How does TDI Line Scan Camera Work?

How Does TDI Line Scan Camera Work?

TDI camera is a line scan camera with Time Delay and Integration technology. The Time Delay and Integration technology is a technology that takes multiple shots of an area and overlaps multiple image data to create a single image.

If you create an image with multiple image data like this, you can take bright and clear images even in a dark environment. This is because the signals of one area are obtained multiple times and overlapped. Its representative feature is that it can take bright and clear images even in dark environments by applying TDI technology.

Image Quality Comparison of Single Line Scan Camera vs TDI CamerasComparison of the quality of images taken with a single line scan camera (left) VS TDI cameras (right). The image on the right is brighter and clearer (same condition).

The image sensor of the camera is composed of several stages, and the stages are used to accumulate signals as shown in the figure below. It is easy to understand if you think that one stage plays a role similar to that of a single line scan sensor.Operating Principle of a TDI Line Scan Camera

[ Operating principle of TDI camera ]
TDI Line Scan sensor consists of several stages. The target moves at a constant speed and is positioned from the shooting area of ​​the first stage to the shooting area of ​​the last stage. The camera shoots the same target at every stage and accumulates the signals output at every stage. Finally, the camera outputs the accumulated shooting signals as many as the number of stages.

The target is positioned in the shooting area of ​​the first stage. The camera shoots the target and accumulates the signal output from the first stage. When the target moves into the shooting area of ​​the second stage, the camera shoots the target and then adds the signal output from the second stage to the signal output from the first stage. In this way, the target moves from the first stage to the last stage, and the camera shoots as many targets as there are stages to accumulate signals.

For example, assuming that the number of stages is 10, when the accumulation of signals output from the 10th stage is completed, the camera creates an image using the accumulated signals. The accumulated signal from 10 stages becomes 1 line image.

The final image has a sensitivity that is twice as high as the number of stages compared to the image created with one shot. An image taken with a TDI line scan camera with 10 stages has 10 times better sensitivity than an image taken with a single line scan camera.

※ Vieworks TDI line scan camera provides up to 256 stages.

A TDI sensor consists of several stages. A camera with a sensor overlaps image signals output from each stage to create one image. The sensitivity of the images taken by the TDI line scan camera is superior to that of the images taken by the single line scan camera by a factor of the number of stages.

When and under what circumstances is it necessary to deploy TDI line scan camera?

When using a single line scan camera, the exposure time of the camera is short and it does not receive much light, making it difficult to obtain clear images. On the other hand , TDI cameras have the best advantage of obtaining bright and clear images even in low light conditions and short exposure times .

What to look for when choosing a camera

The representative three specifications are  the number of stages ,  line rate , and  the type of sensor . The better these three specifications are, the higher the performance of the TDI camera.

  1. ​Number of Stages: The greater the number of stages, the better the sensitivity.
  2. Line rate: The unit is Line per second, which means the number of line images output per second. Just as the frame rate in an area scan camera indicates the camera's output speed, in a line scan camera, the line rate indicates the camera's output speed. If the line rate is high, images can be captured at high speed and the takt time of the process can be reduced.
  3. Type of sensor: There are CMOS and CCD as general TDI line scan sensor types, and there is a hybrid sensor that combines the advantages of the two. CMOS sensors are faster, but have more noise than CCD sensors. Conversely, CCD sensors are relatively quiet and slow. Hybrid sensors are fast (advantages of CMOS sensors) and low noise (advantages of CCD sensors).

Vieworks applies the world's first Hybrid TDI Sensor

Vieworks Hybrid TDI Line Scan Cameras

Vieworks applied Hybrid technology for the first time in the world and launched Hybrid TDI camera in 2016. It offers models with various resolutions from 3K to 23K and supports GigE, Camera Link, and CoaXPress interfaces.

Features of Vieworks Hybrid TDI Line Scan Camera

  • 256 Stages- Provides 256 times higher sensitivity than Single Line Scan cameras.
  • Line speeds of up to 250 KHz– Significantly reduce process times.
  • Application of Hybrid TDI Sensor– By combining the strengths of CCD and CMOS , images are transmitted quickly with less noise.

Learn more about Vieworks Hybrid TDI Line Scan Camera or contact us about your thermal application needs.


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