JP2002176539A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reader which can precisely measure the height of a document surface without being affected by disturbing light such as illumination light when the height is detected by projecting reference light. SOLUTION: The illumination light lighting up the document surface is turned on and a preliminary scan is started to gather information showing the state of the document (P1 to P3). The reference light of a laser light projecting device is turned on and the illumination light is turned off (or dimmed) to measure the height of the document with the reference light (P4 to P5). The preliminary scan is completed, image processing parameters are computed (P6 to P9) from the original height H based upon the distance measurement result according to the gathered information showing the state of the document. While the illumination light is turned on and the reference light is turned off, a main scan is started (P9 to P10) to read the document image. Focus position adjustment parameters are updated (P12) by vertical scanning lines, the main scan is completed as a scan in the vertical scanning direction ends, and the illumination light is turned off, thus finishing the processing.

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 more particularly to a distance measuring means for measuring the height of a book document placed on a document table for reading a book document having one end bound thereto, such as a book. The present invention relates to an image reading apparatus which is capable of adjusting the focus of a scanning optical system according to the document height of a book document.

[0002]

2. Description of the Related Art As an image reading apparatus for reading a book manuscript such as a book, one end of which is bound, the apparatus is placed on a manuscript table with the manuscript surface to be read facing up, and a scanning optical system is adjusted to the height of the manuscript surface. 2. Description of the Related Art A device that reads an image while performing focus adjustment is known.

In this type of apparatus, the height of the original surface from the reference surface (for example, the original platen) is not constant. When the main scanning is performed, the focus of the scanning optical system needs to be adjusted based on the data indicating the measured document height.

For this reason, various methods have been proposed as a method for measuring the height of a document as follows. For example, a mirror for distance measurement is arranged inclining rearward of the document table, and the shape of the end face of the book document reflected on the distance measurement mirror is received by an image sensor such as a CCD, and a pixel indicating the contour shape of the end face is used. Calculating the document height based on the number (JP-A-7-79324), projecting light transmitted through a slit onto a book document, receiving the reflected light with an image sensor, There is one that calculates the document height based on the shape (Japanese Patent Laid-Open No. Hei 5-219323).

[0005] Further, a reflection type photosensor for measuring the height of a specific portion of a book document, or a device for measuring the height of a document using an ultrasonic sensor (Japanese Patent Laid-Open No. Hei 6-313314). An apparatus which measures the height of a document by projection and triangulation (JP-A-10-84461) has been proposed.

[0006]

As described above, there are various methods for measuring the document height of a book document.
In the method of measuring the document height from the shape of the end face of the book document reflected on the distance measuring mirror by arranging a mirror inclined rearward and rearward of the document table, the end face of the book document has a high density such as black. In this case, the distance measurement becomes impossible, and the area where the distance measuring mirror is disposed is read at the same time as the image area, so that the resolution of the read image is reduced.

In the case of projecting reference light onto a book original and measuring the height of the original by triangulation, the reference light is erased by the illumination light of the image reading device, or a blank portion or the like is placed on the original surface. When the high-luminance area exists, a high-luminance area other than the high-luminance area where the reference light is projected is detected, and the projection position of the reference light cannot be specified, so that there is a disadvantage that the distance cannot be measured.

In the method of measuring the document height by triangulation by projecting the reference light, the first preliminary scanning for detecting the document height, the background density of the document, the document size, and the document Two preliminary scans including a second preliminary scan for detecting a finger image position or the like are required to erase an image of a finger to be held, or reference light projected for distance measurement and illumination light for image reading. The configuration is complicated, such as requiring an optical device for separating the light from the light according to the difference in wavelength. An object of the present invention is to solve the above problems.

[0009]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and the invention of claim 1 scans a document surface in an image reading apparatus capable of reading a bound document such as a book. A scanning optical system including a CCD line sensor;
Reference light projection means for projecting reference light for detecting the height of the document onto the document surface, illumination light irradiation means for irradiating illumination light for reading the document surface onto the document surface, and control means, the control means comprising: When detecting the height of the original in the preliminary scanning, the reference light is projected onto the original surface and the reference light projecting means and the illumination light irradiating means are controlled so as to turn off or reduce the illumination light. .

In the prescan, the control means detects the document height based on information on the position where the reference light reflected on the document surface is incident on the CCD line sensor.

The control means may control the illuminating light irradiating means so as to turn off the illuminating light when detecting the document height in the preliminary scanning.

The control means may control the illuminating light irradiating means so as to diminish the illuminating light when detecting the document height in the preliminary scanning.

When collecting information indicating the state of the original in the preliminary scanning, the control means receives the reflected light of the illumination light from the original surface by a CCD line sensor, and changes the state of the original based on the output. The information shown is calculated.

The information indicating the state of the original includes 1 to 4 information selected from original size, original density, original background density, and finger image position information for pressing the original.

In the pre-scanning, the control means repeats the lighting of the reference light / turning off or dimming of the illumination light and the turning off of the reference light / turning on of the illumination light at predetermined time intervals. The reference light projection unit and the illumination light irradiation unit may be controlled so that the detection of the document height and the collection of information indicating the state of the document are simultaneously performed.

Further, it is preferable that the reference light projected from the reference light projecting means is spot light, and is moved in the sub-scanning direction by scanning with a scanning optical system.

Alternatively, the reference light projected from the reference light projection means may be slit light.

[0018]

Embodiments of the present invention will be described below.

FIG. 1 is an external view showing the configuration of an image reading apparatus 10 according to an embodiment of the present invention. In FIG. 1, 1
A scanning unit 1 includes a scanning mirror, a projection lens, and a CCD line sensor. The configuration of the scanning optical system will be described later in detail. Reference numeral 12 denotes an exposure lamp unit.
A lamp for illuminating the original surface when reading the original is arranged. Further, a control panel 13 is arranged in the exposure lamp unit 12 to set various reading modes,
Performs device status, error display, and warning display.

Reference numeral 16 denotes an original table, and 17 denotes a movable recess at the center of the original table. For book originals, a back binding portion having a special structure or a book original having a large back binding portion is provided with a back binding portion. By submerging from the surface, the spread pages of the book document can be made almost flat. Reference numeral 18 denotes a start key for instructing start of image reading, and 19 denotes a power switch.

In this embodiment, the main scanning direction is the direction in which the elements of the CCD line sensor are arranged.
In the illustrated image reading apparatus 10, the direction is from the back to the front, and the sub-scanning direction is a direction orthogonal to the arrangement direction of the elements of the CCD line sensor, and is the direction from right to left in the illustrated image reading apparatus.

FIG. 2 is a perspective view for explaining a state in which the book original is placed on the original platen. 3 shows a state in which an image is read by holding the blank portion with a finger so that the sheet does not move.

When the book document 15 is placed on the document table 16 with the open side up, the document surface is not flat and the height in the front-back direction is substantially constant, but the height in the left-right direction is substantially The two ridges have a valley-shaped curve with a valley in the center where they are bound. Especially, the inclination of the valley in the center is a part where the image distortion that has been read suddenly becomes large. This is an area where highly accurate focus adjustment according to the height of the document 15 is required.

The height of the book document 15 in the front-rear direction when placed on the document table 16, that is, the height in the main scanning direction is substantially constant. If the height is sequentially measured along the sub-scanning direction, the original height of the book original 15 at the measurement position can be obtained.

In FIG. 2, a line L is an image reading line in the main scanning direction read by the CCD line sensor.
A point S indicates a document height measurement point, and a line R indicates a locus of the document height measurement point S in the sub-scanning direction.

Here, a method of measuring the height of a book document will be briefly described. The method of detecting the document height of a book document is based on a known triangulation method, where the document height is defined as the height of the document surface to be read when the book document is opened and placed on the platen. Shall refer to height,
The reference surface is the surface of the document table. By knowing the document height, the focus of the scanning optical system can be adjusted so that the document surface is accurately imaged on the CCD line sensor.

FIG. 3 is a diagram for explaining a method of measuring the height of the original. In FIG. 3, a reference light from a light source P is projected onto the original at a predetermined projection angle θ, and the reflected light is transmitted to a CCD line sensor LS.
It is assumed that light is received. When the document surface is on the reference surface, that is, when the thickness of the book document is zero, the reference light is reflected at point A on the document surface (reference surface), and the reflected light is reflected by the projection lens L.
, And then enters the CCD line sensor LS, a signal having a peak value at point a is output from the sensor. In the case of a book original having a thickness H (original height H), a point B on the original surface
When the reflected light enters the CCD line sensor LS, a signal having a peak value at a point b is output from the sensor.

Here, when the width h of the peak value of the output signal, that is, the interval between the points a and b is obtained from the number of pixels of the CCD line sensor LS, the document height H can be obtained from the following equation. Here, β is the magnification of the projection lens.

2Htan θ = βh FIG. 4 is a perspective view showing the configuration of the scanning optical system. In FIG. 4, reference numeral 21 denotes a scan mirror that rotates around a rotation axis N-N, reference numeral 22 denotes a reflection mirror, reference numeral 23 denotes a projection lens, and reference numeral 24 denotes a CCD line sensor. The reflected light from the book document 15 placed on the document table 16 is
The light enters a CCD line sensor 24 via a reflection mirror 22 and a projection lens 23.

The scanning of the document surface in the main scanning direction is performed by the CCD line sensor 24. The scanning of the document surface in the sub-scanning direction is performed by rotating the scan mirror 21 around the rotation axis N-N so that the document table 16 is moved from one end (for example, the lower right side in FIG. 4) to the other end (the upper left side in FIG. 4). Are scanned toward.

In addition, a laser beam projecting device 25 for projecting a reference beam for measuring the height of the document is provided.
The laser light projected from the laser light projecting device 25 is projected as a high-brightness beam light onto the book document 15 on the document table 16 via the scan mirror 21.

The projection lens 23 is provided with an automatic focusing mechanism (AF mechanism) (not shown). The document height data at the document height measurement point S of the book document 15 and the rotation of the scan mirror 21 are provided. A based on the angle
The F mechanism operates, and the focal position of the projection lens 23 is adjusted.

Next, the outline of the reading operation of the image reading apparatus will be described with reference to FIG. Book manuscript 1 on platen 16
When the image reading surface 5 is placed with the image reading surface facing upward and the start key 18 is turned on, the image reading surface is illuminated by the exposure lamp unit 12.

First, a preliminary scan is started. Reference light is projected from the laser beam projection device 25 onto the book document 15 via the scan mirror 21, and the reflected light is transmitted through the scan mirror 21, the reflection mirror 22, and the projection lens 23 to the CCD.
The light enters the line sensor 24. The projection position of the reference light on the book document 15 (the same position as the document height measurement point S) moves in the sub-scanning direction along the line R due to the rotation of the scan mirror 21 around the rotation axis N-N. Go.

The output signal from the CCD line sensor 24 is processed by the CPU and is output as data indicating the height of the book document 15 and is used for adjusting the focus of the projection lens 23 during the main scanning.

The exposure lamp unit 1 is also used in the preliminary scanning.
2, the image reading surface is illuminated, information indicating the state of the original such as the original size, the original density, and the original background density is collected, and parameters necessary for image processing are calculated. These parameters indicating the state of the original are used for deleting the area outside the original at the time of the main scan and for automatically adjusting the original density.

When the prescan is completed, the main scan is started using the data indicating the document height of the book document 15 obtained by the prescan. That is, the focus of the projection lens 23 is adjusted based on the document height data and the rotation angle of the scan mirror 21. The image of the book document 15 is read, and furthermore, deletion of the area outside the document, automatic adjustment of the document density, and the like are performed using parameters calculated based on information indicating the state of the document.

Here, at the time of preliminary scanning, the illumination light from the exposure lamp unit 12 and the reference light, which is a high-brightness light beam emitted from the laser light projection device 25, are simultaneously projected on the image reading surface. Various problems that occur will be described.

FIGS. 5 to 7 show the exposure lamp unit 12.
Is a diagram showing the state of change in luminance (density) shown in the sensor output when the illumination light and the high-intensity reference light from the laser light projection device 25 are projected under different projection conditions.
The position of the pixel on the CD line sensor 24 is shown, and the vertical axis shows the luminance (density) shown in the sensor output.

FIG. 5 shows a case where the illumination light from the exposure lamp unit 12 and the high-brightness reference light from the laser beam projection device 25 are simultaneously projected on the image reading surface. (The same position as the original height measurement point S)
Indicates a high-brightness sensor output exceeding a predetermined threshold, but if there is also a low-density area on the original image,
This indicates that there is a high-luminance sensor output exceeding the threshold value in that region. As described above, when a plurality of peak values of high luminance exceeding the threshold value occur in the sensor output, it becomes impossible to determine which peak value indicates the document height, and the document height H
Cannot be detected accurately.

As a countermeasure, it is conceivable to reduce or extinguish the illumination light from the exposure lamp unit 12 when detecting the document height H.

FIG. 6 shows a case where a high-brightness reference light is projected onto the image reading surface from the laser light projection device 25 in a state where the illumination light from the exposure lamp unit 12 is reduced. At the position where the reference light is projected (the same position as the document height measurement point S in FIG. 2), a high-brightness sensor output exceeding the threshold value is shown.
In addition, even if there is a low density area on the original image, the illumination light is reduced, so that a high luminance area exceeding the threshold does not occur. Only when one peak value is generated in the output signal of the CCD line sensor 24, the document height H can be reliably detected.

FIG. 7 shows a case where a high-brightness reference light is projected onto the image reading surface from the laser light projection device 25 in a state where the illumination light from the exposure lamp unit 12 is turned off. At the position where the reference light is projected (the same position as the document height measurement point S in FIG. 2), a high-brightness sensor output exceeding the threshold is shown.
The luminance of the other document image areas is close to zero, and no high luminance area exceeding the threshold is generated. Only when one peak value is generated in the output signal of the CCD line sensor 24, the document height H can be reliably detected.

As described above, when projecting the reference light onto the document and detecting the document height H, a high-brightness region exceeding the threshold is detected from the output signal of the CCD line sensor 24. Even if the illumination light for illuminating the peripheral image area is dimmed or extinguished so as not to become a plurality, the reference light is set so that sufficient brightness can be obtained from the peripheral image area to reliably detect the document height H. As the light source, a high-output laser beam is desirable.

On the other hand, since a high-power laser beam may damage the skin and eyes of the operator, a low-power laser beam that emits a laser beam of about class 1 is required for a laser beam emitting device that projects reference light. Since the light emitting device is used, it is difficult to obtain a sufficient contrast with the peripheral image area as a result.

For this reason, conventionally, the illumination light is dimmed or turned off, the first preliminary scanning for detecting the document height H by the reference light, the reference light is turned off, the illumination light is turned on, and the document size is reduced. And the like, after performing the second preliminary scan for detecting a parameter indicating the state of the document such as the original, and then performing the main scan.
An apparatus which performs scanning twice has been proposed, but has a disadvantage that it takes a long time to read an image.

In addition, different optical systems are used for detecting the document height H by the reference light and for detecting the document size and the document density. For example, infrared light is used for detecting the document height H, Although a method using visible illumination light has been proposed for detecting a parameter indicating the state of a document such as a size, there is a disadvantage that the configuration is complicated.

Therefore, in the embodiment of the present invention, the distance measuring operation for detecting the document height H during the execution of the preliminary scanning and the operation for collecting information indicating the state of the document such as the document size are performed in a time sharing manner. They are executed sequentially.

In the distance measuring operation period for detecting the document height H, the laser light emitting device is operated to project the reference light to turn off (or reduce) the illumination light, and in the information collection period indicating the state of the document, the illumination light is used. Is turned on (or increased in brightness), and the illumination switching operation of turning off the reference light is repeated, and the document height H is detected by one preliminary scan, and information indicating the state of the document is collected.

In this method, during the execution of the prescan, the information indicating the state of the document is not collected while the reference light is being projected, and the illumination light is turned on (or increased) while the reference light is being projected. Although the document height H is not detected, the cycle of the above-described illumination switching operation is set to, for example, a moving distance of about 1 mm in the sub-scanning direction by the preliminary scanning, that is, the illumination switching operation is performed every 1 mm of the moving distance in the sub-scanning direction. Is performed, and the distance measurement for detecting the document height H and the collection of information indicating the state of the document are alternately executed, so that the distance measurement and the information collection can be performed with sufficient accuracy for practical use, and the processing is performed. As the amount of data is reduced, the memory capacity and calculation time can be reduced.

FIG. 8 is a diagram showing a first example for explaining the relationship between the timing of switching the illumination between the reference light and the illumination light, the distance measuring operation, and the operation of collecting the information indicating the state of the original. Period (O
During the illumination light period (ON period), the reference light is turned off (OFF) to collect information indicating the state of the document during the illumination light illumination period (ON period). It shows an example of execution.

The provision of a period in which both the reference light and the illumination light are turned off (OFF) when the illumination is switched between the reference light and the illumination light eliminates the possibility that both light up at the same time when the illumination is switched. To do that.

By using laser light as the reference light and using LED or flash light as the illumination light, the response speed of turning on / off (ON / OFF) can be increased. In addition, the response speed can be increased by providing the illumination device with a shutter mechanism.

FIG. 9 is a diagram showing a second example for explaining the relationship between the illumination switching timing between the reference light and the illumination light, the distance measuring operation, and the operation of collecting information indicating the state of the document, and the reference light projection. Period (O
During period N), the illumination light is reduced and the distance measurement operation is performed.
The reference light is turned off (OFF) during the illumination light lighting period (ON period)
Then, an operation of collecting information indicating the state of the original such as the original size is performed.

As described above with reference to FIG. 6, the distance measuring operation can be executed by turning off the illumination light without turning off the illumination light during the reference light projection period (ON period). Generally, a halogen lamp, an incandescent lamp, or a fluorescent lamp is used as an illumination light source, and these light sources are turned on / off (ON / OFF).
If the response speed is slow and the illumination switching cycle is short, tracking may not be possible. However, it is possible to diminish the light in a short cycle with these light sources. In the case where is used, it is preferable that the light is dimmed. Periodic dimming control of the illumination light can be realized by a pulse width modulation (PWM) method using a semiconductor element or the like.

In the distance measuring operation using the reference light, the presence of the illumination light may cause a distance measurement failure or a distance measurement failure.
In the operation of detecting the document size and document density by the illumination light,
Even if the reference light is present, the projection position is limited to a predetermined specific portion, and therefore, the operation of collecting information indicating the state of the document can be executed except for this portion. Therefore, it is also possible to keep the reference light such as laser light on and not turn off the light even during the period of collecting the information indicating the state of the document by the illumination light.

FIG. 10 is a block diagram showing a configuration of a control circuit of the image reading apparatus. The control circuit 30 is configured around the CPU 31. The input / output ports of the CPU 31 include a scan mechanism 41 that rotates the scan mirror 21 (see FIG. 4) around the rotation axis N-N to perform scanning in the sub-scanning direction. An automatic focus adjustment mechanism (AF mechanism) 42 for adjusting the focal position of the projection lens 23, an illumination light control circuit 43 for controlling a lamp of the exposure lamp unit 12, and a laser light projection device 25 for projecting reference light (see FIG. 4). 1, a laser light control circuit 44 for controlling the operation, a ROM 45 storing programs and the like, a RAM 46 for temporarily storing data, and a start key 18 (FIG. 1).
Reference) etc. are connected.

Further, the input / output port of the CPU 31 is connected to a data fetch circuit 34 for fetching data for one line in the main scanning direction and an image processing circuit 36. In addition, the control circuit 30 includes an A / D converter 32, a shading correction circuit 33, a light distribution correction circuit 35, and the like.

In the preliminary scanning, the CPU 31 drives the laser light control circuit 44 and the illumination light control circuit 43 to perform reference light on / off control and illumination light on / off (or dimming) control to perform scanning. The preliminary scanning is executed by driving the mechanism 41.

The image signal output from the CCD line sensor 24 (see FIG. 4) is converted into digital data by the A / D converter 32, and the shading correction circuit 33 reduces the sensitivity difference between the pixels of the CCD and the periphery of the projection lens. The influence of light and the like is corrected, and is taken into the CPU through the data taking circuit 34.
The document height H is determined, and an automatic focus adjustment mechanism (AF mechanism) 4
2 to calculate the focal position adjustment parameters of the projection lens 23, and collect information indicating the state of the original to calculate parameters for image processing.

In the main scanning, lighting control of the illumination light is performed, and the scanning mechanism 4 is controlled using the focal position adjustment parameters.
1 to perform main scanning. CCD line sensor 2
4 (see FIG. 4) is converted into digital data by the A / D converter 32, and the shading correction circuit 33 corrects for the sensitivity difference between the pixels of the CCD and the influence of the peripheral dimming of the projection lens. Is done.

The light distribution correction circuit 35 corrects uneven light distribution and uneven density of the illumination light, and the image processing circuit 36 erases the frame, enhances the edges,
Perform image processing such as enlargement / reduction, binarization, finger image deletion, etc.
Output the processed image.

The outline of the control operation executed by the control circuit 30 will be described with reference to the flowchart of FIG. The control operation is started by turning on the power switch 19 (see FIG. 2), and the illumination light of the exposure lamp unit 12 is turned on (step P1). Preliminary scanning is first started by scanning the start key 18 (see FIG. 2) (step P2), and an operation of collecting information indicating the state of the document is performed (step P2).
3). The reference light is turned on and the illumination light is turned off (or dimmed) by operating the laser light projecting device 25 (step P
4) A document height measuring operation using the reference light is performed (step P5).

It is determined that the scanning in the sub-scanning direction has been completed (step P6).
The reference light is turned off and the illumination light is turned on (or increased) (step P7), and the process returns to step P3. If it is determined in step P6 that the scanning in the sub-scanning direction has been completed, the end of the pre-scanning is determined (step P8).

A focal position adjustment parameter of the projection lens 23 is calculated from the document height H based on the distance measurement result, and a parameter for image processing is calculated based on the collected information indicating the state of the document. Prepare for scanning (Step P
9).

The illumination light of the exposure lamp unit 12 is turned on,
The reference light from the laser beam projector 25 is turned off (Step P10), and the main scanning is started (Step P11). The reading of the original image is executed, and at this time, the focal position adjustment parameter is updated for each sub-scanning line (or for each of a plurality of sub-scanning lines) to a parameter corresponding to the position (step P12).

It is determined whether the scanning in the sub-scanning direction is completed (step P13). If the scanning in the sub-scanning direction is not completed, the process returns to step P12. If the scan in the sub-scanning direction has been completed in the determination of step P13, the main scan is completed.
The illumination light of the exposure lamp unit 12 is turned off (steps P14 and P15), and the process ends.

[0068]

As described above, the present invention relates to an image reading apparatus for reading a stitched original such as a book, and the height (original height) of the original surface from a reference surface in preliminary scanning.
When detecting the reference light, the reference light is controlled by projecting the reference light onto the document surface and controlling the reference light projection means and the illumination light irradiation means so as to turn off or reduce the illumination light. Accuracy is not affected by disturbance light, such as illumination light, because the projection position of the reference light cannot be specified because it is erased or the high-luminance area exists on the document surface other than the projection position of the reference light. Not only can the height of the original document be measured well, but also when using a laser beam projecting device or the like as the reference beam projecting device, there is no danger of harm to the operator since no particularly high output device is required. .

In the preliminary scanning, the reference light is projected such that the operation of turning on / off the illumination light or turning off the illumination light and the operation of turning off / turning off the illumination light of the reference light are repeatedly performed at predetermined time intervals. When controlling the means and the illumination light irradiating means, only one preliminary scan is required to detect the document height and collect information indicating the state of the document at the same time, which is necessary for efficient image processing in a short time. Information can be obtained.

[Brief description of the drawings]

FIG. 1 is an external view illustrating a configuration of an image reading apparatus according to an embodiment of the present invention.

FIG. 2 is a perspective view illustrating a state in which a book document is placed on a document table.

FIG. 3 is a diagram illustrating a method of measuring the height of a book document.

FIG. 4 is a perspective view showing a configuration of a scanning optical system.

FIG. 5 shows the position and luminance (density) of a pixel of a CCD line sensor when both reference light and illumination light are projected on an image reading surface.
The figure which shows the state of the change of.

FIG. 6 is a diagram illustrating a state of a change in a position of a pixel of a CCD line sensor and a luminance (density) when the illumination light is reduced and projected on an image reading surface together with a reference light.

FIG. 7 is a diagram illustrating a change in the position of a pixel of a CCD line sensor and a change in luminance (density) when illumination light is turned off and reference light is projected onto an image reading surface.

FIG. 8 shows an illumination switching operation between a reference light and an illumination light and a distance measurement operation.
FIG. 5 is a diagram illustrating a first example for explaining a relationship with a detection operation.

FIG. 9 shows an illumination switching operation and a distance measurement operation between reference light and illumination light.
FIG. 9 is a diagram illustrating a second example for explaining a relationship with a detection operation.

FIG. 10 is a block diagram illustrating a configuration of a control circuit of the image reading apparatus.

FIG. 11 is a flowchart showing an outline of a control operation executed by the control circuit.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 Image reading device 11 Scanner unit 12 Exposure lamp unit 13 Control panel 15 Book document 16 Document table 17 Movable recess at the center of document table 18 Start key 19 Power switch 21 Scan mirror 22 Reflection mirror 23 Projection lens 24 CCD line sensor 25 Laser Light projection device 30 Control circuit 31 CPU 32 A / D converter 33 Shading correction circuit 34 Data capture circuit 35 Light distribution correction circuit 36 Image processing circuit 41 Scan mechanism 42 Automatic focus adjustment mechanism (AF mechanism) 43 Illumination light control circuit 44 Laser light control circuit 45 ROM 46 RAM

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 5B047 AA01 BA02 BB02 BB09 BC05 BC09 BC14 CA17 CA19 CB04 CB05 CB09 5C072 AA01 CA02 CA12 DA04 DA21 DA23 EA05 LA02 RA04 VA06 WA04

Claims (9)

[Claims] An image reading apparatus capable of reading a stitched original such as a book, a scanning optical system including a CCD line sensor for scanning the original, and a reference light for detecting the height of the original is projected onto the original. Reference light projection means, illumination light irradiating means for irradiating illumination light for reading the document surface onto the document surface, and control means, wherein the control means is configured to detect the document height in the preliminary scanning. An image reading apparatus which controls the reference light projecting means and the illumination light irradiating means so as to project reference light onto a document surface and to turn off or reduce illumination light. 2. The apparatus according to claim 1, wherein the control unit detects a document height based on information on a position where the reference light reflected on the document surface in the preliminary scanning is incident on the CCD line sensor. The image reading device according to claim 1. 3. The image reading apparatus according to claim 1, wherein the control unit controls the illuminating light irradiating unit so as to turn off the illuminating light when detecting the document height in the preliminary scanning. 4. An image reading apparatus according to claim 1, wherein said control means controls the illumination light irradiating means so as to reduce the illumination light when detecting the document height in the preliminary scanning. . 5. When collecting information indicating a state of a document in a pre-scan, the control means receives a reflected light of the illumination light from the document surface by a CCD line sensor, and based on an output of the CCD line sensor, controls the position of the document. 2. The image reading apparatus according to claim 1, wherein information indicating a state is calculated. 6. The information indicating the state of the document includes 1 to 4 information selected from document size, document density, document background density, and finger image position information for pressing the document. Item 6. The image reading device according to Item 5. 7. The control unit according to claim 1, wherein in the pre-scan, the reference light is turned on / off, or the light is turned off or dimmed, and the reference light is turned off / illumination is turned on at predetermined time intervals. 2. The image reading apparatus according to claim 1, wherein the control unit controls the reference light projecting unit and the illuminating light irradiating unit to simultaneously detect the document height and collect information indicating the state of the document. 8. The image reading apparatus according to claim 1, wherein the reference light projected from the reference light projection unit is a spot light, and moves in a sub-scanning direction by scanning of a scanning optical system. 9. An image reading apparatus according to claim 1, wherein the reference light projected from said reference light projection means is slit light.