JP3867588B2 - Mounting device for solid-state imaging device in image reading apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a mounting device for a solid-state imaging device in a digital image reading apparatus.
[0002]
[Prior art]
In a digital image forming apparatus such as a copying machine, an image reading apparatus that reads a document image using a solid-state imaging device, for example, a CCD is used. In such an image reading apparatus, since the positional relationship between the imaging lens and the solid-state imaging device greatly affects the quality of the formed image, precise positioning on the order of microns is required.
[0003]
As a method of positioning the imaging lens and the solid-state imaging device, the imaging lens and the solid-state imaging device are temporarily assembled on a frame, and a test sample image is projected onto the solid-state imaging device through the imaging lens, thereby solid-state imaging. A general method is to adjust the relative position between the imaging lens and the solid-state imaging device while monitoring the output of the device with a monitor.
[0004]
In order to maintain the image quality, the solid-state image sensor after position adjustment must be firmly fixed so that it does not move on the frame, and the position does not change when it is fixed. Must be within range.
[0005]
For this reason, various fixing means have been proposed. For example, a method of fixing a first mounting member to which an imaging lens is mounted and a second mounting member to which a solid-state imaging device is mounted on a frame with screws, the first mounting member and the second mounting member A method of fixing on the frame while adjusting the distance with a screw and a spring member, a method of fixing between the first mounting member and the second mounting member with solder while maintaining a distance between them, and a package of a solid-state imaging device Alternatively, there is a method of fixing the resin part of the solid-state imaging device with an adhesive.
[0006]
[Problems to be solved by the invention]
Among the various fixing means described above, the method of fixing with an adhesive has anxiety in terms of rigidity and earthquake resistance and environmental measures, because resin is present on the bonding surface, and in particular, the rigidity and earthquake resistance are inferior. However, it is not sufficient for application to an image reading apparatus that operates at high speed, and some measures are required to increase rigidity and earthquake resistance.
[0007]
Also, the method of fixing with solder requires a surface treatment such as tin plating when the mounting member is a metal plate, resulting in an increase in cost. In addition, fixing in anticipation of solder shrinkage occurring after fixing is necessary, and management of the fixing operation becomes difficult. Furthermore, some solders contain toxic metals such as lead, and there are concerns about environmental measures.
[0008]
The method of fixing the distance between the first mounting member and the second mounting member on the frame while adjusting the distance between the first mounting member and the second mounting member is complicated in structure and results in an increase in cost. There is an inconvenience.
[0009]
The simplest structure that can withstand long-term aging after shipment and is highly reliable is to fix the mounting member with a screw. In this method, when tightening the screw, the screw is attached between the screw and the mounting member. When the mounting member is displaced due to the frictional force, a displacement of several tens of microns may occur. However, it is required that the displacement is within an allowable error range of several microns. An object of the present invention is to solve this problem.
[0010]
[Means for Solving the Problems]
The present invention solves the above problems, and the invention of claim 1 includes an imaging lens and a solid-state imaging device, and projects an image on the solid-state imaging device via the imaging lens to convert it into an image signal. And a first mounting member to which a solid-state imaging device is mounted, and a second mounting member to which an imaging lens and the first mounting member are mounted, The first mounting member mounted on the second mounting member is mounted so that the position of the solid-state imaging device can be adjusted in the optical axis direction of the imaging lens via a fixing unit, and the fixing unit includes a fixing screw. And an elastic member mounted between the fixing screw member and the second mounting member, and the elastic member constituting the fixing means includes a claw portion that engages with the second mounting member. The claw portion has a spring constant in the optical axis direction of the imaging lens, the solid-state imaging device. A mounting device for a solid-state image sensor in the image reading apparatus characterized in that it is a shape larger than the spring constant of the pixel arrangement direction.
[0011]
And it is good to arrange | position the said fixing means at least two places along the pixel arrangement direction in the position corresponding to the both ends outer side of the pixel arrangement direction of the solid-state image sensor on the said 1st attachment member.
[0013]
And the nail | claw part of the said elastic member is good to arrange | position in the orthogonal | vertical direction with respect to the pixel array direction of the said solid-state image sensor.
[0014]
In addition, the length of the claw portion may be 120% or more and less than 200% of the plate thickness of the first mounting member to which the solid-state imaging element is fixed.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
[0016]
FIG. 1 is an exploded perspective view showing a mounting structure of a solid-state imaging device in an image reading apparatus according to an embodiment of the present invention, and FIG. 2 is a perspective view showing an assembled state thereof.
[0017]
Here, for convenience of explanation, the optical axis direction of the imaging lens L described later is the X axis, the pixel arrangement direction of the solid-state imaging device is the Y axis, and the height direction of the optical axis of the imaging lens L with respect to the frame (X axis) And the direction perpendicular to the Y-axis) is taken as the Z-axis direction.
[0018]
1 and 2, a lens CCD unit 10 that is an internal unit of the image reading apparatus is assembled on a frame 11, and the height relative to the frame 11 (Z-axis direction) can be adjusted on the frame 11. The adjustment substrate 12 is disposed substantially parallel to the frame 11.
[0019]
The adjustment board 12 is formed with a hole that fits the head of the height adjustment screw 11a at a position corresponding to the three height adjustment screws 11a that are screwed on the frame 11. And the head of the height adjustment screw 11a are fitted together so that the adjustment substrate 12 is supported from the back side by a ridge (not shown) provided near the upper end of the height adjustment screw 11a and moves in the vertical direction. Supported as possible. In addition, the adjustment substrate 12 is urged downward toward the frame 11 by a screw 13 with two sets of leaf springs 14 interposed therebetween. With this configuration, the height of the adjustment substrate 12 from the frame 11 can be adjusted by adjusting the screwing amount of the height adjustment screw 11a into the frame 11.
[0020]
The solid-state image pickup device 20 is, for example, a CCD, and the solid-state image pickup device 20 housed in the image pickup device package 21 is detachably mounted on the socket 22. The socket 22 is fixedly attached to the substrate 23 by means such as soldering.
[0021]
The first mounting member 25 has a first mounting surface 25a having a substantially L-shaped cross section, and a second mounting surface 25b perpendicular to the first mounting surface 25a. The first mounting surface 25a has a solid-state imaging device. An opening 25c is formed in a portion corresponding to the package 21, brackets 25d are formed on both outer sides in the pixel array direction of the solid-state imaging device 20 of the opening 25c, and the substrate 23 and the bracket 25d are connected to the screw 26. It is fixed with.
[0022]
The second attachment surface 25b of the first attachment member 25 is a surface for attaching the first attachment member 25 to a second attachment member 27 described later, and is in the pixel arrangement direction (Y-axis direction) of the solid-state imaging device 20. At positions corresponding to the outer sides of both ends, there are two elongated attachment holes 25e extending in parallel to the optical axis direction of the imaging lens L, which will be described later, and a pawl portion of a leaf spring, which will be described later, approaching each of the attachment holes 25e. An engagement hole 25g that engages with 29a is formed.
[0023]
A lens holding frame 30 that holds the imaging lens L is fixed to the second mounting member 27, and the second mounting surface 25 b of the first mounting member 25 is attached to the second mounting member 27. Two screw holes 27e to be fixed are formed.
[0024]
As shown in FIGS. 1 and 2, the fixing means for attaching the first mounting member 25 to the second mounting member 27 includes a fixing screw 28 that is a fixing screw member and a leaf spring 29 that is an elastic member. As apparent from FIG. 3 and FIG. 4, the leaf spring 29 is formed with a claw portion 29a.
[0025]
The second mounting member 27 is fixed on the adjustment substrate 12 with three screws 15, but is configured to be adjustable in the optical axis direction (X-axis direction) of the imaging lens L.
[0026]
Next, a procedure for mounting and adjusting the solid-state imaging device will be described. First, the solid-state imaging device 20 housed in the imaging device package 21 is mounted on the socket 22 and fixed to the substrate 23 by means such as soldering. The image pickup device package 21 on the substrate 23 is fitted into the opening portion 25c formed in the first attachment surface 25a of the first attachment member 25, and the substrate 23 and the first attachment member 25 are fixed with screws 26.
[0027]
The lens holding frame 30 holding the imaging lens L is fixed to the second mounting member 27, and is fixed to the adjustment substrate 12 with the three screws 15 while adjusting the position of the second mounting member 27. Note that when the second mounting member 27 is fixed to the adjustment substrate 12, an approximate position in the X-axis direction may be determined and fixed. Adjustment of the attachment position of the imaging lens L and the solid-state imaging device is precisely adjusted when attaching the first attachment member 25 to the second attachment member 27, as will be described later.
[0028]
Further, the height of the adjustment board 12 from the frame 11 is adjusted and fixed by adjusting the screwing amount of the height adjustment screw 11a.
[0029]
The second mounting surface 25b of the first mounting member 25 is placed at the mounting position of the second mounting member 27, a leaf spring 29 is interposed under the fixing screw 28, and the claw portion 29a of the leaf spring 29 is engaged with the engagement hole. After engaging with 25g, the fixing screw 28 is passed through the mounting hole 25e, screwed into the screw hole 27e formed in the second mounting member 27, and temporarily fixed.
[0030]
The first mounting member 25 can move in a direction parallel to the optical axis of the imaging lens L (X-axis direction), and the adjustment substrate 12 can move in the height direction (Z-axis direction) with respect to the frame 11. The movable range is assumed to be a range sufficient to absorb variations in the conjugate length of the imaging lens L and manufacturing errors of other components.
[0031]
Next, the attachment position of the imaging lens L and the solid-state image sensor is adjusted. A test sample image is projected onto the solid-state imaging device 20 through the imaging lens L, and the output signal from the solid-state imaging device 20 is monitored by a monitor (not shown), while the first mounting member 25 and the imaging lens L are spaced from each other. The distance between the second mounting member 27 and the frame 11 is adjusted so that the monitor output is within the target error range.
[0032]
At this time, the first mounting member 25, that is, the distance between the solid-state imaging device 20 and the imaging lens L is adjusted with a particularly precise micron unit using a tool.
[0033]
When the adjustment of the attachment position is completed, the screw 15 for fixing the second attachment member 27 to the adjustment substrate 12 is finally tightened and firmly fixed. Next, the fixing screw 28 temporarily fixing the first mounting member 25 on the second mounting member 27 is finally tightened and firmly fixed.
[0034]
If the relative position between the first mounting member 25 and the second mounting member 27, that is, the relative position between the solid-state imaging device 20 and the imaging lens L is shifted during the final tightening of the fixing screw 28, the resolving power decreases. Partial magnification change, image distortion, etc. occur and image quality cannot be maintained.
[0035]
As a countermeasure, in this embodiment, when the fixing screw 28 is inserted into the mounting hole 25e on the first mounting member 25, a leaf spring 29 is interposed below the fixing screw 28, and the fixing screw 28 is tightened. When the fixing screw 28 and the first mounting member 25 are in frictional contact with each other, the first mounting member 25 is prevented from being displaced by frictional force. The configuration and operation of the leaf spring 29, its dimensions, etc. will be described in detail later.
[0036]
FIGS. 3 and 4 are views for explaining the configuration and operation of the fixing means constituted by the fixing screw 28 and the leaf spring 29. FIG. 3 shows the first mounting member 25 and the second mounting member 27. FIG. 4 is an explanatory view seen from the side of the state fixed by the fixing screw 28 and the leaf spring 29, and FIG. 4 is an explanatory view seen from the obliquely upward direction.
[0037]
3 and 4, the plate spring 29 is elastically deformed by tightening the fixing screw 28, and the central portion of the plate spring 29 is in frictional contact with the first attachment member 25 to which the solid-state imaging device 20 is attached. For this reason, the solid-state imaging device 20 may be displaced via the leaf spring 29 by tightening the fixing screw 28.
[0038]
Even if the central portion of the leaf spring 29 is in frictional contact with the first mounting member 25, the contact friction force is sufficiently large, and the leaf spring 29 has sufficient rigidity so that it does not elastically deform after tightening. Although the first mounting member 25, that is, the solid-state imaging device 20, does not come off, if the rigidity of the leaf spring 29 is too large, problems such as a decrease in tightening strength occur, and therefore the rigidity cannot be increased unnecessarily. It is necessary to make the plate thickness of the leaf spring 29, the size of the claw portion, and the like appropriate.
[0039]
Here, regarding the leaf spring provided with the claw portion as shown in FIG. 4, the displacement generated by tightening, that is, the deformation amount will be considered. If the deformation amount of the plate spring imaging lens L in the optical axis direction (X-axis direction) is δx and the deformation amount of the solid-state imaging device in the pixel arrangement direction (Y-axis direction) is δy, the pixel arrangement direction (Y-axis) The amount of deformation δy toward (direction) is generally electrically correctable, so that some deformation does not cause a problem. In general, the effective pixel range of the solid-state imaging device extends to the outside of the image area and has a margin, and electrical correction is possible.
[0040]
The deformation amount δx of the plate spring in the optical axis direction (X-axis direction) of the imaging lens L is related to focus adjustment, and it is difficult to electrically correct the deformation amount δx. Therefore, a design of a leaf spring in which the deformation amount δx is smaller than the deformation amount δy will be considered.
[0041]
3 and 4, the force applied to the leaf spring 29 by tightening the fixing screw 28 is F1, the spring constant in the Y-axis direction of the leaf spring 29 is Ey, the spring constant in the X-axis direction is Ex, and the spring constant in the Z-axis direction. Ez, the friction coefficient between the fixing screw 28 and the leaf spring 29 is μ1, the friction coefficient between the leaf spring 29 and the first mounting member 25, or between the leaf spring 29 and the second mounting member 27. Assuming that the smaller friction coefficient is μ2 and the deformation amount of the leaf spring 29 in the Z-axis direction is δz, the deformation amount δy can be expressed by the following equation (1) from the force balance equation. .
[0042]
δy = (μ1−μ2) * F1 / Ey + μ2 * δz * Ez / Ey (1)
From equation (1), the deformation amount δy is inversely proportional to the Y-axis spring constant Ey, the Z-axis direction spring constant is proportional to Ez, and the deformation amount δx is inversely proportional to the X-axis direction spring constant Ex. It can be seen that the spring constant in the Z-axis direction is proportional to Ez.
[0043]
As shown in FIG. 4, when the claw portion 29a is provided in the leaf spring 29 only in the direction parallel to the optical axis direction (X-axis direction), Ex> Ey and the deformation amount is δx <δy. A leaf spring suitable for suppressing the displacement of the direction can be obtained.
[0044]
The length H of the claw portion 29a is proportional to the spring constant Ez in the Z-axis direction and the deformation amount δz in the Z-axis direction, and inversely proportional to the force F1 exerted on the leaf spring 29 by the fixing screw 28.
[0045]
The deformation amount δx in the X-axis direction and the deformation amount δy in the Y-axis direction are proportional to the deformation amount δz in the Z-axis direction, the spring constant Ez in the Z-axis direction, and the force F1 that the fixing screw 28 exerts on the leaf spring 29. The length H of the portion 29a is considered to be highly sensitive to the deformation amount (deviation amount), and is an important parameter in designing the leaf spring 29.
[0046]
If the length H of the claw portion 29a is not at least larger than the plate thickness of the first mounting member 25 to which the solid-state imaging device is mounted, the leaf spring 29 has no spring property and does not make sense as the plate spring 29. If the length H of the claw portion 29a is too large, the spring constant Ez increases, and the deformation amount δx in the X-axis direction and the deformation amount δy in the Y-axis direction also increase. The optimum range of the length H of the claw portion 29a is a range that is larger than 120% and smaller than 200% of the plate thickness T with respect to the plate thickness T of the first mounting member 25, as confirmed by experiments. It is suitable to be inside.
[0047]
Further, in order to make the deformation amount δy smaller than the expression (1), the friction coefficient between the fixing screw 28 and the leaf spring 29 may be reduced by μ1.
[0048]
Although the embodiment of the present invention has been described above, the above-described embodiment includes the invention described below.
[0049]
The elastic member according to claim 1 is made of a material whose friction coefficient is smaller than that of the first mounting member to which the solid-state imaging element is attached. .
[0050]
【The invention's effect】
As described above, the solid-state image sensor mounting device in the digital image reading apparatus according to the present invention has the first mounting member to which the solid-state image sensor is mounted on the second mounting member to which the imaging lens is mounted. When fixing the imaging lens in the optical axis direction so that the position can be adjusted, the fixing means is composed of a fixing screw member and an elastic member, and the elastic member is mounted between the fixing screw member and the second mounting member. Since it is configured, it is possible to greatly reduce the displacement of the position of the second mounting member that occurs when the fixing screw member is tightened with a simple configuration.
[0051]
Then, a pixel arrangement of the solid-state image sensor, in which a claw portion is provided on the elastic member constituting the fixing means, and the spring constant in the optical axis direction of the imaging lens is larger than the spring constant in the pixel arrangement direction of the solid-state image sensor Appropriately determine the shape, arrangement, plate thickness, etc. of the claw portion, such as arranging in a direction perpendicular to the direction, or setting the plate thickness of the claw portion to 120% or more and less than 200% of the plate thickness of the first mounting member. As a result, it is possible to suppress an error in the mounting position of the solid-state imaging device due to tightening of the mounting screw to tens of microns or less.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing a mounting structure of a solid-state image sensor in an image reading apparatus according to an embodiment of the present invention.
2 is a perspective view showing an assembled state of the mounting structure of the solid-state imaging device shown in FIG. 1;
3 is a diagram (part 1) for explaining the configuration and operation of a fixing means of the mounting structure shown in FIG. 1; FIG.
4 is a diagram (part 2) for explaining the configuration and operation of a fixing means of the mounting structure shown in FIG. 1; FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Lens CCD unit 11 Frame 11a Height adjustment screw 12 Adjustment board 13 Screw 14 Leaf spring 20 Solid-state image sensor 21 Image sensor package 22 Socket 23 Substrate 25 First attachment member 25a First attachment surface 25b Second attachment surface 25c Opening Portion 25d bracket 25e mounting hole 25g engagement hole 26 screw 27 second mounting member 27e screw hole 28 fixing screw (fixing screw member)
29 Leaf spring (elastic member)
29a Claw 30 Lens holding frame

Claims (4)

An image reading apparatus that includes an imaging lens and a solid-state imaging device, projects an image on the solid-state imaging device via the imaging lens, converts the image into an image signal, and outputs the image signal .
A first mounting member to which a solid-state imaging element is mounted; a second mounting member to which an imaging lens and the first mounting member are mounted; and a second mounting member mounted on the second mounting member. 1 is attached to the solid-state imaging device via a fixing means so that the position of the solid-state imaging device can be adjusted in the optical axis direction of the imaging lens. The fixing means includes a fixing screw member, the fixing screw member, and the first fixing member. An elastic member mounted between the two attachment members ,
The elastic member constituting the fixing means includes a claw portion that engages with the second mounting member, and the claw portion has a spring constant in the optical axis direction of the imaging lens in the pixel arrangement direction of the solid-state imaging device. A mounting device for a solid-state imaging device in an image reading device, wherein the mounting device has a shape larger than a spring constant . The at least two fixing means are arranged along the pixel arrangement direction at positions corresponding to the outer sides of both ends in the pixel arrangement direction of the solid-state imaging device on the first mounting member. 2. A mounting device for a solid-state imaging device in the image reading apparatus according to 1 . The claw portions of the elastic member, the mounting device of the solid-state imaging device in the image reading apparatus according to claim 1, characterized in that it is arranged in a direction perpendicular to the pixel arrangement direction of the solid-state imaging device. The length of the pawl portion of the elastic member, the image reading apparatus according to claim 1, wherein the solid-state imaging device is less than 120% to 200% of the thickness of the first mounting member secured The solid-state image sensor mounting apparatus in FIG.

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