|Title||Hard knowledge in optical lenses|
|Description||Optical lens shape Machine vision is commonly used for fixed-focus lenses, and both are manually adjusted apertures. Generally, the aperture is not allowed to be automatically adjusted. There are two rings on the lens for focusing and dimming. To prevent accidental touch, the two rings of the zero order/multiple order/achromatic optical waveplate have locking screws. Note that the focus ring is not used to adjust the focal length, but to adjust the image distance to ensure that the clear image falls on the focal plane. Common optical lens parameters: focal length Focal length is a commonly used parameter for lenses. The lenses used in our packaging inspection series are available in 3.5mm, 4mm, 6mm, 8mm, 12mm and other specifications (1/3mm CCD standard lens is 8mm). Use a 28mm wide-angle lens (the standard lens of the line scan camera is about 40mm). The smaller the focal length, the better the lens, the higher the price, the more the edge deformation and other problems, so try to use the standard lens, the cost is higher. Common lens parameters: aperture Aperture is a device for controlling the amount of light that passes through the lens and enters the photosensitive surface of the body. Aperture f value = focal length of the lens / diameter of the lens aperture According to the formula, the smaller the aperture f value, the more the amount of light entering the same unit time. The aperture of each level is generally multiplied, for example, f8 is adjusted to f5.6, and the amount of light is doubled. The smaller the aperture, the larger the depth of field Increase the depth of field In our products, it is often required to increase the depth of field. For example, in the machine, the tobacco leaves are not completely in the same plane. Only by increasing the depth of field can the leaves at different distances be clear. Increasing the depth of field is only achieved by reducing the aperture, while reducing the aperture will also cause the image to darken, which requires an increase in illumination brightness. Common high precision optical waveplate parameters: resolution The lens resolution refers to the logarithm of black and white lines that can be distinguished within 1 mm of the image plane, in units of “pairs/mm”. The computar MP0814-MP lens on the strip detector is a megapixel lens with a resolution of 100 line pairs/mm. This resolution is higher. In fact, in addition to visual measurement, in fact, our products generally do not use such a high resolution. The higher the resolution of the CCD chip, the higher the resolution of the required lens. Common lens parameters: deformation rate The definition of deformation rate: two negative films, one is the negative film taken by the lens (the negative film 1), and the other is the standard negative film without negative film (the negative film 2). The two negative films have the same framing, the center is strictly consistent, first in the Determine the distance from the center point of the film (distance 1) on the film 1, then find the corresponding point on the film 2, and measure the distance from the point to the center point (distance 2), then: (distance 1 - distance 2) /distance 2 *100% All high-quality laser grade optical waveplate have deformation phenomena. They can be tested with a grid line template. In general, the lens with a shorter focal length has a higher deformation rate and a deformation rate of less than 2%. C interface: the lens reference plane to the focal plane (that is, the CCD target surface) is 17.526mm CS interface: the lens reference plane to the focal plane (that is, the CCD target surface) is 12.5mm Note: How the mechanical design determines the focal plane (that is, the CCD target surface) is generally 12.5mm or 17.526mm from the camera lens interface (depending on the camera interface type) Check the CCD manual to get the target size and position, and draw the position of the target on the CAD drawing. Find the center of the lens from the front of the target facing the front f (the focal length of the lens, for example 35mm) Connect to get the CCD's field of view If the field of view does not meet the requirements, you can achieve the goal by replacing lenses with different focal lengths. If the space of the video cabinet is not enough, you can use the mirror to adjust the actual position of the camera. When making the picture, you can use the mirror as the mirror for the central axis. Both ends of the mirror should extend beyond the ends of the field of view to ensure that the field of view is full of mirrors. The camera can't appear in the angle of view, otherwise it will block the camera's field of view. The mirror should not face upwards, otherwise it will be easy to fall. If it is necessary to face up, you must make a cover to seal the camera and mirror in the same closed body.|
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