JPS6262100B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an original reading device that illuminates an original and reads an image of the original using a light receiving element.

In recent years, for example, a document image can be created by reading an image of the document surface with a light-receiving element such as a CCD or BBD, converting this into an electrical signal, and then forming an image corresponding to this electrical signal using a laser or the like. A technique has been developed to reproduce it.

When reading a document with this light-receiving element, two light-receiving elements are sometimes used in parallel in order to increase the resolution and to simultaneously read the entire surface of a large document. When using two light-receiving elements in this way, if the distance between the light-receiving elements becomes larger than the initial setting value, the image cannot be read in the areas where the distance has increased, and when the image is reproduced, there will be no joints. The parts are not connected continuously, and white streaks appear in the reproduced image.

Conversely, if the distance between the light-receiving elements becomes smaller than the initial setting value, images will be read overlappingly by adjacent light-receiving elements, and black lines will appear at the connected portions when the image is reproduced.

Therefore, when using these two light receiving elements, it is necessary to keep the mutual distance between the light receiving elements constant. However, this mutual distance may change due to heat generation from the document illumination light source used when reading the document or an increase in the temperature outside the apparatus main body. One possible solution to this inconvenience is to maintain a constant temperature around the two light-receiving elements, but this requires a large temperature adjustment device, which is expensive and takes up a lot of space, making it impractical. do not have. Furthermore, even if the temperature adjustment device is provided, the temperature detection means has a measurement error, so it is impossible to always keep the temperature around the light receiving element constant.

The purpose of the present invention is to solve the above-mentioned conventional problems, and more specifically, when the temperature around the light receiving elements changes within a common sense range, the change in distance between two light receiving elements arranged in a row is kept within a predetermined range. It is about making it possible to decide.

To achieve the above object, the present invention provides a document reading device that reads a document image using a plurality of light receiving sections, comprising: a support member that is provided corresponding to each of the plurality of light receiving sections and supports the light receiving section;
a connecting member that connects the respective supporting members;
The document reading device is characterized in that the support member is made of a material having a larger coefficient of linear expansion than the coupling member. In the above device, when the first and second upper plates and the middle plate are connected, if they are fixed at two or more points parallel to the optical axis, even if the upper plate and the middle plate are deformed due to thermal expansion, the upper plate 1. It becomes possible to move the second upper plate parallel to the optical axis.

With the above configuration, the distance between each light-receiving element can be changed within the allowable range of this element, so even if the temperature around the light-receiving element changes, black lines and white lines in the document scanning direction as described above will not occur. Formation of a striped image can be prevented. Moreover, such an effect can be obtained by selecting the material of the base for mounting the light receiving element, so that a complicated structure is not required.

Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 is a sectional view of a document reading device using a light receiving element. In the figure, reference numeral 1 denotes an original glass, on which an original 2 is placed. 3 is an optical reading section, and illumination means 4 consisting of a fluorescent lamp, a halogen lamp, etc.
It is integrally constructed with a mirror 5, a lens 6, and a solid-state light receiving element 7 that converts a focused optical image into an electrical signal. When the light receiving and reading section 3 reads a document, the document 2 is illuminated by the illuminating means 4 while being moved along the guide rail 8 in the direction A in the figure, and the solid state light receiving element 7 reads the reflected light. The optical reading section 3 can be moved by, for example, a conventional method of winding up a wire using the driving force of a motor and fixing the reading section 3 to the tip of the wire. On the other hand, numeral 9 is a fan for sucking air from outside the machine into the main body of the apparatus in order to cool the fluorescent lamps and halogen lamps of the illumination means 4.

FIG. 2 is a plan view of the optical arrangement of the reading device shown in FIG.

In the figure, the optical device for reading the original 2 includes a first reading section 81 consisting of a first lens ₆₁ and a first light receiving element ₇₁ , and a first reading section ₈₁ consisting of a second lens ₆₂ and a second light receiving element ₇₂ . 2 reading section ₈ . Here, the diameter of the light receiving elements 7 ₁ and 7 ₂ is usually 10μ.
It is a CCD element in which approximately 2,000 fine light-receiving areas with a size of 20 μm are arranged in a straight line, and each light-receiving element has an independent self-scanning function that reads the projected image. There is. The direction in which the light receiving sections are arranged is perpendicular to the image scanning direction (direction A in FIG. 1), and the area where the light receiving sections are arranged, that is, the light receiving area is indicated by a in FIG. 2. Here, a=(diameter of one light receiving portion)×(number of arrayed portions), and is usually about 20 to 25 mm.

When reading a document by arranging two light-receiving elements in parallel in this way, the image at the center b, which coincides with the scanning direction of the document 2, is detected by the first lens 6 ₁ or the second lens 6 ₂ , respectively. Element 7 ₁ or 7 ₂
imaged on top. Among the images of the central part b, let b ₁ be the image formed on the first light receiving element 7 ₁ , and b ₂ be the image formed on the second light receiving element 7 _2.The self-scanning function In order to combine the electric signals output from each of the light receiving elements 7 ₁ and 7 ₂ again and reproduce the original original image, the distance c connecting b ₁ and b ₂ must always be constant. As mentioned above, if this distance c is larger than the initial setting value, a white stripe-like image will appear at the edge of the combined original image, and conversely, if the distance c is smaller than the initial setting value, a black stripe-like image will appear. Images occur at the same seam.

In this case, the light-receiving area a is the distance d between the optical axes of each lens and light-receiving element (when applied to ordinary copy paper,
Since it is much smaller than 120 to 160 mm, if we ignore the change in the distance d due to thermal expansion in the longitudinal direction of the photodetector itself, it will actually cause a problem even if the distance d is kept constant instead of the distance c. do not have. The present invention differs from the above-mentioned prior art by always keeping the distance d between the centers of the first reading section ₈₁ and the second reading section ₈₂ constant despite changes in the surrounding temperature of the light receiving element. It solves the problem that exists.

FIG. 3 is a perspective view of a specific embodiment of the invention. In the figure, the first lens 6 ₁ constituting the first reading section 8 ₁ is loosely fitted to the mounting plate 9 ₁ so as to be slidable in the direction of the first optical axis k ₁ for focus adjustment. After the optical adjustment is completed, the lens ₆₁ is fixed to the mounting plate ₉₁ using known means such as a double nut or a set screw. The lower end of the mounting plate ₉₁ is fixed to the first upper plate ₁₀₁ .

A light receiving stand 11 ₁ for mounting the first light receiving element 7 ₁ is mounted on the upper plate 10 ₁ at a _position along the optical axis of the first lens 6 1 so as to face the lens 6 ₁ . Between the light receiving table ₁₁₁ and the light receiving element ₇₁ , the light receiving element ₇₁ is moved vertically, horizontally, or in the direction of the optical axis _k1 to adjust the focus and magnification of the image, and the distance between adjacent light receiving elements. An adjustment mechanism 12 ₁ is provided for finely adjusting the continuous state of reproduced images, and this mechanism 12 ₁ is attached to a fixed light receiving table 1.
An adjustment screw member (not shown) is provided to slightly move the light receiving element ₇₂ in the left-right, up-down, and front-back directions with respect to the light receiving element ₁₁ .

The upper plate 10 ₁ to which the first lens 6 ₁ and the first light receiving element 7 ₁ are attached has one end parallel to the optical axis k ₁ fixed to the middle plate 14 with a screw 13 ₁ . When using two or more screws 13 ₁ , make sure that the line m1 connecting the centers of each screw 13 ₁ is parallel to the optical axis k ₁ to prevent thermal expansion of the upper plate 10 ₂ and middle plate 14. Even if it is deformed, it is possible to make this deformation parallel to the optical axis _k1 .

By the way, the other end of the upper plate 10 ₁ on which the screw 13 ₁ is provided is pressed onto the middle plate 14 by a first leaf spring 15 ₁ directly fixed near the center of the middle plate 14 . This leaf spring 15 ₁ is attached on the upper plate 10 _{1 .}
A gap is provided between the side edges of the upper plate 101 to absorb expansion and contraction due to thermal expansion of the upper plate ₁₀₁ . The leaf spring ₁₅₁ prevents the end of the upper plate ₁₀₁ from lifting off from the middle plate due to thermal expansion, vibration, or the like. Note that the central portion of the intermediate plate 14 is fixed to the substrate 17 with two screws 16 at a position parallel to the optical axis _k1 . The board 17 is fixed to a machine frame (not shown) that constitutes the main body of the copying machine. On the other hand, the upper plate 10
₁ and the middle plate 14 are located at the right end in the figure, and the first plate spring 18 ₁ is attached to both plates 10 ₁ and 14 in order to prevent the plates 10 ₁ and 14 from lifting due to thermal expansion, vibration, etc.
is pressed against the substrate 17. And the above spring 1
5 Similar to ₁ , leaf spring 18 ₁ , upper plate 10 and middle plate 1
A gap is preliminarily provided between the side edges of 4 and 4 to absorb expansion and contraction due to thermal expansion.

The configuration of the second reading section ₈₂ is the first reading section 8.
Since the configuration is the same as ₁ , the explanation will be omitted here.

FIG. 4 shows a plan view of FIG. 3 viewed from above. In the figure, the distance between the first and second optical axes k ₁ and k ₂ is d, the distance between the optical axis k ₁ and screw 13 ₁ is l ₁ , the distance between optical axis k 2 and screw 13 2 is l 2 , and the distance between optical axis k ₁ and screw 13 ₂ is l ₂ . 1.Second screw 13 ₁ .
13 ₂ distance L (L=d+l ₁ +l ₂ ), screw 13 ₁
and the distance between screw 16 is L ₁ , screw 16 and screw 13 ₂
Let the distance be L ₂ (L ₁ +L ₂ =L), and the first upper plate 10
₁ , the linear expansion coefficient of the second upper plate 10 ₂ is a _{2 ,} and the linear expansion coefficient of the middle plate 14 is β. At this time, the spacing between the light receiving elements ₇₁ and ₇₂ was adjusted so that when the ambient temperature of the reading section was _t1 °C, the reproduced image was continuously connected to the first and second light receiving elements. Assume that when the ambient temperature changes from t ₁ °C to t ₂ °C, a streak occurs in the center of the reproduced image.

Considering that the cause of the above streak pattern is deformation due to thermal expansion of each plate that makes up the reading section, we can express it in a formula. First, if the ambient temperature is t ₁ ℃
_{The distance d 1 between the} optical axis _{k 1 and k 2} when Optical axis k ₁ when changing to t ₂ °C
The distance d ₂ between k ₂ is: d ₂ =L ₁ {1+β(t ₂ −t ₁ )} +L ₂ {1+β(t ₂ −t ₁ )} −l ₁ {1+α ₁ (t ₂ −t ₁ )} −l ₂ {(1+α ₂ (t ₂ −t ₁ )} = (L ₁ +L ₂ ) {1+β(t ₂ −t ₁ )} −l ₁ {1+α ₁ (t ₂ −t ₁ )} −l ₂ { 1+α ₂ (t ₂ −t ₁ )} =L {1+β(t ₂ −t ₁ )} −l ₁ {1+α ₁ (t ₂ −t ₁ )} −l ₂ {1+α ₂ (t ₂ −t ₁ )} becomes.

Generally, the first and second upper plates 10 ₁ and 10 ₂ are made of the same material and have the same size, so l ₂ = α ₁ = α ₂ = α, l ₁ = l ₂ = l. Since it is possible, d ₂ = L {1 + β (t ₂ − t ₁ )}
−2l{(1+α(t ₂ −t ₁ )}).

Therefore, even if t ₂ °C changes within a reasonable range, the distance between the optical axes remains constant and there are no streaks at the joints in the reproduced image unless d ₁ = d ₂ . No. At this time, from the relational expression mentioned earlier, L-2l=L{1+β(t ₂ -t ₁ )}
−2l{1+α(t ₂ −t ₁ )} Lβ(t ₂ −t ₁ )=2lα(t ₂ −t ₁ ) Lβ=2lα.

Here, if aluminum is used for the upper plate 10 ₁ and 10 ₂ and iron is used for the middle plate 14, the expansion coefficient α = 2.39 × 10 ^-5 , and the expansion coefficient β = 1.07 × 10 ^-5 . , At the same time, when reading the manuscript in the longitudinal direction of an A4 size paper, approximately d = L - 2l = 148 mm, so L = 267.8 mm and l = 59.9 mm. In other words, if the dimensions of the reading section shown in Figure 3 are configured to satisfy this condition, the distance d between the optical axes will always be constant no matter how the ambient temperature changes, so the reproduced image will be It becomes possible to prevent the generation of a striped pattern in the central part.

Next, as an example of materials for obtaining the same effect as the above example, let us consider a case where brass is used for the top plate and iron is used for the middle plate. At this time, the expansion coefficient of brass is α=
1.84×10 ^-5 , and the expansion coefficient of iron is β=1.07×
10 ^-5 , so from the above formula L=353.6mm, l=
It becomes 102.8mm. Also, when zinc is used as the top plate and iron is used as the middle plate, the expansion coefficient of zinc is α = 3.97 × 10 ^-5 , while the expansion coefficient of iron is β =
Since it is 1.07×10 ^-5 , similarly from the above formula, L=
202.6mm, l=27.3mm. Therefore, with regard to the above material, by setting the distance L while it is fixed by the screws 13 ₁ and 13 ₂ on both sides and the distance l from the fixed position to the optical axis of each lens to the above values, Even if the reading section expands or contracts due to temperature changes, it is possible to prevent the formed image from coming off the light-receiving element and creating a striped pattern on the reproduced image.

As described above, the present invention maintains the distance between optical axes constant by utilizing the difference in coefficient of linear expansion of different metals, and its application is not limited to the embodiment shown in the figures. For example, when the present invention is miniaturized and used, the lens and the light receiving element may not be integrally attached to the upper plate, but only the light receiving element or the lens may be attached to the upper plate. In this case, the lens or light receiving element that is not attached to the upper plate is attached to the substrate 17.
It may be attached to a part of. Furthermore, each spring 1 for pressing each plate shown in FIG.
5 and 18 may be used as necessary, and these springs must not restrict the movement of each plate.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an image forming apparatus to which the present invention is applied, FIG. 2 is an explanatory diagram illustrating a state in which a document is divided into two and irradiated onto a light receiving element, and FIG. 3 is a perspective view of the present invention. FIG. 4 shows a plan view of FIG. 3. In the figure, 6 ₁ and 6 ₂ are the first and second lenses, and 7
₁ and 7 ₂ are first and second light receiving elements, 8 ₁ and 8 ₂ are first and second reading sections, 10 ₁ and 10 ₂ are first and second upper plates, and 14 is a middle plate.

Claims (1)

[Claims] 1. In a document reading device that reads a document image using a plurality of light receiving sections, a support member that is provided corresponding to each of the plurality of light receiving sections and supports the light receiving section;
a connecting member that connects the respective supporting members;
A document reading device characterized in that the supporting member is made of a material having a larger coefficient of linear expansion than the connecting member.