Electrochromic filtering in a camera

• US 10,180,615 B2
• Filed: 10/31/2016
• Issued: 01/15/2019
• Est. Priority Date: 10/31/2016
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Google LLC (Alphabet Inc.)
• Inventors: Kilgore, Adam Scott, Volmering, Amber Luttmann
• Primary Examiner(s): Pontius, James
• Application Number:
  US15/339,839
• Publication Number:
  US 20180120661A1
• Time in Patent Office: 806 Days
• CPC Class Codes: G02B 5/208 for use with infrared or ultraviolet radiation, e.g. for separating visible light from infrared and/or ultraviolet radiation
• CPC Class Codes: G02F 1/15 based on an electrochromic effect
• CPC Class Codes: G02F 1/1506 caused by electrodeposition, e.g. electrolytic deposition of an inorganic material on or close to an electrode
• CPC Class Codes: G02F 1/155 Electrodes
• CPC Class Codes: G02F 1/157 Structural association of cells with optical devices, e.g. reflectors or illuminating devices
• CPC Class Codes: G02F 1/163 Operation of electrochromic cells, e.g. electrodeposition cells; Circuit arrangements therefor
• CPC Class Codes: G02F 2001/1555 Counter electrode
• CPC Class Codes: G03B 11/00 Filters or other obturators specially adapted for photographic purposes
• CPC Class Codes: G06V 20/52 Surveillance or monitoring of activities, e.g. for recognising suspicious objects recognising microscopic objects G06V20/69
• CPC Class Codes: H04N 23/11 for generating image signals from visible and infrared light wavelengths
• CPC Class Codes: H04N 23/55 Optical parts specially adapted for electronic image sensors; Mounting thereof
• CPC Class Codes: H04N 23/667 Camera operation mode switching, e.g. between still and video, sport and normal or high- and low-resolution modes
• CPC Class Codes: H04N 23/741 by increasing the dynamic range of the image compared to the dynamic range of the electronic image sensors
• CPC Class Codes: H04N 23/749 by influencing the pick-up tube voltages

Abstract

This application is directed to controlling a camera that includes an electrochromic glass layer. The electrochromic glass layer is disposed in front of a sensor array of the camera and has optical transmission properties that are responsive to voltage applied to the electrochromic glass layer. In accordance with a determination to transition the camera mode to a Day mode, a camera controller generates a first voltage, which is then applied to the electrochromic glass layer to cause the lens assembly to enter a first transmission state. In response to the first voltage, the electrochromic glass layer removes a substantial portion of a predefined band of infrared wavelengths in ambient light incident on the camera, and simultaneously passes by the electrochromic glass layer a substantial portion of visible wavelengths in the ambient light, thereby exposing the sensor array to the substantial portion of the visible wavelengths of the ambient light.

Claims

1. A method for controlling a camera system, comprising:

in a camera including a controller, a sensor array comprising a plurality of sensor elements, and a lens assembly that is configured to focus light on the sensor array, wherein the lens assembly includes an electrochromic glass layer disposed in front of the sensor array and having optical transmission properties that are responsive to voltage applied to the electrochromic glass layer, the lens assembly further including a first transmission state in which the electrochromic glass layer is substantially opaque to a predefined band of IR wavelengths and a second transmission state in which the electrochromic glass layer is substantially transparent to the predefined band of IR wavelengths and visible wavelengths, and in accordance with a determination to transition the camera mode to a Day mode;

generating by the controller a first voltage;

applying the first voltage to the electrochromic glass layer to cause the lens assembly to enter the first transmission state, wherein prior to the transition of the camera mode to the Day mode, the lens assembly was in the second transmission state; and

in response to the first voltage, removing by the electrochromic glass layer a substantial portion of the predefined band of IR wavelengths in ambient light incident on the camera and simultaneously passing by the electrochromic glass layer a substantial portion of visible wavelengths in the ambient light, thereby exposing the sensor array to the substantial portion of the visible wavelengths of the ambient light via the lens assembly.

2. The method of claim 1, further comprising:

in accordance with a determination to transition the camera mode to a Night mode;

generating by the controller a second voltage that is distinct from the first voltage; and

applying the second voltage on the electrochromic glass layer to cause the lens assembly to enter the second transmission state;

in response to the second voltage, passing by the electrochromic glass layer a substantial portion of the predefined band of IR wavelengths and a substantial portion of visible wavelengths in the ambient light incident on the camera, thereby exposing the sensor array exposed to the ambient light via the lens assembly without interference by electrochromic filtering of the electrochromic glass layer.

3. The method of claim 2, wherein the camera includes one or more infrared light emitting diodes that are powered on to illuminate a field of view in accordance with the determination to transition the camera mode to the Night mode.

4. The method of claim 2, wherein the second voltage is substantially equal to zero.

5. The method of claim 2, wherein the electrochromic glass layer includes an electrolyte layer, a first electrode and a counter electrode, and the first and second voltages are applied on the first electrode at the Day mode and at the Night mode, respectively.

6. The method of claim 1, wherein the electrochromic glass layer includes an electrolyte layer, a first electrode and a counter electrode, and the first voltage is applied on the first electrode at the Day mode.

7. The method of claim 6, wherein the first electrode includes a layer of indium tin oxide (ITO) nanocrystals in glass made out of niobium oxide.

8. The method of claim 6, wherein the ITO nanocrystals are combined with niobium-containing ions (also called polyoxometalate (POM) clusters) in solution, and the first electrode is formed when the solution covers a surface of the electrochromic glass layer.

9. The method of claim 1, wherein the electrochromic glass layer includes an optical lens for focusing light on the sensor array, and the optical lens is configured to filter the substantial portion of the predefined band of IR wavelengths in the ambient light at the Day mode.

10. The method of claim 1, wherein the magnitude of the first voltage is not greater than 5V.

11. The method of claim 1, wherein the first voltage is sustained on the electrochromic glass layer at the first transmission state.

12. The method of claim 1, wherein when the camera transitions to the camera mode to the Day mode, the first voltage is applied on the electrochromic glass layer for a predetermined duration of time and is removed after the predetermined duration of time.

13. A camera, comprising:

a sensor array including a plurality of sensor elements;

a lens assembly that is configured to focus light on the sensor array, wherein the lens assembly includes an electrochromic glass layer disposed in front of the sensor array and having optical transmission properties that are responsive to voltage applied to the electrochromic glass layer, and further includes a first transmission state in which the electrochromic glass layer is substantially opaque to a predefined band of IR wavelengths and a second transmission state in which the electrochromic glass layer is substantially transparent to the predefined band of IR wavelengths and visible wavelengths; and

a controller, wherein the controller is configured to in accordance with a determination to transition the camera mode to a Day mode, generate a first voltage that is applied to the electrochromic glass layer to cause the electrochromic lens assembly to enter the first transmission state, wherein;

the lens assembly is configured to operate in the second transition state prior to the transition of the camera mode to the Day mode; and

the electrochromic glass layer is configured to in response to the first voltage, remove a substantial portion of the predefined band of IR wavelengths in ambient light incident on the camera and simultaneously pass a substantial portion of visible wavelengths in the ambient light, thereby exposing the sensor array to the substantial portion of the visible wavelengths of the ambient light via the lens assembly.

14. The camera of claim 13, wherein the camera mode includes a third mode, wherein in accordance with a determination that the camera mode is the third mode, the controller generates a third voltage that is substantially larger than the first voltage, the third voltage is applied on the electrochromic glass layer to cause the electrochromic glass layer to remove a substantial portion of the predefined band of the ambient wavelengths and reduce the intensity of the visible wavelengths in the ambient light to a first visible light intensity, thereby exposing the sensor array to the visible wavelengths of the ambient light having the first visible light intensity.

15. The camera of claim 14, wherein the third mode includes a high dynamic range (HDR) mode, wherein the camera is configured for:

capturing a first image when the first voltage is applied on the electrochromic glass layer;

capturing a second image when the third voltage is applied on the electrochromic glass layer; and

combining at least the first and second images to obtain a HDR image.

16. The camera of claim 14, wherein the third mode includes a high dynamic range (HDR) mode, and the camera is configured for:

generating by the controller a fourth voltage that is distinct from the third voltage;

applying the fourth voltage on the electrochromic glass layer;

in response to the fourth voltage, removing by the electrochromic glass layer a substantial portion of the predefined band of the wavelengths while reducing the intensity of the visible wavelengths in the ambient light to a second visible light intensity;

capturing a first image when the third voltage is applied on the electrochromic glass layer;

capturing a second image when the fourth voltage is applied on the electrochromic glass layer; and

combining at least the first and second images to obtain a HDR image.

17. The camera of claim 13, wherein the camera is configured for:

when the camera mode is a Night mode;

determining whether the ambient light is due to other than an IR light source;

detecting an ambient light level;

based on a determination that the ambient light that is not filtered by the electrochromic glass layer is due to other than an IR light source and that the ambient light level exceeds a first lux threshold, initiating a change of the camera mode to the Day mode;

based on a determination that the ambient light is due to other than an IR light source and that the ambient light threshold does not exceed the first lux threshold, maintaining the camera in the Night mode.

18. The camera of claim 17, wherein the sensor elements include first, second and third pixels, each having respective peak responses at different respective visible light frequencies, and determining whether the ambient light is due to other than an IR light source further includes:

detecting a first light component of the ambient light by averaging output signals from the first pixels;

detecting a second light component of the ambient light by averaging output signals from the second pixels;

detecting a third light component of the 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 ambient light is due to other than an IR light source.

19. The camera of claim 18, wherein the camera is configured for:

determining based on values of the first, second and third light components whether the ambient light is due to sunlight or an incandescent light source; and

based on a determination that the 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 ambient light level exceeds a second lux threshold higher than the first lux threshold.

20. The camera of claim 13, wherein the electrochromic glass layer is a standalone optical filter.