U.S. patent number 3,792,239 [Application Number 05/214,267] was granted by the patent office on 1974-02-12 for device for transmitting wavelengths of the electromagnetic spectrum.
This patent grant is currently assigned to Northern Illinois Gas Company. Invention is credited to Ronald L. Ohlhaber, Donald A. Pontarelli.
United States Patent |
3,792,239 |
Ohlhaber , et al. |
February 12, 1974 |
DEVICE FOR TRANSMITTING WAVELENGTHS OF THE ELECTROMAGNETIC
SPECTRUM
Abstract
A device for transmitting wavelengths of the electromagnetic
spectrum from one or more sources to detector means, comprising one
or more channel plates each having channels therein into which are
disposed conduction elements of a material having a higher index of
refraction than the material of the associated plates. The channels
and associated conduction elements selectively intersect exterior
surfaces of the channel plates such that wavelengths from sources
positioned generally adjacent selected end portions of the
conduction elements are guided to the opposite ends of the
channels. The device finds application in optical encoder systems,
card and punched tape illuminators and readers, and alphanumeric
devices and the like.
Inventors: |
Ohlhaber; Ronald L. (Evanston,
IL), Pontarelli; Donald A. (Chicago, IL) |
Assignee: |
Northern Illinois Gas Company
(Aurora, IL)
|
Family
ID: |
22798428 |
Appl.
No.: |
05/214,267 |
Filed: |
December 30, 1971 |
Current U.S.
Class: |
385/24; 398/200;
235/494; 235/462.03; 235/473 |
Current CPC
Class: |
G02B
6/3508 (20130101); G02B 6/4249 (20130101); G02B
6/43 (20130101); G02B 26/04 (20130101); G06K
7/10 (20130101); G02B 6/3598 (20130101); G02B
6/3556 (20130101) |
Current International
Class: |
G06K
7/10 (20060101); G02B 6/35 (20060101); G02B
6/43 (20060101); G02B 26/02 (20060101); G02B
26/04 (20060101); G02B 6/42 (20060101); G02b
005/14 (); G06k 007/10 () |
Field of
Search: |
;340/347P ;350/96B |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Sloyan; Thomas J.
Attorney, Agent or Firm: Johnson, Dienner, Emrich, Verbeck
& Wagner
Claims
We claim:
1. A stack for providing a plurality of sets of transmission paths
for conducting radiant energy selectively directed toward a first
edge surface of the stack to a second edge surface of the stack,
comprising a plurality of sheets of materials having a first index
of refraction, each of the said sheets having a plurality of
channels formed on a surface thereof extending from a first edge of
the sheet to a second edge of the sheet, and a plurality of
transparent channel members each positioned in a different one of
said channels and extending from the first edge of said sheet to
the second edge of said sheet to provide a transmission path over
said sheet, each of said channel members having an input end
terminating at the first edge of the sheet and an output end
terminating at the second edge of the sheet, said plurality of
sheets being stacked together with the first edges thereof forming
the first edge surface of said stack and the second edges thereof
forming the second edge surface of said stack, each channel member
being of a material having an index of refraction that is greater
than the index of refraction of said sheets to permit radiation
directed toward the first edge surface of said stack to be
transmitted over the transmission paths provided by channel members
to the second edge of said stack, and alignment means for aligning
said sheets in said stack to locate the input ends of certain ones
of said channel members on one sheet at predetermined positions
relative to the input ends of channel members on other sheets at
the first edge surface of the stack and to locate the output ends
of said channel members at predetermined positions at the second
edge surface of the stack to thereby provide a plurality of sets of
transmission paths over said stack, such that radiant energy
selectively directed toward different preselected portions of the
first edge surface of the stack is conducted to the second edge
surface of the stack over different ones of said sets of
transmission paths.
2. An optical stack for providing a plurality of sets of light
paths for conducting light selectively directed toward a portion of
a first edge surface of the stack to a second edge surface of the
stack comprising a plurality of sheets of a material having a first
index of refraction, each of said sheets having a plurality of
channels formed on a surface thereof extending from a first edge of
the sheet to a second edge of the sheet, and a plurality of light
channel members each positioned in a different one of said channels
and extending from the first edge of said sheet to the second edge
of said sheet to provide a plurality of separate light conducting
paths over said sheet, each light channel member having an input
end terminating at the first edge of said sheet and an output end
terminating at the second edge of said sheet, said plurality of
sheets being stacked together with the first edges thereof forming
the first edge surface of said stack having the input ends of the
light channel members exposed thereon at different locations and
with the second edges thereof forming the second edge surface of
said stack having the output ends of said light channel members
exposed thereon at a common location each channel member being of a
material having an index refraction that is greater than the index
of refraction of said sheet to permit light directed toward the
input ends of the light channel members to be conducted over said
stack from the first edge surface to the second edge surface over
said light channel member and alignment means for aligning said
sheets in said stack to locate the input ends of certain ones of
the channel members on one sheet in an overlying relationship with
the input ends of certain ones of the channel members on another
sheet in different preselected portions of said first edge surface
of said stack providing a plurality of separate sets of light
conducting paths to thereby permit transmission of light only over
light channel members of a given set upon selective illumination of
only the portion of the first edge surface of the stack wherein the
input ends of such light channel members are exposed.
3. An optical stack as set forth in claim 2 wherein each of said
sheets includes a pair of alignment apertures and wherein said
alignment means includes a further sheet having a pair of spaced
parallel alignment members which are received through the alignment
apertures in said sheets.
4. A stack for providing a plurality of separate light transmission
paths for conducting light incident on a first edge surface of the
stack to a second edge surface of the stack, comprising a plurality
of light channel plates each including a plate body of a material
having a first index of refraction, said plate body including a
branched channel formed on a surface thereof having a plurality of
first ends which intersect the first edge surface of said light
channel plate at different predetermined locations and a second end
which intersects the second edge surface of said light channel
plate at a predetermined location, and an integrally formed light
channel member disposed in said branched channel and conforming to
the shape thereof, said light channel member having input ends
terminating at said predetermined locations on the first edge
surface of said light channel plate and an output end terminating
at said predetermined location on the second edge surface of said
light channel plate, each said light channel member being of a
material having an index of refraction that is greater than the
index of refraction of said plate member to permit light directed
toward the input ends of said light channel member to be conducted
over said light channel plate from the first edge surface to the
second edge surface thereof, and alignment means for aligning said
sheets in said stack to locate the input ends of certain ones of
the light channel members on one sheet in an overlying relationship
with the input ends of certain ones of the channel members on
another sheet providing a plurality of sets of light conducting
paths to thereby permit transmission of light only over the light
channel members of a given set upon selective illumination of a
surface portion of the first edge of the stack including the input
ends of the light channel members of said given set.
5. A channel plate for transmitting wavelengths of the
electromagnetic spectrum between a source and detection means,
comprising a plate body having top and bottom surfaces and at least
two side surfaces, said plate body having a plurality of channels
formed in one of said top or bottom surfaces, said channels having
first end portions intersecting one of said side surfaces at
separate positions, and said channels having second end portions
intersecting a second side surface of said plate body at a common
point of intersection, and conduction element means disposed in
each of said channels and extending the full length thereof, said
conduction element means being of a material capable of guiding
wavelengths of the electromagnetic spectrum by substantially total
internal reflection through the full length thereof, said plate
body being made from a material having a predetermined index of
refraction, and said conduction element means being made up of a
material having a higher index of refraction than said plate body
material.
6. A channel plate as defined in claim 5 wherein said top and
bottom surfaces are generally planar and parallel to allow stacking
of a plurality of channel plates.
7. A channel plate as defined in claim 5 wherein each channel has a
predetermined cross-sectional by configuration, and wherein said
conduction element means comprises an elongated wave transmitting
body having a cross-sectional configuration allowing said
conduction element means to be received in and engage the wall
surfaces defining said channel.
8. A channel plate as defined in claim 7 wherein said surfaces of
said plate body defining each said channel have smooth polished
finishes, and wherein said conduction element means has an
optically smooth outer peripheral surface.
9. A channel plate as defined in claim 5 wherein said plate body is
made from acrylic plastic having an index of refraction of
approximately 1.49, and wherein said conduction element means is
made of polystyrene having an index of refraction of approximately
1.59.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to wave transmitting
devices and more particularly to a novel transmitting device
employing one or more channel plates having transmitting channels
adapted to transmit wavelengths of the electromagnetic spectrum
through a plurality of predetermined paths from one or more light
sources to detection means.
2. Description of the Prior Art
It is generally known to use optical transmitting means for guiding
light waves from a light source to detection means. For example,
fiber optic bundles comprising lengths of fiber optic rods have
been employed in optical encoders to transmit light waves from a
light source over both linear and non-linear paths to light
detection means. Analog-to-digital computers such as disclosed in
U.S. Pat. No. 3,247,506 to E. O. Grim, Jr. employ optical encoders
wherein optical bundles transmit light from a light source onto one
side of a code disc that is coded with clear and opaque areas.
Light passing through clear areas of the code disc selectively
energize photosensors which are positioned on the opposite side of
the code disc.
The known fiber optic bundles include a plurality of fiber optic
rods each having one end supported in a plate which is positioned
adjacent the light source and another end supported in a plate
which is positioned adjacent the code disc so that light from the
source is conducted over the fiber optic rods and directed toward
the code disc. The intermediate portions of the fiber optic rods
are encapsulated in epoxy. The fiber optic bundles enable optimum
positioning of the photosensors relative to the light source by
permitting bends and twists in the light paths over which light is
conducted from the light source to the code disc and thence to the
photosensors.
A shortcoming of encapsulated fiber optic rod assemblies of the
type disclosed in the references patent to E. O. Grim, Jr. is that
after encapsulation, the individual fiber optic rods cannot be
removed from the assembly and replaced in the event that a rod is
damaged or broken during assembly. Moreover, since the fiber optic
rods are generally of a small diameter, which may be on the order
of 1/32 inch, the fabrication of the fiber optic assemblies
requires insertion of the ends of the fiber optic rods into
apertures in the support plates which can be difficult and time
consuming, particularly where a large number of fiber rods must be
positioned to provide a plurality of individual optical paths.
SUMMARY OF THE INVENTION
One of the primary objects of the present invention is to provide
novel means for transmitting wavelengths of the electromagnetic
spectrum from a source to detection means through the physical
mechanism of total internal reflection.
Another object of the present invention is to provide a novel
channel plate arrangement employing one or more channel plate
members having channel means formed therein into which are disposed
conduction path means adapted to transmit wavelengths of the
electromagnetic spectrum through the mechanism of total internal
reflection.
Another object of the present invention is to provide a channel
plate arrangement as described wherein a plurality of channels are
provided in each of the channel plate members, the channels of each
plate intersecting a common surface of the plate and converging to
a common point of intersection on another surface of the plate, the
conduction path means disposed within each of the channel plates
being adapted to transmit wavelengths from either a common source
to a multiplicity of outlets or from a plurality of sources to a
single detector means.
Another object of the present invention is to provide a novel
wavelength transmitting device as described wherein each of the
wavelength conduction path means is defined by a channel material
having a higher index of refraction than the material of the plate
defining the channels into which the conduction medium is
disposed.
Another object of the present invention is to provide a wavelength
transmitting device comprising a plurality of stacked channel
plates each of which lends itself to low fabrication cost, exact
duplication, simple assembly, and a production process which is
considerably less complex than required by the prior art devices
for transmitting wavelengths of the electromagnetic spectrum.
A feature of the transmitting device in accordance with the present
invention is that it may be used economically and efficiently in
optical encoder systems, card and punched tape illuminators and
readers, and alphanumeric devices and the like.
In carrying out the objects and advantages of the present
invention, there is provided a channel plate arrangement comprising
one or more generally planar channel plate members each having a
plurality of channels formed in one surface thereof. In one
embodiment of the present invention, a plurality of channel plates
are assembled in stacked relation and the channels of each plate
have first end portions intersecting a common edge surface of the
plate and extend to a common point of intersection at a second edge
surface of the plate. Conduction path means are disposed in the
channels and extend the full lengths thereof. The conduction path
means comprises channel material adapted to transmit wavelengths of
the electromagnetic spectrum, the channel material having a higher
index of refraction than the material comprising the associated
plate member.
In one method of manufacture of the channel plate assembly, each
channel plate having channels therein is formed by injection
molding from acrylic plastic having an index of refraction of 1.49.
A second mold is used to inject plastic such as polystyrene having
a higher index of refraction than the acrylic plastic of the plate
body into the channels, the plates being thereafter assembled into
stacked relation to establish the desired unit size.
An alternate method of manufacture of the channel plate assembly in
accordance with the present invention is to fabricate polystyrene
channel elements and position them accurately in sandwich fashion
between plate members made from a transparent material having a
lower index of refraction than the channel elements. The channel
elements constitute guide paths for wavelengths of the
electromagnetic spectrum and are bounded on two sides by air, the
channels being of substantially any desired cross-sectional
configuration such as circular or square.
In a described application of the channel plate assembly in
accordance with the present invention, the channel plate assembly
is employed as an optical encoder in an analog-to-digital
converter.
The analog-to-digital converter provides sets of output signals
representing the angular positions of four shafts and employs a
single optical channel plate assembly which provides separate sets
of light-conducting paths from the code discs associated with the
shafts to a light detector array. Each set of light paths is
defined by a plurality of light transmitting channel elements which
individually intersect a common edge surface of the plate and
converge to form a single light output for the channel plate. In
this manner, only one light detector is required for each optical
channel plate thereby minimizing the number of light detectors
required for the optical encoder and simplifying the output
circuits required to convert the outputs of the light detectors to
digital signals.
The optical encoder employing the optical channel plate assembly in
accordance with the present invention provides encoding of four
shafts using a common optical array and is more compact and
economical in manufacture than prior art optical encoders employing
fiber optic light conducting rod elements.
Further objects and advantages of the present invention, together
with the organization and manner of operation thereof, will become
apparent from the following detailed description of the invention
when taken in conjunction with the accompanying drawings wherein
like reference numerals designate like elements throughout the
several views.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic block diagram of a channel plate assembly
transmitting device in accordance with the present invention
embodied in an analog-to-digital converter;
FIG. 2 is a front elevational view schematically illustrating the
meter portion of FIG. 1;
FIG. 3 is an exploded perspective view showing the channel plate
assembly of FIG. 1 with associated elements which cooperate to
define an optical encoder;
FIG. 4 is an isometric view of the channel plate assembly of the
optical encoder shown in FIG. 3;
FIG. 5 is a sectional view taken along lines 5--5 of the light
plate shown in FIG. 3;
FIGS. 6 and 6a are schematic plan views of the two embodiments for
the code discs of the optical encoder shown in FIG. 1;
FIG. 7 is a front elevational view of the channel plate assembly
and a code disc to show the relationship between the light channels
and the code tracks of the code disc;
FIG. 8 is a schematic circuit diagram of the output circuits of the
encoder shown in FIG. 1;
FIG. 9 is a schematic top plan view of a channel plate assembly and
associated code discs in accordance with a second embodiments of
the invention;
FIG. 10 is a front elevational view of the assembly shown in FIG.
9; and
FIG. 11 is an end view of the assembly shown in FIG. 10.
DESCRIPTION OF PREFERRED EMBODIMENTS
Referring now to the drawings, and in particular to FIG. 1, a
device for transmitting wavelengths of the electromagnetic spectrum
in accordance with one embodiment of the present invention is
schematically illustrated as being incorporated in an optical
analog-to-digital converter indicated generally at 20. By way of
example, the optical encoder 20 is described relative to an
application for converting angular positions of four shafts 21-24
into sets of binary coded output signals which are provided over
output circuits 25. While the transmitting device in accordance
with the present invention will be described as being employed for
transmitting light, it will be understood that the broad concept of
the present invention finds application in transmitting
substantially any selected wavelengths of the electromagnetic
spectrum. In addition, while the transmitting device of the instant
invention is illustrated in use as an optical encoder, the
transmitting device can also be used in various other applications.
For example, the channel plate assembly to be hereinafter described
can be used in card and punched tape illuminators and readers to
conduct light from a common light source to a plurality of light
detector elements, or in segmented numeric readouts.
The four shafts 21-24 may, for example, be part of a register 26 of
a utility meter 27 shown in FIG. 2. The register 26 has four
clock-type dials 28-31 associated with the shafts 21-24,
respectively, for indicating a reading of measured amount of a
commodity used. The register 26 provides a four digit reading with
dials 28-31 representing thousandths, hundredths, tens and units
digits of the reading respectively.
Each dial, such as dial 31, has ten digits 0-9 circumferentially
spaced about the dial 31 and a pointer 32 carried by the associated
shaft 24 for indicating one of the ten positions 0-9 of the shaft
24.
Input drive for the register 26 is provided by measuring means (not
shown) of the meter 27 which effects rotation of shaft 24 of the
units dial 28 in accordance with quantums of a commodity measured
by the measuring means. Shafts 21-24 are interconnected by a gear
train (not shown) of the type which is conventional in the art of
meter registers. Accordingly, shaft 24, driven by the measuring
means effects rotation of shafts 21-23 whereby shafts 23 rotates
one revolution for each ten revolutions of shaft 24, shaft 22
rotates once for each 100 revolutions of shaft 24, and shaft 21
rotates once for each 1000 revolutions of shaft 24.
The angular positions of each of the shafts 21-24 are converted
into digital signals by the optical shaft encoder 20 which provides
a different set of binary coded output signals over output circuits
25 for each of a plurality of predetermined positions for the
shafts 21-24. The encoder provides a separate set of output signals
to represent the angular position of each shaft 21-24, and
correspondingly, the reading of the meter dials 28-31 associated
with the shaft.
The encoder 20 includes a light plate assembly 40 which directs
light through code discs 51-54 toward an optical channel plate
assembly or array 45. As will be described hereinafter, the optical
channel plate assembly 45 provides four separate sets of light
paths which conduct light directed toward the stack from the light
plate 40 to a light detector assembly 41. The code discs 51-54 are
mounted for rotation by shafts 21-24, respectively, and are
interposed between the light plate 40 and the channel plate
assembly 45 to permit selective transmission of light over the
channel plate assembly from the light plate 40 to the light
detector array 41 as a function of the angular positions of the
shafts 21-24 which carry the code discs 51-54.
In the view of the encoder 20 shown in FIG. 3, the light plate
assembly 40 and the light detector assembly 41 are shown spaced
apart from the optical channel plate array 45. The code discs 51-54
are not shown in FIG. 3 for purposes of clarity. As can best be
seen in FIG. 4, the optical channel plate array 45 includes a stack
60 of light channel plates 61-66. Each channel plate, such as
channel plate 61, comprises a base or plate body sheet having four
generally arcuate channels 67-70 formed in the upper surface of the
plate body. Each channel has conductive path means disposed therein
comprising a conductive element, such as indicated at 71-74, which
extends the full length of the associated channel and is adapted to
conduct wavelengths of the electromagnetic spectrum.
Each of the plate bodies or base sheets 61 is made of an acrylic
plastic material which is one embodiment is approximately
one-sixteenth inch in thickness, one-half inch in width, and 31/2
inches in length. The channels 67-70 in the exemplary illustration
have a square cross-section of approximately 1/32 inch by 1/32
inch. The channels 67-70 are defined by smooth wall surfaces and
may be formed in the plastic sheets 61a by molding or casting the
sheet to the desired configuration.
The conductive elements 71-74, which are disposed in the channels
67-70 of channel plate 61, may comprise elongated bodies made of
polystyrene formed to be readily received within the associated
channels. The optic elements 71-74 may, in one method of
manufacture, be drawn and cut to the desired lengths. The ends of
the conductive elements are then trimmed and finished by heating or
chemical polishing so that the ends are smooth. In this manner,
light directed toward the ends of the conductive channel elements
will be conducted over the full lengths and will not be reflected
away from the conductive elements.
In one method of manufacture, the conductive channel elements 71-74
are formed to have square cross-sectional configurations and are
pressed into the square shaped channels 67-70 in the base sheet 61
using an optically smooth die which will maintain the surfaces of
the channel elements optically smooth when they are embedded in the
acrylic plastic base sheet 61. Such precaution is taken to assure
that the surfaces of the conductive elements will remain optically
smooth so as to minimize light scattering. Alternatively, the
conductive channel elements may be formed with circular
cross-sectional configurations and heated and pressed into the
square channels 67-70 in the base sheet 61 to conform to the shape
of the channels. It is also possible to employ channels and
conductive channel elements having circular or semi-circular
cross-sections.
The four channels 67-70 and their associated conductive elements
71-74 have input ends 85-88, respectively, which intersect an edge
surface 89 of the channel plate 61. The channels 67-70 and their
associated conductive elements 71-74 converge together so as to
form a single output channel 95 which terminates at a second edge
surface 96 of the light channel plate 61. Since sharp bends in the
conductive elements are undesirable from the standpoint of
reflection losses, the radius of curvature of the conductive
elements is maximized for a given width of the base sheet.
The conductive channel elements, such as channel elements 71-74 of
channel plate 61, serve as "light paths" to conduct light from the
light plate 40 which impinges on the input ends 85-88 of the
conductive elements to the output end 95 adjacent the light
detector array 41 as shown in FIG. 3. The conductive channel
elements in the respective plate bodies 61-66 conduct light by
total internal reflection. Accordingly, the material of the
conductive elements is selected to have a higher index of
refraction than the material of the plate body sheets. For example,
the conductive elements may be made of polystyrene having an index
of refraction of 1.59 and the base plate sheets may be made of
acrylic plastic having an index of refraction of 1.49.
Consequently, as light is conducted through the channel plate
assembly 45 over the conductive elements, light rays incident on
the walls of the conductive elements 71-74 will be reflected back
into the conductive elements rather than passing to the adjacent
base sheet, and thus, the light will be conducted along the full
lengths of the conductive elements from their input ends to their
output ends.
Alternatively, the present invention contemplates manufacture of
the polystyrene conductive channel elements by the technique of
drawing the elements through a die and cladding them along their
peripheral surfaces with a cladding material such as an epoxy or
acrylic plastic having a lower index of refraction than that of the
conductive elements. The cladded conductive elements would then be
inserted into the respective channels. In this fashion, any
suitable material can be used for the base sheets.
The channel plates assembly 45 may also be made by first forming
the channel plates and associated channels through injection
molding techniques, injecting a liquid polystyrene plastic into the
channels which have a higher index of refraction than that of the
channel plate material. The plastic channel material will find the
channels in the channel plate and conform to the shape of the
channels. When the plastic cools, the material will solidify to
form the desired optical paths through the channel plate with the
output ends of the path being integrally combined at 95.
A further technique for manufacturing the channel plates includes
the steps of forming the polystyrene conductive elements, and then
positioning the conductive elements accurately in sandwich fashion
between a pair of base plates of a material such as acrylic
plastic. In this embodiment, the base sheets do not have preformed
channels. Rather, the conductive elements will be bound on two
sides by air which has an index of refraction of unity. Light will
be transmitted through the conductive paths provided by the
conductive elements. The spaces between the conductive elements and
the base plates may be filled with a suitable material to assure
that the conductive elements remain in position. In such case, the
index of refraction of the material provided between the rods will
be less than the index of refraction of polystyrene material from
which the conductive elements are made.
Referring again to FIG. 4, the channel plates 62-66 are
substantially identical to channel plate 61 with each having four
conductive elements disposed in channels formed so that the
conductive elements have input ends terminating at one edge surface
of the associated base sheet and a common output end terminating at
a second edge surface of the base sheet. For example, channel
plates 62-66 have light conductive elements 101-105, respectively,
which have input ends intersecting edge surfaces corresponding to
edge surface 89 of plate 61. The light conductive elements of each
of the channel plates similarly converge to establish a common
output for the associated channel plate similar to the common
output 95 of the conductive elements of channel plate 61.
The channel plates 61-66 and their associated conductive elements
are secured together in aligned stacked relation so that the input
ends of the conductive elements of the respective channel plates
overlie one another in a common edge surface of the stack. The
channel plate stack also preferably includes spacing plates 75-81
which are interposed between the light channel plates 61-66 to
separate them from each other and thereby establish a desired
spacing between the conductive elements which overlie one another
in the channel plate stack. The spacer 78 has a greater vertical
thickness than the other spacers and serves to support the shafts
of code discs 51-54 as will be more fully described hereinbelow.
The spacing plates 75-81 also increase the rigidity of the stack.
Alternatively, the spacing plates 75-81 may be eliminated and the
thickness of each channel plate 61-66 may be increased. In the
latter case, the thickness of the channel plates 61-66 should be
selected to sufficiently provide the desired isolation between the
vertically aligned conductive elements in the stack.
Referring to the FIG. 3, each of the channel plates 61-66 and
spacer plates 75-81 includes a pair of alignment apertures, such as
apertures 130 and 131 in sheet 61, which are formed in the channel
plates for vertical alignment when the channel plates are assembled
in stacked relation. The encoder assembly 20 includes an alignment
plate 134 which has a pair of spaced parallel alignment pegs 137
and 138 which are received through the alignment apertures 130,131,
respectively, in the channel plates 61-66 and spacers 75-81 to
assure that the input and output ends of the conductive channel
elements will be vertically aligned.
As has been described, each of the six channel plates 61-66
includes four conductive channel elements each of which provides an
individual light path over the corresponding channel plate. With
the input ends of the conductive channel elements being vertically
aligned as shown in FIG. 4, it can be seen that four separate sets
of conductive light paths 46-49 are provided through the channel
plate assembly 45.
Noting FIG. 3, the light plate 40 includes a separate light source
40a-40d for each set of light paths 46-49 for directing light
toward the conductive channel elements of the associated sets of
light paths. The light plate 40 includes alignment apertures
156,157 which receive spaced parallel alignment pegs 158,159 on the
alignment plate 134 to align the light sources 40a-40d relative to
the channel plate stack 60. Referring to FIG. 5, which is taken
along line 5--5 of FIG. 3, each light source, such as source 40d,
includes a light emitting diode 141 and a light guide 142
comprising six polystyrene fiber optic rods 143-148 for directing
light emitted by the diode 141 toward the conductive channel
elements comprising each light path set 46-49 in the channel plate
assembly 45. The light plate 40 includes a hollow support housing
149 having an aperture 150 for receiving the diodes 141. The fiber
optic rods 143-148 are supported by the housing 149 and are merged
at one end 151 adjacent the diode 141. The individual fiber optic
rods 143-148 extend through the housing 149 to openings 152-157 in
a wall 158 of the housing which is adjacent the channel plate stack
60 to permit light from the diode to impinge on the input ends of
the conductive channel elements in the channel plates.
The light emitting diode 141 may be a gallium arsenide phosphide
diode which, when energized, emits light at a peak wavelength of
650 angstroms. A suitable light emitting diode commercially
available is the MV50-light Emitting Diode manufactured by Monsanto
Corp. The polystyrene chosen for the fiber optic rods 143-148 is
adapted to conduct wavelengths of the electromagnetic spectrum.
Referring to FIG. 1, the light emitting diodes, such as diode 141,
are energized by signals extended to the diodes over a select
circuit 160 from an energizing source 161. The select circuit 160
may comprise a gating arrangement for sequentially connecting the
output of the energizing source 161 to the leads of the diodes
which comprise the light sources 40a-40d of light plate 40.
Light sources 40a-40d are associated with dials 28-31,
respectively. Thus, to read out the meter reading, the diode of
source 40a is energized first, then the diode of source 40b, etc.,
so that the angular positions of the shafts 21-24 associated with
the four diodes 28-31, respectively.
To avoid erroneous readings and to permit the use of AC amplifiers
in the output circuits 25, the energizing source 161 provides a DC
signal modulated by an AC signal at 100 HZ rate.
As can be seen in FIG. 1, each of the shafts 21-24 carries a code
disc member 51-54, such as code disc 54 shown in detail in FIG. 6.
The code discs 51-54 are interposed between the light plate 40 and
the optical channel stack 45 to permit selective transmission of
light from the six light outputs of the light sources 40a-40d
comprising the light plate 40 to the six input ends of the
conductive channel elements comprising each of the four input areas
46-49 of the channel plate stack 60.
Code member 54 comprises a disc 170 having a code pattern
comprising six concentric rings 171-176. Each ring or track, such
as track 176, bears coded information in the form of a number of
alternating radiation permeable and opaque angular segments, such
as segments 177,178. In the present example, where the radiation
employed is visible light, the disc 170 may be formed of a light
transparent material, such as plastic, the opaque sections 178
being formed as a coating of an opaque material selectively
disposed on a surface of the disc 170.
The code discs 51-54 are mounted for rotation by associated shafts
21-24, respectively. The shafts 21-24 pass through apertures 166,
shown in FIG. 4, formed in the spacer sheet 78. The apertures 166
serve to align the code tracks of the discs 51-54, such as tracks
171-176 of disc 54, relative to the input ends of the conductive
channel elements in the stacked channel plates.
The locations of the input ends of the conductive channel elements
74 and 101-105 relative to the code tracks 171-176 are indicated by
the circles shown in the code tracks in FIG. 6. Thus, for example,
code tracks 176, 174 and 172 are aligned with conductive elements
74, 101 and 102, respectively, while code tracks 171,173 and 175
are aligned with conductive elements 103-105, respectively. In the
present example, the innermost track 171 comprises a reference
channel and the other five code tracks 172-176 are data tracks.
The data tracks 172-176 of the disc 170 shown in FIG. 6, are coded
in gray code so that, as will be shown, in a sequential change from
any code number representing a given angular position of the
associated shaft to any next adjacent number representing the next
position of the shaft, the change requires that only one digit or
bit of the number be changed.
Reference channel 171 is transparent over the entire extent of the
track such that light from the light plate 40 directed towards the
reference channel area 171 of code member 54 will be passed to the
optical stack 60.
Referring to FIG. 7, code disc 54 is shown mounted on shaft 24. One
end of the shaft 24 passes through the aperture 166 in the spacer
sheet 78 of the stack 60 and serves to align the code tracks
171-178 of the code disc 54 relative to the exposed input ends of
the conductive channel elements in the light channel area 49 of the
plate stack 60. The shaft mounting also references the code member
54 to the light output members 143-148 of the light source 40d.
Accordingly, light from the light rod 143 directed towards the code
disc 54 will pass to conductive element 74 whenever the angular
position of the shaft 24 is such that a clear area, such as area
177, is positioned between the light tube 143 and the input end 88
of the conductive element 74 and be conducted over the conductive
element to the light detector array 41. Alternatively, when the
angular position of the shaft 24 is such that an opaque area, such
as area 178, is positioned between the light rod 143 and the input
end 88 of the conductive channel element 74, transmission of light
between the light member 143 and the optical plate stack 60 will be
blocked.
Code members 51-53 are similar to the code member 54 and have an
identical pattern disposed on the surface of the code members
51-53.
As the light emitting diode of each of the light sources 40a-40d is
sequentially energized over the select circuit 160 by signals from
the power signal generator 161, light is directed through
associated code discs 51-54 to the optical stack 60. The light
directed to the optical stack will be conducted over the conductive
channel elements in the channel plates which are adjacent
transparent areas of the code member as a function of the angular
positioning of the code member. The light is conducted over the
optical channel plate stack to the output edge surface of the stack
to selectively illuminate detectors 41a-41f, shown in FIG. 3, which
comprise the light detector array 41.
The light detector array 41 shown in FIG. 3 includes six detectors
41a-41f, each being associated with one of the six terminal ends of
the conductive channel elements in the channel plates 61-66. The
light detectors 41a-41f may comprise photosensitive transistors,
such as the type FPF 1,100 manufactured by Fairchild
Semiconductors, Inc. Noting FIG. 3, the light detectors 41a-41f are
supported by a plate 187 of the detector array 41 in vertically
spaced alignment. The detectors 41a-41f abut the output edge
surface of the channel plate stack 60 to minimize loss of light
from the stack to the detector elements 41a-41f.
The detector plate 41 includes a pair of horizontally spaced
locating pegs, one of which is shown at 189, which are received in
alignment apertures 191,192 provided in the channel plate stack 60
to align the optical detectors 41a-41f with the output ends of the
conductive channel elements in the channel plate stack.
The photo-transistors which comprise the detector elements 41a-41f
are responsive to light conducted over the optical stack 60 from
the light source 40 to change electrical conductivity. This change
in conductivity is monitored by the output circuits 25 which
provide outputs representing the condition of the detectors 41a-41f
and correspondingly indicate over which channels light is being
transmitted.
Referring to FIG. 8, the output circuits 25 comprise five output
detecting circuits 201-205, each connected to one of the light
detectors 41a-41c, 41e and 41f. Each output circuit, such as
circuit 201, connected to detector 41a includes a differential
amplifier 215 having a first input 217 connected over the detector
device 41a to a voltage source +V and a reference input 218. The
output 219 of the amplifier 215 is connected to a set input 220 of
a phase detecting flip flop 221. A reset input 222 of the phase
detecting flip flop 221 is connected to the reference input 218 of
the differential amplifier 215. The reference signal which is
applied to the reference input 217 of the differential amplifier
215 is provided by the light reference level detector 41d which, as
shown, in FIG. 8, has a first lead 224 connected to the source +V
and a second lead 223 connected to the reference input of each
output circuit, such as lead 218 of output circuit 201.
Whenever a detector such as detector 41a is energized by light, the
resistance of the phototransistor which comprises the detector will
increase and, accordingly, the voltage +V will be extended to the
input 217 of the amplifier 215. The light reference level detector
41d associated with the reference channel will be energized
continuously since the code track 174 of the code disc 54 which
comprises the reference channel is of a transparent material and
accordingly, the reference input will always be +V.
Whenever the detector 41a is energized, the signal levels at inputs
217 and 218 of the amplifier 215 will both be at +V potential, and
accordingly, the signal level at the ground signal level on set
input 220 of phase detect flip flop 221 will cause the flip flop
221 to remain reset providing a logic 0 level at output 225.
On the other hand, if because of the coding of the disc 51,
detector 41a is not energized, input 127 will be at approximately
ground potential whereas the reference lead 218 will be at a
potential of +V. Accordingly, the output 219 of the differential
amplifier 215 will be a +V potential which will set the phase
detect flip flop 221, thereby providing a logic 1 level at output
225 of the flip flop 221.
The output circuits 202-205 similarly provide logic 1 or logic 0
outputs as the function of the angular position of the code disc
51-53 associated therewith which provide selective transmission of
light over the fiber optic array 45 to the light detector array 41.
The five logic level output signals provided by the circuits
201-205 provide the gray code shown in Table 1 which represents
coding for 20 angular positions of the shafts 21-24.
TABLE I
Gray Code for a Twenty Position Encoder
Output Circuit Digit 201 202 203 204 205 Position (176) (174) (172)
(173) (175) 1 1 0 0 0 1/2 0 1 0 0 0 1 0 1 0 1 0 11/2 1 1 0 1 0 2 1
1 0 1 1 21/2 0 1 0 1 1 3 0 0 0 1 1 31/2 1 0 0 1 1 4 1 0 0 1 0 41/2
0 0 0 1 0 5 0 0 1 1 0 51/2 1 0 1 1 0 6 1 0 1 1 1 61/2 0 0 1 1 1 7 0
1 1 1 1 71/2 1 1 1 1 1 8 1 1 1 1 0 81/2 0 1 1 1 0 9 0 1 1 0 0 91/2
1 1 1 0 0 1 1 0 0 0
Thus, for example, when pointer 32 of dial 31 of register 26 shown
in FIG. 2 is indicating a reading of zero, the orientation of the
code disc 54 relative to the optical channel plate assembly 45 will
be as shown in FIG. 6, with opaque areas of code tracks 174 and 176
adjacent light conductive channel elements 74 and 101, and clear
areas of code tracks 171-173 and 175 adjacent light conductive
channel elements 102-105. Therefore, with reference to FIG. 2, when
light source 40d is energized, light directed toward the optical
stack (over code disc 54) will be conducted through the optical
channel plate assembly 45 over the conductive channel elements
102-105 to energize light detectors 40c-40f. Correspondingly, when
light detectors 40c-40f are energized, output circuits 203-205 will
provide logic 0 outputs, and output circuits 201 and 202 controlled
by detectors 40a and 40b which are not energized will provide logic
1 levels as shown in Table I to represent the coding for the digit
position zero.
SECOND EMBODIMENT OF THE OPTICAL ARRAY
A second embodiment of an optical channel plate assembly 245 in
accordance with the present invention is shown in FIGS. 9-11. The
channel plate assembly 245 includes a stack of light channel plates
261-266 each of which has four channels 267-270 formed in the upper
surface thereof to receive conductive channel elements 271-274,
respectively. The methods of manufacture of the channel plates
261-266 may be similar to those described above with reference to
the channel plate assembly 45.
Noting FIG. 9, the forward surface 246 of the channel plate
assembly 260 has a pair of forwardly projecting boss portions 247
and 248 which extend the full vertical height of the assembly 260
and define two recessed areas 249 and 250 adjacent thereto. The
planar areas of the recesses 249 and 250 are sufficient to allow
mounting of code discs 251 and 253, respectively, within the recess
areas as shown. The code discs 251 and 253, as well as code discs
252 and 254, are supported on rotatable shafts 221-224, the code
discs 252 and 254 being supported adjacent the forward surfaces of
the bosses 247 and 248.
By providing forward bosses 247 and 248, and thereby establishing
the peripheral portions of the code discs 251-254 are allowed to
over lap. Thus, for example, as shown in FIG. 10, a portion 255 of
the code disc 252 overlaps a portion 256 of code disc 253, and a
portion 257 of code disc 254 overlaps a portion 258 of code disc
253. The overlapping of portions of adjacent code discs permits a
reduction in the horizontal dimension of the channel plate assembly
245 to approximately half the size of the channel plate assembly 45
shown in FIG. 3, when using similar size code discs for the
respective embodiments of the channel plate assemblies.
Alternatively, larger code discs may be used with the channel plate
assembly 245 if it is the same size as plate assembly 45.
As can be seen in FIG. 9, the overlying portions of the conductive
channel elements 272 and 274 intersect the outer surfaces of the
boss portions 248 and 247, respectively, such that the code discs
251-254 are all spaced approximately the same distance from the
corresponding forward edge surfaces 247, 248, 249 and 250 of the
channel plate assembly 260. Light from a light source (not shown)
would be directed toward portions of the code discs 251-254 that
lie between the overlapping portions of the code discs. As is best
shown in FIG. 11, only one-half of the planar area of each code
disc is positioned forwardly of the channel plate assembly 260.
Therefore, a different pattern of clear and opaque areas is used
for the code discs 251-254. One example for a code disc 254 is
shown in FIG. 6A.
In the channel plate assembly 245, the conductive channel elements
in each channel plate 261-266 coverge, as shown for channel plate
261, and intersect an end surface of the channel plate assembly at
common points of intersection 281-286, as best seen in FIG. 11. The
respective common end terminations 281-286 of the conductive
elements in the stacked plates are staggered to minimize
interference between adjacent light channels, as shown. An
associated light detector array (not shown) would have light
detectors disposed in the same pattern as the output terminal ends
281-286 of the light conductive elements in the channel plate
assembly 245.
While the channel plate assemblies provided in accordance with the
present invention have been described with reference to application
in an optical encoder, it will be understood that the channel plate
assemblies can also be used in various other applications such as
in card and punched tape illuminators and readers to conduct light
from a common light source to a plurality of light detector
elements, or in segmented numeric readouts. In such applications,
the channel plate assemblies would provide an optical transmitting
device which is simpler in construction and more economical to
manufacture than optical assemblies which employ many individual
fiber optic rods as employed in the priot art.
* * * * *