Correlated color temperature detector

• US 5,521,708 A
• Filed: 11/25/1992
• Issued: 05/28/1996
• Est. Priority Date: 11/25/1992
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Information Technology Services Incorporated (Canon Inc.)
• Inventors: Beretta, Giordano B.
• Primary Examiner(s): McGraw, Vincent P.
• Assistant Examiner(s): HANTIS, KAREN
• Application Number:
  US07/981,396
• Time in Patent Office: 1,280 Days
• Field of Search: 356/402, 356/407, 356/414, 356/416, 356/418, 356/419, 355/38, 315/151, 315/293, 315/149, 358/504
• US Class Current: 356/402
• CPC Class Codes: G01J 5/60 using determination of colour temperature
• CPC Class Codes: G01J 5/602 using selective, monochromatic or bandpass filtering
• CPC Class Codes: H04N 1/6088 by viewing conditions, i.e. conditions at picture output

Abstract

A correlated color temperature measuring device for measuring the color temperature of light includes a sensor which individually senses plural light components of light incident thereon and for providing plural corresponding digital color component signals representative thereof, a memory which stores correction data for correcting the plural digital color temperature component signals, and a processor which receives the plural digital color component signals from the sensor. The processor accesses the correction data in the memory, corrects the plural color component signals from the sensor based on the correction data and derives a digital signal representative of the color temperature of the incident light. The derived digital signal may be displayed on a digital display or may be outputted on a digital I/O interface in response to a request for digital color temperature information.

Claims

1. A color temperature measuring device for measuring the color temperature of viewing light, said device comprising:

a sensor for individually sensing plural light components of viewing light incident thereon and for providing plural corresponding color component signals representative thereof, said viewing light including ambient light and light output from an artificial light source;

an A/D converting means for converting plural color component signals from said sensor to plural digital color component signals;

a programmable memory for storing correction data for correcting sensor errors in sensing the plural light components;

a processor for receiving the plural digital color component signals from said A/D converting means, for accessing the correction data in said memory, for correcting the plural digital color component signals based on the correction data, and for deriving a digital signal representative of the color temperature of the viewing light;

a digital I/O interface for interfacing with said processor; and

a digital display for displaying the digital signal derived by said processor,

wherein said processor is responsive to a command on the digital I/O interface for changing to a calibration mode, and when in said calibration mode, said processor is responsive to a command for receiving correction data and, in response to the command, stores the correction data into the programmable memory.

2. A device according to claim 1, further comprising a housing for enclosing the sensor, said housing including a light diffuser for the sensor and means for mounting the digital display on the housing.

3. A device according to claim 1, wherein said memory stores color temperature conversion data for converting color components into a color temperature, and said processor converts the corrected plural digital color component signals into a color temperature based on the color temperature conversion data in said memory.

4. A device according to claim 3, wherein the color temperature conversion data is correlated color temperature conversion data.

5. A device according to claim 1, wherein said memory is programmable.

6. A device according to claim 5, wherein said processor is operable in a calibration mode for storing correction data in said memory.

7. A device according to claim 6, further comprising at least one light source operable by said processor to illuminate said sensor at pre-designated light levels wherein said at least one light source is operable during said calibration mode.

8. A device according to claim 6, further comprising a digital interface accessible by said processor, wherein in said calibration mode said processor writes uncorrected digital color component signals to the digital interface.

9. A device according to claim 1, further comprising an indicator for indicating that the sensed viewing light is so hued that the light can no longer be considered white.

10. A device according to claim 9, wherein said processor activates said indicator based on correlated color temperature conversion data stored in said memory.

11. A device according to claim 1, wherein said processor is responsive to commands on the digital I/O interface that are addressed to a pre-designated address.

12. A device according to claim 11, wherein said processor is responsive to a command for writing the correlated color temperature onto the digital I/O interface.

13. A device according to claim 11, wherein said processor is responsive to a command for changing to a calibration mode.

14. A device according to claim 11, wherein said processor is responsive to a command to change the pre-designated address.

15. A device according to claim 11, wherein said digital I/O interface is comprised by a universal asynchronous receiver/transmitter.

16. A device according to claim 1, wherein said sensor includes plural photosensors each having a corresponding means for providing a respective one of the plural color components.

17. A device according to claim 16, wherein said means comprises corresponding color filters.

18. A device according to claim 16, further comprising an A/D converter for each of said plural photosensors.

19. A color temperature measuring device for measuring the color temperature of viewing light, said device comprising:

a sensor for individually sensing plural color components of viewing light incident thereon and for providing corresponding plural color signals representative of the light, said viewing light including ambient light and light output from an artificial light source;

an A/D converting means for converting plural color signals from said sensor to plural digital color component signals;

a programmable memory for storing correction data for correcting sensor errors in sensing the plural color components of light;

a digital I/O interface; and

a processor for receiving the plural digital color component signals from said A/D converting means, for accessing the correction data in said memory and for correcting the plural digital color component signals, for deriving a digital color temperature signal from said corrected plural digital color component signals, and for outputting the digital color temperature signal on said interface,

wherein said processor is responsive to a command on the digital I/O interface for changing to a calibration mode, and when in said calibration mode, said processor is responsive to a command for receiving correction data and, in response to the command, stores the correction data into the programmable memory.

20. A device according to claim 19, further comprising a housing having a measuring head for mounting the sensor therein.

21. A device according to claim 20, further comprising a digital display mounted on said housing.

22. A device according to claim 21, wherein said processor outputs a digital color temperature signal to said display for displaying a visual indication of the color temperature of light.

23. A device according to claim 19, wherein said memory stores color temperature conversion data for converting color components into a color temperature, and said processor converts the corrected plural digital color component signals into a color temperature based on the color temperature conversion data in said memory.

24. A device according to claim 23, wherein the color temperature conversion data is correlated color temperature conversion data.

25. A device according to claim 19, further comprising at least one light source operable by said processor to illuminate said sensor at pre-designated light levels wherein said at least one light source is operable during said calibration mode.

26. A device according to claim 19, wherein in said calibration mode said processor writes uncorrected digital color component signals to the digital I/O interface.

27. A device according to claim 19, further comprising an indicator for indicating that the sensed viewing light is so hued that the light can no longer be considered white.

28. A device according to claim 27, wherein said processor activates said indicator based on correlated color temperature conversion data stored in said memory.

29. A device according to claim 19, wherein said processor is responsive to commands on the digital I/O interface that are addressed to a pre-designated address.

30. A device according to claim 29, wherein said processor is responsive to a command for writing the correlated color temperature onto the digital I/O interface.

31. A device according to claim 30, wherein said processor is responsive to a command to change the pre-designated address.

32. A device according to claim 19, wherein said digital I/O interface is comprised by a universal asynchronous receiver/transmitter.

33. A device according to claim 19, wherein said sensor includes plural photosensors each having a corresponding means for providing a respective one of the plural color components.

34. A device according to claim 33, wherein said means comprises corresponding color filters.

35. A device according to claim 33, further comprising an A/D converter for each of said plural photosensors.

41. A device according to claim 35, wherein said processor is operable in the calibration mode for storing correction data in said memory.

42. A device according to claim 41, further comprising at least one light source operable by said processor to illuminate said sensor at pre-designated light levels wherein said at least one light source is operable during said calibration mode.

43. A device according to claim 41, wherein in said calibration mode said processor writes uncorrected digital color component signals to the digital interface.

45. A device according to claim 43, wherein said processor activates said indicator based on correction data stored in said memory.

36. A color temperature measuring device for measuring the color temperature of viewing light, said device comprising:

a substrate;

a sensor embedded to said substrate, said sensor for individually sensing plural color components of viewing light incident on said sensor and for providing plural corresponding digital color component signals representative of the color content of the viewing light, said viewing light including ambient light and light output from an artificial light source;

a memory fixed to said substrate, said memory for storing correction data for correcting the plural digital color component signals;

a processor fixed to said substrate and including a digital interface, said processor for executing process steps to receive the plural digital color component signals from said sensor, to access the correction data in said memory, to correct the plural digital color component signals based on the correction data, to derive a color temperature signal from the corrected digital color component signals, to receive a request for providing a color temperature signal, and to output the digital color temperature signal on the digital interface in response to the request; and

a digital I/O interface for interfacing with said processor,

wherein said processor is responsive to a command on the digital I/O interface for changing to a calibration mode, and when in said calibration mode, said processor is responsive to a command for receiving correction data and, in response to the command, stores the correction data into the programmable memory.

37. A device according to claim 36, further comprising a housing having a measuring head for mounting the sensor therein.

38. A device according to claim 37, further comprising a digital display mounted on said housing.

39. A device according to claim 38, wherein said processor outputs a digital color temperature signal to said display for displaying a visual indication of the color temperature of light.

40. A device according to claim 36, wherein the memory stores correction data which is correlated color temperature conversion data.

44. A device according to claim 36, further comprising an indicator for indicating that the sensed viewing light is so hued that the light can no longer be considered white.

46. A device according to claim 36, wherein said processor is responsive to commands on the digital interface that are addressed to a pre-designated address.

47. A device according to claim 46, wherein said processor is responsive to a command to change the pre-designated address.

48. A device according to claim 36, wherein the digital interface is comprised by a universal asynchronous receiver/transmitter.

49. A device according to claim 36, wherein said sensor includes plural photosensors each having a corresponding means for providing a respective one of the plural color components.

50. A device according to claim 49, wherein said means comprises corresponding color filters.

51. A device according to claim 49, further comprising an A/D converter for each of said plural photosensors.

52. A color temperature measuring device according to claim 36, wherein the correction data is data for correcting sensor errors in sensing plural color components of light.

53. A color temperature measuring device according to claim 36, further comprising an A/D converting means for converting the plural color components of light sensed by the sensor into the plural digital color component signals.

54. A calibration device for calibrating a color temperature sensor comprising:

an illuminator, having a predetermined correlated color temperature, for illuminating the color temperature sensor to the predetermined correlated color temperature; and

a controller for automatically controlling the illumination of the illuminator and for receiving color output values from a plurality of color sensors and calculating color sensor calibrations based thereon.

55. A calibration device as defined in claim 54, wherein the illuminator is an LED.

56. A calibration device as defined in claim 54, wherein the illuminator comprises a red, a green, and a blue LED.

57. A calibration device as defined in claim 54, wherein the illuminator is co-mounted with the plurality of color sensors.

58. A calibration device as defined in claim 54, wherein the calibration device comprises a cylinder having a proximal open end adapted to receive the color temperature sensor and wherein the proximal open end includes a light absorbing surface.

59. A calibration device as defined in claim 58, wherein the cylinder further includes a distal closed end having the illuminator mounted thereon.