Lens apparatus

Abstract

To provide a lens device having a simple structure and capable of aligning an arbitrary lens group without disassembling a lens barrel.SOLUTION: A lens device 1 includes a fixed barrel 10, a cam barrel 60 rotatably attached to the fixed barrel 10, and a lens frame 90 holding a lens group, wherein a plurality of cam followers 94 detachably attached to the lens frame 90 are engaged with a cam groove side 34a formed in the fixed barrel 10 and a cam groove side 64a formed in the cam barrel 60, whereby rotational displacement of the cam barrel 60 is converted into movement of the lens frame 90 in an optical axis direction. The lens frame 90 has a plurality of attaching grooves to which the cam follower 94 is attached on the outer peripheral surface, and at least one attaching groove 92b among the plurality of attaching grooves is formed in a shape whose diameter is larger than that of the cam follower 94.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a lens device. [Background technology]

[0002] Conventionally, lens devices have been known that include multiple lens groups within a lens barrel and perform zooming and focusing by moving a specific lens group along the optical axis using a cam mechanism. In such lens devices, the lens groups may be aligned to improve optical performance. The alignment process typically involves disassembling the assembled lens barrel and adjusting the decentering (shift and tilt) of the lens groups. Essentially, to align a lens group located at the back of the lens barrel, the other lens groups located at the front must be removed.

[0003] In response to this, Patent Document 1 (see Japanese Patent No. 6112207) discloses a lens device that can align any lens group without disassembling the lens barrel. Specifically, a through-hole is formed in the lens barrel, and a tool (a screwdriver) is inserted into the through-hole to operate the alignment mechanism inside the lens barrel. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6112207 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the above-mentioned lens device, an alignment mechanism must be provided inside the lens barrel, which complicates the structure inside the lens barrel, and in particular poses the problem of increasing the number of parts and imposing restrictions on part placement, reducing design freedom. [Means for solving the problem]

[0006] The present invention has been made in view of the above circumstances, and has as its object to provide a lens device that has a simple structure and is capable of aligning any lens group without disassembling the lens barrel.

[0007] The present invention solves the above problems by the solution means described below as one embodiment.

[0008] A lens device according to one embodiment is a lens device comprising a fixed tube portion, a cam tube rotatably attached to the fixed tube portion, and a lens frame that holds a group of lenses, wherein a plurality of cam followers detachably attached to the lens frame are engaged with cam grooves formed in the fixed tube portion and the cam tube, thereby converting rotational displacement of the cam tube into movement in the optical axis direction of the lens frame, wherein the cam followers are configured to be eccentric with respect to the fixing screws that fix them, and the lens frame has a plurality of mounting grooves on its outer surface into which the cam followers are attached, and at least one of the plurality of mounting grooves is formed to have a shape with a larger diameter than the cam followers.

[0009] With the above configuration, the position and tilt of the lens frame can be adjusted by loosening the fixing screws that secure the cam followers and decentering the cam followers along the mounting grooves. Therefore, even with a simple alignment mechanism, it is possible to align any lens group without disassembling the lens barrel.

[0010] The large-diameter shape is preferably an elongated hole having a major diameter in the circumferential direction or the optical axis direction. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a lens device that has a simple configuration and is capable of aligning any lens group without disassembling the lens barrel. [Brief explanation of the drawings]

[0012] [Figure 1]1 is a side cross-sectional view illustrating an example of a lens device according to an embodiment of the present invention. [Figure 2] FIG. 2 is an exploded perspective view showing the main parts of the lens barrel. [Figure 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. [Figure 4] FIG. 4 is an enlarged view of part IV in FIG. [Figure 5] 5A is a view of a mounting groove formed in a lens frame viewed from the direction of arrow A in FIG. 3, and FIG. 5B is a view of another mounting groove formed in a lens frame viewed from the direction of arrow B in FIG. 3. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Fig. 1 is a side cross-sectional view (schematic diagram) showing an example of a lens device 1 according to this embodiment. For ease of explanation, arrows in the drawing indicate the left-right direction, the front-rear direction, and the up-down direction of the lens device 1. In addition, in all the drawings used to explain each embodiment, components having the same function are given the same reference numerals, and repeated explanations of such components may be omitted.

[0014] The lens device 1 is a projection lens mounted in a projector.

[0015] Lens device 1 broadly comprises a lens barrel 2 and a plurality of lens groups (not shown) housed inside lens barrel 2. The number of lens groups is arbitrary, and each lens group is made up of one or more lenses. Here, Figure 2 is an exploded perspective view of the main parts of lens barrel 2.

[0016] Lens barrel 2 includes a fixed barrel portion 10, cam barrels 60, 70, and 80, and multiple lens frames (only lens frame 90 is shown) that hold lens groups. Unless otherwise specified, the direction along the side surface of lens barrel 2 will be referred to as the "circumferential direction" below (see FIG. 1).

[0017] The fixed barrel portion 10 includes a fixed barrel 20 and a fixed barrel 50 fixed to the front end of the fixed barrel 20, and is configured to form a single cylindrical body as a whole.

[0018] The cam barrel 60 is a cylindrical body that is housed inside the rear side of the fixed barrel 20 (hereinafter referred to as the "housing chamber 30"). A plurality of guide followers 62 are attached to the outer peripheral surface of the cam barrel 60, and each guide follower 62 is engaged with a guide groove 32 that is formed in the housing chamber 30 and extends in the circumferential direction, and is also engaged with an adjustment gear 36 that is rotatably attached to the outer peripheral surface of the housing chamber 30. With this configuration, the cam barrel 60 can be rotationally displaced relative to the housing chamber 30 (fixed barrel 20) by manually or automatically rotating the adjustment gear 36.

[0019] The cam barrel 70 is a cylindrical body that is housed inside the front side of the fixed barrel 20 (hereinafter referred to as the "housing chamber 40"). A plurality of guide followers 72 are attached to the outer peripheral surface of the cam barrel 70, and each guide follower 72 is engaged with a guide groove 42 that is formed in the housing chamber 40 and extends in the circumferential direction, and is also engaged with an adjustment gear 46 that is rotatably attached to the outer peripheral surface of the housing chamber 40. With this configuration, the cam barrel 70 can be rotationally displaced relative to the housing chamber 40 (fixed barrel 20) by manually or automatically rotating the adjustment gear 46.

[0020] The cam barrel 80 is a cylindrical body that is disposed on the outer circumferential side of the fixed barrel 50 (i.e., that houses the fixed barrel 50 inside). A guide groove 82 that extends in the circumferential direction is formed through the cam barrel 80, and a plurality of guide followers 52 that are attached to the outer circumferential surface of the fixed barrel 50 are engaged with the guide groove 82. The cam barrel 80 is also connected to an adjustment gear 56 that is rotatably attached to the outer circumferential surface of the accommodation chamber 40. With this configuration, the cam barrel 80 can be rotationally displaced relative to the fixed barrel 50 by manually or automatically rotating the adjustment gear 56.

[0021] Each lens frame is a cylindrical body that holds one or more lens groups therein. A plurality of cam followers 94 are attached to the outer peripheral surface of each lens frame. Cam grooves 34, 44, and 54 extending in the optical axis direction are formed through the fixed barrel portion 10 (the housing chambers 30, 40 and the fixed barrel 50), and cam grooves 64, 74, and 84 including grooves inclined with respect to the optical axis are formed through the cam barrels 60, 70, and 80. By engaging each cam follower 94 with the cam grooves 34, 44, and 54 and the corresponding cam grooves 64, 74, and 84, the rotational displacement of the cam barrels 60, 70, and 80 can be converted into forward and backward displacement of each lens frame in the optical axis direction. As a specific example, in the case of the lens frame 90 shown in the figure, by engaging each cam follower 94 with a cam groove 34a formed through the storage chamber 30 and a cam groove 64a formed through the cam barrel 60, the rotational displacement of the cam barrel 60 can be converted into forward and backward displacement of the lens frame 90 in the optical axis direction.

[0022] That is, the lens barrel 2 is configured so that a predetermined lens frame can be driven in the optical axis direction by rotating the adjustment gears 36, 46, and 56. In this embodiment, zooming can be performed by the adjustment gear 36, focusing by the adjustment gear 46, and adjustment of field curvature can be performed by the adjustment gear 56.

[0023] Next, the centering mechanism of the lens device 1 according to this embodiment will be described. Here, Fig. 3 is a cross-sectional view taken along line III-III in Fig. 1, and Fig. 4 is an enlarged view of part IV in Fig. 3.

[0024] The alignment mechanism is constructed by removably attaching multiple cam followers 94 to mounting grooves 92a, 92b formed on the outer surface of the lens frame 90 (the lens frame 90 will be used as an example for explanation, but the same applies to other lens frames not shown in the figure) using fixing screws 100.

[0025] The cam follower 94 includes a collar 96 and a roller 98 attached to the collar 96, and is configured as a single cylindrical body having a through hole 94a through which the fixing screw 100 is inserted. As an example, the collar 96 is formed from a metal material, and the roller 98 is formed from a resin material. Here, the through hole 94a is formed in a perfect circle shape with a diameter larger than that of the fixing screw 100 (shaft portion 100a), and a gap S is provided between the through hole 94a and the fixing screw 100 (shaft portion 100a). In other words, the cam follower 94 is configured to be eccentric within the range of the gap S relative to the fixing screw 100 (shaft portion 100a).

[0026] The mounting grooves 92a, 92b are bottomed grooves into which the cam followers 94 are engaged (fixed), and an insertion hole 93 into which a fixing screw 100 is inserted is formed at the bottom. A plurality of mounting grooves 92a, 92b are formed on the outer peripheral surface of the lens frame 90 along the circumferential direction, with three mounting grooves 92b arranged at 15° pitches and the mounting grooves 92a arranged at 60° pitches relative to each mounting groove 92b. However, the arrangement and number of the mounting grooves 92a, 92b are not limited to this. Here, Fig. 5A is a view of the mounting groove 92a viewed from the direction of arrow A in Fig. 3, and Fig. 5B is a view of the mounting groove 92b viewed from the direction of arrow B in Fig. 3.

[0027] As shown in FIG. 5A, the mounting groove 92a is formed in a circular shape with approximately the same diameter as the cam follower 94 (the flange portion 96a of the collar 96), i.e., in a shape that restricts the movement (eccentricity) of the engaged cam follower 94. On the other hand, as shown in FIG. 5B, the mounting groove 92b is formed in an elongated hole shape with a long diameter in the left-right direction, i.e., in a shape that allows the engaged cam follower 94 to move (eccentricity) in the left-right direction. Specifically, the mounting groove 92b is formed in an elongated hole shape with a ratio of the length of the major axis b to the length of the minor axis (diameter at the mounting groove 92a) a of approximately 1.1, but it is sufficient that a margin width of approximately the aforementioned allowable range (gap) S of the cam follower 94 be provided on the major axis b side. In this embodiment, the cam follower 94 is mounted in one mounting groove 92b and two mounting grooves 92a arranged at a 120° pitch from the mounting groove 92b.

[0028] Here, a method for aligning the lens group held in the lens frame 90 in the lens device 1 equipped with the above-described alignment mechanism will be described. Note that the same method can be used for lens groups held in other lens frames (not shown).

[0029] First, the fixing screws 100 that secure the cam followers 94 engaged in the mounting grooves 92b of the lens frame 90 are loosened with a tool (a screwdriver) to release the cam followers 94. Next, the cam followers 94 are decentered along the mounting grooves 92b to adjust the left-right position of the lens frame 90 (shift of the lens group). Next, the loosened fixing screws 100 are retightened with a tool, and the cam followers 94 are re-fixed in the mounting grooves 92b. This completes the series of steps for alignment, but if good optical performance is not obtained, the same steps can be repeated.

[0030] Therefore, according to the lens device 1 of this embodiment, it is possible to align any lens group without disassembling the lens barrel 2, even though the alignment mechanism has a simple structure.

[0031] The shape of the mounting groove 92b is not limited to the above-described shape, and may be any shape that includes a portion with a larger diameter than the cam follower 94 (the flange 96a of the collar 96) and allows movement (eccentricity) of the cam follower 94. For example, by forming the mounting groove 92b into an elongated hole shape with a major axis in the optical axis direction, that is, a shape that allows movement of the engaged cam follower 94 in the optical axis direction, it is possible to adjust the inclination of the lens frame 90 relative to the optical axis (tilt of the lens group). Furthermore, by forming the mounting groove 92b into a shape in which multiple elongated holes intersect, or into a perfect circle with a larger diameter than the cam follower 94 (the flange 96a of the collar 96), it is possible to perform multiple adjustments of the up-down, left-right position and inclination of the lens frame 90.

[0032] Furthermore, as long as at least one cam follower 94 is mounted in the mounting groove 92b, the mounting positions (either mounting groove 92a or 92b) and the number of the other cam followers 94 are not important. The cam followers 94 may be mounted in multiple mounting grooves 92b (all of the cam followers 94 may be mounted in the mounting grooves 92b), and the cam followers 94 may be configured to be eccentric in each mounting groove 92b. Furthermore, each mounting groove 92b may be formed with a different shape. However, as shown in this embodiment, arranging a small number of cam followers 94 at equal intervals in the circumferential direction and configuring one of them to be eccentric is advantageous in terms of facilitating assembly and alignment operations and reducing the number of parts.

[0033] In this embodiment, the lens device 1 has been described as a projection lens mounted in a projector, but the present invention can also be applied to lenses used in optical devices such as cameras and telescopes. [Explanation of symbols]

[0034] 1 Lens device 2 Lens barrel 10 Fixed cylinder part 60, 70, 80 cam barrel 90 Lens frame 92a, 92b Mounting groove 94 Cam follower 100 fixing screws

Claims

1. The lens barrel includes a fixed barrel portion, a cam barrel rotatably attached to the fixed barrel portion, and a lens frame that holds a lens group, a lens device in which a rotational displacement of the cam barrel is converted into a movement of the lens barrel in an optical axis direction by engaging a plurality of cam followers detachably attached to an outer peripheral surface of the lens frame with cam grooves formed in the fixed cylinder portion and the cam cylinder, the cam follower has a configuration that allows it to be eccentric with respect to a fixing screw that fixes the cam follower, the lens frame has a plurality of mounting grooves to which the cam followers are attached, At least one of the plurality of mounting grooves is formed to have a larger diameter than the cam follower. A lens device characterized by:

2. The large diameter shape is an elongated hole shape with a long diameter in the circumferential direction or the optical axis direction.

2. The lens device according to claim 1, wherein:

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