Automated inspection by image sensors

by lyonOP

For automated inspection, 100% inspection is desirable from the viewpoint of quality assurance, and in recent years, the introduction of image sensors has been progressing. Here, we will introduce the basic knowledge of image sensors, advantages and disadvantages, differences from dedicated inspection devices, how to select peripheral devices such as lenses and lighting that accompany image sensors, and the advantages of automated optical inspection.

What is an image sensor?

In the automated optical inspection, the work recognized by the eyes is compared with the free sample and considered by the brain to judge the quality. The image processing system and image sensor replace the human eyes with a camera and the brain with a controller. The image sensor processes the data captured by the camera, outputs the position, angle, shape, dimensions, quantity, etc. of the object, and collates it with the registered data to make a pass / fail judgment. It is a system that performs inspections and automates instead of the process of making visual judgments by humans.

Advantages and disadvantages of image sensors

Image sensors are an effective way to automated inspection, which has traditionally relied on the human eye. However, if you introduce it without understanding the advantages and disadvantages, you will end up in a situation where the expected effect was not obtained. Therefore, we will introduce some of the advantages and disadvantages of image sensors. In addition to the contents described below, there are various merits such as reduction of labor costs, stable operation 24 hours a day, speeding up of inspection, high versatility, prevention of human error, etc. Let’s introduce it to.


It is possible to distinguish minute foreign substances, scratches, and defects.
Conventional cameras have a small number of pixels, making it difficult to identify minute defects. However, with the development of cameras and image processing technology, it is possible to detect minute changes that required a magnifying glass or microscope, which is difficult to see with the naked eye in recent years. Keyence’s image sensors include a lineup of high-pixel cameras, including the 21-megapixel camera, which has the largest number of pixels in its class, and can be used to inspect foreign objects and scratches that are difficult to detect visually.

Achieves 100% inspection

Visual inspection is generally done offline. However, by utilizing an image sensor, it is possible to accurately inspect foreign matter, scratches, and defects in-line. It is efficient because inspection can be performed while the line is in operation.


Initial cost is required. Compared to visual inspection, initial development cost and installation cost are required, and when performing in-line inspection, it is necessary to review the line design, so initial cost is required.

Difference between image sensor and dedicated inspection device

In addition to image sensors, there are dedicated inspection devices as methods for automated inspection. Both have the same purpose of automating inspection, realizing in-line inspection, and reducing the labor and time of the inspection process. However, each has its advantages and disadvantages.

Dedicated inspection equipment is specialized for inspection, so it is natural that it meets the specifications required for visual inspection. However, it has the disadvantage of being expensive and less versatile. On the other hand, the image sensor is highly versatile and can flexibly respond to changes in line design as well as changes in specifications of parts and products. The advantage is that it can be used not only for visual inspection but also for a wide range of applications such as dimensional measurement, quantity counting, positioning and transportation in combination with industrial robots. Therefore, I bought an expensive dedicated inspection device, but I don’t have to worry about it being wasted because it cannot be used due to specification changes.

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