LabVIEW calculates the camera image sensor resolution and lens focal length

LabVIEW Calculate the resolution of camera image sensor and lens focal length

He is sure to use the right lens 、 Focal length and sensor resolution （ Camera sensors CCD Number of rows and columns per pixel ）？ About the real world , The following definitions have been understood ：

field (FOV) - The detected area that the camera can collect

The resolution of the - The number of object details that the imaging system needs to replicate

Object distance - The distance from the front of the lens to the detected object

Please refer to the following legend ：

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In order to obtain accurate measurements , At least two pixels are required to express the smallest feature you want to detect . Please use the resolution information to select the appropriate camera and lens for the application .

First , It is necessary to determine the resolution required by the image acquisition system . You can first measure the size of the smallest feature to be detected in real-world measurement units . then , Calculate the required sensor resolution by the following formula (S)：

Sensor resolution (S) =(FOV / The resolution of the ) x 2 = (FOV / The size of the smallest feature ) x 2

for example ：

There is a sensor with a resolution of 640x480 The camera , Want to know the resolution of the smallest feature that can be detected in any direction . Because it is required that the measurement does not depend on the direction , So take CCD Short side in dimension parameter , Here is the 480; Suppose you want to capture FOV yes 100mm.

According to the above formula , The minimum feature size that can be detected is FOV Divide by the sensor resolution and multiply by 2（ Minimum feature size =(100/480)*2）. In this way, the minimum feature size that can be detected can be calculated as 0.42mm. Note that this is a rough equation , The lens distortion is not considered 、 Specific feature detection algorithm 、 And whether to use sub-pixel precision .

then , Calculate the required focal length .

Use the following formula ：

The focal length x FOV = Sensor size x Object distance

For the example above , If you want to determine the object distance , First assume that the sensor size is 1/2‘’, Lens focal length is 12.5mm, Then the object distance is 98mm（ Object distance =(12.5*100)/12.7）. Please note that for a unified unit 1/2'' Conversion for 12.7mm.

In the factory lens , Only a portion has a standard focal length . The usual lens focal length includes 6mm,8mm,12.5mm,25mm, as well as 50mm Several kinds . Once a lens with a focal length close to the focal length required by the image acquisition system is selected , It is necessary to adjust the object distance to focus the detected object .

Short focal length （ Less than 12mm） There will be obvious distortion in the image taken by the lens of . If the application is sensitive to image distortion , Please try to increase the object distance and use a lens with a longer focal length . If it is inconvenient to adjust the object distance , When you choose a lens, you will be greatly restricted .

When building the system , It is necessary to adjust various parameters in the focal length formula repeatedly and carefully , Until we find a combination that meets the testing needs and meets the cost requirements .

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LabVIEW Calculate the resolution of camera image sensor and lens focal length - Beijing Hanwen Wangxing Technology Co., Ltd (bjcyck.com)