Temporal Pixel Multiplexing
What is it?
A way to embed time information into a picture, while maintaining the full spatial resolution for the picture. This is done by staggering exposure times for pixels within a picture so we can extract a high speed image sequence.
How it works:
CCD and CMOS camera sensors consist of a rectangular array of pixels.
Each pixel integrates charge generated when light strike its surface for a set integration time (Ti).
TPM controls the way individual pixels are exposed during Ti, to embed high speed information in static images.
Normal vs TPM pictures:
When a picture is taken using a normal camera, each pixel is exposed at the same time for a set duration (Ti). The picture shows a 6x6 pixel sensor being exposed for Ti secs.
A pixel multiplexing camera exposes different pixels at different times during Ti. Here, all pixels #1 are exposed,then all pixels #2 are exposed, and so on. The trick is that the pixels are eventually exposed during Ti so you still have a high res image, but you can group co-exposed pixels to make a image series which can be played back as a movie! And since you still have the same overal resolution, the image takes the same memory as the original.
Key advantages:
Each picture captured by the camera contains both a high-res image plus a high speed, low-res movie. High spatial resolution information from the the camera is not lost.
The user doesn't have to choose between high-res or high-speed image capture as both are obtained at the same time, with no added memory requirements, using one sensor.
The image sensor can capture TPM pictures slowly, avoiding read noise and bandwidth issues associated with high speed imaging.
Movie capture speeds are an order of magnitude faster than what one gets with on-chip binning or region-of-interest methods. For example, a 10 fps, 9 megapixel camera could capture a 1000 fps movie at 300x300 pixel resolution.
Its very flexible: slowly varying events can be monitored in the top half of the image at 100 fps, while rapid changes can be monitored at the bottom of image at 1000 fps (all while maintaining the original camera's frame rate).
The movie can be extracted only if the user has exact information on the exposure sequence. This allows a user to easily control image sequence information with a password or key (which has applications in security or digital content management scenarios).
Find out more:
|
