Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
2000-05-11
2002-03-26
Porta, David P. (Department: 2882)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C340S555000
Reexamination Certificate
active
06362468
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to an optical unit for detecting an object, and its application to a coordinate input apparatus, with a special reference made to the optical unit for detecting an object wherein a plurality of light emitting diodes are used to form a fan shape floodlight pattern, and its application for the coordinate input apparatus.
(2) Description of the Related Art
In digitizers and tablets incorporated as a coordinate input apparatus in processing units, there are various systems for detecting an angle (direction) or a position of an object. Examples are the pressure sensitive resistance membrane system, capacitance system, electromagnetic induction system and the like. There is also an optical system among non-contact systems that is capable of detecting the angle or the position of the object. In
FIG. 9
, a typical configuration of an optical unit used in the position detecting device of an object in accordance with conventional optical systems is shown. Light emitted from a point light source
91
is converted to a planar fan shaped light flux by a cylindrical lens
92
. Then it is reflected in a 90 degree angle by a half mirror
93
, and then is incident on a retroreflective member
95
which possesses retroreflective characteristics. Here, the retroreflective characteristics are the characteristics of a reflection whereby the incident light returns straight back in the direction in which the light was incident. The light incident on the retroreflective member
95
is reflected in the direction reverse to the incident direction, passes through the half mirror
93
, is condensed by a lens
96
and then projected to a linear charge coupled device (CCD)
97
. In the case of a position detecting device using a light interruption system wherein a retroreflective member is provided at an edge of the effective region, and a shadow is used, as the object interrupts the light, in order to detect the direction of the object, the direction of the shadow can be detected from the distribution of the output signals of the linear CCD
97
. However, since this example uses the half mirror
93
, the attenuation or loss of the light at the time of reflection at and at the time of passing through the half mirror
93
cannot be avoided. Also, as illustrated in
FIG. 10
, there is a system, which uses a reflecting mirror
94
with a slit in lieu of the half mirror in the conventional optical unit shown in
FIG. 9. A
problem in this case is that only a portion of the light reflected by the retroreflective member can be used as input light to the linear CCD.
As another example of an object detecting device, which detects the angle or the position of the object optically, there is one disclosed in Japanese Patent Application Laid-Open No. S62-5428. This device is configured such that the two optical units respectively project light in a fan shape, parallel to a coordinate detecting surface, and the linear photoreceptive sensor receive the retroreflective light from a retroreflective surface provided at an edge portion of the coordinate detecting surface, the edge portion being opposite to the location where the two optical units are provided. By interrupting a portion of the light with an object, a finger or a pen, the device detects the direction of the shadow. By conducting this detection from the two optical units which are arranged in the predetermined positions, the coordinates of the finger or the pen can be calculated accurately with the triangulation principle explained later.
Almost the same prior art system is disclosed in the U.S. Pat. No. 4,507,557. This example configures the system with a stand-alone light emitting diode with broad directivity and high-power, in which the light emitting diode is used as a stand-alone light source without inolving a lens or a mirror.
In Japanese Patent Application Laid-Open No. H9-319501, a system which uses a position sensing device (PSD) as a photoreceptive sensor instead of a linear CCD is disclosed. PSD is a component which generates different electric signals by light-receptive spots, having one-to-one correspondence between the light-receptive spot on the PSD and the light-receptive angle of the reflective light from the pen. This light is, then, incident on the angle detective means, so that by predetermining the correspondent relationships among the light-receptive angle, the light-receptive spot on the PSD and the electric signal that the PSD generates, then from the value of the electric signal directly measured by the PSD, the pointing position of the pen can be identified. In this prior art, an LED and a cylindrical lens are arranged in such a way as to cause the emitted light from the LED to become a beam parallel to the coordinate input surface by the cylindrical lens which is placed right in front of the LED. In these types of optical object detecting devices, the field of the photoreceptive sector becomes a fan shape plane, especially, in the case of the detecting device wherein an array of a linear photoreceptor is provided at the photoreceptive sector so that the light from the object or the direction of the shadow of the object is detected. Then, in the case of providing the retroreflective member on the object and using the retroreflective light from the object itself, or in the case of providing the retroreflective member at the opposite edge of the effective region, and using the shadow in the case of the object interrupting the light, the retroreflective light, then, returns back through the same path as the projected light, so that it is necessary that the light source which projects the light in a fan shaped projection pattern and the light-receptive sector to receive the retroreflective light be provided as closely as possible. In recent years, material which has excellent retroreflective characteristics has become available, so that the efficiency of light can be improved greatly by placing the projection pattern and the light-receptive pattern close together. Then, it is possible to arrange that the light projection sector and the light-receptive sector be completely coincided by using the half mirror or the reflective mirror with a slit as in the cases of
FIG. 9
or
FIG. 10
respectively. However, in these cases there is a problem of aforementioned attenuation of the light, or only a portion of the light is effectively received.
In general, a point light source and a cylindrical lens can be used to form a fan shaped projection pattern. For the light component at a surface perpendicular to the projected surface of the fan shaped projection pattern, parallel rays are ideal.
As an example of optical means to realize a so-called electronic blackboard, which has a large input surface, there is Japanese Patent Application Laid-Open No. H11-85377. In this example, a laser beam is used as the light source, and a polygon mirror conducts scanning on the blackboard. A defect in this kind of device is that there is a difficulty to determine the position of the optical unit and to adjust its angle. To solve such a problem of having difficulty to adjust the attachment angle of an optical unit in such devices, Japanese Patent Application Laid-Open No. H11-85399 suggests fine adjustment of the height and inclination of the optical unit with a screw.
The U.S. Pat. No. 4,107,522 can be cited as an example of using a stand-alone optical unit for detecting the object. This is to realize a security system, in which one light emitting diode is used for the projection sector.
In recent years, a so called input/output consolidation type coordinate input device has been realized. Here, the input surface of the coordinate input device and the display surface, such as, the liquid crystal display device are caused to be placed one over the other. Among the input/output consolidation type coordinate input devices, an electromagnetic induction system has been used for the one which can input handwriting letters by using a pen. In this case, antennas for detection of electro
Fukuzaki Yasuhiro
Murakami Azuma
Ogawa Yasuji
Porta David P.
Saeilo Japan, Inc.
Wells St. John Roberts Gregory & Matkin
Yun Jurie
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