JPS6115476B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a paper sheet control circuit, and more particularly to a paper sheet control circuit for optical character readers, mark sheet readers, etc. used as peripheral devices of electronic computers.

Optical character readers (hereinafter referred to as OCR) or mark/sheet readers are equipped with a paper feeding mechanism.
Paper sheets are taken out one by one from a bundle of paper sheets and fed to a reading position. In this case, a paper sheet control circuit is provided to detect whether or not a paper sheet is being fed to the feeding path and to control this.

Conventionally, a photodetector as shown in Fig. 1 has been used in a paper sheet control circuit, which includes a light source (light emitting diode, tungsten lamp, etc.) 3 and a photoelectric conversion element (solar cell, phototransistor, etc.) 1. are made to face each other, and the paper sheet 4 is passed between them.

When the light from the light source 3 passes through the sheet of paper 4 and reaches the photoelectric conversion element 1, it is converted into an electric signal proportional to the amount of transmitted light and amplified by the amplifier 2. Then, as shown in FIG. The signal is digitized by the unit 12 at a preset slice level. As shown in FIG. 2a, the conventional method for setting the slice level is to provide a variable resistor VR1 outside the amplifier 2, or to add a variable resistor VR1 to the reference power supply side of the comparator 12. VR2 is provided and these variable resistors VR1 and VR2 are set by adjusting them in advance, or the gain of the amplifier 2 itself is changed and the variable resistor VR2 is set.
Set by adjusting VR2. When using the operational amplifier 2', the slice level is set by adjusting the variable resistor VR3, as shown in FIG. 2b.

This is because the output of the photoelectric conversion element 1 fluctuates significantly due to variations in the brightness of the light source 3, variations in the sensitivity of the photoelectric conversion element 1, variations in the distance between the light source 3 and the photoelectric conversion element 1, etc. This is because it is necessary to artificially set the slice level.

As described above, the conventional method has a problem in that a variable resistor must be used in order to adjust the slice level. That is,
Since the slice level or amplifier gain is artificially adjusted for each device by attaching a variable resistor, it is not possible to set the optimal slice level due to the accuracy of the measuring device, the setting error of the adjuster, etc.

Furthermore, it is difficult to maintain the optimum slicing level due to changes in the ambient temperature of the device, changes over time due to adhesion of paper waste, etc., and the like.

Furthermore, the failure rate of variable resistors is high, which is one of the bottlenecks in improving the reliability of photodetector circuits.

Therefore, the inventor of the present invention automatically sets an appropriate slice level before starting to use the device, and once set, stable operation can be maintained for a long period of time as shown in FIGS. 3 and 4. proposed a paper sheet control circuit (Japanese Patent Application No. 46462/1983
No. 138182) (see specification). That is, as shown in FIG. 4, flip-flops 5, 6, and 7 output a constant voltage when in the set state, and output OV when in the reset state, and the resistors R ₁ , R ₂ , and R ₃
The operational amplifier 11 constitutes an adder circuit, and the resistor
Current values having weights of 1, ₂ , and 4 are selected by R ₁ , R 2 , and R _{3 ,} respectively, and added by the operational amplifier 11 . Figures 3a and 3b show the relationship between the output of the amplifier 2 and equally spaced levels SL ₀ to SL ₇ when the lighting voltage V _L of the light source 3 is lowered and raised, respectively. When the paper leaf 4 exists between the photoelectric _conversion element 1 and the light source 3, the higher levels L _B (a) and L _B ( _b ) The DC output voltage level of the output OUT1 of the amplifier 2 when the leaf 4 is not present is shown, respectively.

When only flip-flop 5 in FIG. 4 is set, the output of SL ₁ in FIGS. 3a and b is set; when only flip-flop 6 is set, the output of SL ₂ is set; When set, give the output of SL respectively. Further, the comparator 12 is connected to the operational amplifier 1
It compares the output SL(n) of amplifier 1 with the output OUT1 of amplifier 2 and outputs the result, and now level L _B (a) in Fig. 3 is between slice levels SL ₃ and SL ₄ . At some point, the level is one level less than level SL ₃ .
Set SL ₂ to slice level.

In this way, the level setting circuit shown in Fig. 4 generates a plurality of slice levels at equal intervals, but when the output level of the amplifier 2 is small as shown in Fig. 3a, the slice level Wide spacing makes it difficult to set the slice level. Therefore, the spacing must be narrowed, the number of slice-level components increases, and reliability decreases. On the other hand, as shown in FIG. 3b, when the output level of amplifier 2 is high, even if the interval between slice levels is wide, there are several slices between levels L _B (b) and L _D (b). - Since there are levels, you can easily set the slice level.

There are variations in the brightness of light source 3, and the brightness decreases over time, so
In the circuit shown in the figure, it is necessary to narrow the interval between slice levels from the beginning, and the number of parts increases as the number of levels increases.

The purpose of the present invention is to eliminate such conventional drawbacks, and to do so without increasing the number of levels even if there are large variations in the output level of the paper sheet detector.
It is an object of the present invention to provide a sheet control circuit capable of setting a slice level and furthermore, capable of setting an appropriate slice level prior to the start of use of the device.

The paper sheet control circuit of the present invention includes a means for generating a plurality of nonlinear levels for detecting an amplifier output level and a comparator for comparing these nonlinear levels with the amplifier output level, and detects the presence of a paper sheet by the output of the comparator. Peak when not
It is characterized by detecting the level, subtracting a predetermined value from the level, and setting the level as the slice level.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 5 is an explanatory diagram of slice levels generated according to the present invention, and FIG. 6 is a block diagram of a slice level setting circuit according to the present invention.

As shown in FIGS. 5a and 5b, in the present invention, a plurality of slice levels are generated in a non-linear manner, that is, from a low level to a high level at successively narrow intervals to wide intervals, so that the paper sheet is Even if the difference in the output level of the amplifier 2 when it is present and when it is not present is small, the slice level can be easily set, and an appropriate level can be set with a small number of levels.

In FIGS. 5a and 5b, L _B (a) and L _B (b) are the outputs of the amplifier 2 when the paper sheet 4 is not present, that is, when the light from the light source 3 directly enters the photoelectric conversion element 1.
It represents the DC output voltage level of OUT1, and also L _D
(a) and L _D (b) are the outputs of the amplifier 2 when the light from the light source 3 towards the photoelectric conversion element 1 is blocked by the sheet of paper 4 and only a part of the transmitted light enters the photoelectric conversion element 1.
It represents the DC output voltage level of OUT1.

In FIG. 6, in addition to providing flip-flops 5, 6, 7, resistors _R1 to _R5 , an operational amplifier 11, and a comparator 12, as in FIG.
A ROM (read only memory) 8 is inserted and current values having weights of 1, 2, 4, 8, and 16 are selected according to the levels set by flip-flops 5, 6, and 7, and the operational amplifier 11 selects current values with weights of 1, 2, 4, 8, and 16. After the addition, the comparator 12 compares it with the output OUT1 of the amplifier 2.

That is, each output x, yz of the flip-flops 5, 6, 7 has a voltage V _F1 in the set state.
When in the reset state, the voltage V _F0 is output.
(≒OV) is output. Also, ROM8 and resistor _R1
~ _R5 and the operational amplifier 11 are combined to form an adder circuit. Further, the comparator 12 is
Output SL(n) of operational amplifier 12 and output of amplifier 2
Compare the magnitude of the DC potential with OUT1 and find SL(n)<
When 0OUT1, “H” level output OUT2
Conversely, when SL(n)>OUT1, an "L" level output OUT2 is given.

The ROM 8 changes from SL 0 to SL ₀ in FIG.
Conversion constants that give nonlinear outputs as shown in SL ₇ to 0 ₁ to 0 ₅ are stored.

FIG. 7 is a diagram showing the control circuit truth value and ROM table of FIG. 6.

In FIG. 7, flip-flop FF5,
The slice level is set by the combination of states 6 and 7 (“0” is the reset state and “1” is the set state 5).
SL ₀ to SL ₇ are determined and input to ROM8.
In ROM8, the input slice level SL ₀ ~
Outputs 0 ₁ to 0 ₅ corresponding to SL ₇ are selected as shown in FIG. gives levels with nonlinear spacing of . As is clear from FIG. 7, 0 ₁ to 0 ₅ have weights of 6, 8, 4, 2, and 1, and their combination generates a nonlinear level.

Since the output SL(n) of the operational amplifier 11 can generally be approximated by the following equation, the relationship between the resistors R ₁ to R ₅ may be set as shown below.

SL ₍ n)=- _Rf / _R1V01 - _Rf / _{R2V02 - Rf} /R
₃ V ₀₃ −R _f /R ₄ V ₀₄ −R _f /R ₅ V ₀₅ …(1) In addition, V ₀₁ to V ₀₅ are the voltage values of the outputs 0 ₁ to 0 ₅ of the ROM 8, and R _f is the voltage value of the operational amplifier 11. is the feedback resistance of

R ₁ = 2 x R ₂ = 4 x R ₃ = 8 x R ₄ = 16 x R ₅ ...(2) Now, the input OUT of the comparator 12 in Fig. 6
When _the waveform of _FIG . Output OUT2 becomes "H" level because SL(n)<OUT1, and when SL(n) is SL ₁ , output OUT2 of comparator 12 becomes SL(n)>OUT1.
Therefore, it becomes "L" level. That is, L _D (a)
is between the slice levels _SL0 and _SL1 by changing the set states of the flip-flops 5, 6, and 7 and observing the level of the output OUT2 of the comparator 12.

In exactly the same way, level L _B (a) in Figure 5a
is between slice levels SL ₄ and SL ₅ .

Now, when L _B (a) is between slice levels SL ₄ and SL ₅ , if we call SL ₄ the peak level of LB (a), it is 1 higher than the peak level of LB (a).
If the level is set to a lower level, that is, SL ₃ , the level of the output OUT2 of the comparator 12 will be LD(a) or _LB (a) depending on whether it is "H" or "L".
It is possible to determine whether That is, when the output OUT2 of the comparator 12 is at "L" level, the input OUT1 of the comparator 12, that is, the output of the amplifier 2
Indicates that OUT1 is L _D (a) in Figure 5a, and when output OUT2 of comparator 12 is at "H" level, input OUT1 of comparator 12 is L _B (a) in Figure 5a. It shows.

The same holds true for the waveform of FIG. 5b. That is, since the peak level of L _B (b) is the slice level SL ₆ , if it is set to SL ₅ , which is one level less than this, the level of the output OUT2 of the comparator 12 will be "H" or It becomes "L", and it can be determined that the input OUT1 of the comparator 12 is either L _D (b) or L _B (b). That is, in FIG. 1, when there is no paper sheet 4 between the photoelectric conversion element 1 and the light source 3, the peak level of the output OUT1 of the amplifier 2 is set to the set state of the flip-flops 5, 6, and 7 in FIG. The first slice level is detected by changing the combination of the peak level and a predetermined value lower than the peak level.
It becomes possible to detect the presence or absence of the paper sheet 4 shown in the figure.

In FIG. 6, setting and resetting of the flip-flops 5, 6, and 7 can be accomplished by a simple procedure by using a microcomputer used to control the optical character reader and its control program.

FIG. 8 shows the flip-flop 5 of FIG.
Flow when controlling by using 6 and 7 as 3-bit binary counters. It's a chat.

In Figure 8, the start STA is, for example, when the optical character reader is powered on, and the start STA is
END starts slicing after a few seconds after the power is turned on.
Indicates that level setting has been completed.

First, in step 15, the 3-bit binary counter CTR is reset (RST), and then in step 16
Set the 3-bit binary counter CTR to n=1.
(SET). In step 17, it is determined whether the output OUT2 of the comparator 12 is at the low level L, and if it is at the high level H, the 3-bit binary counter is
The value of CTR is set to n+1, and the output OUT2 of the comparator 12 goes low again in step 17.
Determine whether the level is L or not, and set the low level L
Increase n one level at a time until . Then, when the output OUT2 of the comparator 12 becomes low level L for the first time, in step 19, the binary counter CTR is set to a level subtracted by a predetermined value, that is, n-2, which is two levels lower in this case. , becomes the end END.

As described above, what is important in the present invention is that the slice levels SL ₀ to SL ₇ are nonlinear, and in the examples shown in FIGS. 5 and 7, the slice levels SL 0 to SL 7 are About half of _{the B} (a) level is SL2, Figure 5 (b)
Approximately half of the L _B (b) level of is SL4,
In either case, the level difference is two levels, and the slice level settings can be made almost the same depending on the signal magnitude.

Although this embodiment shows the simplest case of one photoelectric conversion element and one light source, in general, even when there are n photoelectric conversion elements 1 and n light sources 3,
Since the adder circuit, comparator, etc. shown in FIG. 6 for generating slice levels can be shared by time-division control, the amount of hardware in the sheet control circuit hardly increases.

As explained above, according to the present invention, the slice levels are set nonlinearly, so even if there is a large variation in the amplifier output level, the number of levels does not increase much compared to the case where the slice levels are set at equal intervals, that is, linearly. Appropriate slice levels can be set. This reduces the number of components in the circuit that generates the slice level, improving reliability, and widens the level interval at positions where the amplifier output amplitude is large and is easy to set the slice level, making the amplifier output amplitude small. Since the level interval is narrowed at positions where it is difficult to set the slice level, the slice level can be set efficiently. Furthermore, since the brightness is detected before use and an appropriate slice level is set according to that level, variations in the brightness of the light source can be avoided.
Even if the amplifier output fluctuates due to variations in the sensitivity of the photoelectric conversion element, variations in the layout dimensions of the light source and photoelectric conversion element, or changes over time in the light source or photoelectric conversion element, no initial adjustment or adjustment during maintenance is required. Stable operation can be obtained over a long period of time.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of a photodetector for sheet control;
Figure 2 is a connection diagram of a variable resistor for slice level setting, Figure 3 is a conceptual diagram of a conventional slice level setting method, Figure 4 is a block diagram of a conventional slice level setting circuit, and Figure 4 is a block diagram of a conventional slice level setting circuit. FIG. 5 is an explanatory diagram of the slice level setting method of the present invention, FIG. 6 is a block diagram of a slice level setting circuit showing an embodiment of the present invention, and FIG. 7 is a diagram showing the truth value of the control circuit of FIG.
FIG. 8, which shows the ROM table, is a control flow chart of FIG. 1: Photoelectric conversion element, 2: Amplifier, ,: Light source, (:
Paper leaf, 5, 6, 7: Flip-flop, 8: Read-on memory, 2, 11: Operational amplifier, 1
2: Comparator, OUT1: Photoelectric conversion output via amplifier, OUT2: Comparator output, RST:
Reset input.

Claims (1)

[Claims] 1. In order to detect the presence or absence of a paper sheet, in a paper sheet control circuit in which a light source and a photoelectric conversion element are opposed to each other while sandwiching the paper sheet, there is a switch from a low level to a high level to detect the amplified photoelectric conversion output level. means for generating a plurality of levels at successively wider intervals starting from a narrow interval, and a comparator for comparing the plurality of levels with the photoelectric conversion output level, detecting the peak level when no paper sheet is present by the output of the comparator, A sheet control circuit characterized in that a level obtained by subtracting a predetermined value from a peak level is set as a slice level.