JPH0954240A - Ranging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent outputting wrong ranging information owing to noises and errors in a ranging device performing triangular ranging wherein an object is irradiated with a beam. SOLUTION: Signals corresponding to ON/OFF of IRED 19 are fed from a sensor array 10 to a control circuit 18 via an integrating/storing section 11, a shift gate 12, a linear CCD 13, a ring CCD 14 and an output section 17. When a signal corresponding to OFF is larger than a signal corresponding to ON in its level in comparison with both signals, ranging information is judged to be null.

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 for measuring a distance to a measuring object, and is suitable for application to, for example, an AF mechanism of a camera.

[0002]

2. Description of the Related Art Conventionally, a distance measuring device shown in FIG. 6 is well known as a distance measuring device for projecting a spot on a measuring object whose distance is to be measured and receiving the reflected light to perform a triangular distance measuring. That is, from the light emitting diode (IRED) 41 to the projection lens 4
The light is projected onto the measuring object 45 via the spot light 3, and the reflected light is transmitted through the light receiving lens 44 to the position detecting element (PSD) 42.
To receive light. Since the PSD 42 outputs signals A and B corresponding to the light receiving position from both terminals, the signals A and B
The light receiving position of the PSD 42 can be detected and the distance to the measurement target 45 can be known from the light receiving position.

FIG. 7 shows a signal processing circuit of this range finder.

The outputs A and B of the PSD 42 are AMP, respectively.
The current-voltage conversion is performed by 1 _A and 1 _B , and the direct current component is removed by the capacitors C _A and C _B. As a result, the blinking signal corresponding to the on / off of the IRED41 becomes A.
It is input to MP2 _A and 2 _B , where it is inverted and amplified. A
The flashing signal amplified by MP2 _A , 2 _B is selectively switched to AMP3 _A , 3 _B in synchronization with the flashing operation through an analog switch controlled by the S / H signal.
Is input to Then, the integration in the capacitor is started by the control of the analog switch by the INT signal. By synchronously integrating with the S / H signal in this way,
A weak signal from the PSD 42 generated by the reflected light from the measurement target is detected, ΣA and ΣB are obtained, and distance measurement is possible.

However, the conventional distance measuring devices shown in FIGS. 6 and 7 have the following problems. That is, S /
Considering the N ratio, AMP1 _A , 1 _B for weak signals
Since the noise generated from the resistance of the PSD 42 and the resistance of the PSD 42 each time the synchronous integration, in order to increase the signal component, the distance measuring block including the light projecting lens 43, the light receiving lens 44, etc. is increased, and the power of the IRED 41 is increased. Therefore, it is difficult to reduce the size of the distance measuring device.

In order to widen the measurement distance range, P
Although it is necessary to lengthen the SD42, if the PSD42 is lengthened, the rate of change of the obtained A and B signals with respect to the distance is reduced, and there is also a problem that the accuracy of position detection is reduced.

Next, FIG. 8 shows an apparatus using a sensor array in place of the PSD proposed in USP 4,521,106.

A sensor block S ₁ having an integration function,
A CCD 62, which is a charge transfer means, is provided in parallel with the sensor array 61 composed of S ₂ , S ₃ , ....
The CCD 62 is configured with the number of stages twice as many as the number of sensor blocks so as to transfer charges corresponding to ON and OFF of the light projecting means for each sensor block, and CK ₁ , C
It is driven by a two-phase clock of K ₂ . The charges transferred by the CCD 62 are transferred to the output stage (FDG: Floating Diffusion).
It is converted into a voltage signal by the Gate) 64 and taken out. Further, the CCD 62 is reset via the MOS gate 63 controlled by the RS signal. SH is a shift gate.

FIG. 9 shows the operation timing of the device of FIG.

The signal IRED is generated by the light projecting means (IRED).
Shows the on / off timing and emits light at a high level
Turns on. The signal SH corresponds to each sensor block S₁,
S₂, S_Three, To transfer charge from CCD to CCD 62
The gate signal that drives the shift gate SH of
Each sensor block outputs 1 pulse of SH by minging
S ₁, S₂, S_Three,… Each sensor is emptied at the same time
-Block S₁, S₂, S _Three, ..., when light emission is off
The accumulation of external light begins. On the other hand, although not shown, R
First of CCD 62 via MOS gate 63 by S signal
Periodization is performed.

At the timing of B, the first CCD 62
Clocking CK₁, CK ₂Stop, and then S
One pulse of H is output and each sensor block S₁, S₂,
S_Three, ... from the accumulated charge from the clock CK of the CCD 62₁so
Transfer every other portion to the driven part. And at a predetermined time
After a lapse of time, CK₁, CK₂Pulse by pulse, CC
The charge in D62 is advanced by one step.

On the other hand, from B to C, the light is turned on,
External light and signal light (reflected light) are applied to each sensor block S ₁ , S
₂ , S ₃ , ... Are accumulated. Then, one pulse of SH is output at the timing of C, and each sensor block S ₁ ,
The accumulated charge is transferred from S ₂ , S ₃ , ... To the clock C of the CCD 62.
Every other part is transferred to the part driven by K ₁ .

In this manner, the charges transferred by the CCD 62 are sequentially read by the output stage (FDG) 64, and the amount of charges accumulated in each sensor block S ₁ , S ₂ , S ₃ , ... Can be detected. it can. When such a multi-division sensor is used, the resolution for detecting the light receiving position is improved as compared with the case where PSD is used.

However, in the device described with reference to FIGS. 8 and 9, the amount of charge output from the CCD 62 is the amount of charge for one cycle of light projection, and since there is no function of synchronous integration, that charge is not present. The amount was small and the S / N ratio was not good. That is, this device had almost no effect in improving the distance measuring ability other than the resolution.

On the other hand, in order to have a synchronous integration function,
It is necessary to provide a plurality of electric circuits as shown in FIG.
Further, even if this electric circuit is not used, if there is no outside light, amplification by signal light integration is possible, but if outside light is large, the amount of signal accumulated in the CCD 62 is determined by the outside light. . That is, in order to prevent the saturation of the CCD 62, the timings of B and C are advanced with respect to A, and the signal component becomes very weak.

Next, FIG. 10 shows a distance measuring device proposed in Japanese Patent Publication No. 5-22843. This device is shown in FIG.
Also, a synchronous integration function is configured on the device in the device described in FIG. 9, and the sensor output is sequentially integrated by the orbiting ring configured by the CCD. Further, it has a so-called skim (SKIM) function for excluding, from the CCD, a direct current signal component equivalent to a pair of on and off light projections.

In the figure, the sensor array 81 is composed of N sensor blocks.
The electric charge stored in the CCD is sent to the 2N-stage linear CCD 83, which is a charge transfer unit, through the N shift gates 82. These sensor array 81 and shift gate 8
2 and the linear CCD 83 are substantially the same as the sensor array 61, the shift gate SH, and the CCD 62 described in FIG.

In the apparatus shown in FIG. 8, CC which is a linear CCD is used.
Electric charges were directly sent from the D62 to the output stage (FDG) 64, but in the apparatus of FIG. 10, the linear CCD 83 is connected to the ring CCD 84 composed of 2N-stage CCDs. The ring CCD 84 has one cycle in synchronization with one cycle of on / off of light projection, the timing of the SH signal is controlled, and the signal charge transferred to each stage by the previous SH signal. Further, the signal charges transferred to each stage by the next SH signal are just added. By this operation, the ring CCD 84 adds the charges while transferring the charges.

The CLR unit 85 is a means for extracting and clearing charges from the ring CCD 84 and the linear CCD 83, and is for initializing the device. Note that this clearing operation is prohibited during charge addition by the ring CCD 84. Reference numeral 87 is a means for non-destructively converting the charge amount into a voltage and reading the voltage.

The SKIM unit 86 turns on the light emission when the charge amount of the light emission off stage, that is, the amount of the external light signal exceeds a predetermined value so that each stage of the ring CCD 84 is not saturated by the addition of charges. This is a means for eliminating a fixed amount of charges from the pair of CCD stages in which the light is turned off so that only the charges due to the signal light are integrated in the continuous addition operation.

By the above operation, the increase of the signal component with respect to the external light component can be achieved. However,
The device shown in FIG. 10 operates at substantially the same timing as the timing shown in FIG.
The transfer clock of D83 and ring CCD 84 is B in FIG.
Most of the time is stopped between C and C, and that time is wasted. Further, since the linear CCD 83 and the ring CCD 84 are stopped at the same timing, there is also a problem that the S / N ratio is significantly reduced due to the occurrence of dark current unevenness between the CCDs. Further, this device has a problem that the transfer clocks of the linear CCD 83 and the ring CCD 84 are relatively complicated.

[0022]

In order to overcome the drawbacks of the conventionally known distance measuring device described above, a device as shown in FIG. 11 has been considered.

This device is the same as the device described in FIG. Transfer clock is complicated 2. Occurrence of uneven dark current 3. It eliminates the drawbacks such as the ineffective use of the period when the transfer clock is stopped, and also has an electronic shutter function (ICG) that controls the amount of signal charge from each sensor block.

The sensor array 91 is composed of a plurality of sensor blocks S ₁ , S ₂ , S ₃ , ..., And the signal charges generated in each sensor block S ₁ , S ₂ , S ₃ ,. Is integrated with. Although the sensor array 91 and the integrating unit 92 are shown separately in this example, they are substantially the same as the sensor array 61 and the sensor array 81 described with reference to FIGS. 8 and 10.

Clear unit 9 driven by ICG signal
Reference numeral 3 denotes a so-called electronic shutter, which has a function of preventing a certain amount of electric charge from the integrating unit 92 to overflow and preventing the overflow of the integrating unit 92, and a function of extracting all electric charges of the integrating unit 92 and initializing the integrating unit 92. .

The signal charge integrated by each integrator 92 is S
The signal is transferred to the storage unit 94 at the timing of the T signal, and the storage unit 9
It is temporarily accumulated and held at 4. Then, the charges held in the storage section 94 are transferred to the linear CCD 96 by the shift gate 95 at the timing of the SH signal. The linear CCD 96 is the same as the linear CCD 83 described in FIG. 10, and is connected to a ring CCD (not shown).

FIG. 12 shows the operation timing of the apparatus shown in FIG.

The signal IRED indicates whether the light projecting means (IRED) is on or off, and the high level is in the on state. An ICG pulse is supplied in correspondence with the on / off timing of the light projecting means, and each integrating unit 92 is cleared (initialized). Then, in the period from the ICG pulse to the next ST pulse, each sensor block S ₁ , S ₂ ,
Only the signal charges generated in S ₃ , ... Are integrated in each integrator 92 and transferred to each accumulator 94. Note that the timing of the ICG pulse moves back and forth according to the brightness of the measurement target, and approaches the timing of the ST pulse as the brightness increases.

As described with reference to the apparatus of FIG. 10, in this apparatus as well, one cycle of turning on and off the light projecting means (IRED) is synchronized with one cycle of the ring CCD (not shown). And
The signal charge integrated while the IRED is off is transferred to each storage unit 94 by the ST pulse a. This is a signal charge due to external light, and is transferred to the linear CCD 96 in the portion driven by the clock CK ₁ by the SH pulse b. At the same time, each storage unit 94 becomes empty.

Next, the signal charge integrated while the IRED is on is transferred to each emptied storage section 94 by the ST pulse c. This is a signal charge due to outside light + signal light. Then, the charge is generated at the timing delayed by one clock from the SH pulse b by the clock CK _1.
By the H pulse d, it is transferred to the linear CCD 96 at an alternate position when the IRED is off.

In this way, the signal charges of IRED off and on which are alternately transferred by the linear CCD 96 are transferred to a ring CCD (not shown) and circulate the ring, as in the case of the device of FIG. Will be added by.

According to this apparatus, since the clock for driving the linear CCD 96 which is the charge transfer means and the ring CCD (not shown) does not need a stop period, the transfer clock is simplified and the clock stop period is not wasted. . Since there is no clock stop period, ring C
The dark currents in the CD and the linear CCD are averaged to eliminate the dark current unevenness. That is, the device of FIG.
By using it instead of SD42, it is possible to perform more accurate distance measurement using the principle of triangulation.

However, in the distance measuring apparatus of FIG. 11, the following noises are accumulated and superposed on the signal generated by actual light projection. 1. Schottky noise in the sensor array 91 due to external light. Noise generated during skim operation 3. Induction noise due to external radio waves

Further, if the signal charge accumulation operation is continued by the distance measuring device of FIG. 11, the following error will be accumulated. 1. The dark current unevenness in the ring CCD and the linear CCD 96, that is, most of the dark current generated in the storage section 94 controlled by the ST pulse is on the IRED off signal. Then, the imbalance of the dark current in the IRED on and off signals is added and amplified by the ring CCD. 2. Error during skimming (error in skimming amount)

Therefore, in the conventional distance measuring apparatus having a lot of noises and errors as described above, not only the accuracy of the distance measuring operation is deteriorated, but in the worst case, the off signal should originally be the on signal. There is a possibility of reverse rotation, and if it reverses, the skim portion described with reference to FIG. 10 may not operate normally, and a measured value with a large distance measurement error may be output as it is. This problem is not so serious if the measurement is performed by projecting light for only one cycle, but for example, considering a long-distance low reflectance measurement object, the detection level of the reflected light is very small, Ring CCD
Since the addition processing by is indispensable, the problem becomes serious.

Therefore, the object of the present invention is, for example, the ring C.
In a distance measuring device capable of skimming with a CD, it is possible to prevent noise or an error from being generated and a measured value with a large distance measuring error to be output as it is, and incorrect distance measuring information to be transmitted to a measurer. It is to provide a possible distance measuring device.

[0037]

In order to solve the above-mentioned problems, the invention of claim 1 spot-projects an object to be measured whose distance is to be measured, and receives the reflected light to perform triangulation. A distance device, a light projecting means for projecting light onto the measurement target, and a sensor array in which a plurality of sensors for receiving and photoelectrically converting reflected light from the measurement target are arranged,
In a distance measuring device, comprising at least a part of charge transfer means for transferring the output charge from each sensor of the sensor array, the output level of the charge transfer means corresponding to when the light projecting means is turned on. And a comparison means for comparing the output level of the charge transfer means corresponding to the time when the light projecting means is turned off, and the result of comparison by the comparison means,
When the output level of the charge transfer unit corresponding to the turning off of the light projecting unit is higher than the output level of the charge transfer unit corresponding to the turning on of the light projecting unit, it is determined that the ranging information is invalid And a determination means.

In the invention of claim 2, the output of the charge transfer means is converted into a digital signal and supplied to the comparison means.

Further, in the invention of claim 3, the comparison means outputs the output of the charge transfer means corresponding to when the light projecting means is turned on when the output level of the charge transfer means corresponding to when the light projecting means is turned off. If greater than the level,
The comparison is repeated until the number of times reaches a predetermined number.

Further, in the invention of claim 4, when the invalidity determining means determines that the distance measuring information is invalid, it sets the distance measuring information to infinite information.

More specifically, the present invention provides an IRED.
When the output level of the corresponding CCD (for example, the charge amount level or voltage level) when the light projecting means such as is off is larger than the output level of the corresponding CCD when it is off, the true signal component is small and the reverse Since the noise and error components are predominant, it is determined that normal distance measurement calculation is impossible. The reason for making such a determination is that in the normal state, the output of the CCD when the IRED is on is naturally larger than the output when it is off by the signal component. In other words, this principle does not hold if there are too many noise or error components.

In one aspect of the present invention, when it is determined that distance measurement is impossible, it is determined that the distance measurement target is at a very long distance.
For example, the shooting lens of a camera incorporating this distance measuring device is set to an infinite position, or even if the object to be measured is at a finite position, it is determined that distance measurement is impossible due to too many noise and error components. Then, the distance measurement operation is performed again.

Normally, in a system in which a signal component and a noise or error component coexist, it is impossible to distinguish between the two. However, in the present invention, the sensor output when the IREDs stored separately are different from the sensor output. By using the sensor output when it is off, it is possible to appropriately determine that the distance measuring operation cannot be performed because the noise and error components are dominant.

[0044]

According to the present invention, the output levels of the charge transfer means when the light projecting means is turned on and off are compared, and as a result of this comparison, the output level of the charge transfer means corresponding to the off state corresponds to the on state. When the output level of the charge transfer means is larger than the output level of the charge transfer means, the distance measurement information is determined to be invalid. It is possible to inform the measurer that the distance information has a large distance measurement error.

According to the second aspect of the present invention, the output of the charge transfer means is converted into a digital signal and supplied to the comparison means, so that accurate and quick comparison can be performed.

According to the third aspect of the present invention, by repeating the comparison until the predetermined number of times, it is possible to extract and output only the distance measurement information with less noise or error.

According to the fourth aspect of the present invention, by setting the distance measurement information to infinite information, appropriate distance measurement information of a distance measurement target which is likely to be at a long distance when there are many noises and errors is obtained. Obtainable. Therefore, it is possible to optimally drive the taking lens of the camera incorporating this distance measuring device.

[0048]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below with reference to FIGS.

FIG. 1 shows a block diagram of a distance measuring device according to an embodiment of the present invention.

In FIG. 1, the sensor array 10 comprises sensor blocks as shown in FIG. The signal charges photoelectrically converted in each sensor block are integrated by an ICG pulse and an ST pulse and an accumulation unit 11
Is integrated and accumulated at. The shift gate 12 uses a SH pulse to linearly charge the charge in the integration unit and the storage unit 11.
Shift to D13. Two-phase transfer clocks CK ₁ and CK ₂
The linear CCD 13 driven by is coupled to a ring CCD 14 which also constitutes charge transfer means. The ring CCD 14 driven by the transfer clock CK _A has one
The cycle of the circumference is synchronized with one cycle of turning on / off the light,
Further, the timings of the SH pulse signal and the transfer clock CK _A are controlled, and the signal charge transferred to each stage by the previous SH signal is just added to the signal charge transferred to each stage by the next SH signal. It is like this. By this operation, the ring CCD 14 adds the charges while transferring the charges.

The CLR section 16 is a means for removing charges from the ring CCD 14 and the linear CCD 13 to clear them, and initializes the device. Note that this clearing operation is prohibited during charge addition by the ring CCD 14. Reference numeral 17 is a means for non-destructively converting the charge amount into a voltage and reading the voltage.

The SKIM section 15 turns on the light emission when the charge amount of the light emitting off stage, that is, the amount of the external light signal exceeds a predetermined value so that each stage of the ring CCD 14 is not saturated by the addition of charges. This is a means for eliminating a fixed amount of charges from the pair of CCD stages in which the light is turned off so that only the charges due to the signal light are integrated in the continuous addition operation. This skimming operation can improve the S / N ratio of distance measurement.

The control circuit 18 is a circuit for controlling the entire distance measuring device shown in FIG. 1, and generates various control signals. That is, the control circuit 18 sends the ST signal and the ICG signal to the integrating section and the accumulating section 11, and
Send SH signal to shift gate 12
The transfer clocks CK ₁ and CK ₂ are sent to the CD 13, and the transfer clock CK _A is sent to the ring CCD 14. Also,
The control circuit 18 detects the output voltage of the output unit 17, outputs a signal for controlling the skim unit 15, and outputs a signal IRED to the operational amplifier 21 to output IRED.
19 is made to blink.

Reference numeral 19 is an infrared light emitting diode (IRED) which is a light projecting means, 20 is a resistor for current detection, 21 is an operational amplifier, and 22 is a transistor for driving the IRED 19.

Next, the structure of the control circuit 18 shown in FIG. 1 will be described with reference to FIG. In FIG. 2, A
The / D converter 30 converts the analog output voltage of the output unit 17 of FIG. 1 into a digital value. Latch circuits 31, 32
Latches the digital output value of the A / D converter 30. The comparison circuit 33, which is comparison means, compares the outputs of the two latch circuits 31 and 32 and outputs the comparison result to the microcomputer 34, which is invalidity determination means.

The inverting circuit 35 is provided in the microcomputer 3
Transfer clock CK of the ring CCD 14 output from 4
_{The A} signal is input, and its inverted signal is supplied to the latch input of the latch circuit 32. Further, the latch input of the latch circuit 31, a transfer clock CK _A signal is supplied directly. Note that 36 and 37 are switches for controlling the microcomputer 34.

The microcomputer 34 includes a comparison circuit 3
3, the output signal IVD and the output signal of the A / D converter 30 are supplied, and as described above, the ST signal, the ICG signal, the SH signal, the transfer clocks CK ₁ and CK ₂ , the transfer clock CK _A , the IRED signal, And a control signal for the A / D converter 30.

The operation of the distance measuring device of the present embodiment having the above-described structure will be described with reference to FIGS.

As described above, in the ring CCD 14, the I from the sensor array 10 is generated by the transfer clock CK _A.
The signal outputs when the RED 19 is on and off are transferred alternately. Therefore, the output voltage corresponding to the output voltage is output from the output unit 17 in time series. FIG. 3A shows a signal waveform from the output unit 17 when there is no influence of noise or error. In FIG. 3A, the ON portion is I
When the projection of RED19 is on, the OFF part is IRED1
9 corresponds to the case where the light projection is off. Thus, with a normal output waveform, the OFF section is always at the ground level, and the level of the OFF section does not exceed the level of the ON section.

The output signal voltage from the output section 17 is A / D
A / D for each pulse of the transfer clock CK _{A in} the converter 30
It is converted and supplied to the latch circuits 31 and 32. At this time, the output unit 17 alternately outputs signals corresponding to ON / OFF of the IRED 19 in time series.
The A / D conversion value when 9 is on is supplied to the latch circuit 31 by the transfer clock CK _A , and the A / D conversion value when IRED 19 is off
/ D converted value is supplied to the latch circuit 32 in response to the inverted signal of the transfer clock CK _A.

Then, the comparison circuit 33 includes the latch circuit 3
The latch circuit 3 compares the time-series latch outputs of 1 and 32.
When the output of 2 is larger than the output of the latch circuit 31,
The high level IVD signal is supplied to the microcomputer 34.

FIG. 3B shows the output waveform of the output section 17 when the noise and the error are large and the output signal is relatively small. In FIG. 3B, the output level of the sixth ON section (corresponding to the sixth ON of the IRED 19) is lower than the output level of the OFF section immediately after that. In this case, the comparison circuit 33 outputs the IVD signal which becomes high level at the timing shown in FIG. 3C, and supplies it to the microcomputer 34. Then, the microcomputer 34 uses such a high level I
When the VD signal is received, the distance measurement information obtained by the distance measurement calculation is ignored.

Next, the control operation by the microcomputer 34 in this embodiment will be described with reference to the flow charts of FIGS.

FIG. 4 is a flow chart for moving the taking lens of the camera incorporating the distance measuring apparatus of this embodiment to an infinite position when the IVD signal becomes high level.

First, the shutter button (not shown) of the camera
When the switch 36 is turned on in the first stroke (step S1), the IRED signal is output to start the blinking operation of the IRED 19 (step S2). Then, the timer operation of the timer circuit in the microcomputer 34 is started (step S3). Further, it is judged whether or not the above-mentioned high level IVD signal is generated (step S4). If not generated, it is determined whether or not the blinking operation of the IRED 19 is continued and the timer circuit counts up (step S5). , The blinking operation of the IRED 19 is terminated (step S6).

Then, the microcomputer 34 uses the A / A of the sensor array 10 stored in the internal RAM.
Distance calculation is performed based on the D-converted output value to calculate distance measurement information (step S7), and the driving amount of the photographing lens corresponding to this distance measurement information is calculated (step S8).

Next, when the switch 37 is turned on by the second stroke of the shutter button (not shown) (step S
9), the microcomputer 34 controls a drive circuit (not shown) to drive the taking lens based on the drive amount obtained in step S8 (step S10).

On the other hand, in step S4, as shown in FIG.
When a high-level IVD signal such as is generated, the microcomputer 34 terminates the blinking operation of the IRED 19 (step S11) and sets infinite distance information as distance measurement information (step S12). Then, the driving amount of the photographing lens is calculated corresponding to the infinite information (step S8). Then, when the switch 37 is turned on by the second stroke of the shutter button (not shown) (step S9), the drive circuit (not shown) is controlled to drive the taking lens according to the drive amount obtained in step S8 ( Step S10). Since the camera operation thereafter is well known, its explanation is omitted.

FIG. 5 shows that when the IVD signal becomes high level, the distance measuring operation is repeated a predetermined number of times and
6 is a flowchart for moving a photographing lens of a camera incorporating the distance measuring apparatus of the present embodiment to an infinite position when a signal is generated.

First, the shutter button (not shown) of the camera
When the switch 36 is turned on in the first stroke (step S21), the variable N is set to 0 (initialized) (step S22), and then the IRED signal is output to output the IRED19.
The blinking operation of is started (step S23). And
The timer operation of the timer circuit in the microcomputer 34 is started (step S24). Further, it is judged whether or not the above-mentioned high-level IVD signal is generated (step S25).
The blinking operation of is continued and the blinking operation of the IRED 19 is ended (step S27) depending on whether or not the timer circuit has counted up (step S26).

Then, the microcomputer 34 uses the A / A of the sensor array 10 stored in the internal RAM.
Distance calculation is performed based on the D conversion output value to calculate distance measurement information (step S28), and the drive amount of the photographing lens corresponding to this distance measurement information is calculated (step S2).
9).

Next, when the switch 37 is turned on by the second stroke of the shutter button (not shown) (step S3).
0), the microcomputer 34 controls a drive circuit (not shown) to drive the taking lens based on the drive amount obtained in step S8 (step S31).

On the other hand, when a high-level IVD signal is generated in step S25, the variable N is first incremented by 1 (step S32), and it is determined whether the value of the variable N at that time is a predetermined value K or more (step S32). S33). As a result, if the value of the variable N is smaller than the predetermined value K, then IR
The blinking operation of the ED 19 is restarted (step S23), and the distance measuring operation is repeated again. If the value of the variable N is greater than or equal to the predetermined value K, the microcomputer 34 determines that the IRED1
The blinking operation of 9 is terminated (step S3
4), infinite distance information is set as distance measurement information (step S35). Then, the drive amount of the photographing lens is calculated in accordance with this infinite information (step S29). Then, when the switch 37 is turned on by the second stroke of the shutter button (not shown) (step S30), the drive circuit (not shown) is controlled to drive the taking lens according to the drive amount obtained in step S29 ( Step S31).

As described above, in the distance measuring apparatus of this embodiment, the magnitudes of the signal levels corresponding to ON and OFF of the IRED 19 are compared, and when the OFF signal becomes larger than the ON signal, the signal is allowed. By determining that noise or error exceeding the range has occurred, it is possible to inform the operator that the distance measurement information is invalid, so the measured value with a large distance measurement error is output as is, and in the worst case Incorrect measurement information is not transmitted to the measurer.

Further, in a camera incorporating this distance measuring device, by driving the photographing lens to a position corresponding to an infinite distance, the subject can be photographed most appropriately when there are many noises and errors.

[0076]

According to the present invention, it is possible to properly judge a situation in which a normal distance measuring operation is difficult due to a large amount of noise and error components, without adding an additional device to the conventional distance measuring device.
It becomes possible to prevent erroneous distance measurement when the distance measurement target is at a long distance and its reflectance is low.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a distance measuring device according to an embodiment of the present invention.

FIG. 2 is a block diagram of a control circuit 18 shown in FIG.

FIG. 3 is a diagram showing an output waveform and an IVD signal of an output unit 17 corresponding to on / off of projection of IRED in the apparatus of FIG.

FIG. 4 is a flowchart showing an operation of a camera incorporating the distance measuring device according to the embodiment of the present invention.

FIG. 5 is another flowchart showing the operation of the camera incorporating the distance measuring device according to the embodiment of the present invention.

FIG. 6 is a schematic diagram showing the principle of measurement by a conventional distance measuring device.

7 is a circuit diagram showing a signal processing circuit of the apparatus of FIG.

FIG. 8 is a schematic view showing a main part of another conventional distance measuring device.

9 is a timing chart showing the operation timing of the device of FIG.

FIG. 10 is a schematic view showing a main part of still another conventional distance measuring device.

11 is a schematic view showing a main part of an apparatus obtained by improving the apparatus of FIG.

12 is a timing chart showing the operation timing of the device of FIG.

[Explanation of symbols]

 10 sensor array 11 integrating part and accumulating part 12 shift gate 13 linear CCD (charge transfer means) 14 ring CCD (charge transfer means) 15 skim part 16 clear part 17 output part 18 control circuit 19 IRED (light projecting means) 33 comparison circuit (Comparison means) 34 Microcomputer (invalidity determination means)

Claims (4)

[Claims] 1. A distance measuring device for projecting a spot onto a measuring object whose distance is to be measured and receiving reflected light thereof to perform a trigonometric distance measurement, and a light projecting means for projecting light onto the measuring object. A sensor array in which a plurality of sensors that receive reflected light from the measurement target and perform photoelectric conversion are arranged, and a charge transfer in which at least a part that transfers the output charge from each sensor of the sensor array is coupled in a ring shape. A distance measuring device comprising means for comparing the output level of the charge transfer means corresponding to when the light projecting means is turned on and an output level of the charge transfer means corresponding to when the light projecting means is off, As a result of the comparison by the comparison means, the output level of the charge transfer means corresponding to the turning off of the light projecting means is higher than the output level of the charge transfer means corresponding to the turning on of the light projecting means. When, the distance measuring apparatus characterized by further comprising a disabling determination means for distance measurement information is determined to be invalid. 2. The distance measuring device according to claim 1, wherein the output of the charge transfer means is converted into a digital signal and supplied to the comparison means. 3. The comparing means, when the output level of the charge transfer means corresponding to when the light projecting means is off is higher than the output level of the charge transfer means corresponding to when the light projecting means is on, The distance measuring device according to claim 1, wherein the comparison is repeated until a predetermined number of times is reached. 4. The invalidity determination means sets the distance measurement information to infinite information when it determines that the distance measurement information is invalid. Ranging device.