JP2002250853A - Lens holding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lens shape and a cell structure by which the eccentricity of a lens fixed to have a specified positional relation at the inside of a cell is suppressed so as to be very small and the intervals of a plurality of lenses arrayed in an optical axis direction at the inside of the cell are set to have a desired relation and which contribute to resource-saving and the reduction of waste by reducing the number of parts. SOLUTION: In a lens holding device having one or more lenses 1 and a lens barrel 2 holding the outer peripheral part of the lens by an inner wall, inclined parts 2-1 respectively inclined in the optical axis direction are provided at the outer peripheral part 1-1 of the lens and the inner wall of the lens barrel, and the inclined part of the outer peripheral part of the lens is engaged with the inclined part of the inner wall of the lens barrel, so that the lens is held.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a lens holding device for a reading lens used in an image reading device used in a scanner, a copying machine, a facsimile, and the like.

[0002]

2. Description of the Related Art In recent years, image reading apparatuses such as scanners, copiers, and facsimile machines have been remarkably improved in image quality. For this reason, the reading lenses mounted on them are also required to have higher performance. Generally, in order to ensure the performance of a lens, it is necessary to satisfactorily correct various aberrations in terms of lens design. In actual manufacturing of the reading lens unit, each parameter (curvature radius, surface interval, refractive index, etc.) of the lens is created within a desired tolerance, and the lens shape and the cell ( (Lens tube) structure. In particular, since the eccentricity of the lens has a large effect on the imaging performance, the structure is designed to minimize the eccentricity between the lens surfaces that mutually affect each other or between the lenses, and to minimize the eccentricity during assembly Need to do. However, in the conventional cell structure, it is necessary to secure a clearance between the outer diameter of the lens and the inner diameter of the cell in order to assemble the lens into the cell, and this clearance causes eccentricity. In the case of a cell structure in which each lens interval is set to a predetermined value by an intermediate ring, the geometrical tolerance of the intermediate ring
(Coaxiality, parallelism, squareness, etc.) and the clearance with the cell for assembly as well as the lens increase the possibility of eccentricity, increase the number of parts, deplete resources and waste Will increase. In addition, in order to reduce the cost of the reading lens, there is a lens unit in which the cell material is made of resin.However, due to the difference in the linear expansion coefficient between the cell material and the lens material (generally, the cell (The resin used has a larger coefficient of linear expansion.) If the ambient temperature changes, the clearance between the lens and the cell will change, and the attitude of the assembled lens will change, ensuring the performance of the initial assembled state. Disappears. Further, in the case of a very high performance lens, even if each parameter of the lens is processed with high accuracy at the current processing limit, the performance may not be satisfied. In such a case, adjustment and other means may be required. Therefore, a method of compensating for the performance degradation using is required. As a target of the adjustment, a tilt correction of an image plane due to an increase or a decrease in a lens interval is generally performed.

Another demand for the image reading apparatus is to make the main body thinner, and the outer diameter of the mounted reading lens needs to be as small as possible. Other conventional techniques for positioning a lens in a lens barrel include, for example, the following. That is, as a method of setting the positional relationship of the lenses in the optical axis direction in the lens barrel, there is a method of directly contacting the lenses as shown in the lens configuration diagram of Japanese Patent Application Laid-Open No. 10-253879.
However, there are problems such as a need to increase the accuracy of the lens and a limitation on the types of applicable lens units.
Also, it is difficult to perform image plane tilt correction by increasing or decreasing the lens interval. As a method of holding a lens with an interval between lenses in a lens barrel, there is a method of securing an interval by the shape of the lens barrel itself as disclosed in Japanese Patent Application Laid-Open No. 10-333007. However, the configuration of the inner wall of the lens barrel becomes complicated, and it is difficult to ensure accuracy.
Moreover, the cost is clearly higher. Also, it is difficult to perform image plane tilt correction by increasing or decreasing the lens interval. As a method of fixing lenses arranged at predetermined intervals, there is a method of screwing a fixing ring having a male thread into a female screw provided at an end of a lens barrel and fixing the lens, as disclosed in JP-A-10-333007. . However, this is a problem because it is used in combination with a lens barrel having the above-mentioned disadvantages. As a method of adjusting the lens interval, there is a method of using an interval ring along the lens curvature as disclosed in JP-A-7-113936. However, it is necessary to form a step on the inner wall of the lens barrel with high precision in advance, which has disadvantages such as an increase in the number of processing steps. The parts cost also increases. Also, it is difficult to perform image plane tilt correction by increasing or decreasing the lens interval.

[0004]

The problem to be solved by the present invention is as follows. 1. To propose a lens shape and a cell structure capable of minimizing the eccentricity of a lens fixed in a predetermined positional relationship in a cell (claims 1 and 3). The distance between a plurality of lenses arranged along the optical axis direction in the cell can be set in a desired relationship, and the eccentricity of the lenses can be suppressed to a very small value. 2. To propose a lens shape and a cell structure that can contribute to the reduction of waste and the amount of waste. To propose a lens shape and a cell structure in which the eccentricity of the lens can be kept very small even when the cell material is made of resin, and the mounting posture of the lens does not change due to temperature change (claim Item 5), 4. 4. To propose a lens shape and a cell structure capable of correcting the tilt of the image plane by adjusting the distance between the lenses and suppressing the eccentricity to a very small value. An object of the present invention is to propose a lens shape and a cell structure that can cope with a reduction in the thickness of an image reading device and can suppress eccentricity to a very small value.

[0005]

According to a first aspect of the present invention, there is provided a lens holding apparatus having at least one lens and a lens barrel holding an outer peripheral portion of the lens with an inner wall. In the above, the outer peripheral part of the lens and the inner wall of the lens barrel are provided with inclined parts inclined in the optical axis direction, and the lens is held by engaging the inclined part of the outer peripheral part of the lens with the inclined part of the inner wall of the lens barrel. It is characterized by doing. The invention according to claim 2 is a lens holding device having at least two or more lenses and a lens barrel that holds an outer peripheral portion of each lens by an inner wall, wherein the outer peripheral portion of the lens and the inner wall of the lens barrel are provided. By providing an inclined portion inclined in the optical axis direction, the lens is held by engaging the inclined portion of the outer peripheral portion of each lens with the inclined portion of the inner wall of the lens barrel, and by changing the maximum outer diameter of each lens. Each lens is held on the inner wall of the lens barrel at a predetermined interval in the optical axis direction. The invention according to claim 3 is characterized in that the inclination angles of the inclined portion of the outer peripheral portion of the lens and the inclined portion of the inner wall of the lens barrel are substantially the same. The invention according to a fourth aspect is characterized in that a spacer is inserted between the inclined portion on the outer peripheral portion of the lens and the inclined portion on the inner wall of the lens barrel. The invention of claim 5 is characterized in that the material of the lens barrel is made of resin, and the spacer and the lens barrel have different linear expansion coefficients. The invention according to claim 6 is characterized in that the distance between the lenses can be arbitrarily changed by changing the thickness of the spacer, and the tilt of the image plane can be corrected. The invention according to claim 7 is characterized in that the outer shape of the lens and the longitudinal sectional shape of the inner wall of the lens barrel are each non-circular.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. FIG. 1 is a longitudinal sectional view showing the structure of a lens holding device according to the first embodiment. In this lens holding device, one or more lenses 1 include a cell (barrel).
2 supported by the inner wall. In the lens holding device according to this embodiment, an inclined portion (surface) having a predetermined inclination angle between the optical axis and the outer peripheral portion of the lens 1.
1-1 is formed, and an inclined portion (surface) 2 having a predetermined inclined angle with respect to the optical axis is also provided on the inner peripheral portion of the inner wall of the cell 2.
-1 is formed. The inclined portion 2-1 in the cell may be located at a part (lens fixing position) of the cell 2, but in this example, an inclined surface extending at a predetermined angle over the entire length is shown. When the lens 1 is mounted on the inner wall of the cell, the inclined portion 1-1 of the outer peripheral portion of the lens and the inclined portion 2-1 of the inner peripheral portion of the cell come into contact with each other, and the lens is held in the cell without any clearance. Any method of fixing the lens to the cell may be used. For example, a method of fixing the lens with an annular screw 3 as shown in FIG. 2A or a method of bonding the lens and the cell with an adhesive 4 as shown in FIG. Or any other method such as caulking. In FIG. 2A, a female screw is formed on the inner periphery of the large-diameter opening of the cell 2, and the screw on the outer periphery of the annular screw 3 is engaged with the female screw.

Next, FIG. 3 is a sectional view showing an embodiment corresponding to claim 2. The lens holding device according to this embodiment is capable of holding a plurality of lenses in a single cell with a desired distance between the lenses and holding the lenses without eccentricity. For example, FIG. 3 shows an example in which the number of lenses is three. Three lenses 1a, 1
b, 1c are provided on the respective outer peripheral portions with inclined portions 1a having substantially the same angle.
-1, 1b-1, and 1c-1 are formed. An inclined portion 2-1 extending in the optical axis direction at a fixed inclination angle is also formed on the inner peripheral portion of the cell 2. In this embodiment, the lens outer diameter is set to a different value for each lens, and each lens 1
By setting dimensions in advance so that a, 1b, and 1c are locked at different positions of the inclined portion 2-1 on the inner peripheral portion of the cell 2,
The distance between the lenses in the optical axis direction can be set to a desired position. In the example of FIG. 3, the outer diameter of the lens 1 a located on the side where the inner diameter of the cell is larger is the largest, and then the outer diameter of the lens is reduced in the order of the lenses 1 b and 1 c so that the distance between the lenses is a desired value. It can be. When the outer diameter of the lens is reduced, the reduction rate of the outer diameter is determined by the slope 2-on the cell side.
It is set according to the tilt angle of 1 and the fixed position of each lens.

The method of fixing the lens to the cell may be the same as the method shown in FIG. 2, and may be any method such as fixing one lens by bonding or screws. The inclined portion 2-1 of the inner peripheral portion of the cell 2 does not need to be continuously formed over the entire length of the cell inner wall in the axial direction as in the example of FIG. 3. For example, as shown in FIG. Each inclined portion 1a-1 of three different lenses 1a, 1b, 1c,
1b-1 and 1c-1, corresponding to each inclined portion 2-
It is also possible to form 1, 2, and 2-3 discontinuously (intermittently with a non-inclined surface or the like interposed therebetween). At this time, it does not matter whether the inclination angles of the inclined portions 2-1, 2-2, and 2-3 are the same or different. Needless to say, a continuous inclined portion and a discontinuous inclined portion can be freely combined. Further, with respect to the mounting direction of the lenses, it is not necessary to configure so that all the lenses can be inserted from one opening in the axial direction. For example, as shown in FIG. By configuring the inclined portions 2-1 and 2-2 so as to expand in a tapered shape, the lenses 1 a and 1 b are assembled from the left opening,
The lens 1c can be assembled from the opening on the right side. It goes without saying that there is no problem if the inclined portions 2-1 and 2-2 are continuous as shown in the figure or discontinuous (intermittent) as shown in FIG. At this time, there is no problem if the angles of the left inclined portion 2-1 and the right inclined portion 2-2 are the same or different. The lens holding device,
With the configuration as shown in FIGS. 3 to 5, the intermediate ring, which is conventionally required to set each lens interval to a desired value, becomes unnecessary, and the number of parts can be reduced.

Next, in the first and second aspects of the present invention, when the area where the outer peripheral portion of the lens and the inner peripheral portion of the cell are in contact with each other is increased, the supporting stability is enhanced, and the lens is securely held on the inner wall of the cell without eccentricity. Therefore, in the invention of claim 3, by making the angles of the inclined portions of the outer peripheral portion of the lens and the inner peripheral portion of the cell substantially the same, the inclined portions of the outer peripheral portion of the lens and the inner peripheral portion of the cell are brought into almost complete contact. It is possible. Next, in the second or third aspect of the present invention, when the outer diameters of the lenses are made different in order to set the lens interval to a desired value, it is necessary to accurately process the outer diameters of the lenses, which is a factor of cost increase. Becomes In addition, when the processing accuracy of the lens outer diameter becomes poor, the positional error of the lens interval in the cell becomes large,
This may cause performance degradation. Then, in the invention of claim 4,
Even if the accuracy of the outer diameter of the manufactured lens is poor to some extent, it is possible to reduce the positional error of the lens interval. That is, in this embodiment, as shown in FIG.
The outer diameter of each of a and 1b is set smaller than the diameter at which the lens interval becomes a desired value, and the thin cylindrical spacers 3-1 and 3-2 are inserted between the lenses 1a and 1b and the inner wall of the cell 2. . The thickness of the spacers 3-1 and 3-2 is arbitrarily changed so that the lens is held in the cell so that the lens interval becomes a desired value with respect to the value of the processed lens outer diameter. As described above, in the present embodiment, assuming that a gap is formed between the outer peripheral portion of the lens and the inner wall of the cell, a spacer is used to fill the gap and determine the fixing position of the lens. By selecting and using spacers having different thicknesses according to the difference in the value of the gap, the lens can be fixed at an arbitrary position on the inner wall of the cell.

According to a fifth aspect of the present invention, in the invention of the fourth aspect, when the cell material is made of resin, even if the cell 2 expands due to a temperature change, the posture of the lens held in the cell does not change. The purpose is to be. That is, when the spacers 3-1 and 3-2 are inserted between the lenses 1a and 1b and the inclined portion 2-1 of the cell 2 as shown in FIG. The value is set so as to compensate for the difference between the coefficient of linear expansion between the resin used for the cell material and the lens. For example, when the coefficient of linear expansion of the cell 2 is larger than the coefficient of linear expansion of the lens, the cell expands more than the lens when the temperature increases, so that a gap is formed between the cell and the lens. The posture of the lens changes from the state in which the lens is assembled, and the imaging performance changes. Therefore, spacers 3-1 and 3-2 having a larger linear expansion coefficient than the cell and being elastic are inserted (press-fitted) between the cell and the lens. The spacer expands at a higher rate than the cell due to the increased temperature, fills the gap between the cell and the lens, and elastically holds the lens. Conversely, when the temperature decreases, the cell shrinks more than the lens, and if there is no spacer, the cell exerts stress on the lens, which has an adverse effect such as deforming the lens surface. So, by inserting a spacer,
The shrinkage of the cell is absorbed by the spacer, so that stress from the cell is not applied to the lens.

Next, in order to actually process the lens,
A processing tolerance is required, and as a result, a processing error occurs in each parameter (a radius of curvature, a surface interval, a refractive index, and the like) configuring the lens from a design median value. Due to this processing error, the performance of the lens unit is degraded from the design median imaging performance. As the demand for the lens becomes higher, the performance degradation due to the processing error cannot be tolerated. In order to suppress the performance deterioration to a small extent, it is necessary to suppress the processing error to a small extent. However, performing high-precision processing greatly increases the cost. Further, it is impossible to reduce the processing error to zero even if the processing accuracy is increased. Therefore, the invention according to claim 6 changes the lens interval (axial position of the lens) when each parameter of the lens is varied due to a processing error and the imaging performance is degraded from the design median.
The performance is returned to the imaging performance substantially equal to the designed median value, and the change in the lens interval can be achieved by changing the thickness of the spacer inserted between any lens and the cell. In other words, when fixing the lens having the inclination on the outer peripheral portion to the inner wall of the cell having the inclination, by using the spacer, the axial position of the lens can be adjusted without being affected by the processing error of the lens. It can be arbitrarily selected,
Even for lenses with poor imaging performance, it is possible to secure imaging performance equivalent to the designed median value by finely adjusting the axial position using spacers with optimal thickness. It is.

FIG. 7 is a schematic view showing an embodiment according to claim 7, in which the outer shape of the lens 1 is made non-circular, and an image reading apparatus using this lens holding device. It can contribute to a reduction in the thickness of the device. For example, as shown in FIG.
Is cut into a flat surface, and an inclined portion 2-1 is formed in the remaining outer circular arc portion 6-3. The lens 1 to be assembled to the inner wall of the cell has a configuration in which the upper and lower portions of the outer periphery are cut similarly to the inner diameter shape of the cell, and the outer peripheral portion (arc surface) of the lens 1 is substantially the same as the inclined portion 2-1 of the inner wall of the cell. An angle inclined portion 1-1 is formed. It goes without saying that the shape of the lens and the cell may be, for example, a shape in which only the upper part is cut or a shape in which only the lower part is cut. Also, in all of the above embodiments, it is needless to say that the angle of the inclined portion provided in the lens and the cell may be any angle as long as the inclined angle of each inclined portion of the lens and the cell is substantially the same.
INDUSTRIAL APPLICABILITY The present invention can be applied to optical devices other than the image reading device, for example, camera lenses and other imaging optical system lens barrel structures.

[0013]

As described above, the present invention has the following excellent effects. First, according to the first aspect of the present invention, an inclined portion is provided on an outer peripheral portion of a lens and an inner peripheral portion of a cell for supporting the lens.
When the lens is assembled to the cell by aligning and attaching the two inclined portions to each other, the clearance between the lens and the cell can be made substantially zero, and the lens can be held without eccentricity. A unit is obtained. The invention according to claim 2 is configured such that an outer peripheral portion of the plurality of lenses,
An inclined part is provided on the inner periphery of the cell that supports this, and the maximum outer diameter of each lens is set to any different value. Since the distance between the lenses can be arranged at a desired value without using a lens, the number of parts can be reduced, resource saving and waste reduction can be achieved, and a low-cost and high-performance lens unit without lens eccentricity can be obtained. Can be According to the third aspect of the present invention, it is possible to increase the contact area between the outer peripheral portion of the lens and the inclined portion of the inner peripheral portion of the cell by making the angles of the inclined portions provided on the outer peripheral portion of the lens and the inner peripheral portion of the cell substantially the same. That is, the lens can be securely held in the cell with less eccentricity.

According to a fourth aspect of the present invention, by inserting a spacer between the lens and the cell, it is possible to arrange the distance between the lenses at a desired value without increasing the precision of the outer diameter processing of the lens. Therefore, a lens processing cost can be greatly reduced, and a low-cost and high-performance lens unit without lens eccentricity can be obtained. According to the fifth aspect of the present invention, even when the cell material is a resin, the lens unit has no lens eccentricity and has a temperature change due to the optimization of the linear expansion coefficient of the spacer inserted between the lens and the cell. Can be compensated for. According to the invention of claim 6, by changing the thickness of the spacer inserted between any lens and the cell, it becomes possible to adjust the performance deterioration due to the deviation of each parameter of the lens from the design center value by processing, A very high performance lens unit without eccentricity can be obtained. According to the seventh aspect of the invention, in addition to the effects of the first to sixth aspects, the thickness of the image reading apparatus can be significantly reduced by making the outer shape of the lens and the shape of the inner wall of the cell non-circular.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a configuration of a lens holding device according to claim 1;

FIG. 2 is a sectional view showing a modification of the embodiment of FIG. 1;

FIG. 3 is a sectional view showing an embodiment corresponding to claim 2;

FIG. 4 is a sectional view showing an embodiment corresponding to claim 3;

FIG. 5 is a sectional view showing another embodiment of the present invention.

FIG. 6 is a sectional view showing another embodiment of the present invention.

FIG. 7 is a schematic view showing an embodiment corresponding to claim 7;

[Explanation of symbols]

1, 1a, 1b, 1c lens, 2 cell (barrel), 1
-1, 1a-1, 1b-1, 1c-1 Inclined portion (surface),
2-1, 2-2, 2-3 Inclined portion (surface), 3 annular screw, 4 adhesive, 3-1, 3-2 Spacer

Claims (7)

[Claims] 1. A lens holding device having at least one or more lenses and a lens barrel holding an outer peripheral portion of the lens with an inner wall, wherein light is respectively transmitted to an outer peripheral portion of the lens and an inner wall of the lens barrel. A lens holding device comprising: an inclined portion inclined in an axial direction; and a lens held by engaging an inclined portion of a lens outer peripheral portion with an inclined portion of an inner wall of a lens barrel. 2. A lens holding device having at least two or more lenses and a lens barrel holding an outer peripheral portion of each lens with an inner wall, wherein the outer peripheral portion of the lens and the inner wall of the lens barrel are respectively provided. By providing an inclined portion inclined in the optical axis direction, holding the lens by engaging the inclined portion of the outer peripheral portion of each lens with the inclined portion of the inner wall of the lens barrel, by changing the maximum outer diameter of each lens, A lens holding device for holding the lens on the inner wall of the lens barrel at a predetermined interval in the optical axis direction. 3. The lens holding apparatus according to claim 1, wherein the inclination angle of the outer peripheral portion of the lens and the inclination angle of the inclined portion of the inner wall of the lens barrel are substantially the same. 4. The lens holding device according to claim 1, wherein a spacer is inserted between the inclined portion of the outer peripheral portion of the lens and the inclined portion of the inner wall of the lens barrel. apparatus. 5. The lens holding device according to claim 4, wherein the lens barrel is made of resin, and the spacer and the lens barrel have different linear expansion coefficients. 6. The image forming apparatus according to claim 4, wherein the distance between the lenses can be arbitrarily changed by changing the thickness of the spacer, and the tilt of the image plane can be corrected. The lens holding device as described in the above. 7. The lens holding device according to claim 1, wherein an outer shape of the lens and a longitudinal sectional shape of the inner wall of the lens barrel are each a non-circular shape.