JPH05188485A - Image reader - Google Patents

Abstract

PURPOSE:To obtain an image reader which can precisely detect a floating quantity (distance) from the contact glass surface of an original and form an image on a photodetection means surface, with the image information of the whole of an original surface, and read the image. CONSTITUTION:A distance detecting means 30 which is integrally moved to a forward position in a scanning direction, with a reading/scanning system, makes optical spots incident on plural regions in a direction in parallel with a slit opening, and detects plural spots reflected from the original surface by a photodetection part 15 composed of plural photodetectors, via an image forming part 12, to obtain the information of the distance from the original surface to a prescribed surface, based on a signal from the photodetection part, when the image information on the surface of the original 1 placed on the surface of an original platen 2, is scanned by the reading/scanning system having the slit opening, and the image is seqentially formed on the surface of a photodetection means 11, and read. Then, the length of an optical path from the original surface to the photodetection means surface is adjusted by a correcting means based on the signal from the distance detecting means.

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, and in particular, as image information, when it is placed on a document table surface such as a thick book-type document whose back is closed, a concave and convex portion is partially depressed. An image reading apparatus suitable for an apparatus such as a copying machine, which can always read image information on a document surface having a portion regardless of the unevenness of the document surface without lowering the resolution. It is about.

[0002]

2. Description of the Related Art Conventionally, various image reading apparatuses used in copying machines and the like have been proposed, in particular, a method of reading image information by placing a document surface downward on a document table surface.

In such an image reading apparatus, when a document surface such as a thick book-type document is placed on the surface of a document table, the document surface to be read is not entirely flat, and image information having uneven portions is formed. In this case, if an attempt is made to read the original surface with the focus position kept constant by the reading means fixed for the image information, the area where the original surface is apart from the original table surface (contact glass) is in a defocused state. As a result, there is a problem that the resolution is lowered.

Therefore, in order to solve the above problems, an image reading apparatus equipped with a focus detection system (distance detection means) has been proposed in, for example, JP-A-60-117232.

In this publication, a light flux is emitted from the exposure member toward the surface of the original during scanning exposure of the original, and the reflected light from the surface of the original is condensed by a condenser lens and focused on the light receiving member. The original surface (scanned position) from the contact glass is read by reading the focusing position of the reflected light on the light receiving member surface.
To the image irradiation position, an optical path length adjusting means for adjusting the optical path length from the scanned position of the document to the image irradiation position, a scanning speed adjusting means for adjusting the scanning speed of the optical traveling body, and the distance. The optical path length adjusting means is adjusted so as to adjust the optical path length on the basis of the signal output from the detecting means, and the displacement amount of the distance between the contact glass and the document per unit scanning time is detected. The image information on the document surface is sequentially read by utilizing the control means for controlling the scanning speed adjusting means so as to adjust the scanning speed of the optical scanning body in accordance with the above.

In addition, a distance detecting means having a light projecting portion and a light receiving portion is provided in the vicinity of the document surface, and the document surface is pre-scanned before the actual exposure scanning by using the distance detecting means. By detecting the position formed on the light receiving element surface of the spot image reflected by, to detect the uneven state of the document surface,
An image reading apparatus has been proposed which reads image information on the surface of the original.

[0007]

However, these conventional image reading apparatuses require a large amount of space around the document surface due to the distance detecting means, which tends to increase the size and complexity of the entire apparatus. ..

Further, since the focus state of the document surface is detected, an image reading apparatus that prescans and reads an image before actual exposure scanning causes a loss of operation time, and it is difficult to increase the reading speed. There was a problem.

In order to reduce the time loss and increase the reading speed, it is desirable that the focus state of the document surface can be detected without prescanning.

According to the present invention, even when a part of image information to be read is a curved surface (unevenness) such as a book-type document, the distance detecting means having a simple structure makes it easy and accurate. By detecting the uneven shape of the document and appropriately adjusting the position of the optical element forming a part of the reading scanning system by the correcting device based on the signal from the distance detecting device, the document surface without prescanning. An object of the present invention is to provide an image reading device that can read the entire image information accurately and quickly.

[0011]

An image reading apparatus of the present invention scans image information on a document surface placed on a document table surface by a reading scanning system having a slit opening and sequentially forms an image on the light receiving surface. When reading by reading, a distance detecting unit that moves integrally with a part of the reading scanning system is provided at a position separated by a predetermined distance in the front in the scanning direction by the slit opening, and the distance detecting unit is provided in a direction parallel to the slit opening. A light spot is made incident on a plurality of areas, a plurality of spots reflected from the document surface are detected by a light receiving section composed of a plurality of light receiving elements via an image forming section, and the spot is detected based on a signal from the light receiving section. It is characterized in that the distance information from the document surface to the predetermined surface is obtained, and the optical path length from the document surface to the light receiving surface is adjusted by the correcting means based on the signal from the distance detecting means.

[0012]

1 is a schematic view of a main part of an image reading apparatus according to a first embodiment of the present invention, FIG. 2 is a perspective view of a main part in the vicinity of a distance detecting means shown in FIG. 1, and FIG. 3 is a distance shown in FIG. It is an enlarged explanatory view of the detection means vicinity.

In FIG. 1, reference numeral 1 denotes an original surface, which is an example of an original surface having a binding portion at a central portion of a book type such as a book. Reference numeral 2 denotes a document table, which is made of, for example, a transparent contact glass. 3 is a light source means for illuminating the original,
It has a light emitting part that is long in the direction perpendicular to the paper surface. Light source means 3
A uniform light is radiated from the light source from the light source through the cylindrical reflecting mirrors 4, 5 and 6 for illumination to a region on the surface of the document table 2 in the direction perpendicular to the paper surface. Reference numeral 7 is a folding mirror.

In the present embodiment, the first scanning section 20 is composed of the elements indicated by the reference numerals 3 to 7. When reading the image information on the one surface of the original document, the unit A having the first scanning unit 20 and the distance detecting means 30 to be described later as one unit is moved along the one surface of the original document at a moving speed V as indicated by an arrow 20a in the figure. Slit exposure scanning is performed.

Reference numerals 8 and 9 are folding mirrors, respectively. The two folding mirrors 8 and 9 constitute a second scanning section 40, and an arrow 40 in the figure at a speed of 1 / 2.V of the unit A.
It is moving along the surface of the original 1 as shown in a.

In this embodiment, a correction means 50 described later is used.
By adjusting the movement amount of the second scanning unit 40, the image forming state of the reading scanning system is corrected.

An image forming means 10 is provided on the surface of the light receiving means 11 which is composed of a one-dimensional line sensor (CCD) or the like in which a plurality of elements are arranged in a direction perpendicular to the paper surface for a light beam based on image information on the surface of the original 1. Is focused on.

Reference numeral 30 denotes a distance detecting means, which detects a floating amount (defocus amount) of the surface of the original 1 from the contact glass 2 by a method described later. The distance detecting means 30 has a slit portion 2 having an opening long in the direction perpendicular to the paper surface.
1 has a light source unit 14 for distance detection, a half mirror 13, an image forming unit 12, and a light receiving unit 15, and is separated from the slit exposure area 30a of the first scanning unit 20 by a certain distance in the front in the scanning direction. It is provided in the position.

The light source unit 14 includes a plurality of point light sources, such as light emitting diodes 14a to 14a.
It is made of 14e.

The image forming unit 12 includes a plurality of image forming lenses 12a to 12a.
The light flux from the light source unit 14 is focused on the surface of the original 1 and the light reflected by the surface of the original 1 is made incident on the surface of the light receiving unit 15 via the half mirror 13.

The light receiving section 15 is, for example, a line sensor (CC
D) and the like, a plurality of light receiving elements 15a to 15e are provided, and as shown in FIG. 3, the light receiving elements 15a to 15e are arranged so as to be deviated by a certain amount in the optical axis direction from the optically conjugate plane with the original 1 surface. Therefore, the image forming states of a plurality of light spots (spot images) which are imaged on the surface of the original 1 and reflected are respectively detected.

That is, in the present embodiment, when one surface of the original is in focus (one surface of the original is flat), the reflected light beam from the one surface of the original is a light receiving element (hereinafter referred to as a light receiving element) on the front side of the one surface of the original. This light receiving element is referred to as a reading reference element.) It is set so as to form an image on the surface 15a, and the amount of deviation of the image forming position is increased from the light receiving element 15a on the front side to the light receiving element 15e on the back side. ing.

Then, the size of the spot diameter formed on each surface of the light receiving elements 15a to 15e is made to increase in order, and the size of the spot diameter and the defocus amount (in the scanning direction from the predetermined surface to the original surface). (Distance in orthogonal direction)
It is related to.

As a result, the size of the spot diameter formed on the surface of the light receiving element 15a, which is the reading reference element, in the actual reading scan and the size of the spot diameter between the respective light receiving elements 15a to 15e obtained in the focused state. The height from the surface of the contact glass 2 (predetermined surface) to the surface of the original 1
That is, the lift amount (distance information in the direction orthogonal to the scanning direction) is calculated and obtained.

In this embodiment, the point light sources 14a to 14e and the image forming lenses 12a to 12e are arranged in the direction orthogonal to the scanning direction.
12e and five light receiving elements 15a to 15e are provided in association with each other, but the number is not particularly limited, and if five or more are provided, the floating amount of one surface of the original document is further increased. The system can be detected well.

Reference numeral 50 is a correction means, which has each element such as a focus position detection circuit 16, a drive amount calculation circuit 17, and a mirror drive unit 18.

The correcting means 50 calculates the amount of movement of the second scanning section 40 in the optical axis direction during image reading based on the output signal from the distance detecting means 30, and based on the calculation result, the second scanning section 40. Is moved to correct the image formation state. As a result, in this embodiment, the light flux based on the image information is accurately formed on the surface of the light receiving means 11 regardless of the change in the unevenness of the contact glass 2 on the surface of the original 1.

Next, the optical principle of the distance detecting means 30 of this embodiment will be described.

In this embodiment, the unit A in which the first scanning section 20 and the distance detecting means 30 are integrated is moved along the surface of the original document 1 and the distance detecting means 30 is read prior to the actual image reading. The amount of floating of one side of the original is detected by.

That is, a plurality of light beams emitted from the light source section 14 composed of a plurality of point light sources 14a to 14e are transmitted through the half mirror 13 and the corresponding imaging lenses 12a to 12a, respectively.
The light is condensed by 2e and a spot image is formed on the surface of the original 1. The spot image formed on the surface of the original 1 is reflected, and the half mirror 13 is formed by the image forming lenses 12a to 12e.
An image is formed on or near the surfaces of the corresponding light receiving elements 15a to 15e via the.

Each light receiving element 1 which constitutes the light receiving section 15
As described above, 5a to 15e are arranged so as to be deviated by a certain amount in the optical axis direction from the optically conjugate surface with the original 1 surface, and therefore the size of the spot diameter formed on each light receiving element 15a to 15e surface is different. Different. For example, in the focus state (the document surface is a flat surface), the relationship between the size of each spot diameter and the defocus amount at this time is previously obtained as distance information, and based on the distance information, when actually performing reading scanning. This distance information and the signal (size of spot diameter) obtained by the light receiving element 15a which is the reading reference element are compared by the focus position detection circuit 16 to detect the defocus amount (the amount of floating of the original 1 surface). There is.

Based on the detected defocus amount, the driving amount calculation circuit 17 obtains a correction value for the moving amount of the second scanning section 40 and transmits it to the mirror driving unit 18 so that the optical path length of the reading scanning system becomes constant. That is, the second scanning unit 40 is moved by an appropriate amount so that the light flux based on the image information is accurately formed on the surface of the light receiving unit 11.

Next, an image reading method in this embodiment will be described.

In the present embodiment, when the image information on the one surface of the original is read, the unit A in which the first scanning unit 20 and the distance detecting means 30 are integrated slits the one surface of the original at the moving speed V. Exposure scanning is performed, and the second detection unit 40 is ½ of the unit A.
-V scanning is performed at the moving speed. Then, the light flux reflected from the first surface of the original is imaged on the surface of the light receiving means 11 by the image forming means 10 via the folding mirrors 7, 8 and 9, and the image information of the original is sequentially read.

At this time, the distance detecting means 30 performs the reading scanning prior to the actual reading scanning to detect the lift amount (focus position) of the original 1 surface, that is, from the contact glass surface (predetermined surface) to the original 1 surface. The distance is detected, and the movement amount of the second scanning unit 40 is corrected by the correction means 50 based on the distance information.

Focusing is controlled by moving the second scanning unit in accordance with the movement amount, and a light beam based on image information on the surface of the original 1 is focused by the image forming unit 10 on the surface of the light receiving unit 11. Imaged. As a result, the original to be read is a book-type original, and image information can be accurately read even if it has a dent such as the spine. For example, when the present invention is applied to a copying machine or the like, copying is performed. An image can be satisfactorily copied over the entire document surface without blurring.

In the present embodiment, the image forming position is shifted from the light receiving element 15a on the front side of the sheet of the original 1 toward the light receiving element 15e on the back side, and a plurality of light receiving portions are formed so that the spot diameter becomes large. Although the elements are arranged, the present invention can be applied to the arrangement having the opposite structure. At this time, the light receiving element 15e on the back side serves as a reading reference element.

FIG. 4 shows the distance detecting means 3 according to the second embodiment of the present invention.
It is a principal part schematic diagram of 0 vicinity. In the figure, the same elements as those shown in FIG. 3 are designated by the same reference numerals.

In the first embodiment, the plurality of light receiving elements forming the light receiving portion are arranged so as to be deviated by a certain amount in the optical axis direction from the original conjugate surface and the optically conjugate surface. Has a plurality of light receiving elements 15a to 15e juxtaposed on a plane perpendicular to the optical axis direction.

Therefore, in order to change the optical position of each of the light receiving elements 15a to 15e in the optical axis direction, a stepped parallel plane plate 19 corresponding to each of the light receiving elements 15a to 15e is provided in front of the light receiving portion 15. ing. As a result, the image forming positions of the light beams on the surfaces of the light receiving elements 15a to 15e are made to differ by a certain amount.

Generally, when a plane parallel plate having a refractive index of n and a wall thickness of d is inserted into a convergent light beam (divergent light beam), the object point (image forming) position is (1-1 / n) d in terms of air conversion rate. Change.

In the present embodiment, by utilizing this optical principle, the thickness of the plane parallel plate 19 corresponding to each of the light receiving elements 15a to 15e is formed stepwise and the image forming positions are shifted. The spot diameters formed on the surfaces of the light receiving elements 15a to 15e are made different from each other.

That is, in the same manner as in the above-described first embodiment, during the actual reading scanning, the signal (the size of the spot diameter) obtained from the light receiving element 15a as the reading reference element and the focus state (the original surface is flat). Each light-receiving element 1 that was obtained in advance at
By comparing the size of the spot diameter between 5a to 15e with the focus position detection circuit, the lift amount (defocus amount) of the document surface is detected. By adjusting the movement amount of the second scanning unit by the correction unit based on the detected defocus amount, the same effect as that of the above-described first embodiment is obtained.

In the present embodiment, the thickness of the plane parallel plate 19 is as shown in FIG.
When the original surface is in focus, a spot image is formed on the surface of the light receiving element 15a on the front side as in the first embodiment. It is set to form an image.

The wall thickness of the plane parallel plate 19 may be formed in a stepwise manner from the back side of the document surface to the front side, contrary to the present embodiment. The reading reference element at this time becomes the light receiving element 15e.

FIG. 5 shows the distance detecting means 3 according to the third embodiment of the present invention.
It is a principal part schematic diagram of 0 periphery. In the figure, the same elements as those shown in FIG. 2 are designated by the same reference numerals.

Also in this embodiment, as in the second embodiment, the plurality of light receiving elements 15a to 15e forming the light receiving portion 15 are arranged side by side on a plane perpendicular to the optical axis. Then, in order to change the spot diameter formed on the surface of each of the light receiving elements 15a to 15e according to the defocus amount, the image forming section 52 is composed of a plurality of image forming lenses 52a to 52e (lens arrays) having different refractive powers. .. That is, the image forming unit 5 of each of the light receiving elements 15a to 15e
The image forming position through 2 is shifted from the document surface by a constant amount in the optical axis direction.

In this embodiment, the refractive powers of the corresponding image forming lenses 52a to 52e are sequentially weakened from the light receiving element 15a on the front side of the document surface toward the light receiving element 15e on the back side. The conjugate surface of the light receiving portion 15 is a surface 51 inclined from the original table surface 2 as shown in FIG.

As a result, each of the light receiving elements 15a to 15e
The size of the spot diameter formed on the surface is made different from that of the signal (size of the spot diameter) obtained by the light receiving element 15a which is the reading reference element at the time of the actual scanning of reading as in the first embodiment. When the focus state (the original surface is a flat surface) is compared with the size of the spot diameter between the light receiving elements 15a to 15e, which is obtained in advance, by the focus position detection circuit, the floating amount (defocus amount) of the original surface is detected. is doing. Then, the movement amount of the second scanning unit is corrected by the correction unit based on the detected defocus amount, and the same effect as that of the first and second embodiments is obtained.

In this embodiment as well, as in the first and second embodiments, a spot image is formed on the surface of the light receiving element 15a on the front side of the document surface in the focused state.

The refracting power of each of the image forming lenses 12a to 12e forming the image forming unit 12 is opposite to that of this embodiment from the image forming lens 52e on the back side of the document surface to the image forming lens 5 on the front side.
It may be configured to weaken toward 2a.
The reading reference element at this time becomes the light receiving element 15e.

In each of the first to third embodiments described above, the document surface 1
Although an example in which the second scanning unit 40 is moved by the correcting unit 50 in order to adjust the optical path length from to the surface of the light receiving unit 11 is shown, for example, instead of the second scanning unit 40, for example, the first scanning unit 2 is used.
Folding mirror 7 or image forming means 10 forming a part of 0
Alternatively, even if any one optical member of the light receiving means 11 is moved, the present invention can be applied in the same manner as the above-mentioned embodiment. Further, these moving members may be moved relatively.

[0053]

According to the present invention, as described above, the distance detecting means is provided at a position separated from the slit exposure area by a predetermined distance in the scanning direction, and the distance detecting means and a part of the reading scanning system are provided at the time of slit exposure scanning. The unit in which one scanning unit is integrated is moved, and the correction unit adjusts the movement amount of a part of the second scanning unit of the reading scanning system based on the output signal from the distance detecting unit. By correcting the image formation state, it is possible to achieve an image reading apparatus that can always read the image information on the document surface with high accuracy without lowering the resolution without prescanning, and can improve the reading speed. be able to.

[Brief description of drawings]

FIG. 1 is a schematic view of a main part of an image reading apparatus according to a first embodiment of the present invention.

FIG. 2 is a perspective view of the vicinity of the distance detecting means according to the first embodiment of the present invention.

FIG. 3 is an enlarged explanatory view of the vicinity of the distance detecting means according to the first embodiment of the present invention.

FIG. 4 is a schematic view of a main part near a distance detecting means according to a second embodiment of the present invention.

FIG. 5 is a schematic view of a main part near a distance detecting means according to a third embodiment of the present invention.

[Explanation of symbols]

 1 Document 2 Document Plate 3 Light Source Means 4, 5, 6 Reflecting Mirror 7, 8, 9 Folding Mirror 10 Image Forming Means 11 Light Receiving Means 12, 52 Image Forming Section 13 Half Mirror 14 Light Source 15 Light Receiving Section 16 Focus Position Detection Circuit 17 Driving amount calculation circuit 18 Mirror driving unit 14a to 14e Point light source 12a to 12e, 52a to 52e Imaging lens 15a to 15e Light receiving element 19 Parallel plane plate 20 First scanning unit 30 Distance detecting unit 40 Second scanning unit 50 Correcting unit 21 slit

Claims (3)

[Claims] 1. When scanning image information on a document surface placed on a document table surface with a reading scanning system having a slit opening and sequentially forming an image on a light receiving means surface to read the image information, the slit opening allows the front side in the scanning direction. Is provided at a position separated by a certain distance from the reading scanning system, and the distance detecting means is moved integrally with a part of the reading scanning system. The distance detecting means makes light spots incident on a plurality of regions parallel to the slit opening, A plurality of light spots reflected from the surface are detected by a light receiving unit composed of a plurality of light receiving elements via an image forming unit, and distance information from the document surface to a predetermined surface is obtained based on a signal from the light receiving unit. An image reading apparatus characterized in that an optical path length from the document surface to the light receiving surface is adjusted by a correcting means based on a signal from the distance detecting means. 2. A plurality of light receiving elements of the light receiving unit are arranged with respect to the image forming unit in a substantially conjugate plane with the original surface and at positions displaced from the conjugate plane by a certain amount in the optical axis direction. The image reading apparatus according to claim 1, wherein: 3. The image forming unit comprises a lens array in which a plurality of image forming lenses having different refracting powers are arranged in a direction parallel to the slit opening, and each image forming lens of the lens array receives the original surface with the light receiving light. 2. The image reading apparatus according to claim 1, wherein the image is formed on the element and the image is formed on the light receiving element by a certain amount at different positions in the optical axis direction.