JPH07229735A - Active range finder - Google Patents

Abstract

PURPOSE:To prevent the deterioration of range finding precision by preventing noise from being generated in a boosting circuit during the range finding. CONSTITUTION:A boosting circuit consisting of a switching regulator of chopper type or the like boosts the voltage of a battery 1 and supplies it to each part. A range finding circuit 4 starts the storage of the current value of a photoelectric transfer element 7 by the incident light from an object before emission of an infrared light emitting element 5 by the control signal (a) from a timing control circuit 9, and when the infrared light is emitted by the control signal (c), the difference between the stored value and the current value of the photoelectric transfer element 7 by the incident light including the reflected light from the object when the infrared light is emitted is obtained, and the distance to the object is measured based on the difference. The timing control circuit 9 stops the boosting of the boosting circuit 2 before the infrared light is emitted by the control signal (b), and re-starts the boosting rapidly after the emission is completed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active distance measuring device for measuring a distance to an object by emitting infrared light toward the object and receiving infrared light reflected from the object.

[0002]

2. Description of the Related Art Generally, an active distance measuring device used for an autofocus device of a compact camera stores a photoelectric conversion element current value due to incident light from a subject before infrared light emission, and stores this stored value and a red value. A distance measuring circuit for measuring the distance to the subject based on the difference between the photoelectric conversion element current value due to the incident light from the subject including the reflected light from the subject when the external light is emitted. In addition, as a method of the distance measuring circuit itself, a PSD is used as a light receiving element, and two outputs of the PSD are amplified and processed by separate amplifying circuits, so that the distance is calculated by the so-called triangulation principle. There are a distance measurement method and an amplitude method in which the output of the SPD is amplified and processed by a single amplification circuit by using the SPD as a light receiving element to discriminate the magnitude of the reflected light amount to calculate the distance.

By the way, an infrared light emitting diode is mainly used as a light emitting element for obtaining infrared light, and a reflected light having a light quantity necessary for distance measurement is returned even to a distant object. A large current of about 0.5 to 1 A is applied to the light emitting element. In addition, since the infrared light emitting element has a relatively high forward voltage, when the battery voltage drops as the battery runs down, not only can the infrared light emitting element not be driven sufficiently, but other circuits of the distance measuring device operate. It may not be possible to supply enough voltage to operate.

Therefore, conventionally, the voltage of the battery is boosted by a booster circuit and supplied to each part of the device. As a booster circuit, there is a type that stores boosting energy in a capacitor like a cockloft circuit, but generally, a type that uses a transformer or an inductor to make an alternating current by an oscillation circuit and boosts the voltage is used. In particular, recently, a chopper type switching regulator in the form of an IC, which requires few external parts, has been widely used.

[0005]

However, the conventional active distance measuring device using such a booster circuit has the following problems.

Since the booster circuit is apt to generate noise, in a device such as an active distance measuring device that handles a very weak signal, the noise deteriorates the distance measuring accuracy.

In the configuration in which the boosted voltage of the booster circuit is directly supplied to the distance measuring circuit, a stable voltage cannot be supplied to the distance measuring circuit, which causes a distance measuring error.

Even if a stabilized power supply circuit is used after the booster circuit to supply a stable voltage to the distance measuring circuit,
Generally, a booster circuit needs a reference voltage for determining a boosted voltage, and a stabilized power supply circuit also needs a reference voltage. Therefore, the circuit configuration becomes complicated to generate these separate reference voltages.

Even if the reference voltage generating circuit is simplified by using the output of the stabilizing power supply circuit as the reference voltage of the boosting circuit, the output of the boosting circuit must naturally be higher than the output of the stabilizing power supply circuit. Therefore, it is necessary to have a configuration in which the output of the booster circuit is detected by resistance division.
In such a configuration, a circuit for turning this resistor on and off is necessary in order to avoid an output leakage current during standby, which complicates the circuit configuration.

[0010]

The present invention adopts the following construction in order to solve the above-mentioned problems.

For the purpose of preventing the adverse effect on the ranging accuracy due to the noise generated in the booster circuit, the booster operation of the booster circuit is stopped before the emission of infrared light and the booster operation of the booster circuit is promptly performed after the end of the light emission. And a timing control circuit for supplying a control signal for restarting to the booster circuit.

Further, for the purpose of shortening the boost stop time as much as possible to maximize the number of times of light emission and distance measurement per unit time, a chopper type switching regulator is used for the boost circuit and the timing control circuit is , The boosting operation is stopped by stopping the operation clock of the booster circuit immediately before the emission of the infrared light by the forced signal, and the operation clock of the booster circuit is restarted at the same time when the emission is stopped to start the boosting operation. There is.

For the purpose of supplying a stable voltage to the distance measuring circuit, a stabilizing power supply circuit is provided, and the output of the booster circuit is supplied to the distance measuring circuit via the stabilizing power supply circuit. ing.

The output voltage of the stabilized power supply circuit is used as the reference voltage of the booster circuit for the purpose of eliminating the waste of separately preparing the reference voltage.

For the purpose of enabling the booster circuit to operate with the output of the stabilized power supply circuit as a reference voltage and a voltage higher than this reference voltage as a target value, the emitter is connected to the output of the booster circuit in the booster circuit. A first PNP transistor, a second PNP transistor whose emitter is connected to the output of the stabilized power supply circuit, and a first and a second PNP transistor.
A first and a second PNP transistor including means for generating a voltage difference between the bases of the NP transistors and a bias circuit for setting the sum of collector currents of the first and second PNP transistors to be a predetermined value. One of the collector currents of the other is inverted by a current mirror circuit or a constant current is connected to one collector, and a signal for controlling driving or stopping of the booster circuit is obtained from this connection point.

The means for generating a voltage difference between the bases of the first and second PNP transistors is a resistor connected in parallel between the base and emitter of one of the first and second PNP transistors. And at least one of the current sources applied to its base, and a resistor connected between the bases of the first and second transistors.

Further, for the purpose of preventing the adverse effect on the distance measuring circuit due to the sharing of the power source between the infrared light emitting element drive circuit and the oscillation circuit and the distance measuring circuit, the driving of the oscillator circuit and the infrared light emitting element. At least one of the circuits is directly driven by the output of the booster circuit without passing through the stabilized power supply circuit.

Further, for the purpose of preventing a voltage from extremely lowering when the boosting is stopped and becoming less than an allowable value of other circuits due to a large current flowing through the infrared light emitting element, a chopper type boosting circuit. Which has two capacitors respectively connected through a diode from a terminal of the inductor which is not connected to the battery, and is an output obtained by comparing the minimum value of the voltages of the two capacitors with a reference voltage, Alternatively, a booster circuit that controls a boosting operation by the logical sum of outputs obtained by comparing respective voltages with a reference voltage is provided, and a current is supplied from one of the two capacitors to the distance measuring circuit,
From the other side, a current is supplied to the drive circuit of the infrared light emitting element.

[0019]

In the active distance measuring apparatus of the present invention, the timing control circuit stops the boosting operation of the booster circuit before the emission of infrared light by the control signal to suppress the generation of noise, and promptly after the emission of light. Control is performed to restart the boosting operation of the booster circuit. Here, since the booster circuit generally has a capacitor at its output, even if the boosting operation is stopped, the current can be continuously supplied by the charge accumulated in the capacitor for a short time after that. By appropriately setting the capacitance of the capacitor in consideration of the current consumption until the next restart of the boosting operation, the voltage of the capacitor immediately before restarting the boosting can be kept above the minimum operable voltage of the distance measuring circuit. Therefore, the distance measuring circuit continues to operate even while the boosting operation of the boosting circuit is stopped, and includes the storage of the photoelectric conversion element current value by ambient light and this stored value and the reflected light from the subject at the time of emitting infrared light. Processing such as obtaining a difference from the photoelectric conversion element current value due to incident light from the subject can be performed under the condition that noise is not generated.

When the input voltage of the distance measuring circuit is applied to the input terminal of the distance measuring circuit with reference to the ground, the voltage between the input terminal and the positive power supply terminal of the distance measuring circuit decreases as the voltage of the capacitor decreases. If there is a parasitic capacitance (between the input terminal and the negative power supply terminal of the distance measuring circuit when the input reference voltage is applied to the positive power supply as a reference), there is a small Also, a current flows, which is superposed on the original photoelectric conversion element current due to the reflected light from the subject at the time of infrared light emission, which causes deterioration in accuracy. However,
The step-up circuit stops the step-up operation before emitting infrared light, and the voltage drop of the capacitor starts from that point.Therefore, at least the final stage of storing the photoelectric conversion element current value by the stationary light, the current flowing through the parasitic capacitance Since the current is added to the original current due to the stationary light, the current due to the parasitic capacitance is canceled out in the end, and the error is not given to the measurement.

However, in the actual circuit, since the current used is difficult to be completely constant, there is a difference in the voltage reduction rate between before the infrared light is emitted and during the infrared light emission. There may be an error of. Therefore, in the present invention, the stabilized power supply circuit is inserted between the booster circuit and the distance measuring circuit. In this way, even if the output voltage of the booster circuit drops, if the voltage difference between the input and output of the stabilized power supply circuit is within the allowable value, the output of the stabilized power supply circuit does not change, so good characteristics can be obtained. Become. In this case, noise is filtered by the stabilized power supply circuit, so it seems that it is not necessary to stop the booster circuit to prevent noise.
Since noise has an adverse effect by being electrostatically coupled to the input terminal through the stray capacitance without depending on the line, it is necessary to stop boosting to suppress the generation of noise itself.

Further, since the driving circuit of the infrared light emitting element consumes a relatively large current, if it is connected to the output of the stabilized power supply circuit together with the distance measuring circuit that amplifies a minute current, the distance measuring circuit is connected. There is a high possibility that it will give noise to. Further, since the oscillator circuit also generates noise due to its nature, sharing the power supply with the distance measuring circuit is likely to cause bad results as well. Therefore, by directly connecting these circuits to the output of the booster circuit and supplying power to the distance measuring circuit via the stabilized power supply circuit, interference from these circuits can be avoided.

Further, the ambient light is stored in the distance measuring circuit before the infrared light is emitted. However, the influence of noise has a great influence on the final stage of the storage. It is sufficient if the noise is stopped, but it actually takes time to stabilize due to problems such as the time constant of the circuit, so it is necessary to stop the boosting, for example, about 120 μs before light emission. , And the emission time of infrared light is 120
Focusing on the fact that the distance measuring circuit has completed the operation susceptible to noise (detection of the current value only by the reflected light of infrared light, etc.) during the time of about μs, The chopper type switching regulator is used for the step-up circuit in order to shorten the stop period and increase the number of times of light emission and distance measurement per unit time. The boosting operation is stopped by stopping the operation clock of the boosting circuit immediately before the light emission, and the operation clock of the boosting circuit is restarted at the same time when the light emission is stopped to start the boosting operation.

[0024]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the active distance measuring apparatus of the present invention. In the figure, reference numeral 1 is a battery, the terminal voltage of which is constantly applied to the booster circuit 2.
The booster circuit 2 is a circuit for boosting the voltage of the battery 1. The booster circuit 2 is provided with a capacitor C1 at the output end as will be described later. The terminal voltage of the capacitor C1 is taken out to the outside via the switch 10 as a boosted voltage, and is supplied to each part of the device. Supplied. here,
The switch 10 is a switch that is turned on in conjunction with the operation of the shutter button when the present invention is applied to an active autofocus camera.

Boosting circuit 2 taken out from the switch 10
Is directly supplied to a switching transistor 6 which constitutes a driving circuit of an infrared light emitting element 5 such as an infrared light emitting diode and an oscillation circuit 8, a timing control circuit 9, and via a stabilizing power supply circuit 3. It is supplied to the distance measuring circuit 4.

The stabilized power supply circuit 3 is a circuit that generates a stable reference voltage (its voltage value is Vs) from the boosted voltage of the booster circuit 2. In this embodiment, the stabilized power supply circuit 3
However, it is also possible to omit it and supply the output voltage of the booster circuit 2 directly to the distance measuring circuit 4. Further, in the present embodiment, the oscillation circuit 8 and the switching transistor 6 are directly driven by the boosted voltage of the booster circuit 10. However, either one or both of them are stabilized by the stabilized power supply circuit 3.
Alternatively, the output may be driven.

The distance measuring circuit 4 is connected to a photoelectric conversion element 7 such as PSD or SPD, and stores the current value of the photoelectric conversion element 7 due to incident light from the subject before infrared light emission by the infrared light emitting element 5. Then, the distance to the subject is measured based on the difference between the stored value and the current value of the photoelectric conversion element 7 due to the incident light from the subject including the reflected light from the subject at the time of infrared light emission.

The oscillation circuit 8 is a circuit for generating a clock P of, for example, 32 KHz required by the booster circuit 2 and the timing control circuit 9. The timing control circuit 9 controls the timing by using the clock P as a reference clock, and various parts of the apparatus. Is a circuit for supplying control signals a, b, and c to. Here, the control signal a is a control signal for causing the distance measuring circuit 4 to store ambient light before emitting infrared light, and the control signal b is a control signal and a control signal for forcibly stopping the operation of the booster circuit 2. Reference numeral c is a signal for controlling light emission of the infrared light emitting element 5 and storage of reflected light at the time of emitting infrared light in the distance measuring circuit 4.

FIG. 2 is an operation timing chart of the embodiment of FIG. 1, and the overall operation of this embodiment will be described below with reference to FIGS. 1 and 2.

When the switch 10 is off, no power is supplied from the booster circuit 2, so the oscillator circuit 8, the timing control circuit 9, the stabilizing power supply circuit 3 and the distance measuring circuit 4 are inoperative. Further, since the voltage of the battery 1 is constantly applied to the booster circuit 2, the capacitor C at the output end is
1 holds a voltage Va slightly lower than the voltage of the battery 1.

When the switch 10 is turned on in this state,
The voltage Va of the capacitor C1 is applied to the oscillation circuit 8, the timing control circuit 9, and the stabilized power supply circuit 3.

The oscillation circuit 8 starts its operation by the applied voltage Va, generates a clock P having a frequency of 32 KHz, and applies it to the timing control circuit 9 and the booster circuit 2.

The timing control circuit 9 initializes the internal state when the voltage Va is applied, and the control signals a, b, c are sequentially applied at a predetermined timing based on the clock P applied subsequently.
To occur.

When the voltage Va is applied, the stabilized power supply circuit 3 starts the operation of generating the reference voltage Vs from the output voltage of the booster circuit 2 and starts applying the voltage Vs to the distance measuring circuit 4. Further, in the present embodiment, the output voltage of the stabilized power supply circuit 3 is used as the reference voltage required in the booster circuit 2 to control the boosted voltage of the booster circuit 2 to the predetermined value Vb (> Vs). The voltage Vs is also applied to the booster circuit 2.

The booster circuit 2 receives the clock P from the oscillator circuit 8.
Is started, the boosting operation is started. As a result, after the switch 10 is turned on, the voltage of the capacitor C1 rapidly rises from Va to Vb, and when it reaches Vb, the function inside the booster circuit 2 temporarily stops the boosting operation, and then the boosted voltage becomes Vb. Resuming and stopping the boosting operation are automatically repeated by the function inside the booster circuit 2 so that they become substantially equal.

Now, when the control signal a from the timing control circuit 9 becomes high level ("1"), the distance measuring circuit 4 becomes
The storage operation of the current value of the photoelectric conversion element 7 by the incident light from the subject before the infrared light emission is started, and this operation is controlled by the control signal a.
Continues for about 20 ms until goes low. Then, when the switching transistor 6 is driven by the control signal c that becomes high level at the timing when the control signal a becomes low level and the infrared light emitting element 5 emits light, the stored value and the infrared light stored immediately before the infrared light emission are stored. Photoelectric conversion element 7 by incident light from the subject including reflected light from the subject at the time of light emission
The difference between the current value and the current value is detected, and the distance to the subject is measured based on the detected value. The control signal c
The high level period of is about 120 μs, and the distance measuring circuit 4
Is the A / D conversion process (in the case of a double integration type A / D converter, in the case of a configuration in which the current value based only on the reflected light is stored during that period and the stored value is A / D converted) 1 integration) is completed.

As described above, since the distance measuring circuit 4 handles a very weak signal generated in the photoelectric conversion element 7, if the noise is generated from the booster circuit 2, the distance measuring accuracy is adversely affected. Become. Therefore, the timing control circuit 9 of the present embodiment stores the current value based only on the reflected light and the A / D conversion process (double integration) 120 μs before the distance measuring circuit 4 finishes the storage operation of the ambient photocurrent. Approximately 240 μs until the end of the first integration in the case of the A / D converter of the formula
By raising the control signal b to the high level only during the period of, the boosting operation of the boosting circuit 2 is stopped and the generation of noise is suppressed.

When the boosting operation of the booster circuit 2 is stopped, the voltage of the capacitor C1 decreases from Vb,
It is designed so that it does not fall below the reference voltage Vs of the stabilized power supply circuit 3 and the output of the stabilized power supply circuit 3 maintains Vs even when the boosting operation is stopped. Further, when the control signal c becomes low level, the booster circuit 2 immediately restarts the boosting operation, that is, in the chopper type booster circuit 2, the transistor Q1 in FIG. 3 is turned on in synchronization with the fall of the signal c. Since the boosting operation is restarted at, the voltage of the capacitor C1 quickly rises to Vb.

FIG. 3 shows a booster circuit 2 and a stabilizing power supply circuit 3.
A configuration example of is shown. In addition, in FIG. 3, the switch 1 in FIG.
0, the infrared light emitting element 5, and the switching transistor 6 are not shown.

The booster circuit 2 shown in FIG. 3 is a chopper type switching regulator, and includes an NPN transistor Q.
1, Q6, Q7, PNP transistors Q2 to Q5, choke coil L, diode D1, capacitor C1, resistor R1, constant current sources I1 and I2, and gate circuit G1. Here, the transistors Q2 to Q7 and the resistor R
1, a part composed of constant current sources I1 and I2 (actuator circuit having an emitter as an input and a voltage difference at the base) is a choke coil L, an NPN transistor Q1, and a diode D.
1 and a capacitor C1 form a comparison circuit of a voltage boosted by a portion and a voltage Vb determined by using a reference voltage Vs supplied from the stabilized power supply circuit 3, and the boosted voltage is a voltage Vb. When it is lower, a high level signal is taken out from the collector of the transistor Q7, and otherwise a low level signal is taken out from the collector of the transistor Q7 and applied to one input of the gate G1. The clock G from the oscillation circuit 8 is also supplied to the gate G1.
And the control signal b from the timing control circuit 9 is applied to the input, and the clock P is applied to the base of the transistor Q1 only when the collector of the transistor Q7 is at the high level and the control signal b is at the low level. It has become.

The stabilized power supply circuit 3 is a series regulator composed of a PNP transistor Q8, an operational amplifier OP1, resistors R2 to R4, a Zener diode ZD1 and a capacitor C2, and its output is supplied to the distance measuring circuit 4 as a driving voltage. Is also supplied to the booster circuit 2 as the reference voltage Vs. Although a circuit in which the reference voltage is generated by the Zener diode ZD1 is illustrated here, a bandgap type stabilized power supply generally used in an IC circuit may be used.

In the booster circuit 2 shown in FIG. 3, the capacitor C1 is constantly charged by the voltage of the battery 1 through the choke coil L and the diode D1 and maintains the voltage Va. In this state, when the switch 10 of FIG. 1 is turned on and the clock P is generated from the oscillation circuit 8 as described above, the clock is applied to the base of the transistor Q1 via the gate G1. As a result, the transistor Q1 is turned on, and the current of the battery 1 flows through the choke coil L and the transistor Q1. In this embodiment, since the frequency of the clock P is 32 KHz, the time during which the transistor Q1 is on is about 16 μs, and the current flowing through the choke coil L at the end of this time changes the voltage of the battery 1 to 3
V and the inductance value of the choke coil L is 100
If it is μH, it will be 3 × 16/100 to about 0.5 A.

After that, the transistor Q1 is turned off during the half cycle of the clock P. At this time, however, the current tends to flow as it is due to the characteristic of the choke coil L, so this current flows into the capacitor C1 via the diode D1. . Therefore, the voltage of the capacitor C1 increases, while the current of the choke coil L decreases.

By repeating the above-described operation for each cycle of the clock P, the voltage of the capacitor C1 rises rapidly, and when the preset voltage Vb is exceeded, the collector of the transistor Q7 becomes low level. Therefore, the gate G1 is closed, the base of the transistor Q1 is always at the low level, and the boosting is stopped.

After that, the electric charge accumulated in the capacitor C1 is consumed by the oscillation circuit 8, the timing control circuit 9, the stabilizing power supply circuit 3, and the distance measuring circuit 4 which functions by the output voltage Vs of the stabilizing power supply circuit 3. Allows capacitor C1
When the voltage of V1 drops below the set voltage Vb, the collector of the transistor Q7 becomes high level, so that the gate G1 opens, the transistor Q1 repeats ON / OFF operation by the clock P, and the voltage of the capacitor C1 returns again. Boosted.

When the control signal b from the timing control circuit 9 becomes high level, the gate G1 is closed.
The clock P is no longer applied to the base of the transistor Q1, and the booster circuit 2 is forcibly stopped. Then, when the control signal b becomes low level, the collector of the transistor Q7 is at high level at that time, so that the gate G1 opens immediately and the clock P becomes the transistor Q1.
Is applied to the base of and the boosting operation is restarted.

Next, in the booster circuit 2, the boosted voltage is the voltage V.
The details of the part that determines whether the value is higher than b will be described.

In FIG. 3, a current source I1 is a current source for providing a difference between the base voltages of the input transistor Q1 and the transistor Q5. When the base current is ignored, this current all flows to the resistor R1. A voltage of R1 × I1 is generated. Since this voltage becomes the difference between the set voltage Vb and the reference voltage Vs supplied from the stabilized power supply circuit 3,
For example, when the reference voltage Vs is set to 3.2 V and the set voltage Vb is set to 3.7 V, I1 may be 10 μA and R1 may be 50 KΩ.

The current source I2 is used to set the bias of the circuit. For example, the transistor Q2 and the transistor Q2.
When the bias is set so that the sum of the collector currents of 5 is 10 μA, I2 is set to 20 μA. This is because I2 and I1 and transistors Q3 and Q are ignored if the base current is ignored.
4 is the sum of the collector currents of the transistors Q3 and Q4
This is because the collector current of is equal to the collector current of the transistors Q2 and Q5, respectively.

In the above setting, the base voltage of the transistor Q2 is higher than the base voltage of the transistor Q5 by 0.5V. Therefore, when the emitter voltage of the transistor Q2 is higher than the emitter voltage of the transistor Q5 by 0.5V, the transistor Q2 has a higher voltage. The collector current is equal to the collector current of the transistor Q5 and 5 μA each flows. When the voltage of the transistor Q2 is higher than the voltage in this case, the collector current of the transistor Q2 becomes larger than the collector current of the transistor Q5, the collector voltage of the transistor Q7 becomes low level, and when it is low, it becomes high level.
At this time, if the current source I1 has a temperature characteristic similar to the temperature characteristic of the resistor R1, the temperature characteristic of the resistor is canceled and the voltage difference of 0.5V can be set with respect to the reference voltage Vs regardless of the temperature. .

If the difference voltage may have a negative temperature characteristic, a resistor R5 may be inserted between the base and emitter of the transistor Q2 instead of the current source I1 to simplify the circuit, as shown in FIG. You can

Further, since it is a current source having a temperature characteristic proportional to absolute temperature that is easy to make in the IC, as shown in FIG. 5, the current source I4 having such a temperature characteristic and the base-emitter of the transistor Q2 are connected. The positive and negative temperature characteristics may be canceled by combining the currents from the resistor R5 connected to the resistor R5 to set a voltage having no temperature coefficient.

FIG. 6 shows the transistor Q6 in FIG.
An example of a booster circuit using a current source I3 (for example, 5 μA) instead of the current mirror circuit of Q7 will be shown. Also in this case, as in the circuit of FIG. 3, when the emitter voltage of the transistor Q3 is higher than the emitter voltage of the transistor Q5 by 0.5 V, the current source and the collector current of the transistor Q5 match, and when the emitter voltage of the transistor Q2 is higher than that. Since the collector current of the transistor Q5 becomes small, the collector voltage becomes low level as in the previous circuit, and becomes low level when it is low. According to this circuit, characteristics such as gain are inferior, but the circuit can be further simplified.

FIG. 7 is a circuit diagram of the main part of the distance measuring circuit 4, which is turned on / off by a control signal a from the operational amplifiers OP2, OP3, NPN transistor Q9, resistors R6 to R8, capacitors C3, C4, and timing control circuit 9. It includes a controlled switch SW1, a switch SW2 that is turned on / off by a control signal c, and a reference voltage.

In the distance measuring circuit 4 of FIG. 7, when the control signal a from the timing control circuit 9 becomes high level, the switch SW1 is turned on. Thereby, the photoelectric conversion element 7
The current flowing out from the operational amplifier OP2 is input to and converted into a voltage, the voltage generated from the operational amplifier OP3 charges the capacitor C4 functioning as a memory element according to the voltage value, and the current value corresponding to the charging voltage. Only the transistor Q9 transfers the current of the photoelectric conversion element 7 to the resistor R.
By flowing to the ground through 6, the operational amplifier OP
Feedback that cancels the voltage due to the stationary light is applied from the output voltage value of 2, and the voltage corresponding to the ambient photocurrent starts to be accumulated in the capacitor C4.

Then, when the control signal a changes from the high level to the low level, the switch SW1 changes from the on state to the off state, and the charging of the capacitor C4 is interrupted.
A voltage corresponding to the ambient photocurrent immediately before the infrared light emission is stored in the capacitor C4, and thereafter, the current value according to the stored voltage is subtracted from the input current.

Therefore, the control signal a falls from the high level to the low level, and at the same time, the control signal c rises from the low level to the high level, and the infrared light emitting element 5 is driven as described above. When the current flowing out from the photoelectric conversion element 7 increases by that amount, the output voltage of the operational amplifier OP2 becomes a voltage corresponding to the photoelectric conversion element current value of only reflected light of infrared light, and this voltage causes the control signal a to have a high level. Then, it is sampled by the switch SW2 which is turned on, and held in the hold circuit composed of the resistor R8 and the capacitor C3. Thereafter, the held voltage is A / D converted by, for example, an A / D converter (not shown) of a double integration type, and the distance to the subject is measured based on the result.

The distance measuring circuit of FIG. 7 is of the amplitude type. In the distance measuring circuit of the triangulation type, PSD is used as the photoelectric conversion element 7, and the PSD of 2 is used.
A circuit as shown in FIG. 7 is provided for each of the two outputs.

FIG. 8 is a circuit diagram of the essential parts of another embodiment of this embodiment. If there is only one boosting capacitor C1 as in the boosting circuit 2 illustrated in FIG. 3, an infrared light emitting element that consumes a large current, such as IRED, can be used as the capacitor C1.
When driven by the voltage of 3, the voltage may drastically drop when boosting is stopped and fall below the allowable value of other circuits such as the distance measuring circuit 4.

The embodiment of FIG. 8 solves such a problem, and two capacitors connected from terminals of the choke coil L not connected to the battery 1 via diodes D1 and D1 ', respectively. C1 and C1 'are provided, and the gate G2 takes the logical sum of the outputs of the respective voltages of the two capacitors C1 and C1' compared with the voltage Vb based on the reference voltage Vs supplied from the stabilized power supply circuit 3. , Using a chopper type booster circuit 2'which controls the boosting operation by applying the output of the gate G2 to the gate G1, from one capacitor C1 to the distance measuring circuit 4, the stabilizing power supply circuit 3, the oscillation circuit 8 and the timing. An electric current is supplied to the control circuit 9, and the infrared emitting element 5 is supplied from the other capacitor C1 '.
In this configuration, a current is supplied to the switching transistor 6 which constitutes the drive circuit of FIG. Note that, in FIG. 8, the same reference numerals as those in the other figures indicate the same parts, and Q2 ′ to Q2
7'is a transistor, R1 'is a resistor, I1' and I2 'are constant current sources, and these are another comparison for comparing the voltage of the capacitor C1' with the voltage Vb determined using the reference voltage Vs. It constitutes the circuit.

In the embodiment of FIG. 8, capacitors C1,
When the voltage of either one of C1 'decreases, the level of one of the collectors of the transistors Q7 and Q7' becomes high level, the output of the gate G2 becomes high level, and the boosting operation is restarted. When the boost operation is started,
When there is an imbalance between the voltages of the capacitors C1 and C1 ′, initially the current flows only to the lower voltage side, and when they become equal, the voltage of both capacitors C1 and C1 ′ is boosted to the voltage Vb.

In the embodiment of FIG. 8, the choke coil L and the transistor Q1 in the booster circuit 2'are connected to both capacitors C1 and C1.
Since it is shared by C1 ′, the configuration is simpler than the configuration having two complete booster circuits, which is suitable for commercial production. A configuration in which the boost control is performed by detecting the voltage of one of the capacitors C1 and C1 'is also conceivable. In that case, however, a large current flows from the capacitor that has not detected the voltage, and Even if the voltage of the capacitor drops drastically, boosting may not be restarted unless the voltage of the capacitor on the detecting side has dropped so much.
On the other hand, in this example, since the voltages of both capacitors C1 and C1 ′ are detected and controlled respectively, if the voltage of either one of the capacitors decreases, boosting will be restarted, and both capacitors will It is possible to perform boosting control so as to maintain Va.

In the example of FIG. 8, the capacitors C1 and C
The boost operation is controlled by the logical sum of the outputs obtained by comparing the respective voltages of 1'with the reference voltage.
The boosting operation may be controlled by the output obtained by comparing the minimum value of the voltage of C1 ′ with the reference voltage. Further, the switch 10 is provided only on the capacitor C1 side,
A similar switch may be provided on the 1'side.

[0065]

According to the active distance measuring apparatus of the present invention described above, the following effects can be obtained.

According to the structure described in claim 1, in the active distance measuring device using the booster circuit, it is possible to prevent the distance measuring accuracy from deteriorating due to noise from the booster circuit. According to the configuration of claim 2, since the operation stop period of the booster circuit can be minimized, it is possible to increase the number of times of light emission and distance measurement per unit time. According to the configuration of claim 3, a stable voltage can be supplied to the distance measuring circuit regardless of whether the booster circuit is operating or stopped. According to the configuration of claim 4, it is not necessary to make the reference voltage of the booster circuit separately from the reference voltage of the stabilized power supply circuit, and the circuit configuration can be simplified. According to the configuration of claim 5, the boosting operation can be controlled by detecting the voltage higher than the reference voltage by the boosting circuit without using the configuration by the resistance division. According to the configuration of claim 7, it is possible to prevent interference from the drive circuit or the oscillation circuit of the infrared light emitting element to the distance measuring circuit. According to the configuration of claim 8,
It is possible to prevent the voltage of other circuits such as the distance measuring circuit from falling below the allowable value due to a large current flowing through the infrared light emitting element when the boosting is stopped and the voltage of other circuits falling below an allowable value. it can.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is an operation timing chart of the embodiment.

FIG. 3 is a circuit diagram showing a configuration example of a booster circuit and a stabilized power supply circuit.

FIG. 4 is a circuit diagram showing a main part of another configuration example of the booster circuit.

FIG. 5 is a circuit diagram showing a main part of still another configuration example of the booster circuit.

FIG. 6 is a circuit diagram showing a main part of still another configuration example of the booster circuit.

FIG. 7 is a circuit diagram showing a configuration example of a distance measuring circuit.

FIG. 8 is a circuit diagram of a main part of another embodiment of the present invention.

[Explanation of symbols]

 1 ... Battery 2 ... Boosting circuit 3 ... Stabilized power supply circuit 4 ... Distance measuring circuit 5 ... Infrared light emitting element 6 ... Switching transistor 7 ... Photoelectric conversion element 8 ... Oscillation circuit 9 ... Timing control circuit 10 ... Switch

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical indication G03B 13/36

Claims (8)

[Claims] 1. A photoelectric conversion element current value due to incident light from a subject before infrared light emission is stored, and photoelectric conversion is performed with incident light from the subject including the stored value and reflected light from the subject at the time of infrared light emission. A distance measuring circuit that measures the distance to the subject based on the difference from the conversion element current value, a driving circuit of the infrared light emitting element that boosts the voltage of the battery, and a boosting circuit that supplies the voltage to the distance measuring circuit. In the active distance measuring device, a timing control circuit that supplies a control signal to the booster circuit to stop the booster operation of the booster circuit before the emission of the infrared light and to restart the booster operation of the booster circuit immediately after the end of light emission. An active distance measuring device comprising: 2. A chopper type switching regulator is used for the booster circuit, and the timing control circuit stops the boosting operation by stopping the operation clock of the booster circuit immediately before the emission of infrared light by the control signal. 2. The active distance measuring apparatus according to claim 1, wherein the boosting operation is started by restarting the operation clock of the boosting circuit at the same time as the light emission is stopped. 3. The active distance measuring device according to claim 1, further comprising a stabilizing power supply circuit, wherein the output of the booster circuit is supplied to the distance measuring circuit via the stabilizing power supply circuit. apparatus. 4. The active distance measuring device according to claim 3, wherein the output voltage of the stabilized power supply circuit is used as a reference voltage of the booster circuit. 5. The booster circuit includes a first PNP transistor whose emitter is connected to the output of the booster circuit and a second PN transistor whose emitter is connected to the output of the stabilized power supply circuit.
A P-transistor and means for producing a voltage difference between the bases of the first and second PNP transistors;
And a bias circuit for setting the sum of the collector currents of the second PNP transistors to be a predetermined value. One collector of the first and second PNP transistors is supplied to the other collector current of the other by a current mirror circuit. 5. The active distance measuring apparatus according to claim 4, wherein an inverted signal or a constant current is connected and a signal for controlling driving or stopping of the chopper type booster circuit is obtained from this connection point. 6. The means for generating a voltage difference between the bases is a resistor connected in parallel between the base and emitter of one of the first and second PNP transistors, and a current applied to the base. The active range finder according to claim 5, wherein the active range finder is constituted by a resistor connected between at least one of the sources and the bases of the first and second transistors. 7. A configuration in which at least one of an oscillation circuit for supplying an operation clock to the booster circuit and a drive circuit for the infrared light emitting element is directly driven by the output of the booster circuit without passing through the stabilized power supply circuit. The active distance measuring device according to claim 3, wherein 8. A chopper type booster circuit, comprising two capacitors respectively connected from a terminal of an inductor not connected to the battery via a diode, and a minimum value of voltage of the two capacitors. Is provided with a reference voltage or an OR of outputs obtained by comparing respective voltages with a reference voltage, and a booster circuit is provided to control a boosting operation, and a current is supplied from one of the two capacitors to the distance measuring circuit. The active distance measuring apparatus according to claim 1, wherein the other is configured to supply a current to the drive circuit of the infrared light emitting element.