JPH09274263A - Original size/position detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely detect the size and the position at an original even when the density thereof is high and reflected light quantity is small. SOLUTION: An original pressing plate 101 is irradiated with light from a light source 104. With the reflected light thereof, the original 103 placed on a contact glass 102 is irradiated from the upper part. Besides, the reflected light is received by a photodetector 106 arranged at the lower part of the original 103. Therefore, the reflected light is received at a position where the original 103 does not exist and shielded by the original 103 at a position where the original 103 exists. Thus, the existence of the original is discriminated by the level of the received light.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a document size / position detecting device used in a copying machine, an image scanner, or the like, and more specifically, when a document pressure plate is opened, light is emitted to the inside of the document pressure plate. The present invention relates to a document size / position detection device that detects position information and size of a document by utilizing that the reflected light obtained by the irradiation is blocked by the document placed on the contact glass.

[0002]

2. Description of the Related Art A document size / position detecting device for detecting size and position information of a document placed on a contact glass surface is disclosed in, for example, Japanese Patent Laid-Open No. 5-58510, "Document Detection Sensor". There is something. As shown in FIG. 10, this document detecting sensor is provided with a light emitting element 10
01, light projecting lens 1002, one grating 1003, light receiving lens 1004, and three light receiving elements 1
And 005.

In such a structure, the light emitting device 100
The light from No. 1 is supplied to the grating 1003 via the light projecting lens 1002, the three projection beams B from the grating 1003 are applied to the original G, and the reflected light L from the predetermined original detection point P on the original G is reflected. Respectively enter the corresponding light receiving element 1005 via the light receiving lens 1004. Each light receiving element 1005 generates a signal according to the amount of light received, and is processed by a level discrimination circuit (not shown) to determine the presence or absence of a document at each document detection point P.

It should be noted that such an operation for detecting the size and position of the original document is usually executed when the original document cover (original pressure plate) is closed. This is because it may be difficult to distinguish between the document cover and the document when the document cover is closed.

[0005]

However, according to the above conventional technique, the size and position of the document are detected before the document cover is completely closed.
At such a detection timing, since the document cover and the document are close to each other, when the document density is high, the difference between the intensity of the reflected light from the document and the intensity of the reflected light from the document cover becomes very small. However, there is a problem in that the difference in the reflected light intensities is reversed, which may prevent accurate detection.

The present invention has been made in view of the above, and even when the original density is high and the reflected light is small,
It is intended to accurately detect the size and position of a document.

[0007]

In order to achieve the above object, in the document size / position detection device according to the first aspect, the size and position information of a document placed on the contact glass surface is stored. In the document size / position detection device for detecting, a light irradiating means which is disposed at a position above the contact glass and which irradiates the document pressure plate for pressing the document against the contact glass with light, and the contact glass A light receiving means disposed at a lower position and receiving reflected light of the light emitted to the original pressure plate, the light emitting means irradiates and scatters light on the original pressure plate to receive the light. Means for detecting reflected light from the original pressure plate by the original placed on the contact glass surface to detect size and position information of the original. That.

That is, light is emitted from the light irradiating means to the original pressure plate, the reflected light is emitted from above the original placed on the contact glass, and the light is received by the light receiving means arranged below the original. It is a thing. Therefore, the reflected light is received at the position where the document does not exist, and the reflected light is blocked at the position where the document exists, so that the presence or absence of the document is determined from the received light level.

Further, in the document size / position detecting device according to the second aspect of the present invention, further, the detection point of the contact glass which is arranged between the contact glass and the light receiving means and which is preset is scanned. The light deflection scanning means for guiding the reflected light from the original pressure plate corresponding to the scanning position to the light receiving means is provided.

That is, by scanning the detection point on the contact glass with the optical deflection scanning means, the coordinate information of the original on the scanning line can be obtained.

Further, in the document size / position detecting device according to the third aspect, a plurality of light irradiating means for irradiating light to different positions of the document pressure plate, and a plurality of light irradiating means, respectively. And a plurality of light receiving means arranged correspondingly.

That is, by providing a plurality of light irradiating means and a light receiving means at a position corresponding to an optical axis irradiated by the light irradiating means, it becomes possible to detect each arbitrary position on the contact glass. The position of multiple points can be detected and the position can be detected with a small amount of light.

Further, in the document size / position detecting apparatus according to the fourth aspect, the light irradiating means irradiates the surface of the document pressure plate with light condensed into a linear shape, and further the linear shape irradiation. It is provided with a light receiving scanning means for scanning light and guiding it to the light receiving means.

That is, by irradiating the original platen with light condensed in a linear shape, irradiating the reflected light obtained by the irradiating light from above the contact glass, and scanning the light transmitted through the contact glass to the light receiving portion. Linear detection is possible, and the size and displacement of the original can be easily obtained.

Further, in the document size / position detecting device according to a fifth aspect, further, there is provided an opening / closing angle detecting means for detecting an opening / closing angle of the original pressure plate, and the substantially parallel light is emitted from the light irradiating means. The original pressure plate is irradiated, and scanning is performed by changing the irradiation position of the original pressure plate depending on the open / closed state of the original pressure plate, and scanning is performed by the light receiving means on the contact glass corresponding to the opening / closing angle of the opening / closing angle detecting means. This is to detect the reflected light at the position.

That is, the change in the detected position on the contact glass due to the opening / closing angle of the original platen is detected by the opening / closing angle detecting means, and the detected angle is used to provide position information (scanning information) on the contact glass to the received reflected light. It is given and the position on the contact glass is obtained accurately.

Further, in the document size / position detecting device according to the sixth aspect, the light irradiating means vertically scans and irradiates light substantially parallel to the document pressure plate, and the light receiving means, Reflected light from the document pressure plate scanned by the light of the light irradiation means is detected for each scanning position, and the document is detected based on the position where the reflected light is blocked. .

That is, light that is substantially parallel to the document pressure plate is vertically scanned and irradiated, the reflected light is detected for each scanning position, and the document is detected based on the position where the scanning light is cut by the document.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment], [Second Embodiment], [Third Embodiment], [Fourth Embodiment], [Embodiment] of a document size / position detecting device of the present invention. Embodiment 5] and [Embodiment 6] will be described in detail with reference to the drawings.

[First Embodiment] (Structure of First Embodiment) FIG. 1 is an explanatory diagram showing the structure of a document size / position detecting apparatus according to the first embodiment. In the figure, 101 is a document pressing plate that presses a document to be read from above, 102 is a contact glass for placing the document, 103 is a document to be read, and the document is placed on the surface of the contact glass 102. Is shown.

Further, 104 is a light source as a light irradiating means for irradiating the inside of the original pressure plate 101 with light, and 105 is a light source 10.
The light irradiated by 4 is reflected by the manuscript pressure plate 101, and a light receiving lens for collecting and forming an image of the reflected light on a light receiving element 106, which will be described later, receives the reflected light collected by the light receiving lens 105. The light receiving element serves as a light receiving means for photoelectrically converting and outputting a light receiving signal according to the intensity of the reflected light. The light receiving signal output from the light receiving element 106 is sent to a detection / processing circuit (not shown).

(Operation of Embodiment 1) The operation of the above configuration will be described. The light emitted from the light source 104 is applied to the entire inside of the original pressure plate 101 as shown in FIG. At this time, it is desirable to uniformly irradiate the entire inside of the original pressure plate 101. Therefore, the light source 104 may have a linear shape such as a fluorescent lamp. Further, in consideration of economy, a light source with low power consumption such as an LED is suitable.

The inside of the original pressure plate 101 is made of general white resin or fiber material, and the light source 104 is provided on the surface thereof.
When the above-mentioned light is irradiated, light scattering occurs and the whole emits light like a surface light source.

This radiated light (reflected light) is transmitted through the contact glass 102 and focused on the light receiving element 106 via the light receiving lens 105 in a portion of the contact glass 102 where the original 103 is not present. That is, the light receiving element 106 is placed at the detection point of the contact glass 102 at the original 10
If there is no document 3, the reflected light from the document pressure plate 101 is received, and if there is a document 103, the document 103 blocks the reflected light. Therefore, the presence or absence of the document 103 at the detection point can be determined by not receiving the light reception signal.

The detection timing is the original pressure plate 1
Since it is desirable that the reflected light from 01 irradiates almost the entire surface of the contact glass 102, it is preferable immediately before the document pressure plate 101 is closed.

Further, although one light receiving portion is shown for the detection point in FIG. 1, other configurations may be adopted as shown in FIGS. 2 and 3.

That is, in FIG. 2, characteristic points of various document sizes are set as detection points, and light receiving portions (light receiving lenses 105a to 105c and light receiving elements 106a to 106c) are provided corresponding to the characteristic points, whereby By the same operation as described above, it becomes possible to discriminate the standard size original 103.

Further, as shown in FIG.
It is also possible to use the lateral magnification of 5 to detect a plurality of detection points with one light receiving lens 105. Further, the resolution of the detection point can be changed by changing the light receiving area of the light receiving element 106 or providing an aperture in the light receiving element 106.

(Effect of First Embodiment) Therefore, according to the first embodiment, in the opened state of the document pressure plate 101, the reflected light obtained by irradiating the inner surface of the original plate 101 with light is received by the light receiving portion (light receiving lens). 105, the light receiving element 106), so that a reliable document 10 that is not affected by the density of the document
3 can be detected.

[Second Embodiment] (Structure of Second Embodiment) FIG. 4 is an explanatory view showing the structure of a document size / position detecting apparatus according to the second embodiment. Here, in addition to the configuration of FIG.
A rotary prism 401 having an optical deflection scanning function as an optical deflection scanning unit for scanning a detection point is provided between the contact glass 102 and the contact glass 102. Therefore, the other components and their functions are similar to those in FIG.
The same reference numerals are given and the description thereof is omitted.

In order to realize this light deflection scanning function, the light for scanning the detection point on the contact glass 102 is deflected,
Rotating prism 4 capable of changing its deflection direction
01 is used. The prism has a high deflection efficiency, and circular scanning is possible simply by rotating the prism.

Further, as another means for realizing the optical deflection scanning function, a rotating mirror or a hollow scanner can be considered. Each means has advantages and disadvantages depending on the application, but the present invention can be realized by using any means.

(Operation of the Second Embodiment) Next, the operation of the document size / position detecting device configured as described above will be described. In FIG. 4, the light source 1 is the same as in FIG.
As shown in FIG.
The entire inside of 01 is irradiated. When the surface is irradiated with the light of the light source 104, light scattering occurs and the entire surface emits light like a surface light source.

This emitted light (reflected light) is reflected by the rotating prism 4
After passing through 01, the light enters the light receiving element 106 through the light receiving lens 105 in the portion where the document 103 is not present. That is, if the original 103 is not present at the detection point of the contact glass 102, the reflected light from the original pressure plate 101 is received and the original 10 is detected.
When there is 3, the reflected light is blocked by the original 103. Therefore, the presence or absence of the document 103 at the detection point is determined by not receiving the light reception signal.

As described above, by using the rotating prism 401, the presence or absence of the original 103 at the detection point (scanned position) can be determined. In particular, the rotating prism 401
It is possible to detect the original 103 of an arbitrary size or obtain the original position information by setting the locus to be scanned with or the position of the locus / position where a lot of information can be obtained, or by increasing the number of this apparatus. it can.

Further, in addition to the structure shown in FIG. 4, as shown in FIG.
The decentered rotation lens 501 having one function may be used.
Also in this case, the same function as in FIG. 4 can be obtained, and moreover,
It is also effective for cost reduction by reducing the number of parts.

(Effect of Embodiment 2) Therefore, according to Embodiment 2 above, in addition to the effect of Embodiment 1 described above, position information of the document 103 at arbitrary plural detection points can be obtained. The size of the document, the position shift of the document 103, and the like can be detected.

[Third Embodiment] (Structure of Third Embodiment) FIG. 6 is an explanatory view showing the structure of a document size / position detecting apparatus according to the third embodiment. Here, in addition to the configuration of FIG.
a. 104b are provided, and correspondingly, a plurality of light receiving portions are installed such as light receiving lenses 105a and 105b and light receiving elements 106a and 106b. Therefore, the other components and their functions are the same as those in FIG. 1, so the same reference numerals as those in FIG.

(Operation of the Third Embodiment) Next, the operation of the document size / position detecting device configured as described above will be described. In the third embodiment, the light sources 104a and 10a
The light emitted from 4b is not irradiated onto the entire inner surface of the original pressure plate 101, but is condensed and irradiated onto the contact glass 102 at a position corresponding to a predetermined position to be detected.

The light emitted from the light sources 104a and 104b is condensed inside the original pressure plate 101, scattered, and then guided to the light receiving portion. The light receiving section 105a, the light receiving lens 105a, sets a predetermined position on the contact glass 102 as a detection point.
Since 105b and the light receiving elements 106a and 106b are arranged, the scattered light is guided to the light receiving elements 106a and 106b with the original pressure plate 101 opened. As a result, a detection signal is obtained.

This detection signal is output at the timing when the document pressure plate 101 reaches a certain opening angle. That is,
Light sources 104a and 104b and a light receiving part (light receiving lens 105a
105b and light receiving elements 106a and 106b) may be arranged so that the light irradiation position and the optical axis of the light receiving unit coincide with each other when the original pressure plate 101 has a predetermined angle.

By arranging a plurality of sets (two sets in this case) of the combination of the light sources 104a and 104b and the light receiving section, a plurality of points on the contact glass 102 can be detected.

The light receiving section may be configured to detect a plurality of detection points by using one light receiving lens 105 as shown in FIG. 3 in addition to the above-mentioned FIG.

(Effect of Embodiment 3) Therefore, according to Embodiment 3 described above, in addition to the effect of Embodiment 1 described above, the irradiation light from the light sources 104a and 104b is not diffused, and Since the optical power density is increased by condensing the light inside, the detection becomes easy, and the outputs of the light sources 104a and 104b can be suppressed low, and the power consumption can be reduced.

[Fourth Embodiment] (Structure of Fourth Embodiment) FIG. 7 is an explanatory diagram showing the structure of a document size / position detecting device according to a fourth embodiment. Here, in addition to the configuration of FIG. 1 described above, the beam shape of the light emitted from the light source 104 is made into a linear shape, and a light receiving scanning section 701 as a light receiving scanning means for receiving and scanning this linear light is provided.

Further, the light-receiving lens 105 and the light-receiving element 106, which are the light-receiving portion, are arranged at positions where the scanning light scanned by the light-receiving scanning portion 701 is guided. Therefore, the other components and their functions are the same as those in FIG. 1, so the same reference numerals as those in FIG.

As the light source 104, a normal LED may be condensed by a cylindrical lens, or a linear surface emitting element or a fluorescent tube may be used.

(Operation of the Fourth Embodiment) Next, the operation of the document size / position detecting device configured as described above will be described. In the fourth embodiment, first, the light emitted from the light source 104 is linearly applied to the inside of the original pressure plate 101. At this time, the original pressure plate 101 is irradiated with linear light, and linear scattered light is generated accordingly.
The linear light scattered by the document pressure plate 101 by the light receiving scanning unit 701 is imaged on the light receiving element 106 through the light receiving lens 105.

(Effect of Fourth Embodiment) Therefore, according to the fourth embodiment, since the linear beam is emitted, the linear detection can be performed even when the original 103 is detected. . Therefore, the size of the original, the original 103
Since the position shift of (1) is linearly scanned by the light receiving scanning unit 701, it can be easily detected without correcting the position information. In addition, a device having such a configuration can be used in the X and Y directions.
By arranging the sets one by one, it is possible to accurately detect the size and misalignment coordinates of the document 103.

[Fifth Embodiment] (Structure of Fifth Embodiment) FIG. 8 is an explanatory diagram showing the structure of a document size / position detecting device according to a fifth embodiment. Here, in addition to the configuration of FIG. 1 described above, it is assumed that the light source 104 emits parallel light, and the rotary encoder 8 as an opening / closing angle detecting means for detecting the opening / closing angle of the document pressure plate 101.
01 and a light receiving element 802 having a linear light receiving surface. Since the other components and their functions are the same as those in FIG. 1, the same reference numerals as those in FIG. 1 are used and the description thereof is omitted.

In consideration of cost and safety, the light source 104 is preferably one that collimates the LED light with a lens. In addition to the rotary encoder 801, the opening / closing angle detector may be provided with, for example, a slit that moves linearly with respect to the original pressure plate 101, and the slit may be detected by a photo interrupter. Further, as the light receiving element 802 of the fifth embodiment, a light receiving element which is long in the moving direction of the document pressure plate 101 is used.

(Operation of the Fifth Embodiment) Next, the operation of the document size / position detecting device configured as described above will be described. In the fifth embodiment, the light source 104 irradiates parallel light, and the irradiating light irradiates the original pressure plate 101 in a state substantially parallel to the contact glass 102. Here, the rotary encoder 801 detects the opening / closing angle of the document pressure plate 101.

That is, the light from the light source 104 is applied to the original pressure plate 101 and scattered at the irradiated part.
The scattered light is condensed by the light receiving lens 105 and detected by the light receiving element 802 unless the original 103 is present on the contact glass 102. Then, at this time, when the document pressure plate 101 is closed as shown in FIG. 8, the scattering point moves, and the projection position on the contact glass 102 also changes accordingly.

Therefore, the detected position on the contact glass 102 is detected by the output of the rotary encoder 801 by correcting the detected position change on the contact glass 102 due to the opening / closing angle of the original pressure plate 101 from the output of the rotary encoder 801. .

Further, the original 1 is placed on the contact glass 102.
03, the light receiving element 8 is located at the position where the original 103 exists.
Since there is no signal from 02, the rotary encoder 801
The position on which the document 103 is placed is determined by detecting the output together with the output.

(Effect of Fifth Embodiment) Therefore, according to the fifth embodiment, even if the light or light receiving position is not scanned by the mechanical driving device, the scanning is performed in a pseudo manner. It is possible to reduce the number of points and downsize the device, and also improve the detection accuracy.

[Sixth Embodiment] (Structure of Sixth Embodiment) FIG. 9 is an explanatory diagram showing the structure of a document size / position detecting apparatus according to the sixth embodiment. Here, in contrast to the configuration of FIG. 1 described above, it is assumed that the light source 104 emits parallel light in the vertical direction, and the position where the light is emitted is converted into a voltage and output using a photoelectric conversion element. Optical position detection element (PSD) 901 as means
Is provided. Therefore, the other components and their functions are the same as those in FIG. 1, so the same reference numerals as those in FIG.

As the scanning mechanism from the light source 104, the pseudo scanning mechanism by opening and closing the original pressure plate 101 described in FIG. 8 may be used. A polygon mirror is generally used as the optical scanning means, but any scanning system may be used.

(Operation of the Sixth Embodiment) Next, the operation of the document size / position detecting device configured as described above will be described. In the sixth embodiment, the light from the light source 104 is applied to the inside of the original pressure plate 101 and scattered. The scattered light is condensed by the light receiving lens 105 unless the original 103 is present on the contact glass 102, and is imaged on the light position detection element (PSD) 901.

The light position detecting element (PSD) 901 is a photoelectric conversion element which converts the position where light is irradiated into a voltage and outputs the voltage. Therefore, when the light is scanned, a voltage corresponding to the irradiation position is output.

Therefore, the output corresponding to the position on which the original 103 is placed disappears and becomes discontinuous, so that the output of the optical position detecting element (PSD) 901 becomes discontinuous and the original 103 Is determined.
Further, the size of the document 103 can be detected by measuring the potential difference which causes the discontinuity.

(Effect of Sixth Embodiment) Therefore, according to the sixth embodiment, the optical position detecting element (PSD) 90
By using 1 as the light receiving element, it is not necessary to make an angle measuring means such as an encoder for detecting the optical scanning position or to make a determination by time division, so that the document size / position detection with a simple structure can be realized.

[0063]

As described above, according to the document size / position detecting device (claim 1) of the present invention, the document size for detecting the size and position information of the document placed on the contact glass surface. In the position detecting device, a light irradiating means which is arranged above the contact glass and irradiates the original pressure plate for pressing the original against the contact glass with light, and a light irradiating means below the contact glass. And a light receiving means for receiving reflected light of the light applied to the original pressure plate, the light irradiating means irradiates and scatters light on the original pressure plate, and the light receiving means operates the original document. Since the reflected light from the pressure plate is blocked by the document placed on the contact glass surface and the size and position information of the document is detected, the document density is high. Even if a small reflected light,
The size and position of the document can be detected accurately.

According to the document size / position detection device of the present invention (claim 2), the coordinate information of the document on the scanning line is obtained by scanning the detection point of the contact glass by the optical deflection scanning means. Therefore, it is possible to detect a document of an arbitrary size and a position shift of the document.

Further, according to the document size / position detection device of the present invention (claim 3), the light receiving means is provided at a position corresponding to the plurality of light irradiation means and the optical axis irradiated by the light irradiation means. Since it is possible to detect each arbitrary position on the contact glass, it is possible to detect the positions of a plurality of points and to detect the position with a small amount of light.

Further, according to the document size / position detecting device (claim 4) of the present invention, linear irradiation light is applied to the original pressing plate, and reflected light obtained by the irradiation light is applied from above the contact glass. By irradiating and scanning the light passing through the contact glass to the light receiving portion, linear detection is possible, and therefore the size and position shift of the document can be easily obtained.

Further, according to the document size / position detecting device (Claim 5) of the present invention, the change of the detected position on the contact glass due to the opening / closing angle of the document pressure plate is detected by the opening / closing angle detecting means, and the detected angle is used. Because of the correction, the position on the contact glass can be accurately obtained.

According to the document size / position detection device (claim 6) of the present invention, the document size / position detection device is substantially parallel to the document pressure plate,
The position of the original is detected with a simple structure because the light is scanned vertically and the reflected light is detected for each scanning position, and the original is detected based on the position where the scanning light is cut by the original. be able to.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of a document size / position detection device according to a first embodiment.

FIG. 2 is an explanatory diagram showing another configuration of the document size / position detection device according to the first embodiment.

FIG. 3 is an explanatory diagram showing another configuration of the document size / position detection device according to the first embodiment.

FIG. 4 is an explanatory diagram showing a configuration of a document size / position detection device according to a second embodiment.

FIG. 5 is an explanatory diagram showing another configuration of the document size / position detection device according to the second embodiment.

FIG. 6 is an explanatory diagram showing a configuration of a document size / position detection device according to a third embodiment.

FIG. 7 is an explanatory diagram showing a configuration of a document size / position detection device according to a fourth embodiment.

FIG. 8 is an explanatory diagram showing a configuration of a document size / position detection device according to a fifth embodiment.

FIG. 9 is an explanatory diagram showing a configuration of a document size / position detection device according to a sixth embodiment.

FIG. 10 is an explanatory diagram showing a conventional document size / position detection device.

[Explanation of symbols]

 Reference numeral 101 original pressure plate 102 contact glass 103 original 104 light source 105 light receiving lens 106 light receiving element 401 rotating prism 501 eccentric rotating lens 701 light receiving scanning unit 801 rotary encoder 802 light receiving element 901 light position detecting element (PSD)

Claims (6)

[Claims] 1. A document size / position detecting device for detecting size and position information of a document placed on a surface of a contact glass, wherein the document size / position detecting device is disposed above the contact glass and the document is contact glass. Light irradiating means for irradiating light onto the original pressure plate to be pressed against
Is disposed at a position below the contact glass, and
A light receiving unit for receiving reflected light of the light applied to the original pressure plate, the light applying unit irradiates and scatters light on the original pressure plate, and the light receiving unit changes the reflected light from the original pressure plate. A document size / position detection device, which detects that the document is blocked by a document placed on the contact glass surface to detect size and position information of the document. 2. The document size / position detecting device according to claim 1, further comprising scanning a preset detection point of the contact glass which is arranged between the contact glass and the light receiving means and which is preset. A document size characterized by including a light deflection scanning means for guiding the reflected light from the document pressure plate corresponding to the scanning position to the light receiving means.
Position detection device. 3. The document size / position detecting device according to claim 1 or 2, further comprising a plurality of light irradiating means for irradiating different positions of the document pressure plate with the plurality of light irradiating means, respectively. A document size / position detection device comprising: a plurality of light receiving means arranged in parallel. 4. The document size / position detection device according to claim 1, wherein the light irradiating unit irradiates light converging linearly on the surface of the document pressure plate,
A document size / position detecting device comprising a light-receiving / scanning unit for scanning the linear irradiation light and guiding it to the light-receiving unit. 5. The document size / position detection device according to claim 1, further comprising an opening / closing angle detecting means for detecting an opening / closing angle of the original pressure plate, wherein substantially parallel light is emitted from the light irradiating means. A position on the contact glass corresponding to the opening / closing angle of the opening / closing angle detection unit is detected by the light receiving means by irradiating the pressure plate and changing the irradiation position on the original pressure plate depending on the open / close state of the original pressing plate. A document size / position detection device characterized by detecting reflected light from the document. 6. The document size / position detecting device according to claim 1, 3 or 5, wherein said light irradiating means vertically scans and irradiates light substantially parallel to said document pressure plate, and said light receiving means , A document size characterized by detecting reflected light from the document pressure plate scanned by the light of the light irradiation means for each scanning position, and detecting the document based on the position where the reflected light is blocked. Position detection device.