at room temperature not cooled, and it shows a great difference, the lines in the picture not cooled, there are no



#1086 vakulenko_sergiy

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Posted 04 October 2016 - 12:52 PM

With cooled CCD small defects/emissions stay visible, because cooling significantly decrease thermal noise.
With uncooled CCD these lines just drown in thermal noise.

 

These lines are visible after full calibration?. If you see similar lines on all frames - simple dark-bias calibration should help to significantly reduce it.


Edited by vakulenko_sergiy, 04 October 2016 - 12:54 PM.


#1087 archimede

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Posted 04 October 2016 - 02:11 PM

With cooled CCD small defects/emissions stay visible, because cooling significantly decrease thermal noise.
With uncooled CCD these lines just drown in thermal noise.

 

These lines are visible after full calibration?. If you see similar lines on all frames - simple dark-bias calibration should help to significantly reduce it.

It is unfortunately the vertical lines are still much more visible after calibration, especially if you check out a little signal to highlight the weak parts, and the problem is also the same on another ccd cam84 equal parts I like, both have the same problem



#1088 archimede

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Posted 05 October 2016 - 05:06 PM

Hello to all !! are able to improve a little the problem of the vertical lines on the left, I shortened the more that I could connect the CCD chip to the printed circuit, its distance before was 6mm, while now the distance between circuit and CCD is 1 mm, it seems that the result is better, obviously the high-frequency signals between electronic and ccd want very close links, these days reassemble everything and try on the telescope as it goes



#1089 archimede

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Posted 05 October 2016 - 05:19 PM

GAIN A 0 Single__2016-10-05_19-33-09_Bin1x1_0.0001s__na.jpg



#1090 BGRE

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Posted 06 October 2016 - 03:42 AM

If its an amplifier turn on transient settling issue MOSFETS get faster as they are cooled.

#1091 archimede

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Posted 06 October 2016 - 02:26 PM

so how do you say, the mosfet when it is cooled should be faster ?? Now with ccd sensor close to the circuit with the ccd it will also cooled the circuit, thus the mosfet transistors will be cooled too, I hope that it works well !!



#1092 BGRE

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Posted 06 October 2016 - 05:57 PM

The output amplifier on the CCD chip uses MOSFET transistors. As the chip temperature decreases MOSFET transconductance increases whist the associated capacitances change very little consequently the MOSFET gain bandwidth increases.
The resistance of on chip diffused resistors also decreases. CCD electrode parasitic interconnection resistances also decrease potentially reducing damping and increasing settling time when driven by fast edges.

#1093 archimede

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Posted 07 October 2016 - 02:48 AM

then I was right to also cool the PCB ??



#1094 BGRE

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Posted 07 October 2016 - 03:00 AM

Cooling the PCB is helpful in that it reduces thermal conduction via the leads which is usually mitigated by using constantan wires to connect the CCD to the PCB.

#1095 archimede

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Posted 07 October 2016 - 05:09 AM

ok, thank you for answering, these days we will see the result as soon as the sky will be clear



#1096 gregj888

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Posted 07 October 2016 - 12:08 PM

Manganin wire is another option.  I have a couple of spools of ~ #30 and some really thin stuff ~#48 if I remember right.  It only makes sense if cooling to a really low temp and these sensors aren't rates for that (i.e. -70c absolute, Dry Ice or below), IMHO.  You need a little bit of length as well, 1-3cm maybe. 

 

I got the Manganin to wire a NIR sensor in a photometer on a 4 stack Peltier.  At about -70c I would drop a degree or two for every copper wire I replace with Manganin (#30, wire-wrap wire).  Way below it's operating temp too, but a very small sensor, so hoping it will be OK.  Next time I'm in the detector I plan to change to the thinner wire and hope to drop another 5c or so...  BTW, this is in a Cryostat and under vacuum... >50mTorr

 

You don't need to play this game with the Cam84 at -10c to -20c, just use a little bigger Peltier if you need to go colder.

 

Those wanting to get crazy, might start here:

http://articles.adsa...000158.000.html



#1097 Juja

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Posted 18 October 2016 - 10:14 AM

Hey guys,

 

I'm pretty new and I found this interesting project! :)

 

Could someone please tell me again, where to donwload the design files (schematics etc.). The link in the first post is not active anymore :/

 

Thanks so far!

Juja



#1098 Toups

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Posted 18 October 2016 - 06:06 PM

Actually the link on the front page should work, http://hippie.com.ua/cloudy/cloudy.zip but it didn't quite go to the right location.  Try this one.


Edited by Toups, 18 October 2016 - 06:06 PM.


#1099 Juja

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Posted 19 October 2016 - 01:59 AM

Thanks Explorer!

 

The DL-link is working fine...

 

Btw: The link on the first page just missed the ":" after http ;)


Edited by Juja, 19 October 2016 - 02:05 AM.


#1100 Juja

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Posted 20 October 2016 - 02:53 AM

Hi again,

 

I hope it is okay when I ask a technical question relating to the electronics design of the camera!

 

I'm actually working on a CCD-Camera with the KAF1001 from OnSemi and I'm also using the AD9826 for sampling the video data (CDS-Mode). My schematics for the AD-conversion are pretty much the same then for the ICX453AQ-chip.

 

I'm having issues with the AD9826: When I connect the ADC to the output buffer circuit (after the KAF1001 output stage) the pixels in the beginning of every line have a higher intensity. This is shown in the camera picture and on the scope.

But when I disconnect the AD9826 from the output buffer the effect is totally gone - the KAF1001 outputs normal pixel values.

 

=> see attachments.

 

My questions:

 

- How do you clock the AD9826? Continuously or triggered? Do you clock the ADC only when you want to have an image (snapshot, triggered) or do you have CDSCLK1, CDSCLK2, ADCCLK running all the time?

- Did you ever had something similar when connecting your CCD with the AD9826 and if yes - how do you solve it?

 

Would be very great to have a response :)

 

Thanks so far!

Juja

Attached Thumbnails

  • higher Pixel output voltage at beginning of every line.png



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