How much do you know about industrial lenses?

01. Basic principles of lenses

      His basic imaging principle: In building an image processing environment, we often need to collect the light reflected by the target object and obtain high-quality images through a camera. So the device that collects light is the lens. 

What are the characteristics of light passing through a convex lens?

     1. Light parallel to the optical axis undergoes refraction and passes through the focal point.

     2. The light passing through the center of the convex lens will maintain its original direction of travel.

     3. The light entering the convex lens through the focal point is refracted and travels parallel to the optical axis.

     The imaging law of convex lens is that an object placed outside the focal point forms an inverted real image on the other side of the convex lens. The real image can be divided into three types: reduction, equal size, and enlargement. It has a converging effect on light and is an optical law. The image that can be presented on a light screen is called a real image.When using CCD for shooting observation, a real image can be mapped onto the CCD target surface.

02. Types of commonly used lenses

     CCTV lens, also known as C-mount industrial lens, is a widely used industrial lens in machine vision systems. It has the advantages of light weight, small size, low cost, and wide variety. Its interface rib parameters are: nominal diameter=1 ", pitch: 32 teeth.

     A variation interface for C installation, which differs from C-MOUNT only in the distance between the positioning surface of the industrial lens and the photosensitive surface of the image sensor. C-MOUNT is 17.5mm, but 12.5mm, with a difference of 5mm between them. Industrial lens products on the market, such as the ZML series small zoom industrial lens, all use standard C interfaces.

    He interface is designed for new CCDs, and with the development of CCDs, the integration level is increasing. The photosensitive array with the same resolution is smaller, making it more suitable for industrial cameras with smaller effective photosensitive sensor sizes. Industrial cameras with CS interfaces can be connected to both C and CS type interfaces, but installing industrial lenses with C requires the addition of a connecting ring; Industrial cameras with a C interface can only be connected to C-mount industrial lenses, and cannot be connected to CS mount industrial lenses. Otherwise, not only can they not achieve good focusing, but they may also damage the CCD target surface.

    Telecentric lens is designed to correct the parallax of traditional lenses. It can maintain the magnification of the obtained image within a certain range of object distance without changing. In simple terms, the images captured by this lens do not have a near far relationship. The telecentric lens is divided into object side telecentric lens, image side telecentric lens, and bilateral telecentric lens.

    1）. The object side telecentric optical path is a method of placing an aperture stop on the image focal plane of an optical system, with the object side principal ray parallel to the optical axis and the convergence center of the object side principal ray located at infinity, known as the object side telecentric optical path. Its function is to eliminate reading errors caused by inaccurate focusing of the object.

    2）. The image side telecentric optical path is a method of placing an aperture stop on the object side focal plane of an optical system, with the convergence center of the image side principal ray parallel to the optical axis located infinitely far from the image side, known as the image side telecentric optical path. Its function is to eliminate measurement errors caused by inaccurate focusing of the image.

    3）. Bilateral telecentric lenses combine the advantages of both types of telecentric lenses mentioned above. In industrial image processing, only the object side telecentric lens is generally used. Occasionally, there are also those who use dual telephoto lenses (of course, at a higher price). In the field of industrial image processing/machine vision, lenses like Fangyuanxin generally do not work, so they are basically not used in this industry.

     Advantages of ordinary lenses: low cost, practical, and versatile.

     isadvantages of ordinary lenses: there may be changes in magnification and parallax.

     Ordinary lens application: imaging large objects.

     The advantages of a telephoto lens are: constant magnification, no variation with depth of field, and no parallax.

     Disadvantages of telecentric lenses: high cost, large size, and heavy weight.

     The application of telecentric lenses: in terms of measurement, based on CCD measurement, microcrystals.