JP4806467B2 - Projection display device - Google Patents

Description

  The present invention relates to a projection display apparatus such as a liquid crystal projector.

FIG. 4 is a graph showing the spectral characteristics of a lamp (for example, an ultra-high pressure mercury lamp) used in a projection display apparatus. As can be seen from FIG. 4, the lamp emission light has a large spectrum at about 578 nm corresponding to the intermediate color light of green light and red light. If the spectrum light is taken in on the green light side, the green color becomes yellowish green, and if it is taken in on the red light side, the red color becomes orange, which degrades the respective color purity. Therefore, in general, a dichroic mirror that transmits light in the red wavelength band and reflects light in the cyan (green + blue) wavelength band is designed to transmit the light of the 578 nm component (lead to the red optical path). In addition, a cut filter having the transmission characteristics shown in FIG. 5 is provided on the red optical path so as to cut the 578 nm component. However, in such a configuration, since the light of the component of 578 nm is always cut, there is a problem that the screen illuminance is lowered.

Patent Document 1 below discloses a projection display apparatus that solves the above problem. That is, in this projection display apparatus, the cut filter is provided so as to be freely inserted into and removed from the red optical path. Therefore, the illuminance when the cut filter is inserted into the red light path is reduced, but the purity of red can be maintained, and when removed from the red light path, the purity of red is reduced but the brightness is maximized. .
JP 2000-137289 A

  However, the conventional projection display apparatus has the following problems. Since the 578 nm component is orange and has a low color temperature, the color temperature of white changes when this component is discarded. That is, in the bright mode that makes the best use of the lamp light, the red color filter is removed from the optical path and the 578 nm component is taken in, so the white color temperature is lowered. As a result, the white color temperature is increased in order to discard the 578 nm component. In short, the color temperature of white changes between the bright mode and the color purity-oriented mode.

  In view of the above circumstances, an object of the present invention is to provide a projection display apparatus that can prevent a change in white color temperature between a bright mode and a color purity-oriented mode.

  In order to solve the above problems, the projection display apparatus according to the present invention separates the white light emitted from the light source into three primary color lights, guides the respective color lights to the respective light valves, and performs light modulation by the respective light valves. In a projection-type image display device for projecting an image by synthesizing each obtained color image light, a filter that cuts intermediate color light of green light and red light on a white light path or a predetermined color light path and reduces blue wavelength band light However, when the filter is inserted into a white light path or a predetermined color light path, the filter cuts intermediate color light between green light and red light and at least 20% of the entire blue wavelength band light. It is characterized by reducing.

  If it is said structure, in the bright mode which utilizes lamp light to the maximum, in order to take in the intermediate color light of green light and red light by removing a filter from an optical path, it becomes the predetermined white color temperature in the said lamp light. In a mode in which color purity is emphasized, by inserting a filter in the optical path, not only the intermediate color light of green light and red light is cut, but also the blue wavelength band light is reduced. The white color temperature can be set to the same level as the temperature. That is, it is possible to prevent the white color temperature from changing between the bright mode and the color purity priority mode.

  As described above, according to the present invention, it is possible to prevent the white color temperature from being changed between the bright mode and the color purity emphasis mode.

It is the block diagram which showed the optical system (filter insertion state) of the liquid crystal projector of embodiment of this invention. It is a block diagram which showed the optical system (filter removal state) of the liquid crystal projector of embodiment of this invention. It is the graph which showed the light transmission characteristic of the filter of embodiment of this invention. It is a spectral characteristic figure of a lamp light source. It is the graph which showed the light transmission characteristic of the filter used in order to cut a 578nm component used on a red optical path.

  A liquid crystal projector according to an embodiment of the present invention will be described below with reference to FIGS.

  1 and 2 are views showing a three-plate liquid crystal projector of this embodiment. The light emitting part of the light source 1 is composed of an ultra-high pressure mercury lamp or the like, and the irradiated white light is emitted as parallel light by a parabolic reflector and guided to the integrator lens 3 through the UV / IR cut filter 2.

  The integrator lens 3 is composed of a pair of lens groups (fly eye lenses) 3a and 3b, and each lens portion guides light emitted from the light source 1 to the entire surface of a liquid crystal light valve to be described later. The partial luminance unevenness existing in the light source 1 is averaged, and the light amount difference between the center of the screen and the peripheral portion is reduced. The light passing through the integrator lens 3 is guided to the first dichroic mirror 7 after passing through the polarization conversion device 4, the condenser lens 5, and the total reflection mirror 6.

  The polarization conversion device 4 is configured by a polarization beam splitter array (hereinafter referred to as a PBS array). The PBS array includes a polarization separation film and a phase difference plate (1 / 2λ plate). Each polarization separation film of the PBS array passes, for example, P-polarized light out of the light from the integrator lens 3, and changes the optical path of S-polarized light by 90 °. The optically polarized S-polarized light is reflected by the adjacent polarization separation film and emitted as it is. On the other hand, the P-polarized light transmitted through the polarization separation film is converted into S-polarized light by the retardation plate provided on the front side (light emitting side) and emitted. That is, in this case, almost all light is converted to S-polarized light.

  The first dichroic mirror 7 transmits light in the red wavelength band and reflects light in the cyan (green + blue) wavelength band. The light in the red wavelength band that has passed through the first dichroic mirror 7 is reflected by the total reflection mirror 8 to change the optical path. The red light reflected by the total reflection mirror 8 is optically modulated by passing through a lens 9 and a transmissive liquid crystal light valve 31 for red light. On the other hand, the light in the cyan wavelength band reflected by the first dichroic mirror 7 is guided to the second dichroic mirror 10.

  The second dichroic mirror 10 transmits light in the blue wavelength band and reflects light in the green wavelength band. The light in the green wavelength band reflected by the second dichroic mirror 10 is guided to the transmissive liquid crystal light valve 32 for green light through the lens 11 and is modulated by being transmitted therethrough. The light in the blue wavelength band transmitted through the second dichroic mirror 10 passes through the relay lens 12, the total reflection mirror 13, the relay lens 14, the total reflection mirror 15, and the lens 16, and is a transmissive liquid crystal light valve 33 for blue light. The light is modulated by being transmitted through this. Each of the liquid crystal light valves 31, 32, and 33 includes an incident-side polarizing plate, a panel portion formed by enclosing liquid crystal between a pair of glass substrates (with pixel electrodes and alignment films formed), and outgoing-side polarized light. And a board.

  The modulated light (each color video light) modulated by passing through the liquid crystal light valves 31, 32, 33 is synthesized by the cross dichroic prism 17 to become color video light. The color image light is enlarged and projected by the projection lens 18 and projected and displayed on the screen.

  A filter plate 21 is detachably provided on the white light path on the light incident side of the first dichroic mirror 7. As a mechanism for this insertion / extraction, as shown in FIG. 2, in addition to a mechanism for sliding the filter plate 21, it is rotated by a shaft (horizontal axis, vertical axis) provided apart from the filter plate 21. A mechanism or a mechanism that tilts on a horizontal axis provided at the lower edge of the filter plate 21 may be employed. Moreover, it can also comprise so that it can insert / extract not only by manual insertion / extraction but by actuators, such as a motor.

The filter plate 21 has a first filter 21A on one surface of a transparent glass plate and a second filter 21B on the other surface. Each filter is formed, for example, by depositing dielectric films in multiple layers. The first filter 21A cuts intermediate color light (having a central wavelength of 578 nm) between green light and red light. The second filter 21B reduces blue wavelength band light (for example, band light of 500 nm or less). Since the change in color temperature due to the removal of the 578 nm component corresponds to about 20% to 40% of the blue wavelength band light, the second filter 21B is designed to reduce about 20% to 40% of the blue wavelength band light. Is done. The light transmission characteristics of the filter plate 21 are shown in FIG.

In the above-described configuration, the filter plate 21 may be removed from the optical path when the bright mode uses the lamp light to the maximum, and the filter plate 21 may be inserted into the optical path in the mode where the color purity is important. When the filter plate 21 is removed from the optical path, all of the lamp light is taken in, so that a white color temperature based on the lamp light can be obtained. On the other hand, when the filter plate 21 is inserted into the optical path, not only the 578 nm component, which is an intermediate color light between green light and red light, is cut by the first filter 21A, but also the blue wavelength band light is about 20 by the second filter 21B. Since the color temperature is reduced by 40% to 40%, a white color temperature comparable to the above color temperature can be obtained.

The first filter 21A and the second filter 21B may be configured separately. However, as described above, when the filter plate 21 is integrated, only one insertion / extraction mechanism is required, and the structure can be simplified as compared with the case where each filter is inserted / extracted. When the first filter 21A and the second filter 21B are separated, the first filter 21A can be disposed on the red optical path, and the second filter 21B can be disposed on the cyan optical path or the blue optical path. . When the first filter 21A is arranged on the red light path, a filter having the characteristics shown in FIG. 5 can be used. In addition, when the second filter 21B is arranged on the blue light path, a filter that has no wavelength selectivity and that uniformly reduces light in the entire band by about 20% to 40% can be used.

  In the above description, a projection display apparatus using a liquid crystal light valve is shown, but the present invention can also be applied to a configuration using other light valves.

DESCRIPTION OF SYMBOLS 1 Light source 7 1st dichroic mirror 10 2nd dichroic mirror 21 Filter board 21A 1st filter 21B 2nd filter 31, 32, 33 Liquid crystal light valve

Claims (1)

The white light emitted from the light source is separated into the three primary color lights, and each color light is guided to the light valve,
In a projection display apparatus that synthesizes and projects images of each color image light obtained by light modulation by each light valve, cuts intermediate color light of green light and red light on a white light path or a predetermined color light path, A filter for reducing blue wavelength band light is provided so as to be freely inserted and removed, and when the filter is inserted on a white light path or a predetermined color light path, the filter cuts an intermediate color light of green light and red light and has a blue wavelength. A projection-type image display device that reduces 20% or more of the entire band light.