JPH06217092A - Picture reader - Google Patents

Abstract

PURPOSE:To directly provide clear and flat pictures from a threedimensional subject having projecting and recessing parts with a direction fixed. CONSTITUTION:At the time of picture reading, the light is irradiated from an LED array 3 to a subject S placed on a contact glass 1 while moving a scanning optical system 2 in one direction. The reflection light is scanned through an optical image forming element 4 on a CCD 5. During the scanning, an AF control circuit 6 detects the focusing state of the optical system 2 based on the picture signal output of the CCD 5. By the detected output, the focusing adjustment operation of the optical image forming element 4 is controlled.

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 in an image forming apparatus such as a copying machine, an image scanner, a facsimile, etc., and more particularly, to obtain a sharp flat image from a stereoscopic object having undulations or steps in one direction. The present invention relates to an image reading device capable of

[0002]

2. Description of the Related Art Conventionally, an image reading apparatus in this type of image forming apparatus is a scanning optical system having a light source and a lens system below a contact glass provided on the upper surface of the apparatus body, and a photoelectric conversion element. It is known that a CCD is provided.

In the image reading apparatus having such a structure, while the scanning optical system is moved in one direction, the subject placed on the contact glass is irradiated with the light of the light source, and the reflected light is passed through the lens system. It operates so that the subject is scanned onto the CCD. The image information photoelectrically converted by each pixel of the CCD is then processed according to the purpose of various image forming devices, such as being processed by a printing device in a copying machine.

As is well known, a conventional image reading apparatus is constructed on the premise of image reading of a subject having excellent flatness that can be brought into close contact with the upper surface of the contact glass as a whole, for example, a sheet of paper. . Therefore, in order to form a sharp subject image on the incident surface of the CCD, the lens system of the scanning optical system has a strict distance between the upper surface of the contact glass and the incident surface of the CCD on the optical path of the reflected light from the light source. It was installed at the set position in a non-displaceable state.

[0005]

However, in the conventional configuration which presupposes that only the subject image having excellent flatness is processed as an image signal, the copy image processed based on the image information output of the CCD is used. However, there is a problem in that only a portion corresponding to a preset focus point of the lens system, that is, a portion in contact with the upper surface of the contact glass can be sharply reproduced.

That is, when a subject is placed on the contact glass, a three-dimensional subject in which the surface to be photographed is partly separated from the glass surface, the part apart from the glass surface is the focus point of the lens system. Therefore, a sharp planar image cannot be obtained because the image is out of focus.

For example, when opening an intermediate page of a thick book having a large number of pages and reading an image of the page, the portion near the binding portion of the book is greatly curved. Therefore, when the book is placed on the contact glass, The curved portion is largely separated from the glass surface. For this reason, when the scanning optical system scans the surface to be imaged, the curved portion is out of focus, and the curved image is significantly blurred and unreadable in a planar image obtained by this.

Even in the above-mentioned conventional structure, it is possible to increase the image reading resolution of a subject having a certain depth by increasing the depth of field by the lens system, but the optical path length from the contact glass to the lens is increased. It is structurally unreasonable to increase the light amount of the light source in order to make it long or to narrow down the lens system greatly, and at present, the image reading of a relief pattern with shallow unevenness is the limit, and the thick book as described above is limited. It is virtually impossible to deal with a three-dimensional object having a large depth such as a curved portion.

Further, a stereoscopic object having a large depth that cannot be processed by such a conventional image reading apparatus has been taken by a general camera, but a sharp image can be obtained by this method. In addition, there is a disadvantage and inconvenience that it is not possible to respond when it is necessary to promptly.

The present invention solves the above-mentioned problems, and has a undulation or a step in one direction, and a solid body having a portion which is separated from the mounting surface when mounted on the subject mounting surface. It is an object of the present invention to provide an image reading apparatus capable of instantly obtaining a sharp planar image from a subject by performing the same operation as in a conventional image forming apparatus.

[0011]

In order to achieve the above object, the image reading apparatus of the present invention is provided with an autofocus control means in addition to a subject mounting surface, a photoelectric conversion element and a scanning optical system. . The scanning optical system irradiates the subject placed on the subject placement surface with light when reading an image, and scans the reflected light to the photoelectric conversion element via a lens system to place the subject on the subject mounting surface. The autofocus control means detects the focus state of the scanning optical system based on the image signal output from the photoelectric conversion element, and the scanning optical system is detected by the detection output. The focus adjustment operation of the lens system in FIG.

[0012]

According to the above construction, when the object is placed on the object mounting surface, not only the object which is in full contact with the object mounting surface but also the part which is separated from the object mounting surface and the scanning optical Focusing from a three-dimensional object such that the end surface facing the mounting surface when cut by an upright surface orthogonal to the scanning direction of the system in the horizontal direction is substantially parallel to the mounting surface at any part in the scanning direction A sharp image without blur can be obtained.

That is, when an image is read, a scanning optical system irradiates a subject placed on a subject mounting surface with light, and when an image formed by the reflected light is scanned by a photoelectric conversion element, autofocus is performed. In the control means,
The focus state of the scanning optical system is detected based on the image signal output of the photoelectric conversion element, and the focus adjustment operation of the lens system in the scanning optical system is controlled by the detected output.

Therefore, when scanning a subject portion that is distant from the placement surface, the lens system operates so that the subject portion is in focus, so that the photoelectric conversion element is always in focus and has a high resolution. Image information will be input.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment in which the present invention is applied to an image reading apparatus of an electronic copying machine. In this figure, reference numeral 1 denotes a contact glass disposed on the upper surface of the device body, and the upper surface of the contact glass 1 is formed as a horizontal flat surface on which the subject S is placed. Reference numeral 1a denotes a light shielding cover that shields the periphery of the subject S placed on the contact glass 1.

Reference numeral 2 denotes a scanning optical system disposed below the contact glass 1 in the main body of the apparatus, which comprises a plurality of LED arrays 3 as a light source for illuminating a subject and a plurality of optical imaging elements 4 as a lens system, which are in contact with each other. The LED array 3 and the optical imaging element 4 are arranged along the front-rear width direction of the glass 1 so that the LED array 3 and the optical imaging element 4 are integrally reciprocated in the left-right length direction of the contact glass 1 by a parallel movement mechanism (not shown). It is configured.

In the illustrated example, a selfoc lens array (selfoc: SELFOC is a registered trademark) having an equal magnification image forming function is used as the optical image forming element 4. Alternatively, the light source may be a halogen lamp, a fluorescent lamp, or the like instead of the LED array 3.

Reference numeral 5 denotes a CCD as a photoelectric conversion element linearly arranged with a length corresponding to the reading width of the subject S, and an optical path B of the optical image forming element 4 below the scanning optical system 2. It is arranged above and is configured to move integrally with the scanning optical system 2 by the parallel moving mechanism.

In this embodiment, the contact glass 1 is fixed, and the scanning optical system 2 and the CCD 5 are moved in one direction by the parallel moving mechanism at the time of reading an image. On the contrary, the scanning optical system 2 and the CCD 5 are moved. May be fixed and the contact glass 1 may be configured to move.

At the time of image reading, the scanning optical system 2 moves in one direction, and during the movement, the subject S placed on the contact glass 1 is irradiated with light from the LED array 3 and is reflected as its reflected light. The obtained subject image is scanned by the CCD 5 via the optical imaging element 4.

Reference numeral 6 denotes an autofocus control circuit (hereinafter referred to as A
F control circuit), 7 is an element drive mechanism,
The control circuit 6 detects the focus state of the scanning optical system 2 based on the image signal output from the CCD 5, and outputs a control signal for controlling the focus adjustment operation of the optical imaging element 4 based on the detected output. The element driving mechanism 7 drives the imaging element 4 in the vertical direction so as to perform the focus adjustment operation of the optical imaging element 4 based on the control output of the AF control circuit 6.

The AF control circuit 6 may be of a type that monitors the high frequency component of the image signal from the photoelectric conversion circuit and controls the focus adjustment operation. That is, the principle is used in which the higher the focus of the subject S and the clearer the contour of the image, the higher the high frequency component of the extracted image signal, and this method is used in video cameras and the like.

The above constitutes the image reading apparatus of the present embodiment. Further, in the copying machine of the present embodiment, the CC
A printing unit control circuit 9 that outputs a signal for controlling the operation of the printing unit 8 of the copying machine based on the image signal output from D5.
And the printing unit 8 based on the output of the printing unit control circuit 9.
And a printing unit drive circuit 10 for driving the.

The printing unit 8 is, for example, a CCD 5
The writing light source composed of a laser diode or the like is controlled on the basis of the image signal data output from the device, and the laser light emitted from the light source is passed through a deflecting device such as a polygon mirror to a pre-charged photoreceptor surface. An electrostatic latent image is formed by irradiation, the latent image is further developed with toner or the like, and the toner image on the surface of the photoconductor obtained by this is transferred to paper. it can.

Next, description will be given of a case where the copying machine of the present embodiment attempts to copy a middle page of a thick book as shown in FIG. 1, for example. Book S so that the page faces the glass surface
Is placed on the contact glass 1. At this time, a portion near the binding portion at the center of the book is greatly curved and separated, but it is necessary to place the separated portion Sa so that it is orthogonal to the scanning direction of the scanning optical system 2.

From this state, if the book S is covered with the light-shielding cover 1a as necessary, the image reading operation is started.
The scanning optical system moves in one direction from one end side of the contact glass 1 to the other end side. During this movement, an intermediate page of the book S is radiated to the LED array 3 which has passed through the contact glass 1, and the reflected light is incident on the CCD 5 via the optical imaging element 4. During that time, the AF control circuit 6 detects the focus state of the optical imaging element 4 based on the image signal output of the CCD 5.

In the normal state, the optical image-forming element 4 has the distance between the upper surface of the contact glass 1 and the incident surface of the CCD 5 strictly set so that the image is correctly formed on the CCD 5 on the optical path B of the reflected light. Exists in a position. Therefore, during scanning, as shown by an imaginary line in the optical imaging element 4, the middle part of the book S is in focus at a portion close to the glass surface, and a high-resolution image is incident on the CCD 5. Therefore, it moves while maintaining the normal set position.

Then, as shown by the solid line, when the optical image forming element 4 reaches the separated portion Sa of the book S, the image incident on the CCD 5 is out of focus, but the AF control circuit is in a state where this image is out of focus. A control signal for controlling the focus adjustment operation of the optical imaging element 4 is output to the element driving mechanism 7 by the detection output of the optical imaging element 6 in real time. Based on the output of the control signal, the element driving mechanism 7 moves the position of the optical imaging element 4 in the vertical direction so that the CCD 5 is in focus and adjusts the focus.

This focus adjusting operation is continuously performed during the scanning of the scanning optical system 2, so that even the subject S having irregularities is not limited to the portion closely contacting the contact glass 1. , The part Sa separated from the glass surface
Throughout the entire area up to, the CCD 5 always receives high-resolution, high-resolution image information. Therefore, a controlled drive current is given to the printing unit 8 by the image signal given from the CCD 5 to the printing unit driving circuit 10, and the printing unit 8 is driven by this current to obtain a sharp copy image. Is.

In the above embodiment, the AF control circuit 6 controls the focus adjustment operation sequentially in real time during scanning by the scanning optical system 2, but the scanning operation of the scanning optical system 2 is divided into two. The AF control circuit 6 may detect the concave and convex state of the subject S the first time, and the element drive mechanism 7 may be operated by the control signal based on the detection data during the second scan.

Although not shown, the photoelectric conversion element is C
Instead of the CD5, a light receiving element that receives a planar image from a subject placed on the contact glass and converts it into an electric signal, and a sensor element that sequentially measures the depth of the portion of the subject that is separated from the glass surface On the other hand, a signal synchronizing circuit that analyzes the image signal output of the light receiving element and the depth detection signal of the sensor element to synchronize both signal outputs,
The AF control circuit may be configured by a focus control circuit that controls the focus according to the ups and downs of the subject based on the output of the synchronizing circuit, so that the element drive mechanism is sequentially operated by the output of the focus control circuit.

[0032]

As described above, in the image reading apparatus of the present invention, the focus state of the scanning optical system is detected based on the image signal which is the output of the photoelectric conversion element, and the detection output outputs the lens system in the scanning optical system. Since the autofocus control means for controlling the focus adjustment operation of is provided, the lens system is based on the control output of the autofocus control means when the subject part that is separated from the subject placement surface is scanned by the scanning optical system. Since the operation of the subject portion is brought into focus, high-resolution image information in focus is always input to the photoelectric conversion element.

Therefore, it is possible to directly obtain a sharp planar image free from out-of-focus without using a camera or the like from a three-dimensional subject having irregularities with a fixed directionality, as well as a two-dimensional subject. That is, it has an excellent effect not seen in the past.

[Brief description of drawings]

FIG. 1 is an explanatory view schematically showing an embodiment of the present invention.

[Explanation of symbols]

 1 Contact Glass 2 Scanning Optical System 3 LED Array 4 Optical Imaging Element (Lens System) 5 CCD (Photoelectric Conversion Element) 6 AF Control Circuit (Auto Focus Control Means) S Subject

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H04N 1/10 7251-5C

Claims (1)

[Claims] 1. A subject placement surface, a photoelectric conversion element, and a subject placed on the subject placement surface is irradiated with light when an image is read, and the reflected light is photoelectrically converted through a lens system. A scanning optical system that relatively moves in one direction with respect to the subject mounting surface to scan an element, and a focus state of the scanning optical system is detected based on an image signal output from the photoelectric conversion element, and its detection output And an autofocus control means for controlling the focus adjustment operation of the lens system in the scanning optical system.