JP2008089927A - Image projecting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve such a problem that a projection lens used in the image projecting device is needed to project a projection image upward at a large projection field angle from a desktop, this necessity makes it necessary to enlarge the shape of the front lens positioned at the foremost stage, with the result that the weight of the front lens using a glass material and accordingly the weight of the image projecting device are increased, this makes it inconvenient to carry the image projecting device. <P>SOLUTION: The image projecting device is provided for projecting an image with a projection lens, which is equipped with a front lens made of a plastic material. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image projection apparatus that displays an enlarged image or a still image displayed by an electro-optic element on a screen, and in particular, among a plurality of lenses constituting a projection lens, the foremost lens is made of plastic. The present invention relates to a configured image projection apparatus.

  2. Description of the Related Art In recent years, image projection apparatuses incorporating an electro-optic element such as a liquid crystal display element or a DMD (digital micromirror device) display element have become widespread. This type of image projection apparatus is easy to carry, is installed on a desk or the like, and is used by projecting image light onto a projection screen obliquely upward that is higher than the height of the desk. For this reason, the optical axis of the projection lens for projecting the image does not match the central portion of the projection screen.

  FIG. 11 is an external view of a conventionally known image projection apparatus 100 of this type. The image projection apparatus 100 includes a casing 101, an operation panel 103, a projection lens 102, a lens group 104 installed in the projection lens 102, and the like. Housed in the housing 101 are a light source unit, an electro-optical element including a liquid crystal display element, a drive circuit for driving the electro-optical element, a power source, a projection lens 102, and the like. The image projection apparatus 100 is usually installed on a desk and projects image light in an obliquely upward direction.

  FIG. 12 is a schematic cross-sectional view showing an example of a lens group constituting the projection lens 110. The first lens group 111 includes a first lens group 111 and a second lens group 112. The first lens group 111 is a focusing lens, and the second lens group 112 is a compensator lens, a relay lens, or the like. The first lens group is held by the front barrel 114 by holding members 120 and 121. In particular, in the first lens group 111, the foremost lens 116 (hereinafter referred to as the front lens) has the largest size and the heaviest weight. The second lens group 112 is housed in the rear barrel 115 and is held by holding members 122 and 123. Then, image light from the liquid crystal display element 125 enters from below the optical axis 124 of the second lens group 112 and exits obliquely upward from above the optical axis 124 of the first lens group 111. Therefore, only the upper half of the first lens group 111 from the optical axis is used.

Patent Document 1 describes that the camera barrel and the objective lens are integrally formed of transparent plastic, thereby reducing the number of assembly steps for assembling the optical member and the exterior member, and realizing an inexpensive camera. Yes.
JP-A-7-209714

  This type of image projection apparatus has a large angle of view. Therefore, it is necessary to make the diameter of the first lens group larger than that of the second lens group. In particular, in order to obtain a projection image with a large angle of view, the surface curvature of the front lens located at the foremost stage of the projection lens must be increased. When this is made of glass, a thick disc shape is used. It was necessary to perform polishing from the sheet glass. For this reason, it is difficult to process the glass and the cost is high, and since the material is glass, the weight of the projection lens is heavy and the entire apparatus is heavy, which is a disadvantageous factor for easy carrying.

  In the present invention, the following means have been taken in order to solve the above problems.

  In the present invention according to claim 1, in the image projection apparatus for projecting an image by the projection lens, the projection lens includes a front lens formed of a plastic material, and did.

  In the present invention according to claim 2, the projection lens includes a holding member that holds the front lens, and the front lens and the holding member are integrally formed of the plastic material. The image projection apparatus according to claim 1 is characterized.

  According to a third aspect of the present invention, in the image projection apparatus according to the second aspect, the holding member constitutes a part of a lens barrel of the projection lens.

  In this invention which concerns on Claim 4, the said projection lens is provided with the position adjustment member which adjusts the position of the said front lens, The said position adjustment member and the said front lens are integrally formed with the said plastic material. The image projection apparatus according to any one of claims 1 to 3, wherein the image projection apparatus is provided.

  In the present invention according to claim 5, the projection lens includes a fixing member for fixing the projection lens, and the fixing member and the front lens are integrally formed of the plastic material. The image projecting device according to claim 1 is provided.

  In this invention which concerns on Claim 6, the said front lens consists of a half-moon shape, It was set as the image projector of any one of Claims 1-5 characterized by the above-mentioned.

  In this invention which concerns on Claim 7, the said front lens consists of a rectangular shape, It was set as the image projector of any one of Claims 1-5 characterized by the above-mentioned.

  According to an eighth aspect of the present invention, in the image projection apparatus according to the first aspect, the front lens has a thread formed on an outer periphery thereof.

  According to a ninth aspect of the present invention, in the image projection apparatus according to the first aspect, the front lens has a position fixing groove or protrusion on an outer periphery.

  According to the image projection apparatus of the present invention, a lens obtained by molding a plastic material is used as the front lens constituting the projection lens. As a result, it is lighter than a front lens made of a glass material cut out from a thick disk-shaped glass plate and polished, and the weight of the image projection device can be reduced, so it is easy to carry. It has the advantage that an image projection apparatus can be obtained.

  Further, when the projection image is enlarged and projected upward from the optical axis of the projection lens, the front lens of the projection lens uses only the upper half with respect to the optical axis. Therefore, the lens does not need to have a circular shape, and an unnecessary area can be cut. Thus, there is an advantage that the projection lens can be reduced in size and weight.

  In the image projection apparatus according to the embodiment of the present invention, a plastic lens obtained by molding a plastic material is provided as the front lens in the foremost stage of the projection lens. The weight of the plastic material can be reduced to ½ or less compared to the lens glass. Therefore, there is an advantage that the weight of the entire image projection apparatus can be reduced and an apparatus that can be easily carried can be configured.

  As the plastic material, transparent polycarbonate resin (hereinafter referred to as PC), polymethyl methacrylate / acrylic resin (hereinafter referred to as PMMA), or the like can be used. These plastic materials have a specific gravity of 1/2 or less as compared with lens glass. This plastic material can be poured into a mold, or inserted into a mold and molded by pressing. In order to use it as a lens, the inner surface of the mold used for these is subjected to high-precision mirror finish.

  In addition, the projection lens includes a holding member that holds the front lens, a lens barrel, a position adjustment member, or a fixing member for fixing the projection lens to the casing, and any of these members or a plurality of members are the same. The plastic lens is molded integrally with the front lens. In addition, in order to prevent unnecessary reflected light, the surface of a member other than the front lens is coated with a black antireflection film. Thereby, the number of parts can be reduced, the manufacturing process can be simplified, and the cost can be reduced. Further, since the specific gravity of the plastic material is smaller than that of the glass material or the metal material, the weight of the entire apparatus can be reduced.

  Further, the front lens can be a half-moon shape or a rectangular shape, and further, a thread groove for engaging the lens barrel is formed on the outer periphery of the front lens, or the front lens is attached to the lens barrel. Grooves or protrusions for rotational positioning are formed. When projecting an image with an elevation angle with respect to the optical axis of the projection lens of the image projection device, the projected image light passes through only the upper half of the front lens, so the front lens is not necessarily circular. There is no need to be. Therefore, a frontal lens having a half-moon shape or a quadrangular shape only in a region through which image light passes can be obtained. When a lens is formed of glass, it is necessary to polish from a circular glass plate. However, since the lens is formed by molding a plastic material, there is no such limitation. Similarly, a thread groove, a concave portion, and a convex portion can be formed on the outer periphery of the front lens. Thereby, the whole projection lens can be formed lightweight and compact.

  Hereinafter, the present embodiment will be described in detail with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view of a projection lens 1 used in an image projection apparatus according to an embodiment of the present invention. The projection lens 1 has a first lens group 2 that arranges image light on the exit side and a second lens group 3 that arranges image light on the incident side. The first lens group 2 is a focusing lens, and the second lens group is a relay lens or a compensator lens group. The foremost lens of the first lens group 2 is a front lens 10, which is made of a transparent plastic material. The front lens 10 is fixed to the inner periphery of the front barrel 6. The front lens 10 is integrally formed with a holding member 11 for holding the rear glass lens 12. The rear glass lens 13 and the composite glass lens 14 are held by holding members 15 and 16 separate from the plastic of the front lens 10 and the holding member 11. The second lens group 3 is composed of a plurality of glass lenses, and is fixed and held on the rear barrel 5 by holding members 17 and 18. The front lens barrel 6 and the rear lens barrel 5 are held by the outer lens barrel 4 so as to freely advance and retract. The projection lens 1 has a symmetric structure around the optical axis 19.

  The front lens 10 can be made of a plastic material such as ABS (acrylonitrile, butadiene, styrene) in addition to a resin made of transparent PC or PMMA. These plastic materials for lens equipment can be formed by injection molding or press molding using a mold. In this case, the inner surface of the mold corresponding to the area of the front lens 10 is subjected to high-precision mirror polishing.

  Thereby, compared with the case where a lens is formed with glass, the weight of a front lens can be made into 1/2 or less. Further, since the holding member for the rear glass lens 12 is integrally formed, the number of parts is reduced.

  FIG. 2 is a schematic cross-sectional view of a projection lens 20 according to another embodiment. The same code | symbol was attached | subjected to the part which represents the same location part or the same function. The difference from FIG. 1 is that the front lens 21 formed by plastic molding is formed by integrally molding the holding member 22 for holding the glass lens 12 and the front barrel 23. In the front barrel 23, the glass lens 13, the holding member 15 holding the glass lens 13, and the composite glass lens 14 and the holding member 15 holding the glass lens 13 are housed therein. Thus, by integrally forming the front lens barrel 23 and the front lens 21, it is possible to reduce the number of parts and the assembly process.

  FIG. 3 is a schematic cross-sectional view of a projection lens 30 according to another embodiment. The same reference numerals are assigned to the same parts or parts representing the same function. 2 differs from the projection lens of FIG. 2 in that a fixing member 33 for fixing the projection lens 30 is made of a plastic material in addition to the front lens 31, the holding member 32 that holds the glass lens 12, and the front barrel 23. It is an integral molding. The glass lens 13 and the composite glass lens 14 are fixed to the front barrel 23 by holding members 15 and 16. The second lens group 3 is fixed to the rear barrel 5 by holding members 17 and 18. The front lens barrel 23 and the rear lens barrel 5 are slidably fixed to the outer lens barrel 4. The entire projection lens 30 is fixed to the front panel 34 by a fixing member 33 and a screw 35. The front lens 31 is transparent, and a light shielding film (not shown) is attached to the inner walls of the other holding members 32 and the front barrel 23 to prevent transmission or reflection of unnecessary light. In the above embodiment, the fixing member 33 integrally molded with the front lens 31 is screwed to the front panel 34, but the front panel 34 and the front lens 31 may be integrally molded. Thereby, the number of parts and the assembly process can be reduced, and the weight of the entire apparatus can be reduced.

  FIG. 4 is a schematic cross-sectional view showing a front lens according to another embodiment. FIG. 4A shows a state before the front lens 41 is inserted into the front lens barrel 43. FIG. 4 (b) represents the state after insertion. The front lens 41 made of a plastic material has an arrowhead-shaped notch portion 42 at a part of its outer periphery. The front lens 41 and the notch portion 42 are formed by integrally molding a plastic material. A V-groove 44 is formed on the inner surface of the front barrel 43. As shown in FIG. 4B, by inserting the front lens 41 into the front lens barrel 43, the notch portion 42 is engaged with the V-groove 44, and the front lens 41 is fixed to the front lens barrel 43. Is done. Thereby, the assembly process of a projection lens is reduced.

  FIG. 5 is a schematic cross-sectional view of a projection lens 50 used in an image projection apparatus according to another embodiment of the present invention. The same parts or parts having the same function are denoted by the same reference numerals. In FIG. 5, the front lens 51 and the front lens barrel 52 are formed by integral molding of a plastic material. The glass lenses 12 and 13 and the composite glass lens 14 of the first lens group 2 are fixed to the front barrel 52 by holding members 15 and 16. In the second lens group 3, a lens made of glass is fixed to the rear barrel 5 by holding members 17 and 18. The front lens barrel 52 and the rear lens barrel 5 are slidably held by the outer lens barrel 4. Further, a plate-like movable portion 53 is formed below the front lens 51. The movable portion 53 is integrally formed of a plastic material together with the front lens 51 and the front barrel 52. A rack 54 is formed on the lower surface of the plate-like movable portion 53 and meshes with a pinion 55 attached to the rotating shaft 61. The rotating shaft 61 is rotatably attached to the lower part or the casing of the outer barrel 4. The rotating shaft 61 further includes a worm wheel 56 and meshes with a worm 57 formed on a part of the rotating member 58. The rotating member 58 can be rotated from the outside by a knob (not shown). A spring 59 is attached to the side of the movable portion 53 opposite to the front lens 51. The other end of the spring 59 is attached to a lower portion of the outer lens barrel 4 or a fixing portion 60 fixed to the housing, and applies stress to the front lens 51 and the front lens barrel backward.

  By rotating the rotating member 58, a rotational force is applied from the worm 57 to the worm wheel 56, and the rack 54 moves back and forth as the pinion 55 rotates. Accordingly, the first lens group 2 can move back and forth with respect to the second lens group 3, and the focus of the projected image can be adjusted.

  FIG. 6 is an external view showing the shape of a front lens used in an image projection apparatus according to another embodiment. In the projection lens for enlargement projection of the image projection apparatus, the image light passes through the upper half region of the first lens group 2 with respect to the optical axis 19. This is because when the image is projected with the elevation angle around the optical axis 19, the projected image is distorted, and this distortion is prevented. Therefore, in the front lens, the lower half from the center of the lens is not used.

  FIG. 6A1 is a front view of a front lens made of a semicircular plastic, and FIG. 6A2 is a cross-sectional view of the X-X ′ portion. A lens is formed in the upper half from the optical axis 19 of the projection lens, and the lower half is cut. Thereby, a lens can be reduced in weight and the usage-amount of the plastic material which comprises a lens can also be reduced. FIG. 6B1 is a front view of a front lens made of a square plastic lens, and FIG. 6B2 is a cross-sectional view of the Y-Y 'portion. A rectangular lens is formed in the upper half from the optical axis 19 of the projection lens, and the lower half is cut. In the image projection apparatus, an image displayed on a liquid crystal display element and an image reflected from a DMD (digital micromirror device) usually have a square shape. Thus, the projection lens need not be circular. Therefore, the front lens is formed in a quadrangle, and the lens is configured in a region through which image light passes. Thereby, a lens can be reduced in weight and the usage-amount of a plastic material can also be reduced. In addition to a half-moon shape or a quadrangular shape, a hexagonal shape or a polygonal shape can be used. These front lens were formed by molding a plastic material, pressing, or the like. Therefore, unlike a glass lens, a lens having an asymmetric shape can be designed relatively freely.

  FIG. 7 is a cross-sectional view illustrating a front lens portion of a projection lens according to another embodiment, and FIG. 7A illustrates a state before the front lens 71 is inserted into the front barrel 73. FIG. 7B shows a state in which the front lens 71 is inserted into the front barrel 73. A male screw groove 72 is formed on the outer periphery of the front lens 71, and a female screw groove 74 is formed on the inner periphery of the front lens barrel 73, and the front lens 71 is screwed onto the front lens barrel 73. And fix it. As a result, it is not necessary to use a holding member when the front lens 71 is installed in the front barrel 73, and the projection lens can be reduced in weight and size.

  FIG. 8 is an explanatory diagram for explaining the alignment mechanism of the front lens for a projection lens according to another embodiment. FIG. 8A1 is a front view illustrating a state in which the front lens 81 is fixed to the front barrel 83, and FIG. 8A2 is a side sectional view thereof. A male thread groove is formed on the outer periphery of the front lens 81, a female thread groove is formed on the inner periphery of the front barrel 83, and the front lens 81 is screwed and fixed to the front barrel 83. Yes. Further, a recess 82 made of a groove is formed on a part of the outer periphery of the front lens 81. In addition, a stopper 84 is installed in the front barrel 83, the tip of the stopper 84 passes through a through-hole 87 provided in the front barrel 83, and the rear end is fixed to an outer barrel or casing (not shown). It is inserted into the opening of the stopper fixing portion 85 and fixed so as to freely advance and retract. The stopper 84 is pressed against and abutted against the front lens 81 by a spring 86 provided between the stopper 84 and the stopper fixing portion 85. In FIG. 8A1, the tip of the stopper 84 is inserted into the recess of the front lens 81, and the rotation angle of the front lens 81 is fixed.

  FIG. 8B1 is a front view of the front lens barrel 83 when the front lens 81 is rotated about 45 ° to the right, and FIG. 8B2 is a side sectional view thereof. By rotating the front lens 81, the stopper 84 is pushed upward. After one rotation, the concave portion 82 of the front lens 81 reaches the upper part and is fixed by the stopper 84. Thus, by providing the concave portion 82 in the front lens 81, the front lens 81 can be reliably fixed at a specific rotation angle in the case of a lens having an asymmetric shape with respect to the optical axis. The front lens 81 may be a rectangular lens or a circular lens in addition to a semicircular lens of an asymmetric lens. In the above embodiment, the concave portion is formed in the front lens, but a convex portion is formed instead of the concave portion, and the convex portion is engaged with the front barrel or the outer barrel at a specific rotation angle. It may be fixed.

  FIG. 9 shows a projection lens 90 according to another embodiment, FIG. 9A is a cross-sectional view of the projection lens 90, and FIG. 9B is an external view thereof. The same parts and the parts having the same functions are denoted by the same reference numerals. In FIG. 9B, the outer lens barrel 94, the front lens barrel 92, and the rear lens barrel 93 have a cylindrical shape with a flat bottom portion 95. In FIG. 9A, a front lens 91 is an asymmetric lens having a flat bottom, and is integrally formed with a front barrel 92 of a plastic material. Similarly, the holding members 15, 16, 17, and 18 that hold the lenses also have asymmetric shapes at the upper and lower portions. That is, the optical axis 19 of the projection lens 90 is located below the center of the lens barrel. In the second lens group 3, image light incident from the rear part passes below the optical axis 19, and in the first lens group 2 passes above the optical axis 19.

  By forming the projection lens 90 in this way, the volume of the front lens 91 can be reduced and the weight can be reduced, and at the same time, the outer barrel 94, the front barrel 92, and the rear barrel 93 can be reduced, Weight reduction can be achieved.

  FIG. 10 is a schematic cross-sectional view showing a projection lens 200 according to another embodiment. The same parts or parts having the same function are denoted by the same reference numerals. The internal structure of the outer lens barrel 94 of the projection lens 200 is the same as that of the projection lens 90 shown in FIG. That is, the projection lens 200 has an asymmetric structure with the optical axis 19 as the center, and the front lens 290 constitutes a lens only in the upper half. As shown in FIG. 5, the movable portion 53 is formed below the front lens 290 below the projection lens 200. The movable portion 53 is integrally formed with the front lens 290 and the front barrel 92. A rack 54 is formed on the lower surface of the movable portion 53 and meshes with a pinion 55 attached to the rotating shaft 61. As described below with reference to FIG. 5, the focus of the projection lens 200 can be adjusted by rotating the rotary member 58. Normally, the focus is adjusted by rotating the front lens 91, but the front lens 290 cannot be rotated when it has an asymmetric structure with respect to the optical axis 19 as in the present embodiment. For this reason, such a configuration using the rack 54 and the pinion 55 is particularly effective.

It is typical sectional drawing of the projection lens used for the image projector which concerns on embodiment of this invention. It is typical sectional drawing of the projection lens used for the image projector which concerns on other embodiment of this invention. It is typical sectional drawing of the projection lens used for the image projector which concerns on other embodiment of this invention. It is typical sectional drawing of the front lens used for the image projector which concerns on other embodiment of this invention. It is typical sectional drawing of the projection lens used for the image projector which concerns on other embodiment of this invention. It is an external view of the front lens used for the image projector which concerns on other embodiment of this invention. It is sectional drawing showing the front lens part of the projection lens used for the image projector which concerns on other embodiment of this invention. It is explanatory drawing of the position alignment mechanism of the front lens used for the image projector which concerns on other embodiment of this invention. It is sectional drawing and the external view of the projection lens used for the image projector which concerns on other embodiment of this invention. It is typical sectional drawing of the projection lens used for the image projector which concerns on this Embodiment. It is an external view of a conventionally well-known image projection apparatus. It is sectional drawing of a conventionally well-known projection lens.

Explanation of symbols

1, 20, 30, 50, 90 Projection lens 2 First lens group 3 Second lens group 4 Outer lens barrel 5 Rear lens barrel 6 Front lens barrel 10, 21, 31, 41, 51, 71, 81, 91 Front Ball lens 11, 15, 16, 17, 18, 22, 32 Holding member 33 Fixing member
12, 13 Glass lens 19 Optical axis

Claims (9)

  An image projection apparatus for projecting an image using a projection lens, wherein the projection lens includes a front lens formed of a plastic material.   2. The image according to claim 1, wherein the projection lens includes a holding member that holds the front lens, and the front lens and the holding member are integrally formed of the plastic material. Projection device.   The image projection apparatus according to claim 2, wherein the holding member constitutes a part of a barrel of the projection lens.   The projection lens includes a position adjusting member that adjusts a position of the front lens, and the position adjusting member and the front lens are integrally formed of the plastic material. The image projector of any one of -3.   The projection lens includes a fixing member for fixing the projection lens, and the fixing member and the front lens are integrally formed of the plastic material. Image projection device.   The image projection apparatus according to claim 1, wherein the front lens has a half-moon shape.   The image projection apparatus according to claim 1, wherein the front lens has a rectangular shape.   The image projection apparatus according to claim 1, wherein the front lens has a thread groove formed on an outer periphery thereof.   The image projection apparatus according to claim 1, wherein the front lens has a position fixing groove or a protrusion on an outer periphery thereof.

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