Light positioning system using digital pulse recognition

• US 8,994,814 B2
• Filed: 08/21/2012
• Issued: 03/31/2015
• Est. Priority Date: 07/26/2011
• Status: Active Grant

• Current Assignee: ABL IP Holding LLC (Acuity Brands, Inc.)
• Original Assignee: Bytelight, Inc. (Acuity Brands, Inc.)
• Inventors: Ganick, Aaron, Ryan, Daniel
• Primary Examiner(s): MOE, AUNG SOE
• Application Number:
  US13/591,014
• Publication Number:
  US 20130028475A1
• Time in Patent Office: 952 Days
• Field of Search: 348/113, 348/116, 348/308, 348/61, 348/370, 348/226.1, 398/118, 398/130, 398/202, 340/13.24, 340/331, 340/332, 362/800, 701/434
• US Class Current: 348/116
• CPC Class Codes: G01C 21/206 specially adapted for indoor navigation
• CPC Class Codes: H04N 23/745 Detection of flicker frequency or suppression of flicker wherein the flicker is caused by illumination, e.g. due to fluorescent tube illumination or pulsed LED illumination
• CPC Class Codes: H04W 4/02 Services making use of location information
• CPC Class Codes: H04W 4/029 Location-based management or tracking services
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management
• CPC Class Codes: H05B 47/195 the transmission using visible or infrared light
• CPC Class Codes: H05B 47/1965 using handheld communication devices

Abstract

In one aspect, the present disclosure relates to a method of detecting information transmitted by a light source in a complementary metal-oxide-semiconductor (CMOS) image sensor by detecting a frequency of light pulses produced by the light source. In some embodiments, the method includes capturing on the CMOS image sensor with a rolling shutter an image in which different portions of the CMOS image sensor are exposed at different points in time; detecting visible distortions that include alternating stripes in the image; measuring a width of the alternating stripes present in the image; and selecting a symbol based on the width of the alternating stripes present in the image to recover information encoded in the frequency of light pulses produced by the light source captured in the image.

Claims

1. A method of detecting information transmitted by a light source with an image sensor of a mobile device by detecting a pattern of light pulses produced by the light source, the method comprising:

capturing on the image sensor an image in which different portions of the image sensor are exposed at different points in time;

detecting patterns that include a first set of image features captured when the light source is in a first state of illumination and a second set of image features captured when the light source is in a second state of illumination;

measuring a feature of the first set of image features;

decoding information encoded in the pattern of light pulses produced by the light source captured in the image based on the measured feature to obtain an identification code that identifies the light source producing the pattern of light pulses; and

sending the identification code from the mobile device to a server to obtain information that allows the mobile device to locate itself indoors.

2. The method of claim 1, wherein the information encoded in the pattern of light pulses produced by the light source includes digital data encoded in a pulse width modulated signal.

3. The method of claim 1, wherein the pattern of the light pulses in the captured in the image repeats at between 60 hertz and 5000 hertz.

4. A method of detecting information transmitted by a light source with an image sensor by detecting a pattern of light pulses produced by the light source, the method comprising:

capturing on the image sensor an image in which different portions of the image sensor are exposed at different points in time;

detecting patterns that include a first set of image features captured when the light source is in a first state of illumination and a second set of image features captured when the light source is in a second state of illumination;

measuring a feature of the first set of image features; and

decoding information encoded in the pattern of light pulses produced by the light source captured in the image based on the measured feature,

wherein the information encoded in the pattern of light pulses is one of a plurality of symbols and the plurality of symbols correspond to different measured feature ranges and each measured feature range corresponds to a frequency range of a pulse width modulated signal of the light source captured in the image.

5. The method of claim 4, further comprising:

capturing a plurality of frames on the image sensor;

measuring in each frame a feature of a set of image features captured when the light source is in the first state of illumination; and

decoding information encoded in the pattern of light pulses produced by the light source captured in the plurality of frames.

6. A method of detecting information transmitted by a light source with an image sensor by detecting a pattern of light pulses produced by the light source, the method comprising:

capturing on the image sensor an image in which different portions of the image sensor are exposed at different points in time;

detecting patterns that include a first set of image features captured when the light source is in a first state of illumination and a second set of image features captured when the light source is in a second state of illumination;

measuring a feature of the first set of image features;

decoding information encoded in the pattern of light pulses produced by the light source captured in the image based on the measured feature;

capturing on the image sensor a second image and detecting a third set of image features captured when the light source is in a third state of illumination; and

measuring a feature of the third set of image features and decoding information encoded in the pattern of light pulses produced by the light source captured in the second image based on the measured feature of the third set of image features.

7. Logic encoded on at least one non-transitory computer readable medium that when executed is configured to:

capture from an image sensor of a mobile device an image in which different portions of the image sensor are exposed at different points in time;

detect a pattern of light pulses that includes a first set of image features captured when a light source is in a first state of illumination and a second set of image features captured when the light source is in a second state of illumination;

measure a feature of the first set of image features;

decode information encoded in the pattern of light pulses produced by the light source captured in the image based on the measured feature to obtain an identification code that identifies the light source producing the pattern of light pulses; and

send the identification code from the mobile device to a server to obtain information that allows the mobile device to locate itself indoors.

8. The logic of claim 7, wherein the information encoded in the pattern of light pulses includes digital data optically encoded in a pulse width modulated signal.

11. The logic of claim 7, wherein the pattern of light pulses from the light source captured in the image repeats at between 60 hertz and 5000 hertz.

9. Logic encoded on at least one non-transitory computer readable medium that when executed is configured to:

capture from an image sensor an image in which different portions of the image sensor are exposed at different points in time;

detect a pattern of light pulses that includes a first set of image features captured when a light source is in a first state of illumination and a second set of image features captured when the light source is in a second state of illumination;

measure a feature of the first set of image features; and

decode information encoded in the pattern of light pulses produced by the light source captured in the image based on the measured feature,

wherein the information encoded in the pattern of light pulses is one of a plurality of symbols and the plurality of symbols correspond to different measured feature ranges and each measured feature range corresponds to a frequency range of a pulse width modulated signal of a light source captured in the image.

10. The logic of claim 9, wherein the logic is configured to:

capture a plurality of frames from the image sensor;

measure in each frame a feature of a third set of image features captured when the light source is in a third state of illumination; and

select one of a plurality of symbols for each measured feature to recover digital data encoded in the plurality of frames.

12. An image detection apparatus that detects information transmitted by a light source in an image sensor by detecting a pattern of light pulses produced by the light source, the image detection apparatus comprising:

an image sensor that is configured to capture an image in which different portions of the image sensor are exposed at different points in time;

a processor in communication with the image sensor that is configured to detect patterns that include a first set of image features captured when the light source is in a first state of illumination and a second set of image features captured when the light source is in a second state of illumination and measure a feature of the first set of image features to decode information encoded in the pattern of the light pulses produced by a light source captured in the image to obtain an identification code that identifies the light source captured in the image; and

a network adapter configured to send the identification code to a server to obtain information that allows the image detection apparatus to locate itself indoors.

13. The image detection apparatus of claim 12, wherein the information encoded in the pattern of light pulses includes digital data encoded in a pulse width modulated signal.

14. The image detection apparatus of claim 12, wherein the image sensor is configured to capture a plurality of images each second and each image is captured in a frame that is sent to the processor to detect whether a pattern is present in the frame.

15. The image detection apparatus of claim 12, wherein the pattern of the light pulses captured in the captured image repeats at between 60 hertz and 5000 hertz.

16. An image detection apparatus that detects information transmitted by a light source in an image sensor by detecting a pattern of light pulses produced by the light source, the image detection apparatus comprising:

an image sensor that is configured to capture an image in which different portions of the image sensor are exposed at different points in time; and

a processor in communication with the image sensor that is configured to detect patterns that include a first set of image features captured when the light source is in a first state of illumination and a second set of image features captured when the light source is in a second state of illumination and measure a feature of the first set of image features to decode information encoded in the pattern of the light pulses produced the light source captured in the image,

wherein the information encoded in the pattern of light pulses is one of a plurality of symbols and the plurality of symbols correspond to different measured feature ranges and each measured feature range corresponds to a frequency range of a pulse width modulated signal of the light source captured in the image.

17. An image detection apparatus that detects information transmitted by a light source in an image sensor by detecting a pattern of light pulses produced by the light source, the image detection apparatus comprising:

an image sensor that is configured to capture an image in which different portions of the image sensor are exposed at different points in time; and

a processor in communication with the image sensor that is configured to detect patterns that include a first set of image features captured when the light source is in a first state of illumination and a second set of image features captured when the light source is in a second state of illumination and measure a feature of the first set of image features to decode information encoded in the pattern of the light pulses produced the light source captured in the image,

wherein the processor is configured to measure in each image of a plurality of images a feature of a set of image features captured when the light source is in a third state of illumination and decode information encoded in the pattern of light pulses produced by the light source captured in the plurality of images.