Difference between area scan camera and line scan camera

There are different types of cameras used for visual inspection imaging. Select the most suitable camera according to the shape and material of the object to be imaged, the type of abnormality you want to detect (scratches, dents, dirt, etc.). There are many points to consider, such as whether to use color or monochrome, and what the resolution should be. The camera used for visual inspection is either an area scan camera (hereinafter “area camera”) or a line scan camera (hereinafter “line camera”). What are the characteristics of each?

Area camera features

An area camera is a camera that captures an object as a “face”. This is the most commonly used camera. Compared to line cameras, it is cheaper and easier to set up and install, making it a versatile camera. However, the following precautions are required.

  • Since the imaging range is limited, it is not suitable for imaging large objects.
  • Since it is necessary to illuminate the entire imaging surface evenly, prevent uneven illumination.

Line camera features

Next, a line camera is a camera that captures an object as a “line”. Images are taken while moving the object, and the images taken with lines are joined together to create a single image. It’s easier to imagine how the light of a machine moves back and forth and left and right to scan with a copier or scanner. Line cameras are suitable for imaging cylindrical or sheet-shaped objects

In order to image a cylindrical object with an area camera, it is necessary to prepare multiple cameras so as to surround the object, and if the object is to be imaged while rotating, the joints of the images and It is not realistic to actually take a columnar image with an area camera, such as uneven lighting.

On the other hand, with a line camera, you can capture an object while rotating it to capture it in a single image.
In addition, a line camera can capture large objects such as long sheets that cannot be accommodated by an area camera.

Illumination unevenness, which has been a problem with area cameras, can be easily dealt with line scan lenses.
With an area camera, you need to illuminate the entire surface you want to capture, but with a line camera, you only need to illuminate the line you are trying to capture. Since the area to be illuminated is small, the difficulty of illuminating is relatively low, and it is easy to illuminate evenly. Uniform lighting is especially important for visual inspection.

With a line camera, it is necessary to keep the moving speed of the object constant. This is because the image will stretch or shrink as the speed changes.

Camera resolution

There are two cameras here.

・ Area camera with 5 million pixels
・ Line camera with 4K pixels (4K pixels is 4096 pixels)

Which is the higher definition camera? The answer is “4K pixel line camera”.

When expressing the resolution of a camera, the area camera is expressed by the number of pixels in the area of ​​”vertical (H) x horizontal (V)”, while the line camera is expressed by the number of pixels of the line. 

The number of pixels in the horizontal direction of the line camera is optional because it depends on the imaging width, although there are restrictions depending on the product. Assuming that the image is taken in the horizontal direction to the same extent as the area camera, the number of pixels in the area exceeds that of the area camera.

In addition, it seems that line cameras often have higher definition products than area cameras. For example, a line camera is suitable when you want to perform high-precision imaging to inspect very small scratches.

In the case of line sensor cameras, the sensor length is relatively long, so it is common to use
Nikon’s F mount or Pentax’s K mount. (There are more F mounts)

Since these are lenses for 35mm film lenses, they can be used with cameras with sensor lengths up to 43mm.
In addition, in order to fix the lens so that there is less play, M42 screw mounts may be used, or if the
sensor length exceeds 43 mm, M42 and M72 screw mounts may be used. 

Camera output

Camera data output includes CoaXP Ress, CameraLink and digital and analog. Currently, analog is used for low-speed low-resolution cameras, and CameraLink is used for high-speed and high-resolution cameras, but since the camera link cable is a standard product, the cable length can be 1, 2, 5, 7, 10, or 15m. Also, please note that the cable length that can be used may be limited when it comes to line sensor cameras with high data rates.

Summary

When selecting a camera, consider lighting and image processing. If you increase the shooting resolution and scan rate unnecessarily, you will need an expensive camera, lens, lighting, and image input board, so total balance is important.

There are different types of cameras used for visual inspection imaging. Select the most suitable camera according to the shape and material of the object to be imaged, the type of abnormality you want to detect (scratches, dents, dirt, etc.). There are many points to consider, such as whether to use color or monochrome, and what the resolution should be. The camera used for visual inspection is either an area scan camera (hereinafter “area camera”) or a line scan camera (hereinafter “line camera”). What are the characteristics of each?

 

Area camera features

 

An area camera is a camera that captures an object as a “face”. This is the most commonly used camera. Compared to line cameras, it is cheaper and easier to set up and install, making it a versatile camera. However, the following precautions are required.

 

  • Since the imaging range is limited, it is not suitable for imaging large objects.
  • Since it is necessary to illuminate the entire imaging surface evenly, prevent uneven illumination.

 

Line camera features

 

Next, a line camera is a camera that captures an object as a “line”. Images are taken while moving the object, and the images taken with lines are joined together to create a single image. It’s easier to imagine how the light of a machine moves back and forth and left and right to scan with a copier or scanner. Line cameras are suitable for imaging cylindrical or sheet-shaped objects

 

In order to image a cylindrical object with an area camera, it is necessary to prepare multiple cameras so as to surround the object, and if the object is to be imaged while rotating, the joints of the images and It is not realistic to actually take a columnar image with an area camera, such as uneven lighting.

 

On the other hand, with a line camera, you can capture an object while rotating it to capture it in a single image.
In addition, a line camera can capture large objects such as long sheets that cannot be accommodated by an area camera.

 

Illumination unevenness, which has been a problem with area cameras, can be easily dealt with line scan lenses.
With an area camera, you need to illuminate the entire surface you want to capture, but with a line camera, you only need to illuminate the line you are trying to capture. Since the area to be illuminated is small, the difficulty of illuminating is relatively low, and it is easy to illuminate evenly. Uniform lighting is especially important for visual inspection.

 

With a line camera, it is necessary to keep the moving speed of the object constant. This is because the image will stretch or shrink as the speed changes.

 

Camera resolution

 

There are two cameras here.

 

・ Area camera with 5 million pixels
・ Line camera with 4K pixels (4K pixels is 4096 pixels)

 

Which is the higher definition camera? The answer is “4K pixel line camera”.

When expressing the resolution of a camera, the area camera is expressed by the number of pixels in the area of ​​”vertical (H) x horizontal (V)”, while the line camera is expressed by the number of pixels of the line. 

 

The number of pixels in the horizontal direction of the line camera is optional because it depends on the imaging width, although there are restrictions depending on the product. Assuming that the image is taken in the horizontal direction to the same extent as the area camera, the number of pixels in the area exceeds that of the area camera.

 

In addition, it seems that line cameras often have higher definition products than area cameras. For example, a line camera is suitable when you want to perform high-precision imaging to inspect very small scratches.

 

In the case of line sensor cameras, the sensor length is relatively long, so it is common to use
Nikon’s F mount or Pentax’s K mount. (There are more F mounts)

 

Since these are lenses for 35mm film lenses, they can be used with cameras with sensor lengths up to 43mm.
In addition, in order to fix the lens so that there is less play, M42 screw mounts may be used, or if the
sensor length exceeds 43 mm, M42 and M72 screw mounts may be used. 

 

Camera output

 

Camera data output includes CoaXP Ress, CameraLink and digital and analog. Currently, analog is used for low-speed low-resolution cameras, and CameraLink is used for high-speed and high-resolution cameras, but since the camera link cable is a standard product, the cable length can be 1, 2, 5, 7, 10, or 15m. Also, please note that the cable length that can be used may be limited when it comes to line sensor cameras with high data rates.

 

Summary

 

When selecting a camera, consider lighting and image processing. If you increase the shooting resolution and scan rate unnecessarily, you will need an expensive camera, lens, lighting, and image input board, so total balance is important.

Related Posts

Leave a Reply

Your email address will not be published. Required fields are marked *