Optical sensor with concave mirror

An optical sensor includes a sensor section provided in a secured manner and including a light emitting element and a light receiving element located opposed to the light emitting element; and a reflective body connected to an operation section and movable with respect to the sensor section. The reflective body is a concave mirror for guiding light from the light emitting element to the light receiving element.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an optical sensor preferably used in an 
input device for moving a pointer or the like on a screen of a personal 
computer or the like or in an input device for an electronic game machine, 
and more specifically relates to a one-dimensional or a two-dimensional 
optical sensor for sensing the movement of a control arm section 
maneuvered by the operator in a wide range of angles with a high 
resolution. 
2. Description of the Related Art 
Conventional pointing devices as an input device for moving the pointer on 
the screen of a computer or the like include a joystick and a button type 
pointing device. 
FIG. 17 is an isometric view of a conventional joystick 8. When a stick or 
control arm 1 moves in an X direction, the movement of the stick 1 is 
conveyed via a guide 2 and a shaft 3 to a rotary encoder 4 for detecting a 
rotation direction and a rotation distance. Based on a detection signal 
from the rotary encoder 4, the rotation direction and the rotation 
distance of the stick 1 in the X direction are detected. Also, a movement 
of the stick 1 in a Y direction is conveyed to a rotary encoder 7 via a 
guide 5 and a shaft 6. Based on a detection signal from the rotary encoder 
7, the rotation direction and the rotation distance of the stick 1 in the 
Y direction are detected. 
With reference to FIGS. 18A and 18B, the principle by which the rotary 
encoders 4 and 7 detect the rotation direction and the rotation distance 
will be described. When a shaft 11 rotates in association with the 
movement of the stick 1, a rotatable plate or disk 12 connected to the 
shaft 11 rotates. The rotatable plate 12 has a plurality of slits 13 
formed radially. The rotatable plate 12 is interposed between two light 
emitting elements 9 and two light receiving elements 10. Light emitted 
from the light emitting elements 9 is transmitted through the slits 13 as 
a pulse signal which is converted into an electric signal by the light 
receiving elements 10. As a result, the rotation direction and the 
rotation distance of the stick 1 in the X and Y directions in accordance 
with the counts of the pulse signal are electrically detected. 
On the screen of the computer which includes the joystick 8 as a part of 
the input device, the pointer moves in accordance with the electric signal 
which indicates the rotation direction and the rotation distance of the 
stick 1 in the X and Y directions. 
FIG. 19 shows a conventional button type pointing device 20 usable as an 
input device. The button type pointing device 20 includes a button-shape 
tiltable operation section 18, a holder 20a provided below the operation 
section 18, a base plate 16 supporting the holder 20a from a bottom 
surface of the holder 20a, and a sensor section 15 attached to a bottom 
surface of the base plate 16. The holder 20a includes an elastic section 
17 provided below the operation section 18 and having a depression for 
attachment of a reflective body in a central part of a bottom surface 
thereof, and a reflective body 19 provided in the depression. The elastic 
section 17 and the reflective body 19 are formed integrally. 
In the button type pointing device 20 having the above-described structure, 
when the operation section 18 is inclined, the elastic section 17 is 
elastically deformed. The reflective body 19 formed on the elastic section 
17 is also inclined in the same direction, and the inclination of the 
reflective body 19 is detected by the sensor section 15. A detection 
signal output by the sensor section 15 is converted into an electric 
signal and output. In accordance with the electric signal, the pointer on 
the screen moves. 
FIG. 20 is an enlarged view of the sensor section 15. The sensor section 15 
is an optical sensor including a light emitting element 15a and light 
receiving elements 15b provided above the light emitting element 15a. A 
lens 22 is provided above the light receiving elements 15b. In FIG. 20, 
reference numeral 23 denotes a secondary mold. 
The conventional joystick 8 involves the following drawbacks when being 
used in an input device. 
(1) The rotary encoders 4 and 7 each include the rotatable shaft 11. A 
space for accommodating the rotation of the shaft 11 needs to be provided, 
and thus it is difficult to completely seal the rotary encoders 4 and 7. 
This provides easy access for dust, which may undesirably clog the slits 
13. Accordingly, malfunctions can occur relatively easily and thus the 
reliability is not sufficient. 
(2) Since the number of the slits 13 which can be formed in the rotatable 
disk 12 is limited, the resolution for sensing is also limited. 
(3) Two-dimensional detection of the movement of the stick 1 requires 
provision of rotary encoders in both the X and Y directions. Such an 
increase in the number of components hampers the size reduction of the 
apparatus including the joystick 1, and is also against space-saving. 
The conventional button type pointing device 20 has the following drawbacks 
when being used in an input device. 
(1) Due to the use of the sensor section 15 which does not require a 
rotatable shaft, the button type pointing device 20 can be sealed and thus 
is substantially free of malfunction caused by dust, like in the case of 
the joystick 1. However, the button type pointing device 20 has a 
relatively narrow range of detection angles of .+-.10 degrees due to the 
structure thereof and cannot perform wide-range sensing. Since the 
reflective body 19 is a plane mirror, when the angle of inclination of the 
reflective body 19 in association with the operation section 18 is 
excessively large, the light reflected by the reflective body 19 is not 
effectively guided to the light receiving elements 15b. 
In the case of the button type pointing device 20 which is used in an input 
device of a game machine, the operation section 18 needs to be movable 
over a wide range of angles so as to increase the fun of playing, 
especially for young children. 
In the conventional button type pointing device 20 which cannot provide a 
satisfactory level of wide-range sensing, the operability of the operation 
section 18 is also restricted. Improvement on this point is required in 
order to provide a more satisfactory input device for a game machine. 
(2) The sensor section 15 requires a lens 22 such as an objective lens for 
collecting light and also requires the secondary mold 23. Such additional 
elements unavoidably increase the thickness of the sensor section 15 as 
indicated by t1 in FIG. 20, which is an obstacle in reducing the size of 
the sensor section 15. 
Accordingly, it would be desirable to have a pointing device as an input 
device that moves through a wide range of motion and has increased 
sensitivity and a more compact size. 
SUMMARY OF THE INVENTION 
According to one aspect of the invention, an optical sensor according to 
the present invention includes a sensor section provided in a secured 
manner and including a light emitting element and a light receiving 
element located opposed to the light emitting element; and a reflective 
body connected to an operation section and movable with respect to the 
sensor section. The reflective body is a concave mirror for guiding light 
from the light emitting element to the light receiving element. 
According to another aspect of the invention, an optical sensor includes a 
sensor section provided in a secured manner and including a light emitting 
element and a plurality of light receiving elements located 
two-dimensionally with respect to the light emitting element; and a 
reflective body connected to an operation section and movable 
two-dimensionally with respect to the sensor section. The reflective body 
is a concave mirror for guiding light from the light emitting element to 
the plurality of light receiving elements. 
In one embodiment of the invention, the concave mirror is pivotally 
supported along a circumferential surface thereof by a support. 
In one embodiment of the invention, the center of curvature of the concave 
mirror is shifted with respect to the center of pivoting of the concave 
mirror. 
In one embodiment of the invention, the concave mirror has an outer 
slidable surface having the center of curvature at the center of pivoting 
of the concave mirror, and the support has an inner guide surface. 
In one embodiment of the invention, the support has a stopper section, and 
the concave mirror has a stopper member contactable with the stopper 
section of the support. 
In one embodiment of the invention, the concave mirror is connected to the 
operation section via a supporting column standing on the concave mirror, 
the sensor section is supported by an arm in a secured manner, and the arm 
is provided at such a position that avoids interference between the 
supporting column which moves integrally with the operation section and 
the concave mirror. 
In one embodiment of the invention, a section including the sensor section, 
the concave mirror, the support, the arm, and the supporting column is 
sealed by a sealing device. 
According to the optical sensor of the present invention, a concave mirror 
is used as a reflective body. Since the concave mirror has a light 
collecting function, a lens such as an objective lens is not required. The 
thickness of the sensor section can be reduced and be closer to the 
concave mirror by the thickness of the lens. Thus, the total thickness of 
the optical sensor can be reduced. This is advantageous in reducing the 
size and production cost. 
The concave mirror, unlike a plane mirror, can effectively guide the 
reflected light to a light receiving element. Such a feature of the 
concave mirror realizes a wide-range sensing with a high resolution. The 
operation section can move in a wide range of angles. The optical sensor 
having such a structure is preferably usable in an input device of a game 
machine and other devices for which the wide-ranging movement of the 
operation section is desired. 
In the case where the optical sensor according to the present invention is 
used for a pointing device of a computer, the moving distance through 
which the pointer is moved can be reduced compared to the moving distance 
of the operation section. Therefore, the pointer can be moved more 
precisely. 
The optical sensor, which can detect light in a non-contact fashion, has 
improved durability. Unlike the rotary encoder, the sensor section does 
not require a rotatable shaft and thus can be sealed. Therefore, 
malfunctions caused by dust can be avoided. Accordingly, high precision 
detection is realized for a long period of time, which improves the 
reliability. 
In the structure where the light receiving elements are arranged 
two-dimensionally with respect to the light emitting element, the angle of 
two-dimensional inclination of the operation section, namely, the 
two-dimensional operation amount of light, can be detected by one sensor 
section. Unlike the case of using rotary encoders, one sensor is 
sufficient. This contributes to further size reductions. 
In the structure where the concave mirror is supported along the 
circumferential surface thereof, the concave mirror and the operation 
section associated with the concave mirror can be moved in an arbitrary 
direction relatively easily. 
In the structure where the center of curvature of the concave mirror is 
shifted with respect to the center of pivoting, the range of sensing 
angles can be adjusted relatively easily as can be appreciated from the 
example presented below. Such an optical sensor is widely applicable to 
various types of input devices in accordance with the required range of 
detection angles. 
In the case where the concave mirror has an outer slidable surface having 
the center of curvature at the center of pivoting of the concave mirror 
and the support has an inner guide surface, the operation section can be 
moved smoothly so as to realize improved operability. 
In the structure where the support has a stopper section and the concave 
mirror has a stopper member contactable with the stopper section of the 
support, the concave mirror and the operation section can be positioned at 
a prescribed angle of inclination with certainty. As a result, the concave 
mirror and the operation section can not be damaged accidentally. 
The structure in which the concave mirror is connected to the operation 
section via a supporting column standing on the concave mirror, the sensor 
section is supported by an arm in a secured manner, and the arm is 
provided at such a position that avoids interfering with the supporting 
column which moves integrally with the operation section and the concave 
mirror is advantageous in increasing the angle of inclination of the 
operation section. 
In the structure where a section including the sensor section, the concave 
mirror, the support, the arm, and the supporting column is sealed by a 
sealing device, external disturbance light is prevented from being 
detected by the sensor section. Thus, the detection accuracy is enhanced. 
Thus, the invention described herein makes possible the advantages of (1) 
providing an optical sensor having a substantially complete sealed 
structure and improved reliability, (2) providing an optical sensor for 
sensing a dynamic movement of the operation section over a wide range of 
angles with a high resolution, and (3) providing a compact and thin 
optical sensor which provides space savings and improved operability when 
being used in an input device of a computer or the like. 
These and other advantages of the present invention will become apparent to 
those skilled in the art upon reading and understanding the following 
detailed description with reference to the accompanying figures.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Hereinafter, the present invention will be described by way of illustrative 
examples with reference to the accompanying drawings. 
With reference to FIG. 1, a basic structure of an optical sensor in an 
example according to the present invention will be described. FIG. 1 shows 
the basic structure of the optical sensor only conceptually, and detailed 
shapes and structures of elements of the optical sensor will become 
apparent from other figures described below. 
As shown in FIG. 1, the optical sensor includes a rod-like stick 29 
extended in a vertical direction, and a disc-shaped connection plate 29a. 
A bottom end of the stick 29 is connected to a central part of the 
connection plate 29a. The optical sensor further includes a concave mirror 
24 as a reflective body, four supporting columns 29b for connecting the 
connection plate 29a and the concave mirror 24, a generally L-shaped arm 
28 standing on a base plate 27, and a sensor section 26 attached to a tip 
of an extension arm 28a. 
FIGS. 2A and 2B show the basic structure of the optical sensor together 
with the other elements. A side wall 27a is disposed around the base plate 
27, and the base plate 27 and the side wall 27a form a casing. The casing 
has an opening at a top central part thereof for allowing the stick 29 and 
other elements attached thereto to move in X and Y directions. 
As shown in FIGS. 2A and 2B, bellows 32 are connected to the connection 
plate 29a at a top side thereof and also are connected to the base plate 
27 at a bottom side thereof. The part of the optical sensor below the 
connection plate 29a is sealed by the bellows 32. External disturbance 
light is thus prevented from being sensed by the sensor section 26 and so 
does not interfere with the detection accuracy of the optical sensor. 
The concave mirror 24 is pivotally supported along a circumferential 
surface thereof by a guide 30 secured to the base plate 27. When the stick 
29 is inclined in the X and Y directions at, for example, 45 degrees, the 
concave mirror 24 is also inclined smoothly in the X and Y directions at 
45 degrees. 
The stick 29 is supported by the bellows 32 so as not to rotate through 360 
degrees about the vertical axis. However, the deformability of the bellows 
32 allows the stick 29 to incline in the X and Y direction at, for 
example, .+-.45 degrees. 
The arm 28 is, as shown in FIG. 1, appropriately positioned among the 
plurality of supporting columns 29b so as not to destroy the concave 
mirror 24 by contact therewith even when the stick 29 is inclined at -45 
degrees as shown in FIG. 3. 
In order to avoid contact between the arm 28 and the concave mirror 24 as 
much as possible when the stick 29 is inclined at -45 degrees as shown in 
FIG. 3, the extension arm 28a connected to the arm 28 which may otherwise 
contact the concave mirror 24 is thinner than the rest of the arm 28. 
With reference to FIGS. 4, 5, 6A and 6B, the concave mirror 24, the guide 
30 and the sensor section 26 will be described in detail. 
The concave mirror 24 has a hollow hemispheric shape, and a circular 
collar-like connection part 33 (FIG. 5) extends from an outer edge of the 
concave mirror 24. On the connection part 33, bottom ends of the four 
supporting columns 29b are connected. An outer, circumferential surface 25 
of the concave mirror 24 is pivotally and slidably supported by the guide 
30 having a guide surface 30a. The radius of curvature of the guide 
surface 30a is substantially equal to that of the outer surface 25 of the 
concave mirror 24. 
On the guide surface 30a, hemispheric projections 31 are provided for 
reducing the contact resistance (frictional resistance) between the guide 
surface 30a and the outer surface 25 of the concave mirror 24. 
Accordingly, the concave mirror 24 is pivotally supported along the 
circumferential surface thereof by the guide 30 in the state of point 
contact. Since the frictional resistance is smaller in the state of point 
contact than in the state of plane contact, the stick 29 connected to the 
concave mirror 24 can move more smoothly. 
The guide 30 has an inclining stopper surface 34 around the guide surface 
30a. When the concave mirror 24 is inclined in association with the stick 
29 at +45 degrees as shown in FIG. 6A or -45 degrees as shown in FIG. 6B, 
the connection part 33 contacts the inclining stopper surface 34 so as to 
avoid further inclination of the concave mirror 24. In other words, the 
connection part 33 also acts as a stopper. Due to such a structure, the 
concave mirror 24 is protected with certainty from being destroyed by an 
excessive load. 
Next, the sensor section 26 will be described. As best shown in FIG. 5, the 
sensor section 26 is provided at a bottom end of the extension arm 28a of 
the arm 28, and includes a light emitting diode 36 and a plurality of 
photodiodes 35 disposed below the light emitting diode 36. A plurality of 
photodiodes 35 are provided both in the X and Y directions. 
Light emitted downward from the light emitting diode 36 is reflected by the 
concave mirror 24, and the reflected light is detected by the photodiodes 
35. Since the concave mirror 24 is inclined in association with the stick 
29, the amount of light detected by the four photodiodes 35 changes in 
accordance with the angle of inclination of the concave mirror 24. By 
detecting the change, the angle of inclination of the concave mirror 24 
and also of the stick 29 is detected. The details will be described later. 
In the above paragraphs, an "inversion-type" optical sensor in which the 
concave mirror 24 is provided below the sensor section 26 is described. 
The present invention is also applicable to a "normal-type" optical sensor 
in which the concave mirror 24 is provided above the sensor section 26. 
FIG. 7 shows such a normal-type optical sensor. Identical elements 
previously discussed with respect to FIGS. 1 through 6B will bear 
identical reference numerals therewith and the descriptions thereof will 
be omitted. As shown in FIG. 7, a pair of arms 28 stands on the base plate 
27 with an appropriate distance therebetween. A concave mirror 24 is 
supported between the arms 28 with the inwardly curved side being directed 
downward. The stick 29 is connected to the outer surface 25 of the concave 
mirror 24. The concave mirror 24 can be inclined in the X and Y directions 
in association with the stick 29. 
On the base plate 27 located below the concave mirror 24, the sensor 
section 26 is secured. The sensor section 26 includes a light emitting 
diode 36 and a plurality of photodiodes 35 provided above the light 
emitting diode 36. The sensor section 26, which does not require a 
rotatable shaft, can be sealed substantially completely. Accordingly, the 
optical sensor is substantially free of malfunctions caused by dust or the 
like. 
With reference to FIGS. 8A through 15, the principle of light detection 
according to the present invention will be described. As an example, the 
normal-type optical sensor will be used. The same principle is applied to 
the inversion-type optical sensor. 
FIGS. 8A and 8B show light propagation in the optical sensor according to 
the present invention. FIG. 8A shows the light propagation when the stick 
29 and the concave mirror 24 are inclined at 0 degrees, and FIG. 8B shows 
the light propagation when the stick 29 and the concave mirror 24 are 
inclined at +45 degrees. 
As shown in FIG. 8A, when the stick 29 and the concave mirror 24 are 
inclined at 0 degrees, the light is emitted upward from the light emitting 
diode 36, and the light reflected downward by the concave mirror 24 is 
uniformly received by the photodiodes 35. 
As shown in FIG. 8B, when the stick 29 and the concave mirror 24 are 
inclined at +45 degrees, the light reflected by the concave mirror 24 is 
received only by the right photodiode 35 as seen in FIG. 8B but not by the 
left photodiode 35. 
By obtaining the difference in the amount of light detected by the two 
photodiodes 35, the angle of inclination of the concave mirror 24 and also 
of the stick 29 can be detected. 
The specifications of an exemplary optical sensor used for the simulation 
shown in FIGS. 8A and 8B are as follows. 
The concave mirror 24 has a radius of curvature R of 4.7 mm, and the center 
of curvature is the center of the light source (light emitting diode 36). 
The distance L between the center of pivoting O of the concave mirror 24 
and the center of the light source (i.e., the center of curvature) is 0.7 
mm. The radius of curvature of the outer surface 25 of the concave mirror 
24 is 7 mm. (See FIGS. 4 and 5). 
The principle of light detection will be described in more detail below. 
As shown in FIGS. 9 and 10, the sensor section 26 includes four photodiodes 
35 (hereinafter, represented as PD1 through PD4) and one light emitting 
diode 36. In this example, the four photodiodes 35 are provided above the 
light emitting diode 36. The specific structure is described in Japanese 
Patent Application No. 8-75008 and will not be described in detail here. 
As seen from FIG. 9, the four photodiodes PD1 through PD4 are arranged 
around the center of the light emitting diode 36 (i.e., the light source) 
at an interval of 90 degrees. A set of the photodiodes PD1 and PD3 is 
arranged in the X direction and a set of the photodiode PD2 and PD4 is 
also arranged in the X direction. A set of the photodiodes PD1 and PD2 is 
arranged in the Y direction and a set of the photodiode PD3 and PD4 is 
also arranged in the Y direction. 
With the sensor section 26 having the above-described structure, the light 
emitted by the light emitting diode 36 is reflected by the concave mirror 
24, and received and converted into an electric signal by the photodiodes 
PD1 through PD4. The four photodiodes PD1 through PD4 respectively output 
electric signals in accordance with the amount of light received. 
FIG. 11 shows a circuit configuration for detecting the light. The outputs 
from the photodiodes PD1 through PD4 are processed by addition and 
subtraction by amplifiers A. 
FIGS. 12A and 12B respectively show directions in which a light spot 
received by the photodiodes PD1 through PD4 moves in the X and Y 
directions in accordance with the inclination of the concave mirror 24. 
When the concave mirror 24 performs Y-axis pivoting (pivoting in the X 
direction about the Y axis), the light spot moves in the X direction as 
shown in FIG. 12A. When the concave mirror 24 performs X-axis pivoting 
(pivoting in the Y direction about the X axis), the light spot moves in 
the Y direction as shown in FIG. 12B. 
When the light spot moves as described above, the subtraction output of the 
photodiodes PD1 through PD4 of the X-axis pivoting, i.e., 
((PD2+PD4)-(PD1+PD3)) and the subtraction output of the photodiodes PD1 
through PD4 of the Y-axis pivoting, i.e., ((PD1+PD2)-(PD3+PD4)) change as 
shown in FIG. 13. By obtaining these outputs, the angle of inclination of 
the concave mirror 24 in the X and Y directions is detected. 
Hereinafter, a specific calculation method for detecting the angle will be 
described. 
Step 1 
Subtraction output A.sub.X of the X-axis pivoting represented by expression 
(1) is obtained. 
EQU A.sub.X =(Isc.sub.(PD2) +Isc.sub.(PD4))-(Isc.sub.(PD1) +Isc.sub.(PD3)) 
expression (1) 
Step 2 
Subtraction output A.sub.Y of the Y-axis pivoting represented by expression 
(2) is obtained. 
EQU A.sub.Y =(Isc.sub.(PD1) +Isc.sub.(PD2))-(Isc.sub.(PD3) +Isc.sub.(PD4)) 
expression (2) 
Step 3 
Addition output B.sub.X,Y of the X-axis pivoting and Y-axis pivoting 
represented by expression (3) is obtained. 
EQU B.sub.X,Y =Isc.sub.(PD1) +Isc.sub.(PD2) +Isc.sub.(PD3) +Isc.sub.(PD4) 
expression (3) 
Step 4 
Changes .DELTA.X and .DELTA.Y of the subtraction outputs of the X-axis 
pivoting and Y-axis pivoting respectively represented by expressions (4) 
and (5) are obtained. 
EQU .DELTA.X=A.sub.X /B.sub.X expression (4) 
EQU .DELTA.Y=A.sub.Y /B.sub.Y expression (5) 
By obtaining the vector of .DELTA.X and .DELTA.Y (direction and absolute 
value of vector sum with respect to the angle of inclination of the 
concave mirror 24) represented by expression (6), the direction and 
magnitude (i.e., angle) of inclination of the concave mirror 24 and also 
of the stick 29 can be obtained. 
EQU .sqroot..sup.- {(A.sub.X /B.sub.X).sup.2 +(A.sub.Y +/B.sub.Y).sup.2 
}expression (6) 
With reference to FIGS. 14 and 15, the relationship between the distance 
from the center of curvature to the center of pivoting O of the concave 
mirror 24, and the detected angle .theta. will be described. The curve in 
FIG. 15 is a qualitative curve, and point P is the point at which the 
light spot does not move even when the concave mirror 24 is inclined. As 
shown in FIG. 15, the movement of the light spot is inverted in the "a" 
side (direction in which the distance L increases with respect to the 
point P) from the "b" side (direction in which the distance L decreases 
with respect to the point P). 
In the optical sensor used in this example in which the radius of curvature 
R of the concave mirror 24 is 4.7 mm, the point P is 0.1 mm away from the 
center of the light source (L=0.1 mm). 
When the distance L is on the "a" side, the light spot moves in the 
opposite direction to the direction of inclination of the concave mirror 
24 (FIG. 8B). When the distance L is on the "b" side, the light spot moves 
in the same direction as the direction of inclination of the concave 
mirror 24. 
In this example, the distance L is on the "a" side and a detection angle 
within .+-.45 degrees is satisfactory. In such a case, from FIG. 15, the 
distance L is set to be 0.7 mm. 
It can be appreciated from FIG. 15 that the sensing angle, i.e., the 
detection angle .theta. can be arbitrarily increased or decreased by 
shifting the center of curvature of the concave mirror 24 (i.e., center of 
the light source) with respect to the center of pivoting O. This indicates 
that an appropriate detection angle .theta. can be selected relatively 
easily in accordance with the device in which the optical sensor is used. 
Thus, the optical sensor according to the present invention is applicable 
to various types of input devices. 
FIG. 16 shows the sensor section 26 of the optical sensor. In this example, 
the concave mirror 24 (not shown in FIG. 16) is used as the reflective 
body. Since the concave mirror 24 has a light collecting function unlike a 
plane mirror, a lens such as an objective lens can be eliminated. The 
thickness of the sensor section can be reduced and be closer to the 
concave mirror by the thickness of the lens. Thus, the total thickness of 
the optical sensor can be reduced. This is advantageous in reducing the 
size and production cost. 
As can be appreciated from the comparison between the optical sensor in 
FIG. 16 in this example and the conventional optical sensor shown in FIG. 
20, the former also does not require the secondary mold. For these 
reasons, the thickness of the optical sensor in this example can be 
reduced from t1 to t2, which realizes size reduction and lower cost. 
Moreover, the optical sensor in this example can sense the light in a wide 
range of angles of .+-.45 degrees. This is a significant improvement from 
the range of .+-.10 degrees in the conventional sensors. Such a wide range 
of sensing angles can significantly increase the inclination angle of the 
stick 29. 
In the above example, two photodiodes are provided both in the X and Y 
directions. Three or more photodiodes can be provided in each direction. 
In the above example, a plurality of photodiodes are provided both in the X 
and Y directions to form a two-dimensional sensor section. Alternatively, 
a plurality of photodiodes can be provided in either direction alone. The 
optical sensor having such a structure can perform wide-range 
one-dimensional sensing. 
In the above example, a plurality of spot-like photodiodes are arranged 
two-dimensionally with respect to the light emitting diode. Alternatively, 
a two-dimensional optical sensor section can be realized by providing one 
area sensor for sensing light in both the X and Y directions. 
The structure of the optical sensor section is not limited to the 
combination of a light emitting diode and a photodiode. 
In the above example, four supporting columns are used. One supporting 
column can support the concave mirror as long as the column is 
sufficiently strong. 
The concave mirror, unlike from a plane mirror, can effectively guide the 
reflected light to a light receiving element. Such a feature of the 
concave mirror realizes wide-range sensing with a high resolution. The 
operation section can move through a wide range of angles. The optical 
sensor having such a structure is preferably usable in an input device of 
a game machine and other devices for which the wide-ranging movement of 
the operation section is desired. 
In the case where the optical sensor according to the present invention is 
used for a pointing device of a computer, the moving distance of the 
pointer can be reduced compared to the moving distance of the operation 
section. Therefore, the pointer can be moved more precisely. 
The optical sensor, which can detect light in a non-contact fashion, has 
improved durability. Unlike the rotary encoder, the sensor section does 
not require a rotatable shaft and thus can be sealed. Thus, malfunctions 
caused by dust can be avoided. Accordingly, high precision detection is 
realized for a long time, thereby improving the reliability. 
In the structure where the light receiving elements are arranged 
two-dimensionally with respect to the light emitting element, the angle of 
two-dimensional inclination of the operation section, namely, the 
two-dimensional operation amount of light, can be detected by one sensor 
section. Unlike the case of using rotary encoders, one sensor is 
sufficient. This contributes to size reduction. 
In the structure where the concave mirror is supported along the 
circumferential surface thereof, the concave mirror and the operation 
section associated with the concave mirror can be moved in an arbitrary 
direction relatively easily. 
In the structure where the center of curvature of the concave mirror is 
shifted with respect to the center of pivoting, the range of sensing 
angles can be adjusted relatively easily as can be appreciated from the 
examples presented above. Such an optical sensor is widely applicable to 
various types of input devices in accordance with the required range of 
detection angles. 
In the case where the concave mirror has an outer slidable surface having 
the center of curvature at the center of pivoting of the concave mirror 
and the support has an inner guide surface, the operation section can be 
moved smoothly so as to realize improved operability. 
In the structure where the support has a stopper section and the concave 
mirror has a stopper member contactable with the stopper section of the 
support, the concave mirror and the operation section can be positioned at 
a prescribed angle of inclination with certainty. Accordingly, the concave 
mirror and the operation section are not damaged accidentally. 
The structure in which the concave mirror is connected to the operation 
section via a supporting column standing on the concave mirror, the sensor 
section is supported by an arm in a secured manner, and the arm is 
provided at such a position that avoids interfering with the supporting 
column which moves integrally with the operation section and the concave 
mirror is advantageous in improving the angle of inclination of the 
operation section. 
In the structure where a section including the sensor section, the concave 
mirror, the support, the arm, and the supporting column is sealed by a 
sealing device, external disturbance light is prevented from being 
detected by the sensor section. Thus, the detection accuracy is enhanced. 
Various other modifications will be apparent to and can be readily made by 
those skilled in the art without departing from the scope and spirit of 
this invention. Accordingly, it is not intended that the scope of the 
claims appended hereto be limited to the description as set forth herein, 
but rather that the claims be broadly construed.