Projection type image display apparatus and image display system

• US 6,890,078 B2
• Filed: 07/01/2003
• Issued: 05/10/2005
• Est. Priority Date: 07/03/2002
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Koide, Jun
• Primary Examiner(s): MAHONEY, CHRISTOPHER E
• Application Number:
  US10/612,795
• Publication Number:
  US 20040008326A1
• Time in Patent Office: 679 Days
• Field of Search: 353/31, 353/52, 353/122, 353/84, 345/76, 359/449, 359/453, 359/460
• US Class Current: 353/31
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2330/025 Reduction of instantaneous peaks of current
• CPC Class Codes: G09G 3/002 to project the image of a two-dimensional display, such as an array of light emitting or modulating elements or a CRT
• CPC Class Codes: G09G 3/2011 by amplitude modulation
• CPC Class Codes: G09G 3/3216 using a passive matrix
• CPC Class Codes: H04N 5/70 Circuit details for electroluminescent devices
• CPC Class Codes: H04N 5/74 Projection arrangements for image reproduction, e.g. using eidophor
• CPC Class Codes: H04N 5/7408 Direct viewing projectors, e.g. an image displayed on a video CRT or LCD display being projected on a screen
• CPC Class Codes: H04N 9/31 Projection devices for colour picture display , e.g. using electronic spatial light modulators [ESLM]
• CPC Class Codes: H04N 9/3138 using arrays of modulated light sources electroluminescent display devices G09G3/30

Abstract

A projection type image display apparatus which suppresses deterioration in luminous efficiency of an organic EL element and reduces flickering of projected images and an amplitude of a power supply capacity is disclosed. The apparatus comprises an electroluminescence (EL) element, a projection optical system, and a controller which generates drive signals to control the emission amount from the EL element. An EL material used for a luminescent layer of the EL element is a phosphorescent material which emits phosphorescence by priority, which is emitted from an excited triplet state. The controller generates drive signals by superimposing an intermittent turning-on signal on emission amount modulating signals to modulate current values to be injected into pixels according to display image signals.

Claims

1. A projection type image display apparatus, comprising:

an electroluminescence element having a plurality of pixels that can be individually modulated, in which the modulating pixels which generate and emit light by means of recombination of excitons formed by injecting electron charge carriers into a luminescent layer are two-dimensionally arranged,

a projection optical system which projects light emitted from the individual modulated pixels of the electroluminescence element,

a controller which generates drive signals to control the emission amount of the electroluminescence element, wherein

an electroluminescence material used for the luminescent layer is a phosphorescent material which emits phosphorescence by priority, which is emitted from an excited triplet state, and

the controller superimposes intermittent turning-on signals with predetermined cycles on emission amount modulating signals which modulate current values to be injected into the pixels according to display image signals.

2. The projection type image display apparatus according to claim 1, wherein the electroluminescence element is structured by repeated matrix arrangement of pixels which emit light in three primary colors, and display additive color images.

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

three electroluminescence elements each of which emits light in one color different from each other among three primary colors, and

a wavelength-combining optical member having dichroic waveband separating films which combine light emitted from the three electroluminescence elements, wherein

light combined by the wavelength-combining optical member is projected by the projecting optical system to display additive color images.

4. The projection type image display apparatus according to claim 1, wherein

in the delaying emission characteristics of the electroluminescence element having the phosphorescent material in its luminescent layer, the time of half attenuation of emission intensity from a peak emission time is shorter than one millisecond.

5. The projection type image display apparatus according to claim 4, wherein

the turning-off time of the intermittent turning-on signal in one cycle is shorter than the time to half-attenuation the emission intensity from a peak emission time in the delaying emission characteristics of the electroluminescence element using the phosphorescent material for its luminescent layer.

6. The projection type image display apparatus according to claim 1, wherein

the intermittent turning-on signal has a turning-on time and a turning-off time equal to each other in one cycle, and

the controller inverts the timing phase of turning-on and turning-off of the pixels handling emission in two out of three primary colors, corresponding to the inversion of the it phase, respectively, in the electroluminescence element.

7. The projection type image display apparatus according to claim 1, wherein

the turning-on time and the turning-off time of the intermittent turning-on signal have a time ratio of 1 to 2, and

the controller delays the timing phases of turning-on and turning-off of pixels handling emission in three primary colors, respectively, in the electroluminescence element by {fraction (2/37)}π

to each other.

8. The projection type image display apparatus according to claim 1, wherein

the turning-on time and the turning-off time in the intermittent turning-on signal has a time ratio of 2 to 1, and

timing phases of turning-on and turning-off of the pixels handling emission in three primary colors, respectively, are delayed by ⅔

π

to each other.

9. An image display system, comprising:

a projection type image display apparatus according to claim 1, and

a screen onto which images are projected by the projection type image display apparatus, and which reflects light from the projection type image display apparatus.

10. An image display system, comprising:

a projection type image display apparatus according to claim 1, and

a screen onto which images are projected by the projection type image display apparatus, and which transmits light from the projection type image display apparatus.

11. A projection type image display apparatus, comprising:

an electroluminescence element having pixels that can be individually modulated, where a luminescent layer of the electroluminescence element is formed of a material containing an organic fluorescent material or an organic phosphorescent material,

a projection optical system which projects modulated light emitted from the respective pixels of the electroluminescence element,

an element temperature detector which detects the temperature of the electroluminescence element,

an outside air temperature detector which detects the outside air temperature,

a cooling unit provided on a surface other than a light emitting surface of the electroluminescence element, and

a controller which controls the cooling unit so that a temperature detected by the element temperature detector becomes equal to or lower than a temperature detected by the outside air temperature detector and the difference from the temperature detected by the outside air temperature falls within a predetermined range.

12. The projection type image display apparatus according to claim 11, wherein

the controller controls the cooling unit from the time of power supply to this projection type image display apparatus so that a difference between a temperature detected by the element temperature detector and a temperature detected by the outside air temperature detector falls within the predetermined range at a predetermined temporal gradient.

13. The projection type image display apparatus according to claim 11, wherein

the cooling unit comprises a Peltier element.

14. The projection type image display apparatus according to claim 11, wherein

at the light emitting surface side of the electroluminescence element, at least two light transmitting windows are provided so that an gas layer is sealed between these.

15. An image display system, comprising:

a projection type image display apparatus according to claim 11, and

a screen onto which images are projected by the projection type image display apparatus, and which reflects light from the projection type image display apparatus.

16. An image display system, comprising:

a projection type image display apparatus according to claim 11, and

a screen onto which images are projected by the projection type image display apparatus, and which transmits light from the projection type image display apparatus.