Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
1999-05-12
2001-11-27
Allen, Stephone B. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C250S226000, C250S216000, C340S555000
Reexamination Certificate
active
06323481
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an optical unit, a photoelectric switch, and a fiber-type photoelectric switch each comprising a plurality of optical elements, and a color discrimination sensor for detecting color of an object.
Hitherto, an optical unit such as a photoelectric switch has been used for emitting light to an object and receiving the light reflected on the object or the light penetrating the object, thereby detecting information on the object. With the photoelectric switch, light is emitted to a transport passage of an object and the presence or absence, the shape, the dimensions, the color, etc., of the object can be detected on the basis of the light reception quantity of the reflected light or penetrating light.
FIG. 11
is a sectional view to show an example of a photoelectric switch in a related art. In the figure, a light emission element
31
and a light reception element
32
are placed in a housing
35
. Light emitted from the light emission element
31
is transmitted through a projection lens
33
to a detection position. Light from the detection position is gathered through a light reception lens
34
at the light reception element
32
. If an object
37
exists at the detection position, light reflected from the object
37
is received on the light reception element
32
through the light reception lens
34
. Therefore, whether or not the object
37
exists can be determined on the basis of the light reception quantity level of the light reception element
32
.
A color discrimination sensor, which is also a kind of photoelectric switch, comprises a light transmission section containing a light source consisting of three light emission elements for respectively generating lights having wavelength bands corresponding to Red, Green and Blue and a projection lens for transmitting light emitted from each light emission element to an object and a light reception section having a detection light reception element for receiving light reflected from the object.
Light emitted from each of the three light emission elements is transmitted through the projection lens to the object in order and reflected light is received on the detection light reception element, then the color of the object can be determined on the basis of the light reception quantity level of each color band, for example, from comparison with reference color.
FIG. 12
is a sectional view of the main part of an optical unit having a plurality of light emission elements in a related art. In the figure, three light emission elements
41
a,
41
b,
and
41
c,
a projection lens
42
, and two dichroic mirrors
43
a
and
43
b
are disposed in a holder
40
. The light emission element
41
c
is placed so that an optical axis LC of the light emission element
41
c
matches an optical axis LX of the projection lens
42
. The light emission element
41
b
is placed so that an optical axis LB of the light emission element
41
b
crosses the optical axis LX of the projection lens
42
at right angles. The light emission element
41
a
is placed so that an optical axis LA of the light emission element
41
a
crosses the optical axis LX of the projection lens
42
at right angles.
If the light emission element
41
a
is turned on, light emitted from the light emission element
41
a
is reflected on the dichroic mirror
43
a
and is transmitted through the projection lens
42
. If the light emission element
41
b
is turned on, light emitted from the light emission element
41
b
is reflected on the dichroic mirror
43
b
and the reflected light penetrates the dichroic mirror
43
a
and is transmitted through the projection lens
42
. If the light emission element
41
c
is turned on, light emitted from the light emission element
41
c
penetrates the dichroic mirrors
43
b
and
43
a
and is transmitted through the projection lens
42
.
In the example in the related art, however, if the optical path lengths from the light emission elements
41
a,
41
b,
and
41
c
to the projection lens
42
differ, different focal lengths of the projection lens
42
result. Thus, the total of the optical path length from the light emission element
41
a
to the dichroic mirror
43
a
and the optical path length from the dichroic mirror
43
a
to the projection lens
42
, the total of the optical path length from the light emission element
41
b
to the dichroic mirror
43
b
and the optical path length from the dichroic mirror
43
b
to the projection lens
42
, and the optical path length from the light emission element
41
c
to the projection lens
42
are set almost equal to each other considering the light wavelength.
Therefore, the distance from the light emission element
41
a
at a position near the projection lens
42
to the optical axis LX of the projection lens
42
becomes long as compared with the distance from the light emission element
41
b
at a position distant from the projection lens
42
to the optical axis LX of the projection lens
42
. Resultantly, the width of the optical unit, L
0
, increases and it is difficult to miniaturize the unit.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide an optical unit, a photoelectric switch, a fiber type photoelectric switch, and a color discrimination sensor, the width of each of which can be shortened for miniaturization.
In addition, it is another object of the invention to provide an optical unit which comprises a plurality of light emission elements and is capable of adjusting the light reception detection output corresponding to each light emission element.
To the end, according to a first aspect of the invention, there is provided an optical unit for emitting or receiving light, comprising a plurality of optical elements for emitting or receiving light, a lens for transmitting or receiving light, and an optical system for guiding light from the optical elements into the lens or guiding light from the lens into the optical elements, wherein the optical elements and the lens are placed so that an optical axis of at least one of the optical elements crosses an optical axis of the lens with an inclination thereto.
According to the configuration of the optical unit, the optical system guides light emitted from the optical elements into the lens or guides light from the lens into the optical elements. In this case, the optical elements and the lens are placed so that the optical axis of at least one of the optical elements crosses the optical axis of at lens with an inclination thereto, whereby the distance between the optical element and the optical axis of the lens is shortened. Therefore, the optical unit can be miniaturized while the optical path lengths from the optical elements to the lens are held equal to each other.
In the first aspect of the invention, the optical axes of the optical elements are preferably placed in three dimensions.
According to the configuration, the optical unit can be miniaturized in the width and thickness directions.
In the first aspect of the invention, it is advantageous that the optical element of the optical elements positioned nearest to the lens is a light emission element for emitting green band light.
According to the configuration, the attenuation effect of the optical system on the light emission element for emitting green band light with the smallest light reception detection output as compared with the light emission element for emitting blue or red band light can be decreased.
According to a second aspect of the invention, there is provided a photoelectric switch for transmitting light to a detection position and receiving light reflected from the detection position or light penetrating the detection position, the photoelectric switch comprising a plurality of light emission elements for emitting light, a projection lens for transmitting light from the light emission elements to the detection position in order, an optical system for guiding light emitted from the light emission elements into the projection lens, and a light reception element for receiving light re
Allen Stephone B.
Keyence Corporation
Morgan & Lewis & Bockius, LLP
LandOfFree
Optical unit, photoelectric switch, fiber-type photoelectric... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Optical unit, photoelectric switch, fiber-type photoelectric..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical unit, photoelectric switch, fiber-type photoelectric... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2598555