Wednesday, September 27, 2023

EETimes article on PixArt Imaging's "smart pixel" sensor


Smart Pixel Optical Sensing – Exerting AI in Pixels Level

The PAC9001LU Smart Pixel Optical Sensing Chip is a Computer Vision ASIC that fits as an always-on motion sensor by leveraging the novel AI-driven pixel architecture into the sensor array design. Based on a CMOS Image Sensor rolling shutter structural design with an array of 36 x 16 pixels, it can support a high frame rate of up to 1000Hz to facilitate image capturing of fast-moving object applications. The design of AI in pixels integrates a frame comparing circuit with AI-powered algorithms to compute differences in pixel luminosity within a configurable image area. It directly provides analog frame differences and event info in Pixel Differences Mode and supports Smart Motion Detection Mode to eliminate the complex image signal processing in the processor. The partial array sensing, such as configurable ROI region, provides supple custom scene capturing for the needs of AIoT edge applications.

 PAC9001LU directly handles the digital conversion of raw image signals. It computes the image subtraction difference between two frames internally in the chip to provide the difference of each pixel in an 8-bit data format. This 8-bit data size is relatively small compared to the raw image data of a whole pixel array, which can effectively reduce data transmission bandwidth and latency issues.

The PAC9001LU chip is in a W2.5 x L2.6 x H0.43 mm3 CSP package body (excluding solder balls). A recommended matching lens set, LST0-2621 is also available to form a complete module when assembled with the PAC9001LU chip and comes in a size of W3.79 x L3.63 x H1.67 mm3 (height is including guide pin).

  • The low-power consumption during the Smart Motion Detection Mode that comes with intelligent informative is the most remarkable building block worthwhile in enabling AI applications. As compare to PIR or CMOS Image Sensor (CIS), higher power consumption is required for further data processing in system level.
  •  The high report rate, which can go up to 1000Hz can achieve motion detection with fast-moving objects, which outperforms the PIR or conventional CIS.
  •  The PAC9001LU is more robust with reliable performance. It has fewer false alarms detecting motion and higher immunity to temperature interference. The external environment factors, such as bright and hot sunlight from outdoors, the indoors thermal noise from heated devices are not affecting its sensing performance. The built-in algorithms can eliminate interferences like background noise too.
  •  The small form factor of the complete PAC9001LU sensor module, including the lens set, can nicely fit into the slim bezel ID design.
  •  The traditional PIR sensors are usually required not to be shielded by plastics or glass front-facing cover, which may impact the detection of thermal IR radiation. Whereas the PAC9001LU solution does not have the restraint of having a front cover of any materials and still can keep the motion sensing quality, even placing the motion sensing device indoors looking out from the glass window is possible. With the cover protection, the PAC9001LU is less prone to external damage.

PAC9001LU sensor can support low-light sensing in low or no-light conditions, which is very suitable for use in a dark environment, such as a basement.

The PAC9001LU can cater to the need for in-chip high-speed motion detection, eliminating the external controller processing.


In addition to motion sensing, the PAC9001LU sensor can provide the coordinate information of a targeted moving object that is in sync with each pixel differences image data. 

The PAC9001KE Evaluation Kit is available for evaluation and design research purposes.

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