JP2008311953A - Image reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance image reading quality by eliminating a deviation of a focal position even if the deviation of the focal position of an original occurs. <P>SOLUTION: The image reader includes a rod lens array 12 for converging light emitted from a transmitting light source part 2 or reflecting light source part 10 and transmitting the original 1 carried in a carrying area and a reference criterion part 8 and reflected light, and a light receiving part 13 for receiving the converged transmitting light and reflected light and converting the transmitting light and the reflected light into electrical signals, converts an electrical signals corresponding to the original 1 in the electrical signals into an image signal to output it, calculates the MTF value of an individual pixel in electrical signals corresponding to the reference criterion part 8, and outputs a correction signal corresponding to the maximum MTF value among MTF values of individual pixels. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image reading apparatus that is applied to, for example, a copying machine or a financial terminal device and performs image reading and image identification.

For example, Patent Document 1 below discloses an image reading apparatus that reads image information such as a transparent original.
In other words, an image reading apparatus that reads a transparent document using the upper moving unit 3A including the transparent plate 2A that presses the document, the transmissive light source 4A for the transparent document 0a, the reflective plate 16 for the reflective document 0b, and the like. It is disclosed.
However, the image reading apparatus disclosed in Patent Document 1 can read a transparent original, but when a deviation of the focal position of the original occurs, a technique for eliminating the deviation of the focal position will be described in detail. Not.

Further, in Patent Document 2 below, a white reference 28 for a reflective original having a highly reflective uniform reflection surface is provided at the peripheral edge of the original table 14, and irradiation of the surface light source unit 56 of the transmissive original unit 37 is performed when reading a film. An image reading apparatus is disclosed in which light is incident on the linear sensor 20 through the white reference windows 72, 91, 93 of the film holders 68, 84, 86.
In the image reading apparatus disclosed in Patent Document 2, the document table 14 is directly irradiated from the white reference window installed in the film folder of the transparent original unit 37. However, the original is a transparent original (film). It is for discriminating whether the document is a reflection document or not, and there is no description on improving the image reading quality for a transparent document.

Further, Patent Document 3 below discloses an image reading apparatus in which an image blur detection mark m is formed on a guide roller 30.
However, in the image reading apparatus disclosed in Patent Document 3, a plurality of regions 32 and 33 on both outer sides of the guide region 31 through which the document S being conveyed passes are extended in the circumferential direction over the entire circumference. An image blur detection mark m composed of parallel lines is formed, but since this mark is provided on the rotating guide roller 31, a highly accurate MTF value is derived due to the influence of blurring of the guide roller 30 and the like. It is difficult to do.

JP-A-6-37972 (FIG. 2) JP 2002-366842 A (paragraph [0038]) Japanese Patent Laying-Open No. 2005-347784 (FIG. 3)

  Since the conventional image reading apparatus is configured as described above, when the focus position shift of the document occurs, the focus position shift cannot be eliminated, and the image reading quality may deteriorate. There were some problems.

  The present invention has been made to solve the above-described problems. Even when the focal position of the document is deviated, the image can be improved by eliminating the deviation of the focal position and improving the image reading quality. An object is to obtain a reading device.

  The image reading apparatus according to the present invention includes a light transmitting body in which a reference standard portion in which patterns having alternately different light transmittances are continuously formed is provided at an outer end portion of a document transport region, and a reflective light source means And a light converging means for converging the light reflected from the original and the reference standard part, and the reflected light converged by the light converging means, and receiving the reflected light as an electrical signal. A light receiving means for converting, and the signal processing means converts the electrical signal corresponding to the original from the electrical signals converted by the light receiving means into an image signal and outputs the image signal, and each of the electrical signals corresponding to the reference standard portion The MTF value of each pixel is calculated, and a correction signal corresponding to the maximum MTF value among the MTF values of the individual pixels is output.

  According to the present invention, the reference standard portion in which patterns having alternately different light transmittances are continuously formed is irradiated from the light transmitting body provided at the outer end portion of the document conveying region and the reflective light source means. A light converging means for converging the light reflected by the original and the reference standard part conveyed in the conveying area, and a light receiving means for receiving the reflected light converged by the light converging means and converting the reflected light into an electric signal. Out of the electrical signals converted by the light receiving means, the signal processing means converts the electrical signal corresponding to the document into an image signal and outputs the image signal, and also outputs the individual pixels in the electrical signal corresponding to the reference reference portion. Since the MTF value is calculated and a correction signal corresponding to the maximum MTF value among the MTF values of the individual pixels is output, even if the focus position of the document is shifted, the shift of the focus position is generated. Eliminate the image There is an effect that can increase the reading quality.

Embodiment 1 FIG.
FIG. 1 is a cross-sectional configuration diagram showing an image reading apparatus according to Embodiment 1 of the present invention. In the figure, a document 1 is a document having a watermark and a transparent area (watermark part). And so on.
The transmissive light source unit 2 is provided so as to sandwich the document 1 outside the main body of a contact image sensor (hereinafter referred to as “CIS”). For example, the transmissive light source unit 2 has a cylindrical shape in the main scanning direction (a direction perpendicular to the paper surface). A light source 3 constituted by a rod-like fluorescent lamp or a cold cathode is provided. However, the light source 3 is not limited to a fluorescent lamp or a cold cathode, and may be a light source such as a columnar or rod-shaped light and a light source such as an LED disposed at the end of the light guide. Good.
The transmissive light source unit 2 constitutes transmissive light source means.

The light transmissive body 4 has a reference standard portion 8 in which patterns having alternately different light transmittances are continuously formed at the outer end portion of the document conveyance region, and the light radiated from the transmissive light source portion 2 is emitted. In order to enter the CIS side, it is made of a glass material or a transparent resin that transmits light.
The light source driving substrate 5 is a substrate provided for driving the light source 3 of the transmissive light source unit 2.
The connector 6 is an interface that receives power supply.
The housing 7 holds the transmissive light source unit 2 and houses the light source 3, the light transmissive body 4, and the light source driving substrate 5.

The reference standard portion 8 is disposed on the outer end portion of the light transmitting body 4 in the conveyance region of the document 1 (see FIGS. 3 and 5), and stripe patterns with alternately different light transmittances are continuously formed. Has been. However, the reference standard portion 8 may be disposed only at one outer end portion of the outer end portion of the conveyance region of the document 1 or may be disposed at both outer end portions.
The light source 3 of the transmissive light source unit 2 irradiates light to the reference standard unit 8 in addition to the conveyance region of the document 1, but the reference standard unit 8 and the reading position of the document 1 are positioned. In addition, the periphery of the light transmitting body 4 may be shielded from light such as black to prevent unnecessary light from being emitted.
The attachment member 9 is a member that fixes the transmissive light source unit 2 to the main body of a reading system (not shown) such as a financial terminal device.

The reflective light source unit 10 is provided on the CIS side, and is constituted by, for example, a columnar or bar-shaped fluorescent lamp or a cold cathode in the main scanning direction.
In the example of FIG. 1, two reflective light source units 10 are provided, and the configuration of the reflective light source unit 10 may be the same as that of the light source 3.
The reflective light source unit 10 constitutes a reflective light source means.

The glass plate 11 is installed in the upper part of the housing | casing 17, and permeate | transmits the light irradiated from the transmissive | pervious light source part 2 or the reflective light source part 10. FIG.
The rod lens array 12 is irradiated from the transmissive light source unit 2 and transmitted through the document 1 and the reference standard unit 8 conveyed through the conveyance region, or from the reflective light source unit 10 and is conveyed through the conveyance region. The light reflected by the original 1 and the reference standard 8 is converged. The rod lens array 12 constitutes a light convergence means.

The light receiving unit 13 is a sensor IC in which a photoelectric conversion unit, a drive circuit for the photoelectric conversion unit, and the like are incorporated. The light receiving unit 13 receives transmitted light and reflected light converged by the rod lens array 12, and transmits the transmitted light and reflected light. A process of converting light into an electrical signal is performed. The light receiving unit 13 constitutes light receiving means.
The sensor substrate 14 is a substrate on which a plurality of light receiving portions 13 are mounted.

The signal processing unit (ASIC) 15 is an A / D converter that converts an analog signal, which is an electrical signal converted by the light receiving unit 13, into a digital signal by A / D conversion, and an output from the A / D converter. A correction circuit that performs shading correction or all-bit correction on the signal output of each pixel (bit) in the digital signal is incorporated, and among the electric signals converted by the light receiving unit 13, an electric signal corresponding to the document 1 is imaged. The signal is converted into a signal and output, and the MTF value of each pixel in the electric signal corresponding to the reference standard unit 8 is calculated, and a correction signal corresponding to the maximum MTF value among the MTF values of each pixel is output. Perform the process.
The signal processing unit 15 supplies a start signal (SI) and a clock signal (CLK) for driving the CIS, and at the time of driving an input signal such as a power source and the transmissive light source unit 2, Power is supplied to the connector 6 and an image signal indicating the content (image information) of the document 1 read by the image reading device is output to the outside.
The signal processing unit 15 constitutes a signal processing means.

The connector 16 is an interface that outputs an image signal indicating the content (image information) of the document 1 to the outside.
The housing 17 is a CIS housing and houses the reflective light source unit 10, the rod lens array 12, and the sensor substrate 14.
The attachment member 18 is a member that fixes the CIS to the main body of a reading system (not shown) such as a financial terminal device.

In the image reading apparatus of FIG. 1, the transmissive light source unit 2, the rod lens array 12 and the light receiving unit 13 constitute a transmissive image sensor, and the reflective light source unit 10, the rod lens array 12 and the light receiving unit 13 are a reflective image sensor. Is configured.
The transmissive image sensor and the reflective image sensor share the rod lens array 12 and the light receiving unit 13, and are configured such that the document 1 is conveyed between the light transmissive body 4 and the glass plate 11.
That is, the transmissive light source unit 2 and the reflective image sensor CIS are combined to constitute an image sensor as a whole.

2 is an external perspective view showing the image reading apparatus according to the first embodiment of the present invention, and FIG. 3 is an external perspective view of the transmissive light source section 2 in the image reading apparatus according to the first embodiment of the present invention.
In the example of FIG. 3, the reference standard portions 8 are installed at both ends in the main scanning direction.

In the first embodiment, when the reflection type light source unit 10 mounted in the CIS is used to read image information (image) of the document 1, the reflection type light source unit 10 is turned on so that the document 1 is irradiated with light from an oblique direction.
As a result, the reflected light that is the scattered light reflected by the document 1 is converged by the rod lens array 12 and then received by the light receiving unit 13 and converted into an electrical signal.

On the other hand, when reading the image information of the document 1 (the watermark portion or the transmission area of the document 1) using the light source 3 of the transmissive light source unit 2 installed outside the CIS side, the light source 3 is turned on. Then, the original 1 is irradiated with light.
As a result, the transmitted light transmitted through the document 1 is converged by the rod lens array 12 and then received by the light receiving unit 13 and converted into an electrical signal.
In this case, the light emitted from the light source 3 is irradiated in a direction perpendicular to the document 1, so that direct light transmitted through the document 1 is received by the light receiving unit 13 via the rod lens array 12 and is electrically Converted to a signal.

FIG. 4 is an overall configuration diagram showing an image reading apparatus according to Embodiment 1 of the present invention.
In FIG. 4, the CIS side configuration such as the signal processing unit 15, the rod lens array 12, and the light receiving unit 13 (including the drive circuit) and the block configuration combining the transmissive light source unit 2 and the output signal of the light receiving unit 13 are amplified. The waveform of the analog signal (SO) after the operation is shown.
A clock signal (CLK) and a start signal (SI) synchronized with the clock signal (CLK) are output from the signal processing unit 15 to the light receiving unit 13, and an analog signal is output from the light receiving unit 13 at the timing.

The waveform diagram of FIG. 4 shows an analog signal after the output signal of the light receiving unit 13 is amplified. Specifically, the image information of the document 1, the reference information of the reference standard unit 8, and the document 1 and the reference are shown. The information between the reference | standard parts 8 is shown.
The analog signal (SO) is converted into a digital signal by the A / D converter of the signal processing unit 15, and the correction circuit performs shading correction including sample and hold or all bit correction.
The correction by the correction circuit is performed by reading the reference signal from the RAM that stores the reference signal data in advance and calculating and processing a digital signal corresponding to the A / D converted image information.

In this case, when the transmissive light source unit 2 is used, the light source 3 of the transmissive light source unit 2 is turned on and the reflective light source unit 10 is turned off, so that the document 1 is not present or an appropriate transparent document is obtained. The transmitted light that has been transmitted is received and photoelectrically converted by the light receiving unit 13, and an electrical signal that is photoelectric conversion data can be applied to correction data during actual operation as reference signal data of the RAM.
In actual operation, the read signal that has been A / D converted or corrected is normally sent to the reading system as a REAL output signal, and image reproduction or image identification is performed.

Further, such a series of operations is performed under the control of the CPU in the signal processing unit 15.
Since the correction data or the reference signal data is for correcting variations between the elements in the light receiving unit 13 and the rod lens array 12, by using the reflective light source unit 10 mounted on the CIS side, Correction data may be created using a correction plate or a reference white reference document in the image reading apparatus.
In FIG. 4, the corrected line data is output as an image signal (SIG), and the reference information of the photoelectric conversion output of the light receiving unit 13 corresponding to the reference standard unit 8 is calculated and processed to generate an MTF correction signal. An MTF measuring unit 20 for outputting is added.
Specific processing contents of the MTF measurement unit 20 will be described later.

Next, the reference standard part 8 is demonstrated.
The reference standard portion 8 is formed on the surface of the light transmitting body 4 so as to be positioned on both outer sides of the conveyance region of the document 1 (see FIG. 3).
When the document 1 is a reflection document (when there is no watermark portion or transmission region), the light emitted from the transmission light source unit 2 is almost reflected by the reflection document and hardly incident on the light receiving unit 13.
On the other hand, when the document 1 is a transmissive document (when there is a watermark portion or the like), the light emitted from the transmissive light source unit 2 passes through the watermark portion of the document 1 and then enters the light receiving unit 13. .
At this time, since the width in the direction perpendicular to the conveyance direction of the document 1 is usually narrower than the irradiation region of the transmissive light source unit 2, some light is directly incident on the light receiving unit 13 without passing through the document 1.

FIG. 5 is a plan view showing the light transmitting body 4 in which the reference standard portion 8 is installed at both ends.
The reference standard portion 8 is an elongated stripe pattern in the document transport direction, and has a black pattern with an optical density of 1.6 OD or more, a white pattern with an optical density of 0.09 or less, and the same shape as the black pattern. The patterns are alternately arranged on the photographic paper over a width of 4 to 8 mm at a pitch of 8 LP (8 line pairs) per 1 mm.
The reference standard portion 8 is affixed to the light transmitting body 4 so that the center of the elongated pattern corresponds to the line reading position.
Therefore, the light emitted from the light source 3 of the transmissive light source unit 2 enters the reference standard unit 8, but is reflected or absorbed by the back surface of the photographic paper and does not reach the rod lens array 12. For this reason, only the image information of the document 1 corresponding to the reading position is converged by the rod lens array 12.

FIG. 6 is a plan view showing the light receiving unit 13 mounted on the sensor substrate 14 on the CIS side.
The light receiving unit 13 is formed of a CMOS semiconductor and has a large number of cells arranged linearly, and light detected in the cell part is photoelectrically converted.
The cells are also installed so as to correspond to the line reading positions. The cells are formed at 400 dpi (arrangement pitch 0.0635 mm), and the cells in the end region face the reference reference portion 8.

FIG. 7 shows an example of the output of the analog signal (SO) when the reflected light of the reference standard unit 8 is received when the irradiation of the transmissive light source unit 2 is stopped and the reflection type light source unit 10 is irradiated. It is explanatory drawing.
When each cell and each stripe pattern of the reference standard portion 8 face each other, the output of the cell reflected from the black pattern is Vmin, and the output of the cell reflected from the white pattern is Vmax.

However, strictly speaking, it is not realistic to position the stripe pattern and the opposing cell in correspondence with high accuracy of 1: 1 because a high-accuracy position mechanism is required.
Therefore, by actively changing the pitch of the stripe pattern and the pitch of the cell slightly different from each other, the output (moire MAX) having the largest interference pattern output by the moire continuously read out can be obtained. Can be considered almost completely opposite.

For example, between a cell set at a pitch of 0.0635 mm and a stripe pattern set at a pitch of 0.125 mm and having a single color width of 0.0625 mm, a deviation from the 0.001 mm pattern occurs for each cell. Instead, in any cell part, an exact match occurs with a maximum deviation of 0.01 mm or less.
FIG. 8 is an explanatory diagram showing the waveform of the analog signal (SO) obtained by reading the stripe pattern, and it can be seen that a peak of moiré output that occurs periodically occurs every approximately 62 pixels (pixels).

FIG. 9 is a waveform diagram showing an output waveform that has been digitally converted after photoelectric conversion when the reflection type light source unit 10 is turned on and the document 1 is read.
In the first embodiment, it is assumed that the resolution of the A / D converted light receiving unit 13 is 400 dpi (arrangement pitch 0.0635 mm) and the number of pixels is 1536 bits (elements).
As for the output value of the output waveform, the corrected output is displayed with 8-bit resolution (256 step digit), and the higher the numerical value, the higher the photoelectric conversion output.

In FIG. 9, for all reading widths in the CIS main scanning direction, the reflected light is incident on the region of the light receiving unit 13 (near the pixel positions 1 to 64) corresponding to the reference standard unit 8 provided at one end. The converted output waveform is expressed.
Further, an area without the document 1 (in FIG. 9, a light-shielding area), an area with the document 1 and an area without the document 1 on the other end are sequentially read, and finally correspond to the reference standard portion 8 installed at the other end. The output waveform obtained by reading the light receiving unit 13 (near the pixel positions 1473 to 1536) is expressed. After reading one line, a blanking period is provided to read the next line.

FIG. 10 is a block diagram showing an internal configuration of the MTF measurement unit 20 in the signal processing unit 15.
Among the signals output from the correction circuit of the signal processing unit 15, output information around the pixels (cells) 1 to 64 corresponding to the reference standard unit 8 is stored in the RAM (1) of the MTF measurement unit 20, and the pixels 1473 to Output information in the vicinity of 1536 is stored in the RAM (2) of the MTF measurement unit 20, and output information in the vicinity of the pixels 65 to 1472 is stored in the RAM (3) of the MTF measurement unit 20.
Note that output information in the vicinity of the pixels 65 to 1472 stored in the RAM (3) is output as it is as an image signal.

The adder / subtractor 21 calculates a difference value (Vmax−Vmin) between the maximum value (Vmax) and the minimum value (Vmin) of the output information for each pixel 1 to 64 whose output information is stored in the RAM (1), and An addition value (Vmax + Vmin) of the maximum value (Vmax) and the minimum value (Vmin) of the output information is substituted into the following equation (1), and an MTF (Modulation Transfer Function) value that is a ratio between the difference value and the addition value. Calculate
MTFn
= [(Vmax−Vmin) / (Vmax + Vmin)] × 100 (%) (1)

When the addition / subtraction unit 21 calculates the MTF value for each of the pixels 1 to 64, the maximum value determination unit 23 selects the maximum MTF value among the MTF values of the pixels 1 to 64.
For example, when the MTF value of the pixels 1 to 64 calculated by the adder / subtractor 21 is FIG. 11A, the MTF value (= 35) of the pixel with the bit number 62 is the largest, so the MTF value (= 35) is select.

  Further, the addition / subtraction unit 22 calculates, for each pixel 1473 to 1536 whose output information is stored in the RAM (2), a difference value (Vmax−Vmin) between the maximum value (Vmax) and the minimum value (Vmin) of the output information. Then, the sum (Vmax + Vmin) of the maximum value (Vmax) and the minimum value (Vmin) of the output information is substituted into the above equation (1), and the MTF value that is the ratio of the difference value and the sum is calculated. .

When the addition / subtraction unit 22 calculates the MTF value for each of the pixels 1473 to 1536, the maximum value determination unit 24 selects the maximum MTF value among the MTF values of the pixels 1473 to 1536.
For example, when the MTF value of the pixels 1473 to 1536 calculated by the adder / subtractor 22 is FIG. 11B, the MTF value (= 30) of the pixel having the bit number 1475 is the largest, so the MTF value (= 30) is select.

When the maximum value determination unit 23 selects the maximum MTF value (= 35) and the maximum value determination unit 24 selects the maximum MTF value (= 30), the MTF level determination unit 25 obtains the MTF level determination result as The larger MTF value (= 35) is selected.
Alternatively, an average value (= 32.5) of the MTF value (= 35) and the MTF value (= 30) is selected as the MTF level determination result.

Although the details will be described later, the MTF level determination unit 25 holds a correspondence table as shown in FIG. 14, and outputs an MTF correction signal corresponding to the MTF level judgment result from the correspondence table.
For example, when an MTF value (= 15) is selected as the MTF level determination result, an MTF correction signal of “0111” is output, and an MTF value (= 23) is selected as the MTF level determination result , “1011” MTF correction signal is output.
In this example, the MTF correction signal is output with 4 bits, but the MTF correction signal of “0000” indicates that both of the MTF values are small and the image blur is large.
The MTF correction signal of “1111” indicates that both MTF values are large and there is almost no image blur.

In the first embodiment, the reference standard portion 8 is disposed at both outer end portions of the document conveyance region. However, in the light transmitting body 4, at one outer end portion of the document conveyance region. The reference standard part 8 may be arranged.
In this case, either one of RAM (1) and RAM (2) is unnecessary in FIGS.

FIG. 12 is a cross-sectional configuration diagram illustrating an image reading apparatus in which a CIS and a transmissive light source unit 2 are mounted in a reading system and the transmissive light source unit 2 is movable up and down.
In FIG. 12, L is the conjugate length between the focal position of the document 1 and the light receiving unit 13, and C / L is the focal position.
δL is the shift amount of the focus (F0) from the focus position C / L.

In the example of FIG. 12, the transmissive light source unit 2 is installed through a gap for conveying the document 1 and the CIS fixed to the system fixing base 31, and is a digital extension / contraction attached to the top plate 32 of the system. The part (focal position adjusting means) 33 extends and contracts so that the transmissive light source unit 2 can move up and down.
This vertical movement is realized as the amount of expansion / contraction of the digital expansion / contraction part 33 changes according to the MTF correction signal.
In FIG. 12, the transmission light source unit 2 is operated to adjust the gap in which the document 1 is conveyed. However, a document guide for controlling the thickness of the document 1 placed on the pulley 35 is shown. 34 may be interlocked.

Here, the MTF will be described.
FIG. 13 is an explanatory diagram showing the MTF characteristics when the focal point is shifted by ± δL in the optical axis direction with respect to the focal position C / L on the side of the document 1 set by CIS.
In the example of FIG. 13, when the focal point (F0) is at approximately the center position (C / L) between the light transmitting body 4 and the glass plate 11 facing each other, the setting position of the stripe pattern is from the center position to the optical axis direction. As it changes, the MTF decreases almost in contrast.

Further, since the 8LP stripe pattern has higher definition than the 4LP stripe pattern displayed for reference, the MTF is greatly reduced.
In the example of FIG. 12, the scattered light irradiated from the CIS reflective light source unit 10 and reflected by the 8LP stripe pattern is converged by the rod lens array 12 and incident on the light receiving unit 13, thereby photoelectric conversion. Then, the MTF value is calculated by the signal processing unit 15, and the MTF value corresponding to the point A shown in FIG. 13 is determined.

FIG. 14 is an explanatory diagram showing a correspondence relationship between an MTF value, a correction signal, position information, and a movable range.
The distance from the focal position to the position where the stripe pattern is read can be known from the MTF value.
In this case, since the MTF value obtained with the 8LP stripe pattern is the MTF value shifted to the + δL side, the digital expansion / contraction part 33 is moved to the CIS side, so that the focal position is determined and at the same time the digital expansion / contraction part 33 The conveyance height position of the document 1 can be adjusted by moving up and down.

  In the first embodiment, this operation has been described with the correction signal for each line reading. However, in the stepwise adjustment for each type of document 1 and the unit of the number of transported documents 1, the system latch signal shown in FIG. You may make it read by an instruction | indication. Moreover, you may use for the check for the periodic focus position accuracy confirmation.

In the example of FIG. 14, the light transmissive body 4 installed in the transmissive light source unit 2 is located at a reference position that is 0.75 mm away from the conjugate length focal point (F0), and depends on the thickness of the document 1. Adjustment of the conveyance path height and the optimum height of the transparent original where the front and back sides of the original are not determined are adjusted.
That is, the transmission light source unit 2 is lowered to control the conveyance gap so that the position of the image information in the optical axis direction matches the focal position.

  In the first embodiment, in consideration of reading a transparent original, the reference standard portion 8 is provided in the light transmitting body 4 of the transmissive light source portion 2 and the transmissive light source portion 2 is moved. When the application is limited to reading only a normal reflection original, only the reflection type image sensor is used, the light transmitting body 4 is used as a simple reflection plate, and the reflection plate is interlocked with the document guide 34. To do. Alternatively, they may be integrated and moved up and down in the optical axis direction.

As is apparent from the above, according to the first embodiment, the reference standard portion 8 in which patterns having alternately different light transmittances are continuously formed is arranged at the outer end portion of the document 1 conveyance region. Light radiated from the light transmitting body 4 and the transmissive light source unit 2 and transmitted through the document 1 and the reference standard unit 8 conveyed through the conveyance region, or radiated from the reflective light source unit 10 and conveyed through the conveyance region The rod lens array 12 that converges the light reflected on the original 1 and the reference standard portion 8 to be received, and the transmitted light and reflected light converged by the rod lens array 12 are received, and the transmitted light and reflected light are converted into electrical signals. And the signal processing unit 15 converts the electrical signal corresponding to the document 1 into an image signal and outputs it to the reference standard unit 8. Corresponding electrical signal The MTF values of the individual pixels are calculated and a correction signal corresponding to the maximum MTF value among the MTF values of the individual pixels is output. Thus, the effect of eliminating the deviation of the focal position and improving the image reading quality is obtained.
In other words, according to the first embodiment, the adjustment of the focal position shift of the document surface due to the thickness of the document 1, particularly in the case of a transparent document, the image information on the front side of the document 1 and the image information on the back side of the document 1 are used. There is an effect that the adjustment with respect to the transmission type light source unit 2 and the document guide 34 can be accurately performed.

Embodiment 2. FIG.
In the first embodiment, the reference standard portion 8 is provided at both ends of the light transmitting body 4 of the transmissive light source unit 2 and the transmissive light source unit 2 is moved up and down. However, in the second embodiment, A description will be given of a case in which the reference standard portion 8 is provided at one end of the light transmitting body 4 and the reference standard portion for transmitted light is provided at the other end of the light transmitting body 4 to move the document guide 34.

FIG. 15 is a cross-sectional configuration diagram illustrating an image reading apparatus according to a second embodiment in which the CIS and the transmissive light source unit 2 are mounted on the reading system. In FIG. 15, the same reference numerals as those in FIG. Reference numeral 40 denotes a light transmitting body.
In FIG. 16, the reference standard portion 8 configured with an 8LP stripe pattern is formed at the end portion on one end side, and the reference standard portion 80 configured with a 4LP stripe pattern is formed on the end portion on the other end side. 2 is a plan configuration diagram showing a transmissive body 40. FIG.
Since the reference standard portion 80 causes the transmitted light to enter the light receiving portion 13 via the CIS rod lens array 12, the 4LP stripe pattern is a black pattern (chrome material) deposited with a width of 0.125 mm and a pitch of 0.25 mm. Are formed in a stripe shape directly on the light transmitting body 40 over a width of 8 mm or more.

Next, the operation will be described.
The document 1 conveyed from the paper-feed-side pulley 35 passes through the transmissive light source unit 2 and the document guide 34 as a conveyance path, and is conveyed to the paper-discharge-side pulley 35.
A digital expansion / contraction unit 33 installed to move the transmissive light source unit 2 and the document guide 34 adjusts the height of the conveyance path in the optical axis direction.
This adjustment is performed by sliding the transmissive light source unit 2 and the document guide 34 up and down in the optical axis direction based on the MTF correction signal output from the signal processing unit 15.

FIG. 17 is a block diagram showing an internal configuration of the MTF measurement unit 20 in the signal processing unit 15 of the image reading apparatus according to Embodiment 2 of the present invention.
Among the signals output from the correction circuit of the signal processing unit 15, output information in the vicinity of the pixels (cells) 1 to 64 corresponding to the reference standard unit 8 configured with an 8LP stripe pattern is stored in the RAM (1) of the MTF measurement unit 20. ) And output information in the vicinity of the pixels 1409 to 1536 corresponding to the reference standard unit 80 configured by a 4LP stripe pattern is stored in the RAM (2) of the MTF measurement unit 20 and output information in the vicinity of the pixels 65 to 1408. Is stored in the RAM (3) of the MTF measurement unit 20.
Note that output information in the vicinity of the pixels 65 to 1408 stored in the RAM (3) is directly output as an image signal.

The adder / subtractor 21 calculates a difference value (Vmax−Vmin) between the maximum value (Vmax) and the minimum value (Vmin) of the output information for each pixel 1 to 64 whose output information is stored in the RAM (1), and The added value (Vmax + Vmin) of the maximum value (Vmax) and the minimum value (Vmin) of the output information is substituted into the above equation (1), and the MTF value that is the ratio between the difference value and the added value is calculated.
When the addition / subtraction unit 21 calculates the MTF value for each of the pixels 1 to 64, the maximum value determination unit 23 selects the maximum MTF value among the MTF values of the pixels 1 to 64.

In addition, the addition / subtraction unit 22 calculates a difference value (Vmax−Vmin) between the maximum value (Vmax) and the minimum value (Vmin) of the output information for each pixel 1409 to 1536 whose output information is stored in the RAM (2). Then, the sum (Vmax + Vmin) of the maximum value (Vmax) and the minimum value (Vmin) of the output information is substituted into the above equation (1), and the MTF value that is the ratio of the difference value and the sum is calculated. .
When the addition / subtraction unit 22 calculates the MTF value for each of the pixels 1409 to 1536, the maximum value determination unit 24 selects the maximum MTF value among the MTF values of the pixels 1409 to 1536.

When the maximum value determination unit 23 selects the maximum MTF value, the MTF level determination unit 26 outputs, for example, a 4-bit MTF correction signal (1) corresponding to the MTF value from the correspondence table shown in FIG. .
For example, if the maximum MTF value is “17”, the MTF correction signal (1) of “1000” is output, and if the maximum MTF value is “25”, the MTF correction signal (1) of “1100” is output. Is output.
When the maximum value determination unit 24 selects the maximum MTF value, the MTF level determination unit 27, like the MTF level determination unit 26, performs 4-bit MTF correction corresponding to the MTF value from the correspondence table as shown in FIG. Output signal (2).

Since the transmissive light source unit 2 and the reflective light source unit 10 are not normally lit at the same time, the MTF correction signal is turned on by turning on the system latch signal (LATCH1) while the transmissive light source unit 2 is lit. The MTF correction signal (2) is allowed to pass by keeping (1) in the previous state and turning off the system latch signal (LATCH2).
On the other hand, while the reflective light source unit 10 is lit, the system latch signal (LATCH2) is turned on to keep the MTF correction signal (2) in the previous state, and the system latch signal (LATCH1) is turned off. By doing so, the MTF correction signal (1) is passed.

  The system latch signal is updated for each line. When the image information is updated for each document or each document type according to an instruction from the reading system, the system latch signal is turned OFF at the time of update. The previous state may be maintained by turning on.

FIG. 18 is an explanatory diagram showing the MTF characteristics when the original reading surface is deviated by ± δL in the optical axis direction with respect to the focal position C / L on the original 1 side set by CIS.
In FIG. 18, the 8LP stripe pattern has higher definition than the 4LP stripe pattern. However, since the direct light from the transmissive light source unit 2 is incident on the 4LP stripe pattern, the reflective light source unit is used. The MTF value is lower than that in which 10 scattered light is incident.

The scattered light irradiated from the CIS reflection type light source unit 10 and reflected by the 8LP stripe pattern is converged by the rod lens array 12 and incident on the light receiving unit 13 to be photoelectrically converted to be a signal processing unit 15. The MTF value is calculated, and the MTF value corresponding to the point A shown in FIG. 18 is determined.
On the other hand, the direct light irradiated from the transmissive light source unit 2 and transmitted through the 4LP stripe pattern is converged by the rod lens array 12 and incident on the light receiving unit 13 to be photoelectrically converted and the signal processing unit 15. The MTF value is calculated, and the MTF value corresponding to the point B shown in FIG. 18 is determined.
Accordingly, the range of the deviation amount on the + δL side of the document 1 is calculated with the light emitted from the reflective light source unit 10, and a rough standard of the deviation amount on the + δL side of the document 1 with the light emitted from the transmissive light source unit 2 is calculated. Can be confirmed.

As described above, even if the reflective light source unit 10 is not turned on as in the case of a transmissive document, the transmissive light source unit 2 and the reference light source unit 2 can be obtained by the reference information from the reference standard unit 80 formed at the other end of the light transmissive body 40. The document guide 34 can be driven.
The glass plate 11 also directly transmits light or unnecessary scattering by shielding the light transmitted from the reference standard part 80 of the light transmitting body 40, the reflected light from the reference standard part 8, and the region other than the vicinity of the reading position of the document 1. Incident light can be prevented, and highly accurate document reading can be performed.

  Incidentally, the conjugate length, which is the focal length (Z) between the light receiving surface of the light receiving unit 13 and the document surface via the rod lens array 12, is determined in advance by a structural design value such as CIS. The light emitted from is not necessarily monochromatic. For example, as shown in FIG. 19, there is a light source unit in which light sources of a plurality of colors having different optical wavelengths are mounted on the end of the reflective light source unit 10 and irradiated from a light guide.

FIG. 20 is an explanatory diagram showing the relationship between the optical wavelength and the conjugate length.
FIG. 20 shows that the conjugate length (L) changes as the light source color changes. For example, an image sensor such as a blue, green, or red light source that has close optical wavelengths has a significant effect. However, the conjugate length varies greatly with a light source having a wavelength outside the visible light region such as an ultraviolet light source or an infrared light source.
Therefore, by changing the transport position of the original, the reading accuracy for each color is improved by adjusting the distance from at least the reflection from the original surface to the incidence on the rod lens array 12 according to the light source wavelength.

Embodiment 3 FIG.
In the first and second embodiments, the transmissive light source unit 2 and the reflective light source unit 10 are mounted. However, in the third embodiment, for example, a document that is transferred at high speed like a banknote. An image reading apparatus for double-sided reading 1 will be described.
In the image reading apparatus for double-sided reading, a reference reference portion is provided at one end portion of the glass plate 11 of the CIS (1), and the end portion of the glass plate 11 of the CIS (2) facing the other end portion of the glass plate 11 is provided. A reference standard part is provided so that the document guide 34 can be moved.

FIG. 21 is a sectional view showing an image reading apparatus according to Embodiment 3 of the present invention. In other words, FIG. 21 is a cross-sectional configuration diagram showing an image reading apparatus in which CIS (1) and CIS (2) are placed facing the document surface. In FIG. 21, the same reference numerals as those in FIG.
The reference standard portion 81 is an 8LP stripe pattern, and is formed in CIS (1) and CIS (2).
On the reading system side, the digital expansion / contraction unit 100 (focal position adjustment means) is provided according to position information (see FIG. 14) corresponding to the MTF correction signals output from the individual CIS (1) and (2) facing each other. By operating, the document guide 34 is moved.

Next, the operation will be described.
FIG. 22 is a block diagram showing an internal configuration of the MTF measurement unit 20 in the signal processing unit 15 of the CIS (1) (2) of the image reading apparatus according to Embodiment 3 of the present invention.
Among the signals output from the correction circuit of the signal processing unit 15 of the CIS (1), output information in the vicinity of the pixels (cells) 1 to 64 or 1473 to 1536 corresponding to the reference standard unit 81 is the MTF of the CIS (1). The output information in the vicinity of the pixels 65 to 1472 is stored in the RAM (3) of the MTF measurement unit 20 of the CIS (1).
Note that output information in the vicinity of the pixels 65 to 1472 stored in the RAM (3) is output as it is as an image signal.

The adder / subtractor 21 calculates a difference value (Vmax−Vmin) between the maximum value (Vmax) and the minimum value (Vmin) of the output information for each pixel 1 to 64 or 1473 to 1536 in which the output information is stored in the RAM (1). ) And the added value (Vmax + Vmin) of the maximum value (Vmax) and the minimum value (Vmin) of the output information are substituted into the above equation (1), and the MTF value that is the ratio of the difference value and the added value is calculated. calculate.
When the addition / subtraction unit 21 calculates the MTF value for each of the pixels 1 to 64 or 1473 to 1536, the maximum value determination unit 23 selects the maximum MTF value among the MTF values of the pixels 1 to 64 or 1473 to 1536.

Among the signals output from the correction circuit of the signal processing unit 15 of the CIS (2), output information in the vicinity of the pixels (cells) 1 to 64 or 1473 to 1536 corresponding to the reference standard unit 81 is the MTF of the CIS (2). The output information in the vicinity of the pixels 65 to 1472 is stored in the RAM (3) of the MTF measurement unit 20 of the CIS (2).
Note that output information in the vicinity of the pixels 65 to 1472 stored in the RAM (3) is output as it is as an image signal.

The adder / subtractor 22 calculates a difference value (Vmax−Vmin) between the maximum value (Vmax) and the minimum value (Vmin) of the output information for each pixel 1 to 64 or 1473 to 1536 in which the output information is stored in the RAM (1). ) And the added value (Vmax + Vmin) of the maximum value (Vmax) and the minimum value (Vmin) of the output information are substituted into the above equation (1), and the MTF value that is the ratio of the difference value and the added value is calculated. calculate.
When the addition / subtraction unit 22 calculates the MTF value for each of the pixels 1 to 64 or 1473 to 1536, the maximum value determination unit 24 selects the maximum MTF value among the MTF values of the pixels 1 to 64 or 1473 to 1536.

When the maximum value determination unit 23 selects the maximum MTF value, the MTF level determination unit 26 outputs, for example, a 4-bit MTF correction signal (1) corresponding to the MTF value from the correspondence table shown in FIG. .
When the maximum value determination unit 24 selects the maximum MTF value, the MTF level determination unit 27 outputs, for example, a 4-bit MTF correction signal (2) corresponding to the MTF value from the correspondence table shown in FIG. .

For example, it is assumed that the glass plate 11 of CIS (2) is initially at the reference position and is at a position separated by 0.75 mm with respect to a predetermined focal point as in the correspondence table shown in FIG.
At this time, when the focal position is shifted by 0.43 mm to the + δL side, it is possible to confirm the focal position by lowering CIS (2) until the MTF value becomes “24 to 26”.
Further, when the focal position is shifted by 0.43 mm to the −δL side, the focal position can be confirmed by raising CIS (1) until the MTF value becomes “24 to 26”.

When the focal position is determined, the CIS (1) and CIS (2) may be moved correspondingly to set the gap in the conveyance path of the document 1, but in the third embodiment, the bill is For documents that are transferred at high speed, such as the above, it is possible to replace them by synchronizing the document guides 34 set on the paper feed side and paper discharge side without moving the CIS (1) and CIS (2). is there.
Further, instead of the pulley, the document guide 34 on the paper feeding side is placed opposite to the gap, and a bill or the like is transferred between the gaps at high speed.

  As described above, according to the third embodiment, the range of the deviation amount on the + δL side of the document 1 is calculated from the image information from the MTF measurement unit 20 by the light emitted from the reflection type light source unit 10 of the CIS (1). The range of the amount of deviation on the −δL side of the document 1 is calculated with the light emitted from the reflective light source unit 10 of CIS (2), and this result is output as reference information from the MTF level determination units 26 and 27. Thus, even when the focal length changes up and down in the optical axis direction, the conveyance position of the document 1 can be brought close to the optimum focal position of each color light source, and problems due to chromatic aberration of the light source can be solved.

In the first to third embodiments, the reference standard portions 80 and 81 are assumed to be a stripe pattern made of a chrome material. Instead of the chrome material, the surface of the glass plate 11 is roughened to obtain a glass plate. The direct light incident on 11 may be scattered to control the light incident on the rod lens array 12.
Further, the light transmitting bodies 4 and 40 and the glass plate 11 are not glass materials but may be any material that transmits light. For example, even if a plastic material or a translucent material is used, a corresponding effect can be obtained. Can do.
Further, although the reference standard portions 8, 80, 81 are assumed to be a stripe pattern, they may be a halftone pattern, and an appropriate effect can be obtained.
Further, the stripe pattern does not have to be the surface of the light transmitting bodies 4 and 40 or the glass plate 11, and has a function as the reference reference portion 8, 80, 81 even if formed on the opposite surface (back surface) facing each other. be able to.

1 is a cross-sectional configuration diagram illustrating an image reading apparatus according to a first embodiment of the present invention. 1 is an external perspective view showing an image reading apparatus according to Embodiment 1 of the present invention. 1 is an external perspective view of a transmissive light source unit 2 in an image reading apparatus according to Embodiment 1 of the present invention. 1 is an overall configuration diagram illustrating an image reading apparatus according to Embodiment 1 of the present invention. It is a top view which shows the light transmission body 4 in which the reference reference | standard part 8 is installed in both ends. It is a top view which shows the light-receiving part 13 mounted in the sensor board | substrate 14 by the side of CIS. FIG. 6 is an explanatory diagram showing an example of an output of an analog signal (SO) when the reflected light of the reference standard unit 8 is received when irradiation of the transmissive light source unit 2 is stopped and irradiation of the reflective light source unit 10 is performed. is there. It is explanatory drawing which shows the waveform of the analog signal (SO) which read the stripe pattern. FIG. 6 is a waveform diagram showing an output waveform that has been digitally converted after photoelectric conversion when the reflection type light source section is turned on and a document 1 is read. It is a block diagram which shows the internal structure of the MTF measurement part 20 in the signal processing part 15 of the image reading apparatus by Embodiment 1 of this invention. It is explanatory drawing which shows an example of the MTF value calculated by the addition / subtraction parts 22 and 24. 2 is a cross-sectional configuration diagram illustrating an image reading apparatus in which a CIS and a transmissive light source unit 2 are mounted in a reading system and the transmissive light source unit 2 is movable up and down. FIG. FIG. 6 is an explanatory diagram showing MTF characteristics when the focal point is shifted by ± δL in the optical axis direction with respect to the focal position C / L on the document 1 side set by CIS. It is explanatory drawing which shows the correspondence of an MTF value, a correction signal, position information, and a movable range. It is a cross-sectional block diagram which shows the image reading apparatus of Embodiment 2 with which CIS and the transmissive | pervious light source part 2 are mounted in the reading system. In FIG. 15, reference numeral 40 denotes a light transmitting body. A light transmission body 40 in which a reference standard portion 8 configured with an 8LP stripe pattern is formed at an end portion on one end side and a reference standard portion 80 configured with a 4LP stripe pattern is formed on an end portion on the other end side. FIG. It is a block diagram which shows the internal structure of the MTF measurement part 20 in the signal processing part 15 of the image reading apparatus by Embodiment 2 of this invention. FIG. 6 is an explanatory diagram showing MTF characteristics when the original reading surface is shifted by ± δL in the optical axis direction with respect to the focal position C / L on the original 1 side set by CIS. It is explanatory drawing which shows the illuminating device used for the transmissive | pervious light source part 2 and the reflective light source part 10. FIG. It is explanatory drawing which shows the relationship between an optical wavelength and conjugate length. It is a cross-sectional block diagram which shows the image reading apparatus by Embodiment 3 of this invention. It is a block diagram which shows the internal structure of the MTF measurement part 20 in the signal processing part 15 of CIS (1) (2) of the image reading apparatus by Embodiment 3 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Original, 2 Transmission type light source part (Transmission type light source means), 3 Light source, 4 Light transmission body, 5 Light source drive substrate, 6 Connector, 7 Case, 8 Reference reference part, 9 Mounting member, 10 Reflection type light source part (Reflective light source means), 11 glass plate, 12 rod lens array (light focusing means), 13 light receiving part (light receiving means), 14 sensor substrate, 15 signal processing part (signal processing means), 16 connector, 17 housing, 18 mounting member, 20 MTF measurement unit, 21, 22 addition / subtraction unit, 23, 24 maximum value determination unit, 25, 26, 27 MTF level determination unit, 31 system fixing base, 32 top plate, 33 digital extendable unit (focal position adjustment) Means), 34 document guide, 35 pulley, 40 light transmitting body, 80, 81 reference standard part, 100 digital extendable part (focus position adjusting means).

Claims (4)

  Reflective light source means for irradiating light and a reference standard part in which patterns having different light transmittances are alternately formed are provided at the outer edge of the document transport area, and are irradiated from the reflective light source means. A light transmitting body through which light is transmitted; a light converging means for converging the light irradiated from the reflective light source means and conveyed in the conveying area and reflected by the reference reference portion; and the light converging means Light receiving means for receiving the converged reflected light and converting the reflected light into an electric signal, and among the electric signals converted by the light receiving means, an electric signal corresponding to the original is converted into an image signal and output. And a signal processing means for calculating the MTF value of each pixel in the electrical signal corresponding to the reference standard part and outputting a correction signal corresponding to the maximum MTF value among the MTF values of each pixel. Image reading Apparatus.   A transmissive light source means for irradiating light and a reference standard portion in which patterns having different light transmittances are alternately formed are provided at the outer end of the document transport area and irradiated from the transmissive light source means. A light transmitting body through which light passes, a light converging means for converging light transmitted from the transmissive light source means and transported through the transport area and the reference standard portion, and converged by the light converging means Receiving the transmitted light, converting the transmitted light into an electrical signal, and converting the electrical signal converted by the light receiving means into an image signal corresponding to the original and outputting the image signal And signal processing means for calculating the MTF value of each pixel in the electrical signal corresponding to the reference standard part and outputting a correction signal corresponding to the maximum MTF value among the MTF values of the individual pixels. Image reading Location.   The first reflective light source means for irradiating light, the second reflective light source means for irradiating light, and a first reference standard portion in which patterns with different light transmittances are alternately formed are formed on the original. A first light transmitting body that is provided at one outer end of the transport region and transmits the light emitted from the first reflective light source means; and is disposed to face the first light transmitting body; In addition, the second reference reference portion on which patterns having alternately different light transmittances are continuously formed is the outer end portion on the side that does not face the first reference reference portion in the outer end portion of the document conveyance region. And a second light transmissive body through which the light emitted from the second reflective light source means is transmitted, and after being irradiated from the first reflective light source means, the first light transmissive body is Light that passes through and is reflected by the second reference reference portion and the original conveyed through the conveyance area is collected. The first light converging means and the second reflective light source means, and then the original transmitted through the second light transmitting body and conveyed in the conveyance area, and the first reference standard. Second light converging means for converging the light reflected by the first part, and first light receiving means for receiving the reflected light converged by the first light converging means and converting the reflected light into an electrical signal; The second light receiving means for receiving the reflected light converged by the second light converging means and converting the reflected light into an electric signal, and the electric signal converted by the first light receiving means, The electrical signal corresponding to the original is converted into an image signal and output, and the MTF value of each pixel in the electrical signal corresponding to the second reference standard part is calculated, and the MTF value of each pixel is calculated. First to output a first correction signal corresponding to the maximum MTF value Of the electric signals converted by the signal processing means and the second light receiving means, the electric signal corresponding to the original is converted into an image signal and output, and the electric signal corresponding to the first reference reference portion An image reading apparatus comprising: a second signal processing unit that calculates an MTF value of each individual pixel and outputs a second correction signal corresponding to the maximum MTF value among the MTF values of each individual pixel.   4. The image reading device according to claim 1, further comprising a focal position adjusting unit that adjusts a focal position of the original in accordance with a correction signal output from the signal processing unit. apparatus.

Images