U.S. patent application number 11/656654 was filed with the patent office on 2008-07-24 for pattern transferable to skin for optical measurements during shaving.
This patent application is currently assigned to The Gillette Company. Invention is credited to Darrell Gene Doughty.
Application Number | 20080176077 11/656654 |
Document ID | / |
Family ID | 39494683 |
Filed Date | 2008-07-24 |
United States Patent
Application |
20080176077 |
Kind Code |
A1 |
Doughty; Darrell Gene |
July 24, 2008 |
Pattern transferable to skin for optical measurements during
shaving
Abstract
A removable tattoo for applying a pattern to the skin for use
with an optical measurement system to measure forces on the skin
such as during shaving. A transfer paper is printed with a random
pattern of different size dots. The pattern can have two or three
different sized dots. The pattern of dots has a pattern density of
between about 40% to about 60%. The pattern is printed with inks
suitable for skin contact that are not water soluble so as to
withstand a moist shaving environment. The pattern is removable
from the test person with alcohol.
Inventors: |
Doughty; Darrell Gene;
(Cincinnati, OH) |
Correspondence
Address: |
THE PROCTER & GAMBLE COMPANY;INTELLECTUAL PROPERTY DIVISION - WEST BLDG.
WINTON HILL BUSINESS CENTER - BOX 412, 6250 CENTER HILL AVENUE
CINCINNATI
OH
45224
US
|
Assignee: |
The Gillette Company
|
Family ID: |
39494683 |
Appl. No.: |
11/656654 |
Filed: |
January 23, 2007 |
Current U.S.
Class: |
428/409 |
Current CPC
Class: |
Y10T 428/31 20150115;
Y10T 428/24802 20150115; A61B 5/0059 20130101; A61B 5/442 20130101;
A61B 5/0048 20130101; A61B 5/444 20130101 |
Class at
Publication: |
428/409 |
International
Class: |
B41M 3/12 20060101
B41M003/12 |
Claims
1. A removable tattoo for patterning a section of skin to provide a
reference marking for use in optical skin deformation measurements,
comprising a substrate (73), and a pattern (45) comprising a
plurality of indicia randomly distributed to form a pattern density
of between about 40% and about 60%.
2. The removable tattoo of claim 1, wherein the indicia comprises
dots.
3. The removable tattoo of claim 2, wherein the dots comprise two
or more different sized dots (70, 71).
4. The removable tattoo of claim 2, wherein the dots comprise three
different sized dots (70, 71, 72).
5. The removable tattoo of claim 1, wherein the pattern density is
about 50%.
6. The removable tattoo of claim 1, wherein the pattern density is
about 42.5%.
7. The removable tattoo of claim 1, wherein the indicia is
transferable to the skin by wetting with an alcohol.
8. The removable tattoo of claim 1, wherein the substrate (73) is a
paper.
9. The removable tattoo of claim 8, wherein the paper is chosen
from a group of paper consisting of blotting paper and cigarette
paper.
10. The removable tattoo of claim 1, wherein the indicia comprises
a substantially water-insoluble ink or dye.
11. The removable tattoo of claim 10, wherein the indicia comprises
an oil-based ink or dye.
12. The removable tattoo of claim 1, wherein the indicia is devoid
of a cover layer formed above said indicia opposite said substrate
(73).
13. The removable tattoo of claim 1 being devoid of an adhesive
layer atop said indicia.
14. A moisture-activated, removable tattoo for patterning a section
of skin to provide a reference marking for use in optical-based
skin deformation measurements, comprising a substrate (73), and a
random pattern (45) comprising a plurality of distributed dots,
said dots comprising an ink or dye, said ink or dye being
substantially water insoluble and being substantially soluble in an
alcohol.
15. The removable tattoo of claim 14, wherein the dots comprise two
or more different sized dots (70, 71).
16. The removable tattoo of claim 14, wherein the dots comprise
three different sized dots (70, 71, 72).
17. The removable tattoo of claim 14, wherein the random pattern
(45) has a pattern density of between about 40% and about 60%.
18. The removable tattoo of claim 17, wherein the pattern density
is about 50%.
19. The removable tattoo of claim 17, wherein the pattern density
is about 42.5%.
20. The removable tattoo of claim 14, wherein the substrate (73) is
a paper.
21. The removable tattoo of claim 20, wherein the paper is chosen
from a group of paper consisting of blotting paper and cigarette
paper.
22. The removable tattoo of claim 14, wherein the dots comprise an
oil-based ink or dye.
23. The removable tattoo of claim 14, wherein the ink or dye
comprises a pigment.
24. The removable tattoo of claim 14, wherein the substrate (73) is
moisture permeable.
25. The removable tattoo of claim 1, wherein the dots are devoid of
a cover layer formed above said dots opposite said substrate
(73).
26. The removable tattoo of claim 14 being devoid of an adhesive
layer atop said dots.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a dot pattern transferable
to the skin and recognized by an optical measurement technique to
detect motion of the patterned area in response to an applied
force, e.g. shaving.
BACKGROUND OF THE INVENTION
[0002] It has been known to use three dimensional (3D) image
correlation photogrammetry as a full-field, non-contact optical
inspection technique to analyze strain in machine parts and
dissected tissue specimens. This technique is described for example
in the literature by Tyson, J., Schmidt, T. Galanulis, K. "Optical
Deformation & Strain Measurement in Biomechanics", in
Biophotonics, September 2003, pages 1 to 7; and by Tyson, J.,
Schmidt, T., Galanulis, K., "Biomechanics Deformation and Strain
measurements with 3D Image Correlation Photogrammetry",
Experimental Techniques, Vol. 26, No. 5, pages 39-42,
September/October 2002 (ProQuest Science Journals). This literature
describes strain testing of dissected bone, knee tendon, and
ligament specimens that have been removed from a cadaver and
ruptured under tensile testing, of a heart of a vivisectioned frog,
and of flexed artificial muscle specimens. Known industrial
applications of this measurement system are for aerospace or
machine parts. These biologic specimen and industrial applications
involve objects held in a fixture during testing. Measurement
systems of this type are in wide use in the aerospace industry and
in public universities (including the Universities of Maine,
Wichita State in Kansas, and Akron in Ohio), with at least 300 of
them in use in Europe and 40 in the United States. For example, the
United States space agency NASA used this technique to make
measurements of the full Space Shuttle wing leading edge (NASA
Johnson Space Flight Center & Southwest Research) as well as
for External Fuel Tank (ET) foam impacts (Lockheed Martin Manned
Space Systems). This technique allows for non-contact determination
of 3D coordinates and 3D displacements, 3D speeds and
accelerations, and plane strain tensor and plane strain rate.
[0003] An example of a commercially widely available 3D image
correlation photogrammetry digital camera system is the system made
by the company GOM mbh marketed under the trade designation ARAMIS
system.
[0004] The preparation of the specimen with a pattern is described
in the above "Biomechanics Deformation" and "Optical Deformation"
articles, or alternatively in the "ARAMIS User Manual", at pages
26-27, published by the GOM company (2005), as a high-contrast
stochastic (random) pattern consisting of a sprayed-on dye
penetrant developer (such as white) overlaid with a sprayed-on
black spray (e.g. a matte black spray or graphite spray), for
example by lightly pressing the spray button on commercially
available cans of spray paint. It is also known to apply the
pattern by means of a pen or a stencil/spray technique. It is known
that smooth specimen surfaces are preferred. The pattern can be a
regular or random pattern. It is known that it is preferred for the
pattern to avoid large areas of constant brightness such as wide
lines. It is known that it is preferred to avoid a shiny pattern
and to prefer a pattern with a matte or dull surface.
[0005] Temporary tattoos made from dyes or inks approved for use in
food or cosmetics are known for novelty purposes, as body
adornment, or to mark a person's hand as having paid an admission
price. These typically involve a recognized, ordered arrangement of
graphic elements, or text, as known for example in U.S. Pat. Nos.
5,578,353 (Drew, III); 7,011,401 (Markey, III); 6,161,554
(Dunlap-Harris); and 6,457,585 (Huffer et al.). Some such tattoos
are transferred to the person by the tattoo's having a
pressure-sensitive adhesive layer. Other such tattoos are printed
on a paper substrate with water soluble ink, and the paper placed
in contact with the skin in the presence of moisture and the ink is
transferred to the skin.
[0006] Dot patterns are known in eye color-blindness tests such as
the Ishihara color chart (named after its designer Dr. Shinobu
Ishihara, a professor at the University of Tokyo, who published his
test in 1917) which uses colored plates having a background of dots
in the middle of which is a recognizable regular pattern,
differentiated by color, usually in the shape of an Arabic number
or English letter, see also U.S. Pat. No. 2,937,567 (Hardy) and
U.S. Pat. Appln. 2005/0213039 (Ohashi). These eye charts are
usually printed on heavy stock and carefully preserved against
soiling so as to be used by eye care professionals to diagnose
patients.
[0007] There remains a need to determine strain fields on the skin
surface of a living human interacting with a product used on the
skin in a manner comfortable to the test subject person.
[0008] There remains a further need to quickly and/or conveniently
apply a removable pattern to a human test subject.
SUMMARY OF THE INVENTION
[0009] It is an object of the invention to provide a method of
measuring strain on the skin of a living person while the person
uses a shaving apparatus such as a dry shaver or a wet razor to
shave hairs on the skin. A wet razor, also referred to as a safety
razor, is an instrument having a sharp razor blade, such as in a
cartridge disposed on a handle, in conjunction with a shave
preparation product such as water typically applied to the skin in
combination with a shaving cream, gel or lotion, to shave hairs on
the skin.
[0010] It is a further object of the invention to provide a method
of measuring skin strain on the external skin of a person while
applying a force to the skin, such as by a finger or blunt probe
object dragged along a portion of skin to which a cosmeceutical
product, such as a lotion, cream or emollient, has been
applied.
[0011] In one aspect, the invention features a method of measuring
a parameter indicative of deformation of skin surface of a living
person resulting from a force applied to the skin surface during
the test. The skin of the person being tested is first provided
with a pattern and then is imaged by two digital cameras. The
cameras then capture reference image data of the undeformed or
reference position of the patterned skin surface. While applying a
force to the skin, the cameras capture second image data indicative
of the deformed position of the patterned skin surface. The
reference data and stressed or deformed condition data is stored
and processed to determine movement of the patterned skin surface
relative its reference position. At least one parameter indicative
of this movement ("deformed state") of the patterned skin surface
relative its reference position ("undeformed state") is determined.
Preferably that parameter is a numerically quantifiable parameter.
More preferably that parameter is a strain. The parameter
determined can be a strain tensor or a strain rate. The parameter
determined can be major strain or minor strain. The parameter
determined can alternatively be positional coordinates,
displacements, speed, or acceleration of the skin.
[0012] In certain implementations of the method: The force applied
to the skin can be from shaving, or by a finger or blunt probe
drawn across the skin. A performance characteristic of a razor can
be quantified such as the strain produced in the skin surface
during use. Comparisons can be made between razors or a prototype
evaluated during development. An efficacy of a cream or lotion
applied to the skin can be evaluated.
[0013] Advantageously in certain implementations of the method, the
quantity of the movement, such as an amount of strain during
shaving with a razor, can be determined over several different
measurement areas of the shaving stroke. An average strain can be
determined for each measurement area. This advantageously allows
quantifying performance of a razor over a representative range of
its intended use. An overall average strain quantity can be
determined from the several measurement areas.
[0014] Advantages of the present invention include that the optical
measurement system is not invasive to the user, it does not touch
the test person's skin not interfere with normal motion using a
product that applies force to the skin. Another advantage of the
inventive method is that allows the test person to freely move his
or her body and act in a normal, unconstrained manner, thus more
realistic replicating conditions of normal use, since translational
or so-called rigid body motions are subtracted out and do not
distort the measurements. The test subject can shave himself or
herself, or draw the finger (or blunt probe) across the skin, or
another a test administrator can apply the force to the test
subject.
[0015] The pattern applied to the skin can be a regular pattern or
a random pattern. A random pattern is also referred to as a
stochastic pattern. The pattern can be applied as a multitude of
"dots" to the test person's skin.
[0016] In another aspect, the invention features a prepared pattern
that is easily applied to the skin of a test subject and is also
removable after the optical measurements. A removable tattoo is
provided with a substrate and a pattern having a plurality of
indicia randomly distributed to form a pattern density of between
about 40% and about 60%. In advantageous embodiments the indicia is
in the form of dots.
[0017] In another aspect, a tattoo to pattern the skin for optical
measurements is provided having a substrate and a random pattern
(45) having a plurality of distributed dots. The dots are made with
an ink or dye that is substantially water insoluble but is
substantially soluble in an alcohol. The substrate can be moisture
permeable, e.g. to alcohol.
[0018] In advantageous embodiments the individual elements that
make up the indicia or dots have two different sizes. In further
embodiments there are three, or more, different sizes present in
the pattern.
[0019] In further advantageous embodiments, the removable tattoo
has a pattern density of about 50%. In other, presently yet more
preferred embodiments, the pattern density is about 42.5%.
[0020] In further embodiments the tattoo is transferable to the
skin by wetting with an alcohol. The substrate can be a paper, such
as paper commonly referred to as blotting paper or cigarette paper.
The tattoo can be printed with an oil-based ink or dye.
[0021] The tattoo is preferably made convenient by being devoid of
a cover layer formed above the pattern on the tattoo, thus
obviating the need to peel off such a layer before applying it to
the skin. The tattoo is also made convenient and economical to
manufacture by being devoid of an adhesive layer.
[0022] Further embodiments are disclosed in the dependent claims
attached hereto.
[0023] The present invention and its advantages will be better
understood by referring, by way of example, to the following
detailed description and the attached Figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 shows a schematic view of a prior art image analysis
system;
[0025] FIG. 2 shows a schematic view of an imaging system of FIG. 1
employed in a method of measuring the skin according to one
embodiment of the invention;
[0026] FIG. 3 shows a perspective view of the image system of FIG.
1;
[0027] FIG. 4 shows a schematic representation of a digital optical
image illustrating pixels and facets in an undeformed state;
[0028] FIG. 5 shows a schematic representation of a digital optical
image illustrating pixels and facets in a deformed state;
[0029] FIG. 6 shows a flowchart of optical image analysis
steps;
[0030] FIG. 7 shows a preferred stochastic pattern transferable to
the skin for use with the method employed in FIG. 2;
[0031] FIG. 8 shows an optical image of the reference pattern on
the skin employed in a method of measuring the skin according to
one embodiment of the invention;
[0032] FIG. 9 shows a schematic view in grey scale of skin strain
at a mid-stroke shaving position;
[0033] FIG. 10 shows a schematic view in grey scale of skin strain
at an end-of-stroke shaving position;
[0034] FIG. 11 shows a schematic view in cross-hatching scale of
skin strain corresponding to FIG. 9;
[0035] FIG. 12 shows a schematic view in cross-hatching scale of
skin strain corresponding to FIG. 10;
[0036] FIG. 13 shows a schematic representation of a strain
measurement area near start of stroke;
[0037] FIG. 14 shows a schematic representation of a strain
measurement area near mid-stroke;
[0038] FIG. 15 shows a schematic representation of a strain
measurement area near end-of stroke;
[0039] FIG. 16 shows a blunt probe employed in a method of
measuring the skin according to another embodiment of the
invention;
[0040] FIG. 17 shows a reference diagram depicting translation and
strain of a line element;
[0041] FIG. 18 shows a reference diagram depicting a geometrical
model of central projection;
[0042] FIG. 19 shows a reference diagram depicting an analytical
calculation of the deformation gradient tensor;
[0043] FIG. 20 shows a reference diagram depicting a 3.times.3
neighborhood for strain calculation;
[0044] FIG. 21 shows a reference diagram depicting a neighborhood
for a four-sided facet; and
[0045] FIG. 22 shows a reference diagram depicting a four-sided
facet with adjacent points.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
The Imaging System
[0046] Reference is made to FIGS. 1-3.
[0047] For the 3D deformation and strain measurements, sample 35
(shown schematically in FIG. 1) to which forces should be applied
(which according to the invention as shown in FIG. 2 is an external
skin surface of a living person 40, for example during shaving), is
viewed by a pair of high resolution, digital CCD cameras 10, 20,
which measure the sample's 3D coordinates and the 3D deformations.
The camera pair is simply placed in front of the object being
tested at a working distance 30. A typical working distance is 1
meter to 2 meters. The 3D image correlation photogrammetry
technology is a combination of two-camera synchronized image
correlation and photogrammetry. A regular pattern or a random
pattern 45, with good contrast, is applied to the surface of the
test object, such as to the surface of the skin, which deforms
during the test. While a regular pattern can be used, such as an
array of dots aligned in repeating columns and rows (such as a
rectangular lattice), a random pattern is preferred so as to avoid
a situation that could theoretically occur with a periodically
repeating or regular pattern that a deformation occurs in an
integer amount of the pattern, such that the camera might mistake
such a deformation for a massive or rigid body translation. The
random pattern does not have to be absolutely random in a strict or
mathematical sense such as from a random number generator, it is
sufficient that the pattern is not perceptibly a periodically
repeating pattern. The deformation of this pattern under the
applied load conditions (which according to an embodiment of the
invention is the act of shaving) is recorded by the CCD cameras and
evaluated. The initial image processing defines unique correlation
areas known as macro-image facets, typically 5-25 pixels square,
across the patterned imaging area. Each facet center is a
measurement point that can be thought of as an extensometer point
and strain rosette. These facets are tracked in each successive
image with sub-pixel accuracy (to 100.sup.th of a pixel). Then,
using conventional photogrammetric principles (such as discussed in
Mikhail, E., Betel, J., and McGlone, J., Introduction to Modern
Photogrammetry, John Wiley and Sons, 2001, which is hereby
incorporated in its entirety by reference), the 3D coordinates of
the patterned surface of the specimen are calculated. The results
are the 3D shape (contour) of the component, the 3D displacements,
and the plane strain tensor of every point on the patterned surface
of the object.
[0048] The 3D image correlation tracks changes in the applied
micro-pattern (stochastic pattern), rather than a projected
pattern, and uses ordinary white light, rather than coherent laser
light. The system tracks the pattern applied to the measurement
surface with sub-pixel accuracy. This means that as long as the
object remains within the field of view of the cameras, all of the
local deformations can be tracked. Thus, large deformations can be
analyzed in a single measurement. Rigid body motion does not affect
the measurements, and can also be calculated from the original
pixel registration. Indeed, measurements can be continued after an
object being studied has been removed, processed and replaced
within the camera viewing zone.
[0049] Sensitivity with 3D image correlation is 1/30,000 the field
of view. For example, with a 3 cm field of view, sensitivity is 1
micron, and with a 30 cm field of view, it is 10 microns. A field
of view of several meters square is not a problem as long as
deformations of several 10's of microns are present. The system
intrinsically measures 3D shape, and therefore 3D deformations are
measured simultaneously, rather than sequentially.
[0050] An example of a commercially widely available 3D image
correlation photogrammetry digital camera system to obtain the
foregoing results is the system made by the company GOM mbh
("Gesellschaft fuer Optische Messtechnik") (address: Mittelweg 7-8,
D-38106 Braunschweig, Germany; website www.gom.com) marketed under
the trade designation ARAMIS system and described in their
publication "ARAMIS User Manual v5.4.1 (year 2005), which is hereby
incorporated in its entirety by reference; this ARAMIS system is
widely distributed in the United States such as by the company
Trilion Quality Systems (address: Four Tower Bridge, 200 Barr
Harbor Drive, Suite 400, West Conshohocken, Pa. 19428; website
www.trilion.com), which is the system described in the above
"Background" section in use for example in the aerospace industry,
the universities and NASA, and in the technical literature therein.
This system permits a large measuring area, since with the same
sensor both small and large objects, such as those in size from 1
mm to 2 meters, can be measured, and strains in the range of 0.05%
up to several hundred %. FIG. 1 schematically illustrates such a
system.
[0051] The left camera 10 has a left camera lens 11, and the right
camera 20 has a right camera lens 21. The cameras are each
connected to a camera adapter plate 13 and mounted to a camera
support 15 such as a rail supported by a camera tripod 16. For
adjustment, the cameras can rotate their camera rotation axis 12,
which are separated from each other by base distance 25. The
cameras 10, 20 are located to the left and right, respectively, of
angle bisector 24 generated by a laser pointer 28 that bisects the
camera angle .alpha. ("alpha") at which the cameras are directed to
the specimen (35, 40) to be measured. Laser pointer 28 is used only
for calibration to align cameras 10, 20, it is not in use during
measurement of the strain such as when the test subject is
shaving.
[0052] Object 35 to be measured is located at an approximate center
34 within a measuring volume defined by a width W, height H and a
length L.
[0053] In operation, the system is a non-contact optical 3D
deformation measuring system, as illustrated in FIG. 1 or FIG. 2.
It analyzes, calculates and documents deformations of the skin
surface. The graphical representations of the measuring results
provides an understanding of the behaviour of the skin surface to
be measured. The system recognizes the surface structure of the
object to be measured in digital camera images and allocates
coordinates to the image pixels. The first coordinates are already
gathered when recording the reference conditions which represents
the undeformed (for example, an unstressed skin condition prior to
the shaving action) state of the skin surface. After or during the
deformation to the skin surface to be measured, further images are
recorded. Then, the system compares the digital images and
calculates the displacement and the deformation of the skin surface
characteristics relative to the reference image. The system is
suitable for 3D deformation measurements under static and dynamic
load in order to analyze deformations and strain of real
components.
[0054] A typical set-up of hardware components is illustrated in
FIG. 3. A suitable arrangement of hardware and software components
to operate the measurement system includes: a pair of 1.3M cameras
(10, 20) with 50 mm lenses (11, 21) connected to a computer via a
"Firewire" connection (Apple Computer, Inc.'s trade designation of
its widely available IEEE-1394 interface, a computer and digital
video serial bus interface standard); and a 64-bit dual processor
computer (18) with a Linux operating system and Aramis application
software version 6.0.0-4 (software is periodically updated by its
manufacturer GOM mbH). The cameras are assembled and sold by the
company GOM using commercially available 50 mm lenses from
Schneider (Jos. Schneider Optische Werke GmbH of Bad Kreuznach,
Germany), but other 50 mm lens can also be used. The designation
"1.3 M" indicates a nominal 1.3 Megapixels, for example a camera
resolution of 1280.times.1024 pixels for each image.
[0055] The typical frame rate for the camera system is 10 fps
("frames per second", referring to the still frames per second).
This frame rate was determined to be adequate for all or most all
of the test subjects except a test subject who shaved exceptionally
fast. It is understood that typical video has a frame rate of about
30 fps, and that the designation "high-speed" can range from 480
fps to 80,000 fps. Other cameras are available for the system that
are higher resolution (4M) but at a lower frame rate (max 7 fps) or
a higher speed (480 fps). The frame rate as "fps" can also be
expressed in terms of Hz, e.g. 12 fps=12 Hz.
[0056] To make measurements, the measuring volume is selected. For
a human face 40 or leg a suitable selected volume for the camera
and lens configuration used here is approximately 135 mm.times.108
mm.times.108 mm. The calibration of the system utilizes a certified
calibration plate based on the selected volume. Volumes ranging
from 10 mm.sup.3 to 1000 mm.sup.3 are possible, and are chosen
depending on the size of the skin area to measure.
[0057] A suitable set of system components is shown in the table
below:
TABLE-US-00001 System 1.3 M camera Facial measuring volume with 50
mm 135 mm .times. 108 mm .times. 108 mm lens Camera resolution 1280
.times. 1024 pixels Camera chip 2/3 inch CCD Max. frame rate 12 fps
Shutter time 0.1 ms up to 2 s Strain measuring range 0.05% up to
100% Strain accuracy up to 0.02% Displacement sensitivity 6
microns
[0058] Instead of the CCD cameras, it is also possible to use
suitable CMOS cameras, which are believed to have similar
parameters.
[0059] While the above described camera speed in the range of 10 to
12 fps preferred, the camera speed is not critical; one of skill in
the art will appreciate that it is possible to use a camera speed
of several thousand frames per minute, e.g. 70,000 fps, and that
one simply needs enough speed to capture enough strain pictures.
One of skill in the art appreciates that the practical limits of
frame speed are determined by the computer memory (RAM) and the
"Firewire" interface, such that the number of pixels decreases with
increasing frame speed, and that the fewer pixels that are present
then the lower the resolution possible.
[0060] A typical procedure for making measurements involves the
following steps:
1. Applying a stochastic pattern to the surface of the skin area of
interest, such as via a temporary tattoo design (described further
hereinbelow); 2. capturing a reference image in the form of
synchronized stereo digital images; 3. applying shaving preparation
(e.g. shave cream) to the area of interest (for shaving
applications). Some of the patterned dots are left free of shave
prep so that the computer can relate to the reference image; 4.
capturing a series of frames in the form of synchronized stereo
digital images that encompass a stroking motion of the razor; and
5. analyzing the series of captured images using the evaluation
mode of the Aramis system software, which recognizes the applied
pattern on the reference image and subsequent strained images. The
3D coordinates, 3D displacements and the plane strain tensor are
calculated using photogrammetric evaluation, and the results
graphically displayed.
[0061] In order to analyze the images, the operator identifies a
start point in the images. The area to be evaluated (computation
mask) and the start point are defined directly in the camera
images. The software then calculates square or rectangular image
details or boxes, which are called facets, over the patterned area.
Preferably the pattern applied to the surface being observed is
smaller than the facet size. Each facet can be chosen to be made up
of, for example, about 15 pixels.times.15 pixels. To improve
resolution, the facets can have an overlap area, for example a 2
pixel overlapping area can be suitable for stationary objects such
as those that are fixtured. It has been determined that for
analyzing a shaving action it is suitable to chose a facet to have
a 25 pixel square (25.times.25 pixels). It is preferred with facets
of this size to use an approximate half-facet size overlap, that is
a 13 pixel overlapping area. This helps with accuracy during
shaving, where the test subject is moving, in order to cover more
points with the facets. In the summary flowchart of FIG. 6 these
steps are referenced in operation blocks 1 and 2.
[0062] The facets will be explained with reference to FIGS. 4 and
5. FIG. 4 shows an example of pixels 50 defining rectangular-shaped
facets, each pixel 50 being the smallest unit and represented as a
square or box. The pixels have individual gray levels. FIG. 4 shows
an exemplary pair of facets (15.times.15 pixels) of the left camera
10 and of the right camera 20. FIG. 4 reflects the applied pattern
in an unstressed state, thus forming the image for the undeformed
reference state. FIG. 5 shows an example of the facets shown in
FIG. 4 having been deformed after the patterned object is taken
through successive, intermediate deformation stages (not shown) to
a final deformation state ("stage F"). The black quadrilateral in
FIG. 4 and FIG. 5 superimposed on the pixels 50 illustrates the
facet in the undeformed state. As seen in FIG. 4 in the undeformed
state, the left camera 10 contributes the left image upon which
facet 52L is constructed, and the right camera 20 contributes the
right image upon which facet 52R is constructed. The facet from
left camera 10 appears as a square, while the facet from right
camera 20 appears tilted resembling a trapezoid, since, relative to
the left camera 10, the right camera 20 is focused on the same
region of the object, e.g. face 40, but is taking a picture at an
angle .alpha. to the left camera 10.
[0063] As seen in comparison in FIG. 5, on the deformed patterned
object, the facets 52L, 52R have undergone deformation and are
shown in dashed lines as deformed facets 54L, 54R, respectively.
For convenient comparison, the undeformed facets 52L, 52R are also
shown on FIG. 5.
[0064] The steps taken in the image processing in order to
calculate major and minor strain are summarized in the flowchart of
FIG. 6.
[0065] A reference condition is compared to a series of deformed
conditions. The Aramis system software determines the 2D
coordinates of the facets from the corner points of the facets and
the resulting center of each facet. Using photogrammetric methods,
the 2D coordinates of a facet, observed from the left camera 10,
and the 2D coordinates of the same facet, observed from the right
camera 20, lead to common 3D coordinates of each corner and center
of each facet. (This is referenced in operational block 3 of the
flowchart in FIG. 6). The change in these coordinates as the
surface is strained is measured for each subsequent image pair
(left-right) and the deformation relative to the reference image is
calculated. The values are reported as various displacement and
strain values. For the measurement of shaving it is preferred to
report "major strain" as a percent change (% change). The major
strain direction follows the razor as it passes over the skin so
this is believed to be the most relevant parameter for studying
shaving.
[0066] The facets act as virtual strain gauges. Each facet can be
thought of as a virtual 3D extensometer. An array of facets acts as
a virtual strain rosette; this is an approximate analogy since a
strain rosette is usually considered as 2D, whereas the facets are
3D. With respect to a facet in its undeformed and deformed states,
the difference in tensor length is calculated by looking at the
change in length of the leg between the deformed state and the
reference state, and expressed as a percent (%) change. Because the
coordinates that are determined are in 3D from a curved surface,
they are translated first into 2D using a transformation (such as a
spline model, as referenced in operational block 4 of the flowchart
in FIG. 6) and then applying engineering strain calculations. With
reference again to the flowchart of FIG. 6, as shown in operational
block 5, the deformation gradient tensors are calculated according
to the known relation:
p.sub.v=u+Fp.sub.u,
[0067] where [0068] p.sub.u=the coordinates of a reference point
[0069] p.sub.v=the coordinates of the deformed point [0070] u
denotes rigid body translation. As noted in operational block 6,
the major and minor strains are derived from the deformation
gradient tensor. The primary direction is the major strain. For
background information, the basic strain relations are discussed in
the Appendix at the end of this application's specification.
[0071] Because rigid body motion that is seen by both cameras is
subtracted out in accordance with the above relation, then any
inadvertent motion of a test subject, while shaving, for example
moving his head or body within the field of view of the cameras (or
even walking within the field of view), does not detract from
imaging the strain in the skin due to the razor's shaving action.
This analytic technique is well suited to measure strains in the
skin as they occur when a person shaves himself or herself in
normal use, without having to unnaturally constrain the test
subject.
[0072] If a person has very coarse beard hair, that may also be
recognized by the imaging system as a pattern; that is not a
disadvantage since beard hair grows in an irregular pattern.
Comparing Shaving Characteristics
[0073] A reference image is shown in FIG. 8, which illustrates a
digital image of pattern 45 prior to shaving (the dark, somewhat
jagged line bounding pattern 45 is an artifact of cropping the
image to enhance visibility). The image shows a generally
strain-free, unloaded condition of the shaving surface.
[0074] The strain patterns on the skin being shaved are illustrated
schematically in FIGS. 9-12. FIG. 11 is a cross-hatched version of
the gray-scale image in FIG. 9. FIG. 12 is a cross-hatched version
of the gray-scale image in FIG. 10. The strain in the areas behind
the razor is represented by bands or regions of similar magnitude,
as depicted by the regions of similar shading, with the scale "%
Major Strain" showing the corresponding scale for the shaded
region. The Aramis imaging system provides these bands in color,
and they are superposed over the black dots of the reference image
shown in FIG. 8; however, the strain bands are rendered herein in
grey scale (and with the black reference dots removed) in FIGS. 9
and 10, and schematically in cross-hatch in FIG. 11 and FIG. 12,
for convenience of photo-reproduction and printing on paper. The
corresponding color is also indicated on the legends in FIGS.
9-12.
[0075] FIG. 9 shows an image of the face being shaved over skin
with pattern 45 with blade unit 77 positioned at about mid-stroke.
FIG. 9 shows the maximum strains present in bands (100, 101, 102,
103, 104) in the respective skin surface portions that have been
shaved. In FIG. 11 the strain bands (100, 101, 102, 103, 104) are
depicted using different cross-hatching to indicate the several
strain levels. For example, the mesh formed by intersecting
vertical and horizontal lines indicates a strain level between
about 6% and 8% in band 101; on a color image available from the
Aramis system that band would be indicated with e.g. a yellowish
color. It will be noted that the higher strain levels are seen
closer to behind the razor, such as in strain band 104. It will be
appreciated that the commercially available Aramis system generates
a color image in which the colored bands or regions tend to blend
into one another, for example a slightly higher strain region is
indicated with e.g. a light green color, and the yellowish colored
lower strain region blends with a somewhat diffuse border into the
next higher strain region, and there is also present the black
reference dots shown in FIG. 8. Such a light green higher strain
region corresponds in FIG. 11 to the cross-hatching of downwardly
slanted alternating solid and dashed lines used to represent the
strain band 102 between about 8% to 10%. In FIGS. 9-12 the grey
scale or cross-hatching depictions schematically indicate that the
various strain regions lie next to one another, and, as mentioned,
the black reference dots of FIG. 8 have also been removed to
facilitate clarity. As seen in FIG. 9 (or FIG. 11), there are about
five (5) readily identifiable bands (100, 101, 102, 103, 104) of
different strain magnitude. Each of FIGS. 9 and 11 illustrates in a
region just behind the razor a strain level of between about 12%
but less than 14% major strain as the highest strain band 104 on
that image, indicated in FIG. 11 with the cross-hatching that is
upwardly slanted alternating solid and dashed lines (to represent a
turquoise color on an image from the Aramis system, as indicated on
the legend).
[0076] FIG. 10 shows an image of the face being shaved over skin
with pattern 45 with blade unit 77 positioned at about the end of
stroke. The image of the type shown in FIG. 10 is about ten (10)
images subsequent to the image of FIG. 9. As shown in FIG. 10,
since the image capture is dynamic the previous strains that were
present in the region depicted in FIG. 9 have decreased since the
razor has moved further away from the FIG. 9 region and is not
pulling it as much, since that region ("midstroke", designated
approximately with bracket 60 in FIG. 10) is now further behind the
razor as the razor has advanced lower on the face towards the jaw.
As seen in FIG. 10, there are eight (8) readily identifiable bands
(100, 101, 102, 103, 104, 105, 106, 107) of different strain
magnitude. FIG. 10 illustrates a region just behind blade unit 77
of strain above 18.5% major strain in band 107. This is illustrated
in FIG. 10 by bands of darker grey shading than are seen in FIG. 9.
In FIG. 12 the strain band 107 corresponding to the highest strain
band seen in FIG. 10 (above 18.5%) is indicated with vertical
dashed lines (to represent a violet color on an image from the
Aramis system).
[0077] Image analysis is explained with reference to FIGS. 13-15.
It is understood that the analysis depicted relative to FIGS. 13-15
is performed on the images shown in, for example FIG. 10, or
equally in FIG. 12 upon completion of shave stroke. For convenience
to show the technique of defining representative spatial regions,
FIGS. 13-15 omit the depictions of the bands of strain and
reference dot pattern 45. To analyze the images, a group of images
is selected that starts just after the shave stroke has begun and
ends approximately near a line extending back from the lip (with
respect to images collected when shaving the face). Sometimes a
pair of images, that is images from the left and right cameras 10,
20, is referred to as a "stage" or "rendered image" since it
reflects a 3D rendering calculated from the left and right camera
individual digital pictures, but for simplicity each "stage" is
referred to as "image". Within that set of images, an area just
behind the razor is selected, and the average strain in that area
is recorded. The "area behind the razor" is meant in the sense that
it trails the razor, in that that area has just been shaved and the
razor has moved past it, exposing it to be imaged.
[0078] As shown in FIG. 13, an imaginary start line 75 is
constructed from the nose to the ear. FIG. 13 depicts an
approximate start-shaving position. An imaginary end line 76 is
constructed approximately parallel to start line 75 extending
backwards from the lip. As the razor blade unit 77 is drawn past
start line 75 a first measurement area 80 is chosen on the image
seen in FIG. 12. The measurement area 80 is chosen to be
approximately the size of blade unit 77, and located just behind
the blade unit ("behind" in the sense of being opposite the
direction of razor travel during the shaving stroke). It is
understood that the imaginary lines 75 and 76 and reference
measurement area 80 are constructed over the strain bands image
resulting for example in FIG. 11 or 12, omitted here for easier
depiction. Since measurement area 80 is constructed over the strain
bands in, for example, FIG. 11, the software in the Aramis system
selects and averages the strains within that bounded measurement
area 80 and reports the average major strain in that measurement
area 80. It will be understood that within a measurement area,
instead of the average strain, other parameters indicative of
shaving performance could be chosen; for example, it is possible to
instead calculate the minimum strain, or the maximum strain, and
the standard deviation.
[0079] As shown in FIG. 14, the user has drawn the razor further
down towards the jaw, and blade unit 77 is approximately at a
mid-stroke position. For illustration purposes, the previous start
position in FIG. 13 is indicated with a phantom-line blade unit
77'. FIG. 14 illustrates how a second measurement area 81 is chosen
at this position, behind blade unit 77, within which the average
strain is calculated.
[0080] As shown in FIG. 15, the user has drawn the razor further
down such that blade unit 77 is approximately at an end-of-stroke
position, prior to the user beginning to lift the blade unit away
from the skin. A third measurement area 82 is chosen at this
position, behind blade unit 77, within which the average strain is
calculated. Any desired number of measurement areas can be provided
between beginning of stroke and end of stroke; it is presently
preferred to use four such measurement areas. The selected
measurement areas can be adjacent to one another and it is also
acceptable if they are slightly overlapping.
[0081] Four measurement areas selected as with the exemplary
measurement areas 80, 81, 82 were selected from the set of images
so as to be distributed over a reasonable amount of the distance of
the entire shave stroke, and then their individual averages were
averaged together. It is preferred that the four such measurement
areas be distributed so as to cover the distance from a start of
stroke to end of stroke over a reasonable length of stroke before
the user starts to lift blade unit 77 off the skin. For example,
over the overall shave stroke between start- and end-of-shave there
may be between eight (8) and twenty (20) images, with twelve (12)
images being common; this varies based on stroke speed. Four (4)
images that encompass the strain just behind the razor over the
total area were selected, approximately every third or fourth image
based on 12 images overall, and corresponding measurement areas
selected and their average strains calculated. It is understood
that another number of measurement areas, e.g. a number more than
four, could have been selected between the start and end of shave
stroke.
[0082] Comparative razor testing: These images provide a
quantitative tool to compare the performance characteristics of
different razors. When comparing razors, one looks at the
difference in average % major strain over the stroke area. It is
also understood that if in the measurement areas 80, 81, instead of
major strain, the maximum strain or the minimum strain or the
standard deviation have been evaluated, then one would look at
differences in the maximum strain or minimum strain or standard
deviation. In this manner a strain exerted on the skin produced by
two different razor blade units can be compared. It is also
possible to evaluate differences between a test and a control blade
unit that has a different feature in the blade unit, such as a
different guard, or even the same blade unit mounted on different
handles to test performance differences possible owing to the
ergonomics of a handle. Such testing can assess differences between
existing razors or facilitate developmental testing of prototype
razors.
[0083] A comparison was made between two razors manufactured by the
assignee of the present application, The Gillette Company, (Boston,
Mass., USA), namely razors marketed to male consumers under the
trade designations "Fusion" and "Fusion Power", each widely
commercially available in the U.S. market since late 2005, and in
other markets. Each of the "Fusion" and "Fusion Power" razors is a
safety razor whose cartridge has five blades on its primary shaving
surface positioned between a guard at the front and a cap at the
rear. This razor cartridge is shown in assignee's U.S. Pat. No.
7,131,202 (Pennell et al.), which is hereby incorporated by
reference, in particular in FIGS. 1-3 therein.
[0084] The manual "Fusion" razor is depicted for example in
assignee's U.S. Design Pat. D534,313 (Provost et al.), hereby
incorporated by reference, and in U.S. Pat. No. 7,131,202 at FIGS.
1-2, and is also seen in FIGS. 9-15 of the present application
(without in any way limiting the generality of the measurement
procedure). This version "Fusion" razor is referred to as "manual"
in the sense that the motion occurs from the manual action of
drawing the razor across the skin and it does not have a motor on
the razor exciting additional blade motion.
[0085] The "Fusion Power" razor is depicted for example in U.S.
Design Pat. D534,315 (Provost et al.) and in pending patent
application U.S. Ser. No. 11/220,008 filed 6 Sep. 2005 (Schnak et
al.) (to publish as US 2007/______A1), which are both hereby
incorporated by reference. This "Fusion Power" razor is referred to
as a "power" version razor since there is a power source (e.g. a
battery) as well as a motor driving an eccentric weight (also
called flyweight) located in the handle that, when energized,
causes during shaving use small amplitude oscillation of the razor
cartridge that is connected to the handle.
[0086] A comparison was made to determine whether the "Fusion
Power" razor in shaving use exhibits less drag than a "Fusion
Manual" razor. Each razor was used in its normal, intended
operational manner, that is, during shaving the "Fusion Power"
razor was energized so that it vibrated. The major skin strain was
measured on the x-, y- and z-axes. Twenty-five test panelists
shaved following a 24-hour hair growth period, and the strokes were
measured during shaving. Differences in major strain were
determined between the two razors. For the manual "Fusion" razor
the average major strain measured was about 14.3%. For the "Fusion
Power" razor the average major strain measured was about 13%. This
shows a difference of at least 9% lower strain when using the
"Fusion Power".
Other Skin Applications
[0087] It is understood that the aforementioned analysis technique
can be applied to other applications of a stressing force applied
to the skin to determine a response characteristic in the skin. For
example, one could measure strain on the skin as hair is being
plucked out for example using an adhesive tape lifting or wax
depilatory strips, as an example of testing hair epilation
products.
[0088] It is theorized that a cleanser agent applied to skin dries
out the skin, that the skin thereby would become stiffer or
otherwise be referred to as less supple. It is thus hypothesized
that, in the presence of the same force as applied to skin that has
been treated with the cleanser as compared to that skin not treated
with the cleanser, then in the cleanser-treated skin there will be
less strain since the skin is stiffer. If a moisturizing agent is
applied to make the skin softer or more supple, then in the
presence of the same force such moisturizer-treated skin would
yield more and show a higher strain.
[0089] In optical image testing of the effect on the skin of a
moisturizing product, such as a lotion, cream or emollient, having
been applied, it is suggested that a finger of a person or as shown
in FIG. 16 a blunt probe object 90 (which emulates a finger) be
dragged along a portion of skin during the test in order to
transmit a force to the skin. Probe 90 has a suitable radius at its
tip to be generally smoothly dragged across the skin. The force
applied can arise not only from an externally applied force such as
a finger or probe 90, but also from internally caused forces; for
example, a test subject can be asked to flex a muscle, such as
smiling, frowning or making a facial expression, in order to apply
a force to the skin and measure the skin deformation.
The Temporary Tattoo Pattern
[0090] One of skill in the art appreciates that for imaging the
skin while shaving, the pattern should desirably not be damaged by
exposure to the shaving environment, typically involving water and
a shave prep such as soap or a shave cream or gel, and it is also
desired that the pattern not be permanent but be generally readily
removable from the skin upon the conclusion of the test. Also, in
general, if the skin is exposed to a lotion such as a moisturizer
as part of testing and imaging, a pattern should be applied that
will not be readily smudged by the material being tested.
[0091] In order to pattern the skin surface to have a suitable
target to generate the reference and deformed images, the skin of a
subject was painted by hand by stippling the paint to the cheek
with a narrow paint brush so as to create "dots". A water-insoluble
paint was chosen such as a commercially available paint from a
hardware store, for example the oil-based enamel paint sold in the
United States under the trade designation "Rustoleum" in the color
black. Dabbing this paint with the point of a fine-tip paint brush
to the skin gave a random pattern of dots of high contrast which
gave suitable results during the imaging and analysis. This method
of applying the skin pattern with paint had the disadvantages,
however, of a strong odor, being messy, exposing the person to
excess paint, requiring careful preparation that was
time-consuming, and being inconvenient to remove from the skin.
While a spray paint technique could possibly be used such as a
spray paint can by intermittently depressing the can's button, or
using an airbrush technique, to more quickly give a suitable random
pattern, in order to adequately protect a person's eyes, nose,
ears, hair and clothing during such an application would require
elaborate masking of those areas, and could still expose the person
to excess paint spray or fumes, and would thus also be
inconvenient.
[0092] In order to provide a pattern 45 that could quickly be
applied to a face or body surface to be shaved and imaged, a
transfer pattern was developed, as shown in FIG. 7. The pattern 45
can be prepared as a temporary body tattoo printed with standard
FDA-approved ink as shown in FIG. 7 and easily transferred to the
skin surface. The tattoo pattern 45 is removable or temporary, as
those words are used herein, in that the pattern 45 can be wiped
off or removed from the skin on which it has been applied such as
by alcohol or by vigorous, normal washing with water and
conventional soaps, make-up or cosmetic removal compositions (such
as petroleum-based lotion), and the like. While the present
temporary tattoo may be removed with repeated washings with soap
and water, it is more quickly removed by use of an alcohol. The
present temporary tattoo is contrasted with permanent tattoos which
cannot be wiped off or removed by washing, and can only be removed
by medical intervention or the like, such as by laser or surgical
means.
[0093] The skin is first cleaned, for example with 70% isopropyl
alcohol, and the transfer paper 73 applied to the skin area to be
patterned. The transfer paper 73 is wetted with alcohol to transfer
the ink pattern 45. It has been determined that the ink used is
resistant to removal with water, resistant to the shave preparation
used (e.g. shaving soap, foam or gel), and resistant to the act of
shaving itself (e.g. the action of rubbing the cartridge over the
skin or the blades moving over the skin), and yet the transferred
pattern is advantageously easily removable with alcohol at the
conclusion of the test.
[0094] It was found convenient to create pattern 45 shown in FIG. 7
as a computer data file using a commercially available desktop
publishing software such as Adobe Photoshop. Pattern 45 has indicia
distributed in a random pattern. It is preferred that the indicia
be three different size dots in a generally random distribution.
The diameters of the respective dots are: small dots 70 of 1.6 mm
(0.063 in), medium dots 71 of 2.1 mm (0.083 in), and large dots 72
of 2.6 mm (0.103 in) diameter. It is not required that the dots be
precise circles having a mathematically true diameter, the dots can
be of a non-circular or arbitrary shape, such as small ovals or
ellipses, or even small polygonal shapes including rectangular. The
distribution of the dot sizes in the overall pattern is
approximately one-third each size. The pattern 45 could be
fashioned of just two different dot sizes; however, three different
dot sizes is preferred. Pattern 45 can comprise more than three
different dot sizes. Pattern 45 with this size distribution is
small enough to allow a good raster of calculation facets during
evaluation, and it also large enough to be resolved by the camera.
(The image of FIG. 7 is printed out as a square of 5 inch.times.5
inch)
[0095] It is preferred that the density of pattern 45 be in the
range of about 40% to about 60%. The lower approximate "40%
density", for example, means that for a given square area of
pattern 45 about 40% is occupied by the darker image (e.g. the
dots, collectively) and 60% occupied by the background space. The
background, in order to give sufficient contrast, is neutral or
so-called "white" space. The upper approximate "60% density", for
example, means that for a given square area of pattern 45 about 60%
is occupied by the darker image (e.g. the dots, collectively) and
40% occupied by the neutral ("white") space. An approximate
midrange value of about 50% pattern density is believed to give
good results. In the preferred embodiment, pattern 45 shown in FIG.
7 was suitable in practice with a pattern density of about 42.5%
(thus the remaining "white" space comprises about 57.5%). Pattern
45 is preferably of a consistent pattern density over its extent,
thus facilitating applying it to the skin surface such as a cheek
or leg.
[0096] The pattern 45 is printed on a substrate 73. Substrate 73
can also be referred to as a web or release web, since in the art
of transfer tattoos it is known that the web releases printed
pattern 45 to transfer it to the skin. Substrate 73 is preferably
moisture-permeable (moisture absorbing, such as absorbing an
alcohol); this assists in releasing the printed pattern when the
substrate is placed against the skin and wetted with alcohol (e.g.
isopropyl alcohol or denatured alcohol). Preferably substrate 73 is
made of paper or cellulose material. It has been found convenient
to use as substrate 73 what is referred to in the paper art as
"blotting paper" or cigarette paper of the type commonly sold for
rolling one's own cigarette. Other substrates could include paper
such as Kraft paper, plastic, or composites thereof. The pattern 45
can be generated on substrate 73 in a long roll similar to
wallpaper or gift-wrapping paper, preferably pattern 45 has a
consistent pattern density over at least a length dimension of a
size of a cheek, at least about 4 inches (approx. 10 cm), which
facilitates application to the cheek.
[0097] The dots of pattern 45 are printed with inks. It will be
appreciated that inks used are suitable for skin contact and are
non-toxic such as those approved for food, drug and/or cosmetic use
("FD&C" or "D&C grade") in the United States. Such inks are
mentioned in the U.S. Code of Federal Regulations at 21 C.F.R.
Parts 73 and 74. These are generally food grade and/or cosmetic
grade inks, being the same colorants manufactured in compliance
with FDA regulated cosmetics. Suitable inks are pigmented and
solvent based. The preferred ink is not water-soluble. A useful
black ink is one containing iron oxide, which is a pigment. Dark
ink is preferred, such as black ink referred to as D&C Black
#2. Such inks are widely commercially available; one such supplier
is the company Temptu at the address 26 West Seventeenth Street,
New York, N.Y. 10011 (website www.temptu.com). It is preferred to
use inks that are termed "certified", meaning certified not to
contain toxins. A blue ink could also be used. Other dark colors or
mixtures of ink could also be used. The ink is typically formed of
an oil dye or a pigment in a carrier, and is soluble in lower
alcohols but has very low water solubility. The ink or dye is
preferably substantially insoluble in water, but is soluble in
alcohol. Such an oil-based ink meets the criteria of being a
temporary tattoo while being sufficiently water resistant to
satisfy the objectives above to provide a pattern to the skin while
withstanding the action of shaving. Many such inks are known in the
medicinal and cosmetic arts as suitable for contact with human
skin. Many such dyes are disclosed in U.S. Pat. No. 4,169,169
(Kitabatake), the teachings of which are incorporated herein by
reference, including at column 3, lines 36 to 68 therein. An oil
dye is formulated into an ink composition; in addition to the dye
the ink will typically contain a binder, a solvent, a plasticizer
and, optionally, other additives. The thickness of the ink layer of
dots 70, 71, 72 will typically be on the order of 10 microns or
less. It will be appreciated that the ink layer of pattern 45
deposited onto the skin is extremely thin, and does not affect the
skin's characteristics, the shaving performance or shaving action,
and does not interfere with taking the measurements.
[0098] The electronic data file containing pattern 45 can be
printed using a conventional computer printer, as is widely
commercially practiced, and for example available from the company
Temptu of 26 West Seventeenth Street, New York, N.Y. 10011. Pattern
45 can be printed onto the substrate 73 paper with any known
printing process such as offset, silk screen or gravure to form the
temporary tattoo. Also, in order to print the tattoo, the digitized
image or electronic file containing pattern 45 can be output from a
computer to a conventional ink jet printer or laser jet printer
whose ink cartridges have been loaded with D&C or FDA approved
inks and printed onto a paper substrate, as is known in the art.
This convenient form of printing is described generally in
accordance with the portion of the teachings directed to printing
onto a substrate as discussed in U.S. Pat. No. 6,042,881 (Ewan),
the entire content of which is incorporated herein by reference.
Other tattoo printing techniques onto a substrate are known in the
art field, such as in U.S. Pat. No. 6,596,118 (Bailey), the
teachings of which are incorporated herein by reference.
[0099] Since an adhesive is omitted, there is no need for a
protective release sheet to cover the finished tattoo. Thus, the
indicia of pattern 45 can be exposed to air during storage, and
this further improves the convenience, simplicity and speed with
which test subject persons can have their skin patterned since
there is no protective or cover layer that needs to be removed and
discarded. Furthermore, since the ink used is not water-soluble,
that is a further reason that a protective release sheet is not
needed.
[0100] The foregoing specification describes numerous embodiments
and variations showing the wide range of possible constructions and
techniques embodying the present invention. Further variants and
embodiments will readily occur to those skilled in the art on the
basis of the foregoing disclosure. All such embodiments and
variants are to be considered as within the scope of the invention
as defined by the claims.
APPENDIX: THE BASICS OF STRAIN
[0101] This section explains basics of strain and strain
calculation, closely following the Aramis User Guide (v5.4.1)
drawing from the books (listed in the below bibliography) Hibbitt
et al.; Becker et al.; Hahn; and Kopp et al.
A.1. The Term "Strain"
[0102] Strain is the measure for the deformation of a line element
and can be defined as follows:
.lamda. = lim l .fwdarw. 0 ( l + .DELTA. l l ) ##EQU00001##
The stretch ratio .lamda. is the relative elongation of an
infinitesimal line element. A strain value .epsilon. can be defined
as the function of the stretch ratio .lamda.: The following known
functions are frequently used strain measures: [0103] Technical
strain:
[0103] .epsilon..sup.T=f(.lamda.)=.lamda.-1 [0104] Logarithmic or
natural strain:
[0104] .epsilon..sup.L=.phi.=f(.lamda.)=1n(.lamda.) [0105] Green's
strain:
[0105] G = f ( .lamda. ) = 1 2 ( .lamda. 2 - 1 ) ##EQU00002##
A.2 The Deformation Gradient Tensor
[0106] The above section defined the stretch ratio in the
one-dimensional case and the general description of a strain
measure. This will now be extended to the two-dimensional case.
A.2.1 Deformation Gradient Tensor Definition
[0107] In order to quantitatively display the deformation of a
surface element, the deformation gradient tensor F is introduced.
The deformation gradient tensor transforms a line element dX into
the line element dx. In both cases, the line element connects the
same material coordinates. Theoretically, it is an infinitesimal
line element. FIG. 17 illustrates this case.
[0108] Thus, the deformation gradient tensor is defined as:
dx=FdX
A.2.2 Decomposing the Deformation Gradient Tensor into Polar
Coordinates
[0109] A disadvantage of the deformation gradient tensor is that
rotation and stretch are modeled using only one matrix. This can be
compensated by splitting the deformation gradient into two tensors:
a purely rotational matrix and a pure stretch tensor. The matrix
can be decomposed in two different ways: [0110] Decomposition into
rotation and right stretch tensor Mathematically, the deformation
gradient tensor is decomposed as follows:
[0110] F=RU [0111] FIG. 18 illustrates this modeling. [0112]
Decomposition into left stretch tensor and rotation.
Mathematically, the deformation gradient tensor is decomposed as
follows:
[0112] F=VR
A.2.3 Major and Minor Strain Derived from the Deformation Gradient
Tensor
[0113] Values .epsilon..sub.x, .epsilon..sub.y and
.epsilon..sub.xy=1/2.gamma..sub.xy can directly be read from the
stretch tensor U. It has the following form:
U = ( U 11 U 12 U 21 U 22 ) = ( 1 + x xy xy 1 + y )
##EQU00003##
[0114] The strain measures .epsilon..sub.x and .epsilon..sub.y have
the disadvantage of being defined as dependent on the coordinate
system. This disadvantage can be eliminated by calculating major
and minor strain. The symmetrical matrix U can be transformed to
the main diagonal form. The two eigenvalues .lamda..sub.1 and
.lamda..sub.2 can be calculated as follows:
.lamda. 1 , 2 = 1 + x + y 2 .+-. ( x + y 2 ) 2 - ( x y - xy 2 )
##EQU00004##
[0115] Depending on the choice of the strain measure, the stretch
ratios .lamda..sub.1 and .lamda..sub.2 can be transformed into
corresponding strain values. The larger eigenvalue is called major
strain.sup.1 .epsilon..sub.1 and the smaller eigenvalue is the
minor strain .sup.2.epsilon..sub.2. The corresponding eigenvectors
determine the two directions of major and minor strain. The strain
values thus determined are independent of the coordinate system and
are universally applicable.
[0116] If the material thickness with respect to the entire surface
is small, it is frequently necessary to deduce the remaining
material thickness from the deformation of the surface. As the
optical measuring techniques used cannot obtain any data in this
dimension, the third principle strain .epsilon..sub.3 can be
calculated from major and minor strain .epsilon..sub.1 and
.epsilon..sub.2, assuming a constant volume. Without determining a
strain value, the relationship between the stretch ratios can be
expressed more generally. The volume constancy can be defined as
follows:
.lamda..sub.1.lamda..sub.2.lamda..sub.3=1
[0117] Frequently, the effective strains are needed. The effective
strains according to von Mises and von Tresca are available. The
effective strain according to von Mises results from the following
formula:
.PHI. V = 2 3 ( .PHI. 1 2 + .PHI. 2 2 + .PHI. 3 2 )
##EQU00005##
The effective strain according to von Tresca results from the
following formula:
.phi..sub.V=|.phi.|max
A.3 Calculation of the Deformation Gradient Tensor from a 2D
Displacement Field
[0118] The deformation gradient tensor F is calculated from a given
2D displacement field of points. For this purpose, the 2D
coordinates of each point must be known both in its undeformed and
in its deformed state. The definition of the deformation gradient
tensor F explains how an undeformed line element is transformed
into a deformed line element. In order to calculate the deformation
gradient tensor for a point, a number of points in the neighborhood
of the observed point is needed. For this model of calculation, a
homogeneous state of strain is assumed for this set of adjacent
points.
[0119] The deformation gradient tensor creates a functional
connection of the coordinates of the deformed points P.sub.v,i with
the coordinates of the undeformed points P.sub.u,i (i being the
index for the different points). The functional connection is as
follows:
p.sub.v=u+Fp.sub.u
[0120] with:
[0121] p.sub.u Coordinates of the undeformed point
[0122] p.sub.v Coordinates of the deformed point
[0123] u Rigid body translation
[0124] Reference is made to FIG. 19.
[0125] This formula describes a linear system of equations whose
unknowns are the four parameters of the deformation gradient tensor
F. The deformation gradient tensor F can be interpreted as an
affine transformation which transforms a unit square into a
parallelogram. This system of equations can be analytically
calculated for three points. If more than three points are chosen,
the result is an overdetermined system of equations which generally
is contradictory. In this case, methods must be used which permit a
calculation with more than three points. Thus, the Gaussian least
squares adjustment is used.
[0126] The number of neighboring points can be adjusted to
calculate the deformation gradient tensor for one point. This thus
sets the length over which the differentiation is made. The
neighborhood for a point is arranged quadratically. The smallest
neighborhood is a 3.times.3 environment which can be increased by
an increment of two. FIG. 20 shows a 3.times.3 neighborhood.
[0127] For an even higher resolution, the deformation gradient
tensor can be calculated for a four-sided facet. A facet consists
of four points. The calculated deformation gradient tensor is
calculated for the virtual center of gravity S. FIG. 21
schematically illustrates a four-sided facet.
[0128] This model of calculation assumes that the pure rigid body
displacement, which the individual line elements received in
addition to their deformation, cannot be modeled by the deformation
gradient tensor F as well. This means that for the calculation of
the deformation gradient tensor F all points of a neighborhood may
undergo a translation. This translation may be different for the
undeformed and the deformed state. The translation is chosen such
that the point for which the deformation gradient tensor is being
calculated is shifted into the origin.
A.4 Calculation of the Deformation Gradient Tensor from a 3D
Displacement Field
[0129] The description so far dealt in detail with the calculation
of strain in 2D. However, the measuring data consist of
three-dimensional Cartesian coordinates of the specimen's surface.
In order to be able to use the above models of calculation, the 3D
data has to be transformed into the 2D space.
A.4.1 The Tangential Model
[0130] The first model assumes that the local neighborhood of a
point can be well approximated by a tangential plane. Due to the
arbitrary deformation of the surface, the tangential plane needs to
be calculated separately for the deformed and undeformed state. The
points in the local neighborhood are then projected perpendicularly
onto the tangential plane. The result is two sets of points, for
the deformed and undeformed state, in the two-dimensional space in
which the strain now can be calculated. Summarized, this process
consists of the following tasks: [0131] Calculation of the
tangential plane [0132] Transformation of the 3D neighborhoods into
the tangential planes [0133] Coordinate transformation of the
tangential plane into the 2D space [0134] Calculation of the
deformation gradient tensor from the 2D sets of points
A.4.2 The Spline Model
[0135] The tangential model described above provides good results
as long as the assumption of the linearization of a local
neighborhood of points is valid. In deep drawing, the deformed
materials are mostly continuously curved planes. The problem then
is to apply the characteristics to be measured to the respective
object in such a frequency that the assumption of local linearity
is still given. However, this characteristic can hardly be provided
in reality. Therefore, it is better to use other models which are
more accurate in modeling the true shape of the surface. Splines
are a good model for continuously curved lines.
[0136] In order to calculate the side length not only according to
a linear model, it is necessary to have more information than two
points on a side. This means that the adjacent points of a
four-sided facet have to be included in the calculations. FIG. 22
shows the adjacent points of the cross-hatched four-sided
facet.
[0137] In the facet, the side lengths are calculated using the
formed splines. The resulting lengths can be used to construct a
quadrangle in the two-dimensional space. Then the strain
calculations described above can be used.
A.5 Bibliography for Strain Theory
[0138] 1) Aramis User Manual v5.4.1 (GOM mbH) at pp. 129-135. 2)
Hibbitt, Karlsson and Lorensen, Inc. ABAQUS--Theory Manual, 5.7
ed.
[0139] 3) Becker und Burger. Kontinuumsmechanik. ["Continuum
Mechanics] Teubner-Verlag, 1975.
4) Malvern. Introduction to the Mechanics of a Continuous Medium.
Prentice-Hall, 1969. 5) Hahn. Elastizitatstheorie. Teubner-Verlag,
1984. 6) Kopp und Wiegels. Einfuhrung in die Umformtechnik.
["Introduction to Transformation Technique"] Verlag der Augustinus
Buchhandlung, 1998. The following reference numbers listed below
are used in the specification:
TABLE-US-00002 Ref. No. Meaning L Length H Height W Width .alpha.
camera angle (alpha) 1 operational block 2 operational block 3
operational block 4 operational block 5 operational block 6
operational block 10 Camera, left 11 Camera lens, left 12 Camera
rotation axis 13 camera adapter plate 15 camera support 16 tripod
18 computer 20 Camera, right 21 Camera lens, right 24 angle
bisector by laser pointer 25 base distance 28 laser pointer 30
measuring distance 34 center of measuring volume 35 specimen to
measure 40 face of person 45 pattern 50 pixel 52L initial facet,
left camera 52R initial facet, right camera 54L deformed facet,
left camera 54R deformed facet, right camera 60 midstroke region 70
small dot 71 intermediate dot 72 large dot 73 transfer paper 75
imaginary nose-ear line 76 imaginary lip line 77 blade unit 77'
displaced blade unit 80 measurement area 81 measurement area 82
measurement area 90 blunt probe 100 strain band 101 strain band 102
strain band 103 strain band 104 strain band 105 strain band 106
strain band
[0140] The dimensions and values disclosed herein are not to be
understood as being strictly limited to the exact numerical values
recited. Instead, unless otherwise specified, each such dimension
is intended to mean both the recited value and a functionally
equivalent range surrounding that value. For example, a dimension
disclosed as "40 mm" is intended to mean "about 40 mm."
[0141] All documents cited in the Detailed Description of the
Invention are, in relevant part, incorporated herein by reference;
the citation of any document is not to be construed as an admission
that it is prior art with respect to the present invention. To the
extent that any meaning or definition of a term in this document
conflicts with any meaning or definition of the same term in a
document incorporated by reference, the meaning or definition
assigned to that term in this document shall govern.
[0142] While particular embodiments of the present invention have
been illustrated and described, it would be obvious to those
skilled in the art that various other changes and modifications can
be made without departing from the spirit and scope of the
invention. It is therefore intended to cover in the appended claims
all such changes and modifications that are within the scope of
this invention.
* * * * *
References