JP2000131583A - Structure for holding optical member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure for holding optical member which can maintain flatness of an optical member even when the ambient temp. changes. SOLUTION: The holding frame 1 to support a thin plate-like dichroic mirror 2 consists of a material having a different linear expansion coefft. from that of the dichroic mirror 2. An elastic adhesive 4 to adhere the dichroic mirror 2 to the holding frame 1 can be elastically deformed large that the difference of linear expansion between the mirror 2 and holding frame 1. The holding frame 1 has three minute projections 3, and the dichroic mirror 2 are supported on the three points of minute projections 3. The elastic adhesive 4 is annularly applied in a minute area slightly distant from each projection 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical member holding structure, for example, a thin plate dichroic mirror holding structure used in a three-plate color separation optical system of a color image input device.

[0002]

2. Description of the Related Art A thin plate optical member such as a filter, a reflection mirror, and a dichroic mirror is used in a three-plate color separation optical system of a color image input apparatus. In order to hold these optical members at predetermined positions, it is necessary to fix the optical members to the positioned holding frame. As the fixing method, the following two types are conventionally known. A method of bonding and fixing an optical member to a holding frame over a wide area using an adhesive (for example, an adhesive made of an ultraviolet curable resin)
(JP-A-5-191733, JP-A-4-133008)
No.). A method in which an optical member is pressed and fixed to a holding frame over a wide area using an elastic member such as a pressing spring.

[0003]

Since three CCD (Charge Coupled Device) units are arranged close to each other in the three-plate type color separation optical system, during actual use, the color separation optical system itself is in a considerably high temperature state. turn into. Therefore,
In the holding structure adopting the above-described fixing method, when the linear expansion coefficient differs greatly between the optical member and the holding frame {for example, the dichroic mirror is made of a glass material, and the holding frame is made of a resin material or a metal material (aluminum material, iron material). ), The optical member is greatly affected by temperature changes in the environment. A dichroic mirror configured to be thin in order to improve the imaging performance of the color separation optical system is more greatly affected. This problem will be described for each fixing method, taking as an example a case where a dichroic mirror is held as an optical member.

In the holding structure employing the fixing method, the dichroic mirror is fixed to the holding frame with a highly rigid adhesive. Therefore, when the environmental temperature changes, the stress due to the difference in linear expansion between the dichroic mirror and the holding frame is increased. Occurs. As a result, distortion occurs in the dichroic mirror having low rigidity, and in the worst case, cracks occur. When the dichroic mirror is distorted, its flatness is impaired, so that the reflection position and the reflection direction of the light beam change, and as a result, a color shift occurs in the input image.

In the holding structure employing the fixing method, the contact area between the holding frame and the elastic member with respect to the dichroic mirror is large, so that the frictional resistance between the members becomes large. Therefore, when the difference in linear expansion occurs due to a change in environmental temperature, the dichroic mirror is dragged by the holding frame, and a stress is generated therein. Therefore, the dichroic mirror, which has a lighter degree than that of the fixed type, still has a low rigidity, and causes distortion.

The present invention has been made in view of such circumstances, and has as its object to provide an optical member holding structure capable of maintaining the flatness of an optical member even when the environmental temperature changes. .

[0007]

In order to achieve the above object, an optical member holding structure according to a first aspect of the present invention comprises a thin plate-shaped optical member, a support member for supporting the optical member, and an optical member. An optical member holding structure comprising: an elastic adhesive that adheres to the support member; wherein the support member is made of a material having a different linear expansion coefficient from the optical member, and the elastic adhesive is the optical member. It is characterized in that it can be elastically deformed more than the difference in linear expansion between the support member and the support member.

In the optical member holding structure according to a second aspect of the present invention, in the configuration of the first aspect, the support member has three minute projections, and the optical member is supported by the three minute projections. The elastic adhesive is applied to a minute area slightly separated from each minute projection.

An optical member holding structure according to a third aspect of the present invention is a thin plate-shaped optical member, a supporting member for supporting the optical member, a pressing member for pressing the optical member toward the supporting member,
An optical member holding structure comprising: an elastic adhesive for bonding the optical member and the pressing member; wherein the pressing member is made of a material having a different linear expansion coefficient from the optical member; Are elastically deformable more than the difference in linear expansion between the optical member and the pressing member.

In the optical member holding structure according to a fourth aspect of the present invention, in the configuration of the third aspect, the pressing member has three minute projections, and the optical member is pressed by the three minute projections. The elastic adhesive is applied to a minute area slightly separated from each minute projection.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an optical member holding structure embodying the present invention will be described with reference to the drawings. Note that the same or corresponding portions in the embodiments are denoted by the same reference numerals, and redundant description will be appropriately omitted. Also, x, y,
z indicates directions orthogonal to each other.

<< Configuration Example of Color Image Input Apparatus (FIG. 21) >>
FIG. 21 shows a schematic configuration of a color image input device. The color image input device includes a scanner 42, a lens 43
(AX: lens optical axis) and a color separation optical system 44. The scanner 42 includes a light source 45, a reflecting mirror 46, and three plane mirrors 47, and scans the image of the document 41 by moving in the direction of the arrow. The lens 43 is a reading optical system of a reduction type, and RGB images are read by a color separation optical system 44 disposed behind the lens 43.

<< Configuration Example of Three-Plate Color Separation Optical System (FIG. 22) >>
FIG. 22 shows a schematic configuration of the color separation optical system 44. The color separation optical system 44 located behind the lens 43 includes dichroic mirrors 48 and 49 having a thin plate shape (thickness of 0.3 to 1 mm) fixed to a holding frame; linear sensors (light receiving elements such as CCDs) 50;
51, 52; transmission filter 53; and reflection mirror 5
4,55. Dichroic mirror 48, 4
Reference numeral 9 denotes a structure in which a dichroic film is formed on a thin plate-shaped transparent substrate.
B is separated into three colors. Two dichroic mirrors 4
The light transmitted through 8, 49 is received by the linear sensor 52 on the lens optical axis AX through the transmission filter 53, while the color light reflected by the dichroic mirrors 48, 49 is reflected by the reflection mirrors 54, 55. Then, the light is received by the linear sensors 50 and 51, respectively.

Since the color lights reflected by the dichroic mirrors 48 and 49 form a shallow angle with respect to the lens optical axis AX, if the linear sensors 50 and 51 are to directly receive the color lights, the linear sensors 50 and 51 Inconvenience arises in the arrangement of. Therefore, here, the configuration is such that the color light is turned back by the reflection mirrors 54 and 55 so that the light receiving surfaces of the linear sensors 50 and 51 are oriented in a direction perpendicular to the lens optical axis AX. Thereby, the linear sensors 50 to 52
The adjustment axes of focus, skew, and registration are aligned, so that each adjustment becomes easy. Each of the dichroic mirrors 48 and 49 has not only a small thickness but also a small thickness.
The surface normal is arranged so as to form a small angle with respect to the lens optical axis AX. Therefore, the amount of on-axis astigmatism is reduced to a negligible level in optical performance.

<< First Embodiment (FIGS. 1 and 2) >> FIG. 1 shows a state of the first embodiment viewed from the upper surface side, and shows an end face structure of a main part in a cross section taken along line YY of FIG. Is shown in FIG. The first embodiment is an optical member holding structure including a holding frame 1, a dichroic mirror 2, and an elastic adhesive 4. The dichroic mirror 2 is the same as the dichroic mirror 4 described above.
This is an optical member having a thin plate shape (thickness of 0.3 to 1 mm) corresponding to 8, 49 (FIG. 22) and made of a glass material.

The holding frame 1 is a supporting member for supporting the dichroic mirror 2, and is made of a material having a different linear expansion coefficient from the dichroic mirror 2, for example, a resin material or a metal material (aluminum material, iron-based material, etc.). . At the center of the holding frame 1, an opening 5 for an effective area for reading color light is formed. The holding frame 1 has hemispherical minute projections 3 at three places around the opening 5.
Supports the dichroic mirror 2 at three points. By using the three minute projections 3 for mirror support in this manner, positioning in the vertical direction (z direction) with respect to the mirror surface of the dichroic mirror 2 can be performed with the smallest contact area. Note that the shape of the minute projection 3 is not limited to a hemisphere, and may be, for example, a cone (a cone or a pyramid), or the tip of the minute projection 3 may be a minute plane.

An elastic adhesive 4 for bonding the holding frame 1 and the dichroic mirror 2 is annularly applied to a minute range slightly separated from each minute projection 3. The elastic adhesive 4 is a silicone-based adhesive having a viscosity of 500 P (poise) or more before curing and an elongation of 100% or more after curing. However, the dichroic mirror 2 and the holding frame 1
An adhesive other than the silicone-based adhesive may be used as long as the adhesive can elastically deform more than the difference in linear expansion from the adhesive.
For example, a polyurethane adhesive, a polysulfide adhesive, a styrene-butadiene rubber (SBR) adhesive, a chloroprene rubber adhesive, a butyl rubber adhesive, a nitrile rubber adhesive, or the like can be used as the elastic adhesive 4. is there. The environmental temperature when the difference in the linear expansion occurs is
This is the maximum environmental temperature when the color separation optical system 44 (FIGS. 21 and 22) is actually used, or a temperature set as necessary.

Further, since the dichroic mirror 2 is a brittle material which is thinly formed in order to improve the image forming performance of the color separation optical system 44 (FIGS. 21 and 22), the elastic adhesive 4 is in a cured state. Those having excellent flexibility are desirable. In general, an adhesive based on a polymer material is a viscoelastic body having two properties of spring elasticity for supporting a mechanical load and viscosity of stickiness. Since the two are related to the amount of deformation and elongation, an adhesive having a property (spring elasticity and viscosity) capable of elastically deforming more than the difference between the linear expansions is suitable as the elastic adhesive 4.

When the environmental temperature changes, both the holding frame 1 and the dichroic mirror 2 undergo linear expansion. However, since the linear expansion coefficients of the materials are different from each other, a difference occurs between the two in the xy directions. The elastic adhesive 4 that adheres and fixes them can be elastically deformed more than the above-mentioned difference in linear expansion. Therefore, the elastic adhesive 4 is deformed in accordance with a change in environmental temperature.
On the other hand, since the elastic adhesive 4 is located away from the minute protrusion 3, there is a space between the minute protrusion 3 and the elastic adhesive 4. Therefore, even if the elastic adhesive 4 is deformed as described above, it does not interfere with the minute projections 3. If the application position of the elastic adhesive 4 is separated from the minute projections 3 as described above, and if the distance between the minute projections 3 and the elastic adhesive 4 is preferably set to be equal to or larger than the above-mentioned difference in linear expansion, the line between them is The stress caused by the difference in expansion is easily absorbed and relaxed by the elastic adhesive 4. Therefore, even if the environmental temperature changes, the flatness of the dichroic mirror 2 is maintained, and the generation of distortion and cracks is prevented. Since no distortion occurs in the dichroic mirror 2, the reflection position and the reflection direction of the light beam do not change, and, of course, no color shift occurs in the input image.

When the elastic adhesive 4 having a viscosity of less than 500 P (poise) is used, the elastic adhesive 4 easily flows. For this reason, it becomes difficult to apply the elastic adhesive 4 only to the area in the vicinity of the minute projection 3, and workability is significantly reduced.
When the elastic adhesive 4 having an elongation of less than 100% is used, it is difficult for the elastic adhesive 4 to effectively absorb and relax the stress caused by the difference in linear expansion between the holding frame 1 and the dichroic mirror 2. , And distortion tends to occur in the dichroic mirror 2.

When the environmental temperature changes, the elastic adhesive 4 also expands linearly. If the elastic adhesive 4 exists between the dichroic mirror 2 and the minute projection 3, the mirror surface position of the dichroic mirror 2 may fluctuate in the z direction due to the linear expansion of the elastic adhesive 4 in the z direction. . However, in the present embodiment, since the elastic adhesive 4 is located away from the minute projection 3, the elastic adhesive 4 does not exist between the dichroic mirror 2 and the minute projection 3. That is, the dichroic mirror 2 is directly supported by the minute projections 3 without the intervention of the elastic adhesive 4. Therefore, the mirror surface position of the dichroic mirror 2 does not change in the z direction, and the reflection position and the reflection direction of the light beam on the dichroic mirror 2 do not change. On the mirror surface of the dichroic mirror 2, light rays are reflected in a certain direction and at a certain position.
No color shift occurs in the input image.

When the application area of the elastic adhesive 4 is large, the properties (spring elasticity and viscosity) of the elastic adhesive 4 easily affect the dichroic mirror 2, and the linear expansion of the elastic adhesive 4 in the xy directions is dichroic. The effect on the mirror 2 cannot be ignored. That is, the elastic adhesive 4 is not easily deformed, and the stress which causes the distortion of the dichroic mirror 2 is easily generated. However, in the present embodiment, since the elastic adhesive 4 is applied to a minute area around the minute projection 3, the elastic adhesive 4 can be easily deformed. Therefore, the stress that causes the distortion of the dichroic mirror 2 is easily absorbed and reduced.

At the time of initial mounting (that is, when the dichroic mirror 2 is adhered and fixed to the holding frame 1), the elastic adhesive 4 contracts with curing. Since the elastic adhesive 4 is capable of elastic deformation equal to or greater than the linear expansion difference, the effect of the degree to which the curing shrinkage of the elastic adhesive 4 exerts on the dichroic mirror 2 is absorbed and reduced by the elastic deformation. Moreover,
Since the elastic adhesive 4 is applied only to the vicinity of the minute projections 3, the bending moment due to the above-described curing shrinkage in the dichroic mirror 2 is effectively suppressed.

In the present embodiment, the elastic adhesive 4 is provided near the periphery of each of the three micro-projections 3, but if the elastic adhesive 4 is used in at least two of these three places, The stress caused by the difference in linear expansion between the holding frame 1 and the dichroic mirror 2 is absorbed and reduced, thereby preventing the dichroic mirror 2 from being distorted. Therefore, an adhesive made of an ultraviolet curable resin may be used only at one place. When an adhesive made of an ultraviolet curable resin is provided at two or more places, stress is generated between the two points,
Distortion occurs in the dichroic mirror 2.

<< Second Embodiment (FIGS. 3 and 4) >> FIG. 3 shows a state of the second embodiment viewed from the upper surface side. FIG. Is shown in FIG. The feature of the second embodiment is that a fluororesin layer 6 is added to the first embodiment (FIGS. 1 and 2). Fluororesin layer 6
Is provided on the surface of the dichroic mirror 2 on the holding frame 1 side so as to surround the application range of each elastic adhesive 4. The fluororesin layer 6 has an opening 6a,
The small projection 3 is provided at the center of the opening 6a, and the opening 5 of the holding frame 1 is not closed. In many cases, the adhesive strength of the elastic adhesive 4 to the fluororesin (for example, polytetrafluoroethylene) is very small. Therefore, the application range and the application area of the elastic adhesive 4 can be controlled by providing the fluororesin layer 6. . Therefore, there is an effect that workability in applying the elastic adhesive 4 is improved.

<< Third Embodiment (FIGS. 5 and 6) >> FIG. 5 shows a state in which the third embodiment is viewed from the upper surface side. FIG. Is shown in FIG. The feature of the third embodiment is that a point-like elastic adhesive 14 is provided in place of the annular elastic adhesive 4 in the first embodiment (FIGS. 1 and 2). Three elastic adhesives 14 are applied in a dotted pattern around each of the microprojections 3, and the three application points are located at the same distance from each of the microprojections 3. This elastic adhesive 14 is, like the elastic adhesive 4 used in the first embodiment (FIG. 1), a silicone adhesive excellent in flexibility {the viscosity before curing is 500 P (Poise) or more. And the elongation after curing is 100% or more}. However, if the adhesive is capable of elastic deformation beyond the difference in linear expansion between the dichroic mirror 2 and the holding frame 1, an adhesive other than the silicone-based adhesive (such as the polyurethane-based adhesive described above)
May be used as the elastic adhesive 14.

<< Fourth Embodiment (FIGS. 7 and 8) >> FIG. 7 shows a state of the fourth embodiment viewed from the upper surface side. FIG. Is shown in FIG. The feature of the fourth embodiment is that a fluororesin layer 6 is added to the third embodiment (FIGS. 5 and 6). Thereby, the second
The same effects as in the embodiment (FIGS. 3 and 4) can be obtained.

<< Fifth Embodiment (FIGS. 9 and 10) >> Fifth Embodiment
FIG. 9 shows an appearance of the fifth embodiment, and FIG. 10 shows a main part cross-sectional structure of a yz section passing through a YY line of FIG. 9 in the fifth embodiment. In the fifth embodiment, a holding frame 1, a dichroic mirror 2, an elastic adhesive 4, three spring members 7
And an optical member holding structure including three holding screws 8.

The spring member 7 is a pressing member that presses the dichroic mirror 2 toward the holding frame 1. The spring member 7 has a different linear expansion coefficient from the dichroic mirror 2, for example, a resin material or a metal material (aluminum material, iron-based material). Etc.). One end of each spring member 7 is fixed to the holding frame 1 with a set screw 8, and has a hemispherical minute projection 7 a at the other end. The minute projection 7a of the spring member 7 is connected to the minute projection 3 of the holding frame 1 via the dichroic mirror 2.
The dichroic mirror 2 is pressed against the minute projection 3 by each minute projection 7a. The shape of the minute projection 7a is not limited to a hemisphere, and may be, for example, a cone (a cone or a pyramid), or the tip of the minute projection 7a may be a minute plane.

As shown in FIG. 10, an elastic adhesive 4 for adhering the dichroic mirror 2 and the spring member 7 is provided in a minute area slightly separated from each minute projection 7a.
As in the first embodiment (FIG. 1), the coating is applied in a ring shape. This elastic adhesive 4 is, like the one used in the first embodiment (FIG. 1), a silicone adhesive excellent in flexibility {the viscosity before curing is 500 P (poise) or more, Is 100% or more}. However,
If the adhesive can be elastically deformed more than the difference in linear expansion between the dichroic mirror 2 and the spring member 7, an adhesive other than the silicone adhesive (such as the polyurethane adhesive described above) is used as the elastic adhesive 4. You may. The environmental temperature at which the difference in linear expansion occurs is determined by the color separation optical system 44 (FIG. 2).
1, FIG. 22) is the maximum environmental temperature when actually used,
Alternatively, the temperature is set as needed.

In the present embodiment, the dichroic mirror 2 is held by the pressing force of the spring member 7 and the adhesive force of the elastic adhesive 4. In other words, the dichroic mirror 2 is fixed to the microprojection 3 by pressure with the microprojection 7a, and is further indirectly fixed to the holding frame 1 by adhesive fixing with the spring member 7 screwed to the holding frame 1. It is. As described above, by using the spring member 7 and the elastic adhesive 4 together, the pressing portion, the pressing area, and the pressing force of the spring member 7 can be minimized as compared with the case where only the spring member 7 is used. . Further, since the contact area of the holding frame 1 with the dichroic mirror 2 is small, the frictional resistance therebetween is small. Therefore, the dichroic mirror 2 is hardly affected by the difference in linear expansion from the holding frame 1, and the dichroic mirror 2 is less likely to generate stress that causes distortion.

When the environmental temperature changes, the dichroic mirror 2 and the spring member 7 also linearly expand. However, since the linear expansion coefficients of the materials are different from each other, a difference occurs between the two in the xy directions. The elastic adhesive 4 that adheres and fixes them can be elastically deformed more than the above-mentioned difference in linear expansion. Therefore, the elastic adhesive 4 is deformed in accordance with a change in environmental temperature. On the other hand, since the elastic adhesive 4 is located away from the minute protrusion 7a, there is a space between the minute protrusion 7a and the elastic adhesive 4. Therefore, even if the elastic adhesive 4 is deformed as described above, it does not interfere with the minute projections 7a. In this way, the application position of the elastic adhesive 4 is
a, and preferably the microprojections 7a and the elastic adhesive 4
If the distance between the and is larger than the difference of the linear expansion,
The stress caused by the difference in linear expansion between the two is easily absorbed and relaxed by the elastic adhesive 4. Therefore, even if the environmental temperature changes, the flatness of the dichroic mirror 2 is maintained, and the generation of distortion and cracks is prevented. Since no distortion occurs in the dichroic mirror 2, the reflection position and the reflection direction of the light beam do not change, and, of course, no color shift occurs in the input image.

When the elastic adhesive 4 having a viscosity of less than 500 P (poise) is used, the elastic adhesive 4 easily flows. For this reason, it becomes difficult to apply the elastic adhesive 4 only to the area in the vicinity of the minute projection 7a, and workability is significantly reduced. When the elastic adhesive 4 having an elongation of less than 100% is used, it is difficult for the elastic adhesive 4 to effectively absorb and relax the stress caused by the difference in linear expansion between the spring member 7 and the dichroic mirror 2. , And distortion tends to occur in the dichroic mirror 2.

At the time of initial mounting (that is, when the dichroic mirror 2 is bonded and fixed to the spring member 7), the elastic adhesive 4 contracts with curing. Since the elastic adhesive 4 can be elastically deformed beyond the linear expansion difference, the elastic adhesive 4
The effect of the curing shrinkage on the dichroic mirror 2 is absorbed and mitigated by its elastic deformation. In addition, since the elastic adhesive 4 is applied only to the vicinity of the minute projections 7a, generation of a bending moment due to the curing shrinkage in the dichroic mirror 2 is effectively suppressed.

In the present embodiment, three minute projections 7a
The elastic adhesive 4 is provided in the vicinity of each of the above. However, if the elastic adhesive 4 is used in at least two of the three positions, the elastic adhesive 4 is caused by a difference in linear expansion between the spring member 7 and the dichroic mirror 2. By absorbing and relaxing the stress, the occurrence of distortion of the dichroic mirror 2 can be prevented.
Therefore, an adhesive made of an ultraviolet curable resin may be used only at one place. If an adhesive made of an ultraviolet curable resin is provided at two or more locations, stress will be generated between the two points, and the dichroic mirror 2 will be distorted.

<< Sixth Embodiment (FIGS. 9 and 11) >>
The appearance of this embodiment is as shown in FIG. 9, as in the fifth embodiment (FIG. 10). FIG. 11 shows a main part cross-sectional structure of a yz cross-section taken along line YY of FIG. 9 in the sixth embodiment. The feature of the sixth embodiment is that a point-like elastic adhesive 14 is provided instead of the annular elastic adhesive 4 in the fifth embodiment (FIG. 10). Around the small projections 7a, three elastic adhesives 14 are applied in a dot-like manner in the same manner as in the third embodiment (FIG. 5), and the three application points correspond to the small projections 7a. It is located equidistant from. This elastic adhesive 14 is, like the one used in the third embodiment (FIG. 5), a silicone adhesive having excellent flexibility {the viscosity before curing is 500 P (Poise) or more, Is 100% or more}. However, if the adhesive can be elastically deformed beyond the difference in linear expansion between the dichroic mirror 2 and the spring member 7, an adhesive other than the silicone-based adhesive (such as the polyurethane-based adhesive described above) may be used. May be used.

<< Seventh Embodiment (FIGS. 9 and 12) >>
The appearance of this embodiment is as shown in FIG. 9, as in the fifth embodiment (FIG. 10). FIG. 12 shows a cross-sectional structure of a main part of a yz section passing through line YY of FIG. 9 in the seventh embodiment. The feature of the seventh embodiment resides in that it has both features of the first and fifth embodiments (FIGS. 2 and 10). That is, the characteristic is that the elastic adhesive 4 is applied in a ring shape to both the minute projections 3 of the holding frame 1 and the minute projections 7a of the spring member 7.

<< Eighth Embodiment (FIGS. 9 and 13) >>
The appearance of this embodiment is as shown in FIG. 9, as in the fifth embodiment (FIG. 10). FIG. 13 shows a cross-sectional structure of a main part of a yz section passing through line YY of FIG. 9 in the eighth embodiment. The feature of the eighth embodiment lies in that it has both features of the third and sixth embodiments (FIGS. 6 and 11). That is, the feature is that the elastic adhesive 14 is applied in a dot-like manner to both the minute projections 3 of the holding frame 1 and the minute projections 7a of the spring member 7.

<< Ninth Embodiment (FIGS. 9, 14, and 1)
6) >> The appearance of the ninth embodiment is as shown in FIG. 9, similarly to the fifth embodiment (FIG. 10). FIG. 14 shows a cross-sectional structure of a main part of a yz cross section taken along line YY of FIG. 9 in the ninth embodiment. The features of the ninth embodiment are as follows.
The fifth embodiment (FIG. 10) is different from the fifth embodiment in that a fluororesin layer 16 is provided instead of the minute projection 3. As a constituent material of the fluororesin layer 16, for example, polytetrafluoroethylene can be used. FIG. 16 shows a state in which the holding frame 1 provided with the fluororesin layer 16 is viewed from above. When the holding frame 1 and the dichroic mirror 2 are brought into contact via the fluororesin layer 16, even if the contact area is large, the frictional resistance therebetween is small. Therefore, the dichroic mirror 2 is hardly affected by the difference in linear expansion from the holding frame 1, and the dichroic mirror 2 is less likely to generate stress that causes distortion.

<< Tenth Embodiment (FIGS. 9, 15, and 16) >> The appearance of the tenth embodiment is the same as that of the fifth embodiment (FIG. 10) as shown in FIG. is there. FIG.
9 shows a cross-sectional structure of a main part of a yz section passing through line YY of FIG. 9 in the tenth embodiment. The feature of the tenth embodiment resides in that a fluororesin layer 16 is provided instead of the minute projections 3 in the sixth embodiment (FIG. 11). (FIG. 14).

<< Eleventh Embodiment (FIGS. 9 and 17) >> The appearance of the eleventh embodiment is the same as that of the fifth embodiment (FIG. 10).
Similarly to FIG. FIG. 17 shows a cross-sectional structure of a main part of a yz section passing through line YY of FIG. 9 in the eleventh embodiment. The feature of the eleventh embodiment is that the dichroic mirror 2 is bonded and fixed to the holding frame 1 by applying an elastic adhesive 24 between the outer peripheral end surface 2a of the dichroic mirror 2 and the holding frame 1. The configuration is the same as that of the fifth embodiment (FIG. 10) except that the elastic adhesive 24 is used instead of the elastic adhesive 4.

The elastic adhesive 24 is made of a silicone adhesive having excellent flexibility like the elastic adhesives 4 and 14 used in the first and third embodiments (FIGS. 1 and 5).
{Viscosity before curing is 500P (poise) or more, elongation after curing is 100% or more}. However, as long as the adhesive can be elastically deformed more than the difference in linear expansion between the dichroic mirror 2 and the holding frame 1, an adhesive other than the silicone adhesive is used.
(Such as the polyurethane adhesive described above) may be used as the elastic adhesive 24. As described above, the environmental temperature at which the difference in linear expansion occurs depends on the color separation optical system 44 (FIG. 2).
1, FIG. 22) is the maximum environmental temperature when actually used,
Alternatively, the temperature is set as needed.

Although there is a square-shaped gap between the dichroic mirror 2 and the holding frame 1, in this embodiment, in the gap, both ends of each long side of the outer peripheral end face 2 a of the dichroic mirror 2 are provided. The elastic adhesive 24 is applied to (four places). The application position of the elastic adhesive 24 is not limited to both ends on each long side. For example, it may be applied to both ends of each short side, applied to the center of each side, applied to two or more places at appropriate positions on each side, or applied to four corners of the dichroic mirror 2. . Further, the elastic adhesive 24 is provided at four locations on the outer peripheral end face 2a, but an adhesive made of an ultraviolet curable resin may be used at one of the four locations. If the adhesive made of the ultraviolet curable resin is provided at two or more places, stress may be generated between the two points and the dichroic mirror 2 may be distorted. Since the stress due to the difference in linear expansion is absorbed and relaxed by the elastic adhesive 24 at other portions, the occurrence of distortion of the dichroic mirror 2 can be prevented.

In this embodiment, the dichroic mirror 2 is formed by the pressing force of the spring member 7 and the adhesive force of the elastic adhesive 24.
Holding. In other words, the dichroic mirror 2 is fixed to the microprojection 3 by pressure with the microprojection 7a, and is further fixed to the holding frame 1 by adhesive fixing at the outer peripheral end surface 2a. As described above, by using the spring member 7 and the elastic adhesive 24 together, the pressing portion, the pressing area, and the pressing force of the spring member 7 can be minimized as compared with the case where only the spring member 7 is used. . Further, since the contact area of the holding frame 1 with the dichroic mirror 2 is small, the frictional resistance therebetween is small. Therefore, the dichroic mirror 2 is hardly affected by the difference in linear expansion from the holding frame 1, and the dichroic mirror 2 is less likely to generate stress that causes distortion.

As described above, when the environmental temperature changes, both the holding frame 1 and the dichroic mirror 2 linearly expand.
Since the linear expansion coefficients of the materials are different from each other, a difference occurs between the two in the xy directions. The elastic adhesive 24 that adheres and fixes them can be elastically deformed more than the difference in linear expansion. For this reason, it deforms (that is, expands or contracts) according to a change in the environmental temperature.
Therefore, the stress caused by the difference in linear expansion between the two is absorbed and relaxed by the elastic adhesive 24, and the dichroic mirror 2
Is kept flat. Since the generation of the distortion of the dichroic mirror 2 is prevented, the reflection position and the reflection direction of the light beam do not change, and the color shift does not occur in the input image.

When the elastic adhesive 24 having a viscosity of less than 500 P (poise) is used, the elastic adhesive 24 easily flows. For this reason, the workability is significantly reduced. When the elastic adhesive 24 having an elongation of less than 100% is used, the holding frame 1
It is difficult for the elastic adhesive 24 to effectively absorb and alleviate the stress caused by the difference in linear expansion between the dichroic mirror 2 and the dichroic mirror 2, and the dichroic mirror 2 is likely to be distorted.

At the time of initial mounting (that is, when the dichroic mirror 2 is bonded and fixed to the holding frame 1), the elastic adhesive 24 contracts with curing. Elastic adhesive 24
Is capable of elastic deformation equal to or greater than the linear expansion difference, the effect of curing shrinkage on the dichroic mirror 2 is as follows:
Absorbed and relaxed by the elastic deformation. Moreover, since the curing shrinkage of the elastic adhesive 24 is a deformation in the direction in which the dichroic mirror 2 is extended, the bending moment due to the curing shrinkage in the dichroic mirror 2 is suppressed.

<< Twelfth Embodiment (FIGS. 9, 16 and 18) >> The appearance of the twelfth embodiment is as shown in FIG. 9, similarly to the fifth embodiment (FIG. 10). is there. FIG.
9 shows a cross-sectional structure of a main part of a yz cross section taken along line YY of FIG. 9 in the twelfth embodiment. A feature of the twelfth embodiment is that a fluororesin layer 16 (for example, a layer made of polytetrafluoroethylene) is provided instead of the minute projections 3 in the eleventh embodiment (FIG. 17).
The operation and effect are the same as in the ninth embodiment (FIG. 14).

<< Thirteenth Embodiment (FIGS. 19 and 20) >>
FIG. 19 shows an appearance of the thirteenth embodiment, and FIG. 20 shows an essential part end surface structure of a yz cross section taken along line YY of FIG. 19 in the thirteenth embodiment. The thirteenth embodiment is
Two dichroic mirrors 2, a holding frame 31, an elastic member 32, a mounting plate 33, fixing screws 34, and a fluororesin layer 35 (for example, a layer made of polytetrafluoroethylene)
It is an optical member holding structure constituted by: The holding frame 31 is a support member that supports the dichroic mirror 2, and the elastic member 32 is
Is a pressing member that presses. Holding frame 31 and elastic member 32
Are made of a material having a different linear expansion coefficient from that of the dichroic mirror 2, for example, a resin material (an elastic material such as rubber in the case of the elastic member 32) or a metal material (aluminum material, iron-based material, etc.). Therefore, when the environmental temperature changes, a difference occurs in linear expansion between the dichroic mirror 2 and the dichroic mirror 2.

The holding frame 31 has a fluororesin layer 35 on the surface on which the dichroic mirror 2 is positioned.
The elastic member 32 has a fluororesin layer 35 on the surface that presses the dichroic mirror 2. Therefore, both ends of the dichroic mirror 2 are sandwiched between the holding frame 31 and the elastic member 32, and the mounting frame 33 and the fixing screws 34 are used to hold the holding frame 3.
When the elastic member 32 is pressed and fixed to the first member 1, each dichroic mirror 2 is divided into two fluororesin layers 35 as shown in FIG.
The state is fixed between the two. When the dichroic mirror 2 is held via the fluororesin layer 35 in this manner,
The frictional resistance during that time is reduced. Therefore, even if a difference in linear expansion occurs between the holding frame 31 or the elastic member 32 and the dichroic mirror 2 due to a change in environmental temperature, the dichroic mirror 2 is hardly affected by the difference in linear expansion. Is less likely to cause stress.

<Others> In each of the above embodiments and problems, a dichroic mirror is mainly described as a thin plate-shaped optical member. However, an optical member to which the optical member holding structure according to the present invention can be applied is a dichroic mirror. Not limited to mirrors. For example, the present invention may be applied to general optical elements such as a reflection mirror, a half mirror, a beam splitter, a prism, a film, a window, a lens, and a diffraction grating.

[0052]

As described above, according to the present invention, even if the environmental temperature changes, the stress generated in the optical member is absorbed and relaxed by the elastic adhesive, so that no distortion or crack occurs in the optical member. Therefore, the flatness of the optical member can be maintained.

[Brief description of the drawings]

FIG. 1 is a top view showing a first embodiment.

FIG. 2 is an end view showing a main part of a cross section taken along line YY of FIG. 1;

FIG. 3 is a top view showing a second embodiment.

FIG. 4 is an end view showing a main part of a cross section taken along line YY of FIG. 3;

FIG. 5 is a top view showing a third embodiment.

FIG. 6 is an end view showing a main part of a section taken along line YY of FIG. 5;

FIG. 7 is a top view showing a fourth embodiment.

FIG. 8 is an end view showing a main part of a cross section taken along line YY of FIG. 7;

FIG. 9 is a perspective view showing a schematic external configuration of the fifth to twelfth embodiments.

FIG. 10 is a sectional view showing a main part of a yz section passing through line YY of FIG. 9 in the fifth embodiment;

FIG. 11 is a sectional view showing a main part of a yz section passing through line YY of FIG. 9 in the sixth embodiment;

FIG. 12 is a sectional view showing a main part of a yz section passing through a line YY in FIG. 9 in the seventh embodiment;

FIG. 13 is a sectional view showing a main part of a yz section passing through line YY of FIG. 9 in the eighth embodiment;

FIG. 14 is a sectional view showing a main part of a yz section passing through line YY of FIG. 9 in the ninth embodiment;

FIG. 15 is a sectional view showing a main part of a yz section passing through line YY of FIG. 9 in the tenth embodiment;

FIG. 16 is a top view showing an external configuration of a holding frame constituting the ninth, tenth, and twelfth embodiments.

FIG. 17 is a sectional view showing a main part of a yz section passing through line YY of FIG. 9 in the eleventh embodiment;

FIG. 18 is a sectional view showing a main part of a yz section passing through line YY of FIG. 9 in the twelfth embodiment;

FIG. 19 is a perspective view showing a schematic external configuration of a thirteenth embodiment.

FIG. 20 is an end view showing a yz section passing through line YY of FIG. 19;

FIG. 21 is a diagram illustrating a schematic configuration of a color image input device.

FIG. 22 is a diagram showing a schematic configuration of a color separation optical system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Holding frame (support member) 2 ... Dichroic mirror (optical member) 3 ... Microprojection part 4 ... Elastic adhesive 6 ... Fluororesin layer 7 ... Spring member (pressing member) 7a ... Microprojection part 14 ... Elastic adhesive 16 Fluoro resin layer 24 Elastic adhesive 31 Holding frame 32 Elastic member 35 Fluororesin layer 42 Scanner 43 Lens 44 Color separation optical system 48 Dichroic mirror 49 Dichroic mirror 50 Linear sensor 51 Linear sensor 52 ... Linear sensor

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroaki Nakauchi 2-3-13-1 Azuchicho, Chuo-ku, Osaka City Inside Osaka International Building Minolta Co., Ltd. (72) Inventor Osamu Yamada 2-3-3 Azuchicho, Chuo-ku, Osaka City No. 13 Osaka International Building Minolta Co., Ltd. F-term (reference) 2H042 DA01 DA12 DA20 DB02 DE00 2H043 AE02 AE08 AE09 AE16 AE22 BC06 BC08

Claims (4)

[Claims] 1. An optical member holding structure comprising a thin plate-shaped optical member, a support member for supporting the optical member, and an elastic adhesive for bonding the optical member and the support member. The optical member, wherein the support member is made of a material having a different linear expansion coefficient from the optical member, and the elastic adhesive is elastically deformable more than a difference in linear expansion between the optical member and the support member. Member holding structure. 2. The optical device according to claim 1, wherein the support member has three minute projections, and the three minute projections support the optical member.
2. The optical member holding structure according to claim 1, wherein the elastic adhesive is applied to a minute area slightly apart from each minute protrusion. 3. A thin plate-shaped optical member, a support member for supporting the optical member, a pressing member for pressing the optical member toward the support member, and bonding the optical member and the pressing member. An elastic member, comprising: an optical member holding structure, wherein the pressing member is made of a material having a different linear expansion coefficient from the optical member, and the elastic adhesive is a line between the optical member and the pressing member. An optical member holding structure capable of being elastically deformed more than a difference in expansion. 4. The pressing member has three minute projections, and the optical member is pressed by the three minute projections.
4. The optical member holding structure according to claim 3, wherein the elastic adhesive is applied to a minute area located slightly apart from each minute protrusion.