JPH07144794A - Sheet-kind discriminating method, sheet-kind discriminating apparatus utilizing this sheet-kind discriminating method, and sheet-feeding device having this sheet-kind discriminating apparatus - Google Patents

Abstract

PURPOSE:To correctly discriminate a sheet kind by catching the patterns of light quantity change, individually changed according to a sheet kind, to be compared. CONSTITUTION:The discriminating apparatus is set at a given output level by reflecting a beam, radiated from the luminous element P1 of a reflecting type sensor P, by a reflecting body M in a condition wherein a sheet S is not carried to be inputted into a light-receiving element P2. Light quantity distribution in accordance with the kind of each sheet S can be obtained by adding light quantity increase, due to that the tip of each sheet S is irradiated from the luminous element P1 and the beam of this irradiation is reflected by a sheet surface to be inputted in a luminous element P2, to light quantity lowering due to cutting the light path of a reflected beam by the tip of the sheet S when the tip of the sheet S enters the visual field of the reflection type sensor P. The kind of the sheet S can be discriminated by comparing output data wherein this light quantity distribution is A/D converted and the reference data of a memory ROM in accordance with a previously stored sheet kind.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to plain paper (white paper, black paper, glossy paper), semi-transparent paper (tracing paper) used as documents and recording paper conveyed and used in printers, copying machines, and other peripheral devices. Sheet) discriminating method for discriminating the sheet type such as paper), OHP paper, film, etc., a sheet type discriminating apparatus using the sheet type discriminating method, and a sheet feeding apparatus (automatic document feeding) using the sheet type discriminating apparatus Device).

[0002]

2. Description of the Related Art Conventionally, a sheet feeding device of this type is shown in FIG.
3A and 3B, the sheet conveyance guide H
Using the cutouts H3 and H4 of 1 and H2,
A reflection type sensor including a light emitting element P1 that emits the light O1 toward the other cutout portion H4 and a light receiving element P2 that receives the reflected light O2 from the sheet S as shown in FIG. Presence / absence is detected by a change in light amount, the change in light amount is converted into an ON / OFF signal using a comparison means (not shown), and this ON / OFF operation also uses a timer (not shown) or the like to convey the amount of the sheet or during the conveyance. It is generally used to control the detection of defective sheet conveyance. Furthermore, some of them are shown in FIG.
As shown in (C), the output data from the light receiving element P2 of the reflective sensor P includes glossy paper Q1, white paper Q2, and semitransparent paper Q.
3, OHP paper Q4 is different depending on the reflectance of each sheet, and by strictly managing the types of sheets that can be used, the sheet types can be simplified using this different output data. It is conceivable to make a judgment.

[0003]

However, among the sheets to be handled, there are some originals having a low reflectance such as black paper, and the sheets themselves are curled. Therefore, when this type of sheet is also detected, it is very sensitive. Has to be high. Further, in this method in which only the light amount change of only the reflected light from the sheet surface is captured, the light amount level of each sheet has a variation range C1, C2, C3, C4 as shown in FIG. Therefore, it is difficult to accurately determine the sheet type.

(Object of the Invention) The present invention has been made in view of the above problems, and is a sheet type discriminating method for accurately discriminating the sheet type, and a sheet type discriminating apparatus using the sheet type discriminating method. And a sheet feeding apparatus using the sheet type discriminating apparatus.

[0005]

[Means for Solving the Problems]

At least one of the sheet is provided by using a light emitting element and a light receiving element arranged on one side facing the front and back surfaces of the sheet and a reflecting surface which reflects light from the light emitting element arranged on the other side to the light receiving element. The light receiving element receives the reflected light from the reflecting surface and the light reflected from the sheet surface emitted by the light emitting element while the tip passes through the light receiving range of the light receiving element, and the output change of the light receiving element Sheet type determination method for determining the type of sheet by means of a light emitting element and a light receiving element arranged on one side facing the front and back surfaces of the sheet, and a reflection surface for reflecting light from the light emitting element arranged on the other side to the light receiving element With and
(At least one of the light receiving element receives the reflected light from the reflecting surface irradiated by the light emitting element while the tip of the sheet passes through the light receiving range of the light receiving element, and the reflected light from the sheet surface. ) The leading edge of the sheet is near both boundaries before and after the sheet feeding direction in the light receiving range of the light receiving element, and near both boundaries before and after the sheet feeding direction in the light receiving range inside which the specularly reflected light of the light emitting element can be received. A sheet type discriminating method for discriminating the type of the sheet by the output variation of the light receiving element at a predetermined position selected according to the type of discriminating sheet among the four locations. The sheet type determination method for determining the sheet type by comparing the height with a preset reference level is the preset reference level in the above sheet type determination method. Sheet type determination method in which the preceding output value is set at a predetermined position selected according to the type of the determination sheet In the above sheet type determination method, the output change of the light receiving element is defined as the difference between the output values between the selected predetermined positions. Sheet type determining method for determining the sheet type by capturing the output inclination from the above, in the sheet type determining methods described above, the output change of the light receiving element, each output of the light receiving element at a predetermined position selected according to the type of the determination sheet. A sheet type determination method for determining the type of a sheet by capturing an output pattern from a value A light emitting element and a light receiving element arranged on one side facing the front and back surfaces of the sheet, and light from the light emitting element disposed on the other side is the light receiving element A light-reflecting surface that reflects light to the light-emitting element while at least the tip of the sheet passes through the light-receiving range of the light-receiving element. The reflected light emitted from the reflecting surface and the reflected light from the sheet surface are received by the light receiving element, and the output data of the light receiving element is compared with reference data corresponding to a sheet type stored in advance. Sheet type determination method for determining the type of a transport sheet A light emitting element and a light receiving element are arranged on one side facing the front and back surfaces of a sheet, and a reflecting surface for reflecting light from the light emitting element to the light receiving element is provided on the other side. With the provision of (provided that the light receiving element receives at least the reflected light from the reflective surface irradiated by the light emitting element and the reflected light from the sheet surface while at least the tip of the sheet passes through the light receiving area of the light receiving element. On the other hand, the front end of the sheet is near both boundaries in the light receiving range of the light receiving element in the front and rear of the sheet feeding direction, and inside the front and rear of the sheet receiving direction in the light receiving range in which the specularly reflected light of the light emitting element can be received. boundary Sheet type discriminating apparatus having discriminating means for discriminating the type of the sheet based on a change in the output of the light receiving element at a predetermined position selected according to the type of the discriminating sheet among the four nearby locations. A sheet type discriminating apparatus that discriminates the type of a conveyed sheet by comparing the output data of the element with the prestored reference data according to the sheet type. Sheet type discriminating apparatus 11 having input means 11 The external input means of 10 above is a sheet type discriminating apparatus provided with storage means for reading and storing each type of reference sheet in advance. A sheet type discriminating apparatus that sets and stores the average value of the output data of the reference sheet as the reference data. The sheet discriminating apparatus 14 stores the data as the reference data and compares it with the output data of the succeeding sheet. The sheet type discriminating apparatuses of the above to 13 are the light receiving elements of only a reflected light from the conveying sheet surface in a predetermined sheet. Sheet type discriminating apparatus including an adjusting unit for setting the difference between the output value of the sheet and the output value of the light receiving element of only the reflected light from the reflector within a predetermined range. Is a sheet type discriminating device 16 for adjusting the inclination angle of one of the reflection type sensor or the reflector with respect to the other opposing surface, or the conveying position of the reflector or the sheet with respect to the reflection type sensor 16 The sheet of the predetermined type is a sheet type determination device using a blank sheet. 17 A sheet feeding tray on which a sheet is placed and a sheet placed on the sheet feeding tray are separated and fed one by one. A sheet feed including a separating unit, a conveying unit that conveys the sheet fed by the separating unit to a predetermined position, and discharges the sheet from the predetermined position, and a discharge tray that stores the sheet discharged by the conveying unit. In the apparatus, a reflection type sensor consisting of a light emitting element and a light receiving element is arranged on one of the conveyance paths facing the front and back surfaces of the conveyed sheet before the conveyance means, and the return reflection type sensor of the return reflection type sensor is arranged on the other side of the conveyance path. Arranging a reflector that reflects light from the light emitting element to the light receiving element, (at least the reflected light from the reflecting surface irradiated by the light emitting element while the tip of the sheet passes through the light receiving range of the light receiving element, The light reflected from the sheet surface is received by the light receiving element, while the front end of the sheet is near the front and rear boundaries in the paper feeding direction in the light receiving range of the light receiving element and inside the light receiving element. Discrimination for discriminating the type of the sheet by the output change of the light receiving element at a predetermined position selected according to the type of the discriminating sheet, out of four locations near both boundaries before and after the sheet feeding direction in the light receiving range capable of receiving the emitted light. Sheet Feeding Device Equipped with Sheet Type Discriminating Device

[0009]

According to the present invention, the tip of the sheet optically cuts off a part of the reflected light when at least the tip of the sheet enters the light receiving range of the light receiving element (in the field of view of the reflection type sensor). As a result, the tip of each sheet is irradiated from the light emitting element (of the reflection type sensor), the light is reflected by the sheet surface and enters the light receiving element, so that the light amount varies depending on the type of each sheet. It changes individually. By capturing this change in light amount (change amount or change pattern), that is, by the configurations of to 17 described above, at least the leading edge of the sheet from the reflection surface illuminated by the light emitting element while passing through the light receiving range of the light receiving element. While the reflected light and the reflected light from the sheet surface are received by the light receiving element, the front end of the sheet is near both boundaries in the light receiving range of the light receiving element before and after the sheet feeding direction and inside the light emitting element. By capturing the change in the output of the light receiving element at a predetermined position selected according to the type of the discrimination sheet, among the four positions near both boundaries before and after the sheet feeding direction in the light receiving range that can receive the specularly reflected light, It is possible to provide a sheet type discriminating method with higher discrimination accuracy than the conventional sheet type discriminating method. By using this sheet type discriminating method, a sheet type discriminating apparatus and its It is also possible to provide a sheet feeding apparatus having a over preparative kind discriminating apparatus.

[0010]

【Example】

(Description of Structure of Sheet Type Discriminating Device) As shown in FIG. 14, this sheet type discriminating device includes notches H3 and H4 of sheet conveying guides H1 and H2, a conveying sheet S, and the conveying guide H2. A reflector M (hereinafter referred to as a mirror) provided in the cutout portion H4, a light emitting element P1 that emits light O1 toward the reflector M, a sheet surface at the front end of the sheet S, and reflected light O2 from the reflector M are provided. The light emitted from the light emitting element P1 is reflected by the reflector M on the reflective sensor P including the light receiving element P2 that receives light, and the light receiving element P2 of the reflective sensor P without conveying the sheet S, and the reflected light enters. The light is set to a predetermined output level by shining, and when the tip of the sheet S penetrates into the field of view of the reflective sensor P under this condition, the tip of the sheet S optically passes a part of the reflected light. Cut off While the amount of light is reduced by, the tip of each sheet S is irradiated from the light emitting element P1 of the reflection type sensor P, and the light is reflected by the sheet surface and is incident on the light receiving element P2. As a result, a light amount distribution according to the type of each sheet S is obtained,
An A / D converter that A / D-converts the data D1 output from this light amount distribution as the output data of the light receiving element P2;
It comprises a discriminating means CPU for discriminating the sheet type by comparing the output data of the A / D converter with the reference data of the memory ROM storing the reference data corresponding to the sheet type stored in advance. The reflector M may be a mirror or a reflecting surface having a reflectance higher than a predetermined value. 15 and 16 specifically show the light receiving element PS.
FIG. 15 (A) conceptually shows the states of the irradiation light from the light emitting element PS1 and the reflected light reflected by the reflecting surface M and received by the light receiving element PS2. Therefore, x1, x2, x3, and x4 are light receiving elements PS
2 shows the position where the output value of 2 is sampled, and with respect to the reference level O, it is judged that the predetermined value or more is a high level H and the predetermined value or less is a low level L. Specifically, FIG. 15B shows the output characteristics of the light receiving element PS2 when a blank sheet S is passed, and the characteristic pattern is [OHL-
O], and the reference pattern of each individual reference sheet is previously captured and compared to determine the sheet type. FIG. 16 shows the characteristic pattern of each reference sheet. By storing this characteristic pattern in the ROM memory of the judging means CPU or by observing the output value of the light receiving element PS2 at each timing according to the sheet movement amount. Can also capture feature patterns. An example of the determination method will be described with reference to FIGS. 17 and 18. First, FIG. 17 shows the light receiving element P.
2 output changes, specifically, changes in the photocurrent value (or converted voltage value) flowing in the phototransistor forming the light receiving element P2 are simply captured, and five types of sheets are determined as shown in the figure. Further, as shown in FIG. 18, five kinds of patterns are stored in advance in the memory ROM of the judging means CPU as reference data, and the judgment is made as an image pattern in which the output from the light receiving element P2 is a function of the movement amount of the sheet. After writing in the rewritable memory RAM of the means CPU, the sheet type is determined by comparing the image pattern with the reference pattern.

(Explanation of Principle of Sheet Discriminating Method Using Sheet Discriminating Device) [Principle of Operation] When there is no document, the light emitted in the α direction from the point A on the light emitting surface in FIG. The light is reflected at the point O (assuming that the reflectance is 100%), and α is set at the point B on the light receiving surface.
Is incident at an angle of. Since the mirror is specularly reflected, there is no other path for light to travel from point A to point B.
Assuming point A as the center of a perfect diffuse surface light source,
Let S be the radiance at point A and point B at the center of the light-receiving surface. The irradiance Ee at the light-receiving surface is Ee = LeΔSCOS ² α / (4h ² + D ² ) = 4h ² LeΔS / (4h ² + D ² ) ² ... Equation (1) is obtained. The relationship between the photocurrent I _L (collector current I _C ) flowing in the phototransistor that constitutes the light receiving element and the irradiance Ee has a relationship of I _L = AEe ^N , where A is a constant, and N
The value is almost 1.1. Therefore, the factors that determine the amount of photocurrent are the distance h between the sensor and the mirror, the distance D between light reception and emission, and the directional characteristics of the sensor (the directional half-value angle θ1 / 2 as a representative value).
Indicate. ). However, in practice, it can be treated as a function of only the sensor-mirror distance h. When the document approaches the sensor, in addition to the specularly reflected light from the mirror as shown in FIG. 1B, the light diffusely reflected at an arbitrary point P on the document surface is also incident. The amount of received light depends on the document surface condition such as reflectance, the distance between the sensor and the document 1, the sensor directivity angle θ1 / 2,
It is determined by the document position x. The actual document passage direction is perpendicular to the paper surface and the sensor surface. When the document is completely under the sensor, only the diffuse reflection light from the document surface is obtained, and in this case as well, like the mirror, it can be treated as a function of only the sensor-document distance 1 in practice. In the case of a translucent paper such as tracing paper, transmitted diffused light is generated and reflected in a wide range of the mirror, so that the mirror shape also affects. As described above, when the light incident on the light receiving section is only the specular reflection light from the mirror,
There are four patterns of four types of patterns, namely, when the light reflected by the document surface is added to the light regularly reflected by the mirror, only when the light reflected by the document surface is added, and when the transmitted light is added to the light reflected by the document surface. Determines the output waveform. Since the characteristics show two characteristics of diffuse reflection type and transmission type, let us consider the output waveform of the mirror reflection type sensor from the output waveforms of both sensors.

[Detection Characteristic Curve] The photocurrent IL-document movement distance x characteristic, which is particularly important among the characteristic curves relating to document movement, will be described. FIG. 2 shows an actual waveform for detecting the leading edge of a blank sheet. In the diffuse reflection type sensor of FIG.
Let I _{Ldr0 be} the photocurrent when there is a document in the entire visible range of 1 to _x2 , R be the reflectance of the document, and f (x, x12) be the reflection distribution function at the document position x in the section [x1, x2]. Then,
When the dark current can be ignored, the photocurrent I _Ldr is I _Ldr = I _Ldr0 Rf (x, x12) (Equation (2)) where 0 ≦ f (x, x12) ≦ 1 When the leading edge of the document is before x1, there is no reflected light and f (x, x12) = 0, and before x2, the reflected light is incident on the entire visible range of the sensor f (x, x12). = 1. In the transmissive sensor of FIG. 2B, x3 to x4 is the visible range.
The position of the light receiving portion is a position obtained by rotating the light receiving portion of the reflective sensor by 180 ° around the x axis. The photocurrent when there is no light blocking at all, I _Ltr0 , the light transmittance of the document is τ, and the interval [x
[3, x4], the transmission distribution function at the document position x is g (x)
Then, the photocurrent I _Ltr is: I _Ltr = I _Ltr0 (1- (1-τ) g (x, x34)) (3) where 0 ≦ g (x, x34) ≦ 1, 0 <Τ <1. If the leading edge of the document is before x3, the transmitted light is not blocked and g (x, x3
After 4) = 0 and x4, the transmitted light is completely blocked when the transmittance τ = 0, and g (x, x34) = 1.
Next, as a feature of the mirror reflection type sensor, there is a two-sided property of a diffuse reflection type and a transmission type. Therefore, assuming that the formula of the mirror reflection type photocurrent I _Lmr is the sum of the photocurrents of both sensors, the following formula is established. I _Lmr = I _Ldr + I _Ltr = I _Ldr0 Rf (x, x12) + I _Ltr0 (1- (1-τ) g (x, x34)) Equation (4) _Specular reflection light from the mirror before x1 Receives only x1
~ X3 is the process in which the diffuse reflection light from the original is added to the regular reflection light from the mirror. x3 to x4 are processes in which specular reflection light from the mirror is blocked by the document, x4 to x2 are processes in which diffuse reflection light from the document is incident on the remaining visible range, x
From 2 onward, the manuscript exists in the entire visible range. Since the section [x3, x4] is included in the section [x1, x2], the diffuse reflection and transmission characteristics are simultaneously shown in the section [x3, x4]. And I _Ldr0 in equation (4), to set the optical path so that I _Ltr0 equal, by placing this value as _{I Lmr0, I Lmr = I Lmr0} {Rf (x, x12) - (1-τ) g (x , X34 + 1} Equation (5) Equation (7) is the basic equation of the mirror reflection type sensor, and Fig. 3 shows the output waveform model according to Equation (5) and the actual output waveform of the mirror reflection type. From the formula (1), the photocurrent I _Lmr0 at the time of non-detection is: I _Lmr0 = A {4h ² LeΔS / (4h ² + D ² ) ² } N ... Formula (6)

[Sensor characteristics and optical path parameters] Four parameters important in determining the sensor characteristics were considered, and the characteristics were measured in a diffuse reflection type sensor. As a result, the optical path is set according to the application. Sensor-mirror distance h In FIG. 1A, when the relationship between the sensor-mirror distance h and the photocurrent IL is measured, a characteristic curve as shown in FIG. 4A is obtained. The focal length h0 of the sensor becomes longer as the directivity angle θ1 / 2 becomes smaller and the light receiving / emitting distance D becomes larger. 0 ≦ h ≦ h
The area around the center of 0 is theoretically a straight line, and in the range of h0 <h, it is almost inversely proportional to the square of the distance h3). Such characteristics are well known in displacement sensors (photonic sensors) using optical fibers, etc. 4), 5), 6), and detailed description thereof is omitted. The measured value was the focal length h0 = 4.2 mm. Sensor-original distance l Shows the same characteristics as the sensor-mirror distance, but the focal length l ₀ is also affected by the smoothness of the document surface. Figure 4
3A, the curve (a) shows the sensor-mirror distance h characteristic of the photocurrent I _L , the curve (b) shows the sensor-document distance l characteristic, and the curve (c) shows the photocurrent ratio S at the same distance between them. /
It shows the distance characteristic of N. Focal length of blank paper l0
The measured value of was 6.0 mm. Mirror area S In FIG. 5, the curve of (a) is the relationship between the photocurrent and the mirror area at the time of non-detection, the curve of (b) is the relationship between the photocurrent and the mirror area at the time of tracing paper detection, and the curve of (c). Shows the relationship between the photocurrent ratio S / N of both and the mirror area. The shape of the mirror is limited to a circle with a radius r. S / N is
It becomes the largest when the beam diameter of the sensor is equal to the actual mirror diameter (area S0) 7). The measured value is S0 = 2.2 (0.
7π) mm2, and it was found that a circle having a radius r = 0.84 mm maximizes the S / N. At this time S / N = 1
It became 0.9. However, in such a small area, the S / N is decreased conversely due to the directivity of the sensor and the deviation in the product assembly. Therefore, a sufficiently large mirror was used in other experiments. In the case of an original having no transmitted light, a constant photocurrent can be obtained regardless of the area of the mirror, so that the S / N curve has the same slope as the curve of FIG. Therefore, a large mirror area is advantageous. Further, the S / N is maximized when a slit having the same shape as the beam diameter of the retroreflective sensor is provided between the sensor and the original and the original is set to pass therethrough. In this experiment, we decided not to provide slits for cost reduction. The directional characteristics of the directional angle θ 1/2 sensor are determined by the characteristics of the light emitting and receiving element alone, the shape of the holder, and the positional relationship between the two. As a representative value, the half-value angle θ1 / 2 is shown. Although the focal length can be extended by narrowing the directivity angle, the amount of light received decreases as the distance from the sensor increases. This time, the pointing half-value angle θ
1 / 2≈20 °.

[Application to Original Detection] (Original Type Discrimination) As an original type discriminating means, an image sensor, a CCD camera, or an optical fiber sensor can be considered, but it is very expensive. With the mirror reflection type sensor, by setting the ratio of the light reflected by the mirror and the light reflected by the document surface appropriately, you can obtain different output waveforms for all five types: white paper, black paper, translucent paper, glossy paper, and OHP paper. Therefore, the type of document can be determined.

Optical Path Determining Method In order to form a characteristic waveform without saturating the output waveform, first, the photocurrent due to the reflection from the mirror is made equal to the photocurrent due to the reflection on the PPC paper surface. In other words, the sensor-mirror distance h and the sensor-document distance l are set so that glossy paper> OHP paper> mirror≈PPC paper> semi-transparent paper> black paper (7). The output voltage at this time is the power supply voltage Vcc / 2 = 2.5 v, and the threshold values are 3.0 v and 2.0 v.
It was installed in two places of 0 v. First, when the distance between the sensor and the original is set to 6.0 mm, which is the focal length, the distance between the sensor and the mirror h = 22 mm according to the conditions of FIG. 4 and Expression (7).
Becomes When the detection waveform is measured in this optical path, the peak voltage of the tracing paper is 3.0 v, which is undetectable. This cause is related to the document position x immediately before blocking the specular reflection light from the mirror, the sensor-document distance l, and the sensor directivity. From Fig. 5, the beam diameter of the mirror reflection type sensor is ± 1 with the optical axis of the sensor as the center.
Since about 0 mm is practical, when the sensor-original distance 1 is 6.0 mm, the directivity angle with respect to the leading edge of the original becomes about 9.5 °. At this time, the light receiving efficiency is reduced to about 67% with respect to the directivity angle of 0 °. Therefore, the distance between the sensor and the document is l = 15 so that the light receiving efficiency is about 90%.
mm. From the conditions of FIG. 4 and the equation (7), the sensor-mirror distance at this time is h = 30 mm. When the detection waveform was measured in this optical path, the peak voltage of tracing paper could be obtained as 3.4 v, but the detection voltage of OHP paper was 2 V because the distance between the sensor and the document was far from the focal length. Only rose to .9v. From the above, the sensor-original distance l = 6.0 mm was decided for OHP paper detection, and the mirror installed horizontally to the sensor surface was set to increase the peak voltage at tracing paper detection. It was arranged diagonally as shown in FIG. The document passage direction is from left to right with respect to the paper surface. When the leading edge of the document enters the visible range of the sensor, the light reflected from the document surface is received, but the directivity angle at this position is large and the output voltage rises only slightly. The reflected light is blocked. Immediately after the specularly reflected light from the mirror is blocked, the sensor has a directivity angle β with respect to the front end of the document and receives only the diffusely reflected light in the range of −θ _1/2 to −β, so the output voltage becomes very low. On the contrary, immediately after the trailing edge of the original passes the beam diameter, the reflected light in the range of -β to + θ _1/2 enters in addition to the reflected light by the mirror, and the output voltage becomes high. The visible range at this time is x3 '~
Let x (4) be the transmission distribution function at the document position x in x4 ', section [x3', x4 '], and the photocurrent I in the optical path of FIG.
_Lmr is expressed by the following equation as in equation (5). I _Lmr = I _Lmr0 {Rf (x, x12)-(1-τ) h (x, x34 ') + 1} Equation (8) Here, _0≤h (x) ≤1. The position of x3, x4 is ltan
Since β is moved to the x1 side, the waveform shape is significantly different from the waveform in FIG. In this experiment, the tilt angle β of the mirror was set to 20 °. The photocurrent ILdp due to the reflection of the white paper and the photocurrent ILmr due to the reflection of the mirror become equal when the sensor-mirror distance h = 20 mm. The sensor sensitivity was exactly the same as when the mirror was horizontal, but a large peak voltage could be obtained in this optical path.

Detected Waveforms Detected waveforms for discriminating the type of original by the optical path of FIG. 6 are shown in FIGS. 7 to 11. * Blank paper (PPC paper) This is the waveform represented by equation (8) when the reflectance R = 1 and the transmittance τ ≈ 0 under the conditions of equation (7). For example 4.2v
The peak voltage of is obtained. * Black paper When the reflectance _R≈0 can be regarded in the equation (11), I _Lmr = I _Lmr0 {-h (x, x34 ') + 1} ... The waveform is represented by the equation (9). As you can see from the above formula,
No more current than when not detected is generated. * Semi-transparent paper (tracing paper) This is the waveform represented when 0 <R <1 in formula (8). Depending on the reflectance and transmittance, the waveform will be similar to white or black paper. For example, a peak voltage of 3.7v was obtained. * Glossy paper (silver gloss sticker) Diffuse reflection is very small and can be regarded as regular reflection only. Assuming that the visible range of specular reflection in the interval [x3, x4] is approximately equal to the visible range of the transmission type, the photocurrent I _Lmr is I _Lmr = I _Lmr0 {Rg (x, x34) -h (x, x34 ' ) +1} ... Formula (10) Here, reflectance R> 1. If there is no common range between the section [x3, x4] and the section [x3 ', x4'], the output voltage immediately after passing through the section [x3 ', x4'] is 0v, and conversely the section [x3, x4] If the original is inside, a very large output can be obtained. * If it can be considered that the transmissivity τ ≈ 1 for the OHP paper, the photocurrent I _Lmr is I _Lmr = I _Lmr0 {Rg (x, x34) +1} ... Formula (11) The reflectance R <1. From the above equation, the output smaller than that at the time of non-detection detection does not occur. The actual detected voltage is 3.6 v
was gotten. * Judgment of presence or absence of original curl Even if the leading edge of the original is curled or curled, the upper curl is PPC or A.
It is one of the causes of paper jams in DF. If the presence or absence of curl is known before the paper passes through the position where the paper jam easily occurs, the trouble due to the paper jam can be prevented. If the leading edge of the paper is curled toward the sensor,
The distance between the sensor surface and the leading edge of the original becomes very short, and as can be seen from FIG. 4, the influence of reflection on the original surface is small. As the document passes, it is gradually affected by the document surface, but since the document tip blocks the specularly reflected light from the mirror before the reflected light from the document surface is added, two lights are present at the same time. There is almost no original position. 12A shows a blank sheet detection waveform when there is no curl, and FIG. 12B shows a blank sheet detection waveform when there is an upper curl. The curl has a file width of 10 mm and a height of 4 mm. The shape of the optical path is exactly the same as in FIG. 6, but the original passage direction is from the right side to the left side of the paper so that the presence or absence of curl can be determined by detecting only the leading edge of the original. In the document type determination, the direction is from left to right in the drawing, but when the document passes in the opposite direction, the waveform is rotated by 180 ° about the Y axis. However, this time, since the signals at two points, the leading edge and the trailing edge, are used, the document type can be discriminated from either the left or the right. In particular, in the case of detecting glossy paper, it may be difficult to detect it depending on its glossiness. In this case, as shown in FIGS. 20 and 21, the reflector M (mirror) is aligned with the glossy paper to be detected. By inclining, the output value of the light receiving element P2 changes and it becomes easy to distinguish it from other sheets (original).

(Structure Description of Copying Machine and Automatic Document Feeding Device Utilizing Sheet Discriminating Device) FIG. 19 shows a copying machine equipped with an automatic document feeding device. First, the automatic document feeding device is mounted on a paper feed tray T1. The sheet type discriminating apparatus PA for discriminating the type of the original S1 is provided on the conveying path before the originals S1 set on the sheet are separated and conveyed to the platen G of the copying machine. Outputs the type of document as a signal to the copier body. Based on this signal, the main body of the copying machine determines, for example, the transparency, glossiness, surface roughness, etc. from the sheet type and corrects the exposure amount etc. to an appropriate value. Also,
In the main body of the copying machine, the recording paper S2 set in the paper feed cassette T3 is processed by the image forming process PS or the fixing unit P.
A sheet type discriminating apparatus PB for discriminating the type of the recording sheet S2 is provided on the conveying path before reaching S1, and the sheet type discriminating apparatus PB is taken into the image forming process PS or the control unit of the fixing unit PS1 as a signal. Image forming process P
In S, for example, the transfer state is adjusted depending on the type of recording paper, and in the fixing means PS1, the states of fixing temperature and fixing pressure are adjusted depending on the type of recording paper.

(Development of Other Applications) In addition to the above-mentioned copying machine equipped with the automatic document feeder, any apparatus having various kinds of sheets can be applied. For example, in a personal printer, generally, thermal paper and plain paper can be selected. In this case, a user can select a predetermined selection key and perform switching, and can automatically select one, which is extremely easy to handle. . As partially explained above, the type of sheet can be discriminated including not only the paper quality but also the curled state of the paper.

[0020]

As described above, according to the present invention, when at least the leading edge of the sheet penetrates into the light receiving range of the light receiving element (in the field of view of the reflection type sensor), the leading edge of the sheet absorbs a part of the reflected light. By optically cutting the optical path, the tip of each sheet is irradiated from the light emitting element (of the reflective sensor),
Due to the change in the light amount caused by the light reflected by the sheet surface and entering the light receiving element, the light amount changes (change amount or change pattern) in which the light amount changes individually according to the type of each sheet, that is, by the above configurations to 17 , At least the front end of the sheet passes through the light-receiving range of the light-receiving element, the reflected light from the reflecting surface irradiated by the light-emitting element and the reflected light from the sheet surface are received by the light-receiving element, The front end of the sheet is in the vicinity of both boundaries before and after the sheet feeding direction in the light receiving range of the light receiving element, and in the vicinity of both boundaries before and after the sheet feeding direction in the light receiving range in which the specularly reflected light of the light emitting element can be received. By comparing with the output change of the light receiving element at a predetermined position selected according to the type of the discrimination sheet among the locations, the discrimination can be performed more accurately than the conventional sheet type discrimination method described above. High sheet type discrimination method of can provide, the sheet type discrimination method utilizing a sheet type discrimination apparatus, and it is possible to provide a sheet feeding apparatus having the sheet type discriminating apparatus.

[Brief description of drawings]

FIG. 1 is an explanatory diagram for explaining a sheet type determination method of the present invention.

FIG. 2 is an explanatory diagram for explaining a sheet type determination method of the present invention. (Characteristic diagram of reflective sensor)

FIG. 3 is an explanatory diagram for explaining a sheet type determination method of the present invention. (Output waveform diagram of reflective sensor)

FIG. 4 is an explanatory diagram for explaining a sheet type determination method of the present invention. (Output waveform diagram of reflective sensor)

FIG. 5 is an explanatory diagram for explaining a sheet type determination method of the present invention. (Output waveform diagram of reflective sensor)

FIG. 6 is an explanatory diagram for explaining a sheet type determination method of the present invention. (Explanation of optical path of reflective sensor)

FIG. 7 is an explanatory diagram for explaining a sheet type determination method of the present invention. (Reflection sensor output waveform diagram for glossy paper)

FIG. 8 is an explanatory diagram for explaining the sheet type determination method of the present invention. (Reflection sensor output waveform diagram for blank paper)

FIG. 9 is an explanatory diagram for explaining a sheet type determination method of the present invention. (Reflection sensor output waveform diagram for black paper)

FIG. 10 is an explanatory diagram for explaining a sheet type determination method of the present invention. (Reflection sensor output waveform diagram for tracing paper)

FIG. 11 is an explanatory diagram for explaining a sheet type determination method of the present invention (output waveform diagram of a reflection type sensor in the case of transparent paper / OHP paper)

FIG. 12 is an explanatory diagram for explaining a sheet type determination method of the present invention. (Output waveform diagram of the reflective sensor depending on curl state)

FIG. 13 is an explanatory diagram for explaining a conventional sheet type determination method.

FIG. 14 is an explanatory diagram for explaining a sheet type determination device of the present invention.

FIG. 15 is an explanatory diagram for explaining the sheet type determination method of the present invention.

FIG. 16 is an explanatory diagram for explaining a sheet type determination method of the present invention.

FIG. 17 is an explanatory diagram illustrating an embodiment of the sheet type determination method of the present invention.

FIG. 18 is an explanatory diagram illustrating another embodiment of the sheet type determination method of the present invention.

FIG. 19 is an explanatory diagram of a sheet feeding device including the sheet type determination device of the present invention.

FIG. 20 is an explanatory diagram for explaining another embodiment of the sheet type determination method of the present invention.

FIG. 21 is an explanatory diagram for explaining another embodiment of the sheet type determination method of the present invention.

[Explanation of symbols]

 H1, H2 ... Sheet transport guides H3, H4 ... Cutout portions of sheet transport guides S. Sheet M. Reflector (mirror) P1. Light emitting element P2. Light receiving element P .. Reflective sensor A / D .. A / D converter CPU .. Discrimination means

Claims (17)

[Claims] 1. A light-emitting element and a light-receiving element arranged on one side facing the front and back surfaces of a sheet, and a reflecting surface for reflecting light from the light-emitting element arranged on the other side to the light-receiving element, at least. The light receiving element receives the reflected light from the reflecting surface irradiated by the light emitting element and the reflected light from the sheet surface while the tip of the sheet passes through the light receiving area of the light receiving element, and Sheet type discrimination method that discriminates sheet type based on output change 2. A sheet using a light emitting element and a light receiving element arranged on one side facing the front and back surfaces of the sheet, and a reflecting surface for reflecting light from the light emitting element arranged on the other side to the light receiving element. 4 points near the front and rear borders in the paper feed direction within the light receiving range of the light receiving element, and inside the front and rear borders in the paper feed direction within the light receiving range where specularly reflected light from the light emitting element can be received. Of the sheet types, the sheet type determining method for determining the sheet type based on the output change of the light receiving element at a predetermined position selected according to the type of the determining sheet 3. A sheet type discriminating method for discriminating a sheet type by judging an output change of the light receiving element by a level comparison with a preset reference level in the sheet type discriminating method according to claim 2. 4. The sheet type discriminating method according to claim 3, wherein the preset reference level is set to a previous output value at a predetermined position selected according to the type of the discriminating sheet. 5. The sheet type determination method according to claim 2,
A sheet type discriminating method for discriminating a sheet type by detecting an output change of the light receiving element from an output value difference between selected predetermined positions and determining an output inclination. 6. The sheet type discriminating method according to claim 2, wherein an output pattern of the output change of the light receiving element is detected from each output value of the light receiving element at a predetermined position selected according to the type of the discriminating sheet. Sheet type determination method to determine the type 7. A light-emitting element and a light-receiving element arranged on one side facing the front and back surfaces of the sheet, and a reflecting surface for reflecting light from the light-emitting element arranged on the other side to the light-receiving element, and at least a sheet. The reflected light from the reflecting surface and the reflected light from the sheet surface, which are irradiated by the light emitting element while the tip of the light passes through the light receiving area of the light receiving element, are received by the light receiving element, and the output of the light receiving element is received. A sheet type discriminating method for discriminating the type of the conveyed sheet by comparing the stored data with reference data corresponding to the sheet type. 8. A light emitting element and a light receiving element are arranged on one side facing the front and back surfaces of the sheet, and a reflecting surface for reflecting light from the light emitting element to the light receiving element is provided on the other side, and the front end of the sheet receives the light receiving element. Judgment is made in the vicinity of both boundaries before and after the sheet feeding direction in the light receiving range of the element and in the vicinity of both boundaries before and after the sheet feeding direction in the light receiving range where the specularly reflected light of the light emitting element can be received inside thereof. Sheet type discriminating apparatus including discriminating means for discriminating the sheet type based on a change in the output of the light receiving element at a predetermined position selected according to the sheet type 9. A sheet type discriminating apparatus for discriminating a type of a conveyed sheet by comparing output data of the light receiving element with reference data according to a sheet type stored in advance. 10. The sheet type discriminating apparatus according to claim 9, wherein the sheet discriminating means comprises an external input means capable of setting the reference data in advance by an external input. 11. The sheet type discriminating apparatus according to claim 10, wherein the external input means includes a storage means for reading and storing in advance when each type of reference sheet is conveyed. 12. A sheet type discriminating apparatus in which the storage means according to claim 11 sets and stores an average value of output data of a plurality of reference sheets as reference data. 13. The sheet discriminating apparatus according to claim 8, wherein the discriminating means stores the output data of the conveyed preceding sheet as the reference data and compares it with the output data of the succeeding sheet. 14. The sheet type discriminating apparatus according to claim 8, wherein the output value of the light receiving element only for the reflected light from the surface of the conveying sheet and the received light only for the reflected light from the reflector on a predetermined sheet. Sheet type discriminating apparatus provided with adjusting means for setting the difference from the output value of the element within a predetermined range 15. The adjusting means of the sheet type discriminating apparatus according to claim 14, wherein one of the reflection type sensor and the reflector is inclined with respect to the opposite surface of the other, or the reflection body or the sheet is conveyed to the reflection type sensor. Sheet type discriminating device for adjusting position 16. The sheet type discriminating device using a blank sheet as the predetermined sheet of the sheet type discriminating device according to claim 15. 17. A paper feed tray on which sheets are placed, a separating means for separating and feeding the sheets placed on the paper feed tray one by one, and a predetermined number of sheets fed by the separating means. Transporting means for transporting to a position and discharging from a predetermined position,
In a sheet feeding device including a paper discharge tray for storing sheets discharged by the conveying means, a light emitting element and a light receiving element are provided on one of the conveying paths facing the front and back surfaces of the conveyed sheet before the conveying means. A reflection type sensor is arranged, a reflector for reflecting the light from the light emitting element of the recursive reflection type sensor to the light receiving element is arranged on the other side of the conveying path, and the leading edge of the sheet is fed in the light receiving range of the light receiving element. A predetermined position selected according to the type of the discrimination sheet, in the vicinity of both boundaries before and after the direction and in the vicinity of both boundaries before and after the paper feeding direction in the light receiving range inside which the specular reflection light of the light emitting element can be received. A sheet feeding device including a sheet type discriminating device configured to discriminate the sheet type based on a change in the output of the light receiving element