JPH0465626A - Moving speed detecting device for object - Google Patents

Abstract

PURPOSE:To detect the moving speed of the object at a high speed with high accuracy and to realize relatively simple constitution by finding the moving speed of the object from an integration result and a range finding result obtained by performing range finding operation plural times. CONSTITUTION:Under the control of a CPU 11, an IRED 12a is made to emit light plural times at equal time intervals. A range finding optical system 12 projects the light from the IRED 12a on the object 10 and converges reflected light from the object 10 to generate signal currents I1 and I2 corresponding to the incidence position of the converged reflected signal light. A distance arithmetic circuit 14 performs the analog processing of the output signal of a PSD 12d based upon the light projected from the IRED 12a to find the distance to the object 10. An integration circuit 15 integrates range finding results in order. A CPU 11 calculates the moving speed of the object 10 to the optical- axis direction from the range finding result ln and integration result VOUT.

Description

Detailed Description of the Invention r Industrial Field of Application This invention relates to, for example, a device for detecting the moving speed of a subject, and more specifically, to automatic focusing photography of a camera that drives a photographing lens to a focus position based on a focus detection output. The present invention relates to a subject moving speed detection device that is applied to a photographic device, etc., and detects the moving speed of the subject in order to prevent defocusing due to movement of the subject in the optical axis direction of the photographic lens.

[Prior Art] Conventionally, when attempting to photograph a subject moving in the optical axis direction of a photographic lens, there has been a drawback that a focus shift occurs as the subject moves during the release time lag.

Therefore, in order to prevent this focus shift, for example, Japanese Patent Application Laid-Open No. 159817/1983 discloses that distance measuring operations are performed multiple times in response to the Lullize signal, and the position of the subject at the start of exposure is predicted and the photographing lens is adjusted. A drive device is disclosed. Furthermore, in fields other than cameras, a method has been proposed in which infrared rays are projected onto an object to be measured and the moving speed of the object is detected based on the reflected signal, as shown in Japanese Unexamined Patent Publication No. 62-232571. has been done.

Here, a conventional speed detection device will be explained using the above-mentioned Japanese Patent Laid-Open No. 63-159817 as an example.

In FIG. 5, 1 is a subject, and 2 to 4 are a distance measuring optical system, a light emitting element drive circuit, and a light emitting element drive circuit, respectively, which constitute a distance measuring device.
This is a distance calculation circuit.

That is, when an infrared light emitting diode (IRED) 2a included in the ranging optical system 2 is driven by the light emitting element drive circuit 3, light from the IRED 2a is transmitted to the light projection lens 2b.
The light is projected onto the subject 1 through. The light projected onto the subject 1 is reflected there, then condensed by a light receiving lens 2c, and formed into an image on a optical position detection element (PSD) 2d. Then, from the PSD 2d, a signal current 1. , I2 are output.

And this signal current ■1. By processing I2 by the distance calculating circuit 4, the distance to the subject 1 is determined.

In the speed detection device, the distance measuring operation as described above is repeated at predetermined time intervals according to the timing circuit 5.

After each distance measurement result is stored in the distance data storage circuit 6, the moving speed of the subject 1 is detected by calculating how much the subject 1 has displaced within a predetermined period of time.

This speed detection device is equipped with a dedicated function determination circuit 7 consisting of an order determination circuit 7a, a linear function determination circuit 7b, and a quadratic function determination circuit 7C in order to determine speed changes as well. It included a distance prediction calculation circuit 8 for predicting the subject distance at a time point (at the start of exposure), a control circuit 9 for controlling them, and the like.

[Problems to be Solved by the Invention] The conventional speed detection device described above is effective when the distance measurement time is negligibly small and there is no error in the distance measurement result.

However, in reality, these must be taken into consideration, and there are also the following drawbacks. That is, in order to accurately determine the order of the function of the motion speed of the subject 1 from the distance data, a complicated circuit is required, which is expensive. Furthermore, if a one-chip microcomputer (for example, a CPU) is used to perform calculations on software, the calculation time cannot be ignored, and the speed of an object moving at high speed, such as a car, cannot be detected. becomes impossible.

For these reasons, what is required in a speed detection device is a distance measuring device that has extremely small distance measurement errors and can perform distance measurement operations at high speeds. However, electronic circuits always contain noise, and it is not easy to create an ideal distance measuring device.

On the other hand, the applicant of the present application has already made a proposal (see, for example, Japanese Patent Application Laid-Open No. 63132110) to realize highly accurate autofocus by the noise canceling effect of integration.

However, as proposed in this proposal, the distance measurement method in which the I RED is emitted many times causes a long time lag.
It was not suitable for a speed detection device.

Therefore, it was expected that it would be very difficult to perform distance measurement with high precision and short time lag, and to detect the speed of a subject using the same concept as in the past.

The present invention provides a method for detecting the moving speed of a subject with high precision and at high speed, since the above distance measuring devices always have distance measurement errors and time lags, and it takes time to read out and calculate the distance measurement results. To provide a device for detecting the moving speed of a subject, which is capable of detecting the moving speed of a subject with high precision and high speed, and which can be realized with a relatively simple configuration. It is intended to.

[Means for Solving the Problems] In order to achieve the above object, the object moving speed detection device of the present invention includes a light projecting means for projecting light onto the object, and a distance measuring means for receiving reflected light from the object and outputting a value dependent on the object distance; a light projection control means for repeating light projection by the light projection means a plurality of times at predetermined time intervals; An integrating means integrates the output of the distance measuring means each time the light projecting means emits light, and the direction of the optical axis of the light projecting means is calculated from the integration result by this integrating means and the output of the distance measuring means. and speed calculation means for calculating the moving speed of the subject relative to the object.

[Function] The present invention is resistant to noise and can be photographed in a short time because it is possible to determine the moving speed of the subject from the integral results and the distance measurement results of multiple distance measurement operations by the above-described means. This makes it possible to process

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a schematic configuration of a moving speed detection device for a subject according to the present invention.

That is, the CPU II controls the entire device, and a driver 13, a distance calculation circuit (AF circuit) 14, and an integration circuit 15 are connected to the CPU II.

The driver 13 drives an infrared light emitting diode (IRED) 12a included in the ranging optical system 12, and is configured to cause the IRED 12a to emit light multiple times at the same time interval under the control of the CPU 11.

II The distance optical system 12 includes the IRED 12g, a light projecting lens 12b that projects light (infrared light signal) from the IRED 12a toward the subject 10, and the subject 10.
a light receiving lens 12c that collects the reflected light from the light receiving lens 12c, and a light position detection element (PS
D) 12d.

The distance calculation circuit 14 calculates the distance p to the subject 10 by calculating the output signal of the PSD 12d in an analog manner based on the light emitted from the IRED 12a.

The integration circuit 15 sequentially integrates the distance measurement results in the distance calculation circuit 14.

The CPU 1 controls the drive timing of the driver 13 and the distance calculation circuit 14, and calculates the light of the subject 10 based on the distance measurement result Cffn) in the distance calculation circuit 14 and the integration result (, Vou, T) in the integration circuit 15. The moving speed in the axial direction is calculated.

FIG. 2 shows an example of the integration result in the integration circuit 15.

Here, the vertical axis is subject distance (g), and the horizontal axis is time (1).
The straight line (N(t)) indicates that the subject 10 moves at a constant speed.

In FIG. 2(a), time 0, t-, 2t.

The distance measurement results at 3t and 4t are respectively 11.12,
I) 3, ri4, IIs, and the case where there is no error in the distance measurement result is shown as an example.

The integration result in this case is the total area of the hatched area in the diagram, that is, the sum of the upper-right shaded area S1 and the lower-right shaded area S0 (S+ +
S. ).

Usually, the speed V can be determined as V-6g/Δt (1). Therefore, the speed V of the subject 10 moving at a constant speed in the time width 4t can be calculated from the following relationship: y oc S+, / 4 t (2).

At this time, the value of Sl is the above integration result (S1+So) and S. Although it cannot be determined unless the value of So is found, the value of So is 5o-j! It can be obtained from the relationship: 5X4t (3).

Therefore, the moving speed V of the subject 10 is the above integration result,
It can be determined according to the last distance measurement result and the time width of the distance measurement.

FIG. 2(b) shows times 0, t, 2t, and 3t.

Each distance measurement result at 4t ll-1, D-2, II 3.
11 4, J? The case where there is variation in s is shown as an example.

In this way, when the variation is thought to occur randomly, the integration result S−++
S″o1 is almost equal to S, +So in Fig. 4(a). Therefore, even if there are variations in the distance measurement results for each measurement, according to the relationship in equation (2) above, ,
Extremely high precision speed detection is possible.

In addition, although the case where the distance measurement number (g,) is five times is explained here as an example, it is not limited to this, and it goes without saying that the effect increases as the number of distance measurements increases.

Also, based on the obtained velocity V and the last distance measurement result F,3, the position Ω8 of the subject 10 after a predetermined time tA is determined.
Since various methods are already known to predict , such as calculating gA=ρ and +v·tA, their explanations will be omitted here.

FIG. 3 shows the details of the configuration of the distance measuring optical system 12.

This distance measuring optical system 12 constitutes a known single point distance measuring device, and is of a so-called active type in which moonlight is projected onto the subject 10 at the same time as AF.

Now, when the IRED 12a emits light, the light becomes AF light and is projected onto the subject 10 via the light projection lens 12b. Then, this AF target is reflected by the subject 10 and focused through the light receiving lens 12c to form an image on the PSDI 2d.

In this case, the incident position aX of the reflected light is expressed as a function of the subject distance p, as shown by the following equation, based on the principle of triangulation.

S is the distance between principal points (baseline length) between the light emitting lens 12b and the light receiving lens 12C, and f is the light receiving lens 12C.
PSDl, 2d is arranged at this position at a distance from .

From the PSD 12d, two current signals 1. , I2 are output. The total signal photocurrent is Ipo
If the length of PSDI2d is tp, then Ω can be expressed as in the following equation.

(7) Here, a is a line parallel to the line connecting the light emission center of the IRED 12a and the principal point of the light emitting lens 12b.
When extended from the principal point of 2c, it is the length from the point where it intersects with PSD 12d to the end of PSD 12d on the rRED 12a side.

FIG. 4 shows the output signals I, , I of the PSD 12d.

This shows a specific circuit configuration for integrating distance information in the integrating circuit 15.

In FIG. 4, 21.22 is the output signal 1.22 of the PSD 12d generated in response to the light emission of IREDI:2a. ,I2
23.24 is the amplified current I,
, I2 only.

25.26 is a buffer, compression diode 23.2
This is for guiding the compressed voltage at 4 to a differential arithmetic circuit 30 consisting of an NPN h range meter 28 and a current source 29.

Here, when the operation of the differential arithmetic circuit 27 is explained using the symbols in the figure, the following relational expression holds true. Note that Is is transistor 2
728 and the reverse saturation current of the diode 23.24, and vl is the thermal voltage.

Moreover, the current 1a and the current 1b are I a + I b = I at
-(10), the above (8), (9), (
From equation 10), the relationship 1x-1a-1c holds true.

Therefore, from the above equations (7) and (11), the following equations are obtained, and a signal current Ia proportional to the reciprocal of the subject distance p is obtained.

Moreover, 31 in the figure is a current source, and the current 1c caused by this current source 31 has the following relationship. , Therefore, the current lx flowing through the compression diode 32 is as follows.

On the other hand, a current of 1 is supplied to the compression diode 33 by the current source 34.
The compressed voltages of the compression diodes 32 and 33 are input to circuits 37 and 38 of the same type as the differential arithmetic circuit 30, respectively, via buffers 35 and 36, respectively.

Therefore, the output current III of the differential arithmetic circuit 37 consisting of the NPN) transistor 39°40 and the current source 41
Now, if we note that the compression diodes 32 and 33 are generating voltage with reference to the power supply side, we have the following equation. Therefore, from the above equation (14), the current Ip is -1t
...(16), which is obtained as a current signal proportional to the subject distance p.

That is, the differential calculation circuit 37 is a circuit for supplying a current signal according to the object distance I to the integrating circuit 15, and
The current source 41 is turned on by a timing signal every time the RED 12a emits light, so that the current lit depending on the subject distance p is integrated by the integrating capacitor 45 of the integrating circuit 15.

The integrating capacitor 45 is reset by a reset circuit 46 before the IRED 12a starts emitting light. Therefore, after completing a series of ranging operations,
A signal corresponding to the integral output shown as St+So in FIG. 2(a) or as shown in FIG. 2(b) is applied to the output terminal 47.
A signal corresponding to the integral output shown as S-1+S'' appears.

On the other hand, NPN) transistors 42, 43 and current source 4
The differential calculation circuit 38 consisting of 4 is a circuit for obtaining the final distance measurement result, that is, the distance measurement result g in FIG. , a current 1112 flows through the resistor 48.

This current 112 is similar to the above equation (16),
This satisfies the relationship that depends on the subject distance g. Therefore, from the voltage signal output to the output terminal 49, only the last distance measurement result p can be detected.

The voltage signal appearing at the output terminals 47 and 49 is taken in by the A/D converter (not shown) built into the CPU II shown in FIG. 1, and the moving speed V of the subject 10 is determined by the method described above. It will be done.

That is, from the above equation (16), 1 g of current is Iρ-A
-47...(18) However, A is a constant.

Further, the position it (t) of the subject 10 is determined as 0uT 1 (i) −I, V (t t
s)...(19) ,,1g-A(Ns-v(t t 5 ))...(20) If the integration time required to integrate this is T, the output appearing at the output terminal 47 is Voltage V. UT is where B is a constant and C is the capacity of the integrating capacitor 45.

In this way, the moving speed V of the subject 10 can be determined from the voltage VoUT appearing at the output terminal 47, that is, the integral output obtained by integrating the distance measurement results, and the information obtained from the output terminal 49, that is, the last distance measurement result ρ5. At the same time,
Naturally, the position of the subject 10 after a predetermined time is also calculated by Sanda (
prediction) is possible.

As described above, the moving speed of the subject is determined using the integral results obtained from a plurality of distance measurement operations and the distance measurement results.

That is, the light emission of the I RED and the integration of the distance measurement results based on the light emission are repeated multiple times, and the moving speed of the subject is determined from the integral results obtained thereby and the final distance measurement results. In addition, in this case, the series of operations such as distance measurement and integration are analog calculations that finish instantaneously.
Relatively time-consuming operations such as A/D conversion and speed detection calculations are performed all at once after the series of operations described above is completed. This makes it possible to offset the distance measurement error that always exists in one distance measurement operation, and also enables high-speed processing. Therefore, highly accurate and high speed speed detection can be achieved with a simple configuration.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and it goes without saying that various modifications can be made without departing from the gist of the invention.

〔Effect of the invention〕

As detailed above, according to the present invention, it is possible to cancel out the aj distance error that always exists in a single distance measurement operation, and also to perform high-speed processing, so that the subject can be detected with high precision and at high speed. It is possible to provide a moving speed detection device for a subject that can detect the moving speed and can be realized with a relatively simple configuration.

[Brief explanation of drawings]

1 to 4 show an embodiment of the present invention, in which FIG. 1 is a block diagram schematically showing the configuration of a moving speed detection device for an object, and FIG. 2 is an example of an integration result in an integration circuit. FIG. 3 is a configuration diagram showing details of the distance measuring optical system, FIG. 4 is a diagram showing a specific circuit configuration example for integrating distance information, and FIG. FIG. 2 is a block diagram of a speed detection device shown to explain the problem. DESCRIPTION OF SYMBOLS 10... Subject, 11... CPU, 12... Distance measuring optical system, 12 a-IRED, 12 d-P
S.D. 13... Driver, 14... Distance calculation circuit, 15.
...Integrator circuit, 23,24,32.33...Compression diode, 9. 34゜... Current source, 30゜37゜8... Differential calculation circuit, 5... Integrating capacitor, 6... Reset circuit, 8... Resistor.

Claims (1)

[Scope of Claims] A light projection means for projecting light onto a subject; a distance measuring means for receiving reflected light from the subject by the projection of the light projecting means, and outputting a value dependent on the distance to the subject; a light projection control means for repeating the light projection of the light projection means a plurality of times at predetermined time intervals; an integrating means for integrating the output of the distance measuring means each time the light projection means emits light; An apparatus for detecting the moving speed of a subject, comprising a speed calculating means for calculating the moving speed of the subject in the optical axis direction of the light projecting means from the result of integration by the integrating means and the output of the distance measuring means. .