Through the contents of the previous chapter, we have some understanding of the imaging characteristics and advantages of telecentric lenses. The telecentric lens is distinguished from other optical lenses and has its own unique parameters. We should choose how to choose the phase of the project. Suitable for your own telecentric lens? What if you can't find a telecentric lens suitable for your needs? This section mainly focuses on these two issues and we will explain in detail.
Telecentric lens selection
A: Match between telecentric lens and camera
The telecentric lens is mainly designed and developed as a series of products to solve the image problem of the machine vision project. Therefore, the telecentric lens is mainly designed to match the industrial camera. The interface between the lens and the camera is generally a standard interface: the C interface, the F interface, the M42 interface, and the M58 interface. These interfaces are the physical standards for the lens and the camera. It not only corresponds to the size of the bayonet or thread corresponding to different sizes, it also corresponds to the standard flange distance (the distance between the camera interface and the chip). The 1.2-inch industrial camera with an extremely low target surface is mainly based on the C interface.
Our choice of dual-telecentric lenses must first be considered in conjunction with the selected camera. The interface must be the same. If the interface is inconsistent, consider whether or not the interface can be added. Generally, the camera with a large flange distance can be considered Matching is done by adding interfaces, but not vice versa.
Corresponding to the physical interface between the camera and the lens, we have to consider the matching of the lens image surface and the camera chip. For a telecentric lens, the image surface generally has a higher price, so we try to consider the camera chip size and lens image when choosing. If the surface area of ​​the lens is larger than the diagonal of the camera chip, the cost of the lens will be wasted, and the visual field will be lost. If the lens surface is smaller than the diagonal of the camera chip, then the final Imaging will have dark corners and black corners.
Main camera lens flange distance on the market
B: Magnification and view of telecentric lens
Through the introduction of the previous chapter, we know that the field of vision of the telecentric lens is equal to the size of the chip/magnification of the lens, because the magnification of the telecentric lens is an inherent parameter, and the magnification is the core problem of the telecentric lens, and it will not change. , so when we choose, we can directly calculate the magnification of the lens.
Here, we must pay particular attention to the fact that the length and width of the rectangular field of view must be calculated separately because the ratios of the lengths of the camera chips are not uniform.
C: working distance, aperture, depth of field of telecentric lens
Telecentric lenses generally have a fixed working distance, because the telecentric lens is an object-like conjugate lens. The object distance and image distance of the lens are proportional. Changes in the image distance will lead to changes in the object distance. The rigorous companies will calibrate the distance of the telecentric lens before leaving the factory. The calibration method will usually refer to the standard flange distance from the lens, because different manufacturers have different flange distances, so the telecentric lens is actually used. There is usually a +-3% gap between objects.
From the previous chapters we can see that lens aperture and depth of field have a direct correspondence. For telecentric lenses, a fixed aperture mechanism is generally used to calibrate the same image illuminance and depth of field, so each lens will have a fixed range of depth of field and aperture specifications. The aperture of a single telecentric lens is generally N. A said that the aperture of a double telecentric lens is generally represented by F#.
For some items such as depth of field, object distance, etc. If you find a product that is close to the product, it is recommended that you generally consult the manufacturer to make specific parameter adjustments on the standard product to meet the project needs. This is the most valuable solution in terms of cost, efficiency, and cycle time.
Customization of telecentric lenses
The telecentric lens is different from the fixed focus and other types of optical lens. It does not have a uniform industry standard, and each product category is not the same. Currently, most machine vision projects are mostly non-standard items, and it is very difficult to choose products that meet their own needs.
The caliber, length, object distance, magnification, aperture (depth of field), and image size of the lens can all be communicated to the lens development company according to the requirements of use. Faces of cycle, cost, etc., may be a lens suitable for the needs of their project. Is the optimal solution.
BTOS telecentric optics relying on Vevey and Xinwei Vision, on the basis of a large number of visual cases, continuously upgrade and update the parameter performance and application innovation of their products, and has developed and developed dozens of telecentric products for many well-known domestic customers. In product customization, we can provide products and services to our customers in a professional and consistent manner.
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