JPH0465627A - 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 by finding the moving speed of the object from a 1st and a 2nd integration output obtained by performing range finding operation plural times. CONSTITUTION:Under the control of a CPU 11, an IRED 12a is made to emit light at equal time intervals. A range finding optical system 12 projects the light from the IRED 12a on the subject 10 and converges reflected light from the subject 10 to generate signal currents I1 and I2 corresponding to the incidence position of the converged reflected signal light. A distance arithmetic circuit 14 processes the output signal of a PSD 12d to find the distance l to the object 10. An integration circuit 16 integrates range finding results supplied through a switch SW 1 in order. An integration circuit 16 integrates range finding results supplied through a switch SW 2 in order. A subtracting circuit 15 finds the difference between the integration outputs. The CPU 11 calculates the moving speed of the object 10 to the optical axis direction according to the output of the circuit 15. The CPU 11 controls the integration timing of the integration circuits 16 and 17.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to, for example, a moving speed detection device for a subject, and more specifically, to automatic focus 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. In fields other than cameras, for example, as shown in Japanese Unexamined Patent Publication No. 62-232571, 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. 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. 6, 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 driving 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.

Then, this signal current 1. , I2 are processed by the distance calculating circuit 4 to determine the distance to the subject 1.

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.

Note that 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 ignored. It becomes impossible to detect.

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, noise is always present in electronic circuits, and it is not easy to create an ideal distance measuring device.

In response to this problem, the applicant of the present invention has proposed realizing highly accurate autofocus by the noise canceling effect of integration (see, for example, Japanese Patent Laid-Open No. 132110/1983). However, as in this proposal, I
The distance measuring method in which the RED is emitted many times has a long time lag, so it is not suitable for a speed detection device.

FIG. 7 shows a general speed detection operation using a conventional distance measuring method.

That is, if it is difficult to ensure accuracy with just one distance measurement operation, noise components randomly appearing in the distance measurement results can be canceled out by performing the distance measurement operation a plurality of times. However, as shown in FIG. 7, if the distance measuring operation is performed a plurality of times (for example, four times in this case) at the timing (a), a time lag will occur. Furthermore, since the distance to the subject changes during the four distance measurement operations, it is difficult to say that this is an effective method for distance measurement of a moving object.

Furthermore, a certain amount of time lag occurs when the distance calculation operation is performed to obtain an accurate distance measurement result from the above-mentioned four distance measurement results at the timing (b).

Following the timing of (b), the distance measurement operation is performed four times at the timing of (c), which is the same as the timing of (a), and (
After performing a distance calculation operation to obtain an accurate distance measurement result from the results at timing d), if you try to calculate the moving speed of the subject from the results of those two calculations, the ), which requires a very long speed detection time.

Furthermore, since the distance is measured from a moving object, the advantage of repeating distance measurement many times is lost due to changes in the moving object during the distance n.

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 the 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-mentioned 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; a first integrating means for integrating the output of the distance measuring means at a first timing when the light projecting means emits light; and a first integrating means for integrating the output of the distance measuring means at a second timing when the light projecting means emits light; It is comprised of a second integrating means for integrating the output, and a speed calculating means for calculating the moving speed of the object with respect to the optical axis direction of the light projecting means using the outputs of the first and second integrating means. ing.

[Operations] The present invention is resistant to noise because the moving speed of the subject can be determined from the first and second integral outputs of a plurality of ranging operations using the above-described means.
Moreover, the process can be completed in a short time.

[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 a subtraction circuit 15 are connected to the CPU II. Further, between the distance calculation circuit 14 and the subtraction circuit 15, the first . A second integration circuit 16.17 is provided.

The driver 13 drives an infrared light emitting diode (IRED) 12a included in the ranging optical system 12.
Under the control of the CPU II, the I RED 12a is caused to emit light multiple times at the same time interval.

The distance measuring optical system 12 includes the IRED 12a and the IR
A light projecting lens 12b that projects the light (infrared light signal) from the ED 12g toward the subject 10, a light receiving lens 12c that collects the reflected light from the subject 10, and a light receiving lens 12c that collects the light. Optical position detection element (PSD) that generates a signal current 11+12 according to the incident position of the reflected signal light
12d.

The distance calculating circuit 14 calculates the distance g to the subject 10 based on the light emission of the IRED 12a (by calculating the output signal of the PSD 12d in an analog manner).

The first integration circuit 16 is turned on/off under the control of the CPU II.
The distance measurement results in the distance calculating circuit 14, which are supplied via the switch SWI which is turned off, are sequentially integrated.

The second integration circuit 17 is turned on/off under the control of the CPU II.
The distance measurement results in the distance calculation circuit 14, which are supplied via the switch SW2 which is turned off, are sequentially integrated.

The subtracting circuit 15 is a subtracting circuit 15 that is connected to the first subtracting circuit 15 described above. Second integration circuit 16.17
This is to find the difference between the integral outputs supplied respectively.

The CPU 1 controls the drive timing of the driver 13 and the operation for extracting the signal light component from the steady light component in the distance calculation circuit 14, and also controls the moving speed of the subject 10 in the optical axis direction based on the output of the subtraction circuit 15. is designed to be calculated.

Further, CPU 1 is the first CPU. Second integration circuit 1617
Integration timing at (switch SWI).

This is to control the switching of SW2. That is,
The CPU 11 uses the IRED 12a via the driver 13.
When emitting light, switch SWI, SW2 each time.
It is designed to control the opening/closing of the

Figure 2 shows the above-mentioned item 1. An example of the integration result in the second integration circuit 16°17 is shown.

Here, the vertical axis is subject distance (Ω), and the horizontal axis is time (1).
The straight line (N(j)) shows the relationship between Ω and t when the subject 10 moves at a constant speed.

In this example, it is actually the switch SWI.

Integral operation is performed by alternately turning on SW2.In order to make it easier to understand, here, first,
The first three distance measurement results are collected by the first integrating circuit 16, and the next three distance measurement results are
A case will be described in which the distance measurement results are integrated by the second integrating circuit 17.

In FIG. 2(a), times 0, t, and 2t.

Each distance measurement result at 3t, 4t, and 5t is g2,
It is expressed as g2, g3, Ω4, Ω5, and II6, and the case where there is no error in the distance measurement result is shown as an example.

In this case, the integration result for the distance measurement results p, , p2, p3 is the area of the upper right diagonal line S1, and the distance measurement result g4,
The integration result for Ω5 and ρ6 is the area of the upper right diagonal line portion S2.

Difference between area S1 and area S2 at this time (difference in integral output)
Then, the area shown by the diagonal line S3 at the lower right on the area S1 can be found. This area S3 becomes speed information.

That is, as shown in the figure, for example, N+=12, Ω2
=11, D3 =10, Ω4-9, ff5-8, J7
Assuming that b = 7 and that the subject 10 approaches one by one during the unit time t, the area S1 and the area S2 are respectively S = 10 + 11 + 12 = 33 (1
)S2=7+8+9=24,=(2
). Therefore, the area S3 is 53=SI 52=9 (3
).

From this result, the difference in the start timing of the integration of the areas Sl and S2 is 3t, and the number of integrations is 3 each, so the speed V is: v-33/3 t X3 = 9/9 t = 1/ l-(4)
It can be found as

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

Each distance measurement result Ω'3, Ω'2, Ω'3 at 4t and 5t
, Ω′4, Ω5, and D′6 are shown as an example.

In this case, due to the noise cancellation effect due to integration, S'3=
S'l S'2→53-9 ... (5) Therefore, similarly to the above equation (4), either the speed detection that the position changes by one per unit time t, or each distance measurement result This is possible despite the inaccuracy of

Next, the operation of the present invention, which enables more accurate speed detection, will be described basically using the same concept as the distance measuring method based on the difference between two integral outputs described with reference to FIG.

In particular, in the case of so-called active AF in which distance measurement is performed by projecting IRED light onto a subject, the farther the subject is, the worse the S/N ratio and the worse the accuracy.

Therefore, as shown in FIG. 2, the integral operation is changed to Dl, I
12. When the far side of D3 is done as one set, and when Ω4. Ω6. There is a large difference in accuracy between the two integration results when the short distance side of fI5 is performed as one set.

Therefore, in the present invention, the first distance measurement result Ω1 is processed by the first integration circuit 16, the second distance measurement result g2 is processed by the second integration circuit 17, and the third measurement result p3 is processed by the second integration circuit 17.
For each distance measurement operation, the first integration circuit 16 and the second integration circuit 16, 17 are switched to perform the integration operation, such as using the first integration circuit 16 again. In this way, the odd-numbered distance measurement results are integrated by the first integration circuit 16, and the even-numbered distance measurement results are integrated by the second integration circuit 17, thereby balancing the errors in the two integration results. be able to.

FIG. 3 specifically shows the timing of the ranging operation and the integrating operation according to the present invention.

That is, for each distance measuring operation, the first integrating operation 1 by the first integrating circuit 16 and the second integrating operation 2 by the second integrating circuit 17 are repeated at the timing shown in the figure. In this case, compared to conventional speed detection devices (see Figure 7), there is no need for the process of calculating distance, so when speed detection is performed in the same amount of time, a noise cancellation effect due to more integration is expected. can. Furthermore, since changes in the subject position for each distance measurement operation are taken into account from the beginning, it is possible to detect speed with much higher accuracy.

Here, when a series of ranging operations are completed, the difference between the integral outputs from the first and second integrating circuits 16 and 17 is calculated by the subtracting circuit 15.
The area S3 obtained by and explained with reference to FIG.
The speed information corresponding to is calculated. The speed information (area S3) in this case is calculated according to the above equation (5): 53=(12+lO+8) (11+9+7)=3
...(6). At this time, unlike the case of equation (4) above, the difference in the integration timing of each integration circuit 16 and 17 is t, but the number of integrations is also 3, so the final speed ■ is calculated as follows. v = 83 / t x 3-1 / t
-L7). Therefore, the above equation (7) becomes the same as the above (4), and the same result as described with reference to FIG. 2 can be obtained.

FIG. 4 shows 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 that projects AF light onto the subject 10.

Now, when the IRED 12a emits light, the light becomes an AF target 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, thereby forming 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 g according to the principle of triangulation as shown by the following equation.

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

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

...(11) 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 projecting lens 12b.
When extended from the principal point of 2C, it is the length from the point where it crosses the PSD 12d to the end of the PSD 12d on the IRED 12a side.

FIG. 5 shows a specific circuit configuration for integrating distance information using the integrating circuits 16 and 17 from the output signals II and 12 of the PSD 12d.

In FIG. 5, 21.22 is a preamplifier that amplifies the output signals I, I2 of the PSD 12d generated in response to the light emission of the IRED 12a with a low input impedance, and 23.24 is the amplified current. 1. ,
This is a compression diode for compressing only I2.

25 and 26 are buffers and compression diodes 2324
This is for guiding all compressed voltages to a differential arithmetic circuit 30 consisting of NPN transistors 27 and 28 and a current source 29.

Here, when the operation of the differential arithmetic circuit 30 is explained using the symbols in the figure, the following relationship holds true.

Therefore, from the above HiE equations (11) and (15), the following relational expressions are established: ...(12) ...(13). Note that Is is transistor 2
7.2B and the reverse saturation current of the diode 23.24, and ■o is the thermal voltage.

Moreover, the current 1a and the current 1b are I a + I b ” I o+
From the relationship ``' (14), the above (12)
From equations (13) and (14), the following is obtained, and a signal current Ia proportional to the reciprocal of the object distance Ω 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 respectively inputted to circuits 37 and 38 of the same type as the differential arithmetic circuit 30 through buffers 35 and 36, respectively.

Therefore, the output current 1p 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 diode 3233 is generating a voltage with reference to the power supply side, then we have the following equation. Therefore, from equation 2 (18) above, the current ■Ω is:
...(20>), which is obtained as a current signal proportional to the subject distance g.

That is, the differential calculation circuit 37 is a circuit for supplying a current signal according to the subject distance g at the first timing to the integrating circuit 16, and the current source is switched on by the timing signal every time the IRED 12a emits light for an odd number of times. 41
When the current Ω is turned on, the current Ω that depends on the object distance Ω is integrated by the integrating capacitor 45 of the integrating circuit 16.

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, the output terminal 47 has r12+1, taking the above equation (6) as an example.
A signal corresponding to 0+8J appears.

(NPN) transistors 42, 43 and current source 44
The differential arithmetic circuit 38 is a circuit for supplying a current signal according to the object distance Ω at the second timing to the integrating circuit 17, and the differential calculation circuit 38 is a circuit for supplying a current signal according to the object distance Ω at the second timing to the integrating circuit 17. source 44
By turning on the current IIJz, which depends on the object distance g, is integrated by the integrating capacitor 48 of the integrating circuit 17.

The current IN2 at this time is similar to the above equation (20), The relationship that depends on the subject distance p is satisfied.

Similarly, the integrating capacitor 48 is reset by a reset circuit 49 before the I RED 12a emits light. For this reason, after completing a series of ranging operations, the output terminal 50 has r
A signal corresponding to ll+9+7J appears.

In this way, after completing the distance measuring operation a plurality of times as shown in FIG.
．． The speed information S3 in the above equation (6) is determined from the difference in the voltage signals appearing at 50. Note that the speed information S is calculated digitally by A/D converting each integral output.
This may be performed using the UII, or may be performed using an analog subtraction circuit composed of an operational amplifier or the like.

Based on this speed information S, for example, the CPU
The moving speed V of the subject 10 is calculated by software processing by I1, that is, by calculation as shown in equation (7) above.

That is, if the voltage signals appearing at the output terminals 47 and 50 are respectively vOIJTl+vOUT2, then the subject position D(t) is determined by the speed V explained with reference to FIG. 2 as follows: 1) (t)=v-t+l) 1 ・
...(22).

Moreover, the above equations (20) and (21) are respectively Iρ−A
−fi (t) = A (Ω+ v−t) ・”
(23) IN 2-A-11(t) -A (J7
r−v·t) (24). However, A
is a constant.

Therefore, if the capacitance of the integrating capacitor 45 is C, then the voltage signal V. UTI is ΔV ojiT -vourz VOLj'T・
...(25) becomes. However, T is the integration time.

On the other hand, the voltage signal V0LIT2 is the voltage signal V. UTI
This is the result of shifting the timing by Δt and integrating by time T, so...(26) is obtained.

As a result, the voltage signal V. U□1+difference Δ of vOUT2
V0LIT becomes -. However, D is a constant.

As described above, two integral outputs V0LIT1. V
0UT2 difference Δ■. The speed V can be easily determined from 0 work.

As described above, the moving speed of the subject is determined from the first and second integral outputs of a plurality of distance measuring operations.

That is, the moving speed of the subject is determined from the difference between the first and second integral outputs obtained by integrating a plurality of distance measurement results. Moreover, in this case, I R
The first step is to integrate the distance measurement results based on the light emission of the ED.
The second integral operation is repeated alternately every time the I RED emits light. As a result, it is possible to expect a noise canceling effect due to a large number of integrations, and it is also possible to make the difference in accuracy between the two integration results extremely small. Furthermore, since the series of operations of distance measurement and integration are analog calculations that are completed instantaneously, high-speed processing is possible. Therefore, high-accuracy and high-speed speed detection can be realized with a simple configuration.

Note that in the above embodiment, the first. Although each of the second integrating circuits is provided with a reset circuit, the present invention is not limited to this; for example, the two integrating circuits may share one reset circuit.

It goes without saying that various other modifications can be made without departing from the gist of the invention.

[Effects of the Invention] As described in detail above, according to the present invention, it is possible to cancel out the distance measurement error that necessarily exists in a single distance measurement operation, and it is also possible to perform high-speed processing, so it is possible to achieve high accuracy. In addition, it is possible to provide a moving speed detection device for a subject that can detect the moving speed of a subject at high speed and can be realized with a relatively simple configuration.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIGS. 1 to 5 show embodiments of the present invention. FIG. 1 is a block diagram schematically showing the configuration of a moving speed detection device for a subject, and FIG. Figure 3 is a timing chart shown to explain the operation. Figure 4 is a configuration diagram showing details of the ranging optical system. Figure 5 is a diagram showing the integration of distance information. FIG. 6 is a diagram showing a specific example of a circuit configuration for the purpose of
The figure is a block diagram of the speed detection device, and FIG. 7 is a timing chart. DESCRIPTION OF SYMBOLS 10... Subject, 11... CPU, 12... Distance measuring optical system, 12 a .= I RE D , 12 d
-=PSD, 13...driver, 14.
Distance calculation circuit, 15... Subtraction circuit, 16... First integration circuit, 17... Second integration circuit, 23, 24, 32
．． 33... Compression diode, 29.31, 34.41.
44... Current source, 30°37.38 ・Differential calculation circuit, 45.48... Integrating capacitor, 46.49...
reset circuit. Applicant's agent Patent attorney Atsushi Tsuboi (a) (b) Figure Figure Figure Figure Procedure Amendment Statement September 14, 1992

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; light projection control means for repeating light projection by the light projection means a plurality of times at predetermined time intervals; and a first light projection control means for integrating the output of the distance measuring means at a first timing when the light projection means performs light projection. an integrating means; a second integrating means that integrates the output of the ranging means at a second timing when the light projecting means emits light; and using the outputs of the first and second integrating means, A moving speed detection device for a subject, comprising: speed calculation means for calculating a moving speed of the object in the optical axis direction of the light projecting means.