Systems and methods for creating full-color image in low light

• US 9,955,127 B2
• Filed: 10/30/2015
• Issued: 04/24/2018
• Est. Priority Date: 12/16/2011
• Status: Active Grant

• Current Assignee: Chromatra, LLC
• Original Assignee: Chromatra, LLC
• Inventors: Jones, Peter W. J., Cargill, Ellen, Purcell, Dennis W.
• Primary Examiner(s): PEREZ FUENTES, LUIS M
• Application Number:
  US14/928,678
• Publication Number:
  US 20160073067A1
• Time in Patent Office: 907 Days
• Field of Search: 348 33
• 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: G06F 18/22 Matching criteria, e.g. proximity measures
• CPC Class Codes: G06T 7/90 Determination of colour characteristics
• CPC Class Codes: H01L 27/14645 Colour imagers
• CPC Class Codes: H04N 23/10 for generating image signals from different wavelengths
• CPC Class Codes: H04N 23/11 for generating image signals from visible and infrared light wavelengths
• CPC Class Codes: H04N 23/555 for picking-up images in sites, inaccessible due to their dimensions or hazardous conditions, e.g. endoscopes or borescopes
• CPC Class Codes: H04N 23/843 Demosaicing, e.g. interpolating colour pixel values
• CPC Class Codes: H04N 23/88 for colour balance, e.g. white-balance circuits or colour temperature control
• CPC Class Codes: H04N 25/11 Arrangement of colour filter arrays [CFA]; Filter mosaics
• CPC Class Codes: H04N 25/135 based on four or more different wavelength filter elements
• CPC Class Codes: H04N 25/585 with pixels having different sensitivities within the sensor, e.g. fast or slow pixels or pixels having different sizes
• CPC Class Codes: H04N 5/33 Transforming infrared radiation cameras or camera modules for generating image signals from infrared radiation H04N23/20; circuitry of SSIS for transforming infrared radiation into image signals H04N25/20
• CPC Class Codes: H04N 9/77 Circuits for processing the brightness signal and the chrominance signal relative to each other, e.g. adjusting the phase of the brightness signal relative to the colour signal, correcting differential gain or differential phase circuits for matrixing H04N9/67

Abstract

Full-color images of low-light scenes are generated by the systems and methods described herein using only two light channels. An array of photosensitive pixels includes two sets of pixels, the first sensitive only to light associated with a first light channel, the second only to light associated with a second light channel. Thus the first set of pixels generate a first set of electrical signals in response to incident light within the first light channel, and the second set of pixels generate a second set of electrical signals in response to incident light within the second light channel. An image processor receives the first and second sets of electrical signals and generates a full-color image of the scene by processing only signals generated by the first and second sets of pixels.

Claims

1. A low-light color imaging system, comprising:

a first photosensitive sensor configured to generate, in response to incident light from a scene, a first set of electrical signals indicative of a first light channel including a first spectrum of wavelengths of light, wherein the first photosensitive sensor includes a first array of photosensitive pixels that are enabled to detect the first spectrum of wavelengths of light;

a second photosensitive sensor configured to generate, in response to incident light from the scene, a second set of electrical signals indicative of a second light channel including a second spectrum of wavelengths of light, wherein the second photosensitive sensor includes a second array of photosensitive pixels that are enabled to detect the second spectrum of wavelengths of light, and wherein the second spectrum of wavelengths of light comprises a different spectrum of wavelengths of light than the first spectrum; and

an image-combining processor connected to the first and second photosensitive sensors and having circuitry configured to;

receive the first set of electrical signals indicative of the first light channel and the second set of electrical signals indicative of the second light channel;

generate a full-color image of the scene based on the first and second sets of electrical signals by combining the first and second sets of electrical signals into a set of color vectors, wherein a color vector comprises an ordered set of numbers describing a color;

translate the set of color vectors into colors in a color space with at least one of using a color lookup table that records associations between color vectors and colors, or using predetermined formulas based on definitions of the first and second light channels, and wherein using the color lookup table comprises at least one of;

search for a color vector in the color lookup table that matches a color vector in the set of color vectors;

search for a color vector in the color lookup table that matches a color vector in the set of color vectors within a predetermined margin;

or

search for a color vector in the color lookup table with a ratio of elements that matches a ratio of elements of a color vector in the set of color vectors; and

display the full-color image.

2. The system of claim 1, wherein the first array of photosensitive pixels and the second array of photosensitive pixels comprise at least one of an array of complementary metal oxide semiconductor (CMOS) pixels, an array of charge-coupled device (CCD) pixels, or an array of organic photodetectors.

3. The system of claim 1, wherein the first photosensitive sensor comprises a first filter for filtering out light other than light in the first light channel to prevent the light other than the light in the first light channel from reaching the first photosensitive sensor.

4. The system of claim 3, wherein the first filter filters out a portion of visible light and does not filter out infrared light.

5. The system of claim 3, wherein the second photosensitive sensor comprises a second filter for filtering out light other than light in the second light channel to prevent the light other than the light in the second light channel from reaching the second photosensitive sensor, wherein the second filter is different from the first filter.

6. The system of claim 5, wherein the first filter filters out a first portion of visible light and does not filter out infrared light and the second filter filters out a second portion of visible light and does not filter out infrared light.

7. The system of claim 1, wherein the pixels in the first array of photosensitive pixels are enabled to detect the first spectrum of wavelengths of light based on the first array of photosensitive pixels being sensitive to the first spectrum of wavelengths of light, and wherein the pixels in the second array of photosensitive pixels are enabled to detect the second spectrum of wavelengths of light based on the second array of photosensitive pixels being sensitive to the second spectrum of wavelengths of light.

8. The system of claim 7, further comprising at least one of:

a first filter included in the first photosensitive sensor for filtering out a portion of light in the first light channel;

or a second filter included in the second photosensitive sensor for filtering out a portion of light in the second light channel.

9. A method for operating a low-light color imaging system, comprising:

receiving, at a first photosensitive sensor, incident light from a scene, wherein the first photosensitive sensor includes a first array of photosensitive pixels that are enabled to detect a first spectrum of wavelengths of light;

receiving, at a second photosensitive sensor, incident light from the scene, wherein the second photosensitive sensor includes a second array of photosensitive pixels that are enabled to detect a second spectrum of wavelengths of light, and wherein the second spectrum of wavelengths of light comprises a different spectrum of wavelengths of light than the first spectrum;

generating, by the first photosensitive sensor, a first set of electrical signals indicative of a first light channel including the first spectrum of wavelengths of light;

generating, by the second photosensitive sensor, a second set of electrical signals indicative of a second light channel including the second spectrum of wavelengths of light;

receiving, by an image-combining processor, the first set of electrical signals indicative of the first light channel and the second set of electrical signals indicative of the second light channel;

generating, by the image-combining processor, a full-color image of the scene based on the first and second sets of electrical signals by combining the first and second sets of electrical signals into a set of color vectors, wherein a color vector comprises an ordered set of numbers describing a color; and

translating the set of color vectors into colors in a color space by at least one of using a color lookup table that records associations between color vectors and colors, or using predetermined formulas based on definitions of the first and second light channels, wherein using the color lookup table comprises at least one of;

searching for a color vector in the color lookup table that matches a color vector in the set of color vectors;

searching for a color vector in the color lookup table that matches a color vector in the set of color vectors within a predetermined margin;

or

searching for a color vector in the color lookup table with a ratio of elements that matches a ratio of elements of a color vector in the set of color vectors; and

displaying by a display, the full-color image.

10. The method of claim 9, wherein the first array of photosensitive pixels and the second array of photosensitive pixels comprise at least one of an array of complementary metal oxide semiconductor (CMOS) pixels, an array of charge-coupled device (CCD) pixels, or an array of organic photodetectors.

11. The method of claim 9, further comprising filtering out, by a first filter included in the first photosensitive sensor, light other than light in the first light channel to prevent the light other than the light in the first light channel from reaching the first photosensitive sensor.

12. The method of claim 11, wherein the filtering out by the first filter filters out a portion of visible light and does not filter out infrared light.

13. The method of claim 11, further comprising filtering out, by a second filter included in the second photosensitive sensor, light other than light in the second light channel to prevent the light other than the light in the second light channel from reaching the second photosensitive sensor, wherein the second filter is different from the first filter.

14. The method of claim 13, wherein the filtering out by the first filter filters out a first portion of visible light and does not filter out infrared light and the filtering out by the second filter filters out a second portion of visible light and does not filter out infrared light.

15. The method of claim 9, wherein the pixels in the first array of photosensitive pixels are enabled to detect the first spectrum of wavelengths of light based on the first array of photosensitive pixels being sensitive to the first spectrum of wavelengths of light, and wherein the pixels in the second array of photosensitive pixels are enabled to detect the second spectrum of wavelengths of light based on the second array of photosensitive pixels being sensitive to the second spectrum of wavelengths of light.

16. The method of claim 15, further comprising at least one of:

filtering out, by a first filter included in the first photosensitive sensor, a portion of light in the first light channel;

or filtering out, by a second filter included in the second photosensitive sensor, a portion of light in the second light channel.