JPH0798429A - Range finder - Google Patents

Abstract

PURPOSE:To provide a range finder capable of finding range to a range-finding object in a wide effective range from a short range to a long range as a range finder using a triangular range-finding system. CONSTITUTION:This finder is provided with plural range-finding modulus M1 respectively having two lenses L1 and L2 and a photosensor S1 converting the image of a substance being the range-finding object, which passes through the lenses and is projected, into an electrical signal, and a range-finding value calculation means 2 performing correlative calculation based on the electrical signal obtained from the photosensors S1 and S2 of the plural range-finding modules M1 and M2 and calculating a range to the substance being the range- finding object by a triangular range-finding system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring device,
Particularly, it relates to a distance measuring device using a triangulation method.

[0002]

2. Description of the Related Art FIG. 4A is a schematic diagram for explaining an external light triangular optical system of a phase difference detection type distance measuring device. Light beams 134B, 13 emitted from the distance measurement object 133
4R is 2 through two lenses 131B and 131R.
It is projected on the pair of optical sensors 132B and 132R.

Light beam 134 passing through reference lens 131B
B is imaged on the reference optical sensor 132B, and the image of the distance measurement object 133 is projected. The light beam 134R passing through the reference lens 131R is imaged on the reference light sensor 132R, and the image of the distance measurement object 133 is projected. The image of the distance measurement object 133 is projected on the reference light sensor 132B and the reference light sensor 132R, respectively.

If the object to be measured is located at infinity from the lens 131, the interval between the image formed on the standard light sensor 132B and the image formed on the reference light sensor is the base line length B. . As shown in the figure, when the distance measurement object 133 is separated from the lens 131 by the distance L, the reference light sensor 132
The distance between the image formed on B and the image formed on the reference light sensor 132R is B + x. That is, an image is formed on the optical sensor 132 with a distance of the phase difference x in addition to the baseline length B.

The distance f between the lens and the sensor is determined by the lens 131.
To the surface on which the optical image of the object for distance measurement is projected on the optical sensor 132. The distance measuring distance L is the distance measuring object 13
3 to the lens 131, and this distance is measured as the distance from the distance measuring device to the object to be measured.

As shown in the figure, it is assumed that the distance measuring object 133 is on the optical axis of the reference lens 131B. At this time, the optical axis of the reference lens 131R, the reference lens 1
The two triangles formed by the light ray passing through the center of 31R, the object plane including the distance measurement object 133, and the image plane on the optical sensor 132 are similar to each other,

[0007]

## EQU1 ## The relationship of L / B = f / x is established.

That is, as shown in FIG.

[0009]

[Equation 2] L = B · f / x (2) holds.

When x is represented by the number n of sensor pitch p,

[0011]

[Formula 3] L = B · f / (n · p) (3)

The sensor pitch p is an interval between a plurality of light receiving elements forming an optical sensor, and takes a value of about 20 [μm], for example. At this time, the denominator represents the precision of an integral multiple of the sensor pitch p.

The sensor pitch p is further converted into k by using an interpolation method.
When it is divided and when x is represented by the subdivision and it corresponds to i, x = i (p / k),

[0014]

[Formula 4] L = B · f / (i / k) p (4) That is, the denominator can express the precision of the integral multiple of p / k by the interpolation method, and the distance measurement distance L with higher precision than the mathematical expression (3) can be obtained.

Next, the correlation calculation performed to obtain the phase difference x between the image on the standard light sensor 132B and the image on the reference light sensor 132R will be described. FIG. 5 is a conceptual diagram for explaining the phase difference detection by the correlation calculation.

FIG. 5A shows an image formed on the optical sensor. The optical sensors 132B and 132R are line sensors in which a plurality of photodiodes are arranged one-dimensionally. The number of photodiodes forming the photosensor 132 corresponds to the number of pixels of the image formed on the photosensor 132. The number of pixels of the reference light sensor 132R is the standard light sensor 132B.
The same or more than the number of pixels of.

The reference optical sensor 132B includes a reference lens 1
An image of the object for distance measurement is formed via 31B. An image of the object to be measured is formed on the reference light sensor 132R separated from the reference light sensor 132B in the horizontal direction of the base line via the reference lens 131R.

When the object to be measured is at the infinity position, the same image is formed on the light receiving elements of the corresponding photodiodes of the standard light sensor 132B and the reference light sensor 132R. If the object to be measured is not at infinity, the optical sensor 13
The images on 2B and 132R are displaced in the horizontal direction. That is, the distance between the images increases as the object to be measured approaches, and the distance between the images decreases as the object to measure distance increases. In order to detect the variation in the distance between the images, the reference light sensor 132R
In many cases, the number of pixels is set to be larger than that of the reference light sensor 132B.

In order to detect the variation in the distance between the image on the standard light sensor 132B and the image on the reference light sensor 132R, the phase difference detection method by the correlation calculation is used. In the phase difference detection by the correlation calculation, the correlation value H (n) of the pair of image formations on the optical sensors 132B and 132R is obtained by the calculation based on the following equation (5), and these image formations are performed until the correlation value becomes the minimum. The relative movement value (phase difference) of is calculated.

[0020]

H (n) = Σ (j = 1 to l) | B (j) -R (j + n) | (5) where Σ (j = 1 to l) is from j to 1 Represents the sum of the functions of. j designates a pixel in the reference light sensor 132B. Further, n is an integer from -6 to 6, for example, and indicates the relative movement amount in the reference light sensor.

B (j) is an electric signal output from each pixel of the reference photosensor 132B in time series, and R (j +)
n) is an electric signal output from the pixel of the reference light sensor 132R in time series.

FIG. 5B shows the relationship between the pixel shift amount and the correlation value. If the calculation of the equation (5) is performed every time the pixel shift amount n is sequentially changed from −6 to 6, correlation values H (−6), H (−5), ..., H as shown in FIG. (6) is obtained. For example, it is set in advance so that the distance to the object to be measured becomes a predetermined value when the correlation value H (0) becomes the minimum value. When the correlation value at the position deviated from this is the minimum value, the deviation of the object to be measured from the predetermined position, that is, the distance to the object to be measured can be detected by the amount of deviation.

By the way, the light receiving elements of the standard light sensor 132B and the reference light sensor 132R are arranged at a pitch of, for example, 20 [μm]. The correlation value is 20 on the image plane.
It is calculated for each distance in units of [μm]. When the distance to the object to be measured corresponds to the middle position of the pitch of the light receiving element, make sure that the correlation value on the right side of the extreme value of the correlation value and the correlation value on the left side are different as shown by the broken line in the figure. Become. In such a case, it is possible to obtain a resolution equal to or greater than the pitch interval by performing interpolation calculation.

FIG. 5C is a schematic diagram for explaining the method of three-point interpolation. X is the position where the minimum correlation value is obtained
2, and the sample positions on both sides thereof are x1 and x3.
The correlation value actually obtained by calculation is shown by a black circle. As shown in the figure, the correlation value y3 at x3 is the correlation value y at x1.
If it is lower than 1, it is considered that the true minimum value exists somewhere from x2 to x3.

If the minimum value is exactly at the position of x2, the correlation value curve bends at x2 as shown by the broken line g1 and if it rises symmetrically, the correlation value y3a at x3 becomes the correlation value y1 at x1. Will be equal.

On the other hand, if the midpoint between x2 and x3 is the position of the true minimum correlation value, the correlation value curve is bent at the midpoint between x2 and x3 as indicated by the broken line g2, and the correlation value y2 at x2 is obtained. The correlation value y3b at x3 becomes equal. As shown in the figure, the difference (y
3a-y3b) is the difference in correlation value between x1 and x2 (y1-
equal to y2). That is, the correlation value of one unit changes as the pitch advances by half a pitch. Therefore, the true correlation value minimum position can be obtained by checking which intermediate position of the above-mentioned two cases the correlation value actually obtained by the calculation is. When the distance between adjacent sample points is 1, the deviation amount d from x2 is

[0027]

## EQU6 ## It is given by d = (y1-y3) / 2 (y1-y2).

As shown in the equation (3), the distance-measuring distance L depends on the sensor pitch p and the integer n corresponding to the size of the sensor. The distance measurement distance L also depends on the base line length B and the lens-sensor distance f due to optical constraints. Therefore, if the ranging module including the lens and the optical sensor is determined,
The measurable distance range is limited.

In a normal camera, when a lens-sensor integrated triangulation module is used, the distance range is 10 m.
Those within are created at low cost.

[0030]

In the distance measuring module, the range of change in the base length B and the phase difference x is almost determined by the design, so that the distance measuring range is difficult to change. The target distance range is almost determined by the distance measuring module, and it is difficult to measure the distance to the distance measuring object at a longer distance.

An object of the present invention is to provide a distance measuring device capable of measuring a distance to a distance measuring object in a wide effective distance range from a short distance to a long distance.

[0032]

A distance measuring apparatus according to the present invention comprises a plurality of lenses each having two lenses and an optical sensor for converting an image of an object to be measured projected through the lenses into an electric signal. It has a distance measuring module and a distance measuring value calculation means for performing a correlation calculation based on electric signals obtained from optical sensors of a plurality of distance measuring modules and calculating a distance to an object to be measured by a triangular distance measuring method.

[0033]

By calculating the distance measurement value by using the image signals of the same object to be measured obtained from the optical sensors of the plurality of distance measurement modules, it is possible to perform distance measurement with a large base line length, and long distance measurement. Is possible. On the other hand, by performing distance measurement by one distance measuring module alone, distance measurement with a short base line can be performed, and short distance measurement can be performed. Thus, one distance measuring device can perform both long distance measurement and short distance measurement.

[0034]

1 shows the structure of a distance measuring device according to an embodiment of the present invention. Two distance measuring modules M1 and M2 having the same characteristics are fixedly installed on the substrate 1. Distance measuring module M
1 has lenses L1 and L2 and an optical sensor S1. The distance measuring module M2 has lenses L3 and L4 and an optical sensor S2.

The lenses L1 and L2 have the same focal length. The sensor S1 is installed in the vicinity of the focal points of the lenses L1 and L2 such that the light receiving elements of the sensor are arranged in a direction perpendicular to the optical axis of the lens. The light beam from the object to be measured is projected as an image I1 of the object to be measured on the sensor S1 via the lens L1 and as an image I2 of the object to be measured on the sensor S1 via the lens L2.

The lenses L3 and L4 are lenses L1 and L.
It has the same focal length as 2. The sensor S2 is a lens L
The light receiving elements of the sensor are arranged near the focal points of L3 and L4 in a direction perpendicular to the optical axis of the lens. The light beam from the object to be measured is projected as an image I3 of the object to be measured on the sensor S2 via the lens L3, and is transmitted via the lens L4 to the sensor S2.
It is projected as an image I4 of the object to be measured.

The optical image projected on the sensor S is converted into an electric signal and output from the sensor S. The sensor S is not limited to the one-dimensional sensor in which the light receiving elements are one-dimensionally arranged, but may be a two-dimensional sensor in which the light receiving elements are two-dimensionally arranged.

The distance measuring modules M1 and M2 are adjusted and fixed so that the light receiving surfaces of the sensor S1 in the distance measuring module M1 and the sensor S2 in the distance measuring module M2 are arranged on the same plane. At this time, the lenses L1 to L4 are also arranged on the same plane. The adjustment method can be realized by an optical method, an electro-optical method, or the like.

When adjusting by an electro-optical method,
A fixed minute point light source is arranged in front of the distance measuring module. First, one distance measuring module M1 is operated, and the angle of the distance measuring module M1 is adjusted and fixed so that two point light source images are similarly projected onto the sensor S1 via the two lenses L1 and L2. To do.

Subsequently, in another distance measuring module M2, similarly, via two lenses L3 and L4,
The angle of the distance measuring module M2 is adjusted and fixed so that the electric signals representing the point light source image have the same level.

After adjusting the angles of the two distance measuring modules M1 and M2 with respect to the same point light source as in the above method, the two distance measuring modules M1 and M2 are fixed to the substrate 1. Even when the number of distance measuring modules is three or more, the distance measuring modules installed on the substrate can be adjusted in the same manner.

An image I1 of the object to be measured is projected on the sensor S1 via the lens L1, and an image I2 of the object to be measured is projected on the sensor S1 via the lens L2. Further, the image I3 of the object to be measured is formed on the sensor S2 via the lens L3.
Is projected, and the image I4 of the object to be measured is projected on the sensor S2 via the lens L4.

When performing distance measurement in the short range, the image I1
And the image I2 by the correlation calculation, or the image I3 and the image I4
The distance measurement value is obtained by the correlation calculation between the two. On the other hand, in the case of performing distance measurement in a long distance range, the image I1
Between the image I4 and the image I4, between the image I2 and the image I3, and between the image I4 and the image I2, the distance calculation value is appropriately selected and output.

From the combination of these four images I1 to I4, it is possible to simultaneously obtain highly accurate distance information in the three ranges of short range, medium range and long range. If two pieces of information, short distance and long distance, are required, the distance measurement value is calculated using the signal of the image I1 and the image I2 or the signal of the image I3 and the image I4 for the short distance. However, at a long distance, the image I1
It is reasonable to choose the image signal to use the signal of image I4.

A system configuration for realizing the above distance measuring value calculating method will be described with reference to the drawings. The microcomputer 2 is, for example, RA
It is a one-chip microcomputer with built-in M. The microcomputer 2 controls the sensors S1 and S2 via the driver 6 and reads an electric signal corresponding to the amount of light received from the light receiving element designated by the microcomputer 2. The microcomputer 2 controls the two distance measuring modules M1 and M2 to operate simultaneously. And 2
The same optical signal storage time of the two sensors S1 and S2
Match signal simultaneity and signal level.

The electric signals read from the sensors S1 and S2 are supplied to the changeover switch 5. The changeover switch 5 is controlled by the microcomputer 2, and the sensor S
1 or the sensor S2 output signal, select A /
Output to the D converter 4.

The analog signal output from the sensor S is
It is converted into a digital signal in the A / D converter 4.
The converted digital signal is supplied to the memory 3 and the image I
Is stored. The signals accumulated in the sensors S are simultaneously or time-sequentially read out from the sensors S and stored in the memory 4.

The microcomputer 2 performs a correlation calculation between the two image signals stored in the memory 4 to calculate the phase difference x between the two images projected on the sensor S. Calculated phase difference x
Is substituted into the equation (2) to calculate the distance measurement distance L to the object to be measured. The above calculation is performed for some combinations of the images I1 to I4 to calculate the distance measurement distance L. Then, the optimum distance measurement value is output as a distance signal.

The microcomputer 2 controls the driver 6, the changeover switch 5, the A / D converter 4 and the memory 3 with the same timing pulse. That is, based on the same timing pulse, an analog signal is read out for each light receiving element that constitutes the sensor S, the signal is converted into a digital signal, and writing to the memory is performed.

FIG. 2 shows a baseline length during distance measurement using one distance measuring module and a baseline length during distance measurement using two distance measuring modules. The distance measuring module M1 includes lenses L1 and L
Have two. The light ray from the object to be measured is projected as an image I1 on the sensor S1 through the lens L1 and the lens L2.
And is projected as an image I2 onto the sensor S1 via.

When performing distance measurement using one of the distance measurement modules M1, the distance calculation distance L is calculated by performing the correlation calculation between the images I1 and I2. The baseline length at this time is the distance B1.

The base line length B1 and the lens-sensor distance f are determined by the design stage of the distance measuring module M1. Then, the phase difference x is obtained by performing the correlation calculation between the image I1 projected through the lens L1 and the image I2 projected through the lens 2. The ranging distance L can be obtained by substituting the obtained phase difference x into the following equation.

[0053]

## EQU00007 ## L = B1.f / x (7) The distance measuring module M2 has lenses L3 and L4. The light beam from the object to be measured passes through the lens L4 and the sensor S2.
It is projected as an image I4 on top. The distance measuring module M1 and the distance measuring module M2 are fixedly installed on the substrate 1, and the relative positional relationship does not change.

Distance measuring module M1 and distance measuring module M2
When performing distance measurement using two modules of
The distance measurement distance L can be calculated by performing the correlation calculation between 1 and the image I4. The baseline length at this time is the distance B2
Is.

The base line length B1 is designed by the distance measuring module M1 alone, while the base line length B2 is determined by the position where the distance measuring module M1 and the distance measuring module M2 are attached to the substrate 1. The base line length B2 increases as the distance between the distance measuring module M1 and the distance measuring module M2 increases.

The phase difference x is obtained by performing a correlation operation between the image I1 projected through the lens L1 and the image I4 projected through the lens 4. The obtained phase difference x
The distance-measuring distance L can be obtained by substituting in the following equation.

[0057]

[Equation 8] L = B2 · f / x (8) When the distance measuring distance L is calculated by the mathematical expression (7) using one distance measuring module, and when the two distance measuring modules are used by the mathematical expression (7) The base line length is different from the case where the distance measurement distance L is obtained in 8). When the same phase difference x is detected by the correlation calculation, the ratio of the distance measurement distances L is B2 / B1. Further, when the same distance measurement distance L is obtained, it is possible to obtain a high distance measurement value approximately B2 / B1 times more accurate by using two distance measurement modules.

FIG. 3 shows a distance measuring area when two distance measuring modules are installed. A distance measuring module M1 having two lenses and a distance measuring module M2 are installed on the substrate 1.

The distance measuring module M1 can measure the distance to the object to be measured in the distance measuring area A1. The distance measuring module M2 can measure the distance to the object to be measured within the distance measuring area A2.

The distance measuring modules M1 and M2 are distance measuring modules for short distance. From the equation (2), the closer the distance-measured object is located, the larger the phase difference x becomes. Therefore, the distance measuring module for short distance is designed to have a large phase difference x, so that the viewing angle becomes wide and the distance measuring areas A1, A
2 becomes wider.

The overlapping area of the distance measuring areas A1 and A2 is the area A3. Therefore, the distance measurement area when the distance measurement is performed using both of the two distance measurement modules M1 and M2 is the area A3.

The wider the viewing angles of the distance measuring modules M1 and M2, the wider the distance measuring area A3 using the two distance measuring modules M1 and M2. In the area (A1-A3) of the distance measuring module M1 only, not in the distance measuring area A2 of the distance measuring module M2, distance measurement can be performed only by the distance measuring module M1.

On the other hand, the distance measuring area A of the distance measuring module M1
The area (A2-A3) of the distance measuring module M2 only, not within 1, can perform distance measurement only by the distance measuring module M2 alone.

The distance measuring area A3 is an area in which the distance measuring module M1 alone or the distance measuring module M2 alone can measure the distance and at the same time the distance measuring can be performed using the two distance measuring modules M1 and M2. Is.

When performing distance measurement, it is possible to obtain a highly accurate distance measurement value by using the two distance measurement modules M1 and M2 to increase the base line length B. The distance measurement value thus obtained has a larger base line length B than the distance measurement module M1 or the distance measurement module M2 alone, but the lens-sensor distance f and the phase difference x are almost the same. Since they can be the same, the short distance measurement distance L cannot be obtained from the equation (2).

Therefore, in the case of performing the short distance measurement, if the distance measurement is performed by the distance measurement module M1 or the distance measurement module M2 alone, the distance measurement value can be obtained even for a distance measured object at a short distance. it can. Further, if the distance measuring module alone measures the distance, the distance measuring area becomes wider.

As described above, by using the two distance measuring modules to process the sensor signals in both distance measuring modules, a highly accurate distance measuring value can be obtained. In the distance measurement using the two distance measurement modules, a distance measurement value can be obtained by performing distance measurement by the distance measurement module alone for a distance-measuring object that is too short to measure. .

Therefore, the distance measurement using the two distance measurement modules is suitable for the long distance measurement, and the distance measurement module alone is suitable for the short distance measurement. Further, for a distance-measured object that does not enter the distance-measurement area using the two distance-measurement modules, either one distance-measurement module alone may perform distance measurement according to the position of the distance-measured object.

Although the case where two distance measuring modules are installed on the substrate has been described above, the number of distance measuring modules may be three or more, and between two or more distance measuring modules suitable for two image signals. It is also possible to output the distance measurement value obtained by performing the correlation calculation.

Further, a plurality of distance measuring modules for a certain distance range can be used to extend the distance measuring range to a long distance without changing the optical system such as the lens of the distance measuring device.

Since a conventional small-sized distance measuring module which is mass-produced and low cost can be used, a low-cost long distance measuring device can be realized. Further, since a plurality of types of distance measuring modules are used, various distance measuring devices that can be easily adjusted and inspected can be provided.

By using a plurality of distance measuring modules, it is possible to measure a distance to an object to be measured at a short distance, a medium distance or a long distance without greatly changing the field of view. It is possible to measure distance without reducing accuracy.

The present invention has been described above with reference to the embodiments.
The present invention is not limited to these. For example, it will be apparent to those skilled in the art that various changes, improvements, combinations, and the like can be made.

[0074]

By calculating the distance measurement value using the image signals of the object to be measured obtained from the optical sensors of the plurality of distance measurement modules, both long distance measurement and short distance measurement can be performed. It is possible to obtain a highly accurate distance measurement value even in long distance measurement.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of a distance measuring device according to an embodiment of the present invention.

FIG. 2 is a conceptual diagram showing a baseline length during distance measurement using one distance measuring module and a baseline length during distance measurement using two distance measuring modules.

FIG. 3 is a conceptual diagram showing a distance measuring area when two distance measuring modules are installed.

FIG. 4 is a schematic diagram for explaining a measuring method of a distance measuring distance. FIG. 4A is a schematic diagram of an external light triangular optical system of the phase difference detection type distance measuring device, and FIG. 4B is an arithmetic expression for calculating the distance measuring distance.

FIG. 5 is a diagram for explaining phase difference detection by correlation calculation. FIG. 5A is a graph showing image signals obtained in the standard portion and the reference portion, FIG. 5B is a graph showing obtained correlation value curves, and FIG. 5C is for explaining a three-point interpolation method. FIG.

[Explanation of symbols]

 M distance measuring module L lens S optical sensor I optical image 1 substrate 2 microcomputer 3 memory 4 A / D converter 5 changeover switch 6 driver

Claims (3)

[Claims] 1. A plurality of distance measuring modules each having two lenses (L1, L2) and an optical sensor (S1) for converting an image of an object to be measured projected through the lenses into an electric signal. (M1) and a distance measurement value calculation means for performing a correlation calculation based on the electric signals obtained from the optical sensors of the plurality of distance measurement modules and calculating the distance to the object to be measured by the triangulation method. Distance measuring device. 2. The distance measuring device according to claim 1, wherein the plurality of distance measuring modules have the same characteristics and are installed on the same plane. 3. A means for calculating the distance to the object to be measured based on an electric signal obtained from the optical sensors of the two distance measuring modules, and the optical sensor of one distance measuring module. 3. The distance measuring device according to claim 1, further comprising means for calculating a distance to a distance-measuring object based on the electric signal obtained.