JP2002171162A - Photoelectric sensor and method for adjusting sensitivity of photoelectric sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoelectric sensor in which a reference value and a hysteresis width of a comparison operating means (comparator function) can be adjusted automatically corresponding to the gain adjustment of a light receiving means and high resolution is realized. SOLUTION: This photoelectric sensor is constituted of a light receiving means 2, a light projecting means 3 and a judging means 4. The light receiving means 2 is equipped with a gain adjusting means 7 for adjusting the gain of an amplifier 6 which amplifies an electric signal VS1, and outputs a position signal VP corresponding to an adjusting position of the gain adjusting means 7. The judging means 4 is equipped with the comparison operating means 12 which can adjust a reference value VK1 and a hysteresis width ΔV1. On the basis of the position signal VP supplied from the gain adjusting means 7, either or both of the reference value VK1 and the hysteresis width ΔV1 are adjusted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectric sensor for determining the presence or absence of an object with high resolution, and a method for adjusting the sensitivity of the photoelectric sensor.

[0002]

2. Description of the Related Art In a conventional photoelectric sensor, the amount of light radiated from a light emitting diode (LED) is adjusted according to the distance to an object by changing the current flowing through the light emitting diode (LED) in a light emitting section. One configured to adjust the sensitivity is known.

Further, there is known a conventional photoelectric sensor which is configured to adjust the gain of an amplifier of a light receiving unit and adjust the sensitivity of the sensor when an object is at a short distance. I have.

Further, some conventional photoelectric sensors are configured to improve the resolution of the sensor by adjusting the sensitivity by adjusting the threshold value (reference value) of a comparator.

[0005]

SUMMARY OF THE INVENTION Conventional photoelectric sensors are:
Since the threshold value (reference value) of the comparator that determines the presence or absence of the object is constant, the light emitting diode (L
Even if the amount of light emitted from the light emitting diode (LED) is adjusted by changing the current flowing through the ED), the level of the received optical signal changes, but the ratio of the optical signal to the noise (S / N ratio) is the same. Therefore, there is a problem that the resolution of the sensor cannot be improved.

The method of adjusting the amount of light radiated from a light emitting diode (LED) is based on the risk that a signal may be saturated in an amplifier of a light receiving unit if the amount of light is increased more than necessary, or an object may be determined if the amount of light is reduced more than necessary. It may not be possible.

In a conventional photoelectric sensor for adjusting the gain of an amplifier in a light receiving unit, when a hysteresis characteristic is set in a comparator for judging the presence or absence of an object, the gain is not adjusted. When set low, the noise component of the signal is reduced, but the signal component is also reduced. On the other hand, the hysteresis width (on-off level) of the hysteresis characteristic is constant, so that there is a problem that the resolution is reduced.

A conventional photoelectric sensor for adjusting a threshold value (reference value) of a comparator has a threshold value (reference value).
Is set to a large level, the gain (gain) of the amplifier of the light receiving unit is set to be high, and unless the signal output from the amplifier is set to a large level, it cannot be determined that there is an object.
The output signal of the amplifier may be saturated.

If the threshold (reference value) is set to a small level in order to improve the resolution, noise when there is no signal (for example, light from a fluorescent lamp) exceeds the threshold (reference value) and returns (when there is no signal). (State without detection output) Failure may occur.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and a first object of the present invention is to provide a comparison operation means (comparator function) corresponding to adjustment of a gain of a light receiving means or adjustment of a light amount of a light projecting means. It is another object of the present invention to provide a photoelectric sensor that can automatically adjust the reference value and the hysteresis width of (1) and realize high resolution.

A second object is to automatically adjust the reference and the hysteresis width of the comparison operation means (comparator function) in accordance with the adjustment of the gain of the light receiving means or the adjustment of the light amount of the light projecting means. It is an object of the present invention to provide a method for adjusting the sensitivity of a photoelectric sensor for improving the sensitivity.

[0012]

According to another aspect of the present invention, there is provided a photoelectric sensor according to the present invention, wherein light receiving means includes gain adjusting means for adjusting the gain of an amplifier for amplifying an electric signal.
In addition to outputting a position signal corresponding to the adjustment position of the gain adjustment means, the determination means includes comparison operation means capable of adjusting the reference value and the hysteresis width, and the reference value is determined based on the position signal supplied from the gain adjustment means. And / or the hysteresis width is adjusted.

In the photoelectric sensor according to the present invention, one or both of the reference value and the hysteresis width of the comparison operation means can be adjusted based on the position signal by adjusting the gain of the light receiving means. Even if the target is at a short distance, the determination can be made with the optimum sensitivity and the optimum resolution, and the target can be determined with high accuracy.

In the photoelectric sensor according to the present invention, the light projecting means includes a light quantity adjusting means for adjusting a light quantity to be radiated,
Along with outputting an adjustment signal corresponding to the adjustment position of the light amount adjustment unit, the determination unit includes a comparison operation unit capable of adjusting a reference value and a hysteresis width, and determines a reference value and a reference value based on the position signal supplied from the gain adjustment unit. It is characterized in that one or both of the hysteresis widths are adjusted.

In the photoelectric sensor according to the present invention, one or both of the reference value and the hysteresis width of the comparison operation means can be adjusted based on the adjustment signal by adjusting the light amount of the light projecting means. Even if the object is at a short distance, the determination can be made with the optimum sensitivity and the optimum resolution, and the object can be determined with high accuracy.

Further, the judging means according to the present invention comprises: A / D conversion means for converting a position signal or an adjustment signal and an electric signal into a digital value; a reference value and a hysteresis corresponding to the digital value of the position signal or the adjustment signal. Storage means for storing the width, when the position signal or the adjustment signal and the electric signal are supplied, the reference value and the hysteresis width stored in the storage means are read, and the electric signal and the reference value are compared by the comparison operation means. It is characterized in that the presence or absence of an object is determined by calculation.

The determining means according to the present invention stores a reference value and a hysteresis width corresponding to the digital value of the position signal or the adjustment signal, and stores the reference value and the stored reference value when the position signal or the adjustment signal is supplied. Since the hysteresis width is read and the electric signal is compared with the reference value to determine the presence or absence of the target, the determination of the target can be realized with an optimum resolution corresponding to the gain or the light amount.

Further, the storage means according to the present invention is characterized in that a reference value is set in a predetermined range with respect to a change in a position signal or an adjustment signal.

The storage means according to the present invention sets the reference value within a predetermined range with respect to a change in the position signal or the adjustment signal, so that a return failure or saturation can be prevented.

Further, the storage means according to the present invention is characterized in that the reference value is set linearly with respect to a change in the position signal or the adjustment signal.

Since the storage means according to the present invention sets the reference value linearly with respect to the change of the position signal or the adjustment signal, it is possible to realize an optimum resolution corresponding to the sensitivity.

Further, the storage means according to the present invention is characterized in that a reference value is set non-linearly with respect to a change in a position signal or an adjustment signal.

The storage means according to the present invention sets the reference value non-linearly with respect to the change of the position signal or the adjustment signal, so that an optimum resolution can be realized in accordance with the sensitivity.

In the method for adjusting the sensitivity of the photoelectric sensor according to the present invention, step 1 for adjusting the gain of the light receiving means and step 2 for A / D converting the position signal and reading the digital value.
Step 3 for reading a reference value and a hysteresis width corresponding to the digital value, Step 4 for setting the reference value and the hysteresis width, and an electric signal amplified and A / D converted with the adjusted gain and the set reference value. The method includes a step 5 of comparing and calculating a hysteresis width, and a step 6 of determining the presence or absence of an object based on a result of the comparison, wherein sensitivity is adjusted.

The method for adjusting the sensitivity of the photoelectric sensor according to the present invention includes Step 1 to Step 6, so that the determination can be made with the optimum sensitivity and the optimum resolution even when the object is at a short distance. Can be determined with high accuracy.

The sensitivity adjustment method for a photoelectric sensor according to the present invention includes a step 1 for adjusting the amount of light of the light projecting means, a step 2 for converting an adjustment signal A / D and reading a digital value, and a method for adjusting the digital value. Step 3 for reading the set reference value and hysteresis width, Step 4 for setting the reference value and hysteresis width, and Step for comparing and calculating the received, amplified, A / D converted electric signal and the set reference value and hysteresis width. 5 and a step 6 of determining the presence or absence of the target object based on the comparison result, wherein the sensitivity is adjusted.

Since the method for adjusting the sensitivity of the photoelectric sensor according to the present invention includes Steps 1 to 6, even if the object is at a short distance, it is possible to determine with the optimum sensitivity and the optimum resolution. Can be determined with high accuracy.

[0028]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram of a main part of an embodiment of a photoelectric sensor according to the present invention. FIG.
, The photoelectric sensor 1 includes a light receiving unit 2, a light projecting unit 3,
An electric signal which is provided with a judging means 4, which emits an optical signal LS from the light projecting means 3 to the object 20, receives light reflected by the object 20 LR reflected by the light receiving means 2, and performs optical-electrical conversion The presence or absence of the object 20 is determined by the determination means 4 based on

The light receiving means 2 includes a light receiving element 5, an amplifier 6, and a gain adjusting means 7. The light receiving element 5 is constituted by a photodiode (PD), and the reflected light L reflected by the object 20
R is received, the reflected light LR is subjected to light-to-electric conversion, and the converted electric signal VS1 of an analog amount is supplied to the amplifier 6.

The amplifier 6 is composed of an operational amplifier or the like whose gain can be changed. The amplifier 6 amplifies the electric signal VS1 supplied from the light receiving element 5 and sends the amplified electric signal VS2 to the A / D conversion means 10B of the judgment means 4. provide.

The gain adjusting means 7 is composed of a variable resistor (volume) or the like capable of changing the gain of the amplifier 6, and externally operates the variable resistor (volume) to adjust the gain (gain) of the amplifier 6. Further, the gain adjusting means 7 determines the position signal VP (DC voltage) corresponding to the position (rotation angle = resistance value) of the variable resistor (volume) by the A / D
It is provided to the conversion means 10A. Note that the variable resistor (volume) of the gain adjusting means 7 is the gain (gain) of the amplifier 6.
Is adjusted so as to increase, the position signal VP (DC voltage) also increases.

The light projecting means 3 includes a light emitting element 8 and a driving means 9. The light emitting element 8 is constituted by a light emitting diode (LED) and projects an optical signal LS having a pulse waveform of a light amount corresponding to the drive signal PD supplied from the drive means 9 to the object 20.

The driving means 9 is constituted by an LED driving circuit such as a constant current source or the like. The driving means 9 has a pulse width TP, The drive signal PD for the idle period TK (T = TP + TK) is supplied to the light emitting element 8. Therefore, the light emitting element 8
Emits light periodically during the period of the pulse width TP of the drive signal PD.

The judging means 4 is basically constituted by a microprocessor, and comprises A / D converting means 10A and 10B,
1, a comparison operation unit 12 and a light emission control unit 13. A
The A / D converter 10A is composed of an A / D converter, and receives the analog position signal VP supplied from the gain adjuster 7.
Is subjected to A / D conversion at a predetermined sampling time, and a digital value position signal VDP is supplied to the storage means 11.

The A / D conversion means 10B comprises an A / D converter, performs A / D conversion on the analog electric signal VS2 supplied from the amplifier 6 at a predetermined sampling time, and outputs a digital electric signal VDS Is supplied to the comparison operation means 12.

The storage means 11 comprises a memory such as a ROM or an EEPROM, and sets a reference value VK1 and a hysteresis width ΔV1 corresponding to the digital value position signal VDP shown in FIG. A / D
When the A / D-converted position signal VDP is supplied from the conversion means 10A, the reference value VK1 and the hysteresis width ΔV1 corresponding to the position signal VDP are read out and set in the comparison calculation means 12.

FIG. 2 shows a reference value VK corresponding to the position signal VDP.
1 is a linear characteristic diagram of a hysteresis width ΔV1. In FIG. 2, the reference value VK1 is set to a large constant value and the hysteresis width ΔV1 is set to a narrow constant value until the position signal VDP reaches VPS. When the position signal VDP is from VPS to VPT, the reference value V
K1 is reduced linearly, and the hysteresis width ΔV
1 is increased linearly so that the hysteresis width ΔV1
Are set to spread with an increase in the position signal VDP.
Further, when the position signal VDP exceeds VPT, the reference value VK1 is set to a small constant value and the hysteresis width ΔV1 is set to a wide constant value. The reference value VK1 is limited to a small constant value, and the noise level is set so as not to exceed the reference value VK1−ΔV1 / 2 when there is no signal, thereby preventing the sensor from returning poorly.

An increase in the position signal VDP corresponds to an increase in the gain of the amplifier 6, that is, the photoelectric sensor 1
Will increase the sensitivity. As is clear from FIG. 2, when the photoelectric sensor 1 has low sensitivity, the reference value VK1 is set large and the hysteresis width ΔV1 is set small, so that the resolution can be set high. When the position signal VDP is lower than VPT (VDP≤VPT), the sensitivity gradually decreases. Therefore, the reference value VK1 is increased linearly (linearly), and the hysteresis width ΔV1 is reduced linearly (linearly). Is gradually narrowed, so that the resolution gradually increases as the position signal VDP decreases.

FIG. 3 shows a reference value VK corresponding to the position signal VDP.
1 is a non-linear characteristic diagram of a hysteresis width ΔV1. 3 differs from FIG. 2 only in that the reference value VK1 is reduced nonlinearly (exponentially) and the hysteresis width ΔV1 is increased nonlinearly (exponentially) when the position signal VDP is in the range of VPS to VPT. . In FIG. 3, the non-linear characteristic is set by an exponential function, but may be set by a step function.

In FIG. 2 or FIG. 3, the position signal VDP
Although the reference value VK1 and the hysteresis width ΔV1 are changed corresponding to the above, one of the reference value VK1 and the hysteresis width ΔV1 may be fixed and the other may be changed.

The comparison operation means 12 has an addition function, a subtraction function, a comparison function, a judgment function and the like under software control.
A calculation is executed based on the electric signal VDS supplied from the / D conversion means 10B, the reference value VK1 supplied from the storage means 11 (set) and the hysteresis width ΔV1, and the judgment signal HO is obtained.
The presence or absence of the target object 20 is determined based on the level of. First,
1/2 of the reference value VK1 and the hysteresis width ΔV1 ΔV1 /
2 is added to calculate a threshold value (= VK1 + ΔV1 / 2).
Next, a threshold value (= VK1−ΔV1 / 2) is calculated by subtracting a half value ΔV1 / 2 of the hysteresis width ΔV1 from the reference value VK1.

Subsequently, the electric signal VDS and the threshold value (= VK1 + Δ
V1 / 2), and the electric signal VDS becomes equal to the threshold value (= VK1 + Δ
(VDS> VK1 + .DELTA.V1 / 2), the determination signal HO at the H level (for example, DC voltage 5 V) is exceeded.
Is output. Note that the electric signal VDS and the threshold value (= VK1 +
If ΔV1 / 2) are equal, a determination signal H0 that rapidly transitions from an L level (for example, ground voltage 0 V) to an H level (for example, DC voltage 5 V) is output.

On the other hand, when the electric signal VDS has a threshold value (= VK1 + ΔV
In the case of (VDS ≦ VK1 + ΔV1 / 2) that is equal to or less than (1), the judgment signal of the H level (for example, DC voltage 5V) or the L level (for example, ground voltage 0V) according to the past (history) value of the electric signal VDS. HO is calculated and output.

When the past (history) value of the electric signal VDS increases after the threshold value (= VK1−ΔV1 / 2),
An L-level determination signal Ho is output. On the other hand, the electric signal VD
If the past (history) value of S decreases after passing the threshold value (= VK1 + ΔV1 / 2), the threshold value (= VK1−ΔV1 / 2)
Until it reaches H, the arithmetic output of the judgment signal H0 at the H level.

When the electric signal VDS has a threshold value (= VK1−ΔV)
(VDS <VK1−ΔV1 / 2)
In this case, an L-level determination signal H0 is output. In addition,
When the electric signal VDS is equal to the threshold value (= VK1−ΔV1 / 2), a determination signal H0 that rapidly transitions from H level to L level is output.

FIG. 4 is a hysteresis characteristic diagram of the comparison operation means according to the present invention. Referring to FIG.
Means that the electric signal VDS increases and the threshold value (= VK1−ΔV
The threshold value (= VK1 + ΔV1 / 2) is at the L level (→ direction) after elapse of 1/2), and when the threshold value (= VK1 + ΔV1 / 2) is slightly exceeded, the L level rapidly transitions to the H level (↑ direction). I do. The determination signal HO is the electric signal VDS
Keeps the H level (→ direction) even if exceeds the threshold value (= VK1 + ΔV1 / 2).

On the other hand, the judgment signal H0 maintains the H level (← direction) from this state even if the electric signal VDS decreases,
The state of maintaining the H level passes through the threshold value (= VK1 + ΔV1 / 2) and continues to the threshold value (= VK1−ΔV1 / 2) (← direction).
I do. Further, the judgment signal HO has a threshold value (= VK1−ΔV1 /
2) When the voltage falls slightly below the level, the level changes rapidly from the H level to the L level (in the direction of ↓), and the electric signal VDS becomes equal to the threshold value (= VK1−Δ).
V1 / 2), the L level is maintained (← direction) even if the voltage further decreases.

As described above, the comparison calculation means 12 calculates the threshold value (= VK1−ΔV1 / 2) and the threshold value (= VK1 + ΔV1 /
Since the electric signal VDS is close to the threshold value due to the hysteresis characteristic of the hysteresis width ΔV1 of 2) and the electric signal VDS changes across the threshold value due to the fluctuation of the signal or noise, the judgment signal HO is changed to the level before the fluctuation (H level). Or L level).

As shown in FIGS. 2 and 3, when the sensitivity is lowered (the gain of the amplifier 6 is small), the hysteresis characteristic shown in FIG. 4 shifts in the direction in which the electric signal VDS becomes smaller. , The hysteresis width ΔV1 is also reduced, so that the resolution of the photoelectric sensor 1 can be improved.

On the other hand, when the sensitivity is increased (gain of the amplifier 6 is large), the hysteresis characteristic shown in FIG. 4 shifts in the direction of increasing the electric signal VDS, and the hysteresis width ΔV1 increases. Since it is possible to prevent erroneous detection of noise at the time, it is possible to prevent a poor return of the photoelectric sensor 1.

The light emission control means 13 includes a pulse generation circuit, and has a pulse width TP and a period T of a pause period TK (= TP + TK).
Is supplied to the driving means 9.

As described above, the photoelectric sensor 1 according to the present invention
By adjusting the gain of the light receiving means 2, one or both of the reference value VK1 and the hysteresis width ΔV1 of the comparing and calculating means 12 can be adjusted based on the position signal VDP. Even at a short distance, the determination can be made with the optimum sensitivity and the optimum resolution, and the object 20 can be determined with high accuracy.

The determining means 4 according to the present invention stores the reference value VK1 and the hysteresis width ΔV1 corresponding to the digital value VDP of the position signal VP, and stores the reference value when the position signal VDP is supplied. Value VK1 and hysteresis width Δ
Since V1 is read and the electric signal VDS is compared with the reference value VK1 to determine the presence or absence of the target 20, the determination of the target 20 can be realized with an optimum resolution corresponding to the gain.

Further, the storage means 11 according to the present invention comprises:
Since the reference value VK1 is set within a predetermined range with respect to the change in the position signal VDP, it is possible to prevent a return failure or saturation.

Further, since the storage means 11 according to the present invention sets the reference value VK1 to linear or non-linear with respect to the change of the position signal VDP, it is possible to realize an optimum resolution corresponding to the sensitivity.

Next, a method of adjusting the sensitivity of the photoelectric sensor 1 will be described with reference to an operation flowchart. FIG. 5 is an operation flowchart of an embodiment of the method for adjusting a photoelectric sensor according to the present invention. In the present embodiment, a reference value of the hysteresis characteristic and a hysteresis width are determined in accordance with the gain (gain) adjustment of the amplifier, and a photoelectric sensor adjustment method for setting an optimum resolution is realized. This will be described with reference to FIG.

First, in step S1, the gain of the amplifier 6 of the light receiving means 2 is adjusted. In step S2, the storage means 11 reads the A / D converted digital value VDP of the position signal VP output along with the gain adjustment.

In step S3, the reference value VK1 and the hysteresis width .DELTA.V1 corresponding to the digital value VDP are read from the data corresponding to the digital value VDP and the reference value VK1 and the hysteresis width .DELTA.V1 set in the storage means 11 in advance.
In step S4, the read reference value VK1 and the hysteresis width ΔV1 are set in the comparison calculation means 12.

In step S5, the A / D of the electric signal VS2
The converted digital value VDS is compared with the reference value VK1 and the hysteresis width ΔV1 by the comparison calculation means 12, and the process proceeds to step S6. In step S6, the digital value VDS is compared with a threshold value (= VK1 + ΔV1 / 2). If the digital value VDS exceeds the threshold value (= VK1 + ΔV1 / 2) (VDS> VK1 + ΔV1 / 2), the process proceeds to step S7. , The digital value VDS is equal to the threshold value (= VK1 + ΔV1)
/ 2) or less (VDS ≦ VK1 + ΔV1 / 2), the process proceeds to step S9.

In step S7, the determination signal HO is set to H level, and in step S8, it is determined that there is an object.
On the other hand, in step S9, the determination signal HO is set to L level, and in step S10, it is determined that there is no target. Steps S5 to S10 are executed by the comparison operation means 12.

As described above, the photoelectric sensor 1 according to the present invention
Since the sensitivity adjustment method includes the steps S1 to S6, even if the object 20 is at a short distance, it is possible to determine with the optimum sensitivity and the optimum resolution.
Can be determined with high accuracy.

FIG. 6 is a block diagram showing a main part of another embodiment of the photoelectric sensor according to the present invention. 6, the photoelectric sensor 15 includes a light receiving unit 16, a light projecting unit 17, and a determining unit 18. The configuration shown in FIG. 6 corresponds to the light receiving unit 3 shown in FIG.
This is basically different from the first embodiment in that the gain adjusting means 7 is deleted and the light receiving means 16 is provided, and the light projecting means 3 is provided with the light amount adjusting means 22 and the light projecting means 17 is basically provided.

The light receiving means 16 includes the light receiving element 5 and the amplifier 6, receives the reflected light LR reflected by the object 20, performs light-to-electric conversion on the reflected light LR, and converts the electric signal into an analog electric signal. The determination means 1 determines the electric signal VS2 obtained by amplifying VS1.
8 to the A / D conversion means 19B.

The light projecting means 17 includes a light emitting element 8, a driving means 9, and a light quantity adjusting means 22. Based on a light emission control signal CD having a pulse waveform of a constant period T provided from the light emission controlling means 13 of the determining means 18. The pulse width TP and the rest period TK (T
= TP + TK) is supplied to the light emitting element 8, and the light emitting element 8 is caused to emit light periodically during the period of the pulse width TP of the driving signal PD, and the optical signal LS is projected on the object 20. Also,
The driving means 9 is adjusted by the light amount adjusting means 22, and the driving signal PD is adjusted.
Of the optical signal LS is adjusted by changing the amplitude of the optical signal LS.

The light quantity adjusting means 22 is constituted by a variable resistor (volume) or the like capable of changing the amplitude of the driving signal PD of the driving means 9, and the driving signal of the driving means 9 is operated by operating the variable resistor (volume) from outside. Adjust the amplitude of PD. Also,
The light amount adjusting means 22 provides an adjustment signal VT (DC voltage) corresponding to the position (rotation angle = resistance value) of the variable resistor (volume) to the A / D converting means 19A of the judging means 18. The variable resistor (volume) of the light amount adjusting means 22 is configured so that when the amplitude of the drive signal PD is adjusted to increase (the light amount increases), the adjustment signal VT (DC voltage) also increases.

The judging means 18 is basically composed of a microprocessor, and includes A / D converting means 19A and 19B, a storage means 23, a comparison operation means 21, and a light emission control means 13.
The A / D conversion means 19A is constituted by an A / D converter,
A / D conversion is performed on the analog amount adjustment signal VT supplied from the light amount adjustment unit 22 for a predetermined sampling time, and a digital value adjustment signal VDT is supplied to the storage unit 23.

The A / D conversion means 19B comprises an A / D converter, performs A / D conversion on the analog electric signal VS2 supplied from the amplifier 6 at a predetermined sampling time, and outputs a digital electric signal VDS Is supplied to the comparison operation means 21.

The storage means 23 is composed of a memory such as a ROM or an EEPROM, and sets a reference value VK2 and a hysteresis width ΔV2 corresponding to the digital value adjustment signal VDT shown in FIG. A / D
When the A / D-converted adjustment signal VDT is supplied from the converter 19A, the reference value VK2 and the hysteresis width ΔV2 corresponding to the adjustment signal VDT are read and set in the comparison operation means 21.

FIG. 7 shows a reference value VK corresponding to the adjustment signal VDT.
2 is a linear characteristic diagram of the hysteresis width ΔV2. In FIG. 7, the reference value VK2 is set to a large constant value and the hysteresis width ΔV2 is set to a narrow constant value until the adjustment signal VDT reaches VTS. When the adjustment signal VDT is from VTS to VTT, the reference value VDT is used.
K2 is reduced linearly, and the hysteresis width ΔV
2 is increased linearly, and the hysteresis width ΔV2
Are set so as to spread as the adjustment signal VDT increases.
Further, when the adjustment signal VDT exceeds VTT, the reference value VK2 is set to a small constant value, and the hysteresis width ΔV2 is set to a wide constant value. The reference value VK2 is limited to a small constant value, and the noise level is set so as not to exceed the reference value VK2−ΔV2 / 2 when there is no signal, thereby preventing the sensor from returning poorly.

The increase in the adjustment signal VDT corresponds to the increase in the light amount of the light emitting element 8, that is, the sensitivity of the photoelectric sensor 15 increases. As is clear from FIG. 7, when the photoelectric sensor 15 has low sensitivity, the reference value VK2 is set to be large and the hysteresis width ΔV2 is set to be small, so that the resolution can be set to be high. When the adjustment signal VDT is equal to or lower than VTT (VDT≤VTT), the sensitivity gradually decreases. Therefore, the reference value VK2 is increased linearly so that the hysteresis width Δ
V2 is reduced linearly, and the hysteresis width Δ
To set V2 gradually narrower, the resolution is also adjusted by the control signal VDT.
It becomes gradually higher with the decrease of.

FIG. 8 shows a reference value VK corresponding to the adjustment signal VDT.
2, a non-linear characteristic diagram of a hysteresis width ΔV2. 8 differs from FIG. 7 only in that the reference value VK2 is reduced non-linearly (exponentially) and the hysteresis width ΔV2 is increased non-linearly (exponentially) within the range of the adjustment signal VDT from VTS to VTT. . In FIG. 8, the non-linear characteristic is set by an exponential function, but may be set by a step function.

Note that, in FIG. 7 or FIG.
Although the reference value VK2 and the hysteresis width ΔV2 are changed in response to the above, one of the reference value VK2 and the hysteresis width ΔV2 may be fixed and the other may be changed.

The comparison operation means 21 has an addition function, a subtraction function, a comparison function, a judgment function, and the like of software control.
A calculation is executed based on the electric signal VDS supplied from the / D conversion means 19B, the reference value VK2 supplied from the storage means 23, and the hysteresis width ΔV2, and the determination signal HO
The presence or absence of the target object 20 is determined based on the level of. First,
The value ΔV2 / which is half of the reference value VK2 and the hysteresis width ΔV2
2 is added to calculate a threshold value (= VK2 + ΔV2 / 2).
Next, a threshold value (= VK2−ΔV2 / 2) is calculated by subtracting a value ΔV2 / 2 of ヒ of the hysteresis width ΔV2 from the reference value VK2.

Subsequently, the electric signal VDS and the threshold value (= VK2 + Δ
V2 / 2), and the electric signal VDS is compared with the threshold value (= VK2 + Δ
V2 / 2) (VDS> VK2 + .DELTA.V2 / 2), the judgment signal H0 of H level (for example, DC voltage 5 V)
Is output. Note that the electric signal VDS and the threshold value (= VK2 +
If ΔV2 / 2) are equal, a determination signal HO that rapidly transitions from an L level (for example, a ground voltage of 0 V) to an H level (for example, a DC voltage of 5 V) is output.

On the other hand, when the electric signal VDS has a threshold value (= VK2 + ΔV
2/2) or less (VDS ≦ VK2 + ΔV2 / 2), a judgment signal of H level (for example, DC voltage 5V) or L level (for example, ground voltage 0V) according to the past (history) value of the electric signal VDS HO is calculated and output.

When the past (history) value of the electric signal VDS increases after the threshold value (= VK2−ΔV2 / 2),
An L-level determination signal Ho is output. On the other hand, the electric signal VD
If the past (history) value of S decreases after passing the threshold value (= VK2 + ΔV2 / 2), the threshold value (= VK2−ΔV2 / 2)
Until it reaches H, a calculation signal of the H level judgment signal HO is output.

When the electric signal VDS has a threshold value (= VK2−ΔV
2/2) (VDS <VK2-ΔV2 / 2)
In this case, an L-level determination signal H0 is output. In addition,
When the electric signal VDS is equal to the threshold value (= VK2-.DELTA.V2 / 2), the determination signal HO that rapidly transitions from the H level to the L level is output.

FIG. 9 is a hysteresis characteristic diagram of the comparison operation means according to the present invention. In FIG. 9, the judgment signal H0
Means that the electric signal VDS increases and the threshold value (= VK2−ΔV2 /
After 2), the signal is at the L level (→ direction) up to the threshold value (= VK2 + ΔV2 / 2). If the threshold value (= VK2 + ΔV2 / 2) is slightly exceeded, the L level rapidly transitions to the H level (↑ direction). The determination signal HO is the electric signal VDS
Keeps the H level (→ direction) even if exceeds the threshold value (= VK2 + ΔV2 / 2).

On the other hand, the determination signal HO maintains the H level (← direction) from this state even if the electric signal VDS decreases,
The state of maintaining the H level passes through the threshold value (= VK2 + ΔV2 / 2) and continues to the threshold value (= VK2−ΔV2 / 2) (← direction).
I do. The determination signal HO is a threshold value (= VK2−ΔV2 /
2) When the voltage slightly falls below the level, the level rapidly changes from the H level to the L level (in the direction of the arrow ↓), and the electric signal VDS changes to the threshold value (= VK2−Δ
V2 / 2), the L level is maintained (← direction) even if it further decreases.

As described above, the comparison operation means 21 calculates the threshold value (= VK2−ΔV2 / 2) and the threshold value (= VK2 + ΔV2 /
2) has a hysteresis characteristic of the hysteresis width ΔV2, so that even if the electric signal VDS is close to the threshold value and changes across the threshold value due to signal fluctuation or noise, the judgment signal HO is not changed to the level before the fluctuation (H level). Or L level).

As shown in FIGS. 7 and 8, when the sensitivity (light quantity of the light emitting element 8) is reduced,
Since the hysteresis characteristic shown in FIG. 9 shifts in the direction in which the electric signal VDS decreases, the hysteresis width ΔV2 also decreases.
The resolution of the photoelectric sensor 15 can be improved.

On the other hand, when the sensitivity (light quantity of the light emitting element 8) increases, the comparison operation means 21 shifts the hysteresis characteristic shown in FIG. 9 to a direction in which the electric signal VDS increases, the hysteresis width ΔV2 also increases, and Can be prevented from being erroneously detected, so that a reset failure of the photoelectric sensor 15 can be prevented.

The light emission control means 13 includes a pulse generation circuit, and has a pulse width TP and a period T of a pause period TK (= TP + TK).
Is supplied to the driving means 9.

As described above, the photoelectric sensor 1 according to the present invention
5 can adjust one or both of the reference value VK2 and the hysteresis width ΔV2 of the comparison / calculation means 21 based on the adjustment signal VDT by adjusting the light quantity of the light projecting means 17; Even when the object 20 is at a short distance, the determination can be made with the optimum sensitivity and the optimum resolution, and the object 20 can be determined with high accuracy.

The determining means 18 according to the present invention stores the reference value VK2 and the hysteresis width ΔV2 corresponding to the digital value VDT of the adjustment signal VT, and stores the reference value when the adjustment signal VDT is supplied. The value VK2 and the hysteresis width ΔV2 are read, and the presence / absence of the object 20 is determined by comparing the electric signal VDS with the reference value VK2, so that the determination of the object 20 can be realized with an optimal resolution corresponding to the light amount. it can.

Further, the storage means 23 according to the present invention
Since the reference value VK2 is set within a predetermined range with respect to the adjustment signal VDT, it is possible to prevent restoration failure and saturation.

Further, since the storage means 23 according to the present invention sets the reference value VK2 to linear or non-linear with respect to the change of the adjustment signal VDT, it is possible to realize an optimum resolution according to the sensitivity.

Next, a method of adjusting the sensitivity of the photoelectric sensor 15 will be described with reference to an operation flowchart. FIG. 10 is an operation flowchart of another embodiment of the photoelectric sensor adjustment method according to the present invention. In this embodiment, a reference value of the hysteresis characteristic and a hysteresis width are determined corresponding to the light amount adjustment of the light emitting element, and an adjustment method of the photoelectric sensor for setting an optimum resolution is realized. It will be described with reference to FIG.

First, in step P1, the light intensity of the light emitting element 8 of the light projecting means 17 is adjusted, so that the photoelectric sensor 15 is adjusted.
Set the sensitivity of. In step P2, the storage means 23 reads the A / D converted digital value VDT of the adjustment signal VT output with the light quantity adjustment.

In step P3, the reference value VK2 and the hysteresis width ΔV2 corresponding to the digital value VDT are read from the data corresponding to the digital value VDT and the reference value VK2 and the hysteresis width ΔV2 set in the storage means 23 in advance.
In Step P4, the read reference value VK2 and the hysteresis width ΔV2 are set in the comparison calculation means 21.

In Step P5, the A / D of the electric signal VS2
The converted digital value VDS is compared with the reference value VK2 and the hysteresis width .DELTA.V2 by the comparing and calculating means 21, and the routine goes to Step P6. In step P6, the digital value VDS is compared with a threshold value (= VK2 + ΔV2 / 2). If the digital value VDS exceeds the threshold value (= VK2 + ΔV2 / 2) (VDS> VK2 + ΔV2 / 2), the flow shifts to step P7. , The digital value VDS is equal to the threshold value (= VK2 + ΔV2)
/ 2) or less (VDS ≦ VK2 + ΔV2 / 2), the program shifts to Step P9.

In step P7, the determination signal HO is set to H level, and in step P8, it is determined that there is an object.
On the other hand, in step P9, the determination signal HO is set to L level, and in step P10, it is determined that there is no target. Steps P5 to P10 are executed by the comparison operation means 21.

As described above, the photoelectric sensor 1 according to the present invention
Since the sensitivity adjustment method of No. 5 includes Steps P1 to P6, it is possible to determine with the optimum sensitivity and the optimum resolution even when the object 20 is at a short distance, and
0 can be determined with high accuracy.

[0094]

As described above, in the photoelectric sensor according to the present invention, by adjusting the gain of the light receiving means, one or both of the reference value and the hysteresis width of the comparison operation means based on the position signal. Can be adjusted, the determination can be made with the optimum sensitivity and the optimum resolution even when the target is at a short distance, and the target can be determined with high accuracy.

In the photoelectric sensor according to the present invention, one or both of the reference value and the hysteresis width of the comparison / calculation means can be adjusted based on the adjustment signal by adjusting the light quantity of the light projecting means. Since it is possible to perform the determination with the optimum sensitivity and the optimum resolution even if the target is at a short distance, the target can be determined with high accuracy.

Further, in the method for adjusting the sensitivity of the photoelectric sensor according to the present invention, the step 1 of adjusting the gain of the light receiving means is performed.
A / D conversion of the position signal and step 2 for reading a digital value, step 3 for reading a reference value and a hysteresis width corresponding to the digital value, step 4 for setting a reference value and a hysteresis width, and an adjusted gain Step 5 for comparing the amplified and A / D-converted electric signal with the set reference value and hysteresis width, and Step 6 for judging the presence or absence of the object based on the comparison result. Even at a short distance, the determination can be made with the optimum sensitivity and the optimum resolution, and the object can be determined with high accuracy.

The sensitivity adjustment method for a photoelectric sensor according to the present invention includes a step 1 for adjusting the light amount of the light projecting means, a step 2 for A / D converting the adjustment signal and reading a digital value, and a step for adjusting the digital value. Step 3 for reading the reference value and the hysteresis width obtained, Step 4 for setting the reference value and the hysteresis width, and Step for comparing and receiving the received, amplified, A / D-converted electric signal with the set reference value and the hysteresis width. 5 and step 6 for judging the presence or absence of the object based on the comparison result, so that the object can be judged with the optimum sensitivity and the optimum resolution even when the object is at a short distance, and Accuracy can be determined.

[Brief description of the drawings]

FIG. 1 is a block diagram of a main part of an embodiment of a photoelectric sensor according to the present invention.

FIG. 2 shows a reference value (VK1) corresponding to a position signal (VDP),
Linear characteristic diagram of hysteresis width (ΔV1)

FIG. 3 shows a reference value (VK1) corresponding to a position signal (VDP),
Non-linear characteristic diagram of hysteresis width (ΔV1)

FIG. 4 is a hysteresis characteristic diagram of the comparison operation means according to the present invention.

FIG. 5 is an operation flowchart of a photoelectric sensor sensitivity adjusting method according to an embodiment of the present invention;

FIG. 6 is a block diagram of a main part of another embodiment of the photoelectric sensor according to the present invention.

FIG. 7 shows a reference value (VK2) corresponding to an adjustment signal (VDT),
Linear characteristic diagram of hysteresis width (ΔV2)

FIG. 8 shows a reference value (VK2) corresponding to an adjustment signal (VDT),
Non-linear characteristic diagram of hysteresis width (ΔV2)

FIG. 9 is a hysteresis characteristic diagram of the comparison operation means according to the present invention.

FIG. 10 is an operation flowchart of another embodiment of the sensitivity adjustment method of the photoelectric sensor according to the present invention.

[Explanation of symbols]

 Reference Signs List 1,15 photoelectric sensor 2,16 light receiving means 3,17 light emitting means 4,18 determining means 5 light receiving element 6 amplifier 7 gain adjusting means 8 light emitting element 9 driving means 10A, 10B, 19A, 19B A / D converting means 11, 23 storage means 12, 21 comparison operation means 13 light emission control means

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takashi Kamei 801 Shidoji Horikawa Higashi-iridani-Fudodoucho, Shimogyo-ku, Kyoto-shi, Kyoto Inside OMRON Corporation (72) Inventor Hiroyuki Inoue Shiokyo-dori, Shimogyo-ku, Kyoto-shi, Kyoto 801 Horikawa Higashiiri Minami Fudodoucho OMRON Corporation F-term (reference) 2G065 AA04 AB22 AB28 BA09 BC10 BC13 BC14 BC21 BC28 BC33 DA15 DA20 5F089 BB01 BC02 CA16 CA17 CA21 FA03 FA05 FA06 5J050 AA12 BB17 BB27 BB29 CC11 DD04 EE35

Claims (8)

[Claims] A light projecting means for emitting light, a light receiving means for receiving light from an object, converting the light into an electric signal, and amplifying the electric signal;
Determining means for comparing the electric signal supplied from the light receiving means with a reference value to determine the presence or absence of the object; and wherein the light receiving means adjusts a gain of an amplifier for amplifying the electric signal. And a position signal corresponding to an adjustment position of the gain adjustment means, and the determination means includes a comparison operation means capable of adjusting a reference value and a hysteresis width, and supplies the comparison signal from the gain adjustment means. A photoelectric sensor that adjusts one or both of a reference value and a hysteresis width based on a position signal to be performed. 2. Light emitting means for emitting light, light receiving means for receiving light from an object, converting the light into an electric signal, and amplifying the electric signal;
Determining means for comparing the electric signal supplied from the light receiving means with a reference value to determine the presence or absence of the object; and a light amount adjusting means for adjusting an amount of emitted light. Output the adjustment signal corresponding to the adjustment position of the light amount adjustment means, the determination means includes a comparison operation means capable of adjusting a reference value and a hysteresis width, the adjustment signal supplied from the light amount adjustment means A photoelectric sensor, wherein one or both of a reference value and a hysteresis width are adjusted based on the following. 3. An A / D converter for converting a position signal or an adjustment signal and an electric signal into a digital value, and a reference value and a hysteresis width corresponding to the digital value of the position signal or the adjustment signal. Storage means for performing
When the position signal or the adjustment signal and the electric signal are supplied, the reference value and the hysteresis width stored in the storage unit are read, and the electric signal and the reference value are compared and calculated by the comparison calculation unit, and the object is read. The photoelectric sensor according to claim 1, wherein the presence or absence of the sensor is determined. 4. The photoelectric sensor according to claim 3, wherein said storage means sets a reference value in a predetermined range with respect to a change in the position signal or the adjustment signal. 5. The photoelectric sensor according to claim 3, wherein said storage means sets a reference value linearly with respect to a change in a position signal or an adjustment signal. 6. The photoelectric sensor according to claim 3, wherein said storage means sets a reference value in a non-linear manner with respect to a change in a position signal or an adjustment signal. 7. Light emitting means for emitting light, light receiving means for receiving light from an object, converting the light into an electric signal, and amplifying the electric signal;
And a determination unit that determines the presence or absence of the object by comparing an electric signal supplied from the light receiving unit with a reference value, and adjusts the sensitivity in the following steps using a photoelectric sensor. Sensor sensitivity adjustment method. Step 1: Adjust the gain of the light receiving means. Step 2: A / D convert the position signal and read a digital value. Step 3: Read a reference value and a hysteresis width corresponding to the digital value. Step 4: Set a reference value and a hysteresis width. Step 5: The electric signal amplified by the adjusted gain and A / D converted is compared with the set reference value and hysteresis width. Step 6: The presence or absence of the object is determined based on the comparison result. 8. Light emitting means for emitting light, light receiving means for receiving light from an object, converting the light into an electric signal, and amplifying the electric signal;
And a determination unit that determines the presence or absence of the object by comparing an electric signal supplied from the light receiving unit with a reference value, and adjusts the sensitivity in the following steps using a photoelectric sensor. Sensor sensitivity adjustment method. Step 1: Adjust the light intensity of the light projecting means. Step 2: Convert the adjustment signal A / D and read the digital value. Step 3: Read a reference value and a hysteresis width corresponding to the digital value. Step 4: Set a reference value and a hysteresis width. Step 5: A comparison operation is performed between the received, amplified, A / D converted electric signal, the set reference value, and the hysteresis width. Step 6: The presence or absence of the object is determined based on the comparison result.