JP6698873B2 - Illumination optical system and projection type image display device - Google Patents

Description

  The present invention relates to a technique of a projection-type image display device, and more particularly, to a technique effective when applied to an illumination optical system that improves utilization efficiency of light from a light source and a projection-type image display device using the illumination optical system.

  Projection-type image display devices (projectors) are widely used. Among them, the utilization efficiency of the light emitted from the light source is improved, that is, in the illumination optical system, the light is emitted from the light source to the panel displaying the image. It has been studied to improve the illumination efficiency when irradiating the emitted light, and various means have been proposed.

  As a technique related to a technique for improving the use efficiency of light in an illumination optical system (hereinafter, may be simply referred to as “efficiency”), for example, JP 2012-155344 A (Patent Document 1) describes a field. There is described an illumination optical system configured to cause a light flux passing through each lens cell of the first integrator to enter a plurality of display panels substantially in parallel and to be superimposed on the plurality of display panels by a lens and a condenser lens. ing. In the case of this configuration, by using a field lens and a condenser lens having a short combined focal length, it is possible to shorten the interval between them, and it is possible to realize an optical system with a short focal length of the first integrator. Becomes Therefore, it is possible to reduce the arc image of the light source formed on the second integrator, reduce the amount of light that deviates from the effective aperture of each polarization conversion unit of the polarization conversion element, and improve the illumination efficiency. To be done.

  Further, in Japanese Patent Laid-Open No. 2006-318922 (Patent Document 2), an LED (Light Emitting Diode) having a diffused emission characteristic and a part or all of the light from the LED captured from the incident end face is reflected by a reflecting surface. A lighting device including a light guide rod or a taper rod that guides light to the emission end face by this, and an illumination lens that converts the intensity intensity of the light distribution of the emission light from these emission end faces into the position intensity within a predetermined irradiation region. Is listed. This makes it possible to realize uniform illumination with high efficiency and desired parallelism by using a minute surface light source such as an LED.

  In addition, International Publication No. 2008/069143 (Patent Document 3) describes an illumination device having a light source and a collimator lens. Here, the light flux emitted from the light source is incident on the spherical surface of the collimator lens substantially perpendicularly, and the light ray of which the angle formed with the optical axis is small is incident on the first elliptical surface and refracted. The first elliptical surface converts a light beam diverging from a light source located at the first focal point into a parallel light beam. A light ray having a large angle with the optical axis is incident on the second elliptical surface and is totally reflected by the second elliptic surface. The second elliptical surface converts a light beam diverging from the light source located at the first focus into a light beam that focuses on the second focus. In addition, the third elliptical surface converts the light beam condensed at the second focal point into a parallel light beam. With these, the light flux emitted from the light source is converted into substantially parallel light by the collimator lens, and it is possible to realize an illuminating device having high directivity, high efficiency, and high uniformity of light amount distribution.

JP, 2012-155344, A JP, 2006-318922, A International Publication No. 2008/069143

  In recent years, in projectors, DLP (Digital Light Processing, registered trademark) projectors using DMD (Digital Micromirror Device) as a panel (video display element) have become widespread. In the case of using a DMD panel, there are cases where the luminous flux must be incident at a certain angle with respect to the normal line of the panel according to its specifications, instead of being incident perpendicularly to the panel. In this case, in order to improve the illumination efficiency, it is necessary to form a light beam having a constant angular space (that is, a numerical aperture NA (Numerical Aperture)) on one point of the panel with as little aberration as possible. In this respect, the related art does not consider such a problem.

  Therefore, an object of the present invention is, in an illumination optical system for irradiating a video display element at a constant angle, a light flux emitted from a light source and passing through an optical element such as an integrator, as a light flux in a constant angular space, It is an object of the present invention to provide an illumination optical system for forming an image on one point on an image display element with as little aberration as possible and a projection type image display device using the illumination optical system.

  The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

  The following is a brief description of the outline of the typical inventions among the inventions disclosed in the present application.

  An illumination optical system according to a typical embodiment of the present invention includes a light source having perfect diffusivity, a collimator that captures an illumination light flux from the light source, converts the illumination light flux into a small NA while having a predetermined diameter, and the collimator. An integrator that uniformizes the brightness of the illumination light flux that has passed through, and a condenser lens that condenses the illumination light flux, and a constant angle with respect to a normal line of the irradiation surface of the illumination target through a prism. And an illumination optical system for irradiating the illumination luminous flux with the following features.

  That is, the condenser lens and the prism are arranged between the integrator and the object to be illuminated so that the illumination light flux passes in this order. The condensing lens and the prism are configured such that the chief ray of the illumination light flux is incident on the irradiation surface of the object to be illuminated at a predetermined angle with respect to the normal to the irradiation surface of the object to be illuminated. To be done.

  Further, in the prism, an incident surface of the illumination light beam is inclined with respect to an exit surface, and a chief ray incident on the incident surface enters from a side opposite to a vertex of the prism with respect to a normal line of the incident surface. , The principal ray emitted from the emission surface is configured to be emitted from the side opposite to the vertex of the prism with respect to the normal to the emission surface, and the emission surface of the prism is substantially parallel to the irradiation surface of the illuminated body. Will be arranged. Further, the condensing lens is configured such that the respective chief rays after being emitted from the condensing lens are substantially parallel to each other, rotate in the same direction as the incident surface of the prism, and are further offset from each other. It

  The effects obtained by the typical ones of the inventions disclosed in the present application will be briefly described as follows.

  That is, according to a representative embodiment of the present invention, in an illumination optical system that irradiates a video display element at a constant angle, a light beam emitted from a light source and passing through an optical element such as an integrator, By forming a light beam with a constant angular space at one point on the image display element with as little aberration as possible, it is possible to improve the light utilization efficiency.

(A), (b) is the figure which showed the example about the external appearance of the projection type video display apparatus in Embodiment 1 of this invention. FIG. 3 is a cross-sectional view showing an example of the configuration of the projection optical system in the first embodiment of the present invention. FIG. 3 is a top view showing an example of the internal structure of the projection-type image display device in the first embodiment of the present invention. FIG. 3 is a top view showing an example of structures of an illumination optical system and a projection optical system of the projection type image display device in the first embodiment of the present invention. (A), (b) is the figure which showed the example about the logical structure of the illumination optical system which is Embodiment 1 of this invention. It is the figure which showed the outline about the structural example of the integrator in Embodiment 1 of this invention. It is a figure explaining the relationship of DMD panel and incident light in Embodiment 1 of this invention. It is the figure which showed the example about the distribution condition of the light intensity on the display surface of an image display element. FIG. 6 is a diagram illustrating a deviation angle of a prism according to the first embodiment of the present invention. It is the figure which showed the example about the structure of the virtual prism which expanded the prism in Embodiment 1 of this invention, a condensing lens, and a DMD panel. FIG. 3 is a diagram showing an example of a situation of light rays that have passed through a condenser lens and a virtual prism in the first embodiment of the present invention. FIG. 3 is a diagram showing an example of configurations of a developed rear prism, a condenser lens, and a DMD panel in Embodiment 1 of the present invention. (A), (b) is the figure which showed the outline about the logical structure of the collimator of the illumination optical system which is Embodiment 2 of this invention, and the example of the condition of a light ray.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In all the drawings for explaining the embodiments, the same parts are designated by the same reference numerals in principle, and the repeated description thereof will be omitted. On the other hand, parts described with reference numerals in a certain drawing may be referred to with the same reference numeral although not shown again in the description of other drawings.

(Embodiment 1)
<Structure of projection type video display device>
FIG. 1 is a diagram showing an example of an external appearance of a projection-type image display device (projector) according to Embodiment 1 of the present invention. FIG. 1A is a front view of the projection-type image display device 1, and FIG. 1B is a side view.

  The projection-type image display device 1 has, for example, a housing 2 having a substantially flat box-like outer shape. Due to this shape, when using it upright on the surface of a desk or a table (when an image is projected on the surface of a desk or a table), the back side of the shape stands upright. It is possible to It should be noted that the housing 2 may have a detachable means or a means such as a stand (not shown) that is built in the housing 2 and can be taken out.

  A mirror cover 3 that can be opened and closed is formed on the upper surface of the housing 2. A reflection mirror (free-form curved mirror) 31 formed in a convex shape and rotationally asymmetrical is attached to the inside of the mirror cover 3. In addition, a projection lens system 52 is arranged inside the convex portion formed in the substantially central portion on the upper side of the housing 2, and an opening portion for guiding the projection light to the outside is formed. In the figure, only a part of the projection lens system 52 is shown through the opening. Further, a part of a so-called focus adjustment ring 6 (projected to the outside from the case 2) for adjusting the focus state of the projected image by changing the lens position by a lens adjusting mechanism (not shown) is provided on the upper side of the case 2. The upper end) is shown.

  FIG. 2 is a sectional view showing an example of the configuration of the projection optical system 5 in the present embodiment. For example, in an illumination optical system (not shown), light from a light source such as an LED or a semiconductor laser is supplied in accordance with an external video signal (for example, a video signal from a mobile terminal, a tablet terminal, a PC (Personal Computer), etc.). , DMD panel 48 and other image display elements are made incident and modulated. Then, the obtained image is combined by a TIR (Total Internal Reflection) prism 51, projected onto a reflection mirror 31 via a projection lens system 52 composed of a plurality of lenses, reflected, and enlarged and projected.

  It should be noted that the projection lens system 52 includes various types of distortion, such as a lens having a free-form curved surface that is not rotationally symmetric and is necessary for correcting various types of distortion associated with enlarged projection of an image, such as distortion due to oblique incidence and trapezoidal distortion. The lens is included. Further, the projection lens system 52 is movably mounted on the projection lens base 53, and a lens adjusting mechanism 54 moves a part of the projection lens or a lens group in the vertical direction in the drawing. It is possible to adjust the focus performance with.

  Further, the image light, which is irradiated onto the DMD panel 48 (image display element) from an illumination optical system (not shown) and is modulated by the DMD panel 48, is enlarged by the projection lens system 52 and is reflected by the reflection mirror 31 as shown by a broken line in the figure. Is reflected on the surface and is projected on the surface of a screen, a wall surface, a desk, a table, or the like (not shown). In the figure, the upper limit light and the lower limit light are respectively indicated by arrows.

  Further, in the present embodiment, the projection optical system 5 including the reflection mirror 31 and the projection lens system 52 is placed on a plane (specifically, in order to make the height of the housing 2 as small as possible to achieve size reduction. , On the projection lens base 53 provided at the bottom of the housing 2) so as to be substantially parallel to the surface thereof. Generally, in order to obtain a larger projected image at a predetermined projection distance, for example, the projection lens system 52 is arranged in a state of being tilted with respect to the bottom surface (a state of being tilted without being perpendicular to the screen or the like). On the other hand, it is conceivable to increase the diffusion angle of the image light on the reflection mirror 31 (for example, the angle formed by the upper limit light and the lower limit light in the figure). However, in this case, by arranging the projection lens system 52 in an inclined manner, the height of the housing 2 increases, which is a disadvantage from the viewpoint of downsizing.

  FIG. 3 is a top view showing an example of the internal structure of the projection-type image display device 1 according to the present embodiment. Further, FIG. 4 is a top view showing an example of the structures of the illumination optical system 4 and the projection optical system 5 of the projection type image display device 1 according to the present embodiment.

  FIG. 3 shows a state in which the upper case of the housing 2 is removed. In FIG. 3, the projection optical system 5 including the reflection mirror 31 and the projection lens system 52 is arranged substantially in the center of the housing 2 along the vertical direction in the drawing. Further, the power source unit 7 and a plurality of (two in the example in the figure) axial fans 81 for heat dissipation are arranged on one side (left side in the figure) of the projection lens system 52 as a center. ing. A sirocco fan 82 for heat dissipation is arranged on the other side (right side in the drawing) of the projection lens system 52.

  As shown in FIGS. 3 and 4, a part of the sirocco fan 82 is substantially integrated with the heat radiation fins, and heat generated by the LED 42G for emitting green (G) light in the LED lighting unit 41 that constitutes the light source. Is propagated to the heat radiation fin via the heat pipe 83G. Similarly, the heat generated by the LED 42R for emitting red (R) light is emitted through the heat pipe 83R, and the heat generated by the LED 42B for emitting blue (B) light is emitted through the heat pipe 83B. Is propagated to. Then, it is cooled by the cooling air generated by the sirocco fan 82 and radiated from the exhaust port provided in the housing 2. The DMD panel 48 is cooled by the heat sink 84 for cooling.

<Structure of illumination optical system>
FIG. 5 is a diagram showing an example of a logical configuration of the illumination optical system 4 according to the present embodiment. FIG. 5A shows a top view in a logical configuration, and its AA′ cross section is shown in FIG. 5B. It should be noted that the upper surface in FIG. 5 and the upper surface in the mounting example shown in FIGS.

  The illumination optical system 4 of the present embodiment has substantially the same components and arrangement as those of an illumination optical system used in a general projector or the like. Here, the LEDs 42R, 42G, and 42B (which may be collectively referred to as “LEDs 42” below) that constitute the LED lighting unit 41, and one or more lenses that parallelize the light emitted from these light sources, respectively. Collimators 43R, 43G, 43B (hereinafter, these may be collectively referred to as collimator 43), a dichroic mirror 44 that synthesizes collimated light beams, an integrator 45 that includes one or more lenses that homogenize the synthesized light, and the like. And other optical elements.

  The condenser lens 46 and at least two prisms 47 are provided between the integrator 45 and the DMD panel 48 in order to irradiate the DMD panel 48 with the light flux that has passed through the integrator 45 at a constant angle. That is, the optical image (illumination area) of each cell 45a of the lens array in the front view of the integrator 45 shown in the diagram on the right side of FIG. 6 is superimposed on the DMD panel 48 by the condenser lens 46 (and the prism 47). .. In the example of FIG. 6, the optical images of 7×7=49 cells 45 a are superimposed on the DMD panel 48.

  It should be noted that “irradiating the DMD panel 48 at a certain angle” means that, as shown in FIG. 7, the principal ray of the illumination light flux (the center of the light flux when focusing on the light flux irradiating each point of the DMD panel 48). Light beam) is incident on the normal line of the irradiation surface of the DMD panel 48 at an angle according to the specifications of the DMD panel 48. Incident light that has entered at a predetermined angle is reflected by the micromirrors formed on the surface of the DMD panel 48 in the substantially normal direction of the DMD panel 48 to become outgoing light.

<Improvement of light utilization efficiency>
Here, in general, in order to improve the light utilization efficiency in the illumination optical system 4, that is, to irradiate the DMD panel 48, which is the illuminated object, with the light emitted from the LED 42, which is the light source, with as little loss as possible. The basic method is to perform matching between the LED 42 and the DMD panel 48 by a quantity called “Entdue” represented by the following equation.

Etendue=π×(light emitting area of light source)×(solid angle of light emitted from light source)
=π×(light emitting area of light source)×(NA) ²
(NA=sin θ, θ is the angle of light from the center of the optical axis)
For example, when the difference between the light source side and the illuminated object side is large, such as when the illuminated object has a very small or very large Etendue with respect to the light source side, the illumination optical system generally The impact of design content on efficiency is relatively small (ie, there is little room for design to cover). On the other hand, when the light source side and the illuminated body side are about equal in Etendue, it is necessary to carefully design the illumination optical system in order to improve efficiency.

  When an LED is used as a light source, it is necessary to increase the size of the die in order to increase the amount of light due to heat dissipation. On the other hand, when the DMD panel is used as the illumination target, the smaller size can reduce the cost. For this reason, the Etendues of both tend to have the same size. Therefore, when the LED 42 is used as the light source and the DMD panel 48 is used as the object to be illuminated as in the present embodiment, it is necessary to carefully design the illumination optical system 4.

The illumination optical system 4 of the present embodiment, as shown in FIG.
(1) Light source having perfect diffusivity (LED 42 in the example of FIG. 5)
(2) Collimator that takes in the light flux from the light source and converts it into a small NA while having a predetermined diameter (collimator 43 in the example of FIG. 5)
(3) An integrator (integrator 45 in the example of FIG. 5) for realizing the uniformity of the luminous flux on the illuminated object (the DMD panel 48 in the example of FIG. 5)
(4) Condensing lens for condensing on the illuminated object (condensing lens 46 in the example of FIG. 5)
It has a basic configuration including each optical element of.

  In order to improve efficiency, it is important to design each of the above stages so that the loss of Etendue is reduced. For example, when the light source and the illuminated object have substantially equal Etendues, it is necessary to design the illumination optical system 4 so that the Etendues at the respective steps (1) to (4) from the light source to the illuminated object are approximately equal. There is. When the etendue increases in the optical element on the way, the increased etendue cannot be reduced without lowering the efficiency, and thus the efficiency cannot be lowered because the etendue of the illuminated object cannot be matched. When the Etendue of the illuminated object is larger than the Etendue of the light source, the illumination optical system 4 is designed so that the Etendues at the respective steps (1) to (4) are substantially equal or monotonically increase. ..

  In the present embodiment, of the stages (1) to (4) above, the condenser lens of (4) is designed to reduce the loss of etendue and improve the efficiency. In addition, regarding the design contents in each of the above-mentioned steps (1) to (4), these and the other various design contents in the illumination optical system 4 influence each other in terms of parameters. It may fit. Therefore, it is necessary to optimize overall while maintaining consistency, but the design content of the condenser lens of (4) in the present embodiment can be considered independently of the design content of other items. ..

<Design conditions around the condenser lens>
In the present embodiment, in order to improve the utilization efficiency of the light from the light source, the condenser lens 46 is designed so that the light flux emitted from the integrator 45 in the preceding stage is condensed on the surface corresponding to the DMD panel 48 with a small aberration. It specifies the conditions for performing.

One of the major factors that determine the light utilization efficiency is how much adjustment margin is secured around the DMD panel 48. For example, if a margin of 10% is secured for the length, the efficiency of actually irradiating the DMD panel 48 is (1.1) ² =1.21, which is a decrease in efficiency of about 20%. In addition to this, when the aberration is large, the boundary area of illumination may be blurred.

  FIG. 8 is a diagram showing an example of light intensity distribution on the display surface of the image display element. For example, as shown in the example of FIG. 6 described above, the optical image (illumination area) of each cell 45a of the lens array in the integrator 45 is superimposed on the DMD panel 48 by the condenser lens 46 (and the prism 47). However, if the precision of the superimposition is deteriorated, the boundary of the illumination area irradiated to the image display element (DMD panel 48) becomes blurred as shown in the example of FIG.

  In the upper diagram of FIG. 8, the ideal light intensity distribution with respect to the effective display width of the image display element (for example, the width of the display surface 48a of the DMD panel 48 shown in the lower diagram) is shown by a solid line. Although the example of FIG. 8 shows the width direction of the image display element (DMD panel 48), the same applies to the height direction. With an ideal light intensity distribution, the light intensity is uniform up to a region slightly outside the effective display width of the display element, while the light intensity is substantially zero outside the region. That is, the distribution has a steep slope at the boundary of the illumination region.

  On the other hand, if the distribution of the light intensity at the boundary of the illumination area is blurred and the inclination is not steep, the light intensity near the end of the effective display width of the display element decreases, and the area outside the effective display width is reduced. The amount of wasted light that is emitted (not incident on the image display element) increases, and the light utilization efficiency decreases. Then, in order to avoid this and obtain a uniform light intensity distribution within the effective display width of the image display element, an adjustment margin amount is further secured, and a region where the light intensity distribution is blurred (sloping) is effective. It is necessary to set it outside the display width, which leads to a further decrease in efficiency.

  Therefore, in the present embodiment, it is designed to suppress the occurrence of aberrations in the condenser lens 46 and prevent the light intensity distribution from being blurred near the boundary of the irradiation region.

The basic conditions for designing are as shown in FIG.
-Condition 1: Between the integrator 45 and the DMD panel 48,
The condenser lens 46 and the prism 47 are arranged in this order.

  Condition 2: At least two prisms 47 are provided.

-Condition 3: The principal ray of the illumination luminous flux is DMD with respect to the DMD panel 48.
The light is incident at an angle with respect to the normal line of the panel 48 (see FIG. 7).

(The conditions are based on the specifications of the DMD panel 48)
Condition 4: One (at least) one surface of the prism 47 is a mirror surface.

(Refraction is totally reflected depending on the angle of incidence of the light beam on the prism 47.
Only if the condition is not satisfied, the condition should be met.)
Is.

  Although it is possible to configure the prism 47 to have a single structure under the condition 2, in this case, the degree of freedom in design is low and the difficulty of aberration correction may be high. Therefore, in the present embodiment, at least two prisms 47 are provided. This makes it possible to improve the imaging characteristics of the illumination light flux by combining the decentering of the condenser lens 46 in the preceding stage and the specific shape of the prism 47. Specifically, as described later, it is effective to make the expanded prism shape into a wedge shape and combine it with the decentered condenser lens 46.

  In the present embodiment, the basic conditions of the above conditions 1 to 4 are satisfied, and the refraction of the light in the prism 47 is minimized by the minimum deviation angle (the deviation angle is defined as the incident light to the prism and the exit light as shown in FIG. It is designed to be closer to the angle formed by the incident light) to reduce aberrations and prevent efficiency deterioration.

  FIG. 10 is a diagram showing an example of the configuration of the virtual prism in which the prism 47 according to the present embodiment is expanded, the condenser lens 46, and the DMD panel 48. In addition, FIG. 11 is a diagram showing an example of a situation of a light beam passing through the condenser lens 46 and the virtual prism 47v. In FIG. 10, an equivalent wedge-shaped virtual prism 47v (developing prism) is obtained from the prism 47b of the two prisms (prisms 47a, 47b) that is developed (first development, second development). The state is shown.

When light passes through a wedge prism such as the virtual prism 47v and is refracted, the occurrence of aberration is minimized when the angles of incident light and outgoing light are equal. Therefore, as shown in FIG.
-Condition 5: The entrance surface of the prism (virtual prism 47v) is relative to the exit surface
It is inclined.

-Condition 6: The principal ray incident on the incident surface of the prism (virtual prism 47v) is
The light enters from the side opposite to the prism apex with respect to the normal to the incident surface.

-Condition 7: A principal ray emitted from the exit surface of the prism (virtual prism 47v)
Is emitted from the side opposite to the prism apex with respect to the normal of the emission surface.
To do.
By designing after satisfying the above conditions, it is possible to reduce the declination angle, reduce aberrations, and prevent efficiency deterioration.

In order to minimize the aberration when irradiating the projection lens system 52 of the projection optical system 5 in the subsequent stage from the DMD panel 48, as shown in FIG.
Condition 8: exit surface of prism (virtual prism 47v) and DMD panel 48
Should satisfy the condition that they are arranged substantially parallel to each other.

  As a premise of this condition, when the rear-stage prism 47b is developed, the state between the exit surface of the prism 47b and the projection lens system 52 of the rear-stage projection optical system 5 becomes the same as a plane-parallel plate. FIG. 12 is a diagram showing an example of the configurations of the expanded prism 47b, the condenser lens 46, and the DMD panel 48 in the present embodiment. Here, when the prism 47b in the latter stage is expanded as shown in the figure, the above-mentioned precondition is that the exit surface (P4-P5 surface) of the prism 47b and the surface (P5) of the expanded prism 47b that faces the projection lens system 52 (P5). '-P6' plane) becomes parallel, that is, the angle of P4 and the angle of P6 are equal.

In the present embodiment, further, as shown in FIG.
-Condition 9: The chief rays emitted from the condenser lens 46 are substantially parallel to each other.
is there.
By designing under the condition (1), it is possible to reduce the aberration by aligning the optical paths of the principal rays illuminating the DMD panel 48 and making them incident at the same angle.

As shown in FIG. 7, based on the specifications of the DMD panel 48, the light needs to be incident on the DMD panel 48 at an angle (condition 3). However, if the light is incident at an angle, aberrations (coma aberration, astigmatism, curvature of field, trapezoidal distortion, etc.) occur and the efficiency decreases. Therefore, in the present embodiment, as shown in FIG.
-Condition 10: The condenser lens 46 is the incident surface of the prism (virtual prism 47v).
It is placed by rotating (tilting) in the same direction as.

Condition 11: The condenser lens 46 is arranged off axis.
Design after satisfying each condition of. As a result, it is possible to reduce the aberration between the integrator 45 and the DMD panel 48 and prevent the efficiency from decreasing.

Further, in order to control many aberrations as described above, when designing the shape of the condenser lens 46, the degree of freedom in design may be insufficient only by decentering the spherical surface. Therefore, in the present embodiment,
Condition 12: The condenser lens 46 has an aspherical shape.
You may make it obey the conditions of. As a result, the degree of freedom in design for controlling the aberration can be further increased, and the aberration can be further reduced. In addition to or instead of making the condenser lens 46 aspherical, a configuration using a plurality of lenses may be used to increase the degree of freedom in design.

  As described above, according to the illumination optical system 4 of the present embodiment, in the condensing lens 46 (and the prism 47, the DMD panel 48), the above conditions 1 to 11 (even if the condition 12 is further added). By performing the design after satisfying (good), the loss of etendue can be reduced and the light utilization efficiency can be improved. That is, in the condenser lens 46, the light flux emitted from the integrator 45 in the previous stage can be condensed on the DMD panel 48 with a small aberration.

(Embodiment 2)
The illumination optical system according to the second embodiment of the present invention has the same configuration as the illumination optical system 4 of the projection type image display apparatus 1 according to the first embodiment described above, and includes the light source shown in FIG. Among the optical elements at the respective stages (1) to (4) up to, the collimator 43 of (2) is designed to reduce the loss of etendue and improve the light utilization efficiency. As in the case of the condenser lens 46 of the first embodiment described above, the design content of the collimator 43 of (2) in the present embodiment can be considered independently of the design content of other items. ..

<Collimator design conditions>
In the present embodiment, when the collimator 43 is designed to expand the luminous flux from the LED 42, which is the light source in the preceding stage, to a predetermined diameter without loss of Ettenue, and to make it enter the integrator 45, which is the equalizing means in the latter stage. Stipulates the conditions of. In other words, the collimator 43 forms a luminous flux in the uniform and effective NA range over the entire surface of the illumination target in order to obtain maximum efficiency in the target surface of the illumination (eg, the integrator 45 closer to the light source). The conditions for designing are specified.

  FIG. 13 is a diagram schematically showing an example of a logical configuration of the collimator 43 of the illumination optical system 4 and an example of the state of light rays according to the second embodiment of the present invention. In the example of FIG. 13A, with respect to the principal ray emitted from the LED 42 of the light source, a collimator 43 (in the figure, a luminous flux near the optical axis, a peripheral luminous flux (outer luminous flux), and an intermediate luminous flux between them are respectively generated. A situation is shown in which the light passes through the first collimator 43a in the front stage, the second collimator 43b in the rear stage) and the dichroic mirror 44. Further, in the example of FIG. 13B, the light collection states of the light flux near the optical axis, the peripheral light flux, and the intermediate light flux are shown.

In the present embodiment, in order to improve the efficiency by effectively using the luminous flux (peripheral luminous flux) emitted from the LED 42 which is the light source at a large angle with respect to the optical axis, as shown in FIG.
-Condition 21: The image height of the chief ray on the target surface of the illumination has the fsinθ characteristic.
Have.
The collimator 43 is designed after satisfying the above condition. In this way, by taking the projection characteristic that the image height of the chief ray is compressed near the periphery of the target surface of the illumination, it is possible to capture even a light flux having an angle of about 90° from the optical axis. The image height is not limited to fsin θ, and the same effect can be obtained by designing the image with large negative distortion.

Here, even if a light beam with a large angle is captured by satisfying the above-mentioned condition 21, the peripheral light beam may cause a loss due to the spread of NA. Therefore, in the present embodiment, in order to reduce this loss, as shown in FIG.
Condition 22: The field curvature on the meridional surface is in the positive direction.
The collimator 43 is designed after satisfying the condition of. As a result, the outer light flux has a longer distance (focal length) to the converging point, so that the NA of the peripheral light flux can be reduced. Therefore, it is possible to reduce the loss when the light enters the integrator 45 in the subsequent stage.

In addition to the above condition 22, in order to further reduce the loss in the peripheral light flux, as shown in FIG.
-Condition 23: The chief ray angle of the peripheral light flux is converged in the optical axis direction.
The collimator 43 is designed after satisfying the above condition. Since the NA of the peripheral light flux is reduced by satisfying the above condition 22, the loss is small even if the angle of the chief ray of the peripheral light flux is controlled. Therefore, such a design can be performed.

Further, in the present embodiment, in relation to the above condition 22, as shown in FIG.
-Condition 24: NA of the light flux on the optical axis (near) is larger than that of the surrounding area.
(Short focal length).
The collimator 43 is designed after satisfying the above condition.

  From the basic idea of etendue, it is desirable to control the luminous flux emitted from the collimator 43 so that the luminous flux has the same NA from the optical axis to the periphery. However, when configured in this way, a loss may occur in the peripheral light flux, as described above. Therefore, as in the present embodiment, the NA of the light flux near the optical axis is intentionally increased, while the NA of the peripheral light flux is decreased and the positive field curvature is provided, thereby reducing loss and improving efficiency. It is possible to achieve both. Note that a part of the light flux having a large NA near the optical axis also has a role of complementing the small NA of the peripheral light flux.

  As described above, the conditions 21 to 24 are related to each other, and by comprehensively applying these conditions, the illumination having the NA in the uniform and effective range over the entire target surface of the illumination is obtained. It is possible to design the collimator 43 that obtains the luminous flux.

  Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. Needless to say. For example, the above embodiments have been described in detail for the purpose of explaining the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the configurations described. Further, part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. .. Further, it is possible to add/delete/replace other configurations with respect to a part of the configurations of the respective embodiments.

  INDUSTRIAL APPLICABILITY The present invention can be used for an illumination optical system that improves the efficiency of use of light from a light source and a projection-type image display device using the same.

DESCRIPTION OF SYMBOLS 1... Projection-type image display apparatus, 2... Casing, 3... Mirror cover, 4... Illumination optical system, 5... Projection optical system, 6... Focus adjustment ring, 7... Power supply unit,
31... Reflective mirror,
41... LED lighting unit, 42, 42R, 42G, 42B... LED, 43, 43R, 43G, 43B... Collimator, 43a... 1st collimator, 43b... 2nd collimator, 44... Dichroic mirror, 45... Integrator, 45a... Cell , 46... Condensing lens, 47, 47a, 47b... Prism, 47v... Virtual prism, 48... DMD panel, 48a... Display surface,
51... TIR prism, 52... Projection lens system, 53... Projection lens base, 54... Lens adjustment mechanism,
81... Axial fan, 82... Sirocco fan, 83R, 83G, 83B... Heat pipe, 84... Heat sink

Claims (7)

An illumination optical system that illuminates an illumination light flux at a constant angle with respect to a normal line of an illumination surface of an illuminated object through a prism,
A light source having perfect diffusivity,
A collimator that takes in the illumination light flux from the light source and converts it into a small NA while having a predetermined diameter,
An integrator for uniformizing the brightness of the illumination light flux that has passed through the collimator,
A condenser lens that condenses the illumination light flux,
Between the integrator and the object to be illuminated, the condenser lens and the prism are arranged so that the illumination light flux passes in this order,
The condensing lens and the prism are configured such that the chief ray of the illumination light flux is incident on the irradiation surface of the illuminated body at a predetermined angle with respect to the normal line of the irradiation surface of the illuminated body,
In the prism, an incident surface of the illumination light beam is inclined with respect to an exit surface, and a chief ray incident on the incident surface enters from a side opposite to a vertex of the prism with respect to a normal line of the incident surface, The principal ray emitted from the emission surface is configured to be emitted from the side opposite to the vertex of the prism with respect to the normal line of the emission surface, and the emission surface of the prism is substantially parallel to the irradiation surface of the illuminated body. Is arranged as
The condenser lens, the respective principal rays after being emitted from the condensing lens is configured so as to be substantially parallel to each other, rotating in the same direction as the incident surface of the prism, disposed shifted further axial Rutotomoni An illumination optical system in which an emission side optical axis direction of the integrator and an emission side optical axis direction of the prism are the same . The illumination optical system according to claim 1,
An illumination optical system including a plurality of the prisms. The illumination optical system according to claim 1 or 2,
An illumination optical system in which at least one surface of the prism is a mirror surface. The illumination optical system according to claim 1,
The illumination optical system, wherein the condenser lens has an aspherical shape. The illumination optical system according to claim 1 ,
The collimator has a negative distortion aberration when the projection characteristic of the image height of the chief ray on the target surface of the integrator that is irradiated by the passing illumination light flux has a negative curvature of field, and the light flux in the peripheral region. The illumination optical system is configured such that the angle of the principal ray is condensed in the optical axis direction and the NA of the light beam near the optical axis is larger than the NA of the light beam in the peripheral region. The illumination optical system according to claim 5,
An illumination optical system in which the projection characteristic of the collimator is an fsin θ characteristic.   A projection-type image display device, comprising the illumination optical system according to claim 1.