JPH06141128A - Black mark detector - Google Patents

Abstract

PURPOSE:To attain highly accurate detection by individually adjusting the dispersion of photocouplers detecting a black mark. CONSTITUTION:The detector is provided with a reflection type photocoupler comprising a light emitting element 11 and a light receiving element 12 that applies photoelectric conversion to a reflected light from a white recording paper roll S having a black mark at its end, an A/D converter 13 converting an output (a) of the photocoupler 10 into a digital value (b), a reference value calculation circuit 14 calculating a reference level (c) by using a slice level being 45% of a white level of the form S at the initial setting of the detector, a storage circuit 15 storing the calculated reference level (c), a comparator 16 comparing the reference level (d) outputted from the storage circuit 15 with the digital value (b) obtained by A/D-converting the output (a) of the photocoupler 10 by the A/D converter 13 after the initial setting of the detector, and a control section 17 controlling each section of the detector. In the case of bad, it is decided that no black mark is in existence and in the case of b>=d, it is decided that a black mark is in existence.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a black mark detecting device which can be used in a sheet presence / absence detecting device, a mark sheet reading device, etc. in a recording device such as a facsimile.

[0002]

2. Description of the Related Art In a facsimile machine, a black end mark is provided at the end of a roll-shaped recording sheet, and when this is detected, a message is sent to the user to urge replacement of the recording sheet. As shown in FIG. 3, the black mark is detected by using a reflective photocoupler 3 which is a combination of a light emitting element 1 and a light receiving element 2, and a paper 5 having a black mark 4 on a white background passes over the photocoupler 3. Then, the light from the light emitting element 1 is reflected by the sheet 5 and enters the light receiving element 2,
Since the output of the light receiving element 2 changes according to the incident light amount, the white background portion and the black mark 4 are detected by comparing the output of the light receiving element 2 with a predetermined reference value by the comparator 6. . That is, when the reflected light from the white background portion of the paper 5 is 100%, the reflected light from the black mark 4 is 30% or less. Therefore, for example, by setting the reference value to 30%, the black mark 4 is removed. Can be detected.

However, in an actual device, the detected value varies due to fluttering during the conveyance of the recording paper, aging of the device, and the influence of ambient temperature and light. For example, the output level of the light receiving element in the white background portion may be 100% at the initial setting stage, but may drop to nearly 50% due to these influences. Further, even in the black mark portion, the initial setting is 30%, but the variation occurs in the range of 20 to 40%. Therefore, conventionally, by considering such variations from the beginning, the slice level for distinguishing the white background from the black marks is set to 45% as shown in FIG. It is configured so that it can be reliably detected.

[0004]

However, even if the slice levels of the white background and the black mark are set to 45%, the photocoupler itself has characteristic variations. Therefore, if the slice level is fixed to 45%, accurate detection is possible. May not be possible. Therefore, conventionally, as shown in FIG. 5, a variable resistor 7 is used to set the reference value, and the reference value is set according to the characteristics of each light receiving element 2, or as shown in FIG.
The variable resistor 8 is connected to and the output of each light emitting element 1 is adjusted so as to accurately correspond to the reference value.

As described above, conventionally, in order to absorb the variation in the characteristics of each photocoupler, the device itself has to be individually adjusted, which requires a lot of labor and time.

SUMMARY OF THE INVENTION The present invention is intended to solve such a conventional problem, and an object of the present invention is to provide a black mark detecting apparatus capable of performing highly accurate detection by easily adjusting the variation of each photocoupler. To do.

[0007]

In order to achieve the above object, the present invention provides a reflection type photocoupler for photoelectrically converting reflected light from a sheet having a black mark on a white background, and a digital output of the photocoupler. An A / D converter for converting, a reference value calculating circuit for calculating a reference level when detecting a black mark on a sheet at the time of initial setting of the apparatus, a storage circuit for holding the calculated reference value, the reference value and the apparatus The comparator is provided with a comparator for comparing the output of the photocoupler after the initial setting of (1) with a value digitally converted by the A / D converter, and a control section for controlling each section of the apparatus.

The present invention also includes a reflection type photocoupler for photoelectrically converting light reflected from a paper having a black mark on a white background, and a reference value setting circuit for setting a reference level when detecting a black mark on the paper. , A comparator for comparing the set reference value with the output of the photocoupler, and adjusting the output of the light emitting element of the photocoupler from the output of the comparator to control the reference value in the reference value setting circuit to a predetermined value. And means.

[0009]

According to the present invention, since the slice level for distinguishing the white background from the black mark is determined from the value actually output from the photocoupler of the apparatus, the value according to the characteristic of the photocoupler can be obtained. Therefore, the black mark can be detected with high accuracy.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a schematic structure of a black mark detecting device according to a first embodiment of the present invention. In FIG. 1, 10 is a reflection type photocoupler, which is composed of a light emitting element 11 and a light receiving element 12 arranged in parallel. 13 is A /
It is a D converter and converts the analog output of the photocoupler 10 into a digital value. A reference value calculation circuit 14 calculates a reference level for detecting a black mark on the paper from the output of the A / D converter 13 when the apparatus is initialized. A storage circuit 15 holds the reference value calculated by the reference value calculation circuit 14. Reference numeral 16 compares the reference value output from the storage circuit 15 with a value obtained by digitally converting the output of the photocoupler 10 after the device is initialized by the A / D converter 13. A control unit 17 controls each unit of the device. A reference value setting switch 18 is turned on at the time of initial setting of the apparatus. S is a white roll-shaped recording paper to be measured, and has a black mark M at its end.

Next, the operation of the first embodiment will be described. At the time of initial setting of the apparatus, first, the white background portion of the recording sheet S is positioned on the photocoupler 10, and the power switch and the reference value setting switch 18 not shown are turned on. As a result, the light emitted from the light emitting element 11 is transmitted to the recording sheet S.
The reflected light is reflected by the white background portion and enters the light receiving element 12, and the output a of the light receiving element 12 at this time is input to the A / D converter 13 and converted into a digital value b. This digital value b is 100
The value c of 45% is calculated by the reference value calculation circuit 14 as%, and the value c is stored in the storage circuit 15. Memory circuit 1
Reference numeral 5 denotes a semi-permanent memory such as an EEPROM, which stores the output value c of the reference value calculation circuit 14 when the write signal e is input from the control unit 17. After a certain time, such as a few seconds,
The reference value setting switch 18 is turned off. Of course, the timer may be started by turning on the switch and turned off after a certain period of time. Thus, the reference value is set in the memory circuit 15.

After the reference value is set, the amount of reflected light on the white background portion of the recording sheet S is measured by the following procedure. Recording paper S
Value a output from the light receiving element 12 by the reflected light from
Is converted into a digital value b by the A / D converter 13,
The value b is compared by the comparator 16 with the reference value d read from the recording circuit 15 by the read signal f from the controller 17. The comparator 16 determines that there is no black mark when signal b ≧ signal d, and determines that there is a black mark when signal b <signal d.

As described above, according to the first embodiment,
Even if the detection value fluctuates during the conveyance of the recording paper S, the detection value varies due to the secular change of the apparatus, the influence of ambient temperature, light, etc., the slice level for distinguishing the white background portion from the black mark is set to 45%. Therefore, even if the detection level of the photocoupler 10 is lowered due to these influences, the white background portion can be detected. The reference value is the photo coupler 10
Since it is obtained directly from the output value of, the characteristic reflects the characteristics of the photocoupler 10 actually used in the device, and the black mark can be accurately detected.

FIG. 2 shows a schematic configuration of the second embodiment of the present invention. Reference numeral 20 denotes a reflective photocoupler, which includes a light emitting element 21 and a light receiving element 22. Reference numeral 23 is a reference value setting circuit for setting a reference level when detecting a black mark on a sheet, and three resistors 24, 25 connected in series,
26 and an analog switch 27 whose input terminals are connected to the connection points of the resistors 24, 25 and 25, 26, respectively. 28 is a reference value setting circuit 23
The reference numeral 29 is a comparator for comparing the output of the photocoupler 20 with the reference value, and 29 is a D / A for adjusting the output of the light emitting element 21 of the photocoupler 20 based on the output of the comparator 28.
A converter, 30 is a storage circuit for storing the value i sent to the D / A converter 29, 31 is a control unit for controlling each unit, 3
Reference numeral 2 is a reference value setting switch. S is a white roll-shaped recording paper to be measured, and M is a black mark provided at the end of the recording paper S.

Next, the operation of the second embodiment will be described. At the time of initial setting of the apparatus, first, the recording sheet S is positioned on the photocoupler 20, and a power switch (not shown) and a reference value setting switch 32 are turned on. Control unit 31
Outputs a value "1" as the signal a to the D / A converter 29 when the reference value setting switch 32 is turned on. The D / A converter 29 outputs the analog potential b based on the value of the signal a. In this embodiment, an 8-bit D / A converter is used, and the relationship between the signal a and the analog potential b is (Vcc / 2).
56) × (a + 1) = b, where a is 0 to 256
Up to b change in the range of 0 to Vcc. Further, the control unit 31 uses the analog switch 27 of the reference value setting circuit 23.
"1" is output as the signal h. Analog switch 2
Signals d and e are input to 7, and the relationship between the signals d and e is set to d × 45% = e. Therefore, when "1" is input as the signal h, the signal d is f
Is output as. The comparator 28 compares the signals c and f, and outputs “1” as the signal g when the signal c ≧ signal f, and outputs “0” as the signal g when the signal c <signal f. The control unit 31 controls the signal a until the signal g becomes “1”.
Is gradually increased and the value of the signal a is stored in the memory circuit 30 as the signal i when the signal g becomes “1”. Next, the control unit 31 sets the signal h to “0” and sets the signal e to the signal f.
As the reference value of the comparator 28. After a certain period of time, the reference value setting switch 32 is turned off. This sets the reference value in the memory circuit 30.

After the reference value is set, the amount of reflected light on the white background portion of the recording sheet S is measured by the following procedure. Control unit 31
Reads the data i in the memory circuit 30, outputs the value to the signal a, sets the signal h to "0", and sets the signal e to the signal f to be the reference value of the comparator 28. Comparator 28
Is the light receiving element 2 due to the signal f and the reflected light from the recording paper S.
The value c output from 2 is compared, and when the signal c ≧ the signal f, it is determined that there is no black mark, and when the signal c <the signal f, it is determined that there is a black mark.

As described above, according to the second embodiment,
Even if the detection value fluctuates during the conveyance of the recording paper S, the detection value varies due to the secular change of the apparatus, the influence of ambient temperature, light, etc., the slice level for distinguishing the white background portion from the black mark is set to 45%. Therefore, even if the detection level of the photocoupler 20 is lowered due to these influences, the white background portion can be detected. Further, since the reference value is obtained directly from the output value of the photocoupler 20, the reference value reflects the characteristics of the photocoupler 20 actually used in the device, and the black mark can be accurately detected.

In each of the above embodiments, the slice level for distinguishing the white background and the black marks on the recording paper S is 45% of the white background detection value at the time of initial setting of the apparatus, which is 45%. This is only an example, because it depends on the device and the usage conditions. Further, the white background portion of the recording sheet S is not limited to pure white, and includes a pale chromatic color.

In the above embodiment, the recording sheet S to be detected is manually set in the apparatus, the reference value setting switch 18 or 32 is turned on, and the storage circuit 15 or 3 is turned on.
Although the data that is the basis of the reference value is written in 0, instead of this, a sensor for detecting the presence or absence of recording paper is provided, and if the recording paper is set in the device when the power switch is turned on, the data is stored in the storage circuit. The data may be written automatically.

[0020]

As is apparent from the above embodiments, the present invention directly determines the slice level for distinguishing a white background and a black mark from the value output from the photocoupler actually used in the apparatus. An accurate value can be obtained according to the characteristics of the photocoupler, and highly accurate detection of a black mark can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a black mark detection device according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a schematic configuration of a black mark detection device according to a second embodiment of the present invention.

FIG. 3 is a block diagram showing a schematic configuration of a conventional black mark detection device.

FIG. 4 is a graph showing a range of detection levels in a conventional black mark detection device.

FIG. 5 is a circuit diagram showing a schematic configuration of a conventional black mark detection device.

FIG. 6 is another circuit diagram showing a schematic configuration of a conventional black mark detection device.

[Explanation of symbols]

 10 Photocoupler 11 Light emitting element 12 Light receiving element 13 A / D converter 14 Reference value calculation circuit 15 Storage circuit 16 Comparator 17 Control section 18 Reference value setting switch 20 Photocoupler 21 Light emitting element 22 Light receiving element 23 Reference value setting circuit 24, 25, 26 resistance 27 analog switch 28 comparator 29 D / A converter 30 memory circuit 31 controller 32 reference value setting switch

Claims (2)

[Claims] 1. A reflection type photocoupler for photoelectrically converting reflected light from a paper on which a black mark is written on a white background, an A / D converter for digitally converting the output of the photocoupler, and the paper at the time of initial setting of the apparatus. A reference value calculation circuit for calculating a reference level when detecting the black mark, a storage circuit for holding the calculated reference value, and the reference value and the output of the photocoupler after the initial setting of the device, A black mark detecting device comprising a comparator for comparing a value digitally converted by a D converter and a control part for controlling each part of the device. 2. A reflection type photocoupler for photoelectrically converting reflected light from a paper having a black mark on a white background, a reference value setting circuit for setting a reference level when detecting a black mark of the paper, and A comparator for comparing the set reference value with the output of the photo coupler, and adjusting the output of the light emitting element of the photo coupler from the output of the comparator so that the reference value in the reference value setting circuit becomes a predetermined value. And a black mark detecting device having means for controlling.