JP3507207B2 - 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 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. 5 is well known as a distance measuring device for projecting a spot on a measuring object whose distance is desired to be measured and receiving reflected light thereof for triangulation. 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. 6 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.
Entered in. 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. 5 and 6 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.

FIG. 7 shows a device using a sensor array instead 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. 8 shows the operation timing of the device shown in 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, S₃, 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, S₃,… Each sensor is emptied at the same time
-Block S₁, S₂, S ₃, ..., 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,
S₃, ... 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. 7 and 8, 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. 9 shows a distance measuring device proposed in Japanese Patent Publication No. 5-22843. This device has a synchronous integration function on the device in addition to the devices described with reference to FIGS. 7 and 8, and sequentially integrates the sensor output by a circular ring composed of a 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 of FIG. 7, 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. 9, the linear CCD 83 has a 2N-stage C
It is connected to a ring CCD 84 composed of a CD.
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 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 an output unit that nondestructively converts the charge amount into a voltage and reads 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. 9 operates at substantially the same timing as the timing shown in FIG.
The transfer clocks of 83 and the ring CCD 84 are almost stopped from B to C in FIG. 8, and the 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 devices described above, a device as shown in FIG. 10 has been considered.

This device is the same as the device described in FIG. Transfer clock is complicated 2. Occurrence of dark current unevenness 3. The present invention solves the drawback that the period during which the transfer clock is stopped is not effectively used, and further has an electronic shutter function (ICG) for controlling 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. In this example, the sensor array 91 and the integrating unit 92 are shown separately, but these are substantially the same as the sensor array 61 and the sensor array 81 described with reference to FIGS. 7 and 9.

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. 9, and is connected to a ring CCD (not shown).

FIG. 11 shows the operation timing of the device of 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.

As described with reference to the apparatus of FIG. 9, 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.

However, the apparatus of FIG. 10 has the following problems.

In the device of FIG. 10, in order to prevent the amount of electric charges generated from the sensor blocks S ₁ , S ₂ , S ₃ , ... A driven clear unit 93 is provided, and the integration time in the integration unit 92 is controlled so as to be short at high brightness and long at low brightness. The integration time at this time is controlled by utilizing the determination result of a skim determination unit (not shown) that performs a skim operation in the ring CCD, whereby a determination unit dedicated to the ICG signal is provided. It does not have to be configured. Specifically, when the output potential of the output means 87 becomes equal to or lower than the skim determination potential in one accumulation operation performed first after the ring CCD is reset, the integration time is shortened to be equal to or lower than the skim determination potential. If not, the integration time is not changed.

FIG. 12 shows the relationship between the skim determination potential and the amount of skim in the apparatus of FIG. In FIG. 12, the reference potential indicates the potential level when the ring CCD is reset (that is, when the charges are not accumulated in the ring CCD). CCD
Since the potential decreases when electric charges are accumulated, the skim determination potential is set to a level lower than the reference potential. The skim amount skipped by the skim portion 86 in FIG. 9 has a certain error due to the variation of the potential of the skim portion 86 itself, and the skim determination potential also has an error. It is set to a level slightly smaller than the skim determination potential in order to prevent the signal of the ring CCD 84 from disappearing during the skim operation.

FIG. 12A shows the case where the brightness is relatively low. In this case, the voltage drop amount V _Q11 due to one accumulation operation in the ring CCD is smaller than the one skim amount. Further, the output potential of the output means 87 does not become lower than the skim determination potential due to the voltage drop due to the first accumulation operation performed after the ring CCD is reset.
The timing of the signals remains set to perform the maximum time integration operation and is unchanged. Then, when the output potential of the output means 87 becomes equal to or lower than the skim determination potential due to the next accumulation operation in the ring CCD, a certain amount of electric charges are extracted by the skim portion 86, and the output potential of the output means 87 is as shown in FIG.
The level becomes V ₁₁ shown in 2 (a).

FIG. 12B shows the case where the brightness is relatively high. In this case, the voltage drop amount V _Q12 by one accumulation operation in the ring CCD is larger than the one skim amount. Further, the output potential of the output means 87 does not become lower than the skim determination potential due to the voltage drop due to the first accumulation operation performed after the ring CCD is reset.
The timing of the signals remains set to perform the maximum time integration operation and is unchanged. Then, the output potential of the output means 87 becomes equal to or lower than the skim determination voltage by the next accumulation operation in the ring CCD, and the skim portion 86 extracts a certain amount of electric charge.

However, in this case, the voltage drop amount V
_{Since Q12} is larger than the amount of skim at one time, the output means 8
As shown in FIG. 12B, the output potential of No. 7 may reach the level of V _{12 which} is lower than the skim determination potential. Further, even if the output potential of the output means 87 after skimming does not fall to the level below the skim determination potential, if the storage operation is further continued, this output potential not only falls to the level below the skim determination potential, but also the output potential Will eventually reach the saturation level.

That is, in the above-described apparatus of FIG. 10, the timing of the ICG signal is set based on the skim determination result of the skim portion 86 when the first storage operation after resetting the ring CCD is performed. Because it is configured
Although it is not necessary to separately provide a means for controlling the timing of the ICG signal, when the brightness is relatively high, the output means 87 is provided.
However, there is a problem in that the output potential of is saturated and accurate distance measurement cannot be performed.

Therefore, an object of the present invention is to provide a ring-ranging device in which the timing of a reset pulse such as an ICG signal for extracting an electric charge from the integrator is controlled based on the output potential of the ring CCD even when the brightness is relatively high. An object of the present invention is to provide a distance measuring device capable of performing accurate distance measurement without saturating the output potential of the CCD.

[0041]

In order to solve the above-mentioned problems, according to the invention of claim 1, spot projection is performed on a measuring object whose distance is desired to be measured, and the reflected light is received to perform triangulation. A distance device, a light projecting unit for projecting light onto the measurement target, a sensor array in which a plurality of sensors for receiving and photoelectrically converting reflected light from the measurement target are arranged, and each of the sensor arrays Integrating means for integrating the output charge from the sensor, gate means for extracting charge from the integrating means, reset pulse generating means for supplying a reset pulse to the gate means, and at least a part of which are coupled in a ring shape, A charge transfer unit that has a ring unit that sequentially transfers charges and transfers the charges integrated by the integration unit, and a switch that removes a certain amount of charges from the charges transferred by the ring unit. In the range finder including the moving means, the potential of the ring portion is not determined by the potential of the ring portion when one accumulation operation is performed, and the potential of the ring portion is determined when the charge is accumulated for a predetermined number of times or more. The sensor array obtained by operating the skim means every time the charge is accumulated a plurality of times or more and storing the charge in the first period in the sensor array when the potential becomes equal to or lower than a predetermined determination potential. Each sensor of the sensor array obtained by sequentially transferring the first output charge from each of the sensors in the ring portion and accumulating charges in the second period after the end of the first period in the sensor array. The second output charge from the first ring at the ring portion.
Therefore, the potential of the ring portion is not determined based on the potential of the ring portion when one accumulation operation is performed, and the potential of the ring portion is determined to be a predetermined value during a plurality of predetermined charge accumulations. The timing of the reset pulse generated by the reset pulse generating means is controlled so that the integration time in the integration section is shortened only when the charge is accumulated for a predetermined number of times when the potential becomes equal to or lower than the determination potential. Control means is further provided.

Further, in the invention of claim 2, the control means compares the detection means for detecting the electric potential of the ring portion with the electric potential of the ring portion detected by the detection means and the judgment electric potential. Means, a skim command means for outputting an operation command to the skim means based on the comparison result by the comparison means, and a timing change of the reset pulse generated by the reset pulse generation means based on the comparison result by the comparison means. And reset change command means for commanding.

Further, in the invention of claim 3, the potential difference between the judgment potential and the reference potential when no charge is accumulated in the ring portion corresponds to the constant amount of charge removed by the skim means. Greater than voltage.

Further, in the invention of claim 4, the control means sets the integration time in the integrating part when the potential of the ring part is equal to or less than the judgment potential when the charges are accumulated a plurality of times. , The potential change due to one-time charge accumulation in the ring portion is controlled to be equal to or lower than the voltage corresponding to the constant amount of charges removed by the skim means.

[0045]

According to the first and second aspects of the present invention, the reset pulse timing is controlled so that the integration time in the integration section is shortened based on the potential of the ring section when the charges are accumulated a plurality of times. As a result, even if the potential change amount (voltage drop amount) of the ring portion due to one charge accumulation is relatively high and the amount of change in the ring portion is larger than the skim amount, the charge of the ring portion can be surely secured by the plurality of charge accumulations. In this case, the potential change amount of the ring portion due to charge accumulation from the next time decreases, and the output potential almost never reaches the saturation level even if the charge accumulation continues. . Further, since the operation control of the skim means and the control of the reset pulse generation means are performed by one control means, it is not necessary to provide separate control means for each, so that the device configuration can be simplified.

According to the third aspect of the invention, since the potential difference between the determination potential and the reference potential is larger than the voltage corresponding to a certain amount of charges removed by the skim means, the signal of the ring portion disappears during the skimming operation. Can be prevented.

According to the invention of claim 4, the charge accumulation is controlled by controlling the potential change due to the charge accumulation of the ring portion once to be equal to or lower than the voltage corresponding to the constant amount of charges removed by the skim means. It is possible to reliably prevent the output potential from reaching the saturation level when continued.

[0048]

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

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

The sensor array 11 is composed of N sensor blocks as shown in FIG. 7 and FIG. 10, and the signal charges photoelectrically converted by each sensor block are integrated by the integrator 12. Each integration unit 12 is provided with an ICG gate unit 13 driven by an ICG pulse.

Storage unit 1 driven by signals ST and SH
4 are arranged in parallel with the sensor array 11, and the output end of the storage section 14 is connected to the 2N-stage linear CCD 15 which is the first charge transfer section of the charge transfer means. Further, the linear CCD 15 is coupled to a 2N-stage ring CCD 16 which is a second charge transfer section of the charge transfer means.
Each of the linear CCD 15 and the ring CCD 16 is composed of a two-phase CCD driven by a two-phase clock. Each stage may be composed of a three-phase CCD, a four-phase CCD, or the like. Sensor array 11, integrator 12, I
The CG gate unit 13, the storage unit 14, the linear CCD 15, and the ring CCD 16 are the same as those described with reference to FIGS. 9 and 10.

The clear gate section 17, which is a skim means provided in the ring CCD 16, carries out an operation of extracting a certain amount of charge from the corresponding CCD of the ring CCD 16. The voltage buffer circuit 18, which is the detection means, is the ring CCD 1
A voltage corresponding to the amount of charge accumulated in the corresponding CCD on 6 is generated. The skim determination unit 19 which is a comparison unit compares the output voltage of the voltage buffer circuit 18 with the skim determination voltage and outputs a determination signal.

The control circuit 20, which is the skim command means and the reset change command means, uses the shift timing signals (ST, SH), the linear CCD 15 and the ring CC.
The transfer clock signal of D16 is generated and output, and the skim determination signal is input from the skim determination unit 19,
In response to this, the control signal of the clear gate unit 17 is output, or the control signal of the reset pulse generating circuit 21 which is the reset pulse generating means for generating the ICG pulse is output. In FIG. 1, the voltage buffer circuit 18 serving as a detection unit, the skim determination unit 19 serving as a comparison unit, the skim command unit, and the control circuit 20 serving as a reset change command unit constitute a control unit.

With the above-described structure, the range finder according to the present embodiment skips the voltage output from the voltage buffer circuit 18 corresponding to the accumulated charge amount of the ring CCD 16 before the full-scale signal accumulation operation in the ring CCD 16. When the determination is made and the potential level is a level that requires a skimming operation as described below, the control circuit 20 changes the reset timing of the ICG gate 13 so as not to overflow the integration time of the integration unit 12. Is configured to control.

FIG. 2 shows a principle diagram of this embodiment corresponding to FIG.

In this embodiment, the ICG control of the integrator 12 is performed based on the result of the skim determination of the output voltage of the ring CCD 16 after the storage operation is performed twice after the reset of the ring CCD 16. In the present embodiment, the ring CC
The output voltage after two accumulation operations after the reset of D16 was used, but due to the magnitude relationship between the skim amount and the skim determination potential,
You may use the output voltage after the accumulation operation of three times or more.

FIG. 2A shows the case where the brightness is relatively high. In this case, the voltage drop amount V _Q1 due to one accumulation operation in the ring CCD 16 is larger than the one skim amount. In the present embodiment, the first 1 after the ring CCD 16 is reset.
When the second accumulation operation is performed, the skim determination is not performed, and the second accumulation operation is subsequently performed. Then, the output potential of the voltage buffer circuit 18 is lower than the skim determination potential. Therefore, the clear gate unit 17 performs skimming to set the potential level of the ring CCD 16 to V _1, and the reset timing of the ICG pulse is changed based on the skim determination result. In this embodiment, the integration time of the integration unit 12 is reduced to 1/2 by changing the reset timing.
Therefore, the accumulated charge amount in the ring CCD 16 from the next time onward becomes V _Q1 / 2.

As described above, in this embodiment, the ring CCD is used.
When the potential of the ring CCD 16 when the charge is stored twice after the reset of 16 is less than the skim determination potential, the reset pulse timing is set so that the integration time in the integration unit 12 becomes 1/2. The output voltage of the voltage buffer circuit 18 is never saturated because the charge storage amount in the subsequent one time is reduced to V _Q1 / 2 and the skimming operation is performed thereafter. Will be able to hold.

FIG. 2B shows a case where the brightness is medium. In this case, the voltage drop amount V _Q2 by one accumulation operation in the ring CCD 16 is slightly smaller than the one skim amount. Then, by the second accumulation operation, the output potential of the voltage buffer circuit 18 becomes lower than the skim determination potential. Therefore, the clear gate unit 17 performs skimming to set the potential level of the ring CCD 16 to V _2, and the reset timing of the ICG pulse should be changed so that the integration time of the integrating unit 12 becomes 1/2 based on the skim determination result. Done. Therefore, the accumulated charge amount in the ring CCD 16 from the next time onward becomes V _Q2 / 2.

Also in this case, the potential of the ring CCD 16 when the charge is stored twice after the reset of the ring CCD 16 is compared with the skim determination potential, and the integration time in the integration unit 12 becomes 1/2. Since the timing of the reset pulse is controlled as described above, the charge accumulation amount in one subsequent time is V _Q2 /
The output voltage of the voltage buffer circuit 18 can be maintained at a level at which the output voltage of the voltage buffer circuit 18 is never saturated because the output voltage of the voltage buffer circuit 18 is reduced to 2 and the skimming operation is performed thereafter.

FIG. 2C shows a case where the brightness is relatively low. In this case, the voltage drop amount V _Q3 by the one-time accumulation operation in the ring CCD 16 is considerably smaller than the one-time skim amount. The output potential of the voltage buffer circuit 18 remains higher than the skim determination potential even by the second accumulation operation, and the voltage buffer circuit 1 is generated by the third accumulation operation.
The output potential of 8 becomes lower than the skim determination potential. Therefore, after the third accumulation operation, the clear gate unit 17 performs skimming to set the potential level of the ring CCD 16 to V ₃ .
At this time, the reset timing of the ICG pulse is not changed. Therefore, the accumulated charge amount in the ring CCD 16 from the next time remains V _Q3 .

In this case, the potential of the ring CCD 16 when the charge is stored twice after the reset of the ring CCD 16 and the skim determination potential are compared, and the reset pulse of the reset pulse is changed so that the integration time in the integration unit 12 does not change. Since the timing is controlled, the charge storage amount in the subsequent one time remains V _Q3 and remains unchanged. However, the output voltage of the voltage buffer circuit 18 is never because the brightness is relatively low and the voltage drop amount V _Q3 by one accumulation operation is considerably smaller than the one skimming operation and the skimming operation is performed thereafter. It will be possible to maintain a level that does not saturate.

Next, the operation timing of the distance measuring apparatus of this embodiment will be described with reference to FIG.

FIG. 3A is a timing chart when the integration time in the integration unit 12 is maximum. Signal IRED
Shows ON and OFF of an infrared light emitting diode (IRED) which is a light projecting means, and a high level is an ON state. The ICG pulse is a signal for controlling the reset timing of the ICG gate 13, and when it is at a high level, the charge is extracted from the integrating unit 12. The ST pulse is a shift pulse to the storage unit 14, and when the ST pulse becomes high level, the electric charge is shifted from the integration unit 12 to the storage unit 14. The SH pulse is a shift pulse to the linear CCD 15, and when the SH pulse is at a high level, the charge is transferred from the accumulator 14 to the linear CC.
Shift to D15.

First, shortly after the signal IRED is turned off, the ICG gate 13 is reset by the ICG pulse a. Thereafter, the ST pulse b immediately before the signal IRED turns on after the period T ₁ shifts the signal charge (external light component) corresponding to the period when the IRED is off from the integrating unit 12 to the accumulating unit 14, and further the signal IRED. Is shifted from the storage unit 14 to the linear CCD 15 by the SH pulse c immediately before turning off.

Then, shortly after the signal IRED is turned on, the ICG pulse d resets the ICG gate 13. After that, the signal charge (external light + signal component) corresponding to the period in which the IRED is on is generated by the ST pulse e immediately before the signal IRED is turned off after the period T ₁ and the integrating unit 1
2 is shifted to the storage unit 14, and further, the SH pulse f immediately after the signal IRED is turned off is shifted from the storage unit 14 to the linear CCD 15.

FIG. 3B is a timing chart when the integration time in the integration unit 12 is half that of FIG. 3A. In this case, the timings of the ST pulse and the SH pulse other than the ICG reset pulse are the same as those in FIG. 3A, and the ICG reset pulse becomes the high level at almost intermediate times between the ON and OFF periods of the signal IRED. As a result, the integration time in the integration unit 12 is as shown in FIG.
It is set to be 1/2 of (a).

First, the ICG gate 13 is reset by the ICG pulse a shortly after 1/2 of the off period of the signal IRED has elapsed. After that, the signal charge (external light component) corresponding to the period when the IRED is off is shifted from the integrating unit 12 to the accumulating unit 14 by the ST pulse b immediately before the signal IRED turns on after the period T _1/2. The SH pulse c immediately before the signal IRED is turned off causes the storage section 14 to shift to the linear CCD 15.

Next, the ICG gate 13 is reset by the ICG pulse d shortly after 1/2 of the ON period of the signal IRED has elapsed. After this, by the ST pulse e immediately before the signal IRED is turned off after the period T _1/2, the signal charge (external light +
Signal component) is shifted from the integration unit 12 to the storage unit 14,
Further, the SH pulse f immediately after the signal IRED is turned off
Is shifted from the storage unit 14 to the linear CCD 15.

As described above, in this embodiment, the integration time in the integration unit 12 is controlled by controlling the timing of the ICG pulse, and the ring CCD 16 by charge accumulation once is performed.
It adjusts the amount of potential change.

Next, the operation of the distance measuring apparatus of this embodiment will be described with reference to FIG.
A description will be given based on the flowchart.

First, when the start signal START is applied to the control circuit 20 (step S1), the control circuit 20 controls the reset pulse generation circuit 21 to the ICG gate unit 13, and the I pulse is generated at the timing of FIG.
A CG pulse, an ST pulse and an SH pulse are generated to set the integration time of the integrator 12 to T ₁ (step S
2).

Next, the ring CCD 16 is reset to 1
The second ring transfer is performed (step S3), and then the second ring transfer is performed (step S4). Whether the output voltage of the voltage buffer circuit 18 at the time when the second ring transfer is completed is higher than the skim determination voltage (whether the output potential is lower than the skim determination potential).
(Step S5), and when the output voltage is larger than the skim determination voltage, the control circuit 20 controls the reset pulse generation circuit 21 to generate the ICG pulse, ST pulse and SH pulse at the timing of FIG. 3 (b). Then, the integration time of the integration unit 12 is set to T _1/2 (step S6), and the accumulation operation in the ring CCD 16 is continued (step S7).

When the output voltage is smaller than the skim determination voltage, the timing of the ICG pulse, ST pulse and SH pulse is not changed and the accumulation operation in the ring CCD 16 is continued (step S7).

As described above, in this embodiment, 2
Based on the potential of the ring CCD 16 when the charge is accumulated twice, the integration time in the integration unit 12 is halved I
By controlling the timing of the CG reset pulse, even if the amount of change in the potential of the ring CCD 16 due to one charge accumulation is relatively high and the amount of change in the potential of the ring CCD 16 is larger than the skim amount, the ring CCD 16 is charged twice.
Since the potential of the ring CCD 1 is certainly lower than the skim determination potential, even in such a case, the ring CCD 1 by the charge accumulation from the next time
Since the potential change amount of 6 is reduced to 1/2, the output potential hardly reaches the saturation level even if the charge accumulation is continued. Particularly, in this embodiment, the ring CC
Electric potential change (V _Q1 / 2, V
_{By controlling Q2} / 2) so that it is below the voltage corresponding to the amount of skim removed by the clear gate section 17, it is possible to prevent the output potential from reaching the saturation level when the charge accumulation is continued. can do.

Further, in the present embodiment, the operation control of the clear gate section 17 which is the skim means and the control of the reset pulse generation circuit 21 are performed by one control means, so that the skim means and the reset pulse generation means respectively. Since it is not necessary to provide another control means, the device configuration can be simplified.

Further, in the present embodiment, since the potential difference between the skim determination potential and the reference potential is larger than the voltage corresponding to the amount of skim removed by the clear gate section 17, the signal of the ring CCD 16 is generated during the skim operation. It can be prevented from disappearing.

[0078]

According to the present invention, even when the brightness is relatively high, the potential change amount of the ring portion due to the charge accumulation can be surely made smaller than the skim amount, and the output potential is maintained even if the charge accumulation is continued. Almost no saturation level is reached. Therefore, it becomes possible to perform accurate distance measurement.

[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 diagram for explaining the operation principle of the embodiment of the present invention.

FIG. 3 is a timing chart showing operation timings of respective parts when charges are transferred from the sensor array to the linear CCD in the device of FIG.

FIG. 4 is a flowchart for explaining the operation of the embodiment of the present invention.

FIG. 5 is a schematic diagram showing a measurement principle of a conventional distance measuring device.

6 is a circuit diagram showing a signal processing circuit of the device of FIG.

FIG. 7 is a schematic view showing a main part of another conventional distance measuring device.

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

FIG. 9 is a schematic view showing a main part of still another conventional distance measuring device.

FIG. 10 is a schematic view showing a main part of an apparatus obtained by improving the apparatus of FIG.

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

FIG. 12 is a diagram for explaining a relationship between a conventional skim determination potential and a skim amount.

[Explanation of symbols]

11 sensor array 12 Integrator 13 ICG gate section 14 Storage 15 linear CCD 16 ring CCD 17 Clear gate 18 Voltage buffer circuit 19 skim judgment section 20 Control circuit 21 Reset pulse generation circuit

Continuation of the front page (56) Reference JP-A-61-48199 (JP, A) JP-A-54-121689 (JP, A) JP-A-60-105270 (JP, A) JP-A-4-330852 (JP , A) JP-A-7-146138 (JP, A) JP-A-7-146139 (JP, A) JP-A-8-233571 (JP, A) JP-A-8-320223 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01C 3/00-3/32 G01B 11/00-11/30 102 G02B ⁷ /28-7/40 G03B 13/32-13/36

Claims (4)

(57) [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 object and photoelectrically convert the array is arranged, an integration unit that integrates the output charge from each sensor of the sensor array, and to extract the charge from the integration unit. Gate means, reset pulse generating means for supplying a reset pulse to the gate means, and a ring portion at least a part of which is coupled in a ring shape and sequentially transfers charges, and transfers the charges integrated by the integrating means. In a distance measuring device including a charge transfer unit that performs a charge transfer and a skim unit that removes a fixed amount of charge from the charge transferred by the ring unit. Not determined by the potential of the ring portion, when the potential of the ring portion is equal to or less than a predetermined determination potential during the charge accumulation for a predetermined number of times or more, when the charge accumulation for the plurality of times or more While operating the skim means every time, the first output charge from each sensor of the sensor array obtained by accumulating charges in the first period in the sensor array is sequentially transferred in the ring portion, The second output charge from each sensor of the sensor array obtained by accumulating charges in the second period after the end of the first period in the array is added to the first output charge in the ring portion. Thus, the potential of the ring portion is not judged by the potential of the ring portion when one accumulation operation is performed, and the potential of the ring portion is determined by the predetermined multiple times of charge accumulation. The timing of the reset pulse generated by the reset pulse generating means is set so that the integration time in the integration unit is shortened only when the charge is accumulated for a predetermined number of times when the potential is equal to or lower than a predetermined determination potential. A distance measuring device further comprising control means for controlling. 2. The control means includes a detection means for detecting the potential of the ring portion, and a comparison means for comparing the potential of the ring portion detected by the detection means with the determination potential.
A skim command means for outputting an operation command to the skim means on the basis of the comparison result by the comparison means, and a reset for instructing a change in the timing of the reset pulse generated by the reset pulse generation means on the basis of the comparison result by the comparison means. The distance measuring device according to claim 1, further comprising a change commanding unit. 3. A potential difference between the determination potential and a reference potential when no charge is accumulated in the ring portion is larger than a voltage corresponding to the certain amount of charge removed by the skim means. The distance measuring device according to claim 1 or 2. 4. The control unit sets an integration time in the integration unit when the potential of the ring unit is equal to or less than the determination potential when the charge is accumulated a plurality of times to 1 of the ring unit.
The control according to any one of claims 1 to 3, wherein the change in potential due to charge accumulation is controlled to be equal to or lower than a voltage corresponding to the constant amount of charges removed by the skim means. Distance device.