JP2001103246A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized economical image reader. SOLUTION: The image reader is provided with a lighting section 16 that lights an image on a base (original 14) while being moved in a 1st direction in parallel with the base made of a translucent material, a mirror 30 that reflects the light transmitted through the base, a motor 56 that drives the mirror around a shaft 32 extended in the 2nd direction orthogonal to the 1st direction, a lens system (optical system) 28 that forms an image of the light reflected from the mirror, and an image receiving section (image pickup element 44) receiving the light of which image is formed. The light source of the lighting section employs a linear light source 18 extended in the 2nd direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illuminating section for scanning and illuminating an image carried on a substrate made of a translucent material, a rotary drive type mirror for polarizing light transmitted through the substrate at a predetermined angular velocity, and a mirror. And an image receiving unit for receiving the light reflected by the image reading device.

[0002]

2. Description of the Related Art Conventionally, as an image reading apparatus, an illuminating section for scanning and illuminating a document carried on a substrate while moving in a first direction in parallel with a substrate made of a translucent material, A mirror for reflecting the reflected light, a rotation drive source for rotating the mirror about an axis extending in a second direction orthogonal to the first direction, a lens system for forming an image of the light reflected by the mirror, and an image forming apparatus. There has been proposed an image reading apparatus including an image receiving unit for receiving the light.

[0003]

However, the illumination section in the conventional image reading apparatus uses a surface light source. This surface light source has a predetermined width in the first direction and the second direction described above. Therefore, the light source and the illumination unit occupy a large space, the image reading device becomes large, and the manufacturing cost increases. Further, since the light emitted from the light source is diffused in the first direction and the second direction, a light source having a large light emission amount must be used in order to allow a sufficient amount of light to enter the image receiving unit. Further, the uneven light amount at the document irradiation position is the first reason.
And the second direction, the sharpness of the received image decreases.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and is characterized in that a line light source extending in a second direction is used as a light source of an illumination unit in an image reading apparatus. And

According to another aspect of the present invention, there is provided an image reading apparatus which controls the driving of the driving source so that an image formed on the image receiving unit moves at a constant speed with respect to the image receiving unit. A first control unit is provided.

Further, in an image reading apparatus according to another aspect of the present invention, the intensity of light incident on a document portion corresponding to the image formed on the image receiving portion is determined by the light intensity of the image combined with the image receiving portion. A second control unit for controlling the movement of the line light source so that the intensity is constant is provided.

In another aspect of the present invention, the illuminating unit includes the line light source and a diffusion plate for diffusing light emitted from the line light source.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (1) Image Reading Apparatus FIG. 1 shows the overall configuration of an image reading apparatus. The image reading device 10 has a support 12 for supporting a material to be illuminated. As a material to be illuminated, a document 14 in which an image is carried on a flat substrate (for example, a film) made of a translucent material
Is used. Above the support 12, an illumination section 16 for illuminating the document 14 is provided. The illuminating unit 16 includes a line light source 18 extending in parallel to the document 14 supported by the support 12 and in the front and back direction (second direction) of the drawing.
Has a parabolic cross-section reflecting umbrella 20 that covers the back (opposite side of the original 14). The line light source 18 is electrically connected to a power supply (not shown), and emits light when electricity is supplied from the power supply.

The illumination section 16 has a guide shaft 24 extending in a direction (first direction) orthogonal to the line light source 18. The illumination unit 16 is mechanically connected to a stepping motor 26 via a guide shaft 24 or another appropriate mechanism. Based on the driving of the stepping motor 26, the illumination unit 16 moves in the first direction. It can be moved back and forth. There are various possible mechanisms for drivingly connecting the stepping motor 26 and the illuminating unit 16. For example, the guide shaft 24 is formed of a screw shaft, and a screw provided on the screw shaft is fixed to the reflector 20. A mechanism for moving the screw and the illumination unit 16 in the first direction by rotating the screw shaft by the rotation of 26 is conceivable.

An optical system 28 is provided on the opposite side of the illumination section 16 with the document 14 interposed therebetween. The optical system 28 has a mirror 30 located immediately below the document 14. The mirror 30 is supported rotatably about an axis 32 extending in a direction (second direction) parallel to the line light source 18. The shaft 32 is mechanically connected to a stepping motor 34, and the mirror 30 is driven based on the driving of the stepping motor 34.
Can be rotated in the direction of arrow 36.

The optical system 28 also has an F.tan.theta. Lens unit (front lens 38 and rear lens 40). The front group lens 38 is arranged between the original 14 and the mirror 30, and makes light transmitted through the original 14 incident on the mirror 30. On the other hand, the rear group lens 40 forms an image of the light reflected by the mirror 30 on an image reading unit described later.

The image reading section 42 has an image pickup device 44.
The imaging element 44 uses a photoelectric conversion element (CCD), and is set at a position where light formed by the rear lens group 40 is incident. The image reading unit 42 also includes the image sensor 4
Analog processing circuit 46 for processing the signal output from 4
An A / D converter 48 for converting an analog signal output from the analog processing circuit 46 into a digital signal;
It has a digital processing circuit 50 that performs image processing on the digital signal output from the converter 48.

A control system 52 for controlling the movement of the illumination unit 16 and the rotation of the mirror 30 includes motor control units 54 and 56 for driving and controlling the stepping motors 26 and 34, respectively. And a microprocessor 58 for controlling in synchronization.

The operation of the image reading apparatus 10 having the above configuration will be described. The microprocessor 58 outputs a signal to the motor control units 54 and 56. Upon receiving the signals, the motor control units 54 and 56 respectively operate the stepping motors 26 and 3
Start 4 By driving the stepping motor 26,
The illuminator 16 and its linear light source 18 move in a first direction. The line light source 18 emits light when electricity is supplied from a power source (not shown). The light emitted from the linear light source 18 is directly or reflected by the reflector 20 and indirectly illuminated on the document 14. The light transmitted through the document 14 is incident on the mirror 30 via the front group lens 38.

The mirror 30 is rotated in synchronization with the movement of the line light source 18 based on the driving of the stepping motor 34. The light reflected by the mirror 30 is imaged on the image sensor 44 via the rear lens group 40. The image forming position on the image sensor 44 moves at a constant speed by controlling the rotation of the mirror 30 described later, and the image included in the document 14 is illuminated on the image sensor 44 by the document scanning illumination of the linear light source 18.

The image sensor 44 creates an image signal corresponding to the intensity of the received light for each pixel,
Output to The analog processing circuit 46 creates an analog signal corresponding to the image signal and outputs the analog signal to the A / D converter 48. The A / D converter 48 converts an analog signal into a digital signal and outputs the digital signal to the digital processing circuit 50. And
The digital processing circuit 50 creates an image reproduction signal according to the digital signal, and outputs it to an appropriate display device.

(2) Mirror Rotation Control In the image reading apparatus 10, the image pickup device 44 outputs a photoelectrically converted signal at a constant time interval. Therefore, in order to reproduce the image of the document 14 at the correct magnification even when the whole or a small portion is taken, the image sensor 4
4, the image height Y in the first direction on the document 14 (corresponding to the distance between the optical axis 62 of the optical system 28 and the image formed on the image sensor 44 on the document). , The rotational speed of the mirror 30 must be controlled so as to move at a constant speed over time.

For this purpose, when the optical system shown in FIG. 2 is assumed, the angle at which the image portion located at the position of the optical axis 62 of the optical system 28 and the image height Y enters the mirror 30 is θ. The temporal change of the angle θ in the F · tan θ system of the device 10 must satisfy the relationship represented by the following equation (1).

[0019]

Here, Ymax is the maximum value of the image height, F is the focal length, and tmax is the time when the end of the document is imaged on the image sensor.

On the other hand, since the rotational angular velocity θ _REF of the mirror 30 is represented by the corresponding θ / 2, the equation (1) is replaced by the equation (2).
Can be represented as

Therefore, the microprocessor 58 and the motor control unit 5 are controlled so as to satisfy the relationship of the equation (2).
The mirror 30 is rotated such that the stepping motor 34 is driven based on the instruction from the controller 6 and the imaging position on the image sensor 44 moves at a constant speed. In addition,
As shown by the equation (2), the mirror 30 near the optical axis 62
Is maximized, and the angular velocity of the mirror 30 is minimized at the time of illumination of the start and end of the document in the first direction.

[0023] (3) In the lighting unit speed control image reading apparatus 10, the intensity of the light emitted from the line light source 18, the document surface indicates the distribution of FIG. 3, the maximum A _MAX becomes just below the line light source 18, Draw a parabolic curve that gradually decreases as it deviates from just below. Then, using the line light source 18 having such a light intensity distribution, as shown in the schematic diagram of FIG. When the system is designed, the light intensity of the image formed on the image sensor 44 changes according to the position of the document portion to be formed (see FIGS. 4B and 7). More specifically, the document portion deviated from the optical axis 62 of the optical system 28 is
The light intensity of the image formed on the image 4 is lower than the light intensity of the image formed on the image sensor 44 of the original portion immediately below the optical axis 62.

For the above reasons, in this embodiment, FIG.
As shown in 6, the copy edge D _L, using a maximum intensity A _MAX in the light intensity distribution curve C is the illumination of D _R, the original central portion D _C
Lower light intensity than the maximum intensity A _MAX is the illumination of the A (+ w /
2) or the moving speed of the illumination unit 16 is adjusted so as to use A (−w / 2). In other words, the document edges D _L , D _R
When illuminating the, the copy edge D _L, set the lighting unit 16 such that the maximum intensity A _MAX immediately above the D _R is located, when illuminating the original central part D _C, the original central portion D _The illumination unit 16 is set such that the weak light intensity A (+ w / 2) or A (−w / 2) is located directly above _C.

Specifically, the angle between the optical axis 62 and the light incident on the mirror is θ, and the light intensity of the image formed on the image sensor 44 is L.
(Θ), the moving speed of the linear light source 18 is V (θ), and the transmittance of the document is T, the moving speed V (θ) of the linear light source 18 is L
The value of w and the moving speed V (θ) of the linear light source 18 are determined so that (θ) is constant.

As shown in FIG. 5, when the light intensity in the right half area of the light intensity distribution curve C is used for document illumination,
From the document left end D _L to the center portion D _C moves slowly illumination unit 16, gradually accelerating from the original central portion D _C to the original right end D _R. On the other hand, as shown in FIG. 6, when using the light intensity of the left half area of the light intensity distribution polarity C for document illumination,
The document moves relatively fast from the left edge D _L to the center D _C ,
Gradually decelerated from the original central portion D _C to the original right end D _R.

FIG. 7 shows the relationship among the rotation speed of the mirror 30, the moving speed of the image height, and the moving speed of the illumination unit 16 described above.

The moving speed V (θ) of the linear light source 18 is
It differs depending on the characteristics (light intensity function) and width (W) of the light intensity distribution curve used for document illumination. Therefore, as in the above-described embodiment, it is desirable to provide the reflector 20 on the line light source 18 and appropriately set the distance (H) from the document to the line light source to prevent a rapid change in the moving speed V (θ). .

(4) Other Embodiments of Illumination Unit In the above embodiment, the illumination unit 16 has one line light source 18
And a reflector 20 surrounding the line light source 18,
The configuration of the illuminating unit 16 is not limited to this, and the following improved examples can be adopted.

First Modification FIG. 8 shows a first modification of the illumination unit. The illumination unit 16 'according to this improved example has a housing 70 having a U-shaped cross section in which a facing portion of the document 14 is opened. In the housing 70, one linear light source 18 and a reflector 20 covering the rear of the linear light source 18 are provided. The opening of the housing 70 is covered with a diffusion plate 72 so that the intensity of light emitted through the diffusion plate 72 is substantially uniform over the entire diffusion plate 72.

Second Modification FIG. 9 shows a second modification of the illumination unit. The illumination unit 16 ″ according to this improved example includes two line light sources 18 and a reflector 20 surrounding each line light source 18 in a housing 70, and has a substantially uniform intensity from the entire surface of the diffusion plate 72. Light can be emitted.

Driving of Illuminating Unit As described above, the illuminating units 16 ′, 1 ′, 1
In the case of 6 ″, since light of almost uniform intensity can be emitted from the entire surface of the diffusion plate 72, the moving distance of the illumination unit 16 can be smaller than that of the illumination unit of the above embodiment. Specifically, FIG.
As shown, when the intersection of the lines 82 and 84 connecting the incident position 80 of the mirror 30 and the document left D _L and right D _R and the movement locus 86 of the diffuser 72 and respectively 88 and 90, the illumination unit 16 Is the intersection of the left and right ends of the diffuser 72
It moves between two positions (two positions shown in FIG. 10) in contact with 8, 90.

Specifically, the moving range of the illumination unit 16 is the first range.
Assuming that the width of the document in the direction of L is L and the width of the illumination unit is W, the following expression (3) is used. Here, since θ _MAX = −θ _MIN , the minimum moving distance (2S) of the illumination unit 16 is expressed by Expression (4). The starting point of the lighting unit 16 is represented by Expression (5). Furthermore, the moving speed of the illumination unit 16 is controlled so that the moving speed of the image height Y in the F-tan θ optical system 28 moves at a constant speed represented by Expression (6).

[0034]

As is apparent from the above description, the image reading apparatus according to the present invention uses a line light source instead of a surface light source. Therefore, the size of the image reading device, particularly its illumination unit, is reduced. In addition, the line light source can be configured at a lower cost than the surface light source, and has a long life, so that a low-cost image reading apparatus can be provided. Further, by controlling the rotation of the mirror and the movement of the illumination unit according to the present invention, it is possible to form an image of the entire document on the image receiving unit with a constant light intensity. According to the image reading apparatus having the diffusion plate in front of the linear light source, the original can be illuminated with light of uniform intensity without illumination unevenness. Further, the moving distance of the light source can be reduced.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing a path of light transmitted through the image reading apparatus shown in FIG.

FIG. 3 is an intensity distribution diagram of light emitted from a linear light source.

FIG. 4 is a diagram illustrating an illumination position of an illumination unit, an image receiving position of an image sensor, and a distribution of light intensity of an image formed on the image sensor.

5 is a diagram showing a relationship between a light amount portion used for document illumination and a document portion formed on an image sensor in the light amount distribution shown in FIG. 3, and a moving speed of an illumination unit.

6 is a diagram showing another relationship between a light amount portion used for document illumination and a document portion formed on an image sensor in the light amount distribution shown in FIG. 3, and a moving speed of an illumination unit.

FIG. 7 is a diagram showing an illumination light amount ratio and the like of a document portion formed on an image sensor.

FIG. 8 is a cross-sectional view of another embodiment of a lighting unit.

FIG. 9 is a cross-sectional view of another embodiment of a lighting unit.

FIG. 10 is a diagram showing a movement range of the lighting unit shown in FIGS.

[Explanation of symbols]

10 image reading device, 14 document, 16 illumination unit, 18
... Line light source, 20 ... Reflector, 26, 34 ... Stepping motor, 30 ... Mirror, 28 ... Optical system, 42 ... Image reading unit, 44 ... Imaging element, 54, 56 ... Motor control unit, 58
... microprocessor.

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 5C072 AA01 BA01 BA05 BA15 CA02 DA02 DA04 DA16 DA21 DA23 EA05 LA01 MA01 MB01 VA03

Claims (4)

[Claims] An illumination unit configured to illuminate an image carried on the substrate while moving in a first direction parallel to the substrate made of a translucent material; and a mirror configured to reflect light transmitted through the substrate. A drive source for rotating the mirror around an axis extending in a second direction orthogonal to the first direction, a lens system for imaging light reflected by the mirror, and receiving the imaged light An image reading apparatus comprising: an image receiving unit; and a line light source extending in the second direction is used as a light source of the illumination unit. 2. The image forming apparatus according to claim 1, further comprising a first control unit that controls driving of the driving source so that an image formed on the image receiving unit moves at a constant speed with respect to the image receiving unit. The image reading apparatus according to claim 1, wherein: 3. The illumination unit according to claim 1, wherein an intensity of light incident on a document portion corresponding to the image formed on the image receiving unit is constant. 3. The image reading apparatus according to claim 2, further comprising a second control unit for controlling movement. 4. The image reading apparatus according to claim 1, wherein said illuminating unit includes said line light source and a diffusion plate for diffusing light emitted from said line light source.