Projection type display apparatus

• US 7,967,452 B2
• Filed: 08/24/2006
• Issued: 06/28/2011
• Est. Priority Date: 08/26/2005
• Status: Active Grant

• Current Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Kasazumi, Kenichi, Itoh, Tatsuo, Mizuuchi, Kiminori, Yamamoto, Kazuhisa
• Primary Examiner(s): Epps; Georgia Y
• Assistant Examiner(s): CHOWDHURY, SULTAN U.
• Application Number:
  US12/064,784
• Publication Number:
  US 20090262262A1
• Time in Patent Office: 1,769 Days
• Field of Search: 353/30, 353/31, 353/38, 353/98, 353/99, 353/119, 353/122, 372/29.01, 372/29.014, 372/29.015, 372/38.02, 372/38.07, 372/29.011, 372/29.02, 372/38.01, 372/39, 372/43.01, 359/239, 359/242, 359/245, 359/246, 359/277, 359/649, 455/556.1, 455/66.1
• US Class Current: 353/99
• CPC Class Codes: G03B 21/14 Details
• CPC Class Codes: G03B 21/2053 Intensity control of illuminating light controlled by video signal processing H04N5/74 or H04N9/31
• CPC Class Codes: G03B 21/208 Homogenising, shaping of the illumination light
• CPC Class Codes: H04N 9/3105 for displaying all colours simultaneously, e.g. by using two or more electronic spatial light modulators simultaneous projection in colour photography G03B33/10; beam splitting or combining systems per se G02B27/10
• CPC Class Codes: H04N 9/3129 scanning a light beam on the display screen scanning a light beam on a screen in displays other than projection devices G09G3/02; scanning systems in general G02B26/10; projectors using laser light sources in general H04N9/3161
• CPC Class Codes: H04N 9/315 Modulator illumination systems general applications of lighting devices F21V; general optical systems G02B; lamp houses for projectors not peculiar to the presence of an electronic spatial light modulator G03B21/20
• CPC Class Codes: H04N 9/3155 for controlling the light source light source control per se H05B35/00 – H05B47/00; control of an illumination source for displays in general G09G3/3406
• CPC Class Codes: H04N 9/3161 using laser light sources using laser beams scanning the display screen H04N9/3129

Abstract

A projection type display apparatus is provided that is safe even when a person looks directly into a laser beam. A laser operation control unit sets the output power of at least one laser source so that intensity A (mW/mm²) of the laser beam on at least one spatial light modulation element satisfies relationship of A<686×B² when numerical aperture B on image side of an illumination optics system is set.

Claims

1. A projection type display apparatus comprising:

at least one laser source;

an illumination optics system that irradiates a laser beam emitted by the at least one laser source;

at least one spatial light modulation element that modulates an intensity of the laser beam irradiated from the illumination optics system in accordance with input information;

a projection optics system that projects the laser beam modulated by the at least one spatial light modulation element onto a screen; and

a laser operation control unit that sets the output power of the at least one laser source so that an intensity A (mW/mm²) of the laser beam on the at least one spatial light modulation element satisfies the following relationship when a numerical aperture B of the illumination optics system is set;

A<

686×

B².

2. The projection type display apparatus according to claim 1,

wherein the at least one laser source is constituted from N laser sources that emit N laser beams of different wavelengths, and

wherein the at least one spatial light modulation element is one spatial light modulation element that modulates the intensities of the N laser beams of different wavelengths irradiated from the illumination optics system in accordance with the input information.

3. The projection type display apparatus according to claim 1,

wherein the at least one laser source is constituted from N laser sources that emit N laser beams of different wavelengths, and

wherein the at least one spatial light modulation element is constituted from N spatial light modulation elements that modulate the intensities of the N laser beams of different wavelengths irradiated from the illumination optics system in accordance with the input information.

4. The projection type display apparatus according to claim 2, wherein the laser operation control unit has a first power control mode in which the output powers of the N laser sources are set so that a total intensity A of the N laser beams of different wavelengths on the spatial light modulation element satisfies the relationship of A<

686×

B².

5. The projection type display apparatus according to claim 4, wherein the laser operation control unit has a second power control mode in which the output power of a laser source that emits the laser beam of the wavelength having the highest luminous efficiency among the N laser beams of different wavelengths is set so that an intensity A of the laser beam of the wavelength having the highest luminous efficiency on the spatial light modulation element satisfies the relationship of A<

686×

B², and oscillations of the other laser sources are shut down.

6. The projection type display apparatus according to claim 5, further comprising an input information judging unit that determines whether the input information is video information or character information,

wherein the laser operation control unit selects the first power control mode when the input information judging unit determines that the input information is video information, and selects the second power control mode when the input information judging unit determines that the input information is character information.

7. The projection type display apparatus according to claim 5, further comprising an extraneous light sensor that measures a luminance of light components of different wavelengths included in extraneous light,

wherein the laser operation control unit has a third power control mode in which the laser operation control unit decreases the output power of a laser source that emits the laser beam having the wavelength, among the different wavelengths of the N laser beams, that corresponds to the wavelength of the highest luminance detected by the extraneous light sensor, in accordance to the luminance detected by the extraneous light sensor.

8. The projection type display apparatus according to claim 7, further comprising a console through which a user'"'"'s instruction is entered,

wherein the laser operation control unit selects either the first power control mode, the second power control mode or the third power control mode, in accordance to the instruction entered by the user through the console.

9. The projection type display apparatus according to claim 1, wherein the numerical aperture B of the illumination optics system is not higher than 0.25, and the intensity A of the laser beam on the at least one spatial light modulation element is not greater than 43 mW/mm².

10. The projection type display apparatus according to claim 1, wherein the illumination optics system includes a beam homogenizer that makes an intensity distribution of the laser beam uniform, and a relay optics system that projects the laser beam, which has been conditioned to have a uniform intensity distribution by the beam homogenizer, onto the at least one spatial light modulation element.

11. The projection type display apparatus according to claim 1, wherein the illumination optics system includes a diffuser plate.

12. The projection type display apparatus according to claim 1, further comprising:

a laser unit that houses at least the at least one laser source and the illumination optics system;

a casing that houses at least the laser unit, the at least one spatial light modulation element, and the projection optics system;

a reverse voltage generating unit that generates a reverse voltage that is equal to or higher than a breakdown voltage of the at least one laser source, and applies the reverse voltage to the at least one laser source when the laser unit is disconnected from the casing; and

a selector that connects the at least one laser source to the laser operation control unit when the at least one laser source is operating, and connects the at least one laser source to the reverse voltage generating unit when the laser source is not operating.

13. The projection type display apparatus according to claim 12,

wherein the laser source includes a semiconductor laser or a semiconductor laser-excited solid state laser, and

wherein the breakdown voltage is a reverse voltage that is higher than the maximum rated reverse voltage of the semiconductor laser.

14. The projection type display apparatus according to claim 12, wherein the reverse voltage generating unit includes a storage battery or an electric double layer capacitor, and applies a charge voltage of the storage battery or the electric double layer capacitor as the reverse voltage to the at least one laser source.

15. The projection type display apparatus according to claim 12, wherein the reverse voltage generating unit includes a coil and a permanent magnet that moves through the coil and induces a voltage across the coil when the laser unit is disconnected from the casing, and applies the voltage induced across the coil to the at least one laser source as the reverse voltage.

16. The projection type display apparatus according to claim 1,

wherein the at least one laser source includes:

a green laser source having a semiconductor laser that emits infrared ray used in excitations;

a rare earth-doped optical fiber of which a rare earth element component is optically excited by the semiconductor laser;

a second harmonics generator element that transforms the infrared ray emitted by the rare earth-doped optical fiber into green light;

a Peltier element that cools down the second harmonics generator element to a predetermined temperature lower than a normal temperature; and

a temperature sensor that senses the temperature of the second harmonics generator element, and

wherein the second harmonics generator element carries out phase matching at the predetermined temperature.

17. The projection type display apparatus according to claim 1,

wherein the at least one laser source includes:

a green laser source having a semiconductor laser that emits infrared ray used in excitation;

a rare earth-doped optical fiber of a which rare earth element component is optically excited by the semiconductor laser; and

a second harmonics generator element that transforms the infrared ray emitted by the rare earth-doped optical fiber into green light,

wherein the projection type display apparatus further comprises;

a laser unit that houses at least the at least one laser source and the illumination optics system; and

a casing that houses at least the laser unit, the spatial light modulation element, and the projection optics system, and

wherein a part of the rare earth-doped optical fiber is fastened indirectly onto the casing via an opening formed in the laser unit so as to be cut off when the laser unit is removed from the casing.

18. The projection type display apparatus according to claim 1,

wherein the at least one laser source is a semiconductor laser made by fastening the N side of a PN junction of a laser diode chip on a common terminal that is connected to a stem, internally connecting the P side of the laser diode chip and a power terminal that penetrates through the stem with a metal wire, mounting a cap having a window on the stem, and sealing the laser diode chip, and

wherein a strength of the power terminal is made weaker in a portion thereof located inside of the at least one laser source so as to become impossible to supply power to the laser diode chip when the semiconductor laser is removed from a wiring board.

19. The projection type display apparatus according to claim 18, wherein the power terminal has a notch so that the power terminal is cut off inside of the at least one laser source by an external force applied thereto.

20. The projection type display apparatus according to claim 1,

wherein the laser source is a semiconductor laser made by fastening the N side of a PN junction of a laser diode chip on a common terminal that is connected to a stem, internally connecting the P side of the laser diode chip and a power terminal that penetrates through the stem with a metal wire, mounting a cap having a window on the stem, and sealing the laser diode chip, and

wherein the power terminal is held by the wiring board with a force greater than a force with which the stem holds the power terminal, by heating a portion of the wiring board where the power terminal is inserted or irradiating the portion with ultraviolet rays, so as to become impossible to supply power to the laser diode chip when the semiconductor laser is removed from the wiring board.