Factors affecting exposure of industrial cameras
During the working process of industrial cameras, exposure is the process of photosensitive by the image sensor. Exposure has a great influence on the quality of the photo. If it is overexposed, the photo will be overexposed and image details will be lost; if it is underexposed, the photo will be too dark and image details will also be lost.
During the exposure process, CCD/CMOS collects photons and converts them into charges. After the exposure is over, CCD/CMOS transfers the charges out in a certain way.
Controlling the exposure is to control the total amount of light passing through, that is, the sum of photons reaching the CCD/CMOS surface during the exposure process;
There are three factors that affect exposure: 1. Aperture; 2. Exposure time; 3. Gain;
1. Aperture
The aperture controls the size of the passage through which light enters. The larger the aperture, the greater the luminous flux per unit time; the smaller the aperture, the smaller the luminous flux per unit time;
2. Exposure time
The exposure time is also the shutter speed.
The shutter is a valve used to control the time of light entering, and it is a component. Digital cameras have two types of shutters, mechanical and electronic;
shutter speed refers to the speed at which the shutter opens to close, and exposure time refers to the time it takes the photosensitive element to expose an image when light hits it. Although the two concepts refer to different objects, they are related to each other. As long as the shutter is open, the photosensitive element will have as much time to respond. So generally speaking the two are the same thing.
3. Gain
There is a video amplifier in the industrial camera that amplifies the signal from the CCD to a usable level, and its amplification is gain. Since the noise signal is also amplified in the process of amplifying the image signal, the amplifier gain is usually set to the minimum.
4. When adjusting, exposure is the main gain, supplemented by
Exposure and gain are the data read out from the direct control sensor (CCD/CMOS), and should be adjusted first, mainly to adjust the exposure time.
Under the premise of not overexposure, increasing the exposure time can increase the signal-to-noise ratio and make the image clear. Of course, for very weak signals, the exposure cannot be increased indefinitely, because with the increase of exposure time, noise will also accumulate. Exposure compensation is to increase the exposure when shooting.
Gain is generally only used when the signal is weak, but you don’t want to increase the exposure time. Generally, camera gain will generate a lot of noise. The imaging quality of industrial cameras is different at different gains. The smaller the gain, the smaller the noise; the larger the gain, the more noise, especially in dark places.
Gain is generally only used when the signal is weak, but you don't want to increase the exposure time. General camera gain is very noisy, so it is rarely used.
5. Differentiate between IOS and exposure compensation:
The ISO of a digital camera is the gain mentioned here. Increasing the ISO is to increase the sensitivity of the photosensitive device to light. High sensitivity is sensitive to low light, but also sensitive to noise signals, and the signal-to-noise ratio is small, so there are many noises at high sensitivity (you can use the noise reduction function of the image software to reduce or remove it).
To put it bluntly, adjusting the brightness gain is to change the ISO and the photosensitive performance of the CMOS sensor, but it will affect the image quality. Adjusting the exposure compensation is to change the shutter speed, and the image quality will not be affected if the ISO is not changed.