Image processing: optical inspection equipment

optical inspection equipment

Fine surface check of products that takes time even in the inspection process. By introducing optical inspection equipment, it is possible to work accurately and at high speed, and productivity improvement can be expected.

On the other hand, many people may be wondering, “Can optical inspection equipment perform accurate inspections?” And “How to choose optical inspection equipment?”

In this article, we will introduce the mechanism of optical inspection equipment, how to select it, recommended manufacturers, etc. for those who have such questions. Please use it as a reference.

What is an optical inspection equipment?

What is an optical inspection device? What is the difference between various inspection equipment and other inspection equipment? Here, we will introduce what kind of optical inspection equipment is.

You can get an overview of optical inspection equipment. Let’s take a look.

Optical inspection equipment can check even the finest surface conditions.

Optical inspection equipment refers to equipment that uses optical equipment for inspection. An optical device is a device that uses the reflection and wavelength of light to check even the finest surface conditions that are normally difficult to recognize.

Rather than relying on the visual and tactile sensations of experts, it is possible to quantitatively inspect small scratches and foreign matter without omission.

Optical equipment illuminates the inspection area of ​​the product and takes a picture with a camera. After that, automated inspection is performed to judge whether the product is good or bad.

Application examples of optical inspection equipment

Here, we will introduce the applications of optical inspection equipment.

Wafer defect inspection

Optical inspection equipment is used to inspect semiconductor wafers.

The circuit patterns of semiconductor devices are becoming finer, and the size of defects to be detected is becoming smaller. In wafer defect inspection, it is necessary to inspect not only foreign matter but also chips, scratches, distortion, and misalignment during pattern transfer.

Optical inspection equipment irradiates a wafer with a laser beam, detects the position of foreign matter by its bounce, and analyzes and evaluates defects in the wafer.

Product surface inspection

Optical inspection equipment is also useful for surface inspection of products.

For surface inspection of products, it is difficult to judge whether they are good or bad, and it is necessary to confirm by a skilled person. It takes time to train and secure skilled workers, and many companies are suffering from labor shortages.

Optical inspection equipment is capable of high-speed inspection while maintaining inspection accuracy that replaces the eyes of experts.

Even if you are an expert, you will start to feel tired over time because you are a person. If you do so, the accuracy and speed of the inspection will inevitably slow down.
The above problems can be solved by introducing optical inspection equipment.

Mechanism of optical inspection equipment

Optical inspection equipment irradiates the inspection target with light and identifies foreign matter and defects from the information of the reflected light.

The degree of light reflection is captured by the camera and detected by automated inspection. The camera plays the same role as the human eye. Automated inspection is the brain. It realizes highly accurate inspection results in a shorter time than conventional visual inspections and micro inspections.

There are various reflection methods such as transmission method, indirect transmission method, diffuse reflection method, specular reflection method, etc., and select the appropriate method according to the shape of the defect you want to detect.

How to choose optical inspection equipment?

You may want to select the most suitable equipment from among the many optical inspection equipment. There are several points to consider when choosing the right optical inspection equipment for your work.

Here are two ways to choose an optical inspection device.

  • camera
  • illumination


The first way to choose an optical inspection device is a camera.

Since the camera plays the role of the human eye, it is necessary to select the appropriate camera type according to the intended use. The types of cameras are divided into the following methods according to the imaging method and color.

Image capture method

  • Area camera: Can take a two-dimensional rectangular image. Digital cameras, mobile cameras, etc.
  • Line camera: Can take one-dimensional images. Copier etc.

Area cameras are good for shooting large or long products, while line sensors are good for inspecting continuous products at high speeds.

Therefore, line sensors are frequently used to inspect industrial products and processed products, and detect damage and pinholes. Area cameras, on the other hand, are used for surveillance, medical care, traffic, security, etc. because they can capture the same image.

Therefore, if you are thinking of introducing a camera for optical inspection equipment, we recommend the line camera.


  • Monochrome camera: Can take black and white images
  • Color camera: Can take colorful images with a large amount of data

Monochrome cameras are superior to color cameras in terms of resolution and speed. A monochrome camera is sufficient if you only need to identify “scratches” or “chips” on the surface of the product.

However, if you need to determine the difference in brightness, you should use a color camera. The subtle differences in color are difficult to distinguish with a monochrome camera.

For example, the ripeness of fruits must be determined with a color camera.


The second way to choose an optical inspection device is lighting.

Even if you say lighting in a nutshell, you can make a difference in how the image remains when it is captured in the image by changing the type of lighting. If the images are different, it will greatly affect the pass / fail judgment when performing automated inspection.

There are three points to choose lighting.

  • Irradiation method: Select an appropriate irradiation method according to the surface shape of the product.
  • Illumination color: Determines which part of the product you want to emphasize and leave as an image. It also depends on whether the detection point is white or black.
  • Illumination shape: Depends on the size of the detection point and the irradiation method

Lighting selection is an important item for stable detection and affects inspection performance, so be careful when selecting it.