JP3180019B2 - Document edge detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a document edge detecting device used in a copying machine or a document reading device.

[0002]

2. Description of the Related Art Conventionally, as described in Japanese Patent Publication No. 59-22992, a rotating hologram disk is irradiated with a laser beam, a scanning line is drawn, and the information carrier is scanned. In the information reading device which reads the information on the information carrier by detecting the reflected light from the photoelectric conversion device and converting it into an electric signal, the hologram used when the photoelectric conversion device scans, or the hologram used when scanning. There is an information reading apparatus that detects light of information alone passing through a hologram having a focus at the same position as a hologram used.

As described in Japanese Patent Application Laid-Open No. 6-242391, in an optical scanning type document reading apparatus, an optical scanning means which enters a document surface, and the scanned light is irradiated on the document surface to form a scanning line. There is an optical scanning type document reading apparatus provided with means for detecting light reflected and scattered by the drawing, and means for calculating the size and inclination of the document based on the intensity of the detected light and positional information of the scanning line.

Further, as described in Japanese Patent Application Laid-Open No. 50-19537, light from a light source is scanned in such a manner as to draw a plurality of scanning trajectories crossing each other in a read portion, and reflected light from the read portion is reflected. Among them, there is an optical reading device that reads light by detecting light returning along the same optical path as that at the time of light irradiation.

[0005]

[Problems to be solved by the invention] Japanese Patent Publication No. 59-2299
Since the information reading device described in Japanese Patent Publication No. 2 assumes scanning with laser light, light with a very small spot diameter is obtained, and information can be read with high resolution. However, various images are formed on the original,
The original presser that holds the original can also become dirty, so a small spot diameter can respond to changes in the intensity of the light input as the edge of the original, changes in the intensity of light corresponding to the contents of the original image, and contamination of the original press. It is difficult to clearly distinguish the change in the intensity of the emitted light, and an error may occur in the detection of the edge of the document, that is, the size of the document. That is,
It may be difficult to distinguish whether the object to be detected is a document, a document presser, or other disturbance light only by a change in the intensity of the received light. (This Gothic part was described as a subject of the additional invention this time.) Depending on the image content of the original, it may be detected as the edge of the original, and the edge detection of the original may be disturbed. In order to eliminate the influence of the image content, it is conceivable to make the scanning beam diameter appropriate. Although the beam diameter can be increased to some extent with laser light,
When laser light is applied to consumer equipment, several safety devices are required in order to comply with safety standards, it is weak against electric noise, driving is troublesome, and costs increase. In these respects, it is considered to be advantageous to use a light emitting diode as a light source.

However, when the hologram of the information reading apparatus described in Japanese Patent Publication No. 59-22992 and a light emitting diode are combined, the light passing through the hologram has a very large cross section due to long optical path and dispersion. And the resolution is reduced to the required resolution. As described above, in this method, it may be difficult to combine with a light emitting diode which is easy to handle.

An optical scanning type document reading apparatus described in Japanese Patent Application Laid-Open No. 6-242391 scans light from a light source over a document surface, and reflects light reflected from the document and light outside the document at a light amount level of the reflected light. The reflected light is discriminated by the threshold value. However, since various images are formed on the document, a sudden change in the light reception waveform of the document image is erroneously recognized as a sudden change in the light reception waveform in edge detection of the document. There is also.

In the optical reader described in Japanese Patent Application Laid-Open No. 50-19537, a laser beam is used.
Problems such as the need for several safety devices as described above, the susceptibility to electrical noise, and the increase in driving costs remain.

[0009]

According to the first aspect of the present invention,
A transparent document table, a document holder that opens and closes the document table, an optical scanning unit that scans a beam from the inner side of the document table toward the document surface, and a document on the document table. A light receiving unit that receives the reflected light from the document holder; a scanning cycle signal output unit that outputs a scanning cycle signal for each scanning cycle of the optical scanning unit; and a light scanning unit that is determined by the scanning cycle signal. Whether the signal to the light receiving means at the beginning or end of the scanning period is the level of no original
And a document edge defining means for defining a sudden rise or fall due to a change from the original document level to a white document level as a light receiving signal from an edge of the document. Therefore, the scanning cycle is recognized based on the scanning cycle signal output by the scanning cycle signal output means, and the sharp rise or fall of the signal to the light receiving means at the beginning or end of this one scanning period is determined by the document edge definition. It is defined by the means as the edge of the document.

According to a second aspect of the present invention, in the first aspect, the diameter of the circular beam scanned by the optical scanning means or the diameter of the short axis of the elliptical beam is set to 2 mm or more on the document surface. This is a document edge detecting device. Therefore, assuming a general pattern of dirt that occurs on the document press, taking into consideration the thickness of the general characters to be printed, the diameter of the circular beam or the diameter of the short axis of the elliptical beam on the document is calculated as follows. Since the value is set to a value larger than the pitch of the stain on the presser, the stain on the document holder and the ripple of the optical density of the image of the document are flattened. As a result, the difference between the received light waveform of the reflected light from the edge of the document and the received light waveform of the reflected light from other portions becomes remarkable.

According to a third aspect of the present invention, in the first or second aspect of the invention, there is no original at the rising edge of the first signal input to the light receiving means in the first scanning of the optical scanning means.
The document edge detecting device is provided with threshold value setting means for setting a threshold value for judging an edge of the document as a reference value using a difference in light intensity from a bell to a white document level as a reference value. Accordingly, the threshold value for determining the edge of the original is set by the threshold setting means so as to be renewable by using the light intensity at the rising edge of the first signal input in the first scanning of the optical scanning means as a reference value. The threshold value is automatically updated in accordance with a change in the reflectance of the document.

According to a fourth aspect of the present invention, in the first, second or third aspect of the present invention, a light emitting diode is used as a light source for optical scanning, and a single light emitting diode is provided in an optical path between the light emitting diode and a document surface. Using a lens, the ratio between the diameter of the light emitting surface of the light emitting diode and the beam diameter on the original surface is defined as the ratio of the optical path length from the light emitting diode to the single lens and the optical path length from the single lens to the original surface. A half mirror for reflecting a beam that is scattered and reflected from the original surface and the original holder is disposed in a return optical path between the light emitting diode and the original surface, and receives the reflected light from the half mirror. The document edge detecting device has a document surface arranged at a light-converging point conjugate to the document surface so that an image of the light receiving device is formed on the light receiving device . Therefore, by making the ratio between the diameter of the light emitting surface of the light emitting diode and the beam diameter on the original surface substantially equal to the ratio of the optical path length from the light emitting diode to the single lens and the optical path length from the single lens to the original surface, The light emitted from the light emitting diode is scanned over the original by a single lens with a desired beam diameter, and the reflected light returning through this scanning optical path is split by a half mirror, and the reflected light from the original surface is focused on the light receiving means in a focused state. The reflected light from other than the document surface is incident on the light receiving means in a non-focused state.

In order to obtain the optimum beam diameter and light intensity of the light incident on the light receiving means from the document surface and the document holder by a compact recursive optical system, a light emitting diode, a single lens, a half mirror Is an essential element, and a compact and high-performance sensor can be realized only by using a half mirror. It is necessary to separate outgoing light and incoming light with a large beam in order to obtain a moderate beam diameter with high light utilization efficiency using a normal light emitting diode, which can be realized by a retroreflective optical system. Is a half mirror or a diffraction grating. The diffraction grating disperses the light of the light emitting diode and cannot collect the light, whereas the half mirror is preferable.

According to a fifth aspect of the present invention, there is provided the document edge according to the fourth aspect, wherein the beam from the light emitting diode is converged by the converging element and then condensed by the condensing element to scan the original surface. It is a detection device. Therefore, since the beam from the light emitting diode is converged by the converging element and then condensed on the document surface by the condensing element, light diffused from the light emitting diode can be efficiently taken in.

According to a sixth aspect of the present invention, in the first aspect of the present invention, the light receiving means for receiving the reflected light from the original on the original placing table and the original presser is out of a scanning optical path toward the original placing base. This is a document edge detecting device that uses a wide-angle light receiving unit that is arranged at an arbitrary position and receives reflected light in the entire scanning area. Therefore, since the wide-angle light receiving means for receiving the reflected light of the entire scanning area is arranged at an arbitrary position deviated from the scanning optical path toward the original mounting table, the reflected light from the original mounting table is reflected on the scanning optical path to the original mounting table. The light is received by the light receiving means without passing through.

According to a seventh aspect of the present invention, there is provided a transparent document table, a document holder for opening and closing the document table, and an optical scanner for scanning a beam from the inner side of the document table to the document surface. Means, a distance detecting light receiving means for receiving reflected light from the original on the document placing table and outputting a signal corresponding to an incident path length, and when the output of the distance detecting light receiving means is a reflected light from the original. A document edge defining means for defining an edge of the document using the output as position information when recognized. Therefore,
The reflected light from the document, the reflected light from the document holder, the disturbance light, etc. are incident on the distance detecting light receiving means, but the output of the distance detecting light receiving means includes the distance to the part emitting light to the distance detecting light receiving means. Since information is included, the reflected light from the original can be clearly distinguished from the light from other parts, and the edge of the original is determined by the scanning position on the scanning line at the time when the reflected light from the original is recognized. It becomes possible to recognize.

According to an eighth aspect of the present invention, in the invention of the seventh aspect, the distance detecting light receiving means has a plurality of light receiving areas arranged at positions symmetrical with respect to the center thereof, and a front surface of the distance detecting light receiving means. Is a document edge detecting device in which a knife edge is arranged. Therefore, based on the principle of the knife edge method, the output of the distance detection light receiving means includes the distance information to the part that emits light to the distance detection light receiving means. Can be clearly distinguished, and the edge of the document can be recognized based on the scanning position on the scanning line at the time when the light is recognized as reflected light from the document.

A ninth aspect of the present invention is the document edge detecting device according to the seventh aspect, wherein the distance detecting light receiving means has a light receiving area arranged at the center and a light receiving area arranged around the center. Therefore, based on the principle of the beam size method, the output of the distance detection light receiving means includes information on the distance to the part that emits light to the distance detection light receiving means. Can be clearly distinguished, and the edge of the document can be recognized based on the scanning position on the scanning line at the time when the light is recognized as reflected light from the document.

According to a tenth aspect of the present invention, in the invention of the seventh aspect, the distance detecting light receiving means has at least four light receiving areas arranged at positions symmetrical with respect to the center thereof.
A document edge detecting device comprising a focusing lens for converging incident light at one point and a cylindrical lens or a wedge on the front surface of the distance detecting light receiving means. Therefore, based on the principle of the astigmatism method, since the output of the distance detection light receiving means includes the distance information to the part that emits light to the distance detection light receiving means, the reflected light from the document is reflected from other parts. Light can be clearly distinguished from the light, and the edge of the document can be recognized based on the scanning position on the scanning line at the time when the light is recognized as reflected light from the document.

According to an eleventh aspect of the present invention, in the seventh aspect of the invention, as the distance detecting light receiving means, a position detecting means for changing an incident position according to an incident path length from a reflection point of light emitted from the light scanning means. This is a document edge detection device using a sensor. Therefore, since the output of the position detection sensor includes the distance information to the part that emits light to the position detection sensor, the reflected light from the document can be clearly distinguished from the light from other parts, and the The edge of the document can be recognized based on the scanning position on the scanning line at the time when the light is recognized as reflected light from the document.

According to a twelfth aspect of the present invention, in accordance with the seventh aspect of the present invention, as the distance detecting light receiving means, the size of a light receiving spot according to an incident path length from a reflection point of light emitted from the light scanning means, shape, a document edge sensing device using a CCD sensor having a two-dimensional light receiving area where the light intensity distribution varies. Therefore, the output of the CCD sensor is C
Since the distance information to the part emitting light is included in the CD sensor, the reflected light from the original can be clearly distinguished from the light from other parts. The edge of the document can be recognized based on the scanning position on the scanning line.

According to a thirteenth aspect of the present invention, in the eighth, ninth or tenth aspect of the present invention, a bias component is subtracted from each output of the bisected light receiving area of the distance detecting light receiving means, and a bias component is subtracted from one of the light receiving areas. The later value,
Document edge detection that sets a threshold value for distinguishing reflected light from the document from light from other parts by comparing the output of the other light receiving area after subtracting the bias component with a value obtained by multiplying the output by a predetermined coefficient. Device. Therefore, even if there is a large difference between the distance information from the document and the distance detection light-receiving means to the distance detection light-receiving means, the distance information from the part where disturbance light occurs to the distance detection light-receiving means is obtained. The difference may be small for information, but the difference becomes extremely large when sunlight or the like enters. This is because the light intensity is too strong. Alternatively, when disturbance light enters under a normal office environment, the difference becomes small. This is because the light from the long path length hits the divided distance detecting light receiving means evenly and the difference becomes small. In this case, it is easily affected by the bias component. In these cases, by using the above-described means, the distance information from the document to the distance detecting light receiving means can be clearly distinguished from other distance information.

The invention according to claim 14 is the invention according to claims 7, 8,
The document edge detecting device according to any one of 9, 10, 11, 12 and 13, wherein a light emitting diode is used as a light source of the optical scanning means. Therefore, it is possible to use an inexpensive light source for the optical scanning means.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an explanatory view schematically showing a document reading apparatus. That is, reference numeral 1 denotes a main body, and the main body 1 has a built-in optical scanning means 2, and a transparent original mounting table 3 on which an original is mounted is provided above the optical scanning means 2.
And a document holder 4 that covers the document table 3 so as to be openable and closable.

A light receiving means (not shown) for receiving the reflected light from the original 5 (see FIG. 2) and the original presser 4 on the original placing table 3 and a scanning cycle for each scanning cycle of the optical scanning means 2 Scan period signal output means for outputting a signal (not shown)
And a sudden rise or fall of a signal to the light receiving means at the beginning or end of one scanning period of the optical scanning means 2 determined by the scanning cycle signal output from the scanning cycle output means. Document edge defining means (not shown) for defining a signal is provided.
The arrow in FIG. 2 is the direction of the scanning line 7 by moving the beam 6.

The light scanning means 2 scans light emitted from a light emitting diode (not shown) on the surface of the original 5 by a rotary deflecting member such as a polygon mirror. And
The scanning cycle signal output means (not shown) for outputting a scanning cycle signal every time one scanning is provided. This scanning cycle signal output means detects a part of the scanning light reflected from the rotary deflecting member by the detector, or detects the part of the light emitting diode in one scanning process by a light receiving sensor provided on a part of the rotary deflecting member. This is realized by a method of detecting light or extracting a reference signal from a control signal for driving a motor for driving the rotary deflection member.

In such a configuration, the size of the original 5 placed on the original placing table 3 is read with the original presser 4 being opened to some extent. That is, the beam 6 scanned by the optical scanning means 2 is applied to the original 5 on the original placing table 3.
And other portions, and the reflected light from the inner surface of the original 5 and the original holder 4, the external light when the original holder 4 is open, and the like are incident on the light receiving means. At this time, the beam 6 deviating from the original 5 is reflected and scattered on the inner surface of the open original presser 4, and the reflected light from the original 5 is incident on the light receiving means with high light intensity. Manuscript 5 by change
Is detected.

In this case, a scanning cycle signal is output from the scanning cycle signal means for each one scan of the optical scanning means 2, and the scanning cycle is recognized based on the scanning cycle signal, and the first or last scanning cycle in the one scanning period is recognized. The sharp rising or falling of the signal to the light receiving means can be defined as a light receiving signal from the edge of the document by the document edge defining means. When the reflectance around the document 5 is high, such as white, the amount of light received by the light receiving means first rises after a scanning cycle signal is output. Can be defined. In addition, since the amount of light received by the light receiving means at the end after the output of the scanning cycle signal suddenly falls within a predetermined time, the other edge of the document 5 can be defined by this falling.

When the periphery of the document 5 has a low reflectance or is close to black, the amount of light input to the light receiving means first after the output of the scanning cycle signal sharply falls within a predetermined time. One edge of the document 5 can be defined by descending. In addition, since the amount of light received by the light receiving means that is finally input after the output of the scanning cycle signal rapidly rises within a predetermined time, the other edge of the document 5 can be defined by this fall.

As described above, only the first abrupt rise or fall and the last abrupt fall or rise after the output of the scanning cycle signal are used as edges of the original 5, and the beam is reflected like the reflected light from the original presser 4. The signal processing for eliminating unnecessary signals whose light intensity changes more slowly than the time when the light passes through a certain line is provided, for example, with a differentiating circuit, and a signal value of a certain differential coefficient or more inputted to the light receiving means is obtained. It is easily realized by a method such as holding. Therefore, manuscript 5
There are cases where various images are formed, and the light receiving waveform at the light receiving means changes depending on the optical density pattern of the image, but the first rising or falling and the last falling or rising are different. Regardless of the state of the generated intermediate waveform, in other words, the edge of the document 5 can be reliably recognized without being affected by the image on the document 5.

The process of defining the sharp rise or fall of the signal to the light receiving means at the beginning or end of one scanning period as the light receiving signal from the edge of the document is as follows.
After the influence of disturbance light is eliminated by an electric or optical filter or the like, only the reflected light component of the scanning light is performed.

Next, an embodiment of the present invention will be described with reference to FIGS. The same parts as those in the above-described embodiment are denoted by the same reference numerals, and description thereof is omitted (the same applies hereinafter). The inner surface of the document holder 4 is generally white but easily stained. In addition, the inner surface is often uneven at intervals of about 1 mm, and spots are generated at intervals of 1 mm when soiled, and optical density data of these spots is also input to the light receiving means, and the original presser 4 is pressed.
The dirty portion may be erroneously recognized as the edge of the document 5. In order to eliminate the influence of the contamination of the document holder 4 as described above, the diameter of the circular beam 6 on the surface of the document 5 (in the case of an elliptical beam, the diameter in the short axis direction) is set to 2 mm or more.

The type of paper is A series in Japan.
There are many B-series and many types of computer paper. on the other hand,
In foreign countries, there is inch size paper. In order to identify these papers with the same detection device or computer software, it is necessary to distinguish them at a minimum interval of 6 mm. The diameter of the beam 6 on the surface of the document 5 needs to be reduced to some extent in order to discriminate the size of the paper or the document 5 without minute ripples in the light receiving waveform of the light receiving means. Therefore, the diameter of the beam 6 on the original 5 is 2 mm or more and 20 mm or less in the case of a circular beam, and 2 mm or less in the minor axis direction in the case of an elliptical beam.
It was set to a large value of not less than 20 mm and not more than 20 mm. In order to efficiently narrow down the reflected light from the original 5 and the original presser 4 and make the reflected light enter the light receiving means, as shown in FIG. 4, the light emitting point (the light emitting diode 8) and the scanning position (the original 5) are set. The beam 6 from the light emitting diode 8 has a substantially conjugate relationship, and the beam 6 is deflected and scanned by the deflecting unit 10 while being condensed by the single lens 9. The deflecting means 10 has a structure in which a mirror or a prism is driven by a motor.

As described above, a general pattern of dirt generated on the document holder 4 is assumed, and the diameter of the circular beam 6 or the short axis of the elliptical beam on the scanning surface is set to 2 mm based on the pitch of the dirt. As described above, the reflected light from the inner surface of the original presser 4 as well as the reflected light from the original 5 is incident on the light receiving unit as described above. The received light waveform input to is flattened,
No ripple appears. Therefore, the difference between the received light waveform having a large rise or fall from the edge of the original 5 and the received light waveform of the reflected light from the original presser 4 becomes significant. As a result, the output signal of the light receiving means can be accurately processed without being affected by the stain on the document holder 4, and the edge of the document 5 can be recognized accurately and easily. In FIG. 3, A is the light intensity of the reflected light from the document holder 4, B is the light intensity of the reflected light from the document 5, and C is the beam diameter on the surface of the document 5.

Further, an embodiment of the invention described in claim 3 will be described. According to the present invention, in the first scan of the optical scanning means 2, the threshold value for setting the threshold value for judging the edge of the original document 5 as a reference value using the difference in the rising light intensity of the first signal input to the light receiving means as a reference value is set freely. Means (not shown).

In such a configuration, the threshold value for recognizing the edge of the document 5 is automatically updated according to the reflectance of the document 5 at all times. Therefore, the document edge can be detected without being affected by the optical density of the document 5.

An embodiment of the present invention will be described with reference to FIGS. In the present embodiment, a light emitting diode 8 is used as a light source for optical scanning, and a single lens 9 is used in the optical path between the light emitting diode 8 and the surface of the document 5 to determine the diameter of the light emitting surface of the light emitting diode 8. The ratio between the beam diameter on the original 5 surface (twice the SR in FIG. 5) and the optical path length from the light emitting diode 8 to the single lens 9 and the optical path length from the single lens 9 to the original 5 surface are substantially equal. A half mirror between the single lens 9 and the light emitting diode 8 and reflecting reflected light that is scattered and returned from the surface of the original 5 or the original holder 4 while the beam 6 from the light emitting diode 8 is diverging. And a light receiving means (detector) 1 for receiving reflected light from the half mirror 11.
2 was arranged so as to be a conjugate light-collecting point with respect to the five surfaces of the document.

The beam 6 condensed by the single lens 9 is configured to be deflected and scanned by a deflecting unit 10 such as a mirror or a prism driven by a motor. In this case, a mirror that generates the astigmatic beam 6 is more preferable than a prism that generates astigmatism. The astigmatism of the prism is generated both when the light is emitted and when the signal light is incident. Even when using a rotating mirror,
As shown in FIG. 7, by using a mirror 13 in which each reflecting surface 13a is inclined with respect to the rotation axis, and making an angle between the incident light and the reflected light, the reflected light from the reflecting surface 13a is transmitted to the light receiving means 12 as noise. The state of incidence can be avoided. Further, as the light emitting diode 8 used in this embodiment, an inexpensive light emitting diode having a light emitting portion having a diameter of about 0.3 mm, which is generally commercially available, is used. Note that the beam diameter on the original 5 is a diameter not on a plane parallel to the original 5 but on a plane perpendicular to the optical path.

In such a configuration, the light emitted from the light emitting diode 8 is scanned on the scanning surface with a desired beam diameter by the single lens 9, and the reflected light returning on the scanning optical path is transmitted to the single lens 9 by the light emitting diode. The beam 6 from 8 is split by a half mirror 11 disposed on the way to diverge, and the reflected light from the surface of the document 5 is incident on the light receiving means 12 in a focused state, and the document presser 4 other than the surface of the document 5 is focused. Is incident on the light receiving means 12 in an out-of-focus state.
Therefore, the signal when the beam 6 passes through the edge of the original 5 is input as an accurate and focused value, and
Can be more reliably recognized.

As described above, a low-cost combination of a commercially available light-emitting diode 8 having a relatively large light-emitting surface and a single lens 9 which does not use a laser diode as a scanning light source, does not require a safety standard, and is easy to drive, Since scanning can be performed with a desired beam diameter, cost can be reduced.

Also, by using the half mirror 11, the optical scanning itself can be made a certain size NA (Numerical Aperture).
Focusing on The light-condensing point is located substantially on the surface of the original 5. For this reason, the diameter of light other than the original 5 on the original presser 4, for example, becomes larger when the original presser 4 is separated from the original 5 and the light having a large diameter that is scattered and reflected is greatly reduced by the light receiving means. (Detector) 12. For this reason, the intensity of light incident on the light receiving means 12 from the document holder 4 is lower than the intensity of light incident on the light receiving means 12 from the surface of the document 5. Therefore, the light from the original 5 and the light from the original presser 4 can be easily distinguished.
In this case, by attaching a small-diameter aperture to the front surface of the light receiving means 12 or by using the small-diameter light receiving means 12, it is possible to collect only the light of the high power portion at the center of the beam, excluding disturbance light. .

As an example of disposing the half mirror 11 in the return optical path between the light emitting diode 8 and the surface of the original 5,
In FIG. 6, the half mirror 11 is arranged on the light emitting diode 8 side of the single lens 9, but as shown in FIG. A half mirror 11 for reflecting the beam is provided,
Focus lens 1 between half mirror 11 and light receiving means 12
9 may be provided.

In this case, the number of focus lenses 19 is increased by one compared with the configuration shown in FIG. 6. However, a commercially available light-emitting diode 8 having a relatively large light-emitting surface and a single lens which does not require a safety standard and is easy to drive. By using an inexpensive combination with 9, scanning can be performed with a desired beam diameter, and cost can be reduced.

Further, an embodiment of the present invention will be described with reference to FIG. The present invention is a document size detecting apparatus in which a beam 6 from a light emitting diode 8 is converged by a converging element (lens) 14 and then condensed by a condensing element 15 to scan a scanning surface. Therefore, the light diffused from the light emitting diode 8 is focused on the focusing element 1.
4, the beam 6 can be focused on the surface of the document 5 by the focusing element 15. Therefore, the light power of the light emitting diode 8 can be used efficiently.

An embodiment of the invention according to claim 6 will be described with reference to FIG. In this example, a wide-angle light receiving unit 16 that receives reflected light in the entire scanning area is arranged at an arbitrary position off the scanning optical path toward the document table (document 5). The light receiving means 16 includes a condensing lens 17 such as a toroidal lens for condensing reflected light of the entire scanning area reflected from the original 5 surface and the original presser 4 in one scan.
And a wide detector 18 that receives the reflected light condensed by the condenser lens 17.

In such a configuration, the beam 6 emitted from the light emitting diode 8 is deflected by the deflecting means 10
The light is scanned toward the surface and the document holder 4, and the reflected light from the document 5 and the document holder 4 is received by the light receiving unit 16 without passing through the scanning optical path to the document 5. Therefore, the light receiving means 16
Can be arranged at any desired position such as near the document table 3.

Next, an embodiment of the present invention will be described with reference to FIGS. 11 and 12. FIG. The main body 1 is provided with an optical scanning means 2 for scanning a beam from the inner side of the document table 3 toward the surface of the document 5. The light scanning means 2 reflects the light emitted from the light emitting diode 8 having the spot diameter of several mm by the half mirror 11 and reflects the reflected light from the half mirror 11 to the focusing lens 1.
The light is condensed by the scanner 9 and scanned by the mirror 13 driven by the polygon motor 10a. In this case, the scanning line 7 draws an arc because it is scanned at a certain incident angle with respect to the normal line of the document table 3. Also, the mirror 13
The scattered light scanned by and reflected by the original 5 and the scattered light deviating from the original 5 and reflected by the original placing table 3 return through the optical path from the mirror 13, and include a half mirror A distance detecting light receiving means 20 for receiving light passing through the optical path 11 and outputting a signal corresponding to an incident path length is provided, and a knife edge 21 is arranged in front of the distance detecting light receiving means 20.

The distance detecting light-receiving means 20 includes a focusing lens 19
Light receiving areas 20 arranged symmetrically with respect to the optical axis of
A, 2B PD having two A and 20B. Document edge defining means (not shown) for defining the edge of the document 5 by using the output as position information when the output of the distance detecting light receiving means 20 recognizes the reflected light from the document 5.
Is provided.

In this configuration, when light emitted from the light emitting diode 8 is scanned by the light scanning means 2 on the surface of the original 5 and the original holder 4 in the state where the original holder 4 is opened, Is the reflected light from the original 5,
The reflected light from the document presser 4 and other disturbance light due to other lighting in the room, etc. are incident thereon. However, since the knife edge 21 is provided on the front surface of the position detection light receiving means 20, the distance is determined based on the knife edge method. The position of the spot S incident on the detection light receiving means 20 is determined by the incident path length (the original 5, the original presser 4,
It changes according to the path length from a disturbance light generating section or the like.

FIG. 12 shows this state. FIG. 12A shows an incident state from a short distance, FIG. 12B shows an incident state from an intermediate distance, and FIG. 12C shows an incident state from a long distance. Since the spots S extending over the two light receiving regions 20A and 20B are different, the output A of the light receiving region 20A and the output B of the light receiving region 20B change according to the incident path length.

Here, for example, the focus lens 1 is set so that A> B when the reflected light from the original 5 is received and A <B when the reflected light from the original presser 4 is received.
9. Position detection light-receiving means 20 and knife edge 21 are arranged at predetermined positions, and the outputs of position detection light-receiving means 20 are compared with a given predetermined threshold value (A = B). The reflected light from the original 5 is correctly recognized as the reflected light from the original 5 even if there is no large difference in the respective light intensities of the reflected light from the original 5, the reflected light from the original holder 4, and the disturbance light. be able to. Therefore, the position of the edge of the document 5 can be accurately detected from the position information of the scanning line 7 based on the relationship between the scanning period of the light scanning unit 2 and the output time point of the detection signal of the position detection light receiving unit 20.

Next, an embodiment of the present invention will be described with reference to FIGS. In this example, a position detection light receiving unit 22 is used in place of the position detection light receiving unit 20 of the previous embodiment. Distance detection light receiving means 22
Is a two-part PD called a Japanese flag having a light receiving area 22A arranged at the center and a light receiving area 22B arranged around the center. Document edge defining means (not shown) is provided for defining the edge of the document 5 by using the output as position information when the output of the distance detecting light receiving means 22 is recognized as reflected light from the document 5. ing.

In such a configuration, when the light emitted from the light emitting diode 8 is scanned by the optical scanning means 2 on the surface of the original 5 and the original presser 4, the reflected light from the original 5 and the original Reflected light from the presser 4 and other disturbance light due to lighting in the room or the like are incident thereon. Based on the beam size method, the diameter of the spot S incident on the distance detection light receiving unit 22 is determined by the incident path length (the original 5). , The original presser 4, the path length from the disturbance light generating section, etc.).

FIG. 14 shows this state. 14A shows an incident state from a short distance, FIG. 14B shows an incident state from an intermediate distance, and FIG. 14C shows an incident state from a long distance. Since the spots S have different diameters, the output A of the light receiving area 22A and the output B of the light receiving area 22B change according to the length of the incident path.

Here, for example, the focus lens 1 is set so that the state when the reflected light from the original 5 is received is A <B, and the state when the reflected light from the original presser 4 is received is A> B.
9. The position detection light-receiving means 22 is arranged at a predetermined position, and a predetermined threshold (A =
B), and when A <B, setting as the reflected light from the original 5 causes a large difference in the respective light intensities of the reflected light from the original 5, the reflected light from the original holder 4, and the disturbance light. If not, the reflected light from the original 5 can be correctly recognized. Therefore, the position of the edge of the document 5 can be accurately detected based on the position information of the scanning line 7 based on the relationship between the scanning period of the light scanning unit 2 and the output point of the detection signal of the position detection light receiving unit 22.

Next, an embodiment of the present invention will be described with reference to FIG. 15 and FIG. The distance detecting light receiving means 23 used in this example has at least four light receiving areas 23A ₁ , 23A ₂ , 23
B ₁ and 23B ₂ . On the front surface of the distance detecting light receiving means 23, there are provided a focusing lens 19 for condensing incident reflected light at the center of the distance detecting light receiving means 23, a half mirror 11, and a cylindrical lens 24 having power only in one direction.
And are arranged. In addition, instead of the cylindrical lens 24,
As shown in FIG. 17, a wedge 24a may be used.

In such a configuration, when the light emitted from the light emitting diode 8 is scanned by the light scanning means 2 on the surface of the original 5 and the original presser 4, the reflected light from the original 5 and the original Reflected light from the presser 4 and other disturbance light due to other lighting in the room or the like are incident thereon.
Are arranged, the shape of the spot S incident on the distance detection light receiving unit 23 is determined based on the astigmatism method by the incident path length (the original 5, the original presser 4, the light from the disturbance light generating unit, etc.). Path length). This is substantially the same even when the wedge 24a (see FIG. 17) is used instead of the cylindrical lens 24.

FIG. 16 shows this state. FIG. 16A shows an incident state from a short distance, FIG. 16B shows an incident state from an intermediate distance, and FIG. 16C shows an incident state from a long distance. At the intermediate distance shown in (b), since the spot S illuminated at the center is a perfect circle, all the light receiving areas 23A ₁ , 2A
3A ₂ , 23B ₁ , and 23B ₂ are evenly irradiated with the spot S. At a short distance, the horizontally elongated spot S as shown in FIG.
At a long distance, a vertically long spot S is formed as shown in FIG. Thus, since the shapes of the spots S are different from each other, the output sum A of the light receiving regions 23A ₁ and 23A _{2 and} the output sum B of the light receiving regions 23B ₁ and 23B ₂ change according to the incident path length.

Here, for example, the focus lens 1 is set so that the state when the reflected light from the original 5 is received is A <B, and the state when the reflected light from the original presser 4 is received is A> B.
9, the cylindrical lens 24 and the position detection light-receiving means 23 are arranged at predetermined positions, and the outputs of the position detection light-receiving means 23 are compared at a given predetermined threshold (A = B).
The reflected light from the original 5 is correctly recognized as the reflected light from the original 5 even if there is no large difference in the respective light intensities of the reflected light from the original 5, the reflected light from the original holder 4, and the disturbance light. be able to. Therefore, the light scanning means 2
And the position of the scanning line 7 based on the relationship between the scanning cycle of the
Can be accurately detected.

Next, an embodiment of the present invention will be described with reference to FIGS. In this example, as the distance detection light receiving means, the incident position changes according to the distance from the reflection point of the light emitted from the light scanning means 2.
This is a document edge detection device using a position detection sensor 25 such as an SD (Position Sensing Device). As shown in FIG. 18, the light emitted from the light emitting diode 8 is
And scans the original 5 and the original presser 4 to make the original 5
Alternatively, the scattered light reflected by the document holder 4 is formed into an image on the position detection sensor 25 by the focusing lens 19.

In this embodiment, as shown in FIG. 19, the reflected light from the original 5 or
The light is incident on the position detection sensor 25 via the light-emitting diode 3, and the position of the position detection sensor 25 is changed on the same plane (on the vertical plane) with respect to the light path emitted from the light emitting diode 8.

In this configuration, when the light emitted from the light emitting diode 8 is scanned by the light scanning means 2 on the surface of the original 5 and the original holder 4 with the original holder 4 opened, the position detecting sensor 25 The reflected light from the document 5, the reflected light from the document holder 4, and other disturbance light due to room lighting are incident. The position of the spot S incident on the position detection sensor 25 is determined by the incident path length (the document 5). , The original presser 4, the path length from the disturbance light generating section, etc.).

As shown in FIG. 20, the incident position of the spot S is closer to the direction a as the incident path length is shorter, and is closer to the direction b as the incident path length is longer. Position detection sensor 25 (PSD)
Since the output voltage changes depending on the incident position of the spot S, the incident path length can be recognized by measuring the voltage. Therefore, similarly to the previous embodiment, the reflected light from the original 5 can be clearly detected. In this case, since the position detection sensor 25 has changed its position on the same plane with respect to the light path emitted from the light emitting diode 8, the spot S is drawn on the position detection light-receiving means 25 on a linear segment which is a primary limitation. Scan. Spot S at this time
The edge of the document 5 can be detected from the position information.

The optical scanning means 2 shown in FIGS.
Instead, the scanning line 7 is drawn on the original 5 or the original presser 4 by moving the entire unit including the light-emitting diode 8, the condensing element such as the single lens 9 and the focus lens 19, and the position detection sensor 25. You may. Further, the position detection sensor 25 is not limited to the PSD, but may be a line type C.
The application of a CD sensor or a two-dimensional CCD sensor is also possible.

Next, a first embodiment of the invention will be described with reference to FIG. This example is shown in FIG.
In place of the position detection sensor 25 shown in FIG. 19, the size, shape, light intensity distribution, and the like of the light receiving spot according to the path length from the reflection point of the light emitted from the optical scanning means 2 as the distance detecting light receiving means Is a document edge detecting device using a two-dimensional CCD sensor 26 having a two-dimensional light receiving area in which the color of light changes.

In such a configuration, as shown in FIG. 21, it is assumed that there are a plurality of reflection surfaces 27, 28, and 29 whose incident path lengths to the two-dimensional CCD sensor 26 are different from far, middle, and near. In this case, the diameter of the spot S on the two-dimensional CCD sensor 26 depends on the reflecting surfaces 27 and 2 that reflect light.
8, 29. Therefore, reflected light from the original 5, reflected light from the original presser 4 having different incident path lengths,
The distinction of disturbance light or the like can be clearly detected.

A twelfth embodiment of the present invention will be described with reference to FIGS. In this example, when the incident path length is short as shown in FIG. 22A, the shape of the spot S on the two-dimensional CCD sensor 26 is changed by using a square lens 30 as a condenser lens. As shown in FIG. 22B, when the incident path length is long as shown in FIG. 23A, the shape of the spot S on the two-dimensional CCD sensor 26 is changed to the shape shown in FIG. As shown in (b), the four sides were determined to have a concave shape. Thus, the shape of the spot S can be recognized by the two-dimensional CCD sensor 26, and the light from the document 5 can be clearly detected.

Further, a third embodiment of the present invention will be described with reference to FIGS. When a collimating lens is arranged in the optical path, the diameter of the ordinary collimating lens is limited, so that the periphery of the beam may be blurred by the collimating lens. Also, when an aperture is arranged in the optical path, the periphery of the beam may be blurred. In this example, by utilizing such a thing, as shown in FIG. 24A, when the incident path length is short, as shown in FIG. The light intensity distribution is raised at the center,
As shown in FIG. 25A, when the incident path length is long, as shown in FIG.
The light intensity distribution on No. 6 was concave at the center. By doing so, the incident path length can be recognized based on the output waveform of the two-dimensional CCD sensor 26, and the light from the document 5 can be clearly detected.

As described above, whether the reflected light from the document 5 is detected by the diameter or shape of the spot S or the light intensity distribution, the scanning is performed on the position detecting light receiving means 26. The edge of the document 5 can be detected from the position information of the spot S.

Next, an embodiment of the invention will be described. In the present embodiment, a bias component (noise component such as disturbance light) is subtracted from each of the outputs of the bisected light receiving areas of the distance detection light receiving means (any of 21 to 23), and a bias component of one of the light receiving areas is subtracted. By comparing a value obtained by subtracting the bias component of the other light receiving means and a value obtained by multiplying the output by a predetermined coefficient, a threshold value for distinguishing the reflected light from the document from the light from other portions is set. This is a document edge detecting device.

In this example, FIG. 15 using the astigmatism method is used.
The configuration will be described with reference to FIG. As described above, in the astigmatism method, the output sum A of the light receiving areas 23A ₁ and 23A _{2 and} the output sum B of the light receiving areas 23B ₁ and 23B ₂ are compared to recognize the reflected light from the original 5. did. Here, as shown in FIG. 26, taking the incident path length on the horizontal axis,
When the output P of the distance detection light receiving means 23 is taken on the vertical axis, the value of P changes according to the length of the incident path. Is the value of P when the reflected light from the document 5 is received, is the value of P when the reflected light from the document holder 4 is received, and is the value of P when the disturbance light such as room illumination light is received. It is.

If there is no influence of disturbance light, the value of P in between is set as the threshold value A, so that the reflected light from the original 5 and the reflected light from the original presser 4 can be clearly distinguished. it can. However, in a use environment in which disturbance light enters the distance detection light receiving unit 23, the difference between the value and the value becomes small, so that it becomes difficult to specify the reflected light from the document 5.

Since the output of the distance detecting light receiving means 23 contains a bias component (a noise component such as disturbance light), the value obtained by subtracting the bias component from the sum of the outputs of the light receiving regions 23A ₁ and 23A ₂ is A. , Light receiving areas 23B ₁ and 23B
B is the value obtained by subtracting the bias component from the output sum of ₂ ,
Comparison between the value of A after the bias component subtraction and the value obtained by multiplying the output B after the bias component subtraction by a predetermined coefficient α (A
−αB), a threshold value for distinguishing the reflected light from the original 5 from the light from other portions is set.

By setting a slightly positive threshold value of the threshold value B (see FIG. 26) for the output of AB, it is possible to exclude the influence of weak disturbance light entering from a distance. However, for example, when sunlight or light from a fluorescent lamp is directly incident on the disturbance light, the light intensity is extremely strong, and thus the output of AB fluctuates extremely toward the plus side or Masunas side. However, the output ratio A / B of that distance detecting light-receiving unit 23, even if the light intensity of the ambient light, no matter how large converges to a constant value B _1. If the distant strong light enters, A / B = B ₁ is satisfied. In this case, A / B when illuminated on the original 5 shows a value in the vicinity of B _2. Set the value α of B ₁ <α <B ₂ ,
By comparing A / B and α, it is possible to distinguish reflected light from the original 5, reflected light from the original holder 4, or disturbance light. However, if the light reflected from the document pressing 4 becomes A / B <B _1. Since it is difficult to directly divide by a circuit, this relationship is determined by a subtraction circuit. That is, (A-αB) makes it possible to distinguish the reflected light from the original 5 from the light from other portions. this is,
In FIG. 26, a threshold value a between the value of the output P when the document 5 is detected and the value of the output P when the document presser 4 is detected is changed to a threshold value B between the value and the value of the output P when the disturbance light is detected. This corresponds to a shift. Thus, the reflected light from the original 5 can be specified without being affected by disturbance light.

As described above, the process of performing a certain amplification (multiplying by α) on the outputs A and B and subtracting them is performed by the outputs A and B.
Is equivalent to comparing by a ratio, and can be easily processed by an analog circuit.

[0076]

According to the first aspect of the present invention, the scanning cycle is recognized based on the scanning cycle signal output by the scanning cycle signal output means, and the signal to the light receiving means at the beginning or end of this one scanning period is recognized. From no original level to white original level
The sharp rise or fall due to the change to the original edge is defined by the original edge defining means as the edge of the original, so that the edge of the original is detected without being affected by the optical density of the image of the original, The document size can be correctly detected.

According to the second aspect of the present invention, the general pattern of dirt generated on the original press is assumed, and the diameter of the circular beam or the diameter of the short axis of the elliptical beam on the original is determined. Since the value is set to a value larger than the pitch, it is possible to flatten the dirt of the document press and the ripple of the optical density of the image of the document. As a result, the difference between the received light waveform of the reflected light from the edge of the document and the received light waveform of the reflected light from other portions can be remarkable, and fine ripples appear in the received light waveform from the light receiving means. Therefore, the output signal of the light receiving means can be accurately processed and the edge of the document can be accurately and easily recognized without being affected by the stain on the document press.

According to a third aspect of the present invention, the threshold value for judging an edge of a document is freely updated by the threshold value setting means using the light intensity at the rising edge of the first signal input in the first scan of the optical scanning means as a reference value. Since the setting is made, the threshold value to be recognized as the edge of the document can always be automatically updated according to the change in the reflectance of the document, and therefore, the size of the document can be detected without being affected by the optical density of the document. be able to.

According to a fourth aspect of the present invention, the ratio between the diameter of the light emitting surface of the light emitting diode and the beam diameter on the original surface is determined by comparing the optical path length from the light emitting diode to the single lens and the optical path length from the single lens to the original surface. , The light emitted from the light emitting diode is scanned over the original by a single lens with a desired spot diameter, and the reflected light returning through the scanning optical path is split by a half mirror and reflected from the original surface. Light is incident on the light receiving means in a focused state, and reflected light from other than the document surface is incident on the light receiving means in a non-focused state,
The reflected light from the original surface and the reflected light from the original presser can be clearly distinguished to accurately detect the edge of the original.
This makes it possible to scan the original surface with a beam using an inexpensive combination of a light emitting diode and a single lens that can be easily driven.

According to the fifth aspect of the present invention, the beam from the light emitting diode is converged on the original surface by the condensing element after being converged by the converging element, so that the light diffused from the light emitting diode can be efficiently taken in. Becomes possible.

According to the sixth aspect of the present invention, since the wide-angle light receiving means for receiving the reflected light of the entire scanning area is arranged at an arbitrary position deviating from the optical path from the optical scanning means toward the original placing table, The reflected light from the table can be received by the light receiving means without passing through the scanning optical path to the document table.
Therefore, the light receiving means can be arranged at a desired arbitrary position.

According to a seventh aspect of the present invention, there is provided a distance detecting light receiving means for receiving reflected light from a document on a document placing table and outputting a signal corresponding to an incident path length; Document edge defining means for defining the output of the document as position information when the light is recognized as reflected light from the document. Although the reflected light from the light source, the disturbance light, etc. are incident, the output of the distance detection light receiving means includes the distance information to the part that emits light to the distance detection light receiving means. Can be clearly distinguished from the light from the portion, and the edge of the document can be detected from the information on the scanning position on the scanning line at the time when the light from the document is recognized. Therefore, even when a large difference is not obtained between the intensity of the reflected light from the original and the intensity of the light from other portions, the position of the edge of the original, the size of the original, the inclination of the original, and the like can be accurately detected.

According to an eighth aspect of the present invention, in the seventh aspect of the present invention, the distance detecting light receiving means has a plurality of light receiving areas arranged at positions symmetrical with respect to the center thereof. Is provided with a knife edge, and based on the principle of the knife edge method, the reflected light from the document can be clearly distinguished from the light from others by the output of the distance detecting light receiving means.

According to a ninth aspect of the present invention, in the invention of the seventh aspect, since the distance detecting light receiving means has a light receiving area arranged at the center and a light receiving area arranged around the center.
Based on the principle of the beam size method, the reflected light from the document can be clearly distinguished from other light by the output of the distance detecting light receiving means.

According to a tenth aspect of the present invention, in the invention of the seventh aspect, the distance detecting light receiving means has at least four light receiving areas arranged at positions symmetrical about the center thereof.
Since a focusing lens and a cylindrical lens or a wedge for condensing incident light at one point are provided on the front surface of the distance detection light receiving means, based on the principle of the astigmatism method, the output of the distance detection light receiving means causes The reflected light can be clearly distinguished from other light.

According to an eleventh aspect of the present invention, in the invention of the seventh aspect, the position detection light-receiving means detects a position at which an incident position changes according to an incident path length from a reflection point of light emitted from the light scanning means. Since the sensor is used, the reflected light from the document can be clearly distinguished from the light from the other by the output of the position detection sensor.

According to a twelfth aspect of the present invention, in accordance with the seventh aspect of the present invention, as the distance detecting light receiving means, the size of the light receiving spot according to the incident path length from the reflection point of the light emitted from the light scanning means, shape, since the light intensity distribution has a CCD sensor with a two-dimensional light receiving area is changed, CC
The reflected light from the document can be clearly distinguished from the light from the other by the output of the D sensor.

According to a thirteenth aspect of the present invention, in the eighth, ninth or tenth aspect of the present invention, a bias component is subtracted from each output of the bisected light receiving area of the distance detecting light receiving means, and a bias component is subtracted from one of the light receiving areas. The later value,
By comparing the output of the other light receiving area after subtracting the bias component with a value obtained by multiplying the output by a predetermined coefficient, a threshold value for distinguishing the reflected light from the original from the light from other parts is set. The distance information from the document holder to the distance detection light-receiving means is different from the distance information from the document holding to the distance detection light-receiving means even if there is a large difference from the distance information from the document press to the distance detection light-receiving means. Although the difference may be small or the output may move up and down unstablely, the distance information from the document to the distance detecting light receiving means can be clearly distinguished from other distance information.

The invention according to claim 14 is the invention according to claims 7, 8,
The document edge detecting device according to any one of 9, 10, 11, 12 and 13, wherein a light emitting diode is used as a light source of the optical scanning means. Therefore, an inexpensive light source can be used for the optical scanning means.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a configuration according to an embodiment of the invention described in claim 1;

FIG. 2 is an explanatory diagram illustrating a relationship between a document and a scanning line.

FIG. 3 is a graph showing a change in the amount of light received by a light receiving means according to the embodiment of the present invention.

FIG. 4 is a scanning light path diagram from a light emitting diode to a document surface.

FIG. 5 is an explanatory view showing a beam in a scanning optical path according to an embodiment of the present invention.

FIG. 6 is an optical path diagram showing an arrangement example of a half mirror.

FIG. 7 is a perspective view showing a deflecting action of a deflecting means by a mirror.

FIG. 8 is an optical path diagram showing another arrangement example of the half mirror.

FIG. 9 is a diagram showing a scanning optical path from a light emitting diode and a diagram showing a reflecting optical path from a scanning surface to a light receiving means in the embodiment of the invention described in claim 5;

FIG. 10 is a diagram showing a scanning light path from a light emitting diode and a reflection light path from a scanning surface to a light receiving means in one embodiment of the invention according to claim 6;

FIG. 11 is an explanatory view showing an embodiment of the invention described in claims 7 and 8;

FIG. 12 is an explanatory diagram illustrating a relationship between an incident path length and a spot incident on a distance detection light receiving element.

FIG. 13 is an explanatory view showing an embodiment of the invention described in claim 9;

FIG. 14 is an explanatory diagram showing a relationship between an incident path length and a spot incident on a distance detection light receiving element.

FIG. 15 is an explanatory diagram showing one embodiment of the invention described in claim 10;

FIG. 16 is an explanatory diagram illustrating a relationship between an incident path length and a spot incident on a distance detection light receiving element.

FIG. 17 is an optical path diagram showing a modified example using a wedge instead of a cylindrical lens.

FIG. 18 is an optical path diagram showing an embodiment of the invention described in claim 11;

FIG. 19 is a perspective view showing a relationship between an optical scanning unit and a position detection sensor.

FIG. 20 is an explanatory diagram illustrating a relationship between an incident path length and a spot incident on a position detection sensor.

FIG. 21 is an optical path diagram showing a first embodiment of the invention described in claim 12;

FIG. 22 shows a second embodiment of the invention according to claim 12, in which (a) is an optical path diagram when the incident path length is short,
(B) is an explanatory view showing a spot shape.

FIG. 23 (a) is an optical path diagram when the incident path length is long,
(B) is an explanatory view showing a spot shape.

FIG. 24 shows a third embodiment of the invention according to claim 12, in which (a) is an optical path diagram in a case where the incident path length is short,
(B) is an explanatory view showing a light intensity distribution.

FIG. 25 (a) is an optical path diagram when the incident path length is long,
(B) is an explanatory view showing a light intensity distribution.

FIG. 26 is a graph showing an embodiment of the invention according to claim 13, and showing a relationship between an incident path length and an output of a distance detection light receiving means.

[Explanation of symbols]

 Reference Signs List 2 light scanning means 3 document placing table 4 document holder 8 light emitting diode 9 single lens 11 half mirror 12 light receiving means 14 focusing element 15 light collecting element 16 wide-angle light receiving means 19 focal lens 20 distance detecting light receiving means 20A, 20B light receiving area 21 Knife edge 22 Distance detecting light receiving means 22A, 22B Light receiving area 23 Distance detecting light receiving means 23A, 23B Light receiving area 24 Cylindrical lens 24 Wedge 25 Distance detecting light receiving means, position detecting sensor 26 Distance detecting light receiving means, CCD sensor

Claims (14)

(57) [Claims] A transparent document mounting table, a document presser for opening and closing the document mounting table so as to be openable and closable, an optical scanning means for scanning a beam from an inner surface side of the document mounting table toward a document surface; A light receiving unit that receives light reflected from the original and the original presser on the table, a scanning period signal output unit that outputs a scanning period signal for each scanning period of the optical scanning unit, and the scanning period signal that is determined by the scanning period signal. Source of a signal to the light receiving means at the beginning or end of one scanning period of the optical scanning means.
A document edge detecting device, comprising: document edge defining means for defining a sudden rise or fall due to a change from a no-document level to a white document level as a light receiving signal from an edge of the document. 2. The document edge detection according to claim 1, wherein the diameter of the circular beam scanned by the optical scanning means or the diameter of the short axis of the elliptical beam is set to 2 mm or more on the document surface. apparatus. 3. An originalless level at the rising edge of the first signal input to the light receiving means in the first scanning of the optical scanning means.
3. The document edge detecting device according to claim 1, further comprising threshold value setting means for setting a threshold value for judging an edge of the document as an updateable value using a difference between light intensities from the original to a white document level as a reference value. 4. A light emitting diode is used as a light source for optical scanning, a single lens is used in an optical path between the light emitting diode and a document surface, and a diameter of a light emitting surface of the light emitting diode and a beam on the document surface. The ratio of the diameter to the optical path length from the light emitting diode to the single lens and the ratio of the optical path length from the single lens to the document surface is substantially equal to the ratio between the light emitting diode and the document surface during the return light path. A half mirror that reflects the beam scattered and reflected from the original surface and the original holder is provided, and the light receiving unit that receives the reflected light from the half mirror is moved so that the image on the original surface forms an image on the light receiving unit. 4. The document edge detecting device according to claim 1, wherein the document edge detecting device is disposed at a convergence point conjugate to a plane . 5. The document edge detecting device according to claim 4, wherein the beam from the light emitting diode is converged by a converging element and then condensed by a condensing element and scanned on the document surface. 6. A light receiving means for receiving reflected light from a document and a document presser on a document table, and disposed at an arbitrary position deviating from a scanning optical path toward the document table to receive reflected light in the entire scanning area. 2. The document edge detecting device according to claim 1, wherein a wide-angle light receiving means is used. 7. A transparent document table, a document holder for opening and closing the document table, an optical scanning means for scanning a beam from the inner side of the document table toward the document surface, and A distance detection light-receiving means for receiving reflected light from the document on the table and outputting a signal corresponding to an incident path length; and when the output of the distance detection light-receiving means is recognized as reflected light from the document, A document edge defining unit for defining an edge of the document using output as position information. 8. The distance detecting light receiving means has a plurality of light receiving areas arranged at positions symmetrical with respect to the center thereof, and a knife edge is arranged in front of the distance detecting light receiving means. The document edge detecting device according to claim 7. 9. The document edge detecting device according to claim 7, wherein the distance detecting light receiving means has a light receiving area arranged at the center and a light receiving area arranged around the center. 10. A distance detecting light receiving means having at least four light receiving areas arranged at positions symmetrical with respect to the center thereof, and a focusing lens and a cylinder for condensing incident light at one point on a front surface of said distance detecting light receiving means. 8. The document edge detecting device according to claim 7, further comprising a lens or a wedge. 11. The position detecting sensor according to claim 7, wherein a position detecting sensor that changes an incident position according to an incident path length from a reflection point of light emitted from the optical scanning unit is used as the distance detecting light receiving unit. Document edge detection device. As 12. The distance detecting light-receiving means, the light-receiving spot in accordance with the incident path length from the reflection point of the light emitted from the optical scanning unit size, shape, two-dimensional light receiving area where the light intensity distribution is changed 8. The document edge detecting device according to claim 7, wherein a CCD sensor having the following is used. 13. A bias component is subtracted from each output of a bisected light receiving area of the distance detecting light receiving means, and a value obtained by subtracting the bias component of one light receiving area and an output obtained by subtracting the bias component of the other light receiving area are determined. 11. The document edge according to claim 8, wherein a threshold value for distinguishing reflected light from the document from light from other portions is set by comparing with a value multiplied by the coefficient of the document edge. Detection device. 14. The light scanning means as claimed in claim 7, wherein a light emitting diode is used as a light source.
13. The document edge detecting device according to 11, 12, or 13.