Optical principle and performance parameters of Robot Vision industrial lens

1. Optical principle

The optical principle of Robot Vision FA industrial lens is mainly based on the convex lens imaging principle, through the combination of lenses to image the light emitted or reflected by the object on the image plane. Specifically, the interior of the lens consists of several sets of lenses, each set of lenses may be a single lens, or may be composed of two or more single lenses glued together. These lenses refract light so that light rays parallel to the light axis pass through the lens and converge on the focus, forming a sharp image.

In machine vision systems, industrial lenses play a central role in transforming optical information about a target object into a digital image that can be analyzed. Through high-performance industrial lenses, the machine vision system can clearly capture the detailed information of the target object, providing high-quality data support for subsequent image processing.

Second, performance parameters

The performance parameters of Robot Vision industrial lenses directly affect its imaging quality and applicable scenes. The following are some key performance parameters:

1. Focal Length

• Definition: Focal length refers to the distance between the center of the lens and the focus of the image square, which determines the range of images that the lens can shoot.

• Impact: the smaller the focal length, the larger the field of view, suitable for large-area target detection; The larger the focal length, the smaller the field of view, suitable for high-precision detection.

2. Aperture

• Definition: Aperture is a device used to control the entry of light through the lens into the sensitive surface of the camera, and its size is usually expressed as the ratio of the focal length of the lens to the effective diameter of the lens entry pupil (F-number).

• Impact: The smaller the F-number, the larger the aperture, the greater the amount of light, suitable for shooting in low light environment; The larger the F-number, the smaller the aperture and the less light, which is suitable for shooting in strong light. In addition, the aperture size also affects the depth of field, the larger the aperture, the smaller the depth of field; The smaller the aperture, the greater the depth of field.

3. Resolution

Definition: Resolution refers to the minimum interval that the lens can observe, and is an important indicator to measure the clarity of the lens. It is usually expressed as the number of black and white stripes (lp/mm) that can be resolved per millimeter of the image plane.

• Impact: The higher the resolution, the clearer the image shot by the lens, which is suitable for application scenarios requiring high image detail.

4. Distortion

• Definition: Distortion refers to the reflected light in the plane of the target object, which should be a straight line but becomes a curve after passing through the imaging system, resulting in distortion of the imaging geometry.

• Impact: Distortion affects the geometry of the object, but does not affect the quality of the image. The common distortions are barrel distortion and pillow distortion. In the packaging industry, application scenarios requiring high dimensional measurement accuracy require special attention to distortion correction.

5. Field of View (FOV)

• Definition: Field of view refers to the range that a lens can capture within its working distance.

• Impact: The size of the field of view directly affects the shooting area that the lens can cover, which is particularly important for the detection of large areas of targets.

6. Working Distance

• Definition: The working distance refers to the distance between the front end of the lens and the measured object, which is less than the minimum working distance.

• Impact: Working distance is one of the important factors to consider when choosing a lens, which limits the space required by the vision system and the equipment working with the vision system.

7. Depth of Field

• Definition: Depth of field refers to the range in which the image is still clear within a certain distance after the subject is clearly focused.

• Impact: The depth of field directly affects the clear range of the image, which is particularly important for application scenarios that require shooting objects at different distances.

8. Interface (Mount)

• Definition: Interface refers to the way the lens is connected to the camera.

• Impact: Different cameras and lenses may require different interface types, and you need to ensure that the interface is compatible with the camera when selecting a lens.

9. Target surface size (Max Image Circle)

• Definition: The size of the target surface refers to the diagonal size of the sensor, that is, the range of its effective perception of light.

• Impact: The size of the target surface determines the maximum size of the CCD chip that the lens can support. When selecting a lens, ensure that the size of the target surface is greater than or equal to the size of the camera CCD chip.

10. Relative Illumination

• Definition: Relative illuminance refers to the ratio of image edge brightness to center brightness, which is one of the important indicators to measure the optical performance of the lens.

• Impact: The smaller the relative illuminance, the lighting performance of the lens in the edge area may be insufficient, which needs to be further optimized.

11. Modulation Transfer Function (MTF)

• Definition: MTF is a function that describes how the optical imaging system transmits the contrast of different frequency components, and is an important parameter to measure the imaging quality of the lens.

• Impact: The MTF curve intuitively shows the contrast transfer ability of the lens to different frequency components, which is of great significance for evaluating the image quality of the lens.

In summary, the optical principle of Robot Vision industrial lens is based on the convex lens imaging principle, and its performance parameters directly affect the imaging quality of the lens and the applicable scene. In the selection and use of industrial lenses, it is necessary to consider the focal length, aperture, resolution, distortion, field of view, working distance, depth of field, interface, target surface size, relative illumination and MTF and other parameters to meet the needs of different application scenarios.