Day and night detection based on one or more of illuminant detection, lux level detection, and tiling

Patent metadata

Field	Value
Publication number	US-9549124-B2
Application number	US-201615158348-A
Country	US
Kind code	B2
Filing date	May 18, 2016
Priority date	Jun 12, 2015
Publication date	Jan 17, 2017
Grant date	Jan 17, 2017

Abstract

A method for controlling a camera mode is executed at a camera including a controller, a sensor array, an IR filter, and a lens assembly. The camera is operated in a night mode. While in the night mode the IR filter is not interposed between the lens assembly and the sensor array, the camera receives at the sensor array ambient light that is not filtered by the IR filter, determines whether the received ambient light is due to a light source other than an IR light source, and detects a light level of the received ambient light. The camera switches the operation of the camera from the night mode to a day mode when it is determined the received ambient light is due to a light source other than an IR light source and that the light level of the received ambient light exceeds a first threshold.

First claim

What is claimed is:

1. A camera mode control system for a camera, comprising:
a controller,
memory storing one or more programs for execution by the controller,
a sensor array comprising a plurality of sensors,
a lens assembly that is configured to focus light on the sensor array, and
an IR filter;
the one or more programs including instructions for:
operating the camera in a night mode, wherein while in the night mode the IR filter is not interposed between the lens assembly and the sensor array, including:
receiving at the sensor array ambient light that is not filtered by the IR filter;
determining whether the received ambient light is due to a light source other than an IR light source;
detecting a light level of the received ambient light;
based on a determination that the received ambient light is due to a light source other than an IR light source and that the light level of the received ambient light exceeds a first threshold, switching the operation of the camera from the night mode to a day mode; and
based on a determination that the received ambient light that is due to a light source other than an IR light source and that the light level of the received ambient light does not exceed the first threshold, continuing operation of the camera in the night mode.

2. The method of claim 1 , further comprising:
determining whether the received ambient light is due to sunlight or an incandescent light source; and
based on a determination that the received ambient light is due to sunlight or an incandescent light source, initiating a change of the camera mode to the day mode only when the light level of the received ambient light exceeds a second threshold higher than the first threshold.

3. The method of claim 1 , wherein whether the received ambient light is due to a light source other than an IR light source is obtained based on respective values of a plurality of color components of the received ambient light.

4. The method of claim 1 , wherein the plurality of sensors includes first, second and third pixels each having respective peak responses at different respective visible light frequencies, and determining whether the received ambient light is due to a light source other than an IR light source further comprises:
detecting a first light component of the received ambient light by averaging output signals from the first pixels;
detecting a second light component of the received ambient light by averaging output signals from the second pixels;
detecting a third light component of the received ambient light by averaging output signals from the third pixels; and
determining based on respective values of the first, second and third light components whether the received ambient light is due to a light source other than an IR light source.

5. The method of claim 4 , further comprising:
obtaining a first ratio of the first to the second lighting components of the received ambient light;
obtaining a second ratio of the third to the second lighting components of the received ambient light; and
obtaining a graph characterizing respective types of light source based on a combination of the first and second ratios associated with the respective types of light sources;
wherein determining whether the received ambient light is due to a light source other than an IR light source includes determining based on the graph whether a light source characterized by the first ratio and the second ratio is other than an IR light source.

6. The method of claim 5 , wherein the graph identifies a first region defined by specific respective ranges of the first and the second ratios as being associated with sunlight or incandescent light sources;
wherein determining whether the received ambient light is due to sunlight or an incandescent light source includes determining based on the graph whether a point defined by the first ratio and the second ratio lies within the first region.

7. The method of claim 5 , wherein determining whether the received ambient light is due to a light source other than an IR light source includes determining that a point defined by the first ratio and the second ratio is substantially different from (1, 1).

8. The method of claim 5 , wherein the camera includes an auto white balance processor that provides the obtained first and second ratios.

9. The method of claim 1 , wherein the sensor array is one tile of a plurality of tiles in a sensor array system and the method of claim 1 is performed for each of the tiles, such that a respective mode change signal is generated for a respective tile for which the received ambient light at that respective tile is due to a light source other than an IR light source prior to initiating the change of the camera mode to the day mode, further comprising:
determining a total number of the mode change signals for the sensor array system;
determining whether the total number of the mode change signals exceeds a predetermined mode change threshold based on a total number of tiles in the sensor array system; and
when the total number of the mode change signals exceeds the mode change threshold, initiating the change of the camera mode to the day mode.

10. A camera mode control system for a camera, comprising:
a controller,
memory storing programs for execution by the controller,
a sensor array comprising a plurality of sensors,
a lens assembly that is configured to focus light on the sensor array, and
an IR filter;
the one or more programs including instructions for:
operating the camera in a night mode, wherein while in the night mode the IR filter is not interposed between the lens assembly and the sensor array, including:
receiving at the sensor array ambient light that is not filtered by the IR filter;
determining whether the received ambient light is due to a light source other than an IR light source;
detecting a light level of the received ambient light;
based on a determination that the received ambient light is due to a light source other than an IR light source and that the light level of the received ambient light exceeds a first threshold, switching the operation of the camera from the night mode to a day mode; and
based on a determination that the received ambient light that is due to a light source other than an IR light source and that the light level of the received ambient light does not exceed the first threshold, continuing operation of the camera in the night mode.

11. The system of claim 10 , wherein the one or more programs further include instructions for:
determining whether the received ambient light is due to sunlight or an incandescent light source; and
based on a determination that the received ambient light is due to sunlight or an incandescent light source, initiating a change of the camera mode to the day mode only when the light level of the received ambient light exceeds a second threshold higher than the first threshold.

12. The system of claim 10 , wherein the system includes a gain controller configured to adjust analog gain of the sensor array based on the light level of the received ambient light, and wherein detecting the light level of the received ambient light comprises obtaining the analog gain of the sensor array.

13. The system of claim 12 , wherein the analog gain of the sensor array varies with a frame rate of the camera, and the one or more programs further include instructions for:
determining a first frame rate of the camera used to detect the first, second and third light components; and
normalizing the obtained analog gain of the sensor array based on a first difference between the first frame rate and a

Assignees

• Google Inc

Inventors

• Duran Bill
• Proca Adrian Mircea

Classifications

• H04N23/74

  by influencing the scene brightness using illuminating means · CPC title

• H04N23/56

  provided with illuminating means · CPC title

• H04N23/88

  for colour balance, e.g. white-balance circuits or colour temperature control · CPC title

• H04N23/667 Primary

  Camera operation mode switching, e.g. between still and video, sport and normal or high- and low-resolution modes · CPC title

• H04N25/134

  based on three different wavelength filter elements · CPC title