Optical three-dimensional shape measuring apparatus

An optical three-dimensional shape measuring apparatus comprising an irradiating optical system for projecting a predetermined patterned image on the surface of a specimen, an observation optical system for observing the patterned image projected on the surface of the specimen and a measuring device for measuring the surface shape of the specimen based on the variation of the observed patterned image, wherein the irradiating optical system includes a focal plane dividing device for forming, along the optical axis thereof, predetermined patterned images respectively on plural focal planes.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an optical three-dimensional shape 
measuring apparatus and, more particularly, to such apparatus of pattern 
irradiation type. 
2. Related Background Art 
In the conventional optical three-dimensional shape measuring apparatus of 
the pattern irradiation type, a predetermined pattern is projected, 
through an irradiating optical system onto the surface of a specimen to be 
measured, then the projected pattern is observed by an observing optical 
system, and the surface shape of the specimen is measured, based on the 
variation of the observed projected pattern. Stated differently, the 
conventional optical three-dimensional shape measuring apparatus of the 
pattern irradiation type utilizes non-contact surface measurement based on 
a pattern projection method. 
This method can measure the surface shape of any object, except for an 
object of which surface reflectivity varies significantly by the incident 
angle, such as an optical mirror surface (an object generating mostly 
normally reflected light but little scattered light) or a transparent 
object scarcely generating reflected (scattered) light. 
In the optical measurement mentioned above, the projected pattern has to be 
made finer, in order to improve the precision of shape measurement, namely 
to improve the resolving power of the measurement. In general, the extent 
of condensing of light depends on the numerical aperture (NA) of the 
optical system, and the projected pattern becomes finer as the numerical 
aperture increases. However a larger numerical aperture reduces the depth 
of focus of the optical system. 
As explained in the foregoing, in the conventional optical 
three-dimensional shape measuring apparatus, the depth of focus of the 
optical system becomes smaller when the surface shape of the specimen is 
to be measured with a higher precision or a higher resolving power. 
Consequently if the surface of the specimen is relatively flat (planar), a 
highly precise shape measurement is possible over the entire projection 
area (corresponding to the area of observation) of the optical system in a 
single operation. On the other hand, if the surface of the specimen is 
irregular, in portions within the projection area of the optical system 
where the focusing does not reach a desired level, the shape measurement 
itself becomes impossible, not to speak of the precision thereof. 
In the conventional optical three-dimensional shape measuring apparatus, 
therefore, when measuring the surface shape of a general specimen with an 
unflat surface with a high precision, it is required to employ an 
extremely simple irradiation pattern consisting for example of a single 
spot, and to repeat the measurement while maintaining precise positioning 
(namely focusing) with the optical system in an extremely narrow area 
corresponding to such small projection pattern. 
SUMMARY OF THE INVENTION 
In consideration of the foregoing, an object of the present invention is to 
provide an optical three-dimensional shape measuring apparatus capable of 
rapid and highly precise shape measurement over a wide surface area. 
The above-mentioned object can be attained, according to the present 
invention, by an optical three-dimensional shape measuring apparatus 
provided with an irradiating optical system for projecting a predetermined 
pattern image onto the surface of a specimen, and an observation optical 
system for observing the pattern image projected on the surface of said 
specimen, in which the surfacial shape of said specimen is measured based 
on the variation of said observed pattern image, wherein said irradiating 
optical system comprises focal plane dividing means for forming said 
predetermined pattern images respectively on plural focal planes 
positioned along the optical axis of said optical system. 
In a preferred embodiment of the present invention, said focal plane 
dividing means is composed of a pair of half mirrors which are positioned 
mutually substantially parallel with a predetermined distance therebetween 
and are substantially perpendicular to the optical axis of said 
irradiating optical system, and which are adapted to divide a pattern 
light into plural pattern lights. Said paired half mirrors preferably vary 
the reflectivity depending on the wavelength of the light, or are 
preferably provided therebetween with light absorbing means for absorbing 
the light of a specified wavelength with a predetermined proportion. 
The focal plane dividing means preferably can be composed of a pair of half 
mirrors which are mutually opposed with a predetermined distance 
therebetween and in which one of said half mirrors is substantially 
perpendicular to the optical axis of said irradiating optical system while 
the other is slightly inclined from a plane perpendicular to said optical 
axis, whereby said paired half mirrors are adapted to divide a pattern 
light into plural pattern lights. 
Furthermore said paired half mirrors preferably vary the reflectivity 
depending on the wavelength of the light, or are preferably provided 
therebetween with light absorbing means for absorbing the light of a 
specified wavelength with a predetermined proportion. 
The focal plane dividing means is preferably composed of a half mirror 
positioned in the optical path, wherein the light transmitted by said half 
mirror forms a first pattern image on a first focal plane while the light 
reflected by said half mirror forms a second pattern image on a second 
focal plane. 
Said observation optical system preferably has an optical axis crossing, at 
a predetermined angle, that of said irradiating optical system. In such 
case, the observation optical system is preferably provided with a first 
observation optical unit having an optical axis crossing that of said 
irradiating optical system at a first predetermined angle, and a second 
observation optical unit having an optical axis crossing that of said 
irradiating optical system at a second predetermined angle. 
The observation optical system preferably has a first observation optical 
unit having a first optical axis substantially parallel to the optical 
axis of said irradiating optical system, and a second observation optical 
unit having a second optical axis substantially parallel to the optical 
axis of said irradiating optical system, wherein the light receiving means 
of said first observation optical unit and that of said second observation 
optical unit are respectively positioned with displacements of 
predetermined distances from said first and second optical axes. 
Furthermore, said observation optical system is preferably provided with 
division means for dividing the light from said pattern image, and plural 
light-receiving means for respectively receiving the plural lights divided 
by said division means. In such case said division means is preferably 
composed of a half mirror provided in the optical path, and first 
light-receiving means is adapted to receive the light transmitted by said 
half mirror while second light-receiving means is adapted to receive the 
light reflected by said half mirror. 
The division means can be composed of a dichroic mirror provided in the 
optical path, and the first light-receiving means is adapted to receive a 
first light of a predetermined color divided by said dichroic mirror while 
the second light-receiving means is adapted to receive a second light of a 
predetermined color divided by said dichroic mirror. In such case the 
optical axis of said observation optical system preferably crosses that of 
said irradiating optical system at a predetermined angle. The optical axis 
of said observation optical system preferably can be substantially 
parallel to that of said irradiating optical system and said dichroic 
mirror is positioned with a displacement of a predetermined distance from 
the optical axis of said observation optical system. 
The optical three-dimensional shape measuring apparatus of the present 
invention is provided with plural focal planes along the optical axis of 
the irradiating optical system, and a predetermined pattern image is 
formed on each focal plane. Stated differently, plural patterns are formed 
at predetermined distances along the optical axis of the irradiating 
optical system, so that there can be realized a state equivalent to the 
formation of a pattern image with a desired focus state and with a 
predetermined depth of focus along the optical axis of the irradiating 
optical system. It is therefore rendered possible to avoid the drawback 
that the depth of focus of the optical system decreases when the resolving 
power is increased by an increase in the numerical aperture of the 
irradiating optical system. 
Therefore, when the surface of the specimen is not flat but shows 
significant irregularity, pattern images are formed with a desired focus 
state over a wide area, in such a manner that there are mixed pattern 
images of the focal planes respectively closest to the surface portions of 
the specimen. Consequently the rapid and highly precise shape measurement 
can be achieved over a wide surface area, in a single measuring operation. 
By positioning the optical axis of the observation optical system so as to 
cross that of the irradiating optical system at a predetermined crossing 
angle, the surface of the observed specimen, corresponding to the 
light-receiving means, can be made to cross the focal planes. It is 
therefore made possible to observe the multiple pattern images, formed 
with predetermined depths along the optical axis of the irradiating 
optical system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Now the present invention will be clarified in detail by embodiments 
thereof shown in the attached drawings. 
FIG. 1 is a schematic view showing the configuration of an optical 
three-dimensional shape measuring apparatus constituting a first 
embodiment of the present invention. 
The apparatus shown in FIG. 1 is a provided with a light source such as a 
strobe light source 1. The irradiating light, emitted from the strobe 
light source 1 positioned on an optical axis AX1 is converted into a 
parallel light beam by a collimating lens 2, then converted into light of 
uniform intensity by a diffusing plate 3 and enters a pattern plate 4. The 
pattern plate 4 is composed of transparent portions and opaque portions, 
and the light transmitted by said transparent portions forms a 
predetermined irradiating pattern. Said pattern can be, for example as 
shown in FIG. 6A, composed of spots arranged regularly in two mutually 
orthogonal directions. 
The pattern light transmitted by the pattern plate 4 enters a focal plane 
dividing plate 5, which is composed, as shown in FIG. 2A, of two half 
mirrors 21, 22 positioned mutually parallel with a predetermined distance 
therebetween and perpendicular to the optical axis AX1. The half mirrors 
21, 22 respectively have predetermined reflectivities. 
Consequently, as shown in FIG. 2B, the incident light 23 into the focal 
plane dividing plate 5 is partly transmitted (as indicated by a solid 
line) by the half mirror 21 while the remaining part is reflected (as 
indicated by a broken line). The light transmitted by the half mirror 21 
is partly transmitted (as indicated by 24) by the half mirror 22, and the 
remaining part is reflected. The light reflected by the half mirror 22 is 
partly transmitted (as indicated by a broken line) by the half mirror 21, 
and the remaining part is reflected (as indicated by a solid line). The 
light reflected by the half mirror 21 is partly transmitted (as indicated 
by 25) by the half mirror 22, and the remaining part is reflected. The 
light reflected again by the half mirror 22 is partly transmitted (as 
indicated by a broken line) by the half mirror 22, and the remaining part 
is reflected (as indicated by a solid line). The light reflected again by 
the half mirror 21 is partly transmitted (as indicated by 26) by the half 
mirror 22, and the remaining part is reflected. Thereafter the reflection 
and transmission are repeated at the two half mirrors. In the present 
embodiment, the present invention will be explained by three divided 
lights 24, 25 and 26. 
If the half mirrors 21, 22 have a reflectivity of 80%, the amount of the 
light 24, transmitted without reflection by the half mirrors, is 4% of the 
incident light 23. Also the amount of the light 25, reflected twice by the 
half mirrors, is 2.56% of the incident light 23. Likewise the amount of 
the light 26, reflected four times by the half mirrors, is 1.64% of the 
incident light 23. 
The patterned lights 24-26, divided by the focal plane dividing plate 5, 
are condensed toward the specimen 7 to be measured, by an irradiating 
objective lens 6, of which numerical aperture NA is determined according 
to the desired measuring resolving power. 
Consequently the pattern lights are focused respectively on three focal 
planes 11, 12, 13 which are mutually parallel and are perpendicular to the 
optical axis AX1. As will be apparent from FIG. 2A, a first patterned 
image corresponding to the light 24, transmitted without reflection by the 
half mirrors, is formed on a first focal plane 13. A second patterned 
image, corresponding to the light 25, reflected twice by the half mirrors, 
is formed on a second focal plane 12, and a third patterned image, 
corresponding to the light 26, reflected four times by the half mirrors, 
is formed on a third focal plane 11. 
The light source 1, collimating lens 2, diffusing plate 3, pattern plate 4, 
focal plane dividing plate 5 and irradiating objective lens 6 are all 
positioned on the optical axis AX1 and constitute the irradiating optical 
system. 
The apparatus shown in FIG. 1 is also provided with an observation optical 
system having an optical axis AX2, crossing the optical axis AX1 of the 
irradiating optical system at a predetermined angle. Said observation 
optical system, for observing the three patterned images, projected on the 
surface of the specimen 7, is provided with an observation objective lens 
8 for condensing the lights from the projected patterned images, and the 
lights transmitted by said observation objective lens 8 enter three CCD's 
constituting the light-receiving means, through a dichroic mirror 9. 
The observation objective lens 8 has optical characteristics substantially 
the same as those of the irradiating objective lens 6, and has a numerical 
aperture NA determined according to the desired measuring resolving power. 
Among the light entering the dichroic mirror 9, a red light component, a 
green light component and a blue light component are respectively received 
by a CCD-R, a CCD-G and a CCD-B. Thus, three CCD's constitute three 
mutually independent observation image planes, and there exist three 
observation object planes 14, 15, 16 which are mutually parallel and are 
perpendicular to the optical axis AX2, respectively corresponding to said 
three observation image planes CCD-R, CCD-G and CCD-B. 
Consequently, it is possible to observe, with a desired resolving power, a 
patterned image formed in a position corresponding to the observation 
object plane 14, 15 or 16 (or position within a predetermined depth of 
focus around the observation object plane) on the surface of the specimen 
7. The projection areas indicated by the three focal planes 11, 12, 13 and 
the observation areas indicated by the three observation object planes 14, 
15, 16 are so positioned that they mutually overlap sufficiently. 
The observation objective lens 8, dichroic mirror 9 and three CCD's are all 
positioned on the optical axis AX2 and constitute the observation optical 
system. 
In the following there will be explained the function of the optical 
three-dimensional shape measuring apparatus as illustrated in FIG. 1. 
The light emitted from the light source 1 enters the pattern plate 4 
through the collimating lens 2 and the diffusing plate 3. The patterned 
light transmitted by the pattern plate 4 is divided by the focal plane 
dividing plate 5, and condensed by the irradiating objective lens 6 to 
form three patterned images, respectively on the first, second and third 
focal planes 13, 12, 11 as explained in the foregoing. 
The entire apparatus (irradiating optical system and observation optical 
system) is so positioned, with respect to the specimen 7, that a patterned 
image is formed with a desired focus state on the surface area to be 
measured of the specimen 7. More specifically, after the optical axis AX1 
of the irradiating optical system is aligned with the specimen 7, the 
entire optical system is moved with respect to the surface of the specimen 
7 as indicated by an arrow to achieve focusing. 
Thus, even if the surface of the specimen is not flat but shows significant 
irregularity, patterned images are formed with a desired focus state over 
a wide area, in such a manner that the patterned images of different focal 
planes respectively closest to portions of the surface of the specimen are 
mixedly present. In general, on the surface area to be measured of the 
specimen 7, three patterned images are projected in such a superimposed 
manner that an area where the first patterned image is formed with a 
desired focus state, an area where the second patterned image is formed 
with a desired focus state and an area where the third patterned image is 
formed with a desired focus state are mixed, so that a patterned image 
showing a desired focus state can be formed over a considerably wide area 
even when the surface to be measured is not flat. 
The observation optical system can observe, with a desired resolving power, 
the pattern images formed in positions corresponding to the three 
observation object planes 14, 15, 16 as explained above. More 
specifically, among the pattern images formed by the irradiating optical 
system with the desired focus state on the surface of the specimen 7, 
those of a wide area formed in positions corresponding to the three 
observation object planes 14, 15, 16 can be observed with a high resolving 
power respectively through the CCD-R, CCD-G and CCD-B. The inclined 
positioning of the three observation object planes 14, 15, 16 with respect 
to the optical axis AX1 is advantageous for the observation of the pattern 
images covering a wide area. 
The method of determining the surface shape of the observed area, based on 
the deformation of the observed patterned image, is already well known as 
the projected pattern method, and will not, therefore, be explained in 
detail. 
It is thus possible to precisely and promptly measure the surface shape of 
substantially the entire surface of the specimen 7, by repeating the 
above-explained measuring operation while suitably rotating the specimen 
7. 
FIG. 3 shows a variation of the focal plane dividing plate. The focal plane 
dividing plate 35 shown in FIG. 3 is same as that shown in FIGS. 2A and 2B 
in that there are provided mutually opposed two half mirrors, but is 
basically different from the latter in that the second half mirror 2 is 
slightly inclined from a plane perpendicular to the optical axis AX1 
though the first half mirror 21 is positioned perpendicularly to the 
optical axis AX1. 
Consequently a light transmitted by the focal plane dividing plate 35 shown 
in FIG. 3, without reflection therein, is focused by the irradiating 
objective lens 6 on a first focal plane 13 perpendicular to the optical 
axis AX1. Also a light reflected twice in the focal plane dividing plate 
35 is focused on a second focal plane 12, slightly inclined from a plane 
perpendicular to the optical axis AX1 and displaced by a predetermined 
distance from the optical axis AX1. Also a light reflected four times in 
the focal plane dividing plate 35 is focused on a third focal plane 11, 
inclined more from the plane perpendicular to the optical axis AX1 and 
displaced further by a predetermined distance from the optical axis AX1. 
In this manner, the focal plane dividing plate 35 shown in FIG. 3 
facilitates distinction from the neighboring pattern images, by the 
inclinations and relative positional displacements of the pattern images 
on said three focal planes. 
FIG. 4A shows another variation of the focal plane dividing plate that has 
a member comprising two half mirrors 21, 22 per se or, as later detailed, 
two half mirrors and an associated filter. The focal plane dividing plate 
45 shown in FIG. 4A is composed of two half mirrors 21, 22 positioned in a 
mutually parallel manner with a predetermined distance therebetween and 
perpendicularly to the optical axis AX1, and is therefore same, in the 
external appearance, as the focal plane dividing plate 5 in FIGS. 2A and 
2B. It is however basically different from the latter in that, as shown in 
FIG. 4B, the reflectivities of the half mirrors 21, 22 are variable 
depending on the wavelength of the light. 
Consequently a first patterned image focused on a first focal plane 13 
without reflection in the focal plane dividing plate 45, a second 
patterned image focused on a second focal plane 12 after two reflections 
in the focal plane dividing plate 45, and a third patterned image focused 
on a third focal plane 11 after four reflections in the focal plane 
dividing plate 45 are mutually different in the spectral transmittances. 
Stated differently, these patterned images are different in their apparent 
hues. 
Thus the focal plane dividing plate 45 shown in FIG. 4A facilitates 
distinction from the neighboring patterned images, by the variation in the 
spectral transmittance among the patterned images on the three focal 
planes. 
Even if the half mirrors 21, 22 lack the variation in reflectivity 
depending on the wavelength of the light, a similar effect can be achieved 
by providing an absorbing member (filter), capable of absorbing a 
predetermined proportion of the light of a specified wavelength between 
the two half mirrors. In such case, the first, second and third patterned 
images formed respectively after passing the absorbing member once, three 
times and five times are mutually different in the spectral transmittance, 
whereby the distinction from the neighboring patterned images can be 
facilitated. 
FIG. 5 shows a variation of the irradiating optical system, wherein plural 
pattern plates are provided for forming multiple patterned images on the 
surface of the specimen. FIG. 5 only illustrates the characteristic 
components, among which the components equivalent in function to those in 
the first embodiment shown in FIG. 1 are represented by same numbers. 
The irradiating optical system shown in FIG. 5 is provided with three 
pattern plates 4a, 4b, 4c and two half mirrors 51, 52 positioned in the 
optical path. The light from an unrepresented first light source is 
transmitted by a first pattern plate 4a and the two half mirrors 51, 52 
provided in the optical path, and enters the irradiating objective lens 6. 
Also the lights from unrepresented second and third light sources are 
respectively transmitted by second and third pattern plates 4b, 4c and 
reflected to the right, by the first and second half mirrors 51, 52, thus 
entering the irradiating objective lens 6. 
Thus the light from the first pattern plate 4a forms a first patterned 
image on the first focal plane 13. Also the light from the second pattern 
plate 4b forms a second patterned image on the second focal plane 12, and 
the light from the third pattern plate 4c forms a third patterned image on 
the third focal plane 11. The first, second and third focal planes 13, 12, 
11 are perpendicular to the optical axis AX1 and are mutually separated by 
predetermined distances. 
FIGS. 6A and 6B show the configuration of an optical three-dimensional 
shape measuring apparatus constituting a second embodiment of the present 
invention, wherein FIG. 6A is a perspective view and FIG. 6B is a plan 
view along a plane containing the optical axes of the irradiating optical 
system and the observation optical system. FIGS. 6A and 6B illustrate only 
the characteristic components within the apparatus of the first embodiment 
shown in FIG. 1, wherein components equivalent in function to those in the 
first embodiment are represented by same numbers. 
The apparatus of the first embodiment shown in FIG. 1 and that of the 
present embodiment shown in FIGS. 6A and 6B are basically different in 
that the apparatus of the present embodiment has only one light-receiving 
means and only one observation object plane for the observation optical 
system, while, in the apparatus of the first embodiment, the observation 
optical system has three light-receiving means and three corresponding 
observation object planes. The light-receiving means 10 is composed, for 
example, of a light-receiving optical element such as a CCD. 
Also in this embodiment, as in the first embodiment, three patterned images 
are respectively formed on the first, second and third focal planes 13, 
12, 11 in the surface area to be measured of the specimen 7, so that there 
can be obtained multiple patterned images having a desired focus state 
over a certain wide area even if the surface area to be measured is not 
flat. On the other hand, the observation optical system has an optical 
axis AX2 crossing the optical axis AX1 of the irradiating optical system 
at a predetermined angle, so that the observation object plane 14 
corresponding to the light-receiving means 10 is formed so as to cross 
said three focal planes 11, 12, 13. Consequently there can be observed, by 
the CCD 10 in a wider area, the patterned images formed in a superimposed 
manner with predetermined depths along the optical axis AX1 of the 
irradiating optical system. 
FIGS. 7A and 7B illustrate the configuration of an optical 
three-dimensional shape measuring apparatus constituting a third 
embodiment of the present invention. The apparatus of the present 
embodiment is basically different from those of the foregoing two 
embodiments, in that there are provided two observation optical systems. 
FIGS. 7A and 7B only show the characteristic components of the second 
embodiment in FIGS. 6A and 6B, wherein components equivalent in function 
to those in the second embodiment are represented by the same numbers. 
The apparatus shown in FIG. 7A is provided with a first observation optical 
system having a first optical axis AX2a crossing the optical axis AX1 of 
the irradiating optical system at a first predetermined angle, and a 
second observation optical system having a second optical axis AX2b 
crossing the optical axis AX1 of the irradiating optical system at a 
second predetermined angle. Thus, in the apparatus shown in FIG. 7A, there 
are formed two observation object planes 14a, 14b, respectively 
corresponding to light-receiving means 10a, 10b such as CCD's, positioned 
on the optical axes AX2a, AX2b. The observation object planes 14a, 14b are 
respectively perpendicular to the optical axes AX2a, AX2b. 
Thus the patterned images, projected in superimposed manner on the surface 
of the specimen 7, can be observed from two angles. Consequently the 
measurement can be made over a wide area even on an extremely irregular 
surface, since a surface area that cannot be observed by one observation 
optical system can be observed by the other optical system. Also when the 
patterned images on a same surface area can be observed at the same time 
by the two observation optical systems, it is made possible to achieve a 
high precision in measurement, for example, by averaging the data of the 
observed patterned images. The number of observation optical systems is 
not limited to two, but there can be employed a larger number of 
observation optical systems. 
In the apparatus shown in FIG. 7B, the optical axes AX2a, AX2b of the two 
observation optical systems are substantially parallel to the optical axis 
AX1 of the irradiating optical system, but the light-receiving means 10a, 
10b are not positioned on said optical axes AX2a, AX2b. Consequently two 
observation object planes 14a, 14b are respectively formed on center lines 
La, Lb, passing through the centers of the light-receiving means 10a, 10b 
and those of the observation objective lenses 8a, 8b. Said observation 
object planes 14a, 14b are respectively perpendicular to the optical axes 
AX2a, AX2b. 
Thus, in the configuration shown in FIG. 7A, the patterned images projected 
in a superimposed manner on the surface of the specimen 7 can be observed 
from two angles. Thus there can be achieved observation over a wide area 
by complementary observation and with a high precision by an averaging 
process. 
FIG. 8 illustrates the configuration of an optical three-dimensional shape 
measuring apparatus, constituting a fourth embodiment of the present 
invention. The apparatus of the fourth embodiment is similar to that of 
the first embodiment, but is basically different from the latter in the 
method of amplitude division in the observation optical system. 
The observation optical system shown in FIG. 8 is provided with two half 
mirrors 81, 82 provided in the optical path, and, among the lights coming 
from the three patterned images projected on the surface of the specimen 
7, the light transmitted by the observation objective lens 8 and the two 
half mirrors 81, 82 is received by a CCD 10a constituting first 
light-receiving means, while the light transmitted by said objective lens 
8 and the half mirror 82 and reflected by the half mirror 81 is received 
by a CCD 10b constituting second light-receiving means. Also the light 
transmitted by said objective lens 8 and reflected by the half mirror 82 
is received by a CCD 10c constituting third light-receiving means. 
Consequently there are formed three observation object planes 14, 15, 16 
respectively corresponding to the CCD's 10a, 10b, 10c, constituting three 
observation image planes. Said three observation object planes 14, 15, 16 
are perpendicular to the optical axis AX2 and are mutually separated by 
predetermined distances. This configuration provides effects substantially 
same as those in the first embodiment. 
FIGS. 9A and 9B illustrate the configuration of an optical 
three-dimensional shape measuring apparatus, constituting a fifth 
embodiment of the present invention, wherein FIG. 9A shows an apparatus in 
which the optical axis AX1 of the irradiating optical system and that AX2 
of the observation optical system mutually cross at a predetermined angle, 
while FIG. 9B shows an apparatus in which said optical axes are mutually 
parallel. The apparatus in FIG. 9A is similar in configuration to that of 
the first embodiment, but is basically different therefrom in that the 
dichroic mirrors are replaced by a half mirror prism. 
In the observation optical system shown in FIG. 9A, the light from the 
patterned images projected on the surface of the specimen 7 is divided 
into three by the half mirror prism 91, and enter CCD's 10a, 10b, 10c 
constituting the light-receiving means. 
Thus there are formed three observation object planes 14, 15, 16, 
respectively corresponding to the CCD's 10a, 10b, 10c constituting the 
three observation image planes. Said three observation object planes 14, 
15, 16 are perpendicular to the optical axis AX2 and are mutually 
separated by predetermined distances. Thus this configuration provides 
effects comparable to those in the first embodiment. 
The observation optical system shown in FIG. 9B is basically different from 
that in FIG. 9A in that the optical axis AX2 is parallel to the optical 
axis AX1 of the irradiating optical system. Also in this case there are 
formed three observation image planes 14, 15, 16 respectively 
corresponding to the CCD's 10a, 10b, 10c constituting three observation 
image planes. Said three observation object planes 14, 15, 16 are 
perpendicular to the optical axis AX2 of the observation optical system 
and mutually separated by predetermined distances, and the light-receiving 
means is displaced from the optical axis AX2 in such a manner that said 
observation object planes are in a position substantially the same as that 
of the three patterned images. Consequently the apparatus shown in FIG. 9B 
evidently provides effects comparable to those of the apparatus shown in 
FIG. 9A. 
FIGS. 10A to 10C show the state of the patterned images projected onto the 
three focal planes and the superposition of the patterns respectively 
observed from said patterned images. 
In the optical three-dimensional shape measuring apparatus of the foregoing 
embodiments, as shown in FIG. 10A, the patterned images, each composed of 
spots arranged regularly in two orthogonal directions, are formed on the 
three focal planes 11, 12, 13. In a mutually corresponding area within the 
spot images formed on said focal planes, the three spots corresponding to 
said focal planes are observed in mutually superimposed manner as shown in 
FIG. 10B. FIG. 10C shows the light intensity distributions corresponding 
to said spots. 
Referring to FIG. 10B, the smallest observed spot corresponds to the spot 
on a focal plane closest to the surface of the specimen, while the largest 
observed spot corresponds to the spot on a focal plane farthest from said 
surface. Since the distances of the focal planes and the projected pattern 
are specific to each apparatus, the mutual positional relationship of the 
observed spots corresponding to the focal plane or the superimposed 
pattern indicates the positional relationship between the focal planes and 
the surface of the specimen, namely between the focal planes and the 
specimen itself. 
Since the positional relationship, for example distance, between the 
apparatus and the specimen can be measured from the state of the 
superimposed patterns, there can be achieved focusing based on thus 
measured distance. In such case it is desirable to construct the patterned 
images, on respective focal planes, in a mutually distinguishable manner, 
as shown in FIGS. 4A and 4B. 
In the foregoing embodiments there has been explained a spot pattern 
arranged regularly in two orthogonal directions, but there may also be 
projected a grating pattern crossing in two orthogonal directions as shown 
in FIG. 11A or crossing in three directions as shown in FIG. 11B. It is 
also preferable to select the pattern of projection according to the 
entire shape of the specimen, for example a rotationally symmetrical 
pattern if the specimen is rotationally symmetrical, or a striped pattern 
if the specimen has striped irregularity. 
Also in the foregoing embodiments the irradiating optical system has three 
focal planes, but the number of the focal planes is not limited to three 
and can be any plural number (2 or larger). 
In the optical three-dimensional shape measuring apparatus of the present 
invention, as explained in the foregoing, plural patterns are formed at 
predetermined distances along the optical axis of the irradiating optical 
system, so that there can be realized a state equivalent to the formation 
of a patterned image with a desired focus state and over a predetermined 
depth of focus along the optical axis of the irradiating optical system. 
Consequently, when the resolving power is improved by an increase in the 
numerical aperture of the irradiating optical system, it is rendered 
possible to avoid the drawback of decrease in the depth of focus of the 
optical system and to achieve rapid and precise measurement of the shape 
over a wide surface area. 
However, in the optical three-dimensional shape measuring apparatus of the 
foregoing embodiments, the irradiating optical system and the observation 
optical system are respectively provided with the objective lenses, so 
that the operating distance (distance along the optical axis from the 
surface of the object to be observed to the lens face closest to the 
object) has to be made large in each objective lens, in order to prevent 
mutual interference of the objective lenses. However, an increase in the 
operating distance leads directly to a reduction in the numerical aperture 
(NA). As a result, it has been impossible to obtain a finer projection 
pattern. 
This drawback can be resolved, according to the present invention, by an 
optical three-dimensional shape measuring apparatus provided with an 
irradiating optical system for projecting a predetermined patterned image 
on the surface of the specimen and an observation optical system for 
observing the projected patterned image, in order to measure the surface 
shape of said specimen based on the difference between said predetermined 
patterned image and said observed patterned image; 
wherein said irradiating optical system and said observation optical system 
have a common objective optical system; and 
said apparatus further comprises wave front dividing means for the pupil 
plane of said objective optical system, for mutually independently 
defining an optical path from said irradiating optical system to the 
surface of said specimen and an optical path from the surface of said 
specimen to said observation optical system. 
In a preferred embodiment, said wave front dividing means is composed of an 
aperture diaphragm having at least two apertures. In such case, said 
apertured diaphragm is preferably provided with plural first apertures for 
defining plural optical paths from plural irradiating optical systems to 
the surface of said specimen, and said plural irradiating optical systems 
are preferably adapted to project, through said plural first apertures, 
mutually different plural patterns or plural patterned lights of mutually 
different colors, onto the surface of said specimen. 
FIG. 12 is a view showing the function of an optical three-dimensional 
shape measuring apparatus embodying the present invention. 
In the apparatus of the present invention, the irradiating optical system 
and the observation optical system have a common objective optical system 
101, and there is provided an apertured diaphragm 105 as the wave front 
dividing means for the pupil plane of the objective optical system 101, in 
order to mutually independently define an optical path 103 from the 
irradiating optical system to a specimen 102 and an optical path 104 from 
said specimen 102 to the observation optical system. 
In FIG. 12, for the purpose of simplicity, an irradiation pattern face 
(pattern plate) of the irradiating optical system and the observation 
image plane of the observation optical system are represented by a common 
number 106, and the components present between the apertured diaphragm 105 
and the pattern face 106 or the image plane 106 are omitted. 
FIGS. 13A to 13C illustrate the configurations of the apertured diaphragm 
105 shown in FIGS. 2A and 2B. 
As shown in FIGS. 13A to 13C, the apertured diaphragm 105, constituting the 
wave front dividing means, is provided with at least two apertures. For 
example, as shown in FIG. 13A, the apertured diaphragm 105 may be 
provided, along the diameter thereof, with two apertures 107, 108, of 
which one 107 defines the optical path 103 from the irradiating optical 
system while the other 108 defines the optical path 104 to the observation 
optical system. 
In the above-explained apparatus of the present invention, the conventional 
interference of the objective lenses can be avoided since an Objective 
lens is used in common. Consequently the projected pattern can be made 
finer by an objective lens of a smaller operating distance, or a larger 
numerical aperture (NA). 
Also the apertured diaphragm 105 may be provided, as shown in FIG. 13B, 
with six apertures 109 positioned circumferentially. Among these six 
apertures 109, three define three optical paths 103 from the irradiating 
optical system while the other three define three optical paths 104 to the 
observation optical system. 
In this case, the patterns may be projected with respectively different 
irradiating conditions, on the plural optical paths of the irradiating 
optical system, and the irradiating conditions may be varied, for example, 
the projected pattern, color of the pattern projecting light, position of 
formation of the patterned images, or size or shape of the apertures. 
It is also possible to observe the patterned images with respectively 
different observing conditions on the plural optical paths of the 
observation optical system, and the observing condition may be varied, for 
example, the focal position, inclination of the observation optical path 
with respect to the irradiating optical path, size or shape of the 
aperture, or magnification of the observed image (by presence or absence 
of a magnification-varying optical system). 
Further, as shown in FIG. 13C, the apertured diaphragm 105 may be provided 
with a central aperture 110 and, for example, six apertures 111 in the 
peripheral area, wherein the central aperture 110 defines the optical path 
103 from the irradiating optical system while the six peripheral apertures 
111 define six optical paths to the observation optical system. 
In such case the irradiating condition is unique in the optical path of the 
irradiating optical system, but the observation of the patterned images 
can be made with respectively different conditions for the plural optical 
paths in the observation optical system. 
The shape measurement can thus be conducted by varying at least one of the 
irradiation condition and the observing condition, so that effective data 
of measurement can be securely collected despite various local changes in 
the shape in the observed area of the specimen. As a result, it is 
rendered possible to reduce the entire measuring time for the specimen and 
to achieve rapid and precise shape measurement over a wide surface area. 
Now there will be explained a sixth embodiment of the present invention. 
FIG. 14 is a schematic view of the configuration of an optical 
three-dimensional shape measuring apparatus constituting a sixth 
embodiment of the present invention. 
The apparatus shown in FIG. 14 is provided, for example, with a strobe 
light source 120 as the light source, and the light therefrom is converted 
into the light of uniform illumination intensity by an unrepresented 
collimating lens and an unrepresented diffusing plate, and enters a 
pattern plate 121. The pattern plate 121 is composed of transparent 
portions and opaque portions, and the light transmitted by said 
transparent portions forms a predetermined irradiating pattern. Said 
irradiating pattern can be, for example, a pattern of spots arranged 
regularly in two orthogonal directions. 
The patterned light transmitted by the pattern plate 121 enters an inclined 
face 122a of a hexagonal truncated conical prism 122, and the light 
reflected downwards by said inclined face 122a passes an aperture 123a of 
an apertured diaphragm 123, which has, as shown in FIG. 13B, two apertures 
along a diameter. The patterned light passing the aperture 123a is 
condensed by a common objective optical system 124 toward a specimen 125. 
The numerical aperture of said common objective optical system 124 is 
determined according to the desired resolving power of measurement. In 
this manner a projected patterned image is formed on the surface of the 
specimen 125. 
The light from the projected patterned image formed on the surface of the 
specimen 125 enters, through the common objective optical system 124 and 
an aperture 123b of the apertured diaphragm 123, an inclined face 122b of 
the prism 122. The light reflected to the right by said inclined face 122b 
enters an image-receiving face 126 of an image pickup device such as a 
CCD. 
In this embodiment, as explained in the foregoing, the irradiating optical 
system and the observation optical system have a common objective optical 
system 124, and the optical path 127 from the irradiating optical system 
to the specimen 125 and the optical path 128 from said specimen 125 to the 
observation optical system are independently defined by the apertured 
diaphragm 123. 
For the purpose of simplicity, the apparatus shown in FIG. 14 has a light 
source and an image plane, but there may also be employed an apertured 
diaphragm with six apertures in the circumferential direction as shown in 
FIG. 13B. In such case, among said six apertures, three apertures may be 
used for defining three optical paths from the irradiating optical system 
and the other three apertures may be used for defining three optical paths 
to the observation optical system. 
In such configuration with three light sources and three image planes, 
there can be projected three different patterns onto the surface of the 
specimen 125, and there can be conducted effective measurement by 
selecting an appropriate irradiating pattern, according to the local 
variation of the surface shape of the specimen 125. 
It is also possible to project patterned lights of three different colors 
onto the surface of the specimen 125. For example it is possible to 
receive projected patterns of red, green and blue components respectively 
with a CCD-R for red light, a CCD-G for green light and a CCD-B for blue 
light. 
Such patterned lights of mutually different wavelengths can form three 
projected patterns at slightly different focal positions, despite of the 
use of a common objective optical system. It is therefore possible to 
achieve observation with satisfactory focus state, even on a surface with 
significant local irregularity, by selective use of the three observation 
optical systems. 
The patterned images of plural colors may be formed by plural light sources 
of mutually different colors, or by filters transmitting the lights of 
mutually different colors, provided in respective light paths. 
FIG. 15 is a schematic view showing the configuration of an optical 
three-dimensional shape measuring apparatus constituting a seventh 
embodiment of the present invention. 
The apparatus of said seventh embodiment is similar, in configuration, to 
that of the fourth embodiment, but is basically different from the latter 
in that six observation optical systems are provided for an irradiating 
optical system. Components in FIG. 15, equivalent in function to those in 
FIG. 14 will not be explained further. 
The apparatus shown in FIG. 15 is provided, for example, with a strobe 
light source 130. The light therefrom enters a pattern plate 131, and the 
light transmitted by the transparent portions thereof forms a 
predetermined irradiating pattern. 
The patterned light transmitted by said pattern plate 131 enters a bottom 
face 132a of a truncated hexagonal conical prism 132, and the light 
transmitted by said bottom face 132a and an upper face 132b of said prism 
132 passes through a central aperture 133a of an apertured diaphragm 133, 
which is provided, as shown in FIG. 13C, with a central aperture and six 
peripheral apertures. The light transmitted by the central aperture 133a 
is condensed by a common objective optical system 134 toward a specimen 
135, whereby a projected patterned image is formed on the surface thereof. 
10 The light from the projected patterned image formed on the surface of 
the specimen 135 is guided through the common objective optical system 134 
and the six peripheral apertures of the apertured diaphragm 133, and 
enters the inclined faces of the prism 132. The lights reflected radially 
in the horizontal direction by the inclined faces of the prism 132 
respectively enter six image planes 136a, 136b composed, for example, of 
CCD's. 
In the present embodiment, the central aperture 133a of the apertured 
diaphragm 133 defines the optical path 137 from the irradiating optical 
system to the specimen 135, while the six peripheral apertures of said 
diaphragm 133 define the six optical paths 138a, 138b from the specimen 
135 to the observation optical systems. 
For the purpose of simplicity, FIG. 15 only shows two CCD's 136a, 136b and 
corresponding optical paths 138a, 138b while other four CCD's and optical 
paths are omitted. 
In such configuration with a light source and six image planes, a patterned 
image projected on the specimen 135 can be observed from various angles 
through the six optical paths. Consequently, even when the surface of the 
specimen 135 has steep local inclination, there can be obtained reliable 
data of measurement at least in one of the six image planes. 
In the example shown in FIG. 13C, the six peripheral apertures are arranged 
regularly on a circle around the central aperture, so that the distances 
from said peripheral apertures to the central aperture are constant. 
However the peripheral apertures may be provided at mutually different 
distances to the central aperture, in order that the inclinations of the 
optical paths 138a, 138b to the observation optical systems mutually vary 
with respect to the optical path 137 from the irradiating optical system. 
Also in such case, there can be obtained further reliable data of 
measurement by suitably selecting the six image planes, even on the 
specimen surface showing various local changes. 
The method of determining the surface shape of the corresponding area based 
on the deformation of the observed patterned image is already known as the 
projection pattern method, and will not, therefore, be explained further. 
The foregoing embodiments employ a truncated hexagonal conical prism and 
show an example of forming six optical paths in total for the irradiating 
optical system and for the observation optical system, and an example of 
forming six optical paths for the observation optical system, but there 
may also be employed a suitable truncated polygonal conical prism 
according to the desired number of the optical paths. 
Also in the foregoing embodiments, a prism is employed as the optical path 
switching means, but there may be employed other suitable optical path 
switching means. 
Also in the foregoing embodiments, the apertured diaphragm is provided with 
circular apertures of a constant size, but the apertures may vary in size 
and/or shape. Such configuration is advantageous as the depth of focus of 
the object field can be modified. 
Also a magnification-varying optical system may be provided in each 
observation optical system, whereby the observation can be achieved with a 
suitable variation in the magnification of the observed patterned image. 
Furthermore, the principle of forming plural observation optical paths of 
the present invention is not limited to the optical three-dimensional 
shape measuring apparatus equipped with the irradiating optical system, 
but is likewise applicable to a two-dimensional image observing apparatus 
which does not require the irradiating optical system. 
In the optical three-dimensional shape measuring apparatus of the present 
invention, as explained in the foregoing, since an objective lens is used 
in common, a finer projected pattern can be obtained with an objective 
lens of a smaller operating distance, namely of a larger numerical 
aperture. 
Also, since the shape measurement can be conducted under the variation of 
at least one of the irradiating condition and the observing condition, it 
is rendered possible to reduce the measuring time for the entire specimen 
and to achieve rapid and precise shape measurement over a wide surface 
area in a single measuring operation.