JP2009294559A - Image projection device - Google Patents

Abstract

Provided is an image projection apparatus in which the luminance ratio between a light source having the slowest response speed and another light source is always constant even during a period in which the luminance of the light source is changed according to the luminance information of the video signal, and the white balance is constant.
The luminance of the light source is detected by using the luminance of the light source having the slowest response speed detected by the luminance detecting unit and the luminance information of the video signal calculated from the input video signal by the video signal control unit. To change. Using the luminance of the light source 12 of the light source unit 11 detected by the luminance detection unit 14 and the luminance of the light source 13 having a response speed faster than that of the light source 12, the response speed of the light source 13 having a response speed faster than that of the light source 12 with respect to the luminance change of the light source 12. The luminance is changed so as to always follow at a constant luminance ratio.
[Selection] Figure 1

Description

  The present invention relates to an image projection apparatus in the video field.

  The present invention relates to an image projection apparatus, and more particularly to a technique for controlling a light source of an image projection apparatus.

  The present invention relates to an image projection apparatus, and can be suitably used particularly for improving image quality.

  A conventional image projection apparatus modulates light from a light source according to an image to be displayed by a spatial light modulator such as a transmissive or reflective liquid crystal panel or DMD (digital micromirror device), and the modulated light. Is enlarged and projected on the screen by the projection optical system. When a discharge lamp such as a metal halide lamp or an ultra-high pressure mercury lamp is used as the light source, it is difficult to achieve appropriate color reproducibility because the light intensity of the red component is generally low.

  As a solution to the problem of this light source, a hybrid image projection apparatus is provided in which a red LED is added to a discharge lamp having a low light intensity of a red component, and a light detection element made of a photodiode is provided for both light sources.

Only the red light is transmitted through the filter as the irradiation light of the discharge lamp, the brightness of the red light is detected by the photodiode, and the brightness of the discharge lamp is controlled. And red LED detects the brightness | luminance of red LED with the photodiode provided separately, and controls red LED. In this way, an image projection apparatus is provided that can project irradiation light having an appropriate spectral distribution and project an image having excellent color reproducibility. (For example, refer to Patent Document 1.)

JP 2007-171660 A

  However, in the conventional configuration, when controlling the iris of the discharge lamp in general, the response speed is slow because the brightness of the discharge lamp is controlled by the mechanical iris provided on the optical path of the discharge lamp.

  Iris control is to control the light source to the luminance of the light source determined from the luminance information of the video signal, and has the effect of making the dark screen darker and improving the contrast ratio.

  The red LED has linearity in the relationship between the driving current and the luminance of the light source, so that the luminance can be controlled by the driving current and the response speed is fast.

  Since each light source is controlled separately, when performing iris control that changes the brightness of the light source according to the brightness information of the video signal, the light source with the slowest response speed due to the difference in response speed due to the difference in the type of light source Until the luminance of the light source follows that of the other light source, the white balance is lost and the image quality is degraded.

  The luminance change of the conventional light source with a fast response speed is as shown in FIG. 4a, and the white light ratio cannot be kept constant within the luminance change time 31 with respect to the luminance change of the light source with the slow response speed shown in FIG. Balance is lost.

  The present invention solves the above-mentioned conventional problems, and in an image projection apparatus using a plurality of light sources having different response speeds of luminance change, even during a period in which the luminance of the light source such as iris control is changed according to the luminance information of the video signal. An object of the present invention is to provide an image projection apparatus in which the luminance ratio between the light source having the slowest response speed and other light sources is always constant, and the white balance is constant.

  In order to solve the above-described conventional problems, an image projection apparatus according to a first aspect of the present invention is a video that digitally converts an input video signal, outputs a digital video signal, and outputs luminance information of the video signal calculated from the input video signal. A signal control unit, a video conversion unit that synthesizes a plurality of irradiation lights and a digital video signal from the video signal control unit to output a projection video, a video display unit that displays a projection video from the video conversion unit, A light source unit that includes a plurality of light sources that can be adjusted in luminance and that have different response speeds of luminance changes, and that outputs a plurality of irradiation lights to the video conversion unit, and a light that corresponds to the luminance of the plurality of light sources from the light source unit. A luminance detection unit that detects the luminance of each light source detected by a detection element, a result obtained by comparing the luminance of each light source from the luminance detection unit, and a video signal from the video signal control unit It is obtained by said that a light source control unit for controlling the respective luminances of light sources of the light source unit by the luminance information.

  An image projection apparatus according to a second invention is the image projection apparatus according to the first invention, and controls the luminance of another light source in response to the luminance change of the light source having the slowest response speed of the luminance change of the light source unit. It is characterized by synchronizing.

  An image projection apparatus according to a third invention is the image projection apparatus according to the first or second invention, wherein the light source having the slowest response speed of the luminance change of the light source unit is a discharge lamp, The light source is a laser.

  An image projection apparatus according to a fourth invention is the image projection apparatus according to the first or second invention, wherein the light source having the slowest response speed of the luminance change of the light source unit is a discharge lamp. The light source is an LED.

  An image projection apparatus according to a fifth invention is the image projection apparatus according to the third or fourth invention, wherein the other light sources of the light source section have at least one of red, green, and blue monochromatic light. It is characterized by that.

  According to the image projection apparatus of the present invention, the luminance ratio between the light source having the slowest response speed and the other light source is always constant even during the period in which the luminance of the light source such as iris control is changed according to the luminance information of the video signal, and the white balance Can be made constant.

Hereinafter, embodiments of an image projection apparatus of the present invention will be described in detail with reference to the drawings.
The configuration and operation of an image projection apparatus according to an embodiment of the present invention will be described below with reference to FIGS.

  The video signal controller 1 receives input video signals such as color difference signals and three primary color signals, and the color difference signals are converted into three primary color signals. The luminance information of the input video signal is calculated by digital signal processing, and the luminance information of the video signal is output to the light source control unit 19. Luminance information is a value obtained by dividing the sum of luminance signals in all pixels per frame by the number of pixels, and is an APL (Average Picture Level) representing the average luminance of the pixels of the entire screen or the luminance signal. A histogram representing a level distribution, MAX representing the highest luminance among luminance signals at all pixels per frame, MIN representing the lowest luminance among luminance signals at all pixels per frame, and the like. The video conversion unit 2 performs image processing such as gamma correction and outputs a digital video signal of a red video signal, a green video signal, and a blue video signal.

  In the video conversion unit 2, red, green, and blue light separated from a plurality of irradiation lights input from the light source unit 11 is converted into red liquid crystal 3, green light into green liquid crystal 4, Blue light is input to the blue liquid crystal 5. Further, from the red video signal, the green video signal, and the blue video signal digital video signal from the video signal control unit 1, the transmittance of red light, green light, and blue light is changed to red liquid crystal 3, green liquid crystal 4, Controlled by the blue liquid crystal 5, the intensity of red light, green light, and blue light is applied to all pixels in each frame. The transmittance of each liquid crystal is set by a value read from the memory 7 provided in the video conversion unit 2 when the image projection apparatus is activated, and the white balance is made constant. The red light, green light, and blue light transmitted through the liquid crystal are combined by the prism 6 to output a projected image.

  In the video display unit 8, the projection video from the video conversion unit 2 is enlarged by the projection lens 9 and displayed on the screen 10.

  The light source unit 11 includes a light source 12 that can be adjusted in luminance by the light source control unit 19 and that has the slowest response speed of luminance change and a light source 13 that has the fast response speed. The light source 12 includes a discharge lamp 27 and a mechanical iris 28 on the optical path. The mechanical iris 28 includes a mechanical iris driving unit 29 and a mechanical iris mechanism unit 30. The discharge lamp is opened and closed by opening and closing the diaphragm of the mechanical iris mechanism unit 30. 27 brightness is controlled. The light source 13 is a red laser.

  In the luminance detection unit 14, a part of the irradiation light of the light source 13 is reflected by the reflector 15 provided on the optical path of the irradiation light of the light source 13 of the light source unit 11, and on the optical path of the irradiation light of the light source 12 of the light source unit 11. A part of the light emitted from the light source 12 is reflected by the provided reflector 16.

  The reflected light reflected by the reflecting plate 15 is applied to the light detecting element 17 that outputs a current corresponding to the luminance, and the reflected light reflected by the reflecting plate 16 is applied to the light detecting element 18. Each current corresponding to the luminance of the light source is output to the light source control unit 19.

  The light source control unit 19 controls the luminance of the light source 12 from the luminance information of the video signal from the video signal control unit 1 and controls the luminance change of the light source 13 so as to be synchronized with the luminance change of the light source 12. The configuration and operation of the control will be described with reference to FIGS. 2, 3b, and 3a.

  First, control of the light source 12 having the slowest response speed of luminance change will be described with reference to FIGS. 2 and 3b.

  A target luminance value 32 of the light source 12 is determined by the target luminance calculation unit 20 from luminance information such as APL, histogram, MAX, and MIN of the video signal from the video signal control unit 1.

  A current value corresponding to the luminance of the light source 12 detected by the light detection element 18 of the luminance detection unit 14 is converted into a voltage by the IV converter 21.

  The luminance of the light source 12 converted into a voltage by the IV converter 21 is input to the positive input terminal of the comparator 25, and the target luminance value 32 determined by the target luminance calculation unit 20 is input to the negative input terminal. 32 and the luminance of the light source 12 converted into voltage are compared. When the luminance of the light source 12 converted into voltage is larger than the target luminance value 32, the output of the comparator 25 becomes a driving voltage for narrowing the diaphragm of the mechanical iris mechanism unit 30, and the diaphragm of the mechanical iris mechanism unit 30 is narrowed. The brightness of is reduced. When the target luminance value 32 is larger than the luminance of the light source 12 converted into a voltage, the output of the comparator 25 becomes a driving voltage at which the diaphragm of the mechanical iris mechanism unit 30 is expanded, and the diaphragm of the mechanical iris mechanism unit 30 is expanded. The brightness of increases.

  The luminance of the light source 12 changes so that the luminance of the light source 12 converted into voltage converges to the target luminance value 32 as shown in FIG.

  Further, the inputs to the positive input terminal and the negative input terminal of the comparator 25 are reversed, and the output of the comparator 25 becomes a driving voltage at which the diaphragm of the mechanical iris mechanism section 30 spreads, and the diaphragm of the mechanical iris mechanism section 30 spreads, and the comparator 25 May be a driving voltage that narrows the diaphragm of the mechanical iris mechanism section 30 and the diaphragm of the mechanical iris mechanism section 30 may be narrowed.

  Next, control of the light source 13 having a fast response speed of luminance change will be described with reference to FIGS. 2 and 3a.

  A current value corresponding to the luminance of the light source 13 detected by the light detection element 17 of the luminance detection unit 14 is converted into a voltage by the IV converter 22.

  In order to enable the comparator 24 to compare the luminance of the light source 13 converted into voltage with the luminance of the light source 12 converted into voltage by the IV converter 22, the luminance of the light source 12 when the white balance is constant is used as the light source. The luminance of the light source 13 converted into a voltage is amplified by the amplifier 23 having an amplification factor of the value divided by the luminance of 13.

  The luminance of the light source 12 converted into a voltage by the IV converter 21 is input to the positive input terminal of the comparator 24, and the luminance of the light source 13 amplified by the amplifier 23 is input to the negative input terminal and converted into a voltage. The brightness of the light source 12 is compared with the brightness of the amplified light source 13. When the luminance of the light source 12 converted into the voltage is larger than the luminance of the amplified light source 13, the output of the comparator 24 becomes a voltage at which the transistor 26 is turned on, and the base current of the transistor 26 increases and the light source 13 is supplied. Current supply is increased, and the luminance of the light source 13 is increased. When the brightness of the amplified light source 13 is larger than the brightness of the light source 12 converted into a voltage, the output of the comparator 24 becomes a voltage at which the transistor 26 is turned off, and the current of the transistor 26 decreases, and the current to the light source 13 decreases. The current supply decreases and the brightness of the light source 13 decreases. The transistor 26 may be configured to use a PNP transistor, a FET (Field Effect Transistor), or the like.

  Therefore, the luminance change of the light source 13 changes so as to always follow the luminance change of the light source 12, the luminance ratio of the light source 12 and the light source 13 is always constant, and the luminance change of the light source 12 ends. It is possible to reduce the collapse of the white balance that occurs during this time.

  According to the present invention, it is possible to reduce the white balance collapse caused by the delay of the luminance change of the light source 12 with respect to the light source 13 during the iris control, and to improve the image quality.

  In the image projection apparatus according to the present invention, the luminance ratio between the light source having the slowest response speed and the other light sources is always constant even during the period in which the luminance of the light source such as iris control is changed according to the luminance information of the video signal, and the white balance is maintained. It has an effect that can be made constant, and is useful for a technique for controlling the light source of the image projection apparatus.

Configuration diagram of image projection apparatus of the present invention Detailed configuration diagram of image projection apparatus of the present invention The figure which showed the brightness | luminance change of the light source with a quick response speed in the iris control of this invention The figure which showed the luminance change of the light source with the slowest response speed in this invention and the conventional iris control. The figure which showed the brightness change of the light source with the quick response speed in the conventional iris control

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image | video signal control part 2 Image | video conversion part 3 Liquid crystal for red 4 Liquid crystal for green 5 Liquid crystal for blue 6 Prism 7 Memory 8 Video display part 9 Projection lens 10 Screen 11 Light source part 12 Light source (light source with the slowest response speed)
13 Light source (light source with faster response speed than light source 12)
DESCRIPTION OF SYMBOLS 14 Brightness detection part 15 Reflector 16 Reflector 17 Photodetection element 18 Photodetection element 19 Light source control part 20 Target brightness | luminance calculation part 21 IV converter 22 IV converter 23 Amplifier 24 Comparator 25 Comparator 26 Transistor 26 Discharge lamp 28 Mechanism Iris 29 Mechanical iris drive unit 30 Mechanical iris mechanism unit 31 Luminance change time 32 Target luminance value of light source with the slowest response speed

Claims (5)

A video signal control unit that digitally converts the input video signal to output the digital video signal and outputs luminance information of the video signal calculated from the input video signal;
A video conversion unit that synthesizes a plurality of irradiation lights and a digital video signal from the video signal control unit and outputs a projection video; and
A video display unit for displaying a projection video from the video conversion unit;
It consists of multiple light sources with adjustable brightness and different response speeds for brightness changes.
A light source unit that outputs a plurality of irradiation lights to the video conversion unit;
A luminance detection unit that detects the luminance of a plurality of light sources from the light source unit by a light detection element corresponding to each light source and outputs the luminance of each light source;
Image projection provided with a light source control unit that controls the luminance of each of the plurality of light sources of the light source unit based on the result of comparing the luminance of each light source from the luminance detection unit and the luminance information of the video signal from the video signal control unit apparatus. The image projection apparatus according to claim 1, wherein the brightness control of another light source is synchronized with the brightness change of the light source having the slowest response speed of the light source unit. 3. The image projection apparatus according to claim 1, wherein the light source having the slowest response speed of luminance change of the light source unit is a discharge lamp, and the other light source is a laser. The image projection apparatus according to claim 1, wherein the light source having the slowest response speed of the luminance change of the light source unit is a discharge lamp, and the other light source is an LED. 5. The image projection apparatus according to claim 3, wherein another light source of the light source unit has at least one of red, green, and blue monochromatic light.

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