Some key professional skills in industrial lenses（1）

The following is a detailed explanation of the technical terms associated with industrial lenses used in machine vision systems:

1. Telecentric Optical System: This refers to an optical system where the principal rays are parallel to the optical axis of the lens. If the light from the object to the lens maintains parallelism with the optical axis, even off-axis, it's called a telecentric optical system.

2. Telecentric Lens: This is an industrial lens where the principal rays are parallel to the lens's optical axis. There are object-side telecentric, image-side telecentric, and double-sided telecentric lenses. Ordinary industrial lenses have an angle between the principal rays and the optical axis, resulting in changes in image size when the workpiece moves up and down.

   • Double-Sided Telecentric Lens: In this lens, both object and image sides have principal rays parallel to the optical axis. It has adjustable apertures and provides greater depth of field, making it more stable for measurement-based image processing optical systems. However, it's generally larger and more costly. Double-sided telecentric lenses are optimal for measurement-based applications.
   • Object-Side Telecentric Lens: Only the principal rays on the object side are parallel to the optical axis. The image size remains relatively stable when the workpiece moves up and down. This lens is suitable for coaxial lighting.
   • Image-Side Telecentric Lens: Only the principal rays on the image side are parallel to the optical axis. It can compensate for installation errors and prevent changes in magnification.

3. Telecentric Optical System Features:

   • Advantages: Consistent size when the object moves vertically. Ideal for coaxial lighting. Can use smaller-sized sensors.
   • Disadvantages: Requires coaxial lighting; larger than standard lenses if not using coaxial lighting.

4. Telecentricity: This is a measure of the magnification error of an object. The smaller the magnification error, the higher the telecentricity.

5. Resolution (μm): The optical system's capacity to distinguish details. It represents the minimum distance between two points that can be discerned before they become indistinct.

6. Resolving Power (Lines/mm): This indicates the number of distinguishable black and white stripes within 1 mm. For example, 100 lines/mm mean the lens can distinguish black and white stripes with a 10μm pitch.

7. Horizontal TV Resolution (TV Lines): This measures the total number of horizontal black and white lines on a TV screen. The aspect ratio is usually 3:4, so horizontal resolution is 3/4 of the total number of lines.

8. Distortion (%): This is the lens's optical distortion, where straight lines appear curved. It includes pincushion distortion (curved towards the center) and barrel distortion (curved outwards).

9. TV Distortion (%): This measures image distortion on a TV screen. A lower value indicates better performance.

10. Television Distortion: This represents the deviation between the actual edge length and the ideal shape as a percentage.

11. Aperture Efficiency: This is the difference in brightness between the center and edges of an image. It's measured in percentage points.

12. Vignetting: This refers to the decrease in brightness from the center to the edges of an image. It's often calculated as a percentage and can be minimized using a telecentric optical system.

13. Chromatic Aberration: This is the variation in the image's position or magnification due to different wavelengths of light. There are axial chromatic aberrations and lateral chromatic aberrations.

14. Working Distance (WD) (mm): This is the distance from the first lens element to the object being observed.

15. Object-to-Imager Distance (O/I): The distance from the object to the image plane.

16. Focal Length (f) (mm): This is the distance from the principal plane to the focal point. It indicates the lens's focal length. The rear focal length is the distance from the last lens to the focal point, and the front focal length is the distance from the first lens to the focal point.

17. Depth of Field: This is the distance range where the focus is sharpest when moving in front or behind the focus point.