JP2000275511A - Focusing adjusting method and document reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To read a document at a proper read speed with proper read quality by selecting and associating an arbitrary adjusting function among multiple adjusting functions concerned in a focusing adjustment and adjusting the focusing of an optical unit. SOLUTION: As an adjustment value used to adjust the focusing of an optical unit group 6 by a focusing adjusting means 14, there is a choice between a device reference adjustment value 14a generated by reading a reference sheet 15 for focusing adjustment is used and an adjustment value 14b which is set in advance. When a document is read, there is also a choice between a read of only a set position on the document 2 and the automatic detection of an image position suitable for adjustment by reading the entire surface of the document 2. Further, when the focusing is adjusted according to the read reference sheet 15 and image data 14d of the document 2, various methods are selectable by means for optical-axis adjustment 14e, power adjustment 14f, and focusing adjustment 14g as adjusting elements and can be associated in various combinations.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technology of a document reading apparatus such as an image scanner for inputting image information of a document surface, and more particularly to a document reading apparatus having a mechanism capable of changing the resolution by using a plurality of optical units. The present invention relates to a focus adjustment method in an apparatus and a document reading apparatus using such a focus adjustment method.

[0002]

2. Description of the Related Art FIG. 22 shows a structure of a conventional general flatbed type document reading apparatus, wherein 1a is a transparent document table, 2 is a document, and 3 is an arrow direction (in the sub-scanning direction). A movable reading unit, 4 is a light source, 5 is a mirror, 6 'is a lens, and 7 is a CCD substrate (solid-state imaging device).

The surface of the original 2 placed on the original table 1a is
Irradiated by the light source 4 of the reading unit 3. The light vertically reflected from the surface of the document 2 is bent at a right angle by the mirror 5, passes through the lens 6 ', reaches the CCD substrate 7, and is converted into an electric signal. The reading resolution of the optical document is
It is determined by the focal length of the lens 6 '. The magnification increases and the resolution increases as the long focal length lens is used, but the angle of view becomes narrower, and the size of the document in the main scanning direction becomes smaller.

Many conventional document reading apparatuses use a single focus lens system using only one lens, and a lens switching system using two lenses having different focal points in part. Some copiers use a zoom lens system in which the magnification, that is, the resolution, can be continuously changed using a zoom lens.

FIGS. 23 (a), 23 (b), and 23 (c) illustrate these systems, and FIG. 23 (a) shows a single focus lens system, in which the angle of view α of the lens is fixed. In this case, the size of the main scanning range for reading a document is constant.

FIG. 23B shows an example of a lens switching method, in which an angle of view α when a lens having a focal length f: 75 mm is used.
₁ and, f: it is possible to select the angle of view alpha ₂ in the case of using a lens of 115 mm. Angle alpha ₁ in the resolution of 800dpi obtained, the resolution of 2400dpi in angle alpha ₂ is obtained.

FIG. 23C shows an example of a zoom lens system. By changing the zoom ratio, the resolution can be continuously changed from 800 dpi to 2400 dpi.

As described above, in the document reading apparatus using the conventional single focus lens system, it is impossible to optically switch the resolution. If necessary, the resolution has to be increased by interpolation processing. There was a problem in image quality compared to.

In a conventional lens-switching type document reading apparatus, a lens group is housed in one unit. However, the lens unit can be moved only in one direction such as a direction perpendicular to an optical path for switching a lens. Had become. On the other hand, as shown in FIG. 23B, lenses having different focal lengths have different positions inserted into the optical path. Since the unused lens must be retracted so as not to obstruct the angle of view of the lens being used, there is a problem that an extra space is generated in the lens unit and the size of the apparatus becomes large. Further, since the lens unit has only moving means for switching the lens, there is a problem that a high-resolution lens having a shallow depth of field and a small depth of focus is easily affected by environmental changes such as floating of a document and temperature.

Further, in the case of the zoom lens system, there is a problem that the cost of the lens becomes extremely high in order to realize high resolution with a small aberration.

Therefore, in the earlier patent application “Japanese Patent Application No. 9-163704” filed by the present applicant, a wide range of
In order to realize a more inexpensive, high-precision, and compact system, a lens unit including a plurality of lenses corresponding to a plurality of different resolutions is provided, and one lens corresponding to a designated resolution in the lens unit is selectively placed in an optical path. The invention of the document reading apparatus which is moved inside is presented.

The principle will be described with reference to FIG. In the figure, 108 is a lens unit, 109 is an image plane, 110
Is an imaging plane. The illustrated lens unit 108
, Three types of lenses of resolution 1, resolution 2 and resolution 3 are accommodated side by side at the top and bottom of the figure. The magnitude of the resolution of each lens is in the order of resolution 3> resolution 1> resolution 2.

The lens unit 108 is moved upward or downward in the drawing so that the lens corresponding to the designated resolution is inserted into the optical path, and the image on the image plane 109 is moved to the image plane 110 by the lens. It is moved right and left in the optical axis direction so that an image is formed correctly. This allows
At the time of reading at a resolution of 2, the lens unit 108 is located at the rightmost position in the moving range in the optical axis direction, and the middle lens is inserted into the optical path. At the time of reading at a resolution of 3, the lens unit 108 is moved to the leftmost position in the moving range in the optical axis direction, and the lower lens is inserted into the optical path. And when reading at resolution 1,
The lens unit 108 is at a predetermined position in the middle of the moving range in the optical axis direction, and the upper lens is inserted into the optical path. In this way, the lens is switched in accordance with the resolution, the lens is optimally positioned in the optical path for focusing, and the angle of view corresponding to the resolution is set.

Although not shown, the image plane 110
The CCD substrate placed on the CCD is also movable in the optical axis direction, and the magnification and the focal point can be adjusted with higher precision by changing the optical path length from the document surface or the lens to the CCD.

FIG. 25 shows a specific example of a reading unit in a document reading apparatus based on the principle shown in FIG. FIG.
5 (a) is a developed view thereof, and FIG. 25 (b) is a schematic sectional view.

In FIG. 25A, an optical unit 115 and an optical unit 126 are mounted on the main frame 111 of the reading unit. The lens unit 121 is mounted on the optical unit 115, and the CCD substrate 127 is mounted on the optical unit 126.

The main frame 111 has mirrors 112a, 112b, and 112c for bending the optical path, holes 113a to 113d for holding the guide shafts 116a and 116b of the optical unit 115, and when the reading unit is moved by sub-scanning. Guide sleeve 114 to guide
a, 114b.

The optical unit 115 includes the guide shaft 1
16a, 116b and holes 117a, 117b for holding the guide shaft 125 of the lens unit 121.
And a motor 118 and a belt 119 for moving the optical unit 115 back and forth within the main frame 111.
And windows 120a and 120b through which light enters and exits the lens of the lens unit 121.

The lens unit 121 includes three lenses 1
22 a, 122 b, and 122 c, a motor 123 and a belt 124 for moving vertically in the optical path in the optical unit 115, and a guide shaft 125.

The optical unit 126 includes a CCD substrate 127 mounted on the back and a window 120 of the optical unit 115.
b, a light input window 128 provided to face the optical unit 115, a guide sleeve 129 and a guide rail 130 on which the guide shafts 116a and 116b of the optical unit 115 are mounted, and a motor for moving the optical unit 126 back and forth. 131 and a belt 132.

FIG. 25B shows the optical unit 115, the lens unit 121, and the optical unit 115 shown in FIG.
The state where the optical unit 126 and the CCD substrate 127 are mounted on the main frame 111 is shown in cross section.

[0022]

As described above, according to the invention of the earlier patent application "Japanese Patent Application No. 9-163704",
Although it has become possible to easily read a high-quality document in a wide range of resolutions, further improvement in reading quality is demanded. Depending on the purpose of use, the reading speed may be the most important, and the actual use environment of the document reading apparatus is various. In general, the higher the quality, the higher the resolution, the longer the scanning time and the higher the focusing accuracy, and the lower the overall speed.

An object of the present invention is to provide a document reading apparatus capable of reading a document at a reading quality and a reading speed appropriate for a use environment.

[0024]

SUMMARY OF THE INVENTION The present invention makes it possible to combine a plurality of element functions relating to the focus adjustment of a document reading apparatus so that an optimum focus adjustment means can be constituted according to the purpose. is there.

The original reading apparatus according to the present invention is configured as follows. (1) A focus adjustment method in a document reading apparatus having a plurality of optical units sharing the same optical path, and performing a focus adjustment by interlocking the plurality of optical units or independently driving the plurality of optical units. , An adjustment function including an adjustment value acquisition unit, an optical axis adjustment unit, a magnification adjustment unit, and a focus adjustment unit related to the focus adjustment, and at least one of the adjustment functions is selected from a plurality of types using different methods. Select and coordinate any adjustment functions from those that are enabled,
The focus adjustment of the optical unit is performed. (2) In the above item (1), the reference sheet is read, the optical axis is adjusted based on the image data, focus detection and magnification error detection are performed, and the optical unit is corrected based on the detected magnification error correction information. A focus adjustment value based on the apparatus is obtained. (3) In the preceding paragraph (1) or (2), the optical unit is adjusted in focus by the focusing adjustment value based on the apparatus or the focusing adjustment value used in the previous reading, and then the original is read by the optical unit. Execute, detect a document position suitable for focus adjustment based on the read image data, read the document again at the detected document position, perform optical axis adjustment based on the obtained image data, and perform focus detection. And a magnification error are detected, an in-document focus adjustment value for the optical unit is obtained based on the detected magnification error correction information, and the focus adjustment is performed again. (4) In the above item (1) or (2), the optical unit is adjusted in focus by the focus adjustment value based on the apparatus or the focus adjustment value used in the previous reading, and then, the The original is read at the focus adjustment position, the optical axis is adjusted based on the image data of the read original, focus detection and magnification error detection are performed, and the original to the optical unit is corrected based on the detected magnification error correction information. An inner focus adjustment value is obtained, and focus adjustment is performed again. (5) In the preceding paragraph (1) or (2), the optical unit is adjusted in focus by the focusing adjustment value based on the apparatus or the focusing adjustment value used in the previous reading, and then the original is read and the reading is performed. A document position suitable for focus adjustment is detected based on the image data of the original document, an image is further read at the detected position, and an optical axis adjustment and focus detection are performed based on the image data read at the position. It is characterized by focusing adjustment. (6) In the above item (1) or (2), the optical unit is adjusted in focus by the focusing adjustment value based on the apparatus or the focusing adjustment value used in the previous reading, and then the original document held in advance is adjusted. A document is read at a focus adjustment position, an optical axis adjustment and focus detection are performed based on image data of the read document, and focus adjustment of the optical unit is performed. (7) In a document reading apparatus having a plurality of optical units sharing the same optical path, and performing the focus adjustment by interlocking the plurality of optical units or independently driving the plurality of optical units,
Adjustment value acquisition means relating to the focus adjustment, optical axis adjustment means,
A plurality of adjusting means including a magnification adjusting means and a focus adjusting means, and at least one of the plurality of adjusting means is provided with a plurality of types using different methods, and an arbitrary adjusting means is selected and cooperated, and an optical unit is provided. The focus adjustment is made possible. (8) In the above item (1), means for reading the reference sheet, means for holding image data of the read reference sheet, means for adjusting the optical axis based on the held image data, and the held image data A means for detecting a focus by means of, a means for detecting a magnification error based on the held image data, and a means for calculating a focus adjustment value based on the apparatus based on correction information of the detected magnification error. It is characterized by having. (9) In the above item (7) or (8), means for adjusting the focus of the optical unit based on the apparatus-based focus adjustment value or the focus adjustment value used in the previous reading, and means for executing the document reading Means for holding image data of the read document, means for adjusting the optical axis with the held image data, means for detecting a document position at which focus adjustment can be performed by the held image data, A means for detecting a magnification error based on the image data of the detected document position and a means for calculating an in-document focus adjustment value based on the detected magnification error are provided. (10) In the above item (7) or (8), means for adjusting the focus of the optical unit based on the device-based focus adjustment value or the focus adjustment value used in the previous reading, and the focus adjustment on the document Means for designating a value acquisition position in advance, means for reading a document at the designated focus adjustment position, means for holding image data of the read document, and optical axis adjustment based on the held image data Means, means for performing focus detection based on the held image data, means for detecting a magnification error based on the held image data, and in-document focus adjustment based on correction information of the detected magnification error Means for determining a value. (11) In the above item (7) or (8), means for adjusting the focus of the optical unit based on the apparatus-based focus adjustment value or the focus adjustment value used in the previous reading, and means for executing the document reading Means for holding image data of a read original, means for detecting a position suitable for focus adjustment based on the held image data, and means for reading an image at a position suitable for the detected focus adjustment And means for adjusting the optical axis based on the read image data, and means for performing focus detection based on the read image data. (12) In the above item (7) or (8), means for adjusting the focus of the optical unit based on the device-based focus adjustment value or the focus adjustment value used in the previous reading, and setting the document focus adjustment position in advance Holding means, means for performing document reading at the document focus adjustment position, means for holding image data of the read document, means for performing optical axis adjustment based on the held image data, Means for performing focus detection based on the held image data.

Referring to FIG. 1, the basic configuration of the present invention will be described.

In FIG. 1, reference numeral 1 denotes a document reading apparatus constructed according to the present invention.

Reference numeral 1a denotes a document table made of transparent glass or the like.

Reference numeral 2 denotes a document to be read.

Reference numeral 3 denotes a reading unit, which is moved in the direction of a white arrow in the illustrated example to sub-scan the document 2.

A light source 4 illuminates the lower surface of the document 2.

Reference numeral 5 denotes a mirror for bending the optical path of the light reflected from the original 2.

Reference numeral 6 denotes an optical unit group, which comprises a plurality of optical units having different resolutions.

Reference numeral 6a denotes an optical unit for low resolution.

Reference numeral 6b denotes an optical unit for medium resolution.

Reference numeral 6c denotes an optical unit for high resolution.

Reference numeral 7 denotes a CCD substrate of the image pickup device.

Reference numeral 8 denotes a resolution switching motor, which drives the optical unit group 6 in a direction orthogonal to the optical path indicated by the arrow to move an optical unit having any one resolution into the optical path.

Reference numeral 9 denotes a motor for adjusting the focus, which drives the optical unit group 6 in the optical axis direction indicated by the arrow.

Numeral 10 denotes a motor for adjusting the focus, which
The D substrate 7 is driven in the optical axis direction indicated by the arrow.

Reference numeral 11 denotes a document reading control unit which controls the reading unit 3 and performs reading of a document.

Reference numeral 12 denotes a resolution switching control means for stopping the sub-scanning, driving the motor 8, and inserting the optical unit in the optical unit group 6 corresponding to the designated resolution into the optical path. I do.

Numeral 13 denotes a resolution instructing means for instructing the resolution switching control means 12 to switch the resolution when the sub-scan has reached the sub-scanning position where the resolution should be switched.

Reference numeral 13a denotes a resolution table which holds the sub-scanning position at which the resolution should be switched and the resolution in the image reading area on the document table 1a in association with each other.

Reference numeral 14 denotes a focus adjusting means, which controls the motors 9 and 10 under predetermined conditions to adjust the focus of the optical unit newly inserted into the optical path by the resolution switching by the resolution switching control means 12. Do.

Reference numeral 15 denotes a focus adjustment reference sheet, which is provided, for example, at a position on the document table 1a corresponding to the home position of the reading unit 3, and has a lower surface on which automatic focusing by an auto focus mechanism is facilitated. Pattern is printed.

The focus adjustment method by the focus adjustment means 14 is as follows.
Basically, in the first stage, the pre-scan original is read by adjusting the focus of the optical unit group 6 with a low accuracy for the time being,
Based on the image data obtained here, focusing adjustment with high accuracy is performed as a second stage, and an acquisition unit for an adjustment value used for focusing adjustment of the optical unit group 6 in the first stage The device reference adjustment value 14a created by reading the focus adjustment reference sheet 15 may be used, or a preset adjustment value 14b such as an adjustment value used in the previous document reading or a preset default adjustment value may be used. In the case where the second-stage original reading is performed by using the optical unit group 6 whose focus has been adjusted with these adjustment values, there is an option such as whether to read only a preset position on the original or the entire original. There are options such as whether or not to automatically detect an image position suitable for adjustment by reading an image.
There is a difference between the time and accuracy required to create c. In the case where the focus adjustment is performed based on the read reference sheet or the image data 14d of the original, various methods are used for each of the optical axis adjustment 14e, magnification adjustment 14f, and focus adjustment 14g, which are adjustment elements. Items are prepared so as to be selectable, and can be linked in various combinations.

Further, the speed can be increased by using a part of the adjustment elements or the shortcut of the entire second stage. The performance can be flexibly changed and responded.

FIG. 2 shows the focus adjustment reference sheet 15 shown in FIG.
It is a flow in the case of performing the focus adjustment with respect to the device reference as described above. The operation will be described with reference to FIG. 1. First, the moving unit to the predetermined position moves the reading unit 3 to the reading position of the focus adjustment reference sheet 15. The optical axis adjusting unit 14e reads the reference sheet 15 on which a predetermined pattern is printed, holds the image data in the read image data holding unit, and sets the optical unit 6 based on the image data pattern.
The shifts of the optical axes a to 6c are detected and adjusted so as to eliminate the shifts.

Subsequently, the magnification adjusting means 14f reads and holds the reference sheet, detects the focal positions of the optical units 6a to 6c based on the pattern of the image data, further detects a magnification error, and based on the error, detects the magnification error. Is driven to correct the magnification. Subsequently, the focusing adjustment means 14g
The reference sheet is read and held, the focus position is detected based on the pattern of the image data, and the position is held in the in-focus position holding unit as an apparatus reference adjustment value.

FIG. 3 is a flowchart of the focus adjustment for the read original.

The reference or previous adjustment value holding means 20 holds the device reference adjustment value obtained in the flow of FIG. 2 or the adjustment value used in the previous document reading.
It is set in the reference or previous adjustment value setting means 21 at the start of the operation. Here, path a is selected when the focus detection position on the document is automatically detected, and path b is selected when the focus detection position is indicated.

To automatically detect the focus detection position, the focus position calculation means 22 is activated. Read start instructing means 23
When the start of document reading is instructed, the read image data of the document is held in the read image data holding unit 24, and the focus detection position calculating unit 25 performs appropriate focusing according to a predetermined algorithm. The detection position is calculated.

When the in-focus detection position is calculated, the moving means 26 for moving to the in-focus detection position moves the reading unit to the in-focus detection position on the document, and activates the magnification calculating means 27 through the path a.

The focus position detecting means 28 reads a document at the focus detection position, holds the read image data in the read image data holding means 29, and detects the focus position of the optical unit. Subsequently, the magnification error detecting means 30 detects a magnification error of the image data read by the read image data holding means 31 in consideration of the previously calculated focal position, and the magnification correcting means 32 detects the detected magnification error. The magnification of the optical unit is corrected based on.

Next, the focus calculation means 33 is started. The focus position detecting means 34 detects the focus position of the optical unit based on the image data subjected to magnification correction held in the read image data holding means 31, and sets the focus position holding means as a focus adjustment value in the document. 36.

[0057]

Next, embodiments of the present invention will be described.
FIG. 4 is a system diagram of an embodiment of the present invention, and shows correspondence between each functional element means related to focusing adjustment and an embodiment number used in the following description. Next, a list of contents of each embodiment is shown. (1) Reference sheet (layout configuration) (1-1) Center mark + magnification line + black and white line pattern (1-2) Center mark + line pattern at fixed intervals (1mm interval) (1-3) Arbitrary reference Line pattern + line pattern at fixed intervals (1 mm interval) (2) Read image data holding means for holding an image acquired while moving one or all of the optical units simultaneously in the optical axis direction or in the direction perpendicular to the optical axis (2-1) Means for simply holding read data (2-2) Means for holding read data multiple times and holding averaged data (2-3) Means for holding difference data of the same read data ; (2-1), (2-2) (2-4) Means for holding difference data from previous read data; (2-1), (2-2) (2-5) Previous difference Means for holding difference data from data Related: (2-1), (2-2), (2-3) (2-6) Means for holding second derivative data of the same read data Related; (2-1), (2-2) (2-7) Means for retaining difference data from the previous second derivative data Related; (2-1), (2-2), (2-6) (2-8) Means to hold the amount of tilt from two consecutive pole position information and levels from the second derivative data of the same read data; (2-1), (2-2), (2-6) (2-9) Means for storing difference data from the previous tilt amount Related; (2-1), (2-2), (2-6), (2-8) (3) Stored image Optical axis adjusting means for adjusting the optical axis from the data (3-1) To calculate the center pixel position of the line image pattern, detect the left and right positions similar to arbitrary values with respect to the line image pattern output level, The intermediate position is determined as the center pixel position.

(3-2) In order to calculate the center pixel position of the line image pattern, the center pixel position for obtaining the extreme value position with respect to the difference data of the line image pattern is set.

(3-3) In order to calculate the center pixel position of the line image pattern, the center pixel position is determined to find the center position of two adjacent extreme values with respect to the second derivative data of the line image pattern.

(3-4) After detecting the center mark, calculating the center pixel position and detecting the difference between the center pixel position of the CCD line and adjusting the optical axis (reference sheet; 1-1,1) -2) (3-5) Means for pre-holding the basic pattern of the center mark, comparing it with the pattern of the read and held image, detecting the degree of coincidence, and adjusting the optical axis (reference sheet; 1-1,1- 2) (3-6) Detect the magnification lines arranged at both ends, calculate the optical axis position from the center pixel position of each magnification line, detect the difference from the center pixel position of the CCD line, and (Reference sheet; 1-1) (3-7) The pattern information of the magnification lines arranged at both ends is held in advance, and it is compared with the pattern of the magnification line of the read and held image, and the matching degree is detected. And means for adjusting the optical axis (reference sheet; 1-1) (3-8) The line pattern arranged at the same position on the left and right from the center mark Means for calculating the optical axis position from the central pixel position on each line, detecting the difference from the central pixel position on the CCD line, and adjusting the optical axis (reference sheet; 1-1,1-2,1- 3) (3-9) Detect patterns on lines arranged at equal positions to the left and right from the center mark, hold the pattern information in advance, collate it with the pattern of the magnification line of the read and held image, and detect the degree of matching. Means for adjusting the optical axis (reference sheet; 1-1,1-2,1-3) (4) magnification adjusting means for adjusting the magnification from the stored image data (4-1) a certain allowable value from the line image (4-2) Means for calculating the center position or one of the left and right positions of each line width with respect to (4-2) Means for detecting each extreme value position from the difference image of the magnification lines at both ends from the line image (4-3) Line From the second derivative image of the magnification lines at both ends of the image, the positions of the two extreme values with respect to one magnification line are detected, and the center position is detected. Or means for calculating one of the left and right positions (4-4) Means for adjusting the magnification from a known magnification line image as a line image; (1-1) (4-5) Equal distance from the center mark as a line image (1-2) (4-6) Means to adjust magnification from line images located at equal intervals from any reference line pattern as line images; (1-2) 1-3) (5) Focus detection means for detecting focus from stored image data (5-1) Means for judging a value larger or smaller than a certain allowable value from read data Related; (2-1), ( 2-2) (5-2) Means for calculating difference data from the read data and detecting the maximum value of the difference data; (2-1), (2-2) (5-3) Floor of read data (2-1), (2-2) (5-4) Means for detecting the maximum sum of difference data from read data Related (2-3) (5-5) From the read data, (2-1), (2-2) (5-6) Means for detecting the minimum value of the existence range of the intermediate level of the gradation from the read data Related; (2- 1), (2-2) (5-7) Means for detecting the maximum value of the difference data from the previous read data to the minimum value; (2-4) (5-8) Difference from the previous read data (2-4) (5-9) Means to detect minimum value of maximum difference data from previous difference data; (2-5) (5- 10) Means for detecting the minimum value of the sum of the difference data from the previous difference data; (2-5) (5-11) Calculating the second derivative data from the read data and detecting the maximum value of the difference data (2-6) (5-12) Means for detecting the maximum value of the sum of the second derivative data from the read data Related; (2-6) (5-13) Maximum value of the inclination amount from the read data (2-8) (5-14) Total tilt amount from read data (2-8) (5-15) Means to detect the minimum value of the maximum value of the difference data from the previous second derivative data; (2-7) (5-16) ) Means for detecting the minimum value of the sum of the difference data with the previous second derivative data; (2-7) (5-17) Means of detecting the minimum value of the maximum value of the difference data with the previous slope amount Related; (2-9) (5-18) Means for detecting the minimum value of the sum of the difference data with the previous inclination amount Related; (2-9) (6) Certain relationship between focus detection and magnification detection Focus detection / magnification detection cooperative control means that controls simultaneously under the conditions (6-1) After detecting the magnification, means to adjust the focus by the relational expression of magnification / focus; related (5) (6-2) Magnification・ Means for adjusting the magnification at the same time as focusing from the relational expression of focusing; (4) or (5) (6-3) Adjust the magnification by referring to the adjustment value from the magnification adjustment table held in advance (4) (6-4) Retained in advance (5) (6-5) Refer to the adjustment values from the magnification / focus adjustment table stored in advance and refer to the adjustment values from the adjusted focus adjustment table. (5) (7) Document focus position detection means for detecting document position for focusing from stored image data (7-1) Scan original image Means for holding read data by means of one or more lines means (2) (7-2) Calculate the maximum and minimum values in one or more lines from the held read data, Means for detecting the line position where the difference between the maximum value and the minimum value is the maximum in the whole (7-3) From the held difference data, the largest extremum in one or more lines and its position are held Means and maximum from the extreme values and extreme positions held respectively over the whole area (7-4) means for detecting and holding three or more upper values and their positions in the descending order of one or more lines from the held difference data; Means for rearranging the data based on the position information, means for excluding the leftmost and rightmost positions, means for retaining the remaining extrema and position information, and poles held over the entire area. (7-5) When the evaluation values of one or more lines are held by means (7-4) and (7-3),・ Detects the ratio in the sub-scanning direction, and if the value is out of the predetermined range, reduces the retained data by means of exclusion. (7-6) Means (7-3) Use (7-7) Use the absolute value of the second derivative data for the difference data by means (7-4) (7-8) Use the amount of inclination for differential data by means (7-3) (7-9) Use the amount of inclination for differential data by means (7-4) (8) Once read Executes, detects the maximum / minimum value of the output level, and adjusts the read gradation at the time of reading again. (8-1) Means to adjust the gain at the time of reading (8-2) CCD at the time of reading Means for adjusting drive frequency (8-3) Means for averaging by multiplying by the coefficient obtained from the maximum / minimum value of output level during averaging means (8-4) Calculated from maximum / minimum value of output level when calculating difference data (8-5) Means for adjusting by adding a predetermined coefficient to the white and black levels stored during shading (9) Adjusting color misregistration in focus position detection by a color reading device Color misregistration adjustment means (9-1) Means (3) or 3 from the read data of three or four signals
From the evaluation value of each color obtained in (4) or (5), a specific 1
Means for selecting color value (9-2) Means (3) or from three or four signals read data
(9-3) Means to adopt the average of the evaluation values of each color obtained in (4) or (5) (9-3) Means from the read data of three or four signals
(4) Means for weighting the evaluation value obtained in (5) for each color to convert the evaluation value (10) Color signal selection means for magnification adjustment and focus adjustment in the color reader (10-1 ) Means for selecting the largest specific one color value from the read data of 3 or 4 signals (10-2) Means for selecting the largest output level from the read data of 3 or 4 signals (10-3) 3 or 4 Means for selecting the largest output level from the differential data of the signals (10-4) Means for selecting the largest output level from the secondary differential data of the three or four signals (10-5) There is from the read data of the three or four signals 1 in conversion formula
(10-6) Means for calculating differential data from one converted level (10-7) Means for calculating second derivative data from one converted level This will be specifically described. (1) Reference Sheet FIG. 5 shows a layout configuration example of Examples (1-1) to (1-3) of the reference sheet. These reference sheets are shown in FIG.
The optical unit is provided at the head of the document table as in the document reading apparatus shown in FIG. 1 and is capable of focusing with substantially the same focus adjustment value as that of the document.

The reference sheet (1-1) includes a center mark, a lens 1, a lens 2, and a lens 3 having different resolutions.
3 pairs of magnification lines and a black and white line pattern are provided. The center mark is used for detecting the deviation of the optical axis, and the three pairs of magnification lines are used for detecting the magnification error of each lens. The black and white line pattern is used for focus detection.

The reference sheet (1-2) has a center mark and a line pattern at regular intervals. Line patterns at regular intervals are used for magnification error detection and focus detection, and have the advantage that there is no restriction on the magnification of the detection target as compared with the reference sheet (1-1).

The reference sheet (1-3) has a reference pattern that can be used for optical axis shift detection and magnification error detection, and a line pattern that can be used for magnification error detection and focus detection. (2) Read image data holding means The image data held for use in focusing adjustment is not limited to the read data itself as shown in FIG.
The difference (first derivative) data shown in (b), the second derivative data shown in FIG. 8 (c), or the amount of inclination can also be used. Further, reading is performed a plurality of times, and those data can be used.

FIG. 7 is a flow chart of an embodiment for holding these various data singly or in combination. Each time read data extracted from the device output data and a plurality of read data are held, and only each read data (2-
1), data obtained by averaging a plurality of read data (2-
2) Data obtained by taking the time difference between the same read data (2-
3), difference data (2-4) between previous read data and current read data, difference data (2-5) between previous difference data and current difference data, second derivative data of the same read data (2-5) 2-6), difference data (2-7) between the previous secondary differential data and the present secondary differential data, and the second differential data of the same read data as shown in FIG. The inclination amount (2-8) obtained from the position information and the level of the two extreme points, and the difference data (2-9) between the previous inclination amount and the current inclination amount are held singly or in combination and used. be able to. (3) Optical axis adjusting means FIG. 9 shows an embodiment method of the optical axis adjusting means.

In the case of using the read data (a), the symmetrical waveform portion of the output level of the line image pattern is sliced at a predetermined level to determine pixel positions X1 and X2, and then (X1
+ X2) / 2 may be calculated to determine the center pixel position (3-1). When the difference data shown in (b) is used, the center pixel position is obtained from the pixel positions X1 and X2 of two adjacent extreme values (3-2). When the second derivative data shown in (c) is used, two zero cross positions X
The center pixel position is determined from 1 and X2 (3-3).

The shift amount of the optical axis is obtained from the difference between the center pixel position of the line image pattern of the read data and the center pixel position of the CCD as shown in (d) (3-3), (3-5),
(3-7) or (3-4), (3-6), (3-8) obtained by performing pattern comparison between read data and reference data prepared in advance as shown in (f). .
(E) shows a formula for calculating the error δ. (4) Magnification Adjusting Means FIG. 10 shows an embodiment method of the magnification adjusting means. (A),
From (b) and (c), the line width and the magnification line interval are obtained,
Adjust to match the reference value. (5) Focus detection means In general, when an image is read out of focus, the level is reduced due to blurring of the image. Therefore, the presence or absence of focus is determined from the maximum value and minimum value of read data and difference data. It is determined or detected by an evaluation function as shown in FIG. (6) Cooperative control of focus detection and magnification detection There is a constant relationship between focus and magnification, and by using an expression table that gives a mutual relationship, it is possible to obtain one value from one detection value. It is possible. FIG. 12 shows a magnification adjustment table for providing a magnification adjustment value based on a focus detection value, and conversely, a focus adjustment table for providing a focus adjustment value from a magnification detection value, and further, from a focus detection value and a magnification detection value. An embodiment using a focus / magnification adjustment value table for giving respective adjustment values is shown. Next, a relational expression is shown.

[0067] the focal length f of the lens, the lens reduction ratio beta, the distance L _b between the CCD and the distance L _a and the lens of the lens and the document to the magnification M, due to geometrical optics formulas, so the number 1.

[0068]

(Equation 1)

In the case of the embodiment (6-1), after the magnification is detected, the detection is performed.
An error ΔM between the output magnification M ′ and the magnification M to be set (=
M′−M) is calculated, and the distance between the lens and the document is calculated according to Equation 2.
Release L _aL between lens and CDD_bCan be adjusted
Wear.

[0070]

(Equation 2)

In the case of the embodiment (6-2), by performing the focus adjustment while maintaining the following relationship, the magnification can be adjusted together with the focus adjustment.

[0072]

(Equation 3)

(7) Document Focusing Position Detecting Unit FIG. 13 shows an embodiment of document focusing position detecting unit. Holds data of one or more lines of the read image, evaluates the maximum / minimum value difference and differential data of image data, secondary differential data, and the maximum value of the amount of inclination for each line, and performs main / sub scanning for changes. The direction is determined, and the position at which the evaluation value is maximum is detected and held.

The edge detection processing of the embodiment (7-5) follows the following equation (4). The edge strength is obtained by Expression 5, and the edge angle is obtained by θ.

[0075]

(Equation 4)

[0076]

(Equation 5)

(8) Reading gradation correction means As shown in the flow of FIG. 14, first, line data is acquired, the maximum value D _max is detected, and the maximum output level _Do of the apparatus is obtained.
And the difference or ratio, the amplification gain, CC
D drive frequency, filter averaging coefficient, difference calculation coefficient,
The gradation is adjusted to an appropriate range by correcting the shading offset value and the like. (9) Color misregistration adjusting means Since the focus position of the optical unit differs depending on the wavelength (color) of light as shown in the graph of FIG. 14, the color reading device corrects the color misregistration and detects an appropriate focus position. Need to be done. As a correction method, FIG.
For example, as shown in the example flow of Red, Gre,
There are a method of selecting an evaluation value of a specific color from three colors of en and Blue to perform focus adjustment using a single color, a method of averaging the evaluation values for each color, and a method of performing a weighting operation. (10) Color Signal Selection Means Similarly, in the color reading apparatus, it is necessary to consider the color signal of the color read data in the magnification adjustment and the focus adjustment, and as shown in the flow of the embodiment of FIG.
It is desirable to perform processing such as giving a color signal selection instruction, selecting the maximum value in each color signal, or applying an appropriate conversion formula.

FIG. 17 is a flowchart showing one embodiment of the all-focus adjustment on the document surface.

The following control conditions were used: ○ Control condition PreSsan condition: Based on the reading conditions expected this time, ・ Main scanning resolution: Optical resolution by the selected lens (g00 /
(1,200 / 2,400dpi)-Sub-scanning resolution: Prescan is executed by changing only 200dpi.

Dmln, Dmax Conditions: In the line by ASIC
Perform Dmin, Dmax hold (14 bit Daia).

Calculation of CTF for each line: CT calculation according to Equation 6 is performed.

[0082]

(Equation 6)

However, Dmax and Dmin represent the maximum luminance and the minimum luminance in the line. n indicates the quantization number (16 in this control). [] Is a Gaussian function.

CTF maximum position calculation condition: (a) Dmax and Dmin
(B) The position where the CTF takes the maximum value. (C) If the CTF value is continuous over a plurality of lines, the center position is taken as the detection position.

(D) A position closest to the center of the reading position is detected.

A position satisfying the above conditions is detected.

Carrier movement to the detection position: The carrier is moved from the detection end position by reverse movement.

FIG. 18 is a flowchart showing another embodiment of the focus adjustment on the document surface.

The automatic adjustment of the position of the optical unit is performed by the automatic focus control (auto focus). An appropriate focus condition is calculated from a change in the focus unit condition and a change in the line image using the following basic method at an appropriate line position on the document surface detected by the method of the embodiment in FIG. .

If one line data of the area to be read is directly sampled and controlled only by the power of the firmware, the following problem is expected.

Colonel of processing data amount → Control time is enormous For example, on a screen of 4 inch width, a maximum of 56 kBytes (= 4 inch × 24
00dpi × 2Byts). Accuracy is affected by the image existing over the entire line → decrease in accuracy There is an edge component having various sharpnesses in one line (particularly, as shown in FIG. When an edge component exists), the convergence of the evaluation function deteriorates.

Thus, an evaluation function for measuring the sharpness of the edge component is defined by adding preprocessing for the extraction of the edge component at the stage of image extraction. First, a notable area is narrowed out of one line data (sub-window method) to reduce the processing time. Next, as the sharpness of the edge component, the sharpness can be known by the rising edge state (the sharper the rising edge, the sharper the image is and the better the focus). Therefore, to detect the rising width of the edge, the first derivative of the image Is determined by the magnitude of the extreme value of

FIG. 20 shows a flow of an embodiment of the pre-processing for extracting the edge component.

The preprocessing conditions are as follows.

Conditions in Preprocessing (a) The conditions of the extraction position and the width in the preprocessing of edge component extraction are performed only at the beginning of the adjustment start.

Reason: To prevent waste of processing time. (B) The edge component extraction condition does not change with the change of the unit condition.

Reason: If a local window changes with a change in magnification, preprocessing is required again, and processing time is wasted.

Target: Operate the Focus Unit and CCD at the same time. (C) The extraction condition is to be performed by an AND process.

Reason: It is often assumed that the user's point of interest is at the center of the document. (D) When the maximum values of the evaluation functions are the same, the condition at the center position in that range is set as the focus condition.

FIG. 21 is a flow chart showing one embodiment of a method of detecting the focal point on the document surface. The control conditions used here are as follows.・ Control condition PreScan condition: reading condition expected this time, 4 inch × 10
Based on 0 dpi, resolution adjustment (up to the maximum required reading resolution) is performed for images smaller than 0 dpi. Main scanning resolution: variable from the minimum resolution to the resolution requested to be read. -Sub-scanning resolution: Variable from the minimum resolution of 100 dpi to the resolution requested to be read. Only change and run Brescan.

Read data condition: RG for color reading
B Each 8-bit data is obtained, and a luminance component is calculated by Expression 7.

[0102]

(Equation 7)

In the case of gray reading, 8-bit data is obtained and processed.

Edge detection processing: According to the following equation 9. The edge strength is obtained by Expression 8, and the edge angle is obtained by θ.

[0105]

(Equation 8)

[0106]

(Equation 9)

Edge detection conditions: (a) The element with the previously detected edge component is 10 pixels or more. → To avoid detection of nearby edges. (B) Regarding the edge angle, only the edge in the range of 30 ° to 90 ° is targeted. (C) In order to distinguish between noise and edges, the intensity is set to 102 or more. → A noise component is set to 10%, and a position that satisfies the above conditions calculated from the error propagation law is detected.

Carrier movement to the detection position: The carrier is moved from the detection end position by reverse and forward movement.

[0109]

According to the present invention, the focus adjustment in a document reading apparatus having a plurality of optical units can be efficiently executed at a balance between various speeds and accuracy according to the purpose of use, and the usability can be improved. It can be significantly improved.

[Brief description of the drawings]

FIG. 1 is a basic configuration diagram of a document reading apparatus according to the present invention.

FIG. 2 is a flowchart of focus adjustment with respect to a device reference.

FIG. 3 is a flowchart of focus adjustment for a read document.

FIG. 4 is a system diagram of an embodiment of the present invention.

FIG. 5 is an explanatory diagram of a layout configuration example of a reference sheet.

FIG. 6 is a schematic configuration diagram of an embodiment of a document reading apparatus.

FIG. 7 is a flowchart of an embodiment of holding read image data.

FIG. 8 is an explanatory diagram of held read image data.

FIG. 9 is an explanatory diagram of an optical axis adjustment embodiment.

FIG. 10 is an explanatory diagram of a magnification adjusting embodiment.

FIG. 11 is an explanatory diagram of an evaluation function used for focus detection.

FIG. 12 is an explanatory diagram of an embodiment of cooperation control of focus detection and magnification detection.

FIG. 13 is a flowchart illustrating an example of document focus position detection means.

FIG. 14 is a flowchart of an embodiment of a read gradation correction unit.

FIG. 15 is a flowchart of an embodiment of a color shift adjusting unit.

FIG. 16 is a flowchart of an embodiment of a color signal selection unit.

FIG. 17 is a flowchart of an embodiment of focus adjustment on a document surface.

FIG. 18 is a flowchart of an embodiment of an automatic focus control method.

FIG. 19 is an explanatory diagram of an image change of an edge component and an evaluation function.

FIG. 20 is a flowchart of an embodiment of preprocessing for edge component extraction.

FIG. 21 is a flowchart of an embodiment of a method of detecting a focus position on a document surface.

FIG. 22 is an explanatory view of a conventional flatbed type document reading apparatus.

FIG. 23 is an explanatory diagram of a conventional resolution switching method.

FIG. 24 is a diagram illustrating the principle of a resolution switching method using a lens unit.

FIG. 25 is an explanatory diagram of one specific example of a reading unit.

[Explanation of symbols]

 1: Document reading device 1a: Document platen 2: Document to be read 3: Reading unit 4: Light source 5: Mirror 6: Optical unit group 6a: Optical unit for low resolution 6b: Optical unit for medium resolution 6c: High resolution Optical unit 7: CCD substrate of image sensor 8: Motor for resolution switching 9: Motor for focus adjustment 10: Motor for focus adjustment 11: Original reading control unit 12: Resolution switching control means 13: Resolution instruction Means 13a: Resolution table 14: Focus adjustment means 15: Focus adjustment reference

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] March 30, 1999 (1999.3.3)
0)

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] All figures

[Correction method] Change

[Correction contents]

FIG.

FIG.

FIG. 5

FIG. 6

FIG. 8

FIG. 2

FIG. 3

FIG. 4

FIG. 7

FIG. 9

FIG. 10

FIG.

FIG. 11

FIG. 13

FIG.

FIG. 14

FIG.

FIG.

FIG.

FIG. 16

FIG.

FIG. 21

FIG. 23

FIG. 24

FIG. 25

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shinobu Yamamoto Unoki-nu, 98, Unoki-cho, Kawakita-gun, Ishikawa Prefecture Within PFU Co., Ltd. (72) Inventor Minoru Masuda Unoki 98, Unoki-cho, Kawakita-gun, Ishikawa No. 2 F-fu Co., Ltd. F-term (reference) 2H051 AA00 BA47 CD01 CD13 CE14 DA11 DD20 EB13 EB20 FA48 GB12

Claims (12)

[Claims] 1. A focus adjustment method for a document reading apparatus, comprising: a plurality of optical units sharing the same optical path, wherein the plurality of optical units are linked to each other or independently driven to perform focus adjustment. Adjustment value acquisition means relating to the focus adjustment, optical axis adjustment means,
An adjustment function including magnification adjustment means and focus adjustment means,
For at least one of them, a plurality of types using different methods can be selected, and an arbitrary adjustment function is selected and linked to perform focus adjustment of the optical unit. Focus adjustment method. 2. The optical unit according to claim 1, wherein the reference sheet is read, the optical axis is adjusted based on the image data, focus detection and magnification error detection are performed, and the optical unit is corrected based on the detected magnification error correction information. A focus adjustment value based on a device with respect to the focus adjustment value. 3. The optical unit according to claim 1, wherein the optical unit is adjusted in focus by a focusing adjustment value based on the apparatus or a focusing adjustment value used in the previous reading, and then the original is read by the optical unit. To detect a document position suitable for focus adjustment based on the read image data, read the document again at the detected document position, perform optical axis adjustment based on the obtained image data, and perform focusing. A focus adjustment method comprising: performing detection and magnification error detection; obtaining an in-document focus adjustment value for the optical unit based on the detected magnification error correction information; and performing focus adjustment again. 4. The optical unit according to claim 1, wherein the focus adjustment of the optical unit is performed by a focus adjustment value based on the apparatus or a focus adjustment value used in the previous reading, and then a predetermined document is read. The original is read at the focus adjustment position, the optical axis is adjusted based on the image data of the read original, the focus is detected, and the magnification error is detected. A focus adjustment method comprising: obtaining a focus adjustment value in a document; and performing focus adjustment again. 5. The optical unit according to claim 1, wherein the optical unit is adjusted in focus by a focusing adjustment value based on the apparatus or a focusing adjustment value used in a previous reading, and then the original is read. The optical unit detects a document position suitable for focus adjustment based on the read image data of the document, further performs image reading at the detected position, performs optical axis adjustment and focus detection based on the image data read at the position, And a focusing adjustment method. 6. An original according to claim 1, wherein the optical unit is adjusted in focus by a focusing adjustment value based on the apparatus or a focusing adjustment value used in previous reading. Scans the original at the focus adjustment position, performs optical axis adjustment and focus detection based on the image data of the scanned original,
A focus adjustment method, comprising adjusting the focus of an optical unit. 7. A document reading apparatus comprising: a plurality of optical units sharing the same optical path, wherein said plurality of optical units are linked to each other or independently driven to adjust focus. Adjustment value acquiring means, optical axis adjusting means,
A plurality of adjusting means including a magnification adjusting means and a focus adjusting means, and at least one of the plurality of adjusting means is provided with a plurality of types using different methods, and an arbitrary adjusting means is selected and cooperated, and an optical unit is provided. A document reading device, wherein the focus adjustment of the document is enabled. 8. The apparatus according to claim 1, wherein said means for reading a reference sheet, means for holding image data of the read reference sheet, means for adjusting an optical axis based on the held image data, and said held image Means for performing focus detection based on the data, means for detecting a magnification error based on the held image data, and means for determining a device-based focus adjustment value based on the detected magnification error correction information. An original reading device, comprising: 9. The means according to claim 7 or 8, wherein the means for adjusting the focus of the optical unit based on the focus adjustment value based on the apparatus or the focus adjustment value used in the previous reading, and the means for executing document reading Means for holding image data of the read document, means for adjusting the optical axis based on the held image data, and means for detecting a document position at which focus adjustment can be performed based on the held image data. A document reading apparatus comprising: means for detecting a magnification error based on the image data of the detected document position; and means for calculating an in-document focus adjustment value based on the detected magnification error. 10. A means for adjusting the focus of an optical unit according to a focus adjustment value based on an apparatus or a focus adjustment value used in previous reading, and focusing on a document according to claim 7 or 8. Means for specifying an adjustment value acquisition position in advance, means for reading a document at the specified focus adjustment position, means for holding image data of the read document, and adjustment of the optical axis by the held image data. Means for performing focus detection based on the held image data, means for detecting a magnification error based on the held image data, and focusing in the document based on the correction information of the detected magnification error. A document reading apparatus comprising: means for obtaining an adjustment value. 11. A means according to claim 7, wherein said means for adjusting the focus of said optical unit by means of a focus adjustment value based on the apparatus or a focus adjustment value used in previous reading, and means for executing document reading. Means for holding image data of the read original, means for detecting a position suitable for focus adjustment based on the held image data, and image reading at a position suitable for the detected focus adjustment A document reading apparatus, comprising: means for adjusting an optical axis based on the read image data; and means for performing focus detection based on the read image data. 12. A means for adjusting the focus of an optical unit according to a focus adjustment value based on a device or a focus adjustment value used in a previous reading operation according to claim 7 or 8, further comprising: Means for holding a document, means for performing document reading at the document focus adjustment position, means for holding image data of the read document, means for performing optical axis adjustment using the held image data, Means for performing focus detection based on the held image data.