Portable colorimeter

• US 20020159066A1
• Filed: 04/27/2001
• Published: 10/31/2002
• Est. Priority Date: 04/27/2001
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: International Business Machines Corporation
• Inventors: Berstis, Viktors
• Granted Patent: US 6,583,880 B2
• Time in Patent Office: Days
• US Class Current: 356/406
• CPC Class Codes: G01J 3/0272 Handheld
• CPC Class Codes: G01J 3/10 Arrangements of light sources specially adapted for spectrometry or colorimetry
• CPC Class Codes: G01J 3/28 Investigating the spectrum using colour filters G01J3/51
• CPC Class Codes: G01J 3/50 using electric radiation detectors
• CPC Class Codes: G01J 3/501 Colorimeters using spectrally-selective light sources, e.g. LEDs
• CPC Class Codes: G01J 3/513 having fixed filter-detector pairs

Abstract

A handheld, pen-like colorimeter for measuring the color of an object is provided. The calorimeter comprises several light emitters, each with distinct color spectra, wherein the emission of each color is modulated at a specific frequency. These light emitters may be Ligh Emitting Diodes (LEDs) and/or lasers. The calorimeter also contains at least one light sensor which samples light reflected from an object illuminated by the light emitters. The rate of sampling is at least twice the modulation frequency of the emitted light. A microprocessor computes the fourier transform of the intensity of the reflected light over time, wherein the fourier transform provides the light intensity at each possible modulation frequency and determines the relative contribution of the reflected light from each light emitter, as well as the contribution of ambient light. The modulation frequency of the light emitters is adjusted to account for the modulation frequency of artificial, ambient light. A color value based on the fourier transform of the reflected light is calculated and then mapped to a list of color values from which a color name is selected and presented to the user.

Claims

1. A handheld calorimeter for measuring the color of an object, comprising:

a plurality of light emitters, each with distinct color spectra, wherein the emission of each color is modulated at a specific frequency;

at least one light sensor which samples light reflected from an object illuminated by said light emitters, wherein the rate of sampling is at least twice the modulation frequency of the emitted light;

a microprocessor which computes the fourier transform of the intensity of the reflected light over time, wherein the fourier transform provides the light intensity at each possible modulation frequency and determines the relative contribution of the reflected light from each light emitter;

a calculating component which calculates a color value based on the fourier transform of the reflected light;

a mapping component which maps the color value to a list of color values and selects a color name from the list that matches the composite color value; and

a presenting component which presents the color name to a user.

2. The calorimeter according to claim 1, wherein the light emitters are light emitting diodes.

3. The calorimeter according to claim 1, wherein the light emitters are lasers.

4. The colorimeter according to claim 1, wherein the colors emitted by the light emitters are red, green, and blue.

5. The colorimeter according to claim 1, wherein the presenting component is a liquid crystal display in a side of the calorimeter.

6. The calorimeter according to claim 1, wherein the presenting component is an audio speaker on the side of the calorimeter.

7. The colorimeter according to claim 1, wherein modulation frequency is used to distinguish ambient light from light emitted from the calorimeter.

8. The calorimeter according to claim 1, wherein the modulation frequency of the light emitters is adjusted to account for ambient light.

9. The calorimeter according to claim 1, further comprising a calibration component which calibrates the colorimeter and stores the calibration settings in memory.

10. The colorimeter according to claim 1, wherein the light sensor further comprises a telephoto lens.

11. The colorimter according to claim 1, further comprising an infrared light emitting diode.

12. The calorimeter according to claim 1, further comprising an infrared laser.

13. The calorimeter according to claim 1, further comprising an ultraviolet light emitting diode.

14. The calorimeter according to claim 1, further comprising a focus adjuster which adjusts the focus of the light sensor and averages the colors over a specified area.

15. The colorimeter according to claim 1, further comprising a storage component which stores measured colors in memory, wherein the measurements can be annotated by the user.

16. The calorimeter according to claim 1, further comprising an algorithm to match and coordinate colors of different objects.

17. The colorimeter according to claim 1, wherein the list of color values and corresponding name is stored in internal memory.

18. The colorimeter according to claim 1, wherein the list of color values and corresponding name is stored in an external memory source.

19. The calorimeter according to claim 1, wherein the colorimeter is incorporated into a camera.

20. A method for measuring the color of an object, comprising:

shining a plurality of light emitters, each with distinct color spectra, on an object, wherein the emission of each color is modulated at a specific frequency;

sampling light reflected from an object illuminated by said light emitters, wherein the rate of sampling is at least twice the modulation frequency of the emitted light;

computing the fourier transform of the intensity of the reflected light over time, wherein the fourier transform provides the light intensity at each possible modulation frequency and determines the relative contribution of the reflected light from each light emitter;

calculating a color value based on the fourier transform of the reflected light;

mapping the color value to a list of color values and selecting a color name from the list that matches the composite color value; and

presenting the color name to a user.