CAMERA QHY268M-PH (MONOCHROME)

Camera QHY268M-PH (monochrome)

Overview

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 amplifier glow. 16-bit A/D gives high-resolution sampling of the whole full well range.  Digitizing 0-65535 levels yields a smooth image with a 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.

Features

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.

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. 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.

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.

Zero Amplify Glow: This is also a zero amplifer glow camera.

Cooling & Anti-dew Control: In addition to dual stage TE cooling, QHYCCD implements proprietary technology in hardware to control the dark current noise. 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.

Sealing Technology: Based on almost 20-year cooled camera design experience, The QHY cooled camera has implemented the sealing control solutions. The sensor itself is kept dry with our silicon gel tube socket design for control of humidity within the sensor chamber. By the way, there’s no oil leaking.

Advanced functions

Multiple Readout Modes
Multiple Readout Modes are special for QHY 16-bit Cameras (QHY600/268/461/411).  Different readout modes have different driver timing, etc., and result in different performance. See details at “Multiple Readout Modes and Curves” Part.

Random change thermal noise suppression function
You may find some types of thermal noise can change with time in some back-illuminated CMOS cameras. This thermal noises has the characteristic of the fixed position of typical thermal noise, but the value is not related to the exposure time.  Instead, each frame appears to have its own characteristics.  The QHY600/268/461/411 use an innovative suppression technology that can significantly reduce the apparent level of such noise.

UVLO Protection
UVLO（Under Voltage Locking) is to protect the electronic device from damage caused by abnormally low voltages.
Our daily life experience tells us that the actual operational voltage of an electrical device must not significantly exceed the rated voltage, otherwise it will be damaged. For such precision equipment as cameras, long-term work at too low input voltage can also be detrimental to the working life of the camera, and may even make some devices, such as power manager, burn up due to long-term overload. In the all-in-one driver and SDK after 2021.10.23 stable version, the camera will give a warning when the input voltage of the camera is below 11V.

Optimizing USB Traffic to Minimize Horizontal Banding
It is common behavior for a CMOS sensor to contain some horizontal banding. Normally, random horizontal banding can be removed with multiple frame stacking so it does not affect the final image. However, periodic horizontal banding is not removed with stacking so it may appear in the final image. By adjust the USB traffic in Single Frame mode or Live Frame mode, you can adjust the frequency of the CMOS sensor driver and it can optimize the horizontal banding appeared on the image. This optimized is very effective to remove the periodic banding in some conditions.

A typical Periodic Horizontal Noise under certain USB_TRAFFIC values.

After Adjusting the USB Traffic to avoid the periodic horizontal noise.

Reboot the camera by power off and on
The camera is designed to use the +12V to reboot the camera without disconnecting and reconnecting the USB interface. This means that you can reboot the camera simply by shutting down the +12V and then powering it back on. This feature is very handy for remote controlling the camera in an observatory. You can use a remotely controlled power supply to reboot the camera. There is no need to consider how to reconnect the USB in the case of remote control.