JP2011209750A - Optical element and optical device having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical element configured so that distortion caused on an optical effective surface by fixing can be reduced or preferably eliminated, and an optical device having the optical element.SOLUTION: The optical element includes the optical effective surface and a holding part for fixing the optical element. The holding part includes a part connected to the optical effective surface, which is provided to have a stepped part between the part connected to the optical effective surface and the optical effective surface, and a cutout is formed in the part connected to the optical effective surface.

Description

  TECHNICAL FIELD The present invention relates to an optical element and an optical apparatus having the optical element, and in particular, a shape capable of reducing (preferably eliminating) distortion generated on an optically effective surface due to fixing when the optical element is attached to a housing or the like. And an optical apparatus having the optical element.

Conventionally, as a method of attaching an optical element to a housing or the like, there are fixing with screws, an adhesive such as an ultraviolet curing type, pinching, pressing, or the like.
In recent years, with the miniaturization of devices, there is an increasing demand for miniaturization of internal optical elements, and the demand for accuracy has become stronger. While it has become difficult to enlarge the fixing portion for mounting due to the miniaturization of the optical element, it is further difficult to hold the optical element that has been reduced in size and fix it on the optical effective surface. It has become even more necessary to reduce the effects of distortion.

  For this reason, in Patent Document 1, when the optical element 6 is pressed and fixed to the optical element holder 1 as shown in FIG. 12, the thickness is more than half of the thickness between the pressing portion and the optical effective surface. A means has been proposed in which the slit 8 is provided to prevent the pressure distortion from propagating to the optically effective surface.

JP 2004-198575 A

  However, as in the optical element of Patent Document 1 of the above-described conventional example, if a slit that is more than half of the thickness direction is provided, a crack will enter from the part where the slit enters due to impact, etc. Problem arises.

  In view of the above problems, an object of the present invention is to provide an optical element having a structure capable of reducing, and preferably eliminating, distortion generated on an optically effective surface by fixing, and an optical apparatus having the optical element. Is.

In order to achieve the above object, the present invention provides an optical element configured as follows and an optical apparatus having the optical element.
That is, the optical element of the present invention is an optical element comprising an optically effective surface and a holding part for fixing the optical element,
The holding portion has a portion connected to the optical effective surface, and a step is provided between the portion connected to the optical effective surface and the optical effective surface, and a notch is formed in the portion connected to the optical effective surface. It is characterized by being formed .
Also, the optical apparatus of the present invention is characterized by having a light optical element described above.

  ADVANTAGE OF THE INVENTION According to this invention, when hold | maintaining an optical element to a housing | casing etc., the distortion which arises on the optical effective surface of an optical element can be reduced, maintaining holding strength.

1 is a diagram showing a configuration of an optical element in Example 1 of the present invention. FIGS. 2A and 2B are views for explaining Example 1 of the present invention, FIG. 2A is a view of the optical element as viewed from the optical effective surface side, and FIG. FIG. Explanatory drawing about the fixing method of the optical element in Example 1 of this invention. The figure which shows the structure of the optical element in Example 2 of this invention. FIGS. 5A and 5B are views for explaining Example 2 of the present invention, FIG. 5A is a view of the optical element as viewed from the optical effective surface side, and FIG. FIG. Explanatory drawing about the fixing method of the optical element in Example 2 of this invention. The figure which shows the other form of the screw hole shape in Example 2 of this invention. The figure which shows the structure of the optical element in the reference example of this invention. The figure which shows the structure of the BB cross section of the optical element of FIG. 8 in the reference example of this invention. Explanatory drawing about the fixing method of the optical element in the reference example of this invention. The figure explaining the necessity of providing a level | step difference between the optically effective surface and fixed plane part in the reference example of this invention. The figure explaining the optical element of patent document 1 which is a prior art example.

Shaped state for carrying out the present invention will be illustrated by the following examples.

Examples of the present invention and reference examples will be described below.
[Example 1]
In Example 1, the present invention was applied to configure an optical element having an optical reflecting surface.
FIG. 1 is a perspective view of the configuration of the optical element of this embodiment.
In FIG. 1, reference numeral 101 denotes an optical element.
Reference numeral 102 denotes an optically effective surface on which a reflective film for reflecting the light beam in the optical element 101 is deposited. This optically effective surface is one surface of the optically effective portion in the optical element 101.
103 (a) and 103 (b) may be fixed plane portions (fixing portions or holding portions) for fixing (holding) the optical element 101, and a holding member for holding the optical element may be bonded or screwed. (It may be referred to as a connecting portion in the sense that the portion is connected through the connector 103).
FIG. 2A shows a configuration in which the above-described optical element is viewed from the optical effective surface side.
FIG. 2B shows a configuration of a cross section BB of the optical element in FIG.
In this embodiment, as shown in FIG. 2B, the optically effective surface 102 is formed of a non-rotationally symmetric surface shape, a so-called free-form surface. Therefore, in order to configure the fixed plane portion 103 as a flat surface, a step is provided between the fixed plane portion 103 and the optically effective surface 102 configured with a free-form surface as shown in FIG. Yes.

Since the optical element of the present embodiment is axisymmetric with respect to the center (A-A line) of the optical element as shown in FIG. 2A, the specific configuration of the cutout portion is mainly on the paper surface. The left part will be explained.
In this embodiment, four cutout portions 201 (a), (b), (c), and (d) are provided on the optically effective surface 102 side of the fixed plane portion 103.
The notch width shown in the figure (the notch width in the horizontal direction in FIG. 2A), ie, the direction in which the fixed portion sandwiches the optical element, b ₁ is 0.1 mm (more preferably 0.5 mm) or more and 3 mm (more preferably Is 1 mm) or less. Thus, by setting the notch width of the fixed plane portion, it is possible to reduce (eliminate) the distortion generated in the optical effective surface 102 due to the fixing (holding) of the optical element. By such notches 201 (a), (b), (c), and (d), a part of the fixed plane portion functions as a beam portion that directly supports the optically effective portion.

Based on the above configuration, L ₁ and b ₁ and the thickness t _{1 of the} fixed portion shown in FIG. 2B can be determined so as to have mechanical characteristics for preventing the beam portion from breaking.
Here, in this embodiment, the notches 201 (a), (b), (c), and (d) are used, but this is not necessarily the case, and the recesses (notches) of another shape are used. It does not matter. However, by providing this recess (notch), the optically effective surface (actually reflects light) due to the force acting on the fixed plane when the fixed plane is fixed (other thermal stress or impact force). It is desirable to have a configuration that can reduce (preferably eliminate) the deformation amount of the surface that is bent or refracted. As one of the means, the transmission rate of the force acting on the fixed plane portion to the optical effective portion is reduced, or even if the force acts on the optical effective portion, the optical effective surface is not deformed so much. For this reason, the position of the optically effective surface is preferably separated from the position where the force transmitted to the optically effective portion works (on the straight line connecting the two beam portions in this embodiment). Here, “releasing the position of the optically effective surface with respect to the position where the force transmitted to the optically effective portion works” at least does not intersect, more preferably the distance between one beam portion and the other beam portion. It is desirable to separate 1/50 (preferably 1/10) or more.

Next, a method for fixing the optical element of this embodiment will be described.
FIG. 3 is an explanatory diagram showing a method for fixing the optical element of this embodiment.
As shown in FIG. 3, the hatched portions on the opposite side of the optically effective surface 102 from the notches are fixed portions 301 (a), (b), (c), and (d). An adhesive is applied within the range of the fixing portions 301 (a), (b), (c), and (d) to fix the optical element 101 to the casing.
As described above, the adhesive is applied within the range of the fixing portions 301 (a), (b), (c), and (d), and is generated by the curing shrinkage of the adhesive to the beam portion connecting the optically effective surface. It is possible to prevent the distortion that occurs from propagating to the optically effective surface 102 and deforming the optically effective surface shape to deteriorate the optical performance.

Moreover, since the notch part 201 also becomes a relief part of the adhesive which has been applied too much, a uniform adhesive layer can be formed.
Further, by increasing a ₁ and b ₂ , the bonding area can be increased, and the bonding strength can be increased. As a result, a ₁ and b ₂ can be determined according to the required adhesive strength, and the shape of the entire optical element can be determined.
According to the present embodiment, it is possible to reduce the distortion generated by the curing shrinkage of the adhesive to the optically effective surface 102 with the above configuration, and it is possible to reduce the thickness of the reflective optical element. . In particular, it is useful in an optical element having a non-rotationally symmetric surface shape that is susceptible to distortion caused by fixation. Moreover, the said notch part can be produced simultaneously when forming an optical effective surface in press molding or injection molding, and can be produced integrally without post-processing.

In this embodiment, the optically effective surface 102 is a free-form surface having a non-rotationally symmetric surface shape, but the optically effective surface 102 may be a flat surface.
In addition, as shown in FIG. 2B, the back side of the optically effective surface 102 is a plane, but the present invention is not limited to this. Although the reflective film is formed on the optically effective surface 102, it may be formed on the fixed portion 103 as well.
In the embodiment, the cutout portion 201 also serves as an escape portion of the adhesive, but a cutout portion or a groove portion different from the cutout portion 201 for preventing the distortion due to fixation from propagating to the optically effective surface 102 may be provided. good.
Moreover, the notch part 201 does not need to be four places. Further, in the embodiments, the lengths of the notches a ₁ and a ₂ are made equal, but the length is not limited to this, and they may not be equal, and all the notches are not symmetrical with respect to the center. The length of the quantity may vary.

[Example 2]
In Example 2, an optical element having a form different from that of Example 1 was configured by applying the present invention.
FIG. 4 shows a perspective view of the configuration of the optical element of this embodiment.
In FIG. 4, 401 is an optical element.
Reference numeral 402 denotes an optically effective surface on which a reflective film for reflecting the light flux in the optical element 401 is deposited.
Reference numerals 403 (a) and 403 (b) denote fixing flat portions for fixing the optical element 101.
FIG. 5A shows a configuration in which the above-described optical element is viewed from the optical effective surface side.
FIG. 5B shows a configuration of a cross section BB of the optical element in FIG.
In this embodiment, as shown in FIG. 5B, the optically effective surface 402 is formed of a non-rotationally symmetric surface shape, a so-called free-form surface. Therefore, in order to configure the fixed plane portion 403 as a flat surface, a step is provided between the fixed plane portion 403 and the optically effective surface 402 configured as a free-form surface as shown in FIG. Yes.

As shown in FIG. 5A, the optical element of the present embodiment is axisymmetric with respect to the center of the optical element (A-A line). The left part will be explained.
Four notches 501 are provided at the boundary portion between the fixed plane portion 403 and the optically effective surface 402. The notch is divided into a fixed portion and an optically effective portion, and a portion indicated by L ₂ serves as a beam connecting the optically effective portion and the fixed portion. Therefore, L ₂ , b ₃ , and the thickness t _{2 of the} fixed portion shown in FIG. 5B can be determined so as to have mechanical characteristics for preventing the beam portion from breaking.

Next, a method for fixing the optical element of this embodiment will be described.
FIG. 6 is an explanatory diagram showing a method for fixing the optical element of this embodiment.
As shown in FIG. 6, the hatched portion on the opposite side of the optically effective surface 402 from the notch is defined as a fixed portion 601 (a), (b), (c), (d). Screw holes 602 (a), (b), (c), and (d) are provided in the fixing portion 601. The screw hole 602 may not be provided in each fixing portion 601. The projected line of the screw head is indicated by a dotted line in the figure. If the head of the screw reaches the beam portion, the fixing strain due to the screwing will propagate to the optically effective surface 402. Therefore, the position of the screwing is determined so that the screw head indicated by the dotted line enters the fixing portion 601. The optical element 401 is fixed to the casing.

By fixing the screw head so that the head of the screw enters the range of the fixing portion 601, distortion generated by screwing the beam portion connecting the optical effective surface propagates to the optical effective surface 402 and the optical effective surface shape It is possible to prevent the optical performance from being deteriorated by deforming the lens. The shape of the screw hole 602 is not limited to this, and may be a notch shape 701 (a), (b), (c), (d) as shown in FIG. 7 or a semicircular shape (not shown). This makes it possible to determine the required cutout amounts a ₃ and a _{4 and} to determine the shape of the entire optical element.
According to the present embodiment, it is possible to reduce the propagation of the distortion generated by fixing the screw to the optical effective surface 402 with the above configuration.

In this embodiment, the optically effective surface 402 is a free-form surface that is a non-rotationally symmetric surface shape. However, the optically effective surface 402 may be a flat surface. May be in the same plane as the optically effective surface 402.
Further, FIG. 5B shows a diagram in which the back surface side of the optically effective surface 402 is a plane, but the present invention is not limited to this. Although a reflective film is formed on the optically effective surface 402, it may be formed on the fixed portion 403 as well.
In the embodiment, there are four notches 501, but the present invention is not limited to this. Further, in the embodiments, the lengths of the notches a ₃ and a ₄ are made equal, but the length is not limited to this, and they may not be equal, and all the notches are not symmetrical with respect to the center. The length of the quantity may vary.

[ Reference example ]
As a reference example, showing an oblique view of the light optical element in FIG.
FIG. 9 shows the configuration of the optical element shown in FIG.
In FIG. 8, reference numeral 801 denotes an optical element.
Reference numeral 802 denotes an optically effective surface on which a reflective film for reflecting the light beam in the optical element 801 is deposited.
Reference numerals 803 (a) and 803 (b) denote fixing flat portions for fixing the optical element 801.
In the present reference example, as shown in FIG. 9, the optically effective surface 802 is constituted by a non-rotationally symmetric surface shape, a so-called free-form surface. Therefore, in order to configure the fixed plane portion 803 as a flat surface, a step is provided between the fixed plane portion 803 and the optically effective surface 802 configured as a free-form surface as shown in FIG.
Grooves 804 (a) and (b) are provided on the left and right sides at a portion where a step between the optically effective surface 802 and the fixed plane portion 803 is provided.
As shown in FIG. 9, the groove portion 804 is divided into a fixed portion and an optically effective portion, and plays the role of beams 901 (a) and (b) connecting the optically effective portion and the fixed portion.
Therefore, as shown in the figure, the thickness t _{3 of the} fixed portion and the digging amount t ₄ can be determined so that the digging amount t ₄ of the groove 804 has mechanical characteristics for preventing the beam 901 from breaking.

In this reference example, since the optically effective surface 802 and the fixed plane portion 803 are stepped, the digging amount t ₄ is set to be more than half of the thickness t ₃ of the fixed plane portion 803 as in the conventional example. In addition, the distance between the optically effective surface 802 and the apex of the groove 804 can be increased. Therefore, in this reference example, by setting the digging amount t ₄ to be a digging amount that is not more than half of the fixed plane portion thickness t ₃ , it is possible to prevent the distortion caused by the fixation from propagating to the optical effective surface 802. It becomes possible.
Further, when the optical element 801 is manufactured by a molding die, if the digging amount t ₄ is set to be more than half the thickness t ₃ of the fixed flat portion 803 as in the conventional example, the flow of the molding material is deteriorated. However, in this reference example, the digging amount t ₄ can be made shallow as described above, which is also advantageous in this respect. In addition, according to the configuration in which the optically effective surface 802 and the fixed flat surface portion 803 are provided with a step as in the present reference example, it is advantageous in that the adhesive is not easily affected even when the adhesive protrudes.

Next, a method for fixing the optical element of this reference example will be described.
FIG. 10 is an explanatory diagram showing a method for fixing the optical element of this reference example.
As indicated by the oblique lines in FIG. 10, the fixed plane portion 803 opposite to the optically effective surface 802 with the groove portion 804 as an axis is defined as fixed portions 1001 (a) and (b). An adhesive is applied within the range of the fixing portion 1001, and the optical element 801 is fixed to the casing.
By applying an adhesive within the range of the fixed part 1001, distortion generated by curing shrinkage of the adhesive with respect to the beam part connecting the optically effective surface propagates to the optically effective surface 802 and deforms the optically effective surface shape. Deteriorating optical performance can be prevented.
Further, since the groove portion 804 also serves as a relief portion for the adhesive that has been applied too much, a uniform adhesive layer can be formed. In addition to the groove portion, another groove portion may be provided for the escape portion of the adhesive.
Further, since it is possible to increase the bonding strength can be increased bonding area by increasing the L _3, b _5, it is possible to determine the L ₃ and b ₅ in accordance with the bond strength to seek, The shape of the entire optical element can be determined.

Next, another reason regarding the necessity of providing a step between the optically effective surface 802 and the fixed flat surface portion 803 when bonding and fixing will be described with reference to FIG.
If there is no step between the optically effective surface 802 and the fixed flat surface portion 803 as shown in FIG. 11A, the adhesive 1101 protrudes from the groove and adheres to the vicinity of the optically effective surface, and distortion due to curing shrinkage of the adhesive 1101 occurs. The possibility of affecting the optically effective surface 802 arises. However, as shown in FIG. 11B, by providing a step between the optically effective surface 802 and the fixed flat surface portion 803, the adhesive 1101 beyond the groove portion 804 adheres to a portion where the optically effective surface 802 is located. The lower portion is less likely to affect the optically effective surface.
According to this reference example, with the above configuration, it is possible to reduce the propagation of distortion due to fixation such as curing shrinkage of the adhesive to the optically effective surface 802. Further, the groove part can be produced simultaneously with the formation of the optically effective surface in press molding or injection molding, and can be produced integrally without any post-processing.

In the present reference example, FIG. 9 shows a configuration in which the back surface side of the optical effective surface 802 is a plane, but the present invention is not limited to such a configuration.
Further, although a reflective film is formed on the optically effective surface 802, it may also be formed on the fixed flat surface portion 803.
In this reference example, the groove portion 804 is semicircular, but other shapes such as a rectangular shape may be used, and a tapered portion may be provided in order to remove the mold.
Further, although the groove portion 804 also serves as a relief portion of the adhesive, a notch portion or a groove portion different from the groove portion 804 for preventing the distortion caused by the fixation from propagating to the optically effective surface 802 may be provided.
Furthermore, the groove portion 804 crosses all between the fixed portion and the optically effective portion. However, the groove portion 804 is not limited to this, and may be intermittently crossed between the optically effective portion. Further, the lengths of all the cutout amounts may be changed instead of being symmetrical with respect to the center.
The optical element examples and reference examples have been described above. However, the optical elements in these examples and reference examples may be reflective optical elements (mirrors), or transmissive optical elements (for example, having a refractive power). A certain lens or a diffractive optical element), or a dichroic mirror, a polarizing beam splitter, a wavelength plate, a polarizing plate, or the like.
Further, the optical elements of these examples and reference examples can be applied to various optical instruments. Moreover, as an optical apparatus using these optical elements, for example, an imaging lens (interchangeable lens), an imaging device (camera), a head mounted display (glasses-type image display device), a projector (liquid crystal projector or the like), and the like are conceivable. . Of course, you may apply to optical apparatuses other than the optical apparatus described here.
Since the optical elements to which these embodiments and reference examples are applied can reduce the deformation of the optically effective surface (preferably without deformation), it is desirable that the optical element be applied to a position with particularly high surface accuracy. For example, when applied to a projector or the like that performs light modulation with a liquid crystal panel or the like (image display element), it is preferably arranged at the rear stage of the liquid crystal panel, and light modulation is performed by controlling light emission with a light source. When applied to a projector or the like that scans using a scanning optical system, it is preferably disposed after the scanning optical system.
Various examples described in this specification may be used in any combination.

101: Optical element 102: Optical effective surface 103: Fixed flat surface portion 201: Notch portion 301: Fixed portion

Claims (5)

An optical element comprising an optically effective surface and a holding part for fixing the optical element,
The holding portion has a portion connected to the optical effective surface, and a step is provided between the portion connected to the optical effective surface and the optical effective surface, and a notch is formed in the portion connected to the optical effective surface. An optical element is formed. The optical element according to claim 1 wherein the optical effective surface and having a non-rotationally symmetric surface shapes, the holding portion, characterized in that it have a flat portion. The optical element according to claim 1 or claim 2 wherein the optical effective surface, characterized in that the reflection film is formed. The notch has an optical element according to any one of claims 1 to 3, characterized in that also serves as a relief portion of the adhesive in fixing the adhesive the optical element. An optical apparatus comprising the optical element according to any one of claims 1-4.

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