A document detecting apparatus

Abstract: A document detecting apparatus for a copying machine, comprising a photo-sensor having a light projecting device which emits a measuring light from an inside of to an outside of a copying machine through an original glass plate, and a light receiving device which is installed at a position deviated from a path symmetric to an optical axis of said measuring light with respect to a normal line set up on a surface of the original glass plate and which is directed to receive a scattered light produced from the measuring light scattered at a surface of an original document placed on the original glass plate; and a microprocessor which judges whether or not the original document exists according to an intensity of a light measured by said photo-sensor.

Description: This invention relates to a document detecting apparatus for a copying machine, which judges whether or not an original document is placed on an original glass plate, and which determines the size of said document. Apparatuses adapted to determine the size of an original document placed on the original glass plate by detecting light reflected from the original document surface are known from JP-A-78849/1981, JP-48759/1982, JP-95367/1983 and JP-10172/1982. In these apparatuses a measuring light beam is irradiated to the original document surface through the original glass plate, and the reflected light is caught through the original glass plate again. Since the measuring light is reflected also by the original glass plate itself, a detection error can arise due to ingress of the light reflected from the original glass plate. Particularly, since a surface of the original glass plate is approximately similar to a mirror surface, almost all parts of light reflected by the original glass plate surface are directed in a concentrated manner in a direction symmetric to the direction of incidence with respect to a line normal to the surface, as in case of reflection at a mirror surface (a light path of this type is called "major path" hereunder). The original glass plate has two surfaces which reflect the measuring light in the above manner. One is the lower side surface where the measuring light enters the original glass plate, and the other is the upper side surface which contacts with the original document, and the major path exists for both surfaces respectively. These major paths are practically overlapping each other if said two surfaces are parallel. In conventional apparatuses, a light receiving device adapted to catch the light reflected by the original document surface is installed in at least one of said two major paths so that it may also catch the light reflected by the original glass plate. Therefore, depending on the original document surface condition, the light reflected by the document surface cannot be distinguished from the light reflected by the original glass plate; thus the original document can not be correctly detected. In another known document detecting apparatus for a copying machine (JP-78849/1981) the light of the measuring light beam is modulated with a frequency different from the commercial power supply frequency in order to prevent external light from disturbing the detection of the size of the original document, and the side of an original cover facing the original glass plate is provided with a light-absorbing member to prevent light reflected by the original cover from causing an incorrect detection of the original document size. In a further prior document detecting apparatus (DE-A-33 36 961) light emitted by the copying light source additionally is used to detect the size of the original document on the original glass plate upon the original cover being completely closed. A light receiving device is installed at a position deviated from a path symmetric to the optical axis of the copying light source with respect to a line normal to the surface of the original glass plate, and the light receiving device is directed to receive scattered light produced by the copying light source and scattered at the surface of an original document placed on the original glass plate. In order to prevent light reflected by the closed original cover from disturbing the detection of the size of the original document, the side of the original cover facing the original glass plate is provided with a mirror reflection surface. Furthermore GB-A-1 458 282 already discloses an apparatus for detecting a presence of a medium and particularly an unwanted continuous presence of a transfer medium still adhering to a photosensitive insulating layer of a xerographic apparatus during its copying and duplicating process. This known apparatus comprises a light projecting device which directs a light beam towards the photosensitive insulating layer at a predetermined angle of incidence which differs from 90°. The apparatus further includes a light receiving device which is disposed so as to be placed outside of the zone to which light from a planar surface, such as the photosensitive insulating layer, is cast, to thereby substantially avoid detecting the light that reflects from the planar surface. The transfer medium, generally paper, however, instead of reflecting the light like a mirror or a planar surface does, bounces back and diffuses the light in a pattern which extends beyong that to which light reflected from the planar surface is cast. Therefore the light receiving device substantially detects light in the presence of a transfer medium but not in the absence of such a medium. An object of the present invention is to provide a document detecting apparatus which can avoid the influence of foreign light and of light reflected from an original glass plate and from the bottom face of the original cover, to securely detect an original document placed on the original glass plate. In conformity with the present invention, this object is reached by a document detecting apparatus comprising optical measuring means having a light projecting device which emits measuring light from the inside to the outside of a copying maching through an original glass plate, and a light receiving device which is installed at a position deviated from a path symmetric to the optical axis of said measuring light with respect to a line normal to the surface of the original glass plate, said light receiving device being directed to receive scattered light produced from measuring light scattered at the surface of an original document placed on the original glass plate; judging means which judges from the intensity of light measured by said optical measuring means whether or not the original document exists; and a cover closing state detecting means which outputs a closing state detecting signal when an original cover of the copying machine has been moved towards the original glass plate to a specified position immediately before being completely closed; said specified position being selected to be sufficiently close to the original cover fully closed position to prevent said optical measuring means from responding to foreign light, but sufficiently remote from the original cover fully closed position to prevent said optical measuring means from responding to light reflected from the bottom face of said original cover; said judging means being controlled so as to perform said judgement when said closing state detecting signal is outputted. The apparatus of the present invention not only provides for a high ratio of light reflected from the original document to light reflected from the original glass plate by the afore-mentioned positioning of the light receiving device, but also avoids undesired influence of foreign light as well as a light reflected from the bottom face of the original cover by measuring the reflected light at a time shortly before the original cover reaches its completely closed position. Thus a secure document detection will be accomplished. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an oblique view of a copying machine incorporating a document detecting apparatus according to the present invention. Fig. 2 is a schematic side view showing a state of closing a cover of the copying machine shown in Fig. 1. Fig. 3 is a schematic sectional view showing an arrangement of a light measuring means installed in the copying machine. Fig. 4 is an explanatory view showing correspondence of the optical measuring means with standard of document size. Fig. 5 is a block diagram of control system for the copying machine shown in Fig. 1. Fig. 6 is a flow chart of document detecting function. Fig. 7 is an explanatory view explaining a reflection of measuring light caused by a original document. Fig. 8 is a schematic sectional view showing relative positions of an original glass plate and the optical measuring means. Fig. 9 is a schematic view of an example of a photo-sensor. Fig. 10 is a characteristic diagram of an intensity of reflected light. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In Fig. 1 and Fig. 2, a copying machine 1 is a type of copying machine which carries out a copying operation with an original cover 2 slidden in a direction of a together with an original document and an original glass plate 3. When setting the original document, the original cover 2 is lifted and opened widely as shown in Fig. 2, the original document is placed on the original glass plate 3, the original cover 2 is closed and a print button of an operation panel 4 is pushed. Then, a sliding member 6 is slidingly driven in the direction of a so that both the original cover 2 and the original glass plate 3 supported by said sliding member 6 slide in the direction of a with the original document G held therebetween as shown in Fig. 3. Since a surface of the original document G passes thereby through a slit 5, its contents are read and copied. The construction of the copying machine 1 with regard to these functions is basically similar to a well-known construction. However, the copying machine 1 differs from a conventional one in the following points that this copying machine 1 is equipped with a document detecting apparatus 20 comprising a cover closing state detecting means 10, optical measuring means 13a ∼ 13d and a judging means induded in a micro- processor 14, and that these optical measuring means 13a ∼ 13d comprise reflection type photosensor formed integrally of an optical projector and an optical receiver and are disposed in such positions as underside of and indined against the original glass plate 3. The cover closing state detecting means 10 is composed of a magnet 11 fitted to the original cover 2 and a reed switch 12 fitted to the sliding member 6 on the opposite side of the magnet 11. Since a distance between the magnet 11 and the reed switch 12 is large when the original cover 2 is opened, the reed switch 12 is under an OFF state. However, since the magnet 11 gets near to the reed switch 12 as the original cover 2 becomes closed, the reed switch 12 becomes to an ON state when the cover 2 is closed to a predetermined position. In this instance, an angle ⊘ made by the original cover 2 and the original glass plate 3 can be properly adjusted by a size or a position of the magnet 11. This angle ⊘ is preferably adjusted to below 15 degrees and further to a range of below 10 degrees and above 5 degrees. The optical measuring means 13a ∼ 13d can be composed of photo-sensors which are formed integrally of pairs of light emitting diodes and photo transistors. These plural optical measuring means 13a ∼ 13d are arranged under the original glass plate 3 respectively corresponding to standard document sizes B5, A4, B4 and A3 used in the copying machine 1. Fig. 4 shows the arrangement of them. A noteworthy point is that these photo-sensors, i.e. optical measuring means 13a ∼ 13d, are inclined by an angle ϑ with respect to the original glass plate 3. This inclination of ϑ will be described later in details. It is preferable to set the angle to ϑ = 15° ∼ 60° and further to a vicinity of 30 degrees. The judging means is included as a part of function in a microprocesser 14 which is provided as a center of control, and judges an existence of the original document depending on an intensity of an incident light measured by said optical measuring means 13a ∼ 13d. Fig. 5 shows a control system of the copying machine 1 in which the optical measuring means 13a ∼ 13d, the reed switch 12 of the cover closing state detecting means 10, a paper cassette size detecting switch 21, a document size indicating device 22, a paper feed dutch 23 and an optical system 24 reading contents of the document are connected to the microprocessor 14. Function will be described hereunder with reference to Fig. 6. First, a step S1 is an operation of setting the original document and means such operation that an operator opens the original cover 2 and places the original document on a specified position of the original glass plate 3. This specified position is indicated on a frame 7 of the original glass plate 3 as shown in Fig. 4. After setting the original document, the operator closes the original cover 2. Then, the reed switch 12 will be switched to ON when the original cover 2 is closed to the specified angle ⊘. A step S2 means an operation of switching ON of the reed switch 12. When the microprocessor 14 detects that the reed switch 12 is switched to ON, the phototransistor measured a reflected light. The light emitting diodes may be made emit light continuously or only at the time of this measurement. Fig. 7 is a view showing this state. In case of the reflected light detecting system, an error of detection due to' an ingress of foreign light would occur. Namely, the detection of foreign light would cause a miss judgement that a document is existing even though such a document does not exist. In conventional apparatuses, such an improvement has therefore been made that the reflected light is identified from the foreign light by using a modulated light. However, this improvement is arising another problems of complicated mechanism etc. While in the document detecting apparatus 20, the reflected light from the original document G is measured under the state immediately before the original cover 2 is closed completely. Namely, the cover closing state detecting means 10 outputs a closing state detecting signal when the original cover 2 of the copying machine 1 is closed onto the original glass plate 3 to the specified position of immediately before being closed completely. Upon the closing state detecting signal being outputted, the optical measuring means 13a ∼ 13d measure the reflected light, which are arranged at specified positions inside of the original glass plate 3 and measure the light entering from outside to inside through the original glass plate 3. Since the foreign light is therefore shut out by the original cover 2 under this state, a bad influence of the foreign light can be eliminated. Further, the original cover 2 is not completely closed so that a bad influence caused by the reflected light from a bottom face of the original cover 2 can be avoided. In this manner, such a timing of securely detecting the existence and size of the original document is taken by eliminating the influence of foreign light using a simple mechanism without creating complication thereof. Now, Fig. 7 shows a case of A4 sized original document G. In this instance, the light rays emitted from the optical measuring means 13a and 13b pass through the original glass plate 3 to the original document G placed thereon and are scattered and reflected thereat, then pass through the original glass plate 3 again to return to the optical measuring means 13a and 13b. Thereby, the scattered reflected rays are measured by the optical measuring means 13a and 13b. In case of the optical measuring means 13c and 13d, however, since no original document G exists in their region, after the rays emitted from those means pass through the original glass plate 3, they pass through it intactly without being scattered and reflected. These rays are irradiated on and reflected from the bottom face of the original cover 2, but the reflected rays do not substantially get to the optical measuring means 13c and 13d because the optical cover 2 is inclined at the time of measurement and distances to the optical measuring means 13c and 13d are large. Further, the foreign light is also shut out by the original cover 2 so that it does not get to the optical measuring means 13c and 13d. Therefore, the reflected light (and the foreign light) will not be detected at these optical measuring means 13c and 13d. Accordingly, the microprocessor 14 of the judging means makes judgements as: the original document is existing at the optical measuring means 13a, existing at 13b, not existing at 13c, and not existing at 13d. The document size B5 corresponds to the optical measuring means 13a and the size A4 corresponds to the means 13b. Since the size A4 is larger than the size B5, the microprocessor 14 makes judgement as: a size of the original document G to be copied next is A4. The above-mentioned decision occurs at step S3. In order to improve a reliability of measurement, the photo-sensors of the optical measuring means 13a ∼ 13d are indined with respect to the original glass plate 3 for avoiding the detection of reflected lights by the original glass plate 3 itself. This will be described later in detail. In a step S4, the document size judged by the microprossessor 14 is displayed on the document size indicating device 22. Further, when "Automatic magnification setting key" is selected, the magnification mode is automatically set to enlargement or reduction, so as to be adapted to a specified paper. On the other hand, when "Automatic paper selection key" is selected, a paper corresponding to the original document size is automatically selected. In the event that the paper corresponding to the original document size is exhausted, the situation is displayed. If desired, a ratio of usable paper size to the original document size is calculated and automatically set the magnification for enlarging or reducing. Further, if a paper corresponding to the original document size can be selected, the paper of that size is automatically selected. The operator looks at the indication of the copying machine 1, and if the situation satisfies him, he pushes the print button on the operation panel 4. Thereby, the original document G sandwiched between the original cover 2 and the original glass plate 3 slides in the direction of a, and the copying operation is thus carried out. The above-mentioned operation occurs at step S5. The copying operation is completed as above, and the reed switch 12 is switched to OFF when the operator opens the original cover 2 in order to take out the original document. At step 6 the OFF state of the reed switch 12 is detected. When the original cover 2 is opened the reed switch 12 is switched to OFF, i.e. the indication of the document size is reset. This occurs at step S7. Incidentally, although not shown in Fig. 6, when the original cover 2 is closed after the original document G is taken out, the microprocessor 14 judges that the original document G has been taken out by detecting absence of original document G. While, if no such fact is recognized even though a comparatively long time (five minutes for example) has elapsed after completion of the copying operation, the microprocessor 14 makes judgement as "failure to take out the original document" and informes the operator of the failure by an alarm. Next, a characteristic of the detected amount of scattered reflected light versus the angle ϑ with which the photo-sensors of the optical measuring means 13a ∼ 13d are inclined with respect to the original glass plate 3 will be described hereunder. Fig. 8 is a schematic arrangement diagram for measuring above characteristic, and in which the original document G is set on the original glass plate 3. The photo-sensor 13 is of type EE-SF5, Omron Tateishi Electronics Co. make, in which a light emitting diode P₁ is integrated with a phototransistor P₂ with a distance of ℓ = 5.4 mm kept therebetween and their optical axes are deviated toward inside by 12 degrees respectively to be intersected at a forward position with an angle of 24 degrees. The distance between the original glass plate 3 and the center position between the light emitting diode P₁ and the phototransistor P₂ on the front face 8 of the photosensor 13 is set by distance of d = 5mm, the photo-sensor is inclined with an inclination angle ϑ so as to position the light emitting diode P₁ to a lower side, and this ϑ is changed from 0 degree to 60 degrees. The same effect will be obtained if the phototransistor P₂ is brought to the lower side. Incidentally, in Fig. 8 the inclination angle ϑ is changed as ϑ₁ = 15°, ϑ₂ = 30°, ϑ₃ = 60°. The measured reflected light is indicated in Fig. 10 as a ratio to a received light amount for no original document G existing (its component is the reflected light from the original glass plate 3). As seen from Fig. 10, in case when the original document G is a white paper, a true scattered reflected light from the original document G can be detected by being preferably separated (at a ratio of more than 3) from the reflected light from the original glass plate 3 if the inclination angle ϑ of the photo-sensor 13 is taken as a value between 15 degrees and 60 degrees. Further, in case when the original document G is a tracing paper, the true scattered reflected light can be separated and detected with the same level if the inclination angle ϑ of the photo-sensor 13 is taken as a value between 23 degrees and 44 degrees. On the contrary, when ϑ = 0 degree i.e. when the photo-sensor 13 is made stand opposite to the original glass plate 3, the reflected light from the original glass plate 3 is detected much more so that the reflected light from the original document G becomes hard to be identified and its detection reliability becomes worse although the original document G is detectable. Moreover, when the angle ϑ is taken as a value more than 60 degrees, the reliability will become worse too. As can be understood from the above result, the bad influence of reflection at the original glass plate 3 can be removed by slantly arranging the optical measuring means 13a ∼ 13d with respect to the original glass plate 3. The reason why such result is induced is supposed to be as follows. Since the surface of the original glass plate 3 is approximately similar to a mirror surface, the reflection at this surface is carried out, as in case of reflection at the mirror surface, in such a way that almost all parts of light reflect in a direction symmetric to an incident direction with respect to the normal line i.e. along the major path in a concentric manner. On the other hand, the surface of the original document G is generally the light scattering surface so that the light is scattered and reflected with some extent of spreading and an influence caused by difference of direction is remarkably small as compared with the reflection at the surface of the original glass plate 3. Therefore, if the light projecting device and the light receiving device are installed at positions deviated from the major path of reflection at said original glass plate 3, a ratio of scattered reflection component at the original document G versus reflection component at the original glass plate 3 among the total received light amount can be improved. This means an improvement in the S/N ratio itself to provide the sure detection of original document. In the present invention, inclining the optical measuring means 13a ∼ 13d corresponds to deviating the path between the light projecting device and the light receiving device from said major path. Another embodiment of this invention includes such an apparatus suitable for a copying machine of a type wherein the original document stands still but an optical system moves and scans the entire area of the original document to read its contents, contrary to a type wherein the original document G is moved and the entire area thereof is scanned to be read its contents as in case of the present invention. In this case, since the optical system moves under the original glass plate, the optical measuring means can not be installed in this range of movement. Therefore, the optical measuring means may be installed out of the moving range of the optical system, the light may be emitted from an oblique lateral side to the original document on the original glass plate and the reflected light caused by scattered reflection at the original document surface may be caught. If a measuring object is the mirror surface, it will be impossible to irradiate the light from the oblique direction and catch the reflected light in the same direction as the incident direction, However, since the original document to be copied is an ordinary paper and the light is scattered at its surface, the detection becomes possible. As seen from the above description, in the said document detecting apparatus 20, the true reflected light at the document surface can be securely detected under situations that the foreign light is shut out by the original cover 2 and the original cover 2 does not completely cover the original glass plate 3 with no reflection at its underside, and further the bad influence of reflection at the surface of the original glass plate 3 is avoided. Therefore, a highly reliable document detection becomes possible.

Claims: A document detecting apparatus comprising optical measuring means (13a - 13d) having a light projecting device which emits measuring light from the inside to the outside of a copying machine (1) through an original glass plate (3), and a light receiving device which is installed at a position deviated from a path symmetric to the optical axis of said measuring light with respect to a line normal to the surfaces of the original glass plate (3), said light receiving device being directed to receive scattered light produced from measuring light scattered at the surface of an original document (G) placed on the original glass plate (3); judging means which judges from the intensity of light measured by said optical measuring means whether or not the original document exists; and a cover closing state detecting means (10) which outputs a closing state detecting signal when an original cover (2) of the copying machine (1) has been moved towards the original glass plate (3) to a specified position immediately before being completely closed; said specified position being selected to be sufficiently close to the original cover fully closed position to prevent said optical measuring means from responding to foreign light, but sufficiently remote from the original cover fully closed position to prevent said optical measuring means from responding to light reflected from the bottom face of said original cover (2); said judging means being controlled so as to perform said judgement, when said closing state detecting signal is outputted. A document detecting apparatus as set forth in claim 1, in which the optical measuring means (13a-13d) is constructed so that the light projecting device and the light receiving device are integrated together and the integrated body is disposed at a specified position under the original glass plate (3) so as to be directed to the original glass plate and inclined at a specified angle (Θ). A document detecting apparatus as set forth in claim 1 or 2, in which the specified angle (Θ) by which the optical measuring means (13a-13d) is inclined with respect to the original glass plate (3) is from 15 to 60 degrees. A document detecting apparatus as seth forth in claim 3, in which the specified angle (Θ) is about 30 degrees. A document detecting apparatus as set forth in one of the preceding claims, in which the optical measuring means (13a-13d) comprises a photocoupler formed integrally of a light emitting diode and a phototransistor. A document detecting apparatus as set forth in one of the preceding claims, in which said specified cover-position immediately before being completely closed is a position where the angle (⊘) defined by the original cover (2) and the original glass plate (3) is from 5 to 10 degrees. A document detecting apparatus as set forth in one of the preceding claims, for a copying machine in which an optical system for scanning the original document moves under the original glass plate, wherein the optical measuring means is installed out of the range of movement of the optical system.

Inventors: HASHIZUME MASAHIRO, KAWAMOTO MASUO, NAGATA KATSUMI, TAKEMURA YOSHINOBU, HASHIZUME, MASAHIRO, KAWAMOTO, MASUO, NAGATA, KATSUMI, TAKEMURA, YOSHINOBU
Applicants: MITA INDUSTRIAL CO LTD, MITA INDUSTRIAL CO. LTD.
Application year: 1986
Main classification: G03G15
IPC codes: G03G15