JPH10301216A - Original detecting sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve original detecting accuracy without increasing a cost and to reduce the number of parts so that the cost is reduced by using a point light source LED having a fine light emitting area as a light emitting source. SOLUTION: When the LED having the small light emitting area is used as the light source 11, the beam of 15 mmϕ can be obtained in the case of the light emitting area of <=0.1 mm, for example. Thus, when the LED 11 having the small light emitting area is used for an original detecting sensor, the diameter of the emitted light beam becomes small, so that the diameter of the light beam on an original surface becomes small and the original detecting accuracy is improved. Besides, the diameter of a hole on the central part of a mirror 13 provided to make this light beam pass through is made small because of the small diameter of the emitted light beam, so that an area for a mirror part becomes large even though the mirror 13 having the same size is used; therefore, reflected light from an original is efficiently taken in a PD 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrophotographic copying machine,
The present invention relates to a document detection sensor used in an image forming apparatus such as a printer and a facsimile machine, and more particularly, to a document detection sensor having greatly improved reading accuracy of a document position or document size.

[0002]

2. Description of the Related Art Generally, an image forming apparatus such as a copying machine has a function of automatically reading the size of a document placed on a contact glass and automatically selecting a recording sheet of the same size. It is. At this time, a document detecting sensor shown in FIG. 11 is conventionally known as a mechanism for reading the document size. FIG. 11 shows a document 2 placed on a contact glass 1 of a copying machine, a pressure plate 3 covering the document 2,
FIG. 5 is a diagram showing a relationship between a document placement position and a document detection sensor 4 for detecting a document size by detecting an edge of the document, and illustrating the principle of an astigmatism optical system. . FIG. 12 is an enlarged view of a portion of the document detection sensor 4. The apparatus shown in this example irradiates the document 2 on the contact glass 1 and reflects light reflected from the document surface into light / electricity. It leads to a photodiode (hereinafter abbreviated as “PD”) 5 used as a converter. First, the light output from the light source LED 11 is reflected rightward in the drawing by the half mirror 6 used as an optical isolator, and reaches the rotating mirror 8 via the lens 7. The rotating mirror 8 is provided with a polygon mirror, and is rotated at a predetermined cycle by a motor 9 connected thereto. Light guided through the lens 7 by the rotation of the mirror scans the surface of the original 2 as a scanning beam 10. It is configured to be. Various technologies have been proposed as such a document detection sensor. For example, Japanese Patent Application Laid-Open No. 7-77746 discloses a document position sensor that uses a rotating hologram disc and an LED to prevent the influence of noise. The spot diameter on the document is increased to some extent in order to reduce the size of the document and improve the reading accuracy of the document position. ing. The knife / edge method using a two-part PD and the astigmatism method using a four-part PD and a wedge or cylindrical lens, and the sun-shaped two-part PD are also used as the light / electricity conversion means and the document edge detection means. Beam size method, etc. exist. FIG. 13 is a diagram showing an example of a conventional document detection sensor. In this example, light output from an LED 11 is condensed by a lens 12 and irradiates the document 2 via a hole provided in the center of a mirror 13. The light reflected from the document surface is reflected by the mirror 13 in the direction of the condenser lens 14 and further guided to the PD 5.

[0003]

However, in the means disclosed in Japanese Patent Application Laid-Open No. 7-77746, since the emission wavelength of a normal LED has a certain distribution width, the diffraction angle changes greatly depending on the wavelength. When a hologram is used, the scanning beam spreads, and the influence of noise such as dust and spots on the document can be reduced, but there is a disadvantage that the accuracy of detecting the position and size of the document is reduced. In addition, the light emitting area of the conventionally used LED is 0.3 mm ×
Since it was relatively large, about 0.3 mm, the beam width expanded during the process of irradiating the document surface through various lenses and mirrors and leading to the PD, and consequently the light receiving area of the PD for detecting this light was inevitable. Inevitably, the entrance of disturbance light increases, and thus there is a drawback that the SN decreases. Further, similarly, when the beam diameter increases, the divided PD due to astigmatism
, Or the output difference due to the knife edge is reduced, which limits the improvement of the original position detection accuracy. For example, in the document detection sensor shown in FIG.
When the emission beam of the ED becomes large, the area of the central hole of the mirror 13 becomes large, and the area of the mirror for guiding the reflected light from the document to the PD becomes small. there were. In order to increase the size of the reflection mirror, the entire mirror must be enlarged,
This causes the device to become large. An object of the present invention is to solve the various problems related to the above-described conventional document detection sensor, to provide a document detection sensor having improved document detection accuracy without increasing cost, and to further reduce the number of parts. It is an object of the present invention to provide a document detection sensor that achieves cost reduction.

[0004]

According to a first aspect of the present invention, there is provided a document detecting sensor according to the first aspect of the present invention, comprising: a point light source LED; a means for shaping light from the light source into a fine beam; Or means for scanning the original surface by irradiating the original surface with the fine beam via a vibrating light reflecting member, and an optical isolator means for separating light reflected from the original surface and traveling backward along the irradiation path in the optical path, An optical / electrical conversion means for condensing the separated light and converting it into an electric signal; and detecting an original size and an original mounting position by detecting an original edge based on the converted electric signal and the original surface scanning timing. And means for performing the operation. According to a second aspect of the present invention, in the first aspect, the optical / electrical conversion means and the document edge detection means use a knife edge method using a two-division photodiode or a four-division photodiode and a wedge or cylindrical lens. The method is characterized by using either the astigmatism method used or the beam size method using a two-part split photodiode in the shape of a circle. In the invention according to claim 3, claim 1 or 2
Wherein the optical isolator means for separating the light reflected from the document surface and traveling backward through the irradiation path in the middle of the optical path is obtained by mirroring a part of the transparent member. According to a fourth aspect of the present invention, in the first, second or third aspect, at least the condenser lens and the cylindrical lens are integrally formed. According to the fifth aspect of the present invention, at least the optical isolator, the condenser lens, and the cylindrical lens as necessary are formed integrally with each other, and the means for separating the original reflected light or the light source is reflected. The means is a mirror formed at a portion protruding from a part of the integrated component. According to a sixth aspect of the present invention, in the first to fifth aspects, the diameter of the light emitting portion of the point light source LED is 0.1 mm or less.

[0005]

According to the first aspect of the present invention, a point light source LED having a fine light emitting area is used as a light emitting source.
The spread of the beam in the optical path is reduced, and the beam diameter focused on the PD is reduced. According to a second aspect of the present invention, in the first aspect, the light / electricity converting means and the document edge detecting means use a knife edge method using a two-part photodiode or a four-part photodiode and a wedge or cylindrical lens. Astigmatism method,
Alternatively, in any of the beam size methods using a round-shaped two-part photodiode, a point light source LED having a small light emitting area is used as a light emitting source, so that the beam spread in the optical path is reduced and the light is focused on the PD. Therefore, the characteristics of the original detection sensors of the respective types function remarkably. According to the third aspect of the present invention, in the first or second aspect, the optical isolator means for separating the light reflected from the document surface and traveling backward along the irradiation path in the middle of the optical path is obtained by mirroring a part of the transparent member. , The beam path loss is reduced. According to the fourth aspect of the present invention, since at least the condenser lens and the cylindrical lens are integrally formed in the first, second, or third aspect, light loss is reduced and the sensor shape is reduced. According to the fifth aspect of the present invention, at least the optical isolator, the condenser lens, and the cylindrical lens as necessary are formed integrally with each other, and the means for separating the original reflected light or the light source is reflected. Since the means is a mirror formed at a part protruding from a part of the integrated part, the number of parts is further reduced. According to the sixth aspect of the present invention, since the diameter of the light emitting portion of the point light source LED is 0.1 mm or less in the first to fifth aspects, a small light beam necessary for detecting a document position of various sizes is generated. be able to.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on illustrated embodiments. FIG. 1 is a principle diagram of an embodiment of a document detection sensor according to the present invention, which is an improvement of the conventional document detection sensor shown in FIG. 13 based on the present invention. This example is characterized in that an LED having a small light-emitting area is used as the light source 11, and the focal length of the collimating lens arranged close to the light source is usually about 5 mm, as an example, but is not limited to the document surface. Is about 250 mm. The light emitting surface is 0. When a conventional LED of about 3 mm is used, the beam spot on the document surface is about 15 mmΦ if it is simply geometrically calculated, but in order to accurately detect various document sizes of A, B series and inch series, Requires a resolution of 6 mm. Therefore, in the present invention, an LED having a light emitting area of 0.1 mm or less is used. In practice, the emitted light beam becomes somewhat larger due to aberrations of the lens and mirror in the process of being guided to the document surface. However, if the light emission area is 0.1 mm or less, a beam diameter of 15 mmΦ can be obtained. FIG.
The LE with the small light emission area is attached to the original detection sensor shown in
If D11 is used, the diameter of the light-emitting beam is reduced, and the light beam diameter on the document surface is reduced as described above, so that document detection accuracy is improved. Further, since the diameter of the light-emitting beam is reduced, the mirror 1 provided to pass this beam is used.
The diameter of the hole at the center of 3 can also be reduced, and
Even if the mirrors 13 have the same dimensions, the area of the mirror part becomes large, and the reflected light from the document can be efficiently taken into the PD 5. Reference numeral 2 denotes an original, 13 denotes an optical isolator, and 14 denotes a condenser lens.

Next, a case where the present invention is applied to a document detection sensor based on the knife edge method will be described. In the knife edge method, light reflected from a document is separated and guided to a two-divided PD via a condenser lens. A knife edge is arranged on one PD side, and the document reflected light guided to one PD is converted to a knife edge. It is configured to diffract at. According to this configuration, the magnitude relationship between the signal voltages output from the two divided PDs is reversed depending on the magnitude of the beam diameter converged on the PD. The edge of the document is detected by distinguishing the reflected light from the farther pressure plate, thereby detecting the position and size of the document. However, when a conventional LED having a large light emitting area is used, there is a disadvantage that a difference between two divided PD outputs does not appear remarkably, and the detection accuracy is reduced. 2 and 3 are diagrams for explaining the operation and effect when the present invention is applied to a document detection sensor using the knife edge method. FIG. 2 shows a case where a conventional LED having a large light emitting area is used. FIG. 3 is a diagram for explaining the principle of operation of the document detection sensor according to the knife edge method of the present invention, and FIG. 3 is a diagram for explaining the effect of the document detection sensor using the knife edge method according to the present invention.

As shown in FIG. 2, when a conventional LED having a large light emitting area is used, light reflected from a distant object is received (FIG. 2A) and light reflected from a nearby object is used. 2 (b), no significant difference appears in the output of the two divided PD1 and PD2, and the detection accuracy is reduced. On the other hand, as shown in FIG. If an LED with a small light emitting area is used, the diameter of the light beam reaching the PD will not be blurred. Reflected light (Figure 3 (b), reflected light from original)
, The magnitude relationship between the outputs of the divided PDs PD1 and PD2 is reversed, and it is possible to clearly distinguish them, and the document position can be detected with high accuracy.

Further, there is an astigmatism method as a document detection sensor, and the present invention can be applied thereto. FIGS. 4 and 5 are diagrams for explaining the effect when the present invention is applied to a document detection sensor based on the astigmatism method.
FIGS. 5A and 5B show the case where a conventional LED is used, and FIGS. 5A and 5B show the case where the present invention is applied.
9 illustrates a beam shape on D. The astigmatism method is to guide light reflected from a document to a 4-split PD via a condenser lens and a cylindrical lens. The astigmatism is given by passing the document reflected light through a cylindrical lens, and a reflection object is formed. This utilizes the phenomenon that the shape of light reaching each of the four-divided PDs changes depending on the difference in the distance. However, even in this method, when the LED light emitting area is large, the condensed beams reaching A1, A2, B1, and B2 of the four-divided PD are blurred as shown in FIGS. As a result, the shape change on the PD due to the difference in perspective of the reflecting object does not appear remarkably, and there is a disadvantage that the edge detection accuracy of the document eventually decreases.

On the other hand, in the present invention, since the light emitting area of the LED is reduced, the beam reaching the four-divided PD is not blurred, and as shown in FIGS. Since the beam shape condensed on the PD clearly appears vertically and horizontally, document edge detection accuracy is greatly improved. The present invention is also effective when applied to a document detection sensor using a beam size method using the day-and-round two-divided PDs 21 and 22 shown in FIG. 6 as the light / electric conversion means.
In other words, basically, in the beam size method, if the light emitting area of the LED is large, the beam diameter formed in the two-part PD is increased, and the shape of the PD itself needs to be increased accordingly. The shape of the whole sensor must be large. Further, in a PD having a large light receiving area, the penetration of disturbance light becomes large, which causes a decrease in SN. On the other hand, in the present invention, an LED having a small light emitting area is used as a light source, so that the above-mentioned problems can be eliminated at once. That is, since the shape of the PD can be reduced, the overall shape of the sensor can be reduced, and at the same time, the penetration of disturbance light decreases, so that there is an SN improving effect.

FIGS. 7 and 8 show still another embodiment of the present invention. The present invention provides a light source having a small light emitting area L
Although the ED is used, if the optical isolator for separating the reflected light from the original is configured as follows, it is effective in utilizing the advantages of the present invention. That is, in the example shown in FIG.
As shown in (a), a mirror portion is formed by partially depositing aluminum or the like on a part of a transparent glass plate as an optical isolator 23, and this is, for example, a light from a light source 11 as shown in (b). The beam is reflected by the partial mirror of the isolator 23 in the direction of the original, and the light reflected from the original is passed through a transparent portion other than the mirror portion to be guided toward the condenser lens 14 and the PD 5. According to this configuration, the light transmittance is greatly improved as compared with the case where a conventional half mirror is used as an isolator, so that light loss is reduced. When the light loss is reduced, the light source light amount can be reduced by that amount, so that power consumption is reduced, the degree of wear of the light source is reduced, measures against heat generation are reduced, etc.
It has a great effect. In an isolator having a fine hole in the center of the mirror as shown in FIG. 1, reflected light or irradiation light may be diffracted or irregularly reflected at the edge of the hole. This is more effective in improving the original detection accuracy. Further, as shown in FIG. 8, an isolator 24 in which the mirror section and the transmission section are reversed may be used. That is, the isolator 24 shown in FIG.
Is mirrored by evaporating aluminum or the like over the entire surface, leaving a part of the central part of the transparent glass. In this case, the method of use is different from that of the above embodiment. For example, as shown in (b), the light from the light source 11 is transmitted through the unmirrored portion in the center of the glass and guided toward the original, and the reflected light from the original is reflected. The light is reflected by the mirror portion of the isolator 24 and is guided to the condenser lens and the PD. Also in this example, the advantage of using the point light source LED having a small light emitting area of the present invention makes it possible to realize a document detection sensor having excellent light use efficiency.

FIG. 9 shows another embodiment of the present invention, in which a single lens and a cylindrical lens are integrated. That is, conventionally, as shown in FIG. 9A, the condenser lens 26 and the cylindrical lens 27 were used as separate parts, but these were made of a material such as plastic as shown in FIG. 9B. When integrally molded, the number of components is reduced, so that the size of the entire sensor can be reduced, the number of mounting steps can be reduced, component costs can be reduced, and light loss due to reflection on the component surface can be reduced. Further, by utilizing the advantages of the present invention, it becomes possible to use optical components as shown in FIG. In this example, an optical isolator and a condensing lens are integrated, and FIG.
As shown in (a), the optical isolator 23, the condenser lens 26 for guiding the document reflected light to the PD, and the cylindrical lens 27 if necessary are used as individual components. On the other hand, in the present invention, LE having a small light emitting area is used.
Since D is used, for example, as shown in FIG. 10B, the optical isolator 23, the condenser lens 26, and, if necessary, the cylindrical lens 27 can be integrally formed of plastic or the like. At this time, L
In order to reflect the light beam from the ED 11 in the direction of the original,
A projection is formed on a part of the condenser lens, and aluminum or the like is vapor-deposited on the part to be mirrored. According to this configuration, an optical isolator and a condensing lens can be formed by a single component, and if necessary, an optical component integrally formed of three components including a cylindrical lens can be used. The effect of miniaturization and cost reduction is further enhanced.

[0013]

As described above, according to the first aspect of the present invention, since the point light source LED having the small light emitting area is used as the light emitting source, the spread of the beam in the optical path is reduced, and Since the diameter of the beam condensed on the PD becomes smaller and the edge of the original can be detected accurately, the accuracy of the original position detection is greatly improved. According to a second aspect of the present invention, in the first aspect, the light / electricity conversion means and the document edge detection means use a knife edge method using a two-part photodiode or a four-part photodiode and a wedge or a cylindrical lens. Astigmatism method,
Alternatively, a point light source LED having a small light emitting area is used as a light emitting source in any of the beam size methods using a round-shaped two-segment photodiode, so that the beam spread in the optical path is reduced and the light is focused on the PD. Since the beam diameter becomes smaller, the features of the original detection sensors of the respective systems function remarkably, and accurate original position detection becomes possible. According to the third aspect of the present invention, in the first or second aspect, the optical isolator means for separating the light reflected from the original surface and traveling backward along the irradiation path in the middle of the optical path is formed by mirroring a part of the transparent member. The loss of the beam path is reduced, and the light from the light emitting source can be used effectively. According to the fourth aspect of the present invention, since at least the condenser lens and the cylindrical lens are integrally formed, the light loss is reduced, the sensor shape is reduced, and the number of parts is reduced. The cost can be reduced by the reduction. According to the fifth aspect of the present invention, at least the optical isolator, the condenser lens, and the cylindrical lens as necessary are formed integrally with each other, and the means for separating the original reflected light or the light source is reflected. Since the means is a mirror formed at a part protruding from a part of the integrated part, the number of parts is further reduced, and the cost is reduced. According to the sixth aspect of the present invention, since the diameter of the light emitting portion of the point light source LED is 0.1 mm or less in the first to fifth aspects, a small light beam necessary for detecting a document position of various sizes is generated. As a result, the detection accuracy can be greatly improved as compared with the conventional document detection sensor.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of a document detection sensor to which the present invention is applied.

FIGS. 2A and 2B are diagrams for explaining a problem in a conventional knife-edge type document detection sensor.

FIGS. 3A and 3B are diagrams for explaining an effect when the present invention is applied to a knife-edge type original sensor; FIGS.

FIGS. 4A and 4B are diagrams showing a beam shape of a PD in a document detection sensor based on an astigmatism method using a conventional 4-division PD.

FIGS. 5A and 5B are diagrams showing a beam shape of a PD in a document detection sensor by an astigmatism method using a four-divided PD to which the present invention is applied.

FIG. 6 is a view showing a day circle PD divided into two parts.

7A is a diagram illustrating an example of an optical isolator according to the present invention, and FIG. 7B is a diagram illustrating an example of how to use the isolator.

8A is a diagram illustrating an example of an optical isolator according to the present invention, and FIG. 8B is a diagram illustrating an example of how to use the isolator.

9A and 9B are diagrams illustrating an example of an optical component according to the present invention, in which FIG. 9A illustrates an example of a conventional optical component, and FIG. 9B illustrates an example of an optical component according to the present invention.

FIGS. 10A and 10B are diagrams illustrating an example of an optical component according to the present invention, in which FIG. 10A illustrates an example of a conventional optical component, and FIG. 10B illustrates an example of an optical component according to the present invention.

FIG. 11 is an overall view of an optical system of a document detection sensor using a conventional astigmatism method.

FIG. 12 is an enlarged configuration diagram of a document detection sensor according to a conventional astigmatism method.

FIG. 13 is a diagram illustrating a document detection sensor using a conventional LED.

[Explanation of symbols]

1: contact glass, 2: manuscript, 3: pressure plate, 4:
... Document detection sensor, 5 ... PD, 6, 13, 23, 24
... Optical isolator, 7,12,14,26 ... Condenser lens, 8 ... Rotating mirror, 9 ... Motor, 10 ... Beam, 11 ... LED, 15 ... Divided PD, 16 ... Knife edge, 21,22 ... Sun round shape 2 split PD, 2
5 ... 4-division PD, 27 ... cylindrical lens, 2
9: Composite optical component.

Claims (6)

[Claims] 1. A point light source LED, means for shaping light from a light source into a fine beam, and means for scanning the original surface by irradiating the original surface with the fine beam via a rotating or vibrating light reflecting member. And an optical isolator means for separating light reflected from the original surface and traveling backward along the irradiation path in the optical path,
An optical / electrical conversion means for condensing the separated light and converting it into an electric signal; and detecting an original size and an original mounting position by detecting an original edge based on the converted electric signal and the original surface scanning timing. Document edge detecting means for
A document detection sensor comprising: 2. The method according to claim 1, wherein the light / electricity converting means and the document edge detecting means are a knife edge method using a two-division photodiode, an astigmatism method using a four-division photodiode and a wedge or a cylindrical lens, or a Japanese flag. 2. A document detection sensor according to claim 1, wherein the beam detection method is any one of a beam size method using a two-part photodiode. 3. An optical isolator means for separating light reflected from a document surface and traveling backward along an irradiation path in the middle of an optical path, wherein a part of a transparent member is mirrored. Document detection sensor. 4. The document detection sensor according to claim 1, wherein at least a condenser lens and a cylindrical lens are integrally formed. 5. An integrated optical system comprising at least an optical isolator, a condenser lens, and a cylindrical lens if necessary, wherein said means for separating original reflected light or the means for reflecting a light source is a part of said integrated component. 2. A mirror formed at a portion protruding from the mirror.
An original detection sensor according to 2, 3, or 4. 6. The point light source L according to claim 1, wherein
An original detection sensor, wherein a light emitting part diameter of the ED is 0.1 mm or less.