JP2000019657A - Picture projecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the utilization efficiency of luminous flux from a light source, to illuminate a picture by absolute minimum lens constitution and to improve the quality of a projected picture by providing an optical element having an incident surface and an emitting surface, at least either of which has an aspherical surface. SOLUTION: A Fresnel groove having refractive power is formed on the incident surface of the optical element 3 in order to make luminous flux from a condenser lens 9 parallel beams, and it is formed as an aspherical Fresnel lens. The Fresnel groove having the refractive power is formed also on the light emitting surface of the element 3. The incident angle of the luminous flux from an illumination system 11 on the element 3 is set so that the emitted light from the lens 9 may be the parallel beams inside the Fresnel lens after removing its residual aberration, and the luminous flux becomes the parallel beams from which the aberration is removed. The Fresnel groove on the light emitting side of the element 3 has a focal distance that the light is condensed on the pupil position 5a of a projection lens 5. Then, the luminous flux excellent in light condensing property is obtained on the Fresnel surface on the emitting side and is mostly condensed on the pupil surface 5a of the lens 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image projection apparatus for projecting an image to be projected, such as a reflection type document surface or a transmission type document surface illuminated by a light beam from a light source such as a projector, and a liquid crystal panel onto a predetermined surface. Things.

[0002]

2. Description of the Related Art There have been proposed various image projection apparatuses for projecting an image to be projected on a screen surface or a document table surface.

FIG. 5 is a schematic view of a main part of an image projection apparatus such as a conventional liquid crystal projector for projecting a transmission type image. In the figure, as a lamp 41 arranged as a light source, an arc lamp type or filament type halogen lamp such as a metal halide lamp or xenon is usually used.

The light source 41 is set so that its light emitting point is located at the center of curvature of the reflecting mirror 42 or at the focal position.
The light beam emitted from the light source 41 is reflected by the reflection mirror 42 to become parallel light, and passes through the heat absorption filter 46 and the color correction filter 47 to become illumination light for a transmission type image 44 such as a liquid crystal. Incident on.

At this time, in order to make the light flux from the reflection mirror 42 more parallel, the lamp tube is arranged perpendicular to the reflection mirror 42 in the arc lamp type. This makes the light beam from the reflection mirror 42 a light beam with better parallelism.

Further, a filter for cutting off an infrared region unnecessary for image formation, such as a heat ray absorption filter or an infrared cut filter 46, a filter for cutting off heat due to far infrared rays, or a color correction for correcting a color balance of a lamp. In many cases, the filter 47 and the like form a filter by vapor deposition on the surface of the filter member.
47 is disposed near this parallel light where the incident angle is not as large as possible because of the wavelength dependence by the incident angle.

The condenser lens 43 has a function of condensing the light that has passed through the image 44 toward the pupil plane of the projection lens 45, thereby uniformly illuminating the entire image and providing a good projected image. Have gained.

On the other hand, a filament type halogen lamp or the like is usually arranged as a light source at a finite distance.

FIG. 6 is a schematic view of a main part of a conventional image projection apparatus. In the figure, of the light beams emitted from the lamp (light source) 51, the light beam in the direction opposite to the projected image 54 is reflected back to the light source 51 side by the reflection mirror 52.

The luminous flux emitted from the light source 51 is converted into substantially parallel light by condenser lenses 58 and 59, where it passes through an infrared cut or heat shielding filter 56 and a color correction filter 57, as described above. Incident on. The projected image 54 is illuminated with the light beam that has passed through the condenser lens 53.

The condenser lens 53 condenses the light beam from the light source 51 on the pupil plane of the projection lens 55. As a result, the projection image 54 is projected onto the predetermined surface by the projection lens 55 with uniform illuminance.

[0012]

The method of illuminating a projected image in the image projection apparatus shown in FIGS. 5 and 6 has the following problems.

In an apparatus using only a reflection mirror to convert a light beam from a light source into parallel light, the light emitting surface of the light source has a size that cannot be ignored even though it is almost a point light source. Therefore, even if it is referred to as parallel light, it is not a single exit angle, so when condensing the light source image on the pupil plane of the projection lens with a condenser lens, not all of the light beam can be taken into the pupil of the projection lens, The luminous flux could not be used effectively.

For this reason, for example, as an image projection apparatus using an arc lamp type, in Japanese Patent Application Laid-Open No. 6-160766, measures have been taken such as making the peripheral portion of the condenser lens aspherical to increase the light collection efficiency.

In the case of a filament type lamp, a condenser lens for condensing a light beam from a light source is made aspherical, so that the light beam can be condensed with a minimum lens configuration. Generally, an aspheric lens is generally effective for a narrow range of light emitting points on the optical axis. However, even with the use of an aspherical surface, it has been difficult for one or two condenser lenses to make a light beam emitted from a light-emitting surface of a certain size into good parallel light.

In particular, since the light beam emitted from the condenser lens is a light beam containing a large amount of residual aberration, the light beam emitted from the condenser lens arranged near the image plane does not entirely enter the pupil plane of the projection lens. The luminous flux utilization efficiency has been considerably reduced.

According to the present invention, when illuminating an image to be projected by using a light beam from a light source having a light emitting surface of a predetermined size, such as a filament type lamp, an appropriately configured optical element is arranged in an illumination optical path. Accordingly, it is an object of the present invention to provide an image projection apparatus capable of increasing the utilization efficiency of a light beam from a light source and illuminating an image with a minimum necessary lens configuration, thereby obtaining a projected image with good image quality.

[0018]

According to the present invention, there is provided an image projection apparatus comprising: (1-1) a light source means, an illumination system for condensing a light beam from the light source means, and illuminating an image to be projected; An image projection apparatus having a projection lens for projecting an image on a predetermined surface, an incident surface having a refractive power between the illumination system and the image to be projected, wherein the incident light beam is substantially a parallel light beam; An exit surface having a refracting power for converging a parallel light beam in a predetermined direction, and
An optical element having at least one surface having an aspherical surface is provided.

(1-2) An image having light source means, an illumination system for condensing a light beam from the light source means and illuminating an image to be projected, and a projection lens for projecting the image to be projected onto a predetermined surface In the projection device, an incident surface having a refractive power that converts the incident light beam into a substantially parallel light beam between the illumination system and the image to be projected, and a condensing action of the parallel light beam from the incident surface in the sagittal direction and the meridional direction. An optical element having different emission surfaces and at least one of the surfaces having an aspherical surface is provided.

In particular, in the constitution (1-1) or (1-2), (1-2-1) the refracting power of the exit surface of the optical element focuses a parallel light beam from the entrance surface on the pupil surface of the projection lens. Light value.

(1-2-2) The refractive power of the exit surface of the optical element is a value that converges on the pupil plane of the projection lens in one of the sagittal direction and the meridional direction of the parallel light beam from the incident surface. There is.

(1-2-3) The entrance surface of the optical element is formed of a concentric Fresnel lens.

(1-2-4) The emission surface of the optical element is characterized by being formed of a concentric or one-dimensional Fresnel lens.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory diagram of a basic configuration of a first embodiment of an image projection apparatus according to the present invention.

In FIG. 1, a reflecting mirror 2 is installed behind a light source (lamp) 1 for returning a light beam emitted in a direction opposite to the illumination system toward the illumination system, and the light reflected by the reflection mirror 2 is directed to the light source 1 side. I'm going back.

Reference numerals 8 and 9 denote aspherical condenser lenses which collect the light beam from the light source 1. A heat ray absorption filter 6 and a color correction filter 7 are arranged near the condenser lenses 8 and 9.

The light source 1 is positioned at the focal position of the condenser lens 8 so that the condenser lenses 8 and 9 become substantially parallel light.
Are arranged so that the filaments (light-emitting surfaces) of the two coincide.

Each element 8, 9, 6, 7 constitutes one element of the illumination system 11. An optical element 3 guides a light beam from the illumination system 11 to the projected image 4. The optical element 3 is composed of a Fresnel lens, and has Fresnel grooves on both sides.

Reference numeral 5 denotes a projection lens, which is condensed by the optical element 3 and is projected onto a predetermined surface using transmitted light from the illuminated image surface 4. The light emitting point of the light source 1 is focused on the pupil of the projection lens 5. The focus position of the image on the image plane 4 is adjusted so that the image is projected by the projection lens 5 at a predetermined magnification.

Here, the optical element 3 is provided with a Fresnel groove having a refractive power on the incident surface so as to make the light beam from the condenser lens 9 into parallel light, and this Fresnel groove is formed as an aspherical Fresnel lens. Fresnel grooves having refractive power are also formed on the light exit surface of the optical element 3.

The angle of incidence of the light beam from the illumination system 11 on the optical element 3 is set so that the light emitted from the condenser lens 9 has its residual aberration removed and becomes parallel light inside the Fresnel lens. .

The light beam inside the Fresnel lens is a parallel light from which aberration has been removed. The Fresnel groove on the light emission side of the optical element 3 has a focal length at which light is focused on the pupil position 5a of the projection lens 5. On the exit side Fresnel surface, a light beam with good light collecting property is obtained, and almost all of the light beam is a pupil surface 5a of the projection lens 5.
Focus on

In the present embodiment, by configuring each element in this manner, the efficiency of illumination is significantly improved.
In particular, the amount of light in the peripheral portion is increased to improve the sharpness of image quality.

Further, by making the incident side of the optical element 3 an aspherical Fresnel lens, a light beam thereafter can be easily used.

As the optical element 3, if the state of the light beam on the light source 1 side is poor and further correction is required, it is preferable that the surface on the output side following the incident side is also an aspherical Fresnel lens.

FIG. 2 is a second embodiment of the image projection apparatus according to the present invention.
FIG. FIG. 2 shows a configuration in a case where a projector function is used in a copying machine or the like.

In a copying machine, a reflection original is normally illuminated with a light beam from an illumination system, and image information on the original is projected and formed on a drum surface for forming a toner image or a CCD surface by a reading lens. Then, image information on the document surface is read using the drum surface or the CCD. FIG. 2 shows the platen 41
While scanning the image information projected on the
An example is shown in which a reduced image is formed and read on a CD surface.

FIGS. 3A and 3B are explanatory views in which the optical paths at that time are developed, and are explanatory views in planes orthogonal to each other.

In FIG. 3, light emitted from the lamp 31 is reflected by a condenser lens 38, a heat ray absorbing filter 36,
The light is condensed (relayed) by the condenser lens 39 and the color filter 37, and irradiates the transmission original 45. Then, image information on the original 45 is projected onto the surface of the original table 41 by the projection lens 44 via the optical element 33 composed of a double-sided Fresnel surface. The light beam incident on the optical element 33 is converted into parallel light by the Fresnel surface of the incident surface.

In this case, the entrance surface of the optical element 33 is constituted by a concentric Fresnel surface, and the exit surface is constituted by a concentric Fresnel lens or a linear Fresnel lens having different powers on a sagittal surface and a meridional surface.

That is, in the sagittal plane, as shown in FIG. 3A, the power of the sagittal plane among the exit planes is set to 0 so that all the emitted light beams become parallel light. As a result, of the incident light that has entered the optical element 33, light in the sagittal plane is emitted from the Fresnel lens while being parallel light in the Fresnel lens.

The luminous flux in the meridional plane is shown in FIG.
The imaging lens 3 arranged on the exit side as shown in FIG.
The focal length is set so that light is converged on the pupil plane 35a of No. 5.

The significance of this setting is as follows.

When copying a transparent original by a so-called digital copying machine or the like using a line sensor such as a CCD element, a light beam from the light source 31 is irradiated onto the transparent original 45 shown in FIG. The pupil of the projection lens 44 is disposed at the center. The image of the transparent original 45 is projected and formed at a predetermined magnification on the original table 41 by the projection lens 44.

The light beam emitted from the lamp 31 is condensed (relayed) by the condenser lenses 38 and 39, and the optical element 3
In 3, the power is set on the Fresnel surface so as to converge on the pupil surface of the imaging lens 35 in the sagittal plane into parallel light and on the meridional plane on the pupil plane.

When the long first mirror 42 inside the copier scans the document surface, two second mirrors 43 start scanning at half the speed, and the document table 41 and the line are started. An image projected on the surface of the document 41 by the imaging lens 35 is formed on the surface of the line sensor 40 as needed while maintaining the image forming relationship on the surface of the sensor 40. Then, an output signal obtained from the line sensor 40 is subjected to electrical image processing.

In such a use method, the light beam relayed by the condenser lenses 38 and 39 on the light source 1 side becomes a light beam containing aberration in the relaying process, and this light beam is converted by a normal spherical lens. Even if the light is collimated, the emitted light does not become excellently parallel, and is emitted including convergent light or divergent light.

Such a light beam is supplied to the imaging lens 35 as it is.
When the light enters the lens, the emitted light has the same effect as the image formation of the angled light beam, and the light beam that has passed through the imaging lens 35 is not focused on the axis.

For this reason, although the image 34 is formed on the axis of the image forming lens 35 as an image forming relation, most of the luminous flux of the illuminating light is incident on a place away from the image forming point. However, the substantially formed image becomes an image with a low light amount on the line sensor 40.

For this reason, in the present invention, the incident surface of the optical element 33 is an aspherical Fresnel lens surface, and both the axial light and the peripheral light are incident on the original 41 as substantially parallel light.

With this effect, the light beam that has passed through the inside of the optical element 33 in parallel with the optical axis is effectively condensed on the linear Fresnel surface on the exit side, and the emitted light is converged on the pupil plane of the imaging lens 35 ahead. Are focused on an axis to increase the amount of light of the image, thereby forming a bright image.

FIG. 4 is a sectional view of a main part of a third embodiment of the present invention. In the present embodiment, the image projection apparatus is made more compact than the first embodiment shown in FIG.

In order to make the entire optical system compact, if the focal lengths of the condenser lenses 73 and 74 are set short, the total length of the lenses can be shortened. However, in this case, since the lens is close to the light source 1, there is a concern that the heat from the light source 1 may affect the lens, expand, and sometimes break.

On the other hand, if the focal length is set to be long while the aperture is small, the luminous flux from the light source cannot be completely picked up as a matter of course, resulting in an inefficient illumination system.

Therefore, in the present embodiment, the optical element 77 is formed so that the light emitted from the condenser lens 74 becomes convergent light, thereby forming a compact projector using all the light beams from the light source 1. are doing.

In FIG. 4, a light beam emitted from a light source 71 is supplied to a condenser lens 73, a heat ray absorbing filter 75,
The light is incident on the optical element 77 as a condensed light beam via a condenser lens 74 and a color correction filter 76.

The heat shielding filter 75 and the color filter 76 are arranged near the condenser lenses 73 and 74 as in the first embodiment.

Here, the light beam from the illumination system 11 is
7 is condensed and incident. The entrance surface of the optical element 77 is provided with a concentric Fresnel surface as an aspherical concave lens, and the light beam passing through the Fresnel surface is set to be a parallel light beam.

On the Fresnel lens surface on the exit surface side of the optical element 77, the focal length is set so that the light beam is directed (condensed) to the pupil surface of the projection lens 79.

As described above, in the present embodiment, a compact projector can be constructed by effectively using the light beam from the light source 1 and by separating the condenser lenses 73 and 74 from the light source 1.

[0061]

As described above, according to the present invention, when a projection image is illuminated by using a light beam from a light source having a light emitting surface of a predetermined size, such as a filament type lamp, an optical system appropriately configured. By placing the element in the illumination light path,
An image projection apparatus that can obtain a projected image with high image quality is achieved by illuminating an image with a minimum necessary lens configuration by increasing the use efficiency of a light beam from a light source.

In particular, according to the image projection apparatus of the present invention, it is possible to efficiently illuminate the original surface by using the optical element using the aspherical Fresnel surface, and to effectively use the illumination light. Thus, an image projection apparatus with improved image quality can be constructed.

[Brief description of the drawings]

FIG. 1 is a schematic view of a main part of an image projection apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram of a main part of an image projection device according to a second embodiment of the present invention.

FIG. 3 is an explanatory diagram of an optical path when the optical path of FIG. 2 is developed.

FIG. 4 is a schematic diagram of a main part of a third embodiment of the image projection apparatus of the present invention.

FIG. 5 is an explanatory view showing an example of a conventional arc lamp type image projection apparatus.

FIG. 6 is an explanatory diagram showing an example of a conventional filament-type image projection device.

[Explanation of symbols]

 1. Lamp 2. Reflecting mirror 3, 33, 77. Optical element 4. Transparent manuscript 5,44. Projection lens 6,36,75. Heat ray absorption filter 7, 37, 76. Color correction filters 8, 9, 38, 39, 73, 74. Condenser lens 35. Imaging lens 11. Lighting system

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H087 KA06 LA24 PA02 PA17 PB02 RA01 RA43 RA47 UA01 2H088 EA13 HA21 HA24 HA27 HA28 MA06 MA20 2H091 FA01Z FA14Z FA26X FA26Z FA27X FA41Z LA11 LA16 MA07 2H108 AA01 CA07 CB01

Claims (6)

[Claims] An image projection apparatus comprising: a light source unit; an illumination system that collects a light beam from the light source unit and illuminates an image to be projected; and a projection lens that projects the image to be projected onto a predetermined surface. An illumination surface between the illumination system and the image to be projected having a refractive power for converting the incident light beam into a substantially parallel light beam, and an exit surface having a refractive power for condensing the parallel light beam from the incident surface in a predetermined direction; And
And an optical element having at least one surface having an aspherical function. 2. An image projection apparatus comprising: a light source unit; an illumination system that collects a light beam from the light source unit and illuminates an image to be projected; and a projection lens that projects the image to be projected onto a predetermined surface. An incident surface between the illumination system and the image to be projected, the refracting power of the incident light being substantially parallel, and an exit surface having different light condensing functions in the sagittal direction and the meridional direction from the incident surface. And an optical element having at least one of the surfaces having an aspherical function. 3. The image projection apparatus according to claim 1, wherein the refractive power of the exit surface of the optical element is a value that focuses a parallel light beam from an incident surface on a pupil plane of the projection lens. 4. The optical system according to claim 1, wherein the refractive power of the exit surface of the optical element is a value condensed on the pupil plane of the projection lens in one of the sagittal direction and the meridional direction of the parallel light beam from the incident surface. 3. The image projection device according to claim 2, wherein 5. The optical element according to claim 1, wherein the incident surface of the optical element is formed of a concentric Fresnel lens.
2, 3 or 4 image projection devices. 6. An emission surface of the optical element has a concentric shape or 1
6. The image projection device according to claim 5, comprising a two-dimensional Fresnel lens.