WHITE LIGHT EMITTING APPARATUS AND LINE ILLUMINATOR USING THE SAME IN IMAGE READING APPARATUS

• US 20100320928A1
• Filed: 08/10/2010
• Published: 12/23/2010
• Est. Priority Date: 02/13/2008
• Status: Active Grant

• Current Assignee: Canon Components Incorporated (Canon Inc.)
• Original Assignee: Canon Components Incorporated (Canon Inc.)
• Inventors: Asai, Shozo, Kaihotsu, Takahiro
• Granted Patent: US 8,531,126 B2
• Time in Patent Office: Days
• US Class Current: 315/250
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/48257 connecting the wire to a die pad of the item
• CPC Class Codes: H01L 25/0753 the devices being arranged next to each other
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 33/50 Wavelength conversion elements
• CPC Class Codes: H05B 45/20 Controlling the colour of the light
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

A white light emitting apparatus includes a light source section in which a first white LED that emits white light whose chromaticity deviates to a blue side from a predetermined white region of a CIE chromaticity diagram and a second white LED that emits white light whose chromaticity deviates to a yellow side from the predetermined white region are adjacently disposed so as to emit light with optical axes in substantially the same direction, and a current regulator that independently drives the blue LED chip in the first and second white LEDs, respectively. A color mixture of lights emitted from the first and second white LEDs is adjusted to a chromaticity of the predetermined white region using the current regulator.

Claims

1. A white light emitting apparatus for an image reading apparatus, that uses a white LED having a blue LED chip and a phosphor, comprising:

a light source section in which a first white LED that emits white light whose chromaticity deviates to a blue side from a predetermined white region of a CIE chromaticity diagram and a second white LED that emits white light whose chromaticity deviates to a yellow side from the predetermined white region are adjacently disposed such that optical axes thereof are in substantially the same direction; and

a current regulator that independently drives the blue LED chip of the first and second white LEDs, respectively;

wherein the current regulator performs PWM control for a drive current of at least one of the first and second white LEDs, and by setting respective pulse widths for driving the first and second white LEDs that are inversely proportional to a distance from a target chromaticity point to a chromaticity point of emitted light of the first white LED and a distance from the target chromaticity point to a chromaticity point of emitted light of the second white LED on a CIE chromaticity diagram,

adjusts a color mixture of lights emitted from the first and second white LEDs to a chromaticity of the predetermined white region.

3. A line illuminator configured to emit light that is incident from a light source disposed toward a light incident surface provided at an end surface in a length direction of a bar-shaped light guide member formed of a clear member from a light emitting surface provided along a length direction while causing the light to be reflected by an inner surface of the bar-shaped light guide member, wherein the light source is a white light emitting apparatus according to claim 1.

5. The line illuminator according to claim 3, wherein an external shape of a radiating surface that radiates a light of the white light emitting apparatus is of dimensions that can be included in an external shape of the light incident surface of the light guide member.

2. A white light emitting apparatus for an image reading apparatus, that uses a white LED having a blue LED chip and a phosphor, comprising:

a light source section in which a first white LED that emits white light whose chromaticity deviates to a blue side from a predetermined white region of a CIE chromaticity diagram and a second white LED that emits white light whose chromaticity deviates to a yellow side from the predetermined white region are adjacently disposed such that optical axes thereof are in substantially the same direction; and

a current regulator that independently drives the blue LED chip of the first and second white LEDs, respectively;

wherein, the current regulator;

continuously supplies a constant current to one white LED among the first and second white LEDs that emits white light whose chromaticity is nearer to a target chromaticity point on the CIE chromaticity diagram, and supplies a PWM-controlled current to another white LED among the first and second white LEDs,

sets a duty ratio of the PWM control to a value of an inverse ratio between a distance between a chromaticity of the one white LED and the target chromaticity point and a distance between a chromaticity of the other white LED and the target chromaticity point on the CIE chromaticity diagram, and

adjusts a color mixture of emitted lights from the first and second white LEDs to a chromaticity of the predetermined white region.

4. A line illuminator configured to emit light that is incident from a light source disposed toward a light incident surface provided at an end face in a length direction of a bar-shaped light guide member formed of a clear member from a light emitting surface provided along a length direction while causing the light to be reflected by an inner surface of the bar-shaped light guide member, wherein the light source is a white light emitting apparatus according to claim 2.

6. The line illuminator according to claim 4, wherein an external shape of a radiating surface that radiates a light of the white light emitting apparatus is of dimensions that can be included in an external shape of the light incident surface of the light guide member.

7. A white light emitting apparatus, comprising:

a first white light emitting diode emitting yellowish white;

a second white light emitting diode emitting bluish white in the same direction of emission by the first white light emitting diode; and

a current controller controlling drive currents of the first and second white light emitting diodes.

8. The white light emitting apparatus according to claim 7, wherein the current controller controls duty ratios of outputs of the drive currents.

9. The white light emitting apparatus according to claim 7, wherein the current controller controls values of the drive currents.

10. The white light emitting apparatus according to claim 7, wherein

each of the first and second white light emitting diodes comprises:

a blue light emitting diode chip; and

a wavelength conversion layer for wavelength conversion of a part of blue light from the blue light emitting diode chip into yellow light.

11. The white light emitting apparatus according to claim 10, wherein the wavelength conversion layer in the second white light emitting diode has a thickness smaller than that of the wavelength conversion layer in the first white light emitting diode.

12. A white light emitting diode, comprising:

first and second blue light emitting diode chips; and

a wavelength conversion layer for wavelength conversion of a part of blue light from the first and second blue light emitting diode chips into yellow light, wherein

the wavelength conversion layer

emits yellowish white after wavelength conversion of a part of blue light from the first blue light emitting diode chip into yellow light, and

emits bluish white after wavelength conversion of a part of blue light from the second blue light emitting diode chip into yellow light.

13. The white light emitting diode according to claim 12, wherein

the wavelength conversion layer comprises:

a first fluorescent layer covering the first and second blue light emitting diode chips; and

a second fluorescent layer covering only the second blue light emitting diode chip of the first and second blue light emitting diode chips.

14. A white light emitting apparatus, comprising:

first and second blue light emitting diode chips;

a wavelength conversion layer for wavelength conversion of a part of blue light from the first and second blue light emitting diode chips into yellow light; and

a current controller controlling drive currents of the first and second blue light emitting diode chips, wherein

color mixture with the yellow light obtained by the wavelength conversion of a part of blue light from the first blue light emitting diode chip by the wavelength conversion layer and the remained part of blue light from the first blue light emitting diode chip results in yellowish white, and

color mixture with the yellow light obtained by the wavelength conversion of a part of blue light from the second blue light emitting diode chip by the wavelength conversion layer and the remained part of blue light from the second blue light emitting diode chip results in bluish white.

15. The white light emitting apparatus according to claim 14, wherein the current controller controls duty ratios of outputs of the drive currents.

16. The white light emitting apparatus according to claim 14, wherein the current controller controls values of the drive currents.

17. A linear illuminator, comprising:

a white light emitting apparatus; and

a light guide member guiding a light incident from the white light emitting apparatus and linearly illuminating an object to be illuminated, wherein

the white light emitting apparatus comprises;

a first white light emitting diode emitting yellowish white;

a second white light emitting diode emitting bluish white in the same direction of emission by the first white light emitting diode; and

a current controller controlling drive currents of the first and second white light emitting diodes.

18. A linear illuminator, comprising:

a white light emitting apparatus; and

a light guide member guiding a light incident from the white light emitting apparatus and linearly illuminating an object to be illuminated, wherein

the white light emitting apparatus comprises;

first and second blue light emitting diode chips;

a wavelength conversion layer for wavelength conversion of a part of blue light from the first and second blue light emitting diode chips into yellow light; and

a current controller controlling drive currents of the first and second blue light emitting diode chips, wherein

color mixture with the yellow light obtained by the wavelength conversion of a part of blue light from the first blue light emitting diode chip by the wavelength conversion layer and the remained part of blue light from the first blue light emitting diode chip results in yellowish white, and

color mixture with the yellow light obtained by the wavelength conversion of a part of blue light from the second blue light emitting diode chip by the wavelength conversion layer and the remained part of blue light from the second blue light emitting diode chip results in bluish white.

19. A linear illuminator, comprising:

a white light emitting diode; and

a light guide member guiding a light incident from the white light emitting diode and linearly illuminating an object to be illuminated, wherein

the white light emitting diode comprises;

first and second blue light emitting diode chips; and

a wavelength conversion layer for wavelength conversion of a part of blue light from the first and second blue light emitting diode chips into yellow light, wherein

color mixture with the yellow light obtained by the wavelength conversion of a part of blue light from the first blue light emitting diode chip by the wavelength conversion layer and the remained part of blue light from the first blue light emitting diode chip results in yellowish white, and

color mixture with the yellow light obtained by the wavelength conversion of a part of blue light from the second blue light emitting diode chip by the wavelength conversion layer and the remained part of blue light from the second blue light emitting diode chip results in bluish white.