Light emitting apparatus and method for controlling the same

• US 9,699,861 B2
• Filed: 01/14/2013
• Issued: 07/04/2017
• Est. Priority Date: 01/18/2012
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Ohno, Tomoyuki
• Primary Examiner(s): Taningco, Alexander H
• Assistant Examiner(s): Luque, Renan
• Application Number:
  US13/740,556
• Publication Number:
  US 20130181612A1
• Time in Patent Office: 1,632 Days
• Field of Search: 315151, 315297, 315291, 315307, 345204, 345207, 345102, 345690
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2330/12 Test circuits or failure detection circuits included in a display system, as permanent part thereof
• CPC Class Codes: G09G 2360/145 the light originating from the display screen
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: H05B 45/28 using temperature feedback
• CPC Class Codes: H05B 47/10 Controlling the light source

Abstract

A light emitting apparatus having a plurality of light sources comprises a brightness sensor; a first malfunction detecting unit configured to detect any malfunction of each of the light sources; a second malfunction detecting unit configured to detect any malfunction of the brightness sensor; a storage unit configured to store a target value of a detected value of the brightness of each of the light sources; and a control unit configured to determine a light emission control value of each of the light sources so as to decrease a difference between the target value and the detected value of the brightness of each of the light sources; wherein the control unit allows the light emission control value to be set to a fixed value if the malfunction of at least any one of the light source and the brightness sensor is detected.

Claims

1. A light emitting apparatus having a plurality of light sources for which light emission is controllable independently from each other, the light emitting apparatus comprising:

a brightness sensor which detects a brightness of at least one of the plurality of light sources;

a first detecting unit configured to detect any malfunction of each of the light sources;

a second detecting unit configured to detect any malfunction of the brightness sensor;

a storage unit configured to store a target value of a detected value of the brightness of each of the light sources to be detected by the brightness sensor; and

a control unit configured to determine a light emission control value of each of the light sources so as to decrease a difference between the target value and the detected value of the brightness of each of the light sources detected by the brightness sensor, wherein;

the control unit allows the light emission control value of each of the light sources to be set to a fixed value regardless of the difference between the target value and the detected value detected by the brightness sensor if the malfunction of at least any one of the light source and the brightness sensor is detected.

2. The light emitting apparatus according to claim 1, wherein:

the storage unit stores, as an initial control value, the light emission control value previously determined for each of the light sources so that a dispersion of the brightness in a light emission plane of the light emitting apparatus is within a predetermined allowable level; and

the control unit allows the light emission control values of the light sources other than the malfunctioning light source to be set to the initial control values if the malfunction of the light source is detected.

3. The light emitting apparatus according to claim 1, wherein:

the storage unit stores the light emission control value of each of the light sources determined by the control unit; and

the control unit allows the light emission control values of the light sources other than the malfunctioning light source to be set to the light emission control values determined by the control unit before the malfunction is detected if the malfunction of the light source is detected.

4. The light emitting apparatus according to claim 1, wherein:

the storage unit stores, as an initial control value, the light emission control value previously determined for each of the light sources so that a dispersion of the brightness in a light emission plane of the light emitting apparatus is within a predetermined allowable level; and

the control unit allows the light emission control values of the respective light sources to be set to the initial control values if the malfunction of the brightness sensor is detected.

5. The light emitting apparatus according to claim 1, wherein:

the storage unit stores the light emission control value of each of the light sources determined by the control unit; and

the control unit allows the light emission control values of the respective light sources to be set to the light emission control values determined by the control unit before the malfunction is detected if the malfunction of the brightness sensor is detected.

6. The light emitting apparatus according to claim 1, wherein:

each of the light sources is a white light source composed of light elements of a plurality of colors for which light emission is controllable independently from each other;

the storage unit stores, as an initial control value, the light emission control value previously determined for each of the light elements so that a dispersion of the brightness in a light emission plane of the light emitting apparatus is within a predetermined allowable level;

the first detecting unit is configured to detect any malfunction of the light element for constructing each of the white light sources; and

the control unit is operated, if the malfunction of at least one light element of the light elements for constructing each of the white light sources is detected, such that the light emission control values of the malfunctioning light element and all of the light elements other than the malfunctioning light element for constructing the white light source including the malfunctioning light element are allowed to be set to zero, and the light emission control values of the light elements for constructing the other white light sources are allowed to be set to the initial control values.

7. The light emitting apparatus according to claim 1, wherein:

each of the light sources is a white light source composed of light elements of a plurality of colors for which light emission is controllable independently from each other;

the storage unit stores the light emission control value of each of the light elements determined by the control unit;

the first detecting unit is configured to detect any malfunction of the light element for constructing each of the white light sources; and

the control unit is operated, if the malfunction of at least one light element of the light elements for constructing each of the white light sources is detected, such that the light emission control values of all of the light elements for constructing the white light source together with the malfunctioning light element are allowed to be set to zero, and the light emission control values of the light elements for constructing the other white light sources are allowed to be set to the light emission control values determined by the control unit before the malfunction is detected.

8. The light emitting apparatus according to claim 1, further comprising:

a temperature sensor which detects a temperature around each of the light sources; and

a third detecting unit configured to detect any malfunction of the temperature sensor, wherein;

the storage unit stores a relationship between the temperature around the light source and a light emission characteristic of the light source;

the control unit corrects the detected value of the brightness of each of the light sources detected by the brightness sensor on the basis of the temperature around each of the light sources detected by the temperature sensor and the relationship to determine the light emission control value of each of the light sources so that a difference between the target value and the detected value after the correction is decreased; and

the control unit allows the light emission control value of each of the light sources to be set to the fixed value regardless of the difference between the target value and the detected value after the correction if the malfunction of at least any one of the light source, the brightness sensor, and the temperature sensor is detected.

9. A light emitting apparatus comprising:

a plurality of light sources;

a brightness sensor which detects a brightness of at least one of the plurality of light sources;

a detecting unit configured to detect malfunction of at least any one of the light source and the brightness sensor;

a storage unit configured to store a target value for a detected value of the brightness of each of the light sources to be detected by the brightness sensor; and

a control unit configured to determine a control value of each of the plurality of light sources so as to decrease a difference between the target value and the detected value of the brightness sensor, wherein;

in a case where the detecting unit detects the malfunction, the control unit determines the control value of each of the plurality of light sources to a fixed value regardless of the difference between the target value and the detected value detected by the brightness sensor; and

the storage unit stores an initial control value of each of the plurality of light sources, which is the control value previously determined for each of the light sources so that a dispersion of the brightness in a light emission plane of the light emitting apparatus is within a predetermined allowable level; and

in a case where the detecting unit detects the malfunction of the brightness sensor, the control unit controls the control values of respective light sources to the initial control values of the respective light sources of which the brightness sensor detects brightnesses.

10. A light emitting apparatus having a plurality of light sources for which light emission is controllable independently from each other, the light emitting apparatus comprising:

a brightness sensor which detects a brightness of at least one of the plurality of light sources;

a detecting unit configured to detect malfunction of at least any one of the light source and the brightness sensor;

a storage unit configured to store a target value for a detected value of the brightness of each of the light sources to be detected by the brightness sensor; and

a control unit configured to perform a correcting process in which a light emission control value of each of the light sources is determined so as to decrease a difference between the target value and the detected value of the brightness of each of the light sources detected by the brightness sensor, wherein;

the control unit is operated, in response to the malfunction of at least any one of the light source and the brightness sensor being detected, such that the correcting process is not performed.

12. The light emitting apparatus according to claim 10, wherein:

the storage unit stores an initial control value of each of the plurality of light sources, which is the light emission control value previously determined for each of the light sources so that a dispersion of the brightness in a light emission plane of the light emitting apparatus is within a predetermined allowable level; and

in a case where the detecting unit detects the malfunction of a first light source among the plurality of light sources, the control unit determines the light emission control value of each of second light sources to the initial control value of each of the second light sources, the second light sources being other light sources among the plurality of light sources than the first light source.

13. The light emitting apparatus according to claim 10, wherein:

the storage unit stores an initial control value of each of the plurality of light sources, which is the light emission control value previously determined for each of the light sources so that a dispersion of the brightness in a light emission plane of the light emitting apparatus is within a predetermined allowable level; and

in a case where the detecting unit detects the malfunction of the brightness sensor, the control unit controls the light emission control values of respective light sources to the initial control values of the respective light sources of which the brightness sensor detects brightnesses.

14. The light emitting apparatus according to claim 10, wherein:

each of the light sources is a white light source composed of light emitting elements of a plurality of colors for which light emission is controllable independently from each other;

the storage unit stores an initial control value of each of the plurality of light emitting elements, which is the light emission control value previously determined for each of the light emitting elements so that a dispersion of the brightness in a light emission plane of the light emitting apparatus is within a predetermined allowable level; and

the detecting unit is configured to detect any malfunction of the light emitting element for constructing each of the white light sources, wherein

in a case where the malfunction of at least one of the light emitting elements is detected, the control unit determines the light emission control values of the light emitting elements of a white light source which includes the malfunctioning light emitting element to zero, and the light emission control values of the light emitting elements of the other white light sources to the initial control values.

15. The light emitting apparatus according to claim 10, wherein:

the storage unit stores the light emission control value of each of the plurality of light sources determined by the control unit; and

the control unit determines the light emission control values of light sources other than the malfunctioning light source to be set to the light emission control values determined by the control unit before the malfunction is detected if the malfunction is detected.

16. The light emitting apparatus according to claim 10, wherein:

each of the plurality of light sources emits light based on the light emission control value of each of the plurality of light sources.

17. The light emitting apparatus according to claim 10, wherein:

the brightness sensor outputs an output value according to the detected brightness;

the malfunction is detected in a case that the output value is not within a predetermined range.

18. The light emitting apparatus according to claim 10, wherein the light emitting apparatus is a backlight apparatus of a liquid crystal display.

11. A method for controlling a light emitting apparatus having a plurality of light sources for which light emission is controllable independently from each other, the method for controlling the light emitting apparatus comprising:

a step of detecting a brightness of at least one of the plurality of light sources by means of a brightness sensor;

a detecting step of detecting malfunction of at least any one of the light source and the brightness sensor; and

a control step of performing a correcting process in which a light emission control value of each of the light sources is determined so as to decrease a difference between a target value for a detected value of the brightness of each of the light sources to be detected by the brightness sensor and the detected value of the brightness of each of the light sources detected by the brightness sensor, the target value being stored in a storage unit, wherein;

the correcting process is not performed in the control step in response to the malfunction of at least any one of the light source and the brightness sensor being detected.