JPH02115710A - Method and instrument for measuring distance - Google Patents

Abstract

PURPOSE:To perform measurement with a high precision by detecting the in- focus state based on the picture signal which is obtained by relatively oscillating an illuminance means. CONSTITUTION:Optical systems which have lenses 1 and 2 having the same focal length F are so arranged that their optical axes 1A and 2A are parallel with each other, and photo diode arrays 3 and 4 are arranged at the same distance behind respective optical systems. These optical systems and arrays 3 and 4 are so moved that images in positions of the same distance in directions of optical axes 1A and 2A are formed on arrays 3 and 4 in the in-focus state with the same arrangement. Arrays 3 and 4 are equally and minutely moved relatively to optical systems in directions of base lines orthogonal to directions of optical axes through an oscillating actuator 6 by a high frequency to measure the illuminance by arrays 3 and 4. Thus, coincidence between outputs of photodetectors corresponding to each other of arrays 3 and 4 and the amplitude longer than a prescribed value are detected to calculate the distance and the direction to an object point corresponding to photodetectors corresponding to each other in accordance with a length F, these photodetectors corresponding to each other, and positional relations of optical systems corresponding to them.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a distance measuring method and apparatus, and more particularly to a method and apparatus effective for optically measuring the distribution of distances to objects in the surrounding environment. Such distance measurement is effectively used, for example, as a visual means for environmental recognition of a visual robot.

[Prior Art and Problems to be Solved by the Invention] As a method of optically measuring the distance to an object, there is a method called the so-called stereo method. In this method, two objective lenses with the same focal length are kept in parallel with their optical axes parallel and separated by a predetermined distance, and an illuminance distribution measuring means is placed behind each objective lens, and these two objective lenses are The distance to the object can be calculated from the positional relationship of the same illuminance distribution pattern measured by the means.

Incidentally, an image is generally formed over the entire illuminance distribution measuring means, and it is difficult to identify images of the same object point on the same object. Therefore, in the stereo method as described above, a correlation is established between the illumination distribution in one measuring means and the illuminance distribution in the other measuring means.

For example, in the case of a repetitive pattern image, different portions may be determined to have a pseudo correspondence when correlation is determined. Furthermore, when attempting to determine the distance distribution to objects in the surrounding environment by performing distance measurements in each direction based on the correlation method described above, the number of calculations required to take the correlation becomes extremely large, and the measurement equipment There is a problem that the processing circuit becomes complicated.

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art and to provide an optical distance measuring method and apparatus that can easily perform measurements with high accuracy.

[Means for Solving the Problems] According to the present invention, two or more optical systems having substantially the same focal length are arranged so that their optical axes are parallel to each other in order to achieve the above objects. and the same at the rear of each optical system.
The illuminance measuring means is arranged at a distance, and the optical system and/or the illuminance measuring means are moved so that all the illuminance measuring means are focused at the same distance position in the optical axis direction, and each optical system is On the other hand, the illuminance is measured by each illuminance measuring means while moving the illuminance measuring means finely and relatively reciprocally at high frequency in the direction orthogonal to the optical axis direction, and the corresponding light receiving element of the two appropriate illuminance measuring means is selected. It is detected that the output signals match and the amplitude is greater than a predetermined value, and the corresponding received light is determined based on the focal length of the optical system, the corresponding light receiving elements of the two illuminance measuring means at that time, and the positional relationship of the corresponding optical systems. It is characterized by calculating the distance and direction to an object point corresponding to an element. A distance measuring method and apparatus thereof are provided.

In the present invention, distance distribution can be measured by using illuminance measuring means having a plurality of light receiving elements arranged in parallel.

In the device of the present invention, when moving the optical system and/or the illuminance measuring means, the distance between the reference axis parallel to the optical axis and the illuminance measuring means is kept constant, and the distance between the reference axis and the optical axis of the optical system is The product of the distance in the optical axis direction between the optical system and the illuminance measurement means can be maintained approximately constant, and the distance between the reference axis parallel to the optical axis and the optical axis of the optical system can be maintained constant. The ratio between the distance between the reference axis and the illuminance measuring means and the distance in the optical axis direction between the optical system and the illuminance measuring means can be maintained substantially constant.

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

FIG. 1 is a block diagram showing the configuration of an instant embodiment of the apparatus of the present invention for implementing the distance distribution measuring method according to the present invention, and fJJZ diagrams (a) and (b) are partial schematic diagrams of the apparatus. be.

In FIGS. 2(a) and 2(b), reference numeral 20 indicates a lens barrel of a lens l, and the lens barrel is fixed to a frame (not shown).

Note that IA is the optical axis of lens l. 21 is a lens barrel of the lens 2. Note that 2A is the optical axis of the lens 2. Lens barrel 21
A pair of attached members 21&, 21b are attached to the base line direction. #Elongated guide holes 13a and 13b extending in the base line direction are formed in each of the attached members.

Guide pins 14a and 14b are respectively fixed to a frame (not shown), and these are fitted into the guide elongated holes 13a and 13b, respectively. The lens barrel 21 also has a direction perpendicular to both the optical axis direction and the base line direction (hereinafter referred to as
A guide pin 15 that can protrude in the P direction is attached. The focal lengths of the lenses 1 and 2 are both F.

7 is a crank lever, and this lever is almost orthogonal to 2.
It has two arms 7a and 7b. Arm 7a extends substantially in the optical axis direction, and arm 7b extends substantially in the base line direction. This f
A rotation shaft 7C in the P direction is provided at the connecting portion of the 22 arms. The rotating shaft is rotatably connected to a frame (not shown). A guide elongated hole 16a extending toward the center of the rotating shaft 7 is formed at the tip of the upper two arms 7a, while a guide hole 16a extending toward the center of the rotating shaft 7 is formed at the tip of the arm 7b. A guide elongated hole 16b extending in the direction is formed. The guide pin 15 attached to the lens barrel 21 is fitted into the guide length 16a.

3.4 is a photodiode array (hereinafter referred to as "photodiode array") having the same number of light-receiving elements arranged corresponding to each lens 1.2.
(referred to as a PD array), and each of the PD arrays is fixed to a slide holder 5 along the base line direction.

A guide elongated hole 23 extending in the base line direction is formed in the holder. Further, the holder is slidably mounted on a support 8, and a guide pin 22 extending in the optical axis direction is attached to the support, and the guide pin is inserted into a guide elongated hole 23 of the holder. It is fitted.

A vibration actuator 6 is arranged on the support 8 . The actuator is, for example, an A-layer pressure element, and can vibrate at high frequency and minute amplitude. The action portion of the actuator is connected to the slide holder 5, and thus the slide holder is capable of micro-vibration back and forth in the base line direction. The support body 8 is provided with a guide pin 19 that can protrude in the P direction. The guide pin is fitted into the elongated guide hole 16b of the crank lever. Further, the support body 8 is formed with a guide elongated hole 17 extending in the optical axis direction. 18a.

Guide pins 18b are aligned along the optical axis direction and fixed to a frame (not shown), and the guide pins are fitted into the guide elongated holes 17.

A driving means for reciprocating the support in the optical axis direction is connected to the support 8. The drive means includes a motor 11 and a male screw member 9 attached to the drive rotation shaft of the motor.
and a female screw member lO attached to the support body so as to mesh with the male screw member. Note that 24 is an encoder attached to the motor 11 for detecting the motor rotation angle.

In FIG. 2(a), the center of lens 1 and the center of lens 2 are located apart from each other by a distance ftL in the baseline direction, and similarly, the center of PD array 3 and the center of PD array 4 are located in the baseline direction. are located at a distance from each other, and the lens 1.2
and the PD arrays 3 and 4 are located apart from each other by the focal pressure fiF of the lens 1.2.

FIG. 2(b) shows a state in which the crank lever 7 is rotated counterclockwise in the figure by an angle of 0 around the rotating shaft 7C from the state of FIG. 2(a). Due to this rotation, the lens barrel 21 changes the coupling relationship between the guide elongated hole 16a and the guide pin 15, the guide elongated holes 13a and 13b and the guide via 14a,
Based on the connection relationship with 14b, it moves by a distance ΔL to the left in the figure in the base line direction. On the other hand, due to this rotation, the support body 8
is moved downward in the figure by a distance ΔF in the optical axis direction based on the coupling relationship between the guide elongated hole 16b and the guide pin 19 and the coupling relationship between the guide elongated hole 17 and the guide pins 18a and 18b. In FIG. 2(b), the distance between lens 1 and lens 2 is L' (=L-ΔL), and lens 1.2
The distance between and FD array 3.4 is F' (=F+ΔF)
It is.

Here, when the arm 7a of the crank lever 7 is in the optical axis direction,
From the center of the rotating shaft 7C of the crank lever 7 to the lens barrel 2
The distance to the center of the guide bin 15 attached to 1 is A-
Let L be the distance from the center of the rotating shaft 7C to the center of the guide bin 19 attached to the support 8 as A·F (here, A is a proportionality constant).

In this case, if the above rotation angle θ (radian) is small, it can be approximated as ΔL=A-L・θ ΔF=A-F・0, and therefore L′ work F′=(L−A・L・θ) - (F+A-F・θ)=L−F−A2 LP01, and since A2LFθ2 can be ignored when 0 is small, it can be approximated as L'・F'=L・F.

In FIG. 1, the output signals from each light-receiving element of the PD arrays 3 and 4 are amplified by respective amplifier circuits. In FIG. Although the output signals from the other light-receiving elements are shown to be input to the amplifier circuit . Further, the support body 8 is moved in the optical axis direction by the rotation of the motor li, and the actuator 6 moves the PD arrays 3 and 4 via the holder 5 in the baseline direction in synchronization at a frequency of about 10 kHz and an amplitude of about 20 tom. It is made to vibrate.

A constant pixel signal can be obtained from each light receiving element of the PD array 3.4, and is amplified by an amplifier circuit.

The outputs of the amplifier circuits 25 and 26 are input to the difference circuit 27,
Here, a difference signal between the two signals is obtained.

The output of the difference circuit 27 is input to a comparison circuit 28, where the amplitude of the input signal or its square mean is compared with a predetermined first threshold (a small value close to 0), and the input signal is A signal is output only when the amplitude or the root mean square of is smaller than the threshold.

Further, the output of the amplifier circuit 25 is input to a comparison circuit 29, which compares the amplitude of the input signal with a predetermined second threshold (the first
(a value sufficiently larger than the threshold value) is performed,
A signal is output only when the amplitude of the input signal is greater than the threshold.

Tagata of the comparator circuit 28 and the output of the comparator circuit 29 are input to an AND circuit 30, where the A of both input signals is
An ND signal is obtained and is input to the gate circuit 31 as a control signal.

On the other hand, a signal representing the rotation angle of the motor is input from the encoder 24 to the conversion circuit 33, and the conversion circuit 33 always calculates the distance between the lens 1.2 and the PD arrays 3 and 4 based on the rotation angle. ing.

That is, the conversion circuit calculates the focusing distance using the following relational expression %, based on the movement distance 6 of the lens 2 obtained through the information regarding the movement distance Δf of the PD array 3.4 inputted from the encoder. It x t'ta is output, and the signal is output to the gate circuit 31.

Then, only when there is an output from the AND circuit 30, the gate circuit 31 is opened to allow the focusing distance signal from the conversion circuit 33 to pass through, and is stored in the storage circuit 32. If the output of the conversion circuit 33 is a voltage, the storage circuit 3
2 can be composed of a capacitor.

The memory circuit 32 is connected to a gate circuit 35, which is controlled by a scanning circuit 34. That is, P
Processing similar to the above is performed for each corresponding light receiving element of the D sensors 3 and 4, and the focusing distance signal stored in each memory circuit corresponding to the memory circuit 32 is transferred to each gate circuit corresponding to the gate circuit 35. The scanning circuit 34 controls the output order.

Hereinafter, the operation of this embodiment, that is, one embodiment of the method of the present invention, will be described with reference to the above-mentioned FIGS. 1 and 2, as well as the drawings from FIG.

FIGS. 3(a) and 3(b) are optical diagrams for explaining the details of the measurement in this example.

It is assumed that the object M exists at a position separated by a finite distance X along the optical axes IA and IB.

First, as shown in FIG. 3(a), the distance between lenses 1 and 2 is set to L, which is the same as the distance between the PD arrays, and
．． 2 and the PD array 3.4 is defined as the focal length F of the lens, which corresponds to the state shown in FIG. 2(a) above.

In this state, the PD of the edge part of the object M by the lens l is
The image on the array 3 is as shown in FIG. 4(a), in which the image of the object M is blurred. On the other hand, the image on the PD array 4 produced by the lens 2 is as shown in Figure 4(a'), where the image of the object M is blurred and is formed at a position shifted to the right from that in Figure 4(a). There is. The image on the PD array 4 is an image obtained by moving the image on the PD array 3 to the right by a predetermined distance.

Next, the motor 11 is rotated to move the support 8 a predetermined distance in the optical axis direction, and to move the lens barrel 21 a predetermined distance in the base line direction.

In this state, the images on the PD array 3.4 by the lens 1°2 of the edge portion of the object M are shown in FIG. 4(b) and (
b'), the image position is closer and closer to the in-focus state than in the above case.

Thereafter, when the motor 11 is driven in the same manner, as shown in FIG. A state in which the distance between them is F' is realized. This corresponds to the state fB shown in FIG. 2(b) above.

In this embodiment, when the crank lever 7 is rotated,
Maintaining the relationship L'-F'=L-F as above, ΔF
and ΔF change, the image m1. of the object M changes. m2 will be positioned on the PD arrays 3 and 4 in a focused state, respectively.

That is, as mentioned above, in FIGS. 3(a) and (b), L
Since 'LiangF'=L-F, LφF= (L-ΔF
) (F+ΔF) holds, and also from the similarity relationship in FIG. 3(b).

(L-ΔF)/X= L/[X+(F+ΔF)] From these equations, 1/F=l/X+1/(F+AF) is derived.

As a result, the object M and the images ml and m2 in Fig. 3(b)
It can be seen that these satisfy the formula for focused imaging for lenses 1 and 2, respectively.

In this focused state, the images on the PD array 3.4 by the lens 1.2 of the edge portion of the object M are shown in FIG. 4(c).
, (c'), the image positions are the same.

When the motor 11 is further driven, the images on the PD array 3.4 by the lens 1.2 of the edge portion of the object M will become as shown in FIGS. 4(d) and 4(d'), and the image position will change. It moves away and moves away from the in-focus state.

By the way, in this embodiment, since minute high-frequency vibrations are applied to the PD array by the actuator 6, the fourth
Before and after the states shown in Figures (a), (a') to (d) and (d'), the output signals from the corresponding light-receiving elements of the PD array 3゜4 (corresponding to the outputs from the amplifier circuits 25 and 26) are The fifth factors are (a), (a') to (d), and (d'), respectively. The amplifier circuits 25 and 26 correspond to the light receiving elements located at the center of ranges A and A' in FIG. 4, respectively, and the ranges A and A' correspond to the amplitude of minute vibrations.

Therefore, the shapes in Fig. 4 (a), (a'), (b), (b'), (d), and (d') are due to differences in the output levels of the amplifier circuits 25 and 26. , the output signal level of the difference circuit 27 is high, so no signal is output from the comparison circuit 28, therefore, there is no output from the AND circuit 30, and no signal is output from the gate circuit 31.

On the other hand, in the states shown in FIGS. 4(c) and 4(c'), the outputs of the amplifier circuits 25 and 26 are the same and the amplitudes of the outputs are sufficiently large, so the output signal level of the differential circuit 27 is sufficiently small. , Therefore, the comparison circuit 28 outputs a signal, and the comparison circuit 29 also outputs an output. Thus, the AND circuit 30 outputs, and the gate circuit 31 outputs the current focusing distance signal, which is stored in the memory Wt storage 32.

Note that since the light-receiving elements of the PD array correspond to specific directions, the correspondence between the calculated distance and the direction of the object point can be easily established. Although the above calculated distance 1IIIx is along the optical axis, it can be converted to a distance in the direction of the object point if necessary.

In this embodiment, since the object point image at the focal distance is continuously detected while changing the focal distance, the detection accuracy is high.
Further, distance distribution measurement can be performed at high speed. Also,
Since the illuminance is measured by vibrating the PD array relative to the lens, the amplitude of the detection signal corresponds to the position differentiation of the image, and therefore a special differentiation circuit for edge image detection is not required.
In addition, only a focused state in which both amplitude and phase match can be accurately detected.

Note that each block in FIG. 1 can be constructed with a relatively simple circuit.

In the above embodiments, an example is shown in which the object has only one edge, but generally there are many such object edges at various distances in the surrounding environment. By moving the lens and PD array from the state of focusing at infinity as shown in Figure (a) to the state of focusing at close distance through the state shown in Figure 3(b). , a distance measurement is performed for each edge portion, and a distance distribution is measured. At this time, as in the above embodiment, PD
Although high frequency vibrations may be applied to the array, the same effect can be achieved by applying Takaoka wave vibrations to the lens.

Note that the first threshold value 1 in the comparison circuit 28 and the second threshold value in the comparison circuit 29 are such that the first threshold value is a relatively small value almost close to O, and the second threshold value is It can be appropriately set as a relatively large value depending on desired specifications.

In the above embodiment, the lens 2 and the PD array 3.4 are moved while maintaining a predetermined relationship using a mechanism as shown in FIG. A predetermined positional relationship may be maintained during this movement by driving with a drive means such as a motor.

In the above embodiments, the case where the illuminance distribution measuring means is a PD array is exemplified, but in the present invention, the illuminance distribution measuring means only needs to have sufficiently high response characteristics.
Alternatively, it may be a two-dimensional image sensor.

In the above embodiment, when moving the optical system and/or the illuminance distribution measuring means, the distance between the reference axis parallel to the optical axis and the illuminance distribution measuring means is kept constant, and the distance between the reference axis and the optical axis of the optical system is maintained constant. The distance between the reference axis parallel to the optical axis and the optical axis of the optical system is kept constant. The ratio of the distance between the reference axis and the illuminance distribution measuring means and the distance between the optical system and the illuminance distribution measuring means can also be maintained substantially constant. Figures 6(a) and 6(b) show diagrams corresponding to Figures 3(a) and 6(b) above in this case.The reference axis referred to here is the same as in Figures 3(a) and 6(b) above. coincides with the optical axis of one lens, but the present invention also includes cases where they do not coincide.

The present invention is effective in measuring the distance to an object point in a specific direction even when each illuminance measuring means has one light receiving element.

Further, although the above embodiment is an example in which there are two optical systems, by using three or more optical systems, performing similar processing on two optical systems in an appropriate combination, and using a plurality of systems,
In addition to the effects similar to those of the above embodiments, it is possible to suppress the influence of occlusion.

[Effects of the Invention] According to the present invention as described above, the in-focus state is detected based on the image signal obtained by vibrating the illuminance measuring means relative to the optical system, and then the in-focus state is detected. Since the distance and direction to the focused area are calculated based on the arrangement of the optical system, etc., it is possible to prevent measurement errors based on false correspondence that may occur with the correlation method, and a special differentiation circuit for edge image detection is used. Distance Jl can be measured quickly and accurately with a simple configuration without the need for
ll measurements can be made.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of the apparatus of the present invention. FIGS. 2(a) and 2(b) are partial schematic diagrams of the apparatus of the present invention. FIGS. 3(a) and 3(b) and FIGS. 6(a) and 6(b) are optical diagrams of the apparatus of the present invention. FIG. 4 is a diagram showing an image obtained in the method of the present invention, and FIG.
The figure is a diagram showing signals in the method of the present invention. 5 Nislide holder. 6: Vibration actuator. 7: Crank lever 8: Support body, 24: Encoder. M: object, ml, m2 2@.

Claims (6)

[Claims] (1) Two or more optical systems having substantially the same focal length are arranged so that their optical axes are parallel to each other, and an illuminance measuring means is arranged at the same distance behind each optical system, and the optical system and/or moving the illuminance measuring means to all the illuminance measuring means so that the same distance position in the optical axis direction is focused and imaged in the same arrangement, and moving each illuminance measuring means for each optical system in a direction perpendicular to the optical axis direction. The illuminance is measured by each illuminance measuring means while making a minute relative reciprocation at a high frequency equivalent to that of the illuminance measuring means, and the output signals of the corresponding light receiving elements of the two appropriate illuminance measuring means match and the amplitude is greater than a predetermined value. Detects this, and calculates the distance and direction to the object point corresponding to the corresponding light receiving element from the focal length of the optical system, the corresponding light receiving elements of the two illuminance measuring means at that time, and the positional relationship of the corresponding optical system. A distance measurement method characterized by: (2) The distance measuring method according to claim 1, wherein the distance distribution is measured using a device having a plurality of light receiving elements arranged in parallel as the illuminance measuring means. (3) A distance measuring device implementing the distance measuring method according to claim 1. (4) The distance measuring device according to claim 3, wherein a device having a plurality of light receiving elements arranged in parallel is used as the illuminance measuring means to measure the distance distribution. (5) When moving the optical system and/or illuminance measuring means,
The distance between the reference axis parallel to the optical axis and the illuminance measuring means is kept constant, and the product of the distance between the reference axis and the optical axis of the optical system and the distance in the optical axis direction between the optical system and the illuminance measuring means is almost constant. The distance measuring device according to claim 3 or 4, wherein the distance measuring device is maintained at . (6) When moving the optical system and/or illuminance measuring means,
The distance between the reference axis parallel to the optical axis and the optical axis of the optical system is kept constant, and the ratio of the distance between the reference axis and the illuminance measuring means and the distance in the optical axis direction between the optical system and the illuminance measuring means is almost constant. The distance measuring device according to claim 3 or 4, wherein the distance measuring device is maintained at .