JP2517120B2 - Image reader - Google Patents

Description

The present invention relates to an image reading apparatus mainly applied to an analog copying machine, a digital copying machine, and the like.

(B) Conventional technology Conventionally, in this type of reading device, a document placed on a contact glass is exposed and scanned, and its image light is passed through an imaging lens to a photosensitive element such as a photoconductor or a CCD memory. I am trying to project.

(C) Problems to be Solved by the Invention However, in the conventional image reading apparatus of this type, the optical path length is set so that the image of the document surface that is in close contact with the contact glass is formed on the photosensitive element. However, when the original is lifted from the contact glass, the optical path length thereof becomes long, the original image is not sufficiently formed on the photosensitive element, and the read image becomes unclear.

The present invention has been made in consideration of such circumstances, and even when an original is lifted from the contact glass, the image light thereof is sufficiently focused on the photosensitive element to read a clear image at all times. A device is provided.

(D) Means for Solving the Problems The present invention is directed to a contact glass on which an original is placed, an exposure lamp for scanning the original that illuminates the surface of the original on the contact glass, and a photosensitive element provided below the contact glass. A first mirror that reflects the light reflected from the original by the exposure lamp in parallel to the original scanning direction; a second mirror that reflects the light from the first mirror; and a first mirror that reflects the light from the second mirror. From the second mirror to the second mirror, a lens for forming an image of the light from the third mirror on the photosensitive element, an exposure lamp and a first mirror are mounted to scan an original. A first moving frame that is movable in a direction, a second moving frame that mounts second and third mirrors and is movable following the first moving frame, and a first moving frame that moves the first and second moving frames, respectively. Exposure scanning is performed with the first and second motors. Document distance measuring means for measuring the distance between the document surface and the contact glass,
A control for driving the first motor to expose and scan the document and controlling the driving speed of the second motor in accordance with the measured distance to maintain a constant optical path length from the surface of the document to be exposed and scanned to the lens. And an image reading apparatus including means.

(E) Action For example, in a document such as a book, the binding portion at the center is lifted up from the contact glass. When reading such an original, when the control means drives the first motor and the second motor to move the first and second moving frames in the original scanning direction, the exposure lamp irradiates the original surface to expose the original. The reflected light from the surface is focused on the photosensitive element via the first, second and third mirrors and the lens, and the photosensitive element reads the original image. Since the document distance measuring means measures the distance between the surface of the document to be exposed and scanned and the contact glass, when the binding part of the document (book) lifted from the contact glass is exposed, the control means is controlled by the document distance measuring means. The driving speed of the second motor is increased so that the optical path length from the contact glass to the lens is shortened by the measured distance. As a result, the optical path length from the surface of the original to be exposed and scanned to the lens is maintained constant, and the original image is clearly read by the photosensitive element.

(F) Embodiment Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings. This does not limit the invention.

FIG. 1 is a schematic configuration diagram of an image reading apparatus used in a digital copying machine, and FIG. 2 is a detailed configuration diagram of essential parts thereof. In these figures, 1 is an image reading apparatus main body, 2 is a contact glass on which an original 3 is placed, 4 is an exposure lamp for scanning an original, 5 is a reflector, and 6 is an image of the original placed below the contact glass 2. A CCD memory for reading, 7 is a first mirror that reflects the light reflected from the document by the exposure lamp 4 in parallel to the document scanning direction, 8 is a second mirror that reflects the light from the first mirror 7, and 9 is a second mirror. A third mirror that reflects the light from the mirror 8 in the opposite direction to the light from the first mirror 7 to the second mirror 8.
A mirror, 10 is a lens for focusing the light from the third mirror on the CCD memory 6, and 11 is an original distance measuring device for measuring the distance between the original surface to be exposed and scanned and the upper surface of the contact glass 2. Reference numeral 12 denotes a first moving frame, on which the exposure lamp 4, the reflection plate 5, the first mirror 7, and the document distance measuring device 11 are mounted. Reference numeral 13 is a second moving frame, on which the second mirror 8 and the third mirror 9 are mounted. As shown in FIG. 2, the first moving frame 12 and the second moving frame 13 are both slidably supported by a sliding shaft 14 and pulled by wires 15 and 16 respectively to move. . wire
The wire 15 is stretched between the driven roller 17, the drive roller 18 and the driven roller 19, and the wire 16 is stretched between the driven roller 20, the drive roller 21 and the driven roller 22. The drive roller 18 is driven by the rotational force of the stepping motor 24 transmitted via the gears 22 and 23. Also,
The drive roller 21 is driven by the rotational force of the stepping motor 27 transmitted via the gears 25 and 26. That is, when the stepping motor 24 rotates in the normal direction, the first moving frame 12 moves in the arrow A direction (original scanning direction), and in the reverse direction, it moves in the arrow B direction. When the stepping motor 27 rotates in the forward direction, the second moving frame 13 moves in the direction of arrow A, and in the reverse direction, it moves in the direction of arrow B.

FIG. 3 is an explanatory view of the structure of the manuscript distance measuring device 11, which has a laser diode 11a for irradiating the surface of the manuscript 3 through the contact glass 2 and a CCD memory 11b for receiving the reflected light from the manuscript surface. There is. When the laser light emitted from the laser diode 11a is reflected on the document surface and received by the CCD memory, the distance from the contact glass 2 to the surface of the document 3 is measured by the light receiving position.

FIG. 4 is a block diagram of the control unit of the image reading apparatus shown in FIG. 1. MC is a microcomputer consisting of CPU, ROM, RAM and I / O ports, KB is an image reading start command and image reading conditions. Keyboard for setting, DM is CCD memory 6
It is an image data memory for storing the image data read in. Microcomputer MC is keyboard KB, CCD
The output from the memory 11b and the CCD memory 6 is received and output to the stepping motor 24, the stepping motor 27, the exposure lamp 4 and the image data memory DM.

The operation in such a configuration will be described below. First,
As shown in FIG. 5, when a document (a document bound like a book) is placed on the contact glass 2 and a reading start command is input from the keyboard KB, the exposure lamp 4 is turned on and the stepping motor 24, 27 are driven respectively, and the first moving frame 12 and the second moving frame 13 are at their home positions (2 in FIG. 1).
The movement starts in the direction of arrow A from the position indicated by the dashed line).
As a result, the light from the exposure lamp 4 illuminates the document surface, and the reflected light is incident on the CCD memory 6 via the first mirror 7, the second mirror 8, the third mirror 9 and the lens 10. The image light from the document surface is exactly CCD by the lens 10.
The optical path length S from the upper surface of the contact glass 2 to the lens 10 is set to S1 as shown in FIG. Then, in order to maintain the optical path length S1, both the first moving frame 12 and the second moving frame 13 start moving in the arrow A direction at a speed V1 and a speed 1 / 2V1 as shown in FIG. When the document distance measuring device 11 approaches the binding portion of the document, the document distance measuring device 11 detects the distance at which the document floats above the surface of the contact glass 2. The microcomputer MC uses the speed of the stepping motor 27 corresponding to the distance,
That is, the moving speed of the second moving frame 13 is increased as shown in FIG. As a result, the optical path length S (optical path length from the upper surface of the contact glass 2 to the lens 10) is reduced by the floating distance of the document as shown in FIG. Therefore, the actual optical path length S from the document surface to the lens 10 is maintained at S1, and the document image is always accurately formed on the CCD memory 6. In this way, even when the surface of the document is lifted from the contact glass, the document image can be clearly read without blurring.

In the above embodiment, only the speed of the second moving frame 13 is controlled according to the floating distance of the document.
It is also possible to reduce the speeds of the first moving frame 12 and the second moving frame 13 as the document surface moves away from the contact glass, and to correct the image distortion due to the lifting of the document. Also,
In the above embodiment, the case where the original image is converted into digital data using the CCD memory has been described, but the original image may be converted into so-called analog data by, for example, a photoconductor.

(G) Effect of the Invention According to the present invention, it is possible to clearly read the image of a document that has floated from the contact glass.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an image reading apparatus of the present invention, FIG. 2 is a detailed configuration diagram of an essential part of FIG. 1, FIG. 3 is an explanatory diagram of an essential part of FIG. 2, and FIG. FIG. 5 is a block diagram of a control section of the embodiment shown in FIG. 5, FIG. 5 is an explanatory view showing a document placing state in the embodiment shown in FIG. 1, and FIG. 6 is an optical path changing corresponding to the positional relationship shown in FIG. FIG. 7 is a graph showing the length, and FIG. 7 is a graph showing the velocities of the first moving frame and the second moving frame which change corresponding to the positional relationship shown in FIG. 1 ... Main body, 2 ... Contact glass, 3 ... Original, 4 ... Exposure lamp, 5 ... Reflector, 6 ... CCD memory, 7 ... First mirror, 8 ... Second mirror, 9 ... … Third mirror, 10 …… Lens, 11 …… Document distance measuring device, 12 …… First moving frame, 13 …… Second moving frame, 24,27 …… Stepping motor.

Front page continuation (72) Inventor Ikuichi Kitagawa 1-2-2 Tamatsukuri, Chuo-ku, Osaka-shi Mita Kogyo Co., Ltd. (72) Hideki Ishida 1-228 Tamatsukuri, Chuo-ku, Osaka-shi, Osaka Mita Kogyo Co., Ltd. (56) Reference Japanese Patent Laid-Open No. 58-106565 (JP, A) Actually developed 63-80542 (JP, U)

Claims (1)

(57) [Claims] 1. A contact glass on which an original is placed, an exposure lamp for scanning the original that illuminates the original surface on the contact glass, a photosensitive element provided below the contact glass, and reflection from the original by the exposure lamp. A first mirror that reflects light parallel to the document scanning direction, a second mirror that reflects light from the first mirror, and light from the second mirror with respect to light from the first mirror to the second mirror And a third mirror that reflects in the opposite direction, a lens that focuses light from the third mirror on the photosensitive element, an exposure lamp and a first mirror, and a first moving frame that is movable in the document scanning direction. A second moving frame that is movable by following the first moving frame by mounting second and third mirrors, first and second motors that move the first and second moving frames, and exposure scanning Distance between the original and the contact glass Controls and document distance measuring means for measuring the driving speed of the second motor in response to said measured distance with by driving the first motor to expose and scan the document and,
An image reading apparatus including a control unit for maintaining a constant optical path length from a document surface to be exposed and scanned to a lens.