JPH09229675A - Distance measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent drop of the distance measuring ability for an object located remotely. SOLUTION: A distance measuring device concerned comprises a signal electric charge supplying means C which receives a pulsated light flux SL reflected by an object to be measured A, integrates the fed signal electric charges, and transfers the result according to the specified electric charge transfer pulses, a signal electric charge injecting means D which injects the transferred signal electric charges S1 , a circulative shift register E which accumulates gradually the injected signal electric charges S1 , and a blinking interval altering means F which alters the blinking intervals of a light projecting means B in accordance with the situation of the object A. If the object A is located remotely, the blinking intervals of the projecting means B are widened so that the influence of stagnating electric charges is suppressed relatively, and thereby measurement of the distance of object A located remotely is made practicable.

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 an object to be measured, and more specifically, a plurality of charge transfer channel portions are connected in a loop to form a cyclic shift register, The present invention relates to a distance measuring device using a cyclic shift register that operates so as to gradually add signal charges while circulating the signal charges according to the charge transfer pulse.

[0002]

2. Description of the Related Art For example, Japanese Patent Publication No. 5-22843 proposes a skim means for forming a charge transfer portion in a ring shape to integrate a signal and remove external light. According to this, when the signal charge is not at a sufficient level, the signal charges are sequentially added while transferring the cyclic shift register, and S /
A signal charge with a good N ratio can be obtained.

Further, in this configuration, the distance measuring means is turned off, and the distance from the signal charge due to the brightness of the image of the object to be measured formed on the plurality of photoelectric conversion elements to the distance to the object is measured. It is also possible to take action.

Further, a plurality of light receiving means are provided for flashing and projecting the pulsed light beam toward the object to be measured, and a plurality of light beams receiving the pulsed light beam reflected and returned by the object to be measured are received. The photoelectric conversion element and the signal charges output from the photoelectric conversion elements are gradually accumulated, and the distance measurement object is calculated using the accumulated signal charges. There has also been proposed a hybrid type distance measuring device that shifts to the passive distance measuring operation when a certain distance measuring result cannot be obtained.

[0005]

By the way, in the process of injecting the signal charges generated in the plurality of photoelectric conversion elements into the charge transfer channel from the signal charge injecting means through the signal charge supplying means, a part of the signal charges is generated. There is a problem in that the distance is lost and the distance measuring ability of the distance measuring device is significantly reduced.

Further, the pulsed light beam projected toward the object to be measured whose distance is to be measured is received and accumulated when the object is reflected and returned by the object to be measured, and also accumulated. In the active distance measuring operation in which the distance to the object to be measured is calculated using the signal charge, when the reliable distance measuring result cannot be obtained, the passive distance measuring operation is performed. However, there is a problem that the distance measurement time is unnecessarily extended when the passive distance measurement operation is performed in a dark situation where the brightness of the distance measurement object and its surroundings is extremely low.

In addition, in the active distance measuring system, in order to widen the range in which the distance can be measured in the long distance direction, an allowable current is often supplied to the IRED (light emitting diode) as the light projecting means. However, if the cycle of blinking the IRED is set too long, there is a problem that the heat generated by the current flowing inside the IRED intermittently exceeds the allowable value and the deterioration gradually progresses.

In view of the above problems, it is a first object of the present invention to prevent deterioration of the distance measuring ability for a distance measuring object existing at a long distance. Also,
A second object is to prevent the distance measuring time from being unnecessarily extended by shifting to the passive distance measuring operation in a dark situation. A third object is to maximize the long-distance measuring ability of the distance measuring device.

A fourth object is to prevent the temperature of the light projecting means from rising to a temperature causing deterioration.

[0010]

The distance measuring device of the present invention is a distance measuring device having a light projecting means for flashing and projecting a pulsed light beam toward a distance measuring object whose distance is to be measured. It has a plurality of photoelectric conversion elements that receive the pulsed light flux reflected by the object to be measured and returned and output signal charges, and integrate the signal charges respectively output from the plurality of photoelectric conversion elements to obtain a predetermined value. Signal charge supplying means for transferring the signal charges according to the charge transfer pulse, the signal charge injecting means for injecting the signal charges transferred by the signal charge supplying means into the circulation shift register, and the signal charges injected from the signal charge injecting means. And a blinking cycle changing means for changing the blinking cycle of the light projecting means according to the condition of the object to be measured.

Another feature of the present invention is that
In a distance measuring device having a light projecting means for flashing and projecting a pulsed light beam toward an object to be measured whose distance is to be measured, the pulsed light beam reflected by the object to be returned and returned is received. And a plurality of photoelectric conversion elements for outputting signal charges, the signal charges supplying means for integrating the signal charges respectively output from the plurality of photoelectric conversion elements, and transferring the signal charges according to a predetermined charge transfer pulse. Signal charge injecting means for injecting the signal charge transferred by the means into the cyclic shift register, a plurality of charge transfer channel portions arranged at least partially coupled in a loop, and on each of the charge transfer channel portions. A plurality of transfer electrodes provided via a gate insulating film, and a signal transferred through a charge transfer channel section operated by a transfer clock applied to each transfer electrode. A cyclic shift register having a floating gate electrode provided through a gate oxide film for detecting the amount of electric charge, circulating electric charges in the loop-coupled portion and accumulating the electric charges cumulatively; And a blinking cycle changing means for changing the blinking cycle of the light projecting means according to the condition of the object to be measured.

Another feature of the present invention is that the light projecting means is caused to blink for a predetermined period to accumulate the output charges of a plurality of photoelectric conversion elements, and a distance measurement operation is performed from the accumulated signal charges. The active distance measuring means for performing, the reliability determining means for determining the reliability of the result of the distance measuring operation to the distance measuring object whose distance is to be measured, and the calculation result of the active distance measuring means by the reliability determining means. When it is determined that the reliability is poor, the signal charge resetting unit that turns off the light projecting unit and resets the accumulated signal charge, and the accumulated signal charge is reset by the signal charge resetting unit Sometimes, a signal charge generation unit that newly generates a signal charge from the luminance signal of the image of the object to be measured formed on the plurality of photoelectric conversion elements,
The passive distance measuring means for performing a passive distance measuring operation for obtaining the distance to the distance measuring object based on the signal charge generated by the signal charge generating means, and the blinking cycle of the light projecting means are larger than a predetermined cycle. In this case, the distance measuring operation transition prohibiting means for prohibiting the transition to the passive distance measuring operation is provided.

Another feature of the present invention is that the light emitting means blinks and emits a pulsed light beam toward the object to be measured, and the object is reflected and returned by the object to be measured. A photoelectric conversion element that receives a pulsed light beam is provided, the signal charge output from the photoelectric conversion element is integrated to obtain a light receiving position on the photoelectric conversion element, and the distance measurement object is based on the obtained light receiving position. According to the blinking frequency changed by the blinking cycle changing means, a blinking cycle changing means for changing the blinking frequency of the light projecting means according to the condition of the object to be measured, And maximum current limiting means for limiting the maximum value of the current flowing through the light projecting means.

Another feature of the present invention is that the function setting means for continuously calculating the distance measurement to the object to be measured and the distance measurement continuously by the function setting means. It is further characterized by further comprising blinking frequency limiting means for inhibiting the blinking frequency for blinking the pulsed light flux from being lower than a predetermined value when a selection is made to operate.

[0015]

Since the present invention comprises the above-mentioned technical means, the pulse-shaped light flux is blinked on the object to be measured by blinking the pulsed light flux within a range in which each charge storage portion, the circulation shift register, etc. are not saturated with the electric charge by the external light and the signal light. The flashing cycle of the projecting means for projecting light is increased, and the timing of each signal that operates in synchronization with the flashing cycle of the pulsed light flux is also changed so that the charge is transferred from the signal charge injecting means. Due to the phenomenon that part of the signal charge is lost during the process of injecting a signal into the channel, the distance measurement becomes impossible when the distance measurement target is at a long distance. By increasing the amount of charge, the amount of charge integrated during the period is increased by the lengthening of the period, and the amount of charge transfer per transfer is increased, thereby relatively reducing the effect of charge accumulation. Keep small And so, to permit the distance measurement of the distance measurement object existing in farther distance.

Further, according to another feature of the present invention, when a reliable distance measurement calculation result cannot be obtained due to a small amount of signal charges accumulated even if the light projecting means is blinked for a predetermined period. By prohibiting the transition to the passive distance measuring operation, it is possible to prevent the distance measuring time from being unnecessarily extended and the release time lag becoming longer.

According to another feature of the present invention, the blinking cycle of the light projecting means is changed according to the condition of the object to be measured, and the light projecting means is changed according to the changed flashing frequency. By limiting the maximum value of the current to be supplied to, it becomes possible to flow a current of a size that does not deteriorate the light projecting means, and it is possible to maximize the distance measuring ability of the distance measuring device. .

According to another feature of the present invention, when the operation for continuously measuring the distance to the object to be measured by continuously repeating the distance measuring operation is selected, the blinking frequency of the light projecting means is set. By prohibiting lowering than a predetermined value, when a current is continuously applied to the light projecting means,
Even when there is a risk of deterioration due to temperature rise due to heat generation, the temperature rise due to heat generation can be suppressed.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a distance measuring device according to the present invention will be described below with reference to the drawings. First, the schematic configuration of the distance measuring device of the present invention will be described with reference to FIG. In FIG. 1, A is an object to be measured, B is a light projecting unit, C is a signal charge supplying unit, D is a signal charge injecting unit, E is a cyclic shift register, F is a blinking cycle changing unit, and G is an active distance measuring unit. ,
H is reliability determining means, J is signal charge generating means, K is passive distance measuring means, L is distance measuring operation transition prohibiting means, M is distance measuring result outputting means, and N is signal charge resetting means.

The light projecting means B is for flashing and projecting the pulsed light beam S _L toward the object A whose distance is to be measured. The signal charge supplying means C is a pulsed light beam S _L that is reflected by the object A to be measured and returns.
A plurality of photoelectric conversion elements for outputting the signal charges S ₁ by receiving (not shown) integrates the signal charges S ₁ respectively outputted from said plurality of photoelectric conversion elements, a predetermined charge transfer pulses S _For transfer according to ₂ .

The signal charge injection means D supplies the signal charge.
Signal charge S transferred by means C₁Cycle shift
It is for injecting into Dista. Circular shift register
The signal E is a signal charge injected from the signal charge injection means D.
Load S ₁For gradually accumulating.

The blinking cycle changing means F changes the blinking cycle of the light projecting means B according to the condition of the object A to be measured. The active distance measuring means G blinks the light projecting means B for a predetermined period of time to perform the distance measuring operation from the signal charge S ₁ that has accumulated the output charges of the plurality of photoelectric conversion elements.
The reliability determining means H determines the reliability of the result of the distance measurement calculation up to the distance measurement target A whose distance is desired to be measured.

The signal charge resetting means N turns off the light projecting means B and accumulates the light when the reliability determining means H determines that the calculation result of the active distance measuring means G is unreliable. The signal charge S ₁ is reset. The signal charge generating means J has a signal charge S ₁ accumulated by the signal charge resetting means N.
When the signal is reset, the signal charge S ₁ is newly generated from the luminance signal of the image of the object A to be measured formed on the plurality of photoelectric conversion elements.

The passive distance measuring means K is for performing a passive distance measuring operation for obtaining the distance to the distance measuring object A based on the signal charge S ₁ generated by the signal charge generating means J. The distance measuring operation shift prohibiting means L is for prohibiting the shift to the passive distance measuring operation when the blinking period of the light projecting means B is longer than a predetermined period. The distance measurement result output means M is for outputting the result of distance measurement performed by the active distance measurement means G and the passive distance measurement means K.

According to the thus constructed distance measuring device, the pulsed luminous flux S _L is flickered within a range in which the respective charge accumulating portions, the circulation shift register E, etc. are not saturated with the electric charges due to the external light and the signal light. Then, the blinking cycle of the light projecting means B for projecting light toward the object A to be measured is increased, and the timing of each signal which operates in synchronization with the blinking cycle of the pulsed light beam S _L is also changed. It becomes possible.

Therefore, in the process of injecting a signal from the signal charge injecting means D into the charge transfer channel, the signal charge S
Due to the phenomenon that a part of ₁ is missing and distance measurement becomes impossible when the object A to be measured is at a long distance, by increasing the blinking cycle of the light projecting means B, It is possible to increase the amount of electric charges integrated during the extension as much as the extension.

In this way, the amount of charge movement per transfer can be increased, and the influence of charge accumulation can be suppressed to a relatively small value. The distance measurement of the object A can be performed.

If a reliable distance measurement calculation result cannot be obtained because the accumulated signal charge S ₁ is small even if the light projecting means B is blinked for a predetermined period, the passive distance measurement operation is started. Since the transition is prohibited, it is possible to prevent the release time lag from being lengthened unnecessarily due to an unnecessary extension of the distance measurement time in a dark situation in which the distance measurement capability in the passive distance measurement is significantly reduced.

Next, referring to FIG. 2, a schematic configuration of the second characteristic of the distance measuring device of the present invention will be described. In FIG. 2, the same functions as those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 2, the distance calculating means Q is a pulsed light beam S _L which is reflected by the object A to be measured and returns.
Has a photoelectric conversion element (not shown) for receiving light, and integrates the signal charge S ₁ output from the photoelectric conversion element to obtain a light receiving position on the photoelectric conversion element. Then, the distance to the target object A is calculated based on the obtained light receiving position.

The maximum current limiting means R limits the maximum value of the current flowing through the light projecting means B according to the blinking frequency changed by the blinking cycle changing means F. The function setting means S is for continuously calculating the distance measurement to the object A to be measured.

The blinking frequency limiting means T makes the blinking frequency for blinking the pulsed light beam S _L lower than a predetermined value when the function setting means S is selected to continuously operate the distance measurement. It is to prohibit doing.

According to the distance measuring device thus constructed, the blinking period of the light projecting means B is changed according to the situation of the object A to be measured, and the light projecting means B is also produced according to the blinking frequency. It is possible to limit the maximum value of the current flowing to the.

By doing so, a current as large as possible can be made to flow without deterioration of the light projecting means B, so that the distance measuring ability of the distance measuring device can be utilized to the maximum.

When the operation for continuously measuring the distance to the object A to be measured by continuously repeating the distance measuring operation is selected, the blinking frequency of the light projecting means B should be set lower than a predetermined value. By prohibiting the
Even when there is a possibility that deterioration due to temperature rise due to heat generation may occur due to continuous current flowing through the device, the temperature rise due to heat generation can be suppressed, and the temperature of the light projecting means B rises until deterioration occurs. Can be prevented.

The distance measuring apparatus of the present invention will be described in detail below with reference to FIGS. FIG. 3 is a diagram showing the features of the distance measuring device of the present invention, and shows an example in which the cyclic shift register is applied to a distance measuring device of an autofocus device of a camera. The signal of the autofocus device handles from a short distance / high reflectance subject to a long distance / low reflectance subject.
It has an extremely large dynamic range (usually about 1: 1000).

Therefore, it is difficult to secure a sufficient dynamic range in the signal processing circuit, and various measures have been taken. In the cyclic shift register described here, when the signal is at a high level, the accumulation and addition operation is stopped after several times of accumulation, and when the signal is at a weak level, the accumulation operation is repeated several hundred times to perform the distance measurement operation. It is designed so that a sufficient signal level can be obtained.

First, the operation of the cyclic shift register section will be described in detail with reference to FIG. In FIG. 4, reference numeral 11 denotes a sensor array including a plurality of photoelectric conversion elements as a signal charge supply unit that receives light and converts it into charges. The sensor array 11 includes the first pixel sensors S1 to S1.
The description will be given assuming that the fifth pixel sensor S5 includes five pixels.

Reference numeral 12 denotes an integrating section, which is a sensor array 11
The electric charges photoelectrically converted by the respective pixel sensors S1 to S5 are integrated in their respective integrating units. Reference numeral 13 is a clearing section provided in the integrating section 12, and when an ICG pulse is applied, the charge integrated in the integrating section is emptied (clear state).

Reference numeral 14 denotes a first accumulating section, 15 denotes a second accumulating section, the first accumulating section 14 receives the electric charge from the integrating section 12 by the ST1 pulse, and the second accumulating section is the integrating section by the ST2 pulse. It operates so as to receive charges from 12.

Reference numeral 16 denotes a shift section, which is a sample hold pulse S at the timing shown in the timing chart of FIG.
When H is applied, all the charges in the first storage section 14 and the second storage section 15 are moved to the linear CCD 17 that operates as signal charge injection means.

Transfer clock pulses CK1 and CK2 are alternately applied to the linear CCD 17, and charges transferred from the first storage section 14 and the second storage section 15 are generated by the transfer clock pulses CK1 and CK2. First
Is transferred in the transfer direction 1.

A ring CCD 18, which operates as a cyclic shift register in which a plurality of charge transfer channels are connected in a loop, is connected to the end of the linear CCD 17 on the first transfer direction 1 side, and the transfer clock pulses CK1 and CK2 are also connected thereto. The charges that are alternately applied and are present in each charge transfer channel are transferred in the second transfer direction 2 and are transferred to the ring CCD.
It will rotate around the inside of 18.

The charges in each charge transfer channel of the linear CCD 17 are transferred in the first transfer direction 1 by the transfer clock pulses CK1 and CK2. And the first
The charges in the charge transfer channel 1A are transferred to the adjacent charge transfer channel by the transfer clock pulse CK2.

Further, it is transferred to the twelfth charge transfer channel 12B of the ring CCD 18 by the next transfer clock pulse CK1. However, since the charge originally existing in the charge transfer channel 1B of the ring CCD 18 is also transferred to the twelfth charge transfer channel 12B at this time, the respective charges are added together in the twelfth charge transfer channel 12B.

Here, the number of charge transfer channels of the linear CCD 17 and the number of charge transfer channels of the ring CCD 18 are made equal to each other, and the first charge transfer channels 1A and 1A are connected.
B, the second charge transfer channels 2A and 2B, the third charge transfer channels 3A and 3B, ..., And the charge of the twelfth charge transfer channels 12A and 12B are always added together. There is.

However, the first charge transfer channel 1A,
Since no signal charge is injected from the sensor array into the second charge transfer channel 2A, it becomes a non-signal charge part in which only charges of noise components such as dark current are accumulated.

Reference numeral 19 denotes a CCD clear section, which is the CCD
When the CCD CLR signal is applied to the clear section 19, the charge in the first charge transfer channel 1B becomes empty. Therefore, in the initialization mode shown in the timing chart of FIG.
When the transfer clock pulses CK1 and CK2 are applied until the electric charges make one round in the ring CCD 18 by applying the CDCLR signal, the electric charges originally existing in the ring CCD 18 always pass through the first electric charge transfer channel 1B. At this point, the electric charge becomes empty, and eventually all the electric charge in the ring CCD can be made empty (reset state).

Next, reference numeral 20 is for converting the amount of charge existing in the fifth charge transfer channel 5B into a voltage through the floating electrode portion 102 provided on the fifth charge transfer channel 5B and outputting the voltage to an external device. It is an output part, and FIG.
The OS signal is output at the timing shown in the timing chart.

RD in the output section 20 is the reset potential, and when the reset pulse RS1 is applied as shown in FIG. 8, the floating electrode section 102 is reset to the reset potential R.
Reset to D.

Further, FIG. 5 is an enlarged view from the photoelectric conversion of the cyclic shift register shown in FIG. 4 to the linear CCD 17, and is a diagram for explaining the flow of charges. 10 and 11 are cross-sectional views taken along line XX 'shown in FIG. 5, and are views for explaining the state of charge transfer.

FIG. 10A shows a situation in which the charges generated by the light applied to the sensor array 11 are collected in the integrating unit 12. As shown in FIG. 10 (A), a constant positive voltage + Vc is applied to the electrode of the integration unit 12, and electric charges are collected in the potential formed below this.

In FIG. 10B, ST is stored in the first storage unit 14.
The state where one pulse is applied is shown in FIG.
It shows that the electric charge in is transferred to the first storage unit 14. The numeral 40 shown here is called a barrier and should not be inherently present.

However, since the potential of the barrier 40 is complicatedly formed, the potential is disturbed due to misalignment of the mask for manufacturing the device during the manufacturing process. The barrier 40 blocks a part of the charges that move to the first storage portion 14. The amount of electric charge is almost constant, and is referred to as a charge pool here and is represented by γ.

FIG. 11C shows how charges are transferred from the first storage section 14 to the linear CCD 17 via the shift section 16. Also at this time, a new current flows from the sensor array 11 into the integrating unit.

FIG. 11D shows a state in which an ICG pulse is applied to the clearing section 13 in FIG. 4, and all the charges in the integrating section 12 are removed. Due to the mechanism as described above, a phenomenon occurs in which a part of the signal charge is lost during the process in which the signal charge generated in the photoelectric conversion element is injected into the charge transfer channel from the signal charge injection means through the signal charge supply means. obtain.

Here, if the charge generated by the signal light with which the sensor array 11 is irradiated is β, the amount of charge transferred to the first integrating unit 14 is (β−γ). Here, if the signal light is extremely small, the signal charge β generated there may be smaller than the charge accumulation γ described above and (β−γ) <0.

In such a case, all the signal charges β are blocked by the integrating section 12, and the signal charges are not transferred to the first integrating section 14. Therefore, the signal charge is not transferred to the linear CCD 17, and as a result, the charge is not transferred to the circular shift register connected thereafter as shown in FIG. Therefore, no signal can be obtained at the output unit 102.

That is, in the distance measuring device of the camera auto-focus device, when the object to be measured is at a long distance, if the amount of light hitting the photoelectric conversion element is small and the resulting charge is small, the charge is almost all. However, there is a problem that the distance is impeded by the barrier 40 and the distance measurement becomes impossible.

Even when the object to be measured is located at a long distance and the surroundings are dark and passive distance measurement is impossible, the hybrid type distance measuring device first has the light projecting means. Although it blinks to perform the active distance measurement operation, the distance measurement target is present at a long distance, so the pulsed light flux emitted from the light projecting means and reflected by the distance measurement target is extremely weak. It is not possible to obtain a reliable distance measurement calculation result up to the object.

Therefore, although the active operation is ended and the operation shifts to the passive operation, the surroundings are dark and a reliable distance measurement calculation result cannot be obtained even in the passive distance measurement, so that the focus eventually matches the predetermined distance. To drive the lens.

Therefore, when the object to be measured is located at a long distance and the surroundings are dark and passive distance measurement is impossible, the time required for the distance measurement operation and distance calculation is the longest. Therefore, the shutter release timing will be delayed accordingly. In other words, the camera has a large release time lag and is difficult to use.

Therefore, this embodiment is described below. That is, in FIG.
The control circuit 206 sends an IR signal via the IRED drive circuit 202.
Blink ED201.

The light emitted by blinking the IRED 201 strikes the subject 221 through the light projecting lens 207. Then, it is reflected by the subject 221 and enters the sensor arrays 11R and 11L through the light receiving lenses 208R and 208L.

As a result, the light receiving images 222R and 222L formed on the sensor arrays 11R and 11L are formed.
Also flashes. That is, when the IRED 201 is turned on, the received light images 222 are formed on the sensor arrays 11R and 11L.
R and 222L appear, and this signal and external light are converted into charges by the photoelectric conversion element.

When the IRED 201 is turned off, the sensor arrays 11R and 11L receive only external light, and the photoelectric conversion element converts the external light into electric charges. Note that AF
The control circuit 206 includes sensor arrays 11R and 11L, signal integrators 12R to 16R and 12L to 16L, a linear CCD.
17R and 17L and a function to generate drive pulses 203 for driving the ring CCDs 18R and 18L provided as cyclic shift registers and control their operations.

In FIG. 5, the signal charge photoelectrically converted by the sensor S2 which is one pixel in the sensor array 11 is given to the integration section 12 through the course of the arrow 301 and integrated (see FIG. )reference). Then, by applying the ICG pulse to the ICG line connected to the clearing section 13 at the timing shown in FIG. 6, the signal charge in the integrating section 12 is eliminated through the progress of the arrow 302 (FIG. 11 ( See D)).

That is, the charge of the integrating section 12 is cleared. Therefore, by controlling the ICG pulse, it is possible to obtain a function as a so-called electronic shutter in which the time for accumulating charges in the integrating unit 12 is arbitrarily changed.

From the ICG pulse shown in FIG. 6, ST1, ST
Times t1 and t2 up to two pulses are integration times. The first accumulation unit 14 and the second accumulation unit 15 which are adjacent to each integration unit are provided.
And the ST is stored in the first storage unit at the timing shown in FIG.
With one pulse, the charge flows from the integrating unit 12 through the path of 304 (see FIG. 10B).

In addition, the ST2 pulse causes electric charges to flow from the integrating unit 12 through the path 303 in the second storage unit. The first storage section 14 and the second storage section 15 are alternately arranged as shown in FIG. 4, and the shift section 16 is provided below the first storage section 14 and the second storage section 15.

When the shift pulse is applied to the shift section 16, the charge stored in the first storage section 14 is transferred to the charge transfer channel of the linear CCD 17 shown in FIG. See C)). Further, the charges accumulated in the second accumulation unit 15 are transferred to the charge transfer channel of the linear CCD 17 via the path indicated by the arrow 305.

By the way, as shown in FIG. 6, since the AF control circuit 206 operates so that the ST1 pulse is output in synchronization with the extinguished state of the IRED 201, the first storage unit 1
An external light charge that strikes the sensor is accumulated at 4.

The AF control circuit 206 outputs the ST2 pulse in synchronization with the lighting state of the IRED 201.
Is operated, the electric charge obtained by adding the signal reflected from the subject hitting the sensor and the external light is accumulated in the second accumulation unit 15. The charges stored in the first storage unit 14 and the second storage unit 15 by the sample hold pulse SH are transferred to the charge transfer channels 3A to 12A in FIG.

Therefore, the charge transfer channels 3A, 5
Charges corresponding to external light are transferred to A, 7A, 7A, 9A and 11A, and charge transfer channels 4A, 6A, 8A and 10
The signals obtained by adding the electric charges of the signal reflected from the subject and the external light are transferred to A and 12A.

Since the sample hold pulse SH is generated in synchronization with one round of the ring CCD 18, the IRED field is turned on / off and ST1 and ST are turned on as shown in FIG.
Since the two pulses are synchronized with the sample hold pulse SH, the signal charges obtained by integrating the charges from the same sensor are always added to each charge transfer channel of the ring CCD 18.

The distance measuring apparatus shown in FIG. 3 outputs the ICG pulse in the initialization mode shown in FIG. 7 at the timing of t1 = t2 = 0. That is, t1 = t2 =
By setting the value to 0, the charge in the integration unit 12 becomes empty.

When the pulse of CCD CLR is applied for a period in which the charge makes the ring CCD 18 for three weeks or more, the first
Storage unit 14, second storage unit 15, linear CCD 17,
All the charges remaining in the ring CCD 18 are the CCD shown in FIG.
It is eliminated through the clearing unit 19. After the charge in each part is completely emptied, the CCD CLR pulse is stopped as shown in FIG. 7, and the mode is changed to the integration mode.

Here, under the condition that t1 = t2> 0, ICG, ST1, ST2, SH, CK1,
Each pulse of CK2 and IRED are operated at a predetermined timing shown in FIG.

The charge due to external light when the IRED is turned off is the first
Is transferred to the charge transfer channels 3A, 5A, 7A, 9A, 11A of the linear CCD 17 via the storage section 14 of the linear CCD 17 and further accumulated and accumulated in the ring CCD 18 one after another. Similarly, the electric charge obtained by adding the signal component reflected from the subject and the external light component when the IRED is turned on is transferred via the second storage unit 15 to the charge transfer channel 4 of the linear CCD 17.
The data is transferred to A, 6A, 8A, 10A, and 12A, and then added one after another by the ring CCD 18 and accumulated.

The OS signal, which is the output signal of the output unit 20, is A / D converted by the A / D converter 204 by the bait via the amplifiers 101R and 101L and is transmitted to the AF control circuit 206. Since the OS signal is output as follows, the level of the non-signal part is the level of the non-signal part The external light component that hits S1 The external light component that hits S1 + the external light component that hits S2 The light component that hits S2 External light component + signal ... External light component that hits S5 External light component + signal that hits S5 The AF control circuit 206 calculates the difference in charge amount of the same sensor that is continuously output. When the charge amount of the signal component reflected from the object to be measured reaches a predetermined level sufficient for performing the distance calculation, the reading mode shown in FIG. 7 is entered, and the sample hold pulse SH is stopped to stop the signal. Stop adding charges.

After that, the charges are further transferred inside the CCD, the OS output is A / D converted by the A / D converter 204 provided in the AF control circuit 206, and the following calculation is executed in the CPU 210 so that only the charge amount of the signal is obtained. Is written in the memory 211. Level of no-signal portion-Level of no-signal portion = 0 (external light component that hit S1 + signal component)-(external light component that hit S1) = (signal component that hit S1) (external light hit on S2 Light component + signal component)-(external light component that hits S2) = (signal component that hits S2) ... (S5 external light + signal)-(S5 external light) = (S5 signal)

The above process is performed by the two rings C shown in FIG.
From the result of carrying out to CD18R, 18L, the received light image 222
The position of R, 222L can be obtained. Further, the distance D from those positions Xr and Xl to the subject can be calculated. Here, the light projecting lens 207 and the light receiving lens 2
08R and the light receiving lens 208L are on the same straight line, the distance between the light receiving lenses is B, the distance between the light receiving lens 208R and the light projecting lens 207 is K, and the subject 221 is separated from the light projecting lens 207 by a distance D in the vertical direction. It has a structure that

The distance between the sensor array 11R and the sensor array 11L is also B, and the light receiving lens 208R,
It is installed at a distance from the light receiving lens 208L. From the one end of the sensor array 11R, the received light image 222
Let Xr be the distance to R, ΔX be the distance from the principal point of the light receiving lens 208R to the point dropped vertically, and similarly be X1 the distance from one end of the sensor array 11L to the light receiving image 222R, and be the main of the light receiving lens 208L. Let ΔX be the distance from the point to the point dropped vertically.

Then, D / K = f / (Xr-ΔX) ... (1) D / (B + K) = f / (X1-ΔX). (2) holds, and the above equation ( 1), Eliminating K from equation (2) and D
Solving for, D = B × f / (X1-Xr) ... (3)

That is, since B and f are constant and have known values, the distances D to the object 221 are obtained by substituting the positions Xr and Xl of the received light image on the sensor array into the equation (3). Returning to FIG. 4, the skim section 21 indicates that "a signal component of the photoelectric conversion element when the light projecting means is turned on and a signal component of the photoelectric conversion element when the light is turned off are set as a pair, and an equal DC signal component (external light (Assuming a minute) is excluded from the CCD, and is a part that performs an action called “skim motion”.

In FIG. 4, the charge transfer channel SK1
The internal potentials of SK2 and SK2 are formed so as to leave a certain amount of charges. Therefore, the charges exceeding a certain amount of the charges transferred from the eleventh charge transfer channel 11B flow out to DC1.

After the charge from the eleventh charge transfer channel 11B is distributed to the first charge transfer channels SK1 and DC1, each charge is transferred to the second charge transfer channels SK2 and DC2 by the transfer clock pulse CK2.
Is forwarded to.

In the second charge transfer channel SK2, the internal potential is formed so as to leave a constant amount smaller than that in the first charge transfer channel SK1, and the overflowed charges flow out to DC2, where they are transferred from DC1. Added to the charge.

Reference numeral 22 denotes an SK output section, which has a reset signal R
When S2 is applied, the floating gate 104 is reset to the RD level. When the charge is transferred from DC2, the SKOS output appears from the floating gate via the amplifier 103 according to the charge amount.

Further, in FIG. 3, reference numerals 21L and 21R denote portions for performing a skim operation, and floating gate portions 104L and 1L.
The potential of 04R is connected to the skim comparators 105L and 105R via the amplifiers 103L and 103R.

As shown in FIG. 9, the SKOS output is output from the comparator 1 of FIG. 3 at the timing when the IRED is turned off.
Reference voltage + Vref predetermined in 05R and 105L
When the SKOS output exceeding the reference voltage is detected, it is determined that "there are many charges in the charge transfer channel and there is a risk of saturation". Then, the SKCLR pulse is output at the timing shown in FIG. 9 for the charge and the charge to be transferred next.

Reference numeral 23 in FIG. 4 denotes a skim clear portion, which is S
When the KCLR pulse is applied, the charges existing in the eighth charge transfer channel 8B (the second charge transfer channel SK
A constant amount determined in 2 and designated as α) is flowed to a ground line (not shown) to make it empty.

Since the SKCLR pulse is also input to the CPU 210, its timing can be known. When the SKCLR pulse is not output, the charges existing in the eighth charge transfer channel 8B are transferred to the seventh charge transfer channel 7B and added to the charges transferred from the floating electrode section 104.

Therefore, when the SKOS output due to the electric charge of the external light above the reference voltage is detected by the comparator (not shown), the electric charge of the external light hitting the same sensor, the signal component reflected from the object, and the external light component are detected. An equal charge amount α is extracted from the sum of the charges.

However, at the time of reading the signal, as described above, it is obtained when the calculation of (external light component hit on S1 + signal component −α) − (external light component hit on S1−α) is carried out. The obtained result is (the signal corresponding to S1) and does not have any influence on the charge amount of the target signal.

Therefore, even if the object to be measured is in a condition where the external light is strong, the skim operation is repeatedly executed to prevent the charge transfer channel from being saturated by the electric charge of the external light and reflected from the object. It becomes possible to store the electric charge of the signal until it reaches a sufficient level for distance measurement calculation.

When the distance is measured by the distance measuring device of the autofocus device of the camera having the above-mentioned structure, first, the distance shown in FIG.
Ring CCD 18 and linear CC in the initialization mode shown in
The electric charge inside D17 is made empty (reset state).

Then, the mode is shifted to the integration mode, the IRED blinks at the lowest allowable frequency, and the times t1 and t2 are reached.
The ICG pulse is output at the timing at which the maximum value becomes maximum, and at the same time, the accumulation of the signal charge is started. If the driving frequency of the IRED is low, the charge accumulation time per charge becomes long and the accumulated charges also increase, so that the gradual influence of the signal charges due to the accumulation of charges can be made relatively small.

When the distance measuring operation is performed in a bright environment, the timing at which the skim comparators 105L and 105R are reversed is advanced due to the large amount of outside light, and the skimming is caused by the charge accumulated at the first blinking depending on the brightness of the distance measuring object. An action will also be performed.

In such a case, the charge storage time per time of the sensor 11 is shortened so that the transfer channel of the ring CCD 18 does not become saturated by the charge storage per time. Set to.

However, since the frequency for driving the IRED is synchronized with the charge transfer rate, it cannot be increased indefinitely. The frequency of the transfer clock of the ring CCD 18 is limited to about 500 KHz, and if the frequency is higher than this, the transfer efficiency is remarkably reduced and the adverse effect is exerted.

Therefore, when the frequency for driving the IRED reaches the limit, the timing for outputting the ICG pulse is changed to shorten the times t1 and t2, and the charge storage time per operation is made optimum. . In a bright environment, the electric charge for the external light is large. Therefore, the loss of the signal charge due to the accumulated electric charge becomes a part of the electric charge for the external light, and the electric charge for the signal is not affected.

Further, the sensor array obtains a signal charge from the luminance signal of the image of the object to be measured formed on the sensor array composed of a plurality of photoelectric conversion elements in the distance measuring apparatus of this embodiment, and the signal charge is obtained. Therefore, the distance to the object to be measured can be obtained.

In FIG. 3, the IRED 201 which is the light projecting means.
When the lighting and the skim operation are prohibited and the signal charges are accumulated, the OS output is as follows. Level of no-signal part Level of no-signal part External light component that hit S1 External light component that hit S1 External light component that hit S2 External light component that hit S2 ・ ・ ・ ・ ・ ・ S5 hit External light component External light component that hit S5

When the maximum value of these signals does not saturate the charge transfer channel and has reached a level suitable for correlation calculation, new charge accumulation is stopped, and the OS signal is set every other signal. If it is stored in the memory 211, the amount of electric charge depending on the brightness of the image hitting each sensor can be obtained.

By performing the above processing on the charge output of the sensors 11R and 11L shown in FIG. 3, the image signal of the object to be measured formed on each sensor is obtained, and the relative positional relationship between them is calculated. It is possible to obtain the distance to the object to be distance-measured by performing the correlation calculation processing obtained in.

In this embodiment, the light projecting means is blinked for projecting a pulsed light beam for the predetermined period described above.
A so-called active distance measurement is performed in which the output charges of a plurality of photoelectric conversion elements that receive the pulsed light flux reflected from the object to be measured are subjected to distance calculation from the accumulated signal charges.

Then, the CPU 210 as the reliability determining means determines the distance measurement result, and if the result is "no reliability", the distance measurement is shifted to the passive distance measurement. This is because when measuring a long-distance subject under bright conditions, the pulsed luminous flux reflected from the subject is extremely weak and it is difficult to obtain reliable active ranging results. This is extremely effective because it often becomes possible to measure the distance by shifting to the distance. However, in a dark condition, the distance measurement performance is significantly deteriorated because the passive object distance measurement reduces the brightness of the object and a sufficient signal charge cannot be obtained.

In the distance measuring device of this embodiment, the intensity of the external light that strikes the sensor can be known from the blinking cycle of the IRED during active distance measuring. Therefore, even when the reliable distance measurement result cannot be obtained by the active distance measurement, the blinking cycle of the IRED at that time corresponds to the brightness at which the distance measurement performance is deteriorated by the passive distance measurement. If it is longer than the cycle, the transition to passive distance measurement is prohibited and a predetermined fixed distance is output as the distance measurement result.

By the way, as described above, in the active distance measuring method, in order to widen the range in which the distance can be measured, an electric current of a permissible amount can be applied to the IRED as the light projecting means. Many. However, I
If the cycle of blinking the RED is lengthened, there is a problem that the heat generated by the current flowing inside the IRED intermittently exceeds the allowable value and the deterioration gradually progresses.

FIGS. 12A and 12B show the relationship between the blinking cycle of the IRED and heat generation. In FIG. 12 (A), the temperature of the light emitting portion rises when the IRED is turned on and drops when the light is turned off repeatedly, until a thermal equilibrium state is reached and the maximum temperature is stabilized. At this time, since the lighting time per blinking is short, the peak of the heat generation amount is small, and the temperature of the light emitting unit does not reach the allowable limit temperature. In this case, there is no fear of deterioration due to heat.

On the other hand, in FIG. 12B, the cycle is doubled while applying the same current as that in FIG. 12A to the IRED. In this case, since the lighting time per blinking becomes long, the maximum value of the temperature of the light emitting part becomes large as shown in FIG. 12B, and the temperature of the light emitting part is intermittent when the thermal equilibrium state is reached. The allowable limit temperature is exceeded, and this causes deterioration of the IRED.

Therefore, it is necessary to avoid excessively lengthening the blinking cycle of the IRED because it causes deterioration, and there is a problem that the purpose of reducing the influence of partial loss of electric charges cannot be sufficiently dealt with.

In order to solve such a problem, the distance measuring apparatus of this embodiment is as follows. That is, the sequence of the camera having the single distance measurement mode and the continuous distance measurement mode will be described with reference to FIGS.

S401: When the release button (not shown) is pushed to the first stroke, the first switch is turned from OFF to ON, and the distance measuring operation is started.

S402: Ring CCD 18 shown in FIG.
The charges inside the R and 18L and the linear CCDs 17R and 17L are made empty (reset state). S403: The integration mode is entered and the state of the distance measurement mode changing means (not shown) is detected. In the single distance measurement mode, the distance measurement result obtained once is held, and the photographing operation is performed using the distance measurement result. When the single distance measurement mode is selected, S
Move to 404.

In the continuous distance measuring mode, the distance measuring operation to the object to be measured is repeated until the shutter release timing, and the distance measuring information immediately before the shutter release is used for photographing. If called, it moves to S405.

S404: The ICG pulse is output at the timing when the times t1 and t2 are maximized. Further, the IRED is set to the lowest allowable driving frequency and the maximum IRED current value allowed at that frequency.

When the driving frequency of the IRED is low, the charge accumulation time per time becomes long and the accumulated charge also increases, so that the influence of the loss of the signal charge due to the accumulation of charges can be made relatively small. .

S405: The ICG pulse is output at the timing when the times t1 and t2 are maximized. The frequency for driving the IRED is set to twice the lowest allowable value and the maximum IRED current value allowed at that frequency is set. IR in continuous ranging mode
Since the electric current is repeatedly applied to the ED and the distance measuring operation is repeated, the heat generation of the light emitting portion of the IRED becomes large.

Therefore, in the continuous distance measurement mode, the IR
When the driving frequency of the ED is lowered, the peak temperature of heat generation of the light emitting unit is higher than that in the single distance measurement mode. Therefore, there is a risk of deterioration if the driving frequency of the IRED is set to the limit.

Therefore, in the continuous distance measurement mode, IRE
The driving frequency of D is prohibited from decreasing to the limit value. In the present embodiment, the IR in the single distance measurement mode
A frequency that is twice the lower limit of the ED drive frequency is the lower limit of the IRED drive frequency in the continuous distance measurement mode.

S406: The storage time is optimized so that the charge storage amount per time is set to the optimum value. That is, when the distance measurement operation is performed in a bright environment, the timing at which the skim comparators 105L and 105R in FIG. 3 are reversed is advanced due to the large amount of external light, and the charge accumulated in the first blinking depends on the brightness of the distance measurement target. The skimming action will be performed.

In such a case, the cyclic shift register may be saturated with electric charges. Therefore, as shown in detail in FIG. 15, the accumulation time is optimized in steps after S501. In a bright environment, the electric charge for the external light is large. Therefore, the loss of the signal charge due to the accumulation of electric charge becomes a part of the electric charge for the external light, and the electric charge for the signal is not affected.

S502: It is possible to increase the drive frequency of the IRED to reduce the charge storage amount per time. However, since the frequency for driving the IRED is synchronized with the charge transfer speed, there is no limit. It cannot be raised. The transfer clock frequency of the ring CCD 18 is 500 KHz
The limit is the degree, and if the frequency is higher than that, the transfer efficiency is remarkably reduced and the adverse effect is exerted. Therefore, when the frequency for driving the IRED reaches the limit, the frequency is fixed at that point and the process proceeds to S504.

S503: The drive frequency of the IRED is increased to reduce the charge storage amount per time. Although the driving frequency is doubled here, this magnification may be appropriately determined. The IRED current is set to the maximum value allowed at this drive frequency, and the process returns to S501.

S504: Since the charge storage time per charge is made optimum by changing the timing of outputting the ICG pulse and shortening the times t1 and t2, the time t1,
If t2 is not the minimum value, the process proceeds to S505.

S505: The accumulation time is shortened. Here, the accumulation time is halved, but this magnification may be set appropriately. After that, the process returns to S501. S407: Charges are accumulated for the charge accumulation time determined in the steps so far, and the signal charges are grown to a level sufficient to perform the distance measurement calculation. The details will be described with reference to FIG.

S506: Charges are accumulated for the charge accumulation time determined in the steps so far. S507: It is determined whether or not the accumulated signal charge has reached a predetermined value sufficient for distance measurement calculation. If the signal level is sufficient, the process proceeds to S408. If insufficient, the process proceeds to S508.

S508: It is determined whether or not the number of charge accumulation times has reached the maximum value. When the signal to be measured is at a long distance, such as when the signal is weak, sufficient charge cannot be stored, but the maximum number of storages is set to prevent the distance from being unnecessarily lengthened. Provide and compare with this. When the maximum value is reached, the process proceeds to S408. If the maximum value has not been reached, the process returns to S506 to continue the accumulation of signal charges.

S408: The distance to the object to be measured is calculated from the accumulated signal charges. S409: Based on the reliability data regarding the distance to the object to be measured obtained in S408, it is determined whether or not the result of the distance measurement calculation is adopted.

S410: When it is determined that the distance measurement calculation result is reliable, the distance measurement calculation result is set as the distance measurement result. S411: When it is determined that the result of the distance measurement calculation is not reliable, a predetermined fixed point is set as the distance measurement result. The fixed point is set to a long distance or infinity.

S412: Release the release button (not shown) to the second position.
When pushed to the stroke, the second switch turns from OFF to ON, ending the distance measurement operation. Also, the second switch is OF
If F, move to S413. S413: If it is the continuous distance measurement mode, the process returns to S401 and the distance measurement operation is continued again. In the single distance measurement mode, wait until the second switch turns from OFF to ON.

S414: When the second switch is turned from OFF to ON, the lens is driven to the in-focus position, the shutter is opened / closed, the film is wound, and a series of photographing operations are performed. Incidentally, S402 is the initialization mode shown in FIG.
407 is the integration mode, and S408 to S411 are the read modes.

[0135]

As described above, according to the first invention of the present application, the present invention provides a light projecting means for flashing a pulsed light beam toward an object to be measured whose distance is to be measured. Since the blinking cycle is changed according to the situation of the object to be measured, the distance measurement to the object to be measured at a long distance caused by the partial loss of the signal charges inside the signal charge injecting means is performed. It is possible to prevent a decline in ability.

Further, according to the second invention of the present application, when the blinking period of the light projecting means is larger than a predetermined value, the transition to the passive distance measuring operation is prohibited. It is possible to prevent the distance measurement time from being unnecessarily lengthened by performing distance measurement in a dark situation in which the distance measurement ability in distance measurement is significantly reduced.

According to the third invention of the present application, the maximum value of the current flowing through the light projecting means is limited according to the blinking frequency of the light projecting means, whereby the light projecting means is provided. It is possible to project the maximum energy of the light projecting means without causing heat destruction and deterioration of the light, and it is possible to maximize the long-distance measuring capability of the distance measuring device.

Further, according to the fourth invention of the present application, when the function of continuously operating the distance measuring device to constantly calculate the distance to the object to be measured is selected, Since it is prohibited to set the blinking frequency lower than a predetermined value, it is possible to prevent the temperature of the light projecting unit from rising to a temperature causing deterioration, and prevent deterioration caused by the temperature increase. It will be possible.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic functional configuration of the present invention.

FIG. 2 is a block diagram showing another example of a schematic functional configuration of the present invention.

FIG. 3 is a configuration diagram showing a distance measuring device using a cyclic shift register according to an embodiment of the present invention.

FIG. 4 is a configuration diagram showing an example of a circular shift register.

FIG. 5 is a diagram illustrating the flow of charges from the sensor array.

FIG. 6 is a timing chart for explaining an operation sequence of the cyclic shift register.

FIG. 7 is a timing chart for explaining an operation sequence of the cyclic shift register.

FIG. 8 is a timing chart for explaining an operation sequence of the cyclic shift register.

FIG. 9 is a timing chart for explaining an operation sequence of the cyclic shift register.

FIG. 10 is a diagram showing a state of charge transfer inside a charge transfer unit.

FIG. 11 is a diagram showing how charges are transferred in the charge transfer means.

FIG. 12 is a diagram for explaining how heat is generated in a light emitting unit of a light projecting unit.

FIG. 13 is a flowchart for explaining a distance measuring sequence of a camera equipped with the distance measuring device of the present invention.

FIG. 14 is a flowchart for explaining a distance measuring sequence of a camera equipped with the distance measuring device of the present invention.

FIG. 15 is a flowchart for explaining a distance measuring sequence of a camera equipped with the distance measuring device of the present invention.

[Explanation of symbols]

11 sensor array 12 integration part of photoelectrically converted charge 13 clear part for emptying charge of integration part 14 first storage part 15 for storing charge of integration part 15 second storage part for storing charge of integration part 16 Charge shift unit 17 Linear CCD 18 Ring CCD 19 CCD CLR unit that extracts charges from the ring CCD 20 Output unit 21 Skim unit 22 SK output unit 23 Skim clear unit 40 Barrier inside the charge supply unit 101 Output amplifier 102 Output Floating gate unit 103 Skim output Amplifier 104 Skim output Floating gate unit 105 Skim comparator 201 IRED 202 IRED drive circuit 203 Drive pulse 204 A / D converter 206 AF control circuit 207 Light projecting lens 208 Light receiving lens 210 CPU 211 Memory 221 Covered Body 222 Light-receiving image on sensor array 301 Path of charge moving from sensor to integrating section 302 Path of emptying charge of integrating section 303 Path of moving charge of integrating section to second storage section 304 Charge of integrating section To move to the first storage unit 305 Path to move electric charge of the second storage unit to the ring CCD 306 Path to move electric charge of the first storage unit to the ring CCD

Claims (5)

[Claims] 1. A distance measuring device comprising a light projecting means for flashing and projecting a pulsed light beam toward an object to be measured whose distance is to be measured, and a pulse reflected by said object to be returned and returned. A plurality of photoelectric conversion elements for receiving a light beam and outputting signal charges, integrating the signal charges respectively output from the plurality of photoelectric conversion elements, and transferring the signal charges according to a predetermined charge transfer pulse. A signal charge injecting means for injecting the signal charge transferred by the signal charge supplying means into the cyclic shift register; a cyclic shift register for gradually accumulating the signal charge injected from the signal charge injecting means; And a blinking cycle changing means for changing the blinking cycle of the light means according to the situation of the distance measurement object. 2. A distance measuring device comprising a light projecting means for flashing and projecting a pulsed light beam toward a distance measuring object whose distance is to be measured, and a pulse reflected by said distance measuring object and returning. A plurality of photoelectric conversion elements for receiving a light beam and outputting signal charges, integrating the signal charges respectively output from the plurality of photoelectric conversion elements, and transferring the signal charges according to a predetermined charge transfer pulse. A signal charge injecting means for injecting the signal charge transferred by the signal charge supplying means into the circulating shift register, a plurality of charge transfer channel portions at least part of which are coupled in a loop and arranged, A plurality of transfer electrodes provided on the charge transfer channel part via a gate insulating film, and a charge transfer channel part operated by a transfer clock applied to each transfer electrode. And a floating gate electrode provided through a gate oxide film for detecting the amount of signal charges transferred to the circuit, and circulating the charges in the loop-coupled portion to cumulatively add the charges. A distance measuring apparatus comprising: a shift register; and a blinking cycle changing means for changing a blinking cycle of the light projecting means according to a situation of the distance measuring object. 3. An active distance measuring means for flashing the light projecting means for a predetermined period to accumulate output charges of a plurality of photoelectric conversion elements, and for performing a distance measuring operation from the accumulated signal charges, and for measuring the distance. In the case where the reliability determination means for determining the reliability of the result of the ranging calculation up to the object to be measured and the reliability determination means determine that the calculation result of the active ranging means is poor in reliability, A signal charge resetting means for turning off the light projecting means and resetting the accumulated signal charges; and a plurality of photoelectric conversion elements on the photoelectric conversion elements when the accumulated signal charges are reset by the signal charge resetting means. A signal charge generation unit that newly generates a signal charge from the luminance signal of the image of the object to be formed, and based on the signal charge generated by the signal charge generation unit. Passive distance measuring means for performing a passive distance measuring operation for obtaining the distance to the object to be measured, and when the flashing cycle of the light projecting means is longer than a predetermined cycle, prohibiting the transition to the passive distance measuring operation 3. The distance measuring device according to claim 1, further comprising: a distance measuring operation transition prohibiting unit. 4. A light projecting means for flashing and projecting a pulsed light beam toward an object to be measured, and a photoelectric conversion element for receiving the pulsed light beam reflected and returned by the object to be measured. Then, a distance calculation means for calculating a light receiving position on the photoelectric conversion element by integrating the signal charges output from the photoelectric conversion element, and calculating a distance to the distance measuring object based on the calculated light receiving position. A blinking cycle changing means for changing the blinking frequency of the light projecting means according to the condition of the object to be measured, and a maximum current flowing through the light projecting means according to the blinking frequency changed by the flashing cycle changing means. A distance measuring device comprising: maximum current limiting means for limiting a value. 5. When a function setting means for continuously calculating the distance measurement to the object to be measured and an operation for continuously operating the distance measurement by the function setting means are selected. The distance measuring apparatus according to claim 4, further comprising: a blinking frequency limiting unit that prohibits a blinking frequency for blinking the pulsed light flux from being lower than a predetermined value.