JPS59218421A - System for reading original with variable magnification - Google Patents

Abstract

PURPOSE:To make a device small-sized and low-cost and obtain high-quality read images by focusing the variable magnification image of an original picture on a light receiving face of an image pickup element by change of the length from a main lens to the original surface and insertion and removal of an auxiliary lens. CONSTITUTION:A main slider 102 is moved to a preliminarily determined position, and an auxiliary slider 107 is so placed that the center of a through hole 109c coincides with an optical axis 101 of the main lens approximately. The light which is emitted from a fluorescent lamp 113 and is reflected on the surface of an original 112, namely the original image passes through the through hole 109c and the main lens and is focused on the light receiving face of a solid- state image sensor 105 with a reference magnification and is converted photoelectrically. In case that the original picture is read with a magnification other than the reference magnification, the main slider 102 is slid to a position corresponding to this magnification, and the auxiliary slider 107 is so moved that the optical axis of an auxiliary lens 109a or 109b corresponding to this magnification coincides with an optical axis 101 of the main lens practically.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a variable magnification reading system for reading an original image at variable magnification using a lens system and an image sensor.

Conventional Structure and Problems The following methods 1) to iv) are known as methods for reading images of manuscripts (paperbacks, drawings, etc.) at variable magnification.

1] A method that includes a plurality of combinations of lenses and image sensors, and reads a document image using one combination that corresponds to a desired magnification.

11) A method in which multiple lenses are arranged on a turret (rotating disk) placed between the original and the image sensor, and the turret is rotated so that the lens corresponding to the desired magnification is in front of the image sensor.

1ii) Using a pair of lens and image sensor, the distance between the lens and the document surface and the distance between the lens and the image sensor 11
A method that simultaneously changes the values according to the magnification.

iv) Using a pair of lens and image sensor, the document image is read once at a constant magnification with the distance between the lens and the document surface and the distance between the lens and the image sensor fixed, and then read by thinning processing of the output signal of the image sensor. A method that changes the magnification.

However, the methods i) and ii) above have a problem in that the increase in the number of lenses and image sensors increases the cost and size of the reading system. The problem with the above method 111) is that the distance between the lens and the image sensor must be controlled with extremely high precision (preferably to suppress the error to 10 μm or less) using a sophisticated mechanism, and the cost of this mechanism is high. There is also the problem that image quality deterioration is likely to occur due to control errors.

The above-mentioned method iv) has a problem in that the image quality is inferior to the above-mentioned method 111) in which magnification is changed optically.

OBJECTS OF THE INVENTION The present invention solves the above-mentioned conventional problems, and provides a new document magnification reading method that allows the reading system to be made smaller and lower in cost, and that can obtain read images of high quality. The purpose is to

Structure of the Invention The present invention constantly fixes the distance between the main lens and the image sensor, and changes the distance between the main lens and the document surface, and inserts and removes an auxiliary lens to visualize the document image in a variable magnification image. By forming an image on the light-receiving surface of an image sensor, the objective is to achieve a closed-loop image.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. Fig. 1 6J is a diagram showing the principle of the variable magnification reading system of the present invention. In this figure, 1 is an image sensor, 2 is a main lens (single lens or compound lens), and 3 is an auxiliary lens (single lens or compound lens).

The distance l between the main lens 2 and the image sensor 1 is always fixed.

4 is the optical axis of the main lens.

FIG. 1A shows a case where an image of a document 5 having a width W1 is read, and the relative positions of the main lens 2 and the document 6 are set so that the distance between the image sensor 1 and the document 5 is L.sub.2. The auxiliary lens 3 is placed at a position away from the optical axis 3. The image of the original 5 is multiplied by m1 by the main lens 2, focused on the light-receiving surface of the image sensor 1, and converted into an image.

Figure 1 shows the case of reading an image of a document 6 having a width of W2.
The relative positions of the main lens 2 and the original 6 are set so that The auxiliary lens 3 is placed in a position where its optical axis substantially coincides with the optical axis 4 of the main lens 2. The image of the original 6 is expressed in m2 by the combination of the main lens 2 and the auxiliary lens 3.
The image is multiplied and imaged on the light-receiving surface of the image sensor 1. This formed image is converted into a width electrical signal.

FIG. 2 shows the distance L1. L2. FIG. 5 is a conceptual diagram for explaining the focal lengths of the main lens 2 and the auxiliary lens 3;

In this figure, if the focal length of the main lens 2 (acting as a convex lens) is fl and the focal length of the auxiliary lens 3 (acting as a concave lens) is f2, then the following equation holds true.

and fo are the combined focal lengths of the main lens 2 and the auxiliary lens 30.

b -33,3θmm, a2-=343.9mm
, fO=30.41-mm, f2=-2233mm, 1L=a2-a1=
It is designed as Ll-L2==45.9m. In this case, use only the main lens 2 to read an 84-size original at a semi-magnification of m1, and add the auxiliary lens 3 to read an A3-size original at a magnification of m2.
e can be taken. In this way, the auxiliary lens 3 is f
--2233mmf, lens action force (J) is always 〇- weak.

Although the upper auxiliary lens 3 is used as a weak concave lens, it is also possible to use an auxiliary lens that acts as a weak convex lens. This case will be explained with reference to the conceptual diagram of FIG. 3.

In Figure 3, 7 is an auxiliary lens (single lens or compound lens) with a weak convex lens effect.

Reference numeral 8 denotes an original that is read by the combination of the auxiliary lens 7 and the main lens 2. An image can be formed on Complement 1 and read so that the following equation holds true (m3>ml>m2).

Here, f0' is the combined focal length of the main lens 2 and the auxiliary lens 7.

In this case as well, a convex lens similar to flat glass with a sufficiently large focal length (weak lens action) can be used as the auxiliary lens 7.

FIG. 4 is a schematic perspective view showing a reading system of a variable magnification reading apparatus according to an embodiment of the present invention.

In this figure, 100 is a linear rail, which is fixed parallel to the optical axis 101 of the main lens. A through hole 104 is bored in the base 103 of the main slider 102, which is slidably supported by the rail 100, and the through hole 104 is centered entirely on the optical axis 101. The light-receiving surface of the main slider 106 is inserted into the through hole 104 and extends to the rear side of the main slider base 103. A cylindrical body 106 coaxial with the optical axis 101 is attached to the front side of the main slider base 103, and a main lens (not shown in the figure) is attached within this cylindrical body 106.

1o7ij is a sub slider, and is supported at the tip of the arm portion 108 of the main slider 102 so as to be slidable in a direction perpendicular to the optical axis 101. This sub-slider 107 includes two auxiliary lenses (single lens or compound lens) 109a having different focal lengths.

Two through holes with 1o9b attached and a through hole 109c without a lens are bored. Although not shown in Figure 1, means for moving the main slider 102 along the rail 100 and means for moving the sub-slider 107 in a direction orthogonal to the optical axis 101 of the main lens are provided. 110
is a signal cable for extracting the output signal of the line-type solid-state image sensor 105, and the connector 1 is provided at the tip thereof.

1 in 112 is a manuscript. Reference numeral 113 denotes a fluorescent lamp for illuminating the original 112, and has a length that can illuminate the range of the maximum original width W with a sufficiently uniform amount of light.

To explain the operation, when reading at the standard magnification, the main slider 102 is moved to a predetermined position, and the center of the through hole 109C of the sub slider 107 is approximately aligned with the optical axis 10 of the main lens.
Position it so that it matches 1. The light emitted from the fluorescent lamp 113 and reflected on the surface of the original 112, that is, the original image, passes through the through hole 109C and the main lens, forms an image on the light receiving surface of the solid-state image sensor 105 at a standard magnification, and is photoelectrically converted. .

In addition, when reading a document image at a magnification other than the standard magnification, the main slider 102 is slid in a position corresponding to the magnification, and the auxiliary lens 109 corresponding to the magnification is
The sub slider 107 is moved so that the optical axis of a4 or 109b substantially coincides with the optical axis 101 of the main lens. The original image is transmitted to the solid-state image sensor 10 at the magnification through the auxiliary lens 109a or 109b and the main lens.
The light condenses on the light receiving surface of 5 and is converted into an electrical signal.

In this way, the original image can be read at different magnifications including the reference magnification.

Now, in general, the good image area (depth of focus area) that can be accommodated by π on the light receiving surface (imaging surface) of a solid-state image sensor is approximately proportional to the pixel pitch of the solid-state image sensor. For example, for a COD image sensor with a pixel pinch of 14 μm, if the numerical aperture F of the imaging lens is 4, the allowable depth of focus range δ to guarantee good image quality is estimated to be about ±20 to ±30 μm. Ru. If the pixel pinch is 7μm and the number of pixels is 4
In the case of a solid-state image sensor of about 096, the allowable depth of focus range δ is about ±10 to ±20 μm. From this, it is clear that it is extremely difficult to guarantee good image quality by switching the distance between the solid-state image sensor and the lens as in the conventional method described in 111) above.

In contrast, in the present invention, the relative distance between the main lens and the solid-state image sensor is fixed after focusing at the reference magnification and does not change at all.

Further, as described above, a concave lens or a convex lens similar to flat glass, which has a weak lens effect, can be used as the auxiliary lens, and a distance error between both lenses and a shift in the optical axis can be tolerated to some extent. In the case of the example given in the explanation with reference to Figure 2, the distance error and optical axis deviation between the main lens and the auxiliary lens are ±0.
．． The inclination of one optical axis for three cabinets is allowed to be approximately ±1°. Therefore, the mechanical precision associated with the movement of the optical block including the main lens and the auxiliary lens is approximately converted to the depth of focus area on the light receiving surface of the solid-state image sensor, and δ is usually −'=;100δ (m is the magnification) It's very gradual.
? be. Therefore, in the above embodiment, the accuracy requirements for the mechanism for moving the rail 100, the main slider 02, the sub slider 07, and both sliders are significantly relaxed, and the mechanism can be realized at low cost. In addition, the reliability is also improved because these mechanical parts are not affected by wear, vibration, etc.

FIG. 5 is a schematic plan view showing another example of auxiliary lens selection means in place of the auxiliary slider in the above embodiment. In this figure, 200 is a disk, 2018 to 201iiJ are auxiliary lenses attached to through holes formed in this disk 200, and 201j is a through hole to which no lens is attached. With this disk 200 at its center, for example, the main block 10 in FIG.
2 and rotate the disk 200 so that the center of the through hole 201j and the optical axis of any one of the auxiliary lenses 201a to 2011 coincide with the optical axis of the main lens. Similar variable magnification reading is possible.

FIG. 6 is a block diagram showing an example of a variable magnification reading device including the reading system as described above.

In this figure, 300 is a document, 301 is a fluorescent pair for illuminating the document, and 302 is an optical block including a main lens and an auxiliary lens. 303 is a COD image sensor, which is integrated with the optical block, but is shown separately in the figure. 304 is a drive mechanism, and a control circuit 306
The entire optical block 302 moves and the auxiliary lens is selected under the control of the optical block 302. When a certain magnification is specified by the magnification setting signal 306, the control circuit 305 controls the drive mechanism 304.
By controlling the operation of the optical block 302, the optical block 302 is moved to a position corresponding to the specified magnification, and the auxiliary lens corresponding to the specified magnification is selected (if the reference magnification is specified, the auxiliary lens is not selected). As a result, the original 301
is formed on the COD image sensor 303 at a specified magnification.

307 is an amplifier, 308 is an arithmetic unit, and 309 is a ROM. The image signal output from the COD image sensor 303 is amplified by the amplifier 307 and then sent to the arithmetic unit 308.
is input. This image signal includes non-uniformity in the light amount distribution of the fluorescent pair 301, optical distortion of the main lens and auxiliary lens, C
The OD image sensor 303 is subjected to distortion due to bit-by-bit sensitivity variations, etc., that is, so-called shading distortion.

The arithmetic unit performs calculations to correct this shading distortion, and the correction parameters used for the calculations are output from the ROM 309 in synchronization with the image signal. Since the shading distortion characteristics change depending on the document reading magnification, correction parameters for each magnification are stored in the ROM 309 in advance. When a magnification is designated by the magnification designation signal 306, a correction parameter for that magnification is selected and output from the ROM 309, and a shading distortion correction calculation using the correction parameter is performed by the computing unit 309.
08, and the image signal from which shading distortion has been removed is output from the arithmetic unit 308.

In this way, since shading distortion correction calculations are performed by selecting appropriate correction parameters according to the magnification, an image signal free of shading distortion can be obtained at all magnifications.

Effects of the Invention As described above, the present invention always fixes the distance between the main lens and the image sensor, changes the distance between the main lens and the document, and inserts the auxiliary lens to perform variable magnification reading. Since the lens control mechanism can be simplified, made smaller, and lowered in cost, it is possible to read a document image at variable magnification with good image quality using a small and inexpensive reading system.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an apparatus to which the variable magnification reading method of the present invention is applied, FIGS. 2 and 3 are schematic diagrams for explaining the focal lengths of the main lens and auxiliary lens, etc., and FIG. FIG. 5 is a schematic plan view showing a modification of the auxiliary lens selection means, and FIG. 6 is a block diagram of the variable magnification reading device according to the present invention. be. 1...Image sensor, 2...Main lens, 3
, 7... Auxiliary lens, 5.6.8...
Manuscript, 100...Rail, 102...
Main slider, 106...Solid image sensor,
107... Sub slider, 109a. 109b... Auxiliary lens, 109C...
・Through hole, 112... Manuscript, 113...
Fluorescent light, 200...Disc, 201a-2011
...Auxiliary lens, 2011...Through hole,
300... Manuscript, 301... Fluorescent light,
302...Optical block, 303...
COD image sensor, 304... Drive mechanism,
306...Control circuit, 307...Amplifier, 308...Calculation 2 diagnosis, 309...-
ROM. Name of agent Patent attorney Toshio Nakao I1 Riki/1 person Figure 1

Claims (1)

[Claims] By setting the main lens and the surface of the document at a specific relative distance, and forming an image of the document via the main lens on the light-receiving surface of an image sensor located at a fixed relative distance with respect to the main lens. , read the original image at a specific magnification,
The main lens and the document surface are set at another specific relative distance, and an auxiliary lens is positioned near the main lens so that the optical axes substantially coincide with each other, and the main lens and the auxiliary lens are A document magnification variable reading method characterized in that the document image is read at another specific magnification by focusing the document image on the light receiving surface of the image sensor.