Relative position indicator

Apparatus is provided for giving a visual indication of increments of position over a predetermined range of positions to either side of and including a predetermined zero reference point. The apparatus includes a plurality of pattern generating units, each including first and second surfaces, each of these first and second surfaces having a plurality of spaced-apart opaque areas having translucent areas therebetween. The second surface is superimposed upon the first surface for creating a plurality of patterns in response to movement therebetween. The plurality of pattern generating units are arranged adjacent one another and are respectively configured for producing a unique and identifiable set of patterns for each of a plurality of increments over a predetermined range to either side of and including a predetermined zero reference point.

FIELD OF THE INVENTION 
The invention concerns a novel apparatus for providing a visual indication 
of the relative positions of, or offset between, two members. More 
specifically, the invention provides a novel indicator which utilizes a 
plurality of patterns to indicate a predetermined number of increments of 
offset or movement between two members over a predetermined range to 
either side of a predetermined zero reference point. The invention also 
extends to a novel form of pattern generator for use in such an indicator 
apparatus. 
BACKGROUND OF THE INVENTION 
While the invention may find use over a wide variety of applications, the 
description of the invention will be facilitated by specific reference to 
the problem of providing level or aiming indicators for automotive vehicle 
headlamp systems. Regulations currently exist in the United States for 
vehicle headlamp aiming devices (VHAD) which provide standards for 
headlamp aim inspection and adjustment about both the vertical and 
horizontal axes. In the case of vertical inclination, these regulations 
(49CFR, Ch.V) provide that "references and scales" shall be provided in 
the VHAD to assure correct vertical aim including an equal number of 
graduations, each graduation representing 0.19 degree (1 in. at 25 ft.) to 
provide for variations in aim at least 1.2 degrees above and below the 
horizontal. For horizontal aim, these regulations provide that each 
graduation shall represent a change in horizontal position not greater 
than 0.38 degree to provide for variations in aim of at least 0.76 degree 
to the left and right of the longitudinal axis of the vehicle. 
Among level indicators which have been used in the past, perhaps most 
common is the spirit level or so-called "bubble" level. Such levels tend 
to be relatively bulky, in addition to having a degree of fragility, that 
is, the container for the liquid and bubble may be fractured or damaged, 
leading to loss of liquid and thus, to loss of function of the level. 
Moreover, the reading must be taken on the bubble itself, which presents 
some difficulty. Since the bubble will normally have some considerable 
length or width, even with finely marked graduations on the transparent 
housing, it may be difficult to determine the correct reading. That is, 
will the reading be taken from one edge of the bubble consistently, or 
from an estimated center line of the bubble? Moreover, bubble levels tend 
to be relatively easy to jar and disturb, thus making readings even more 
difficult to obtain. 
Also, bubble levels are temperature-sensitive. That is, the liquid will 
expand with increasing temperature, causing the bubble to shrink and 
vice-versa. This can cause inconsistencies among readings taken at 
different ambient temperatures. Special liquids can be specified to 
minimize this effect; however, this can be relatively expensive when 
dealing with the wide temperature ranges specified for automotive 
applications. 
A number of patents have heretofore disclosed the use of various moire 
patterns for indicating a level condition or lack thereof. Among these 
patents are U.S. Pat. Nos. 4,995,169, 4,343,090, 4,336,659 and 4,288,056. 
However, each of these patents is limited in that the moire patterns are 
disclosed for indicating only an aligned or a non-aligned condition. That 
is, these moire patterns are disclosed only for indicating whether the 
monitored condition is or is not at its "level" or zero reference point. 
The above-referenced U.S. Pat. No. 4,995,169 discloses that observation of 
the pattern will indicate whether the offset is in a positive or negative 
direction from the zero reference . Thus, none of these patents discloses 
providing separately identifiable or unique indications of a number of 
increments of movement in either direction from a level or zero reference 
point. In U.S. Pat. No. 4,995,169, an additional external scale with 
angular markings is provided. This scale is utilized in connection with 
the moire pattern to first set an arrow or indicator line at a zero 
position when the level condition is obtained, as indicated by the moire 
pattern. Thereafter, when the vehicle or other object on which the 
indicator device is mounted is moved away from a level or horizontal 
condition, rotation of the moire pattern back to its zero reference or 
level appearance should result in the arrow or indicator line being moved 
to an angular marking corresponding to the angular offset from the level 
or horizontal condition of the vehicle or other object on which the 
indicator is mounted. However, the moire pattern in and of itself is 
incapable of providing any such incremental angular indications. It will 
be appreciated that the device that is presented in this patent is 
relatively complicated to assemble and operate, relying as it does on the 
alignment of the angular markings relative to the moire pattern, and on 
the operator accuracy both in initially zeroing and later manipulating the 
device.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT 
Referring now to the drawings and initially to FIG. 1, there is illustrated 
in somewhat diagrammatic form a set of pattern generating units in 
accordance with the invention. These pattern generating units are 
configured and may be arranged, as will be described, for providing a 
visual indication of increments of position over a predetermined range of 
positions to either side of, and including, a zero reference point. These 
pattern generating units in accordance with the invention are configured 
for producing a unique and identifiable set of patterns for each of the 
plurality of increments within this predetermined range to either side of 
a zero reference point. 
In FIG. 1, a plurality of pattern generating units are diagrammatically 
illustrated for achieving such sets of patterns in response to relative 
linear movement between two members or surfaces. In FIG. 2, there is 
illustrated a similar set of pattern generating units constructed in 
accordance with the invention for measuring relative angular displacement 
between two members or surfaces. 
In FIG. 1, three such pattern generators or generating units are shown and 
indicated by reference numerals 10, 12 and 14. Each of the pattern 
generators 10, 12, and 14 includes first and second surfaces 16, 18. In 
the illustrated embodiment, one half or portion of each of the pattern 
generators 10, 12 and 14 is located on each of the two surfaces 16, 18. 
The first pattern generating unit 10 includes a plurality of spaced-apart 
opaque areas 22 formed on the first surface 16 and a plurality of 
spaced-apart opaque areas 24 formed on the second surface 18. Similarly, 
the remaining two pattern generating units 12 and 14 include first and 
second spaced-apart opaque areas 26, 28 and 30, 32 respectively, formed on 
the surfaces 16 and 18. In accordance with the invention, a translucent 
area is defined intermediate respective ones of the opaque areas. Thus, in 
the illustrated embodiment, these translucent areas are indicated by 
reference numerals 23 and 25, 27 and 29, 31 and 33 in the respective 
pattern generating units 10, 12 and 14. These respective opaque and 
transparent bars or areas may be created by placing a series of dark bars 
on a translucent or transparent surface such as a sheet of a transparent 
plastic material or the like. 
In operation, one of the two surfaces 16, 18 is superimposed on the other 
such that the respective areas 22 and 24, 26 and 28, 30 and 32 are 
respectively superimposed for creating patterns as the spaced-apart opaque 
areas are moved linearly relative to each other. In the illustrated 
embodiment, these opaque areas 22, 24, 26, 28, 30 and 32 comprise elongate 
opaque bars, such that movement in the direction transverse to the length 
of these bars will produce a desired pattern when they are respectively 
superimposed as just described. 
In accordance with the invention, a unique series of patterns is produced 
by the respective pattern generating units 10, 12, 14 by selecting the 
respective cross-sectional dimensions or widths of the respective opaque 
areas or bars and of the translucent areas or spaces therebetween. In the 
illustrated embodiment, the cross-sectional dimension or width of each of 
the opaque areas or bars is a dimension ML, and the cross-sectional 
dimension or width of each of the intermediate translucent areas is NL, 
where M and N are integers and L is the smallest increment of position to 
be measured. Thus, for example, if it desired to measure linear movement 
in increments of one millimeter, the dimension L is equal to one 
millimeter. 
The three pattern generating units 10, 12 and 14 are provided with 
differing respective cross-sectional dimensions of the opaque areas and 
translucent areas by varying the integers M and N utilized in each 
instance. In the illustrated embodiment, in the first pattern generator 
10, these integers M and N are equal to one on both of the surfaces 16 and 
18. Thus, the opaque bars 22 and 24, as well as the translucent spaces 23 
and 25, are all of width L. 
In the second pattern generator 12, on the surface 16 the integer M is 
equal to one and the integer N is equal to two, while on the surface 18 
the integer M is equal to two and the integer N is equal to one. Thus, on 
the surface 16 the opaque bars 26 are all of a width L, while the spaces 
27 therebetween are of a width 2L, while on surface 18 the opaque bars 28 
are of a width 2 L, with translucent areas 29 of width L therebetween. 
Finally, in the third pattern generating unit 14, on the surface 16 the 
integer M is equal to one and the integer N is equal to three, while on 
the surface 18 integer M is equal to three and integer N is equal to one. 
Thus, on the surface 16 the opaque bars 30 are width L with translucent 
spaces 31 of width 3L therebetween, while on the surface 18 the opaque 
bars 32 are of width 3L with translucent areas 33 of width L therebetween. 
Accordingly, and referring to the right-hand side of each of the pattern 
generating units of FIG. 1, the respective opaque areas will either 
prevent or permit transmittal of light through the translucent areas, 
depending upon the relative alignment of opaque areas between the two 
surfaces 16 and 18 in each of the pattern generating units. These two 
conditions are referred to as "black" (B) and "white" (W) in the drawings. 
Thus, in the pattern 10, for each increment of relative movement L between 
the two surfaces 16 and 18, the pattern will shift from white to black or 
vice-versa, as indicated by the letters W and B at equal increments L 
alongside the unit 10. Similarly, in the pattern generating unit 12, for 
increments of relative movement L between the surfaces 16 and 18, a series 
of indications will be given of two whites followed by a black or WWB, as 
indicated alongside of this unit. Finally, in the third pattern generating 
unit, with successive increments of relative movement L the series of 
patterns generated will be three whites and one black (WWWB). 
Referring briefly to FIG. 2, a similar set of pattern generators for 
measuring angular increments of movement, at an incremental angle a, is 
illustrated. Thus, in this embodiment, the unit of measurement L of FIG. 1 
comprises a unit of angular measurement .alpha.. Thus, for example, if the 
smallest desired unit of measurement is 0.1.degree., then the angle 
.alpha. is equal to 0.1.degree.. In most respects, the pattern generating 
units and their series of opaque areas and translucent areas are formed 
with the same relative cross-sectional dimensions as described above with 
reference to FIG. 1. However, these dimensions are angular measurements, 
such that each of the opaque areas and translucent areas in effect 
comprises a segment of a sector of a circle. 
Therefore, the respective elements of FIG. 2 are indicated by like 
reference numerals to those utilized in FIG. 1 together with the prefix 1; 
such that the first pattern generating unit is designated 110, the second 
112, and the like etc. However, for the unit 110, only the first surface 
116 is shown, it being understood that the pattern of opaque and 
translucent areas will be identical on the second surface, as indicated by 
the marking X2. 
Accordingly, pattern generating unit 110 has opaque bars 122 of angular 
extent .alpha. and translucent areas 123 of angular extent .alpha.. 
Pattern generating unit 112 has, on surface 116, opaque bars 126 of 
angular extent 2.alpha. and translucent areas 127 of angular extent 
.alpha.; and on surface 118, opaque bars 128 of angular extent .alpha. and 
translucent spaces 129 of angular extent 2.alpha.. Finally, pattern 
generating unit 114 has, on surface 116, opaque bars 130 of angular extent 
3.alpha. and translucent areas 131 of angular extent .alpha., and on 
surface 118, opaque bars 132 of angular extent .alpha. and translucent 
areas 133 of angular extent 3.alpha.. 
As with the embodiment of FIG. 1, these patterns of opaque areas and 
translucent areas may be formed by superimposing a plurality of such 
spaced-apart opaque segments of circular sectors upon a translucent 
surface such as a transparent sheet of plastic or the like. The respective 
sets of opaque and translucent areas defined in FIG. 2 of each pattern 
generating unit are aligned along radial lines which emanate from a common 
center point for each of the two surfaces. 
In the embodiment illustrated in FIG. 2, each of the pattern generating 
units 110, 112, 114 includes, on each surface 116, 118, two sets of opaque 
bars and translucent areas, spaced at different radial distances from a 
common center point. In pattern generating units 112 and 114, on the 
surface 116, the respective opaque bars of these two sets are angularly 
offset. This angular offset is a for unit 112 and 2.alpha. for unit 114. 
Referring now to FIG. 3, an embodiment of the invention constructed in 
accordance with the principles illustrated in FIG. 2 is shown. In FIG. 3, 
respective sections of pattern generating units are indicated by suffixes 
"a" and "b" for the sections on the surface 116, and by suffixes "c" and 
"d" for the sections on the surface 118. As mentioned above, each of the 
pattern generating units of FIG. 2 includes two sets of pattern generating 
groups of opaque areas which are aligned along radial lines emanating from 
a common center point for each surface. This results in two pattern 
generating areas or "blocks" for each of the pattern generating units, for 
a total of six such pattern generating blocks, as best seen in FIG. 4. In 
FIG. 4, wherein surfaces 116 and 118 are superimposed, for simplicity, 
these blocks are designated 1, 2, 3, 4, 5 and 6. As in FIG. 2, the two 
sets of opaque bars are angularly offset in units 112 and 114. 
In the embodiment illustrated in FIGS. 3 and 4, the angular increment a is 
equal to 0.180 and the patterns are arranged for displaying a unique set 
of patterns for each such angular increment of movement of 0.180 between 
the surfaces 116 and 118 over a range of .+-.1.260 to either side of a 
zero reference point. 
In order to aid in aligning the respective pattern generating units formed 
on the respective surfaces 116 and 118, the embodiment of FIG. 3 provides 
a pair of perpendicular axes, one of which forms a zero reference radius 
with respect to the pattern generating units. These axes are indicated by 
reference numerals 50, 52 on the surface 116, and reference numerals 54, 
56 on the surface 118. In addition, on the surface 118 there are formed an 
additional two radial lines 58, 60 emanating from the same center point as 
the axis 54. These lines 58 and 60 indicate a range of angular movement of 
.+-.1.26.degree.from the center axis 54 which forms the zero reference 
point for angular movement in the illustrated embodiment. 
Referring to FIG. 4, the pattern generating units of FIG. 3 are shown 
superimposed with zero angular offset, that is, with the axis 50 aligned 
with axis 54. As mentioned above, in FIG. 4 six "blocks" are defined, 
which are numbered from 1 through 6. These "blocks" display a unique 
pattern for each 0.18.degree. of angular movement from -1.26.degree. to 
+1.26.degree. . 
Referring to Table 1 hereinbelow, the patterns in accordance with the 
illustrated embodiment will give a unique set of so-called "black" (B) and 
"white" (W) indications, as described hereinabove, for each 0.18.degree. 
increment of movement to either side of the zero reference point, that is, 
alignment of the axis 50 with the axis 54. It should be remembered that 
the designation of "B" for black indicates that respective opaque bars or 
areas are aligned such that no light passes through a given one of the 
blocks, whereas the indication "W" for white indicates that light will be 
visible through translucent areas between the opaque areas, that is, that 
some of the opaque areas of the respective surfaces 16 and 18 are 
superimposed, leaving some portions of the translucent areas exposed 
therebetween. 
It will be recognized that other patterns may be utilized, giving 
incremental indications of other increments of linear movement or angular 
movement without departing from the invention. 
While particular embodiments of the invention have been shown and described 
in detail, it will be obvious to those skilled in the art that changes and 
modifications of the present invention, in its various aspects, may be 
made without departing from the invention in its broader aspect, some of 
which changes and modifications are matters of routine engineering or 
design, while others are apparent only after study. As such, the scope of 
the invention should not be limited by the particular embodiments and 
specific constructions described herein but should be defined by the 
appended claims and equivalents thereof. Accordingly, the aim in the 
appended claims is to cover all such changes and modifications as fall 
within the true spirit and scope of the invention. 
TABLE 1 
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1 2 3 4 5 6 
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1.26 B W W W B W 
1.08 W B W B W W 
.90 B W B W W W 
.72 W B W W W B 
.54 B W W B B W 
.36 W B B W W W 
.18 B W W W W W 
0 W B W B W B 
-.18 B W B W B W 
-.36 W B W W W W 
-.54 B W W B W W 
-.72 W B B W W B 
-.90 B W W W B W 
-1.08 W B W B W W 
-1.26 B W B W W W 
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