Optics: measuring and testing – Velocity or velocity/height measuring – With light detector
Reexamination Certificate
2003-01-31
2004-01-06
Buczinski, Stephen C. (Department: 3662)
Optics: measuring and testing
Velocity or velocity/height measuring
With light detector
C356S615000
Reexamination Certificate
active
06674517
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an optical motion detector, transport system, and transport processing system, for detecting a paper feed speed and the quantity of movement of paper in a variety of equipment such as a printer and a copier or measuring in a non-contact manner the speed and the quantity of movement of another object whose surface is not a mirror surface.
Conventionally, as shown in
FIG. 9
, there has been an optical motion detector that has two distance measuring sensors
101
and
102
and a processing unit
103
. The principle of the distance measuring sensors
101
and
102
of this optical motion detector will be described with reference to FIG.
10
. As shown in
FIG. 10
, the distance measuring sensors
101
and
102
have a light-emitting section
104
, a lens
105
that concentrates diffused light from the light-emitting section
104
, a light-receiving section
107
that receives light reflected on a measurement object
106
and a lens
108
that concentrates the reflected light from the measurement object
106
on the light-receiving section
107
. In this case, a light beam from the light-emitting section
104
is perpendicularly incident on the measurement object
106
, and the reflected light from this position is concentrated on the light-receiving section
107
by the lens
108
. The light-receiving section
107
employs a PSD (Position Sensitive Device; position detection device), and a ratio of a first output and a second output varies in correspondence with the position of the spot light concentrated on the light-receiving surface. A distance can be measured by utilizing the phenomenon that the ratio of first output/second output varies in accordance with the distance between this PSD and the measurement object.
In
FIG. 9
, if the measurement object
106
moves in the direction of arrow, then the two distance measuring sensors
101
and
102
obtain outputs corresponding to the unevenness of the measurement object
6
, and these outputs representing the distance between the distance measuring sensors
101
and
102
and the measurement object
106
, fluctuate corresponding to the quantity of unevenness. As shown in
FIGS. 11A and 11B
, with regard to the output waveforms obtained at this time, the distance measuring sensor
102
of B (shown in
FIG. 11B
) has an output waveform delayed by &Dgr;t from that of the distance measuring sensor
101
of A (shown in
FIG. 11A
) in accordance with the travel speed of the measurement object
6
. This delay &Dgr;t is calculated by the processing unit
103
to obtain the travel speed and the quantity of movement of the measurement object
106
.
The aforementioned optical motion detector, which needs the two distance measuring sensors
101
and
102
that employ the light-emitting section
104
, the light-receiving section
107
and the two lenses
105
and
108
, has a problem that it has many components and a large size in terms of shape, which leads to high manufacturing cost. Moreover, there is a problem that a measurement object having a comparatively smooth surface (surface having minute unevenness) is hard to measure, dissimilarly to the fortunate case where the measurement object has an uneven surface that can be detected as a difference in distance by the distance measuring sensors
101
and
102
.
Furthermore, although there is a laser Doppler type as another conventional optical motion detector, this laser Doppler type optical motion detector is large in size and expensive.
SUMMARY OF THE INVENTION
Accordingly, the object of the present invention is to provide an optical motion detector, transport system and transport processing system capable of reducing the number of components with a simple construction, reducing the size and cost and measuring at least one of the travel speed and the quantity of movement of a measurement object even when the measurement object has a comparatively smooth surface unless the measurement object has a surface of mirror state.
In order to achieve the above object, there is provided an optical motion detector comprising:
a light-emitting device;
a collimator lens for collimating a light beam emitted from the light-emitting device;
an object lens, which concentrates the light beam collimated by the collimator lens and applies the light beam to a measurement object that moves in a prescribed direction, forming a light spot that has a prescribed spot diameter on the measurement object;
a beam splitter, which splits a reflected light which belongs to a reflected light from the light spot of the measurement object and is concentrated via the object lens;
a light-receiving lens, which concentrates the reflected light split by the beam splitter;
two pinholes, through which reflected lights pass, wherein the lights belong to the reflected light concentrated by the light-receiving lens and come from two regions inside the light spot located at a prescribed interval on a straight line parallel to a measurement object travel direction;
two light-receiving sections on which the reflected lights, which have passed through the two pinholes, are respectively made incident; and
a measuring section, which measures at least one of a travel speed and a quantity of movement of the measurement object on the basis of outputs of the two light-receiving sections.
According to the optical motion detector of the above-mentioned construction, the light beam emitted from the light-emitting device is collimated by the collimator lens and thereafter applied to a measurement object that moves in the prescribed direction via the object lens, forming a light spot on the measurement object. Among the reflected light from this light spot, the reflected light concentrated via the object lens is split by the beam splitter and concentrated by the light-receiving lens. Thereafter, only the reflected light from the two regions located at the prescribed interval on the straight line parallel to the measurement object travel direction inside the light spot is made to pass separately through the two pinholes, and the reflected light that has passed through the two pinholes is made incident on two light-receiving sections. Then, on the basis of the outputs of the two light-receiving sections, at least one of the travel speed and the quantity of movement of the measurement object is measured by the measuring section. That is, when the measurement object moves, one output waveform of the output waveforms detected by the two light-receiving sections has a shape delayed timewise from the other output waveform. By preparatorily setting a distance between the two regions inside the light spot, the travel speed or the quantity of movement of the measurement object can be obtained on the basis of the time of delay of the output waveform of this light-receiving section and the distance between the two regions inside the light spot. Therefore, the number of components of the motion detector can be reduced with a simple construction, and this allows a size reduction in terms of shape and a reduction in manufacturing cost to be achieved. Moreover, even a measurement object that has a comparatively smooth surface can be measured unless the surface state (state of unevenness) of the measurement object is a mirror surface.
In one embodiment of the present invention, the light-emitting device is a semiconductor laser device.
According to the optical motion detector of the above-mentioned embodiment, which employs the light-emitting device of a semiconductor laser that has a small light-emitting section and is tantamount to a point light source, is therefore able to efficiently concentrate light by the lens and obtain a quantity of reflected light required for the signal detection by the light-receiving device from the measurement object.
In one embodiment of the present invention, an optical axis of emitted light concentrated by the object lens is perpendicular to the measurement object.
According to the optical motion detector of the above-mentioned embodiment, the optical axis of the emitted
Sugiyama Hisakazu
Yamaguchi Akifumi
Birch Stewart Kolasch & Birch, LLP.
Buczinski Stephen C.
Sharp Kabushiki Kaisha
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