JP2001320551A - Device and method for reading image and computer readable storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reader capable of simultaneously reading both faces of an original to increase image read speed and also made small and inexpensive. SOLUTION: This image reader is provided with a light source 207, a CCD linear image sensor 201 for receiving reflected light of the light source 207, a CCD linear image sensor 202 for receiving transmitted light from the light source 207, lenses 203 and 204 and mirrors 205 and 206, arranges a reflection scanning position by the sensor 201 so as to precede a transmission scanning position by the sensor 202 and also arranges the light source 207 so that the distance (a) between the source 207 and the transmission scanning position is shorter than the distance (b) between the source 207 and the reflection scanning position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus such as a scanner or a copying machine, and is particularly suitable for reading both sides of a document.

[0002]

2. Description of the Related Art Due to the expansion of networks, "network printers" have been established from a configuration of one set of a personal computer and a printer to a configuration of a plurality of personal computers and one printer.

[0003] Nowadays, there is an increasing demand for a "network scanner" in which a scanner which has been considered as a pair with a personal computer or a printer is configured by one scanner and a plurality of personal computers or printers.

FIG. 9 shows a configuration of an image reading apparatus using a conventional CCD linear image sensor. 101 is CC
D is a linear image sensor, 102 is a lens, and 103 is a mirror. Reference numeral 104 denotes a light source, and reference numeral 105 denotes a platen glass. Reference numeral 106 denotes a document, 107 denotes a conveyance roller for conveying the document 106, and 108 denotes a guide roller for guiding the document 106.

Next, with reference to FIG. 10, an operation of reading both sides of the document 106 by the image reading apparatus shown in FIG. 9 will be described. In FIG. 10, reference numerals are omitted, and
The image reading operation is performed in the order shown in (a) to (f).
When performing double-sided reading of the document 106, the document 106 is moved onto the platen glass 105 and one side thereof is read (FIGS. 10A to 10C). Thereafter, the original 106 is inverted by the guide roller 108, and the original 106 is moved onto the original platen glass 105 again to read the other side (FIGS. 10D to 10F).

[0006]

As described above, the demand for "network scanners" has been increasing, and users have been demanding higher image reading speeds.

However, when reading both sides of a document, two scans must be performed for one double-sided document, as described above, which has the disadvantage that the image reading speed is significantly reduced. .

Further, there is an image reading apparatus which uses two contact type sensors as an image reading apparatus for reading both sides of a document at the same time. However, in this case, a sensor of a size of the document is required, which results in an increase in size and cost. Would.

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, it is an object of the present invention to increase the image reading speed by simultaneously reading both sides of a document and to reduce the size and cost.

[0010]

According to an image reading apparatus of the present invention, an image reading apparatus for reading images on both sides of a document, comprising: a light source for irradiating the document; and light reflected by the light source. And a second image reading means for reading the image of the document by the transmitted light by the irradiation of the light source.

Another feature of the image reading apparatus according to the present invention is that the scanning position by the first image reading means and the scanning position by the second image reading means are relatively moved with respect to the original. Thus, the configuration is such that the image of the entire surface of the document is read.

Another feature of the image reading apparatus of the present invention resides in that the first original is fixed to the fixed original.
And a scanning position moving means for moving the scanning position by the image reading means and the scanning position by the second image reading means.

Another feature of the image reading apparatus of the present invention resides in that the original is moved relative to the fixed scanning position by the first image reading means and the scanning position by the second image reading means. Document conveying means for conveying the document.

Another feature of the image reading apparatus of the present invention is that the scanning position by the first image reading means is more constant in the relative movement direction than the scanning position by the second image reading means. The point is that it is configured to advance by the interval.

Another feature of the image reading apparatus of the present invention is that a distance from the light source to a scanning position by the first image reading means and a scanning position from the light source by the second reading means. It is different from the distance to.

Another feature of the image reading apparatus of the present invention is that the influence of the reflection side image of the original on the transmission side image data obtained by the second image reading means is eliminated. And an image processing circuit for performing a separation process for performing the separation process.

Another feature of the image reading apparatus of the present invention is that the image processing circuit can select a mode in which the separation processing is performed and a mode in which the separation processing is not performed. .

Another feature of the image reading apparatus of the present invention is that when the black level of the transmission side image data obtained by the second image reading means is larger than a predetermined value, the separation processing is performed. The point is that the mode that does not perform is selected.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an image reading apparatus according to the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 shows the configuration of an image reading apparatus. In FIG. 1, 201 and 202 are C
This is a CD linear image sensor, and is arranged with a platen glass interposed therebetween. 203 and 204 are lenses. 2
Reference numerals 05 and 206 denote mirrors, each of which is a CCD from the original 210.
By moving the optical path lengths to the linear image sensors 201 and 202 so as to keep them constant, reflected light and transmitted light due to irradiation of the light source 207 are transmitted to each CCD linear image sensor 20.
1, 202. A light source 207 irradiates the document 210. Reference numerals 208 and 209 denote standard white plates for obtaining shading correction values used in the shading correction processing.

In the CCD linear image sensor 201,
Light reflected by the light source 207 is received via the mirror 205 and the lens 203. Further, the CCD linear image sensor 202 receives transmitted light by irradiation of the light source 207 via the mirror 206 and the lens 204. Then, photoelectric conversion is performed in each of the CCD linear image sensors 201 and 202, and an image signal is sent to an image processing circuit described later.

Here, as shown in FIG. 1, the light reflected by the light source 207 is reflected by the CCD linear image sensor 201.
The scanning position (scanning position on the reflection side) for reading by the CCD is the scanning position (scanning position on the transmission side) for reading the transmitted light by irradiation of the light source 207 with the CCD linear image sensor 202.
Is placed ahead of the other.

This is to implement high-precision double-sided reading and to reduce the cost in performing image processing therefor. That is, when the front and back sides of the document 210 are read, the raw image data on the transmission side is affected by the reflection side image of the document 210 as shown in FIG. Therefore, as will be described in detail later, it is necessary to perform a separation process for removing the influence of the reflection side image from the transmission side image.

In this case, it is possible to store the data on the reflection side and the data on the transmission side in the page memory and perform the image processing after scanning the original, but this increases the cost. On the other hand, by setting the reflection side scanning position ahead of the transmission side scanning position as in the present embodiment,
Even without having a page memory for one page, the above-described image processing (separation processing) can be performed only by having a line memory for the difference between the scanning positions.

Further, in this embodiment, the light source for transmission and the light source for reflection are shared by one light source 207, but the light amount required for transmission and the light amount required for reflection are required. Differs from light intensity. In other words, the light amount for transmission requires a larger amount of light for transmitting the document 210.

Therefore, in this embodiment, as shown in FIG. 3, the distance a from the light source 207 to the transmission side scanning position is defined as
It is shorter than the distance b from the light source 207 to the reflection side scanning position (a ≦ b). Thus, the distance a from the light source 207
While the light amount for transmission is secured at the transmission side scanning position, the light amount for reflection at the reflection side scanning position at a distance b longer than the distance a can be adjusted to be an appropriate amount. Common use becomes possible.

Next, the operation of the image reading apparatus according to the first embodiment will be described in detail. First, the transmission side scanning position and the reflection side scanning position are moved to the positions of the standard white plates 208 and 209, and by reading these standard white plates 208 and 209, a shading correction value is obtained.

Next, the image of the document 210 is read.
By moving the mirrors 205 and 206 so as to keep the optical path length to the CD linear image sensors 201 and 202 constant,
The image of the document 210 is read. At this time, scanning is performed such that a predetermined interval is always maintained between the reflection side scanning position and the transmission side scanning position.

The reflected light and the transmitted light are transmitted through the lens 20 respectively.
CCD linear image sensor 20 via 3, 204
The CCD linear image sensors 201 and 202 convert light signals into electric signals. The raw image data on the reflection side read in this way is multiplied by the shading correction value of each pixel obtained by reading the standard white plate 208 to become image data.

Here, as described above, the raw image data on the transmission side is affected by the reflection side image of the document 210. Specifically, as combinations of the transmission-side image, the reflection-side image, and the transmission-side raw image data of the document 210, there are four combinations shown in Table 1 below.

[0031]

[Table 1]

It should be noted that "when the transmission side image of the document 210 is black, it is read as black regardless of the reflection side image". When the transmission side image raw data shown in Figure 2 is described as an example, the range R ₁ of a right triangle is the permeate side image of black document 210, the reflective side image regardless of whether it is white or a black , Read as clear black.

Here, in order to remove the influence of the reflection side image, it has been described that the reflection side image data may be subtracted from the transmission side image raw data.
When both the transmission side image and the reflection side image are black, the black data is divided from the black data, so that black is not recognized in the transmission side image.

[0034] Therefore, the "case where the transmission-side image of the black" as shown in the range R ₁ in FIG. 2, "a transmission-side image is white, when the reflection side image is a black" as shown in a range R ₂ in FIG. 2 than the By using the fact that the reading levels are different, it is determined whether or not to perform the subtraction processing. That is, in the case where “the transmission side image is black” shown in the range R ₁ , the black of the transmission side image is read as it is and the black reading level is high, whereas the “transmission side image shown in the range R ₂ is In the case of “white and the reflection-side image is black,” the reflection-side image appears black, but the black reading level is low. Therefore, when it is determined that the transmission side image raw data is black having a high level, that is, when “the transmission side image is black”, the subtraction processing of the reflection side data is not performed, and otherwise, the subtraction processing is performed. To do.

FIG. 4 shows a configuration of an image processing circuit for performing the above-described image processing. In FIG. 4, reference numerals 602 and 603 denote image processing units which respectively extract signal components from transmission-side image data and reflection-side image data.

The signal from which the signal component has been extracted by the image processing unit 603 is output as it is as the reflection-side image data.

The signals from which the signal components have been extracted by the image processing unit 602 are subjected to black and white level adjustment by a multiplying unit and an adding unit controlled by the CPU 601.

The adjusted data of each pixel is compared with a predetermined value set in the CPU 601 by the comparing unit 604. The predetermined value is a constant for determining whether or not the image on the transmission side of the document 210 is black having a high level. The comparison unit 604 determines whether each pixel data on the transmission side is black or black. I do.

When the comparing section 604 determines that "the transmission side image is not high-level black", the data of the pixel is affected by the reflection side image and not by the transmission side image. Switching unit 60
In modes 5 and 606, a mode for selecting a system via the subtraction circuit 607 is set. In this mode, the subtraction circuit 607 subtracts the image data on the reflection side corresponding to the scanning position from the raw image data on the transmission side, and outputs the result as transmission-side image data.

On the other hand, if the comparing section 604 determines that the image on the transmission surface is black with a high level, it is not necessary to subtract the image data on the reflection side.
In modes 5 and 606, a mode is selected in which a system not involving the subtraction circuit 607 is selected. In this mode, the image data on the reflection side is not subtracted from the raw image data on the transmission side, and is output as it is as transmission-side image data.

The image processing in the image processing circuit will be described below with reference to FIGS. In FIGS. 5 to 7, 0 indicates black, and 255 indicates white.

FIG. 5 shows a state at the scanning position where both the transmission side image and the reflection side image are white (see FIG. 5 (a)). As shown in FIG. 5B, the white level of the transmission side raw image raw data is low due to the influence of the reflection side image. In this case, the comparison unit 604 determines that “the transmission side image is not black having a high level”, and thus the system via the subtraction circuit 607 is selected. Therefore, the reflection-side image data is subtracted, and as shown in FIG. 5C, the white level of the transmission-side image data can be increased.

FIG. 6 shows a state at a scanning position including a black portion of the transmission side image. At this scanning position, in the white portion of the transmission side image, the reflection side image is also exactly white, and in the black portion of the transmission side image, the reflection side image is also exactly black (see FIG. 6A). As shown in FIG. 6B, the black portion of the transmission-side image is read as high-level black, and the white level of the transmission-side raw image data decreases in the white portion of the transmission-side image due to the influence of the reflection-side image. ing. In this case, in the black portion of the transmission-side image, the comparing unit 604 determines that “the transmission-side image is black having a high level”.
A system that does not go through 07 is selected. Therefore, the reflection-side image data is not subtracted, and the black level of the transmission-side image data can be kept high as shown in FIG. In the white portion of the transmission side image, the comparison unit 604 determines that the transmission side image is not black having a high level as in the example of FIG. 5, so that the system via the subtraction circuit 607 is selected. . Therefore, the reflection-side image data is subtracted, and as shown in FIG. 6C, the white level of the transmission-side image data can be increased.

FIG. 7 shows a scanning position where a black portion of the transmission side image is included and a white portion of the transmission side image includes a black portion of the reflection side image (FIG. 7).
(a)). As shown in FIG. 7B, a black portion of the transmission side image is read as a high level black, but a white portion of the transmission side image is affected by the reflection side image, and in particular, a portion where the reflection side image is black. In FIG. 7, the transmission-side raw image data is read as low-level black (see reference numeral 71 in FIG. 7B). In this case, in the black portion of the transmission side image, the comparison unit 604 determines that “the transmission side image is black having a high level” as in the example of FIG. 6, so that a system that does not pass through the subtraction circuit 607 is selected. You. Therefore, the reflection-side image data is not subtracted, and the black level of the transmission-side image data can be maintained at a high level as shown in FIG.
In the white portion of the transmission side image, since the comparison unit 604 determines that “the transmission side image is not high-level black”, the system via the subtraction circuit 607 is selected. Accordingly, the reflection-side image data is subtracted, and as shown in FIG. 7C, the white level of the transmission-side image data including the portion indicated by reference numeral 71 in FIG. 7B can be increased.

According to the embodiment described above, one light source and the CCD linear image sensor 2 for receiving the reflected light
01 and the CCD linear image sensor 202 that receives the transmitted light can read the image of the double-sided original,
It is possible to provide an image reading device that is low in cost and has an increased image reading speed.

(Second Embodiment) In the second embodiment, an image reading apparatus of a type in which an original 710 is transported by an original transport mechanism (not shown) and scanning is performed.

FIG. 8 shows the configuration of the image reading apparatus. In FIG. 8, reference numerals 701 and 702 denote CCD linear image sensors, which are arranged with a platen glass therebetween. 7
03 and 704 are lenses. Reference numerals 705 and 706 denote mirrors that make reflected light and transmitted light by irradiation of the light source 707 incident on the CCD linear image sensors 701 and 702, respectively. A light source 707 irradiates the document 210.

In the CCD linear image sensor 701,
Light reflected by the light source 707 is received via a mirror 705 and a lens 703. Further, the CCD linear image sensor 702 receives the transmitted light by the irradiation of the light source 707 via the mirror 706 and the lens 704. Then, the image signals obtained by the respective CCD linear image sensors 701 and 702 are sent to the image processing circuit described in the first embodiment.

Also in the second embodiment, as described in the first embodiment, by arranging the reflection-side scanning position ahead of the transmission-side scanning position, the difference between the scanning positions can be reduced. The above image processing (separation processing) is enabled only by having a line memory. Also, the distance from the light source 707 to the transmission-side scanning position is made shorter than the distance from the light source 707 to the reflection-side scanning position to adjust the amount of light, thereby enabling a common light source.

Next, the operation of the image reading apparatus according to the second embodiment will be described. First, when the standard white portions 708 and 709 of the document 710 come to the scanning position, a shading correction value is obtained by reading the standard white portions 708 and 709. The original 710 has a standard white portion 70.
Although an example in which 8 and 709 are added has been described, in practice, a shading correction value may be obtained from a base of a document by setting a predetermined region of the document as a write-protection region.

Next, when the image of the original 710 is read, each CCD linear image sensor 70 is read from the scanning position.
The optical path lengths up to 1, 702 are fixed, and an image is read while the original 710 is being conveyed. At this time, a predetermined interval is always maintained between the reflection side scanning position and the transmission side scanning position.

The reflected light and the transmitted light are respectively transmitted to the lens 70.
CCD linear image sensor 70 via
The CCD linear image sensors 701 and 702 convert light signals into electric signals. Since the subsequent image processing has been described in the first embodiment, a detailed description thereof will be omitted here.

(Other Embodiments) In order to operate various devices to realize the functions of the above-described embodiments, an apparatus connected to the various devices or a computer in a system is used in the above-described embodiments. Supply the software program code to realize the functions of
The present invention also includes those implemented by operating the various devices according to programs stored in a computer (CPU or MPU) of the system or apparatus.

In this case, the program code of the software realizes the functions of the above-described embodiment, and the program code itself and means for supplying the program code to the computer,
For example, a recording medium storing such a program code constitutes the present invention. As a recording medium for storing such a program code, for example, a floppy (registered trademark) disk, hard disk, optical disk, magneto-optical disk, C
D-ROM, magnetic tape, nonvolatile memory card, R
OM or the like can be used.

When the computer executes the supplied program code, not only the functions of the above-described embodiment are realized, but also the OS (operating system) or other operating system in which the program code runs on the computer. It goes without saying that such program codes are also included in the embodiments of the present invention when the functions of the above-described embodiments are realized in cooperation with the application software or the like.

Further, after the supplied program code is stored in a memory provided in a function expansion board of the computer or a function expansion unit connected to the computer, the function expansion board or the function expansion unit is specified based on the instruction of the program code. It is needless to say that the present invention also includes a case where the CPU or the like provided for performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

It should be noted that the shapes and structures of the respective parts shown in the above-described embodiments are merely examples of the embodiment for carrying out the present invention, and the technical scope of the present invention is thereby reduced. It should not be interpreted restrictively. That is, the present invention can be implemented in various forms without departing from the spirit or main features thereof.

[0058]

As described above, according to the present invention, an image on a double-sided document is read by one light source, first image reading means for receiving reflected light, and second image reading means for receiving transmitted light. It is possible to provide an image reading apparatus which is low in cost and has an increased image reading speed.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of an image reading apparatus.

FIG. 2 is a diagram for explaining that transmission side image raw data is affected by a reflection side image;

FIG. 3 is a diagram illustrating a relationship between a light source 207 and a reflection-side scanning position and a transmission-side scanning position.

FIG. 4 is a diagram illustrating an image processing circuit.

FIG. 5 is a diagram illustrating a state of image processing.

FIG. 6 is a diagram illustrating a state of image processing.

FIG. 7 is a diagram for explaining a state of image processing.

FIG. 8 is a diagram illustrating a configuration of an image reading apparatus.

FIG. 9 is a diagram illustrating a configuration of a conventional image reading apparatus.

FIG. 10 is a diagram for explaining a double-sided reading operation of a document in the image reading apparatus shown in FIG. 9;

[Explanation of symbols]

201, 202, 701, 702 CCD linear image sensor 203, 204, 703, 704 Lens 205, 206, 705, 706 Mirror 207, 707 Light source 208, 209 Standard white plate 708, 709 Standard white part 210, 710 Original 601 CPU 602 , 603 Image processing unit 604 Comparison unit 605, 606 Switching unit 607 Subtraction circuit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 1/40 H04N 1/40 101Z F-term (Reference) 2H108 AA01 AA05 AA19 BA07 CB01 FA01 HA00 5C072 AA01 BA01 BA03 CA02 CA09 DA02 DA04 DA21 EA05 MA01 MB04 NA01 UA12 VA03 WA02 XA01 5C077 MM03 PP06 PP15 PP44 PP45 TT06

Claims (11)

[Claims] 1. An image reading apparatus for reading images on both sides of a document, comprising: a light source for irradiating the document; and first image reading means for reading an image on the document by light reflected by the light source. And a second image reading means for reading an image of the document by transmitted light by irradiation of the light source. 2. A structure in which an image on the entire surface of the document is read by relatively moving the document with respect to the scanning position of the first image reading means and the scanning position of the second image reading means. The image reading device according to claim 1, wherein: 3. The method according to claim 1, wherein the first original is fixed to the fixed original.
3. The image reading apparatus according to claim 2, further comprising a scanning position moving unit that moves a scanning position by the image reading unit and a scanning position by the second image reading unit. 4. A document conveying means for conveying the document to a fixed scanning position by said first image reading means and a scanning position by said second image reading means. Item 3. The image reading device according to Item 2. 5. A scanning apparatus according to claim 2, wherein a scanning position of said first image reading means is set ahead of a scanning position of said second image reading means by a predetermined interval in said relative movement direction. The image reading device according to any one of claims 1 to 4. 6. A distance from the light source to a scanning position by the first image reading unit and a distance from the light source to a scanning position by the second reading unit. The image reading device according to any one of claims 1 to 5. 7. An image processing circuit for performing a separation process on the transmission side image data obtained by the second image reading means to remove the influence of the reflection side image of the document. The image reading apparatus according to any one of claims 1 to 6, wherein 8. The image reading apparatus according to claim 7, wherein the image processing circuit can select a mode in which the separation processing is performed and a mode in which the separation processing is not performed. 9. A mode in which the separation processing is not performed when the black level of the transmission-side image data obtained by the second image reading means is larger than a predetermined value. 9. The image reading device according to 8. 10. An image reading method for reading images on both sides of a document, comprising: a step of irradiating the document with one light source; and a step of reading an image of the document by reflected light from the light source. Reading an image of the document using transmitted light by irradiation of the light source. 11. A computer-readable storage medium storing a program for executing a process for reading images on both sides of a document, the process comprising: irradiating the document with one light source; and irradiating the light source. Computer-readable storage for storing a program for executing a process of reading an image of the document by reflected light of the document and a process of reading an image of the document by transmitted light by irradiation of the light source. Medium.