1、sensor
Feel the ambient light through the CMOS image sensor, output the image for us to analyze, and learn about the sensor performance and situation through the sensor brochure. The figure below takes Stewie SC8238 as an example.
2、
Important parameters related to sensor:
2.1 Resolution
8MP: The sensor has 8 million pixels
Resolution refers to the total number of effective pixels of the sensor.
The total number of pixels is one of the main technical indicators to measure the CMOS image sensor. Among the total pixels of the CMOS image sensor, the pixels that are used for effective photoelectric conversion and output image signals are effective pixels. The number of effective pixels directly determines the capability of the CMOS image sensor. .
The total number of pixels in most sensors is equal to the number of effective pixels. Some sensors have a black level reference area. The pixels in this area are used for black level calibration and are not used as final output pixels.
2.2 Pixel Array
3872H x 2180V: resolution width and height, a total of 3872 columns of pixels in the vertical direction, and a total of 2180 rows of pixels in the horizontal direction
The ability to distinguish light and dark details in a scene.
2.3 Pixel Size
1.5um x 1.5um
Pixel size refers to the actual physical size of each pixel on the chip pixel array. Common sizes include 14um, 10um, 9um, 7um, 6.45um, 3.75um, 3.0um, 2.0um, 1.75um, 1.4um, 1.2 um, 1.0um, etc.
The pixel size can reflect the chip's ability to respond to light to a certain extent. The larger the pixel size, the more photons it can receive. Under the same lighting conditions and exposure time, the greater the number of charges generated. For low-light imaging, pixel size is a representation of chip sensitivity.
2.4 Target surface size (Optical Format)
1/2.7 inches
The larger the size of the image sensor, the larger the size of the imaging system, the more photons captured, the better the photosensitive performance, and the lower the signal-to-noise ratio. At present, the common sizes of CMOS image sensors are 1, 2/3, 1/2, 1/3, 1/4 inches, etc.
2.5 Maximum output frame rate (Max Frame Rate)
3872H x 2180V：@30fps
Frame rate is a measurement used to measure the number of display frames. The measurement unit is the number of image frames of the video stream that the camera can output per second (Frames per Second, referred to as: FPS). General-purpose cameras output high frame rate videos with smoother vision. In the field of industrial cameras, objects on the assembly line are photographed and defects can be detected faster.
2.6 Output data type (Output Interface)
12/10/8 bit 4lane MIPI
12/10/8 bit 4lane LVDS
1. The number of output data bits is subject to the amount of data transmission. The larger the data bit width and the higher the frame rate, the more data is transmitted per unit time.
2. The amount of information in 12 and 10 bit is more than that in 8 bit, and the number of gray levels is much larger, which facilitates subsequent processing, including defect detection, image processing, data analysis and other operations.
3. Ordinary monitors also display 8-bit data. Even if 12 or 10-bit is output, it will be processed into 8-bit later to facilitate image display.
2.7 Output data (Output Format)
RAW RGB
Supports raw format output. The color sensor has RGB filters, which can be demosaic processed according to the bayer mode and restored to color images.
2.8 CRA
15 degrees
From the sensor side of the lens, the maximum angle at which light can be focused onto a pixel is defined as the principal angle (CRA). It is close to zero degrees near the lens axis. The greater the distance from the axis, the greater the angle. . If the CRA of the lens is smaller than the CRA of the sensor, there will definitely be a color cast.
2.9 Sensitivity
1160mv/lux.s
Sensitivity is one of the important parameters of the chip, and it has two physical meanings.
1. The photoelectric conversion capability of an optical device has the same meaning as the response rate. That is, the sensitivity of the chip refers to the output signal voltage (current) per unit exposure within a certain spectral range. The unit can be nanoampere/lux nA/Lux, volt/watt (V/W), volt/lux (V/Lux) ), volts/lumens (V/lm).
2. The ground radiation power (or illumination) that the device can sense has the same meaning as the detection rate, and the unit can be expressed in watts (w) or lux (Lux).
2.10 Dynamic Range
HDR mode up to 100dB
Linear mode 70dB
The dynamic range is determined by the signal processing capabilities and noise of the CMOS image sensor, and reflects the operating range of the CMOS image sensor. Its value is the ratio of the signal peak voltage at the output end to the root mean square noise voltage, usually represented by DB.
Calculation formula to calculate the ratio of the maximum response value to the noise:
S N R = 20 l o g 10 ( M a x / N ) SNR=20log_{10}(Max/N) SNR=20log10(Max/N)
2.11 Signal-to-noise ratio (SNR)
36dB
SNR is used to measure the image quality output by the Sensor. Generally, the manual provides the maximum SNR value and the conditions for calculating the SNR value, such as exposure time, gain gear, etc.
Calculation formula to calculate the ratio of signal to noise:
S N R = 20 l o g 10 ( S / N ) SNR=20log_{10}(S/N) SNR=20log10(S/N)
2.12 Operation Temperature Range
-30~85 degrees
The sensor has a suitable operating range. When the operating temperature range is exceeded, the performance will be compromised or even may not work. Mainly in the image quality of signal-to-noise ratio.
2.13 Best IQ Temperature
-20~60 degrees
Best image quality operating temperature
reference
Detecting Traffic Lights Using RCCB Sensors – Knowledge Base: Image Quality and Color Technical Data