JP4690816B2 - Lens holding unit - Google Patents

Description

  The present invention relates to a lens holding unit and a lens unit suitable for an image display device that enlarges and projects an image displayed on a light modulator such as a liquid crystal display device or DMD onto a screen.

  2. Description of the Related Art A rear-type projector device (hereinafter referred to as a rear projector device) that projects projection light from a light modulator that modulates light using an image signal onto a screen from a back side using a projection lens is known.

Patent Document 1 discloses a lens device including a moving lens unit. This lens apparatus has a lens barrel having a plurality of cam grooves provided on the outer periphery thereof in parallel to the central axis direction, and a plurality of cam grooves provided obliquely to the central axis of the lens barrel. A cam ring, a moving lens unit arranged in the cam ring, a plurality of cam pins installed on the outer periphery of the moving lens unit, and a cam pin holding frame connected to the outer periphery of the moving lens unit to hold the cam pins And. In this lens device, the cam pin and the cam pin holding frame are each provided with a through hole that integrally penetrates, and an adjustment screw that contacts the outer periphery of the moving lens unit is screwed into the through hole, so that the outer periphery of the moving lens unit is adjusted by the adjustment screw. Is configured to extrude.
JP-A-8-327872

  The rear projector device enlarges and projects an image formed by a light modulator (light valve or image forming device) such as a liquid crystal display device or DMD (digital mirror device) onto the screen from the back side using a lens unit (projection lens). To do. This rear projector device is attracting attention as a next-generation image display device because it is thin and can display a large image. In the rear projector apparatus, since the positional relationship between the light valve and the screen is fixed, it is desirable that the focal point of the lens unit is fixed.

  Even if a lens unit having a plurality of lenses is of a fixed focus type, there is a manufacturing tolerance in each lens and in a lens holding unit that holds these lenses, and the optical axis position between the lenses is different. Fine adjustment is required. Further, since there are individual differences in the rear projector apparatus in addition to the individual differences in the lens units, it is required that the focus can be finely adjusted when the lens unit is incorporated into the rear projector apparatus.

  Further, the projection lens unit for the rear projector device enlarges and projects the image formed by the light modulator. For this reason, the quality of the image formed on the screen easily deteriorates even with a slight defocus. In particular, in the future, the rear projector device is expected as a product that replaces a type of display that directly looks at a light valve such as a cathode ray tube, a liquid crystal display device, or a plasma display. Therefore, the image projected on the screen of the rear projector device is required to have the same clarity as that of a conventional direct-view display. Therefore, it is not preferable that the lens unit be out of focus due to an impact applied during shipment or transportation to the user after the lens unit is finely adjusted and attached to the rear projector apparatus.

  One embodiment of the present invention is a lens holding unit, which is an inner cylinder for holding a lens, and an outer cylinder arranged coaxially (concentrically) outside the inner cylinder, the inner cylinder being the outer cylinder An outer cylinder for supporting the inner cylinder so as to slide linearly back and forth in the central axis direction along the inner surface of the outer cylinder, and one of the outer cylinders rotatably attached to the outer surface of the outer cylinder and facing the outer surface of the outer cylinder A disc-shaped cam having a spiral guide on the end face, a drive pin that passes through the outer cylinder, connects the inner cylinder and the spiral guide, and can drive the inner cylinder back and forth when the disc-shaped cam rotates, and an outer And a holding mechanism for stopping the rotation of the disc-shaped cam with respect to the cylinder. The drive pin can be displaced in the radial direction of the inner cylinder with respect to at least one of the inner cylinder and the spiral guide.

  In addition to the inner and outer cylinders, a cylindrical member that functions as a cam is combined coaxially (concentrically) to move the inner cylinder back and forth along the central axis with respect to the outer cylinder to fine-tune the focus. be able to. After fine adjustment, it is necessary to fix the movement of the inner cylinder with respect to the outer cylinder. In order to fix the inner cylinder for holding the lens to the outer frame serving as a base that supports the lens, the inner cylinder that becomes the lens frame even if the inner cylinder is pulled or pushed in the radial direction with a fixing screw, Alternatively, stress is applied to the outer cylinder serving as a base. The cylindrical member that functions as a cam may be fixed to the outer cylinder, but even if the cylindrical member that functions as a cam is pulled in the radial direction (radial direction) of the inner cylinder by a fixing screw, However, there is a high possibility that stress is applied to the inner cylinder or the outer cylinder combined concentrically. Therefore, by finely adjusting the focus, the optical axis finely adjusted before shipment may be shifted.

  In the lens holding unit of one embodiment of the present invention, the inner cylinder and the outer cylinder are arranged coaxially (concentrically). A disk-shaped cam provided with a spiral guide is rotatably attached to the outer surface of the outer cylinder, and the inner cylinder is driven back and forth when the disk-shaped cam rotates via a drive pin that penetrates the outer cylinder. . That is, the cam mechanism for moving the inner cylinder with respect to the outer cylinder is mounted by a disk attached to the outside of the outer cylinder, not the ring or the cylinder, and the cam mechanism is not arranged coaxially with the outer cylinder and the inner cylinder. Further, the disc-shaped cam is fixed to the outer cylinder on the outer side of the outer cylinder by the holding mechanism. The drive pin that connects the disc-shaped cam and the inner cylinder is displaced in the radial direction (radial direction) of the inner cylinder with respect to at least one of the inner cylinder and the spiral guide. Therefore, even if the disc-shaped cam is fixed to the outer cylinder, it is possible to prevent a force that pushes or pulls in the radial direction from acting on the inner cylinder housed inside the outer cylinder. For this reason, in the lens unit adjusted by attaching a plurality of lenses to the inner cylinder of the lens holding unit, it is possible to prevent the optical axis from shifting when finely adjusting the focal point. Therefore, by mounting the lens unit employing the lens holding unit of the present invention on an image display device such as a rear projector, the lens unit or lens is provided for each image display device without degrading the optical performance of the lens unit. Fine adjustment of the focus of the system is possible, and an image display device that displays a clear image can be provided.

  Further, when the rotation of the disk-shaped cam with respect to the outer cylinder is stopped, the inner cylinder is connected to the spiral guide of the disk-shaped cam via the drive pin, so that the movement of the inner cylinder in the longitudinal direction with respect to the outer cylinder is performed. Is also fixed. Since the spiral guide is inclined obliquely with respect to the central axis, the longitudinal movement of the drive pin along the central axis is efficiently inhibited by the spiral guide. Therefore, after moving the disk-shaped cam to finely adjust the focus, fixing the rotation of the disk-shaped cam can suppress the movement of the inner cylinder with respect to the force in the central axis direction (thrust direction). For this reason, after the lens unit using this lens holding unit is incorporated in an image processing device such as a rear projector, the lens unit is prevented from defocusing even if force is applied in the thrust direction due to conveyance or the like. it can.

  A preferred example of the spiral guide of the disc-shaped cam is a spiral groove, one end of the drive pin is fitted into a receiving portion such as a hole provided on the outer surface of the inner cylinder, and the other end is spiral. It is preferable to move the inside of the groove. Since the movement of the drive pin in the thrust direction is defined by the spiral groove, the movement of the inner cylinder can be easily controlled. In addition, since the other end of the drive pin is displaced in the radial direction inside the spiral groove, one end of the drive pin can be fitted into a receiving portion provided in the inner cylinder, and the drive pin can be adjusted for the optical axis. Can be used for both.

  The outer cylinder is preferably provided with an elongated slit for linearly guiding the inner cylinder in the front-rear direction of the central axis, and the drive pin preferably passes through the slit. Since the movement of the drive pin becomes a linear shape along the central axis direction by the slit, the drive pin not only drives the inner cylinder back and forth with respect to the outer cylinder, but also prevents the inner cylinder from rotating, The inner cylinder is slid linearly back and forth in the central axis direction inside the outer cylinder.

  The disc-shaped cam may be directly rotated by hand. Furthermore, it is desirable that the disc-shaped cam has a passive gear on the outer peripheral surface. The outer cylinder preferably includes a protrusion or a recess for detachably mounting the operation knob provided with the operation gear at a position where the operation gear meshes with the passive gear of the disc-shaped cam. By selecting the gear ratio between the passive gear and the operation gear, the rotation angle of the disk-shaped cam with respect to the movement of the operation knob can be changed, and the amount of movement of the inner cylinder can be controlled. Therefore, fine adjustment of the focus can be easily performed. Further, after the focus adjustment, the operation knob can be removed, so that the lens unit becomes compact, and the operation knob can be shared with other lens units.

  As the outer cylinder and the inner cylinder of the lens holding unit, what is called a clamshell type including a subunit in which a cylindrical member is divided into at least two in a plane passing through the central axis can be adopted. The clamshell type holder joins two subunits manufactured from one mold, so that the lens holding unit can be manufactured and assembled at low cost. In addition, subunits having the same structure and having the same tolerance are supported from the radial direction (radial direction) as one holder, so that the center of the lens or the optical axis can be easily aligned. Therefore, it is preferable to use a clamshell type holder for the lens unit for the rear projector apparatus.

  One aspect of the present invention is a lens unit having the above-described lens holding unit and at least one lens held in an inner cylinder, which allows fine adjustment of the focal point, and has high impact resistance. Optical performance can be stably maintained. Another embodiment of the present invention is an image display device that includes the lens unit, a light modulator that forms an image to be projected onto the screen through the lens unit, and a screen. It can be projected.

  FIG. 1 shows an outline of a rear projector device 1 as an image display device. The rear projector apparatus 1 includes a light source 3, a light modulator (light valve) 4 that forms an image by modulating light from the light source 3 using an image signal, and an image of the light valve 4. A lens system 5 for projecting and a mirror 7 for reflecting the projection light 8 and guiding it to a screen 9 are provided. A screen 9 is disposed on the surface of the housing 2, and an image of the light valve 4 is enlarged and projected onto the screen 9 from behind via the lens system 5. As the light valve 4, a liquid crystal display panel, a DMD panel using a micromirror element, or the like can be adopted.

  FIG. 2 shows a schematic configuration of the lens system 5 for projection. This lens system 5 is configured by connecting several lens units. In this example, an output side (enlargement side) lens unit 5a, a lens unit 5b housing a prism 6 for bending an optical path therein, and an input side lens unit 5c are provided. The lens system 5 is L-shaped as a whole, and the projection light 8 is output by bending light by 90 degrees inside the prism system 6. The projection light 8 is projected onto the screen 9 via the mirror 7 of the rear projector device 1 to form an image. The lens unit 5c on the input side includes an inner cylinder 30 holding a lens, an outer cylinder 40 that supports the inner cylinder 30 so as to be slidable in the optical axis direction for focus adjustment, and a disk for sliding the inner cylinder 30. Shaped cam 50.

  FIG. 3 is a perspective view showing an appearance of a portion where the disc-like cam 50 of the lens unit 5c is installed. FIG. 4 is a developed view showing a schematic configuration of the lens unit 5c. 5 and 6 show a schematic configuration of the lens unit 5c by a longitudinal sectional view along the central axis L. FIG.

  The lens unit 5 c includes a lens holding unit 20 including an inner cylinder 30, an outer cylinder 40, and a disc-shaped cam 50, and at least one lens, in this example, two lenses 10 are attached to the inner cylinder 30. It is stored. That is, the lens holding unit 20 includes a substantially cylindrical inner cylinder 30 for holding the lens 10 and an outer cylinder 40 disposed coaxially (concentrically) outside the inner cylinder 30. The outer tube 40 for supporting the inner tube 30 and the outer surface 40b of the outer tube 40 rotate so that the tube 30 slides linearly along the inner surface 40a of the outer tube 40 in the direction of the central axis L of the inner tube 30. The disc-shaped cam 50 attached so that it was possible was provided. As shown in FIG. 7, the disc-shaped cam 50 is provided with a spiral cam groove 51 on one end surface 53 facing the outer cylinder 40, as shown by extracting the disc-shaped cam 50.

  Further, the lens holding unit 20 penetrates the outer cylinder 40 and connects the inner cylinder 30 and the spiral guide 51 of the disk-shaped cam 50. When the disk-shaped cam 50 rotates, the inner cylinder 30 can be driven back and forth. The drive pin 60 is provided. As shown in FIG. 4, one end 61 of the drive pin 60 is inserted into the receiving portion 31 provided on the outer surface 30 b of the inner cylinder 30, and the other end 62 moves inside the cam groove 51. The size of the other end 62 of the drive pin 60 and the cam groove 51 is such that the other end 62 can be displaced in the radial direction (radial direction) of the inner cylinder 30 with respect to the spiral cam groove 51. Yes. Further, in the lens holding unit 20, a hole 42 for attaching a screw 70 for stopping the rotation of the disk-shaped cam 50 with respect to the outer cylinder 40 is provided on the outer surface 40 b of the outer cylinder 40 as a holding mechanism.

  The inner cylinder 30 and the outer cylinder 40 are molded from resin. The inner cylinder 30 and the outer cylinder 40 may each be a clamshell type holder. In this example, the inner cylinder 30 is a clamshell type holder, which is substantially coincident with the optical axis of the lens unit 5c, and is divided into two parts vertically and horizontally by a surface including the central axis L of the inner cylinder 30. The clamshell type subunit 39 is provided. The subunits 39 are joined by bolts or the like to form one substantially cylindrical shell.

  The inner cylinder 30 includes a protrusion 38 for holding the lens 10 on the inner peripheral surface 30a. Further, the inner cylinder 30 is provided with a plurality of holes (receiving portions) 31 in the circumferential direction of the outer peripheral surface 30b. A fitting portion 61 at one end of the drive pin 60 can be fitted into the hole portion 31. On the outer peripheral surface 30 b of the inner cylinder 30, annular flanges 32 a and 32 b projecting outward are formed at two positions along the central axis L. When the inner cylinder 30 is inserted into the outer cylinder 40, these flanges 32 a and 32 b are in contact with the inner surface 40 a of the outer cylinder 40. Therefore, the inner cylinder 30 slides in the front-rear direction along the central axis L without rattling with respect to the outer cylinder 40.

  The outer cylinder 40 is a cylinder having an inner peripheral surface 40a for guiding the inner cylinder 30, and further includes a ring-shaped cam support portion 41 for attaching the disk-shaped cam 50 to the outer surface 40b. The cam support portion 41 has a substantially circular caldera shape that protrudes from the outer peripheral surface 40 b of the outer cylinder 40 in a direction perpendicular to the central axis L. Six fixing holes 42 are provided at substantially equal intervals on the outer ring 48 of the cam support portion 41. The fixing hole 42 functions as a holding mechanism for stopping the rotation of the disk-shaped cam 50 relative to the outer cylinder 40, and the disk-shaped cam 50 is screwed into the hole 42 through the disk-shaped cam 50. The rotation is stopped. The center of the cam support 41 is a hole 43 for attaching the disk-shaped cam 50 to the outer cylinder 40 so as to be rotatable. The disc-shaped cam 50 is attached to the hole 43 by an attachment pin 59 that also serves as a rotation shaft.

  Further, the outer cylinder 40 is formed with an elongated linear slit 45 that passes through the outer cylinder 40 along the central axis L from the mounting hole 43 toward the outer ring 48. The slit 45 includes a drive pin 60 that connects the disc-shaped cam 50 and the inner cylinder 30, and connects the disc-shaped cam 50 and the inner cylinder 30 through the outer cylinder 40, and A function of linearly guiding the moving direction with respect to the cylinder 40 in the front-rear direction of the central axis L is achieved. That is, the movement of the inner cylinder 30 in the circumferential direction with respect to the outer cylinder 40 can be suppressed by the drive pin 60 and the slit 45.

  The disc-shaped cam 50 attached to the cam support portion 41 of the outer cylinder 40 is a disk with a small thickness, and includes a passive gear 52 on the outer peripheral surface thereof. Further, the disc-shaped cam 50 includes a spiral groove 51 serving as a spiral guide on an end surface 53 facing the outer cylinder 40. The spiral guide is not limited to such a spiral groove 51, and may be a spiral slit or a spiral convex portion penetrating the disk-like cam 50. In the case of a spiral convex portion, a groove is provided that meshes with the convex portion on the drive pin 60 side.

  The disc-shaped cam 50 of this example further includes a through hole 55 through which a mounting pin 59 serving as a shaft is passed. Further, four arc-shaped slits 54 are provided at substantially equal intervals along the periphery. When the disc-shaped cam 50 is attached to the cam support portion 42 of the outer cylinder 40, at least one of the fixing holes 42 appears through the slit 54. Therefore, the rotation of the disk-shaped cam 50 can be stopped by screwing the fixing screw 70 into the hole 42 through the slit 54.

  The drive pin 60 penetrates the outer cylinder 40 and connects the spiral groove (cam groove) 51 of the disk-shaped cam 50 and the inner cylinder 30. When the disk-shaped cam 50 is screwed to the outer cylinder 40 with the screw 70 serving as a holding mechanism, the radial stress is not propagated to the inner cylinder 30 even if the disk-shaped cam 50 moves in the radial direction. In addition, the drive pin 60 can be moved or displaced in the radial direction (radial direction) with respect to at least the inner cylinder 30 and the spiral groove 51. In this example, one end 62 of the drive pin 60 is a passive part that moves inside the spiral groove 51, and as shown in FIGS. 5 and 6, the passive part 62 and the bottom surface of the spiral groove 51 It is designed so that a gap S is opened between them. Therefore, the drive pin 60 can be displaced in the radial direction of the inner cylinder 30 with respect to the spiral groove 51, and even if the disk-shaped cam 50 is screwed to the outer cylinder 40, the radial direction stress is internally generated. It does not propagate to the cylinder 30.

  Further, the outer surface 40 b of the outer cylinder 40 is provided with a recess 44 in which an operation knob 80 for operating the disk-like cam 50 can be attached and detached at a position close to the cam support portion 41. The operation knob 80 includes a columnar operation portion 85, a protrusion 82 for attaching to the recess 44, and an operation gear 81 connected coaxially with the operation portion 85. The operation knob 80 is attached to the recess 44. Then, the operation gear 81 meshes with the passive gear 52 of the disc-like cam 50. The form in which the operation knob 80 is rotatably attached to the outer cylinder 40 is not limited to the recess 44, and the unevenness may be reversed.

  The lens unit 5c including the lens holding unit 20 is assembled as follows. First, the lens 10 is mounted inside the inner cylinder 30. Since the inner cylinder 30 is a clamshell type, the respective lenses 10 can be mounted so as to be supported by the protrusions 38 provided on the inner peripheral surface 30a. Next, the inner cylinder 30 is inserted into the outer cylinder 40, and the fitting portion 61 of the drive pin 60 is inserted into the hole 31 of the inner cylinder 30 through the slit 45 of the outer cylinder 40. At this time, the lens system 5 is assembled together with the other lens units 5a and 5b by the lens unit 5c, and the optical axis of the lens system 5 is adjusted. That is, in order to adjust the positional relationship of the plurality of lenses held in each of the lens units 5a to 5c, the inner cylinder 30 is rotated with respect to the outer cylinder 40, and the position with the best imaging performance is selected. Of the plurality of holes 31 arranged on the outer peripheral surface 30 b of the inner cylinder 30, when the optical axis is adjusted, the drive pin 60 is fitted into the hole 31 located closest to the slit 45. The inner cylinder 30 cannot be turned with respect to the outer cylinder 40 by the drive pin 60, and the lens system 5 including the lens unit 5c can be shipped with the optical axis adjusted.

  Further, a disc-like cam 50 is mounted on the cam support portion 41 of the outer cylinder 40 and attached to the outer cylinder 40 by the attachment pin 59 so that the cam 50 rotates. At this time, the disc-shaped cam 50 is set on the support portion 41 so that the passive portion 62 of the drive pin 60 is loosely fitted in the spiral groove 51 of the disc-shaped cam 50. One end of the spiral cam groove 51 is connected to a hole 56 penetrating the disk-shaped cam 50, and the position of the drive pin 60 and the cam groove 51 can be aligned using this hole 56.

  Thus, the lens system 5 assembled and shipped by the lens unit 5c including the inner cylinder 30, the outer cylinder 40, and the disk-shaped cam 50 and the other lens units 5a and 5b is incorporated into an image apparatus such as a rear projector. Sometimes the focus is finely adjusted. First, as shown in FIG. 5, the operation knob 80 is attached to the recess 44 of the outer cylinder 40 so that the operation gear 81 thereof meshes with the passive gear 52 of the disc-like cam 50. The operation knob 80 is operated to rotate the disc-shaped cam 50. Thereby, the inner cylinder 30 slides linearly back and forth in the direction of the central axis L along the inner surface 40a of the outer cylinder 40 via the drive pin 60, and focus adjustment can be performed.

  After the focus adjustment is completed, as shown in FIG. 6, the fixing screw 70 is screwed into the hole of the outer cylinder 40 that is a holding mechanism through the slit 54 of the disk-shaped cam 50, and the disk-shaped cam is inserted into the outer cylinder 40. Fix 50 so that it does not rotate. At this time, the cam groove 51 has a play (gap) S in which the drive pin 60 can be moved or displaced in the radial direction. It is not pushed in the radial direction via the drive pin 60, and no radial force acts on the inner cylinder 30. Therefore, by fixing the disc-shaped cam 50 after the focus adjustment, the focus can be fixed without causing the shaft blur in a state where the optical axes of the lenses 10 are aligned.

  By fixing the rotation of the disc-like cam 50, the drive pin 60 inserted into the cam groove 51 does not move in the front-rear direction along the central axis direction. Therefore, the movement in the front-rear direction of the inner cylinder 30 connected by the drive pin 60 is limited. Furthermore, the spiral cam groove 51 provided in the disc-shaped cam 50 crosses the slit 45 provided in the outer cylinder 40 in a straight line in the front-rear direction obliquely at an angle close to substantially vertical, The drive pin 60 is held at the intersecting position. Therefore, the drive pin 60 is supported by the cam groove 51 and the slit 45 so as not to move substantially forward and backward and left and right. For this reason, the inner cylinder 30 moved by the drive pin 60 is also supported so as not to move substantially forward and backward and left and right with respect to the outer cylinder 40.

  Therefore, even if an impact or force is applied after the focus adjustment, in particular, even if a large force is applied in the front-rear direction (thrust direction), it is possible to prevent the focus and the optical axis from shifting. Therefore, once the focus is finely adjusted and the lens system 5 is incorporated in the rear projector apparatus 1, the focus is hardly deviated and a clear image can be stably projected on the screen.

  During focus adjustment, the amount of movement of the inner cylinder 30 relative to the amount of operation of the operation portion 85 can be changed by attaching / detaching the operation knob 80 having a different gear ratio to the outer cylinder 40. Therefore, at the initial coarse adjustment of the focus adjustment, the inner cylinder 30 is moved largely by using the operation knob 80 having a small gear ratio, and then the movement amount of the inner cylinder 30 is reduced by using the operation knob 80 having a large gear ratio. Fine adjustments can be made. Then, after the focus adjustment, the operation knob 80 can be detached from the outer cylinder 40. For this reason, it can prevent that the operation knob 80 is carelessly operated and a focus shifts | deviates. Further, by removing the operation knob 80, it is possible to prevent the lens holding unit 20 and the lens unit 5c from becoming large. Further, the operation knob 80 is common to other units and can be used repeatedly, which is economical.

  In the above description, the rear projector apparatus, the lens system and the lens holding unit suitable for the rear projector apparatus have been described. However, the lens holding unit and the lens unit according to one embodiment of the present invention can be applied to all systems that project an image. It is. Further, the present invention is not limited to a system that projects an image, and can be applied to an optical device or an optical system that uses a lens.

The figure which shows schematic structure of a rear projector apparatus. The figure which shows the lens system of a rear projector apparatus. FIG. 3 is a perspective view of the lens unit shown in FIG. 2. FIG. 4 is a developed perspective view of the lens unit shown in FIG. 3. FIG. 4 is a longitudinal sectional view showing a state in which the focus of the lens unit shown in FIG. 3 is adjusted. FIG. 4 is a longitudinal sectional view showing a state in which the focal point of the lens unit shown in FIG. 3 is fixed. The perspective view which expands and shows a disk shaped cam.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rear projector apparatus (image display apparatus), 4 Optical modulator 5 Lens system, 5c Lens unit 9 Screen, 10 Lens 20 Lens holding unit, 30 Inner cylinder 40 Outer cylinder, 50 Disc-shaped cam 60 Drive pin, 80 Operation knob

Claims (6)

An inner cylinder for holding the lens;
An outer cylinder arranged coaxially on the outer side of the inner cylinder, for supporting the inner cylinder so that the inner cylinder linearly slides back and forth in the central axis direction along the inner surface of the outer cylinder. The outer cylinder,
A disc-shaped cam that is rotatably attached to the outer surface of the outer cylinder and includes a spiral guide on one end surface facing the outer surface of the outer cylinder;
A drive pin that passes through the outer cylinder and connects the inner cylinder and the spiral guide and is capable of driving the inner cylinder back and forth when the disc-shaped cam rotates, the inner cylinder and the spiral A drive pin displaceable in the radial direction of the inner cylinder with respect to at least one of the guides of
A lens holding unit having a holding mechanism for stopping the rotation of the disk-shaped cam with respect to the outer cylinder; The spiral guide according to claim 1, wherein the spiral guide is a spiral groove,
One end of the drive pin is fitted into a receiving portion provided on the outer surface of the inner cylinder, and the other end moves inside the spiral groove. In Claim 1, the outer cylinder is provided with an elongated slit for linearly guiding the inner cylinder in the front-rear direction along the central axis.
The driving pin is a lens holding unit that passes through the slit. The disc-shaped cam according to claim 1, comprising a passive gear on an outer peripheral surface,
The outer cylinder includes an operation knob having an operation gear and a protrusion or a recess for detachably mounting the operation knob at a position where the operation gear meshes with a passive gear of the disc-shaped cam. unit.   A lens unit comprising: the lens holding unit according to claim 1; and at least one lens held by the inner cylinder.   6. An image display device comprising: the lens unit according to claim 5; a light modulator; and a screen, wherein projection light from the light modulator is projected onto the screen.

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