Imager is also called optical image measuring instrument and image precision mapping instrument. Optical image measuring instrument is a qualitative leap on the basis of measuring projector, which promotes industrial measurement mode from traditional optical projection alignment to computer screen measurement based on digital image era. It is worth mentioning that there is a transitional product of digital display screen and computer on the market at present. Strictly speaking, this kind of equipment that only uses computer as aiming tool is not an image measuring instrument, but can only be called "image measuring projector" or "image aiming projector". In other words, the image measuring instrument is based on computer screen measuring technology and powerful space geometry calculation software. Image measuring instrument is divided into digital image measuring instrument (also known as CNC image measuring instrument) and handheld image measuring instrument. The difference between them is mainly manifested in the following aspects: 1. What to do with digital technology: the operation of hand-held image measuring instrument in measuring the distance between point A and point B is as follows: first, shake the handle in X and Y directions to aim at point A, then lock the platform, change hands and operate the computer and click the mouse to confirm; Open the platform again, point your finger at point B, and repeat the above actions to determine point B. Every time you click the mouse, you should read the displacement value of the optical ruler at this point into the computer, and the calculation function can only be operated after all the values of this point are read in. This first-class equipment is like a technical "building block platter", and all functions and operations are separated; Shake the handle for a while and click the mouse for a while. When shaking hands, you should also pay attention to uniformity, light and slow, and you can't turn; Usually, a simple distance measurement by a skilled operator takes several minutes. Digital image measuring instrument is different. Based on micron-scale precision numerical control hardware and humanized operation software, it completely integrates various functions, thus becoming a truly modern precision instrument. Have the basic abilities of stepless speed change, gentle movement, research and operation of enterprise production points, electronic locking, synchronous reading and so on; After the mouse moves to find the points A and B you want to measure, the computer will help you calculate the measurement results and display graphics for verification. Images and shadows are synchronized, and even beginners can measure the distance between two points in just a few seconds. Second, the digital technology has realized the arbitrary placement of the workpiece: when the hand-held image measuring instrument carries out the reference measurement, it needs to rotate the indexing plate on the object platform and adjust the reference edge of the part to the coordinate axis parallel to the platform, because its primary software cannot support the extremely complicated spatial geometric transformation. Digital image measuring instrument can use software technology to complete the rotation of spatial coordinate system and the complex transformation between multiple coordinate systems. The measured workpiece can be placed at will, the coordinate origin and reference square can be established at will, the production direction of the enterprise can be studied and the measured value can be obtained. At the same time, by displaying marks on the screen, the coordinate direction and measuring points can be seen intuitively, which makes the most common reference distance measurement very simple and intuitive. Since then, the product of the mechanical age-the indexing plate, together with the crank, has become history. Thirdly, digital technology realizes real-time error correction: in the process of finding the target point and measuring the displacement, manual operation will cause certain deviation of the main and auxiliary guide rails of the mobile platform, and continuous back-and-forth movement will also produce return clearance. In micron-scale accurate measurement, it will directly affect the measurement accuracy of enterprise production. The digital image measuring instrument has the ability of motion locking, and the design adopts the technology of no return error, thus completely eliminating these errors and improving the stability of motion and measuring accuracy. The longer the measuring distance, the greater the error and the lower the measuring accuracy with the length. Hand-held image measuring instrument does not have nonlinear real-time correction function, and can not eliminate nonlinear errors caused by environmental factors such as temperature and vibration. Digital image measuring instrument has excellent error correction ability in enterprise production. Based on strict mathematical model, it is corrected by software calculation and real-time control, so as to minimize nonlinear error, improve measurement accuracy and break through the technical bottleneck of speed and accuracy. Fourth, digital technology can be used for rapid measurement by numerical control: when measuring the same workpiece in batches, the hand-held image measuring instrument needs to be manually moved one by one, sometimes it needs to shake tens of thousands of turns a day, and only dozens of complex workpieces can be measured, so the work efficiency is low. Digital image measuring instrument can establish numerical control coordinate data through sample measurement, drawing calculation and numerical control data import. The instrument can automatically move to the target point one by one to complete various measurement operations, saving manpower and improving efficiency. Under the working ability of hand-held image measuring instrument, the operator is relaxed and efficient.