JP2010169729A - Projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projector capable of suppressing uniformity deterioration of in-plane light intensity distribution of illumination light when reducing the aperture diameter of a variable diaphragm, thereby capable of obtaining a clear projected image with less uneven luminance. <P>SOLUTION: The projector includes: an illumination optical system for emitting the illumination light; and a projection optical system including a DMD having a rectangular image display area, for modulating the illumination light emitted from the illumination optical system and the variable diaphragm whose aperture shape is adjustable, for projecting the light modulated by the DMD toward a projection screen through the variable diaphragm. The illumination optical system includes: a light source; a light condensing optical system for condensing the light emitted from the light source; a rod integrator whose cross section vertical to the optical axis is rectangular, for emitting the light coming from the light condensing optical system while enhancing the uniformity of the in-plane intensity distribution; a relay optical system for guiding the light coming from the rod integrator to the DMD. The light emitting surface of the rod integrator and the image display area of the DMD are conjugate. The aperture shape of the variable diaphragm upon a small diaphragm is long flat in a direction equivalent to the longitudinal direction of the image display area of the DMD. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a projection apparatus, and more particularly, to a rod integrator and a projection apparatus provided with a variable aperture.

  In recent years, projection apparatuses that project illumination light modulated by an image display element such as a digital micromirror device (hereinafter also referred to as “DMD”) onto a projection surface such as a screen are widely used as projectors for home theaters and the like. It has come to be used.

  Such a projection apparatus usually includes an illumination optical system that emits illumination light, an image display element that modulates illumination light from the illumination optical system according to image information, and a modulated light modulated by the image display element, such as a screen. A projection optical system for projecting onto the projection surface.

  In the projection apparatus having such a configuration, an illumination optical system having a rod integrator is conventionally known as an illumination optical system (see, for example, Patent Document 1). According to the illumination optical system described in Patent Document 1, since the illumination light emitted from the light source enters the rod integrator and is emitted after repeating internal reflection, the surface of the illumination light emitted from the light source Even if the internal light intensity distribution is not uniform, the illumination light emitted from the illumination optical system can be changed to illumination light having a more uniform in-plane light intensity distribution by the action of the rod integrator. Then, by irradiating the image display area of the image display element with illumination light having such a substantially uniform in-plane light intensity distribution, the brightness of the image projected on the projection surface can be made substantially uniform. It becomes possible.

  Incidentally, since the light exit surface of the rod integrator and the image display area of the image display element have a conjugate relationship, the shape of the light exit surface of the rod integrator and the planar shape of the image display area are substantially similar. Usually, the vertical dimension orthogonal to the illumination optical axis in the image display area is different from the horizontal dimension orthogonal to the illumination optical axis (for example, the aspect ratio is 3: 4 or 9:16). Similarly, the light emitting surface of the integrator is different in the vertical dimension and the horizontal dimension. As a result, the conventional illumination optical system has the following problems.

  FIG. 4 is a diagram showing a state of internal reflection of illumination light traveling in the rod integrator.

  4A is a view of the rod integrator 15 viewed from above (long side direction), FIG. 4B is a view of the rod integrator 15 viewed from the side (short side direction), and FIG. FIG. 4 is a view showing a light exit surface 15o of the rod integrator 15.

  Here, the case where the illumination optical system is used in a projection apparatus having an image display element having a rectangular shape in plan view with an aspect ratio of the image display area of 3: 4 is described as an example. The light exit surface 15o has a shape of a rectangular shape in plan view with an aspect ratio of 3: 4 (see FIG. 4C). Further, the light incident surface 15i of the rod integrator 15 has the same shape as the light emitting surface 15o.

  In the illumination optical system having such a rod integrator 15, as shown in FIG. 4, the dimension Ds in the vertical direction (short side 15s direction) and the horizontal direction (long side 15l direction) of the light exit surface 15o of the rod integrator 15 are provided. Therefore, the number of internal reflections differs between the illumination light incident from the long side direction shown in FIG. 4A and the illumination light incident from the short side direction shown in FIG. 4B. End up. That is, the illumination light incident on the light incident surface 15i of the rod integrator 15 from the short side direction (illumination light shown in FIG. 4B) is longer than the light incident surface 15i of the rod integrator 15 from the long side direction. Incident illumination light (illumination light shown in FIG. 4A) reduces the number of internal reflections and weakens the light uniformity effect. For this reason, in order to obtain a predetermined light uniforming effect, there is a problem that the length of the rod integrator 15 needs to be increased. As a result, there is a problem that it is not easy to downsize the illumination optical system. Therefore, various methods have been studied to deal with such problems.

  For example, an anamorphic lens having a refractive power in the long side direction larger than that in the short side direction with respect to the light incident surface of the rod integrator is provided between the light source and the rod integrator, and the illumination light is incident from the long side direction. A projection device is known in which the in-plane light intensity distribution of illumination light is made more uniform by increasing the incident angle of the illumination light in comparison with the incident angle of illumination light incident from the short side direction (Patent Document 2). reference). In such a projector, the illumination light incident from the long side direction travels through the rod integrator while being totally reflected at a deeper angle (with a reflection angle smaller than the reflection angle of the illumination light incident from the short side direction). Therefore, the number of internal reflections is suppressed from being reduced compared to illumination light incident from the short side direction. As a result, the in-plane light intensity distribution of the illumination light emitted from the illumination optical system is made more uniform.

JP 2002-90883 A JP 2007-65016 A

  Thus, the illumination optical system described in Patent Document 2 increases the number of internal reflections of illumination light incident from the long side direction of the rod integrator by the anamorphic lens, and increases the number of light source images in the long side direction. The in-plane light intensity distribution of the illumination light emitted from the illumination optical system is made more uniform.

  However, the NA (Numerical Aperture) increases by increasing the incident angle of the illumination light incident from the long side direction. Further, the number of light source images in the long side direction increases, but the distribution pitch is the same as in the case where no anamorphic lens is provided, and is sparser than the distribution pitch in the short side direction. As a result, in order to increase the contrast, when the aperture of the variable stop is made small, that is, when the stop is made small, the number of light source images in the long side direction passing through the stop is larger than the number of light source images in the short side direction. There is a problem that the uniformity of the in-plane light intensity distribution of the illumination light emitted from the illumination optical system is reduced.

  The present invention has been made in view of the above problems, and in a projection apparatus provided with a rod integrator and a variable stop, the uniformity of the in-plane light intensity distribution of illumination light when the aperture diameter of the variable stop is reduced is reduced. An object of the present invention is to provide a projection apparatus capable of suppressing the brightness and obtaining a beautiful projected image with little unevenness in illuminance.

  The above object is achieved by the invention described in any one of 1 to 4 below.

1. An illumination optical system that emits illumination light, a DMD that modulates the illumination light from the illumination optical system based on image information and has a rectangular image display area, and a variable aperture that can adjust the aperture shape. In a projection apparatus comprising: a projection optical system that projects modulated light onto a projection surface via the variable aperture;
The illumination optical system includes a light source, a condensing optical system that condenses the light emitted from the light source, and the light that is collected by the condensing optical system and incident from the incident surface has a uniform in-plane intensity distribution. A rod integrator having a rectangular cross section perpendicular to the optical axis that is emitted from the exit surface, and a relay optical system that guides the light emitted from the exit surface of the rod integrator to the DMD,
The exit surface of the rod integrator and the image display area of the DMD are conjugate,
The projection apparatus according to claim 1, wherein an aperture shape of the variable aperture when the aperture is small is a flat shape that is long in a direction corresponding to a long side direction of the image display area of the DMD.

  2. 2. The projection apparatus according to 1, wherein a flatness ratio of the aperture shape when the variable stop is small is larger than a ratio of a long side to a short side of the image display area of the DMD.

  3. When the variable stop is a small stop, the number of light source images that can pass through the aperture of the variable stop is three in the direction corresponding to the long side direction and the short side direction of the image display area of the DMD. 3. The projection apparatus according to 1 or 2 above, which is as described above.

  4). The relay optical system includes a variable aperture having an aperture shape that is optically equivalent to the variable aperture included in the projection optical system, and the two variable apertures are controlled to interlock with each other to have the same aperture shape. 4. The projection apparatus according to any one of 1 to 3, wherein:

  According to the present invention, the aperture shape at the time of the small stop of the variable stop provided in the projection optical system is a flat shape that is long in the direction corresponding to the long side direction of the image display area of the DMD.

  As a result, at the time of the small aperture, the light source image in the direction corresponding to the long side direction of the image display area of the DMD that passes through the variable aperture, that is, the light source image of the illumination light incident from the long side direction on the incident surface of the rod integrator. You can increase the number. As a result, it is possible to suppress a decrease in uniformity of the in-plane light intensity distribution of illumination light when the aperture diameter of the variable stop is reduced, and to obtain a beautiful projected image with little illuminance unevenness.

It is a figure which shows schematic structure of the projection apparatus which concerns on embodiment of this invention. It is a figure which shows the mode of distribution of a light source image. It is a figure which shows schematic structure of a variable aperture. It is a figure which shows the mode of the internal reflection of the illumination light which advances the inside of a rod integrator. It is a figure which shows another example of the opening shape at the time of the small aperture stop of a variable aperture.

  Hereinafter, an embodiment of a projection apparatus according to the present invention will be described with reference to the drawings. In addition, although this invention is demonstrated based on embodiment of illustration, this invention is not limited to this embodiment.

  First, a schematic configuration of the projection apparatus will be described with reference to FIG. FIG. 1 is a diagram showing a schematic configuration of the projection apparatus 1.

  The projection apparatus 1 includes an illumination optical system 19 that emits illumination light, a DMD 24 that modulates illumination light from the illumination optical system 19 based on image information, and a variable aperture 40 that can adjust the aperture shape. The projection optical system 20 projects onto the projection surface via the variable aperture 40.

  The illumination optical system 19 is a discharge lamp 11 (light source), a lamp reflector 12 (condensing optical system) that collects light emitted from the discharge lamp 11, and light that is collected by the lamp reflector 12 and incident from the incident surface. It comprises a rod integrator 15 that emits from the exit surface with increased uniformity of the internal intensity distribution, a relay optical system 18 that guides the light emitted from the exit surface of the rod integrator to the DMD 24, and the like.

  As the light source, it is preferable to use a discharge lamp 11 that emits white light and has a large amount of light per unit area. There is no restriction | limiting in particular in the kind of discharge lamp 11, It can select from the light source lamps used for the projection apparatus 1, such as an ultrahigh pressure mercury lamp and a metal halide lamp, and can use it suitably.

  The lamp reflector 12 corresponding to the condensing optical system in the present invention has an ellipsoidal reflecting surface, and the discharge lamp 11 is disposed at the focal position. Therefore, the luminous flux from the discharge lamp 11 is emitted as convergent light and enters the color wheel 14. In addition, the condensing optical system may be configured to use a lamp reflector having a paraboloid and to convert parallel light emitted from the lamp reflector into convergent light using a condenser lens.

  The color wheel 14 includes three color filters that respectively transmit light having wavelengths of R (red), G (green), and B (blue). By rotating this, the color of the illumination light is sequentially switched over time, so that the projection information can be colored by sequentially switching and displaying the image information corresponding to each color on the DMD 24. The color filter is not limited to the combination of three colors of R, G, and B. For example, other combinations capable of displaying a color image such as a combination of three colors of C (cyan), M (magenta), and Y (yellow). Combinations may be used. The color wheel 14 may be omitted in the case of a monochrome image projection device or a projection device having a DMD and an illumination optical system for each color.

  The light beam that has passed through the color wheel 14 enters the rod integrator 15. The rod integrator 15 is made of glass, and is formed into an elongated quadrangular prism whose section perpendicular to the optical axis is rectangular. The light beam incident on the rod integrator 15 is mixed by repeating total reflection on the wall surface, and the uniformity of the in-plane light intensity distribution is improved on the exit surface of the rod integrator 15.

  The luminous flux emitted from the rod integrator 15 forms a plurality of light source images at the pupil position of the relay optical system 18 in accordance with the number of reflections at the rod integrator 15, and illuminates the DMD 24 by superimposing these light sources. High lighting is realized. The details of the rod integrator 15 are omitted since they are generally the same as those described with reference to FIG.

  FIG. 2A shows the distribution of a plurality of light source images K formed at the pupil position of the relay optical system 18. In FIG. 2A, the left-right direction on the paper surface corresponds to the long side direction of the exit surface 15 o of the rod integrator 15.

  As shown in FIG. 2A, the light source image K is distributed at the position reflected and turned back by the wall surface of the rod integrator 15, and the distribution pitch Pl in the direction corresponding to the long side direction of the rod integrator 15 is the short side direction. Becomes larger than the distribution pitch Ps.

  Returning to FIG. 1, a relay optical system 18, a prism unit 23, and a DMD 24 are disposed behind the rod integrator 15, and light emitted from the rod integrator 15 illuminates the DMD 24 through the relay optical system 18. Of the reflected light from the DMD 24, ON light again enters the projection optical system 20 through the prism unit 23, and an image is projected onto the screen.

  The relay optical system 18 includes three lenses 16 a, 16 b, 16 c, a variable diaphragm 17, and the like, and functions together with the prism unit 23 to guide the light emitted from the exit surface 15 o of the rod integrator 15 to the DMD 24. The exit surface 15o of the rod integrator 15 is conjugate with the image display area of the DMD 24. By making the shape of the exit surface 15o of the rod integrator 15 substantially similar to the image display area of the DMD 24, illumination can be performed efficiently. Therefore, the long side direction of the cross section of the rod integrator 15 corresponds to the long side direction of the rectangular image display region of the DMD 24.

  The prism unit 23 includes two prisms, a first prism 21 and a second prism 22. The first prism 21 has a first entrance surface 21a, a critical surface 21b, and a first exit surface 21c, and the second prism 22 has a second entrance surface 22a and a second exit surface 22b. The critical surface 21b of the first prism 21 and the second incident surface 22a of the second prism 22 are arranged to face each other with an air layer interposed therebetween.

  Further, the entrance lens 16 c is bonded to the first incident surface 21 a of the first prism 21. The entrance lens 16c is provided to make the illumination light telecentric. The entrance surface 21a of the first prism 21 may be curved to provide the function of the entrance lens 16c.

  The illumination light from the relay optical system 18 enters the first prism 21 from the first incident surface 21a through the entrance lens 16c. The critical surface 21b of the first prism 21 is arranged so that the incident illumination light is totally reflected. The illumination light is reflected by the critical surface 21b and emitted from the first exit surface 21c of the first prism 21. Illuminate the DMD 24.

  The DMD 24, which is a reflective image display element, has an image display area in which a number of micromirrors are arranged in a matrix, and one micromirror constitutes one pixel of a display image. The inclination of the micromirrors is configured to be individually driven and controlled, and each micromirror can take two inclination states, an ON state and an OFF state. The illumination light is reflected toward the projection optical system 20 by the micromirror in the ON state, and the illumination light is reflected in a direction not entering the projection optical system 20 by the micromirror in the OFF state. Therefore, only the light reflected by the micromirror in the ON state reaches the screen by the projection optical system 20, and the target image is displayed on the screen.

  The DMD 24 has a rectangular image display area, and each pixel (micromirror) of the DMD 24 has a deflection axis that forms an angle of 45 degrees with the long side and the short side of the image display area, and the pixel is centered on the deflection axis. The image is displayed by deflecting ± 12 ° to deflect the illumination light reflection direction. The light beam reflected by the pixel in the image display state (ON state), that is, projection light (modulated light) enters the first prism 21 again from the first exit surface 21 c of the first prism 21, and The critical surface 21b is reached. Since the projection light is incident on the critical surface 21b at an angle that does not satisfy the total reflection condition, the projection light passes through the critical surface 21b, enters the second prism 22 from the second incident surface 22a through the air layer. Then, the light exits from the second exit surface 22 b of the second prism 22 and enters the projection optical system 20.

  The projection optical system 20 includes four lenses 20a, 20b, 20c, and 20d, a variable aperture 40, and the like, and projects projection light emitted from the prism unit 23 onto a screen.

  The pupil position of the relay optical system 18 and the pupil position of the projection optical system 20 are configured to have an optically conjugate relationship, and the above-described FIG. 2A formed at the pupil position of the relay optical system 18 is used. Similarly, a light source image K as shown is also formed at the pupil position of the projection optical system 20.

  Here, the configuration of the variable stop 17 provided in the relay optical system 18 and the variable stop 40 provided in the projection optical system 20 will be described with reference to FIG. FIG. 3A is a diagram illustrating an open state in which the aperture opening of the variable aperture 17 is most opened, and FIG. 3B is a diagram illustrating a closed state in which the aperture opening is most closed. Since the configuration and opening shape of the variable diaphragm 40 are the same as those of the variable diaphragm 17, the description thereof is omitted.

  The variable diaphragm 17 includes a fixed diaphragm plate 171 that determines the opening shape 171o in the open state, two variable diaphragm blades 173, and the like.

  Gears 175 are provided on the two rotation shafts of the variable aperture blade 173 and are arranged so as to mesh with each other.

  A diaphragm drive motor 33 is connected to one of the rotation shafts, and one variable diaphragm blade 173 is moved by rotation of the diaphragm drive motor 33, and the other variable diaphragm blade 173 is transferred in the opposite direction via the gear 175. Then, the opening state is changed.

  The variable diaphragm having such a configuration is provided in the projection optical system 20 and the relay optical system 18, and the variable diaphragm 40 of the projection optical system 20 and the variable diaphragm 17 of the relay optical system 18 system are interlocked to optically. It is controlled by the diaphragm control unit 36 so as to have an equivalent opening shape. Here, the optically equivalent aperture shape means that the respective apertures of the relay optical system 18 and the projection optical system 20 are in an optically conjugate positional relationship, and the shape of the optical image of one aperture aperture and the other aperture shape. It means that the shape of the aperture opening substantially matches.

  When DMD 24 is used as an image display element, the cause of contrast reduction is mainly scattering generated on the display surface. In black display (OFF state), the reflected light from the micromirror does not enter the projection optical system 20, but there is a scattering component such as the edge of the micromirror, and the scattered light generated there is projected optically. It enters the system 20 and reaches the screen, raising the black level. Such scattered light can be effectively reduced by narrowing the variable aperture 40 of the projection optical system 20. Therefore, when the DMD 24 is used as an image display element, the effect of improving the contrast by reducing the aperture diameter of the variable aperture 40 of the projection optical system 20 is very large.

  2A shows the opening shape 171o in which the variable diaphragm 17 (40) is open, and FIG. 2B shows the opening shape 173c in which the variable diaphragm 17 (40) is closed. The inside of these opening shapes 171o and 173c is a range through which an effective light beam passes.

  As shown in FIG. 2B, the aperture area 173c at the time of the small aperture of the variable aperture 17 is made flat and long in the direction corresponding to the long side direction of the image display area of the DMD 24, so that the aperture area is the same. However, the number of light source images K in the long side direction of the DMD 24 that passes therethrough can be increased. In order to enhance the superposition effect of the light source images K, it is desirable that there are at least three light source images K in that direction.

  Further, since the ratio of the size (area) of the light source image K is smaller in the long side direction than in the short side direction and is less uniform than the short side direction, more light source images K than in the short side direction are obtained. It is desirable to let it pass. Therefore, a projection image with a sufficiently uniform in-plane intensity distribution can be obtained by making the flatness ratio of the closed opening shape 173c larger than the aspect ratio (long side / short side) of the DMD 24. Here, as shown in FIG. 3B, the flatness ratio is the maximum opening dimension A in the direction corresponding to the long side direction of the image display area of the DMD 24 and the direction corresponding to the short side direction of the image display area of the DMD 24. The ratio A / B with the maximum opening dimension B.

  In addition, the variable aperture 17 provided in the relay optical system 18 allows a light beam of a component that does not originally pass through the projection optical system 20 to reach the DMD 24 and is scattered and passed through the projection optical system 20 even though it is unnecessary light. Can be prevented, more dark black can be expressed, and contrast can be further enhanced.

  Thus, in the projection apparatus 1 according to the embodiment of the present invention, the aperture shape 141c at the time of the small stop of the variable stop 40 provided in the projection optical system 20 is set in a direction corresponding to the long side direction of the image display area of the DMD 24. Long flat shape.

  Thereby, at the time of small aperture, the light source image K in the direction corresponding to the long side direction of the image display area of the DMD 24 that passes through the variable aperture 40, that is, the light source of the illumination light incident from the long side direction on the incident surface of the rod integrator The number of images K can be increased. As a result, it is possible to suppress a decrease in the uniformity of the in-plane light intensity distribution of the illumination light when the aperture diameter of the variable stop 40 is reduced, and to obtain a beautiful projected image with little illuminance unevenness.

  The present invention has been described above with reference to the embodiments. However, the present invention should not be construed as being limited to the above-described embodiments, and can be changed or improved as appropriate. For example, the aperture shape 173c at the time of the small apertures of the variable apertures 17 and 40 is not limited to the elliptical shape as shown in FIG. 3 (b), but can be various as shown in FIGS. 5 (a) to 5 (d). Shape is conceivable. In the above-described embodiment, the projection apparatus 1 having a single DMD 24 and the color wheel 14 has been described. However, three DMDs corresponding to R, G, and B colors and color separation / combination are performed. You may apply to the projector of the structure provided with the color prism to perform.

DESCRIPTION OF SYMBOLS 1 Projector 11 Discharge lamp 12 Lamp reflector 14 Color wheel 15 Rod integrator 16a, 16b, 16c Relay lens 17, 40 Variable aperture 171 Fixed aperture plate 173 Variable aperture blade 175 Gear 18 Relay optical system 19 Illumination optical system 20 Projection optical system 20a , 20b, 20c, 20d Projection lens 21 First prism 22 Second prism 23 Prism unit 24 DMD
33 Aperture drive motor 36 Aperture controller

Claims (4)

An illumination optical system that emits illumination light, a DMD that modulates the illumination light from the illumination optical system based on image information and has a rectangular image display area, and a variable aperture that can adjust the aperture shape. In a projection apparatus comprising: a projection optical system that projects modulated light onto a projection surface via the variable aperture;
The illumination optical system includes a light source, a condensing optical system that condenses the light emitted from the light source, and the light that is collected by the condensing optical system and incident from the incident surface has a uniform in-plane intensity distribution. A rod integrator having a rectangular cross section perpendicular to the optical axis that is emitted from the exit surface, and a relay optical system that guides the light emitted from the exit surface of the rod integrator to the DMD,
The exit surface of the rod integrator and the image display area of the DMD are conjugate,
The projection apparatus according to claim 1, wherein an aperture shape of the variable aperture when the aperture is small is a flat shape that is long in a direction corresponding to a long side direction of the image display area of the DMD.   The projection apparatus according to claim 1, wherein a flatness ratio of the aperture shape when the variable stop is a small stop is larger than a ratio of a long side to a short side of the image display region of the DMD.   When the variable stop is a small stop, the number of light source images that can pass through the aperture of the variable stop is three in the direction corresponding to the long side direction and the short side direction of the image display area of the DMD. The projection apparatus according to claim 1, wherein the projection apparatus is as described above.   The relay optical system includes a variable aperture having an aperture shape that is optically equivalent to the variable aperture included in the projection optical system, and the two variable apertures are controlled to interlock with each other to have the same aperture shape. The projection apparatus according to claim 1, wherein: