JP2001285586A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reader that can reliably sense original edge information, even when the original is of translucent nature, such as a thin paper sheet or an overhead projector OHP sheet. SOLUTION: The image reader where light from a light source is emitted onto an image read face of an original placed on an original platen, while an original cover is laid over and an image read sensor receives the reflected light to read the original is provided with a specific pattern formed by applying a reaction material which reflects invisible light of a specific wavelength to the entire face of the original cover opposite to the original platen, a specific sensor for sensing the invisible light with the specific wavelength to obtain the original edge information, first and second storage means, that store a detection signal from the specific sensor as both initial image data, corresponding to a state where no original is placed and original image data corresponding to a state where the original is placed, and a detection means that compares the signals of the initial image data and the original image data stored in the first and second storage means, so as to calculate the light transmittance of the specific pattern in the original image data, thereby detecting the original information.

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 for reading a document placed on a document table.
In particular, the present invention relates to an image reading device used in an image forming apparatus having at least a copying function.

[0002]

2. Description of the Related Art An image forming apparatus (copying machine) having a normal copying function, when reading a document, mounts the document directly on a platen, The document is conveyed onto the document table by the automatic document feeder, and the document is read by the optical system with the document cover covered.

The copying machine has a function of automatically detecting the size of the document and selecting an appropriate sheet for copying (automatic sheet size selection function), an automatic magnification selection function, a black frame erasing function, and the like. It is normal to be. Then, in order to detect the document size in each of the above functions, the contour (edge) of the document placed on the document table is detected.

[0004] Normal document edge detection is performed based on the difference in density level between the document edge and the document cover. In this case, the document edge may not be accurately detected due to the color and thickness of the document. For example, when the color of the document and the color of the document cover are close to each other, a sufficient difference in density level between the edge of the document and the document cover may not occur, and the document edge may not be detected. Normally, the paper used in the original is white paper, and the color of the surface of the original cover facing the original is also white. Therefore, in the above method, the edge detection density is reduced even in a translucent original such as OHP.

Therefore, methods for more accurately detecting the edge of a document are disclosed in, for example, Japanese Patent Application Laid-Open Nos. 1-17562 and 8-139848. In the method disclosed in Japanese Patent Application Laid-Open No. 1-17562, a black-and-white pattern is formed on the surface of the document cover facing the document reading unit. The black-and-white pattern is a striped pattern formed to be inclined with respect to each side of the document. When the document is a positive image, the edges of the document are clearly recognized by the black pattern, and the document is negative. In the case of an image, the edge of the document is clearly recognized by the white pattern.

However, according to the method described in the above publication, in the case of a light-transmitting original such as thin paper or an OHP sheet, the black and white pattern formed on the original cover at the time of copying is simultaneously copied in the copy image. There is a problem.

In the method disclosed in Japanese Patent Application Laid-Open No. Hei 8-139848, an absorbing material that absorbs light (for example, infrared light) in an invisible light region is applied to the surface of the original cover facing the original reading unit, and the invisible light is applied. The edge of the document is detected by detecting the non-visible region light reflected from the document by a sensor that detects the light region light. That is, in the above method, when a document is placed on the document table, reflected light of infrared light from the document is detected in the document region, and infrared light is absorbed by the document cover in a region where there is no document. This makes it possible to detect a document edge based on a difference in detection level of the infrared sensor.

However, according to the method described in the above publication, for a light-transmitting original such as thin paper or an OHP sheet, infrared rays emitted from the light source toward the original are transmitted through the original and the original cover is not covered. Is absorbed by the infrared absorbing material applied to the surface. For this reason, the difference in the detection level of the infrared sensor between the area where the document exists and the other area becomes smaller,
There is a problem that it is difficult to detect a translucent document.

Further, in the above method, the image data of the original is read by each of the R, G, and B sensors, and these sensors also detect invisible light to some extent. For this reason, in each of the R, G, and B sensors, the light in the invisible region is cut by a filter in order to eliminate the influence of the invisible light, and the cost is increased by requiring the filter.

The present invention has been made in view of the above circumstances, and is capable of reliably detecting original edge information even when the original is a light-transmitting original such as thin paper or an OHP sheet. An apparatus is provided.

[0011]

SUMMARY OF THE INVENTION According to the present invention, an image reading surface is irradiated with light from a light source on a document placed on a document table in a state where a document cover is covered, and the reflected light is reflected by an image reading sensor. In the image reading apparatus that reads the original by receiving the original at a specific pattern formed by applying a reactive material that reflects invisible light of a specific wavelength on the entire surface of the original cover facing the original plate, A special sensor that obtains document edge information by sensing non-visible light of a specific wavelength, and a detection signal from the special sensor is converted to initial image data corresponding to a state where the document is not placed in advance, and a state where the document is placed. First and second storage means for storing both the corresponding original image data, and comparing the signals of the original image data and the original image data stored in the first and second storage means, and comparing the original image data with the original image data. There is provided an image reading apparatus having a detecting means for detecting the original information by calculating the light transmission of a specific pattern.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a transparent plate, for example, a plate made of glass can be used as a document table. In that case, a material that hardly absorbs invisible light,
For example, it is preferable to use a material such as an ultraviolet transmitting glass.

The document cover may be of any type as long as it covers the document table and can shield light. For example, a cover made of plastic or metal may be used.

The specific pattern provided on the surface of the document cover facing the document table can be provided by applying an ink which strongly reflects invisible light in a pattern having a predetermined shape.

The shape of the specific pattern can be various shapes such as a lattice shape and a diagonal line shape. For example,
In the case of a grid shape, the grid can be a grid of about 1 mm to about 5 mm, and the thickness of the line of the specific pattern is about 1 mm.
mm to about 5 mm. Although the specific pattern is a fine pattern, the detection accuracy of the document edge information can be improved.However, the number of pixels to be processed by the detecting means when detecting the document edge information by the finer pattern of the specific pattern. Will increase.

The ink that reflects non-visible light does not necessarily have to be in the form of a pattern. For example, the non-visible light reflecting layer formed by coating the entire surface of the document cover facing the document table may be a non-visible light reflecting layer. Is also good. However, in order to reduce the number of pixels to be processed by the detection means, it is preferable that the detection means has a pattern.

The special sensor may be any sensor that can sense the reflected light in the invisible light region and convert it into an electrical detection signal.

In this specification, a location where the detection signal from the special sensor is stored as initial image data in which no original is placed on the original table is referred to as first storage means. Also,
The location where the detection signal from the special sensor is stored as document image data of a document placed on a document table is referred to as second storage means.

The initial image data is image data in a state where no original is placed on the original platen. On the other hand, original image data is an image data in a state where an original is placed on the original platen. That is. The first and second storage means only need to be able to separately store the detection signal by the special sensor before the document is placed and after the document is placed.
The first and second storage units may be provided separately, or one storage unit may be divided into two storage areas.

As a specific storage means, for example, a RAM
Etc. can be used. In addition, the initial image data and the original image data from the special sensor are
The data may be compressed and stored in the storage means, and the compressed data may be sequentially restored to be processed by the detection means. With this configuration, the memory size required by the first and second storage units can be reduced.

The detecting means compares the signal of the original image data with the signal of the original image data stored in the first and second storage means to calculate the light transmittance of a specific pattern in the original image data. It is used for detecting edge information of a document based on the light transmittance of a specific pattern. The detection means may be any as long as it can achieve the above functions, and for example, a microcomputer having a CPU, a ROM, a RAM, and the like can be used.

The light transmittance of the specific pattern calculated by the detecting means is, specifically, the density value of the specific pattern in the original image data stored in the second storage means,
A value obtained by dividing by a density value of a specific pattern in the initial image data stored in the storage means. The density value is
Each pixel constituting a specific pattern in the original image data;
It is calculated on a pixel-by-pixel basis by comparing the density values of the pixels that correspond in position on the image reading surface among the pixels that form the specific pattern in the initial image data.

In the image reading apparatus according to the present invention, the detecting means compares the light transmittance of each pixel on the image reading surface with a preset threshold value to thereby make the entire image reading surface non-translucent. Are divided into a first area where the original exists, a second area where the original does not exist, and a third area where there is a possibility that the translucent original exists. If the third area is present in terms of area, This area may be determined as an area where a translucent document exists, and document edge information may be detected.

Here, the preset threshold value is a value arbitrarily set between 100% and 0% light transmittance. Specifically, for example, the determined light transmittance is 100
If it falls within the range of 90% to 90%, it is determined that there is no original, and if it falls within the range of 90% to 30%, it is determined that there is a possibility that there is a translucent original. 30
If it falls within the range of 0% to 0%, it is determined that the area includes the non-light-transmitting original.

According to the present invention, as described above, the detecting means calculates the light transmittance of the pattern by comparing the specific pattern in the initial image data with the specific pattern in the original image data,
The platen is set to the first position based on the calculated light transmittance of the pattern.
To the third region. If the document is non-translucent, the boundary between the first and second areas is traced and the trace is determined to be the edge of the document, while if the document is translucent, The boundary between the first area and the third area is traced, and the trace is determined to be the edge of the document. Therefore, it is preferable that the invisible light that irradiates the specific pattern has low light transmittance when transmitted through the translucent document, that is, is invisible light that is easily absorbed by the translucent document. As such invisible light, for example, a wavelength of 3
Ultraviolet light of about 00 nm to 380 nm can be used.

According to the image reading apparatus of the present invention, the invisible light which is easily absorbed by the translucent original as described above is used, and the detecting means calculates the light transmittance of a specific pattern in the original image data. The image reading area is divided into one of the first to third areas based on the calculated light transmittance. This makes it possible to reliably detect edge information of a light-transmissive original such as thin paper or an OHP sheet, which is difficult with an image reading apparatus.

In the image reading apparatus according to the present invention, the detection signal from the image reading sensor is converted into initial image data corresponding to a state where no original is placed and original image data corresponding to a state where the original is placed. A third and a fourth storage unit for storing the image data on both sides of the image reading surface. The specific pattern in the document image data in the fourth storage unit may be deleted by subtracting the initial image data in the storage unit. Here, the image reading sensor is a sensor that senses visible light and reads a document image to be output from the image reading device.

The image reading sensor originally senses visible light, but may actually slightly sense invisible light reflected from a specific pattern on the document cover. For this reason, when the original is translucent, if the original image data sensed by the image reading sensor is output as it is, a specific pattern may appear in the original image. In order to prevent such a phenomenon, the original image data in the second storage means
The initial image data in the first storage means is subtracted and output, thereby preventing a specific pattern from appearing in the original image.

In the original image data of the first storage means, if the specific pattern and the characters of the original are stored in a state of being overlapped with each other, the character of the portion which overlaps with the specific pattern when the initial image data is subtracted. And so on may be erased together. In such a case, erased characters and the like may be complemented by image processing.

In the image reading apparatus according to the present invention, the initial image data in the first storage means may be updated to the latest initial image data after a predetermined time has elapsed and after a predetermined number of documents have been read. .

In this way, the initial image data stored in the first storage means can always be updated, so that the original cover may become dirty due to long-term use, or the amount of irradiated light may decrease. However, data inconsistency does not occur between the original image data and the original image data stored in the second storage means. The predetermined time can be, for example, every day or every several days, and the predetermined number of sheets can be, for example, every 1000 readings, every 10,000 readings, or the like.

In the image reading apparatus according to the present invention, the light source may emit visible light and invisible light, and the invisible light may be invisible light having wavelengths in a plurality of different wavelength ranges. This is because, depending on the type of the original, even if the original is translucent, the invisible light of a specific wavelength is absorbed without being transmitted, so that the special sensor cannot detect the invisible light transmitted through the original. To deal with that.

If the invisible light is invisible light having wavelengths in a plurality of different wavelength ranges, the document edge information can be detected by the invisible light in any one of the wavelength ranges. When the light source is configured to emit invisible light having a wavelength in a different wavelength range, it is necessary to additionally provide a special sensor and a storage unit so as to correspond to each wavelength range. If a plurality of types of specific patterns are provided, and these specific patterns reflect invisible light having wavelengths in a plurality of different wavelength ranges, processing with higher accuracy based on a plurality of pieces of information can be performed.

In the image reading apparatus of the present invention, the first
Since the document edge information is detected by tracing the boundary between the region and the second region or the boundary between the first region and the third region,
Document edge information can be accurately detected even if the document is a document of any shape other than a rectangular document. Also, edge information of a perforated document can be detected. Furthermore, in addition to the determination of the document size based on the detected document edge information, skew correction (correction of document tilt and rotation) can be performed.

Note that the image reading apparatus of the present invention is not necessarily limited to an apparatus used by being incorporated in an image forming apparatus having a copying function and the like, and may be used alone as an image reading apparatus such as a scanner. it can.

[0036]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on embodiments shown in the drawings. The present invention is not limited by the embodiment.

An embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, an image reading apparatus 1 includes a light source 5 on an image reading surface of a document (not shown) placed on a document table 2 with a document cover 4 covered.
The original is read by receiving the reflected light from the image reading sensor 6 and reading the original. A reactive material that reflects ultraviolet light is applied to the entire surface of the original cover 4 facing the original table 2. A special pattern 7 formed by performing the above operation, a special sensor 7 which detects original light by detecting ultraviolet light,
First and second storage means 8a for storing detection signals from the special sensor 7 both as initial image data corresponding to a state where no original is placed and original image data corresponding to a state where an original is placed. , 8b and the signals of the original image data and the original image data stored in the first and second storage means 8a, 8b are compared to calculate the light transmittance of the specific pattern 3 in the original image data. A detecting means 9 for detecting information is provided.

The document table 2 is made of an ultraviolet transmitting glass. The light source 5 can emit visible light and ultraviolet light, and is unitized with the first mirror 10 to form the first light source.
The unit 11 is constituted. The first unit 11 can move along the document table 2 from left to right at a constant speed. Second
Second unit 14 including mirror 12 and third mirror 13
When the first unit 11 moves, the first unit 1
It moves at half the speed of one. As a result, the document cover 4 and the document are irradiated with visible light and ultraviolet light for each line, and the visible light and the ultraviolet light reflected from the document cover 4 and the document are reflected by the first mirror 10, the second mirror 12,
The light is guided to a spectral mirror (dichroic mirror) 16 via a third mirror 13 and a lens 15 in this order.

Of the visible light and the ultraviolet light guided to the spectral mirror 16, the visible light passes through the spectral mirror 16, while
The ultraviolet light is reflected by the spectroscopic mirror 16 and its direction is changed. The visible light transmitted through the spectral mirror 16 is sensed by the image reading sensor 6 and converted into an electrical detection signal, while the ultraviolet light reflected from the spectral mirror 16 is sensed by the special sensor 7 and converted into an electrical detection signal. Is converted. Note that the image reading apparatus 1 detects the detection signal from the image reading sensor 6 that senses visible light, using both the initial image data when the document is not placed on the platen and the document image data when the document is placed on the platen. Further, there are provided third and fourth storage means 8c and 8d for storing the data in.

The lattice-shaped specific pattern 3 shown in FIG. 2 is formed on the document cover 4 by ultraviolet light reflective ink which strongly reflects ultraviolet light having a wavelength of about 300 nm to 380 nm. The grid of the specific pattern 3 is about 5 mm square, and the line thickness of the specific pattern 3 is about 5 mm.

The image reading sensor 6 shown in FIG. 1 is a CCD sensor and can detect visible light having a wavelength of about 380 nm to 780 nm and convert it into an electrical detection signal. It is not necessary to provide the image reading sensor 6 with a filter for cutting off ultraviolet light. This is because image processing is performed based on the flow of FIG.

On the other hand, the special sensor 7 has a wavelength of about 300 nm
380 nm ultraviolet light can be sensed and converted to an electrical detection signal.

The light source 5 is used for reading an original.
Visible light having a wavelength of 80 nm to 780 nm and ultraviolet light having a wavelength of about 300 nm to 380 nm for irradiating the specific pattern 3 can be irradiated.

As shown in the block diagram of FIG. 3, the detection signal input via the image reading sensor 6 is stored in the third and fourth storage means 8c and 8d, and the detection signal input via the special sensor 7 The signal is stored in the first and second storage means 8a, 8b. The detection signal from the image reading sensor 6 before the document is placed is stored as initial image data in the third storage unit 8c, while the image reading sensor 6 after the document is placed is stored in the fourth storage unit 8d. Is stored as original image data. The detection signal from the special sensor 7 before the document is placed is stored in the first storage means 8a as initial image data, while the detection signal from the special sensor 7 after the document is placed is stored in the second storage means 8b. The detection signal is stored as document image data.

The comparison section 9a of the detection section 9 compares the initial image data stored in the first storage section 8a with the original image data stored in the second storage section 8b. If the document is found to be translucent by the comparison result of the comparing unit 9a,
The specific pattern erasing unit 9c performs a process of subtracting the initial image data stored in the first storage unit 8a from the original image data stored in the second storage unit 8b, thereby deleting the specific pattern 3 reflected in the original image. I do. Also, based on the comparison result of the comparison unit 9a, the document edge detection unit 9b detects the edge of the document, and based on the detected document edge information, the document image selection unit 9d calculates the document image data from the document image data stored in the first storage unit. A document image (document area) is selected, and the image reading is completed.

As shown in FIG. 4, the specific pattern 3 appears faintly in the image of the initial image data stored in the third storage means 8c (FIGS. 1 and 3). This is because the image reading sensor 6 (FIGS. 1 and 3) originally senses only visible light, but actually also slightly senses ultraviolet light. As shown in FIG. 5, the specific pattern 3 is clearly shown in the image of the initial image data stored in the first storage unit 8a (FIGS. 1 and 3). This is because the specific pattern 3 strongly reflects ultraviolet light and the special sensor 7 (FIGS. 1 and 3) can detect ultraviolet light.

When an opaque original is placed as shown in FIG. 6, the image of the original image data stored in the fourth storage means 8d (FIGS. 1 and 3) is an opaque rectangular original. 17
The specific pattern 3 is missing in the region where the original 18 having a non-translucent shape is placed. When a non-translucent document is placed as shown in FIG. 7, the image of the document image data stored in the second storage means 8b (FIGS. 1 and 3) is also changed to the non-transparent rectangular document 17. The specific pattern 3 is missing in the region where the original 18 having a non-translucent shape is placed. Note that the first region 21 and the second region 2
2 will be described in detail when described later with reference to the flowchart of FIG.

When a translucent original is placed as shown in FIG. 8, the image of the original image data stored in the fourth storage means 8d is a translucent rectangular original 19 or a translucent arbitrary-shaped original 20. The specific pattern 3 is slightly faintly reflected in the area where is placed. Further, as shown in FIG. 9, when a translucent document is placed, the second storage unit 8b
The specific pattern 3 is lightly reflected in the area where the translucent rectangular original 19 and the translucent arbitrary-shaped original 20 are placed. The third region 23 will be described in detail when it is described later with reference to the flowchart of FIG.

That is, as shown in FIGS. 8 and 9, in the region where the translucent rectangular original 19 and the translucent arbitrary-shaped original 20 are placed, the light transmittance of the specific pattern 3 is reduced and the image reading is performed. It is detected by the sensor 6 and the special sensor 7 (FIGS. 1 and 3).

A method for detecting the document edge information by the image reading apparatus 1 shown in FIG. 1 will be described with reference to a flowchart shown in FIG. The first and third storage means 8
It is assumed that initial image data are already stored in a and 8c. When the document image data is input, in step 1, the document image data is stored in the second and fourth storage units 8b and 8d, respectively.

Next, the process proceeds to step 2, where the first storage means 8
a and the second image data (see FIG. 5)
The light transmittance of the specific pattern 3 in the document image data is calculated by comparing the document image data (see FIG. 7 or FIG. 9) stored in the storage unit 8b with the detection unit 9. Here, the light transmittance of the specific pattern 3 is (density value of the specific pattern 3 in the original image data) / (density value of the specific pattern 3 in the initial image data). It is calculated on a pixel-by-pixel basis by taking the ratio of the densities of the pixels that correspond in position on the image reading surface among the constituent pixels of the specific pattern 3 in the image data.

The light transmittance of the specific pixel constituting the specific pattern 3 in the original image data calculated in this way is:
Threshold values L0 to L3 (light transmittance 0% = L0 <L) shown in FIG.
1 <L2 <L3 = light transmittance 100%). In the examples, the threshold value L1 was set to 30% light transmittance, and L2 was set to 90% light transmittance. Next, proceeding to step 3, it is determined whether or not the light transmittance determined in step 2 satisfies a condition of L2 <light transmittance ≦ L3. Region 21 (FIG. 7)
And FIG. 9).

On the other hand, in step 3, L2 <light transmittance ≦ L3
If the condition is not satisfied, the process proceeds to step 5, where the light transmittance determined in step 2 is L0 ≦ light transmittance <L1
It is determined whether or not the condition of (FIG. 11) is satisfied. If so, the process proceeds to step 6 where it is determined that the pixel constitutes the second area 22 (see FIG. 7) where the non-light-transmitting document exists.

If none of the conditions in Steps 3 and 5 is satisfied, the process proceeds to Step 7 in which the pixels constituting the third area 23 (see FIG. 9) in which a translucent document may be present exist. Is determined. This is because the light transmittance of a pixel determined as No in both Step 3 and Step 5 always satisfies the condition of L1 <light transmittance <L2 (FIG. 11).

When step 7 is completed, the process proceeds to step 8 where it is determined whether or not the processing of steps 2 to 7 has been completed for all the pixels constituting the specific pattern 3 on the image reading surface. If not, the process proceeds to step 9 to change the pixel of interest and returns to step 2. By repeating the above steps, the specific pattern 3 on the image reading surface
Is divided into any of the first to third regions.

If it is determined in step 8 that the processing has been completed for all the pixels, the process proceeds to step 10 where the boundary between the first area 21 and the second area 22 (see FIG. 7) is traced, and the trace is traced. It is determined that the edge is a non-translucent original. When Step 10 is completed, the process proceeds to Step 11, and the third area 23 determined in Step 7 (see FIG. 9).
Is determined in terms of area. Third area 23
Is present in the area, it is determined that a translucent document exists in the third region 23. On the other hand, when the third area 23 does not exist in terms of area, it is determined that the third area is caused by dust on the document table 2 or the like.

If it is determined in step 11 that the third area 23 is a translucent original, the process proceeds to step 12 and the first area 2
Trace the boundary between the first region and the third region 23 (see FIG. 9),
The trace is determined to be the edge of the translucent document.

When the edge of the translucent original is determined in step 12, the process proceeds to step 13, where the original image data (see FIG. 8) in the fourth storage unit 8d is converted to the initial image data (see FIG. 4) in the third storage unit 8c. (See Reference). This is because the image reading sensor 6 (FIG. 1) that senses visible light also slightly detects the specific pattern 3, so that if the original image data of the fourth storage unit 8d is output as it is, the specific pattern 3 is included in the output image. This is because it may be reflected and become unsightly.

If step 13 is completed or if it is determined in step 11 that the third region is not large, step 1
Proceeding to step 4, it is determined whether or not the processing of steps 10 to 13 has been completed for all of the first, second, and third areas 21, 22, and 23 (see FIGS. 7 and 9). If the processing has not been completed for all the areas, the process returns to step 10 and steps 10 to 10 until the processing has been completed for all the areas.
Step 14 is repeated. On the other hand, if the processing has been completed for all areas, the process proceeds to step 15 and
Alternatively, a document image is selected from the document image data in the fourth storage unit 8d based on the document edge information detected in step 12, and the image reading is completed.

[0060]

According to the present invention, a specific pattern for reflecting non-visible light of a specific wavelength is provided on the surface of the document cover facing the document table, and the non-visible light reflected from the specific pattern is sensed by the special sensor. The detection signal from the special sensor is stored in the first and second storage means as both the initial image data when the document is not placed on the platen and the document image data when the document is placed on the platen. The original image data stored in the first and second storage means is compared with the original image data to calculate the light transmittance of a specific pattern in the original image data, and based on the calculated light transmittance of the specific pattern. Since the edge information of the document is detected, even if the document is a light-transmitting document such as thin paper or an OHP sheet, the document edge information can be reliably detected.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram showing a specific pattern formed on a document cover.

FIG. 3 is a block diagram illustrating the relationship and operation of each unit of the image reading apparatus illustrated in FIG. 1;

FIG. 4 is an explanatory diagram showing an image image of initial image data stored in a third storage unit.

FIG. 5 is an explanatory diagram showing an image image of initial image data stored in a first storage means.

FIG. 6 is an explanatory diagram showing an image image of document image data stored in a fourth storage unit when the document is non-translucent.

FIG. 7 is an explanatory diagram showing an image image of document image data stored in a second storage unit when the document is non-translucent.

FIG. 8 is an explanatory diagram showing an image image of document image data stored in a fourth storage unit when the document is translucent.

FIG. 9 is an explanatory diagram showing an image image of document image data stored in a second storage unit when the document is translucent.

10 is a flowchart illustrating a method in which the image reading apparatus shown in FIG. 1 detects document edge information.

FIG. 11 is an explanatory diagram illustrating a relationship between a light transmittance and a threshold, which is a criterion when dividing the image reading surface into first, second, and third regions based on the light transmittance of a specific pattern. .

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Image reading device 2 ... Original platen 3 ... Specific pattern 4 ... Original cover 5 ... Light source 6 ... Image reading sensor 7 ... Special sensor 8a ... First storage Unit 8b Second storage unit 8c Third storage unit 8d Fourth storage unit 9 Detecting unit 10 First mirror 11 First unit 12 Second 2 mirror 13 3rd mirror 14 2nd unit 15 lens 16 spectral mirror

Continued on the front page F term (reference) 2H012 CA07 CA14 2H108 AA01 CA04 CB01 5B047 AA01 BC11 BC14 BC20 CB09 CB12 5C062 AA05 AB03 AB42 AC66 AC67 AD02 AF00 AF07 BA00 5C072 AA01 BA04 BA13 CA02 EA05 LA07 RA02 RA04 VA03 X01

Claims (6)

[Claims] An image reading surface is irradiated with light from a light source while a document placed on a document table is covered with a document cover, and reflected light is received by an image reading sensor to read the document. In the image reading device, a specific pattern formed by applying a reactive material that reflects non-visible light of a specific wavelength is applied to the entire surface of the document cover facing the platen, and the non-visible light of the specific wavelength is sensed. A special sensor that obtains document edge information, and outputs a detection signal from the special sensor to both original image data corresponding to a state where a document is not placed in advance and document image data corresponding to a state where a document is placed. And comparing the signals of the original image data and the original image data stored in the first and second storage means with each other to determine the light transmittance of a specific pattern in the original image data. An image reading apparatus comprising a detecting unit for detecting document information by calculating. 2. The image forming apparatus according to claim 1, wherein the detecting unit compares the light transmittance of each pixel on the image reading surface with a preset threshold value, so that the entire image reading surface has a first area where a non-light-transmitting original exists. And a second area where a document does not exist, and a third area where a translucent document may exist.
2. The image reading apparatus according to claim 1, wherein when the area exists in terms of area, the area is determined to be an area where a translucent document exists, and document edge information is detected. 3. A detection signal from the image reading sensor,
The apparatus further includes third and fourth storage means for storing both initial image data corresponding to a state where a document is not placed in advance and document image data corresponding to a state where a document is placed. When it is determined that a translucent document exists on the image reading surface, the initial image data in the third storage device is subtracted from the document image data in the fourth storage device to specify the document image data in the fourth storage device. 3. The image reading device according to claim 2, wherein the pattern is erased. 4. The image according to claim 1, wherein the initial image data in the first storage unit is updated to the latest initial image data after a predetermined time has elapsed and after a predetermined number of documents have been read. Reader. 5. The image according to claim 1, wherein the light source emits visible light and invisible light, and the invisible light is invisible light having wavelengths in a plurality of different wavelength ranges. Reader. 6. The image reading apparatus according to claim 1, wherein the specific pattern has a lattice shape.