Standard measurement scale and markers for defining standard measurement scale

A standard scale used in a photogrammetric measurement system has a polygonal plate having three apexes which are arranged to define a reference plane, where each of the apexes defines a reference point. Another standard scale has a light-guide plate member which has three light-emitting spots for defining reference points. Yet another standard scale has a frame member, and reference-point-forming elements, for defining reference points, arranged on the frame to define a reference plane. A marker used in a photogrammetric measurement system for defining a standard scale has a light-guide plate having a light emitting spot for defining a reference point. Another marker has a polygonal-pyramidal-shaped optical assembly formed from light-guide plates, including a core layer containing fluorescent substances, such that an apex of the optical assembly is defined by an emission of fluorescent radiation therefrom.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a standard measurement scale and markers for 
defining a standard measurement scale, which are used in photogrammetric 
analytical measurement systems. 
2. Description of the Related Art 
For example, photogrammetry measurement is carried out at a traffic 
accident site. Namely, the traffic accident site is photographed by a 
camera or cameras, and a survey map is established on the basis of 
pictures photographed by the camera. Before real distances and lengths can 
be reproduced on the survey map, a standard measurement scale must be 
recorded in the pictures. 
Conventionally, the standard measurement scale is defined by at least two 
cone-shaped markers which are formed of, for example, a suitable plastic 
material. In particular, for example, at a traffic accident site, two 
markings are indicated on the ground with chalk, and a distance between 
the markings is obtained using a measuring tape. Then, the cone-shaped 
markers are positioned at the respective indications. Thereafter, the 
traffic accident site is photographed by the camera(s), such that the 
cone-shaped markers are included in the field of view to be photographed. 
Before a survey map can be exactly drawn, the cone-shaped markers must be 
positioned with respect to the indications on the ground, such that an 
apex of each cone-shaped marker is just above the corresponding 
indication, because each of the apexes of the cone-shaped markers serves 
as a reference point for defining a standard measurement scale. 
Nevertheless, it is difficult and troublesome to align the apex of the 
marker with the indication, because the indication is lost from sight due 
to the enlarged bottom of the cone-shaped marker during positioning. 
Further, when the ground is not horizontal, i.e., when the ground is 
sloped, the positioning of the cone-shaped marker is further complicate, 
because a fine positional adjustment of the cone-shaped marker is 
necessary before the apex of the cone-shaped marker can exactly coincide 
with the corresponding indication. 
Also, conventionally, the apex of the cone-shaped marker is painted with a 
light-color, such as white, yellow or the like, so that the apex is 
conspicuous when recorded in a photographed picture. Nevertheless, the 
apex of the marker is ot necessarily conspicuously recorded in the 
picture, e.g., when the tone of color of the background is similar to the 
apex color. 
Furthermore, it is troublesome to obtain a distance between the indications 
using the measuring tape. Especially, in photogrammetry, in which a 
reference plane must be defined by at least three reference points, it is 
necessary to measure the three distances between the three reference 
points by using the measuring tape. 
SUMMARY OF THE INVENTION 
Therefore, an object of the present invention is to provide a standard 
measurement scale, to be used in a photogrammetric measurement system, 
having at least three fixed reference points. 
Another object of the present invention is to provide such a standard 
measurement scale as mentioned above, which is constituted such that the 
reference points can be conspicuously recorded in a photographed picture. 
Yet another object of the present invention is to provide a marker for 
defining a standard measurement scale in a photogrammetric measurement 
system, which is constituted such that a reference point of the marker can 
be easily aligned with an indication on the ground. 
Still yet another object of the present invention is to provide such a 
measurement-standard-scale-defining marker as mentioned above, which is 
constituted such that the reference point can be conspicuously recorded in 
a photographed picture. 
In accordance with a first aspect of the present invention, there is 
provided a standard measurement scale, to be used in a photogrammetric 
measurement system, comprising a polygonal plate member having at least 
three apexes, which are arranged so as to define a reference plane, and 
each of which defines a reference point. Preferably, the three reference 
points are equally spaced apart from each other by a predetermined 
distance. Each of the triangular apexes, of the polygonal member, includes 
a reference point and may be marked with a conspicuous material. The 
conspicuous material may comprise a light color paint. Preferably, the 
light color paint is a fluorescent paint. The conspicuous material may 
comprise a piece of reflective sheet. 
In accordance with a second aspect of the present invention, there is 
provided a standard measurement scale, to be used in a photogrammetric 
measurement system, comprising a light-guide plate member including a core 
layer containing fluorescent substances, said light-guide plate member 
having at least three light-emitting spots for defining respective 
reference points. Preferably, the three reference points are equally 
spaced apart from each other by a predetermined distance. Each of the 
light-emitting spots may be defined as a cone-shaped or 
polygonal-pyramidal-shaped recess formed in the light-guide plate member 
for emitting fluorescent radiation therefrom. Also, each of the 
light-emitting spots may be defined as a hemispherical projection attached 
to the light-guide plate member for emitting fluorescent radiation 
therefrom, or may be defined by at least two V-shaped grooves formed in 
the light-guide plate member and extending radially from the center 
thereof for emitting fluorescent radiation therefrom. 
In accordance with a third aspect of the present invention, there is 
provided a standard measurement scale, to be used in a photogrammetric 
measurement system, comprising: a frame member, and at least three 
reference-point-forming elements, for defining respective reference 
points, arranged on the frame member so as to define a reference plane. 
The standard scale may further comprises a plate member mounted on the 
frame member. In this case, the three reference-point-forming elements are 
arranged on the plate member so as to define a reference plane. 
Preferably, the three reference points are equally spaced apart from each 
other by a predetermined distance. 
Each of the reference-point-forming elements may be formed as a projection 
for defining the reference point thereof. In this case, the projection may 
be a light-emitting projection including an electrical lump or a 
light-emitting diode, and may be formed from at least two light-guide 
plate elements, including each a core layer containing fluorescent 
substances, which are arranged such that the reference point of the 
projection is defined by an emission of fluorescent radiation therefrom. 
Also, each of the reference-point-forming elements may be formed as a 
cone-shaped projection or polygonal-pyramidal-shaped projection, an apex 
of which defines one of the reference points. In this case, the 
cone-shaped projection or polygonal-pyramidal-shaped projection may be 
coated with a fluorescent paint, or may be covered with a reflective 
sheet. 
Further, each of the reference-point-forming elements may be formed as a 
polygonal-pyramidal-shaped projection constructed from at least two 
light-guide plate elements, including each a core layer containing 
fluorescent substances. Preferably, the light-guide plate elements are 
arranged such that the apex of the polygonal-pyramidal-shaped projection 
is defined by an emission of fluorescent radiation therefrom. 
Furthermore, each of the reference-point-forming elements may be formed as 
a small circular-shaped element for defining the reference point thereof. 
Preferably, the small circular-shaped element is formed from a reflective 
sheet. 
Yet further, each of the reference-point-forming elements may be formed as 
a circular-shaped plate element, a center of which defines one of the 
reference points. In this case, the circular-shaped plate element may be 
formed as a light-guide plate element including a core layer containing 
fluorescent substances. Preferably, the light-guide plate element may 
have: a cone-shaped recess formed at the center thereof for emitting 
light-rays therefrom; a polygonal-pyramidal-shaped recess formed at the 
center thereof for emitting fluorescent radiation therefrom; a 
hemispherical projection attached to the center thereof for emitting 
fluorescent radiation therefrom; or at least two V-shaped grooves formed 
therein, which extend radially from the center thereof, for emitting 
fluorescent radiation therefrom. 
In accordance with a fourth aspect of the present invention, there is 
provided a standard measurement scale, to be used in a photogrammetric 
measurement system, comprising: a frame member, and a light-guide plate 
member mounted on the frame member and including a core layer containing 
fluorescent substances, the light-guide plate member having at least three 
light-emitting spots for defining respective reference points. Preferably, 
the three reference points are equally spaced apart from each other by a 
predetermined distance. 
Each of the light-emitting spots may be defined as a cone-shaped recess or 
a polygonal-pyramidal-shaped recess formed in the light-guide plate member 
for omitting fluorescent radiation therefrom. Also, the light-emitting 
spot may be defined as a hemispherical projection attached to the 
light-guide plate member for emitting fluorescent radiation therefrom, or 
may be defined by at least two V-shaped grooves formed in the light-guide 
member and extending radially from the center thereof for emitting 
fluorescent radiation therefrom. 
In accordance with a fifth aspect of the present invention, there is 
provided a marker, to be used in a photogrammetric measurement system for 
defining a standard measurement scale, comprising a light-guide plate 
member including a core layer containing fluorescent substances and having 
a light emitting spot for defining a reference point. 
In accordance with a sixth aspect of the present invention, there is 
provided a marker, to be used in a photogrammetric measurement system for 
defining a standard measurement scale, comprising a 
polygonal-pyramidal-shaped optical assembly, formed from at least two 
light-guide plate elements, including each a core layer containing 
fluorescent substances, such that an apex of the 
polygonal-pyramidal-shaped optical assembly is defined by an emission of 
fluorescent radiation therefrom. 
The polygonal-pyramidal-shaped optical assembly may be produced as a 
generally-triangular-pyramidal-shaped optical assembly, from three 
isosceles-triangular light-guide plate elements, in such a manner that an 
inner triangular-pyramidal space is defined therewithin. Preferably, two 
contiguous slanting side faces of two adjacent isosceles-triangular 
light-guide plate elements form a V-shaped trough extending along a 
corresponding ridgeline of the inner triangular-pyramidal space, and the 
predominant emission of fluorescent radiation occurs from the side faces. 
Also, the polygonal-pyramidal-shaped optical assembly may be produced as a 
generally-quadrilateral-pyramidal-shaped optical assembly, by crosswisely 
interlinking two isosceles-triangular light-guide plate elements. 
Preferably, the predominant emission of fluorescent occurs the slanting 
side faces of each isosceles-triangular light-guide plate element. 
Preferably, each of the isosceles-triangular light-guide plate elements has 
a slit formed therein, whereby the light-guide plate elements are 
detachably and crosswisely interlinked via the slits formed therein. In 
this case, the isosceles-triangular light-guide plate elements preferably 
have the same isosceles-triangular shape.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 conceptually shows a photogrammetric measurement System, using a 
standard measurement scale 10, constructed according to the present 
invention. The standard measurement scale 10 is placed beside a cubic 
object 12 to be measured, and the standard scale 10 and the cubic object 
(three dimensional) 12 are photographed in two different directions by an 
electronic still video camera 14. Namely, as shown in FIG. 1, the standard 
scale 10 and the cubic object 12 are photographed by the camera 14 placed 
at a first photographing position M.sub.1, shown by a solid line, and are 
then photographed by the camera 14 placed at a second photographing 
position M.sub.2, shown by a dashed line. At the first photographing 
position M.sub.1, an optical axis of the camera 14 is indicated by 
reference O.sub.1, and, at the second photographing position M.sub.2, the 
optical axis of the camera 14 is indicated by reference O.sub.2. 
Note, each of the first and second photographing positions M.sub.1 and 
M.sub.2 may be defined as a back principal point of the photographing lens 
system of the camera 14. 
The standard measurement scale 10 is shaped as an equilateral-triangular 
plate member, and has three reference points P.sub.1, P.sub.2 and P.sub.3 
positioned in the vicinity of the apexes of the equilateral-triangular 
plate member, such that an equilateral triangle is defined by the 
reference points P.sub.1, P.sub.2 and P.sub.3, as shown by a hatched area 
in FIG. 1. The sides of the equilateral triangle, defined by the reference 
points P.sub.1, P.sub.2 and P.sub.3, have a length of L. 
FIG. 2 shows a first picture photographed by the camera 14 at the first 
photographing position M.sub.1. As is apparent from this drawing, a 
rectangular x.sub.1 -y.sub.1 coordinate system is defined on the first 
picture, and an origin c.sub.1 of the x.sub.1 -y.sub.1 coordinate system 
is at the photographing center of the first picture. In this coordinate 
system, the reference points P.sub.1, P.sub.2 and P.sub.3 are represented 
by coordinates p.sub.11 (px.sub.11, py.sub.11), p.sub.12 (px.sub.12, 
py.sub.12) and p.sub.13 (px.sub.13, Py.sub.13), respectively. 
FIG. 3 shows a second picture photographed by the camera 14 at the second 
photographing position M.sub.2. As is apparent from this drawing, a 
rectangular x.sub.2 -y.sub.2 coordinate system is defined on the second 
picture, and an origin c.sub.2 of the x.sub.2 -y.sub.2 coordinate system 
is at the photographing center of the second picture. In this coordinate 
system, the reference points P.sub.1, P.sub.2 and P.sub.3 are represented 
by coordinates p.sub.21 (px.sub.21, py.sub.21), p.sub.22 (px.sub.22, 
py.sub.22) and p.sub.23 (px.sub.23, py.sub.23), respectively. 
FIG. 4 shows a relative-positional three-dimensional relationship between 
the standard scale 10, the camera 14, and the first and second pictures. 
In this case, the standard scale 10 is relatively reproduced on the basis 
of the first and second pictures placed at the first and second 
photographing positions M.sub.1 and M.sub.2, but a size of the standard 
scale 10 is relative. Thus, a length of the sides of the equilateral 
triangle, defined by the reference points P.sub.1, P.sub.2 and P.sub.3, is 
indicated by L'. 
In order to calculate three-dimensional coordinates of the cubic object 12, 
it is necessary to define an X-Y-Z three-dimensional coordinate system, as 
shown in FIG. 4, and the reference points P.sub.1, P.sub.2 and P.sub.3 of 
the standard scale 10, recorded on each of the first and second pictures, 
must be positionally determined with respect to the three-dimensional 
coordinate system. 
As shown in FIG. 4, an origin of the three-dimensional coordinate system is 
at the first photographing position M.sub.1. Namely, the first 
photographing position M.sub.1 is represented by the origin coordinates 
(0, 0, 0) of the three-dimensional coordinate system. Also, a Z-axis of 
the three-dimensional coordinate system coincides with the optical axis 
O.sub.1 of the camera 14 placed at the first photographing position 
M.sub.1. The second photographing position M.sub.2 is represented by 
coordinates (X.sub.0, Y.sub.0, Z.sub.0), and the optical axis O.sub.2 of 
the camera 14, placed at the second photographing position M.sub.2, is 
represented by angular coordinates (.alpha., .beta., .gamma.). Namely, the 
optical axis O.sub.2 of the camera 14 defines angles of .alpha., .beta. 
and .gamma. with the X-axis, Y-axis and Z-axis of the three-dimensional 
coordinate system, respectively. 
The reference points P.sub.1, P.sub.2 and P.sub.3 of the standard scale 10 
are represented by three-dimensional coordinates P.sub.j (PX.sub.j, 
PY.sub.j, PZ.sub.j) (j=1, 2, 3). As shown in FIG. 4, each of the reference 
points [P.sub.1 (PX.sub.1, PY.sub.1, PZ.sub.1), P.sub.2 (PX.sub.2, 
PY.sub.2, PZ.sub.2) and P.sub.3 (PX.sub.3, PY.sub.3, PZ.sub.3)], the image 
point [p.sub.11 (px.sub.11, py.sub.11), p.sub.12 (px.sub.12, py.sub.12), 
p.sub.13 (px.sub.13, py.sub.13)] of the corresponding reference point 
recorded on the first picture, and the back principal point (M.sub.1) of 
the camera 14 are aligned with each other on a straight axis. Similarly, 
each of the reference points [P.sub.1 (PX.sub.1, PY.sub.1, PZ.sub.1), 
P.sub.2 (PX.sub.2, PY.sub.2, PZ.sub.2) and P.sub.3 (PX.sub.3, PY.sub.3, 
PZ.sub.3)], the image point [p.sub.21 (px.sub.21, py.sub.21), p.sub.22 
(px.sub.22, py.sub.22), p.sub.23 (px.sub.23, py.sub.23)] of the 
corresponding reference point recorded on the second picture, and the back 
principal point (M.sub.2) of the camera 14 are aligned with each other on 
a straight axis. 
Accordingly, the three-dimensional coordinates P.sub.j (PX.sub.j, PY.sub.j 
/PZ.sub.j) can be determined by the following collinear equations: 
##EQU1## 
Herein: 
a.sub.11 =cos .beta.*sin .gamma. 
a.sub.12 =-cos .beta.*sin .gamma. 
a.sub.13 =sin .beta. 
a.sub.21 =cos .alpha.*sin .gamma.+sin .alpha.*sin .beta.*cos .gamma. 
a.sub.22 =cos .alpha.*cos .gamma.+sin .alpha.*sin .beta.*sin .gamma. 
a.sub.23 =-sin .alpha.*sin .beta. 
a.sub.31 =sin .alpha.*sin .gamma.+cos .alpha.*sin .beta.*cos .gamma. 
a.sub.32 =sin +*cos .gamma.+cos .alpha.*sin .beta.*sin .gamma. 
a.sub.33 -cos .alpha.*cos .beta. 
Note that, in these equations, "C" indicates a principal focal length of 
the camera 14, which is defined as a distance between the back principal 
point (M.sub.1) and the photographing center (c.sub.1) of the first 
picture, and a distance between the back principal point (M.sub.2) and the 
photographing center (c.sub.2) of the second picture. Also note, "i" 
corresponds to a number of the pictures; and "j" corresponds to a number 
of the reference points P.sub.1, P.sub.2 and P.sub.3 of the standard scale 
10. 
FIG. 5 shows a flowchart for a photogrammetric 0measurement routine, in 
which a survey map is made on the basis of the first and second pictures, 
shown in FIGS. 2 and 3. This routine is executed by a computer (not 
shown). Before the execution of the routine, the video data of the first 
and second pictures is fed from the electronic still video camera 14 to 
the computer, and the first and second pictures are simultaneously 
displayed on a TV monitor connected to the computer, as shown in FIGS. 2 
and 3. 
At step 501, as coordinate data (X.sub.0, Y.sub.0, Z.sub.0) of the second 
photographing position M.sub.2 and as angular coordinate data (.alpha., 
.beta., .gamma.) of the optical axis O.sub.2, suitable initial values 
(except for zero) are inputted to the computer through, for example, a 
keyboard. Then, at step 502, the respective reference points P.sub.ij 
(px.sub.ij, py.sub.ij) are successively designated, on the first and 
second pictures displayed on the TV monitor, with a cursor manipulated by 
a mouse. Namely, the two sets of coordinates P.sub.11 (px.sub.11, 
py.sub.11) and P.sub.21 (px.sub.21, py.sub.21), the two sets of 
coordinates P.sub.12 (px.sub.12, py.sub.12) and P.sub.22 (px.sub.22, 
py.sub.22), and the two sets of coordinates P.sub.13 (px.sub.13, 
py.sub.13) and P.sub.23 (px.sub.23, py.sub.23) are retrieved by a central 
processing unit (CPU)or of the computer. 
After the designation of the reference points P.sub.ij (px.sub.ij, 
py.sub.ij) and P.sub.ij (px.sub.ij, py.sub.ij), at step 503, a counter k 
is made to be "1". Then, at setp 504, a suitable point Q.sub.1(k=1) of the 
cubic object 12 is selected, and image points q.sub.ik (FIGS. 2 and 3) of 
the point Q.sub.1, displayed on the first and second pictures of the TV 
monitor, are designated with the cursor manipulated by the mouse. Namely, 
the two sets of coordinates q.sub.11 (qx.sub.11, q.sub.11) and q.sub.21 
(q.sub.21, qy.sub.21) of the image point Q.sub.1 is retrieved by the 
central processor of the computer. 
At stop 505, the above-mentioned collinear equations are solved on the 
basis of the retrieved coordinates, and three-dimensional coordinates 
P.sub.j (PX.sub.j, PY.sub.j, PZ.sub.j of the reference points P.sub.1, 
P.sub.2 and P.sub.3, and three-dimensional coordinates Q.sub.1 (QX.sub.1, 
QY.sub.1, QZ.sub.1) of the object point Q.sub.1 are determined. Then, 
primary-approximate data of the three-dimensional coordinates (X.sub.0, 
Y.sub.0, Z.sub.0) of the second photographing position M.sub.2 and the 
angle coordinates (.alpha., .beta., .gamma.) of the optical axis O.sub.2 
are determined, i.e. the initial coordinate data (X.sub.0, Y.sub.0, 
Z.sub.0) and the initial angular coordinate data (.alpha., .beta., 
.gamma.), inputted at stop 501, are revised by the primary-approximate 
data. 
At step 506, a coefficient "m" is calculated as follows: 
EQU m=L/L' 
Note, "L" is the real length between the reference points P.sub.1, P.sub.2, 
and P.sub.3 and "L" is the relative length obtained from the determined 
three-dimensional coordinates P.sub.j (PX.sub.j, PY.sub.j, PZ.sub.j). 
At step 507, scaling is executed, using the coefficient "m", between the 
determined three-dimensional coordinates P.sub.j (PX.sub.j, PY.sub.j, 
PZ.sub.j) and Q.sub.1 (QX.sub.1, QY.sub.1, QZ.sub.1), so as to obtain a 
real spatial relationship therebetween. Then, at step 50B , the X-Y-Z 
three-dimensional coordinate system is transformed into an X'-Y'-Z' 
three-dimensional coordinate system defined as shown in FIG. 6. 
As is apparent from FIG. 6, an origin of the X'-Y'-Z' three-dimensional 
coordinate system is at the reference point P.sub.1, and the X'-axis 
thereof is defined by the reference points P.sub.1 and P.sub.2. Also, The 
X'- and Z'-axes of the coordinate system define a plane "Ps" which 
includes a hatched triangular plane area defined by the reference points 
P.sub.1, P.sub.2 and P.sub.3. Note, in the example of FIG. 6, although the 
origin of the X'-Y'-Z' three-dimensional coordinate system coincides with 
the reference point P.sub.1, the origin may be at any location included in 
the plane "Ps". 
At stop 509, for example, the X'-Z' plane or plane on which the reference 
points P.sub.1, P.sub.2 and P.sub.3 and the object point Q.sub.1 are 
recorded, is displayed as a survey map on another TV monitor. 
Nevertheless, the displayed survey map is not accurate, because the 
revised coordinate data (X.sub.0, Y.sub.0, Z.sub.0) and angular coordinate 
data (.alpha., .beta., .gamma.) are not sufficiently approximated. 
At step 510, it is determined whether or not another set of points q.sub.1k 
and q.sub.2k should be designated with respect to the cubic object 12. 
When the other set of points q.sub.1k and q.sub.2k should be further 
designated, i.e. when the renewed coordinate data (X.sub.0, Y.sub.0, 
Z.sub.0) and angular coordinate data (.alpha., .beta., .gamma.) are not 
sufficiently approximated, at step 511, the counter k is incremented by 
"1". Thereafter, the routine comprising steps 504 to 510 is again 
executed. 
At step 510, when a further set of points q.sub.1k and q.sub.2k should not 
be designated, i.e. when the renewed coordinate data (X.sub.0, Y.sub.0, 
Z.sub.0) and angular coordinate data (.alpha., .beta., .gamma.) are 
sufficiently approximated, this routine is completed. 
Before the approximation of the coordinate data (X.sub.0, Y.sub.0, Z.sub.0) 
and angular coordinate data (.alpha., .beta., .gamma.) is acceptable, it 
is necessary to designate at least two sets of points q.sub.1k and 
q.sub.2k with respect to the cubic object 12, i.e. the approximation 
calculation should be repeated at least twice. Preferably, more than two 
sets of object points q.sub.1k and q.sub.2k should be designated, i.e., 
the approximation calculation should be repeated more than twice. 
FIG. 7 shows a first embodiment of the standard measurement scale 10 
according to the present invention. In this embodiment, the standard 
measurement scale 10 comprises an equilateral-triangular plate 16, a 
thickness of which may be from about 2 mm to about 3 mm. Although it is 
preferable to form the triangular plate 16 of a suitable resin material, 
such as acrylic resin, the triangular plate 16 may be formed of another 
material, such as a wood, a suitable metal and so on. Three respective 
apexes 18, 20 and 22 of the triangular plate 16 define the points P.sub.1, 
P.sub.2 and P.sub.3 of the standard scale 10, and a distance between the 
reference points P.sub.1, P.sub.2 and P.sub.3 may be 1 m. 
Preferably, the small triangular area including each of the reference 
points P.sub.1, P.sub.2 and P.sub.3 is marked with a suitable material, 
such as a reflective paint, a fluorescent paint, a piece of reflective 
sheet and so on, because the reference points P.sub.1, P.sub.2 and P.sub.3 
are required to be conspicuously recorded on a photographed picture. Thus, 
the designation of the reference points P.sub.1, P.sub.2 and P.sub.3 with 
a cursor on a TV monitor, as mentioned above, can be easily carried out. 
FIG. 8 shows a second embodiment of the standard measurement scale 10 
according to the present invention. In this second embodiment, the 
standard measurement scale 10 comprises an equilateral-triangular frame 
24, and three respective projections 26, 28 and 30 securely mounted on the 
apex areas of the frame 24. The triangular frame 24 may be assembled from 
rectangular wood lumbers having, for example, a width of about 30 mm to 
about 50 mm and a thickness of about 50 mm. Of course, the frame 24 may be 
formed of another material such as a suitable resin, a suitable metal and 
so on. Similarly, the projections 26, 28 and 30 may be shaped from a wood, 
a suitable resin, a suitable metal and so on. 
In this embodiment, although each of the projections 26, 28 and 30 is 
formed as a quadrangular pyramid, each projection may be shaped into 
another form such as a circular cone, a triangular-based pyramid, a 
polygonal-base pyramid, a hemisphere or the like. Three respective apexes 
26A, 28A and 30A of the projections 26, 28 and 30 define the reference 
points P.sub.1, P.sub.2 and P.sub.3 of the standard scale 10, and a 
distance between the points P.sub.1, P.sub.2 and P.sub.3 may be 1 m. Note, 
each of the bottom sides of the quadrangular-pyramidal-shaped projection 
(26, 28, 30) may have a length of about 50 mm. 
In order to conspicuously record the reference points P.sub.1, P.sub.2 and 
P.sub.3, defined by the projections 26A, 28A and 30A, on a photographed 
picture, each of the projections 26, 28 and 30 may be coated with a 
reflective paint, a fluorescent paint or the like. Also, the surfaces of 
each projection 26, 28, 30 may be covered with a piece of reflective sheet 
and so on. 
FIG. 9 shows a third embodiment of the standard measurement scale 10 
according to the present invention. In this third embodiment, the standard 
measurement scale 10 comprises an equilateral-triangular frame 32, an 
equilateral triangular-plate 34 securely attached to the frame 32, and 
three respective projections 36, 38 and 40 securely mounted on the apex 
areas of the plate 34. The triangular frame 32 may be assembled from 
elongated wood boards, and the triangular plate 32 may be shaped from a 
wood board. Of course, the frame 32 and the plate 34 may be formed of 
another material such as a suitable resin, a suitable metal and so on. The 
projections 36, 38 and 40 may be made and shaped in substantially the same 
manner as the projections 26, 28 and 30 of the second embodiment. 
Similar to the second embodiment, three respective apexes 36A, 38A and 40A 
of the projections 36, 38 and 40 define the reference points P.sub.1, 
P.sub.2 and P.sub.3 of the standard measurement scale 10, and a distance 
between the points P.sub.1, P.sub.2 and P.sub.3 may be 1 m. Further, in 
order to conspicuously record the reference points P.sub.1, P.sub.2 and 
P.sub.3 on a photographed picture, each of the projections 36, 38 and 40 
also may be coated with a reflective paint, a fluorescent paint or the 
like, or the surfaces of each projection 36, 38, 40 may be covered with a 
piece of reflective sheet and so on. 
FIGS. 10 and 11 show a fourth embodiment of the standard measurement scale 
10, according to the present invention. In this fourth embodiment, the 
standard measurement scale 10 comprises an equilateral-triangular 
light-guide plate 42. Note, in FIG. 10, only an apex area of the 
triangular light-guide plate 42 is illustrated. 
As shown in FIG. 11, the light-guide plate 42 is constituted from a core 
layer 42A containing fluorescent substances uniformly distributed therein, 
a first clad layer 42B formed over an upper surface of the core layer 42A, 
and a second clad layer 42C formed over a lower surface of the core layer 
42A. In this embodiment, the core layer 42A is made of an acrylic resin 
material, and the first and second clad layers 42B and 42C are made of an 
acrylic resin material exhibiting an index of refraction smaller than that 
of the acrylic resin material of the core layer 42A. 
Although light rays, which become incident upon the clad layers 42B and 42C 
at a right angle with respect to the surfaces thereof, can pass through 
the light-guide plate 42, light rays, which become incident upon the clad 
layers 42B and 42C at a slanting angle with respect to surfaces thereof, 
are trapped in the light-guide plate 42. Also, light-rays, which become 
incident upon the core layer 42A via the peripheral side faces of the 
light-guide plate 42, cannot be substantially emitted from the core layer 
42A through the first and second clad layers 42B and 42C. 
When the fluorescent substances, contained in the core layers 42A, are 
subjected to the light rays, the fluorescent substances generate 
fluorescent radiation as visible light. The generated fluorescent 
radiation is trapped between the first and second clad layers 42B and 42C, 
i.e. the fluorescent radiation cannot be emitted from the core layer 42A 
through the first and second clad layers 42B and 42C. Note, of course, the 
fluorescent radiation can be emitted from the peripheral side faces of the 
plate 42. 
As representatively shown in FIGS. 10 and 11, three small cone-shaped 
recesses 44 are respectively formed at the apex areas of the upper surface 
of the light-guide plate 42, and define the reference points P.sub.1, 
P.sub.2 and P.sub.3 of the standard scale 10, where a distance between the 
points P.sub.1, P.sub.2 and P.sub.3 may be 1 m. As best shown in FIG. 11, 
each of the cone-shaped recesses 44 penetrates the core layer 42A, so that 
a part of the fluorescent radiation is emitted from each of the 
cone-shaped recesses 44. Thus, when the standard scale 10 of the fourth 
embodiment is photographed by the camera 14, the reference points P.sub.1, 
P.sub.2 and P.sub.3. which are defined by the cone-shaped recesses 44, are 
conspicuously recorded on a photographed picture. 
Note, in the fourth embodiment, it should be understood that 
polygonal-pyramidal-shaped recesses such as triangular-pyramidal-shaped 
recesses, quadrangular-pyramidal-shaped recesses, or the like, may be 
substituted for the cone-shaped recesses 44. 
FIG. 12 shows a fifth embodiment of the standard measurement scale 10, 
according to the present invention. Note, in this drawing, only an apex 
area of the standard plate 10 is illustrated. The fifth embodiment is 
substantially similar to the third embodiment (FIG. 9), except that three 
pieces of reflective sheet 46 are respectively substituted for the 
projections 36, 38 and 40 for defining the reference points P.sub.1, 
P.sub.2 and P.sub.3. Of course, the reflective pieces 46, defining the 
reference points P.sub.1, P.sub.2 and P.sub.3, are conspicuously recorded 
on a photographed picture due to the reflectivity thereof. 
FIGS. 13 and 14 show a sixth embodiment of the standard measurement scale 
10, according to the present invention. Note, in this drawing, only an 
apex area of the standard plate 10 is illustrated. This sixth embodiment 
also is substantially similar to the third embodiment (FIG. 9), except 
that three hemispherical lenses 48 are respectively substituted for the 
projections 36, 38 and 40 for defining the reference points P.sub.1, 
P.sub.2 and P.sub.3 of the standard scale 10. 
In the sixth embodiment, each of the hemispherical lenses 48 is associated 
with an electrical light source 50, such as an electrical lamp, a light 
emitting diode (LED) or the like. As shown in FIG. 14, the electrical 
light source 50 is connected to an electric power source 52 through an 
ON/OFF switch 54. When the switch is turned ON, the light source 50 is 
electrically energized by the power source 52, resulting in emitting light 
rays from the light source 50 The light rays are radiated in all 
directions from the hemispherical lens 48. Accordingly, the hemispherical 
lenses 48, defining the reference points P.sub.1, P.sub.2 and P.sub.3, are 
conspicuously recorded on a photographed picture due to the omission of 
the light rays from the light source 50. 
FIGS. 15 and 16 show a seventh embodiment of the standard measurement scale 
10, according to the present invention. Note, in FIG. 15, only an apex 
area of the standard plate 10 is illustrated. This seventh embodiment also 
is similar to the third embodiment (FIG. 9), except that three 
generally-triangular-pyramidal-shaped optical projections 56 are 
respectively substituted for the protections 36, 38 and 40 for defining 
the reference points P.sub.1, P.sub.2 and P.sub.3 of the standard scale. 
In the seventh embodiment, each of the optical projections 56 comprises 
three isosceles-triangular light-guide plate elements 58 having, for 
example, a thickness of about 2 mm, a bottom length of about 50 mm, and a 
height of about 50 mm. Each of the light-guide plate elements 58 has the 
same optical structure as the light-guide plate 42 of the fourth 
embodiment (FIGS. 10 and 11). Namely, the light-guide plate element 58 is 
constituted from a core layer containing fluorescent substances uniformly 
distributed therein, a first clad layer formed over an upper surface of 
the core layer, and a second clad layer formed over a lower surface of the 
core layer. The core layer is made of an acrylic resin material, and the 
first and second clad layers are made of an acrylic resin material 
exhibiting an index of refraction smaller than that of the acrylic resin 
material of the core layer. 
Each of the optical projections 56 is assembled from the three light-guide 
plate elements 58, in such a manner that an inner triangular-pyramidal 
space is defined therewithin. As best shown in FIG. 16, two contiguous 
side faces 58A of two adjacent light-guide plate elements 58 form a 
V-shaped trough extending along a corresponding ridgeline of the inner 
triangular-pyramidal space, and an apex 58B of the inner 
triangular-pyramidal space defines one of the reference points P.sub.1, 
P.sub.2 and P.sub.3. 
The fluorescent radiation, generated and trapped in the core layer of each 
light-guide plate element 58, cannot be substantially emitted from a 
triangular surface 58C thereof, but a part of the fluorescent radiation 
can be emitted from the side faces 58A thereof. Thus, the V-shaped troughs 
of the optical projection 56 are conspicuously recorded on a photographed 
picture, whereby the convergent canter 58B of the V-shaped troughs can be 
easily located from the photographed picture. 
FIGS. 17, 18 and 19 show an eighth embodiment of the standard measurement 
scale 10, according to the present invention. Note, in FIG. 17, only an 
apex area of the standard plate 10 is illustrated. This eighth embodiment 
also is substantially similar to the third embodiment (FIG. 9), except 
that three generally-quadrilateral-pyramidal-shaped optical projections 60 
are respectively substituted for the projections 36, 38 and 40 for 
defining the reference points P.sub.1, P.sub.2 and P.sub.3 of the standard 
scale. 
In the eighth embodiment, each of the optical projections 60 comprises two 
isosceles-triangular light-guide plate elements 62 and 64 having each a 
thickness of about 2 mm. Each of the light-guide plate elements 62 and 64 
has the same optical structure as the light-guide plate 42 of the fourth 
embodiment (FIGS. 10 and 11). Namely, each of the light-guide plate 
elements 62 and 64 is constituted from a core layer containing fluorescent 
substances uniformly distributed therein, a first clad layer formed over 
an upper surface of the core layer, and a second clad layer formed over a 
lower surface of the core layer. The core layer is made of an acrylic 
resin material, and the first and second clad layers are made of an 
acrylic resin material exhibiting an index of refraction smaller than that 
of the acrylic resin material of the core layer. 
The optical projection 60 is assembled from the two light-guide plate 
elements 62 and 64 into the generally-quadrilateral-pyramidal-shape, as 
shown FIGS. 17 and 18. To this end, as shown in FIG. 19, the light-guide 
plate element 62 has an upper half slit 62A formed therein and extended 
from the apex thereof to the middle position of the height thereof, and 
the light-guide plate element 64 has a lower half slit 64A, formed therein 
and extended from the center of the bottom side thereof to the middle 
position of the height thereof. Thus, the 
generally-quadrilateral-pyramidal-shaped projection 60 is obtained from 
the light-guide plate elements 62 and 64 by crosswisely interlinking them 
via the upper and lower half slits 62A and 64A. Note, a width of each of 
the slit 62A and 64A is approximately 2 mm, which is equal to the 
thickness of the light-guide plate elements 62 and 64. 
As shown in FIGS. 17 and 18, an apex of the light-guide plate element 64 is 
shaped as a small square area 65, which defines one of the reference 
points P.sub.1, P.sub.2 and P.sub.3 of the standard scale 10. 
A part of the fluorescent radiation, generated and trapped in the core 
layer of each light-guide plate element (62, 64), is predominantly emitted 
from the slanting side faces (62B, 64B) thereof, but the fluorescent 
radiation cannot be substantially emitted from the triangular surfaces 
62C, 64C thereof. Thus, the slanting side faces 62B and 64B of the 
light-guide plate elements 62 and 64 are conspicuously recorded on a 
photographed picture, whereby the apex or small square area 65 of each 
optical projection 60 can be easily located from the photographed picture. 
FIGS. 20, 21 and 22 show a ninth embodiment of the standard measurement 
scale 10, according to the present invention. Note, in FIG. 20, only an 
apex area of the standard measurement plate 10 is illustrated. This ninth 
embodiment also is substantially similar to the third embodiment (FIG. 9), 
except that three cross-shaped optical projections 66 are respectively 
substituted for the projections 36, 38 and 40 for defining the reference 
points P.sub.1, P.sub.2 and P.sub.3 of the standard measurement scale 10. 
In the ninth embodiment, each of the cross-shaped optical projections 66 
comprises two parallelepiped-shaped light-guide plate elements 68 and 70 
having each a suitable thickness. Each of the light-guide plate elements 
68 and 70 has the same optical structure as the light-guide plate 42 of 
the fourth embodiment (FIGS. 10 and 11). Namely, each of the light-guide 
plate elements 68 and 70 is constituted from a core layer containing 
fluorescent substances uniformly distributed therein, a first clad layer 
formed over an upper surface of the core layer, and a second clad layer 
formed over a lower surface of the core layer. The core layer is made of 
an acrylic resin material, and the first and second clad layers are made 
of an acrylic resin material exhibiting an index of refraction smaller 
than that of the acrylic resin material of the core layer. 
The optical projection 66 is assembled from the two light-guide plate 
elements 68 and 70 into the cross-shape, as shown FIGS. 20 and 21. To this 
end, as shown in FIG. 22, the light-guide plate element 68 has an upper 
half slit 68A, formed therein and extended from the center of the top side 
thereof to the middle position of the width thereof, and the light-guide 
plate element 70 has a lower half slit 70A, formed therein and extended 
from the center of the bottom side thereof to the middle position of 
the-width thereof. Thus, the cross-shaped projection 66 is obtained from 
the light-guide plate elements 68 and 70 by crosswisely interlinking them 
via the upper and lower half slits 68A and 70A. Note, a thickness of each 
slit 6&A, 70A is equal to each other. Note, a width of each of the slit 
68A and 70A is equal to the thickness of the light-guide plate elements 68 
and 70. 
As shown in FIGS. 20 and 21, a central area 72 of the light-guide plate 
element 70 defines one of the reference points P.sub.1, P.sub.2 and 
P.sub.3 of the standard measurement scale 10. 
A part of the fluorescent radiation, generated and trapped in the 
light-guide plate elements 68 and 70, can be predominately emitted from 
only the top side face 68B and 70B and end side faces 68C and 70C thereof, 
but the fluorescent radiation cannot be substantially emitted from the 
side wall surfaces 68D and 70D thereof. Thus, the top side faces 68B and 
70B and the end side faces 68C and 70C of the light-guide plate elements 
68 and 70 are conspicuously recorded on a photographed picture, and the 
central area 72 of the light-guide plate element 70 can be easily located 
from the photographed picture. 
In the ninth embodiment, preferably, the two light-guide plate elements 68 
and 70 are identical to each other. Namely, only one kind of light-guide 
plate elements (68, 70) is produced, and the cross-shaped optical 
projection 66 is obtained from two light-guide plate elements by 
interlinking them crosswise via the slits thereof. Accordingly, the 
cross-shaped optical projection 66 can be obtained at a low cost. 
FIGS. 23 and 24 show a tenth embodiment of the standard measurement scale 
10, according to the present invention. This tenth embodiment also is 
substantially similar to the third embodiment (FIG. 9), except that three 
circular-shaped light-guide plate elements 74 are respectively substituted 
for the projections 36, 38 and 40 for defining the reference points 
P.sub.1, P.sub.2 and P.sub.3 of the standard measurement scale 10. 
In the tenth embodiment, each of the circular-shaped light-guide plate 
elements 74 has the same optical structure as the light-guide plate 42 of 
the fourth embodiment (FIGS. 10 and 11). Namely, each of the light-guide 
plate elements 74 is constituted from a core layer containing fluorescent 
substances uniformly distributed therein, a first clad layer formed over 
an upper surface of the core layer, and a second clad layer formed over a 
lower surface of the core layer. The core layer is made of an acrylic 
resin material, and the first and second clad layers are made of an 
acrylic resin material exhibiting an index of refraction smaller than that 
of the acrylic resin material of the core layer. Note, for example, the 
light-guide plate element 74 has a diameter of about 100 mm and a 
thickness of abut 50 mm. 
As best shown in FIG. 24, each of the light-guide plate elements 74 has a 
hemispherical projection 76 attached to and placed at the center thereof, 
and the three projections 76 define the reference points P.sub.1, P.sub.2 
and P.sub.3 of the standard measurement scale 10. 
Each of the projections 76 may be formed of a suitable transparent resin 
material, having an index of refraction different from that of the clad 
layers of the light-guide plate element 74 or that of air, so that a part 
of the fluorescent radiation, generated and trapped in the core layer of 
the light-guide plate element 74, is emitted from the projection 76. Of 
course, another part of the fluorescent radiation can be emitted from the 
peripheral side face of the light-guide plate element 74, but the 
fluorescent radiation cannot be emitted from the circular surface 78 (FIG. 
24) of the plate element 74. Accordingly, the three hemispherical 
projections 76 of the plate elements 74 defining the reference points 
P.sub.1, P.sub.2 and P.sub.3 of the standard measurement scale 10, are 
conspicuously recorded on a photographed picture. 
Preferably, the hemispherical projection 76 is formed of a transparent 
plastic material exhibiting softness, so that the hemispherical projection 
76 can be detachably adhered to the center of the light-guide plate 
element 74, due to the softness of the projection 76. 
FIG. 25 shows a modification of the circular-shaped light-guide plate 
element 74. In this modification, eight V-shaped grooves 80 are formed in 
the light-guide plate element 74, so as to radially extend from the center 
thereof. Each of the V-shaped grooves 80 has a width of about 2 mm, and 
penetrates the core layer of the light-guide plate element 74, so that a 
part of the fluorescent radiation is predominantly emitted from the 
grooves 80. Of course, the convergent center of the grooves 80 defines one 
of the reference points P.sub.1, P.sub.2 and P.sub.3 of the standard 
measurement scale 10. 
FIG. 26 shows another modification of the circular-shaped light-guide plate 
element 74. In this modification, a cone-shaped recess 82 is formed in the 
light-guide plate element 74, at the center thereof, and the cone-shaped 
recess 82 has a diameter of about 6 mm and a depth of about 3 mm, 
penetrating the core layer of the light-guide plate element 74, so that a 
part of the fluorescent radiation can be emitted from the cone-shaped 
recess 82. Of course, the center of the recess 82 defines one of the 
reference points P.sub.1, P.sub.2 and P.sub.3 of the standard measurement 
scale 10. 
FIG. 27 shows an eleventh embodiment of the standard measurement scale 10, 
according to the present invention. In this eleventh embodiment, the 
standard measurement scale 10 comprises an equilateral-triangular frame 
84, and an equilateral-triangular light-guide plate 86, securely attached 
to the frame 84. The triangular frame 84 may be assembled in the same 
manner as the triangular frame 32 of the third embodiment (FIG. 9). The 
equilateral-triangular light-guide plate 86 has the same optical structure 
as the light-guide plate 42 of the fourth embodiment (FIGS. 10 and 11). 
Namely, the light-guide plate 86 is constituted from a core layer 
containing fluorescent substances uniformly distributed therein, a first 
clad layer formed over an upper surface of the core layer, and a second 
clad layer formed over a lower surface of the core layer. The core layer 
is made of an acrylic resin material, and the first and second clad layers 
are made of an acrylic resin material exhibiting an index of refraction 
smaller than that of the acrylic resin material of the core layer. 
As shown in FIG. 27, three small hemispherical projections 88 are 
respectively attached to the apex areas of the upper surface of the 
light-guide plate 86, which define the reference points P.sub.1, P.sub.2 
and P.sub.3 of the standard measurement scale 10, where a distance between 
the points P.sub.1, P.sub.2 and P.sub.3 may be 1 m. 
Similar to the projection 76 of the tenth embodiment (FIG. 24), the 
projection 88 may be formed of a suitable transparent resin material, 
having an index of refraction different from that of the clad layers of 
the light-guide plate 86, so that a part of the fluorescent radiation, 
generated and trapped by the light-guide plate 86, is predominantly 
emitted from the projections 88. Of course, another part of the 
fluorescent radiation can be emitted from the peripheral side faces of the 
light-guide plate 86, but the fluorescent radiation cannot be 
substantially emitted from the upper and lower surfaces of the light-guide 
plate 86. Accordingly, the three hemispherical projections 88 of the 
light-guide plate 86, defining the reference points P.sub.1, P.sub.2 and 
P.sub.3 of the standard measurement scale 10, are conspicuously recorded 
on a photographed picture. 
In the eleventh embodiment, each of the hemispherical projections 88 may be 
formed of a transparent soft plastic material exhibiting softness, so that 
each projection 88 can be detachably adhered to the light-guide plate 86, 
due to the softness of the projection 88. 
FIG. 28 conceptually shows a stereo-photogrammetric measurement system, 
using markers for defining a standard measurement scale, constructed 
according to the present invention. In this drawing, an intersection 
point, at which a traffic accident has occurred, is illustrated. Two 
cameras "L" and "R" are positioned at a suitable location, so as to be 
spaced apart from each other by a predetermined distance of d. Two 
respective broken lines, indicated by references "l" and "r", are optical 
axes of the cameras "L" and "R". The camera "L" has an angle of view 
indicated by reference .theta..sub.1, and the camera "R" has an angle of 
view indicated by reference .theta..sub.2. 
As shown in FIG. 28, a photographing area of the camera "L" is defined by 
the view angle of .theta..sub.1, and a photographing area of the camera 
"R" is defined by the view angle of .theta..sub.2. The photographing areas 
of the camera "L" and "R" overlap with each other, as shown by a hatched 
area in FIG. 28. This hatched area or overlapped area is used in the 
stereo-photogrammetric measurement. Then, the standard-scale-defining 
markers must be positioned within the overlapped area. Namely, as shown in 
FIG. 28, for example, the standard-scale-defining markers are positioned 
at locations A and B, and a distance between the markers, at the locations 
A and B, is meausured. 
FIGS. 29, 30 and 31 show a first embodiment of the marker for defining a 
standard measurement scale, according to the present invention. The marker 
comprises a circular-shaped light-guide plate 90 having a diameter of 
about 100 mm, and a hemispherical projection 92 placed at the center of 
the light-guide plate 90. In the stereo-photogrammetric measurement, as 
shown in FIG. 28, the two markers are prepared, and are positioned at the 
locations A and B, respectively, such that the hemispherical projection 92 
of each marker coincides with an indication marked at the location (A, B). 
Namely, the hemispherical projection 92 of the marker serves as a 
reference point for defining the standard measurement scale. 
As shown in FIG. 31, the light-guide plate 90 is constituted from a core 
layer 90A containing fluorescent substances uniformly distributed therein, 
a first clad layer 90B formed over an upper surface of the core layer 90A, 
and a second clad layer 90C formed over a lower surface of the core layer 
90A. In this embodiment, the core layer 90A is made of an acrylic resin 
material, and the first and second clad layers 90B and 90C are made of an 
acrylic resin material exhibiting an index of refraction smaller than that 
of the acrylic resin material of the core layer 90A. Namely, the 
light-guide plate 90 has the same optical structure as the light-guide 
plate 42 shown in FIGS. 10 and 11. 
On the other hand, the hemispherical projection 92 may be formed of a 
suitable transparent resin material, having an index of refraction 
different from that of the clad layers 90B and 90C of the light-guide 
plate 90 or that of air, so that a part of the fluorescent radiation, 
generated and trapped in the core layer 90A is predominantly emitted from 
the projection 92. Note, another part of the fluorescent radiation can be 
emitted from the peripheral side face of the light-guide plate 90, but the 
fluorescent radiation cannot be substantially emitted from the first and 
second clad layers 90B and 90C of the light-guide plate 90. Accordingly, 
the hemispherical projection 92 of the marker is conspicuously recorded on 
a photographed picture. Namely, the designation of the hemispherical 
projection or reference point 92 of the marker, with a cursor on a TV 
monitor, can be easily carried out. 
Further, the marker comprising the light-guide plate 90 can be easily 
positioned, such that the reference point 92 thereof exactly coincides 
with the indication marked at the location (A, B) due to the flatness of 
the marker or light-guide plate 90 and the transparency of the marker per 
se. 
In the first embodiment of the maker according to the present invention, 
the hemispherical projection 92 may be formed of a transparent plastic 
material exhibiting softness, so that the projections 92 can be detachably 
adhered to the light-guide plate 90, due to the softness of the 
projection. 92. 
FIGS. 32 and 33 show a second embodiment of the marker for defining a 
standard measurement scale, according to the present invention. This 
marker also comprises a circular-shaped light-guide plate 94 having the 
same optical structure of the light-guide plate 90 of the first embodiment 
(FIGS. 29, 30 and 31). Namely, as shown in FIG. 33, the light-guide plate 
94 is constituted from a core layer 94A containing fluorescent substances 
uniformly distributed therein, a first clad layer 94B, formed over an 
upper surface of the core layer 94A, and a second clad layer 94C, formed 
over a lower surface of the core layer 94A. 
In the second embodiment, the marker features a cone- shaped recess 96, 
formed at the center of the upper surface of the light-guide plate 94. As 
best shown in FIG. 33, the cone-shaped recess 96 penetrates the core layer 
94A, so that a part of the fluorescent radiation is emitted from the 
cone-shaped recess 96. of course, the cone-shaped recess 96 of the marker 
serves as a reference point for defining the standard measurement scale. 
Similar to the first embodiment of the marker (FIGS. 29, 30 and 31), the 
cone-shaped recess 96 of the marker is conspicuously recorded on a 
photographed picture due to the emission of fluorescent radiation 
therefrom. Also, the marker comprising the light-guide plate 94 can be 
easily positioned, such that the reference point 96 thereof exactly 
coincides with the indication marked at the location (A, B), due to the 
flatness of the marker or light-guide plate 94 and the transparency of the 
marker per se. 
FIGS. 34, 35 and 36 show a third embodiment of the marker for defining a 
standard measurement scale, according to the present invention. This 
marker also comprises a circular-shaped light-guide plate 98, having the 
same optical structure as the light-guide plate 90 of the first embodiment 
(FIGS. 29, 30 and 31). Namely, as shown in FIG. 36, the light-guide plate 
98 is constituted from a core layer 98A containing fluorescent substances 
uniformly distributed therein, a first clad layer 98B, formed over an 
upper surface of the core layer 98A, and a second clad layer 98C, formed 
over a lower surface of the core layer 98A. 
In the third embodiment, as best shown in FIG. 35, the marker features 
eight V-shaped grooves 100, formed in an upper surface of the light-guide 
plate 98, radially extending from the center 102 thereof. Each of the 
V-shaped grooves 100 penetrates in the core layer 98A of the light-guide 
plate 96, as shown in FIG. 36, so that a part of the fluorescent radiation 
is predominantly emitted from the V-shaped grooves 100. The convergent 
center 102 of the eight V-shaped grooves 100 serves as a reference point 
for defining the standard measurement scale. 
Similar to the first and second embodiments of the marker (FIGS. 29, 30 and 
31; and FIGS. 32 and 34), the V-shaped grooves 100 of the marker are 
conspicuously recorded on a photographed picture due to the emission of 
fluorescent radiation therefrom. Also, the marker comprising the 
light-guide plate 100 can be easily positioned, such that the center or 
reference point 102 thereof exactly coincides with the indication marked 
at the location (A, B) due to the flatness of the marker or light-guide 
plate 98 and the transparency of the marker per se. 
FIGS. 37 and 38 show a fourth embodiment of the marker for defining a 
standard measurement scale, according to the present invention. This 
marker comprises a generally-triangular-pyramidal-shaped optical assembly 
104, constructed from three isosceles-triangular light-guide plate 
elements 106, a bottom side of which may have a length of about 100 mm. 
Each of the light-guide plate elements 106 has the same optical structure 
as the light-guide plate 90 of the first embodiment (FIGS. 29, 30, and 
31). Namely, each of the light-guide plate elements 106 is constituted 
from a core layer containing fluorescent substances uniformly distributed 
therein, a first clad layer formed over an upper surface of the core 
layer, and a second clad layer formed over a lower surface of the core 
layer. 
The generally-triangular-pyramidal-shaped optical assembly 104 is assembled 
from the three light-guide plate elements 106 in such a manner that an 
inner triangular-pyramid space is defined therewithin. As best shown in 
FIG. 38, two contiguous slanting side faces 106A of two adjacent 
light-guide plate elements 106 form a V-shaped trough extending along a 
corresponding ridgeline of the inner triangular-pyramid space, and an apex 
106B of the inner triangular-pyramidal space serves as a reference point 
for defining a standard measurement scale. 
The fluorescent radiation, generated and trapped in the core layer of each 
light-guide plate element 106, cannot be substantially emitted from a 
triangular surface 106C thereof, but a part of the fluorescent radiation 
can be emitted from the side faces 106B thereof. Thus, the V-shaped 
troughs of the optical assembly 104 are conspicuously recorded on a 
photographed picture, due to the predominant emission of fluorescent 
radiation therefrom, whereby the center 106B of the V-shaped troughs can 
be easily located from the photographed picture. Also, the marker 
comprising the optical assembly 104 can be easily positioned, such that 
the apex or reference point 106B thereof exactly coincides with the 
indication marked at the location (A, B) due to the transparency of the 
marker per se. 
FIGS. 39, 40, and 41 show a fifth embodiment of the marker for defining a 
standard measurement scale, according to the present invention. This 
marker comprises a generally-quadrilateral-pyramidal-shaped optical 
assembly 108 constructed from two isosceles-triangular light-guide plate 
elements 110 and 112, a bottom side of which may have a length of about 
100 mm. Each of the light-guide plate elements 110 and 112 has the same 
optical structure as the light-guide plate 90 of the first embodiment 
(FIGS. 29, 30, and 31). Namely, each of the light-guide plate elements 110 
and 112 is constituted from a core layer containing fluorescent substances 
uniformly distributed therein, a first clad layer formed over an upper 
surface of the core layer, and a second clad layer formed over a lower 
surface of the core layer. 
The optical assembly 108 is assembled from the two light-guide plate 
elements 110 and 112 into the generally-quadrilateral-pyramidal-shape as 
shown FIGS. 39 and 40. To this end, as shown in FIG. 41, the light-guide 
plate element 110 has a lower half slit 110A, formed therein and extended 
from the center of the bottom side thereof to the middle position of the 
height thereof, and the light-guide plate element 112 has an upper half 
slit 112A, formed therein and extended from the apex thereof to the middle 
position of the height thereof. Thus, the 
generally-quadrilateral-pyramidal-shaped optical assembly 108 is obtained 
from the light-guide plate elements 110 and 112 by crosswisely 
interlinking them via the lower and upper half slits 110A and 112A. Note, 
of course, a width of each slit 110A and 112A is equal to the thickness of 
the light-guide plate element 110, 112. 
As is apparent from FIGS. 39, 40 and 41, an apex of the light-guide plate 
element 110 is shaped as a small square area 114, which serves as a 
reference point for defining a standard measurement scale. 
A part of the fluorescent radiation, generated and trapped in the core 
layer of each light-guide plate element (110, 112), are predominantly 
emitted from both slanting side faces (110B, 112B) thereof, but the 
fluorescent radiation cannot be substantially emitted from both triangular 
surfaces (110C, 112C) thereof. Thus, the slanting side faces 110B and 110B 
of the light-guide plate elements 110 and 112 are conspicuously recorded 
on a photographed picture, whereby the apex or small squar area 114 of the 
optical assembly 108 can be easily located from the photographed picture. 
Also, the marker comprising the optical assembly 108 can be easily 
positioned, such that the apex or reference point 114 thereof exactly 
coincides with the indication marked at the location (A, B) due to the 
transparency of the marker per se. 
In the fifth embodiment of the marker shown in FIGS. 39, 40 and 41, it is 
preferable to detachably and crosswisely interlink the light-guide plate 
elements 110 and 112, because the disassembled light-guide plate elements 
110 and 112 can be compactly stored, and can be carried without bulkiness. 
Finally, it will be understood by those skilled in the art that the 
foregoing description is of preferred embodiments of the device and 
assembly, and that various changes and modifications may be made to the 
present invention without departing from the spirit and scope thereof. 
The present disclosure relates to subject matter contained in Japanese 
Patent Applications No. 8-310029 (filed on Nov. 6, 1996), No. 8-310030 
(filed on Nov. 6, 1996), and No. 9-276546 (filed on Sep. 24, 1997) which 
are expressly incorporated herein, by reference, in their entireties.