Understanding the relevant parameters of industrial cameras can help us better understand the camera functions, and then help us to complete the selection of cameras. The so-called amateurs look at the crowd, the expert look at the door, the door of the industrial camera from its parameters.

1. Resolution

The sensor sensor of the camera has many pixels arranged in the form of a matrix, and the resolution is represented by pixels in the horizontal and vertical directions. The higher the resolution, the higher the number of pixels after imaging, the clearer the image. The resolution of the commonly used industrial array camera is 1.3 million, 2 million, 5 million, etc. For linear array cameras, resolution is the number of pixels in the horizontal direction of the sensor, commonly 1K, 2K, 6K, etc.

The selection of camera resolution depends on the needs of our project. The higher the resolution is, the better it is. The higher the resolution brings, the larger the amount of image data, and the higher the complexity of the later algorithm processing.

2. Sensor size

Sensor sizes are expressed in effective area (W x h) or diagonal size (in inches). Common sensor sizes are as follows:

The larger the sensor size, to some extent, means that the camera can hold more pixels, the larger the image.

3. Pixel size

Pixel size is the area of each pixel. The area of a single pixel is small, the number of pixels in a unit area is large, and the resolution of the camera is increased, which is conducive to the detection of small defects and increase the detection field of view. As the pixel area shrinks, so does the capacity to fully trap (the amount of charge each pixel can store), resulting in a lower dynamic range of the camera.

4. Pixel depth

Pixel depth refers to the number of bits per pixel. In general, each pixel has more bits and has a strong ability to express the details of the image, so the color value of the pixel is richer and finer, and the color depth is deeper. General pixel depths are 1 bit, 8 bit, 16 bit, 24 bit, and 32 bit.

One - bit pixel depth is represented by binary, also known as monochrome display.

8 bit pixel depth is the most common, with 8 binary bits to represent the color, can represent 256 colors, this is often referred to as gray display.

16 bits is to use 16 binary bits to represent, can represent 65536 colors, then you can color display.

The color information of 24 and 31 bits is richer.

5. Dynamic range

Dynamic range is used to describe the level of gray that can be resolved by each pixel. It is the ratio of saturation voltage (the maximum output level) to the noise of the camera's output. The wide dynamic range allows details in both very bright and very dark parts of the scene to be shown clearly. In general, low dynamic range cameras tend to be noisy, and photos will miss light and dark details.

6. Maximum frame rate

The maximum frame rate represents the maximum number of frames per second that can be collected and output by an array industrial camera, which is often related to the sensor chip and the bandwidth of the data output interface. According to project requirements, it is recommended to select a high frame rate camera for shooting moving objects, and the specific frame rate should be determined according to the shooting accuracy.

7. Exposure method

Common exposure methods of industrial cameras include global shutter and rolling shutter.

Frame exposure refers to the simultaneous exposure of all pixels in the sensor array, and the exposure period is determined by a preset shutter time. This type of exposure camera is suitable for shooting moving objects, the image will not be offset, no distortion.

Row exposure means that pixels in the same row are exposed at the same time. The starting time of exposure is different for different rows. The exposure time of each row is the same, and the delay between rows is unchanged. This type of exposure camera is suitable for shooting still objects, shooting moving objects, the image will be shifted.

8. Exposure time

The sensor converts optical signals into electrical signals to form a frame image. The process of each pixel receiving optical signals is called exposure, and the time spent is called exposure time, also known as shutter speed.

9. Collection mode

The collection mode is divided into three types: continuous collection, external trigger collection and soft trigger collection.

Continuous acquisition refers to the continuous exposure of the camera and the output of real-time images.

External trigger acquisition means that when the camera is in the external trigger mode, the camera is in standby mode without exposure. Only when the camera receives a single pulse (square wave) signal specified by the camera through the I/O port, the sensor is exposed once. Some cameras support the triggering of the rising edge, falling edge and high and low level of the signal.

Soft trigger means that when the camera is in the external trigger mode, the camera is in standby mode and does not expose. Only when the camera software gives instructions, the sensor is exposed once.

10. gain

Industrial cameras usually have a video amplifier that amplifies the signal from the sensor, and the amplification is called the gain. The larger the gain, the larger the noise will be. Generally, it is not recommended to increase the gain value.

11. Spectral response characteristics

Spectral response characteristics refer to the sensitive characteristics of the image sensor to different light waves, realizing the quantum efficiency QE of the sensor.

12. Analog camera and digital camera

Industrial cameras are divided into analog cameras and digital cameras according to the output image signal format. Early industrial cameras mostly use PAL/ NTSC/ CCIR/ EIA-170 and other standard analog output, but also use non-standard analog output products. With the development and popularization of digital interface technology such as GigE/IEEE 1394/USB 2.0/ USB 3.0/ CameraLink/CameraLink HS/ CoaXPress, more and more industrial digital cameras appear in various machine vision systems instead of traditional analog cameras.

The signal of digital camera is less disturbed by noise, so the dynamic range of digital camera is high, and the image quality is better. However, the analog camera collects the analog signal, which is converted to the digital signal through the digital acquisition card. It is greatly affected by noise, has low resolution, and the frame rate is generally fixed.