JP2008026793A - Image projection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image projection device using an optical element having a free curved surface as a light condensing optical system which condenses and irradiates an optical modulation unit for forming an image with illuminating luminous flux from a light source unit. <P>SOLUTION: The illuminating luminous fluxes 3 from a plurality of light sources 2 are condensed to almost one point on a projection lens 8 to form a small light source image 9. The lens 6 having the free curved surface is used as a light condensing element. The free curved surface is used for a reflection mirror for condensing light. The illuminating luminous fluxes from the plurality of light sources 2 are condensed to almost one point on the projection lens 8 to form the small light source image 9. The reflection mirror 10 having the free curved surface is used as a light condensing element. In reflection, the same reflection angle is obtained to all the wavelengths differently from refraction by a lens. The illuminating luminous fluxes emitted from the respective light sources 2 of the light source unit 4 are reflected by two concave mirrors 8a having the free curved surface, and then irradiated the optical modulation unit 7 and condensed to almost one point on the projection lens 8 to form the small light source image 9. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image projection apparatus in an illumination optical system.

  In recent years, with the growing needs for displaying images on personal computers and televisions on large screens and for displaying beautiful images, with the development of liquid crystal technology, it is necessary to improve the performance of image projection devices such as projectors. It is done. Increasing projector performance leads to higher image quality, smaller size, and lighter weight. Along with these, what is mainly expected is improvement of the brightness of the screen, and various techniques have been developed with the aim of improving the light utilization efficiency with respect to the illumination optical system.

  For example, Patent Document 1 proposes a large-screen oblique projection optical system and image projection apparatus that are advantageous in terms of mass productivity and cost while maintaining a good optical function, and that are thin and have compact optical components.

  Further, in Patent Document 2, in order to enlarge the projection screen and reduce the projection space outside the projection apparatus, an imaging optical system including a reflecting mirror is employed, and a projection optical system capable of correcting chromatic aberration, and this An enlargement projection optical system and an image projection apparatus using such a projection optical system are proposed.

  Further, in Patent Document 3, a light beam emitted with an opening angle of 10 degrees or more is a first optical system in the vicinity of the reference axis, and a second optical system having a diverging action of the light beam in the vicinity of the reference axis. And an oblique imaging optical system with a wide field angle of 60 degrees or more and a small distortion regardless of the type of optical element used according to the position where the light beam passes through the first optical system. .

  In Patent Document 4, the first optical component having a reflection curved surface and the second optical component arranged on the reduction side with respect to the first optical component, and when tracing from the reduction side to the enlargement side, The second optical component forms a reduction-side conjugate point on the enlargement side with respect to the first optical component, obtains a desired zoom ratio, suppresses the occurrence of various aberrations such as lateral chromatic aberration, and has a compact configuration. Has proposed.

  Further, in Patent Document 5, using at least one free-form curved reflecting surface, a projection optical system having a reference optical axis on the reference plane and a cross dichroic prism that synthesizes a plurality of color lights are positioned at conjugate positions. Each color illumination plane is composed of a plurality of image modulation elements whose image display surfaces are rectangular, and the color light modulated by the plurality of image modulation elements is color-synthesized by a cross dichroic prism, and a color synthesis plane The image modulation elements are cross dichroic so that the short side direction of the display surface of the plurality of image modulation elements is parallel, the reference plane of the projection optical system and the color synthesis plane are parallel to each other, and the projected image is horizontally long By arranging the prism and projection optical system, the combination of the projection optical system and the optical engine by the reflection optical system can be reduced in size and handling can be simplified. It has proposed an image projection apparatus Tsu.

  Further, in Patent Document 6, a plurality of mirrors including a non-rotating target aspherical mirrors are used in the projection optical system so that portions other than the reflection surface inside the cylindrical structure do not interfere with the projection optical path. Projected outside air from the outside air intake port through the inside of the cylindrical structure, the surfaces of the plurality of mirrors are cooled by the outside air, and are not easily affected by heat and temperature rise. A device is proposed.

  Furthermore, in Patent Document 7, by dividing and superimposing the light beam uniformed by the light beam shape conversion, even if there is uneven emission distribution of the light source, the uniformity of the illuminance distribution, light A lighting device for a projection display device such as a liquid crystal projector, which can improve utilization efficiency, reduce unevenness in illuminance, and obtain a projected image with little unevenness in luminance, has been proposed.

  In any of the above-mentioned patent documents, a free-form surface is used for the imaging optical system from the projection lens to the screen, particularly for the reflecting mirror that bends the optical path. A spherical surface (such as a parabolic mirror) is used.

  Further, as a light source of a general projector, a high output light source such as a metal halide lamp or an ultrahigh pressure mercury lamp is widely used. However, these light sources require relatively large power. On the other hand, LEDs capable of emitting light with less power have been used particularly as light sources for small projectors.

  In addition to the advantages that the LED has better luminous efficiency and power saving than the conventional lamp, the LED itself is small and the power supply circuit for lighting can be designed to be small, which is advantageous for downsizing of the entire device.

Furthermore, the LEDs can emit light in a single wavelength in a narrow wavelength range, and the color filters are formed by sequentially turning on the single color LEDs that emit light in the three primary colors R (red), G (green), and B (black). Color images can be generated without the need for a color wheel. This also contributes greatly to downsizing of the apparatus. Further, light is not absorbed by the color filter, and the light utilization efficiency is further improved. Since the lifetime is extremely long compared with the conventional lamp, there is an advantage that almost no lamp replacement is required.
JP 2004-295042 A JP 2004-258620 A JP 2004-234015 A JP 2004-295107 A JP 2005-338138 A Japanese Patent Laid-Open No. 2006-3541 Japanese Patent Laid-Open No. 11-273441

  However, the light beams obtained by various conventional technological developments are not yet satisfactory in the uniformity of illuminance, and means for further improving the illuminance uniformity in order to make the screen brightness uniform. Is needed.

  Accordingly, an object of the present invention is to provide an image projection apparatus using an optical element having a free-form surface in a condensing optical system for condensing and irradiating an illumination light beam from a light source unit to a light modulation unit for image generation. .

  In order to achieve the above object, an invention according to claim 1 is an image projection apparatus having a light source unit in which light emitting elements are two-dimensionally arranged, and an illumination light beam from the light source unit is used for image generation. The light modulation unit includes a condensing optical system for condensing and irradiating the light modulation unit, and the condensing optical system is an image projection apparatus using an optical element having a free-form surface.

  According to a second aspect of the present invention, in the image projection apparatus according to the first aspect, the optical element is a transmissive lens.

  According to a third aspect of the present invention, in the image projection apparatus according to the first aspect, the optical element is a reflecting mirror.

  According to a fourth aspect of the present invention, in the image projection device according to the third aspect, the reflecting mirror is at least two concave mirrors.

  According to a fifth aspect of the present invention, in the image projection apparatus according to the third aspect, the reflecting mirror is at least one concave mirror and at least one convex mirror.

  According to a sixth aspect of the present invention, in the image projection device according to the fourth aspect, the arrangement interval of the two concave mirrors is variable.

  According to a seventh aspect of the present invention, in the image projection apparatus according to the fifth aspect, the arrangement interval between the concave mirror and the convex mirror is variable.

  The invention according to claim 8 is the image projection apparatus according to claim 1, wherein the light modulation unit is a reflection type light modulation unit.

  According to a ninth aspect of the present invention, in the image projection apparatus according to the second aspect, the transmission lens is at least one positive lens and at least one negative lens.

  According to a tenth aspect of the present invention, in the image projection apparatus according to the ninth aspect, the arrangement interval between the positive lens and the negative lens is variable.

  According to the present invention, it is possible to provide an image projection apparatus using an optical element having a free-form surface in a condensing optical system for condensing and irradiating an illumination light beam from a light source unit to a light modulation unit for image generation. .

  In the present embodiment, an illumination optical system that contributes to miniaturization of a projector by efficiently using a light beam from a light source in an image projection apparatus using a light source unit in which solid-state light emitting elements such as LEDs are two-dimensionally arranged is provided. The purpose is to do.

  Hereinafter, a process until a condensing element (lens or reflecting mirror) using a free-form surface is used for an illumination system of a projector as an example of an image projection apparatus in the present embodiment will be described.

  First, a single LED element will be described with reference to FIG. FIG. 11A shows an overview of a single LED element. FIG. 11B shows a first side view of a single LED element. FIG. 11C shows a second side view of the single LED element.

  There is a light emitting portion 12 at the center of the light emitting surface (front side in the figure) of the LED element 11, and an illumination light beam is emitted from the light emitting portion 12 to a region 13 shown in the figure. In the following description, a simplified side view as shown in FIG. 11B or FIG. 11C is also used. In FIG. 11C, the light emission direction is simply represented by only the central ray 3a of the illumination light beam.

  Next, the light source unit will be described with reference to FIG. FIG. 12A shows an overview of the light source unit (LED array). FIG.12 (b) shows the perspective view of the integral display of a light source unit. FIG. 12C shows a side view of the integral display of the light source unit.

  A problem with LEDs is that the amount of light per element is small. In order to compensate for this, a light source unit 14 in which a large number of LED elements 11 are arranged is used as shown in FIG. In the following description, the LED element 11 in FIG. 12A is simplified as an integrated light source unit 14 and shown in a perspective view as in FIG. 12B or a side view as in FIG. .

  Further, the illumination light beam region 5 emitted from the light source unit 14 is shown in FIG. Fig.13 (a) shows the 1st side view of a light source unit and a light emission area | region. FIG. 13B shows a second side view of the light source unit and the light emitting region. FIG.13 (c) shows the side view of a light source unit, a light emission area | region, and a center ray. In FIG. 13C, the central ray 15a of the light emitting region 15 is also shown.

  FIG. 14A shows an example of a general illumination optical system. In the illumination optical system of a general projector, as shown in FIG. 14A, after the illumination light beam emitted from the light source 12 is irradiated to the light modulation unit 17 by the condensing optical system 16 such as a condenser lens or a reflecting mirror, The light is condensed in the projection lens 18. This forms an image 19 of the light source in the projection lens 18. The light source image 19 is also called a virtual light source. The light modulation unit 17 is an image generation unit also called a light valve, and a transmissive liquid crystal panel, a reflective micromirror array (DMD), and the like are widely known.

  In FIG. 14A, there is a screen for projecting an image to the left of the projection lens 18, and the image formed on the light modulation unit 17 is folded directly on the screen by the projection lens 18 or with a reflecting mirror or the like. Thereafter, an image is formed on the screen, but the illustration of the optical system from the projection lens 18 to the screen is omitted here. In the following explanatory drawings, only the illumination optical system from the light source 12 to the projection lens 18 is shown.

  FIG. 14B shows an overview of a light source image when the light source is an LED array. In order to secure a sufficient amount of light, the light source unit 14 in which a necessary number of LED elements are arranged has a certain light emitting area as a unit. As shown in FIG. 14B, if the light source unit 14 is large, the light source image 19 on the projection lens 18 also spreads widely, and the diameter of the projection lens 18 must be increased. Further, the luminous flux emitted from the light source 12 becomes wider, and the diameter of the condensing optical system 16 needs to be increased.

  FIG. 14C shows an overview of an illumination system arranged so that the light source image becomes small. In order to condense the light source image 19 to one small point, as shown in FIG. 14C, the distance between the light source 12 and the condensing optical system 16 is widened, and the imaging magnification by the condensing optical system 6 is reduced. There is also. However, this method inevitably increases the diameter of the condensing optical system 16. Further, the light modulation unit 7 is irradiated with a light beam diameter larger than necessary, and the light use efficiency is lowered.

  As shown in FIG. 14A, in the case of a lens or reflecting mirror using a normal spherical surface, when the light source 12 is a single point, the light is condensed at almost a single point although it has a certain extent due to spherical aberration. However, when the number of the light sources 12 is two or more, all the light source images 19 cannot be condensed on the same point.

  On the other hand, by using an aspherical surface for the refractive surface of the lens and the reflecting surface of the reflecting mirror, the plurality of light sources 19 arranged on the optical axis can be condensed at almost one point.

  FIG. 15 is a schematic diagram illustrating an aspherical surface. As shown in FIG. 15, in a coordinate system in which the optical axis passing through the center of the optical element is the X axis and the axis perpendicular to the optical axis is the Y axis, the distance measured in the Y axis direction from the optical axis (also called the optical axis height). ) Is H, the displacement in the optical axis direction (also called the sag amount) measured from the Y axis at the height H is expressed by a function with H as a variable, such as ΔX = F (H). Can do. A curved surface called an aspheric surface is formed by rotating a curve drawn by this function around the optical axis (X-axis), and is a subject of rotation about the optical axis.

  The above function is usually a high-order function using only even-order coefficients. A special case with only a quadratic coefficient or less is also called a quadratic curve, and a quadratic curved surface obtained by rotating the quadratic curve includes a paraboloid, an ellipsoid, a hyperboloid, and the like. Particularly on the ellipsoid, it is known that a light beam emitted from one focus completely converges to the other focus. When an aspherical surface is used, light fluxes from a plurality of light sources scattered on the optical axis or parallel to the optical axis can be collected almost at one point by appropriately setting the value of the high-order coefficient.

  However, when the LED elements are two-dimensionally arranged on the light source unit and there is a light source other than the optical axis, the aspherical surface is a rotationally symmetric curved surface and cannot be focused on the same point. This will be described using an example in which a reflecting mirror is used in the condensing optical system.

  FIG. 16A shows an example of an illumination system using a reflecting mirror. In this example, the illumination light beam emitted in the direction opposite to the projection lens 18 is returned to the projection lens 18 direction while being condensed by the reflecting mirror 20. When a reflecting plate is used in the condensing optical system, unlike a lens, there are advantages such that no chromatic aberration occurs and the optical path can be made relatively short. However, when the reflecting mirror 20 and the light source 12 are both arranged in a line on the optical axis as in the example of FIG. 16A, the light beam reflected by the reflecting mirror 20 is shielded by the light source unit 11, and the light use efficiency is increased. Falls.

  In order to solve this, there is an example in which only the upper half of the reflecting mirror 20 is used as a reflecting surface, as shown in a cross-sectional view in FIG. FIG. 16B shows an example of an illumination system that partially uses a reflecting mirror. This will be described with reference to FIG. FIG. 17A shows an overview of a bowl-shaped reflector. FIG. 17B shows a schematic view of a reflecting mirror obtained by cutting a saddle type reflecting mirror in half. As shown in FIG. 18, the reflecting mirror 20 is disposed together with the light source unit 14, the light modulation unit 17, and the projection lens 18 facing upward. That is, FIG. 18 shows a layout diagram of the reflecting mirror, the light source unit, the light valve, and the projection lens. Hereinafter, this example will be mainly described.

  Next, the convergence state of the illumination light beam will be described with reference to FIG. 19 showing cross sections of the light source unit 14 and the reflecting mirror 20. FIG. 19A shows a condensing state when the reflecting mirror is a secondary aspherical surface. FIG. 19B shows a state of light collection when the reflecting mirror is a high-order aspherical surface.

  When a spherical surface or a secondary aspherical surface is used for the reflecting mirror 20, as shown in FIG. 19A, the light beams from the plurality of light sources 12 cannot be collected at one point. However, when higher-order aspherical surfaces are used, they can be collected at almost one point as shown in FIG. This state is shown in a perspective view in FIG. FIG. 20A shows a state of light collection when the light source exists parallel to the optical axis. In FIG. 20A, for easy understanding, the luminous fluxes emitted from the plurality of light sources 2 are represented by only one central ray.

  As shown in FIGS. 19B and 20A, when the light sources 12 are arranged in a line on the optical axis or parallel to the optical axis, a higher-order aspheric surface is used as the reflecting surface. To collect light at almost one point.

  FIG. 20B shows a light collection state when the light source exists away from the optical axis. However, since the aspherical surface is rotationally symmetric, when the light source 12 is away from the optical axis, that is, when it is arranged in a direction not parallel to the optical axis, as shown in FIG. Does not collect light at one point. FIG.20 (c) shows the figure of the condensing state when a light source is arranged in two dimensions. In order to obtain a sufficient amount of light, when the light source unit 14 in which the light sources 2 are two-dimensionally arranged is used, as shown in FIG. 20 (c), compared with the case of FIG. 20 (b). The light source image 19 has a spread. In FIG. 20C, light rays emitted from the respective light sources 12 are not drawn in order to avoid the complexity of illustration.

  There is a free-form surface to compensate for the disadvantages of these aspheric surfaces. FIG. 1 is an explanatory diagram of a free-form surface, and the free-form surface will be briefly described.

In the coordinate system as shown in FIG. 1, YZ composed of a Y axis and a Z axis perpendicular to the optical axis (X axis).
The plane is a reference plane (not shown), and the coordinates (height from the X axis) measured on the reference plane from the X axis to the Y axis direction and the Z axis direction are represented by ΔY and ΔZ, respectively. X from the plane
If the sag measured in the axial direction is ΔX, a curved surface defined by a higher-order function such as ΔX = F (ΔY, ΔZ) or a higher-order function using an auxiliary function including ΔY and ΔZ as variables is free. It is a curved surface and generally has no symmetry.

  Define the sag amount (ΔX) at an arbitrary coordinate (ΔY, ΔZ) on the reference plane, and interpolate between each point on the defined curved surface with an interpolation function such as a cubic spline. In some cases, each definition point is smoothly connected to form a free-form surface.

FIG. 2 is a diagram showing an example in which a free-form surface lens is used in the condensing optical system in the present embodiment.
The effect of light condensing by a free-form surface will be described with reference to FIG. 2 using an example using a transmission lens. As shown in FIG. 2, in the condensing lens using a free-form surface as the refracting surface, it is possible to freely set the refraction direction of the portion where the light beam 7 from each light emitting point is refracted. Thereby, the illumination light beam 7 from the plurality of light sources 1 can be condensed at almost one point of the projection lens 4. FIG. 3 is a diagram showing an example in which a free-form curved mirror is used in the condensing optical system in the present embodiment. That is, FIG. 2 is a perspective view of FIG. 2, and illumination light beams from the light source unit 2 in which many light sources 1 are two-dimensionally arranged gather at one point to form a small light source image 3.

  In FIG. 3, similarly to FIG. 10C, light rays emitted from the respective light sources 1 are not drawn in order to avoid the complexity of illustration.

  As described above, in this embodiment, by using a condensing element (lens or reflecting mirror) using a free-form surface for the illumination system of the projector, the illumination light beam of the light source unit having a relatively large spread is reduced to a small point. Can be condensed. Accordingly, it is possible to provide an image projection apparatus that is small in size, consumes less power, and has sufficient brightness.

  Next, a best mode for using a condensing element (lens or reflecting mirror) using a free-form surface for an illumination system of a projector as an example of an image projection apparatus will be described in detail.

  This embodiment is a projector that uses a light source unit in which a plurality of light sources are arranged two-dimensionally, such as an LED array, and uses a free-form surface as shown in FIG. 1 as a condensing element of an illumination optical system. Therefore, the light condensing characteristic is extremely enhanced as compared with the projector apparatus using a conventional spherical surface or aspherical surface for the illumination system. 10 (a) to 10 (c) show examples of the condensing state on a conventional spherical surface or aspherical surface, and FIGS. 2 and 3 show examples of the condensing state when a free-form surface is used.

  In the present embodiment, the illumination light beam from the light source unit 5 can be condensed at almost one point in the projection lens 4 by using a free-form surface for the condensing element of the illumination system. In addition to reducing the diameter and shortening of the projection optical system, it is possible to give the condensing element (lens, reflector, etc.) strong power (convergence) without degrading the performance of the illumination system. This greatly contributes to the miniaturization of the projection apparatus. In addition, since the light condensing performance equivalent to that of the conventional method can be obtained with a smaller number of light condensing elements, cost reduction can be sufficiently expected.

  In this embodiment, a free-form surface is used for the transmission type condensing lens. FIG. 2 shows an example in which a free-form surface is used for the condenser lens 6, and the illumination light beam 7 from a plurality of light sources 1 is condensed at almost one point in the projection lens 4 to form a small light source image 3.

  In the present embodiment, a lens 6 having a free curved surface is used as the light condensing element. In general, in a lens, a free-form surface can be applied to each of two surfaces on the incident side and the exit side, so that the number of parameters that can be used for design, that is, the degree of freedom in design increases. This makes it possible to design a high-performance illumination optical system with fewer optical elements.

  In this embodiment, a free-form surface is used for the reflecting mirror for condensing. FIG. 3 is an example in which a free-form surface is used for the reflecting mirror 8, and in the same way as in the example of FIG. 2, illumination light beams (not shown) from a plurality of light sources 2 are condensed at almost one point in the projection lens 8. A small light source image 3 is formed.

  In the present embodiment, the reflecting mirror 8 having a free curved surface is used as the light condensing element. In reflection, unlike refraction by a lens, the same reflection angle is obtained for all wavelengths. For this reason, when a reflecting mirror is used, no chromatic aberration occurs. This makes it possible to design a projector device that maximizes the excellent color characteristics of a light source capable of monochromatic light emission, such as an LED.

  FIG. 4 is a diagram showing an example in which a concave mirror having at least two free-form surfaces is used in the condensing optical system in the present embodiment. The illumination light beam emitted from each light source 1 of the light source unit 2 is reflected by two concave mirrors 8a having a free-form surface, irradiates the light modulation unit 7, and is condensed at almost one point in the projection lens 4. A small light source image 3 is formed.

  In this embodiment, as shown in FIG. 4, a concave mirror 8a having at least two free-form surfaces is used in the condensing optical system. Even in a configuration using only one concave mirror, if the power (convergence) of the reflecting mirror is increased, the imaging position of the light source image 3 becomes closer, and the illumination optical system can be designed smaller. However, when the power is too strong, various aberrations are likely to occur. In particular, it is easily affected by installation errors of light sources and reflectors, that is, optical decentration (tilt and axis deviation). As in this example, in the configuration using two or more concave mirrors 8a, it is possible to appropriately disperse the required power on each reflecting surface, and the illumination system has a stable performance as compared with the case of only one. Can be designed.

  FIG. 5 is a diagram illustrating an example in which the concave mirror having at least one free-form surface and the convex mirror having at least one free-form surface are used in the condensing optical system according to the present embodiment. The illumination light beam emitted from each light source 1 of the light source unit 2 is reflected by the concave mirror 8a having a free curved surface and the convex mirror 8b having a free curved surface, and then irradiates the light modulation unit 5 to almost one point in the projection lens 4. The light is condensed to form a small light source image 3. In an illumination optical system having a configuration in which a concave mirror and a convex mirror are combined, the illumination light beam is emitted in a nearly parallel state as compared with a configuration having only a concave mirror. Also in this example, the light source image 3 is formed farther than the example of FIG. In the example shown here, after being reflected by the convex mirror 8 b, the light modulation unit 5 is irradiated by bending the optical path with the plane mirror 9. This is devised to lay out the optical system small, but the light modulation unit 5 may be directly irradiated without using the plane mirror 9. The projection lens in that case is upward in the figure.

  In this embodiment, as shown in FIG. 5, a concave mirror 8a and a convex mirror 8b each having a free curved surface are used. An optical system that combines an optical element with positive power (convergence), such as a convex lens or concave mirror, and an optical element with negative power (divergence), such as a concave lens or convex mirror, is composed of only positive power optical elements. Compared to the optical system, the emitted light beam is more nearly parallel.

  In the present embodiment, light beams that are closer to parallel are emitted as compared with the configuration of only a concave mirror as shown in FIG. When emitted from the illumination system as a substantially parallel light beam, it is also called a telecentric optical system. In a light valve device such as a liquid crystal panel, which requires an incident angle close to perpendicular to obtain desired image characteristics, a telecentric optical system is often used for an illumination system. In the configuration in which the concave mirror and the convex mirror are combined in the present embodiment, a telecentric optical system or an optical system close to telecentric can be realized by appropriately setting the power and arrangement relationship of convergence or divergence.

  FIG. 6 shows an example of a condensing optical system using a concave mirror having at least two free-form surfaces in the present embodiment, and the arrangement interval of the concave mirrors can be varied. The basic configuration of this example is the same as that of the example of FIG. 4, but by changing the positional relationship between the light source unit 2 and the two concave mirrors 8a having free curved surfaces, the convergence position of the illumination light beam, that is, the light source image 3 is formed. The position is changed further from FIG.

  In the present embodiment, the arrangement interval of the concave mirrors 8a is variable in the configuration shown in FIG. By changing the interval, the focal length of the combination by the respective optical elements changes, and the irradiation area on the light modulation unit (light valve) 5 also changes. In a projector that projects various images, the size of the image formed on the light modulation unit 5, that is, the light modulation unit 5 actually depends on the size (number of pixels) and the aspect ratio (aspect ratio) of the image to be projected. May change the area used. In such a projector apparatus, by changing the irradiation area as in the present embodiment, only a necessary area on the light modulation unit 5 can be irradiated and the illumination light beam can be used efficiently.

  FIG. 7 is a diagram showing an example of a condensing optical system using a concave mirror having at least one free-form surface and a convex mirror having at least one free-form surface in the present embodiment, and the arrangement interval between the concave mirror and the convex mirror can be varied. Indicates. The basic configuration in this example is the same as in the example of FIG. 5, but by changing the positional relationship of the light source unit 2, the concave mirror 8a having a free curved surface, and the convex mirror 8b having a free curved surface, the convergence position of the illumination light beam, that is, the light source image The position where 3 is formed changes farther with respect to FIG.

  In the present embodiment, the arrangement interval between the concave mirror 8a and the convex mirror 8b is variable in the configuration of FIG. As a result, in addition to the effect of being emitted with a nearly parallel light beam as described in the example of FIG. 5, the irradiation area on the light modulation unit 5 can be adjusted in the same manner as described with reference to FIG. 6. .

  In the present embodiment, a reflective light modulation unit will be described with reference to FIG. FIG. 8A shows a first overview of a light source image formed by using the reflection type light modulation unit in the present embodiment. FIG. 8B shows a second overview of a light source image formed by using the reflection type light modulation unit in the present embodiment.

  An example is shown in a reflection type light modulation unit. In the example of FIG. 8A, the reflection type light modulation unit 10 is used in place of the transmission type light modulation unit 5 in the optical arrangement as in the example shown in FIG. In the example of FIG. 8B, the light modulation unit 10 is used in the optical arrangement of the example shown in FIG. In any of the examples, a reflecting mirror having a free curved surface is used in the condensing optical system, but a lens having a free curved surface may be used instead of the reflecting mirror.

  In the present embodiment, the reflection type light modulation unit 10 is used as the light modulation unit. In particular, in an example in which a reflecting mirror is used as the light condensing element, the whole can be made compact by folding the optical path of the illumination system. At this time, the optical path can be bent by the plane mirror 9 as in the examples shown in FIGS. 5 and 7, but the reflection type light modulation unit 10 is used as in the example shown in FIG. In addition to downsizing the apparatus, the number of parts can be reduced. A small apparatus that further utilizes the advantage of downsizing the illumination system by using an optical element having a free-form surface can be realized.

  In many cases, the reflection type light modulation unit 10 using a micromirror array (DMD or the like) in which a large number of minute reflection plates are arranged is required to have an incident angle closer to the vertical than a liquid crystal panel or the like. In such a reflection-type light modulation unit 10, it is preferable to use a telecentric optical system as shown in FIG. 5 or FIG. 6 or an illumination optical system close to telecentric.

  FIG. 9 is a diagram illustrating an example in which at least one positive lens (convex lens) having a free curved surface and at least one negative lens (concave lens) having a free curved surface are used in the condensing optical system according to the present embodiment. The illumination light beam emitted from each light source 1 of the light source unit 2 is reflected by the positive lens 6 a having a free curved surface and the negative lens 6 b having a free curved surface, and then irradiates the light modulation unit 7. The light is condensed at one point to form a small light source image 3. In an illumination optical system having a configuration in which a positive lens and a negative lens are combined, a beam of illumination light that is more nearly parallel than the configuration of only a positive lens is emitted. Also in this example, the light source image 3 is formed farther than the example of FIG.

  In this embodiment, a positive lens and a negative lens each having a free curved surface are used as the condensing elements. As described in the example using the reflecting mirror, the refractive index of the glass material generally used in manufacturing the lens changes with respect to different light wavelengths, and as a result, chromatic aberration occurs. This chromatic aberration cannot be eliminated by using only one lens or only two or more positive lenses. However, it is widely known that chromatic aberration can be corrected by combining a positive lens and a negative lens made of glass materials having different wavelength characteristics (chromatic dispersion).

  In this embodiment, it is possible to correct chromatic aberration by combining a positive lens and a negative lens, and to emit a light beam that is closer to parallel, similarly to the configuration shown in FIG.

  FIG. 10 shows a condensing optical system using a positive lens having at least one free-form surface and a negative lens having at least one free-form surface in the present embodiment. The arrangement interval between the positive lens and the negative lens is variable. An example diagram that can be shown is shown. The basic configuration in this example is the same as that in the example of FIG. 9, but by changing the positional relationship of the light source unit 2, the positive lens 6a having a free curved surface, and the negative lens 6b having a free curved surface, the convergence position of the illumination light beam, that is, The position where the light source image 3 is formed changes with respect to FIG.

  In the present embodiment, the arrangement interval between the positive lens and the negative lens is variable in the configuration of FIG. In addition to the lens effect described with reference to FIG. 9, it is possible to efficiently use the illumination light beam by irradiating only the necessary area on the light valve, as in the configurations of FIGS. it can.

  If the projector apparatus of this invention is utilized, a video image and a computer output can be applied to screen projection.

It is the figure which showed the description of the free-form surface typically. It is the figure which showed an example using the free-form surface lens for the condensing optical system in this embodiment. It is the figure which showed an example using the free-form curved mirror for the condensing optical system in this embodiment. It is the figure which showed an example using the concave mirror which has at least 2 free-form surface for the condensing optical system in this embodiment. It is the figure which showed an example using the concave mirror which has at least 1 free-form surface, and the convex mirror which has at least 1 free-form surface in the condensing optical system in this embodiment. It is the figure which showed an example which can vary the arrangement | positioning space | interval of each concave mirror in the condensing optical system using the concave mirror which has at least 2 free-form surface in this embodiment. It is the figure which showed an example which can change the arrangement | positioning space | interval of these concave mirrors and convex mirrors in the condensing optical system using the concave mirror which has at least 1 free-form surface in this embodiment, and the convex mirror which has at least 1 free-form surface. . (A) is the 1st general-view figure of the light source image formed by using the reflection type light modulation unit in this embodiment. (B) is the 2nd general-view figure of the light source image formed by using the reflection type light modulation unit in this embodiment. It is the figure which showed an example using the positive lens (convex lens) which has at least 1 free-form surface, and the negative lens (concave lens) which has at least 1 free-form surface in the condensing optical system in this embodiment. An example in which the arrangement interval between the positive lens and the negative lens can be varied in the condensing optical system using the positive lens having at least one free-form surface and the negative lens having at least one free-form surface in the present embodiment is shown. It is a figure. (A) is a general-view figure of a single LED element. (B) is a first side view of a single LED element. (C) is a second side view of a single LED element. (A) is a general-view figure of the light source unit (LED array) in this embodiment. (B) is a perspective view of integral display of the light source unit. (C) is a side view of integral display of the light source unit. (A) is a 1st side view of a light source unit and a light emission area. (B) is the 2nd side view of a light source unit and a light emission area | region. (C) is a side view of a light source unit, a light emitting region, and a central ray. (A) is a figure showing an example of a general illumination optical system. (B) is a general-view figure of the light source image in case the light source in this embodiment is an LED array. (C) is an overview of an illumination system arranged so that the light source image in the present embodiment is small. It is the figure which showed the description of the aspherical surface typically. (A) is a figure which shows an example of the illumination system using a reflective mirror. (B) is a figure which shows an example of the illumination system which partially used the reflective mirror in this embodiment. (A) is a general-view figure of a bowl-shaped reflective mirror. (B) is the general-view figure of the reflective mirror which cut the saddle type reflective mirror in half. It is the figure which showed an example of arrangement | positioning of a reflective mirror, a light source unit, a light valve, and a projection lens. (A) is a figure which shows the condensing state in case a reflective mirror is a secondary aspherical surface. (B) is a figure which shows the condensing state in case a reflective mirror is a high-order aspherical surface. (A) is a figure which shows the condensing state in case a light source exists in parallel with an optical axis. (B) is a figure which shows the condensing state in case a light source exists away from an optical axis. (C) is a figure which shows the condensing state when a light source is arranged in two dimensions.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 12 Light emission part 2, 14 Light source unit 3,19 Condensing point 4,18 Projection lens 5,17 Light modulation unit 6 Condensing optical system 6a Positive condensing lens 6b Negative condensing lens 7,13 Light emission area 8 , 20 Reflective mirror 8a Concave mirror 8b Convex mirror 9 Plane mirror for bending the optical path 10 Reflective light valve 11 LED element 15 Light emitting area of the light source unit 15a Central beam of the emitted light beam

Claims (10)

An image projection apparatus having a light source unit in which light emitting elements are two-dimensionally arranged,
A condensing optical system for condensing and irradiating an illumination light beam from the light source unit to a light modulation unit for image generation;
An image projection apparatus characterized in that the condensing optical system uses an optical element having a free-form surface.   The image projection apparatus according to claim 1, wherein the optical element is a transmission lens.   The image projection apparatus according to claim 1, wherein the optical element is a reflecting mirror.   The image projector according to claim 3, wherein the reflecting mirror is at least two concave mirrors.   The image projector according to claim 3, wherein the reflecting mirror is at least one concave mirror and at least one convex mirror.   The image projection apparatus according to claim 4, wherein an interval between the two concave mirrors is variable.   The image projection apparatus according to claim 5, wherein an arrangement interval between the concave mirror and the convex mirror is variable.   The image projection apparatus according to claim 1, wherein the light modulation unit is a reflective light modulation unit.   The image projector according to claim 2, wherein the transmission lens is at least one positive lens and at least one negative lens.   The image projection apparatus according to claim 9, wherein an arrangement interval between the positive lens and the negative lens is variable.

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