JP2003037713A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reader that has diversified read systems in matching with originals to be read. SOLUTION: The image reader is provided with a first optical system, comprising first mirrors 18, 19, 20, 21 and a first condenser lens 22, and a second optical system comprising a second mirror 23 and a second condenser lens 26 and forming an image of a transparent original onto a second photosensor 25. The magnifying power of the second condenser lens 26, placed on an optical path of the second optical system, is selected twice that of the first condenser lens 22 placed on an optical path of the first optical system. Since the image reader uses the independent optical systems and independent photosensors in the case of reading a reflection original and of reading the transparent original, the image reader can read the originals with high accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading device for reading an image by performing a main scan and a sub scan using a linear image sensor (hereinafter, a linear image sensor is referred to as an "optical sensor").

[0002]

2. Description of the Related Art A scanner or the like is known as an image reading device for reading an image on a document. The flatbed scanner irradiates an image of an original with a light source and photoelectrically converts the reflected light or transmitted light through an optical system by an optical sensor to read a part of the image in a line, and the optical system and the optical sensor. The entire image is read by repeating the operation of shifting the relative position between the document and the optical sensor by moving the carriage on which is mounted. The position information of the pixel acquired by the optical sensor and the information corresponding to the spectral reflectance or the spectral transmittance are subjected to various kinds of signal processing and output as digital information to a personal computer or the like. In recent years, a scanner capable of reading both a reflective original and a transparent original has been put into practical use. In such a scanner, light sources are provided on both sides of the original.

In general, an optical system used in a scanner makes reflected light or transmitted light of a document incident on a single optical sensor by a single optical path, and the magnification of the optical system is fixed. In such a scanner, the magnification of the optical system is fixed so that the maximum width of the readable original corresponds to the width of the optical sensor.

In a scanner capable of reading both a reflective original and a transparent original, an optical path of light reflected by the original to reach an optical sensor and an optical path of light transmitted through the original to reach the optical sensor. By using a movable mirror that moves on one of the optical paths, and by switching the
A method is known in which two optical paths are selectively used and a single optical sensor reads a reflective original and a transparent original.

[0005]

However, in an image reading apparatus that always reads the original using the same optical sensor,
The image tone of the read image is determined on the hardware by the number of pixels of the optical sensor, the pixel arrangement, the charge transfer method, etc., and it was not possible to select various reading methods on the hardware according to the document to be read. .

Further, in a scanner that reads both a reflective original and a transparent original using a movable mirror and a single optical sensor, it is difficult to accurately make light incident on the optical sensor using the movable mirror. There is a problem that the reading accuracy becomes low.

The present invention was created in view of the above problems, and it is an object of the present invention to provide an image reading apparatus having various reading methods adapted to the original to be read. Another object of the present invention is to provide an image reading apparatus having high reading accuracy when an image is read by properly using a plurality of optical paths.

[0008]

According to the image reading apparatus of the present invention, the light projected from the light emitting portion and reflected by the document or the light transmitted through the document is reflected by the optical system. The light is focused on the imaging unit having the optical sensor and the second optical sensor. In the imaging unit, the image of the original is read by converting the light received by either the first optical sensor or the second optical sensor into an electric signal. Since the optical sensor can be selectively used depending on the image quality of the image to be read, it is possible to combine various reading methods according to the document to be read.

According to the image reading apparatus of the second aspect of the present invention, the first mirror reflects the light reflected by the document or the light transmitted through the document and causes the light to enter the first optical sensor, and the second mirror comprises: The light reflected by the manuscript or the light transmitted through the manuscript is reflected and made incident on the second optical sensor, and each of the two lights is independent.
Since the images are formed on the two optical sensors via one optical path, the reading accuracy is high.

According to the image reading apparatus of the third aspect of the present invention, the first mirror causes the light reflected by the document to enter the first optical sensor, and the second mirror reflects the light transmitted through the document as the second light. Since the light is incident on the sensor, it is possible to properly use the reading of the reflective original using the first mirror and the reading of the transparent original using the second mirror according to the original, thereby realizing the reading of the image according to the image quality of the original. it can.

According to the image reading apparatus of the fourth aspect of the present invention, the first condensing lens is arranged on the optical path from the document to the first photosensor via the first mirror and the first light. The image is formed on the sensor, and the second condensing lens is arranged on the optical path from the document to the second optical sensor via the second mirror and forms the image on the second optical sensor. Therefore, it is possible to properly use each condensing lens and read an image according to the image quality of the document.

According to the image reading apparatus of the fifth aspect of the present invention, since the magnification of the second condenser lens is an integral multiple of the magnification of the first condenser lens, the transparent original larger than the reflection original is enlarged. The image can be projected on the optical sensor, and the transparent original can be read with higher resolution.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A plurality of embodiments showing an embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 2 shows a flatbed scanner 1 as an image reading apparatus according to an embodiment of the present invention.

An original table 12 made of a transparent plate such as glass is provided on the upper surface of the box-shaped lower housing 11. A document guide 30 that positions the reading position of the document 13 and regulates the movement of the document 13 at the time of reading the document is provided around the document table 12. A white reference 31 having a uniform reflection surface with high reflectance is provided on the lower surface of the document guide 30. Lower housing 11
A carriage 14 that is reciprocally movable in parallel with a document 13 placed on a document table 12 by a driving device (not shown) is provided inside the. On the upper part of the lower housing 11,
An upper housing 16 accommodating a second light source 15 that can reciprocate in parallel with the original 13 in synchronization with the carriage 14 by a drive device (not shown) is installed. As the second light source,
Not limited to such a movable type, a fixed type surface light source can be used.

The carriage 14 is shown in FIG. The carriage 14 accommodates a first light source 17, a first optical system, a second optical system, and a first optical sensor 27 and a second optical sensor 25 that form an imaging unit. Fluorescent lamps or the like are used for the first light source 17 and the second light source 15 that form the light emitting unit, and are provided horizontally long in a direction perpendicular to the moving direction of the carriage 14.

The first optical system comprises the first mirrors 18, 19, 2
It is composed of 0, 21, and a first condenser lens 22. The first optical system converts the light projected from the first light source 17 by the first mirrors 18, 19, 20, and 21 into the light reflected by the original 13.
By being reflected once, the first light source 17 to the first optical sensor 2
The optical path to 7 is formed. The focus of the first condenser lens 22 is fixed at a distance to the surface of the document table 12 on the document 13 side.

The second optical system comprises a second mirror 23 and a second mirror.
It is composed of a condenser lens 26. The second optical system reflects the light projected from the second light source 15 by the second mirror 23 and transmitted through the manuscript 13 so that the second optical system outputs the second light from the second light source 15.
An optical path leading to the optical sensor 25 is formed. Second condenser lens 2
By using a lens having a magnification of 2 times that of the first condenser lens 22 for 6, the resolution when reading a transparent original is optically increased. The magnification of the second condenser lens 26 is not limited to twice that of the first condenser lens, but is preferably an integral multiple. Further, the focus of the second condenser lens is the original table 1
It is fixed in accordance with a position separated by about 2 mm from the surface of the second document 13 side. As shown in FIG. 3, the transparent original 28 is held by the holder 29 at the time of reading, and the transparent original 28 moves from the original table 12 to about 2 mm.
This is because it is lifted up by mm, and also to prevent interference fringes (Newton's ring) that are generated when the transparent original 28 and the original table 12 are in close contact.

Color CCD linear image sensors are used for the first photosensor 27 and the second photosensor 25.
Charges corresponding to the amount of light incident on the photodiodes forming the first photosensor 27 or the second photosensor 25 are accumulated, and the accumulated charges are taken out after a predetermined period has elapsed and the signal processing unit 32 shown in FIG. Is processed in. The A / D conversion unit 34 receives the first optical sensor 2 input via the amplifier 33.
7 or the data from the second optical sensor 25 is converted into a digital signal and transmitted to the shading correction unit 35. The shading correction unit 35 uses the data obtained by reading the white reference 31 before the start of reading to vary the sensitivity of each pixel of the first optical sensor 27 or the second optical sensor 25 and to determine whether the first light source 17 and the second light source 15 are the main components. The variation of the light amount in the scanning direction is corrected. The gamma correction unit 36 performs gamma correction using a predetermined gamma function, and converts the light amount signal output from the shading correction unit 35 into an image signal. The other correction unit 37 performs various conversions such as color correction, edge enhancement, and area enlargement / reduction. The control unit 38 includes a CPU, RAM and R
It is composed of a microcomputer such as OM,
The flatbed scanner 1 is controlled as a whole, and is connected to an image processing apparatus such as a personal computer (not shown) via the interface 39.

The operation of the flatbed scanner 1 will be described below. The user controls the flatbed scanner 1 with a personal computer connected to the interface 39 and gives a reading start instruction.

(1) When a reflective original is read When the user specifies that the original to be read is a reflective original before giving a reading start instruction, the flatbed scanner 1 turns on the first light source 17 and outputs the first light. The reflection original is projected onto the first optical sensor 27 using the first optical system. When a reading start instruction is given, the flatbed scanner 1 repeatedly executes main scanning and sub-scanning continuously. In the main scanning, the light projected from the first light source 17 onto the original 13 and reflected by the original 13 enters the first optical sensor 27 via the first optical system.

(2) When reading a transparent original When the user specifies that the original to be read is a transparent original before giving a reading start instruction, the flatbed scanner 1 turns on the second light source 15 and The transparent original is projected onto the second optical sensor 25 using the two optical systems. When a reading start instruction is given, the flatbed scanner 1 repeatedly executes main scanning and sub-scanning continuously. In the main scan, the light projected from the second light source onto the document 13 and transmitted through the document 13 enters the second optical sensor 25 via the second optical system.

The sub-scanning of the reflection original and the transmission original is performed by repeatedly and continuously executing main scanning for reading a line by moving the carriage 14 by a driving device. When reading the transparent original, the second light source 15 causes the control unit 38 to synchronize with the movement of the carriage 14.
It is moved by a drive controlled by.

First optical sensor 27 or second optical sensor 25
The electric charge accumulated for a predetermined period is output to the amplifier 33. The output signal from the amplifier 33 is supplied to the A / D converter 34.
Is converted into digital light amount signal data by the shading correction unit 35, the gamma correction unit 36, and the other correction unit 37, and various signal processes are performed, and output to the personal computer through the interface 39.

Comparing the case of reading the reflective original with the case of reading the transparent original, as shown in FIG. 5B, when the transparent original is read, the image projected on the second optical sensor 25 (see the figure). The shaded portion) is doubled by using the second condenser lens 26 to substantially improve the resolution. At this time, as shown in FIG. 6, the width L2 of the original document projected on the second optical sensor 25 when reading the transparent original document is the same as the width L1 of the original document projected on the first optical sensor 27 when reading the reflective original document. It will be halved.

In the present embodiment, since the reading range is switched depending on the original, even when the original having a half width L1 is read with respect to the maximum readable width L2, an image is formed on all pixels of the first photosensor 27. It is possible to project, and it is possible to double the substantial resolution by using an optical sensor having the same width and the same number of pixels.

Further, since all the mirrors for making the light reflected by the original document and the light transmitted through the original document incident on the optical sensor are fixed to the carriage, they are read as compared with an image reading apparatus having a movable mirror for switching the optical path. The accuracy of is high.

Further, it is equipped with two optical systems and has a fixed focus of 2.
Since it is possible to set the location, it is possible to always reproduce a sharp image without the transparent original being read in a so-called “out of focus” state.

In the above embodiment, only the image reading apparatus for reading the reflective original and the transparent original has been described, but the present invention can be realized even if the image reading apparatus reads only one of the reflective original and the transparent original. It is possible. Further, the present invention can be applied to various image reading devices such as a sheet feed type scanner as well as the flatbed type scanner.

[Brief description of drawings]

FIG. 1 is a schematic view showing a carriage of a flatbed type scanner according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a flatbed scanner according to an embodiment of the present invention.

FIG. 3 is a schematic diagram showing a reading position of a transparent original according to an embodiment of the present invention.

FIG. 4 is a block diagram showing a flatbed scanner according to an embodiment of the present invention.

FIG. 5A is a schematic diagram for explaining the size of an image formed on the optical sensor when the first optical system is used in the embodiment of the present invention. FIG. 6B is a schematic diagram for explaining the size of an image formed on the optical sensor when the second optical system is used in the embodiment of the present invention.

FIG. 6 is a schematic diagram for explaining a readable range on a document table in one embodiment of the present invention.

[Explanation of symbols]

1 Flatbed scanner (image reading device) 11 Lower case 12 Platen 13 manuscript 15 Second light source (light emitting part) 17 First light source (light emitting part) 18, 19, 20, 21 1st mirror 22 First condenser lens 23 Second mirror 25 Second optical sensor 26 Second condenser lens 27 Optical sensor

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04N 1/10 H04N 1/10 1/107 F term (reference) 2H108 AA01 AA26 CB01 HA01 JA00 5B047 AA01 AB04 BA02 BB02 BC05 BC09 BC11 BC14 CB16 5C051 AA01 BA03 DA02 DB01 DB22 DB24 DB28 DC02 DC04 DC05 DC07 DE09 DE26 FA04 5C062 AB03 AB33 AB41 AB42 AB53 AC02 AC08 AE03 AE15 BA02 5C072 AA01 BA04 CA02 DA02 DA04 EA05 LA20 VA03

Claims (5)

[Claims] 1. A light emitting unit for irradiating a document, a first optical sensor for converting the received light into an electric signal, and a second optical sensor.
An image reading apparatus comprising: an image pickup unit having an optical sensor; and an optical system that reflects light projected from the light emitting unit and reflected by a document or light transmitted through the document and focuses the light on the image pickup unit. . 2. The first optical mirror reflects the light reflected by the document or the light transmitted through the document and makes the light incident on the first optical sensor, and the light reflected by the document or the light transmitted through the document. The image reading apparatus according to claim 1, further comprising a second mirror which makes the second optical sensor incident on the second mirror. 3. The first mirror causes light reflected by a document to enter the first optical sensor, and the second mirror causes light transmitted through the document to enter the second optical sensor. The image reading device according to claim 2. 4. The optical system includes a first condenser lens arranged on an optical path from an original to the first optical sensor via the first mirror, and an optical system from the original to the second mirror via the second mirror. The image reading device according to claim 2, further comprising a second condenser lens arranged on an optical path reaching the two optical sensors. 5. The magnification of the second condenser lens is the first magnification.
The image reading device according to claim 4, wherein the magnification is an integral multiple of the magnification of the condenser lens.