JP2005227405A - Optical device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To hold a diffraction optical element unit without causing the deformation of the diffraction optical element unit and upsizing thereof. <P>SOLUTION: The optical device is provided with the diffraction optical element unit DU obtained by superposing 1st and 2nd diffraction optical elements D1 and D2 where diffraction gratings 1, 3 and 4 are formed on base members 12 and 13 so that the diffraction grating sides may face to each other, a holding member 15 having a 1st abutting part A1 on which the 1st diffraction optical element abuts in a 1st direction along an optical axis and holding the diffraction optical element unit, and a presser means 16 pressing the 2nd diffraction optical element in the 1st direction. The 1st and the 2nd diffraction optical elements respectively have a 2nd abutting part A2 where either of them abuts on the other in the optical axis direction out of the area where the diffraction element is formed. The 1st and the 2nd abutting parts and the pressing position A3 of the 2nd diffraction optical element by the presser means are arranged on the same axis A parallel with the optical axis. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical apparatus using a diffractive optical element, and more particularly to an optical apparatus that needs to hold a laminated diffractive optical element unit.

  Conventionally, as a method of holding an optical element including a diffractive optical element, as shown in FIG. 5, one surface of the optical element 200 is brought into contact with a holding member 201, and the other end 201a of the holding member 201 is heated. There is a heat caulking method in which the other surface of the optical element 200 is caulked.

  Further, as shown in FIG. 6, one surface of the optical element 200 is brought into contact with the holding member 201, and a holding ring 202 is tightened to the other end side of the holding member 201 with a screw, and the other surface of the optical element 200 is There is also a way to hold down.

  Further, as shown in FIG. 7, one surface of the optical element 200 is brought into contact with the holding member 201, and a so-called C ring 203 is fitted into a recess formed on the other end side of the holding member 201. There is also a method of pressing the other surface of the optical element 200 on the inner peripheral side. In addition, there is a method of bonding the optical element to the holding member.

As a method for holding the diffractive optical element, as proposed in Patent Document 1, a surface on which the diffraction grating is not formed is provided as a fixing region on the outer peripheral side of both surfaces of the optical element and is held there. There is a method of sandwiching between the part and the holding ring.
Japanese Laid-Open Patent Publication No. 10-274706 (paragraphs 0016, 0023, FIG. 5, etc.)

  However, in a diffractive optical element unit in which two diffractive optical elements, each of which has a diffraction grating formed of a resin or the like on a base member, are stacked so that the diffraction grating side faces each other, Provided. In addition, a sealing material for sealing the air layer is disposed on the outer periphery of both elements. For this reason, when a holding force (pressing force) in the optical axis direction is applied to the outermost peripheral portion of the diffractive optical element unit, the distance between the two elements (air layer) cannot be maintained at a predetermined distance, and the diffractive optical element unit is distorted. As a result, the optical performance required for the diffractive optical element unit may not be exhibited.

  In order to reduce the size, if the outer diameter of the diffractive optical element unit is reduced without changing the effective diameter of the diffractive optical element unit (the diameter of the region where the diffraction grating is formed), the diffraction grating and the diffractive optical element unit Therefore, harmful light reflected on the outer peripheral portion (for example, a light beam traveling toward the image side without contributing to the original image formation) is likely to be generated.

  An object of the present invention is to provide an optical device that holds a diffractive optical element unit without causing deformation or the like and without increasing its size, and that is less susceptible to harmful light.

  In order to achieve the above object, an optical device according to one aspect of the present invention includes a first diffractive optical element and a second diffractive optical element, each having a diffraction grating formed on a base member, so that the diffraction grating side faces each other. The diffractive optical element unit, the first diffractive optical element has a first abutting portion that abuts in the first direction along the optical axis, and holds the diffractive optical element unit; Pressing means for pressing the diffractive optical element in the first direction. Each of the first and second diffractive optical elements has a second abutting portion that abuts the other diffractive optical element in the optical axis direction outside the region where the diffraction grating is formed. The first abutting portion, the second abutting portion, and the pressing position of the second diffractive optical element by the pressing means are on the same axis parallel to the optical axis (or at a substantially equidistant position from the optical axis). Is arranged.

  According to the present invention, the diffractive optical element unit can be held without causing deformation, and appropriate optical performance required for the diffractive optical element unit can be obtained.

  Embodiments of the present invention will be described below with reference to the drawings.

  First, FIG. 1 shows a configuration of an interchangeable lens apparatus as an optical apparatus that is an embodiment of the present invention. In this figure, 101 is a fixed barrel constituting the main body of the interchangeable lens apparatus, and 102 is a first lens barrel that is movable with respect to the fixed barrel 101 in the optical axis direction. Reference numeral 103 denotes a second lens barrel that can move in the optical axis direction with respect to the first lens barrel 102.

  L1 to L6 are first to sixth lens units arranged in order from the object side (left side in the drawing). Of these first to sixth lens units L1 to L6, the focal length can be changed by moving the first, third, fourth and sixth lens units L1, L3, L4 and L6 in the optical axis direction. it can. In the drawing, the upper half shows the tele end state, and the lower half shows the wide end state.

  A mount 105 for mounting on a camera (not shown) is attached to the rear end portion of the fixed cylinder 101.

  Reference numeral 106 denotes a focus driving unit for performing focus driving of a predetermined lens unit. Reference numeral 107 denotes a shake correction unit that shifts the second lens unit L2 in the direction perpendicular to the optical axis to correct image shake caused by vibration of the lens device. An electromagnetic diaphragm unit 108 moves in the optical axis direction integrally with the third lens unit L3.

  1 and 2 show a first lens unit L1 fixed in the second lens barrel 103 of the lens device and a holding structure thereof.

  In FIG. 1, the first lens unit L1 includes a first lens element 11 disposed closest to the object side, and a second lens element 12 and a third lens element 13 in order from the object side. Between the second lens element 12 and the third lens element 13, as shown in detail in FIG. 3, three layers of diffraction gratings 1, 3, and 4 are laminated.

  Here, the second lens element 12, the diffraction gratings 1, 3, 4 and the third lens element 13 constitute a diffractive optical element unit (laminated diffractive optical element) DU.

  As shown in FIG. 3, the diffractive optical element unit DU includes a second lens element 12 as a base member, and a blazed first diffraction grating 1 formed on the image-side surface of the second lens element 12. The first diffractive optical element D1 and the third lens element 13 are used as a base member, and a blazed second diffraction grating 3 is formed on the object side surface of the third lens element 13, and is also shared with the second diffraction grating 3. And a second diffractive optical element D2 on which a third diffraction grating 4 having the above-described grating surface is formed. That is, the diffractive optical element unit DU is configured as one unit by overlapping the first and second diffractive optical elements D1 and D2 so that the diffraction grating side faces each other. In the present embodiment, the second and third lens elements 12, 13 are made of an optical glass material, and the first to third diffraction gratings 1, 3, 4 are made of a resin material. The resin material may have a different refractive index for each diffraction grating or may be the same.

  Further, the object side surface of the resin material forming the third diffraction grating 4 in the diffractive optical element unit DU is a smooth surface, and an air layer S is formed between the smooth surface and the first diffraction grating 1. Is formed. Further, a portion of the smooth surface in the region A2 on the outer peripheral side of the region G where each diffraction grating is formed, and a smooth surface on the image side in the resin material forming the first diffraction grating 1, the region A2 The inner portions abut on each other in the direction of the optical axis L (see FIG. 2) of the diffractive optical element unit DU. This abutting portion (second abutting portion, hereinafter referred to as A2) keeps the distance (air layer S) between the first diffraction grating 1 and the second and third diffraction gratings 3 and 4 constant. To function as a spacer.

  Further, the outermost peripheral portion of each of the image side surface of the second lens element 12 and the object side surface of the third lens element 13 and a region on the outer peripheral side of the contact portion A2 (each diffraction grating and smoothing surface). A sealing material 6 that seals the air layer S and prevents the influence of the environment on the diffraction grating is disposed in the ejector abutting region when releasing from the surface.

  Note that the air layer S also exists between the sealing material 6, the resin material forming the first diffraction grating 1, and the resin material forming the third diffraction grating 4 on the outer peripheral side of the contact portion A <b> 2. Exists.

  The diffractive optical element unit DU configured as described above is held by the holding structure shown in FIGS.

  1 and 2, reference numeral 15 denotes a holding cylinder for holding the first lens unit L1 (first to third lens elements 11 to 13) (however, the first lens element 11 is omitted in FIG. 2). .

  As shown in FIG. 2, a first holding portion 15 c that holds the first lens element 11 is formed at the front end portion (however, the upper end portion in FIG. 2) of the holding cylinder 15. On the lower side in FIG. 2, the object side surface (upper side in FIG. 2) of the second lens element 12 of the diffractive optical element unit DU inserted from the image side (lower side in FIG. 2) into the holding cylinder 15. A ring-shaped contact portion (first contact portion) 15a is formed in which the outer peripheral portion contacts the object direction (first direction along the optical axis L). A contact position between the contact portion 15a and the second lens element 12 is indicated by A1 in FIG.

  Further, when the diffractive optical element unit DU is inserted into the holding cylinder 15 so as to abut on the abutting portion 15 a, the second lens element 12 is lightly press-fitted into the front inner peripheral portion 15 d of the holding cylinder 15. The As a result, the entire diffractive optical element unit DU is positioned with respect to the holding cylinder 15 in the direction perpendicular to the optical axis.

  A ring-shaped elastic member 17 is arranged on the outer peripheral portion of the image side surface of the third lens element 13 in the diffractive optical element unit DU which is positioned in the holding cylinder 15 in the optical axis direction and the optical axis orthogonal direction. Is done. As the elastic member 17, rubber, a washer, etc. can be used. Then, the holding ring 15 is fastened to the holding cylinder 15 using a female screw 15 b formed on the inner peripheral surface of the holding cylinder 15.

  Here, the holding ring 16 extends from the front end of the cylindrical portion 16a toward the inner peripheral side in which a male screw (not shown) corresponding to the female screw 15b of the holding cylinder 15 is formed. And a pressing portion 16b.

  When the pressing ring 16 is tightened with respect to the holding cylinder 15, the pressing portion 16b presses the third lens element 13 (that is, the diffractive optical element unit DU) in the object direction via the elastic member 17. A position where the pressing ring 16 pushes the diffractive optical element unit DU (actually, a position where the elastic member 17 and the third lens element 13 abut) is indicated by A3 in FIG. Thereby, the diffractive optical element unit DU is fixed in a state where the position in the optical axis direction is determined with respect to the holding cylinder 15.

  In the present embodiment, in a state where the diffractive optical element unit DU is held by the holding cylinder 15, the contact position A1 between the diffractive optical element unit DU and the contact portion 15a of the holding cylinder 15 and the corresponding position in the diffractive optical element unit DU. The dimensions of the respective portions are set so that the contact portion A2 and the position A3 where the pressing ring 16 pushes the diffractive optical element unit DU are arranged on the axis A parallel to the optical axis L. In other words, the dimensions of each part are set so that the contact position A1, the contact part A2, and the pressing position A3 are arranged at substantially equal distances from the optical axis L.

  Thereby, the stress generated in each part of the diffractive optical element unit DU by the pressing ring 16 pushing the diffractive optical element unit DU acts around the axis A passing through the contact part A2 in the diffractive optical element unit DU. Therefore, deformation such as distortion or displacement inside the diffractive optical element unit DU (for example, bending of the diffraction grating with the contact portion A2 as a fulcrum, or the first diffractive optical element of the second diffractive optical element D2 along the smooth surface) (Displacement with respect to the element D1) can be made difficult to occur.

  The elastic member 17 is interposed between the pressing ring 16 and the diffractive optical element unit DU, so that the pressing force applied from the pressing ring 16 to the diffractive optical element unit DU can be uniformly dispersed. That is, the pushing force can be uniformly applied to a certain range around the axis A of the diffractive optical element unit DU, and local stress concentration can be prevented.

  In the present embodiment, the case where the elastic member 17 is disposed between the presser ring 16 and the diffractive optical element unit DU has been described. However, the presser ring 16 itself is formed as a member having appropriate elasticity, and elasticity as a separate member. The member 17 may be unnecessary.

  Further, when the presser ring 16 is rotated with respect to the holding cylinder 15 for screw connection, the elastic member 17 may be deformed by friction with the presser ring 16 to cause uneven pressure. In this case, as shown in FIG. 4, the sliding member 18 is sandwiched between the elastic member 17 and the pressing ring 16 or between the elastic member 17 and the diffractive optical element unit DU, thereby causing the pressure unevenness as described above. Further, deformation of the diffractive optical element unit DU due to this can be avoided.

  In this embodiment, the holding method using the pressing ring 16 has been described. However, as a method for pressing the diffractive optical element unit DU (that is, a holding method), a heat caulking method can also be employed. In this case, the position where the diffractive optical element unit DU is pushed by heat caulking may be set on the axis A shown in FIG.

  Moreover, although the present Example demonstrated the case where the pressing ring 16 was attached to the holding cylinder 15 with a screw, you may make it press-fit a holding ring with respect to a holding cylinder.

  Furthermore, in the present embodiment, a case where the contact portion (first contact portion) 15a of the holding cylinder 15 and the pressing position by the pressing ring 16 are set so as to extend over almost the entire circumference of the diffractive optical element unit DU. As described above, the corresponding contact portion and the pressing position may be set at a plurality of places in at least three places in the circumferential direction. In this case, each contact portion, the pressing position, and the contact portion (second contact portion) in the diffractive optical element unit DU may be arranged on the same axis A.

  Further, due to the miniaturization of the diffractive optical element unit DU (that is, the miniaturization of the entire lens apparatus), the difference between the outer diameter of the diffractive optical element unit DU and the effective diameter of the light incident thereon tends to be small. . That is, there is a possibility that the diffraction grating is formed to the limit of the contact portion A2 of the diffractive optical element unit DU. For this reason, harmful light (that is, light that should not be used for image formation by the photographing optical systems (L1 to L6) in the lens device) is likely to be generated due to reflection on the contact portion A2 and the surrounding surface. For this reason, as shown in FIG. 2, the harmful light R may be cut by the pressing ring 16 or the elastic member 17 to avoid the occurrence of ghosts or the like. In addition, as shown in FIG. 4, you may give this sliding member 18 the function to cut this harmful light.

  As described above, according to this embodiment, the diffractive optical element unit can be held by the holding member while preventing deformation of the air layer of the diffractive optical element unit. Performance can be obtained.

  Moreover, according to the present Example, it can hold | maintain to the holding cylinder 16 in the part close | similar to a diffraction grating among diffractive optical element units DU. Therefore, the diffractive optical element unit DU can be reduced in size without reducing the effective beam diameter of the diffractive optical element unit DU.

  In addition, since harmful light generated in the second contact portion is performed by the pressing member 16, the elastic member 17, and the sliding member 18, it is not necessary to separately provide a member dedicated to harmful light cutting.

  In this embodiment, the interchangeable lens device has been described. However, the present invention may be applied to a diffractive optical element holding structure in a lens-integrated camera or a video camera, or a diffractive optical element holding structure in a projection lens of a projector. You may apply to.

Sectional drawing of the interchangeable lens apparatus which is an Example of this invention. Sectional drawing explaining the holding structure of the diffractive optical element unit in an Example. The expanded sectional view of the diffractive optical element unit in an Example. Sectional drawing which shows the modification (example using a sliding member) of an Example. The figure which shows the holding method (heat caulking) of the conventional optical element. The figure which shows the holding method (holding ring) of the conventional optical element. The figure which shows the holding method (C ring) of the conventional optical element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st diffraction grating 3 2nd diffraction grating 4 3rd diffraction grating 6 Sealing material,
12, 13 Lens element 15 Holding cylinder 16 Holding ring 17 Elastic member 18 Sliding member DU Diffractive optical element unit D1, D2 Diffractive optical element

Claims (10)

A diffractive optical element unit in which first and second diffractive optical elements each having a diffraction grating formed on a base member are overlapped so that the diffraction grating sides face each other;
A holding member that holds the diffractive optical element unit, the first diffractive optical element having a first abutting portion that abuts in a first direction along the optical axis;
Pressing means for pressing the second diffractive optical element in the first direction;
Each of the first and second diffractive optical elements has a second contact portion that contacts the other diffractive optical element in the optical axis direction outside the region where the diffraction grating is formed,
The first contact portion, the second contact portion, and the pressing position of the second diffractive optical element by the pressing means are arranged on the same axis parallel to the optical axis. An optical device. The diffractive optical element unit has a sealing material for sealing a space between the first diffractive optical element and the second diffractive optical element,
The optical device according to claim 1, wherein the second contact portion is provided between the diffraction grating and the sealing material in a direction orthogonal to the optical axis.   The optical device according to claim 1, wherein the diffraction grating and the second contact portion are made of resin.   The optical apparatus according to claim 1, wherein the pressing unit is a pressing member attached to the holding member.   5. The optical device according to claim 1, wherein an elastic member is disposed between the pressing unit and the second diffractive optical element.   The optical device according to claim 4, wherein the pressing member is made of an elastic material.   The optical apparatus according to claim 1, wherein the pressing unit blocks a light beam generated at the second contact portion.   The optical device according to claim 5, wherein the elastic member blocks a light beam generated at the second contact portion. The pressing means is a pressing member that is attached to the holding member by rotation.
A sliding member that is arranged between the elastic member and the pressing member or between the elastic member and the diffractive optical axis element unit, and that allows sliding in the rotational direction;
The optical device according to claim 5, wherein the sliding member blocks a light beam generated at the second contact portion.   10. The interchangeable lens apparatus according to claim 1, wherein the interchangeable lens apparatus is attached to a photographing apparatus.

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