JP3077998B2 - Moving speed detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to, for example, a moving speed detecting device, and more specifically, an automatic focus photographing device of a camera that drives a photographing lens to a focus position based on a focus detection output. Applied to
The present invention relates to a moving speed detecting device that detects a moving speed of a subject in order to prevent a focus shift due to a movement of the subject in the optical axis direction of the photographing lens.

[Prior Art] Conventionally, when an image of a subject moving in the direction of the optical axis of a photographing lens is to be photographed, there is a disadvantage that the subject is shifted during the release time lag, resulting in defocus.

In order to prevent this defocus, for example, Japanese Patent Application Laid-Open No. 63-159817 discloses a photographic lens in which a distance measurement operation is performed a plurality of times in response to a first release signal, and a position of a subject at the start of exposure is predicted. Is disclosed. In fields other than cameras, for example,
As disclosed in Japanese Patent Application Laid-Open No. 62-232571, a method has been proposed in which infrared rays are projected onto an object to be measured and a moving speed of the object to be measured is detected based on a reflected signal.

Here, a conventional speed detecting device will be described with reference to the above-mentioned Japanese Patent Application Laid-Open No. 63-159817.

In FIG. 8, reference numeral 1 denotes a subject, and reference numerals 2 to 4 denote a distance measuring optical system, a light emitting element drive circuit, and a distance calculation circuit, respectively, which constitute a distance measuring device.

That is, when the infrared light emitting diode (IRED) 2a included in the distance measuring optical system 2 is driven by the light emitting element driving circuit 3, the light from the IRED 2a is projected on the subject 1 via the light projecting lens 2b. You. The light projected on the subject 1 is reflected there, then condensed by a light receiving lens 2c, and is imaged on a light position detecting element (PSD) 2d. Then, the signal currents I ₁ and I according to the incident position of the reflected signal light are output from the PSD 2d.
₂ is output. The distance to the subject 1 is obtained by processing the signal currents I ₁ and I ₂ by the distance calculation circuit 4.

In the speed detecting device, the distance measuring operation as described above is repeated at predetermined time intervals according to the timing circuit 5. Then, after each distance measurement result is stored in the distance data storage circuit 6, the movement speed is detected by calculating how much the position of the subject 1 has changed within a predetermined time.

In addition, this speed detecting device includes a dedicated function determining circuit 7 including an order determining circuit 7a, a linear function determining circuit 7b, and a quadratic function determining circuit 7c in order to determine a speed change. It includes a distance prediction calculation circuit 8 for predicting the subject distance at the time (at the start of exposure), and a control circuit 9 for controlling them.

[Problems to be Solved by the Invention] The conventional speed detection device described above is effective when the distance measurement time is so small that it can be ignored and the distance measurement result has no error.

However, in practice, these must be considered, and there are the following disadvantages. That is, a complicated circuit is required to strictly obtain the order of the function of the movement speed of the subject 1 from the distance data, which is expensive.
In addition, when a software operation is performed using a one-chip microcomputer (for example, a CPU) or the like, the operation time cannot be ignored and the speed of an object moving at a high speed such as an automobile is detected. It becomes impossible.

For these reasons, what is required in the speed detection device is a distance measurement device that has a very small distance measurement error and that can perform a distance measurement operation at a high speed. However, noise always exists in electronic circuits, and it is not easy to create an ideal distance measuring device.

On the other hand, the applicant of the present application has already proposed (for example, see Japanese Patent Application Laid-Open No. 63-132110) realizing high-precision autofocus by a noise canceling effect by integration. However, the distance measurement method that emits IRED repeatedly as in this proposal still has a long time lag, and is not suitable for a speed detection device.

FIG. 9 shows a general speed detecting operation employing a conventional distance measuring method.

That is, when it is difficult to ensure accuracy by only one distance measurement operation, noise components randomly appearing in the distance measurement result can be canceled by performing a plurality of distance measurement operations. However, as shown in FIG. 9, if the distance measurement operation is performed a plurality of times (here, for example, four times) at the timing of (a), a time lag occurs only by itself. In addition, since the subject distance changes during the four distance measurement operations,
It is hard to say that it is an effective method for distance measurement of moving objects.

Also, at the timing of (b), a reasonable time lag occurs in the distance calculation operation for obtaining an accurate distance measurement result from the four distance measurement results described above.

Following the timing of (b), four ranging operations are performed at the same timing of (c) as the timing of (a),
After performing a distance calculation operation for obtaining an accurate distance measurement result from the result at the timing of (d), if an attempt is made to obtain the moving speed of the subject from the two calculation results, ( The timing of e) is required, and a very long speed detection time is required.

In addition, since the moving object is measured, the advantage of repeating the distance measurement many times due to a change in the moving object during the distance measurement is lost.

Therefore, it was expected that it would be very difficult to measure the distance with high accuracy and with a short time lag, and to detect the speed of the subject in the same way as in the related art.

In addition, when the subject is moving at the same speed, the conventional speed detecting device has the following problems when applied to an automatic focus photographing device of a camera.

As shown in FIG. 10, in a general photographing lens, between the subject distance 1 and the focal length f _{L of} the lens, and the distance (extending amount) K between the film and the lens, K · l = f _L ² , K = f _L ² · 1 / l holds.

Therefore, in the case of a subject moving 1 m during the same shutter time lag, when the subject moves from 3 m to 2 m or when moving from 2 m to 1 m, the degree of out-of-focus becomes larger as the distance becomes shorter. For this reason, if the speed is detected with the same time lag for a subject at a short distance as in the case of a long distance, the amount of advance correction by moving object prediction becomes too large and the error increases, or in extreme cases, At the timing when the exposure starts, the subject may pass by the camera position, and the shooting may end in failure.

In addition, in the case of the so-called active method, in which the IRED emits light to measure the distance, if the distance between the distance measurement operations, that is, the light emission interval of the IRED is reduced, the IRED is heated by the drive current, and the amount of light is reduced or destroyed. There is, briefly,
It was impossible to shorten the interval of the distance measurement operation for speed detection.

According to the present invention, a distance measuring apparatus always has a distance measuring error and a time lag, and it takes time to read and calculate a distance measuring result. A first object of the present invention is to detect a moving speed capable of reducing the influence of a time lag in accordance with the distance. A second object is to provide a moving speed detecting device capable of reducing a time lag when an object is at a short distance, and a third object is to provide a time lag in a so-called active type distance measuring device. A fourth object of the present invention is to provide a moving speed detecting device capable of detecting the moving speed with high accuracy and high speed.

[Means for Solving the Problems] In order to achieve the above object, in the moving speed detecting device of the present invention, a distance measurement for repeatedly measuring a distance to a moving object at a predetermined time interval a predetermined number of times. Means, when the initial distance measurement result is closer than a predetermined value, a switching means for shortening the predetermined time interval, or changing the predetermined number of times smaller, and an even number and an odd number of the distance measurement result respectively. It comprises first and second integrating means for integrating, and calculating means for calculating the moving speed of the object based on the difference between the first and second integration results and the predetermined time interval.

[Operation] According to the present invention, the distance of an object is measured a predetermined number of times at predetermined time intervals by the above-described means, the moving speed of the object is calculated based on the result, and based on the initial output of the measurement. Since the predetermined time or the predetermined number of times is switched, the processing can be performed in a short time while being resistant to noise, and the time lag can be reduced without lowering the accuracy.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a schematic configuration of a subject moving speed detecting apparatus according to the present invention.

That is, the CPU 11 controls the entire apparatus, and the CPU 11 is connected to the timing circuit 13, the distance calculation circuit (AF circuit) 14, and the subtraction circuit 15.
Further, switches SW1, SW2 and first and second integration circuits 16, 17 are connected in parallel between the distance calculation circuit 14 and the subtraction circuit 15, respectively.

The timing circuit 13 operates the distance calculation circuit 14, the switches SW1 and SW2, and the driver 18 under the control of the CPU 11.

The driver 18 drives an infrared light emitting diode (IRED) 12a included in the distance measuring optical system 12 according to an instruction from the timing circuit 13.

The distance measuring optical system 12 condenses the IRED 12a, the light projecting lens 12b that projects light (infrared light signal) from the IRED 12a toward the subject 10, and the reflected light from the subject 10. It comprises a light receiving lens 12c and a light position detecting element (PSD) 12d that generates signal currents I ₁ and I ₂ according to the incident position of the reflected signal light condensed by the light receiving lens 12c.

The distance calculation circuit 14 is a PSD based on the light emission of the IRED 12a.
According to the output signal of 12d, that is, the signal light component is extracted from the steady light component in accordance with the instruction from the timing circuit 13, and the extracted signal light component is calculated in an analog manner to obtain the distance 1 to the subject 10.

The first integration circuit 16 sequentially integrates the distance measurement results in the distance calculation circuit 14 supplied when the switch SW1 is turned on (closed) in accordance with an instruction from the timing circuit 13.

The second integration circuit 17 sequentially integrates the distance measurement results in the distance calculation circuit 14 supplied when the switch SW2 is turned on (closed) in accordance with an instruction from the timing circuit 13.

The subtraction circuit 15 calculates the difference between the integrated outputs supplied from the first and second integration circuits 16 and 17, respectively.

The CPU 11 calculates the moving speed of the subject 10 in the optical axis direction based on the output of the subtraction circuit 15.

Further, the CPU 11 sets the interval or the number of distance measurement operations for the timing circuit 13 based on the first distance calculation output (distance measurement result) supplied from the distance calculation circuit 14. . That is, the CPU 11
In accordance with the distance 1 to 0, the light emission interval or the number of times of light emission of the IRED 12a is varied, and in synchronization with the light emission operation, the integration timing in the first and second integration circuits 16 and 17 (switches of the switches SW1 and SW2) Switching).

Here, the concept of changing the interval or the number of distance measurement operations according to the present invention will be described.

First, in the distance measurement operation, if the interval is not sufficient, as described above, the amount of signal light is reduced by heating the IRED.

Generally, in the case of an active type distance measuring device, depending on the amount of light emitted and the influence of circuit noise or external light noise,
The greater the distance of the subject, the greater the accuracy degradation.
On the other hand, in the case of the short distance, the signal light quantity to be projected is not required as much as in the case of the long distance, so that a slight decrease in the light quantity does not matter. Conversely, shortening the interval between the distance measuring operations is effective as a measure against the time lag described above. Therefore, in the case of a short distance, the time lag is more important than the light quantity, that is, the speed detection is performed by shortening the interval of the distance measurement operation.

On the other hand, increasing the number of distance measurement operations leads to prevention of deterioration of the S / N ratio for a distant subject as described above. In other words, for the same reason as in the case of the distance measurement operation, sufficient S / N
This means that the ratio is obtained, and it is not necessary to repeat the ranging operation many times to increase the accuracy. Therefore, in the case of a short distance, it is possible to emphasize the reduction of the time lag rather than the improvement of the S / N ratio by increasing the number of distance measurement operations. Therefore, in the case of a short distance, the speed detection is performed by reducing the number of distance measurement operations.

Based on the above concept, the IRED 12a emits light a plurality of times according to the time interval or the number of times set in the timing circuit 13. Then, the calculation of the subject distance 1 and the integration output thereof are obtained each time the light is emitted, so that more effective speed detection can be performed for a subject at a short distance.

FIG. 2 shows an example of the integration result in the first and second integration circuits 16 and 17.

Here, the vertical axis indicates the subject distance (l), the horizontal axis indicates time (t), and the straight line (l (t)) indicates the l-to-t relationship when the subject 10 moves at a constant speed. Note that the time width of t in FIG alter according to the first subject distance l ₁ is by varying the spacing of the distance measuring operation of the present invention, also first a distance measuring operation, which shows a six alter depending on the object distance l ₁ of is to vary the number of distance measuring operation of the present invention.

In the case of this embodiment, the integration operation is actually performed by alternately turning on the switches SW1 and SW2. Here, for the sake of easy understanding, first, the results of the first three distance measurements will be described. Here, the case where the first integration circuit 16 integrates the results of the next three distance measurements with the second integration circuit 17 will be described.

In FIG. 2 (a), time 0, t, 2t, 3t, 4t,
Each distance measurement result at 5t is represented by l ₁ , l ₂ , l ₃ , l ₄ , l ₅ ,
l ₆ is shown as an example where there is no error in the distance measurement result.

In this case, the integration result of the distance measurement results l ₁ , l ₂ , and l ₃ is the area of the upper right oblique line portion S ₁ , and the distance measurement results l ₄ , l ₅ , and l ₆
Integration result for is a area of the right upstream hatched portion S _2.

Taking the difference between the area S ₁ and the area S ₂ of the time (the difference between the integration output), the area indicated by the hatched portion S ₃ downward sloping on the area S ₁ is determined. The area S ₃ is speed information.

That is, as shown in the figure, for example, l ₁ = 12, l ₂ = 11,
Assuming that the subject 10 is approaching one by one during the unit time t, such as l ₃ = 10, l ₄ = 9, l ₅ = 8, l ₆ = 7, the area S ₁ and the area S ₂ are respectively S ₁ = 10 + 11 + 12 = 33 ... (1) a _{S 2 = 7 + 8 + 9} = 24 ... (2). Therefore, the area S ₃ becomes _{S 3 = S 1 -S 2 =} 9 ... (3).

From this result, the difference between the start timings of the integration of the areas S ₁ and S ₂ is 3t, and since the number of integrations is three each, the speed v becomes: v = S ₃ / 3t × 3 = 9 / 9t = 1 / t (4)

FIG. 2B shows the distance measurement results l ′ ₁ , l ′ ₂ , l ′ ₃ , l ′ ₄ , at time 0, t, 2t, 3t, 4t, 5t.
An example is shown in which random noise is added to l ′ ₅ and l ′ ₆ .

In this case, the area S ′ ₃ becomes S ′ ₃ = S ′ ₁ −S ′ ₂ ≒ S ₃ = 9 (5) due to the noise canceling effect due to the integration. Speed detection in which only one position per time t changes is possible despite the inaccuracy of each distance measurement result.

Next, the operation of the present invention that enables more accurate speed detection based on the same concept as the distance measurement method based on the difference between the two integrated outputs described with reference to FIG. 2 will be described.

In particular, in the case of a so-called active AF in which the distance is measured by projecting the IRED light to the subject, the S / N ratio is deteriorated and the accuracy is deteriorated as the subject is farther away. Therefore, as shown in FIG. 2, when the integration operation is performed with the long distance side of l ₁ , l ₂ , l ₃ as one set, the short distance side of l ₄ , l ₅ , l ₆ is set as one set. When performed as a set, a large difference in accuracy appears between the two integration results.

Therefore, in the present invention, the first distance measurement result l ₁ is obtained by the first integration circuit 16, and the second distance measurement result l ₂ is obtained by the second integration circuit 17. _{For 3} , the first and second integrating circuits 16 and 17 are switched every time the distance measurement operation is performed, as in the case of the first integrating circuit 16 again. As described above, the result of the odd-numbered distance measurement is integrated by the first integration circuit 16, and the result of the even-numbered distance measurement is integrated by the second integration circuit 17 to balance the error between the two integration results. be able to.

FIG. 3 specifically shows the timing of the distance measurement operation and the integration operation according to the present invention.

That is, for each distance measurement operation, the integration operation 1 by the first integration circuit 16 and the integration operation 2 by the second integration circuit 17 are repeated at the timing shown in the figure. In this case, the process of calculating the distance is not required even in comparison with the conventional speed detecting device (see FIG. 9). Therefore, when speed detection is performed in the same time, a noise canceling effect by more integration is expected. it can. In addition, since the change in the position of the subject for each distance measurement operation is also considered from the beginning, much more accurate speed detection can be performed.

As described above, the opening and closing of the switches SW1 and SW2 are controlled by the timing circuit 13 each time the IRED 12a emits light, and the distance measurement results from the distance calculation circuit 14 are sequentially integrated in the integration operations 1 and 2 as described above. This is performed by being supplied to the circuits 16 and 17.

When a series of distance measuring operations is completed, the first and second integrating circuits
The difference of the integral output from 16, 17 is obtained by the subtraction circuit 15,
Speed information corresponding to the area S ₃ described with reference to the Figure 2 is calculated. When the speed information (area S ₃ ) in this case is obtained according to the above equation (5), S ₃ = (12 + 10 + 8) − (11 + 9 + 7) = 3 (6) At this time, unlike the case of the above equation (4), the difference between the integration timings of the integration circuits 16 and 17 is t. However, since the number of integrations is also three, the speed v finally obtained is v = S ₃ / t × 3 = 1 / t (7) Therefore, the above equation (7) becomes the same as the above (4), and the same result as that described with reference to FIG. 2 is obtained.

FIG. 4 shows the details of the configuration of the distance measuring optical system 12.

The distance measuring optical system 12 constitutes a known one-point distance measuring device, and is a so-called active method of projecting AF light onto the subject 10.

Now, when the IRED 12a emits light, the light becomes AF light and is projected on the subject 10 via the light projecting lens 12b. Then, the AF light is reflected by the subject 10, and is condensed via the light receiving lens 12c to be formed as an image on the PSD 12d.

In this case, the incident position x of the reflected light is expressed as a function of the subject distance l as shown by the following equation according to the principle of triangulation.

Here, S is the distance between the principal points (base line length) between the light projecting lens 12b and the light receiving lens 12c, f is the focal length of the light receiving lens 12c, and the PSD 12d is arranged at this position. .

The PSD 12d outputs two current signals I ₁ and I _{2 that} are functions of the incident position x. The total signal photocurrent and Ip _0, PSD12d
Assuming that the length of tp is tp, l can be expressed as in the following equation.

Here, a is the emission center of the IRED 12a and the projection lens 12b.
When a line parallel to the line connecting to the principal point is extended from the principal point of the light receiving lens 12c, the point that crosses the PSD 12d
Is the length up to the end on the IRED12a side.

FIG. 5 shows the output signals I ₁ and I ₂ of the PSD 12d,
17 shows a specific circuit configuration for integrating the distance information.

In FIG. 5, reference numerals 21 and 22 denote preamplifiers which attenuate the output signals I ₁ and I ₂ of the PSD 12d generated in response to the light emission of the IRED 12a with low input impedance and amplify them.
Is a compression diode for compressing only the amplified currents I ₁ and I ₂ .

Reference numerals 25 and 26 denote buffers for guiding the compression voltage of the compression diodes 23 and 24 to a differential operation circuit 30 including NPN transistors 27 and 28 and a current source 29.

Here, the operation of the differential operation circuit 30 will be described using symbols in the drawing. Holds. Is is the transistor 27,2
8 and a reverse saturation current of the diode 23, 24, V _T is the thermal voltage.

Further, the current Ia and the current Ib are calculated from the above equations (12), (13), and (14) from the relationship of Ia + Ib = I ₀₁ (14). The relationship holds.

Therefore, from the above equations (11) and (15), And a signal current Ia proportional to the reciprocal of the subject distance 1 is obtained.

Further, 31 in the figure is a current source, and a current Ic flowing by the current source 31 is: Has the relationship Therefore, the current Ix flowing through the compression diode 32 is Becomes

On the other hand, a current Id is supplied to the compression diode 33 by the current source 34, and the compression voltage of the compression diodes 32, 33 is supplied to the respective buffers 35, 36 via the buffers 35, 36, respectively. Entered into 38 respectively.

Therefore, this NPN transistor 39,40 and current source
Note that the output current Il of the differential operation circuit 37 composed of 41 now has a voltage generated by the compression diodes 32 and 33 on the power supply side reference. Becomes Therefore, from the above equation (18), the current Il is Which is obtained as a current signal proportional to the subject distance l.

That is, the differential operation circuit 37 is a circuit (SW1) for supplying a current signal corresponding to the subject distance 1 at the first timing to the integration circuit 16, and the timing circuit is provided every time the odd-numbered light emission of the IRED 12a is performed. When the current source 41 is turned on by the timing signal from 13, the current Il depending on the subject distance l is integrated by the integration capacitor 45 of the integration circuit 16.

The integration capacitor 45 is reset by a reset circuit 46 prior to the emission of the IRED 12a.
For this reason, a signal corresponding to “12 + 10 + 8” appears at the output terminal 47 after a series of distance measurement operations is completed, for example, in the above equation (6).

On the other hand, the differential operation circuit 38 including the NPN transistors 42 and 43 and the current source 44 is a circuit (SW2) for supplying a current signal corresponding to the subject distance 1 at the second timing to the integration circuit 17, and the IRED 12a When the current source 44 is turned on by the timing signal from the timing circuit 13 every time the light emission of the even number is performed, the current Il ₂ depending on the subject distance l is integrated by the integration capacitor 48 of the integration circuit 17. You.

The current Il _{2 at} this time is, as in the above equation (20), Satisfies the relationship depending on the subject distance l.

Similarly, the integration capacitor 48 is reset by the reset circuit 49 prior to the emission of the IRED 12a. For this reason, the output terminal 50 after a series of distance measuring operations is “11 + 9 +
A signal corresponding to "7" appears.

In this way, after the end of the plurality of distance measurement operations as shown in FIG. 3, the subtraction circuit 15 outputs the output terminals 47,5.
From the difference of the voltage signal appearing at 0 speed information S ₃ in the above expression (6) is obtained. The calculation of the speed information S ₃ is to each integrated output may be performed by digitally CPU11 converted A / D, may be performed by analog subtraction circuit implemented with an operational amplifier.

Then, for example, on the basis of the speed information S ₃ CPU 11
, The moving speed v of the subject 10 is calculated by the calculation shown in the above equation (7).

That is, assuming that the voltage signals appearing at the output terminals 47 and 50 are V _OUT1 and V _OUT2 , respectively, the subject position l (t)
Is given by l (t) = − v · t + l ₁ (22) according to the speed v described with reference to FIG.

In addition, the above equations (20) and (21) are as follows: Il = A · l (t) = A (l ₁ −v · t) (23) Il ₂ = A · l (t) = A (l ₁ ) −v · t) (24) Where A is a constant.

Therefore, assuming that the capacitance of the integrating capacitor 45 is C, the voltage signal V _OUT1 becomes Becomes Here, T is the integration time.

On the other hand, the voltage signal V _OUT2 is, Delta] t with respect to the voltage signal V _OUT1
Since the timing is shifted and integration is performed only for time T, Becomes

Thus, the difference ΔV _OUT between the voltage signals V _OUT1 and V _OUT2 is Becomes Where D is a constant.

As described above, the difference ΔV between the two integrated outputs V _OUT1 and V _{OUT2
From OUT} , the speed v can be easily obtained.

Next, an operation when the interval or the number of distance measurement operations is changed will be described.

Figure 6 is for shortening the interval of the ranging operation on a nearby subject, the first range finding results l _1, comprising the step of determining the timing of the subsequent distance measurement operation .

That is, the first measurement result l _1, spacing distance measuring operation
t ₂ is determined according to the relationship t ₂ = t ₀ −t ₁ · 1 / l ₁ (29). In this case, the shorter the subject distance l, the interval t ₂ is reduced.

Incidentally, where considered destruction by heating IRED12a can be solved by providing a power control circuit to reduce the drive current of IRED12a in accordance with the intervals t ₂ separately.

Figure 7 is to reduce the number of distance measuring operations intended to reduce the time lag for a nearby subject, the first range finding results l _1, the number of distance measuring operation are determined.

Generally, in the case of an active distance measuring device, its S / N
The ratio can be expressed as S / N∝1 / l ² (30) where l is the subject distance.

In addition, the noise canceling effect is given by Becomes

Therefore, by setting the number n of the distance measuring operation in response to the first ranging result _{l 1 n = n 0 · l} 1 2 ... (32), be equal to S / N ratio at each distance it can.

The operations of the above equations (31) and (32) are, for example,
The processing is performed in the CPU 11.

In addition, in consideration of these results, the value of D in the speed detection calculation expression shown in the above expression (28) is changed.

As described above, when the moving speed of the subject is obtained from the integrated outputs of the plurality of distance measuring operations, the interval or the number of distance measuring operations can be changed according to the subject distance.

That is, the moving speed of the subject is obtained from the difference between the first and second integrated outputs obtained by varying the interval or the number of distance measurement operations according to the first distance measurement result and integrating the distance measurement result. I have to. This makes it possible to perform processing in a short time while being resistant to noise.
In particular, it is possible to reduce the influence of a time lag, which is a problem in measuring a subject at a short distance. Therefore, high-accuracy and high-speed speed detection can be realized with a simple configuration.

Further, when the present invention is applied to an automatic focus photographing apparatus for a camera, an apparatus which is hardly out of focus and extremely easy to use can be obtained.

In the above embodiment, each of the first and second integrating circuits is provided with a reset circuit. However, the present invention is not limited to this. For example, two resetting circuits may share one resetting circuit. .

Further, the present invention is not limited to the one that obtains the speed information from the difference between the outputs of the two integrators, but may be applied to, for example, one configured to obtain the speed information from the output of one integrator.

Furthermore, based on the results of the first (first) distance measurement, IRED
Although the light projection interval or the number of times of light projection is made variable, the present invention is not limited to this. For example, the light emission distance or the number of light projections may be made variable based on a plurality of initial distance measurement results.

Of course, various modifications can be made without departing from the scope of the present invention.

[Effects of the Invention] As described above, according to the present invention, the interval or the number of distance measurement operations is changed according to the initial distance measurement result to be repeatedly measured, and the distance measurement result obtained by integrating the distance measurement result is obtained. Since the moving speed of the subject is obtained based on the difference between the first and second integrated outputs, the moving speed of the subject can be detected with high accuracy and high speed, and is realized with a relatively simple configuration. In addition to this, it is possible to reduce the influence of a time lag, which is a problem when measuring the distance of a subject at a short distance.

[Brief description of the drawings]

1 to 7 show an embodiment of the present invention. FIG. 1 is a block diagram schematically showing a configuration of a moving speed detecting device for a subject, and FIG. 2 explains an outline of an integrating operation. FIG. 3 is a timing chart for explaining the operation, FIG. 4 is a configuration diagram showing details of a distance measuring optical system, and FIG. 5 is a specific circuit for integrating distance information. FIG. 6 is a diagram showing a configuration example, FIG. 6 is a flowchart for explaining an operation when the interval of the distance measurement operation is varied, and FIG. 7 is a diagram for explaining an operation when the number of distance measurement operations is varied. 8 to 10 are flowcharts for explaining the prior art and its problems, FIG. 8 is a block diagram of a speed detecting device, FIG. 9 is a timing chart, and FIG. Indicates the subject distance and lens extension of a general shooting lens It is a figure which shows the relationship with quantity. 10… Subject, 11… CPU, 12… Distance measuring optical system, 12a…
... IRED, 12d ... PSD, 13 ... Timing circuit, 14 ... Distance calculation circuit, 15 ... Subtraction circuit, 16 ... First integration circuit,
17: second integration circuit, 18: driver, 23, 24, 32, 33
…… compression diode, 29,31,34,41,44 …… current source, 30,3
7,38 …… Differential operation circuit, 45,48 …… Integration capacitor, 4
6,49 …… Reset circuit.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-240109 (JP, A) JP-A-63-159817 (JP, A) JP-A-62-2232571 (JP, A) 81519 (JP, A) JP-A-4-65627 (JP, A) JP-A-4-65629 (JP, A) JP-A-60-113573 (JP, U) Patent 2916882 (JP, B2) JP-B-7 -104156 (JP, B2) JP 5-78767 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01S 17/00-17/95 G01C 3/00-3/32 G02B 7/32

Claims (1)

(57) [Claims] 1. A distance measuring means for repeatedly measuring a distance to a moving object at a predetermined time interval a predetermined number of times, and when the initial distance measurement result is shorter than a predetermined value, the predetermined time interval is shortened. Or switching means for changing the predetermined number to a small number, first and second integrating means for respectively integrating even and odd times of the distance measurement result, and a difference between the first and second integration results and a time interval. And a calculating means for calculating the moving speed of the object based on the above.