Camera flash, a camera, and a method of generating a flash

• US 8,301,024 B2
• Filed: 11/23/2010
• Issued: 10/30/2012
• Est. Priority Date: 11/26/2009
• Status: Expired due to Fees

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Mather, Jonathan, Kay, Andrew, Montgomery, David James, Suckling, James Rowland, Walton, Emma Jayne, Kanazawa, Yasunori, Watanabe, Yukio, Oda, Hirofumi, Sugita, Taro
• Primary Examiner(s): FULLER, RODNEY EVAN
• Application Number:
  US12/952,306
• Publication Number:
  US 20110123184A1
• Time in Patent Office: 707 Days
• Field of Search: 396/176
• US Class Current: 396/176
• CPC Class Codes: G02B 6/001 the light being emitted along at least a portion of the lateral surface of the fibre
• CPC Class Codes: G02B 6/0036 2-D arrangement of prisms, protrusions, indentations or roughened surfaces
• CPC Class Codes: G02B 6/0051 Diffusing sheet or layer
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: G02B 6/0065 Manufacturing aspects; Material aspects
• CPC Class Codes: G02B 6/0068 Arrangements of plural sources, e.g. multi-colour light sources
• CPC Class Codes: G02B 6/0073 Light emitting diode [LED]
• CPC Class Codes: G03B 15/05 Combinations of cameras with electronic flash apparatus; Electronic flash units
• CPC Class Codes: G03B 2215/0567 Solid-state light source, e.g. LED, laser
• CPC Class Codes: G03B 2215/0571 With second light source
• CPC Class Codes: G03B 2215/0582 Reflectors
• CPC Class Codes: G03B 2215/0592 installed in front of light emitter
• CPC Class Codes: H04M 19/048 Arrangements providing optical indication of the incoming call, e.g. flasher circuits
• CPC Class Codes: H04N 23/56 provided with illuminating means

Abstract

A camera flash comprises a light guide arranged to extract light at least through one surface; and one or more light sources arranged, in use, to emit light into the lightguide. Each light source is an LED or a laser diode. The camera flash is connectable, in use, to drive circuitry, the drive circuitry being for driving the light source(s) to emit a pulse of light. The waveguide spreads out the light from the light source(s), so that a flash of light from the camera flash does not present a safety risk, while minimizing loss of the light from the light source(s). The camera flash can thus provide a high overall optical output, spread over an extended area (as defined by the waveguide). The lightguide may for example be disposed around a camera module of a mobile telephone camera.

Claims

1. A camera flash for a camera, the camera flash comprising:

a lightguide arranged to extract light at least through one surface;

one or more light sources arranged, in use, to emit light into the lightguide, and three or more optical films;

wherein the or each light source is an LED or a laser diode;

wherein the flash is connectable in use to drive circuitry, the drive circuitry being for driving the light source(s) to emit a pulse of light,

wherein the lightguide is a planar lightguide having two opposed major surfaces and at least one minor surface, the lightguide being arranged to extract light at least through one major surface,

wherein each of the three or more optical films is provided over a major surface of the lightguide,

wherein light extraction features for extracting light from the lightguide are arranged on at least one major surface of the lightguide, wherein the number density of the extraction features vary so as to be greater further away from the light sources so that there is more extraction further away from the light sources, and

wherein an angular range of light emitted by the camera flash is substantially equal to a field of view of the camera.

2. A camera flash as claimed in claim 1, wherein light extraction features for extracting light from the lightguide are arranged within the lightguide.

3. A camera flash as claimed in claim 1 wherein the light extraction features are so configured as to extract light from the lightguide into a pre-defined angular range.

4. A camera flash as claimed in claim 1 wherein the light extraction features are prisms.

5. A camera flash as claimed in claim 4 wherein the prisms extend generally perpendicular to a direction of propagation of light within the lightguide.

6. A camera flash as claimed in claim 1 wherein the light extraction features are selected from the group consisting of microlenses and scattering bumps.

7. A camera flash as claimed in claim 1 wherein a phosphor layer covers the lightguide surface.

8. A camera flash as claimed in claim 1 wherein at least one of the three or more optical films is arranged to, in use, direct light extracted from the lightguide into a pre-defined angular range.

9. A camera flash as claimed in claim 1 wherein at least one of the three or more optical films is a reflector disposed behind the other major surface of the lightguide.

10. A camera flash as claimed in claim 1 wherein the lightguide comprises an optical fibre.

11. A camera flash as claimed in claim 10 and comprising a reflector disposed around part of the circumference of the optical fibre.

12. A camera flash as claimed in claim 1 and comprising one or more other lightguide, the or each other lightguide having at least one associated light source arranged to emit light into the other lightguide.

13. A camera comprising a camera flash as defined in claim 1.

14. A camera as claimed in claim 13 wherein the camera is a mobile telephone camera.

15. A camera as claimed in claim 13 and comprising a drive circuit for driving, in use, the light source(s) to emit a pulse of light.

16. A camera as claimed in claim 13 and further comprising at least one second light source arranged to emit light into the lightguide, and a control circuit for causing the at least one second light source to emit light upon receipt of an indication that a predefined event has occurred.

17. A camera as claimed in claim 16, wherein the one or more light sources are arranged to cause the camera flash to emit light having a first spectral distribution and wherein the second light source is arranged to cause the camera flash to emit light having a second spectral distribution different from the first spectral distribution.

18. A camera flash as claimed in claim 17 wherein the first spectral distribution is a white light spectral distribution.

19. A camera as claimed in claim 17 wherein the predetermined event is receipt of an SMS message or receipt of an incoming call.

20. A camera as claimed in claim 13 wherein the angular range of light emitted by the camera flash is substantially equal to the field of view of the camera.

21. A camera as claimed in claim 13 wherein the lightguides(s) substantially define an annulus or an approximation thereto, the annulus being centred on an axis passing through substantially the centre of the lens of the camera.

22. A method of generating a flash for flash photography, the method comprising driving light source(s) of a camera flash of a camera to emit a pulse of light, the camera flash further comprising:

a lightguide arranged to extract light through one surface, the light source(s) being arranged, in use, to emit light into the lightguide; and

three or more optical films;

wherein the or each light source is an LED or a laser diode,

wherein the lightguide is a planar lightguide having two opposed major surfaces and at least one minor surface, the lightguide being arranged to extract light at least through one major surface,

wherein each of the three or more optical films is provided over a major surface of the lightguide, and

wherein light extraction features for extracting light from the lightguide are arranged on at least one major surface of the lightguide, wherein the number density of the extraction features vary so as to be greater further away from the light sources so that there is more extraction further away from the light sources

wherein an angular range of light emitted by the camera flash is substantially equal to a field of view of the camera.