Electro optical transducer utilizing aligned light conductors

Opaque/translucent-transparent markings on a flat track pass through a gap defined by a carrier body sealed in a casing and having peripheral grooves ending at the gap of the body for embedding light conductors connected to light emitting and receiving means aranged generally on opposite sides of the gap.

BACKGROUND OF THE INVENTION 
The present invention relates to an increment sensor, transducer and/or 
pick-up and constructed for the conversion of either rotational or 
straight linear movements into a sequence of electric pulses, and more 
particularly the invention relates to a device of the foregoing kind which 
includes a light source or other radiation source and a photoelectric 
transducer and defining between them a monitoring or scanning gap in which 
a marking track moves, the track being established as a sequence of 
transparent or translucent markings alternating with opaque markings. 
Increment transducers and pick ups of the type to which the invention 
pertains are generally known and are used, for example, for the open loop 
or closed loop control of machines, devices or other parts which usually 
undergo or are supposed to undergo a uniform movement, usually a 
rotational one or a reciprocal one. A particular example for example is 
the reciprocating motion of a carriage for a print head in a matrix 
printer. The matrix head drive runs uniformly and continuously or in 
uniform steps in order to move the part in between specific positions. 
Certain operations are to be carried out in these positions. In the case 
of a printer, of course, these positions are the print positions. The 
increment sensor generally and the photoelectric device in particular 
produces pulses which are fairly weak electrical pulses, and they are 
amplified in suitable circuitry to be raised to a more useful level for 
purposes of obtaining electrical control. 
A known increment sensor is disclosed for example in German printed patent 
application No. 23 39 874. The particular construction of that publication 
is chosen to avoid a tumbling motion of the slotted disk vis-a-vis the 
scanning head. Moreover this known device is usually comprised of four 
photoelectric receivers such as photo transistors which are arranged along 
a line being oriented transversely to the direction of movement of the 
marking track. Each of the tracks will provide in the respective receiver 
a sinusoidal output and these outputs have respectively relative phase 
positions 0.degree., 90.degree., 180.degree. and 270.degree.. This 
multiple transducer arrangement is used in order to improve pick-up 
generally as far as the marking and slot distances are concerned. 
Accordingly two scanning devices for two sinusoidal signals are associated 
with a single slot. This arrangement is supposed to suppress the effect 
any tumbling motion of the disk in relation to the phase relations, pulse 
sequences is supposed to have. These phase relations are apparently easily 
adjustible because the two scanning devices, each including light source 
and receiver, are arranged on a common carrier which is pivotable and 
arrestable for pivot motion about a point which is situated between the 
two scanning devices. It was found, however, that an angle adjustment of 
the row of the transducers is not quite adequate to solve the problem; not 
even a major aspect of the problem because during initial installation and 
adjusting of the parts vis-a-vis each other further inaccuracies and 
tolerances arise, so that in fact the adjustibility of the increment 
sensors vis-a-vis two parallel arranged marking tracks becomes 
increasingly difficult. 
Another aspect of the known device is that the mere mechanical adjustment 
of parts does not suffice. Particularly in the case of high speed 
operation electrical problems related to that high speed are encountered. 
Such a problem relates for example to the requisite adjusting of the 
operating point in the receiver and the transducers. Also, problems arise 
on account of varying operating temperatures of light source and receiver; 
the light source in particular is subject to aging if, as is common, such 
a source is constructed as a light emitting diode. 
Another problem is to be seen in that any photo transistor when used as a 
pick-ip transducer offers per se two basic drawbacks. One drawback is that 
with rising temperature their gain increases while on the other hand with 
increasing frequency the gain reduces. The light emitting diode when used 
as source photo transistors because the luminous output decreases also 
with increasing temperature. However, this type of compensation is 
effective only if the temperature dependency of the photo transistor is at 
least approximately expressable by the same factor as the power drop of 
the light emitting diode. Generally speaking this equality cannot be 
expected. Therefor, on the basis of the physical conditions, manufacturing 
problems are to be expected. 
DESCRIPTION OF THE INVENTION 
It is an object of the present invention to provide a new and improved 
track increment sensor overcoming the drawbacks outlined above and 
particularly reducing expenditure for adjustment, both electrical and 
mechanical, while increasing accuracy concerning signal formation while 
reducing complexity of scanning several marking tracks as far as optical 
arrangements are concerned. 
It is therefore a specific object of the present invention to provide a new 
and improved increment track sensor, transducer and pick-up for the 
conversion of linear movement such as straight linear of rotational 
movement into electrical pulse sequences and including a light source and 
a photoelectric transducer, as well as at least one marking track moving 
in and through an operating or sensing gap situated between the source and 
the transducer. 
In accordance with the preferred embodiment of the present invention, the 
improvement as it relates to the specific object is comprised of providing 
an optical connection between light source and transducer by means of 
light wave conductors, whereby, basically, a single light wave conductor 
that interconnects source and pick-up is merely interrupted in the 
operating gap area in which the marking track is moving under observation 
of the condition that adjacent to this gap and as hypothetically continued 
through the gap, the axis of the light conductor extends precisely 
transverse to the direction of movement of the marking track in that gap. 
The conductors are provided in the plurality for reasons of multiple 
scanning which is to be understood in a twofold fashion: there are 
multiple marker tracks and each track is scanned in a multiple fashion. 
The gap is structurally realized, established and maintained by a carrier 
body which includes its own gap and is positioned so that the latter gap 
in fact coincides with the gap between the conductors so that one can 
speak of a common gap. The carrier body has peripheral grooves in and 
along its periphery. These grooves extend towards the common gap and in 
pairs from opposite sides thereof; the grooves end at that common gap and 
they receive the conductors and have them embedded. A common casing for 
all these parts holds them and they are all sealed therein. 
The invention, first of all, avoids certain problems that arise during 
manufacture, assembly and adjustment of individual parts. Moreover, the 
direct optical connection as proposed here and involving the conduction of 
light through plural light conductors from transmitters and light sources 
to the pick-up transducers establishes per se a higher accuracy concerning 
the multiple path light transmission, generally and on account of their 
relationship because the ends of the light wave conductor can be 
positioned directly adjacent to the operating gap in a very accurate 
manner and, therefore, in relation to each other and to different portions 
of the tracks. Subsequent adjustment is completely avoided because the 
position of the light conductors remains invariant and is basically 
dependent upon the chosen initial method of manufacture of the device. 
This advantageous solution of the problem of well defined scanning of 
marking tracks is based on the recognition that the fibers may have 
diameters from 1/10 to 1/2 of a mm and the manipulation of such fibers in 
accordance with the invention during manufacture simplifies the 
construction of the increment sensor considerably. 
In furtherance of the invention, it is suggested that the grooves receive 
different groups of fiber bundles pertaining to different functional 
circuits. One utilizes here specific property of light conducting fibers: 
they do not accept interfering light from the outside. Hence, several 
fibers or fiber bundles can be placed next to each other, they may even 
touch each other but there is no interference between them as far as the 
conduction of light is concerned. 
Another improvement in accordance with the invention is to be seen in that 
the carrier body is generally of a construction having a preferred length 
dimension. One end thereof is provided with the operating gap for the 
marking track being for example a slotted disk while the other end of this 
carrier member is provided with a common connection structure for both the 
light source and the transducer or transducers. The common connection 
avoids that during installation light source and receiver circuit are 
confused so that another manufacturing problem is avoided. Moreover, 
adjustment of optical structure can be avoided as the light fibers are 
sufficiently accurately positionable by the device and structure itself. 
Any inaccuracies concerning position and other optical error sources are 
avoided by inserting the carrier body into a particular housing. The body 
assumes a definite position in the housing and is sealed therein 
subsequently. An accurate position of all the parts in relation to each 
other is moreover enhanced by providing the aforementioned housing with a 
latching or locking structure for groups of elements, respectively being 
light source and receiver groups. These locking means force the 
aforementioned groups against the carrier body and thus ensure integrity 
of positioning. The disposition of individual parts is ensured further by 
using a filler for the grooves so as to embed the light conducting fibers 
and/or to fill any cavities or spaces between carrier and housing. 
The formation of accurate signals without adjustment and without special 
assembly and mechanical adjusting problems is a desired feature. For this 
one should use triple diodes and triple photo transistors. Therefore, 
groups of three light fibers each are associated with the respective 
making tracks in the operating gap. 
Another advantage is derived from covering the common connection member 
with a light impermeable i.e. opaque cover keeping interfering signals 
from the generally transparent connecting structure. Compactness, 
moreover, of the transducer and sensor assembly is attained further by 
using the aforementioned cover as a printed circuitlike plate to provide 
for short conductors and a closed compact structure and design.

Proceeding now to the detailed description of the drawings, the figures 
show generally a rotating machine or equipment part 2 having a shaft 3 
carrying a disk 7. The disk is provided with a plurality of altogether 
three marking tracks 8a, 8b and 8c. The figures, moreover, show a sensing 
transducing and pick-up system 1 arranged so as to receive in parts the 
disk 7 and generally scanning the tracks 8a, 8b and 8c. In principle it 
makes no difference whether these tracks are on a disk and therefore have 
a curved configuration or are for example on a reciprocating template 
member or the like. Decisive is that in the range of the scanning of the 
pick-up device there is strictly a linear movement as far as each of the 
tracks are concerned. The device 1 generally is provided for generating a 
plurality of electrical pulses. These pulses are used in open loop or 
closed loop configuration to control for example the motor or another 
drive of the shaft, and/or to control other pieces of equipment. Systems' 
aspects generally are shown in applicant's U.S. Pat. No. 4,673,810, issued 
on June 16, 1987. 
Flange parts 4,5 and 6 and fasteners 6a are provided to connect the round 
planar disk 7 to the shaft 3. The connection is such that the rotational 
movement of the disk 7 is an exact 1:1 replica of the rotation of the 
shaft 3 and therefore of the motor which drives the shaft 3. Generally 
speaking, motor shaft 3 may be a part of a device or drive to be 
controlled but amy also pertain to an extremely accurately running 
calibrating structure in relation to which some other equipment is to be 
calibrated and the device illustrated therefore produces calibrating pulse 
sequences. 
The marking tracks 8a, 8b and 8c are comprised of slots 12 separated by 
bars 13. The slots are of course transparent or translucent while the bars 
13 are opaque. Preferably bars and slots are equally wide. The disk 7 
itself is usually made of metal. Alternatively, the disk 7 may be made of 
glass or other transparent material upon which opaque markings have been 
placed for example by photographic process or otherwise. In any event, 
these marking are about 0.1 mm wide, and in case disk 7 is made of glass, 
aluminum may have been vapor deposited and photographic-etching procedure 
established the marking and slot pattern. 
Turning now to the transducer assembly, there is shown a housing or casing 
10, generally, which carries a carrier body 11. Both have a certain gap 
defining specifically the gap 9 in which disk 7 moves. Housing or casing 
10, moreover, includes a light transmitter - light receiver modular group 
14 which gapfree abuts and bears against the carrier 11. This group 14 
includes a light source 15 and, a particularly advantageous feature, the 
transducer 16 is also included in that group. Both, element 15 and element 
16 are arranged in a uniform body 17 made of transparent material and they 
are provided with embedded connecting lines 18 and 19. 
The connecting lines 18 and 19 run to an amplifier circuit outside of the 
system, not shown, which raises the signal level to a more practical one 
and possibly provides modulation - demodulation and/or digitalization. In 
other words, the amplification circuit changes for example the sinusoidal 
signals into square shaped pulses. This is not part of the present 
invention (see e.g. the copending application). 
The optical connection between light source 15 and transducer 16 is 
provided generally through light wave conductors 20. Reference numeral 21 
defines a zone in the gap 9 in which the light conductors 20 run precisely 
perpendicular to the extension of the gap 9 and particularly to the plane 
of rotation of disk 7. The light conductors are, moreover, arranged in 
pairs along the same axis 22 so that in fact one can postulate a 
hypothetical continuation of each of these light fibers through the gap 9. 
This gap 9 is thus a common gap for the carrier body 11 and for the light 
wave conductors 20. 
The light conductors 20 are made, as stated, from glass fibers being 
between 1/10 and 1/2 mm thick. These fibers are identified individually by 
reference numerals 28b and 28c. Prior to cutting gap 9, for example, by 
way of milling these fibers are wound in peripheral grooves 23 of the 
carrier body 11 so that particularly their position in the range 21 
depends exclusively on the arrangement and extension and configuration of 
the respective bottom 23a of each groove. Following winding, the grooves 
23 are closed by an embedding and filling mass 24 being e.g. of a pasty or 
more or less solid state and fixing the position of the fibers 20a, 20b, 
20c in the groove. Moreover, additional filling material 24 may be 
provided to fill any and all other gaps between the housing or casing 10 
and the carrier 11 so that in fact no cavities remain. 
Basically, for each light transmitter and for each transducer 16 one needs 
just two light conductors such as 20 in order to obtain a particular phase 
shifted signal at the output lines 18 and 19. These signals are fed to an 
amplifier circuit as was mentioned above. However, in accordance with the 
particular illustrated embodiment of the invention and reference is made 
here particularly to FIGS. 2 and 4 a maximum degree of accuracy is 
attempted an and the system provides that the grooves 23 receive groups of 
three conductors 20 whereby particularly in the central groove 23b, fibers 
20a, 20b and 20c are provided. The copending application elucidates on the 
advantages. 
The light source 15 is established by a triple light emitting diode and the 
transducer 16 is realized by a triple photodiode. Fibers 20a and 20c 
establish the outermost position; these light fibers 20a and 20c produce 
signals which lead and lag respectively by 90 degrees in relation to a 
reference signal that runs through the central fiber 20b. 
The reference signals is, as far as time is concerned, always, so to speak, 
in the middle between the signals from the outer path (track borders or 
margins), so that in terms of desired sinusoidal modulation the two 
outermost signals are phase shifted by 180.degree. in relation to each 
other. The phase relation can be maintained with sufficient accuracy. The 
outer two signals are digitized, i.e. squared in the amplifier as was 
mentioned above. 
The carrier body 11 is of oblong construction, i.e. the shape 11a has a 
preferred dimension of extension including two ends 11b and 11c. The 
operating (common) gap 9 is provided adjacent the end 11b while a common 
connecting member 26 for light transmitter 15 and transducer 16 is 
provided at the other end 11c. A step 26a is provided for positioning the 
devices 15 and 16 in relation to the light wave conductor system 20. 
The transparent connecting member 26, moreover extends into a recess 27 of 
body 11 to obtain optical coupling to the highest degree of accuracy 
possible. After carrier body 11 has been inserted in the housing 10 the 
body is additionally sealed as illustrated by the connecting "points" 28 
and 29 in FIG. 2. Subsequently the connection member 26 is slipped onto 
the end 11c of the carrier 11 and is held in addition by a locking 
structure 30 including a spring 31 in order to maintain positive contact 
and connection to the body 11. 
The locking member 30 is provided, moreover, with guide pins 32 and 33 
covered by a cover 34 being in turn held by means of screw 26 in the 
respective threaded appertures 36 of the housing 10. The light 
transmitter-receiver group 14 constitutes as stated as such a uniform 
module, i.e. it is a separate self container unit which can be easily 
exchanged without changing any of the physical parameters of the sensor as 
such. 
FIG. 3 taken in conjunction with FIG. 2 illustrates the invention in fuller 
detail as far as an extensive system is concerned and commensurate with 
the system in our copending application. The three marking tracks 8a, 8b 
and 8c can for example be scanned independently from each other. 
Therefore, there are three groups of three light fibers 28,b,c and they 
are arranged above the slots 12a,b,c oriented at an acute angle 37 but 
being parallel to a plane in the cross section as far as the gap 9 is 
concerned. The angle 37 is required in order to make sure that there is 
180 degrees phase shift between each of the outer signals of a marking 
track 8a,b,c. The angle 37 so to speak translates the modulation provided 
by the marking and the lateral extension of the markings into relation 
that permits extraction of the desired phase between different signals as 
derived from the same track. A lateral extension 38a of the housing 10 has 
a lateral nose 39a. A portion of housing 10 in opposite orientation 
carries a latching nose 39b. These noses are provided in order to fix the 
position of the sensor 1 as a whole in relation to other stationary 
equipment. 
FIG. 2, moreover, illustrates a particular parallel circuit connection 
involving all three marking tracks and the respective scanning and pick-up 
equipment. In this case particularly one combines from all three marking 
tracks 8a,8b,8c the respective radially outer light conducting fibers 28a 
as inputs for a triple transducer provides in form of a triple photo diode 
16. The respective middle light conducting fibers 20b are associated with 
another element of the threefold transducer (triple diode) 16 and the 
other respective outer light conducting fibers 20c are associated with a 
third element of the triple diode 16. 
The individual elements of the threefold light emitting diode 15 are 
associated with light conducting fibers 20a,20b, and 20c respectively for 
each marking track 8a,8b and 8c. By way of example, a alight conductor of 
fiber such as 20a runs from one of the three diodes 15 to the common gap 
so that its light emitting exit window is situated above a margin of one 
of the tracks such as 8a and is continued on the other side of gap 9 and 
of disk 7 towards one of the transducers 16. The same transducer will 
receive light from two other fibers beginning at that two other diodes and 
traversing comparable margins of the two other tracks 8b and 8c. The 
situation is analogous as far as the light from the two other light 
emitting diodes is concerned. Therefore, the threefold light transmitter 
15 and the threefold transducer 16 provide in all of the three groups of 
three light conducting fibers 20a,20b and 20c similar physical 
quantities. This feature makes sure that a very accurate mode of signal 
formation is provided which does not require any adjustment tuning, 
trimming or the like and will in fact adjust to the respective temperature 
conditions prevailing throughout. The cross-over feature is shown in 
detail in our copending application. 
The invention is not limited to the embodiments described above but all 
changes and modifications thereof, not constituting departures from the 
spirit and scope of the invention, are intended to be included.