JPH0789058B2 - Distance measuring device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a distance measuring device, and in particular, can measure a distance to an arbitrary position of an object by an active method, and can also be applied to measurement of a three-dimensional shape of the object. The present invention relates to a distance measuring device.

<Prior Art> Conventionally, as a method of acquiring distance information and information about a three-dimensional shape using an image sensor or the like, a light cutting method (slit method), a stereo method, and the like are known.

The light-section method is to obtain slit light on the surface of an object, observe a projection line on the surface of the object from a direction different from the projection direction, and obtain information such as the cross-sectional shape and distance of the object. In this method, the imaging side is fixed, and the three-dimensional information is acquired by changing the slit projection direction little by little and capturing an image for each of a plurality of image slits.

The stereo method in Japanese Patent Application No. 59-44920 proposed by the applicant is such that two-dimensional image pickup elements combined with an optical system having the same image magnification are arranged apart from each other by a predetermined base line length and viewed from different directions. A three-dimensional image is obtained, and the height of each position of the object (distance to the image pickup system) is calculated from the deviation of the image information of the two images.

However, the optical cutting method has a problem that the control of the slit projection direction at the time of image capturing is troublesome and the image capturing takes time. Also,
Since three-dimensional information is obtained from a plurality of slit images, the amount of information to be processed is large, and it takes a long time to obtain the final information.

Further, the stereo method does not require control such as slit scanning, but since the conventional method is generally the passive method, two image pickup elements are used when the object surface is smooth and has uniform brightness. The contrast of the image obtained with
There is a problem that distance measurement cannot be performed by comparing two images. The case where such measurement becomes impossible has a drawback that the appearance frequency is high at a short distance where the image magnification becomes large, and thus the shape, color, size, distance, etc. of the object are limited. It was

<Summary of the Invention> An object of the present invention is to provide a distance measuring device capable of always performing accurate measurement in a relatively short time regardless of the type of the object in view of the above-mentioned conventional problems.

In order to achieve the above object, a distance measuring device according to the present invention targets a plurality of optical fluxes arranged parallel to an optical axis and spaced from each other by a baseline distance, and a plurality of patterned light fluxes through one of the optical systems. A light source means for irradiating an object and a two-dimensional image sensor for receiving an image of the pattern light beam on the object through an optical system different from the above are provided, and the pattern light beam on the object detected by the two-dimensional image sensor. Is a device for measuring the distance from the position of the optical image to a predetermined position of the object, wherein the moving direction of the optical image by the pattern light flux emitted from the light source means and the scanning line direction of the two-dimensional image sensor are It is characterized in that a plurality of light images formed by the pattern light fluxes are aligned in the scanning line direction while matching.

Further features of the present invention will be described in the following embodiments.

<Example> FIG. 1 is a schematic view of an optical system showing an example of a distance measuring apparatus according to the present invention. In the figure, 1 and 2 are lenses arranged at a distance of a base line, their optical axes are parallel to each other, and the object-side main planes of the lenses 1 and 2 are on the same plane.
In this embodiment, the lenses 1 and 2 have the same focal length. 3 is a light source device in which a plurality of small light emitting sources 3 ₁ , 3 _2, ... 3 _n such as light emitting diodes and laser diodes are arranged on a substrate, 4 is an image sensor including a CCD, and 5 is an object for distance measurement , 6 are masks for pattern projection, which are provided in the light-shielding member with an opening pattern consisting of a plurality of light-transmitting parts 6 ₁ , 6 ₂ , ..., 6 _n, and are arranged near the focal point of the lens 1. .

In FIG. 1, P ₁ and P ₂ respectively indicate different positions of the subject, and the depth of field of the lenses 1 and 2 is assumed to have a depth sufficient to cover these two positions.

FIG. 2 shows an example of the opening pattern of the mask 6. As described above, a plurality of thin rectangular slit-shaped light transmitting portions 6 _n are arranged on the mask 6. In the figure,
The light-transmitting portion 6 _n has an arrangement pattern in which the horizontal center thereof is sparse in the horizontal direction and relatively dense in the vertical direction, as shown by the thin line AX, and as a result, slit rows extending in the diagonal direction are formed. There is. The density and arrangement of the light-transmitting portions 6 _n may be determined according to the required measurement accuracy and the vertical and horizontal resolution of the image sensor used, and thus the present invention is not limited to the above-described configuration, and various patterns are used. It is possible. The light-transmitting portion 6 _n of the mask 6 has a relatively low horizontal density as shown in FIG.
This is because the position of the optical image on the image sensor 4 moves in the horizontal direction depending on the distance of the object 5 as will be described later, so that the distance range in which detection can be performed is widened.

Figure 1, in the configuration of FIG. 2, is illuminated by the light source device 3, the light flux having passed through the transparent portion ₆₁ passes through the lens 1, reference symbol P on each object 5 in accordance with the position of the object 5 Form an optical image at the positions shown in ₁ and P ₂ . Then P _1, P ₂ on the optical image F _1, F ₂ position on the image sensor 4, respectively through the lens 2 is D _1, D ₂
Connect the light image to.

As can be seen from the principle of the stereo method, the position of the optical image D _n depends on the distance of the reflection point, that is, the distance between the positions P ₁ and P ₂ of the object 5 on a straight line parallel to the arrangement direction of the lenses 1 and 2 ( Baseline direction)
Will be moved. Therefore, the distance distribution of the surface of the object 5 from the measuring device can be detected as the distribution of the horizontal density of the optical image D _n . That is, by observing the output waveform of the image sensor 4 with an image processing device using a computer system or the like, the distance to the light image position (beam projection point) on the surface of the object 5 is easily obtained by the principle of triangulation. be able to.

Now, in this embodiment, in order to expand the distance range in which distance measurement is possible, not only the depth of field of the lenses 1 and 2 is increased,
The pattern light flux with which the object 5 is irradiated is devised.
That is, in FIG. ₁ , the translucent portions 6 ₁ , 6 ₂ ...
6 _n can be regarded as a point light source, and when illuminating the opening pattern of the mask 6 by a normal illumination method, each of the translucent parts 6 ₁ ,
The light emitted from 6 ₂ ... 6 _n is diffused, passes through the entire pupil of the lens 1 and is directed to the object 5 via the lens 1.
When the object 5 is irradiated with the pattern light flux by such a method,
Even if a lens with a large depth of field is used for the lens 1, there is a limit to the range that can be obtained, and the image sensor 4
A blurred image of the optical image of the aperture pattern is formed on the top, which makes it difficult to detect the optical image position.

However, in the present embodiment, the light source device 3 is arranged at a position away from the mask 6, and the small light source existing on the light source device 3 is arranged.
The light emitted from 3 ₁ , 3 ₂ ... 3 _n passes through the corresponding single light-transmitting part 6 ₁ , 6 ₂ ... 6 _n and enters the pupil. With such a configuration, each of the plurality of pattern light fluxes obtained through the mask 6 has a light flux diameter smaller than the pupil diameter of the lens 1, and therefore an extremely thin light beam is generated as shown in the figure. In order to be directed to the object 5,
Even if the object 5 is located far away from the in-focus position, the blur of the optical image on the image sensor 4 can be suppressed to a small level. Further, in this embodiment, each small light emitting source 3 ₁ , 3 ₂ ...
Each of the translucent parts is configured so that the line connecting 3 _n and the corresponding translucent part 6 ₁ , 6 ₂ ... 6 _n passes near the center of the lens 1.
Light from sources other than the corresponding small-sized light sources that enter 6 ₁ , 6 _2, ..., 6 _n does not enter the pupil of the lens 1.
Incidentally, or by increasing the thickness of the mask 6 If necessary, or providing a light shielding frame between each transparent portion 6 _1, 6 ₂ · · · · 6 _n, each small light emitting source and the light transmitting portion May be configured so as to surely correspond to 1: 1.

Further, in the present embodiment, even if the object 5 is present at a short distance,
When the object 5 is located within the measurement range, each element is arranged so that the light source image is not focused on the object 5 and the accuracy is always maintained within the measurement range. Good distance measurement is possible.

FIG. 3 shows an output waveform O of one scanning line (corresponding to the thin line AX in FIG. 2) when a two-dimensional CDD sensor for a TV camera is used as the image sensor 4. Here, the horizontal direction of the figure corresponds to the horizontal distance of the image sensor 4. As is clear from the above, the output value shows the maximum value M corresponding to the light transmitting portion 6 _n of the mask plate 6 which is on the same straight line as this scanning line. The left and right positions of the maximum value of the output waveform appearing corresponding to one light-transmitting part 6 _n are limited in position, and are separated from the maximum value appearance range by other light-transmitting parts. 6 _n and the incident position of the light flux passing through the window on the image sensor 4 can be easily associated with each other. Therefore, unlike the conventional stereo method, the distance to the arbitrary position of the target object 6 and the three-dimensional information can be reliably acquired without causing the inconvenience such as the inability to measure due to the contrast reduction at a short distance. Further, unlike the conventional stereo system, the active system in which the light source is used to illuminate is employed, so that there is an advantage that the light amount of the light source can be small when measuring an object at a short distance. It is also possible to estimate the tilt angle of the optical image position of the object from the maximum value of the image sensor output.

As described above, the distance of the surface of the object 5 from the measurement system can be measured via the two-dimensional image sensor 4.
According to the above configuration, it is possible to extract the three-dimensional information of the entire surface of the object 5 by one-time image reading without the need for performing mechanical scanning as in the light cutting method.

Further, since the subsequent image processing may be performed only on the distribution of the light image in the left-right direction, simple and high-speed processing is possible. Furthermore, according to the present embodiment, the image of the structure on the image sensor 4 can be binarized as it is, and can be output to a CRT display or a hard copy device for visual three-dimensional expression.

The distance measuring method or the three-dimensional information processing method according to the present embodiment is a method in which a large number of stylus are pressed against an object and the object shape is perceived by a change in the amount of protrusion of the stylus from the reference surface, without contact. Since it is performed, high-speed and accurate processing can be performed, so that it can be used as a visual sensor for a robot or the like that requires real-time processing. In particular, this is effective in the case of perceiving the shape, posture, and the like of an object placed at a relatively short distance and performing an action such as grasping or avoiding the object.

Although the light beam projection pattern for the object 5 is formed by the light source and the mask 6 in the above, the same effect can be obtained by disposing a plurality of point light sources having directivity at the plane position of the mask 6.

FIG. 4 is a schematic view of an optical system showing another embodiment of the distance measuring device according to the present invention. In the figure, the same members as those in the embodiment of FIG. 1 are designated by the same reference numerals, 7 is a lens array composed of minute convex lenses, and 8 is a field lens.

The distance measuring device of this embodiment has the same basic configuration as that of the device shown in FIG. 1, and the principle of distance measurement is exactly the same. The difference between this embodiment and the embodiment shown in FIG. 1 lies in the construction of the light source means for obtaining the pattern light flux. As shown in FIG. Small light source 3 ₁ ,
A lens array 7 having micro-convex lenses is arranged so as to correspond to 3 ₂ ... 3 _n and 1: 1. Further, the mask is arranged so that the light flux transmitted through the mask 6 surely enters the pupil of the lens 1. The field lens 8 is installed in the latter part of 6. That is, a small emission sources 3 _1, 3 ₂ ... 3 The light emitted from the _n lens array 7
The light is condensed by the action of the corresponding micro-convex lens, and is efficiently directed to the corresponding light-transmitting portions 6 ₁ , 6 _2, ... 6 _n of the mask 6.
Therefore, the light quantity of the pattern light flux obtained through the mask 6 can be increased, and the aperture pattern image of the mask 6 projected on the image sensor 4 is brightened to improve the measurement sensitivity. Also in this embodiment, the transparent portions 6 ₁ , 6 ₂ ... of the mask 6
The divergence angle of the light flux passing through 6 _n is small, and the object 5 is irradiated with the pattern light flux as a thin light beam. Therefore, even if the positions P ₁ and P _{2 of the} object 5 are largely different, the blur of the optical image of the aperture pattern on the image sensor 4 is small, and accurate measurement is always possible.

In addition, the field lens 8 is a transparent portion 6 ₁ , 6 ₂ ... of the mask 6.
..6 _n , lens array 7, small light source 3 _{1 of} light source device 3,
It can be omitted as shown in FIG. 1 depending on the method of aligning the positions of 3 ₂ ... 3 _n .

Further, in the above description, for simplification, only the main part of the device is illustrated, and the illustration of the signal processing system and the enclosure for blocking is omitted, but these members may be used by those skilled in the art as needed. In the above, a suitable one may be provided as usual. Although only a single lens is shown in the optical system, an optical system including a plurality of elements or an optical system including a mirror may be used. Furthermore, in each of the above-described embodiments, a configuration using two optical systems having the same focal length has been shown, but it is also possible to use three or more optical systems having different focal lengths if necessary. However, it is the simplest to use the same optical system having the same focal length with various aberrations.

In each of the above embodiments, the light source is shown as an array of small light emitting sources such as LEDs arranged and arranged on one substrate.
It is also possible to use ordinary individual parts side by side or to arrange the individual parts sealed with glass in the shape of a convex lens to omit the lens array 7 shown in FIG. It is also conceivable to seal the substrate of the small light source array with a transparent body in the form of a convex lens array.

Further, in the above-described embodiment, an optical image of an aperture pattern having a plurality of light-transmitting portions arranged two-dimensionally is displayed on a CCD or the like.
Although the method of detecting with a three-dimensional image sensor and performing measurement has been described, for example, an aperture pattern in which a plurality of light-transmitting portions are one-dimensionally arranged at predetermined intervals is symmetrically projected, and an optical image of the aperture pattern is elongated. An image sensor having a sensor array in a direction may receive an image to detect the shape of the object along a specific direction.

It is also possible to widen the field of view for distance measurement by using two or more second optical systems that receive the pattern light flux from the object.
Further, the visual field for distance measurement can be widened by moving the second optical system in parallel using a predetermined driving device. On the contrary, the same function can be obtained even if the first optical system for irradiating the object with a plurality of pattern light beams and the light source means are moved in parallel by using a predetermined driving device.

According to the present invention, it is preferable that the pattern light beam with which the object is irradiated is a thin light beam having a divergence angle as small as possible. However, since the limit mainly depends on the sensitivity of the image sensor, the sensitivity of the usable sensor or It is determined according to the light source output, required measurement accuracy, and specifications.

Further, the magnification of the optical system and the length of the base line, that is, the distance between the first optical system and the second optical system in FIG. 1, the pitch of the transparent portion of the mask, etc. It should be decided in consideration of.

<Effects of the Invention> As described above, the distance measuring apparatus according to the present invention achieves distance measurement with high accuracy in a short time regardless of the position of the type of the object by adopting the active method, and particularly in the case of the optical image. Since the moving direction and the scanning line direction of the two-dimensional image sensor are coincident with each other and a plurality of optical images by the pattern light flux are arranged in the scanning line direction, the object is accurately and in a short time. It is a suitable device as a visual sensor for a robot or the like that can acquire the three-dimensional information of.

[Brief description of drawings]

FIG. 1 is a schematic view of an optical system showing an embodiment of a distance measuring device according to the present invention. FIG. 2 is a diagram showing an example of an opening pattern of a mask. FIG. 3 is a diagram showing an output waveform of one scanning line when a CCD is used as an image sensor. FIG. 4 is a schematic view of an optical system showing another embodiment of the distance measuring device according to the present invention. 1,2 ...... lens 3 ...... light source device 3 _1, 3 ₂ ...... 3 _n ...... small emission sources 4 ...... image sensor 5 ...... object 6 ...... mask 6 _1, 6 ₂ ...... 6 _n ...... Light-transmitting part 7 ... Lens array 8 ... Field lens

Claims (2)

[Claims] 1. A plurality of optical systems arranged in parallel with an optical axis and spaced from each other by a base line, a light source means for irradiating a plurality of pattern light fluxes to the object through one of the optical systems, and on the object. A two-dimensional image sensor that receives an image of the pattern light flux through an optical system different from the above is provided, and from the position of the optical image of the pattern light flux on the object detected by the two-dimensional image sensor, a predetermined object is determined. A device for measuring a distance to a position, wherein a moving direction of an optical image by a pattern light beam emitted from the light source means and a scanning line direction of the two-dimensional image sensor are coincident with each other, and the pattern light beam is in the scanning line direction. 1. A distance measuring device, characterized in that a plurality of optical images are arranged. 2. The light source means comprises a mask having a plurality of light transmitting portions and a plurality of light emitting portions for illuminating the mask in a one-to-one correspondence with the plurality of light transmitting portions. The range-measuring device according to item (1).