JPH11239252A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the size of an original accurately even in the case of a reflection original whose light transmissivity is high through the radiation of a transmission light source. SOLUTION: The image reader is provided with a transmission light source 10 that illuminates a reflection original 1 or a transmissive original 1 in the case of detecting the size of the reflection original 1 and reading the transmissive original 1, a luminous quantity control means 17 that adjusts an emitted luminous quantity of the transmission light source 10, an image pickup element 5 that receives a transmission light when the transmission light source 10 illuminates the reflection original 1 and converts the light into an electric signal, and an original size detection means 15 that adjusts a luminous quantity of the transmission light source 10 through the luminous quantity control means 17. With the above configuration, a difference between an output signal level of the transmission light at a position where the reflection original 1 is in existence and an output signal level of the transmission light at a position where the reflection original 1 is not in existence is of a prescribed one or over, thereby enabling the detection of the size of the reflection original 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus, and more particularly to a technique which is effective when applied to detection of a document size in the image reading apparatus.

[0002]

2. Description of the Related Art Conventionally, an image reading apparatus used for inputting an image, such as a facsimile or a copying machine, has various processings such as automatically selecting the size of paper to be printed in accordance with the size of a read original. In order to perform this operation, a document size is detected. In recent years, there has also been a need for flatbed scanners to automatically display a preview screen at an optimal size on a screen by detecting a document size. Therefore, there has been an increasing demand for detecting a document size. I have.

Here, as a technique for detecting the size of a reflection original placed on the original glass, a sensor for detecting the size of the original is generally used. However,
Since this document size detection sensor is expensive and the size of a document that can be detected by a single document size detection sensor is limited, the number of document size detection sensors increases when trying to detect a plurality of types of document sizes. Will increase. This leads to a large increase in cost of the entire image reading apparatus.

Conventionally, in an image reading apparatus having both a transparent original reading mechanism (hereinafter, referred to as a "transmissive unit") and a reflective original reading mechanism, a technique for detecting an original size without using an original size detection sensor is as follows. 2. Description of the Related Art A document size is detected by reading the presence or absence of a shadow of a reflection document generated by a light source on the transmission unit side by an image sensor.

Hereinafter, a conventional document size detection technique using a transmission unit will be described with reference to FIGS.

FIG. 4 is a schematic view showing the structure of a conventional image reading apparatus, FIG. 5 is a block diagram showing a control mechanism of the image reading apparatus shown in FIG. 4, and FIG. FIG. 7 is an explanatory diagram showing an example of the output of the image sensor when reading the document size, and FIG. 7 is an explanatory diagram showing another example of the output of the image sensor when the document size of the reflective document is read by irradiating a transmission light source. is there.

[0007] As shown in FIG.
A document (reflection document / transmission document) 101 includes a reflection light source 102 for irradiating light from below and a transmission light source 110 of a transmission unit 111 for irradiating light from above. The imaging apparatus further includes a plurality of reflection mirror groups 103 that guide light reflected from the document 101 to the imaging lens 104, and an imaging element 105 that converts an image formed on the imaging lens 104 into an electric signal.
Reflection light source 102, reflection mirror group 103, imaging lens 10
The optical carriage 106 constituted by the carriage 4 and the image sensor 105 is fixed to a driving force transmission belt 109 stretched over two pulleys driven by a carriage motor 107 and is movable in the sub-scanning direction. The optical carriage 106 is further slidably supported by a guide shaft 108 fixed to a side wall of the apparatus main body 100.

First, an operation of reading the reflection original 101 in such an image reading apparatus will be described.

When reading the reflection original 101, the reflection original 101 is irradiated from below by the reflection light source 102. As a result, the reflected light from the reflecting original 101 is reflected by the reflecting mirror group
After being reflected a plurality of times at 03, an image is formed on the imaging lens 104. Then, the photoelectric conversion elements are imaged on the imaging elements 105 arranged in one row, and one line of image data is converted into an electric signal. The optical carriage 106 receives the driving force of the carriage motor 107 via the driving force driving belt 109 and moves in the sub-scanning direction, which is a direction perpendicular to the arrangement of the photoelectric conversion elements. Are sequentially read.

Next, the operation of reading the transparent original 101 will be described. When reading the transparent original 101, the transparent original 101 is illuminated from above by the transmission light source 109. Thus, the transmitted light from the transmission original 101 is reflected by the reflection mirror group 103 a plurality of times, and then is imaged on the imaging lens 104. Then, the photoelectric conversion elements are imaged on the imaging elements 105 arranged in one row, and one line of image data is converted into an electric signal. The reading in the sub-scanning direction is performed by the same operation as the reading of the reflection original 101.

As shown in FIG. 5, the image reading apparatus comprises:
Analog processing means 112, A / D converter 113, image processing means 114, central processing means 115, motor driving means 1
16 and a light source ON / OFF means 117.

Here, the image data converted into an electric signal by the image pickup device 105 is converted into a signal level suitable for digitization by the analog processing means 112 and input to the A / D converter 113. The A / D converter 113 converts analog image data into digital image data and outputs the digital image data to the image processing unit 114. The image processing means 114 performs image processing such as resolution conversion and color conversion on the digital image data, and the central processing means 115
5 so that the image signal input thereto can be read. The central processing unit 115 switches the transmission light source 110 to the light source ON / OFF unit 1 when reading the transparent original 101 or detecting the original size.
17 and the motor driving means 11
6 to the carriage motor 107.
To move the carriage 106 in the sub-scanning direction.

Next, detection of the size of the reflection original 101 in the conventional image reading apparatus configured as described above will be described.

At the time of reading a normal reflection original 101,
As described above, the reflection light source 102 is turned on, and the reflected light is read by the image sensor 105. When the document size is detected, the transmission light source 110 is turned on with a predetermined light amount (for example, 10,000 lx) instead of the reflection light source 102. Let it.

FIG. 6 shows the output of the image sensor 105 when the reflection original 101 is read in this state.

As shown in FIG. 6, since the light transmittance of the reflective original 101 is low, the amount of light incident on the image sensor 105 is small in the portion where the reflective original 101 is placed. The image pickup device 10
5, the amount of light incident on 5 becomes large. For this reason, the imaging device 10
The output of No. 5 is high at the position where the reflection document 101 exists,
It will be lower in places where it does not exist.

The central processing unit 115 detects such a difference between the outputs of the image sensor 105 and determines a low range and a high range of the output of the image sensor 105, thereby detecting the document size in the main scanning direction. . The original size in the sub-scanning direction is determined by moving the optical carriage 106 in the sub-scanning direction by the carriage motor 107, and similarly, the central processing unit 115 determines the low range and the high range of the output of the image sensor 105 by the reflective document 101. It is detected by the judgment.

[0018]

According to the document size detection technology in such a conventional image reading apparatus, the reflection document 101 has a thickness sufficient to block light from the transmission light source 110, and the presence of the reflection document 101 When there is a sufficient difference in the output of the image sensor 105 between a portion where the image does not exist and a portion where the document does not exist, it is possible to accurately detect the document size.

However, due to the material and thickness of the reflection document 101, the light from the transmission
If not sufficiently shut off by 1 as shown in FIG.
The output of the image sensor 105 does not make a sufficient difference depending on the presence or absence of the reflection document 101. In this case, the central processing unit 115 cannot judge the magnitude of the output well, and there is a possibility that the document size is erroneously determined.

Accordingly, it is an object of the present invention to provide an image reading apparatus capable of accurately detecting the size of an original even when the original is a reflection original having a high light transmittance, by irradiation from a transmission light source.

[0021]

In order to solve this problem, an image reading apparatus according to the present invention comprises: a transmitting light source for irradiating a reflecting original or a transmitting original when detecting the original size of the reflecting original and reading the transmitting original; Light amount control means for adjusting the irradiation light amount of the transmission light source, an image sensor for receiving the transmission light when the reflection original is irradiated by the transmission light source and converting it into an electric signal, and transmission light at a position where the reflection original exists The document size for detecting the size of the reflected document by adjusting the light amount of the transmitted light source through the light amount control means so that the difference between the output signal of the transmitted document and the output signal of the transmitted light at the place where the reflected document does not exist is a predetermined level or more. And detecting means.

This makes it possible to accurately detect the size of a document even when the document is a reflective document having a high light transmittance, by irradiation from a transmission light source.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to a first aspect of the present invention is directed to a transmission light source for irradiating a reflection original or a transmission original when detecting the original size of the reflection original and reading the transmission original, and an irradiation light amount of the transmission light source. Light amount control means for adjusting the reflection light, an image sensor for receiving the transmitted light when the reflection original is irradiated by the transmission light source and converting the transmitted light into an electric signal, an output signal of the transmitted light at the location where the reflection original exists, and the reflection original And a document size detecting means for detecting a document size of a reflected document by adjusting a light amount of a transmission light source through a light amount control means so that a difference between output signals of transmitted light in a portion where no image is present becomes a predetermined level or more. This is a reading device, and has an effect that even if it is a reflection original having a high light transmittance, the size of the original can be accurately detected by irradiation from the transmission light source.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. In these drawings, the same members are denoted by the same reference numerals, and duplicate description is omitted.

FIG. 1 is a schematic diagram showing a configuration of an image reading apparatus according to an embodiment of the present invention, FIG. 2 is a block diagram showing a control mechanism of the image reading apparatus of FIG. 1, FIG.
FIG. 4B is an explanatory diagram illustrating an example of an output of the image sensor when the original size of the reflection original is read by irradiating the transmission light source.

As shown in FIG. 1, the image reading apparatus comprises:
The apparatus includes a reflection light source 2 that irradiates light from below to a document (reflection document / transmission document) 1 placed on an upper portion of the apparatus main body 18 and a transmission light source 10 of a transmission unit 11 that irradiates light from above. Here, in the case of a reflection original 1 such as paper, light is emitted from the reflection light source 2, and in the case of a transmission original 1 such as OHP film, light is emitted from the transmission light source 10.

Further, the image reading apparatus includes a plurality of reflecting mirror groups 3 for guiding the reflected light from the original 1 to the imaging lens 4.
And an image sensor 5 that converts an image formed on the imaging lens 4 into an electric signal.

An optical carriage 6 comprising a reflection light source 2, a reflection mirror group 3, an imaging lens 4, and an image pickup device 5.
Is fixed to a driving force transmission belt 9 stretched over two pulleys driven by a carriage motor 7 and is movable in the sub-scanning direction. The optical carriage 6 further includes
It is slidably supported by a guide shaft 8 fixed to a side wall of the apparatus main body 18.

As shown in FIG. 2, the image reading device
It has an analog processing unit 12, an A / D converter 13, an image processing unit 14, a central processing unit (document size detection unit) 15, a motor driving unit 16, and a light amount control unit 17.

Here, the image data converted into an electric signal by the image pickup device 5 is converted into a signal level suitable for digitization by the analog processing means 12 and the A / D converter 1
3 is input. The A / D converter 13 converts analog image data into digital image data and outputs the digital image data to the image processing unit 14. The image processing unit 14 performs image processing such as resolution conversion and color conversion on the digital image data, and enables the central processing unit 15 to read the image signal input to the image sensor 5. The central processing unit 15 controls the light amount control unit 1 when reading the transparent original 1 and detecting the original size.
At the same time as controlling the irradiation light amount of the transmission light source 10 to a predetermined value, the motor drive signal is issued to the motor drive means 16 to rotate the carriage motor 7 and move the optical carriage 6 in the sub-scanning direction.

The operation of reading the original 1 in the image reading apparatus having such a configuration will be described.

When reading the reflection original 1, the reflection original 1
Is irradiated from below by the reflection light source 2. As a result, the reflected light from the reflecting original 1 is reflected by the reflecting mirror group 3 a plurality of times, and then is imaged on the imaging lens 4. Then, the photoelectric conversion elements are imaged on the imaging elements 5 arranged in one line, and one line of image data is converted into an electric signal. The optical carriage 6 receives the driving force of the carriage motor 7 via the driving force driving belt 9 and moves in the sub-scanning direction which is a direction perpendicular to the arrangement of the photoelectric conversion elements.
Sequentially reads a plurality of lines in the sub-scanning direction.

In the reading operation of the transparent original 1, the transmitted light from the transparent original 1 illuminated from above by the transmission light source 9 is formed on the imaging lens 4 via the reflection mirror group 3, Thereafter, the photoelectric conversion elements are imaged on the imaging elements 5 arranged in one row, and one line of image data is converted into an electric signal. The reading in the sub-scanning direction is performed by the same operation as in the case of reading the reflection original 1.

Next, detection of the size of the reflection original 1 will be described. When reading the reflection original 1, the reflection light source 2 is turned on, and the reflected light is read by the image sensor 5. When detecting the document size, the transmission light source 10 is turned on with a predetermined light amount (for example, 10,000 lx) instead of the reflection light source 2.

When the reflection original 1 is read in this state, as described above, the amount of light incident on the image sensor 5 is small in the portion where the reflection original 1 is placed, and large in the portion where the reflection original 1 is not placed. The central processing unit 15 detects such a difference between the outputs of the image pickup device 5 and detects the document size (see FIG. 6).

Here, a case will be described in which the light from the transmission light source 10 is not sufficiently blocked by the reflection document 1 because the light transmittance of the reflection document 1 is high.

When the light transmittance of the reflective original 1 is high, the same amount of light as when reading the transparent original 1 (for example, 10,000 lx)
When the reflective original 1 is irradiated with the light, as shown in FIG.
There is little difference in the output of the image sensor 5 depending on the presence or absence of the reflective original 1, and there is a possibility that the original size is erroneously determined.

Therefore, in the image reading apparatus of the present embodiment, when detecting the original size of the reflection original 1, the central processing unit 15 transmits the light from the transmission light source 1 via the light amount control unit 17.
The light amount of 0 is set to, for example, half or less (for example, about 4,000 lx) of reading a transparent original.

Then, as shown in FIG. 3B, the output of the image sensor 5 at the place where the reflective original 1 does not exist is smaller than the output before the light amount is reduced, but at the place where the reflective original 1 exists. In this case, since sufficient light is not transmitted due to the reduction in the amount of light, the output is further reduced. Therefore, FIG.
As shown in (b), when the light amount of the transmission light source 10 is reduced, the difference between the outputs of the image sensor 5 due to the presence or absence of the reflection original 1 increases. Thereby, the reflection original 1 having a high light transmittance is obtained.
Even so, the central processing unit 115 can reliably determine the magnitude of the output, and the original size can be accurately detected by irradiation from the transmission light source 10.

It should be noted that the light amounts shown in the above description are merely examples, and the present invention is not limited to these numerical values, and the output signal of the transmitted light at the location where the reflective original 1 exists is not limited to these values. The light amount of the transmission light source 10 may be reduced to a light amount at which the difference between the output signals at the non-existent portions becomes equal to or higher than a predetermined level at which the document size can be detected.

[0041]

As described above, according to the present invention, the light amount of the transmission light source is adjusted so that the difference between the output signals of the transmitted light at the portion where the reflection original exists and at the portion where the reflection original does not exist becomes a predetermined level or more. Since the document size of the reflection document is detected, an effective effect of being able to accurately detect the document size by irradiation from the transmission light source is obtained even for a reflection document having a high light transmittance.

[Brief description of the drawings]

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

FIG. 2 is a block diagram illustrating a control mechanism of the image reading apparatus of FIG. 1;

FIGS. 3A and 3B are explanatory diagrams illustrating an example of an output of an image sensor when a document size of a reflection document is read by irradiating a transmission light source;

FIG. 4 is a schematic diagram showing a configuration of a conventional image reading apparatus.

FIG. 5 is a block diagram illustrating a control mechanism of the image reading apparatus of FIG. 4;

FIG. 6 is an explanatory diagram showing an example of an output of an image sensor when a document size of a reflection document is read by irradiating a transmission light source;

FIG. 7 is an explanatory diagram showing another example of the output of the image sensor when the size of the reflection document is read by irradiating the transmission light source;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Original (reflection original / transmission original) 5 Image sensor 10 Transmission light source 15 Central processing means (original size detection means) 17 Light intensity control means

Claims (1)

[Claims] A transmission light source for irradiating the reflection original or the transmission original when detecting the original size of the reflection original and reading the transmission original; a light amount control unit for adjusting an irradiation light amount of the transmission light source; An image sensor that receives transmitted light when irradiating the reflective original and converts it into an electric signal; and an output signal of transmitted light at a location where the reflective original exists and a transmission signal at a location where the reflective original does not exist. A document size detecting means for adjusting the light quantity of the transmission light source via the light quantity control means so as to make the difference between the output signals equal to or more than a predetermined level and detecting the document size of the reflection document. Reader.