Range finder and camera

Details Range finder and camera Range finder and camera

2000-03-30

2003-07-01

Tarcza, Thomas H. (Department: 3662)

Optics: measuring and testing

Range or remote distance finding

Triangulation ranging to a point with two or more projected...

C356S141100

Reexamination Certificate

active

06587183

ABSTRACT:

This application is a U.S. National Phase Application of PCT International Application PCT/JP99/02715 filed May 24, 1999.
TECHNICAL FIELD
The present invention relates to a range finder device for measuring a three-dimensional shape of an object.
A range finder device for performing three-dimensional shape measurement based on triangulation of projected light and an observed image, such as real-time operable range finder device shown in, for example,
FIG. 40
has been proposed.
In
FIG. 40
, reference numerals
101
A and
101
B denote laser light sources having slightly different wavelengths;
102
, a half mirror for synthesizing laser light from the laser light sources having the different wavelengths;
103
, a light source control part for controlling light intensity of the laser light source;
104
, a rotary mirror for scanning laser light;
105
, a rotation control part for controlling the rotary mirror;
106
, an object;
107
, a lens for forming an image on a CCD;
108
A and
108
B, light wavelength separation filters for separating light having wavelength from the laser light source;
109
A and
109
B, CCDs for picking up a monochromatic image;
109
C, a CCD for picking up a color image;
110
A and
110
B, signal processing parts for a monochromatic camera;
111
, a signal processing part for a color camera;
112
, a distance calculation part for calculating a distance or a shape of an object from intensity of laser light photographed by CCDs
109
A and
109
B; and
113
, a control part for adjusting synchronization of the entire device. Hereinafter, the description will be made of the operation of a range finder device thus configured.
The laser light sources
101
A and
101
B emit laser light having slightly different wavelengths. This laser light is a line light having a light cross-section perpendicular to the scanning direction of a rotary mirror (to be described later), and becomes a line light in the perpendicular direction when a rotary mirror scans in the horizontal direction.
FIG. 41
shows wavelength characteristics for these two light sources. The reason why two light sources having close wavelengths to each other are used resides in the fact that it is less influenced by dependency of the reflection factor of the object on a wavelength. The laser light emitted from the laser light sources
101
A and
101
B is synthesized by the half mirror
102
, and is scanned on the object
6
by the rotary mirror
104
.
Scanning of the laser light is performed when the rotation control part
105
drives the rotary mirror
104
at one field period. At that time, light intensities of both light sources is varied as shown in FIG.
42
(
a
) within one field period. The variations in the laser light intensity are synchronized by driving of the mirror angle, whereby the intensities of those two laser lights are monitored by CCD
109
A and
109
B to calculate the light intensity ratio, making it possible to measure time at one scanning period. If the light intensity is Ia/Ib, as shown in, for example, FIG.
42
(
b
), the scanning time is measured to be t
0
, and a rotation angle (&phgr;) of the rotary mirror
104
can be determined from the measured value.
The ratio of the intensities of those two laser lights and the mirror angle (that is, angle of the object as viewed from the light source side) are caused to have a one-to-one correspondence therebetween, whereby the distance or shape of the object can be calculated from a ratio of signal levels on which light from both light sources has been photographed in a distance calculation part (to be described later), in accordance with the principle of triangulation.
The lens
107
forms an image of the object on CCDs
109
A,
109
B and
109
C. The light wavelength separation filter
108
A transmits light in wavelength of the light source
101
A, and reflects light in another wavelength. The light wavelength separation filter
108
B transmits light in wavelength of the light source
101
B, and reflects light in another wavelength. As a result, reflected light from the light sources
101
A and
101
B from the object is photographed by the CCDs
109
A and
109
B, and light of another wavelength is photographed by the CCD
109
C as a color image.
The light source A signal processing part
101
A and light source B signal processing part
110
B perform similar signal processing to the output from the CCDs
109
A and
109
B. The color camera signal processing part
111
performs an ordinary color camera signal processing to the output from the CCD
109
C.
The distance calculation part
112
calculates a distance for each pixel using the signal level ratio, base length and coordinate values of pixels which have been photographed by the CCDs
109
A and
109
B for wavelength of each light source.
FIGS.
43
(
a
) and (
b
) are explanatory views useful for graphically illustrating the distance calculation. In the figures, the reference character O denotes a center of the lens
107
; P, a point on the object; and Q, a position of an axis of rotation of the rotary mirror. Also, for brevity, the position of the CCD
109
is shown turned around on the object side. Also, assuming the length of OQ (base length) to be L, an angle of P as viewed from Q in the XZ plane to be &phgr;, an angle of P as viewed from O to be &thgr;, and an angle of P as viewed from O in the YZ plane to be &ohgr;, the three-dimensional coordinate of P can be calculated by the following formula (1) from the graphical relation.
Z=D
tan &thgr; tan &phgr;/(tan &thgr;+tan &phgr;)  (1)
 
X=Z
/tan &thgr;
Y=Z
/tan &ohgr;
The &phgr; in the formula (1) is calculated by the light intensity ratio of laser light sources
101
A and
101
B monitored by the CCDs
109
A and
109
B, as described above, and &thgr; and &ohgr; are calculated from coordinate values of pixels. Of the values shown in the formula (1), if all of them are calculated, the shape will be determined; and if only Z is determined, the distance image will be determined.
On the other hand, for photography of a place where light from the light source cannot be directly irradiated onto an object, there has been known a camera which uses an optical fiber. For example, in endoscopes to be used for examining the interior of a human body, there is a gastrocamera and the like. In the case of the gastrocamera, the inner walls of the stomach are normally irradiated by light irradiation from the optical fiber, and reflected light from the inner wall portion is received by another optical fiber which is guided by an external camera part, and this is two-dimensionally processed to display a normal image on a monitor.
As a conventional object extraction method, the technique called “Chroma key” used in broadcasting stations is generally used.
This method arranges an object in front of a studio set configured by the background of a single color (blue) for photographing, and judges that the blue portion is the background and any portions other than it as an attention object.
In such a conventional configuration as described above, however, a modulated light source and light source sweeping means are indispensable, and since mechanical operations are included, the reliability of the device is low and the device is expensive.
Also, although the laser element is normally modulated for use, the output and wavelength of the laser element vary depending upon the temperature, and, therefore, it is difficult to obtain stable measurements.
Also, as in case of the conventional endoscope or the like, for photography in a place. where light from the light source cannot be directly irradiated onto an object, it is difficult to determine whether or not there is any projecting region, because the image is of two-dimensional data in a camera using the optical fiber.
DISCLOSURE OF THE INVENTION
The present invention has been achieved in light of such problems, and aims to provide a stable range finder device free from any mechanical operations, at a low cost.
It is another object of the present invention to provide

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