CMOS image sensor parameters
July 12, 2023
1. Sensor size
The larger the size of the CMOS image sensor, the larger the size of the imaging system, the more captured photons, the better the photosensitive performance, and the lower the signal-to-noise ratio. Currently, common sizes of CMOS image sensors are 1 inch, 2/3 inch, 1/2 inch, 1/3 inch, 1/4 inch, etc.
2. The total number of pixels and the number of effective pixels
The total number of pixels refers to the sum of all pixels, and the total number of pixels is one of the main technical indicators for measuring CMOS image sensors. Among the overall pixels of the CMOS image sensor, the pixels that are used to perform effective photoelectric conversion and output image signals are effective pixels. Obviously, the total number of effective pixels belongs to the set of total number of pixels. The number of effective pixels directly determines the resolving power of the CMOS image sensor.
3. Dynamic range
The dynamic range is determined by the signal processing capability and noise of the CMOS image sensor, reflecting the working range of the CMOS image sensor. Referring to the dynamic range of the CCD, its value is the ratio of the signal peak voltage at the output terminal to the root mean square noise voltage, usually expressed in DB.
4. Sensitivity
The ability of an image sensor to respond to incident light power is known as responsivity. For CMOS image sensors, the current sensitivity is usually used to reflect the response capability, and the current sensitivity is the signal current generated by the unit optical power.
5. Resolution
Resolution refers to the ability of the CMOS image sensor to distinguish bright and dark details in the scene. It is usually represented by the modulation transfer function (MTF), but it can also be represented by the spatial frequency (lp/mm).
6. Photoelectric response inhomogeneity
The CMOS image sensor is a discrete sampling imaging device, and the photoelectric response non-uniformity is defined as the ratio of the peak-to-peak noise voltage of each pixel to the signal voltage of the CMOS image sensor under standard uniform illumination conditions.
7. Spectral response characteristics
The signal voltage Vs and signal current Is of the CMOS image sensor are functions of the wavelength λ of the incident light. The spectral response characteristic refers to the relationship between the response capability of the CMOS image sensor and the wavelength, which determines the spectral range of the CMOS image sensor.