Scanning lenses are widely used in AOI, printing inspection, non-woven fabric inspection, leather inspection, railway track inspection, screening and color sorting and other industries. This article brings an introduction to line scan lenses.

Introduction to Line Scan Lens

1) Concept of line scan lens:

The line array CCD lens is a high-performance FA lens for line sensor series cameras corresponding to image size, pixel size, and can be applied to various high-precision inspections.

2) Features of line scan lens:

1. Specially designed for high-resolution scanning applications, up to 12K;

2. The maximum compatible imaging target surface is 90mm, using a longer line scan camera;

3. High resolution, minimum pixel size up to 5um;

4. Low distortion rate;

5. Magnification 0.2x-2.0x.

Considerations for Selecting a Line Scan Lens

Why should we consider the lens selection when choosing a camera? Common line scan cameras currently have resolutions of 1K, 2K, 4K, 6K, 7K, 8K, and 12K, and pixel sizes of 5um, 7um, 10um, and 14um, so that the size of the chip ranges from 10.240mm (1Kx10um) to 86.016mm (12Kx7um) varies.

Obviously, the C interface is far from meeting the requirements, because the C interface can only connect chips with a maximum size of 22mm, that is 1.3 inches. The interface of many cameras is F, M42X1, M72X0.75, etc. Different lens interfaces correspond to different back focus (Flange distance), which determines the working distance of the lens.

1) Optical magnification(β, Magnification)

Once the camera resolution and pixel size are determined, the sensor size can be calculated; the sensor size divided by the field of view(FOV) is equal to the optical magnification. β=CCD/FOV

2) Interface(Mount)

There are mainly C, M42x1, F, T2, Leica, M72x0.75, etc. After confirming, you can know the length of the corresponding interface.

3) Flange Distance

The back focus refers to the distance from the camera interface plane to the chip. It is a very important parameter and is determined by the camera manufacturer according to its own optical path design. Cameras from different manufacturers, even with the same interface, may have different back focus.

4) MTF

With the optical magnification, interface, and back focus, the working distance and the length of the joint ring can be calculated. After selecting these, there is another important link, which is to see if the MTF value is good enough? Many visual engineers do not understand MTF, but for high-end lenses, MTF must be used to measure optical quality.

MTF covers a wealth of information such as contrast, resolution, spatial frequency, chromatic aberration, etc., and expresses the optical quality of the center and edge of the lens in great detail. Not only the working distance and field of view meet the requirements, but the contrast of the edges is not good enough, but also whether to choose a higher resolution lens should be reconsidered.