The IMX462 sensor is back-illuminated and incorporates new technology that gives it a significant advantage over other planetary cameras: first, the IMX462 sensor has sHCG (super high conversion gain) for very low read noise at high gain. This is ideal for stacking hundreds or thousands of short planetary images. Second, it is exceptionally sensitive in the NIR.
In this latest generation of sensors, the photodiode portion of the pixel is physically deeper than in previous Sony BSI sensors, allowing longer wavelength photons to penetrate deeper into the substrate. This dramatically increases the sensor's sensitivity to red and near-infrared (NIR) light. The RGB filters on the pixels become transparent at NIR wavelengths, so the sensor exhibits nearly equal maximum sensitivity to NIR light as to light in the visible spectrum.
The peak QE in the NIR around 800 nm is as high as the peak QE at visible wavelengths. For planetary imagers using a methane filter that lets light through around 880 nm, this is good news.
BSI
One of the benefits of the back-illuminated CMOS structure is improved sensitivity. 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 structure of the wiring reflects some of the photons and reduces the efficiency of the sensor.
In the back-illuminated sensor, light is allowed to enter the photosensitive surface from the reverse side. In this case, the integrated wiring structure of the sensor is located below the photosensitive layer. As a result, more incoming photons hit 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, therefore, the more sensitive it is at capturing an image of something faint.
Extended near infrared sensitivity
Logically, one would think, each generation of Exmor sensors would build on and incorporate all the improvements of the immediately preceding generation. However, this was not the case with the fifth generation Exmor R sensors.
Early back-illuminated sensors used shallower pixel wells (like the third-generation front-illuminated designs) than the physically deeper pixels of the fourth generation. So, while the back-illuminated structure increased sensitivity in the visible range by 2X, the shallower pixels did not improve the NIR. The answer to this is seen in the newer sixth generation Sony Exmor R sensors, such as the IMX462. The use of physically deeper pixels along with the back-illuminated structure has dramatically improved the sensor's sensitivity to visible and near-infrared wavelengths.
SHCG mode
Another advantage of the QHY5III462 is the camera's "super high conversion gain" capability. By using a lower capacitance, a small amount of charge can be converted to a high voltage, resulting in higher sensitivity in low light conditions. The QHY5III462's read noise in high gain mode is as low as 0.5 electrons!
The test exposures below demonstrate the low light improvement over the IMX290 sensor. The QHY5III462C image is on the left and the corresponding QHY5III290C image is on the right. The low light conditions and exposures are identical for each top and bottom image pair and a UV/IR filter was installed for each camera. So, this test demonstrates the increased sensitivity and signal-to-noise ratio of the QHY5III462C over the QHY5III290C under the same conditions in the visual light spectrum alone.
Color and monochrome images with one camera
The filter matrix of the IMX462 uses organic dye filters. These filters are very efficient at visible wavelengths but become completely transparent in the NIR. For this reason, good RGB color balance requires an external UV/IR filter that blocks the NIR wavelengths.
Many color cameras incorporate this UV/IR filter in the camera or in the optical window to obtain normal color images. However, to take full advantage of the 462C sensor's capabilities, in the QHY5III462C camera the optical window has an AR coating only with no UV or IR blocking. Instead, the QHY5III462C camera includes two 1.25 ″ screw-in filters, a UV/IR cut-off filter to isolate visible wavelengths for normal RGB imaging and an IR850 filter that will cut visible wavelengths but let through wavelengths above 850 nm.
Specifications
| Model |
QHY5III462M/C |
| Image sensor |
SONY IMX462 |
| Single Color/Color |
Both available |
| FSI/BSI |
BSI |
| Sensor size |
Typical 1/2.8 in |
| Pixel size |
2.9 µm*2.9 µm |
| Effective pixel area |
1920*1080 |
| Effective pixels |
2 megapixels |
| Total well capacity |
12ke- |
| Read noise |
0.5e- |
| ADVERTISEMENT |
12 bits (output as 16 bits and 8 bits) |
| Built-in image buffer |
- |
| Full frame rates |
135 FPS at 8 bits |
| Return on investment (ROI) frame rates |
to be confirmed |
| Exposure time range |
7μs-900sec |
| Type of shutter |
Electronic rolling shutter |
| Computer interface |
USB3.0 type B |
| Port guide |
ST-4 customized |
| Telescope interface |
1.25 inch, C-mount |
| Optical window |
AR anti-reflective glass |
| Additional filter |
IR850nm filter included
IR cut-off filter included in 462C only |
| Rear focal length |
12mm |
| Weight |
88g |
Curves
Mechanical dimensions
Accessories
