JP5002158B2 - Projection-type image display device - Google Patents

Description

  The present invention relates to a projection-type video display device that forms an optical image corresponding to a video signal by a video display element and projects the optical image onto a screen or the like.

  Light from a light source is irradiated onto a small image display element (also called a light modulation element or light valve) using a lens or mirror, and the image (optical image) formed by modulation by the image display element is enlarged. 2. Description of the Related Art Projection-type video display devices that project and display are known. For example, there is a projection type liquid crystal display device (liquid crystal projector) that uses a liquid crystal display element (liquid crystal light valve) as an image display element and projects an enlarged projection onto a screen through a projection lens. In such a projection-type image display apparatus, the following techniques have been proposed in order to improve the dynamic range (contrast) and color reproducibility (white balance) of the display screen.

  In patent document 1, it is installed on the optical axis of the light emitted from the light source, is provided with a dimming means that adjusts the amount of light emitted from the light source, and controls the dimming means based on information from the outside. An illumination device is disclosed in which the amount of light emitted from the illumination means can be adjusted. Accordingly, it is stated that light having brightness according to the image can be obtained in the illuminated area even if the light output intensity of the light source remains constant, which contributes to the expansion of the dynamic range of the projection display device.

  In Patent Document 2, a liquid crystal projector having a configuration in which polarizing plates are provided on the incident sides of three liquid crystal panels that respectively modulate R, G, and B monochromatic lights, and a polarizing filter is disposed in front of each polarizing plate. Is disclosed. It is stated that white balance can be adjusted without adjusting the video signal by adjusting the amount of light incident on each liquid crystal panel by changing the rotation angle of the polarizing filter.

  Further, Patent Document 3 discloses a liquid crystal projector apparatus having a configuration in which an attenuation plate that attenuates part of a light beam incident on a liquid crystal panel is provided according to the viewing angle characteristics of the liquid crystal panel. The attenuation plate is disposed in the optical path of the blue light of the illumination optical system, and the attenuation plate is a light shielding plate that blocks a part of the light beam incident on the liquid crystal panel. Accordingly, it is stated that the contrast of the entire color image projected on the screen can be improved according to the viewing angle characteristics of the liquid crystal panel (the contrast ratio of blue light is poor due to wavelength dependency).

International Publication No. 03/032080 Pamphlet JP-A-6-167717 Japanese Patent Laid-Open No. 2001-222002

  In the projection type image display device, when trying to improve both the dynamic range (contrast) and color reproducibility (white balance), the techniques described in the above-mentioned patent documents are combined. At that time, it is necessary to individually incorporate new parts such as the light control means and the polarizing filter, which increases the size of the apparatus and causes an increase in cost.

  Further, when comparing the amounts of R, G, and B light used in a general projector, the amount of B light is the smallest. In Patent Document 3, the attenuation plate is disposed in the optical path of B light of the illumination optical system. Therefore, the B light originally having a small amount of light is further attenuated, and as a result, the white balance may be deteriorated.

  The present invention has been made in view of the above, and it is an object of the present invention to provide a small and inexpensive projection-type image display apparatus having a wide dynamic range and excellent color reproducibility.

  The present invention includes a light source, an illuminating unit that separates and collects light beams emitted from the light source into red, green, and blue color lights, an image display element that optically modulates each of the collected light beams, and light modulation. A projection-type image display device comprising: a light combining means for combining images from the respective light fluxes; and a projection means for enlarging and projecting the combined images; and the illumination means includes a green light flux among the separated light fluxes. The light shielding means for shielding a part of the light is provided.

  Here, the illumination means is provided with a relay lens system that corrects the image forming position in the optical path of green light having a longer optical path length than the others among the separated light beams, and the light shielding means is disposed inside the relay lens system.

  The light shielding means passes through the central portion of the incident light beam and shields the peripheral portion, and the shape of the opening that passes is made symmetrical with respect to the optical axis of the light beam. Alternatively, the area of the opening of the light shielding means is variable and is adjusted according to the input video signal.

  ADVANTAGE OF THE INVENTION According to this invention, the small and cheap projection type video display apparatus with a wide dynamic range and excellent color reproducibility can be provided.

  Hereinafter, the best mode of the present invention will be described in detail with reference to the drawings. In each figure, the subscripts R, G, and B denote elements of red, green, and blue optical paths, respectively.

  FIG. 1 is a block diagram showing an embodiment of a projection type image display apparatus according to the present invention. The light emitted from the light source 1 is separated into three-color light (R, G, B) by dichroic mirrors (color separation means) 11, 12, and passes through three light valves 14 R, 14 G, 14 B made of liquid crystal display elements. After being transmitted and synthesized, the projection lens 20 enlarges and projects it onto the screen 50. The optical axis of each optical path is indicated by a broken line 100. The optical system until the light emitted from the light source 1 irradiates the liquid crystal display element is called illumination means.

  The light source 1 is a white lamp such as an ultra-high pressure mercury lamp, a metal halide lamp, a xenon lamp, a mercury xenon lamp, or a halogen lamp. The reflecting mirror 2 has, for example, a parabolic reflecting surface and a circular or polygonal exit opening. The light emitted from the light source 1 is reflected by the reflecting mirror 2 and becomes parallel to the optical axis. The first array lens 3 includes a plurality of lens cells arranged in a matrix, and splits the light incident from the reflecting mirror 2 into a plurality of lights, which are efficiently supplied to the second array lens 4 and the polarization conversion element 5. Lead well. The polarization conversion element 5 aligns the light from the second array lens 4 in a predetermined polarization direction. The polarized light is collected by the condenser lens 6, reflected by the reflection mirror 7, and then reflected by the dichroic mirrors 11 and 12, with R light (red light), B light (blue light), and G light ( Green light).

  The R light is reflected by the dichroic mirror 11, is further reflected by the reflection mirror 10, and enters the light valve 14R for R light through the condenser lens 13R. Here, the R light incident on the light valve 14R is LR. Of the B light and G light transmitted through the dichroic mirror 11, the B light is reflected by the dichroic mirror 12 and enters the B light light valve 14B through the condenser lens 13B. Here, the B light incident on the light valve 14B is LB.

  On the other hand, the G light passes through the dichroic mirror 12, is reflected by the reflection mirrors 8 and 9, and passes through relay lens systems 15, 16, and 17 to be described later, and enters the light valve 14G for G light. The light path length until each color light enters the light valve is configured such that the G light is larger than the other R and B lights. Here, G light incident on the light valve 14G is LG.

  By the optical system (illuminating means), the projection image of each lens cell of the first array lens 3 is converted into a light valve 14R by the condenser lens 6, condenser lenses 13R and 13B, and relay lens systems 15, 16, and 17, respectively. , 14B, 14G are superimposed on the video display elements 18R, 18B, 18G. In other words, the first array lens 3 and the video display element 18 are arranged so as to have a relationship (conjugate relationship) between an object and an image.

  Further, the second array lens 4 and the condensing lens 6 irradiate the image display element 18 in each light valve 14 with the light flux divided into a plurality by the first array lens 3 with a highly uniform illuminance distribution. Let Thus, a uniform illuminance distribution can be obtained by the illumination means between the first array lens 3 and the video display element 18.

  Here, the optical path of the G light will be further described. The G light passes through the dichroic mirror 12, is reflected by the reflection mirror 8, passes through the light shielding means 30, and forms an image once at a position optically conjugate with the light valve 14G. The light shielding means 30 improves the dynamic range and color reproducibility as will be described later. Further, the first relay lens 15, the reflection mirror 8, the second relay lens 16, the reflection mirror 9, and the third relay lens 17 form an image again on the light valve 14 G for G light. Here, the optical system between the first relay lens 15 and the third relay lens 17 is referred to as a relay lens system. As described above, by providing the relay lens system, even when the optical path length of the G light is longer than the optical path lengths of the other R and B lights, it is possible to correct the image at a normal position.

  Each video display element 18 in each light valve 14 is optically modulated in accordance with a video signal (not shown) to form an optical image. The R light, B light, and G light transmitted through these image display elements 18 are combined as a color image by a light combining prism (light combining means) 19. Thereafter, the light passes through a projection lens (projection means) 20 such as a zoom lens and is enlarged and projected on a screen 50.

  FIG. 2 is a block diagram showing an optical system for G light after the dichroic mirror 12 in FIG. Of these, the first relay lens 15, the light shielding means 30, and the third relay lens 17 are denoted by reference numerals 150, 300, and 170 as front views thereof (viewed from the optical axis direction).

  The G light (LG) transmitted through the dichroic mirror 12 first forms and condenses a conjugate image 151 of the first array lens 3 in the vicinity of the first relay lens 15, is reflected by the reflection mirror 8, and then is blocked. Incident on the means 30. The light shielding means 30 is disposed in the vicinity of the relay lens 16 and shields a part of the incident light LG. The outgoing light LG that has passed through the light shielding means 30 focuses and condenses a conjugate image (secondary light source image) 301 of the second array lens 4 in the vicinity of the second relay lens 16. Further, after being reflected by the reflection mirror 9, the conjugate image 171 of the first array lens 3 is again formed on the light valve 14G for G light in a state where the light is made substantially parallel by the third relay lens 17. Shine.

  Here, the light shielding unit 30 shields a part (peripheral part) of the incident light LG by the light shielding part 31 (hatched part), but in the vicinity of the relay lens 16, a conjugate image (secondary light source image) of the second array lens 4. ) 301 is focused and focused, and does not affect the illuminance distribution in the light valve 14G. The luminous flux emitted from the light shielding means 30 is superposed by the second relay lens 16 provided in the subsequent stage as a superimposing lens, so that the illuminance distribution of the outgoing light from the original light source is made uniform. Can do. At this time, in order to narrow the light flux of the relay lens system, the F value (optical aperture) of the optical path is set to a value larger than the F value of the other optical paths.

  Next, effects (dynamic range, color reproducibility) of the light shielding means 30 will be described.

  FIG. 3 is a diagram showing the relationship between the area of the opening of the light shielding means 30 and the contrast performance. As shown in the figure, the contrast performance is improved by reducing the aperture area. This is based on the incident angle dependency of contrast of a video display element such as a liquid crystal display element. That is, the contrast performance deteriorates as the incident angle (the angle of the incident light with respect to the normal of the element surface) increases. For this reason, by narrowing the area of the opening of the light shielding means 30, it is possible to shield the light of the high incident angle component in the peripheral portion that deteriorates the contrast performance, and improve the contrast performance.

  In this embodiment, the light shielding means 30 is provided only in the optical path of G light. This is because the G light is dominant in the ratio of the amounts of light of the three primary colors in a normal projection type video display. That is, a high-pressure mercury lamp is usually used as a light source, but the spectrum of the high-pressure mercury lamp contains a large amount of G light component (occupies about 70%). Therefore, the contrast performance of the entire projection display apparatus can be improved efficiently only by improving the contrast performance of the light valve 14G for G light by using one light shielding means.

  Further, in this embodiment, since the light shielding means is provided in the optical path of the relay lens system in which the luminous flux is narrowed down, it is possible to reduce the size of the component as compared with the case where the light shielding means is provided in the vicinity of another optical path, for example, the lens array. .

  As described above, a small and inexpensive projection-type image display device having a desired dynamic range can be realized by efficiently using the light shielding means having the opening area corresponding to the desired contrast performance.

  Next, FIG. 4 is a diagram showing the relationship between the area of the opening of the light shielding means 30 and the color temperature. As shown in the figure, by reducing the aperture area and reducing the light amount of the outgoing light LG, the color temperature of the light obtained by combining the RGB lights by the color combining prism 19 can be increased. This is to reduce the G light having the largest light quantity among the three primary colors in the projection type video display apparatus, thereby improving the white balance and improving the color reproducibility.

  That is, by using the light shielding means 30 having an opening area corresponding to a desired color temperature, a projection-type image display device having a desired color reproducibility can be obtained.

  As described above, in this embodiment, the light shielding means is provided in the optical path of the G light having the largest light quantity among the three primary color lights emitted from the light source, so that the dynamic range is wide and the color reproducibility is excellent. A projection-type image display device can be provided.

  In the present embodiment, the light shielding means 30 can be easily exchanged from the outside. Then, by preparing a plurality of light shielding means having different opening areas as the light shielding means, and selecting and attaching the light shielding means having the optimum opening area from these light shielding means, variations in contrast performance and color temperature are achieved. The projection type image display device with a small amount can be mass-produced. In addition, there is a margin in the contrast performance required for the light valve 14G, which increases the degree of freedom in designing the projection display apparatus.

  Next, an example of a specific shape of the light shielding unit 30 will be described.

  FIG. 5 is a perspective view showing an example of the light shielding means 30. The shaded portion indicates a light shielding portion 31 that shields incident light, the inside thereof indicates an opening portion 32 through which incident light passes, and the broken line indicates an optical axis 100. FIG. 5A shows a case where the opening 32 is elliptical, and FIG. 5B shows a case where it is rectangular. In any case, the optical axis 100 is the center, and the shape is symmetrical in the left-right direction (x-axis) and the up-down direction (y-axis). By making the openings symmetrical, it is possible to eliminate unevenness of the illuminance distribution.

  In the vicinity of the relay lens 16 adjacent to the light shielding means 30, a conjugate image (secondary light source image) 301 of the second array lens 4 is focused. When the light beam is shielded by using the light shielding means 30, it must be taken into consideration that the uniformity of the illuminance distribution is not impaired. For example, when the light beam is shielded from only one side, the illuminance distribution in the illuminated area is biased. When the light is shielded symmetrically with respect to the axis 100 passing through the center of the light beam as in this embodiment, the illuminance distribution in the illuminated area is also symmetrical with respect to the axis passing through the center of the illuminated area. Therefore, the image quality of the projected image can be improved. Further, if the light is concentrically shielded with respect to the center of each lens (optical axis 100), the light is matched with the illuminance distribution of the original light source, and the illuminance distribution can be made more uniform.

  According to the projection-type image display device using the light shielding means having this configuration, it is possible to provide not only an excellent dynamic range and color reproducibility but also a uniform projection image without luminance unevenness.

  FIG. 6 is a perspective view showing another example of the light shielding means 30. Here, the light shielding portion 31 is configured by the shielding blade 33, and the area of the opening 32 is variable. The shape of the opening 32 in this case is a substantially circular shape that is symmetric with respect to the optical axis 100. The shielding blade 33 is moved by a driving device such as a motor to adjust the area of the opening 32. For example, to increase the dynamic range and color reproducibility of the projected image, the shielding blade 33 is moved in the direction of the arrow to reduce the opening area. Conversely, to increase the brightness of the projected image, the shielding blade 33 is opened to increase the area of the opening.

  According to the projection-type image display device using the light shielding means of this configuration, the brightness, dynamic range, and color reproducibility of the projection image can be optimally adjusted according to the input image signal, thereby providing a higher-quality projection image. can do.

  In the above-described embodiments, the light shielding means for shielding the separated green light has been described. However, the light shielding means may be provided for the light flux of the color having the largest ratio of the incident light amount, and the same effect is thereby obtained. can get. In addition, although the liquid crystal display element is described as an example of the video display element, the present invention is not limited to this, and a digital mirror device (DMD) or the like can also be applied. The shape of the opening of the light shielding means is an example, and any shape that is symmetrical with respect to the optical axis is effective.

The block diagram which shows one Example of the projection type video display apparatus by this invention. The block diagram which shows the optical system of the green light (G light) in FIG. The figure which shows the relationship between the area of the opening part of the light-shielding means 30, and contrast performance. The figure which shows the relationship between the area of the opening part of the light-shielding means 30, and color temperature. The perspective view which shows an example of the light-shielding means 30. FIG. The perspective view which shows the other example of the light-shielding means 30. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Light source, 2 ... Reflection mirror, 3 ... 1st array lens, 4 ... 2nd array lens, 5 ... Polarization conversion element, 6 ... Condensing lens, 7, 8, 9, 10 ... Reflection mirror, 11, DESCRIPTION OF SYMBOLS 12 ... Dichroic mirror (color separation means), 13 ... Condenser lens, 14 ... Light valve, 15 ... 1st relay lens, 16 ... 2nd relay lens, 17 ... 3rd relay lens, 18 ... Image | video display element, DESCRIPTION OF SYMBOLS 19 ... Photosynthesis prism, 50 ... Screen, 20 ... Projection lens, 30 ... Light-shielding means, 31 ... Light-shielding part, 32 ... Opening part, 33 ... Shielding blade, 100 ... Optical axis.

Claims (3)

A light source; illumination means for separating and condensing light beams emitted from the light source into red, green, and blue color light; an image display element that optically modulates each of the collected light beams; In a projection-type image display device comprising light combining means for combining images from each light beam and projection means for enlarging and projecting the combined images,
The illuminating means is provided with a relay lens system for correcting the imaging position in the optical path of green light having a longer optical path length than the other of the separated luminous fluxes, and one of the luminous fluxes of only the green light is provided inside the relay lens system. A light shielding means for shielding the part ,
The light shielding means passes through the central portion of the incident light beam and shields the peripheral portion, and the shape of the opening that passes through is an elliptical shape symmetric with respect to the optical axis of the light beam,
A projection-type image display apparatus characterized in that the area of the opening of the light shielding means is variable and is adjusted according to an input image signal. In the projection type video display device according to claim 1,
A projection-type image display apparatus, wherein an F value of an optical path of the relay lens system is set larger than an F value of other optical paths . In the projection type video display device according to claim 1 ,
A projection type image display device characterized in that the ratio of the amount of green light is the largest among the components of light emitted from the light source .

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