JPS60168140A - Original size detecting device of copying machine - Google Patents

Abstract

PURPOSE:To detect exactly an original size by delaying an exciting pulse supplied to a light source by prescribed time, a synchronizing this delayed pulse and an output pulse by the exciting light from a phosphor, and cutting noise mixed into the output pulse. CONSTITUTION:A pulse generating circuit 22 is connected to a delaying circuit 24, and a delay pulse V4 delayed by a prescribed time Td from an exciting pulse V1 is generated. In a part where an original 14 exists, near infrared ray emitted from a light emitting element 16 is reflected by a platen glass 12 and the original 14, and reaches a filter 17. In such a case, the filter 17 does not make the infrared ray transmit through, therefore, a photodetector 18, etc. go to a high level, and other part goes to a low level. An irregularly mixed noise is almost eliminated and an input voltage V5 to a controlling circuit 23 goes to a low level. A noise mixed into a output pulse is cut, therefore, the adverse influence caused by noise, disturbance, etc. is prevented, and an original size can be discriminated exactly.

Description

Detailed Description of the Invention (Technical Field of the Invention) The present invention relates to a Jg size detection device for a copying machine that determines the size of various originals placed on a platen glass. The present invention relates to a document size detection device for a copying machine that eliminates noise and prevents malfunctions.

(Prior Art) Conventionally, as a document size detection device of this type, the one disclosed in Japanese Patent Application Laid-Open No. 56-62274, for example, is known.

The outline of this detection device is shown in FIGS. 1 to 3. This detection device is provided with a colored member 2 on a platen cover 1 of a copying machine, and uses a document exposure device 3 for copying to detect a platen glass 5.
A detection signal shielded by the original 6 placed above is obtained from the color sensor 4. A plurality of color sensors 4 are arranged at predetermined intervals depending on the size of the original, and detect the difference in color between the ground color of the original 6 and the coloring member 2, thereby detecting the size of the original.

The outputs of the photodiodes PDI and PD2, which have different spectral sensitivity characteristics in the color sensor 4, are logarithmically compressed by the circuit shown in FIG. Predetermined paper feeding control is performed.

However, in the above method, as the number of documents to be detected increases, the number of color sensors 4 must be increased, which complicates the circuit and increases manufacturing costs. Furthermore, if the background color of the original 6 and the color of the coloring member 2 are the same or similar, the size of the original cannot be detected.

(Object of the Invention) The present invention has been made in view of the above-mentioned circumstances. The present invention provides a document size detection device that operates reliably and can accurately detect the document size even when the size of the document is large.
In particular, it is intended to eliminate the adverse effects of noise and ambient light mixed into the original size detection signal.

(Summary of the Invention) The present invention is characterized in that a phosphor that is excited by light of a specific wavelength and emits light of a wavelength different from the specific wavelength is arranged on the inner surface of the platen cover over a range where the document size changes, and is placed under the platen glass. A movable sensor unit equipped with means for detecting only the light emitted from the phosphor is provided at a position corresponding to the phosphor, and the size of the portion where the document is present or the portion where the document is not present can be determined. By detecting the size of the original, the excitation pulse applied to the light source is delayed by a predetermined period of time, and this delayed pulse is synchronized with the output pulse of the excitation light from the phosphor and mixed into the output pulse. It is designed to cut noise.

(Embodiment of the invention) An embodiment of the invention will be described below with reference to the drawings.

FIG. 4 is a perspective view of a part of a copying machine showing the mounting location of a phosphor related to an uninvented document size detection device, and FIGS.
The figure is a longitudinal sectional view for explaining the operating state of the configuration of the detection device.

In these figures, a platen cover 11 of a copying machine 10 is shown.
The phosphor 13 is disposed on the inner surface of the scanner, that is, the surface in contact with the platen glass 12, in a necessary range depending on the size of the document to be detected, by means of coating, pasting, or the like.

This phosphor 13 is, for example, LnF3: Yb", Er"
Ytterbium ion Yb3+
absorbs excitation light with a specific wavelength of 940 nm, transmits this absorbed energy to erbium ion Er3+, and this Er3+ emits visible light with a wavelength of 550 nm different from the specific wavelength.

A horizontally movable sensor unit 15 is arranged below the platen glass 12 on which the original 14 is placed.

Inside this sensor unit 15 are a light emitting element 16 serving as a light source for exciting the phosphor 13, a filter 17 for transmitting only visible light among the light emitted from the phosphor 13, and a filter 17 for transmitting only visible light among the light emitted from the phosphor 13. A light receiving element 18 is provided behind the filter 17 and driven by the light transmitted through the filter 15.

As the light emitting element 16, for example, as shown in FIG. 7, a near-infrared light emitting diode or the like whose relative emission intensity peaks at a wavelength of 940 nm is used.

Further, as the light-receiving element 18, a photodiode, phototransistor, CDS, or the like sensitive to visible light with a wavelength of 550 nm is used.

Further, as the filter 17, for example, a filter having characteristics such as BO29 in FIG. 8 is used.

The optimal filter is one that has a transmittance of -0 for near-infrared light at 940 nm and a transmittance of -100 for visible light at 550 nm.

A cam 19 is provided on the outside of the sensor unit 15, and the cam 19 is configured to turn on and off the reference position detection switch 20.

Further, the sensor unit 15 is connected to a circuit shown in FIG. 9 to electrically process the optical signal.

That is, the light emitting element 16 in the sensor unit 15 is connected to a light emitting element drive circuit 21 and to a control circuit 23 via an excitation pulse generation circuit 22 connected to this drive circuit 21. The excitation pulse generation circuit 22 generates an excitation pulse (1), and the pulse width of both Ton and Toff is set to several ms in relation to the excitation time and afterglow time of the phosphor 13.

The pulse generating circuit 22 is also connected to a delay circuit 24, which generates a delayed pulse ■ which is delayed by a predetermined time Td from the excitation pulse ■1.
Generate 4. An example of the delay circuit 24 is shown in FIG.

The delay circuit 24 is connected to the CLK of the D-type flip 70 tube 25.
Connected to the terminal, the delay Palme V4 is powered. A comparator circuit 26 is connected to the D terminal of the flip flop 25, and this comparator circuit 26 is connected to an amplifier circuit 27 for amplifying the signal of the light receiving element 18. On the other hand, the output terminal Q of the flip flop 25 is connected to the control circuit 23. and inputs the output v5 to the control circuit 23.

Note that the control circuit 23 includes a start print switch 28.
and the reference position detection switch 20 are electrically connected to each other.

In addition, in the figure, the symbol ■2 is the output voltage of the amplifier circuit, and the symbol ■3 is the output voltage of the amplifier circuit.
is the output voltage of the comparator circuit.

Next, the operation of the detection device having the above configuration will be explained with reference to the waveform diagram of FIG. 11.

First, the original 14 is placed in a predetermined position and the platen cover 1 is closed.
1 is closed and the start print switch 28 is turned on. Then, the sensor unit 15 starts scanning in the direction of arrow A in FIG. 5, and the cam 19 provided on the sensor unit 15 turns on the reference position detection switch 20.

Next, the sensor unit 15 changes the scanning direction in the direction of arrow B and starts a document detection operation.

At this time, as shown in FIG.
2 and the original 14 and reaches the filter 17 . Here, since the filter 17 does not transmit near-infrared light, the output voltage V2 of the light receiving element 18, the amplifier circuit 27, and the comparator circuit 22. V3 is the noise part nl.

It is at a high level at n2, and at other parts it is at a low level because it is lower than the predetermined reference voltage VREF of the comparator circuit 22.

In the subsequent D-type flip-frog 25, a delayed pulse v4 delayed by a certain time Td from the excitation pulse 1 is input, and if the data (DATA), that is, the output 3 of the comparator circuit 26, is at a low level at the rising edge of the pulse V4, V5 as the output Q becomes a low level as shown in FIG. Therefore, most of the noise mixed into the anti-rule is removed here, and the input voltage 5 to the control circuit 23 becomes low level.

Next, when the sensor unit 15 moves in the direction of arrow B and reaches the state shown in FIG. 6, a portion where the document 14 does not exist appears, so the phosphor 13 is excited by the light from the light emitting element 16, and the wavelength Emit visible light of 550 nm.

This visible light reaches the filter 17, but since this filter 17 transmits the visible light, the light receiving element 18 provided behind the filter 17 is turned on.

At this time, the output voltage V3 via the light receiving element 18, the amplifier circuit 27 and the comparator circuit 26 is the reference voltage VRE.
It exceeds F and becomes a high level.

Here, the output voltage V3 is delayed from the excitation pulse V1 by the excitation time of the phosphor 13, but at the rise of the delayed pulse 4 delayed by the predetermined time Td by the delay circuit 24, the output voltage V3 is at a high level. Therefore, the output Q from the flip-flop 25, that is, the input voltage v5 to the control circuit 23 becomes high level.

In the above case, since the mixed noise n3 does not coincide with the rising edge of the delayed pulse v4, it is almost eliminated.

As a result of the above, the scanning speed of the sensor unit 15 is set to ν,
The reference position detection switch 20 is the cam 1 of the sensor unit.
The input voltage v to the control circuit 23 after being turned on by 9
5 changes from low level to high level is Tx, and the length of the original 14 in the scanning direction, that is, the original size, is L, then the original size can be determined by the formula L=ν・Tx. , it is possible to electrically process this to determine the document size.

In addition, the error time T from the time corresponding to the actual document size
y cannot be avoided, but the scanning speed ν = 3
At a speed of about 0.00 mm/sec, the error in detecting the original size due to the error time 'ry is about 1 mm, which poses almost no problem in practice.

In the above embodiment, the sensor unit 15 is movable, but the sensor unit 15 may be fixed, and a plurality of units may be installed depending on the document size to be detected.

Further, the filter 17 of the sensor unit 15 can be omitted by using a photodiode having a characteristic of exhibiting a relative sensitivity of 100 degrees at a wavelength of 550 degrees, as shown in FIG. 12, for example.

Furthermore, in the above embodiment, the document size is directly determined, but by detecting the size of the part of the fluorescent material that is not covered by the document, the size of the document can be determined indirectly from this size. It can also be detected. This is possible, for example, by using the circuit described above to detect the time when the input voltage vy is at a high level.

(Effects of the Invention) As described above, the present invention includes disposing a phosphor that is excited by light of a special wavelength and emits light of a wavelength different from the specific wavelength in a platen cover, and disposing the phosphor under the platen glass. A movable sensor unit equipped with a means for detecting only the light emitted from the phosphor is provided at a position corresponding to the phosphor. The document size can be steplessly determined, and the document size can be reliably determined without erroneously operating a detection device no matter what the background color of the document.

In addition, the excitation pulse applied to the light source from the excitation pulse generation circuit is delayed by a predetermined time by a delay circuit, and this delayed pulse and the output pulse from the excitation light from the phosphor are synchronized by a D-type flip-flop, and the output pulse is Since the noise mixed in the document is cut out, the adverse effects of noise, disturbance, etc. are effectively prevented, and the document size can be accurately determined.

In addition, since the light emitting element as a light source is lit in pulses, the forward current IFM can be increased, and it is possible to improve the SZN ratio and increase the detection distance.

The phosphor mentioned above is usually achromatic or white, but if it is a so-called drop color, which is less noticeable to the photoreceptor of a copying machine, even originals with high light transmittance will not have negative effects such as capri phenomenon on copies. There is no risk of giving it away.

In addition, although the above embodiment did not specifically mention the moving device for the sensor unit, it is possible to use the optical system of an existing copying machine as it is, and also to share the reference position detection switch with the home position switch, etc. The configuration can be simplified and manufacturing costs can be reduced.

[Brief explanation of drawings]

1 to 3 show an example of a conventional document size detection device for a copying machine, FIG. 1 is a perspective view showing the main parts thereof, FIGS. 2A and 2B are cross-sectional views of the main parts, FIG. 3 is a circuit diagram of the above device, and FIGS. 4 to 12 are graphs showing an embodiment of the document size detection device for a copying machine according to the present invention, and wavelength characteristics of a light emitting element provided in the first unit. 8 is the same (a graph showing the characteristics of the filter provided in the sensor unit, FIG. 9 is a block diagram showing the circuit of the detecting device, FIG. 10 is a circuit diagram showing an example of the delay circuit in the above circuit, Fig. 11 is a waveform diagram showing the circuit operation of the detection device, and Fig. 12 is a graph showing the wavelength characteristics of the photodiode when only the light receiving element is used instead of the filter. 11...Platen cover 12. ...Platen glass 13...Firefly light body 14...Original 15...Sensor unit 16...Light emitting element 17...Filter 18...Light receiving element 22...Excitation pulse generation circuit 23...Control circuit 24...Delay circuit 25...D
Shape flip-flop 1゜2゛To 2B 4th 5゛7

Claims (1)

[Claims] Excited by light of a specific wavelength on the inner surface of the platen cover,
A phosphor that emits light at a wavelength different from this specific wavelength,
Documents of various sizes are placed at predetermined positions on the platen, and the fluorescent material is excited at a position opposite to the fluorescent material across the platen glass. A light source and a known means for detecting light of a wavelength emitted from the phosphor but not for detecting light of the specific wavelength are provided, and the detection means detects the part of the phosphor covered by the document or A document size detection device for a copying machine that detects the document size by detecting the size of an uncovered portion includes a pulse generation circuit that applies an excitation pulse to the excitation light source, and an excitation pulse generated by this circuit. a delay circuit that delays the output current by a predetermined time, and synchronizes the output cuckle of the detection means for detecting light from the phosphor with the delayed pulse delayed by the delay circuit, and synchronizes the output cuckle and the delayed pulse. A document size detection device for a copying machine, characterized in that it is provided with a synchronization circuit that outputs a reference only when synchronized.