Cooled cameras for scientific applications and astronomy Ian Alderton Alrad Imaging division of Alrad Instruments Ltd www.alrad.co.uk
History 1970 - started as Wenzel Elektronic UK in NIM modules and radiation measurement, based in Egham Surrey 1976 - became Alrad Instruments ltd 1980 - purchased factory unit, moved to Newbury, started producing night vision systems 1985 - purchased second unit in Newbury 1992 - set up marketing division Alrad Imaging 1995 - second marketing division Alrad electronics for electro optics and HV 2012 - Alrad Photonics new marketing division
Alrad Instruments Ltd Consists of 3 marketing Divisions Alrad Imaging Alrad Photonics Alrad Electronics
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CCD sensors Due to the high quantum efficiencies of CCDs, linearity of their outputs (one count for one photon of light), ease of use compared to photographic plates, and a variety of other reasons, CCDs were very rapidly adopted by astronomers for nearly all UV-to-infrared applications. Thermal noise and cosmic rays may alter the pixels in the CCD array. To counter such effects, astronomers take several exposures with the CCD shutter closed and opened. The average of images taken with the shutter closed is necessary to lower the random noise. Once developed, the dark frame average image is subtracted from the openshutter image to remove the dark current and other systematic defects (dead pixels, hot pixels, etc.) in the CCD. 5
Why Cool? Cooling reduces the array's dark current, improving the sensitivity of the CCD to low light intensities, even for ultraviolet and visible wavelengths. Professional observatories often use liquid cooling with liquid nitrogen to reduce the dark current, and therefore the thermal noise, to negligible levels. Thermoelectric coolers operate by the Peltier effect. The device has two sides, and when DC current flows through the device, it brings heat from one side to the other, so that one side gets cooler while the other gets hotter. The "hot" side is attached to a heat sink so that it remains at ambient temperature, while the cool side goes below room temperature. 6
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Dark Count Dark count refers to that property of all CCD sensors to generate charge in each pixel on its own with Time. The lower the temperature of the sensor, the lower the dark count. Dark count is usually expressed in electrons per unit of time at a given temperature. The sole reason that CCDs are cooled is to reduce the dark count effect. For example, a Kodak KAF-0402e and KAF- 1602e sensor is specified to have a dark count of 50 electrons per second at 25 C. Taking a one-minute exposure at this temperature would generate 3000 electrons of thermally induced charge! 27/10/2014
November 25, 2008
Although the dark count can be subtracted, the dark noise cannot. The dark noise is approximately the square root of the dark count. In this example, the dark noise is about 55 electrons. This could easily degrade any low-light image you attempted to capture over this period of time. These sensors specify a "doubling temperature" of 5-6 C. Cooling the CCD to +10 C would reduce the dark count in a one-minute exposure from 3000 to about 530 electrons. At -5 C this number reduces to about 97. At -20 C it lowers to 17 electrons. These calculations assume a 6 doubling temperature. Not all CCDs exhibit the same dark count characteristics. For example, the Kodak KAF-1301e and KAF-1001e can exhibit 10 to 20 times higher dark count than those cited in the above example. Some back-illuminated sensors generate over 1 electron/sec. dark count at -40 C. November 25, 2008
Apogee Products Alta Delta -55 0 C Full Frame & Interline 31 sensor options USB Aspen New Platform high end Delta -60 0 C Full Frame & Interline 36 sensor options USB & Ethernet 11
Alta vs Aspen 60
Alta - Aspen Full frame - imaging Model CCD Array Size Megapixels Pixel size (um) Array Size (mm) Imaging Area (mm2) Diagonal (mm) X Y X Y CG1 KAF-0402ME 768 512 0.4 9 6.9 4.6 31.9 8.3 M CG2 KAF-1603ME 1536 1024 1.6 9 13.8 9.2 127.4 16.6 M CG6 KAF-1001E 1024 1024 1.0 24 24.6 24.6 604 34.8 M CG9 KAF-6303E 3072 2048 6.3 9 27.6 18.4 509.6 33.2 M CG32 KAF-3200 2184 1472 3.2 6.8 14.9 10 148.7 17.9 M CG47 E2V CCD47-10 1024 1024 1.0 13 13.3 13.3 177 18.8 M CG77 E2V CCD77-00 512 512 0.3 24 12.3 12.3 151 17.4 M CG260 KAF-261E 512 512 0.3 20 10.2 10.2 104.9 14.5 M CG8300 KAF-8300CE 3326 2504 8.3 5.4 18.6 13.9 259 23.2 M,C CG3041 Fairchild 3041 2048 2048 4.2 15 30.7 30.7 944 43.4 M CG42 E2V CCD42-40 2048 2048 4.2 13.5 27.6 27.6 764 39.1 M CG230 E2VCCD230-42 2048 2048 4.2 15 30.7 30.7 944 43.4 M CG9000 KAF-9000 3056 3056 9.3 12 36.7 36.7 1346.6 51.9 M CG16 KAF-16801E 4096 4096 16.8 9 36.9 36.9 1359 52.1 M CG16M KAF-16803 4096 4096 16.8 9 36.9 36.9 1359 52.1 M Price Mono/ (Grade 1 e2v; Color Grade 2 TS)
Alta - Aspen Interline - imaging Model Array CCD Size Megapixels Pixel size (um) Array Size (mm) X Y X Y Imaging Diagonal Mono/ Area (mm2) (mm) Color CG285 ICX285AL 1360 1024 1.4 6.45 8.8 6.6 57.9 11 M,C CG1050 KAI-1050 1024 1024 1.0 5.5 5.6 5.6 34.8 8.3 M,C CG2000 KAI-2020 1600 1200 1.9 7.4 11.8 8.9 105.1 14.8 M,C CG2050 KAI-2050 1600 1200 1.9 5.5 8.8 6.6 58.1 11 M,C CG2150 KAI-2150 1920 1080 2.1 5.5 10.6 5.9 62.7 12.1 M,C CG4000 KAI-4022 2048 2048 4.2 7.4 15.2 15.2 229.7 21.4 M,C CG4050 KAI-4050 2336 1752 4.1 5.5 12.8 9.6 123.8 16.1 M,C CG8050 KAI-8050 3298 2472 8.2 5.5 18.1 13.6 246.5 22.7 M,C CG11002 KAI-11002 4072 2720 11.1 9.0 37.25 25.7 957.3 43.3 M,C CG16000 KAI-16000 4872 3248 15.8 7.4 36 24 866.5 43.3 M,C CG16050 KAI-16050 4896 3264 16.0 5.5 26.9 17.95 478 32.4 M,C CG16070 KAI-16070 4932 3300 16.3 7.4 36 24 860.4 43.2 M,C CG29050 KAI-29050 6576 4384 28.8 5.5 36 24 872 43.5 M,C Price (Grade 2 TS)
Alta Aspen Spectroscopy Model CCD Array Size Megapixels Pixel size (um) Array Size (mm) X Y X Y Imaging Diagonal Mono/ Area (mm2) (mm) Color CG30 E2V CCD30-11 1024 256 0.3 26 26.6 6.7 177 27.4 M CG30-OE E2V CCD30-11 1024 256 0.3 26 26.6 6.7 177 27.4 M CG1007 Hamamatsu S10140-1007 1024 122 0.1 12 12.3 1.5 18 12.4 M CG1008 Hamamatsu S10140-1008 1024 250 0.3 12 12.3 3 36.9 12.6 M CG1009 Hamamatsu S10140-1009 1024 506 0.5 12 12.3 6.1 74.6 13.7 M CG1107 Hamamatsu S10140-1107 512 122 0.1 12 24.6 1.5 36 24.6 M CG1108 Hamamatsu S10140-1108 1024 250 0.3 12 24.6 3 73.7 24.8 M CG1109 Hamamatsu S10140-1109 2048 506 1.0 12 24.6 6.1 149.2 25.3 M Price (Grade1 e2v; Ham Grade S)
Aspen / Alta CCD Options
Apogee Filter Wheels The AFW50 series of filter wheels provide large format filtering solutions for all Aspen and Alta cameras NEW! AFW31-17R 17 positions for 31mm round filters
Face plate adapters These flange adapters allow you to attach anything from an SLR camera lens to a large instrument pack to your Apogee camera. We have sizes to fit all Aspen Alta and Ascent cameras. These units are machined precisely for accurate concentricity. Lens & Slip-fit Adapters Apogee Imaging Systems will make sure that you have an adapter for whatever you would like to interface to. If we don't have it, we'll locate it for you. If it doesn't exist, we will provide superior mechanical engineering support to provide a custom solution. Filters Apogee carries all major brands and types of filters; from single notch to multi notch, short pass to long pass, Chroma to Astrodon and everything in between. We even provide custom sizing and coating options upon request in order to support all industry of filters your project demands.
Adapters Change our camera threads to most popular threads for maximum accessory compliance SBIG and QSI have most after market accessories. 19
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