JPH0267918A - Automatic adjusting circuit and automatic adjusting method of optical medium detecting device - Google Patents

Abstract

PURPOSE:To detect the presence or absence of a medium reliably by providing a storage means for storing a set value of an electric signal and a switching controlling means for controlling a switching means by said set value of electric signal stored in said storage means. CONSTITUTION:When a medium handling unit 14 outputs an instructing signal to start detection of a medium, a controlling circuit 7 generates a voltage VREF as a reference voltage selecting signal SEL3 to a comparison circuit 11. In order to start detection of the medium from an optical sensor S1, a sensor No.N=1 is set. Then, a sampling circuit 10 reads, in response to an instruction by the circuit 7, a variable for a sensor SN stored in a storage means 13 and generates corresponding resistance selecting signals SEL21-SEL2m to a variable resistance circuit 9. The circuit 7 outputs a sensor selecting signal SELIN to a sensor selecting circuit 8, the circuit 10 and a comparison signal latch circuit 12. As a result, after a stable time, the unit 14 becomes able to detect the presence or absence of the medium for the sensor SN.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an automatic adjustment circuit and an automatic adjustment method for adjusting the output characteristics of an optical medium detection device that detects a medium such as a paper sheet using an optical sensor. It is something.

(Prior art) Conventionally, in devices that handle media such as paper sheets, in order to monitor the running of media and detect residual media, for example, a light-emitting diode and a light-receiving transistor are placed facing each other to detect the difference in transmitted light. A detection method is used in which a change in the photocurrent of a light-receiving transistor is converted into a voltage signal, and the presence or absence of a medium is detected based on the voltage signal.

FIG. 2 is a diagram of the conventional medium detection circuit described above.

In the figure, 1 is a constant current circuit, 2 is a light emitting diode of an optical sensor, and the light emitting diode 2 is supplied with a current ID from the constant current circuit 1. 3 is a light receiving transistor of the photosensor, RL is a variable resistor, 4 is a comparator consisting of an operational amplifier,
Reference numeral 5 denotes a medium to be detected that passes between the light emitting diode 2 and the light receiving transistor 3. The light receiving transistor 3 has a collector side connected to a bias voltage Vcc via a variable resistor RL, an emitter side grounded, and a light emitting diode A current XC corresponding to the amount of light received from the second side is output.

Comparator 4 receives comparison reference voltage V REP on its negative input side,
The collector-emitter voltage VCE of the light-receiving transistor 3 is received on the positive input side, and the voltage VCIE is the voltage Vl? E
When it is smaller than P, a low-level off signal indicating that the medium 5 is not present is output, and the voltage VCE is lower than the voltage Vl.
? When it is larger than BP, a high-level ON signal indicating that the medium 5 is present is output.

FIG. 3 is an output characteristic diagram of the circuit shown in FIG. Since the amount of light is large, the current IC is large, and therefore, the voltage-current characteristic of the light receiving transistor 3 due to light emission from the light emitting diode 2 becomes a curve C1. When the medium 5 is interposed between the light emitting diode 2 and the light-receiving transistor 3 (hereinafter referred to as "with medium"), the amount of light received by the light-receiving transistor 3 is reduced because it is blocked by the medium 5, and therefore the current Ic is As the voltage-current characteristic becomes smaller, the voltage-current characteristic becomes curve C2.
become that way.

Therefore, the voltage VCE for actually detecting the presence or absence of the medium 5 is expressed by the formula VCE-VCC-I C-RL, I
Points VCE (OFF), vcE (ON) are obtained by projecting the intersection points A and B of the straight line g1 of C-(VCC-VCE)/RL and each of the curves C1 and C2 onto the axis of the voltage VC[E].
becomes.

When the resistance value of variable resistor RL is reduced, the straight line g1 becomes 0 point (
1! ! Flow IC-0, iIS pressure V CC > is the center and the characteristic has a steep slope like the straight line gl°, and when the resistance value is increased, the characteristic has a gentle slope like the straight line J71', so the intersection point A , B are A'A', B', B, respectively.
', and in this way, each voltage VCE in the absence of a medium or in the presence of a medium can be adjusted to a desired voltage value by the variable resistor RL.

In addition, in devices that handle paper sheets, etc., the optical sensor is often severely contaminated by dust caused by paper powder, etc. t, the third factor M constitutes the initial margin against contamination.

Initially, the straight line gl intersects at point A in the non-saturated region of the curve C1, so there is almost no change in the voltage VCH due to the intersection point with respect to changes in the current IC, but due to contamination, the point A in the unsaturated region of the curve C1 This is because when the curve descends to point A, it intersects with the saturation region, so that the voltage vCE changes rapidly. Therefore, in order to secure this contamination margin, the medium-free curve C1 and the straight line Ut must intersect in the non-saturation region shown in FIG. However, in the adjustment in the non-saturation region, the voltage V
CE-V CE (OFF) f;! In other words, when the medium 5 is not interposed between the light emitting diode 2 and the light receiving transistor 3, the variable resistor RL cannot be adjusted.

Therefore, to adjust the variable resistor RL, the medium 5 is interposed between the light emitting diode 2 and the light receiving transistor 3, and the output voltage V is determined by the intersection B of the curve C2 with the medium and the straight line IHI.
This is handled by using CE-V CE (ON).

(WJ to be solved by the invention) However, in a device that handles media such as paper sheets, a plurality of media detection devices with the above configuration are required, and when adjusting them, the media can be used to intervene. There is the complication of having to manually adjust the resistance, and there is also the risk of making an adjustment error. Furthermore, each variable resistor is mounted on a separate board from the light-emitting diode and light-receiving transistor, so if that board is replaced or each unit is replaced, the variable resistor must be adjusted again. It was annoying.

The first object of the present invention is to automatically adjust the output characteristics of the light receiving section due to light emission from the optical sensor, and the second object is to adjust the output characteristics appropriately when the optical sensor becomes dirty and its sensitivity changes. An object of the present invention is to provide an automatic adjustment circuit and an automatic adjustment method for an optical medium detection device.

(Means for Solving the Problem) In order to solve the above-mentioned problems, in the inventions of claims (1) to (3), the light emitting part and the light receiving part are connected to the path of the medium to be detected. It has a load resistance circuit for converting changes in the photocurrent of the light receiving part due to the difference in transmitted light due to the presence or absence of a medium to be detected into a voltage signal. In an automatic adjustment circuit for an optical medium detection device that determines the presence or absence of a detection medium, the load resistance circuit includes a variable resistor and a switching means for switching the resistance value of the variable resistance according to a set value of an electric signal, an automatic adjustment circuit having a storage means for storing a set value of the signal, and a switching control means for controlling the switching means according to the set value of the electric signal stored in the storage means, or the detected medium The determining means for determining the presence or absence of the detected medium is configured to set a comparison reference value to be compared with the voltage signal with a first comparison reference value for determining the presence or absence of the detected medium. It is possible to switch between a predetermined second and third comparison reference value in which a region that is determined as “absent” is set;
Alternatively, the variable resistor is composed of a plurality of fixed resistors,
The switching means includes a plurality of switch control means, and the resistance value of the fixed resistor can be changed stepwise by the switch control means based on the setting value of the electric signal.

In the invention of claim (4), an optical sensor is used in which a light-emitting part and a light-receiving part are arranged astride the passage of the medium to be detected, and a photocurrent in the light-receiving part is caused by the difference in transmitted light depending on the presence or absence of the medium to be detected. In an automatic adjustment method for an optical medium detection device, which has a load resistance circuit for converting a change in voltage into a voltage signal, and determines the presence or absence of a medium to be detected based on the change in the voltage signal,
A first comparison reference value for determining the presence or absence of a medium to be detected is used as a comparison reference value to be compared with the voltage signal in a state where there is no detection medium when the detection operation is not in progress; Alternately setting predetermined second and third comparison reference values of the area determined without the detected medium;
The resistance value of the load resistance circuit is sequentially switched according to the set value of the electric signal, and the switching value when the voltage signal falls within the range of the second and third comparison reference values is stored, and during the detection operation, The automatic adjustment method sets the resistance value of the load resistance circuit based on the stored switching value and compares the voltage signal with the first comparison reference value.

(Function) According to the invention of claim (1) or claim (3), when the sensing operation is idle, the resistance value of the load resistance circuit is adjusted according to the output characteristics of the light receiving part of the optical sensor without a sensing medium. is switched under switch control by the set value of the electrical signal,
The set value of the electrical signal is stored, and during the detection operation, the resistance value of the load resistance circuit is set by controlling the switch according to the stored set value. According to the invention of claim (2) or claim (4), when the sensing operation is idle, the voltage signal taken out from the light receiving part is adjusted according to the output characteristics of the light receiving part of the optical sensor without a sensing medium. 2nd and 3rd
The resistance value of the load resistance circuit is switched under switch control according to the set value of the electrical signal so that it is within the range of the comparison reference voltage, and the set value of the electrical signal is stored. The resistance value of the load resistor circuit is set by switch control according to the set value, and the voltage signal is compared with the first comparison reference voltage under the resistance value to determine the presence or absence of the medium to be detected.

(Embodiment) FIG. 1 shows an automatic medium detection device showing an embodiment of the present invention:
FIG. 2 is a block diagram of an Ari circuit.

In the same figure, 5l-3n are light-emitting diodes D1 to Dn as light-emitting parts and light-receiving transistors Tr as light-receiving parts.
The light-emitting diodes Di=Dn are connected in series with each other, and a constant current ID is supplied from the constant current circuit 6. The spaces between each of the light emitting diodes Di to Dn and each of the light receiving transistors Try-Trn serve as transport paths for the respective detection media X1 to Xn, and when the detection media X1xXn is interposed between each one, each From the light emitting diode DI-Dn to each light receiving transistor Trl-Trn
This reduces the amount of light that reaches the area.

7 is a control circuit that controls this automatic adjustment circuit by a program to be described later, and 8 is a sensor selection signal 5E of the control circuit 7.
This is a sensor selection circuit that selects each sensor Sl-8n for automatic adjustment or medium detection control using LIN. 9
is a variable resistance circuit as a load resistance circuit, and under the control of the control circuit 7, each resistance circuit corresponding to the variable resistance RL in FIG. 2 is formed by switch control, and each sensor S1 selected by the sensor selection circuit 8 The collector current corresponding to the amount of light received by each of the light receiving transistors Trl to Trn of ~Sn and the voltage drop of the bias voltage Vcc due to the resistor, that is, the voltage at the collector-emitter voltage VCrICP point are adjusted. Reference numeral 10 denotes a sampling circuit which, when receiving the sensor selection signal 5ELIN from the control circuit 7, sends resistance selection signals 5EL21 to 5EL2n for switching the variable resistance circuit 9 in a predetermined time series, and also sends out resistance selection signals 5EL21 to 5EL2n for switching control of the variable resistance circuit 9 to a comparison signal latch circuit 12 to be described later. Provides latch signal LA.

When the control circuit 7 receives a storage instruction signal SM, which will be described later, during the idle state of the detection operation, the storage section 13, which will be described later,
The resistance selection signal SEL21 to SEL at that time
2m is stored in correspondence with the sensor selection signal 5ELIN,
During the detection operation, each resistance selection signal S E L21 to S E L2m is read out and applied to the variable resistance circuit 9 every time the sensor selection signal 5ELIN is received.

FIG. 4 is a detailed circuit diagram showing one embodiment of the variable resistance circuit 9. R1-Rn are connected in series with each other and the resistance value is R.
/2. R/2, R/23...R2" resistors, SW1 to 5W11, are the selection signals 5EL21 to SEL2+al of the sampling circuit 10. When on/off, each resistor R1 to Rm is short-circuited. It is an analog switch and serves as a switching means for switching this variable resistance.

According to this configuration, the combined resistance RL between the bias voltage (power supply) VCC and the point P is Ul, if the resistance when the switches SWI to SWi are on is ignored.

U2. ... Ull, each switch SWl, SW2,
...If SWm is a variable number that is '0'' when it is on and '1' when it is off, then RL - (Ul /2 + U2 /
2+U3/23+...10m/2)R.

Therefore, the variable number U l = U 2- =--U m
-0, the combined resistance RL becomes O, which is the minimum, and when the variable number Ul-U2-...-Us-1, the combined resistance R
L becomes maximum at (1-1/2)R, and its resolution is given by R/2''.

Reference numeral 11 denotes a comparison circuit as a discrimination means, which is basically equivalent to the comparator 4 in FIG. A voltage V REP similar to that in comparator 4 is received on the negative input side as a comparison reference voltage of 1, and a voltage VCE is received on the positive input side, and a comparison signal CP is similarly turned on/off.
During idle, the voltage V! is used as the second reference voltage. ? A predetermined voltage VC, which will be described later, is lower than EP.
E(A') and the voltage VCH are similarly received, and the third
A predetermined voltage VCE (A') similar to the reference voltage of
It receives voltage VCE and outputs an on/off signal.

FIG. 5 is an output characteristic diagram of the circuit in FIG. 1, and each curve CI
, C2 and the first comparison reference voltage V REP are respectively equivalent to those having the same symbols in FIG.

VCE (A') is the second comparison reference voltage of the comparison circuit 11,
VCE(A') is also a third comparison reference voltage, which is lower than the voltage V REF and is
Voltage-current characteristics C1 of the light-receiving transistors Tri-Trn when sensors Sl-Sn are not contaminated in the absence of sensors 1-Xn, or characteristics C1' when they are contaminated, which will be described later.
A predetermined voltage level range in the saturation region is set, and the voltage is switched and applied by a program in place of the voltage V REP during idle.

Reference numeral 12 denotes a comparison signal latch circuit, which connects each sensor St to SI selected by the sensor selection signal 5ELIN of the control circuit 7.
The comparison signal CP(
The on/off signal) is latched by the latch signal LA of the sampling circuit 10, and the result during idle is provided to the control circuit 7, and the result during the sensing operation is provided to the medium handling device 14, which will be described later. Reference numeral 13 denotes a storage unit that stores the resistance selection signals S E L21-3 E L2m when receiving the following storage instruction signal SM from the control circuit 7. The control circuit 7 receives each on/off signal from the comparison signal latch circuit 12 during idle, and based on the results, calculates the relationship between the resistance value characteristic line I11 and the curve CI shown in FIG. 5, which are adjusted by the variable resistance circuit 9. The voltage at the intersection AI is each voltage V
CECA') and VCE(A'), and at this time, a storage instruction signal SM is given to the sampling circuit 10 to send the resistance selection signals 5EL21 to 5EL21 to the storage section 13.
5EL2a+ is stored. 14 is a media handling device;
The conveyance control of each medium to be detected X1...Xn and its respective processing are performed.

Next, the operation of the circuit shown in FIG. 1 will be explained. Figure 6 is a timing chart showing each operation, Figure 7 (A), Figure 7 (
B) is a flowchart showing the operation.

Once in the idle state, the media handling device 14
Medium X1 to Xn in the transport path of each optical sensor S1 to Sn
Output characteristics: J! J adjustment operation is started. To start adjusting the output characteristics from optical sensor S1,
The control circuit 7 sets sensor No. N-1 (step pi).

Then, in order to maximize the combined resistance RL of the variable resistance circuit 9, the sampling circuit 10 sets Ul-U2-...-Ua=1 to turn off each switch SWI to SW by 1 (P2). Sensor selection signal S E from control circuit 7
LIN is connected to the sensor selection circuit 8, the sampling circuit 10,
The comparison signal is output to the latch circuit 12 (P3). In response to this, the sampling circuit 10 sets the variable number Ul set in step P2.

U2. ...Resistance selection signal SEL21-S according to Us
EL2m is output to the variable resistance circuit 9 during the output period of the sensor selection signal 5ELIN (P4). At this time, the combined resistance RL becomes RL - (1-1/2) R.

Next, after waiting the time TI until the combined resistance RL is settled, the control circuit 7 supplies the reference voltage selection signal 5EL (as the voltage VCE (A') shown in FIG. 4) to the comparison circuit 1.
1 (P5).

Comparison circuit 11 compares voltage VCH with voltage VCH (A') and outputs the result to comparison signal latch circuit 11. Waiting for the stabilization time T2 of the variable resistance circuit 9 and comparison circuit 11,
A latch signal LA is output from the sampling circuit 10,
The comparison signal CP of the comparison circuit 11 for the sensor S1 is output from the comparison signal latch circuit 12. The control circuit 7 reads the signal CP and makes an on/off determination (P6)
. When off, a straight line g1 is formed by the characteristic curve C1 without medium shown in Fig. 5 and the combined resistance RL - (1-1/2") R.
Since the intersection point A1 is to the left of the voltage VCE (A'), the sampling circuit 10 makes the slope of the straight line ρl larger than the slope of the straight line f11' so that the voltage VCE is to the right of the intersection point Al'. The variable numbers Ul to Um are subtracted (P7).

This subtraction is realized by an algorithm predetermined by the control circuit 7. For example, the initial combined resistance RL is
Then, sequentially RL -RLO/2 (-RLI),
RL■RLl/ 2-RLO/4 (-RL2),
...and... If subtraction was possible at this time (P
8''), each step P based on the respective subtraction results.
4 to P8, when the comparison signal CP is turned on initially or as a result, the control circuit 7 outputs the voltage VC to the comparison circuit 11 as the reference voltage selection signal 5EL3.
E(A') is specified to be supplied (P9). Then, in the same way as in step P6, it is determined whether the signal CP is on or off (PIO), and when it is on, since the intersection A1 is to the right of the voltage VCE (A'), the voltage VCE is lower than the intersection A1'. The variable number Ul-Us is added so that Ul-Us is also on the left (P11). This addition, for example, RL −
(RLO+RLO/2) /2 3RLO/4 <-R
LI), RL-(RLO+RLl/2)/2-
7RLO/8 (■RL2), . . . If addition is possible at this time (PI3), each state P4 to P8 or P4 to PL2 is repeated as described above, and as a result, if the comparison signal CP turns off (PIO), then Each variable number Ul-U for the optical sensor SN of
The value of a+ is stored in the storage unit 13 (P13). Then, add N until sensor No. and N become n (PI4
．． PI3), the operations of each step P2 to P15 are repeated, and when Nmn is reached (P14), and if it is idle at that time (PiB), the process returns to step pt and the above-mentioned operations are repeated.

In addition, in the step P8, if the subtraction in the step P7 is not possible, that is, before the subtraction, the variable number Ul -U2-...UimO, or in the step P12, the addition in the step PIO is not possible. , that is, the variable number 0l−U before the addition
2--Us -1, an error is displayed (PI3) and the process ends.

Next, when the medium handling device 14 outputs a command to start the medium detection operation, such as when it is no longer idle in step PlG, the control circuit 7 outputs the reference voltage selection signal 5E.
As L3, the voltage VREP is output to the comparison circuit 11 (P1B). Then, in order to start the medium detection operation from optical sensor S1, sensor No. N-1 is set (
P19). The sampling circuit 10 receives a variable number Ul for the sensor SN stored in the storage unit 13 according to an instruction from the control circuit 7.

U2. . . . reads Us (820), and outputs resistance selection signals 5EL21 to SEL2m according to this to the variable resistance circuit 9 (P21). And the control circuit 7 is
The sensor selection signal SELIN is sent to the sensor selection circuit 8,
The signal is output to the sampling circuit 10 and the comparison signal latch circuit 12 (P22). As a result, the medium handling device 14 can detect the presence or absence of the medium with respect to the sensor SH after the stabilization time T2 similar to that in step P8 has elapsed.

Then, add N until sensor No. and N become n (P
23. ? 24) Repeat the operations of each step P21 to P24, and when reaching N-n (P23), if the medium detection operation is continuing according to an instruction from the medium handling device 14 (P25), each step P19 to P25 is performed. Perform an action repeatedly. When the medium detection operation is completed, the operations after step P1B are executed.

FIG. 8 is a diagram showing changes in output characteristics depending on whether or not the optical sensors are contaminated in the circuit of FIG.
When the is soiled with paper dust etc., the characteristics without a medium shift from curve C1 to curve CI', and the characteristics with medium shift from curve C2 to curve C2', but in that case, according to the characteristics shown in Fig. 5. In the same way as when adjusted to straight line, Ql, the predetermined 1 pressure range VCE(A'), VCE(A') during idling.
The intersection point A2 is determined and adjusted to a straight line g2.

In addition, in this example, an example using a comparator with an operational amplifier configuration as shown in Fig. WS2 was explained.
Each voltage VCE instead of the comparator circuit 11.

VCE (A'), VCIE (A'),
VREF or the like may be converted into analog-to-digital data, these numerical values may be compared by a program, and the comparison signal CP may be sent out based on the comparison result.

Furthermore, it goes without saying that the configuration and connection method of the variable resistance circuit 9 can be inferred in various ways, not only according to the embodiments, but as long as they have similar effects.

(Effects of the Invention) As explained above, according to the present invention, when the detection operation is idle, the resistance value of the load resistance circuit of the light receiving section is switched in a state where there is no medium to be detected, according to the set value of the electric signal, and the switching value is stored, and during the detection operation, the resistance value of the load resistance circuit can be set based on the stored switching value, so that the output characteristics of the optical sensor for determining the presence or absence of a medium can be set appropriately. Automatic adjustment is possible. Furthermore, even if the optical sensor is soiled, the output characteristics can be tracked in accordance with the soiling, so the presence or absence of the medium can be reliably detected.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an automatic adjustment circuit of a medium detection device showing an embodiment of the present invention, Fig. 2 is a conventional medium detection circuit diagram, Fig. 3 is an output characteristic diagram of the circuit of Fig. 2, and Fig. 4 is a detailed circuit diagram of the variable resistance circuit, Figure 5 is a diagram of the operating characteristics of the circuit in Figure 1,
6 is a timing chart showing the operation of the circuit in FIG. 1, FIG. 7 (A), FIG. 7 CB) is a flowchart showing the operation of the circuit in FIG. It is an output characteristic diagram depending on whether the optical sensor is contaminated or not. 7... Control circuit, 9... Variable resistance circuit, 10...
Sampling circuit, 11... Comparison circuit, 13... Storage section, XI-Xn... Medium to be detected, S1-Sn...
Optical sensor, SWI-8Wm...analog switch. Patent Applicant Oki Electric Industry Co., Ltd. Agent Patent Attorney Yoshi 1) Takashi Sei Figure 1 Colloquial Output T11 Live Diagram 5 Figure 6

Claims (4)

[Claims] (1) Using an optical sensor in which a light-emitting part and a light-receiving part are placed across the path of the detected medium, the change in the photocurrent of the light-receiving part due to the difference in transmitted light depending on the presence or absence of the detected medium is converted into a voltage signal. In an automatic adjustment circuit for an optical medium detection device that has a load resistance circuit and determines the presence or absence of a medium to be detected based on a change in the voltage signal, the load resistance circuit has a variable resistor and a resistance value of the variable resistor that is electrically adjusted. a switching means that switches according to a set value of the signal, a storage means for storing the set value of the electric signal, and a switching control means that controls the switching means according to the set value of the electric signal stored in the storage means. An automatic adjustment circuit for an optical medium detection device, comprising: (2) The determining means for determining the presence or absence of the detected medium is configured to set a comparison reference value to be compared with the voltage signal to a first comparison reference value for determining the presence or absence of the detected medium. The optical medium detection device according to claim 1, characterized in that the optical medium detection device according to claim 1 is capable of switching between predetermined second and third comparison reference values in which a region determined as having no medium to be detected is set based on the comparison reference value. automatic adjustment circuit. (3) The variable resistor is composed of a plurality of fixed resistors, the switching means is composed of a plurality of switch control means, and the switch control means, based on the set value of the electric signal,
The automatic adjustment circuit for an optical medium detection device according to claim 1, wherein the resistance value of the fixed resistor can be changed in stages. (4) Using an optical sensor in which a light emitting part and a light receiving part are placed across the path of the medium to be detected, changes in the photocurrent of the light receiving part due to differences in transmitted light due to the presence or absence of the medium to be detected are converted into voltage signals. In an automatic adjustment method for an optical medium detection device, which has a load resistance circuit for detecting a medium and determines the presence or absence of a medium to be detected based on a change in the voltage signal, the voltage signal A first comparison reference value for determining the presence or absence of a detected medium, and a predetermined second and second comparison value of an area determined to be free of a detected medium by the first comparison reference value. 3 are set alternately, and the resistance value of the load resistance circuit is sequentially switched according to the set value of the electric signal, so that the voltage signal is set as the second comparison reference value.
and a third comparison reference value, and during the detection operation, the resistance value of the load resistance circuit is set according to the stored switching value, and the voltage signal is set to the first
1. An automatic adjustment method for an optical medium detection device, characterized in that the presence or absence of a medium to be detected is determined by comparing with a comparison reference value.