JP2018004846A - Illumination optical system and image projection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an illumination optical system in which the position of an optical element is adjusted and the position of an illumination light range relative to an image display element is adjusted, with which it is possible to lower adjustment sensitivity than by a conventional adjustment method and further reduce the margin of an illumination light range, and to maintain high illumination efficiency.SOLUTION: Provided is an illumination optical system characterized by a light source and modulation means for applying modulation that corresponds to an image signal to a beam emitted from the light source. On an optical path between the light source and the modulation means there are arranged a first lens array equipped with a plurality of lenses for dividing the beam emitted from the light source into a plurality of beams and a second lens array equipped with a plurality of lenses for condensing the plurality of divided beams, There is a translucent plate between the first and second lens arrays, the plate's angle of attachment to an incident optical axis being adjustable.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an illumination optical system and an image projection apparatus using the illumination optical system.

  An illumination optical system is used to uniformly and efficiently illuminate an image display element such as a liquid crystal light valve. FIG. 3 shows a general configuration of the illumination optical system.

  The light beam emitted from the light source 12 is condensed by a parabolic reflector 13 as a condensing device and emitted as substantially parallel light. An ultra-high pressure mercury lamp or a xenon lamp is used as the light source. The parallel light beam emitted from the paraboloid reflector is divided and collected by the first fly-eye lens 14, and each divided light beam is collected near the second fly-eye lens 15. Here, the minute lens cell constituting the first fly-eye lens 14 has a rectangular shape that is similar to the image display element that is the illuminated surface. The plurality of split light beams emitted from the second fly-eye lens are aligned with polarized light in a predetermined direction by the polarization conversion element 16.

  The light beam emitted from the polarization conversion element is condensed by the condenser lens 17 and superimposed on the image display element 19 to form a rectangular and uniform illuminance distribution 18 corresponding to the display area of the image display element. Illuminate the element. Here, a liquid crystal light valve is assumed as the image display element, but a DMD (digital micromirror device) or the like may be used.

  Here, in the illumination optical system as shown in FIG. 3, due to the positioning accuracy of the first and second fly-eye lenses, the eccentricity error of each lens cell, the positioning of the condenser lens, the eccentricity error, the curvature error, etc. There is a possibility that the illumination light may be displaced with respect to the image display area of the image display element, or the illumination range may be reduced, and the display area may not be illuminated uniformly. Then, the bad effect which a shadow produces in the peripheral part of a projection image generate | occur | produces.

  Therefore, in general, the range of illumination light formed on the image display element (hereinafter referred to as the illumination area) is a certain margin larger than the image display area in consideration of the positioning accuracy of each element and the tolerance setting of parts. (M in the figure) is secured.

  On the other hand, in order to make the projected image brighter, it is necessary to increase the light utilization efficiency on the image display element. However, if the margin is taken as described above, the light utilization efficiency is lowered and the projection image becomes dark. There was a problem.

  Therefore, a position adjustment mechanism is provided in the optical element of the illumination optical system to absorb the position movement of the illumination area relative to the image display element due to the positioning accuracy of the optical element, and to realize a bright projection image by reducing the margin of the illumination area. A method has been devised.

  In Patent Document 1, the position of the illumination area with respect to the image display element is adjusted by making it possible to adjust the attachment position of the first or second fly-eye lens in the direction orthogonal to the optical axis direction, thereby adjusting the margin of the illumination area. To achieve a bright projected image.

  In Patent Document 2, by adjusting the mounting position of the condenser lens in the direction orthogonal to the optical axis direction, the position of the illumination area with respect to the image display element is similarly adjusted, thereby reducing the margin of the illumination area, A bright projected image is achieved.

Japanese Patent No. 3791130 Japanese Patent No. 3473335

  However, when the position of the illumination light is adjusted with respect to the display area of the image display element, it is necessary to allow a certain amount of displacement of the illumination light due to the effects of adjustment errors, vibration, and heat.

  For example, in Patent Document 1, the mounting position adjustment for the direction orthogonal to the optical axis direction of the first or second fly-eye lens is realized by a rotation adjustment mechanism using a screw, but a desired adjustment is performed when the screw is tightened and fixed. There is a possibility of shifting from the position. In addition, after adjusting the position of the fly's eye lens in the direction perpendicular to the optical axis direction, a method such as fixing directly with an adhesive is also conceivable, but there is a concern that the adhesive may be displaced after adjustment due to softening due to heat. The In addition, there is a possibility that a position shift occurs due to deformation of the adjustment member due to vibration or heat.

  The influence of the shift after adjustment becomes more prominent as the ratio of the movement amount of the illumination area to the movement amount of the optical element to be adjusted, that is, the movement sensitivity increases. As the movement sensitivity of the illumination light area of the element for adjusting the mounting position is higher, it is necessary to secure a margin of the illumination area in view of such an error, and there is a problem that the projected image becomes dark.

  Therefore, the present invention has been made in view of such problems, and in an illumination optical system that adjusts the position of the optical element and adjusts the position of the illumination light range with respect to the image display element, it is more sensitive than the conventional adjustment method. An object of the present invention is to provide an illumination optical system capable of maintaining high illumination efficiency by reducing the degree of illumination and reducing the margin of the illumination light range, and an image projection apparatus using the illumination optical system.

In order to achieve the above object, an illumination optical system according to the present invention includes:
A light source, a modulating unit that modulates a light beam emitted from the light source in accordance with an image signal, and a light beam emitted from the light source on a light path between the light source and the modulating unit. A first lens array having a plurality of lenses to be divided into a plurality of lenses and a second lens array having a plurality of lenses for condensing the plurality of divided light beams, and the first lens array and the second lens array It has a light-transmitting flat plate in between, and the flat plate is characterized in that the mounting angle with respect to the incident optical axis can be adjusted.

  According to the present invention, in the illumination optical system that adjusts the position of the optical element and adjusts the position of the illumination light range with respect to the image display element, the adjustment sensitivity is lower than that of the conventional adjustment method, and the margin of the illumination light range is increased. It is possible to provide an illumination optical system that can be made smaller and maintain high illumination efficiency, and an image projection apparatus using the illumination optical system.

First embodiment of the present invention Diagram showing a general illumination optical system Diagram showing conventional illumination optical system

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 shows a first embodiment of the present invention.

  The light beam generated from the ultra high pressure mercury lamp 1 is reflected by the parabolic reflector 2 and becomes substantially parallel light. The parallel light beam emitted from the paraboloid reflector 2 is divided and collected by the first fly-eye lens 3, and each divided light beam is collected near the second fly-eye lens 5. Here, 4 is a UV light absorption filter that absorbs ultraviolet light contained in the ultra-high pressure mercury lamp, and the mounting angle with respect to the optical axis can be adjusted. Specifically, the angle can be adjusted by pushing one end of the filter with an eccentric roller (the adjusting mechanism is not shown in the figure). The plurality of split light beams emitted from the second fly-eye lens are aligned with polarized light in a predetermined direction by the polarization conversion element 5.

  The light beam emitted from the polarization conversion element 6 is bent on the optical path by the total reflection mirror 7 and condensed on the liquid crystal light valve 9 while being condensed by the condenser lens 8. Here, the lens cell of the first fly-eye lens has a conjugate relationship with the image display area of the liquid crystal light valve, and the lens cell has a rectangular shape with an aspect of 16:10, while the display area of the liquid crystal light valve is also 16:10. Aspect. Since the illuminance distribution on each lens cell of the first fly-eye lens is superimposed on the liquid crystal light valve as a rectangular shape, the image display area of the liquid crystal light valve is illuminated with a rectangular and uniform illuminance distribution.

  In this embodiment, the pitch of the lens cells of the first fly-eye lens is 5 mm, and the size of the image display area of the liquid crystal light valve is 15 mm. Therefore, in this embodiment, the illuminance distribution on the lens cell of the first fly-eye lens is imaged on the liquid crystal light valve at a magnification of about 3 times.

  In the prior art described in Patent Document 1, the illumination area is moved by moving the first fly-eye lens or the second fly-eye lens in a direction perpendicular to the optical axis. When this technology is applied to the optical arrangement of the present embodiment, it is possible to absorb the displacement of the illumination area due to the positioning accuracy of the condenser lens and the mirror, so that the margin of the illumination area can be reduced, and the brightness of the projected image Can be improved. Here, the movement amount of the illumination range on the liquid crystal light valve with respect to the movement amount of the first and second fly-eye lenses is 3 mm / mm (illumination area movement amount / fly eye movement amount).

  Here, assuming that the deviation from the optimum position is 0.1 mm due to vibration and heat after position adjustment of the fly-eye lens, or screwing after adjustment, etc., an illumination area of 3 × 0.1 = 0.3 mm Deviations need to be anticipated. Therefore, there is a restriction on the amount of reducing the margin of the illumination area, and there is a restriction on improving the brightness of the projected image.

  In the prior art described in Patent Document 2, the illumination area is moved by moving the condenser lens in a direction perpendicular to the optical axis. When this technique is applied to the optical arrangement of this embodiment, the movement amount of the illumination range on the liquid crystal light valve with respect to the movement amount of the condenser lens is 1 mm / mm (illumination area movement amount / fly eye movement amount). Here, assuming that the displacement amount with respect to the optimum position is 0.1 mm due to vibration and heat after position adjustment of the condenser lens, or screwing after adjustment, etc., the illumination area displacement of 1 × 0.1 = 0.1 mm. It is necessary to anticipate. Therefore, the amount of reducing the margin of the illumination area is similarly limited.

  On the other hand, in this embodiment, the UV-absorbing glass 4 is provided with a first fly-eye lens and a second fly-eye lens, and the mounting angle can be adjusted.

  FIG. 2 shows an example of a mechanism for adjusting the mounting angle. One end of the UV-absorbing glass 4 is abutted against the wall of the case where the optical element is disposed, and is suppressed by a leaf spring 10 from the rear. The other end is pressed against the front eccentric roller 11 while being held back by a leaf spring. Here, by rotating the eccentric roller as shown in (b) and (c), the other end is pushed down (pushed up), and the attachment angle of the UV absorbing glass changes. Thereby, it can adjust to arbitrary angles. Also, the adjustment stroke can be arbitrarily set by adjusting the shape of the eccentric roller.

  When the glass flat plate is tilted between the first fly-eye lens and the second fly-eye lens, a relative optical axis shift between the first fly-eye lens and the second fly-eye lens occurs due to the light refraction action. For example, when a glass plate having a refractive index n and a thickness tmm is inclined by θ, the relative movement δ of the optical axis of the first and second fly's eye lenses is expressed by the following equation.

As a result, the same action as in the case of moving the fly-eye lens in the direction perpendicular to the optical axis in Patent Document 1 occurs, and movement of the illumination area occurs. In this embodiment, it is possible to move and adjust the illumination area to an arbitrary position by adjusting the mounting angle of the UV absorbing glass, and to absorb the positional deviation of the illumination area due to the positioning tolerance of the optical element. The margin to be secured can be reduced and a bright projected image can be realized.

  Here, the refractive index of the UV absorbing glass in this example is 1.5, the thickness is 2 mm, and the length is 25 mm. When one end of the UV absorbing glass is fixed and the other end is moved by 1 mm and the angle is adjusted, the amount of movement of the illumination area on the liquid crystal light valve is 0.08 mm. The movement sensitivity can be reduced by 10 times or more. Therefore, if a deviation from the optimal position of 0.1 mm occurs during adjustment or after adjustment, an illumination area deviation of 0.08 × 0.1 = 0.008 mm will occur, which is extraneous to the prior art. The margin to be secured can be reduced by 10 times or more. Thereby, the margin of the illumination area can be further reduced, and a brighter projected image can be realized.

  In the present invention, by using an element for removing UV light arranged between the first fly-eye lens and the second fly-eye lens, the position of the illumination area can be adjusted without requiring an additional optical element. Realized. In general, UV light generated from an ultra-high pressure mercury lamp affects the durability of an adhesive used for a liquid crystal light valve, a polarization conversion element, and prisms, and therefore must be removed before the optical stage. Therefore, in the present invention, since an indispensable element disposed in the projector is used, the problem of reducing the margin of the illumination area while avoiding the loss of brightness and the increase in the number of parts due to the addition of the optical element is solved. be able to. Further, the position of the illumination area may be adjusted by tilting a UV cut filter obtained by depositing a UV reflection film made of a dielectric multilayer film on a general glass such as BK7, instead of UV absorbing glass. .

  The second advantage of the present invention is that the sensitivity of the illumination area adjustment can be adjusted by the thickness and refractive index of the translucent flat plate disposed between the first and second fly-eye lenses. In general, in the design of an illumination optical system in the prior art, the focal length of a fly-eye lens or a condenser lens is uniquely determined when the size of the image display element to be used, the F value of the optical system, and the number of divisions of the fly-eye lens are determined. At this time, since the sensitivity of the illumination area adjustment is also determined by the focal length of the fly-eye lens or condenser lens, it is difficult to adjust the adjustment sensitivity to a desired value. On the other hand, in this invention, arbitrary adjustment sensitivity can be implement | achieved by adjusting the thickness, refractive index, and length of the translucent flat plate arrange | positioned between the 1st, 2nd fly eye lenses.

When the refractive index of the translucent flat plate is n, the thickness is t, the length is L, the pitch of the lens cell of the first fly's eye lens is d ₁ , and one side of the rectangle of the corresponding image display element is d ₂ The amount of movement Δ of the illumination area is expressed below using equation (1).

From the formula (2), the sensitivity can be adjusted by adjusting the refractive index, thickness, and length of the translucent flat plate. Here, assuming that the area adjustment sensitivity when the position is adjusted in a direction perpendicular to the optical axis of the condenser lens is 1 mm / mm, the present invention reduces the sensitivity more than the illumination area adjustment using the condenser lens. In order to reduce the margin to be secured in the area, it is desirable to satisfy at least the following expression.

Moreover, you may combine the illumination area adjustment by this invention with another adjustment element. For example, the mounting position of the first or second fly-eye lens is adjusted to absorb the displacement of the illumination area due to the positioning accuracy of other elements and optical eccentricity, while the glass plate is mounted between the fly-eye lenses according to the present invention. By adjusting the angle, it may be configured to finely adjust an illumination area shift caused by an adjustment error of the first or second fly-eye lens mounting position or a shift after the adjustment. The adjusting element to be combined may be a condenser lens, a reflecting mirror, or a dichroic mirror when combined with a color separation optical system.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

1.12 Discharge arc, 2.13 Parabolic reflector,
3.14 First fly-eye lens, 4 UV absorbing glass,
5.15 Second fly-eye lens, 6.16 Polarization conversion element, 7. Reflection mirror,
8.18 condenser lens, 9.19 liquid crystal image display element, 18 illumination area,
10 leaf spring, 11 eccentric roller

Claims (5)

A light source, a modulating unit that modulates a light beam emitted from the light source in accordance with an image signal, and a light beam emitted from the light source on a light path between the light source and the modulating unit. A first lens array having a plurality of lenses to be divided into a plurality of lenses and a second lens array having a plurality of lenses for condensing the plurality of divided light beams, and the first lens array and the second lens array An illumination optical system having a light-transmitting flat plate in between, and the flat plate being adjustable in mounting angle with respect to an incident optical axis. The thickness of the translucent flat plate is t, the length is L, the refractive index is n, the length of the long side of the lens cell of the first lens array is d ₁ , and the length of the long side of the corresponding pre-modulation means is the illumination optical system according to claim light 1 and satisfies the following condition when the d _2.
The illumination optical system according to claim 1, wherein the flat plate has a function of absorbing ultraviolet light. The illumination optical system according to claim 1, wherein the flat plate has a function of reflecting ultraviolet light. An image projection apparatus comprising the illumination optical system according to any one of claims 1 to 4 and a projection optical system.