Analysis of several factors to pay attention to when choosing an industrial lens

Depth of field

的 The performance of the optical system depends on the allowed degree of image blurring. Blur may originate from the position drift of the object plane or image plane. Depth of field refers to the acceptable range of blur caused by the movement of the detector. It depends on the working F number (F / #) and can be used to measure the lens's ability to focus light. F / # increases as the lens aperture decreases. Decreasing the lens aperture means increasing F / #, that is, increasing the depth of field of the system, but reducing the amount of light entering the sensor, so the illumination level must be increased to compensate. Industrial lens

深 Depth of field effect (DOF) refers to the blur caused by the movement of objects. DOF is the maximum object depth that is completely within the focal length range, and it is also the allowable amount of movement of the object (moving back and forth from the optimal focal length) while maintaining the ideal focus. When the object is placed closer or farther than the working distance, it is out of focus, so the resolution and contrast will be adversely affected. For this reason, DOF works with the specified resolution and contrast. When the depth of field is constant, the DOF can be increased by reducing the lens aperture (that is, increasing the F / # value), and it also requires light enhancement.

The DOF range of a lens depends on the effective focal length and acceptable blur diameter. Some lenses are designed to be hyper-focusing or hyper-focusing, which means that the far point in focus can be extended to infinity. This technique is usually applied to fixed-focus lenses. The depth of field effect is very deep, but it can be adjusted with the help of iris.

Be careful not to confuse telecentric lens with large depth of field lens. A telecentric lens allows the machine vision system to control the magnification and eliminate potential errors, so objects of the same size have the same height in the photo, no matter how far away it is from an industrial camera. An example of a practical application of this lens is analyzing a computer circuit board. Telecentric lenses usually have a working distance range that forms a limited depth of field at each working distance point. When integrators choose a telecentric lens for a project, they need to consider both the working distance range and the depth of field effect.

Industrial lenses have a profound impact on machine vision systems. According to the actual application, choosing lenses that meet the system requirements can ensure the stability of the system and ultimately give play to its advantages.