Implementing Back-Side Illuminated Sensor (BSI) in High-Speed Applications


Implementing Back-Side Illuminated Sensor (BSI) in High-Speed Applications

At speeds surpassing 1 million frames per second, high-speed imaging serves as an invaluable tool for research, capturing even the most fleeting occurrences in scientific and engineering domains. However, attaining such speed entails trade-offs. Most high-speed cameras are engineered to balance gigapixel-per-second (Gpx/sec) throughput against frame rate and resolution. For instance, a camera operating at 25 Gpx/sec achieves 25,700 frames per second (fps) with a resolution of 1280 x 800 pixels, while it can hit a higher frame rate of 28,500 fps at a reduced resolution of 1280 x 720. Despite different resolutions, both setups offer similar throughput. Extremely high frame rates, like 1 million fps, correspond to significantly smaller resolutions, posing challenges in visualizing subject matters.

As frame rates rise, the duration each pixel is exposed to light decreases. At 25,700 frames per second, each frame allows a maximum exposure of 39 microseconds (μs), while at 1 million frames per second, the maximum exposure time reduces dramatically to just 733 nanoseconds (ns). These brief exposure periods necessitate intense levels of illumination to compensate for the limited time the pixel receives light. Consequently, many high-speed applications suffer from insufficient light—a condition known as being "light-starved." This condition arises due to the extremely short exposure times at high frame rates, where the available illumination fails to provide adequate light to the camera's imaging sensor, resulting in less-than-ideal images and presenting practical challenges in certain applications.

High Speed & High Sensitivity 9k TDI Line Scan Camera with Charge-domain BSI Image SensorBSI Image Sensor

The latest VT-9K5X2-H550I-256 camera, utilizing a new Time Delayed Integration (TDI) line scan camera system paired with a Back-Side Illuminated (BSI) image sensor through charge-domain CMOS technology, offers superior line rates and heightened sensitivity compared to existing TDI line scan cameras.

Main Features
• 9k TDI, BSI(Back-Side Illuminated), Charge-domain CMOS
• CoaXPress Interface up to 543 kHz at 50 Gbps using 4 CH
• Bidirectional Operation with up to 256 TDI Stages in a Single Band, or 32 TDI Stages in a Dual Band
• Advanced DSNU and PRNU Correction
• Strobe Output Control
• GenICam Compatible - XML based Control

Unlike Front Side Illumination (FSI), the BSI variant significantly improves quantum efficiency in the near ultraviolet and visible spectra while elevating the signal-to-noise ratio, particularly beneficial for imaging in low-light scenarios.

Front Side IlluminationFigure 1: The light receiving surface located at the top does not inhibit the way of light coming in, capturing more photon and allowing for higher sensitivity.

Equipped with Gpixel's cutting-edge BSI sensor, this camera captures 9k resolution images with a sensitivity boosted by 256 times. Moreover, it supports HDR functionality using both photosensitive bands, featuring 256 and 32 stages respectively.

With its combination of high speed and heightened sensitivity, this camera serves as an optimal choice for demanding applications such as semiconductor inspection, PCB (Printed Circuit Board) scrutiny, flat panel display assessment, and fluorescence imaging.

HDR Function


 The cycling of two bands enables HDR (High Dynamic Range) Mode

Figure 2: The cycling of two bands enables HDR (High Dynamic Range) Mode

By combining Band1 and Band2 images, users can detect objects that were not detectible before because the image was too dark or saturated.

Figure 3: By combining Band1 and Band2 images, users can detect objects that were not detectible before because the image was too dark or saturated.

UV, NIR Wavelength

UV and NIR Wavelength

Find out more on TDI Line Scan Cameras and how does TDI Line Scan Camera work

For further information on how TDI Line Scan Cameras with BSI sensor can address your specific application, please contact us.

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