JP2007010787A - Projector, video display device, and projection system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve the simplification of constitution and miniaturization in size and to reduce space required for video projection. <P>SOLUTION: The projection system includes: a projector 2 to emit light; and a video display device to display a video based on light emitted from the projector 2. The projector 2 includes: a light source to emit light; a light condensing body to condense the light emitted from the light source; a liquid crystal display part to modulate the light emitted from the light condensing body; and a composing part composing the light beams passing through the liquid crystal display part. The video display device includes: a screen 1 provided with the projector 2 at its back; a concave mirror 3 to condense the light beams emitted from the projector 2; a reflection mirror 4 to reflect the light condensed by the concave mirror 3 to the front side from the back side of the screen 1; and a convex mirror 5 diffusing and projecting the light reflected by the reflection mirror 4 to the screen 1. Thus, the light emitted from the projector 2 is projected to the screen 1 so as to go around to the front side from the back side of the screen 1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a projector that projects an image on a screen, an image display device, and a projection system.

  In recent years, front projection type projection systems have been widely used from business use to educational use. This projection system includes a projector and a screen, and the screen is generally arranged at a position away from the projector so as to be perpendicular to the optical axis (coaxial) of the projector.

  The projector has a high output for large screen projection, and is composed of an illumination optical system and an imaging optical system. The illumination optical system includes optical components such as a light source, a lens, and a display device. As the display device, a liquid crystal panel, a digital micro-mirror device (DMD), a grating light valve (GLV), or the like is used.

  The imaging optical system includes an imaging lens for imaging light emitted from the illumination optical system on a screen (see, for example, Patent Document 1). By providing the imaging lens in this way, the projection space between the projector and the screen can be omitted to some extent, so that it can be used indoors.

JP 2003-287676 A

  However, the above-described front projection type projection system has the following two problems. First, the first problem is that it is difficult to simplify the configuration and size of the projector. As described above, the imaging optical system is provided with an imaging lens. Since this imaging lens is made of glass or plastic having a refractive index, light passes through the imaging lens and aberration is generated. Will occur. In order to correct this aberration, it is necessary to use a plurality of lenses having wide angles and different refractive indexes, which complicates the configuration of the projector and increases the size of the projector.

  A second problem is that a wide space is required for video projection. Since the projector is arranged facing the screen, a certain amount of space is generated between the projector and the screen. As described above, when a space is generated between the screen and the projector, if an object or a person is present in the space during the projection of the image, a shadow is generated in the image on the screen, and projection cannot be performed well.

  Accordingly, an object of the present invention is to provide a projector, a video display device, and a projection system that can realize a simplified configuration and a reduced size.

  Another object of the present invention is to provide a projector, a video display device, and a projection system that can reduce the space required for video projection.

In order to solve the above-mentioned problem, the first invention
A projector that emits light;
An image display device that displays an image based on the light emitted from the projector,
The projector
A light source that emits light;
A light collector for condensing light emitted from the light source;
A liquid crystal display that modulates the light emitted from the condenser;
And a combining unit that combines the light that has passed through the liquid crystal display unit,
The video display device
A screen with a projector on the back;
An imaging optical system that projects the light emitted from the projector onto the screen,
The imaging optical system
A concave mirror that collects the light emitted from the projector;
A reflection mirror that reflects the light collected by the concave mirror from the back side of the screen toward the front side;
A projection system comprising: a convex mirror that diffuses light reflected by a reflection mirror and projects the light onto a screen.

The second invention is
A light source that emits light;
A light collector for condensing light emitted from the light source;
A liquid crystal display that modulates the light emitted from the condenser;
And a combining unit that combines the light that has passed through the liquid crystal display unit.

The third invention is
Screen,
An imaging optical system that projects light emitted from a projector provided on the back side of the screen onto the screen,
The imaging optical system
A concave mirror that collects the light emitted from the projector;
A reflection mirror that reflects the light collected by the concave mirror from the back side of the screen toward the front side;
And a convex mirror for diffusing the light reflected by the reflecting mirror and projecting the light onto a screen.

In the first and second inventions, the light collector is
An incident side end face;
An exit side end face that is coaxially opposed to the center line of the incident side end face and has a larger area than the incident side end face;
A side surface formed of a parabola including one or more parabolas focusing on an end point of the incident side end surface in a cross section including the center line;
It is preferable that the light incident through the incident side end face is collected and emitted from the emission side end face within a range of a fixed emission angle.

In the first and second inventions, the projector further includes a morphing unit between the light collector and the liquid crystal display unit,
It is preferable that the shape of the morphing portion is continuously changed from the shape of the emission side end surface of the light collector to the shape of the display surface of the liquid crystal display portion.

  In the first invention, typically, the projector, the imaging optical system, and the screen have a common optical axis. In the third invention, typically, the imaging optical system and the screen have a common optical axis. In the first and third aspects of the invention, the image forming optical system is preferably provided in the vicinity of the screen in order to reduce the size of the video display device.

  In the first and second inventions, the light emitted from the projector is collected by the concave mirror and directed upward, downward or sideward of the screen, and reflected from the back side of the screen to the front side by the reflecting mirror, Since the light is diffused by the convex mirror and projected onto the screen, the light emitted from the projector can be projected onto the screen by turning from the back side to the front side of the screen.

  As described above, according to the present invention, since an image can be formed by the plurality of mirrors provided on the back side and the front side of the screen, an image forming optical system is provided in the projector as in the past. There is no need. Therefore, the configuration of the projector can be simplified and the size can be reduced.

  In addition, the light emitted from the projector can be collected by the concave mirror, guided from the back side of the screen to the front side by the reflecting mirror, and then projected to the front side of the screen by the convex mirror. The required space can be reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings of the following embodiments, the same or corresponding parts are denoted by the same reference numerals.

  The projection system according to the first embodiment is a front projection type projection system that can form an image on a screen without using an illumination / imaging system lens having a refractive index. In this projection system, for example, an image of about 20 to 30 inches can be projected on a screen.

  FIG. 1 is a schematic diagram showing the external appearance of the projection system according to the first embodiment. FIG. 2 is a side view showing a schematic configuration of the projection system according to the first embodiment. The projection system according to the first embodiment includes a projector (illumination optical system) 2 that emits light, a concave aspherical mirror 3 having positive lens power, a flat mirror 4 that changes the optical path by 90 °, for example, and a negative A convex aspherical mirror 5 having a lens power of 5 and a screen 1 on which an image is projected. In the following, the side on which the image of the screen 1 is projected is referred to as the front side, and the opposite side is referred to as the back side.

  The projector 2, the concave aspherical mirror 3 and the flat mirror 4 are provided on the back side of the screen 1, and the convex aspherical mirror 5 is provided on the front side of the screen 1. All the parts constituting these projection systems are arranged in a coaxial system.

  A housing 6 is provided on the back side of the screen 1, and a projector 2, a concave aspherical mirror 3 and a flat mirror 4 are accommodated in the housing 6. An arm 7 is provided on the front side of the screen 1, and the convex aspherical mirror 5 is supported by the arm 7.

  The projector 2 and the screen 1 are integrated. The projector 2 is provided so that the optical axis along which the light of the object point of the projector 2 travels and the main surface of the screen 1 are parallel. In order to prevent the light reflected by the concave aspherical mirror 3 from being blocked by the projector 2, the projector 2 is not installed on the common axis (optical axis) of the entire system, but is separated from the common axis. Provided in position.

  FIG. 3 shows an example of the relationship between the distance from the center (center of gravity) of the liquid crystal panel provided in the projector 2 to the coaxial and the distance from the coaxial to the center of the image projected on the screen 1. As shown in FIG. 3, the distance from the coaxial axis to the center of the image projected on the screen 1 increases in proportion to the distance from the center (center of gravity) of the liquid crystal panel to the coaxial axis. This distance relationship is represented by a straight line y = 28.716x, for example.

  The concave aspherical mirror 3 is provided near the exit side of the projector 2 so that the concave surface faces the projector 2. The concave aspherical mirror 3 is positioned on the same axis as the optical axis of the projector 2.

  The plane mirror 4 is provided below the screen 1. The flat mirror 4 reflects the incident light from the concave aspherical mirror 3 from the back side to the front side of the screen 1, and the optical path of the incident light from the concave aspherical mirror 3 is, for example, 90 clockwise. ° Set to change.

  The convex aspherical mirror 5 is provided on the lower side of the screen 1 so that the mirror itself does not enter the projected image when viewed from the viewer, and projects the image obliquely on the screen 1. The convex aspherical mirror 5 is set at the same height as the flat mirror 4, for example.

Next, each part which comprises the above-mentioned projection system is demonstrated sequentially.
Projector FIG. 4A is a top view showing a schematic configuration of the projector according to the first embodiment of the present invention. FIG. 4B is a side view showing a schematic configuration of the projector according to the first embodiment of the invention. The projector 2 includes a support 11, light emitting units 12R, 12G, and 12B, waveguide pipes 13R, 13G, and 13B, liquid crystal panels 14R, 14G, and 14B, and a prism 15.

  The support 11 is for supporting the light emitting portions 12R, 12G, 12B, the waveguide pipes 13R, 13G, 13B, the liquid crystal panels 14R, 14G, 14B, and the prism 15. The support 11 has, for example, a T-shape, and a prism 15 is provided at the intersection of the T-shape. Light emitting portions 12R, 12G, and 12B are provided at the ends of the portions extending in the three directions, respectively, and the liquid crystal panels 14R, 14G, and 14B are disposed on the three surfaces of the prism 15 that face the light emitting portions 12R, 12G, and 12B, respectively. Is provided. Waveguide pipes 13R, 13G, and 13B are provided between the light emitting units 12R, 12G, and 12B and the liquid crystal panels 14R, 14G, and 14B, respectively.

  The light emitting units 12R, 12G, and 12B can emit red (R), green (G), and blue (B) light, respectively, and include a light source such as an LED (Light Emitting Diode).

  The waveguide pipes 13R, 13G, and 13B are for guiding the light emitted from the light emitting units 12R, 12G, and 12B to the liquid crystal panels 14R, 14G, and 14B, respectively. The waveguide pipes 13R, 13G, and 13B are made of, for example, glass, plastic, or quartz. As the glass, for example, optical glass such as crown glass or flint glass can be used. Specifically, for example, BK7 which is an optical glass containing boron and silicon can be used. As the plastic, for example, acrylic resin (PMMA) can be used.

  As shown in FIG. 4B, the waveguide pipes 13 </ b> R, 13 </ b> G, and 13 </ b> B are composed of a light collector 21 and a morphing pipe 22. The condenser 21 and the morphing pipe 22 are integrally formed. The light collecting body 21 collects light emitted from the light emitting units 12R, 12G, and 12B with high efficiency. For example, 98% of light emitted from the light emitting units 12R, 12G, and 12B is collected in the light collecting body. It is possible to collect light.

  The light entrances of the waveguide pipes 13R, 13G, and 13B have a circular shape due to the characteristics of the light collector 21, whereas the light exits have the same shape as the display surfaces of the liquid crystal panels 14R, 14G, and 14B. It has a square shape. With such a configuration, the light emitted from the light emitting units 12R, 12G, and 12B is condensed, the optical path from the light emitting units 12R, 12G, and 12B to the display surfaces of the liquid crystal panels 14R, 14G, and 14B is shortened and the in-plane luminance is increased. The distribution can be made uniform.

  The shapes of the waveguide pipes 13R, 13G, and 13B are not limited to the above-described example, and the waveguide pipes 13R, 13G, and 13B can be a rotationally symmetric system with respect to the optical axis. However, when the waveguide pipes 13R, 13G, and 13B are rotationally symmetric with respect to the optical axis, the pipe cross section is circular, whereas the display surfaces of the liquid crystal panels 14R, 14G, and 14B have a quadrangular shape ( In order to irradiate light all over the liquid crystal panels 14R, 14G, and 14B, a part of the light emitted from the pipe is discarded. On the other hand, as described above, when a morphing technique that continuously changes the cross-section of the waveguide pipes 13R, 13G, and 13B from a circle to a square is used, the waveguide pipes 13R, 13G, Since the liquid crystal panels 14R, 14G, and 14B can be irradiated with light without throwing away a part of the light emitted from the 13B, the light emitted from the light emitting units 12R, 12G, and 12B can be effectively used.

  FIG. 5 is a cross-sectional view illustrating a configuration example of the light emitting unit 12 </ b> G and the light collector 21. The light emitting unit 12G includes a support 31 with a light reflecting mirror, a light source 32 provided on the support 31 with a light reflecting mirror, and a joint 33 that joins the support 31 with a light reflecting mirror and the light collector 21. With.

  The support 31 with a light reflecting mirror is a support for the light source 32 and also reflects a part of the green light emitted from the light source 32 and guides it toward the light collector 21. The support 31 with a light reflecting mirror includes, for example, a support and a reflective film provided on the surface of the support that faces the light collector 21. The reflective film is an aluminum film formed on the support by, for example, a vapor deposition method. The configuration of the light emitting units 12R and 12B is the same as that of the above-described light emitting unit 12G except that the light source 32 includes a light source that emits red light and blue light.

  The light source 32 arranged on the support 31 with a light reflecting mirror may be constituted by either a point light source or a surface light source. Examples of the former include a cold cathode fluorescent lamp (CCFL), and examples of the latter include a light emitting diode (LED).

  The condensing body 21 condenses incident light from the light emitting unit 12G and emits the light within a range of a fixed emission angle. The condenser 21 is disposed on the light emitting unit 12G.

  FIG. 6 is a perspective view showing an example of the shape of the light collector 21. The light collector 21 has a substantially truncated cone shape. Hereinafter, the upper bottom side (lower side in FIG. 6) of the light collector 21 is referred to as an incident side end face 42, and the lower bottom side (upper side in FIG. 6) of the light collector 21 is referred to as an outgoing side end face 43.

  The incident side end surface 42 is a surface on which the incident light LI from the light source 32 is incident. The incident side end surface 42 faces the light source 32, and the shape of the end surface is, for example, a circular shape centered on the point C1.

  The side surface 41 is a surface that collects the incident light LI incident on the incident side end surface 42. The side surface 41 is, for example, a parabola obtained by rotating a parabola around the center line LC, and the parabola is, for example, within the plane including the center line LC, with one end point of the incident-side end surface. The focal point passes through the other end point of the incident side end face 42 and the other end point of the emission side end face 43.

  The exit-side end face 43 is a face that emits the incident light LI collected on the side face 41 as the outgoing light LO. The emission side end face 43 has, for example, a circular shape centered on the point C2. The exit side end face 43 has a larger area than the entrance side end face 42. Further, the incident side end face 42 and the emission side end face 43 are parallel to each other, and the point C1 of the incident side end face 42 and the point C2 of the emission side end face 43 are included in the center line LC.

FIG. 7 shows a cross section when the light collector 21 is cut so as to include the center line LC. As shown in FIG. 7, the cross-section of the light collector 21 includes a line segment ab passing through the point C1 in the incident side end face 42 and a line segment a ₀ − passing through the point C2 in the output side end face 43. and b _0, is defined by a pair of parabolic _{a-b 0, b-a} 0.

The parabola b-a ₀ is focused on one end point a of the line segment ab, and passes through the other end point b of the line segment ab and one end point a ₀ of the line segment a ₀ -b _0. Is part of. The parabola a-b ₀ is focused on the other end point b of the line segment ab, and passes through one end point a of the line segment ab and the other end point b ₀ of the line segment a ₀ -b _0. Is part of. Moreover, the straight lines A1 and B1 in FIG. 7 represent the symmetry axes of the parabolas A and B, respectively, and the angle θ represents the angle formed by the target axes A1 and B1.

To the condenser 21, for example, when the light emitting light L1 from the light source 32 is incident, the light is totally reflected on the parabolic b-a _0, is emitted from between the line segment a ₀ -b ₀ on the exit side. Further, for example, when the emitted light beam L2 is incident from a direction substantially along the line segment ab on the incident side, the light is near the focal point a or the focal point b on the parabola ab ₀ or ba _0. Totally reflected (totally reflected near the focal point a in the example shown in FIG. 7) and emitted from the end point a ₀ or the vicinity of the end point b ₀ on the outgoing line segment a ₀ -b ₀ (shown in FIG. 7). In the example, the light is emitted from the vicinity of the end point a ₀ ). In this case, the optical path of the emitted light beam L2 is parallel to the symmetry axis B1 or the symmetry axis A1 (in the example shown in FIG. 7, it is parallel to the symmetry axis A1), so that the relationship of the following expression (2) is established. .
(Angle formed by the target axes) = (Maximum emission angle of emitted light from the emission side end face) = θ (1)

  Therefore, if the emission angle of the light emitted from the light source 32 is less than 180 °, the light source 32 is disposed below the light collector 21 as shown in FIG. 5, and the light is emitted from the light source 32 to the incident side end face 42. By making the light incident, most of the light can be collected on the side surface 41 and emitted from the emission side end surface 43 within the range of the maximum emission angle θ. In this way, the utilization efficiency of the light emitted from the light source 32 can be greatly improved.

For example, in the example of FIG. 6, assuming that the diameter of the incident side end face 42 is Rin, the diameter of the emission side end face 43 is Rout, and the maximum emission angle of the emitted light is θ, Rin, Rout and θ are expressed by the following equation (2). Satisfy the relationship.
Rout = Rin / sinθ (2)

  Therefore, as described above, since the emission angle of the emitted light is less than 180 °, the diameter Rout of the emission side end face 43 is larger than the diameter Rin of the incident side end face 42. That is, as described above, the area of the emission side end face 43 is larger than the area of the incident side end face 42.

With such a configuration, the light emitted from the light source 32 is incident on the light collector 21 from the incident side end face 42, is collected on the side surface 41 made of a predetermined paraboloid, and has an area larger than that of the incident side end face 42. The light is emitted from the large emission side end face 43. The side surface 41 has, for example, a part of parabolas A and B (parabolas ab ₀ and ba ₀ ) having focal points at end points a and b of the line segment ab on the incident side, and a center line LC as an axis. It is a paraboloid made by rotating as As a result, the angle θ formed between the symmetry axes A1 and B1 of the parabolas A and B is equal to the maximum emission angle θ of the light emitted from the condenser 21. Therefore, if the emission angle of light emitted from the light source 32 is less than 180 °, the light source 32 is disposed below the light collector 21 as shown in FIG. 5 and the light is incident from the incident side end face 42. Thus, most of the light can be condensed at the side surface 41 and can be emitted from the emission side end face 43 within the range of the maximum emission angle θ.

  Next, the light utilization efficiency of the light collector 21 will be described. The light utilization efficiency of the light collector 21 is obtained, for example, by comparing the amount of light emitted from the light source 32 and the amount of light emitted from the light collector 21. For example, an integrating sphere is used for measuring the amount of light flux.

  FIG. 8 shows the result of measuring the amount of luminous flux of the condenser 21 (using a large LED of 3 mm × 3 mm as the light source 32) using an integrating sphere. In this figure, the vertical axis represents the amount of light flux per unit wavelength (lm / nm), and the horizontal axis represents the wavelength (nm) of light emitted from the condenser 21. In addition, a waveform P1 in the figure represents the amount of light emitted from the light source 32, and the waveform P2 represents the amount of light emitted from the light collector 21, that is, the amount of light after being condensed in the light collector 21. .

  As shown in FIG. 8, it can be seen that the waveform P1 and the waveform P2 are substantially similar waveforms. Further, the difference in the amount of light flux in these waveforms is about 2 (lm / nm), and the condenser 21 is about 94% of the light emitted from the light source 32 made of LEDs, that is, most of the light. It can be seen that the light is condensed.

  The morphing pipe 22 is for guiding the light condensed by the light collector 21 to the liquid crystal panels 14R, 14G, and 14B. The shape of the morphing pipe 22 continuously changes from the shape of the emission side end surface of the light collector 21 to the shape of the display surface of the liquid crystal panels 14R, 14G, and 14B. That is, the incident-side end surface of the morphing pipe 22 has the same shape as the exit-side end surface of the light collector 21, and the exit-side end surface of the morphing pipe 22 has the same shape as the display surface of the liquid crystal panels 14R, 14G, and 14B.

  The liquid crystal panels 14R, 14G, and 14B are controlled by a control unit (not shown), and each R, G, and B color light emitted from the light emitting units 12R, 12G, and 12B is spatially modulated and supplied to the prism. As the liquid crystal panels 14R, 14G, and 14B, for example, light transmissive liquid crystal panels 14R, 14G, and 14B are used.

  The prism is for synthesizing outgoing light from the liquid crystal panels 14R, 14G, and 14B into one outgoing light beam and emitting it to the concave aspherical mirror 3.

Concave Aspherical Mirror The concave aspherical mirror 3 is an aspherical mirror having a concave shape, and is a light reflecting mirror having a positive lens power for condensing light by its basic shape (concave surface). The reflective surface of the concave aspherical mirror 3 is coated with, for example, an aluminum film by vapor deposition, and the reflectance in the visible light region is set to, for example, about 98%. The radius of curvature | r1 | of the concave aspherical mirror 3 is, for example, 160 mm. The concave aspherical mirror 3 has an aspherical shape because it has a function of reducing aberration and correcting distortion of a projected image in addition to the function of condensing light. The definition formula representing this aspherical surface is
Z = (y ² / r) / (1+ (1− (1 + k) y ² / r ² ) ^1/2 ) + Ay ⁴ + By ⁶ + Cy ⁸ + (3)
It becomes.
However, each character included in Equation (3) is
Z: displacement of an aspheric surface from a reference plane that includes the intersection of the optical axis and the aspherical mirror and is perpendicular to the optical axis Y: distance from the optical axis r: radius of curvature of the mirror k: conic coefficient A: Fourth-order aspheric coefficient B: Sixth-order aspheric coefficient C: Eighth-order aspheric coefficient. The conic coefficient k is, for example, k = −1.5. The high-order terms of Expression (3) are all 0, for example, and in this case, there is no inflection point on the reflecting surface of the concave aspherical mirror 3.

The plane mirror plane mirror 4 reflects incident light from the concave aspherical mirror 3, changes its optical path in the clockwise direction, for example, by 90 °, and emits incident light from the back side to the front side of the screen 1. It is a mirror. The reflecting surface of the concave aspherical mirror 3 is coated with, for example, an aluminum film by vapor deposition, and the reflectance in the visible light region is set to about 98% by this coating, for example.

Convex Aspherical Mirror The convex aspherical mirror 5 is an aspherical mirror having a convex shape, and is a light reflecting mirror having a negative lens power that diffuses light by its basic shape (convex surface). The reflecting surface of the convex aspherical mirror 5 is coated with, for example, an aluminum film by vapor deposition, and the reflectance in the visible light region is set to, for example, about 98%. The radius of curvature | r2 | of the convex aspherical mirror 5 is, for example, 165 mm.

  The convex aspherical mirror 5 has an aspherical shape because it has a function of reducing aberrations and correcting distortion of a projected image in addition to the function of condensing light. The definition of the aspherical surface is the same as the above equation (3), and the conic coefficient k is, for example, k = −6.45. The aspheric coefficients are all 0, for example. In this case, there is no inflection point on the reflection surface of the convex aspherical mirror 5.

Next, the operation of the projection system configured as described above will be described.
The RGB color lights emitted from the light emitting units 12R, 12G, and 12B are condensed by the waveguide pipes 13R, 13G, and 13B made of, for example, acrylic resin, and the in-plane luminance distribution is made uniform. The light enters the display surface of the liquid crystal panels 14R, 14G, and 14B. Then, the RGB color lights incident on the display surfaces of the liquid crystal panels 14R, 14G, and 14B pass through the liquid crystal panels 14R, 14G, and 14B on which the images of the respective colors are created, and then are combined by the prism 15 to be emitted from the projector 2 The light is emitted toward the concave aspherical mirror 3 located on the same axis as the axis.

  The light incident on the concave aspherical mirror 3 is reflected by the concave aspherical mirror 3 and enters the flat mirror 4. The light incident on the plane mirror 4 is tilted by, for example, 90 ° in the clockwise direction by the plane mirror 4 and enters the convex aspherical mirror 5 from the back side of the screen 1 toward the front side. Light incident on the convex aspherical mirror 5 is enlarged and focused by the convex aspherical mirror 5 and projected onto the screen 1. As described above, the image created by the projector 2 is imaged on the screen 1 through the above-described mirror group.

  In the projection system according to the first embodiment, for example, when the size of the liquid crystal panels 14R, 14G, and 14B is 0.7 inches and an image is enlarged and projected on the screen 1 to about 20 to 30 inches, a concave aspheric surface is used. The relationship between the radius of curvature r1 of the mirror 3 and the radius of curvature r2 of the convex aspherical mirror 5 is | r2 | ≈ | r1 |. That is, when the magnification is 30 to 40 times, the radius of curvature has the above relationship. Further, for example, there is no inflection point on the surface of the aspherical mirror used. This is because all of the aspheric coefficients are 0 from the above-described definition formula (3) of the aspheric surface.

An example of the dimension value of the optical design is shown below.
LCD panel to concave aspherical mirror distance = 90.4mm
Concave Aspherical Mirror to Flat Mirror Distance = 314.2mm
Flat mirror to convex aspherical mirror distance = 319.2 mm
Convex aspherical mirror to screen distance = 249.2 mm
In addition, although the above-mentioned dimension value is attached | subjected also in FIG. 2, these numerical values are examples and this invention is not limited to these numerical values.

According to the first embodiment of the present invention, the following effects can be obtained.
The light emitted from the projector 2 provided on the back side of the screen 1 is reflected by the concave aspherical mirror 3 coaxially positioned with the projector 2, and the optical path is provided by the flat mirror 4 provided on the lower side of the screen 1. Is reflected in a clockwise direction, for example, by 90 degrees, and is enlarged and projected onto the screen 1 by the convex aspherical mirror 5 provided on the front side of the screen 1, so that an imaging lens is not used as in the prior art. The image can be formed on the screen 1 by the concave aspherical mirror 3, the plane mirror 4 and the convex aspherical mirror 5. Therefore, the configuration of the imaging optical system can be simplified as compared with the conventional art. In addition, the space required for video projection can be reduced as compared with the prior art.

  By constructing the imaging optical system using an aspherical mirror, a projection system in which the imaging optical system and the screen 1 are integrated can be constructed, so that the entire projection system can be made compact.

  In addition, since the image can be formed on the screen 1 by the concave aspherical mirror 3, the flat mirror 4, and the convex aspherical mirror 5 without using a plurality of lenses, the entire projection system can be made inexpensive and light. be able to. Further, since the entire projection system can be reduced in weight, the projection system can also be used as a display device such as a television that can be wall-mounted.

  In addition, the light collector 21 is configured in a predetermined shape including a side surface 41 having a predetermined paraboloid, and most of the light emitted from the light source 32 is collected and emitted. The utilization efficiency of the emitted light can be improved.

  Further, the condensed light can be emitted within the range of the maximum emission angle θ that is equal to the angle θ formed by the parabolic target axes in the cross section including the center line LC of the side surface 41 of the light collector 21. Therefore, it becomes possible to grasp the maximum emission angle of the emitted light in advance at the time of design or the like.

  In addition, the shapes of the incident side end face 42 and the emission side end face 43 may be set so as to satisfy the above-described formula (2), and thus can be easily formed.

  Further, the light source 32 may be constituted by either a point light source or a surface light source, for example, and can have various configurations, so that the degree of freedom in design can be improved.

Further, when the LED is used as the light source 32, the size of the light emitting portions 12R, 12G, and 12B itself can be reduced to several mm ² , and the cross sections of the waveguide pipes (morphing type condensers) 13R, 13G, and 13B are also obtained. The size of the liquid crystal panels 14R, 14G, and 14B can be maximized. That is, since the optical components of the projector 2 can be reduced in size, for example, the capacity of the projector 2 can be reduced to about 500 cc.

Next explained is the second embodiment of the invention.
FIG. 9A is a top view showing a schematic configuration of the projector according to the second embodiment of the invention. FIG. 9B is a side view showing a schematic configuration of the projector according to the second embodiment of the invention. The projector 2 includes a support 11, light emitting units 12 R, 12 G, and 12 B, a light collector 21, liquid crystal panels 14 R, 14 G, and 14 B and a prism 15 provided on the support 11. The light emitted from the light emitting units 12R, 12G, and 12B is collected by the light collector 21 and enters the display surfaces of the liquid crystal panels 14R, 14G, and 14B. Since other than that is the same as that of the above-mentioned 1st Embodiment, description is abbreviate | omitted.

  The first and second embodiments of the present invention have been specifically described above. However, the present invention is not limited to the first and second embodiments described above, and is based on the technical idea of the present invention. Various variations based on this are possible.

  For example, the numerical values given in the first to second embodiments are merely examples, and different numerical values may be used as necessary.

  Further, a projector such as a conventional rear projection type projection system can be used instead of the projector in the first to second embodiments described above. As such a projector, for example, an LCD (Liquid Crystal Display) type or DLP (Digital Light Processing) (registered trademark) type projector can be used.

  The projectors according to the first and second embodiments described above can also be used in a conventional rear projection type projection system. Thereby, the effect that the conventional rear projection type projection system can be reduced in size can be obtained.

  Further, in the first to second embodiments described above, as shown in FIG. 10, the refractive index of the condensing body 21 is at the junction between the light source 32 and the incident side end face of the condensing body 21. A matching layer 34 that matches the refractive index may be provided. The matching layer 34 is made of, for example, immersion oil or water. For example, when the light collector 21 is made of glass (BK7; refractive index 1.49) or plastic (PMMA; refractive index 1.50) as described above, the matching layer 34 has a refractive index of 1.50, for example. An acrylic solution or the like having a degree can be used. In addition, as shown in FIG. 11, even when the light sources of the light emitting units 12R, 12G, and 12B are configured by the LED light source 35 that is a surface light source, the above-described joint portion between the light emitting region 36 and the light collector 21 Such a matching layer 34 can be provided. By providing such a matching layer 34, for example, even when there is a gap between the LED light source 35 and the light collector 21, the interface from the LED light source 35 at the interface between the matching layer 34 and the light collector 21. Incident light is incident on the condenser 21 without being reflected or largely refracted, and the utilization efficiency of light emitted from the LED light source 35 can be further improved.

  In the first to second embodiments described above, the case where the entire waveguide pipes 13R, 13G, and 13b are filled with the above-described material has been described. For example, the waveguide pipes 13R, 13G, and 13b You may comprise so that the inside may be hollow. Even in such a case, the same effects as those of the first and second embodiments described above can be obtained.

  In the first to second embodiments described above, the shapes of the incident side end face 42 and the emission side end face 43 of the light collector 21 are circular with the intersections C1 and C2 with the center line LC as the center. Although an example has been described, the shape is not necessarily circular, and may be, for example, an ellipse or a polygon centered on the intersections C1 and C2. That is, the shape of the side surface 41 only needs to be configured by a paraboloid that includes one or more parabolas that focus on the end point of the incident side end surface 42 in the cross section including the center line LC. Even in the case, it is possible to obtain the same effects as those of the first and second embodiments described above.

  In the first and second embodiments described above, a case has been described in which the projection system has a configuration for projecting an image onto the screen 1 from below the screen 1, but the direction of image projection is in this example. However, the present invention is not limited, and a configuration in which an image is projected onto the screen 1 from above or from the side of the screen 1 may be employed.

1 is a schematic diagram showing an external appearance of a projection system according to a first embodiment of the present invention. It is a side view which shows the example of 1 structure of the projection system by 1st Embodiment of this invention. It is a graph which shows an example of the relationship between the distance from the center (gravity center) of a liquid crystal panel to a coaxial, and the distance from the coaxial to the center of the image | video projected on a screen. FIG. 1 is a top view and a side view showing a schematic configuration of a projector according to a first embodiment of the invention. It is sectional drawing which shows the example of 1 shape of the condensing body with which the projector by 1st Embodiment of this invention was equipped. It is a schematic diagram which shows the example of 1 shape of the condensing body with which the projector by 1st Embodiment of this invention was equipped. It is a schematic diagram for demonstrating the shape of the condensing body with which the projector by 1st Embodiment of this invention was equipped. It is a characteristic view showing the measurement result of a high bundle amount. It is the top view and side view which show the projector by 2nd Embodiment of this invention. It is sectional drawing which shows the other structural example of a light emission part. It is sectional drawing which shows the other structural example of a light emission part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Screen 2 Projector 3 Concave aspherical mirror 4 Flat mirror 5 Convex aspherical mirror 11 Support body 12R, 12G, 12B Light emission part 13R, 13G, 13B Waveguide pipe 14R, 14G, 14B Liquid crystal panel 15 Prism 21 Condensing body 22 Morphing Pipe 32 light source

Claims (5)

A projector that emits light;
An image display device for displaying an image based on the light emitted from the projector,
The projector
A light source that emits light;
A light collector for condensing the light emitted from the light source;
A liquid crystal display that modulates the light emitted from the light collector;
A combining unit that combines the light that has passed through the liquid crystal display unit,
The video display device
A screen provided with the projector on the back;
An imaging optical system for projecting light emitted from the projector onto the screen,
The imaging optical system is
A concave mirror for collecting the light emitted from the projector;
A reflection mirror that reflects the light collected by the concave mirror from the back side of the screen toward the front side;
A projection system comprising: a convex mirror that diffuses light reflected by the reflection mirror and projects the light onto the screen. The light collector is
An incident side end face;
The exit side end face that is coaxially opposed to the center line of the incident side end face and has a larger area than the incident side end face,
Having a parabolic surface including one or more parabolas with a focal point at the end point of the incident side end surface in a cross section including the center line,
The projection system according to claim 1, wherein the light incident through the incident side end face is condensed and emitted from the emission side end face within a range of a predetermined emission angle. The projector further includes a morphing unit between the light collector and the liquid crystal display unit,
The projection system according to claim 1, wherein the shape of the morphing portion continuously changes from the shape of the emission side end surface of the light collector to the shape of the display surface of the liquid crystal display portion. A light source that emits light;
A light collector for condensing the light emitted from the light source;
A liquid crystal display that modulates the light emitted from the light collector;
A projector comprising: a combining unit that combines light that has passed through the liquid crystal display unit. Screen,
An imaging optical system that projects light emitted from a projector provided on the back side of the screen onto the screen;
The imaging optical system is
A concave mirror for collecting the light emitted from the projector;
A reflection mirror that reflects the light collected by the concave mirror from the back side of the screen toward the front side;
An image display device comprising: a convex mirror that diffuses light reflected by the reflection mirror and projects the light onto the screen.

Images