The invention relates to the reproduction of images. More particularly
it relates to the production of scaled images on a two-dimensional surface from
a two-dimensional or three-dimensional original.
In this specification, where a document, act or item of knowledge
is referred to or discussed, this reference or discussion is not an admission that
the document, act or item of knowledge or any combination thereof was at the priority
- (i) part of common general knowledge; or
- (ii) known to be relevant to an attempt to solve any problem with which this
specification is concerned.
Artists, craftsmen and some hobbyists often wish to transfer the dimensions
or proportions from an original object to a surface on which it is desired to produce
an image. Often this will be done so that the reproduced image is of a different
size from the original image.
Traditionally, artists often check the dimensions by holding an elongated
object (such as a paint brush or pencil) at arms length and positioning their thumb
or finger on the object so as to compare an apparent dimension of the original and
the image. This method is only approximate and is usually only suitable when the
image is the same size or smaller than the original. Similarly draftsmen sometimes
wish to copy at least part of an existing scaled drawing, photograph or other image
to a new drawing at a different scale.
Therefore, a device which could be used to transfer multiple measurements
at a constant size ratio would be of benefit.
US Patent 3,634,942 and GB 2,301,799 both propose devices having two,
pivotally connected straight arms of equal length, having reference marks at the
distal end of each arm and corresponding marks at various positions along the edges
of the arms wherein the various positions represent certain scale ratios. In use
the arms are adjusted so that the separation of the reference marks at the ends
of the arms corresponds to the separation of two points of interest on the original
object. The required separation on the reproduced image is then represented by the
separation of the two marks at the position along the edges of the arms corresponding
to the desired scale ratio. Scale ratios of greater than one can be generated by
reversing the process. These devices have a number of limitations: they are not
well adapted to use when a scaling factor which is not marked on the device is required,
such as when the original object is part of a photograph and the reproduced image
is to be fitted onto a sheet of paper; the technique of using marks on an edge is
imprecise, especially at large scale factors (this is the reason why in navigation
and similar precision mensuration processes, lengths are not determined directly
with a ruler, but through the agency of dividers); the legs obscure surrounding
markings on the original object and the reproduced image with a resulting increased
probability of making errors.
GB 2,085,810 proposes a proportioning device comprising three legged
callipers wherein the legs are linked so that two of the three remain parallel in
use. Such a device can be used for marking a scaled fraction along a straight line
but it is unsuited for more general use. Also, it is difficult to adjust the scaling
factor of the device.
GB 2,232,381 proposes a scissor-action proportional divider wherein
a pair of arms with pointers at each end can be pivoted at any one of a series of
fixed pivot positions such that various fixed scaling ratios are obtained. This
overcomes many of the precision problems associated with other prior art, but it
is still restricted to fixed scaling factors.
It is an object of the present invention to provide a device which
is useful in the creation on a surface of an image of a two-dimensional or three-dimensional
According to one form of the invention, there is provided a proportioning
whereby in use, separation of the pointing elements at one corresponding
end of the elongated members by a first distances will result in the pointing elements
at the other ends of the elongated members in being separated by a second distance
which is at a substantially constant proportion of the first distance, and the said
constant proportion is capable of being adjusted.
- two elongated members of substantially equal length which are adapted so that
both ends of both elongated members have pointing elements, and the separation of
the pointing element at one end of each of the elongated members from the pointing
element at the other end of the same elongated member is capable of being adjusted;
the two elongated members are capable of being uncouplably joined together by means
of a pivotable joint at various predetermined points along their lengths such that
the pointing elements on the corresponding ends of the two elongated members are
capable of being substantially the same radially measured distance from the pivotable
According to a preferred form of the invention, both of the elongated
members have a series of corresponding holes along their lengths whereby the pivotable
joint may be formed by inserting a pivot means through one pair of the corresponding
holes. Preferably a means of retaining the pivot is included. In one convenient
form of the invention, the pivot is in the form of a threaded bolt and the means
of retaining the pivot is a nut.
According to another preferred form of the invention, at least one
pair of corresponding pointer elements is capable of adjustment to alter the distance
of the pointer elements from the pivot. This arrangement may be used for fine adjustment
of the proportion of the distances between the pointing elements at the two ends
of the device.
According to another preferred form of the invention, one of the pointer
elements is a marker capable of forming a legible mark, such as a pencil. This embodiment
can be used to directly mark proportioned distances onto the surface on which the
image is to be reproduced.
In use, the device is adjusted such that the position of the pivotable
joint relative to the pointing elements results in the required proportion between
the distances of separation of the two pairs of corresponding pointing elements.
The user then moves the first pair of corresponding pointing elements so that their
separation distance equals a dimension of interest on the original image. Without
significantly disturbing the relative position of the elongated members, the user
then uses the second pair of corresponding pointing elements to transfer the proportioned
dimension to the surface on which the image is to be reproduced. It will be apparent
that this process is facilitated if one of the pointing elements of the second pair
of corresponding pointing elements is a marker such as a pencil or pencil lead.
It will be apparent that the device can also be used when a three-dimensional
reproduction is to be made from a three-dimensional original, as in sculpting and
some forms of model making. In such a case the method of use will be similar to
that when a two-dimensional image is to be produced, but the device will be used
as a proportioning calliper. With the device adjusted such that the position of
the pivotable joint relative to the pointing elements results in the required proportion
between the distances of separation of the two pairs of corresponding pointing elements.
The user moves the first pair of corresponding pointing elements so that their separation
distance equals a dimension of interest on the original image. Without significantly
disturbing the relative position of the elongated members, the user then uses the
second pair of corresponding pointing elements to check the proportioned dimension
on the three-dimensional reproduction.
The elongated members can be of any convenient shape, but straight
members are usually preferred. The elongated members can be of any suitable material
and cross-sectional shape, preferably they will be sufficiently rigid to maintain
the separation distance of the pointing elements to within the acceptable tolerance
for the particular purpose for which they are used. The length of the elongated
members is such as to be suitable for the size of the original and the reproduced
image. It will be apparent that for very large images the device may become too
heavy or cumbersome for convenient use In broad form, then, the invention provides
a proportioning device is provided having two elongated members of substantially
equal length which are adapted so that both ends of both elongated members have
pointer elements, wherein the two elongated members are capable of being uncouplably
joined together by means of a pivotable joint at various predetermined points along
their length, such that the pointing elements on the corresponding ends of the two
elongated members are capable of being substantially the same radially measured
distance from the pivotable joint, whereby in use separation of the pointing elements
at one corresponding end of the elongated members by a first distance will result
in the pointing elements at the other ends of the elongated members in being separated
by a second distance which is at a substantially constant proportion of the first
According to another form of the invention there is provided an imaging
aid for use by a user viewing an object, the imaging aid including:
- an image zone means defining the position of an image zone relative to the object,
at which image zone the user views an image of the object;
- a positioning means capable of defining a viewing position of the user's eyes;
- a spacing means capable of maintaining the relative positions of the image zone
means and the viewing means.
The invention therefore provides an imaging aid which the user can
position so that with his eyes in the viewing position defined by the positioning
means he can view an object through the zone defined by the image zone means. He
can then make a series of measurements relating to the object at the image zone
and transfer these measurements, after scaling if required, to a receiving surface.
The positioning means permits the user to repeatedly place his head in substantially
the same position so that the relative position of the user's eyes, the image zone
and the object can be reproduced as a series of measurements are transferred to
the receiving surface. In this way substantial errors due to parallax can be avoided.
A consistent series of measurements can be transferred to the receiving surface
and these can assist the user in preparing a substantially accurate representation
of the object on the receiving surface.
Typically the user may be an artist or draftsman who wishes to draw
the object. The image zone is a defined region within the reach of the user when
his eyes are in the viewing position. The image may merely be a hypothetical image
formed in a plane between the viewer and the object, on which plane the user focuses
his eyes when using the imaging aid. Preferably the image or hypothetical image
is at a physical, transparent surface. The positioning means allows interaction
with the user's head or part of the user's head so that the user is able to remove
his head from the imaging aid and then replace it in substantially the same position,
by bringing the same portion(s) of his head into contact with the same portion(s)
of the positioning means each time he uses the imaging aid. Preferably the spacing
means is adjustable so that the distance between the image zone means and the positioning
means can be varied prior to the start of the image transfer process e.g. to suitably
frame the object in the image zone means or to provide a comfortable eye focus distance
for the user.
It will be apparent that the imaging aid can be employed to assist
in the preparation of two-dimensional scaled images of three-dimensional or two
dimensional objects. One particular use is to produce images which are very much
smaller than the original, such as where the original is a building or natural feature.
According to a preferred form of the invention, the imaging aid has
supporting means which may be employed to support it at an appropriate elevation
above a generally horizontal solid surface. Conveniently the supporting means is
a stand, which is preferably adjustable so as to permit variation of the height
of the imaging aid.
According to another preferred form of the invention, the spacing
means is extensible such that the distance between the image zone means and the
positioning means is capable of being varied.
According to another preferred form of the invention, the positioning
means includes one or more rests adapted such that the position of at least one
eye of a user relative to the positioning means can be substantially restored when
the user returns his head to the positioning means. Preferably the positioning means
includes a chin rest and a rest capable of contacting another part of the head of
a user, such as the side of his head.
According to another preferred form of the invention, the image zone
means includes a substantially planar transparent plate connected by a suitable
means to the spacing means such that it is maintained with its plane substantially
parallel with the line between the eyes of the user when his eyes are in the viewing
position. More preferably the image zone is maintained with its plane substantially
parallel with the notional plane of the face of a user when his eyes are in the
viewing position. Preferably the transparent plate is held in a frame or other mounting
means. Conveniently the transparent plane may have a grid of markings.
According to another, less preferred form of the invention, the image
zone means includes a frame which defines at least one or more edges of a viewing
space but does not include a transparent plate.
In use the imaging aid is positioned and adjusted such that when the
user rests his head on the positioning means he can see the two-dimensional or three-dimensional
original object of which he wishes to make an image through the image zone means.
The user then closes or covers one eye, measures the distances between various features
of the original as seen at the image zone and transfers these measurements in an
appropriate manner, after applying a scaling factor if required, to locate a position
on a receiving surface on which he wishes to produce the image. It is generally
necessary for the user to remove his head from the positioning means when transferring
each measurement, but the positioning means enables the user to return his head
to substantially its previous position relative to the positioning means prior to
taking the next measurement. By this arrangement errors due to parallax effects
are minimised. The accuracy of the process is further improved if the user closes
or covers the same eye on taking each measurement.
The user makes and transfers a sufficient number of measurements to
enable him to complete the image by free hand drawing. It will be apparent that
the number of measurements to be made will depend on a number of factors including
the complexity of the original object, the skill of the user and the degree of similitude
which he requires.
One particularly convenient manner of transferring measurements is
to use two reference lines on the image zone means which reference lines are preferably
substantially perpendicular to each other. These lines may be edges of the image
zone means or marks on the viewing surface. Corresponding lines are drawn onto the
receiving surface. For each point on the original which is to be transferred to
the receiving surface, perpendicular distances from both of the reference lines
are measured on the image zone and transferred to the receiving surface after scaling
if required. It will be apparent that if the reference lines are substantially vertical
and horizontal, the process just described will be equivalent to transferring the
"x and y" co-ordinates from the image zone to the receiving surface.
Measurements on the image zone and on the receiving surface may be
made by any convenient means including but not limited to a ruler, dividers or a
pencil or brush with the appropriate distance from its end indicated by the placement
of the user's finger or thumb. If the scale of the image is to be different from
that of the original object, then it will be necessary to determine the measurement
to be transferred to the receiving surface by means such as calculation or a geometric
construction from the measurement taken from the image zone. Such a process is prone
- Preferably the measurements will be transferred using a proportioning device
as described herein.
- The invention also provides a method for transferring dimensions from an original
object to a receiving surface whereby:
- the original object is viewed through an imaging aid as described above;
- a series of original measurements relating to the original object are taken
on the image zone of the imaging aid by means of a proportioning device constructed
such that it generates a corresponding series of derived measurements whereby each
original measurement taken using the proportioning device generates a derived measurement
which is in substantially constant proportion with the original measurement; and
- using said proportioning device to transfer each derived measurement to the
appropriate place on the receiving surface.
In another form, the invention provides a method for transferring
dimensions from an original object to a receiving surface according to the method
described above wherein it is required to restore the original object to its position
after it has been moved during the course of transferring dimensions, whereby:
- the original object is placed in a first position between a light source and
a solid surface, both of which are maintained in substantially fixed positions,
such that a shadow of the subject is cast on the solid surface;
- marks are applied on the solid surface to define part or all of the edge of
the shadow; such that
- after the original object has been moved to a new position, it may be substantially
restored to the first position by moving it until the edge of the shadow it casts
on the solid surface is substantially co-incident with the marks previously applied
to said solid surface.
The invention will now be further explained and illustrated by reference
to the accompanying drawings of a non-limiting example in which:
- Figure 1 is a side view of a proportioning device according to one form of the
- Figure 2 is a perspective view of the device shown in Figure 1
- Figure 3 is a perspective view of part of the device shown in Figure 1 with
extended pointer pieces.
- Figure 4 is a perspective view of a proportioning device according to a form
of the invention having a different pivoting arrangement from that shown in Figure
- Figure 5 is an exploded view of the pivot retaining means of the device shown
in Figure 4.
- Figure 6 is a sectional side view of a proportioning device according to a form
of the invention having a different pivoting arrangement from that shown in Figures
1 and 4.
- Figure 7 is an end view of the pivot piece shown in Fig 6;
- Figure 8 is a perspective view of an imaging aid according to one form of the
- Figure 9 is an exploded perspective view of another form of the positioning
In Figures 1 to 3 one form of a proportioning device 10 is shown which
is suitable for use with the imaging aid shown in Figure 6. The proportioning device
has a first elongated member 12 and a second elongated member 14 of equal length.
A series of holes 16 are provided along the length of the first elongated member
and another series of holes 18 are provided along the length of the second elongated
member such that at least some of the holes are at substantially equal distances
from corresponding ends of the two elongated members. In one form, the holes are
approximately equally spaced.
A pivot means 20 is removably insertable through one pair of corresponding
holes. Conveniently the pivot means may be a bolt 22 and a nut 24.
Pointing assemblies 26, 28, 30, 32 are provided at or near to both
of the ends of both of the elongated members. Conveniently, one of these pointing
assemblies may have a marking element such as a pencil, a pen, or a length of pencil
Each of the pointing assemblies has a pointer piece 34, a housing
36 and one or more retainers 38. The housing has a first hole (not shown) which
is of suitable size to receive the pointer pieces and which is aligned substantially
parallel to the long axis of the associated elongated member. The housing also has
a second hole (not shown) provided with a screw thread and positioned to intersect
the first hole, preferably the axis of the second hole is substantially perpendicular
to that of the first hole. A first set screw 38 is provided which may be screwed
into the second hole to retain the pointer piece. Preferably a third hole (not shown)
is provided which is similar to the second hole and capable of receiving a second
set screw 40. The set screw(s) can be partly unscrewed, the pointer piece can be
inserted in the housing with the required protrusion and orientation and then the
set screws can be tightened to hold the pointer piece in position.
Various forms of pointer piece may be employed to suit the application
and the preference of the user.
A simple pointer piece 46 has an attachment rod section 44 which is
insertable in the housing 36, a bend 46 and a tapered section 48 terminating in
a pointing element 50 which may be in the form of a sharp point as shown in the
drawing or alternatively may be in the form of a ball or other swelling. It has
been found that in some circumstances it is easier for a user to discern the location
of a ball-like termination against the image zone than when a sharp point is employed
A cranked pointer piece 52 has an attachment rod section 44 which
is insertable in the housing 36, a first bend 56 which is outwardly directed, an
outwardly extending section 58, a second bend which is substantially in the same
plane as the first bend but which is inwardly directed, and an inwardly extending
section 62 which has a tapered section 64 terminating in a pointing element 66.
This arrangement permits the tapered section of the pointer piece to be at a increased
angle to the plane of movement of the elongated elements. This type of pointer piece
is also particularly useful when producing a three-dimensional image from a three-dimensional
Figure 3 shows an elongated pointer piece 68 which is generally similar
to the simple pointer piece except that the attachment rod section 70 is longer
than the corresponding part 44 of the simple pointer piece. In the form shown in
Figure 3, the pointing element is in the form of a ball or swelling 71. If required,
an elongated form of the cranked pointer piece 52 or of a marker assembly 72 can
also be employed.
The marker assembly 72 has an attachment rod section 74, a first bend
76 which is outwardly directed, an outwardly extending section 77, a second bend
78 which is substantially in the same plane as the first bend but which is inwardly
directed, and an inwardly extending section 79 on which is mounted a housing 80
with one or more set screws similar to item 36 which has already been described.
A section of pencil lead 82 can be inserted in the housing. One end of the pencil
lead 84 can function as both a marker and as a pointing element.
Different types of pointer piece can be combined to suit the requirements
of the user, except that if an elongated pointer piece is used at one end of an
elongated member it is normally desirable to use another elongated pointer piece
on the corresponding end of the other elongated member.
It will be obvious to one skilled in the art that if the holes in
the elongated members 16, 18 are not arranged so that their axes are parallel, then
there should preferably be means by which the pointer elements may be rotated, this
may be conveniently achieved in the method of attachment/adjustment shown in the
figures and previously described herein.
In use the pair of holes through which the pivot means is inserted
is selected to give approximately the required proportional separation of the pointing
elements at the two ends of the divider. If the exact proportional separation is
not achieved by the positioning of the pivot, fine adjustment may be made by axially
moving one or more corresponding pairs of pointer pieces relative to their respective
housings. The pointers at corresponding ends of the elongated members are usually
adjusted so that the points are in close proximity when the long axes of the elongated
members are parallel, as is shown in Figure 1.
If the pivot means is a nut and bolt, they are left in a slightly
slackened position and the relative position of the elongated members is adjusted
so that one corresponding pair of points is separated by the required distance.
The nut and bolt are then tightened sufficiently to inhibit relative movement of
the elongated members.
If the pivot means is not a nut and bolt it is desirable for there
to be some other means of inhibiting the relative movement of the two elongated
members during the transfer of a dimension from the original image to the surface
on which the image is to be reproduced. One such arrangement is shown in Figures
4 and 5 wherein there is a pivot assembly 100. The pivot assembly has a first retaining
member 102 and a second retaining member 104. The first and second retaining members
are of an elongated form and are substantially identical. Each retaining member
has a circular blind hole 106 formed on one side at a point about half way along
its length and circular through holes 108 near to the ends of the retaining members
wherein the axes of the through holes are parallel to that of the blind hole. The
blind holes are of the same diameter as the holes disposed along the lengths of
the first and second elongated members 16 and 18. The pivot means consists of a
rod 110 of slightly smaller diameter than the blind holes and of a length such that
it is capable of being retained when it is passed through corresponding holes in
the first and second elongated member and the first and second retaining members
are positioned such that each end of the rod 110 protrudes into one of the blind
holes but the retaining members are capable of simultaneously being in contact with
the elongated members. The retaining members are aligned so that each is generally
parallel to the direction defined by the separation of the pointing elements at
a corresponding end of the elongated members. A first bolt 112 passes through the
through holes 108 in one pair of corresponding ends of the retaining members and
a first nut 114 is screwed onto the first bolt. A second bolt 114 passes through
the through holes 108 in the other pair of corresponding ends of the retaining members
and a second nut 118 is screwed onto the second bolt. The through holes 108 are
positioned at a sufficient distance from the blind holes that the bolts 112, 114
do not unduly inhibit the range of movement of the first and second elongated members
relative to each other.
In use the first and second nuts are screwed in or out to induce the
required degree of resistance to movement of the first and second elongated members
relative to each other.
A further pivoting arrangement is shown in Figures 6 and 7. In this
form of the invention, the pivot means 150 comprises a coach bolt 152 and a retaining
nut 156 wherein the coach bolt 152 has a threaded section 156, a head section 158
which is of larger maximum cross-sectional area than the threaded section 156, and
a shoulder section 160 which has a cross-sectional area intermediate between that
of the threaded section 156 and the maximum of the head section 158. In use it is
found that, because the shoulder section 160 has a smaller cross-sectional area
than that of the head of the bolt 22 (which is a conventional engine bolt) shown
in Figure 1, it imparts a lesser degree of friction to the elongated member 12'
with which it is in contact. This reduced degree of friction is found to facilitate
adjustment of the proportioning device.
One embodiment of the imaging aid is shown in Figure 8. The imaging
aid comprises a positioning means 202, image zone means 204, a spacing means 206
capable of maintaining the relative position of the image zone means and the positioning
means and a stand 208.
The positioning means is capable of being used to assist the user
in repeatedly positioning his head generally, and the eye used for viewing in particular,
in substantially the same position with respect to the image zone means. The direction
from the positioning means generally, and the eye of a user particularly towards
the image zone means is indicated on Figure 6 by arrow X.
The positioning means has a chin rest 208, a head rest 210 and a connecting
means 212. The chin rest has an elongated rest piece 213 having an upwardly facing
flat surface 214 running perpendicularly to direction X on which flat surface the
underside of the chin of the user may be rested. One end of the elongated rest piece
is extended vertically upwards to form a resting piece 216 against which a user
may position the side of his jaw. At least a portion of the long edge of the elongated
rest piece on the side nearest to the image zone means is extended vertically upwards
to form a front rest 218 against which a user may rest the point of his chin.
The connecting means 212 has a first vertical post 220 connected to
the underside of the elongated rest piece. the first vertical post is connected
to the first end of a horizontal connecting member 222 which runs perpendicular
to direction X. A second vertical post 224 is connected to the second end of the
connecting member in an upwardly pointing direction. The head rest 210 is connected
to the top portion of the second vertical post on the side of the second vertical
post facing the chin rest. The side of the head rest most distant from the second
vertical post has a flat vertical surface 226 which is parallel to direction X.
The lengths of the first and second vertical posts and the connecting member are
such that when the chin of the user is positioned on the chin rest, the user can
conveniently place his head so that the flat vertical surface of the head rest comes
in contact with the side of the users head, preferably at a point just above the
The construction of the connecting means is such that it maintains
the relative position of the head rest with respect to the chin rest in normal use.
Conveniently the length of one or more of the first and second vertical posts and
the connecting member are adjustable to accommodate the specific head size of the'user.
The adjustment means (not shown) may be by means of telescoping components with
locking devices or other convenient methods.
The image zone means 204 comprises a flat, rectangular sheet 230 of
transparent material, such as glass or Perspex, mounted in an image zone frame 232.
The image zone frame consists of four edge pieces of 'C' or 'F' section material
234, conveniently wood, metal or polymer, wherein one edge piece is positioned on
each side of the rectangular sheet such that the edges of the sheet lie within the
opening of the 'C' or 'F' section and the ends of each edge piece are joined to
the adjacent ends of the adjacent edge pieces.
The image zone means 204 and the positioning means 202 are attached
to the opposite ends of the spacing means 206 such that the planes defined by the
flat rectangular sheet 230 and the connecting means 212 are parallel to each other
and perpendicular to the spacing means.
The spacing means includes three nesting members of square section
tube 236, 238, 240 whereby the length of the spacing means, and hence the separation
of the positioning means from the image zone means may be adjusted by telescopically
extending or retracting the nesting members. The spacing means may be maintained
at the required length by tightening locking screws (not shown). Optionally distance
markings can be provided along the lengths of the inner nesting members 238, 240
to facilitate restoring the length of the spacing means to some previous value.
The positioning means is attached to one end of the spacing means either demountably
or undemountably. At the other end of the spacing means there is rigidly attached
a horizontal fixing member 242 wherein the fixing member is perpendicular to the
nesting members. The fixing member may conveniently be of a 'C' section. The image
zone frame 232 is demountably attached to the fixing member by'bolts, clips or other
convenient means (not shown) such that it may be positioned with either the long
sides or the short sides vertical. Alternatively, the image zone frame may be permanently
attached to the fixing member, in which case the orientation of the image zone may
be changed by completely withdrawing the nesting member to which the fixing member
is attached, rotating this nesting member through 90° about its axis and re-nesting
it with the other nesting members.
The spacing means is supported by a stand 208 which may take any convenient
form. In the embodiment shown in Figure 8 the stand includes three legs 250 connected
to a vertical hollow tube 252 so as to form a tripod. A support member 254 is slidably
inserted in the vertical hollow tube. The support member is attached to the spacing
means at a point 256 selected such that any net turning moment due to the weights
of the image zone means, the positioning means and the spacing means is not sufficient
to topple the imaging aid. A cross brace is attached to the support member and the
nesting member to which the support member is attached in order to increase the
rigidity of the connection between the support member and the spacing means.
In use, the position of the support member relative to the vertical
hollow tube is adjusted so that the components of the imaging device are at the
desired elevation and a set screw 260 is then tightened to maintain the relative
position of the support member and the vertical hollow member.
Figure 9 shows a variant of the arrangement of the positioning means
wherein a forehead rest is provided to give even greater uniformity when repositioning
the head of the user in the positioning means. The elongated rest piece 213 is attached
to the first vertical post which is formed from a flat bar 270 which extends vertically
above the upwardly facing flat surface 214 such that the extension forms the front
rest 272. The horizontal connecting member is also formed from a flat bar 274 which
may be curved or bent if required to suit the positioning of other components. A
locating nut 276 is attached to the distal end of the horizontal connecting member
with the axis of its hole vertical so as to receive a threaded first end 280 of
a second vertical post 278 which is in the form of a metal bar of circular section.
A locking nut 282 may be applied to the first end of the second vertical post which
protrudes through the locating nut in order to inhibit unwanted rotation of the
second vertical post relative to the locating nut. A support nut 284 is applied
to the threaded second end 281 of the second vertical post. Above the support nut
are positioned a washer 286, a side rest holder 288, a forehead rest member 290
and a retaining nut 292.
The side rest holder consists of two square apertured block elements
293, 294 each pierced by a hole with its axis central to and perpendicular to the
square sides. One of these hole is a plain hole 296, the other hole is a threaded
hole 298. The apertured block elements are conjoined at non-pierced sides such that
the axes of the holes 296, 298 are perpendicular to each other but do not intersect,
as shown in the figure. The second vertical post passes through the plain hole 296.
The threaded hole 298 is capable of receiving a side rest 300 which is mushroom
shaped having a circular flat or domed head 302 and a stem 304 which is threaded
along at least part of its length 306. The threaded portion of the stem is screwed
into the threaded hole 298 and a securing nut 308 may be applied to the protruding
portion of the stem to inhibit unwanted rotation of the side rest.
The forehead rest member 290 comprises a short bar 310 connected to
a long bar 312. One end of the short bar is joined to an end of the long bar such
that the long axes of the bars are substantially parallel and the planes of the
long bar and the short bar are perpendicular. The short bar is pierced by a hole
314 which passes over the second vertical post as already described, such that the
forehead rest member is directed generally towards the image zone. The long bar
has a bend 316 such that its end distal 317 from the short bar is directed generally
towards the first vertical post and that surface of the distal end of the long bar
which faces generally towards the first vertical post forms a forehead rest surface
In use the user places his chin on the elongated rest piece 213 so
that his chin contacted the resting piece 216 and the front rest 272. He then adjusts
the side rest 300 so that its head 302 is positioned against the side of the user's
head, and the forehead rest member so that the forehead rest surface was positioned
against the user's forehead. The locking nut 282, the retaining nut 292 and the
securing nut are then tightened to inhibit unwanted relative movement of the components
of the positioning means. It will be apparent that the additional locating surface
for the forehead of the user will result in even greater uniformity when repositioning
One difficulty often experienced when painting portraits is correct
repositioning of the subject after a rest period or unintentional movements by the
subject. This problem may be substantially overcome by positioning the subject between
a light source and a solid surface, both of which are maintained in substantially
fixed positions, such that a shadow of the subject is cast on the solid surface.
When the subject has assumed the required pose, the artist can apply marks on the
solid surface to define part or all of the edge of the shadow. Thereafter, whenever
the subject has moved, the artist can request re-adjustment of the subject's position
until the subject's shadow is aligned with the marks on the solid surface. If required
the light can be extinguished except when applying the marks to the solid surface
and when re-adjusting the subject's position. It will be apparent that this method
can also be used in other situations wherein the original object is moved during
the course of transferring dimensions.
It will be apparent that this invention or part of this invention
is capable of other uses.
For example an artist seeking to improve his skill can draw an image
using visual judgement of proportions only and then use the invention to check the
proportions of the image against those of the original.
Also the proportioning device can be made in different sizes to suit
different purposes. For example, a very large proportioning device adjusted to give
a large increase in size could be used to transfer dimensions from a comparatively
small image to a wall in preparation for producing a mural.
The word 'comprising' and forms of the word 'comprising' as used in
this description does not limit the invention claimed to exclude any variants or
The term 'image zone' and related terms as used in this description
refer to the portion of the imaging aid at which measurements of the original object
are taken and does not imply that an image is actually produced there.
Modifications and improvements to the invention will be readily apparent
to those skilled in the art. Such modifications and improvements are intended to
be within the scope of this invention.