JPH04242767A - Judging device for size of paper sheet, etc. - Google Patents

Abstract

PURPOSE:To equalize the incident light quantity of each light receiving element in a device for emitting a number of optical beams onto a paper sheet, detecting the sheet by use of their reflected lights and light receiving elements, and judging the size of the sheet on the basis of the detection result. CONSTITUTION:In a device for dividing the optical beam from a light emitting diode 11 into a plurality of optical beams by use of a grating element 13, projecting the optical beams in different places according to the size of a paper sheet, receiving their reflected lights, and judging the size of the paper sheet by the combination of the received lights, the grating element 13 is formed of a plurality of grating areas 13a-13d and constituted in such a manner that, as the distances between beam sports P1-P4 and photo diodes 21-24 correspondingly receiving the optical beams reflected thereby are longer, or the incident angles of the reflected optical beams to the optical axis of an imaging lens 25 are larger, the areas of the grating areas for projecting the beams to the beam spots P1-P4 are enlarged.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for determining the size of paper, etc., typified by a document size determining device used in a copying machine.

0002

2. Description of the Related Art Conventional document size determination devices installed in copying machines include a type that uses a photoelectric sensor for pre-scanning, and a type that includes a proximity switch or the like built into the top cover of the copying machine.

[0003] In the type of pre-scanning using a photoelectric sensor, a movable arm is provided inside the copying machine, and a large number of reflective photoelectric sensors are attached to this arm. Before the copying operation, the movable arm moves and the photoelectric sensor scans the original on the glass plate (prescan), and the size of the original is determined based on the output signal of the photoelectric sensor at this time.

[0004] This type of device has the advantage of being able to discriminate between a wide variety of document sizes, but because of the movable parts, the entire device becomes large and its mechanism is complicated, and pre-scanning is required. However, this time becomes loss time, and there is a problem that prompt copying cannot be performed.

[0005] In the type of copying machine in which multiple proximity switches (for example, photomicro sensors, etc.) are built into the top cover, when an original is placed on the glass plate and the top cover is closed, each proximity switch activates its function. The presence or absence of a document at the location where the proximity switch is installed is detected, and the document size is determined based on the detection signals of the multiple proximity switches.

This type has an advantage over the prescan type in that it can save space. However, since the sensor is located on the top lid, it is not possible to determine the document size without the top lid, it cannot be applied to copying machines with an automatic document feed (ADF) function, and even the slightest unevenness on the sensor can cause problems. There are problems such as pressure marks left on the original document, and if the copy paper size is larger than the original size, the shadow of the sensor that is not hidden by the original image will appear on the copy paper.

In order to solve this problem, the applicant proposed a paper discrimination device using a multi-beam light source (Japanese Patent Application No. 1-313419).

A schematic diagram of this discrimination device is shown in FIG.

Referring to FIG. 6, the light emitted from the light emitting diode 11 is collimated by the collimating lens 12, and is divided into a plurality of light beams, for example four light beams, by the composite grating 1 to form beams of appropriate areas. The glass plate 30 or the original 31 is irradiated with spots P1 to P4.

[0010] As a result, the light beam is projected onto different locations depending on the size of the paper to be determined.

The composite grating 1 is composed of a plurality of grating elements having the same area and different diffraction directions arranged in a plane.

The light irradiated onto the original 31 is diffusely reflected by the original 31, as shown in FIG. 8, and the brightness of the spot on the original 31 is almost constant from any direction.

On the other hand, reflection on the front and back surfaces of the glass plate 30 is close to specular reflection, and as shown in FIG. 9, reflected light (regularly reflected light) having a reflection angle α equal to the incident angle α
component becomes larger.

Photodiodes PD1 to PD4 are as follows:
It is arranged at a position where it does not receive specularly reflected light from the glass surface 30 via the imaging lens 25. Thereby, the four photodiodes PD1 to PD4 can detect the diffused light from the original 31.

The presence or absence of diffused light is detected by level-discriminating the light reception signals from the photodiodes PD1 to PD4, and the size of the original 31 is determined based on the combination of the presence or absence of the detected diffused light.

[0016]

FIG. 10 shows the relationship between the optical axis of the imaging lens and the incident angle (off-axis angle) of light with respect to the optical axis of the imaging lens 25. In FIG. FIG. 11 is a graph showing the relationship between the off-axis angle and the amount of transmitted light incident on the imaging lens 25. In the graph shown in FIG. 11, the imaging lens 2
The amount of transmitted light when the light is incident perpendicularly to 5 (off-axis angle is 0) is used as a reference.

As can be seen from FIG. 11, the larger the off-axis angle, the smaller the amount of light transmitted through the imaging lens 25.

Therefore, the larger the off-axis angle of the reflected light beam to the imaging lens, the smaller the amount of light transmitted through the imaging lens, and the larger the off-axis angle of the photodiode PD1 receiving the reflected light beam, the smaller the amount of incident light It becomes less.

[0019] Also, photodiodes PD1 to PD4
detects diffused light that is scattered and spread by the original, so the longer the distance between the beam spots P1-P4 and the photodiodes PD1-PD4, the less the amount of light incident on the photodiodes PD1-PD4.

As a result, as shown in FIG. 7, the larger the angle of incidence with respect to the imaging lens 25 is for a photodiode that detects reflected light, and the longer the distance to the beam spot is, the smaller the amount of light incident on the photodiode is. Become.

In this way, each photodiode P
Since there is a difference in the amount of incident diffused light between D1 to PD4, it is necessary to change the threshold level for level discrimination for each light receiving element. Therefore, the same level discrimination processing circuit cannot be used in common for each light receiving element.

[0022] An object of the present invention is to make the amounts of reflected light beams incident on each light-receiving element substantially equal in the above-mentioned discrimination device.

[0023]

[Means for Solving the Problems] A paper size discrimination device according to a first invention includes a light emitting means for emitting collimated light, diffracting the collimated light from the light emitting means in different directions, and determining the size of paper to be discriminated. A composite grating element composed of a plurality of grating areas that project to different locations depending on their size, and a plurality of light receiving elements for respectively receiving the plurality of reflected light beams from the paper to be discriminated regarding the plurality of light beams. , and an imaging optical system that guides the plurality of reflected light beams to the corresponding light-receiving elements, and the longer the distance between the light beam projection location and the light-receiving element that receives the reflected light beams, the more It is characterized in that the area of the grating region for projecting onto the projection location increases as the angle of incidence of the reflected light beam with respect to the optical axis of the imaging optical system increases.

[0024] The light receiving element may include a plurality of apertures arranged in front of the light receiving elements to limit the amount of reflected light beam incident on the plurality of light receiving elements in order to equalize the amount of light received by the plurality of light receiving elements. preferable.

Furthermore, the diffraction efficiency may be adjusted by varying the height of the grating in each region of the grating element.

[0026]

[Operation] The light beam emitted from the light emitting means is divided into a plurality of light beams by the grating element composed of a plurality of grating regions, and each light beam is irradiated to a different location depending on the size of the paper to be discriminated.

The longer the distance between the projection location of the light beam and the light-receiving element that receives the corresponding reflected light beam, or the greater the angle of incidence of the reflected light beam with respect to the optical axis of the imaging optical system, the greater the grating element becomes. Since the area of the grating area for projecting onto the corresponding projection location is determined to be large, the longer the distance between the projection location of the light beam and the light receiving element that receives the corresponding reflected light beam,
Alternatively, the larger the angle of incidence of the reflected light beam with respect to the optical axis of the imaging optical system, the larger the beam spot generated at the projection location of the light beam, and the greater the amount of reflected light.

Since the amount of the reflected light beam decreases in accordance with the distance to the light receiving element and the magnitude of the off-axis angle, the amounts of light received by the light receiving elements that receive the reflected light from the paper become approximately equal.

Since the projected light is projected to different locations, the combination of light-receiving elements that receive reflected light and light-receiving elements that do not receive reflected light changes depending on the size of the paper placed. Therefore, the size of the paper placed can be determined according to the combination of output signals of the light receiving elements.

By changing the size of the grating area in the composite grating element, the amount of light received by the plurality of light receiving elements can be made almost equal as described above, but in order to control the amount of light received more precisely, it is possible to A diaphragm is placed in front to adjust the amount of incident light.

Furthermore, the diffraction effect of the grating element may be adjusted for each grating region by changing the height of the grating in each region.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a perspective view showing an example of the configuration of a document size determining apparatus according to the present invention.

A light projector 10 and a light receiving device 20 are arranged below a transparent glass plate 30. Documents of various sizes are placed at predetermined positions on the glass plate 30. Floodlight 1
0 projects a plurality of (four in this embodiment) light beams toward different positions P1, P2, P3, and P4 within the place where the document is placed on the glass plate 30. Light receiving device 20
determines the original size by receiving reflected light from the glass plate or the original, or outputs a detection signal for the determination.

The projector 10 is composed of a light emitting diode 11, a collimating lens 12 for collimating the spread light from the light emitting diode 11, and a composite grating element 13.

The composite grating element 13 is for dividing the collimated light into four lights by diffraction.

Composite grating element 1 is shown in FIG. 3(A).
A top view of the composite grating element 13 is shown in FIG. 3, and a side view of the composite grating element 13 is shown in FIG. 3(B).

Composite grating element 13 is composed of four grating regions 13a to 13d.

These grating regions 13a to 13
d, the direction of the grating is set to each position P1 so that the diffracted light can be projected to different positions P1 to P4.
~P4.

The grating regions 13a to 13d also have beam spots P1 to P1 formed thereby.
4 and the corresponding photodiodes 21 to 24 that receive the reflected light beams, and the larger the incident angle of the reflected light beams from the beam spots P1 to P4 with respect to the optical axis of the imaging lens 25. Its area is large.

In this embodiment, the beam spot where the distance between the photodiode and the beam spot is the longest and the off-axis angle of the reflected light beam is the largest is P1. Therefore, the area of the grating region 13d for projecting onto the beam spot P1 is the largest. And the other beam spot P2 ~
Corresponding to P4, the areas of grating regions 13c, 13b, and 13a adjacent to grating region 13d become smaller in this order.

The composite grating element 13 can be manufactured, for example, by separately manufacturing four gratings and then bonding them together. Alternatively, four grating regions may be formed at once using a stamper.

An enlarged view of the light receiving device 20 is shown in FIG. The light receiving device 20 includes four light receivers 21 to 24 and an imaging lens 25.

Photodiodes PD1-PD4 are housed inside the light receivers 21-24. Photoreceiver 21~
Openings 21a to 24a are formed in the upper surface of 24, respectively. The sizes of these apertures 21a to 24a are set so that the amounts of light incident on the photodiodes PD1 to PD4 are equal, and the corresponding beam spots P1 to P4 are adjusted.
It is set according to the amount of light reflected from the

As described above, the spreading light emitted from the light emitting diode 11 is split into four light beams by the composite grating element 13, collimated, and beam spots P1 to P4 of appropriate areas are placed on the glass plate 30. Alternatively, the original 31 is irradiated with light.

Beam spots P1 to P4 generated by grating regions 13a to 13d of composite grating element 13 are
Beam spot P1 projected by grating region 13d having the largest area corresponding to the size of
is the largest.

The diffused emitted light beams of the beam spots P1 to P4 are respectively imaged by the imaging lens 25 and received by the photodiodes PD1 to PD4 of the light receiving device 20, respectively.

If the amount of reflected light beam is constant, as described above, the longer the distance between the beam spots P1 to P4 and the photodiodes PD1 to PD4, the smaller the amount of light received by the photodiodes PD1 to PD4. The larger the off-axis angle of the reflected beam of the imaging lens 27, the smaller the amount of light received by the photodiodes PD1 to PD4. In this invention, beam spots P1 to P
The size of the grating regions 12a to 12d is determined according to the distance between the photodiodes 4 and the photodiodes PD1 to PD4 and the off-axis angle, and the size of the beam spot is determined thereby. The amounts of light received by the photodiodes PD1 to PD4 are approximately equal.

The amount of light received by the photodiodes PD1 to PD4 may not always be fully adjusted depending on the size of the grating regions 12a to 12d of the grating element 13.

[0049] Therefore, grating regions 12a to 12
The adjustment error in the amount of light received due to the area d is determined by
This is corrected by changing the sizes of the openings 21a to 24a. This makes it possible to finally equalize the amount of light received by all the photodiodes PD1 to PD4.

Further, in the composite grating element 13, the height of the grating is adjusted to the grating regions 13a to 13a.
It may be different for each 13d. Since the diffraction efficiency of the grating element depends on the height of the grating, the diffraction efficiency changes for each grating area, and by adjusting the height of the grating, the amount of light incident on the photodiode can be adjusted to be constant.

This embodiment has four light beam spots P.
1 Using the diffuse reflected beam light from P4, B5, B
Seven types of document sizes, 5R, A4, A4R, F4, B4, and A3, are discriminated. F4 has the same width as A4, but is longer than A4. B5R and A4
R has a vertical and horizontal arrangement opposite to that of the other A5 to A3. Since the positions on the document table 40 where the originals of each size are placed are determined in advance, each beam spot P1 to P4 is formed at a position as shown in FIG. 5 in relation to the document position. The projector 10 is adjusted.

Depending on the size of the original, some of the diffusely reflected beams from the four light beam spots P1 to P4 are received by the photodiodes PD1 to PD4, while others are not. can be determined. That is, the document size can be determined based on a combination of binary signals obtained by level-discriminating the light reception signals of the photodiodes PD1 to PD4 using an appropriate threshold value.

By changing the positions of the beam spots P1 to P4 or increasing the number of beam spots, it becomes possible to discriminate many types of sizes.

[0054]

[Effects of the Invention] According to the present invention, a light beam from a light emitting means is divided into a plurality of light beams using a grating element, each of which is projected to a different location depending on the size of paper, and the reflected light is received. , in a device that determines the paper size based on a combination of the presence or absence of light reception, the longer the distance between the projection location of the light beam and the light receiving element that receives the reflected light beam, or the greater the distance from the optical axis of the imaging optical system. The larger the angle of incidence of the reflected light beam, the larger the area of the grating area for projecting it to the projection location.
The longer the distance between the projection location of the light beam and the light-receiving element that receives the reflected light beam, or the greater the angle of incidence of the reflected light beam with respect to the optical axis of the imaging optical system, the greater the amount of the reflected light beam.

Therefore, even if the distance between the projection location of the light beam and the light receiving element that receives the reflected light beam is different, or the angle of incidence of the reflected light beam with respect to the optical axis of the imaging optical system is different, The amount of incident light on the plurality of light receiving elements can be made substantially equal to each other.

Furthermore, by arranging the diaphragm in front of the light receiving element, it becomes possible to make the amounts of reflected light beams incident on the light receiving element more precisely equal.

By varying the height of each grating region in the grating element and varying the diffraction efficiency, the amount of light incident on the light receiving element can also be adjusted.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a paper size determination device according to an embodiment of the present invention.

FIG. 2 is a graph showing the level of incident light on a photodiode.

[Figure 3] Shows an example of a composite grating element.
(A) is a plan view, and (B) is a side view.

FIG. 4 is an enlarged view showing a light receiving lens and each light receiver of the paper size discrimination apparatus shown in FIG. 1;

FIG. 5 is a diagram showing the relationship between the beam spot position and various document sizes.

FIG. 6 shows the optical system of the paper size determination device of the prior invention.

FIG. 7 is a graph showing the incident light level of the photodiode of the prior invention.

FIG. 8 is a diagram showing the state of diffuse reflection from the document surface.

FIG. 9 is a diagram showing specular reflection from a glass plate.

FIG. 10 shows the relationship between the off-axis angle of light incident on the lens and the optical axis.

FIG. 11 is a graph showing the relationship between the off-axis angle of the lens and the amount of transmitted light.

[Explanation of symbols]

10 Emitter 11 Light emitting diode 12 Collimating lens 13 Composite grating elements 13a to 13d Grating area 20 Light receiving devices 21 to 24 Light receiving device 25 Imaging lens

Claims (6)

[Claims] [Claim 1] A light emitting means for emitting collimated light, diffracting the collimated light from the light emitting means in different directions,
A composite grating element composed of a plurality of grating areas that project to different locations depending on the size of the paper to be discriminated, and for receiving the plurality of reflected light beams from the paper to be discriminated regarding the plurality of light beams. a plurality of light receiving elements, and an imaging optical system that guides the plurality of reflected light beams to the corresponding light receiving elements, and the distance between the light beam projection location and the light receiving element that receives the reflected light beams is A sheet of paper characterized in that the longer it is, or the larger the angle of incidence of the reflected light beam with respect to the optical axis of the imaging optical system, the larger the area of the grating area for projecting onto the projection location. etc. size discrimination device. 2. A plurality of apertures, each disposed in front of the light receiving element, for limiting the amount of reflected light beam incident on the plurality of light receiving elements so that the light incident on the plurality of light receiving elements is equal. The apparatus for determining the size of paper, etc. according to claim 1. 3. The apparatus for determining the size of paper or the like according to claim 1, wherein the height of the grating in the grating element is different for each region in order to adjust the diffraction efficiency. 4. A multi-beam light source that projects a plurality of light beams to different locations depending on the size of the paper to be determined, and a multi-beam light source that respectively receives a plurality of reflected light beams from the paper to be determined regarding the plurality of light beams. a plurality of light-receiving elements, an imaging optical system that guides the plurality of reflected light beams to the corresponding light-receiving elements, and a plurality of light-receiving elements arranged in front of the light-receiving elements to equalize the amounts of light received by the plurality of light-receiving elements. An apparatus for determining the size of paper, etc., comprising a plurality of apertures that limit the amount of reflected light beams incident on the plurality of light receiving elements. 5. A composite grating element comprising a plurality of grating regions that diffract collimated light from the light emitting means in different directions and project the collimated light to different locations depending on the size of the paper to be discriminated; It is equipped with a plurality of light receiving elements for respectively receiving a plurality of reflected light beams from the paper to be discriminated regarding light beams, and an imaging optical system that guides the plurality of reflected light beams to the corresponding light receiving elements, thereby improving diffraction efficiency. An apparatus for determining the size of paper, etc., characterized in that the height of the grating in the grating element is different for each area for adjustment. 6. The apparatus according to claim 1, wherein the size of the paper or the like is determined by level-discriminating the level of the light reception signal obtained from the light reception means using a determination threshold level. A device for determining the size of paper, etc.