JPH11142122A - Range finder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a range finder for reducing the error of a laser beam intensity ratio due to the noise of an optical system and a signal processing system and improving measurement accuracy. SOLUTION: A rotary mirror 104 lets a laser beam from a light source 101 emitting lights of plural wavelengths sweep over an object. A light intensity control part 103 fixes the intensity of one laser beam and linearly changes the intensity of the other laser beam in the first half section of a scanning cycle and linearly changes the intensity of one laser beam and fixes the intensity of the other laser beam in the second half section of the scanning cycle. The laser beams are scanned by the rotary mirror 104, the angle of a measurement point is calculated from the light intensity ratio of the light separated from reflected laser beams from the object 106 and a distance to the object is calculated in a distance calculation part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a range finder for measuring a three-dimensional shape of an object.

[0002]

2. Description of the Related Art As a range finder device for performing three-dimensional shape measurement based on triangulation of projection light and observation image,
For example, the one shown in FIG. 25 has been proposed.

In FIG. 25, 1A and 1B are laser light sources having slightly different wavelengths, 2 is a half mirror for synthesizing laser light from the laser light sources having different wavelengths, and 3 is a light source control for controlling the light intensity of the laser light sources. , 4 is a rotating mirror for scanning the laser light, 5 is a rotation control unit for controlling the rotating mirror, 6 is a subject, 7 is a lens for forming an image on the CCD, and 8A and 8B are light of the wavelength of the laser light source. 9A and 9B are CCDs for capturing a monochrome image; 9C is a CCD for capturing a color image;
A and 10B are signal processing units of a monochrome camera, 11 is a signal processing unit of a color camera, 12 is a distance calculation unit that calculates the distance or shape of a subject from the intensity of laser light captured by the CCDs 9A and 9B, and 13 is the entire apparatus. This is a control unit for adjusting synchronization. Hereinafter, the operation of the range finder device thus configured will be described.

[0004] The laser light sources 1A and 1B emit laser light having slightly different wavelengths. This laser light is line light having a light section perpendicular to the scanning direction of the rotating mirror described later, and becomes vertical line light when the rotating mirror scans in the horizontal direction. The wavelength characteristics of these two light sources are shown in FIG.
Shown in The two light sources having similar wavelengths are used in order to reduce the influence of the wavelength dependence of the reflectance of the subject. The laser beams emitted from the laser light sources 1A and 1B are combined by the half mirror 2 and scanned on the subject 6 by the rotating mirror 4.

[0005] The scanning of the laser beam is performed by the rotation controller 5 driving the rotating mirror 4 at a field cycle. At this time, the light intensities of both light sources are changed within one field cycle as shown in FIG. By synchronizing the change of the laser light intensity with the driving of the mirror angle, the two laser light intensities are monitored by the CCDs 9A and 9B and the light intensity ratio is calculated, so that the time in one scanning cycle can be measured. it can. For example, FIG.
As shown in (b), when the light intensity is IA0 / IB0, the scanning time is measured as t0, and the rotation angle (φ) of the rotating mirror 4 is determined from the measured value.

As described above, the ratio between the two laser beam intensities and the mirror angle (ie, the angle of the subject viewed from the light source side) is 1
By associating with one-to-one, a distance calculation unit, which will be described later, calculates the distance or shape of the subject from the ratio of the signal levels obtained by capturing the light of both light sources, based on the principle of triangulation.

The lens 7 forms an image of a subject on the CCDs 9A, 9B, 9C. The light wavelength separation filter 8A includes a light source 1A
, And reflects light of other wavelengths. The light wavelength separation filter 8B transmits light of the wavelength of the light source 1B and reflects light of another wavelength. As a result, the reflected light of the light of the light sources 1A and 1B from the subject is photographed by the CCDs 9A and 9B, and the light of other wavelengths is photographed by the CCD 9C as a color image.

The light source A signal processing unit 10A and the light source B signal processing unit 10B perform the same signal processing on the outputs of the CCDs 9A and 9B as in a normal monochrome camera. The color camera signal processing unit 11 performs normal color camera signal processing on the output of the CCD 9C.

The distance calculator 12 calculates the distance for each pixel from the ratio of the signal levels photographed by the CCDs 9A and 9B, the base line length, and the coordinate value of the pixel for each light source wavelength.

FIGS. 28 (a) and 28 (b) are diagrams for graphically explaining the distance calculation. In the figure, O is the center of the lens 7, P is a point on the subject, and Q is the position of the rotation axis of the rotating mirror. Further, for simplicity of explanation, the position of the CCD 9 is shown folded back toward the subject. If the length of OQ (base line length) is L, the angle of P as viewed from Q in the xz plane is φ, and the angle of P as viewed from O in the yz plane is ω, P Are calculated by the following equation.

[0011]

(Equation 1) As for φ in the equation (1), as described above, the CCD 9A,
9B is calculated based on the light intensity ratio of the laser light sources 1A and 1B monitored, and θ and ω are calculated from the coordinate values of the pixels. When all of the values shown in Expression (1) are calculated, the shape is obtained, and if only z is obtained, the distance image is obtained.

[0012]

However, in the above configuration, since both of the two laser beam intensities are changed within the scanning field, as shown in FIG. The rate of change is not linear, but varies in a curve between the scan start time and the scan end time. CCD 9A,
The error in the laser light intensity ratio caused by noise in the image data captured by 9B is a major cause of the distance or shape measurement error. However, when the rate of change in the laser light intensity ratio is not constant, the error is caused by the noise. There is a problem that a light intensity measurement error easily occurs.

The present invention has been made in view of the above problems, and has as its object to provide a range finder device that reduces the influence of noise in an optical system and a signal processing system and improves measurement accuracy.

[0014]

The present invention employs the following structure in order to solve the above-mentioned problems.

According to a first aspect of the present invention, there is provided scanning means for scanning a subject with laser light from a light source emitting light of a plurality of wavelengths, and changing the light intensity of the laser light in synchronization with a scanning cycle of the scanning means. Light intensity control means for causing light to be separated from light having the same wavelength as the plurality of wavelengths from the reflected laser light from the subject; and an angle of a measurement point in the scanning means based on a light intensity ratio of the separated light. And a distance calculating means for calculating the distance to the subject.

With this configuration, the angle error of the measurement point in the scanning means due to the error of the laser intensity ratio can be reduced, so that the influence of noise in the optical system and the signal processing system is reduced, and the measurement accuracy is improved. A finder device can be obtained.

According to a second aspect of the present invention, in the first half of the scanning period, the light intensity control means keeps one laser light intensity constant and linearly changes the other laser light intensity, In the latter half section, one laser light intensity is changed linearly and the other laser light intensity is made constant.

According to this configuration, the rate of change of the laser beam intensity ratio can be always kept constant in all scanning sections, and the range of the laser beam intensity ratio can be widened. The measurement error of the ratio can be minimized, and as a result, the angle (φ) of the measurement point viewed from the light source side can be accurately determined.

According to a third aspect of the present invention, in the range finder device of the second aspect, the distance calculating means includes:
The angle of the measurement point in the scanning means is determined from both the magnitude relationship of the laser beam intensity and the ratio of the laser beam intensity.

With this configuration, it is possible to reliably detect which point in the first half or the second half of the scanning section the current scanning point exists.

According to a fourth aspect of the present invention, in the range finder device of the second or third aspect, the light intensity control means corrects the laser light intensity in accordance with a noise level characteristic measured in advance. Configured.

According to this configuration, the laser beam intensity can be controlled so as to correct the noise caused by the optical system and the signal processing system of the apparatus measured in advance, the influence of the noise is further reduced, and the measurement accuracy is significantly improved. An improved range finder device can be obtained.

According to a fifth aspect of the present invention, in the range finder device according to any one of the first to fourth aspects, the distance calculating means calculates the laser light intensity ratio of a plurality of peripheral pixels near the pixel of interest. Average, weighted average,
Alternatively, the laser intensity ratio at the target pixel is calculated using the median value of the target pixel and the peripheral pixels.

With this configuration, the noise of the laser intensity ratio can be reduced in the region where the laser light intensity ratio is uniform, and the noise level of the randomly generated noise is reduced to 1 / n (where n is the peripheral pixel of interest). ), And the measurement accuracy is improved.

According to a sixth aspect of the present invention, in the range finder device according to any one of the first to fourth aspects, the distance calculating means includes a vertical intensity distribution of the laser light of each light source and each of the light receiving portions. The light intensity is corrected in consideration of the sensitivity characteristics of the unit, and the distance is calculated using the corrected light intensity ratio.

With this configuration, the vertical intensity distribution (vertical profile) of the line light from the two laser light sources
Even if does not match, the measurement accuracy can be maintained.

According to a seventh aspect of the present invention, in the range finder device according to any one of the first to fourth aspects, the distance calculating means includes: a vertical intensity distribution of the laser light of each light source; The light intensity ratio is corrected in consideration of the sensitivity characteristics of the unit, and the distance calculation is performed using the corrected light intensity ratio.

With this configuration, the vertical intensity distribution (vertical profile) of the line light from the two laser light sources
Even if does not match, the measurement accuracy can be maintained.

According to an eighth aspect of the present invention, in the range finder according to the sixth or seventh aspect, there is provided a camera for receiving the reflected laser light from the object, and the camera and the light source are connected to a light source. Are arranged in such a manner that the epipolar lines, which are the trajectories of the light rays from the camera within the visual field of the camera, become parallel.

With this configuration, the effect of improving the distance measurement accuracy by correcting the light intensity or the light intensity ratio at the reference distance can be obtained even when the subject distance is far from the reference distance.

According to a ninth aspect of the present invention, in the range finder device according to the first to eighth aspects, when changing the light intensity of the laser light, a high frequency is superimposed on the intensity modulation signal of the laser light. And

With this configuration, speckle noise can be reduced, distance measurement accuracy can be improved, and the measurable distance range can be expanded.

[0033] The tenth aspect of the present invention is the first aspect of the present invention.
In the range finder according to the ninth aspect, the scanning means uses a galvanomirror and a polygon mirror to scan the object with laser light.

With this configuration, laser beam scanning with a constant light intensity ratio in the vertical direction can be performed, and distance measurement can be performed without correcting the light intensity or the light intensity ratio.

The invention according to claim 11 is the same as the invention according to claim 1.
The range finder device according to any one of claims 10 to 10,
The wavelength separating means is configured to perform wavelength separation by using an interference filter that is arranged to be inclined with respect to the imaging surface.

With this configuration, it is possible to reduce the occurrence of moire fringes caused by the coherence of the light source.

According to a twelfth aspect of the present invention, there is provided a distance measuring method according to the present invention, wherein a high frequency wave whose amplitude changes with time is superimposed on a light intensity modulation signal for a one-wavelength laser light source, and the intensity-modulated laser light is rotated by a rotating mirror. The object is scanned, and the reflected light from the object is imaged by the CCD.
For the light intensity distribution in the vicinity of the target pixel of the CD, two envelope detections of the upper limit and the lower limit are performed, and local average detection is performed. Based on the ratio of the difference between the two envelopes and the local average value, the object is viewed from the light source. Angle information to the subject viewed from the CCD based on the coordinate value of the pixel of interest, and the distance for each pixel for each field period using the calculated angle information and the base line length. Measured.

With this configuration, it is possible to measure the distance of each pixel for each field from one scan by the laser light source of one wavelength.

[0039]

(Embodiment 1) Hereinafter, a range finder device according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of a range finder device according to Embodiment 1 of the present invention. In FIG. 1, 101A and 101B are laser light sources having slightly different wavelengths, 102 is a half mirror for synthesizing laser light from the laser light sources having different wavelengths, 103 is a light source control unit for controlling light intensity of the laser light sources, 104
Is a rotating mirror that scans a laser beam, 105 is a rotation control unit that controls the rotating mirror, 106 is a subject, 107 is a CC
Lenses for forming an image on D, 108A and 108B are optical wavelength separation filters for separating light of the wavelength of the laser light source,
09A and 109B are CCDs for capturing monochrome images, 1
09C is a CCD for capturing a color image, 110A, 10C.
B is a signal processing unit of a monochrome camera, 111 is a signal processing unit of a color camera, 112 is a distance calculation unit that calculates the distance or shape of a subject from the intensity of laser light captured by the CCDs 109A and 109B, and 113 is a synchronization unit. It is a control unit for adjustment. The operation of the above configuration will be described below.

Each of the laser beams 101A and 101B emits a laser beam having a slightly different wavelength (line light having a light cutting plane perpendicular to a scanning direction by a rotating mirror 104, which will be described later). This wavelength characteristic is the same as that shown in FIG. The two light sources having similar wavelengths are used in order to reduce the influence of the wavelength dependence of the reflectance of the subject. Laser beams emitted from both light sources are combined by the half mirror 102, and the object 106 is scanned by the rotating mirror 104.

At that time, the light intensities of both laser light sources are changed within the field period as shown in FIG. That is, in the first half of the scanning cycle, the light intensity of one laser light is kept constant and the light intensity of the other laser light is changed linearly, while in the second half of the scanning cycle, the intensity of one laser light is changed linearly. To make the latter laser beam intensity constant. Furthermore, it is configured to calculate the ratio of the signal levels as a value of the low level / a value of the high level.

Accordingly, the rate of change of the laser light intensity ratio is always constant in the entire scanning section.

The rotation control unit 105 drives a rotating mirror at a field cycle to scan with a laser beam. By synchronizing the change in the laser light intensity with the driving of the mirror angle, the distance calculation unit, which will be described later, can determine the angle of the measurement point viewed from the light source from the ratio of the two laser light intensities and the magnitude relationship between the two.

FIG. 3 is a timing chart of the vertical synchronization signal (a) from the control unit 113, the intensity modulation signals (b) and (c) of the light sources 101A and 101B, and the drive signal (d) of the rotating mirror 104. As shown, as shown in FIG.
01B intensity modulated signals (b) and (c) and rotating mirror 104
Is synchronized with the vertical synchronization signal (a) from the control unit 113 to scan the laser light while changing the laser light intensity ratio.

The lens 107 is a CCD 109A, 109
B and 109C form an image of the subject. The light wavelength separation filter 108A transmits light of the wavelength of the light source 101A and reflects light of another wavelength. The optical wavelength separation filter 108B is
The light of the wavelength of the light source 101B is reflected, and the light of another wavelength is transmitted. As a result, the reflected light of the light of the light sources 101A and 101B from the subject is photographed by the CCDs 109A and 109B, respectively, and the light of the other wavelengths is captured as a color image by the CCD 109A.
Photographed by C.

The light source A signal processing unit 110A and the light source B signal processing unit 110B perform the same signal processing as that of a normal monochrome camera on the outputs of the CCDs 109A and 109B. The color camera signal processing unit 111 performs a normal color camera signal processing on the output of the CCD 109C.

The distance calculator 112 calculates the distance for each pixel from the ratio of the signal levels photographed by the CCDs 109A and 109B, the base line length, and the coordinate value of the pixel for each light source wavelength.

This distance calculation is performed by the equation (1) in the same manner as described with reference to FIG.

With respect to φ in equation (1), as described above,
Laser light sources 1A, 1 monitored by CCDs 9A, 9B
B is calculated from the light intensity ratio of B, and θ and ω are calculated from the pixel coordinate values. The calculation of φ is performed by the same method as that in the related art, but in the first embodiment, one laser light intensity is made constant and the other laser light intensity is changed linearly in a half cycle of the scanning cycle, and two From the ratio of the laser beam intensity and the magnitude relationship between the two, the scanning time within one scanning period is measured to calculate the rotation angle of the rotating mirror 104. The laser beam intensity ratio can be kept constant and the range of the laser beam intensity ratio can be widened, so that the measurement error of the laser beam intensity ratio due to the influence of noise can be minimized. The angle (φ) of the measurement point as viewed from above can be determined. In order to calculate the rotation angles of the rotary mirror 104 from the ratio of the two laser beam intensities and the magnitude relationship between the two, these can be tabulated in advance and prepared and referred to each time to speed up the processing.

The angle (φ) of the measurement point obtained in this way
Is used, the shape can be obtained by calculating all of x, y, and z among the values shown in Expression (1), and the distance image can be obtained by using only z.

As described above, according to the first embodiment, the rate of change of the laser intensity ratio is kept constant irrespective of the angle, thereby reducing the angle error and the shape or distance measurement error due to the laser intensity ratio measurement error. can do.

(Embodiment 2) In Embodiment 2 of the present invention, the laser light intensity is changed within the scanning period in accordance with the noise level of the video signal photographed by the camera, whereby the laser light intensity ratio is changed. An example in which the angle error due to the above error is reduced to improve the measurement accuracy will be described.

FIG. 4 is a configuration diagram of a range finder device according to Embodiment 2 of the present invention. In FIG. 4, components that perform the same operations as those in Embodiment 1 are given the same reference numerals, and descriptions thereof are omitted. In the second embodiment, the light source control unit 4
03 and the operation of the distance calculation unit 412 are different from those of the first embodiment. Hereinafter, operations of the light source control unit 403 and the distance calculation unit 412 will be described.

The light source control unit 403 includes a CCD 109A,
In accordance with the noise level of the video signal captured in step 09B, the intensity modulation that minimizes the angle error is performed. The intensity modulation in the light source control unit 403 will be described below.

The calculation of the laser intensity ratio in the distance calculation unit 412 is performed by using the signal level photographed by the CCD 109A as SA and the signal level photographed by the CCD 109B as SB.
Assuming that the γ characteristic of the camera is 1, if SB <SA, ideally, it is calculated by the following equation (2).

(Equation 2) Actually, since each signal level contains noise, equation (3) is calculated.

(Equation 3) Here, n (SA) and n (SB) are distributions of the noise level with respect to the signal level.
Signals SA and SB obtained by capturing the wavelengths of A and 101B have the same distribution.

Now, assuming that the representative value of the noise level stochastically distributed with respect to the signal level is RMS value σ, the laser intensity ratio in the distance calculation unit 412 is as follows:

(Equation 4) And conversely, if the laser light intensity ratio is estimated to be small,

(Equation 5) Becomes

Therefore, the range of the error of the laser intensity ratio is given by the following equation.
(4) From the difference between Expression (5) and Expression (2), the range shown in Expression (6) is obtained.

(Equation 6) Since SA and n (SA) are constant during the first half of the field period, the error of the laser light intensity ratio in equation (6) is determined by the numerator of equation (6).

Since the laser light intensity ratio and the drive signal of the rotating mirror change with time within the field period as shown in FIG. 3, the observed laser light intensity ratio error is a time error, that is, as viewed from the light source. This results in an angle error. In order to reduce the angle error, the intensity of the light source 1B should be changed in proportion to the error of the laser light intensity ratio, and the intensity of the light source 1B needs to increase monotonically in the first half of the field period. From the condition that there is a noise level distribution with respect to the signal level, the intensity modulation function IB (t) of the light source 1B for minimizing the angle error is expressed by the equation (7).
It can be determined by numerically solving under the boundary condition (8).

(Equation 7)

(Equation 8) Here, the constant A in Expression (7) is a constant determined from the boundary condition in Expression (8). By solving equation (7) so as to satisfy the boundary condition of equation (8), it is possible to determine an intensity modulation function that makes the angle error constant within the field period and minimize the angle error.

Note that the intensity modulation function IB from equation (7)
It is a matter of course that substantially the same effect can be obtained even if curve fitting such as a quadratic function or a hyperbola is used as a method for determining (t).

FIG. 5 shows a case where a laser light source having an output of 30 mW and a wavelength of 830 nm is used to project laser light at a uniform laser power density onto color indexes of a plurality of colors at a distance of 1 m, and photographed with a CCD having infrared sensitivity. It shows the noise level (RMS value) measured for the video signal in the center area of the screen. This noise level is measured in a form including a plurality of noise components such as dark current noise of the CCD, shot noise, noise of the amplifier, and speckle noise. A dominant component of these noises is speckle noise caused by coherence of the light source.

FIG. 6 is a diagram of an intensity-modulated signal corrected so that the angle error becomes constant within the field period with respect to the relationship between the signal level and the noise level for the subject at a distance of 1 m in FIG. When the distance of the subject is other than 1 m, the error at the set distance can be reduced by measuring the relationship between the signal level and the noise level according to the distance of the subject in advance or by predicting the relationship from the relationship of the subject distance of 1 m. Measurement accuracy can be improved. The relationship between the signal level and the noise level when the subject distance is other than 1 m is that the signal level decreases in inverse proportion to the square of the distance, and the value of the noise level with respect to the signal level is the same regardless of the distance. Can be predicted.

It is known that an increase in noise level (shot noise) with an increase in signal level is proportional to a half power of the signal level. FIG. 7 shows such a relationship between the noise level and the signal level. In the case of the relationship between the noise level and the signal level as shown in FIG. 7, the intensity modulation function can be determined by the same method as the above-described method of determining the intensity modulation function from the relationship between the noise level and the signal level in FIG.

The distance to the subject is not limited to the one set in advance, and the average value of the distance in the image of the measured value in the previous field and the weighted average in which the center is preferentially weighted may be used as the noise in the current field. The subject distance for determining the level may be used.

As described above, according to the second embodiment, the laser beam intensity is corrected according to the relationship between the signal level of the video signal captured by the camera and the noise level, and
By changing within the scanning cycle, an angle error due to an error in the laser light intensity ratio can be reduced, and measurement accuracy can be improved.

The speckle noise which is the main component of the noise in the second embodiment is caused by the coherence of the laser light source. A method for reducing the coherence of the light source will be described below.

FIG. 20 is an explanatory diagram of an intensity modulation signal of a light source on which a high-frequency signal is superimposed. As shown in the figure, by superimposing a high-frequency signal on the intensity modulation signal of the light source, the laser power can be changed at high speed without changing the local average level (broken line in FIG. 20). When the laser power changes, the laser oscillation mode changes, and the speckle intensity also changes. Accordingly, the frequency is higher than the original modulation signal (60 Hz) (for example, several kHz).
By superimposing high frequencies (of the order of magnitude), the level of speckle noise can be reduced, and such a method is also included in the present invention.

(Embodiment 3) In Embodiment 3 of the present invention, the laser light intensity ratio at a pixel of interest is calculated using the laser light intensity ratios at a plurality of neighboring pixels, thereby obtaining the laser light intensity ratio. An example in which the error is reduced and the measurement accuracy is improved will be described.

FIG. 8 is a configuration diagram of a range finder device according to Embodiment 3 of the present invention. In FIG. 8, components that perform the same operations as those in the first or second embodiment of the present invention are given the same reference numerals as those in FIG. 1 or FIG. Hereinafter, operations of the light source control unit 803 and the distance calculation unit 812 will be described.

The light source control unit 803 performs the same operation as the light source control units in the first and second embodiments of the present invention, and controls the light intensity ratio of the laser light source. Further, the distance calculation unit 812 calculates the laser light intensity ratio of the target pixel as an average of the laser light intensity ratios of a plurality of surrounding pixels (for example, 3 × 3 pixels), and uses the value to calculate the laser light intensity ratio in the first embodiment. The same distance calculation as in the second embodiment is performed.

In the third embodiment, when calculating the distance, the average of the laser light intensity ratios of a plurality of pixels around the pixel of interest is used as the laser light intensity ratio. In this case, the noise of the laser intensity ratio can be reduced. By calculating the average of the laser light intensity ratios in the surrounding n × n pixels, the noise level can be reduced to 1 / n, and as a result, the measurement accuracy can be improved.

The calculation of the laser beam intensity ratio in the distance calculation unit 812 does not need to be limited to the calculation of the average of the pixel of interest and its surrounding pixels. For example, by determining the laser light intensity ratio by a weighted average in which the weight becomes smaller as the difference between the average values becomes larger, it is possible to reduce a measurement error near the object contour where the laser light intensity ratio changes rapidly.
Alternatively, the laser light intensity ratio may be determined as the median value of the pixel of interest and its surrounding pixels.

Also, instead of calculating the laser beam intensity ratio from the values of the pixel of interest and its surrounding pixels, the distance calculation unit 812 calculates the distance measurement value of the pixel of interest and the distance measurement value of the pixel of interest and its surrounding pixels. A similar effect can be obtained by calculating as an average value, a weighted average value, or a median value, and is included in the present invention.

As described above, according to the third embodiment, the laser light intensity ratio at the pixel of interest is calculated using the laser light intensity ratios at a plurality of neighboring pixels, thereby reducing the error in the laser light intensity ratio. , Measurement accuracy can be improved.

Fourth Embodiment In a fourth embodiment of the present invention, an example will be described in which the influence of the vertical intensity distribution (vertical profile) of a laser light source is corrected by signal processing to improve measurement accuracy.

FIG. 9 is a configuration diagram of a range finder device according to Embodiment 4 of the present invention. In FIG. 9, components that perform the same operations as those of the first to third embodiments of the present invention are denoted by the same reference numerals as those in FIG. 1, FIG. 4, or FIG. Hereinafter, the operation of the distance calculation unit 901 will be described.

The distance calculation unit 901 corrects the laser light intensity (ie, luminance) at the pixel of interest according to the y coordinate value of the pixel, and uses the corrected laser light intensity to obtain the same distance as in the first to third embodiments. Calculation is performed.

In the fourth embodiment, when calculating the distance, the laser light intensity is corrected in consideration of the vertical distribution (vertical profile) of the laser light intensity, and the distance is calculated from the corrected laser light intensity. Measurement accuracy can be maintained even when the vertical profiles of the two laser light sources do not match.

Hereinafter, the vertical distribution (vertical profile) of the laser beam intensity will be described.

FIG. 10 is an explanatory diagram of a laser light source and an optical system for generating slit light. In FIG. 10, 10
01 is a laser oscillator, 1002 is a laser diode, 1003 is a collimator lens, and 1004 is a cylindrical lens.

The laser diode 1002 is driven by a drive circuit in the laser transmitter and emits light of a fixed wavelength.

FIG. 11 is a characteristic diagram showing the directionality of the light intensity of the laser diode 1002. As shown in the figure, the intensity of light emitted from the laser diode has a Gaussian distribution centered on the peak intensity.

The collimator lens 1003 condenses the laser light emitted from the laser diode 1002 and generates a light beam.

The cylindrical lens 1004 expands the beam light generated by the collimator lens 1003 in the vertical direction to generate slit light. As shown in FIG. 11, since the intensity of the light emitted from the laser diode has a Gaussian distribution, the light intensity of the slit light obtained by condensing the light and expanding in the vertical direction is not uniform in the vertical direction. The light intensity distribution in the horizontal direction is not a problem because the distribution width is small.

FIG. 12 shows an example of a vertical light intensity distribution (vertical profile) of two laser light sources. Since the directionality of the light intensity of the laser diode differs for each laser, the vertical profiles of the two laser light sources do not match.

In the range finder according to the present invention,
Since distance measurement is performed using a change in the laser intensity ratio in the horizontal direction, a change in the laser intensity ratio in the vertical direction causes an error in the distance measurement accuracy. In the fourth embodiment, the light intensity at the target pixel is corrected so that the vertical profile becomes flat (that is, the correction using the ratio of each data and the peak value P1 or P2 in FIG. 12), and the corrected light intensity is obtained. Was used to calculate the distance.

FIG. 13 is a configuration diagram of distance calculation section 901 according to the fourth embodiment. In the figure, 1301A,
1301B is a vertical profile correction table, 1302
Is an LU that converts two light intensities into angle information from a light source
T, 1303 is a LUT for converting the x coordinate value of the pixel of interest into angle information from the camera, and 1304 is a memory for storing the base line length (distance between the light source and the lens center of the camera) required for distance calculation. Hereinafter, the operation of the above configuration will be described.

Vertical profile correction table 1301
A and 1301B hold the correction coefficients of the vertical profiles of the laser beams of the light sources A and B, respectively. The correction coefficient is obtained as a ratio between the peak value P1 or P2 in FIG. 11 and each vertical profile data for each y coordinate of the image.
The vertical profile data is obtained by irradiating a laser beam that is not time-modulated on a plane having a fixed distance and imaging the laser light. The vertical profile is corrected by multiplying by a correction coefficient according to the y coordinate value of the pixel of interest.

In the fourth embodiment, the following equation (9) is calculated by modifying the equation for calculating z in equation (1).

(Equation 9) The LUT 1302 calculates the ratio of the two laser beam intensities after correction to angle information from the light source.

(Equation 10) Convert to

FIG. 14 shows the relationship between the ratio of the two laser beam intensities and the angle information (Equation 10) from the light source. The method for calculating the conversion characteristics in FIG. 14 will be described below.

First, a time-modulated laser beam shown in FIG. 2 is projected onto a reference plane at a known constant distance, and this is imaged. Next, vertical profile correction is performed on the captured image. Then, using the camera parameters (focal length and pixel size on the imaging surface), the light intensity ratio and the value of the angle information equation (10) from the light source according to the magnitude relationship of the light intensity after the vertical profile correction for each pixel. Is calculated.

FIG. 19 is an explanatory diagram showing the distribution of the light intensity ratio and the angle information equation (10) after performing such a calculation. Due to the noise included in the light intensity, the calculated light intensity ratio and the angle information expression (10) have a distribution having a width. The relationship between the ratio of the laser light intensity and the angle information formula (10) from the light source is represented by the magnitude relationship of the light intensity (the light intensity of the light source 101A ≦ the light intensity of the light source 101B and the light intensity of the light source 101A ≧ the light of the light source 101B). Function (for example, 3
It can be obtained by applying the following equation). At the time of function fitting, the condition that the light passes through the average value (point A in FIG. 15) of the angle information equation (10) when the light intensity ratio is 1 in FIG. Accuracy can be improved. That is, if there is no such condition,
The two functions applied according to the magnitude relationship of the light intensity intersect at a light intensity ratio of 1 or less, or intersect at a value of 1 or more, and the distance measurement accuracy decreases near the light intensity ratio of 1. The reason is that in the vicinity of the light intensity ratio 1, the magnitude relation of the light intensity may be reversed due to noise included in the light intensity.

The LUT 1303 calculates the x coordinate of the pixel of interest by an expression
In order to convert the angle information from the camera shown in (11),
Holds the value for one line.

[Equation 11] The value at each x-coordinate of the image of Expression (11) can be determined from the lens focal length and the size of one pixel on the imaging surface from the above-described graphic relationship in FIG.

From the angle information from the LUTs 1302 and 1303 and the base line value from the memory 1304, the triangulation equation (9) can be calculated, and the distance z for each pixel of the image is calculated.
Can be calculated.

The calculation of the distance z can be realized by a memory reference such as an LUT, an addition, and a multiplication circuit, other than the final division as shown in FIG. Also, the final division can be realized by referring to the memory by storing the calculation result for the input value in the memory. Therefore, the distance calculation for each pixel can be sufficiently processed at the video rate.

FIG. 16 shows a processing procedure in the fourth embodiment. Vertical profile correction data is calculated as an initial setting process (ST1601), and a conversion characteristic from the light intensity ratio to 1 / tanφ is calculated using the result (ST160).
2). Then, as video rate processing, distance calculation is performed using the vertical profile correction data and the conversion characteristic from light intensity to 1 / tan φ (ST1603).

As described above, according to the fourth embodiment, when calculating the distance, the laser light intensity is corrected in consideration of the vertical distribution (vertical profile) of the laser light intensity, and the distance calculation is performed from the corrected laser light intensity. Is performed, even if the vertical profiles of the two laser light sources do not match,
Measurement accuracy can be maintained.

In the correction of the influence of the vertical profile in the fourth embodiment, the case where the vertical profile is flattened before the calculation of the light intensity ratio has been described.
Even if the light intensity ratio is corrected after calculation according to the y coordinate value of the pixel of interest and the corrected light intensity ratio is converted into angle information, it is mathematically the same process, and it is apparent that the process is included in the present invention. It is.

In the correction of the influence of the vertical profile in the fourth embodiment, since the correction based on the vertical profile on the reference plane is performed, it is conceivable that the measurement accuracy will deteriorate if the subject moves away from the reference plane. In consideration of this point, the arrangement of the imaging surface and the light source for realizing the vertical profile correction independent of the distance between the subject and the reference surface will be described below.

FIG. 17 is an explanatory diagram of imaging of line light. In the figure, 1701 is a laser light source, 1702
Denotes a collimating lens, 1703 denotes a cylindrical lens, 1704 denotes a rotating mirror, and 1705 denotes a camera.
Laser light emitted from a laser light source 1701 is collimated by a collimating lens 1702 to become a beam light, and is diffused only in a vertical direction by a cylindrical lens 1703 to become a line light, and becomes a rotating mirror 1704.
Scans the measurement space. Here, consider where in the image the light traveling in each direction of the line light is captured in the image.

FIG. 18 shows a point a shown in FIG.
1, a2, b1, b2, c1, and c2 indicate positions appearing in the image at the time of imaging. FIG. 18 shows that light traveling in space (a straight line in a three-dimensional space) is projected onto a straight line in an image (a straight line in a two-dimensional space) by imaging (perspective transformation).

In FIG. 18, the straight line projected in the image is such that the left side in the image is far from the camera in the three-dimensional space,
Conversely, the right side is closer to the camera in the three-dimensional space. Since this straight line is generally not horizontal in the image, if the distance between the reference distance and the subject is large, the vertical profile cannot be correctly corrected.

If the trajectories of light traveling in all directions included in the line light become horizontal in the image at the time of capturing the line light, the light intensity correction based on the vertical profile at the reference distance can be applied regardless of the distance to the subject. . This is because the vertical profile correction is performed according to the y coordinate value in the image. The arrangement of such a light source and an imaging surface will be described below.

FIG. 19 is an explanatory diagram of the formulation of the projection of a straight line in the space onto the imaging surface. In the figure, O is the center of the lens, and A is the light source position (the main position of the fan-shaped line light). For simplicity, it is assumed that the imaging surface is at the position of Z = f. A
Is (lx, ly, lz), and the direction vector of the light from the light source is (dx, dy, dz). The straight line through which the light passes

(Equation 12) The perspective transformation of this to the imaging plane is given by the equation (1)
A plane including the straight line 2) and passing through the origin O (center of the lens)

(Equation 13) And finding the intersection of the plane Z = f. Equation (1
Since the normal vector of the surface 3) is perpendicular to both (dx, dy, dz) and (lx, ly, lz),

[Equation 14] I can go. Here, from the condition a = 0 that the intersection line is horizontal,

(Equation 15) Is led. Here, the traveling direction of light (dx, dy, d
z) is not constant because the line light is scanned by the rotating mirror. From the condition satisfying (Equation 15) for any (dx, dy, dz),

(Equation 16) Get. That is, by arranging the light source so that the line segment connecting the lens center and the light source is horizontal to the x-axis of the imaging surface, vertical profile correction can be performed regardless of the distance between the reference distance and the subject.

In the light intensity correction according to the fourth embodiment, the correction of the influence of the vertical profile which can be realized by the correction table for one vertical line has been described. However, the correction table for one screen can be used by using the correction table for one screen. Correction according to the x-coordinate value and the y-coordinate value (for example, correction of dimming around the lens) can be performed with the same configuration, and is included in the present invention.

In the fourth embodiment, the line light is generated from the laser beam light, and the line light is horizontally scanned by the rotating mirror (galvanometer mirror). It may be used to perform two-dimensional scanning.

FIG. 21 is an explanatory diagram of the scanning of the laser beam by the galvanometer mirror and the polygon mirror. FIG.
In 1, reference numeral 2101 denotes a galvanomirror. Reference numeral 2102 denotes a polygon mirror. The galvanometer mirror 2101 scans the laser beam light vertically, and the polygon mirror 2102 scans the laser beam light horizontally. The laser beam can be scanned in the object space by both scanning. In the fourth embodiment, two laser light sources are used as light sources. However, the scanning by the galvanometer mirror and the polygon mirror makes it easy to keep the laser intensity ratio constant in the vertical direction, and the vertical profile is not corrected. Distance measurement can be performed and is included in the present invention.

In the fifth embodiment, the measurement of the distance z has been described. However, by measuring all of x, y, and z in Expression (1), the three-dimensional coordinate values (x, y, z) can be calculated. Of course, measurement can be performed.

In the distance measurement according to the first to fourth embodiments of the present invention, the distance is measured for each field using a two-wavelength light source. However, the laser intensity for each wavelength in the above-described embodiment is used. By switching the modulation signal (two types) for each field and controlling the light intensity of one laser light source, the distance measurement for each frame may be performed by a light source of one wavelength.

(Embodiment 5) Embodiment 5 of the present invention
Refers to an embodiment in which one-wavelength light source performs distance calculation for each field. FIG. 22 is a configuration diagram of a range finder device according to Embodiment 5 of the present invention. Components that perform the same operations as those of the first to fourth embodiments of the present invention are denoted by the same reference numerals as those of the above-described embodiment, and description thereof is omitted. The difference from the above embodiment is that the light source control unit 220
1. Laser light source 2202, infrared transmission filter 2203 that reflects visible light and transmits infrared light, laser light source 22
An interference filter 2204 that transmits only light having a wavelength of 02,
The point is that a distance calculation unit 2205 and a control unit 2206 for controlling synchronization of the entire apparatus are provided.

The light source control unit 2201 uses the intensity modulation signal shown in FIG.
02 is driven. In the intensity modulated signal shown in FIG. 23, the ratio of the difference between the envelopes (upper and lower) and the local average uniquely corresponds to the time within the field period (that is, the angle of the subject viewed from the rotating mirror 104). I have.

The reflected light from the subject 106 is separated into infrared light and visible light by an infrared transmission filter, and the visible light is imaged by the color CCD 109C. On the other hand, only the light of the light source wavelength is transmitted by the interference filter 22204, and the infrared light is imaged by the monochrome CCD 109A having infrared sensitivity.

Note that the interference filter 265 is used for the monochrome CC.
When arranged in parallel with D109A, moiré fringes occur in the captured image due to the coherence of the laser light source.

The transmission wavelength characteristic of the interference filter is such that when the incident light is incident at an angle away from the angle perpendicular to the filter surface,
Since the transmission wavelength peak shifts to the shorter wavelength side, an interference filter having a transmission wavelength peak on the longer wavelength side than the light source wavelength is used in consideration of the shift amount in advance.

The distance calculation unit 2205 performs envelope detection and local average detection for each line of light intensity obtained as an image, and calculates a distance.

FIG. 24 shows one of the configurations of the distance calculation unit 2205.
It is a block diagram showing an example. As shown in the figure, the distance calculation unit 2205 converts the ratio between the difference between the envelope values (upper and lower) and the local average to the angle information from the light source. LUT 2402, LUT 240 that converts the x coordinate of the pixel of interest into angle information from the camera
3, a memory 2404 for holding the value of the base line length.

The envelope of the light intensity is detected by spatially interpolating the detection results of the maximum value and the minimum value of the light intensity near the target pixel.

The distance for each pixel can be calculated from the outputs of the LUT 2402 and LUT 2403 and the value of the base line length of the memory 2404.

As described above, according to the fifth embodiment, by using the laser light source of one wavelength, the angle information from the light source is given by the ratio of the difference between the envelope of the light intensity modulation signal and the average light intensity. The distance measurement for each pixel can be performed for each field cycle by triangulation using the angle information from the CCD and the base line length.

Further, by disposing an interference filter that transmits only the wavelength of the laser light source at an angle with respect to the CCD, the occurrence of moire fringes due to the coherence of the laser light can be reduced.

[0121]

As described above, according to the present invention,
By keeping one laser intensity constant and changing the other laser intensity linearly and changing the laser intensity ratio linearly within the field period, the rate of change of the laser intensity ratio can be kept constant regardless of the angle. In addition, it is possible to reduce an angle error due to a measurement error of a laser beam intensity ratio and a measurement error of a shape or a distance.

Further, the laser beam intensity is corrected in accordance with the relationship between the signal level of the video signal photographed by the camera and the noise level, and is then changed within the scanning period, whereby the angle due to the error in the laser beam intensity ratio is changed. Reduce the error,
Measurement accuracy can be improved.

Further, by calculating the laser light intensity ratio at the pixel of interest using the laser light intensity ratios at a plurality of neighboring pixels, it is possible to reduce errors in the laser light intensity ratio and improve measurement accuracy.

In calculating the distance, the laser light intensity is corrected in consideration of the vertical distribution (vertical profile) of the laser light intensity, and the distance is calculated from the corrected laser light intensity. Even when the profiles do not match, measurement accuracy can be maintained.
Furthermore, by arranging the light source such that a line segment connecting the lens center of the imaging system and the light source is horizontal to the x-axis of the imaging surface, vertical profile correction is accurately performed regardless of the distance between the reference distance and the subject. be able to.

Further, by using both the galvanometer mirror and the polygon mirror for laser beam scanning, a range finder which does not require vertical profile correction can be constructed.

Using a one-wavelength laser light source, angle information from the light source is given by the ratio of the difference between the envelope of the light intensity modulation signal and the average light intensity. The distance measurement for each pixel can be performed for each field cycle by triangulation.

Further, by disposing an interference filter that transmits only the wavelength of the laser light source at an angle to the CCD, the occurrence of moire fringes due to the coherence of the laser light can be reduced, and the practical effect is large.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a range finder device according to a first embodiment of the present invention.

FIG. 2 is a characteristic diagram of intensity modulation of a laser light source of the range finder device in the first embodiment.

FIG. 3 is a timing chart of an operation in the first embodiment.

FIG. 4 is a block diagram showing a configuration of a range finder device according to a second embodiment of the present invention.

FIG. 5 is a characteristic diagram showing a relationship between a signal level and a noise level according to the second embodiment.

FIG. 6 is a characteristic diagram of intensity modulation of a laser light source according to the second embodiment.

FIG. 7 is a characteristic diagram of a noise level that increases in proportion to a half power of a signal level in the second embodiment.

FIG. 8 is a block diagram illustrating a configuration of a range fan device according to Embodiment 3 of the present invention.

FIG. 9 is a block diagram showing a configuration of a range finder device according to a fourth embodiment of the present invention.

FIG. 10 is an explanatory diagram of an optical system that generates line light from a laser light source according to a fourth embodiment.

FIG. 11 is a characteristic diagram showing directional characteristics of a laser diode according to a fourth embodiment.

FIG. 12 is an explanatory diagram of a vertical profile of line light according to a fourth embodiment.

FIG. 13 is a configuration diagram of a distance calculation unit according to the fourth embodiment.

FIG. 14 is a characteristic diagram showing a relationship between laser beam intensity and angle information 1 / tanφ in the fourth embodiment.

FIG. 15 is an explanatory diagram showing a distribution of angle information 1 / tanφ with respect to a light intensity ratio in the fourth embodiment.

FIG. 16 is a flowchart of a process according to the fourth embodiment.

FIG. 17 is an explanatory diagram of line light imaging in the fourth embodiment (part 1)

FIG. 18 is an explanatory diagram of imaging of line light in the fourth embodiment (part 2)

FIG. 19 is an explanatory diagram of formulation of projection of a straight line in a three-dimensional space onto an imaging surface according to the fourth embodiment.

FIG. 20 is an explanatory diagram of an intensity modulation signal of a light source on which a high-frequency signal is superimposed according to the fourth embodiment.

FIG. 21 is an explanatory diagram of scanning of a laser beam by a galvano mirror and a polygon mirror in the fourth embodiment.

FIG. 22 is a configuration diagram of a range finder device according to a fifth embodiment of the present invention.

FIG. 23 is an explanatory diagram of an intensity-modulated signal of laser light according to the fifth embodiment.

FIG. 24 is a block diagram illustrating a configuration of a distance calculation unit according to the fifth embodiment.

FIG. 25 is a configuration diagram of a conventional range finder device.

FIG. 26 is a characteristic diagram showing wavelength characteristics of a light source of a conventional range finder device.

FIG. 27 is a characteristic diagram of intensity modulation of a light source of a conventional range finder device.

FIG. 28 is a diagram illustrating a measurement principle in a range finder.

[Explanation of symbols]

 101A, 101B Laser light source 102 Half mirror 103 Light source control unit 104 Rotating mirror 105 Rotation control unit 106 Subject 107 Lens 108A, 108B Optical wavelength separation filter 109A, 109B Monochrome CCD 109C Color CCD 110A, 110B Monochrome camera signal processing unit 111 Color camera signal Processing unit 130 Distance calculation unit 113 Control unit

Claims (12)

[Claims] A scanning unit that scans a subject with laser light from a light source that emits light of a plurality of wavelengths; and a light intensity control unit that changes the light intensity of the laser light in synchronization with a scanning cycle of the scanning unit. A wavelength separating unit that separates light having the same wavelength as the plurality of wavelengths from the reflected laser light from the subject; and calculating an angle of a measurement point in the scanning unit from a light intensity ratio of the separated light to the subject. A range finder device comprising: a distance calculating means for performing a distance calculation. 2. The light intensity control means sets one laser light intensity constant in the first half section of the scanning cycle and linearly changes the other laser light intensity in the first half section of the scanning cycle. 2. The range finder according to claim 1, wherein the light intensity is changed linearly and the other laser light intensity is made constant. 3. The range finder according to claim 2, wherein the distance calculation means determines the angle of the measurement point in the scanning means from both the magnitude relation of the laser light intensity and the ratio of the laser light intensity. . 4. The range finder according to claim 2, wherein the light intensity control means corrects the laser light intensity in accordance with the characteristic of the noise level measured in advance. 5. The method according to claim 1, wherein the distance calculation means uses a laser light intensity ratio average value, a weighted average value, or a median value between the target pixel and the peripheral pixel in a plurality of peripheral pixels in the vicinity of the target pixel. The range finder according to any one of claims 1 to 4, wherein an intensity ratio is calculated. 6. The distance calculation means corrects the light intensity in consideration of the vertical intensity distribution of the laser light of each light source and the sensitivity characteristics of each light receiving unit, and calculates the distance using the corrected light intensity ratio. The range finder according to any one of claims 1 to 4, wherein the range finder is performed. 7. The distance calculation means corrects the light intensity ratio in consideration of the vertical intensity distribution of the laser light of each light source and the sensitivity characteristics of each light receiving unit, and calculates the distance using the corrected light intensity ratio. The range finder according to any one of claims 1 to 4, wherein the range finder is performed. 8. A camera having a camera for receiving a reflected laser beam from the subject, wherein the camera and the light source are positioned so that epipolar lines, which are trajectories of light beams from the light source in the field of view of the camera, become parallel to each other. The range finder device according to claim 6 or 7, wherein the range finder device is disposed. 9. The range finder according to claim 1, wherein said light intensity control means superimposes a high frequency on an intensity modulation signal of the laser light when changing the light intensity of the laser light. . 10. The range finder according to claim 1, wherein the scanning means scans the object with a laser beam by using a galvanometer mirror and a polygon mirror. 11. The range finder according to claim 1, wherein said wavelength separating means separates the wavelength by using an interference filter arranged to be inclined with respect to the imaging surface. 12. A light intensity modulation signal for a one-wavelength laser light source is superimposed with a high-frequency wave whose amplitude changes over time, and the intensity-modulated laser light is scanned over a subject by a rotating mirror, and reflected light from the subject is reflected by a CCD. On the other hand, an upper limit and a lower limit of two envelope detections and a local average detection are performed on the light intensity distribution near the pixel of interest of the CCD based on the ratio of the difference between the two envelopes and the local average value. Calculates angle information to the object viewed from the light source, calculates angle information to the object viewed from the CCD based on the coordinate value of the pixel of interest, and uses the calculated angle information and the base line length to calculate a field period. A distance measurement method that measures the distance for each pixel for each pixel.