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Claims  |
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What is claimed is:
1. A three-dimensional information processing apparatus which measures
distances from a reference position to a plurality of positions on an
object to obtain three-dimensional information regarding the object, said
apparatus comprising:
a first optical system having a principal plane on the object side thereof,
and having an optical axis;
projection means for radiating a plurality of pattern beams onto the object
through said first optical system;
a second optical system having a principal plane on the object side
thereof, the principal planes of said first and second optical systems
being located in a substantially identical plane, said second optical
system having an optical axis substantially parallel to the optical axis
of said first optical system; and
a sensor for receiving a plurality of optical images on a surface thereof,
said optical images formed by the plurality of pattern beams reflected by
said object, through said second optical system, and being separated from
each other, and for respectively detecting positions of the received
optical images on said receiving surface.
2. An apparatus according to claim 1, wherein focal lengths of said first
and second optical systems are equal to each other.
3. An apparatus according to claim 1, wherein said sensor is arranged to be
perpendicular to the optical axis of said second optical system.
4. An apparatus according to claim 1, wherein said sensor is arranged on a
focal plane of said second optical system.
5. An apparatus according to claim 1, wherein said projection means has a
mask member having a plurality of light-transmitting portions arranged on
the focal plane of said first optical system, and a light source arranged
at a side of said light-transmitting portions opposite to said first
optical system.
6. An apparatus according to claim 1, wherein said projection means has a
plurality of point sources arranged on the focal surface of said first
optical system.
7. An apparatus according to claim 1, further comprising parallel beam
projection means for projecting a parallel beam to the object through said
first optical system.
8. An apparatus according to claim 1, wherein focal lengths of said first
and second optical systems are different from each other.
9. An apparatus according to claim 1, wherein said projection means has a
light source, a mask member having a plurality of light-transmitting
portions for forming the plurality of pattern beams upon reception of
light emitted from said light source, deflection means for deflecting at
least part of the light emitted from said light source toward said mask
member, and light-shielding means for shielding part of the light emitted
from said light source so as to cause light beams propagating in
directions uniquely corresponding to said light-transmitting portions
respectively to be incident on said corresponding light-transmitting
portions.
10. An apparatus according to claim 1, wherein said projection means is
arranged so that each of the plurality of pattern beams is formed as a
thin light beam as compared to a pupil diameter of said first optical
system and passes through said first optical system.
11. An apparatus according to claim 1, wherein said projection means is
arranged so that the plurality of pattern beams pass through the vicinity
of the optical axis of said first optical system.
12. An apparatus according to claim 5, wherein said plurality of
light-transmitting portions of said mask member are arranged at a
relatively low density along a direction corresponding to a moving
direction of optical images on said sensor in accordance with the distance
to the object, and are arranged at a relatively high density along a
direction perpendicular to the moving direction.
13. An apparatus according to claim 7, wherein said parallel beam
projection means has a laser light source, and optical means for focusing
laser light from said laser light source onto the focal plane of said
first optical system.
14. An apparatus according to claim 8, wherein the focal length of said
first optical system is larger than that of said second optical system.
15. An apparatus according to claim 8, wherein the focal length of said
first optical system is smaller than that of said second optical system.
16. An apparatus according to claim 9, wherein said light-shielding means
is arranged at substantially the center of said mask member, and wherein
said deflection means comprises a reflection mirror arranged on one side
of said light-shielding means, and wherein said light source is arranged
on the other side of said light-shielding means.
17. An apparatus according to claim 9, wherein said light source is
arranged on an extended line of the optical axis of said first optical
system, and wherein said light-shielding means is arranged between said
mask member and said light source, and wherein said deflection means
comprises two reflection mirrors arranged on both sides of said
light-shielding means.
18. An apparatus according to claim 10, wherein said projection means has a
mask member having a plurality of light-transmitting portions, and a light
source having a plurality of light-emitting portions having a one-to-one
correspondence with said light-transmitting portions for illuminating said
mask member.
19. An apparatus according to claim 18, wherein said projection means
further comprises a lens array arranged between said mask member and said
light source, and having small convex lens portions in correspondence with
said light-emitting portions.
20. An apparatus according to claim 11, wherein said projection means
comprises a mask member having a plurality of light-transmitting portions,
a light source, and an elliptic reflection mirror for directing light from
said light source toward said mask member, said light source being
arranged outside an optical path of light beams directed toward said mask
member.
21. An apparatus according to claim 20, wherein said light source and said
first optical system are respectively arranged at two focal points of said
elliptic reflection mirror.
22. A three-dimensional information processing method in which distances
from a reference position to a plurality of positions on an object are
measured to obtain three-dimensional information regarding the object,
said method comprising the steps of:
radiating a plurality of pattern beams onto the object through a first
optical system;
receiving a plurality of optical images on a predetermined receiving
surface, said optical images being formed by the plurality of pattern
beams reflected by the object, through a second optical system, and being
separated from each other, to respectively detect positions of the
received optical images on said receiving surface, said second optical
system having an optical axis substantially parallel with an optical axis
of the first optical system, the principal planes of said first and second
optical systems on the object side being substantially identical; and
measuring distances from the reference position to the plurality of
positions on the object based on the positions of the optical images
detected by the receiving step to obtain three-dimensional information
regarding the object.
23. A distance measuring method comprising the steps of:
disposing first and second optical systems at a distance from an object,
said first and second optical systems having substantially parallel
optical axes and substantially co-planar principal planes on the side of
the object;
radiating a plurality of pattern beams onto an object through the first
optical system;
receiving a plurality of optical images on a predetermined receiving
surface, said optical images being formed by the plurality of pattern
beams reflected by said object and passed through said second optical
system, and being separated from each other, to respectively detect
positions of the received optical images on said receiving surface; and
measuring the distance regarding said plurality of positions on said object
based upon the positions of the optical images detected in the receiving
step.
24. A distance measuring device comprising:
a light source;
means for forming a plurality of light emitting points arranged
two-dimensionally with respect to the light from the light source;
a projection lens for forming images of the plurality of light emitting
points formed by said forming means onto an object;
a two-dimensional sensor array providing an output signal;
an imaging lens for imaging again a plurality of emitting point images
formed on the object onto the light-receiving surface of the
two-dimensional sensor array, the optical axis of the imaging lens being
substantially parallel with the optical axis of the projection lens and
the principle planes of the imaging lens and the projection lens on the
side of the object being set in a substantially identical plane, distance
information regarding the plurality of positions on said object being
related to the output signal from two-dimensional sensor array. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
The present invention relates to a three-dimensional information processing
method and apparatus and, more particularly, to a three-dimensional
information processing method and apparatus for measuring the shape of an
object with an active method.
As a conventional method for obtaining information associated with a
three-dimensional shape using an image sensor or the like, a light-cutting
method (slit method), a stereo method, and the like are known.
In the light-cutting method, slit light is projected onto the surface of an
object, and the projected beam is observed from a direction different from
the projection direction, thereby obtaining information such as a
sectional shape of an object, a distance to the object, and the like. With
this method, a plurality of images are imaged slit by slit by a stationary
imaging means while the slit projection direction is changed slightly for
each projection, thereby obtaining three-dimensional information.
In the stereo method described in U.S. patent application Ser. No. 706,727
filed be the same assignee of the present invention, a pair of
two-dimensional imaging elements combined with an optical system and
having an equal image magnification are arranged to be separated by a
predetermined base length, and two-dimensional images of an object viewed
in different directions are obtained thereby. Then, a distance from each
position of the object to the imaging system is calculated from a
deviation between the two pieces of image information.
In the light-cutting method, however, control of the slit projection
direction during imaging is cumbersome, and imaging is time-consuming.
Since the three-dimensional information is obtained from a plurality of
slit images, a large volume of information is to be processed, and a great
deal of time is required for obtaining final information.
In the stereo method, slit scanning control is not required However, the
conventional methods normally adopt a passive method. Therefore, when an
object has a smooth surface and exhibits a uniform luminance, a contrast
between images obtained by two imaging elements is decreased, and distance
measurement by comparing two images is rendered impossible. Such a case
frequently occurs in a near distance with a large image magnification.
Therefore, the shape, color, size, and distance of an object which can be
measured are limited.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a
three-dimensional information processing method and apparatus which can
perform accurate measurement regardless .of types of objects, and can
obtain three-dimensional information of an object, such as a distance to
an arbitrary position of an object, in a relatively short period of time.
It is another object of the present invention to provide a
three-dimensional information processing method and apparatus having a
wide measurement range.
In order to solve the above problems, an apparatus according to an aspect
of the present invention comprises: a plurality of optical systems; means
for radiating a plurality of pattern beams (beams having a given
cross-section) onto an object through one group of the optical system; and
an image sensor for receiving images formed by the pattern beams through
another group of the optical system. Distances to the images of the
pattern beams on the object are measured in accordance with the positions
of optical images on the sensor detected by the image sensor, thereby
obtaining three-dimensional information of the object.
In order to solve the above problems, an apparatus according to another
aspect of the present invention comprises: a plurality of optical systems
whose optical axes are parallel to each other, which are arranged at
predetermined base distances from each other, and whose principal planes
on the side of an object are matched on a substantially identical plane;
means for radiating a plurality of pattern beams onto an object through
one group of the optical systems; and an image sensor for receiving images
of the pattern beams on the object through another group of the pattern
beams Distances to images of the pattern beams are measured in accordance
with the positions of the optical images of the pattern beams on the
object detected by the image sensor, thereby obtaining three-dimensional
information of the object.
Note that the principal plane is a plane which passes through a pair of
conjugate points (principal points) providing a lateral magnification of
an optical system of 1, and is perpendicular to an optical axis.
In order to achieve the above object, an apparatus according to still
another aspect of the present invention comprises: a plurality of optical
systems; projection means for radiating a plurality of pattern beams onto
an object through one group of the optical systems; and an image sensor
for receiving images of the pattern beams on the object through another
group of the optical system. Distances to predetermined positions of the
object are measured in accordance with the positions of the optical images
of the pattern beams on the object detected by the image sensor. The
projection means has a light source; a mask having a plurality of
light-transmitting portions for forming pattern beams upon reception of
light emitted from the light source; a reflection mirror for reflecting at
least part of light emitted from the light source to be directed toward
the mask; and a light shielding member for partially shielding light
emitted from the light source so as to cause a light beam from a direction
uniquely determined for each light-transmitting portion to become incident
on the corresponding light-transmitting portion.
In order to achieve the above object, an apparatus according to still
another aspect of the present invention comprises: a plurality of optical
systems; projection means for radiating a plurality of pattern images onto
an object through one group of the optical systems; and an image sensor
for receiving images of the pattern beams on the object through another
group of the optical system. Distances to predetermined positions on the
object are measured in accordance with positions of optical images of the
pattern beams on the object detected by the image sensor. The projection
means is arranged such that when the pattern beams emitted from the
projection means pass through the one group of the optical systems, they
become sufficiently small beams as compared to a pupil diameter of the
optical systems.
In order to achieve the above object, an apparatus according to still
another aspect of the present invention comprises: a plurality of optical
systems; projection means for radiating a plurality of pattern images onto
an object through one group of the optical systems; and an image sensor
for receiving images of the pattern beams on the object through another
group of the optical system. Distances to predetermined positions on the
object are measured in accordance with positions of optical images of the
pattern beams on the object detected by the image sensor. The projection
means has a light source, a mask for forming pattern beams upon reception
of light emitted from the light source, and an elliptic reflection mirror
for causing the light emitted from the light source to be directed toward
the mask. The light source is arranged outside an optical path of the
light beams directed toward the mask.
BRIEF EXPLANATION OF THE DRAWINGS
FIG. 1 is a schematic view for explaining a three-dimensional information
processing apparatus and method according to a first embodiment of the
present invention;
FIG. 2 is an illustration for explaining the arrangement of a mask plate;
FIG. 3 is a waveform chart for explaining the operation of the arrangement
shown in FIG. 1;
FIG. 4 is a schematic view for explaining a modification of the arrangement
of FIG. 1;
FIG. 5 is a waveform chart showing the operation of the arrangement shown
in FIG. 4;
FIGS. 6 and 7 are schematic views for explaining different arrangements of
an apparatus and method according to a second embodiment of the present
invention;
FIG. 8 is a schematic view for explaining an apparatus and method according
to a third embodiment of the present invention;
FIG. 9 is a schematic view for explaining a modification of the arrangement
shown in FIG. 8;
FIG. 10 is a schematic view for explaining an apparatus and method
according to a fourth embodiment of the present invention;
FIG. 11 is a schematic view for explaining an apparatus and method
according to a fifth embodiment of the present invention; and
FIG. 12 is a schematic view for explaining an apparatus and method
according to a sixth embodiment of the present invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
The present invention will now be described with reference to embodiments
in conjunction with the accompanying drawings.
FIG. 1 shows a first embodiment of a measurement apparatus which adopts a
three-dimensional information processing methods of the present invention.
In FIG. 1, lenses 1 and 2 of the same focal length are arranged with a
predetermined base distance therebetween so that their optical axes are
parallel to each other. A mask plate 3 and an image sensor 4 consisting of
a two-dimensional charge-coupled device are respectively arranged behind
the lenses 1 and 2. The mask plate 3 and the image sensor 4 are arranged
on the identical plane perpendicular to the optical axes of the lenses 1
and 2.
An illumination light source (e.g., a halogen lamp) 5 is arranged behind
the mask plate 3. The lens 1 projects slit patterns of the mask plate 3
onto an object 6 upon illumination of the light source 5.
In FIG. 1, the depths of field of the lenses 1 and 2 can sufficiently cover
positions 6 and 6' on the object.
In this embodiment, two optical systems, i.e., an irradiation system
consisting of the lens 1 and an image receiving system consisting of the
lens 2 are illustrated as single lens systems having the same focal
length.
The two optical systems are arranged to be separated by a predetermined
base length, and each has a single lens configuration. Their principal
planes on the side of the object coincide with a substantially identical
plane. In other words, object distances of the two optical systems are
equal to each other.
However, when two optical systems having the same focal length are used,
conditions in that the principal planes are located on the side of the
object on the identical plane and that their optical axes are arranged to
be parallel to each other can be most easily attained, and
three-dimensional information processing can be facilitated. However,
these conditions need not always be satisfied.
FIG. 2 shows an opening pattern of the mask plate 3. In this embodiment, a
plurality of rectangular slit-like windows Wn are formed on the mask plate
3. In FIG. 2, the centers of the windows Wn in the lateral direction are
aligned at low density in the horizontal direction and at relatively high
density in the vertical direction, as indicated by a dotted line 3'. As a
result, slit arrays extending obliquely are formed. The density and
alignment of the windows Wn can be determined in accordance with a
required measurement precision and longitudinal and lateral resolutions of
the image sensor 4 used, and hence are not limited to the above arrangement
and various patterns can be used. The horizontal density of the windows Wn
of the mask plate 3 is set to be relatively low as shown in FIG. 2, since
the positions of optical images on the image sensor 4 move in the
horizontal direction in accordance with the distance to the object 6, as
will be described later. With the above arrangement, a possible distance
range for detection can be widened.
In the arrangement shown in FIGS. 1 and 2, light beams passing through
windows W1 and W2 of the window Wn illuminated with the light source 5
form optical images at positions F1 and F2 on the object 6 through the
lens 1. The optical images F1 and F2 form optical images at positions Dl
and D2 on the image sensor 4 through the lens 2.
As can be understood from the principle of the stereo method, the positions
of optical images Dn move along a line (a base direction) parallel to the
arrangement direction of the lenses 1 and 2 in accordance with the
distances to reflection points, i.e., the distances to optical images Fn
on the object 6. Therefore, a distance distribution on the surface of the
object 6 from the measurement apparatus can be detected as a density
distribution of the optical images Dn in the horizontal direction. More
specifically, when the output waveform of the image sensor is observed by
an image processing apparatus using a computer system, the distances to
the optical image positions on the surface of the object 6 can be easily
obtained on the basis of the principle of triangulation.
FIG. 3 shows an output waveform O of a single scanning line (corresponding
to the line 3' in FIG. 2) when a two-dimensional CCD sensor for a TV
camera is used as the image sensor 4. In FIG. 3, the right-and-left
direction of the figure corresponds to the dimension of the image sensor 4
in the horizontal direction. As can be seen from the above description, an
output value exhibits maximum values M in correspondence with the windows
Wn on the mask plate 3 located along the same line as the scanning line in
FIG. 3. The range of the maximum value of the output waveform corresponding
to a single window Wn is limited in the right-and-left direction, and is
separated from output value appearing ranges of other windows Therefore,
it is easy to obtain correspondence between a specific window Wn and the
incident position on the image sensor 4 of a light beam passing through
this window. Therefore, measurement will not be rendered impossible due to
a decrease in contrast in a near distance range unlike in the conventional
stereo method. Since an active method for illuminating using a light
source is adopted, the amount of light of the light source can be
advantageously reduced for measurement of an object in a near distance
range. Furthermore, an inclination of the optical image positions of an
object can be determined in accordance with maximum values of the image
sensor output.
As described above, the distance from the measurement system to the surface
of the object 6 can be measured through the two-dimensional image sensor 4.
With the above arrangement, a mechanical scanning operation need not be
performed unlike in the light-cutting method, and three-dimensional
information on the entire surface of the object 6 can be extracted by a
single image scanning operation.
Since post image processing can be performed in association with only an
optical image distribution in the right-and-left direction, it can be
easily performed at high speed. Furthermore, the optical images on the
image sensor 4 are binarized and are output to a CRT display or a
hard-copy device, thus allowing visual three-dimensional representation.
The three-dimensional information processing method of the present
invention is an optical method which replaces a method wherein a plurality
of probes are urged against an object to perceive the shape of the object
in accordance with a change in projection amounts of the probes from a
reference plane, and can achieve high-speed, accurate processing. The
method of the present invention can be applied to a visual sensor of a
robot requiring real-time processing. In particular, the method of the
present invention is effective when the shape or posture of an object
located in a relatively near distance range is perceived to grasp the
object or to escape from it. In particular, when the lenses 1 and 2 are
arranged so that their principal planes are located on substantially the
identical plane, and their object distances are equal to each other, as
described above, the following advantages are obtained.
In view of geometrical optics, the geometrical relationship between the
mask plate 3, the lens 1, and the object 6 is quite symmetrical with the
geometrical relationship between the image sensor 4, the lens 2, and the
object 6.
In this case, if the mask plate 3 is replaced with an image sensor, two
two-dimensional images of an object received by the two image sensors have
the same image magnification and the shapes of the two images have a
difference in accordance with the imaging positions (the positions of the
lenses 1 and 2). The difference between the shapes of the two-dimensional
images is associated with a deviation of images in the right-and-left
direction caused by a difference between angles formed by directions of
the object and the optical axes of the lenses 1 and 2. Since angles formed
by the directions of the object and the optical axes of the lenses 1 and 2
are equal to each other in terms of the vertical direction of the lenses 1
and 2, no image deviation occurs.
The same relationships will be provided in a direction opposite to the
light propagation direction. Therefore, the position of the optical image
Dn in the right-and-left direction only moves in the base direction in
accordance with the distance of the optical image Fn on the object 6.
In the above description, the main part of the apparatus is illustrated in
the drawings for the sake of simplicity, and a focusing optical system,
e.g., a reflection mirror, a condenser lens, and the like behind the light
source, and a shielding housing are omitted. These members can be
appropriately arranged by those skilled in the art as needed. In the
optical systems, only single lenses are illustrated. However, optical
systems comprising of a plurality of elements, or optical systems
including a mirror can be used.
FIG. 4 shows a modification of the first embodiment shown in FIGS. 1 and 2.
In the aforementioned measurement range within the depths of field of the
lenses 1 and 2 in order to achieve accurate measurement. However, the
arrangement shown in FIG. 4 can attain control for locating an object
within the measurement range prior to detection of three-dimensional
information.
Referring to FIG. 4, a semiconductor laser element 7 is arranged as a
second light source behind the mask plate 3. A laser beam emitted from the
semiconductor element 7 is focused on a focal surface of the lens 1 by the
lens 8, is reflected by a reflection mirror 9, and is then projected onto
an object 6 through one of windows Wn of the mask plate 3. Other
arrangements are the same as those described above.
When the object 6 is located outside the measurement range, since it falls
outside the focusing positions of the optical systems, images of
projection light beams emitted from the light source 5 are largely
blurred. However, since the laser beams are projected as parallel light
beams by the optical system 8 and the lens 1, they are not so blurred.
Since a projection energy density is high, an output waveform O of the
image sensor 4 exhibits a high maximum value ML corresponding to an object
point image on the object 6, as shown in FIG. 5, and the maximum value ML
can be distinguished from other outputs of optical images. Therefore, the
distance to a point on the object irradiated with the laser beam is
calculated by the principle of triangulation, and can be used as
information for locating the object within the measurement range. In the
same manner as described above, the distance to the object 6 can be
measured as a position of an optical image on the image sensor 4 in the
horizontal direction. Therefore, when the measurement system or the object
6 is moved in accordance with the measured distance, the object 6 can be
located within the measurement range.
In the first embodiment described previously, two optical systems having
the same focal length are used. Alternatively, optical systems having
different focal lengths can be used as needed. In this case, in order to
facilitate image processing, the objective principal planes of the optical
systems, i.e., the irradiation and image-receiving systems, are preferably
located on a substantially identical plane so as to reliably prevent
optical image movement in directions other than the base direction.
FIG. 6 shows a second embodiment wherein a lens 17 of an irradiation system
and a lens 18 of an image-receiving system have different focal lengths.
The same reference numerals in FIG. 6 denote the same parts as described
above, and a detailed description thereof will be omitted. In the case of
FIG. 6, the lens 17 has a longer focal length than that of the lens 18.
Principal planes 17' and 18' of the lenses 17 and 18 on the side of an
object are located on a substantially identical plane. Principal planes
17" and 18" on the opposite side have no limitations, and do not coincide
with each other in this case.
Distances between a mask 3 and the image sensor 4 and the lenses 17 and 18
are determined so that the mask 3 and the image sensor 4 are located on
the focal surfaces of these lenses. In this case, the distances from the
lenses 17 and 18 to the mask 3 and the image sensor 4 correspond to the
focal lengths of the respective lenses.
With the above arrangement, the projection magnification of the mask
pattern of the lens 17 and the imaging magnification of the lens 18 are
only different from the arrangement shown in FIG. 1, and the projection
state of the light beams and imaging state of the optical images are the
same as those in FIG. 1. In this embodiment, the principal planes of the
lenses 17 and 18 on the side of the object are preferably arranged on the
identical plane so that their object distances are equal to each other. An
optical image Dn of a window Wn of the mask plate 3 on the image sensor 4
linearly deviates along a scanning line in the right-and-left direction of
the sensor in accordance with the distance of the object, and will not be
moved in the up-and-down direction in accordance with the distance of the
object. Therefore, the range of positions of the optical image Dn is
limited, and this facilitates the post-image processing in the same manner
as in the above embodiment.
The arrangement shown in FIG. 6 is effective when a relatively large mask 3
and a relatively small image sensor 4, such as a CCD sensor, must be used.
When the mask 3 is used in an equal magnification system as in the first
embodiment, it must have the same size as that of the sensor 4 and the
windows Wn must be formed at a density corresponding to the resolution of
the sensor. However, formation of such a small mask poses a technical
problem. It is difficult for a small mask area to project pattern beams
having a sufficient amount of light with respect to the object. This
limits the measurement range of the object, or a light source having an
excessively large amount of light is required.
Therefore, a relatively large mask 3 and a relatively small image sensor 4
are preferably used. In this case, magnification conversion can be
realized by the arrangement shown in FIG. 6.
In the arrangement in FIG. 6, the same image processing can be performed as
in the above embodiment. Although an optical image obtained by the image
sensor 4 is reduced, its perspective in the up-and-down direction will not
be shifted in a direction different from the scanning line, and the same
easy three-dimensional information processing is allowed.
In contracts to FIG. 6, the focal length of an irradiation lens 19 can be
shortened and the focal length of an image-receiving lens 20 can be
increased, as shown in FIG. 7. The conditions for principal planes 19' and
20' of the lenses on the side of the object, and the like are the same as
those in FIG. 6. In this case, a light source array 10 in which point
sources such as a surface emission type semiconductor laser array or an
LED array are aligned like windows Wn in FIG. 2, is used. Referring to
FIG. 7, W1 and W2 are not windows as in the above description but are
light sources in the light source array 10. An LED or semiconductor laser
array which is normally formed in a large number on a substrate and is
separated for use can be used as the light source array 10.
Since light emitted from the light source array normally has a high
emission intensity in a given direction, a condenser lens 11 add the like
is preferably arranged adjacent to the light source array in accordance
with conditions, such as an effective diameter of the lens 19, and the
like, so that light from the light source is effectively directed toward
the lens 19.
With the above arrangement, three-dimensional information can be obtained
through the same processing although the magnifications are different from
those in FIG. 6. In this case, limitations associated with an irradiation
system comprising of the light source array 10 and an image-receiving
system comprising of the image sensor 4 can be moderated, so that a system
design with further advantageous manufacturing conditions is achieved.
FIG. 8 schematically shows an optical system according to a third
embodiment of the present invention. The same reference numerals in FIG. 8
denote the same parts as described above, and a detailed description
thereof will be omitted.
A light source 23 preferably has a relatively small emission section 23'. A
reflection mirror 27 reflects part of light emitted from the light source
23. A light-shielding member 28 is arranged at substantially the center of
a mask 3 so as to shield part of light emitted from the light source 23, so
that a direct light component from the light source 23 and a light
component directed toward the mask 3 through the reflection mirror 27 do
not become incident on identical light-transmitting portions W1, W2 and
W3.
In the arrangement shown in FIG. 8, light beams emitted from the light
source 23 and passing through light-transmitting portions W1 and W5
propagate through a lens 1, and respectively form optical images at
positions F1 and F2 on an object 6 in accordance with the position of the
object 6. The optical images F1 and F2 respectively form optical images at
positions D1 and D2 on an image sensor 4 through a lens 2.
In this embodiment, in order to widen a possible distance-measurement
range, depths of field of the lenses 1 and 2 are widened and specific
pattern beams are radiated to the object 6. More specifically, in FIG. 8,
the light-transmitting portions W1, W2, W3, W4 and W5 of the mask 3 can be
regarded as point sources. Therefore, when opening patterns of the mask 3
are illuminated by a normal illumination technique, light components
emerging from the respective light-transmitting portions W1, W2, . . . W5
are diffused and pass through the entire pupil of the lens 1 to be
directed toward the object 6 through the lens 1. When the pattern beams
are radiated onto the object 6 with this method, even if the lens 1 having
a large depth of field is used, the resultant distance-measurement range is
limited, and blurred optical images of the opening patterns are formed on
the image sensor 4, thereby making position detection of the optical
images impossible.
However, in this embodiment, the light source 23 is arranged to be
separated from the mask 3, and the light-shielding member 28 is arranged
at substantially the center of the mask 3, so that the light-transmitting
portions W4 and W5 on the right side of the light-shielding member 28 are
illuminated with direct light from the light source 23 and the
light-transmitting portions W1, W2 and W3 on the left side of the
light-shielding member 28 are illuminated with light via the reflection
mirror 27. More specifically, the light-transmitting portions W1, W2 and
W3 on the left side of the member 28 do not receive the direct light from
the light source 23, and the light-transmitting portions W4 and W5 on the
right side of the member 28 do not receive the light from the reflection
mirror 27. Therefore, the light beams incident from given directions pass
through the respective portions W1, W2, W3, W4 and W5 of the mask 3. Then,
these beams become incident on the lens 1 as thin light beams, and a
plurality of pattern beams are directed toward the object 6. In this
embodiment, since a relatively small light emitting section 23' is used in
the light source 23, a direct light component or a light component
reflected by the reflection mirror 27 is diffused at a small diffusion
angle. Therefore, the pattern beams radiated on the object 6 become thin
light beams through the mask 3. Even if the distance to the object 6 is
largely changed, the optical images of the light-transmitting portions W1,
W2, . . . projected on the image sensor 4 are not so blurred. In this way,
when a projection means is only slightly modified, a possible
distance-measurement range can be greatly widened.
FIG. 9 shows a modification of the projection means of the apparatus shown
in FIG. 8. A light-emitting section 33' of a light source 33 is arranged
along the extended line of the optical axis of a lens 1, and two
reflection mirrors 37 and 37' are used to direct light beams from the
light source 33 toward a mask 3, thereby obtaining pattern beams. In the
projection means of this modification, a light-shielding member 38 is also
arranged between the mask 3 and the light source 33, so that a plurality of
light-transmitting portions Wn of the mask 3 only receive light beams
reflected by the reflection mirrors 37 and 37' to be directed toward given
directions. The pattern beams converted to thin light beams through the
mask 3 are incident on the pupil of the lens 1. Therefore, when the
projection means of this modification is used as that in the
distance-measurement apparatus shown in FIG. 8, the same effect as in the
above embodiment can be obtained.
As a reflection mirror, a special shape mirror, e.g., an elliptic mirror or
a corner cube, can be used in addition to a flat mirror shown in the above
embodiment. In this case, a light-shielding means is arranged at a
predetermined position so that a direct light component from the light
source and a light component through the reflection mirror do not become
incident on identical light-transmitting portions.
FIG. 10 shows a fourth embodiment of the present invention. The same
reference numerals in FIG. 10 denote the same parts as in the above
embodiments, and a detailed description thereof will be omitted.
A light source device 43 consists of a plurality of small light-emitting
sources 43.sub.1, 43.sub.2, . . . 43.sub.n, e.g., light emitting diodes,
laser diodes. or the like, which are arranged on a substrate.
In this embodiment, in order to widen a possible distant range, the depths
of field of lenses 1 and 2 are widened and specific pattern beams are
radiated on an object 6. More specifically, in FIG. 10, light-transmitting
portions W1, W2, . . . Wn of a mask 3 can be regarded as point sources, and
pose a similar problem to that described in the third embodiment in a
normal illumination technique.
However, in this embodiment, the light source device 43 is arranged at a
position separated from the mask 3, and light components emitted from the
small light-emitting sources 43.sub.1, 43.sub.2, . . . , 43.sub.n pass
through the corresponding light-transmitting portions W1, W2, . . . , Wn
and become incident on the pupil of the lens 1. With this arrangement, a
plurality of pattern beams obtained through the mask 3 have a small beam
spot size as compared with the pupil aperture of the lens 1, and hence,
very thin light beams are directed toward the object 6. Therefore, even if
the object 6 is located at a position considerably separated from a
just-focus position, blurring of optical images on an image sensor 4 can
be suppressed. In this embodiment, lines connecting the small
light-emitting sources 43.sub.1, 43.sub.2, . . . , 43.sub.n and the
corresponding light-transmitting portions W1, W2, . . . , Wn pass through
the vicinity of the center of the lens 1, and light components other than
those from the corresponding small light-emitting sources and incident on
the light-transmitting portions W1, W2, . . . , Wn are not incident on the
pupil of the lens 1. Note that the thickness of the mask 3 can be increased
or a light-shielding frame can be provided between the adjacent
light-transmitting portions W1, W2, . . . , Wn, if necessary, so that the
small light-emitting sources 43.sub.n and the light-transmitting portions
Wn can reliably provide a one-to-one correspondence.
In this embodiment, even if the object 6 is present in a near distance
range, if it is located within a measurement range, the respective
components are arranged so that light-source images are not formed on the
object 6 in a just-focus state. Within the measurement range, distance
measurement can be performed with high precision.
In the above description, pattern beams on the object 6 are formed by the
light sources and the mask 3. However, when a plurality of point sources
having a directivity are arranged at a planar position of the mask 3, the
same effect can be obtained.
FIG. 11 shows a distance-measurement apparatus according to a fifth
embodiment of the present invention. The same reference numerals in FIG.
11 denote the same parts as in the above embodiments. The apparatus of
this embodiment includes a lens array 27 comprising small convex lenses,
and a field lens 58.
The distance-measurement apparatus of this embodiment has the same basic
arrangement as that of the apparatus shown in FIG. 10, | | |
