ILLUMINATION DEVICE AND METHOD, AND APPARATUS FOR IMAGE TAKING

• US 20080232079A1
• Filed: 03/18/2008
• Published: 09/25/2008
• Est. Priority Date: 03/19/2007
• Status: Active Grant

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Inventors: AWAZU, Kouhei
• Granted Patent: US 8,385,735 B2
• Time in Patent Office: Days
• US Class Current: 362/3
• CPC Class Codes: G03B 15/02 Illuminating scene
• CPC Class Codes: H04N 2101/00 Still video cameras
• CPC Class Codes: H04N 23/56 provided with illuminating means
• CPC Class Codes: H04N 23/74 by influencing the scene brightness using illuminating means

Abstract

An illumination device for a camera includes a light source, in which LED chips are supplied with a drive current, for emitting light of a first color at intensity according to the drive current. An encapsulant is disposed in front of each LED chip, for changing an illuminating color of the light. An EEPROM stores a data table for representing a correlation between the illuminating color and the drive current. An illumination control unit obtains first drive current associated with a target color of light for use by referring to the data table, to drive the LED chips with the first drive current. Phosphor in the encapsulant sets color temperature of the light lower upon passage through the encapsulant than upon emission from the LED chips.

Claims

1. An illumination device comprising:

at least one light emitting diode for emitting illuminating light with an illuminating color changeable according to a drive current applied thereto;

a memory for storing a data table of a correlation between said drive current and said illuminating color; and

an illumination control unit for controlling said drive current according to said illuminating color by referring to said data table.

2. An illumination device as defined in claim 1, wherein said light emitting diode includes:

a light emitting diode chip for emitting light of a first color at intensity according to said drive current; and

a cover for covering said light emitting diode chip, said cover having a phosphor component for emitting light of a second color by excitation with said light of said first color, wherein said illuminating color is defined according to a relative amount of said light of said first and second colors.

3. An illumination device as defined in claim 2, wherein said drive current is a pulse current, and said illumination control unit controls a duty cycle of said pulse current with an unchanged level of said pulse current, to change said light amount of said light emitting diode.

4. An illumination device as defined in claim 2, further comprising a temperature sensor for measuring temperature of said light emitting diode;

wherein said data table is associated with each one of temperature levels of said light emitting diode, and said illumination control unit selectively designates said data table according to said temperature measured by said temperature sensor.

5. An illumination device as defined in claim 2, further comprising a temperature control unit for controlling temperature of said light emitting diode to keep said illuminating color unchanged or to change said illuminating color.

6. An illumination device as defined in claim 2, wherein said at least one light emitting diode is plural light emitting diodes.

7. An illumination device as defined in claim 6, wherein said illumination control unit controls a number of said light emitting diodes to be driven according to said drive current determined for said illuminating color and a light amount of light to be used.

8. An illumination device as defined in claim 6, wherein said data table is associated with each one of said light emitting diodes, and said illumination control unit controls said drive current of said light emitting diodes according to said data table corresponding thereto.

9. An illumination device as defined in claim 6, further comprising a temperature sensor for measuring temperature of said light emitting diode;

wherein said data table is associated with each one of temperature levels of said light emitting diode, and said illumination control unit selectively designates said data table according to said temperature measured by said temperature sensor.

10. An illumination device as defined in claim 6, further comprising:

a temperature sensor for measuring temperature of said at least one light emitting diode;

a temperature control unit for controlling temperature of said light emitting diode according to said measured temperature, to keep said illuminating color unchanged or to change said illuminating color.

11. An illumination device as defined in claim 6, further comprising a plurality of temperature sensors for measuring temperature of respectively said light emitting diodes;

wherein said data table is associated with each one of temperature levels of said light emitting diodes, and said illumination control unit selectively designates said data table according to said temperature measured by said temperature sensors, to control said drive current discretely for said light emitting diodes.

12. An illumination device as defined in claim 6, further comprising:

a plurality of temperature sensors for measuring temperature of respectively said light emitting diodes;

a controller for interrupting emission of a first one of said light emitting diodes when temperature of said first light emitting diode becomes higher than a predetermined level, and for driving a second one of said light emitting diodes to illuminate.

13. An apparatus for image taking of an object, comprising:

at least one light emitting diode for emitting illuminating light toward said object with an illuminating color changeable according to a drive current applied thereto;

a memory for storing a data table of a correlation between said drive current and said illuminating color;

a color temperature sensor for measuring color temperature of ambient light present around said object; and

an illumination control unit for controlling said drive current by referring to said data table according to color temperature of illuminating light determined by considering said color temperature of said ambient light.

14. An apparatus for image taking as defined in claim 13, wherein said light emitting diode includes:

a light emitting diode chip for emitting light of a first color at intensity according to said drive current; and

a cover for covering said light emitting diode chip, said cover having a phosphor component for emitting light of a second color by excitation with said light of said first color, wherein said illuminating color is defined according to a relative amount of said light of said first and second colors.

15. An apparatus for image taking as defined in claim 14, further comprising:

a controller for causing pre-emission of said light emitting diode and causing said light emitting diode to illuminate for image taking;

an exposure amount determiner for determining an optimized exposure amount during said pre-emission; and

a determiner for determining an exposure condition according to said optimized exposure amount.

16. An apparatus for image taking as defined in claim 15, wherein said exposure condition is constituted by at least one of ISO sensitivity, shutter speed, and aperture stop value.

17. An illumination method of illuminating an object with illuminating light;

said illuminating light being emitted by at least one light emitting diode for illumination with an illuminating color changeable according to a drive current applied thereto, said illumination method comprising steps of;

determining said illuminating color of said illuminating light; and

controlling said drive current according to said illuminating color by referring to a data table of a correlation between said drive current and said illuminating color.

18. An illumination method as defined in claim 17, wherein said drive current is a pulse current, and a duty cycle of said pulse current is controlled with an unchanged level of said pulse current, to change said light amount of said light emitting diode.

19. An illumination method as defined in claim 17, wherein said at least one light emitting diode is plural light emitting diodes, and a number of said light emitting diodes to be driven is controlled according to said drive current determined for said illuminating color and a light amount of light to be used.