JPH05292314A - Picture reader - Google Patents

Abstract

PURPOSE:To obtain a sharp picture without out-of-focus or distortion regardless of the shape of an original face. CONSTITUTION:A spot reflected light reflected by an original 5 is received by a picture read section 1 and the shape of an original face is calculated by a microcomputer 14 based on the light receiving signal. Then based on the result of arithmetic operation, the focus of an original 5 by an optical image forming system 6 is adjusted by a focus control mechanism section 7 and the original picture is read by the picture read section 1. Furthermore, the read signal of a bent part of the original 5 in the read original picture signal is expanded and corrected in density based on the data of the original shape calculated by the arithmetic operation at a distortion picture processing circuit 13 and a sharp pattern without out-of-focus or distortion is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus for forming an optical image of a document image on a solid-state image pickup device by using an optical image forming means, and converting the image into an electric signal. The present invention relates to an image reading apparatus that improves image distortion and image blurring caused by a change in relative position of an image sensor.

[0002]

2. Description of the Related Art As an image reading apparatus used in a facsimile, a digital copying machine, a scanner for a personal computer, etc., for example, as shown in FIG. 7, a casing 101 having a platen glass (not shown) on its upper surface is used. On the top side of the document 103
Is arranged so that the original image is read.
An illumination light source 105, a mirror 107, a lens 109, and a solid-state image pickup device (for example, CCD) 111, which constitute a reduction optical system, are installed in the above-mentioned housing 101.

As another type of image reading apparatus, as shown in FIG. 8, an illumination forming a unit-magnification optical imaging system is provided in a housing 101 having a platen glass (not shown) on its upper surface. In some cases, the light source 105, the rod lens array 113, and the contact sensor 115 are installed. Then, the light emitted from the illumination light source 105 is reflected by the original 103, and the reflected light is passed through the reduction optical system or the same-magnification optical imaging system, and the solid-state image sensor 111 or the contact sensor 115.
The reflected light that is imaged on the upper surface and that corresponds to the shading of the document surface is converted into an electric signal.

[0004]

However, in the above-mentioned image reading apparatus, since the signal read is processed on the assumption that the entire original is in close contact with the platen glass (in other words, the original surface is read). Because the focal length is constant irrespective of the shape of the book), when reading a book such as a relatively thick book, the back of the book pops up just by turning it over on the platen glass. In addition to the problem that the read image of this part will be blurred or distorted, if you press the book against the platen glass to reduce the blur or distortion of such image even a little, the original such as the book is easy to damage There was a problem of causing damage or missing pages.

The present invention has been made in view of the above-mentioned circumstances, and an image which can faithfully obtain an original image without blurring and distortion without a blurred focal length regardless of how closely the platen glass and the original are closely attached. An object is to provide a reading device.

[0006]

In order to solve the above problems, an image reading apparatus according to the present invention comprises an optical image forming means for forming an image of reflected light from a surface to be read at a desired position, and the optical image forming means. The image forming means for receiving the optical image formed by the means and converting it into an electric signal; and the optical image forming means and the image forming means while keeping the relative positional relationship between the optical image forming means and the image forming means constant. A scanning unit that rotates in two directions orthogonal to each other;
Spot light irradiating means for irradiating a desired position on the surface to be read, and output of the image pickup means for reflected light of the spot light from the document received by the image pickup means through the optical image forming means. The surface shape calculation means for calculating the shape of the document surface based on the signal, the focus adjustment means for adjusting the focus of the optical image forming means based on the calculation result of the surface shape calculation means, and the surface shape calculation means. And a correction means for expanding the image signal of the curved portion of the document based on the calculation result and setting the image density of the expanded portion based on the difference in image density of the curved portion before expansion. is there.

[0007]

The surface to be read is irradiated with the spot light by the spot light irradiation means before the reading of the original image, and the reflected light (spot reflected light) is received by the image pickup means and converted into an electric signal. In the surface shape calculation means, the shape of the surface to be read is calculated based on the output signal of the image pickup means with respect to the spot reflected light, and the focus of the optical image forming means is adjusted by the focus adjustment means based on the calculation result of the surface shape calculation means. It is adjusted and after that the image of the surface to be read is read,
The image is always obtained under an appropriate focal length. Further, the reduced image of the curved portion of the surface to be read is expanded to the original size based on the calculation result of the surface shape calculation means, and the density of the image portion newly generated by the expansion processing is newly generated. Since it is set based on the actual amount of change in density near the image portion, an image that is easy to see without distortion or blurring can be obtained.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image reading apparatus according to the present invention will be described below with reference to FIGS. Here, FIG. 1 is a configuration diagram showing a configuration of an image reading apparatus according to the present invention, and FIG. 2 is an overall perspective view showing an embodiment of an external appearance of a main part of the image reading apparatus according to the present invention. This image reading apparatus is roughly divided into an image reading unit 1 that reads an original image and an original surface shape, and a spot light generation unit 2 that irradiates the original surface with spot light.

The image reading section 1 includes a drive processing circuit 4 for controlling the operation of the solid-state image pickup device 3, a solid-state image pickup device 3 as an image pickup means such as a CCD, and a reflection from a document 5 on the solid-state image pickup device 3. An optical imaging system 6 including a lens for condensing light, and a focus of the optical imaging system 6 on the original 5 while keeping a relative position of at least the solid-state imaging device 3 and the optical imaging system 6 constant. A focus control mechanism section 7 for adjusting the distance,
Focus / imaging system control unit 8 for controlling the focus control mechanism unit 7
And are provided.

The spot light generation section 2 includes a spot light source 9 for generating spot light, a rotary mirror 10 for reflecting the spot light from the spot light source 9, and a spot for controlling the rotation of the rotary mirror 10. Light irradiation direction control unit 11
And, and. Here, rotating mirror-10
For example, a polygon mirror or the like formed in a hexagonal column shape is suitable. Then, the reflected light of the spot light (hereinafter, referred to as “spot reflected light”) irradiated on the original 5 via the rotating mirror 10 is received by the solid-state image sensor 3 of the image reading unit 1 described above. (See below for details).

Further, the image reading apparatus includes a memory 12 for storing a document surface shape, a distorted image processing circuit 13, and a known / known microprocessor 14 for controlling the operation of the apparatus.
And have. The document surface shape storage memory 12 stores the data of the document surface shape calculated by the arithmetic processing in the microprocessor 14 based on the spot reflected light received by the image reading unit 1 (details will be described later). It is a thing. Further, the distorted image processing circuit 13 corrects the image signal based on the data relating to the document surface shape stored in the document surface shape storage memory 12 (details will be described later).

Next, an example of the external appearance of the main part of the image reading apparatus in this embodiment will be described with reference to FIG. The image processing apparatus of the present embodiment has a structure capable of reading an original image and reading the shape of the original surface without turning over the original surface, unlike the prior art. That is,
The image reading device includes a flat plate-shaped document placing plate 15 on which the document 5 is placed, and a light-shielding plate 16 which is vertically provided on one side of the document placing plate 15. , Light shield 1
An image reading section 1 and a spot light generating section 2 are provided at both ends of the upper part of 6 (upward in FIG. 2). Here, the image reading unit 1 does not need to house all the constituent elements shown in FIG. That is, at least the solid-state imaging device 3, the optical imaging system 6, and the focus control mechanism unit 7 are housed, and it is sufficient that all of them are rotated in two directions orthogonal to each other. The elements do not necessarily have to be housed in the same housing. In addition, the two orthogonal directions in which the image reading unit 1 is rotated are, in the case of FIG. 2, the X direction indicated by the solid arrow in FIG. 2 (the width direction of the document placing plate 15, that is,
In FIG. 2, the right and left sides of the paper surface and the y direction (original platen 1
5 is the depth direction, that is, the direction orthogonal to the width direction). Therefore, in FIG. 2, the image reading unit 1 is designed to scan in the X and Y directions.

On the other hand, unlike the image reading unit 1, the spot light generating unit 2 does not move the entire housing in which it is housed, and is itself fixed to the light shielding plate 16 at an appropriate angle. As a result of the rotating mirror 10 housed inside being rotated under the control of the spot light irradiation direction control unit 11, the spot light is irradiated to an arbitrary point on the document surface. In this apparatus, when the image reading unit 1 reads the document surface shape, the image reading unit 1
Is rotated, that is, scanned so that the viewing direction of the image reading unit 1 coincides with the irradiation point of the spot light generation unit 2 on the document (see FIG. 2).

FIG. 3 shows a specific example of the scanning mechanism of the image reading section 1, and the structure thereof will be described below with reference to the figure. In the scanning mechanism of the image reading unit 1, a horizontally movable casing 17 is attached to a supporting unit 18, and the horizontally movable casing 17 has an X-axis centered on a horizontal scanning axis 19.
It is installed so that it can rotate in any direction. This horizontal scanning axis 19
Is configured to rotate the horizontally movable casing 17 by being rotated by a horizontal scanning mechanism 20 provided at one end thereof. The support portion 18 is fixed to the light shielding plate 16.

A vertically movable housing 21 is attached to the horizontally movable housing 17, and a vertical scanning shaft 22 fixed to the vertically movable housing 21 is driven by a vertical scanning mechanism 23. The vertically movable housing 21 is adapted to be rotated in the Y direction. Further, in the vertically movable casing 21 in the present embodiment, the solid-state image pickup device 3 (for example, CCD forming a two-dimensional image sensor), the optical image forming system 6,
The focus control mechanism unit 7 and the focus / imaging system control unit 8 are
The drive processing circuits 4 are housed in the above-mentioned horizontally movable casings 17, respectively.

FIG. 4 shows the contents of a series of image reading processes performed by the microprocessor 14 as a flow chart, and the contents will be described below with reference to the same figure. The microprocessor 14 detects that the reading start switch (not shown) is pressed (step 20).
0) Start a series of processing. And the spot light source 9
Is driven to irradiate spot light through the rotary mirror 10 along the X direction of the original 5, and the image reading section 1 is rotated in synchronization with the movement of the spot light to reflect the spot in the X direction. Light is read (step 202).
Then, in the next step 204, based on the output signal of the solid-state image sensor 3 with respect to the spot reflected light received by the solid-state image sensor 3 in the above-mentioned step 202, the document surface shape in the X direction, that is, the document platen. The magnitude of the undulation of the document surface in the direction perpendicular to 15 is calculated (details of the calculation will be described later), and the calculation result is stored in the document surface shape storage memory 12 and the process proceeds to the next step 206.

In step 206, the spot reflected light is read in the Y direction in the same manner as in step 202 above, and in step 208, the document surface shape in the Y direction is calculated in the same manner as in step 204 above. The calculation result is stored in the document surface shape storage memory 12. In the next step 210, the scanning direction for starting the document reading is determined based on the data of the document surface shapes in the X and Y directions calculated in steps 204 and 208 described above. That is, in the present embodiment, the original is read with the scanning direction as the direction having the large undulations on the original surface.
When the document 5 is thick like a book as shown in FIG. 2, the X direction is set as the document reading direction.

In step 212, the document is read. This reading of the original is performed in the scanning direction determined in step 210, and in the present embodiment, it is performed by scanning the X direction a plurality of times. That is, the orientation of the image reading unit 1 is adjusted so that the light receiving direction of the solid-state image pickup element 3 is directed to the original reading start position (step 212a), and the focus of the optical imaging system 6 is adjusted at the reading position. In this focus adjustment, the focus of the optical image forming system 6 is adjusted by the focus control mechanism section 8 based on the data of the document surface shape which has already been calculated (see steps 204 and 208).

After the focus adjustment, the original image of one line in the X direction is read (step 212c), and then the process returns to the previous step 212a, and the reading for each remaining line is repeated. When the reading of the entire document is completed, distortion correction (details will be described later) is performed on the read signal (step 214), and then the final read image is output. In the above-mentioned flow chart, the spot light is read from the X direction, but it is not always necessary to start from the X direction, and it may be started from the Y direction.

Next, the document surface shape calculation processing in steps 204 and 208 described above will be specifically described with reference to FIG. In FIG. 5, the portion indicated by a slightly thick solid line at the bottom of the paper is the shape of the document surface that appears on the end surface of the document 5 when the document 5 placed on the document mounting platen 15 is viewed in the Y direction. is there. In addition, the lens 2 that constitutes the optical imaging system 6
4 and the solid-state image sensor 3 are arranged such that the optical axis of the lens 24 is located at the center of the solid-state image sensor 3.

Then, in FIG. 5, the solid-state image pickup device 3
The center of is the origin O of the two-dimensional coordinates represented by the X axis and the Z axis, and the distance between the lens 24 and the solid-state image sensor 3 is represented by f in the Z axis direction. In addition, the rotary shaft 10a of the rotary mirror 10 is provided in the front and back direction of the paper surface in FIG. 5, the distance from the origin in the X-axis direction is indicated by x _m , and the reflection surface from the origin in the Z-axis direction. The distance of is denoted by z _m . Further, the coordinates of the point on the reflecting surface of the rotating mirror 10 on which the spot light from the spot light source 9 is reflected are represented by M (x _m , z _m ).

Then, assuming that the spot light incident on the reflection point M of the rotating mirror 10 is reflected at the reflection angle α and is incident on the original surface, the coordinates of the incident point on the original surface are represented by P (x, z). Shall be done. The incident point P is also a reflection point at the same time, and the spot light reflected here passes through the lens 24 at an angle of β with respect to the Z axis and is incident on the surface of the solid-state image pickup device 3, but the coordinates of the incident point. Is represented by S (-xs, 0). Under the above conditions, the value of the coordinate z of the incident point P of the original 5, that is, the distance z between the solid-state imaging device 3 and the original 5 is determined.

First, X of the rotary shaft 10a of the rotary mirror 10
Direction position x _m , side Pa of triangle Pab in FIG.
(Here, the point b is the center point of the lens 24) and the triangle PcM.
Since it is obtained as the sum of the lengths of the sides Mc of, it is expressed by the following equation. That is, x _m = (z−f) tan β
+ (Z−z _m ) tan α Equation (1) Also, tan β
= Xs / f ... Equation 2 can be expressed. Then, the above Expression 1 is expanded to the expression for z, and the following Expression 3 can be obtained by substituting the relationship of Expression 2. z = (x _m + z _m tan α + xs) / (tan α + xs / f) ... Equation 3

This calculated value is stored in the memory 15 for storing the document surface shape.
However, it is read through the microprocessor 14 at the time of focus adjustment (see step 212b in FIG. 4) in the reading processing of the entire original image by the image reading unit 1, and this reading is performed as described above. The focal length of the optical image forming system 6 is adjusted based on the data thus obtained, and the original image is read at the optimum focal length.

Next, the distortion correction in step 214 of FIG. 4 will be described with reference to FIG. This distortion correction is performed if the original surface has a curved portion as shown in FIG.
The read image in this portion is clear without blurring due to the previous focus adjustment, but the distortion is corrected because the image is reduced in the reading direction and has distortion. First, FIG. 6A shows the Y-axis direction when the document surface is along the X-axis (the horizontal direction of the paper surface in FIG. 6) and the back side of the document 5 (the side in contact with the document placing plate 15) is facing upward. 3 shows a document surface shape viewed from (same as Y-axis shown in FIG. 2).
On the other hand, FIG. 6B is an approximate shape of the document surface obtained by plotting the values of the document surface shape calculated by the arithmetic processing in the same positional relationship as in FIG. 6A.

In FIG. 6B, two points of x _i and x _{(i +1 ) on} the X axis which is the scanning direction of the image reading section 1 (these two points respectively correspond to the pixel positions). Note that the coordinates of the document surface at x _i are represented by P _i and the coordinates at x _{(i + 1)} are represented by P _{(i + 1)} . Since the document 5 is curved between the coordinates P _i and P _{(i + 1)} as shown in the drawing, if the document 5 is straight in the X-axis direction without being curved, the pixels existing in this portion are x _i and Not only two points of x _{(i + 1)} . Therefore, the coordinates P _i and P
_{When (i + 1)} is located in the X-axis direction, that is, when the document surface is straight, the number of pixels that would be located between these two coordinates is calculated to obtain P _i along the document surface. The distance from P _{(i + 1)} is [P _i P _{(i + 1)} ] and the pixel interval is [x _i −
x _{(i + 1)} ], and the number of pixels that may exist between P _i and P _{(i + 1)} is [P _i P _{(i + 1)} ] / [x _i −
x _{(i + 1)} ].

Next, if the document surface is straight, the read value (density value) that will be obtained for each pixel obtained by the above calculation is obtained by the interpolation method. First, in order to simplify the processing, it is assumed that there are two image densities, an intermediate part where the density value changes smoothly and an edge part where the density value changes rapidly such as a character or a line drawing. Next, the density value of P _i is I
Assuming that the density values of _i and P _{(i + 1)} are I _{(i + 1)} ,
The density difference between the two is set to [I _i −I _{(i + 1)} ]. Then, it is determined whether or not this density difference is equal to or more than a predetermined value Θ, and if it is equal to or more than the predetermined value Θ, it is determined that an edge portion is present between P _i and P _{(i + 1),} and P _i and P Pixels located closer to P _i from the midpoint of _{(i + 1)} have uniform density values I _i, and pixels located closer to P _{(i + 1)} have uniform density values I _{(i +). 1)} and two values are assigned to each pixel.

On the other hand, the density difference [I _i −I _{(i + 1)} ] is a predetermined value Θ.
If it is smaller, it is assumed to be the intermediate portion described above, and the number of pixels ([P _i P _{(i + 1)} ] / [x _i −
x _{(i + 1)} ]) is n, the density value Ik of the k-th (k = 1 to n) pixel among them is set by the following equation. That is, Ik = I _i + {(I _{(i + 1)} −I _i ) /
It is calculated as (n + 1)} × k. Hereinafter, the correction is similarly performed for each coordinate P. In the correction of the present embodiment, the original 5
The image read by being reduced by the curvature of is expanded, and the density of the expanded part is set based on the density difference of the pixel before the expansion so that an appropriate image can be obtained.

In this embodiment, the spot light generator 2 is used.
Is provided, the surface of the original is irradiated with spot light before reading the original image, the reflected light is read by the image reading unit 1, the original surface shape is calculated based on the read signal, and based on the calculated value. Since the original image is read by the image reading unit 1 after the focus adjustment has been performed, the original is always read with an appropriate focus. Further, the distorted image correction circuit 16 expands the image of the curved portion of the document 5 based on the calculated value of the document surface shape, and
Since the image density of the expanded part is set based on the actual density difference in the vicinity, it is possible to obtain an image of the original size with an appropriate density even if there is a curved part in the document. Become.

[0030]

As described above, the image reading apparatus according to the present invention illuminates the surface to be read with spot light, obtains the shape of the surface to be read from the reflected light, and determines the shape of the surface to be read. The focal length is adjusted accordingly, and the reduced image of the curved part of the document is expanded to its original size based on the shape of the surface to be read obtained by irradiation of the spot light, and it is generated by the expansion process. The configuration is such that the density of the newly created image portion is set based on the amount of change in the density of the actual image in the vicinity of the newly created image, so that the shape of the document surface is corrected. However, since the image is always read at an appropriate focal length, a blur-free image is obtained, and the portion where the image is read such that the original surface is curved and reduced is approximately the original size. Stretched image Since the image obtained and appropriate concentration is obtained, in which a marked effect of distortion yet clear image without obtain.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a configuration of an image reading apparatus according to an embodiment of the present invention.

FIG. 2 is an overall perspective view showing an example of an external appearance of a main part of the image reading apparatus according to the present invention.

FIG. 3 is an explanatory diagram illustrating a schematic structure of an image reading unit in the image reading apparatus according to the present invention.

FIG. 4 is a flowchart for explaining an image reading process in the image reading apparatus according to the present invention.

FIG. 5 is an explanatory diagram for explaining calculation of a document surface shape in the image reading apparatus according to the present invention.

FIG. 6 is an explanatory diagram for explaining distortion correction in the image reading apparatus according to the present invention.

FIG. 7 is a schematic configuration diagram showing an example of a conventional image reading apparatus.

FIG. 8 is a schematic configuration diagram showing another embodiment of a conventional image reading apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Image reading part, 2 ... Spot light generation part, 3 ... Solid-state imaging device, 6 ... Optical imaging system, 7 ... Focus control mechanism part,
9 ... Spot light source, 10 ... Rotating mirror, 11 ... Spot light irradiation direction control unit, 12 ... Memory for storing original surface shape

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location H04N 1/10 7205-5C

Claims (1)

[Claims] 1. An optical image forming means for forming an image of reflected light from a surface to be read at a desired position, and an image forming means for receiving an optical image formed by the optical image forming means and converting it into an electric signal. ,
Scanning means for rotating the optical image forming means and the image pickup means in two directions orthogonal to each other while keeping the relative positional relationship between the optical image forming means and the image pickup means constant, and at a desired position on the surface to be read. Spot light irradiating means for irradiating the spot light, and a document surface of the document based on an output signal of the image capturing means with respect to reflected light of the spot light from the document received by the image capturing means via the optical image forming means. Surface shape calculation means for calculating the shape, focus adjustment means for adjusting the focus of the optical image formation means based on the calculation result of the surface shape calculation means,
Correction means for expanding the image signal of the curved portion of the document based on the calculation result of the surface shape calculation means and setting the image density of the expanded portion based on the difference in image density of the curved portion before expansion; An image reading apparatus comprising: