JP2927199B2 - Document reading device, image forming device, and platen cover - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CCD (Charge
Coupled Device) or PDA (Photo
o, an image reading member having an image reading member such as an O.D. Diode, for converting document image information into electrical image data, an image forming apparatus such as a digital copier equipped with the document reading device, and The present invention relates to a platen cover used in a document reading apparatus, and more particularly, to an improvement in a function of identifying a document area using the image reading member.

[0002]

2. Description of the Related Art Conventionally, this kind of document reading apparatus is shown in FIG.
As shown in FIG. 2, a platen 21 on which a document is placed, a document pressing member 22 having a flat document pressing surface 22a for bringing the document into close contact with the platen 21, and a document pressing member 2
An illumination member 23 for irradiating the original closely adhered onto the platen 21 by the light source 2, and an illumination member 23 disposed at a position where the reflected light reflected by the original is incident, and the amount of the reflected light corresponding to the image information of the original is converted into an electric image. And an image reading member 24 that converts the data into data. In the case of a glossy document, surface reflection occurs on the surface, and the light amount of the regular reflection light L1 reflects the shape of the illumination member 23 in addition to the image information of the document, and the light amount is high. Since the scattered reflected light including the information of the density of the original in the regular reflected light is erased (that is, the illumination means is visible when the platen 21 is viewed from the direction in which the regular reflected light L1 is reflected), the image reading is performed. Member 24
Is disposed at a position where the scattered reflected light L2 of the reflected light reflected by the document is incident and the regular reflected light L1 is not incident. In the document reading apparatus, the document is placed on the platen 21 and the document pressing member 22 is closed, and the document is illuminated by the illumination means 23 and the image reading member 24 outputs image data. Is reading. The image forming means performs image processing using the image data of the document and forms an image based on the image data on which the image processing has been performed. The image forming apparatus includes at least the document reading device and the image forming unit.

In order to inform the image forming means of which image data among the image data output from the image reading member corresponds to the document area, the document reading apparatus is preceded by the document reading operation. In some cases, a document area identification function for checking a document area on a platen is provided.

For example, in Japanese Patent Application Laid-Open No. Sho 59-68728, one surface of an original pressing surface is formed as a mirror surface, and in a non-original region, that is, in a region where there is no original between the original pressing surface and a platen, illumination light is reflected in a regular reflection direction. To make the image data output from the image reading member correspond to true black, and illuminate the entire platen prior to the document reading operation. The image data is output from the image reading member by irradiating means, and an area where the image data does not correspond to true black is identified as an original area, that is, an area where the original is located between the original pressing surface and the original platen. . Also, by forming the entire surface of the original pressing surface black, and absorbing all the illumination light in the non-original region, the original region can be identified by the same identification method. However, in this case, there is a problem that the whole image data becomes darker when reading a tracing paper or a thin original than when the entire original pressing surface is a mirror surface. Further, in Japanese Patent Application Laid-Open No. 63-280569, one surface of the original pressing surface is colored, for example, yellow, and when identifying the original region, reflected light of the same color as the coloring is blocked before the image reading member. An optical filter is inserted so that the scattered reflected light from the non-document area does not enter the image reading member at all, and the area having a large amount of light is identified as the document area.

In these original reading apparatuses, since data for identifying an original area is fetched by using an image reading member, the original reading apparatus is used to identify a fixed original such as A4, B4 or A3. There is no need to provide a separate photo sensor, and the entire platen can be divided into a matrix and the presence or absence of a document can be determined for each cell. The original area can be identified regardless of where the original is placed on the original table (hereinafter, the former is referred to as an irregular original area identification function, and the latter is referred to as a free-register original area identification function). ).

However, in the above document reading apparatus, a solid pattern of a single color such as a mirror surface, a black surface, or yellow is formed on one surface of the document pressing surface, and the amount of light reflected by the document pressing surface and the amount of light reflected by the document. Since the document area is identified based on the difference from the amount of reflected light, in the case of a document or the like bordered with the same color as the solid pattern formed on the document pressing surface, the document area is determined. The image data of the non-document area becomes the same as the image data of the non-document area, and the document area cannot be correctly identified. Then, since the image forming apparatus extracts the image data of the original from the image data of the entire platen using the erroneous original area information, it is not possible to form an appropriate image. Cannot be formed on the recording sheet.

Further, in the above document reading apparatus, when performing a document reading scan of a transparent document such as an OHP sheet or a translucent document such as a tracing paper, only the image data in the non-image area has the color of the solid pattern. In addition to the data, the image data in the document area is also covered with the solid pattern color. Since the image forming apparatus performs image processing using the image data covered with the solid pattern color, it cannot form an appropriate image. For example, in a copying machine, an image formed on a recording sheet is Reflection and solidness will occur.

In order to solve such a problem, Japanese Patent Application Laid-Open No. Sho 60-100138 discloses a document pressing member having an EL (Electro-Luminescent).
e) The light emitting surface is formed on a plate, and the light emitting surface is turned on prior to the original reading operation to output image data from the image reading member, and an area where the image data corresponds to true black is identified as an original area. A document reading device has been proposed. However, in this document reading apparatus, an EL plate is necessary only to identify a document area, and the construction of a document pressing member is complicated to incorporate the EL plate, leading to a significant cost increase. It is difficult to secure the amount of emitted light necessary to identify the document area.

[0009]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an original reading apparatus capable of identifying an original area irrespective of the color of the original and without using an optical element dedicated to identifying the original area. An object of the present invention is to provide a device and a platen cover used for the document reading device.

Another object of the present invention is to provide an original reading apparatus capable of realizing an irregular original area identifying function and a free registration original area identifying function, and a platen cover used in the original reading apparatus. Is to do.

Further, a third object of the present invention is to provide a method for extracting image data of an original from image data of the entire platen properly, and furthermore, the image data is not affected by the color of the original press-contact surface. It is an object of the present invention to provide an image forming apparatus capable of forming a simple image.

[0012]

That is, the present invention provides a platen on which a document is placed, a document pressing member for bringing the document into close contact with the platen, an illuminating member for scanning the platen, and a platen by the scanning. A document reading device having an image reading member that receives scattered reflected light generated on the original or the original contact surface of the original pressing member and reads image information of the original included in the scattered reflected light; A plurality of reflectors for regularly reflecting the scanning light emitted from the illumination member toward the image reading member are provided on the original contact surface of the original pressing member, while the original or the original contact surface received by the image reading member is provided. The light amount reflected from the surface is compared with a reference light amount value based on the scattered reflected light from the white reference document, and a non-document region and a document region are discriminated from the region on the platen based on the comparison result. A document reading apparatus characterized in that a document area identifying means.

According to another aspect of the present invention, there is provided a document reading apparatus comprising:
Image processing means for extracting image information of a document from image information on the entire surface of a platen outputted from the image reading member, using document area information obtained from document area identification means of the document reading apparatus; An image forming apparatus comprising: an image forming unit that forms a recording image based on document image information obtained by a processing unit.

In general, a CC in a document reading apparatus
The optical sensor such as D outputs an electric signal such as a voltage and a current corresponding to the amount of light incident on the optical sensor during a predetermined measurement time, and thus can handle this output signal as the amount of light. At this time, the output signal itself may be compared, or the output signal may be compared using a calculated value. Further, in a digital image reading apparatus, these electric signals are usually converted into digital signals of about 8 to 24 bits using an A / D converter, and the digital signals are subjected to shading correction as necessary. After these calculations are performed, these are used as data corresponding to the light amount.
Therefore, in the present invention, when a common reference light amount of a fixed value is used by a plurality of optical sensors, comparison using the data after the above calculation is simpler because the number of additional components is small. In addition, in the above calculation, in addition to the shading correction, a fluctuation factor of a detection value of the optical sensor such as a fluctuation of a light emission time or a light emission temperature of a lamp may be corrected.

The platen is not particularly limited as long as a document can be placed on the platen and the document can be illuminated by illumination means from below the platen. For example, the platen can be formed of glass.

The illuminating member may be any member that can illuminate the entire platen. For example, a linear halogen lamp or a fluorescent lamp extending in the main scanning direction of the platen and a driving device for driving the same in the sub-scanning direction of the platen. And means.

The image reading member is disposed at a position where the scattered reflected light out of the reflected light reflected by the original is incident and the regular reflected light is not incident, and the image reading member is configured to read the image information of the original which the scattered reflected light has. Anything that can be read, such as a CCD or P
An imaging lens may be provided in front of the DA or the like, and the scattered and reflected light incident on the imaging lens may be imaged on a CCD or PDA. The optical system for forming an image by compressing the size of the document area using the imaging lens in this way is called a reduction optical system. The position where the specularly reflected light is incident is a position in a direction in which the illumination unit appears to overlap with the original when surface reflection occurs due to the gloss of the original. Area.

The document pressing member may be a member for bringing a document placed on a platen into close contact with the platen and having a reflecting portion for reflecting specularly reflected light in the direction of the image reading member. For example, a platen cover or A
It is sufficient to form the reflection portion on the document pressing surface of the DF. Thus, the document pressing member can mix information indicating that the document is not the document area into the image data.

The area for forming the reflection portion in the original pressing surface can be appropriately set according to the type of the original to be identified. For example, in the case of a standard original set at the registration reference position, When a fixed-size original is placed on a platen and the fixed-size original is pressed by an original pressing member, the fixed-form original may be provided so as to generate regular reflection light in a unique pattern for each size of the fixed-size original. In order to realize the standard document identification function, the original may be formed so as to cross the entire surface of the original pressing surface from the position corresponding to the registration reference position to the opposite side. , May be formed on the entire surface of the original pressing surface. In the case where the irregular document identification function or the free registration document identification function is realized, the reflection section may be formed continuously over the entire area or may be formed discretely in the area. Good. And the arrangement of the plurality of reflecting portions may be in a matrix shape based on corners such as triangles and quadrangles,
By randomly arranging, the plurality of reflecting portions located in the vicinity are set to coordinates of different values in the main scanning direction and the sub-scanning direction respectively, and the main scanning direction and the sub-scanning direction of the platen are set to be equal to or more than the distance between the reflecting portions. Since the image data can be finely divided, the boundary between the document area and the non-document area can be finely detected.

The reflecting section may have a reflecting surface formed at an angle for reflecting at least the specularly reflected light in the direction of the document reading member.
The shape may be a protrusion. The former concave shape is effective in that the reflective portion is not worn even for long-term use, and the latter protruding shape is effective when the original pressing member and the original are used. Since an air layer is formed between the platens, it is preferable in that the document is hardly sucked when the document pressing member is opened from the platen, and the document placed on the platen can be exchanged efficiently. The reflecting surface may be a flat surface or a curved surface.
Even when the original press-contact surface is slightly inclined with respect to the platen when copying a thick original, for example, the inclination can be absorbed to reflect a predetermined amount of specularly reflected light toward the original reading member without fail. Furthermore, by making the curvature of the curved surface constant, the amount of regular reflected light can be made constant regardless of the reflection portion of the reflection surface.

When the width of the image reading member 4 is smaller than the width of the platen 1 in the main scanning direction, a reduction optical system in which an imaging lens 8 is disposed in front of the image reading member 4 is used. Then, as shown in FIG. 5, when the illuminating means is composed of one lamp 3 extended in the main scanning direction of the platen, the regular reflection light from each of the reflecting portions 5c to 5i arranged in the main scanning direction is The light enters the image forming lens 8 and the image reading member 4 while maintaining the arrangement of the reflection portions 5c to 5i. However, FIG.
As shown in (1), when the illuminating means includes a plurality of light emitting units 3a to 3e arranged in the main scanning direction of the platen, such as a linear halogen lamp, the light emitting units 3a to 3e
There are reflecting portions 5d and 5h which cannot obtain specularly reflected light in the direction of the imaging lens 8 (image reading member 4) due to the positional relationship between the reflecting portions 5c to 5i arranged in the main scanning direction. Cannot be made to enter the imaging lens 8 (image reading member 4) while maintaining the arrangement of the reflection portions 5c to 5i, as shown in FIG. 4) Reflecting portion 5d that cannot obtain specularly reflected light in the direction,
In the case of 5h, it is necessary to form an angle on the reflection surface according to the positional relationship with the light emitting units 3b and 3d. Further, as shown in FIG. 8, the reflecting surfaces of the reflecting portions 5c to 5i may be formed as curved surfaces in the main scanning direction. In this case, even if the document pressing surface 2a is slightly inclined with respect to the platen 1, it is possible to absorb the inclination and always reflect a predetermined amount of specularly reflected light in the direction of the imaging lens 8 (image reading member 4). Becomes Further, if the reflecting portion is formed in a spherical shape, all of these problems can be solved.

The document area identifying means compares the amount of reflected light incident on the image reading member using a preset reference light amount, and determines the amount of reflected light incident on the image reading member as the reference light amount. If it exceeds, it is sufficient if the area is recognized as a non-document area and the document area on the platen is determined. The reference light amount value is set for distinguishing between the light amount of the reflected light from the placed document and the light amount of the reflected light from the reflecting portion, and may be set to be between them. Lambert's cosine law that scatters and reflects all incident light without absorbing it, and that the directional distribution of the intensity of the scattered reflected light is proportional to cos θ (θ is the angle between each direction and the normal to the surface) with respect to the normal to the surface. Is set on the basis of the perfect reflection surface according to the formula (1), even when any original is read, the original area is not erroneously recognized as a non-original area due to scattered reflected light from the original. This reference light amount value may be set in advance, or a white reference document stuck on the back surface of the platen may be exposed at any time, the scattered reflected light thereof may be read, and the reference light value may be directly or calculated based on this value.

When comparing the light quantity of the reflected light with the reference light quantity, the output image data of the image reading member is read one by one.
May be compared, but for each of several image data, that is, the light amount in a predetermined area of the reflected light incident on the image reading member may be compared with a reference light amount value. In the latter case, Although the accuracy of discriminating the document area is reduced, the comparison process can be performed at high speed. Further, in the case of identifying the area of the irregular-size original or the area of the free-register original, it is not necessary to perform the above-described comparison processing on the entire original area, and one or a plurality of detection areas are set. May be made to recognize the non-document area.

[0024]

According to the present invention, since the reflecting portion corresponding to the non-document area causes the specularly reflected light to enter the image reading member, information of a light intensity higher than the reference light quantity value is included in the image data of the non-document area. There are things to have. Then, the light quantity of the image data is compared with a preset reference light quantity value, and when the light quantity of the reflected light incident on the image reading member exceeds the reference light quantity value, the area is recognized as a non-document area. Thus, the document area on the platen can be determined.

In the present invention, the non-document area is recognized based on image data having a light quantity larger than the reference light quantity value, and the other area is determined as the document area. And the light amount of the scattered light by the reflecting portion does not become the same level.

Further, in the present invention, by forming the above-mentioned reflecting portion on a predetermined region of the original pressing surface, for example, the entire surface, it is possible to determine whether the original is a non-original region over the entire platen.

Further, in the present invention, the color of the original pressing surface is not limited at all, and can be formed in white, so that the color of the original pressing surface may not overlap the image data during the original reading operation. Absent.

[0028]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a document reading apparatus according to an embodiment of the present invention; (Note that in the following embodiment, there are second and third scanning mirrors for keeping a constant optical path length between the imaging lens and the document, but they are omitted for simplicity of description. The present invention can also be used for an image reading apparatus in which the line sensor is moved directly in the sub-scanning direction, or an image reading apparatus in which the original is moved to fix the line sensor.)

Embodiment 1 FIG. 1 shows an original reading apparatus according to Embodiment 1 of the present invention. The document reading device includes a platen 1 on which a document A is placed,
White document pressing surface 2 for bringing document A into close contact with platen 1
a, a document pressing member 2 disposed to be openable and closable with respect to the platen 1, an illumination member 3 for irradiating the platen 1 from an oblique direction of 45 degrees, and an illumination position below the illumination unit 3 That is, a mirror 7 disposed in a direction perpendicular to the irradiation position of the platen), an image reading member 4 for receiving light reflected by the mirror 7, and a mirror 7 disposed between the image reading member 4 and the mirror 7. And an image forming lens 8 for reducing the image superimposed on the reflected light and forming an image on the image reading member 4 to identify the A4, B4 and A3 fixed originals. Then, the digital color copying machine selects a recording sheet based on the identification result of the document area A.

The illumination member 3 comprises a plurality of linear halogen lamps 3a arranged in a line in the width direction of the platen 1 (hereinafter, main scanning direction). The platen (original) is linearly driven by being driven in the direction (hereinafter, the sub-scanning direction).

In this embodiment, as shown in FIG. 2, two reflecting portions 5 are formed on the original pressing surface 2a. When the B4 original is placed on the platen 1, the first reflecting section 5 a blocks irradiation light from the illumination member 3, and
4 is formed at a position where the irradiation light from the illumination member 3 is not blocked when the original is placed, and the second reflecting portion 5b
It is formed at a position where the irradiation light from the illumination member 3 is blocked when the A3 document is placed thereon, and is not blocked when the B4 document is placed. For this reason, when a fixed size detection is performed on a document placed on the platen 1, regular reflection light is generated in a unique pattern according to the size. By identifying this pattern, the standard size of the document can be determined. Further, the first reflecting portion 5a and the second reflecting portion 5b were formed to be separated by 10 mm in the sub-scanning direction.

As shown in FIGS. 3 and 4, these reflecting portions 5 are formed in a concave shape, and the reflecting surface 5c has a white and glossy flat shape, and the sub-scanning direction of the original pressing surface 2a. Is formed at an angle of 22.5 degrees. Therefore, the illumination means 3 is driven in the sub-scanning direction, and
At a 45-degree angle, the specularly reflected light is reflected right below the reflecting surface 5 and enters the image reading member 4 via the mirror 7 disposed directly below the irradiation position of the platen 1. . Therefore, the light amount of the scattered light from the document A and the light amount of the specularly reflected light from the reflection unit 5 do not have the same light amount level. Can be. Further, since the reflecting portion 5 is formed on the original pressing surface 2a of the original pressing member and the regular reflection light is reflected by the reflecting portion 5 to the original reading member 4, an optical element dedicated for identifying the original area A is used. No need to do
Further, the configuration of the document pressing member 2 does not become complicated.

The image reading member 4 includes a CCD sensor that divides analog image data corresponding to the amount of incident reflected light into a plurality of pixels and outputs the image data, and a pixel clock generator that outputs a sampling timing signal to the CCD sensor. 4b
And the image data is compared with a predetermined amount of scattered reflected light from the white reference document. If the amount of reflected light exceeds the amount of scattered reflected light from the white reference document, the area is set to non-display. And a document area identifying means 6 for recognizing the document area and determining the document area A on the platen.

The document area discriminating means 6 uses the addresses of the two reflecting portions 5 and the light amount value of the scattered reflected light from the perfect reflecting surface as a reference light amount value to correspond the identification result of the two reflecting portions 5 to the document size. The illuminating unit 3 is driven in the sub-scanning direction, and compares the image data at the above address with the reference light intensity value to determine whether the region is a non-document area or a document area. And determines the size of the original based on the determination table, and outputs it to the copying machine main body. For example, the first reflector 5a
When the light amount higher than the reference light amount value is not detected in the second reflection portion 5 and the light amount higher than the reference light amount value is detected in the second reflecting portion 5b, the document area identification means 6 determines that the document is the B4 document A. And outputs it to the copier body.

In the image forming apparatus using the document reading device, the document area A and the non-document area can be distinguished regardless of the color of the document. Since the color of the original pressing surface 2a can be appropriately extracted and the color of the original pressing surface 2a is formed in white, the color of the original pressing surface 2a does not overlap the image data at the time of the original reading operation, and an appropriate image is formed. can do.

Embodiment 2 This embodiment is the same as Embodiment 1 except that the original pressing member 2 and the original area identifying means 6 are changed to realize an irregular original identification function and a free registration original identification function. .

As shown in FIG. 9, a large number of reflecting portions 5 are discretely and randomly arranged on the entire surface of the original pressing surface 2a of the original pressing member 2, and the distance between the reflecting portions 5 is equal to the original area. Was set to 0.5 to 1 mm in consideration of the detection accuracy of. The shape of each reflecting portion 5 is a dimple shape having a constant curvature composed of a part of a spherical surface, and is 0.5 mm to 1 m so that a sufficient amount of specularly reflected light can be given to the image reading member 4.
The size is formed within the range of m.

By the way, the above dimples are actually
Conditions for making specularly reflected light incident on the image reading member 4 at the end of the dimple, that is, conditions for obtaining specularly reflected light in a cross section in the main scanning direction, and for obtaining specularly reflected light in a cross section in the sub-scanning direction. In the present embodiment, as shown in FIG. 10, the illumination means 3 in which a plurality of linear halogen lamps 3a to 3c are arranged in the main scanning direction is used and reduced. Since the optical system is used, the reflection direction of the specularly reflected light is not limited to the direction directly below the platen. Here, a method for obtaining the depth of a dimple for causing regular reflection will be described.

FIG. 11 shows the relationship of specular reflection when illumination light enters the dimple under the above conditions. A normal vector s at a portion of the reflection surface 5a where regular reflection occurs,
Using a vector t perpendicular to the normal vector s and an illumination direction vector a from the lamp to the dimple and a vector b from the dimple downward, a = −α · s + β · t b = α · s + β -There is a relationship of t. Then, from the condition that the absolute value of the vector s is 1, the direction cosine vector s of the dimple surface
Is obtained, s = (ba) / | ba |... From this, the normal vector s of the curved surface at the end of the dimple necessary for causing regular reflection can be obtained.

The downward component of this normal vector s (z
Component) is represented by the angle θ between the normal vector s and the z-axis.
(see FIG. 12), and assuming that the dimple is a part of a spherical surface having a radius r, the depth d of the dimple is as shown in FIG.
As shown in FIG. 2, d = r · (1−cos θ) Expression 2. Applying this relational expression when the original is illuminated at 45 degrees and read from directly below,

[0041]

(Equation 1) Because

[0042]

(Equation 2) And the z component of this is

[0043]

(Equation 3) Becomes From this, if r = 0.5 mm, it can be seen from Equation 2 that the dimple depth should be d = 0.5 × (1-0.9239) = 0.038 mm. In the general case, when the positional relationship with the linear halogen lamp or the positional relationship in the main scanning direction on the platen surface is changed, the above formula is also applied.
The depth of the dimple may be set according to the worst condition (the depth of the dimple becomes deeper). And
As shown in FIG. 13, each of the reflecting portions 5m, 5n, and 5p generates specular reflection at different portions in the reflecting surface according to the positional relationship with the illumination means 3a and 3b.

As shown in FIG. 14, when reading an original such as paper or tracing paper that diffuses light on the front surface, the illumination light transmitted to the back surface of the original is scattered almost uniformly. Since the illumination light is also scattered almost uniformly by the dimple, the shape of the dimple and the like are not mixed in the scattered reflected light, and eventually in the image data, and there is no show-through during printing.

As shown in FIG. 15, the document area discriminating means 6 includes an amplifier 6a having gain adjusting means for amplifying analog image data from the CCD sensor, and an amplifier according to a sampling timing signal of the pixel clock generator 4b. An A / D converter 6b for converting the output of the CCD 6a into digital image data, a shading correction circuit 6c to which the digital image data is input and correcting variations in pixel sensitivity of the CCD sensor, and an output of the shading correction circuit 6c And a reference light amount value. If the output is larger than the reference light amount value, a comparator 6d for outputting a dimple detection signal T, and a line signal output from the illumination means driving motor are counted to obtain a sub-part of the analog image data. A line counter 6e that outputs an SS address in the scanning direction;
A pixel counter 6f that counts the sampling timing signal and outputs an FS address of the analog image data in the main scanning direction, and a document area A based on the FS address and the SS address when the dimple detection signal T is input.
And a discriminating circuit 6g for performing a document area discriminating process for discriminating.

The shading correction data for each pixel used by the shading correction circuit 6c is read from a reference reflector (not shown) having a constant reflectance of 82%, which is provided at one end of the platen 1 and has a constant reflectance of 82%. A value obtained by multiplying the image data of each pixel by 1.2 (that is, a reflectance of 9)
Use a value equal to the image data when 8% of the reference reflector is read). Then, the shading correction data is stored in the shading correction data storage memory 6h, and the shading correction data is sequentially output to the shading correction circuit 6c in accordance with the FS address. The shading correction circuit 6c uses the shading correction data. The shading correction is performed by dividing the digital image data. Further, the digital image data is divided by using a value equal to the image data when a reference reflector having a reflectance of 98% is read as a reference light amount value, and shading when reading a document A having a reflectance of 98% or less is performed. While the output value of the correction circuit 6c becomes 1 or less, the output value of the shading correction circuit 6c when reading the reflection section 5 becomes larger than 1. Therefore, in the comparator 6d, for example, only by comparing whether the output is greater than 1 or not, even when reading a glossy original A having a reflectance of about 95%, the dimple detection signal T can be output.

The document area discriminating process performed by the discriminating circuit 6g includes a sub-scanning direction detecting area for discriminating the edge of the document in the sub-scanning direction, and a main scanning direction detecting area for discriminating the main scanning direction of the document. Is set in advance, and the address closest to the document area A in the area is detected, and the document area A is determined from those addresses. Processing modes are slightly different.

First, in the irregular document identification mode, FIG.
Since the registration position R is provided at the back left (upper left in the figure) of the platen as shown in FIG. 5, the main width having the full width in the main scanning direction (FS) and the predetermined width in the sub scanning (SS) direction is provided. The scanning direction detection area PFS is set at a position on the left side of the platen 1 and the full width in the sub-scanning direction (SS) and a predetermined width in the main scanning (FS) direction (the value of the FS counter is 100 to 300 lines) The sub-scanning direction detection area PSS having an eye is set at a position on the far side of the platen 1.

The width of the document area in the main scanning (FS) direction is detected by the main scanning direction end detection circuit 6p shown in FIG. 17 using the main scanning direction detection area PFS. Each time the dimple signal is present, the main scanning direction end detection circuit 6p determines whether or not the address is within the main scanning direction detection area, and is closer to the document area than the address value stored in the address register at that time. Is determined, and when both conditions are satisfied, the address of the address register is updated, and after reading the image data of the entire platen, the address in the address register closest to the edge of the original in the area is stored in the address register. Is stored. Specifically, as shown in FIG. 17, it is determined whether or not the FS address register 6m and the SS address from the line counter 6e are within the area. In some cases, the area comparison unit 6i that outputs an area match signal and the FS address from the pixel counter 6f are stored in the FS address register 6m
It is determined whether or not the register value is closer to the platen than the register value, and if so, the address comparison unit 6j that outputs the nearest signal and the determination that all of the dimple signal T, the area match signal, and the nearest signal are present And a condition determining means 6k for outputting a write signal in the case of (1). The value of the FS address register 6m is updated to the FS address by using the write signal as a trigger.
At the end of scanning of S, the FS address register 6m stores the dimple pfsmin located closest to the document end.
Are stored in the main scanning direction.

The width of the document area in the sub-scanning direction is detected by the sub-scanning direction end detection circuit using the sub-scanning direction detection area. The sub-scanning direction end detection circuit determines whether or not the FS address from the FS counter is within the area.
In some cases, an area comparison unit that outputs an area match signal, a condition determination unit that outputs a write signal only once when it is determined that there is a dimple signal and an area match signal, and an SS of the line counter triggered by the write signal
It consists of an SS address register that stores the address,
When scanning of the sub-scanning direction detection area is completed, the sub-scanning direction coordinates of the dimple closest to the document end are stored in the SS address register.

Finally, the size of the document is specified by setting the value of the SS address register as the width of the document in the sub-scanning direction and the value of the FS address register as the width of the document in the main scanning direction. Output a signal. Thus, A
The original size can be detected even for originals other than fixed-size originals such as 3 and A4.

Next, in the free registration document identification mode, as shown in FIG. 18, four detection areas each extending from the side edge of the platen to the center of the platen are set on each side of the platen.

Each time the dimple signal is present, it is determined in which detection area the address is located and whether the address is closer to the document area than the address value stored in the address register corresponding to the detection area at that time. If both conditions are satisfied, the address of the address register is updated, and after reading the image data of the entire platen, the address closest to the document edge is stored in all the address registers. It is composed. Also,
The four sides of the document area are obtained based on the four addresses of the four detection areas arranged side by side on each side of the platen. Specifically, first, as shown in FIG. 19, it is assumed that the side of the document is a straight line Lss2 of y = a * x + b.
Each detection area PFS5, PFS6, PFS7, PFS
8, four addresses pfs5min, pfs6min,
The slope a of the straight line is obtained from pfs7min and pfs8min by the method of least squares, and the straight line is translated to obtain b from the condition that the straight line is closer to the document area A than the address of four points (that is, four points in FIG. 19). Find the minimum b that satisfies Yi ≦ a * Xi + b for address (Xi, Yi))
To obtain the document area end Lss2. Further, after obtaining straight lines on the four sides of the document area A, the intersections of the straight lines are obtained, the document area A is specified by using the addresses of the four intersections as square addresses, and a document area signal is output. In this way, even if the document is not placed at the registration position R, the document area A can be detected.

In the image forming apparatus using the document reading device, the document area and the non-document area can be distinguished regardless of the color of the document, so that the image data of the document can be appropriately converted from the image data of the entire platen. Since the color of the original pressing surface is formed in white,
The color of the original pressing surface does not overlap the image data at the time of the original reading operation, and an appropriate image can be formed.

In the present embodiment, the shading data is set to a large value in advance to discriminate between a white background of the document and data brighter than that (that is, data by specular reflection light). By switching the input signal level to the shading correction circuit by adjusting the gain of the amplifier between the time of reading the document and the time of reading the document, for example, setting the gain of the amplifier at the time of detecting the document area smaller than that at the time of reading the document, The same discrimination is possible by switching the reading level of the white background so as not to reach the saturation level in the document detection unit. In the case of a monochrome copy machine in which the number of gradations of an A / D converter is small (for example, 6 bits), this method effectively allocates reading gradations between a black level and a white level and performs high-precision reading. This is an effective method because the white level of the document and the signal of the specular reflection light can be determined when the document area is detected.

Embodiment 3 In this embodiment, as shown in FIG. 20, a fixed form is formed by the same method as in Embodiment 2 except that the shape of the reflecting portion 5 is formed on the side of the original pressing surface of the original pressing member 2. , An image forming apparatus configured to detect an irregular document size. Such a projection-type reflecting portion 5 may be easily worn by being rubbed against the original, but since an air layer is formed between the original pressing surface 2a and the original, the reflecting portion 5 in addition to the operation and effect of the second embodiment can be obtained. In addition, when the document pressing member 2 is opened from the platen 1, the document becomes difficult to be attracted, and when a reflection portion is formed on the document conveyance belt of the automatic document feeder, the document transportability is improved. If the document area is identified in combination with 5, the document can be read more effectively and reliably. The shape of the projection may be a dome shape obtained by extracting a part of a spherical surface, or a shape having a waveform peak if the reflection surface is oriented in a random direction.

[0057]

According to the present invention, a reflection portion is formed on the original pressing surface, and when the non-image region corresponds to the portion, the regular reflection light stronger than the scattered reflection light from the white reference original is imaged. Since the light is reflected by the reading member and the presence or absence of the specularly reflected light is detected to determine the document area on the platen, the light amount of the scattered light by the document and the light amount of the scattered light by the reflection section are at the same level. That is, the document area and the non-document area can be distinguished regardless of the color of the document.

Further, in the present invention, since the reflecting portion is formed on the original pressing surface of the original pressing member, and the reflecting portion reflects the regular reflection light to the original reading member, the optical element dedicated to the identification of the original region is provided. Need not be used, and the configuration of the document pressing member does not become complicated.

In the image forming apparatus using the document reading device, the document area and the non-document area can be distinguished regardless of the color of the document, so that the image data of the document can be appropriately converted from the image data of the entire platen. In addition, since the color of the original pressing surface can be formed in white, the color of the original pressing surface does not overlap with the image data at the time of the original reading operation, and an appropriate image can be formed. Can be.

[Brief description of the drawings]

FIG. 1 is a perspective view of a document reading apparatus (standard document identification function) according to a first embodiment of the present invention.

FIG. 2 is a bottom view of a document pressing member used in the document reading apparatus of FIG. 1;

FIG. 3 is an explanatory diagram of specularly reflected light in the document reading apparatus of FIG. 1;

FIG. 4 is an explanatory side view of the document reading apparatus of FIG. 1;

FIG. 5 is an explanatory diagram of specular reflected light in a reduction optical system (in the case of one lamp).

FIG. 6 is an explanatory diagram of specular reflection light in a reduction optical system (in the case of a plurality of lamps).

FIG. 7 is an explanatory view of countermeasures in the reduction optical system of FIG. 6 (when the reflecting surface is inclined).

FIG. 8 is an explanatory view of countermeasures in the reduction optical system of FIG. 6 (when dimples are used).

FIG. 9 is a perspective view of an original reading apparatus (an irregular original identification function and a free registration original identification function) according to a second embodiment of the present invention.

FIG. 10 is a view for explaining the relationship between dimple size and specular reflection conditions (part 1).

FIG. 11 is an explanatory diagram of the relationship between dimple size and specular reflection conditions (part 2).

FIG. 12 is an explanatory diagram of specular reflection conditions in a reduction optical system.

FIG. 13 is an explanatory diagram of a regular reflection position in a dimple.

FIG. 14 is an explanatory diagram of the state of scattering of illumination light in dimples during reading.

FIG. 15 is a configuration diagram of a document area identification unit in the document reading device of FIG. 9;

FIG. 16 is an explanatory diagram of a detection area in the irregular document identification mode.

FIG. 17 is a circuit diagram of a discrimination circuit in the document area discriminating means of FIG.

FIG. 18 is an explanatory diagram of a detection area in a free cashier document identification mode.

FIG. 19 is an explanatory diagram of a document area edge detection method in a free registration document identification mode.

FIG. 20 is an enlarged sectional view of a reflector according to a third embodiment of the present invention.

FIG. 21 is an explanatory side view of a conventional document reading apparatus.

[Explanation of symbols]

1: Platen 2: Document pressing member 3: Lighting member 4:
Image reading member, 5: reflection section, 6: document area identification means.

Claims (6)

(57) [Claims] A platen on which a document is placed; a document pressing member for bringing the document into close contact with the platen; an illumination member for scanning the platen; and a document on the platen or a document pressing member of the document pressing member by the scanning. An image reading member that receives the scattered reflected light generated at the contact surface and reads image information of the document included in the scattered reflected light; While a plurality of reflecting portions for regularly reflecting the scanning light emitted from the member toward the image reading member are provided, the amount of reflected light from the document or the document contact surface received by the image reading member and scattering from the white reference document are provided. Document area identification means for comparing a reference light amount value based on the reflected light and discriminating a non-document area and an original area from areas on the platen based on the comparison result is provided. Document reading device that. 2. The document according to claim 1, wherein said document area identification means compares a plurality of light quantity data sequentially output from said image reading member with said reference light quantity value for each predetermined number of data. Reader. 3. When a fixed original placed on the platen is brought into close contact with the platen by the original pressing member, a reflecting portion provided on the original contact surface is provided for each size of the fixed original. 3. The document reading device according to claim 1, wherein the document reading device is arranged so as to generate regular reflection light in different combinations. 4. The document reading apparatus according to claim 1, wherein the reflection portion is formed in a concave shape with respect to the document contact surface. 5. The image forming apparatus according to claim 1, wherein the reflecting portion is formed in a dimple shape composed of a part of a concave spherical surface, and is provided discretely on the entire surface of the original contacting member of the original pressing member. 2. The document reading device according to item 2. 6. A platen output from the image reading member by using the document reading device according to claim 1 and document region information obtained from document region identification means of the document reading device. Image processing means for extracting image information of a document from image information on the entire surface; and image forming means for forming a recording image based on document image information obtained by the image processing means. Image forming apparatus.