#telecentric

https://www.canrilloptics.com/what-should-i-pay-attention-to-when-choosing-an-industrial-camera-lens.html

As a critical component of the machine vision system, the industrial camera is usually installed on the machine assembly line to replace human eyes to do measurement and judgment. Thus, choosing the right camera lens is also an essential part of machine vision system design. How should we choose the right industrial camera lens? What problems should be paid attention to when choosing an industrial camera lens? Let's learn about it.

 Basic Consideration Regarding Choosing Industrial Cameras Lens

 Choosing CCD or CMOS camera according to different applications

 The CCD industrial cameras lens is mainly used in the image extraction of moving objects. Of course, with CMOS technology development, the CMOS industrial camera is also applied for many chip mounters. The CCD industrial camera is widely used in vision automatic inspection. CMOS industrial cameras are widely used because of their low cost and low power consumption.

 Resolution of industrial cameras lens

 Firstly, by considering the object's accuracy to be observed or measured to select the resolution accordingly. If camera pixel accuracy = single direction field of view size/camera single direction resolution, then the camera's resolution in one direction = the size of the field of view in one direction / the theoretical accuracy.

 If the single field of view is 5mm and the theoretical accuracy is 0.02mm, the single direction resolution is 5 / 0.02 = 250. However, to increase the stability of the system, not only one-pixel unit is used to correspond to one measurement/observation accuracy value. Generally, multiple four or higher can be selected. In this way, the camera needs a single direction resolution of 1000 and 1.3 million pixels.

 Secondly, considering an industrial camera's output, high resolution is helpful for posture observation or machine software analysis and recognition. If it is the VGA or USB output, It should be observed on display; thus, it also depends on the resolution of the display. No matter how high the resolution of an industrial camera lens with industrial vision technology is, it isn't very meaningful if the resolution of the display is not enough. If you use the memory card or the photo-taking function, the high resolution of an industrial camera also helps.

 Camera frame number of industrial cameras lens

 When the measured object is moving, the industrial camera lens with high frame number should be selected. But generally speaking, the higher the resolution, the lower the number of frames.

 The match of the industrial lens

 The size of the sensor chip should be less than or equal to the lens size, and the C or CS-mount should also match.

 Additional Considerations over Choosing the Right Camera Lens

 C interface or CS interface. The interface distance of the C interface is 17.5mm, while that of the CS interface is 12.5mm. Only the right interface could lead to focus.

 Choosing a camera lens should also consider the size of the photosensitive device. For a 2/3-inch photosensitive chip, the industrial cameras lens corresponding to the imaging coil should be selected. If 1/3"or 1/2" is selected, there will be a large dark angle.

 Select the focal length; that is, select the industrial lens whose field of view is slightly larger than the observation range.

 Depth of field and light environment should match. For areas with enough light or light source illumination, a small aperture can be chosen to increase the depth of field, thereby improving the shooting clarity. Where there is not enough light, a slightly larger aperture or a sensitive chip with high sensitivity would be selected.

 Current Trends over Industrial Cameras Lens Choices

For choosing the right camera lens, here are several popular trends nowadays.

 Firstly, image sensors have made great strides in recent years. The trend is to have more and more pixels for better resolution of industrial cameras lens, as well as a greater sensitivity (backlight image sensor).

 What's more, the CCD technology becomes more efficient and now shares more and more features with CMOS technology sensors.

 In terms of communication interfaces, they transmit data faster and faster. The trend over the next few years will be to transmit data wirelessly, namely using Wifi.

https://www.canrilloptics.com/what-is-a-telecentric-lens.html

Industrial lenses are very important imaging components in machine vision systems. For the system to fully perform its functions, industrial lenses must meet the requirements. At the beginning of the 21st century, with the widespread application of machine vision systems in the field of precision inspection, it is difficult for ordinary industrial lenses to meet the inspection requirements. To make up for the shortcomings of ordinary lens applications and meet the needs of precision inspection, telecentric lenses came into being.

 Telecentric lens design is based on its unique optical characteristics: high resolution, ultra-wide depth of field, ultra-low distortion, and unique parallel light design, which brings a qualitative leap in precise machine vision inspection.

 Ⅰ. Industrial Telecentric Lens Definition

 Telecentric lens is mainly designed to correct the parallax of the traditional industry lens. It can be within a certain object distance range so that the image magnification will not change, which is suitable for the situation where the measured object is not on the same object surface. It is a very important application. Telecentric lenses have always been favored by machine vision applications that require high lens distortion due to their unique parallel optical path design.

 Industry Lens

 Ⅱ. Types of Industry Inspection Lens

 Generally, the industry lens with industrial vision technology consists of FA lens, Zoom lens and telecentric lens.  When the inspected object has serval surfaces or has angles with lens, or the object is moved up and down, or requires high precision and low distortion, the telecentric lens will be required.

 Ⅲ. Application Advantages Of Industrial Inspection Lens

 The telecentric industry lens of the telecentric optical system is mainly used for precision measurement. In the precision optical measurement system, due to the ordinary optical lens, there will be certain constraints, such as image distortion, errors caused by the choice of viewing angle, and boundary uncertainty caused by improper light source interference, which will affect the accuracy of measurement. The industrial inspection telecentric lens can effectively reduce or even eliminate the above-mentioned problems. Therefore, the industrial inspection lens has become a decisive component of a precision optical measurement system, and its application fields are becoming more and more extensive.

https://www.canrilloptics.com/what-are-the-classifications-of-telecentric-lenses.html

Ⅰ. The classifications of a telecentric lens

The telecentric lens types are mainly divided into the object-space telecentric lens, image-space telecentric lens and bi-telecentric lens.

 Ⅱ. Introduction of different telecentric lens types

1. Object space telecentric lens

 The object space telecentric lens places the aperture diaphragm on the image space focal plane of the optical system. When the aperture diaphragm is placed on the image-side focal plane, even if the object distance changes, the image distance also changes, but the image height does not change. There is no change, that is, the measured object size will not change. Object space telecentric lenses are used for industrial precision measurement, with minimal distortion, and high performance can achieve no distortion.

 2. Image-space telecentric lens

 The image space telecentric lens, by placing an aperture stop on the object focal plane, makes the chief ray of the image side parallel to the optical axis so that although the installation position of the CCD chip is changed, the projected image size on the CCD chip remains unchanged.

 3. Bi-telecentric lens

 The bi-telecentric lens combines the advantages of the above two telecentric lenses. In industrial image processing, generally, only object space telecentric industrial lenses are used. Sometimes there are telecentric lenses on both sides (of course the price is higher). In the field of industrial image processing/machine vision, the image space telecentric lens generally does not work, so this industry basically does not use it.

https://www.canrilloptics.com/what-are-the-accessories-of-the-machine-vision-system.html

1. Image processing system of machine vision system

Optical text, recognition system, automation/robot technology, infrared image system.

 2. Machine vision integration

Character processing and recognition system, automation/robot technology, infrared imaging system, tobacco, banknote printing, electronic assembly, quality inspection, automatic recognition (OCR/OCV), measurement, intelligent vision, surface inspection, printing, packaging, complex industrial object vision online, automobile manufacturing, license plate, biometric identification, medical testing, optical inspection and other systems.

 3. Machine vision technology

Machine vision technology is a high-tech system that integrates modern computer, optics, and electronic technologies. Machine vision technology uses a computer to process the images taken by the system, analyze the information in it, and make corresponding judgments, and then issue control instructions to the device.

 4. The specific application process of the machine vision system:

(1) Image acquisition uses a light source to illuminate the object or environment to be observed, acquires images through an optical imaging system, and converts optical images into digital images through cameras and image acquisition cards. This is the front end and information source of the machine vision system.

 (2) Image processing and analysis. The computer processes the image through image processing software and analyzes and obtains useful information. For example, whether there is a circuit break in the image of the PCB board, whether there is a defect in the image of the textile, and what text is in the image of the document, etc. This is the core of the entire machine vision system.

 (3) The machine vision program judges and controls the information obtained by image processing, and then uses it to judge the object (measured object, environment), and forms the corresponding control command, which is sent to the corresponding organization. For example, in the captured part image, calculate whether the size of the part is consistent with the standard, and if the part is inconsistent, an alarm will be issued, marking or rejection will be made.

 In the whole process, the information of the measured object is reflected as image information, and then after analysis, the characteristic description information is obtained from it, and then judgments and actions are made according to the obtained characteristics.

 A typical telecentric lens machine vision system generally includes: a light source, an optical imaging system, a camera, an image capture card, an image processing hardware platform, an image and visual information processing software, and a communication module.

 In general, a successful machine vision solution needs to focus on the key technologies of image acquisition (including light source, optical imaging, digital image acquisition and transmission), image processing and analysis.

 The machine vision optics system is a highly integrated system of opto-electromechanical computers, and its performance is not only determined by a certain link. Every link is perfect, and it does not necessarily mean that the final performance is satisfactory. System analysis and design is the difficulty and foundation of machine vision system development, and it is also something that many developers are not good at, and urgently need to be strengthened.

https://www.canrilloptics.com/the-advantages-of-machine-vision-system.html

1. The high social benefits of machine vision system

 The main benefits of machine vision to society are: saving time; reducing production costs; improving productivity and product quality; reducing the labor intensity of testing and inspection personnel; reducing the number of unqualified products; improving machine utilization and so on.

 2. The strong peripheral advantages of machine vision system

 The history of the development of automation technology is the history of machines gradually replacing humans. The human brain, limbs, senses, and nerves correspond to CPU, motion control, sensors and networks respectively. However, in many cases, human vision is increasingly unable to meet the requirements. Compared with human vision, machine vision has the advantages of high speed, high precision, supervision, macrospur, objectiveness, no fatigue, and environmental restriction.

 3. The wide applications of machine vision system

 The advanced machine vision system is often used for measurement, inspection (such as presence detection, defective product detection, digital statistics, defect detection), positioning, identification (such as code reading, color recognition), etc.

 Founded in 2009, Shenzhen Canrill Technologies Co., Ltd is the first company in China to focus on the design, manufacturing and marketing of telecentric lenses. It is also the only company that has its own mechanical factory and optical factory in the entire industrial lens industry to build a complete supply chain. If necessary, please consult us.

https://www.canrilloptics.com/selection-method-of-telecentric-lens.html

The industrial lens is an important part of the machine vision acquisition system. As a relatively young member of the lens family, the telecentric camera lens selection is becoming more popular with its unique performance.

 To know how to make a telecentric lens, you must first understand the telecentric lens's basic knowledge, from its operation principles, applications, to its type selection, and other aspects.

 However, since the telecentric lens has not been introduced for a long time, many of its characteristics have not been widely known. This article will comprehensively review the telecentric lens and reveal the mysterious journey of light in the telecentric system.

 Part one: Explanation of the working principle of the telecentric lens

First, we would start with several problems about the non-telecentric lens.

 The first problem is that in the imaging process when the working distance of the lens changes, the size of the image would change accordingly. As a result, the lens with the same focal length would have different magnifications for different working distances. This phenomenon is similar to the visual aberration of the human visual system; if you look at things near you, they are more significant than things far away. This problem can be ignored or even utilized in some applications. However, This problem can also be a significant obstacle when our vision system performs precision measurement.

 The second problem is that ordinary lenses usually have a specific range of depth of field. When the measured object is not covered by the depth of the lens's field, the image would become blurred and cannot be focused clearly. Therefore, designers have designed a focusing ring on the ordinary lens. When the working distance changes, the interesting region can be seen clearly by adjusting the focal plane. If the depth of the measured object itself exceeds a specific range, both ends of the objects cannot be seen by the lens simultaneously. Thus, to solve this problem, we have to find other methods.

 The third problem is that with the continuous improvement of imaging chips' resolution, users have more stringent requirements on measurement accuracy. As ordinary lenses are subject to the principle of optical imaging, the lens can only achieve the best measurement accuracy of about 10um. In the field of visual inspection, imaging products with higher accuracy are needed.

 A double telecentric lens is designed to solve these problems. By placing an aperture in the middle of the optical system, the leading light could pass through the center of the aperture. Then the leading light of the object side and the imaging side could enter the lens parallel to the optical axis. The parallel incident light ensures a large enough range of depth of field. Also, the parallel light from the lens ensures that even if the working distance changes significantly within the range of field depth, the imaging height, i.e., the magnification, would not change.

 Part two: Applications of the telecentric lens

When should a machine vision telecentric lens be used? We suggest that the double telecentric lens can be chosen in the following situation.

 When the object is too thick, and more than one plane needs to be measured, such as food boxes, beverage bottles, etc.

 When the object's defects need to be measured, while they can only be measured under parallel illumination in the same direction.

 When necessary to ensure the measurement accuracy; for example, when the allowable error is 1 um.

 When the object has an aperture or is three-dimensional.

 When the low distortion rate and the brightness of the image effect are required to be almost the same.

 When the measured object's position is uncertain but maybe at a certain angle with the lens.

 When the object jumps up and down in the measurement process, such as the production line's vibration leading to the change of the working distance.

 Part three: Type selection of the telecentric lens

 The type selection method of the telecentric lens machine vision is similar to that of the ordinary optical system. The following points should be paid attention to:

 Compatible CCD target surface size

 As the selection of ordinary lens, the CCD target surface compatible with the telecentric lens must be greater than or equal to the matching camera target surface; otherwise, the resolution would be wasted.

 Interface type

 At present, the interface type of telecentric lens is similar to that of the ordinary lens, including C port and F port, which can be used as long as it is matched with the camera.

 Magnification, or imaging range

 When the magnification and CCD target surface is determined, the imaging range is determined, and vice versa.

 Working distance

 Generally, when the above three points are specified, the working distance has also been determined within a specific range, which is determined by the optical imaging path. It should be noted whether the working distance meets the actual requirements. When using the telecentric system for measurement, we suggest that the lens be selected first, and other mechanical structures should be designed according to its working distance.

 Range of the depth of field

 If the conditions above are satisfied, the larger the depth of field, the better the far center system's optical characteristics, which can be used as a reference in the selection of the system.