Relative Position Estimation Using Cross Filter for Rolling-Shutter Cameras

We propose an estimation method of light emitting diode(LED) position with a cross filter (CF) for rolling-shutter (RS) camera. The CF is set in front of the camera lens so that incident light can be scattered into two straight lines extending ±π/4 from the horizontal row of the CMOS image sensor (IS). With the geometry of a right-angled isosceles triangle, our method makes it possible to estimate the coordinates of the LED in the IS plane when the scattered light is captured at two points in a scanline. Furthermore, our method makes it possible rows by rows when multiple LEDs are used or when they are moving. Without the CF, estimation is done only once per frame when the scan of the sequentially activated operation of the RS camera reaches a row that has just captured the whole image of the target LED, and the estimated coordinates are not updated in that frame. Experiments verify that our estimation method works with the estimation error less than 5pixels, and to extend the region of a frame in which estimated coordinates are output, even in a moving environment, while the conventional method (without CF) obtains the estimated coordinates only once when the scan reaches a row that captures entire LED.