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QHY268M-PH CMOS IMAGER



With the advantage of low readout noise and high-speed readout, CMOS technology has revolutionized astronomical imaging.  A monochrome, back-illuminated, high-sensitivity, astronomical imaging camera is the ideal choice for astro-imagers.

The QHY268M/C is a new generation of back-illuminated CMOS cameras with true 16-bit A/D and 3.76um pixels.  This new Sony sensor is an ideal CMOS sensor exhibiting no amplifer glow. 16-bit A/D gives high resolution sampling of the whole full well range.  Digitizing 0-65535 levels yields a smooth image with continuous gradation of greyscale levels. The QHY268M/C is a cooled, back-illuminated, CMOS camera based on the Sony IMX571 sensor with native 16-bit A/D and 3.76um pixels.

 

1GB DDR3 image buffer

In order to provide smooth uninterrupted data transfer of the entire 26MP sensor at high speed, the QHY268 has 1GB DDR3 image buffer. The pixel count of the latest generation of CMOS sensors is very high resulting in greater memory requirements for temporary and permanent storage.  The QHY268 has adopted a large-capacity memory of up to 1GB.  Data throughput is doubled. This large image buffer meets the needs of high-speed image acquisition and transmission of the new generation of CMOS, making shooting of multiple frames smoother and less stuttered, further reducing the pressure on the computer CPU.

 

Extended Full Well Capacity and Multiple Read Modes

With a pixel size of 3.76um, these sensors already have an impressive full well capacity of 51ke.  Nevertheless, QHYCCD has implemented a unique approach to achieve a full well capacity higher than 51ke- through innovative user controllable read mode settings.  In extended full well readout mode, the QHY268 can achieve nearly 75ke-.  Greater full-well capacity provides greater dynamic range and large variations in magnitude of brightness are less likely to saturate. 

 

Internal Humidity Sensor

QHY268M has a unique internal humidity sensor (while QHY268C doesn’t). The Blue curve shown below represents humidity.

 

Native 16 bit A/D

The new Sony sensor has native 16-bit A/D on-chip. The output is real 16-bits with 65536 levels. Compared to 12-bit and 14-bit A/D, a 16-bit A/D yields higher sample resolution and the system gain will be less than 1e-/ADU with no sample error noise and very low read noise.

 

BSI

One benefit of the back-illuminated CMOS structure is improved full well capacity. This is particularly helpful for sensors with small pixels.In a typical front-illuminated sensor, photons from the target entering the photosensitive layer of the sensor must first pass through the metal wiring that is embedded just above the photosensitive layer. The wiring structure reflects some of the photons and reduces the efficiency of the sensor.

In the back- illuminated sensor the light is allowed to enter the photosensitive surface from the reverse side. In this case the sensor’s embedded wiring structure is below the photosensitive layer. As a result, more incoming photons strike the photosensitive layer and more electrons are generated and captured in the pixel well. This ratio of photon to electron production is called quantum efficiency. The higher the quantum efficiency the more efficient the sensor is at converting photons to electrons and hence the more sensitive the sensor is to capturing an image of something dim.

 

Zero Amplify Glow

This is also a zero amplifer glow camera.

 

TRUE RAW Data

In the DSLR implementation there is a RAW image output, but typically it is not completely RAW.  Some evidence of noise reduction and hot pixel removal is still visible on close inspection.  This can have a negative effect on the image for astronomy such as the “star eater” effect.  However,  QHY Cameras offer TRUE RAW IMAGE OUTPUT and produces an image comprised of the original signal only, thereby maintaining the maximum flexibility for post-acquisition astronomical image processing programs and other scientific imaging applications.

 

Anti-Dew Technology

Based on almost 20-year cooled camera design experience, The QHY cooled camera has implemented the fully dew control solutions. The optic window has built-in dew heater and the chamber is protected from internal humidity condensation. An electric heating board for the chamber window can prevent the formation of dew and the sensor itself is kept dry with our silicon gel tube socket design for control of humidity within the sensor chamber.

 

Cooling

In addition to dual stage TE cooling, QHYCCD implements proprietary technology in hardware to control the dark current noise.

 

Model QHY268M QHY268C
COMS Sensor SONY IMX571 M SONY IMX571 C
Mono/Color Mono Color
FSI/BSI BSI
Pixel Size 3.76um x 3.76um
Effective Pixel Area 6280*4210 (includes the optically black area and overscan area)
Effective Pixels 26MP
Sensor Size APS-C
A/D Sample Depth

 

 

Native 16-bit (0-65535 greyscale) A/D
Full Well Capacity (1×1, 2×2, 3×3) 51ke-
75ke- or above in extended full well mode
Full Frame Rate USB3.0 Port:
Full Resolution  6.8FPS  @8BIT         6FPS @16BIT
2048lines         13.6FPS  @8BIT     11.5FPS@16BIT
1080lines         25.4FPS  @8BIT     19.5FPS@16BIT
768lines           35FPS     @8BIT        25FPS@16BIT
480lines           50FPS     @8BIT        34FPS@16BIT
Readout Noise 1.1e- High Gain,

 

3.5e- Low Gain

(5.3e- to 7.4e- in extended full well mode)

Dark Current -20C,0.0005e /pixel/sec

 

-10C,0.001e /pixel/sec

Exposure Time Range 30us-3600sec
Unity Gain* 0(PH Mode)

 

30(Extended Full Well Mode)

 

*With the improvement of the CMOS technology, the 16bit CMOS camera has been released, like QHY600/268/411/461. For these cameras, even in lowest gain it has beyond the requirement of unit gain (less than 1e/ADU due to sufficient samples) So you can directly set gain0 as start. Please note QHY600/268C/411/461 has extend full well mode. In this mode you still need to find out the unit gain position.

 

Amp Control Zero Amplifer Glow
Firmware/FPGA remote Upgrade Fully support via Camera USB port
Shutter Type Electronic Shutter
Computer Interface USB3.0
Built-in Image Buffer 1Gbyte DDR3 Memory
Cooling System Two-stage TEC cooler

 

Less than 1S lower than ambient temperature -30C in continuous mode

More than 1S continuous mode or lower than ambient temperature -35C in single frame mode

Optic Window Type AR+AR High Quality Multi-Layer Anti-Reflection Coating
Anti-Dew Heater Yes
Humidity Sensor* Yes No
Telescope Interface Support M54 and M48 (with standard adapters ) M54/0.75 (with CAA)and M48 (with standard adapter)
Back Focal Length QHY268M: 12.5mm (with CAA)
If used with the QHY filter wheel, the actual calculated intercept is 12.5mm.The actual BFL (the intercept from the CMOS chip to the top of the camera) is 14.5mm. Since most uses will match CFW with monochrome cams, please take 12.5mm as major reference. Check the mechanical drawing below for details.
Note 14.5mm rear intercept does not include adapter thread, which must be used with adapters of various sizes through the top 6 screw holes.
QHY268C: 17.5mm (without CAA)
This intercept does not include CAA. If CAA is used, it increases by 6mm (23.5mm total). Please check the mechanical drawing below for details.
Weigth 855g 780g

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