Increasing Sensitivity of CMOS Image Sensor.

You might want to look at what astronomers (including amateur astronomers) do with CCD and other image sensors. I think cooling the sensor is part of it.

Best regards, Spehro Pefhany

"david cowan" wrote in message news: snipped-for-privacy@posting.google.com...

Remember that the 'point' of CMOS sensors, compared to CCD's, is that the complete camera can be built much more cheaply because major parts of the electronics can be included in the CMOS chip. Hence it is rare for them to provide access to the analogue signals. Also the presence of these components increases the thermal noise inside the chip. Realistically, what you want to do, is easier to do with a CCD. The Sony CCD's, are 'favoured', because they have some of the lowest dark current levels for any chip. Refrigerate the chip, and you can integrate the signal for minutes (hours!...). The cheapest 'mass production' camera on the market of this sort, is the Meade DSI. This has a 16bit ADC, instead of the normal webcam 8/10bit unit, and will accept exposure times of several minutes if required. It is limited by the fact that the CCD is not directly coooled, so thermal noise on the chip, builds relatively quickly. However for exposures up to a few minutes, it is the cheapest solution. Going slightly 'up market', Starlight Express in the UK, do a number of astronomical cameras based on the larger versions of this chip, and some industrial cameras based on the same chassis. These use unregulated Peltier cooling to keep the thermal noise better controlled. Some of the mono models o these have quantum efficiencies well over 60%. SBIG, do cameras based on the Kodak CCD's (which at room temperature, exhibit more dark current than the Sony CCD's), with multi-stage Peltier coolers, which allow the chips to be taken to around 45C below the ambient, and temperature regulated. Some models of their cameras, reach QE levels over

Look at the DSI. It may well be useable, if not the CCD is readily available, and sounds as if it might be usable as the basis of such a unit.

Best Wishes