Detecting coded light

Patent metadata

Field	Value
Publication number	US-2016112126-A1
Application number	US-201414893662-A
Country	US
Kind code	A1
Filing date	May 23, 2014
Priority date	May 24, 2013
Publication date	Apr 21, 2016
Grant date	—

Abstract

A device comprising an input for receiving image data representing light captured by a camera, and an image analysis module for detecting a coded light component modulated into the light with a modulation frequency. The camera has an exposure time, and the light is captured over a sequence of exposures each lasting for an instance of the exposure time. The detection performed by the image analysis module experiences a frequency blind spot in said detection due to an effect of said exposure time. To address this issue, the device further comprises an output for controlling one or more parameters of the camera which affect the exposure time, and a controller configured to control the one or more parameters to avoid that the modulation frequency corresponds to the frequency blind spot.

First claim

1 . A device comprising:
an input adapted to receive image data representing light captured by a camera, the camera having an exposure time and the light being captured over a sequence of exposures each lasting for an instance of the exposure time; an image analysis module adapted to detect a coded light component modulated into the light with a modulation frequency, there being a frequency blind spot in said detection due to an effect of said exposure time; an output adapted to control one or more parameters of the camera which vary a length of the exposure time; and a controller configured to control the one or more parameters to avoid that the modulation frequency corresponds to the frequency blind spot.

2 . The device of claim 1 , wherein the controller is configured to perform said control by: varying the one or more parameters to try out at least two different lengths of the exposure time, and operating the image analysis module to attempt said detection under each of the different lengths of the exposure time.

3 . The device of claim 2 , wherein the controller is configured, based on said attempts, to determine a value or values of the one or more parameters resulting in detection of the coded light component, and to set the determined value or values to be used for further detection of the coded light component.

4 . The device of claim 1 , wherein the light is captured over a sequence of frames, and in each frame the light is captured by exposing a sequence of spatial portions within the frame, each of the spatial portions in the sequence being exposed to the light for an instance of the exposure time.

5 . The device of claim 4 , wherein the camera is a rolling shutter camera, each of said spatial portions being lines of the frame.

6 . The device of claim 4 , wherein the controller is configured to try out the different lengths of exposure time in different ones of the frames.

7 . The device of claim 1 , wherein the one or more parameters comprise an exposure time setting explicitly specifying the length of the exposure time.

8 . The device of claim 1 , wherein the one or more parameters comprise an exposure index specifying a sensitivity to light.

9 . The device of claim 1 , wherein the one or more parameters comprise an exposure value setting specifying a degree of under or over exposure.

10 . The device of claim 6 , wherein the frames have a frame area and the one or more parameters comprise a region-of-interest setting specifying a region within the frame area, which affects the exposure time in dependence on a brightness or darkness of the region.

11 . The device of claim 1 , wherein there are multiple frequency blind spots in said detection due to the effect of said exposure time, and the controller is configured to control the one or more parameters to avoid that the modulation frequency corresponds to any of the multiple blind spots.

12 . The device of claim 11 , wherein the blind spots are at integer multiples of 1/T exp where T exp is the exposure time.

13 . The device of claim 11 , wherein said detection has a sinc shaped transfer function in the frequency domain, the blind spots being due to zeros in the sinc shaped transfer function.

14 . The device of claim 1 , wherein the image analysis module detects multiple coded light components modulated into the light at different respective modulation frequencies, and the controller is configured to control the one or more parameters to avoid that any of the modulation frequencies of the multiple coded light components correspond to the blind spot or blind spots.

15 . A computer program product comprising code embodied on a computer-readable storage medium and configured so as when executed on a processor to perform operations of:
receiving image data representing light captured by a camera, the camera having an exposure time and the light being captured over a sequence of exposures wherein each exposure lasts for an instance of the exposure time; performing a detection process for detecting a coded light component modulated into the light with a modulation frequency, there being a frequency blind spot in said detection process due to an effect of said exposure time; and controlling one or more parameters of the camera which vary a length of the exposure time to avoid that the modulation frequency corresponds to the frequency blind spot.

Assignees

• Koninkl Philips Nv

Inventors

• Nijssen Stephanus Joseph Johannes
• De Bruijn Frederik Jan
• Gritti Tommaso

Classifications

• H04N23/73

  by influencing the exposure time · CPC title

• H04N23/80

  Camera processing pipelines; Components thereof · CPC title

• H04N25/531

  by controlling rolling shutters in CMOS SSIS · CPC title

• H04B10/116 Primary

  Visible light communication · CPC title

• G03B7/093

  for control of exposure time · CPC title