JPH1089952A - Distance measuring equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent useless power consumption while keeping accuracy of distance measurement even when a high permittivity capacitor is employed in an A/D converter by resetting an integration capacitor every first predetermined time and prohibiting the reset operation if a specific operation is not performed for a second predetermined time. SOLUTION: A projection circuit 18 drives an infrared light emitting diode 16 to project infrared rays toward an object through a projection lens 28. A reflected light the object passes through a light receiving lens 30 and enters into a position detection element(PSD) 20. A photocurrent produced from the PSD 20 is taken out while being distributed depending on the ratio of infrared ray incident position. It is then inputted to a distance measurement processing circuit 12 where the ratio of two signals is operated and delivered to an A/D converter. Subsequently, it is subjected to first integration and then subjected to second integration through an integration capacitor 26 to produce a digital signal. A CPU 10 resets the integration capacitor 26 for first predetermined time and prohibits the reset operation if a specific operation is not performed for a second predetermined time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring apparatus, and more particularly, to an electronic control camera having a distance measuring apparatus for performing distance measurement using a triangular distance measuring method.

[0002]

2. Description of the Related Art Conventional distance measuring devices include, for example, Japanese Patent Application No.
As shown in Japanese Patent No. 340722, there is a double integration type analog / digital converter (hereinafter abbreviated as A / D converter) using a ceramic capacitor. In order to prevent dielectric absorption, which is a problem when a high dielectric constant capacitor such as a ceramic capacitor is used for the A / D converter, a predetermined time elapses when the camera is turned on or after the battery is replaced. It is shown that performing a series of distance measurement operations later resets the influence of dielectric absorption.

[0003]

However, in the above-described method, when the power is on, a series of distance measuring operations are always repeated at fixed time intervals, so that the life of the IRED and the power supply is shortened. On the other hand, if a series of distance measurement operations is not performed, there is a problem that the distance measurement accuracy is reduced.

The distance measuring apparatus of the present invention has been made in view of such a problem.
An object of the present invention is to provide a distance measuring device that can prevent useless power consumption while maintaining the distance measuring accuracy even when a high dielectric constant capacitor is used for the / D converter.

[0005]

In order to achieve the above object, a distance measuring apparatus according to a first aspect of the present invention includes a light projecting means for projecting light to a subject, and receiving reflected light from the subject. A distance measuring means having a light receiving means, a signal processing circuit for processing an output signal from the light receiving means, and an analog / digital converting means for converting an analog output signal from the signal processing circuit into a digital signal using a capacitor; The apparatus includes reset means for resetting the capacitor every first predetermined time, and prohibition means for prohibiting the reset when there is no predetermined operation during the second predetermined time.

A distance measuring apparatus according to a second aspect of the present invention comprises a first distance measuring apparatus.
In the distance measuring apparatus according to the present invention, the reset means resets the capacitor by performing a distance measuring operation. Further, a distance measuring apparatus according to a third aspect of the present invention provides a light projecting means for projecting light to a subject, a light receiving means for receiving reflected light from the subject, and a signal processing for processing an output signal from the light receiving means. A distance measuring means having an analog / digital conversion means for converting an analog output signal from the signal processing circuit into a digital signal using a capacitor; and a reset means for resetting the capacitor every first predetermined time. Prohibiting means for prohibiting the reset after a second predetermined time if there is no predetermined operation;
Control means for controlling the reset means to operate again when a predetermined operation is performed.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. First, a first embodiment of the present invention will be described. FIG. 1 is a diagram illustrating a configuration of a distance measuring apparatus according to the first embodiment of the present invention. In FIG. 1, a central processing unit (hereinafter, referred to as a CPU) 10 for controlling the overall operation of the distance measuring apparatus and calculating various information includes a distance measuring processing circuit 12 for processing a distance measuring signal, and a CPU 10. Is connected to a memory 14 such as an EEPROM for storing information output from the memory.

Further, the distance measuring circuit 12 includes a light emitting circuit 18 to which an infrared light emitting diode (hereinafter, referred to as IRED) 16 is connected, a position detecting element (hereinafter, referred to as PSD) 20, and a hold. The capacitors 22 and 24 and the integration capacitor 26 are connected. Note that a ceramic capacitor having a high dielectric constant is used as the integration capacitor 26. A light projecting lens 28 is provided in front of the IRED 16, and a light receiving lens 30 is provided in front of the PSD 20.

The distance measuring apparatus thus configured operates as follows. Light emitting circuit 18 according to an instruction from CPU 10
Drives the IRED 16 to project infrared light through the light projecting lens 28 toward the subject a plurality of times. The projected infrared light impinges on the subject, is diffused, is collected as reflected light by the light receiving lens 30, and is incident on the PSD 20.

The PSD 20 has a pair of output terminals for extracting a photocurrent generated in accordance with the amount of infrared light received and distributing the photocurrent in accordance with the ratio of the incident position of the infrared light. doing. The pair of output terminals output a signal light current generated when the reflected light is received and a stationary light current generated when the light other than the reflected light is received.

FIG. 2 is a block diagram showing a circuit configuration of the distance measurement processing circuit 12. As shown in FIG. A pair of signal light currents obtained from the PSD 20 are amplified by a pair of head amplifiers 32 and 34 and further logarithmically compressed by compression circuits 36 and 38. The two signals logarithmically compressed by the compression circuits 36 and 38 are output to an arithmetic circuit 40, which calculates the ratio of these two signals and outputs the result to a double integral A / D converter 42. Is done. Double integral type A
The / D converter 42 performs a first integration on the calculation result of the calculation circuit 40, and then performs a second integration.
The calculation result is converted from an analog signal to a digital signal. In this way, the conversion from the analog signal to the digital signal is performed by the double integration type A / D converter 42 while receiving the reflected light from the subject a plurality of times. Note that the second integration means that a constant current is supplied to the integration capacitor 26 from the potential after the completion of the first integration, and the time required to reach the reference voltage Vref is counted by a certain constant clock. The pair of stationary light currents is discarded by the pair of stationary light extraction circuits 44 and 46 to a reference potential point (GND).

These circuit blocks in the distance measuring circuit 12 are controlled by a control circuit 48.
8 is controlled by a signal from a CNTL (control) terminal of the CPU 10. The distance measurement data is sent serially from the control circuit 48 to the DATA (data) terminal of the CPU 10. The CPU 10 supplies or cuts a bias current to the distance measurement processing circuit 12 by controlling an output from a CEN (chip enable) terminal.

FIG. 3 is a timing chart at the time of operation of the distance measuring apparatus. “H” from the CEN terminal of the CPU 10
When the (High) ”signal is output, a bias current is supplied to the distance measurement processing circuit 12, and“ L (Low) ”
Is output, the bias current is cut. C
When a rising signal of “L → H” is output from the CTRL terminal of the PU 10, the distance measurement processing circuit 12 starts a distance measurement and receives a clock signal after a certain period of time in order to output distance measurement data. .

The output from the distance measurement processing circuit 12 to the DATA terminal of the CPU 10 is "L →" of the CTRL terminal.
The signal rises from "L to H" in response to the rising signal of "H", and the distance measurement processing circuit 12 outputs the distance measurement data in synchronization with the clock signal after a predetermined time.
From the CINT terminal indicates the potential of the integrating capacitor 26 accumulated by the output of the double integrating A / D converter 42.

The portion indicated by A in the figure indicates a state in which the CPU 10 operates in the second operation mode in which the current consumption is suppressed as compared with the normal operation (hereinafter, referred to as a standby state). . At this time, the bias current to the distance measurement processing circuit 12 is cut off, and the potential of the CINT terminal is undefined due to a leak current from the power supply Vcc or the reference potential point (GND). In FIG. 3, the power supply V
This shows a state where the potential of the CINT terminal is gradually raised due to the leak current from the cc.

In the portion indicated by R in the figure, a power switch (power SW) (not shown) of the distance measuring apparatus is turned on,
The figure shows a state in which the CPU 10 is performing an initialization operation for shifting the distance measuring apparatus from the second operation mode to the first operation mode in which normal operation is performed (hereinafter, referred to as an initialization state).

Further, a portion indicated by C in the figure shows a state where the distance measuring apparatus, that is, the CPU 10 is waiting for a switch input (hereinafter, referred to as a key weight state).

Next, referring to a flowchart shown in FIG. 4, a CP as an operation of a camera equipped with this distance measuring device will be described.
The process of U10 will be described. When no operation is performed by the photographer, the CPU 10 sets the distance measuring apparatus to the standby state (A) (step S1). Next, CPU1
0 determines whether or not the photographer has turned on a power switch (not shown) to start photographing (step S2). Then, the apparatus is made to stand by in a standby state until the power switch is turned on, and when the power switch is turned on, the distance measuring apparatus is set to the initialization state (B) (step S).
3). The CPU 10 operates the distance measuring device at the end of the initialization operation to execute the distance measurement to reduce the influence of dielectric absorption.

After the initialization operation is completed, the CPU 10 resets the timer (step S3-1), and sets the distance measuring apparatus to the key wait state (C) (step S3-1).
4). As a result, the distance measuring apparatus can shoot. Even during this key wait state, the terminal of the integration capacitor 26 of the double integration type A / D converter 42 (CINT terminal)
Has a potential gradually rising due to a leak current from the power supply Vcc. Therefore, the CPU 10 determines that the potential of the CINT terminal is at the same level as the minimum resolution of the double integration type A / D converter 42, that is, after a predetermined time (for example, 4 hours) has elapsed since the last distance measurement (step S5). The range finder is again set to the standby state (step S6).
After that, the process ends.

FIG. 5 is a flowchart showing the processing in the "initialized state" in the flowchart shown in FIG. First, the CPU 10 clears the RAM in the CPU 10 and substitutes an initial value (step S11). Subsequently, the CPU 10 reads data from the memory 14 such as an EEPROM or the like, and writes the data to a predetermined address in the RAM (step S12).

Next, the CPU 10 checks the state of the battery loaded in the camera. That is, it is determined whether or not the capacity of the battery is larger than the predetermined capacity (step S1).
3). Here, when the battery capacity is smaller than the predetermined capacity, a warning indicating that the battery capacity is small is displayed (Step S).
14) Lock all the switches arranged on the camera (step S15), and prompt the photographer to replace the battery.
Then, when the battery is replaced (step S16), the process returns to step S11, and the processing after step S11 is repeated.

If the battery capacity is larger than the predetermined capacity in step S13, that is, if the battery capacity is sufficient, the CPU 10 determines whether or not the mechanical mechanism of the camera (not shown) is at a predetermined position. (Step S17). When the mechanical mechanism is not at the predetermined position, the mechanical mechanism is driven to the predetermined position (Step S18), and the process proceeds to Step 19.

Then, when the mechanical mechanism of the camera is at a predetermined position, the CPU 10 checks the charging voltage of the main capacitor for lighting a strobe (not shown). That is, it is determined whether the charging voltage of the main capacitor is higher than a predetermined voltage (step S19). Here, when the charging voltage is equal to or lower than the predetermined voltage, the main capacitor is charged to the predetermined voltage (step S20), and the process proceeds to step S21.

When the charging voltage of the main capacitor is higher than a predetermined voltage and the distance measurement is executed, an erroneous measurement is made due to the dielectric absorption of the integrating capacitor 26 charged due to a leak current from the power supply Vcc. In order to prevent the distance, the distance measurement is executed in advance (step S21). After that, the process ends.

FIG. 6 is a diagram showing a model circuit of a high dielectric constant capacitor used for the integration capacitor 26.
In addition to the ideal capacitor CR, resistors and capacitors that cause dielectric absorption exist in parallel from the first to n-th order.

FIG. 7 is an enlarged view of the output of the CINT terminal in the initialized state in the timing chart shown in FIG. In the standby state and the key wait state, the leakage current from the power supply Vcc passes through the capacitor CR and the resistor R1 shown in FIG.
, R2, C2, R3,... And Cn-1 and Rn, and charges are slowly stored in the capacitor Cn. Therefore, the distance measurement is performed in this state in the initialization operation.

Originally, the potential after the reset operation in the initialized state is equal to the reference voltage V
ref. However, in this state, since there are R1 C1, R2 C2, R3 C3,..., Rn Cn which cause dielectric absorption, the movement of the charges stored in C1, C2, C3,. As a result, the potential after the reset operation is raised by ΔV from the reference voltage Vref. Thereafter, when the first integration and the second integration are performed, the voltage reaches the reference voltage Vref earlier by ΔT, and a distance measurement error occurs.

However, once the distance measurement operation is performed here,
The electric charges stored in the capacitors C1, C2, C3,..., Ck-1 are discharged to a level that hardly affects the resolution of the distance measurement (the above-described double integration type A / D converter 42) by a series of distance measurement operations. Is done. As a result, at the next distance measurement, distance measurement can be performed in a state where the influence of dielectric absorption is reduced, that is, in a state where erroneous distance measurement does not occur.
The electric charges stored in the capacitors Ck to Cn are ignored because the time constant is much larger than the distance measurement time and does not affect the distance measurement.

Although the potential of the CINT terminal may be unstable even when the photographer replaces the battery, the influence of dielectric absorption is reduced at the next distance measurement by performing the initialization operation. The distance can be measured in a state where the distance is measured.

FIG. 8 is a flowchart showing details of the key wait state in FIG. First, step S10
At 4, it is determined whether the power switch of the camera (not shown) is ON. If the power switch is off, the subroutine is exited. Otherwise, the process proceeds to step S105.

In this step S105, it is determined whether or not a rewind switch (rewind switch) not shown is ON. If the rewind switch is ON, rewinding is performed in step S106, the timer is reset in step S122, and the process exits the subroutine. Otherwise, the process proceeds to step S107.

In step S107, it is determined whether 20 minutes have elapsed since the timer was set. If 20 minutes have elapsed, the process proceeds to step S110. Otherwise, the distance measuring operation is performed in step S108, the flash is charged in step S109, and the process proceeds to step S110. The distance measurement operation here has the same meaning as the distance measurement in step S21 described above (hereinafter, the distance measurement operation performed in this sense is referred to as dummy distance measurement). Flash charging is
If the charging voltage of the main capacitor is equal to or higher than a predetermined value, it is not necessary to perform the operation.

In step S110, a photometric operation is performed to determine the exposure. Normally, photometry is performed in response to half-pressing of a release button (not shown) (1RSW ON), but in the case of this camera, photometry is performed at this position in order to reduce the time lag from the release. .

In step S111, it is determined whether or not a release button (not shown) is half-pressed (1RSW is ON). If 1RSW is OFF, the subroutine is exited as it is, and if 1RSW is ON, step S112
Proceed to. Therefore, if nothing is done while the camera switch is ON, steps S104, S105,
Step S107, Step S108, Step S10
9, Step S110, Step S111 → Step S
The loop of 5 → step S104... Is continuously performed for 4 hours. If it is within 20 minutes, dummy distance measurement is also performed during that time. Note that the dummy distance measurement in step S108 is not performed every time the camera passes through the loop, but is performed once every 60 seconds in the present camera at predetermined time intervals.

In step S112, it is determined whether 20 minutes have elapsed since the timer was set, and if 20 minutes have elapsed, dummy distance measurement is performed in step S113 to reset the integrating capacitor. This is because if 20 minutes have elapsed, the distance measuring operation will not be performed in the above loop, so that the electric charge accumulates in the integrating capacitor, which may cause a decrease in the distance measuring accuracy.
If 20 minutes have not elapsed, the integration capacitor has been reset, and there is no need to perform dummy distance measurement here again, so the process proceeds directly to step S114. In step S114, distance measurement is performed. This is not a resetting of the integrating capacitor described above, but a so-called ordinary distance measurement for obtaining data for photographing.

In step S115, step S110,
Exposure calculation for exposure determination is performed based on the data obtained in step S114. In step S116, step S
A lens driving amount for focusing is calculated based on the data obtained in step 114. In step S117, it is determined whether or not a release switch (not shown) has been fully pressed (2RS
(W is turned ON). If 2RSW is O
If N, the lens is driven in step S119 according to the lens drive amount calculated in step S116, the exposure operation is performed in step S120, and step S121 is performed.
After performing a series of photographing operations of feeding the film in step, the timer is reset in step S122 and the subroutine is exited.

In step S117, 2RSW is turned off.
If F, proceed to step S118, where 1RSW is performed again.
Is ON, if it is ON, the process returns to step S117. If it is OFF, the timer is reset in step S122 and the process exits the subroutine. That is, if the state where the release switch is half-pressed is held, the exposure data at the time when the release switch is half-pressed is held, and the exposure data is rotated between steps S117 and S118. This is a so-called focus lock state.

Focusing on dummy distance measurement for resetting the integration capacitor in the subroutine described above, dummy distance measurement is performed every 60 seconds for 20 minutes after the timer is set. After that, the dummy distance measurement is not performed. However, if 1RSW is turned on even after 20 minutes have elapsed, the timer is reset, so 1
The distance measurement operation is performed again every 60 seconds for 20 minutes after the RSW is turned on.

Hereinafter, a second embodiment of the present invention will be described. The configuration of the second embodiment is the same as that of the first embodiment.
In the first embodiment described above, after the dummy ranging is stopped, 1R
Although the dummy distance measurement is restarted by the SW, for example, if the camera has a zoom function, the dummy distance measurement may be restarted by operating a zoom button. FIG.
Is a flowchart showing the operation at this time. Basically, it is obtained by adding steps S201 to S203 to the flowchart of FIG.

First, in step S201, it is determined whether a zoom-up button (not shown) is pressed (ZMUP).
SW is ON or OFF). If the zoom-up button has been pressed, the flow advances to step S203 to perform zooming. Otherwise, the process proceeds to step S202.

In step S202, also in step S2
Similarly to 01, it is determined whether or not a zoom-down button (not shown) is pressed (ZMDNSW is ON or OFF). If it is determined that the zoom button has been pressed, the flow advances to step S203 to perform zooming. If not, the subroutine ends.

After zooming is performed in step S203, the process proceeds to step S122. In step S122, the timer is reset and restarted. In this case, the timer is reset by operating the zoom button. Therefore, even when the dummy distance measurement is not performed after 20 minutes from the timer operation, the dummy distance measurement can be performed by operating the zoom button. Can be resumed.

In order to resume such dummy distance measurement, 1RSW, ZMUPSW, ZM
The switch is not limited to the DNSW, but includes various switches such as a photographing mode switch and a strobe mode switch.

According to the above embodiment of the present invention, the following configuration can be obtained. (1) Light projecting means for projecting light to a subject, light receiving means for receiving reflected light from the subject, a signal processing circuit for processing an output signal from the light receiving means, and an analog output from the signal processing circuit. Distance measuring means having an analog / digital converting means for converting a signal into a digital signal using a capacitor; a first operation mode for performing a normal operation;
Reset means for resetting the capacitor every first predetermined time during the first operation mode among the second operation modes which consume less current than the second operation mode;
Prohibiting means for prohibiting the reset when a predetermined operation is not performed during the predetermined time. (2) The reset means resets the capacitor by performing a distance measuring operation. (1)
3. The distance measuring device according to 1. (3) The distance measuring apparatus according to (1), wherein the reset means controls the number of resets according to a state of the capacitor. (4) The distance measuring apparatus according to (3), wherein the reset means resets the capacitor by performing a distance measuring operation. (5) a light projecting means for projecting light to a subject, a light receiving means for receiving light reflected from the subject, a signal processing circuit for processing an output signal from the light receiving means, and an analog signal from the signal processing circuit. Distance measuring means having an analog / digital conversion means for converting an output signal into a digital signal using a high dielectric constant capacitor, a first operation mode for performing a normal operation, and a lower current consumption than in the first operation mode Second
Of the above operation modes, control is performed such that a distance measurement operation is performed at every first predetermined time during the first operation mode in order to cancel an influence on a distance measurement result due to dielectric absorption of the high dielectric constant capacitor. Control means for performing a second predetermined time,
Prohibiting means for prohibiting the operation of the control means when there is no predetermined operation. (6) Light projecting means for projecting light to a subject, light receiving means for receiving reflected light from the subject, a signal processing circuit for processing an output signal from the light receiving means, and an analog output from the signal processing circuit. Distance measuring means having an analog / digital converting means for converting a signal into a digital signal using a capacitor; a first operation mode for performing a normal operation;
Reset means for resetting the capacitor every first predetermined time during the first operation mode, among the second operation modes which consume less current than the operation mode of Prohibiting means for prohibiting the reset when a predetermined operation is not performed, and control means for controlling the reset means to operate again when a predetermined operation is performed after the prohibition of the reset. Distance measuring device. (7) The reset means resets the capacitor by performing a distance measuring operation. (6)
3. The distance measuring device according to 1. (8) The distance measuring apparatus according to (6), wherein the reset means controls the number of resets according to the state of the capacitor. (9) The distance measuring apparatus according to (8), wherein the reset unit resets the capacitor by performing a distance measuring operation. (10) Light projecting means for projecting light to a subject, light receiving means for receiving light reflected from the subject, a signal processing circuit for processing an output signal from the light receiving means, and an analog signal from the signal processing circuit. Distance measuring means having an analog / digital conversion means for converting an output signal into a digital signal using a high dielectric constant capacitor, a first operation mode for performing a normal operation, and a lower current consumption than in the first operation mode Second
Of the above operation modes, control is performed such that a distance measurement operation is performed at every first predetermined time during the first operation mode in order to cancel an influence on a distance measurement result due to dielectric absorption of the high dielectric constant capacitor. Control means for performing a second predetermined time,
Prohibiting means for prohibiting the operation of the control means when there is no predetermined operation, and resuming means for operating the control means again when a predetermined operation is performed after prohibiting the operation of the control means. Distance measuring device. (11) a light projecting means for projecting light to a subject, a light receiving means for receiving reflected light from the subject, a signal processing circuit for processing an output signal from the light receiving means, and an analog output from the signal processing circuit. A distance measuring unit having an analog / digital conversion unit for converting a signal into a digital signal using a capacitor; a strobe charging unit for charging a strobe for illuminating a subject; a first operation mode for performing a normal operation; The second mode which consumes less current than the first operation mode
Reset means for resetting the capacitor at every first predetermined time during the first operation mode, and when there is no predetermined operation for a second predetermined time,
Control means for prohibiting the reset and prohibiting the flash charging. (12) The reset means resets the capacitor by performing a distance measuring operation.
The distance measuring device according to 1). (13) The reset means controls the number of resets according to the state of the capacitor.
The distance measuring device according to 1). (14) The reset means resets the capacitor by performing a distance measuring operation. (13)
3. The distance measuring device according to 1. (15) Light projecting means for projecting light to a subject, light receiving means for receiving reflected light from the subject, a signal processing circuit for processing an output signal from the light receiving means, and an analog output from the signal processing circuit. Distance measuring means having analog / digital conversion means for converting a signal into a digital signal using a capacitor, a first operation mode for performing a normal operation, and a second operation which consumes less current than the first operation mode Reset means for resetting the capacitor at every first predetermined time during the first operation mode; strobe means for illuminating a subject; and strobe means during the first operation mode. A strobe charging unit for charging the strobe, a prohibition unit for prohibiting the reset and prohibiting the charging of the strobe when a predetermined operation is not performed during a second predetermined time, After serial reset disabled and strobe charging prohibition, the distance measuring apparatus characterized by comprising a control means for controlling to actuate said reset means and strobe charging means again when there predetermined operation. (16) The reset means resets the capacitor by performing a distance measuring operation.
The distance measuring device according to 5). (17) The reset means controls the number of resets according to the state of the capacitor.
The distance measuring device according to 5). (18) The reset means resets the capacitor by performing a distance measuring operation. (17)
3. The distance measuring device according to 1.

[0045]

As described above, according to the present invention, A
Even when a high dielectric constant capacitor is used for the / D converter, useless power consumption can be prevented while maintaining the ranging accuracy.

[Brief description of the drawings]

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

FIG. 2 is a block diagram showing a circuit configuration of a distance measurement processing circuit 12 in the distance measurement device shown in FIG.

FIG. 3 is a timing chart showing an operation of the distance measuring apparatus shown in FIG.

FIG. 4 is a flowchart showing a process of a CPU 10 as an operation of a camera equipped with the distance measuring device shown in FIG. 1;

FIG. 5 is a flowchart showing processing in an “initialized state” in the flowchart shown in FIG. 4;

6 is a diagram showing a model circuit of a high dielectric constant capacitor used for an integrating capacitor 26 in the distance measuring device shown in FIG.

FIG. 7 is an enlarged view showing an output of a CINT terminal in an initialized state in the timing chart shown in FIG. 3;

FIG. 8 is a flowchart showing details of a key wait state in FIG. 4;

FIG. 9 is a flowchart illustrating details of a key wait state according to the second embodiment of the present invention.

[Explanation of symbols]

Reference numeral 10: central processing unit (CPU), 12: distance measurement processing circuit, 14: memory, 16: infrared light emitting diode (IRE)
D), 18: light emitting circuit, 20: position detecting element (PS
D), 22, 24 ... hold condenser, 26 ... integration condenser, 28 ... light emitting lens, 30 ... light receiving lens, 3
2, 34 ... head amplifier, 36, 38 ... compression circuit, 40
... arithmetic circuit, 42 ... double integration type A / D converter, 4
4, 46: steady light extraction circuit, 48: control circuit.

Claims (3)

[Claims] A light projecting means for projecting light to a subject; a light receiving means for receiving reflected light from the subject; a signal processing circuit for processing an output signal from the light receiving means; Distance measuring means having analog / digital conversion means for converting the analog output signal of the above into a digital signal using a capacitor; resetting means for resetting the capacitor every first predetermined time; and for a second predetermined time Prohibiting means for prohibiting the reset when there is no predetermined operation. 2. The distance measuring apparatus according to claim 1, wherein said reset means resets said capacitor by performing a distance measuring operation. 3. A light projecting means for projecting light to a subject, a light receiving means for receiving reflected light from the subject, a signal processing circuit for processing an output signal from the light receiving means, and A distance measuring means having an analog / digital conversion means for converting an analog output signal into a digital signal by using a capacitor; a reset means for resetting the capacitor at every first predetermined time; Prohibiting means for prohibiting resetting after a second predetermined time; and control means for controlling the resetting means to operate again when a predetermined operation is performed after the resetting prohibition. Distance device.