JP3382734B2 - Distance measuring device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring device, and more particularly to a distance measuring device having an integrating capacitor.

[0002]

2. Description of the Related Art Conventionally, in an integrating type distance measuring device,
As the / D converter, a double integration type A / D converter is often used.

When an inexpensive capacitor having a large dielectric absorption such as a high dielectric constant is used as the capacitor used in the double integration type A / D converter, there are problems as described below. A small and expensive film capacitor is used.

An equivalent circuit of the high dielectric constant capacitor is shown in FIG.
As shown in, to be in parallel with the capacitor C10,
The circuit includes a dielectric absorption resistor R10 and a capacitor C11.

For this reason, such a high dielectric constant capacitor is charged with a voltage V0 as shown in FIG. 14, and once the switch S is closed and then opened, as shown in FIG. Voltage may remain due to absorption.

Since the high dielectric constant capacitor has such a property, when used in an A / D converter of a distance measuring device,
A deviation amount occurs in the integrated output, which causes an error in the distance measurement data.

As one of means for solving this difficulty,
Japanese Unexamined Patent Publication No. 6-42955 discloses a device in which a predetermined voltage is applied to a high dielectric constant capacitor and a distance measurement operation is started after waiting for a time for stabilization of dielectric polarization (absorption).

[0008]

However, in the one disclosed in Japanese Patent Laid-Open No. 6-42955, the time until the dielectric polarization stabilizes after a predetermined voltage is applied to the high dielectric constant capacitor (in the publication, Is described as 400 ms or more.) However, this will increase the time required for distance measurement. This causes a release time lag to increase, which in turn results in missing a camera shutter opportunity.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an inexpensive distance measuring device capable of suppressing a distance measuring error without increasing the distance measuring time.

[0010]

In order to achieve the above object, a distance measuring device according to the present invention includes a light projecting means for projecting light onto an object and a light reflected from the object. A light receiving unit that outputs a photoelectric conversion signal, a distance calculating unit that calculates a distance to the object based on the photoelectric conversion signal and outputs a distance signal, an integrating capacitor that stores the distance signal, and an integrating capacitor of the integrating capacitor. The dielectric absorption amount detecting means for detecting the dielectric absorption amount and the converting means for converting the distance signal accumulated in the integrating capacitor into a digital signal are provided, and the output of the dielectric absorbing amount detecting means and the integrating capacitor are accumulated. The distance to the object is determined based on the distance signal thus generated.

Further, the distance measuring device according to the present invention comprises a light projecting means for projecting light onto an object, a light receiving means for receiving reflected light from the object and outputting a photoelectric conversion signal, and the photoelectric conversion. A distance calculating means for calculating a distance to the object based on a signal and outputting a distance signal, an integrating capacitor for accumulating the distance signal, and a dielectric absorption amount detecting means for detecting a dielectric absorption amount of the integrating capacitor, The distance signal accumulated in the integrating capacitor is converted into a digital signal, and the converting means performs digital conversion based on the output of the dielectric absorption amount detecting means.

[0012]

In the distance measuring device according to the present invention, the light projecting means projects light to the object, the light receiving means receives the reflected light from the object and outputs a photoelectric conversion signal, and the distance calculating means The distance to the object is calculated based on the photoelectric conversion signal and a distance signal is output, the integrating capacitor accumulates the distance signal, and the dielectric absorption amount detecting means detects the dielectric absorption amount of the integrating capacitor and converts the distance. Means converts the distance signal accumulated in the integrating capacitor into a digital signal, and the distance measuring device determines the distance to the object based on the output of the dielectric absorption amount detecting means and the distance signal accumulated in the integrating capacitor. Determine the distance.

Further, in the distance measuring device according to the present invention, the light projecting means projects light onto the object, the light receiving means receives the reflected light from the object and outputs a photoelectric conversion signal to calculate the distance. The means calculates the distance to the object based on the photoelectric conversion signal and outputs a distance signal, the integrating capacitor stores the distance signal, and the dielectric absorption amount detecting means detects the dielectric absorption amount of the integrating capacitor. The converting means converts the distance signal accumulated in the integrating capacitor into a digital signal based on the output of the dielectric absorption amount detecting means.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 5 show a first embodiment of the present invention, and FIG. 1 is a block diagram showing an outline of a distance measuring device.

This distance measuring apparatus has a light projecting element 10 as a light projecting means for projecting an optical pulse toward an object not shown.
A light projecting lens 11 for condensing the light projected from the light projecting element 10, a light projecting element drive circuit 9 for driving the light projecting element 10, and an object for distance measurement projected by the light projecting element 10. A light receiving element (referred to as PSD in the drawing) 2 as a light receiving means for receiving the light pulse reflected by the light pulse, and this light receiving element 2
Light receiving lens 1 for condensing light to the light source, photocurrent detection circuit units 3 and 4 for removing background photocurrent from the photocurrent output from the light receiving element 2, and outputs of the photocurrent detection circuit units 3 and 4. A distance calculation circuit unit 5 which is a distance calculation means for calculating information on the distance to the subject, and an integration capacitor 6 which accumulates the distance signal output from the distance calculation circuit unit 5,
A counting unit 7 which is a converting unit for converting the distance signal accumulated in the integrating capacitor 6 into a digital signal, and a digital signal from the counting unit 7 are received, and the light projecting element drive circuit 9 is driven to further provide each circuit unit. In order to detect the dielectric absorption amount by the CPU 8 as the control means for sending the control signal, the dielectric absorption amount detecting means 12 for detecting the dielectric absorption amount of the integrating capacitor 6 provided in the CPU 8, and the dielectric absorption amount detecting means 12. And a storage means 13 provided in the CPU 8 for storing a reference value used for the above.

Next, the circuit of the distance measuring device will be described in detail with reference to FIG. The light projecting means in this distance measuring device includes a light projecting element 10 and a transistor Tr11 for controlling ON / OFF of the light projecting element 10. The base of the transistor Tr11 is a terminal of the CPU 8 via a resistor R1. It is connected to T1.

That is, the CPU 8 outputs a pulse waveform signal to the terminal T1 to cause the transistor Tr11 to operate.
Is controlled to be turned on / off, and light is projected from the light projecting element 1 to the object to be measured via the light projecting lens 2.

The light reflected from the object to be measured is received by the light receiving lens 1.
The light is incident on the light receiving element 2 via and is output from the light receiving element 2 as a photocurrent. The photocurrent output from the light receiving element 2 is not only the signal photocurrent IN or IF, but also IN + IS1 or IF + IS2 containing the background photocurrent IS1 or IS2.

The photocurrents IN + IS1 and IF + IS2 containing the background photocurrents IS1 and IS2 are input to the photocurrent detection circuit unit 3 and the photocurrent detection circuit unit 4, respectively, and the background photocurrents IS1 and IS2 are removed. It is supposed to be.

The photocurrent detection circuit sections 3 and 4 include operational amplifiers OP1 and OP2, transistors Tr1 and Tr2, and
It is configured to have capacitors C1 and C2 and switches SW1 and SW2.

The switches SW1 and SW2 are the CPU 8
It is controlled by the output from the terminal T3.

That is, when the light is not projected, the CPU 8 outputs an ON signal to the terminal T3, and the switches SW1, S
W2 turns on. Thereby, the operational amplifiers OP1 and O
P2 becomes an active state, and negative feedback is applied by the operational amplifiers OP1 and OP2 so that the photocurrent due to the background light all flows through the transistors Tr1 and Tr2. At this time,
The capacitors C1 and C2 have a charge Is that corresponds to the background light.
1 and IS2 are stored respectively.

Immediately before the light is projected, the terminal T of the CPU 8 is
An off signal is output from 3 and switches SW1 and SW
2 is off. As a result, the operational amplifiers OP1 and OP
2 becomes non-active, and the transistors Tr1 and
The amount of current discharged from Tr2 is calculated by the capacitors C1 and C2.
It is determined by the retained charge of.

Here, the photocurrent IN + IS1 from the light receiving element 2
And IF + IS2 are input, the background photocurrents IS1 and IS2 are discharged from the transistors Tr1 and Tr2, respectively, and are reflected by the object to be measured I.
Only N and IF are detected.

The signal photocurrents IN and IF are input to the collectors of the transistors Tr3 and Tr6, respectively. Amplifiers Amp1 and Amp2 are connected to the bases of these transistors Tr3 and Tr6, respectively.

The transistors Tr3 and Tr5 and the transistors Tr6 and Tr8 form a current mirror circuit, and their collector currents are equal to the signal photocurrents IN and IF, respectively.

In the transistors Tr5 and Tr8, the collector current flows through the diodes D1 and D2, whereby the signal photocurrent is converted into a compression voltage.

The compressed voltage thus obtained is supplied to the bases of the transistors Tr9 and Tr10 of the distance calculation circuit section 5 via a buffer.

The transistors Tr9 and Tr10 are composed of a constant current source I0, an integrating capacitor 6, and a terminal T of the CPU 8.
And a switch SW3 controlled by the output from the transistor 4 forms a logarithmic expansion circuit,
Are controlled by the output from the terminal T6 of the CPU 8.

When light is not projected, the switch SW5 controlled by the output from the terminal T8 of the CPU 8 is turned on to set the potential of the integrating capacitor 6 to the reference voltage Vref, and the switch SW5 is turned off by the terminal T8 immediately before light projection. .

At the time of light projection, the switch SW3 controlled by the output from the terminal T4 of the CPU 8 is turned on, the voltage input to the bases of the transistors Tr9 and Tr10 is calculated for each light projection, and {IN / (IN + IF )} · I0 charges the integrating capacitor 6.

When the light emission for a predetermined number of times is completed, a signal is output from the terminal T5 of the CPU 8 to turn on the switch SW4,
The integrating capacitor 6 is discharged by the constant current I1. At the same time, the counter built in the CPU 8 starts to operate, and the operational amplifier O monitored by the terminal T7 of the CPU 8
Counting is continued until the output of P3 is inverted (“H” → “L”).

As a result, the electric charge stored in the integrating capacitor 6 is A / D converted and obtained as the count value of the timer.

The terminal T2 of the CPU 8 is connected to the constant voltage circuit.

Next, FIG. 3 is a flow chart showing a distance measuring sequence, which will be described with reference to FIG.

When the control starts, the CPU 8 causes the terminal T4,
A control signal is issued from T6 to turn on the switch SW3 and the transistor Tr10 (step S1) to charge the integrating capacitor 6.

It is judged whether or not the charging of the integrating capacitor 6 is completed (step S2), and if it is completed, the CPU
8 sends a control signal from the terminals T4 and T6 to switch S
W3, transistor Tr10 is turned off (step S
3) Stop charging the integrating capacitor 6.

Then, the CPU 8 operates the built-in counter (step S4), and at the same time, issues a control signal from the terminal T5 to turn on the switch SW4 (step S5) to discharge the integrating capacitor 6.

The CPU 8 monitors the output of the operational amplifier OP3 via the terminal T7 (step S6), the discharge progresses, the terminal voltage of the integrating capacitor 6 becomes higher than the reference voltage Vref, and the output of the operational amplifier OP3 becomes "H" → After switching to "L", the counter operated in step S4 is stopped, and the reference value D0 is called from the built-in storage means (memory) 13 (see FIG. 1) (step S7).

Here, the reference value D0 is obtained by an adjusting operation as shown in FIG.

That is, the CPU 8 issues a control signal from the terminals T4 and T6 to generate the switch SW3 and the transistor Tr.
10 is turned on (step S120), and the integrating capacitor 6 is charged.

It is judged whether or not the charging of the integrating capacitor 6 is completed (step S121), and if it is completed, C
The PU 8 issues a control signal from the terminals T4 and T6 to turn off the switch SW3 and the transistor Tr10 (step S122), and stops the charging of the integrating capacitor 6.

Then, the CPU 8 operates the built-in counter (step S123), and at the same time, issues a control signal from the terminal T5 to turn on the switch SW4 (step S124) to discharge the integrating capacitor 6.

The CPU 8 monitors the output of the operational amplifier OP3 via the terminal T7 (step S125), the discharge progresses, the terminal voltage of the integrating capacitor 6 becomes higher than the reference voltage Vref, and the output of the operational amplifier OP3 becomes "H" → "L"
After switching to, the counter operated in step S123 is stopped (step S126).

Then, the count value obtained in step S126 is set as the reference value D0 in the memory (memory means 13).
(Step S127).

The above is the method of obtaining the reference value, but when performing this adjustment, it is necessary to perform it under a constant environment or to use an ideal capacitor with a small dielectric absorption.

Hereinafter, the reference value D0 means the above step S1.
It is assumed that it is obtained from 20 in step S127.

Returning to FIG. 3, the description of the operation of the distance measuring sequence will be continued. The count value D1 obtained in steps S1 to S7 described above is compared with the reference value D0, and the difference is set to DD (step S8), and this DD is stored in the memory (storage unit 13) (step S9).

The above steps S1 to S9 are the operations for detecting an error due to dielectric absorption.

From the subsequent step S10, the actual distance measuring operation is started. The CPU 8 outputs a control signal from the terminal T8 to turn on the switch SW5 to reset the integrating capacitor 6 (step S10), and outputs a control signal from the terminal T3 to turn on the switches SW1 and SW2 to "R". The background light removing capacitors C1 and C2 are rapidly charged (step S11).

While resetting the integrating capacitor 6 and rapidly charging the background light removing capacitors C1 and C2, 4 ms is waited (step S12).

Next, the CPU 8 outputs a control signal from the terminal T3 to switch the switches SW1 and SW2 to "N", and normally charges the background light removing capacitors C1 and C2 (step S13).

The terminals of the rapid charge "R" and the normal charge "N" of the switches SW1 and SW2 are used for the processing for charging the capacitors C1 and C2 with the voltage corresponding to the background light.

Here, a rapid charging is performed by increasing the current value of "R", and a high-precision charging is performed by decreasing the current value of "N". , Highly accurate charging is performed in a relatively short time.

Wait 4 ms while the background light removing capacitors C1 and C2 are normally charged (step S14).

Then, the CPU 8 outputs a control signal from the terminal T3 to turn off the switches SW1 and SW2, and finishes charging the background light removing capacitors C1 and C2 (step S15).

In subsequent steps S16 to S23, the light projecting element 10 is driven. The CPU 8 outputs a pulse signal from the terminal T1, which causes the light projecting element 10 to operate.
Is turned on (step S16). Then, after waiting for 32 μs (step S17), a signal is output from the terminal T4 to turn on the switch SW3 to operate the distance calculation circuit unit 5,
The accumulation of the calculation result in the integrating capacitor 6 is started (step S18), and the process waits for 36 μs (step S19).

After 36 μs has elapsed, the CPU 8 next
A signal is output from the terminal T4, the switch SW3 is turned off to end the accumulation in the integrating capacitor 6 (step S20), and a signal is output from the terminal T1 to output the light projecting element 10.
Is turned off (step S21), and the off time is 400μ.
After waiting for s (step S22), it is determined whether light is projected from the light projecting element 10 to the object to be measured a predetermined number of times (for example, 16 times) (step S23).

When the predetermined number (16 times) is not reached, the process returns to step S16, and when the predetermined number of light projections are completed, the CPU 8 outputs a signal from the terminal T8 to turn off the switch SW5, The operational amplifier OP3 is used as a comparator (step S24).

Then, the CPU 8 starts the built-in counter (step S25), and at the same time, the terminal T5.
To output a signal to turn on the switch SW4 to start discharging the integrating capacitor 6 (step S26).

The terminal voltage of the integrating capacitor 6 is the reference voltage V
It becomes larger than ref and the output of the operational amplifier OP3 is "L".
The discharging of the integrating capacitor 6 is continued until it becomes (step S27).

The output of the operational amplifier OP3 becomes "L",
After discharging the integrating capacitor 6, the CPU 8 stops the counter started in step S25 (step S28).

Steps S25 to S28 described above
The count value obtained in step S8 is used as the distance measurement output in consideration of the DD calculated in step S8 and stored in step S9 (step S29).

Next, FIG. 5 is a diagram showing changes in the voltage of the integrating capacitor 6. In the period a, the integration capacitor 6 is reset, but the reference voltage Vref is changed due to dielectric absorption.
Therefore, a voltage deviation of ΔV occurs.

The next period b is a period in which the distance measurement data is accumulated in synchronization with the light projection of the light projecting element 10.

Further, during the periods c and c ', the accumulated data is counted by the counter,
With an ideal capacitor, counting ends in period c, but with an actual capacitor, counting ends in period c'because a deviation of ΔV occurs in period a, and due to the deviation of the counting time from the ideal capacitor, DD occurs as a deviation of the count value.

Therefore, this DD is obtained by comparing it with the reference value D0, and the DD is taken into consideration in the obtained ratio integration result, thereby obtaining a distance measuring output almost equal to that when an ideal capacitor is used. be able to.

According to the first embodiment as described above, even if a capacitor having a large dielectric absorption but a relatively low cost and a small volume is used in the double integration type A / D converter, the distance measuring time is lengthened. It is possible to provide an inexpensive and small distance measuring device that has little variation due to dielectric absorption.

6 to 8 show a second embodiment of the present invention. In the second embodiment, description of the same parts as those of the first embodiment described above will be omitted, and mainly different points will be described.

This distance measuring device has almost the same configuration as that of the first embodiment described above, but as shown in FIG. 6, the input voltage to the non-inverting input terminal of the operational amplifier OP3 is the CPU8.
By outputting a control signal from the terminal T9, the voltage can be switched between the predetermined voltage Vref and Vref2 that can be set arbitrarily.

Next, FIG. 7 is a flowchart showing a distance measuring sequence, which will be described with reference to FIG. When the control is started, the CPU 8 issues a control signal from the terminals T4 and T6 to turn on the switch SW3 and the transistor Tr10 (step S41) to charge the integrating capacitor 6.

It is judged whether or not the charging of the integrating capacitor 6 is completed (step S42), and if it is completed, CP
U8 issues a control signal from the terminals T4 and T6 to turn off the switch SW3 and the transistor Tr10 (step S
43), charging of the integrating capacitor 6 is stopped.

Then, the CPU 8 operates the built-in counter (step S44), and at the same time, the terminal T5
Generates a control signal to turn on the switch SW4 (step S45) to discharge the integrating capacitor 6 with the constant current I1.

The CPU 8 monitors the output of the operational amplifier OP3 via the terminal T7 (step S46), the discharge progresses, the terminal voltage of the integrating capacitor 6 becomes higher than the reference voltage Vref, and the output of the operational amplifier OP3 becomes "H" → After switching to "L", the counter operated in step S44 is stopped, and the reference value D0 is read from the memory (storage means 13).
Is called (step S47).

Steps S41 to S47 described above
The count value D1 obtained in step S1 is compared with the reference value D0, and the difference is set to DD (step S48).

The input voltage to the non-inverting input terminal of the operational amplifier OP3 is obtained from the DD obtained in step S48 (see FIG. 8) (step S49). Vref2 = Vref-f (DD) Here, f is a predetermined function indicating the relationship between the count value and the voltage.

Although calculated here, the relationship between DD and the input voltage is set as a table, and the input voltage to the non-inverting input terminal of the operational amplifier OP3 is selected from the table by referring to the table. You may

Operational amplifier O obtained in step S49
The input voltage Vref2 of P3 is stored in the memory (storage unit 13) (step S50).

The CPU 8 outputs a control signal from the terminal T8 to turn on the switch SW5 and reset the integrating capacitor 6 (step S51).

The CPU 8 outputs a control signal from the terminal T3 to turn on the switches SW1 and SW2 to "R" to rapidly charge the background light removing capacitors C1 and C2 (step S52).

Wait 4 ms while resetting the integrating capacitor 6 and rapidly charging the background light removing capacitors C1 and C2 (step S53).

Next, the CPU 8 outputs a control signal from the terminal T3 to switch the switches SW1 and SW2 to "N", and starts the normal charging of the background light removing capacitors C1 and C2 (step S54). Wait 4 ms while the light removing capacitors C1 and C2 are normally charged (step S55).

Then, the CPU 8 outputs a control signal from the terminal T3 to turn off the switches SW1 and SW2, and finishes charging the background light removing capacitors C1 and C2 (step S56).

In subsequent steps S57 to S64, the light projecting element 10 is driven. The CPU 8 outputs a pulse signal from the terminal T1, which causes the light projecting element 10 to operate.
Is turned on (step S57). Then, after waiting for 32 μs (step S58), a signal is output from the terminal T4 to turn on the switch SW3 to operate the distance calculation circuit unit 5,
After the integration operation is started, the calculation result is started to be accumulated in the integration capacitor 6 (step S59) and waits for 36 μs (step S59).
60).

After 36 μs has elapsed, the CPU 8 next
A signal is output from the terminal T4, the switch SW3 is turned off to end the accumulation in the integration capacitor 6 (step S61), and a signal is output from the terminal T1 to output the light projecting element 10.
Is turned off (step S62), and the off time is 400μ.
After waiting for s (step S63), it is determined whether light is projected from the light projecting element 10 to the object to be measured a predetermined number of times (for example, 16 times) (step S64).

When the predetermined number (16 times) is not reached, the process returns to step S57, and when the projection of the predetermined number of times is completed, the CPU 8 outputs a signal from the terminal T8 to turn off the switch SW5, The operational amplifier OP3 is operated as a comparator (step S65).

Then, the CPU 8 outputs a signal from the terminal T9 and switches the input voltage to the non-inverting input terminal of the operational amplifier OP3 from Vref to Vref2 (step S6).
6).

In the subsequent steps S67 to S70, the inverse integration operation is started. The CPU 8 starts the built-in counter (step S67), and at the same time, the terminal T5
Signal is output to turn on the switch SW4 to start discharging the integrating capacitor 6 (step S68).

The terminal voltage of the integrating capacitor 6 is the reference voltage V
It becomes larger than ref2, and the output of operational amplifier OP3 is "L".
The integration capacitor 6 continues to be discharged until it becomes (step S69).

The output of the operational amplifier OP3 becomes "L",
After discharging the integrating capacitor 6, the CPU 8 stops the counter started in step S67 (step S70).

In this embodiment, since the deviation of the count value is corrected by switching the reference voltage of the operational amplifier OP3, the counter value obtained in step S70 becomes the distance measurement output as it is.

According to the second embodiment as described above, the deviation DD
By using the voltage Vref2 that differs by a voltage corresponding to the above as the reference voltage at the time of inverse integration, the same effect as that of the above-described first embodiment is obtained.

9 to 12 show the third embodiment of the present invention. In the third embodiment, description of the same parts as those of the first and second embodiments described above will be omitted, and only different points will be mainly described.

The distance measuring apparatus according to the third embodiment is the same as the first embodiment described above.
The configuration is similar to that of the embodiment. However, there are two types of current I1 when discharging from the integrating capacitor 6, Ia and Ib, and these have a relation of Ia> Ib.

Next, a method of measuring the deviation amount DD of the integrating capacitor 6 will be described with reference to the diagram showing the voltage change of the integrating capacitor 6 in FIG. 10 along the flowchart of FIG.

The CPU 8 outputs a control signal from the terminals T4 and T6 to turn on the switch SW3 and the transistor Tr10 to charge the integration capacitor 6 (step S8).
1).

It is judged whether or not the charging of the integrating capacitor 6 is completed (step S82), and if it is completed, it waits for a predetermined time TIM1 (see FIG. 10) to elapse (step S83).

When the predetermined time TIM1 has passed, the CPU
8 outputs a control signal from the terminals T4 and T6 to turn off the switch SW3 and the transistor Tr10 (step S
84).

Next, the CPU 8 first sets the discharging current I1 of the integrating capacitor 6 to Ia, outputs a control signal from the terminal T5 to turn on the switch SW4, and as shown in FIG. Is discharged (step S8)
5).

The CPU 8 monitors the output of the operational amplifier OP3 via the terminal T7 (step S86). When the output of the operational amplifier OP3 is switched from "H" to "L", the discharging of the integrating capacitor 6 is completed, so that the terminal T5 is reached. To output a control signal to turn off the switch SW4 and complete the discharge of the integrating capacitor 6 (step S87).

In FIG. 13 which is an equivalent circuit to the integrating capacitor 6, a predetermined time T elapses until the charge accumulated in the capacitor C11 moves to the capacitor C10.
Wait for IM2 (see FIG. 10) (step S88).

When the predetermined time TIM2 has elapsed, C
The counter built in PU8 is started (step S89).

At this time, the CPU 8 sets the discharging current I1 of the integrating capacitor 6 to Ib which is smaller than Ia as described above, outputs a control signal from the terminal T5, and turns on the switch SW4 ( (See FIG. 10) (Step S
90).

The CPU 8 monitors the output of the operational amplifier OP3 via the terminal T7 (step S91). When the output of the operational amplifier OP3 switches from "H" to "L", the discharging of the integrating capacitor 6 is completed. S8
The counter started at 9 is stopped (step S92).

From the count value obtained in step S92, the value of DD is obtained with reference to the graph showing the relationship between the count value and the deviation amount DD as shown in FIG. 12 (step S93). The amount of deviation D
D is required.

The operation for obtaining the deviation amount DD may be performed immediately before the distance measuring operation as described in the first and second embodiments, but in this embodiment, when the power switch of the camera is operated. I am going to do it. The operation in this case will be described with reference to FIG.

First, the displacement amount DD is measured as described with reference to FIGS. 9 and 10 above (step S101), and when DD is obtained, the on / off state of the power switch is confirmed (step S102).

At this time, if the power switch is off, the display unit such as the LCD is turned off and the power of the camera body is turned off (step S115).

On the other hand, if the power switch is turned on in step S102, the display on the LCD or the like is turned on (step S103).

Then, the first release switch is monitored (step S104). If the first release switch is off, step S104 is repeated to continue the monitoring of the release switch, and the first release switch is turned on. In this case, the distance measuring operation is performed in the same manner as described in step S10 to step S28 in FIG.
The distance measurement output at this time is considered in consideration of the deviation amount DD obtained in the above step S101 (step S10).
5).

Then, the switch SW4 is kept on and the integrating capacitor 6 is continuously discharged (step S10).
6).

A photometry operation for measuring the brightness of the subject is performed (step S107), and the second release switch is monitored (step S108). If the second release switch is off, the second release is performed in step S108. The switch monitoring is further continued, and if the second release switch is on, the process proceeds to the next step S109.

The subject distance and subject brightness are calculated based on the distance measuring data and the photometric data obtained in steps S105 and S107 (step S109).

The photographing lens is extended based on the subject distance calculated in step S109 (step S110), and the shutter is controlled based on the subject brightness calculated in step S109 to perform photographing (step S110). Step S111).

When the photographing is completed, the film is wound up one frame (step S112), and then the photographing lens is retracted and returned to the initial position (step S113).

When the switch SW4 of the distance measuring circuit (see FIG. 2) is turned off, and the discharging of the integrating capacitor 6 is completed (step S114), the process returns to step S102, and the same process is performed to take the next frame. Repeat the operation.

In this embodiment, since the displacement amount DD is measured only by operating the power switch, even if the measurement takes a long time, the release time lag does not occur.

When it is desired to measure and correct the deviation amount with higher accuracy, the deviation amount DD as shown in the above-described first and second embodiments is measured while the distance measuring operation is being performed in step S105. Detection and correction may be included.

Further, by keeping the switch SW4 in the distance measuring circuit (see FIG. 2) on from step S105 to step S113, a long time (400 ms to 50 ms) can be obtained.
Since the integration capacitor 6 can be discharged and the distance measuring operation is performed with almost no electric charge, a constant deviation amount DD can be generated (also in the first and second embodiments). The same.).

By discharging the electric charge of the integrating capacitor before the distance measurement in this way, the state of the integrating capacitor during the distance measurement is made the same.

On the contrary, the state of the integrating capacitor during distance measurement may be made constant by fully charging the integrating capacitor. This may be achieved by replacing step S106 described above with turning on the switch SW3 and replacing step S114 with turning off the switch SW3.

As described above, whether the electric charge of the integrating capacitor is completely discharged or fully charged before the distance measurement can be selected by taking into consideration the circuit configuration of the distance measuring Ic and the like. .

According to the third embodiment as described above, a constant displacement amount DD is generated by discharging or fully charging the charge of the integrating capacitor before distance measurement, and the displacement amount DD is measured by operating the power switch. Since it is performed when the release time lag does not occur, such as during the distance measurement operation and the distance measurement operation, it has substantially the same effects as those of the first and second embodiments.

[Additional Notes] According to the above-described embodiment of the present invention as described in detail above, the following constitution can be obtained.

(1) A light projecting means for projecting light onto an object, a light receiving means for receiving reflected light from the object and outputting a photoelectric conversion signal, and the above-mentioned photoelectric conversion signal based on the photoelectric conversion signal. The distance calculating means for calculating the distance to the object and outputting the distance signal, the integrating capacitor for accumulating the distance signal, the dielectric absorption amount detecting means for detecting the dielectric absorption amount of the integrating capacitor, and the integrating capacitor A conversion means for converting the accumulated distance signal into a digital signal, and based on the output of the dielectric absorption amount detecting means and the distance signal accumulated in the integrating capacitor, calculates the distance to the object. Distance measuring device characterized by determining.

(2) In Appendix 1, the dielectric absorption amount detecting means measures the dielectric absorption amount of the integration capacitor by measuring the discharge time at a predetermined discharge current value after charging the integration capacitor to a predetermined voltage. To detect.

(3) In Appendix 1, the dielectric absorption amount detecting means measures the integrating capacitor voltage after charging the integrating capacitor to a predetermined voltage, and based on the difference between the measured voltage and the reference voltage. The amount of dielectric absorption of the integrating capacitor is detected.

(4) In Appendix 1, the dielectric absorption amount detecting means charges the integrating capacitor to a predetermined voltage, discharges it for a first predetermined time, and then leaves it for a second predetermined time, and then discharges it for a predetermined time. The amount of dielectric absorption of the integrating capacitor is detected by measuring the discharge time according to the current value.

(5) In Appendix 1, the dielectric absorption amount detecting means is operated immediately before the operation of the light projecting means.

(6) In Appendix 1, the dielectric absorption amount detecting means is operated immediately after the operation of the power switch.

(7) In Appendix 1, the distance measuring device is provided in the camera.

(8) In Supplementary Note 7, the dielectric absorption amount detecting means short-circuits the integrating capacitor at least after distance measurement and until the winding of one film of film is completed.

(9) A light projecting means for projecting light onto an object, a light receiving means for receiving reflected light from the object and outputting a photoelectric conversion signal, and the above-mentioned photoelectric conversion signal based on the photoelectric conversion signal. The distance calculating means for calculating the distance to the object and outputting the distance signal, the integrating capacitor for accumulating the distance signal, the dielectric absorption amount detecting means for detecting the dielectric absorption amount of the integrating capacitor, and the integrating capacitor And a converting means for converting the accumulated distance signal into a digital signal, wherein the converting means performs digital conversion based on the output of the dielectric absorption amount detecting means.

(10) In Supplementary Note 1 or Supplementary Note 9,
The storage unit stores the reference value, and the dielectric absorption amount detection unit finds the dielectric absorption amount based on the reference value stored in the storage unit.

(11) In Supplementary Note 10, the reference value stored in the storage means is obtained by adjustment.

(12) In Supplementary Note 1 or Supplementary Note 9,
The light projecting means projects a pulsed light.

[0137]

As described above, according to the present invention, an inexpensive distance measuring device capable of suppressing the distance measuring error without increasing the distance measuring time is provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing an outline of a distance measuring device according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing details of the distance measuring device according to the first embodiment.

FIG. 3 is a flowchart showing the operation of the distance measuring device of the first embodiment.

FIG. 4 shows a reference value D in the distance measuring device according to the first embodiment.
The flowchart which shows the adjustment operation | movement for calculating | requiring 0.

FIG. 5 is a diagram showing a change in voltage of an integrating capacitor of the distance measuring apparatus according to the first embodiment.

FIG. 6 is a circuit diagram showing a distance measuring device according to a second embodiment of the present invention.

FIG. 7 is a flowchart showing the operation of the distance measuring apparatus according to the second embodiment.

FIG. 8 is a diagram showing a change in voltage of an integrating capacitor of the distance measuring apparatus according to the second embodiment.

FIG. 9 is a flowchart showing the operation of the distance measuring apparatus according to the third embodiment of the present invention.

FIG. 10 is a diagram showing a change in voltage of an integrating capacitor of the distance measuring apparatus according to the third embodiment.

FIG. 11 is a flowchart showing an operation of obtaining a deviation amount DD when a power switch is operated in the third embodiment.

FIG. 12 is a diagram showing an example of changes in the deviation amount DD with respect to a count value in the distance measuring device according to the third embodiment.

FIG. 13 is a circuit diagram showing an equivalent circuit of a conventional high dielectric constant capacitor.

FIG. 14 is a schematic circuit diagram when a voltage V0 is applied to a conventional high dielectric constant capacitor.

FIG. 15 is a diagram showing a discharging state of a conventional high dielectric constant capacitor.

[Explanation of symbols]

2 ... Light receiving element (light receiving means) 3, 4 ... Photocurrent detection circuit section 5: Distance calculation circuit section (distance calculation means) 6 ... Integrating capacitor 7 ... Counting unit (converting means) 8 ... CPU 10 ... Projecting element (projecting means) 12 ... Dielectric absorption amount detection means 13 ... Storage means

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-363619 (JP, A) JP-A-8-110222 (JP, A) JP-A-8-114741 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) G01C 3/06 G02B 7/32 G03B 13/36

Claims (2)

(57) [Claims] 1. A light projecting means for projecting light onto an object, a light receiving means for receiving reflected light from the object and outputting a photoelectric conversion signal, and the object based on the photoelectric conversion signal. Distance calculating means for calculating the distance to an object and outputting a distance signal, integrating capacitor for accumulating the distance signal, dielectric absorption amount detecting means for detecting the dielectric absorption amount of the integrating capacitor, and accumulating in the integrating capacitor. And a conversion means for converting the distance signal thus converted into a digital signal, and determines the distance to the object based on the output of the dielectric absorption amount detection means and the distance signal accumulated in the integrating capacitor. A distance measuring device characterized by: 2. A light projecting means for projecting light to an object, a light receiving means for receiving reflected light from the object and outputting a photoelectric conversion signal, and the object based on the photoelectric conversion signal. Distance calculating means for calculating the distance to an object and outputting a distance signal, integrating capacitor for accumulating the distance signal, dielectric absorption amount detecting means for detecting the dielectric absorption amount of the integrating capacitor, and accumulating in the integrating capacitor. A distance measuring device comprising: a converting means for converting the distance signal thus converted into a digital signal, wherein the converting means performs digital conversion based on an output of the dielectric absorption amount detecting means.