referring to the figures and more particularly to fig1 an impression block 10 of the present invention is shown . block 10 is made from pressure sensitive materials , which compress when a person &# 39 ; s foot is pressed into the block . preferably , block 10 comprises a casting material having low density , high flexural modulus and low shear strength . accordingly , block 10 provides a material , which is easily deformed , with little or no memory , and retains the deformed shape indefinitely . expanded phenolic materials such as those commonly used for insulation and ultra low density expanded polystyrene are suitable for block 10 . in the preferred embodiment , block 10 is expanded phenolic material . preferably , block 10 has a hardness or density from about 0 . 5 to about 25 pounds per square inch ( hereinafter “ psi ”). selection of the correct block 10 density depends on factors such as body weight , lifestyle or desired usage ( e . g ., sport , casual , or formal ). for example , a soft density is a density from about 0 . 5 to 5 psi , preferably 2 to 3 psi . such soft density blocks 10 are selected for casting a foot in block 10 while in the sitting position . a medium density is a density from about 5 to 10 psi and is selected for casting a foot in block 10 while in standing position . a hard , weight bearing density is a density from about 5 to 25 psi , preferably 8 to 15 psi . such hard density blocks 10 are selected for taking a dynamic casting of a foot in block 10 . shown in fig1 block 10 has a thickness 12 , a front or toe receiving end 14 and a rear or heel - receiving end 16 . importantly , thickness 12 is sufficient to form an impression of at least a portion of the overall height of the user &# 39 ; s plantar contour . in a first embodiment , thickness 12 is equal to less than half of the height of the plantar contour . in another embodiment , thickness 12 is equal to less than one third of the height of the plantar contour . more specifically , thickness 12 is in a range from about 8 mm to about 15 mm . in a preferred embodiment , thickness 12 of front end 14 is substantially identical to the thickness of rear end 16 . in alternate embodiments , thickness 12 of front end 14 is less than the thickness of rear end 16 . accordingly , block 10 of the present invention is adapted to form at least a partial measurement of the user &# 39 ; s plantar contour . as described herein by example , block 10 is adapted to form at least a partial measurement of the user &# 39 ; s entire plantar contour . however , it is considered within the scope of the present invention for block 10 to be adapted to form at least a partial measurement of the only specific portion of user &# 39 ; s plantar contour , such as , but not limited to , heel , arch and the like . as discussed above , a scanning system is used to digitize the measured contour . the digitized contour is provided to a computer controlled milling machine . the milling machine uses the digitized information to manufacturing a custom insole matching the digitized contour from an insole blank . the inventors have found that a complete plantar contour can be extrapolated from the partial measurement of the user &# 39 ; s entire plantar contour . preferably , block 10 is disposed in carrier or container 40 . carrier 40 includes a front or toes receiving end 44 and a rear or heel - receiving end 46 . block 10 is disposed in carrier 40 such that rear end 16 of the block is adjacent rear end 46 of the carrier and front end 14 of the block is adjacent front end 44 of the carrier . carrier 40 is adapted for use as for taking an impression of either a left foot or a right foot . preferably , carrier 40 shown in fig2 is symmetrical about its longitudinal axis 41 . thus , carrier 40 provides for sufficient surface area in both front end 44 and rear end 46 so as to allow the carrier to be used for either foot . accordingly , carrier 40 reduces manufacturing costs by enabling a single mold to be used to manufacture the carrier and by eliminating the need to carry specific right foot carriers and left foot carriers in inventory . in an alternate embodiment , block 10 includes a guide 18 to ensure the user properly aligns the foot in the block . guide 18 , shown in fig3 is an indentation 19 formed within block 10 . accordingly , guide 18 forms a natural locator for the user to place at least a portion of their foot into in order to align their foot in block 10 . preferably , indentation 18 is adjacent rear end 16 of the block and is of sufficient depth to allow the user to align their heel with block 10 . in an alternate embodiment , indentation 18 is adjacent front end 16 of the block and is of sufficient depth to allow the user to align their toes with block 10 . by way of example , the use of block 10 to measure a person &# 39 ; s plantar contour is described below with reference to the embodiment of block 10 shown in fig1 . the user positions one foot over block 10 with their toes toward front portion 14 and their heel towards rear portion 16 and moves their foot into the block as shown in fig4 . next , the user applies weight to the foot on block 10 until the block is deformed to form a negative impression of at least a partial plantar contour 11 . next , the user removes that foot from block 10 leaving the impression of the partial plantar contour 11 as shown in fig5 . as described above , impression of the partial plantar contour 11 formed in block 10 is used in the manufacture of custom insoles . the process of converting impression of the partial plantar contour 11 into the custom insole often times requires using a scanner to digitize the contour directly from the impression or by forming a positive model from the impression . by way of example the present invention is described using a scan taken directly from impression of the partial plantar contour 11 . however , it is considered within the scope of the present invention to include scanning from a positive model made from the impression . partial plantar contour 11 is extrapolated to form a complete plantar contour 11 ′. complete plantar contour 11 ′ is provided to a computer controlled milling machine . the milling machine uses complete plantar contour 11 ′ to manufacturing the custom insole from an insole blank . however , when desirable the partial plantar contour is all that is required for low profile insole supports . the scanning system forms a digitized model of partial plantar contour 11 . periodic cross sections of partial plantar contour 11 are then generated . for example , a plurality of cross sections 15 shown in fig6 through 8 formed along lines 6 - 6 through 8 - 8 of fig5 are generated . a sufficient number of cross - sections 15 to extrapolate complete plantar contour 11 ′ are formed . in the preferred embodiment , cross - sections 15 are generated in intervals of about 2 mm . however , for purposes of clarity only three cross sections 15 are described . by way of example , the formation of complete plantar contour 11 ′ from partial plantar contour 11 is described by the tangential line method shown in fig6 through 8 . in this method , each cross - section 15 is analyzed at points 13 where partial plantar contour 11 exits block 10 . a tangent line 17 to partial plantar contour 11 at each point 13 is derived . finally , the partial plantar contour 11 is continued along tangent line 17 to form complete plantar contour 11 ′. thus , analysis of a plurality of cross sections 15 of block 10 having partial plantar contour 11 extrapolates complete plantar contour 11 ′. while the present invention is described above using the tangential line method , other prior art numerical methods including , but not limited to linear interpolation , quadratic interpolation , newton &# 39 ; s forward - backward - difference interpolation , everett interpolation , lagrange interpolation and the like , are considered within the scope of the present invention for forming complete plantar contour 11 ′ from partial plantar contour 11 . reduction in thickness 12 of block 10 provides numerous advantages over prior art blocks . for example , thickness 12 reduces shelf space requirements for block 10 at the point of sale , reduces packaging costs for block 10 , reduces the amount of block 10 that it required , thus reducing manufacturing costs and shipping costs , as well as damage that may occur during shipping . in the instance where block 10 is directed for use at home by the user and then to be shipped to a location for manufacture of the insole , reduced shipping costs provides a significant advantage . additionally , thickness 12 enables the foot of the user to completely deform or bottom out in block 10 , which can provide a more accurate impression of the plantar contour . in an alternate embodiment , the present invention not only extrapolates complete plantar contour 11 ′, but also ensures that the complete plantar contour smoothly intersects the insole blank at a desired point . this requires a digitized model of , for example , the insole blank . the present invention is describe herein by example using types of insole blanks are commonly used to form custom insoles , namely die cut blanks 20 and molded blanks 30 . however , other types of blanks , such as , but not limited to , sheets of blank material are considered within the scope of the present invention . die cut blank 20 is shown in fig9 through 12 . a plurality of die cut blanks 20 are cut from a single sheet of insole forming material into the desired shape . for example , fig9 a shows die cut blank 20 in the form of a left foot insole . however , die cutting allows die cut blank 20 to be cut into other shapes , such as a right foot insole or a universal insole . shown in fig9 b , die cut blank 20 has a constant thickness 22 across its length 23 . thickness 22 of die cut blank 20 is typically between about 30 mm to about 35 mm . in order to ensure that the complete plantar contour smoothly intersects the insole blank , periodic cross - sections of the blank that correspond to cross - sections 15 of partial plantar contour 11 are generated . for example , a plurality of cross sections 25 shown in fig1 through 12 formed along lines 10 - 10 through 12 - 12 of fig9 a are generated of blank 20 . shown in fig6 a through 8 a , cross section 15 of complete plantar contour 11 ′ is compared to each cross section 25 of blank 20 . the present invention smoothes intersection 27 of the complete plantar contour and blank 20 . in an alternate embodiment , the height of the sole of the shoe that the custom insole is to be placed is the desired point used to define intersection 27 . this requires a digitized model of , for example , the sole of the shoe that the custom insole is to be placed . in this embodiment , the point where each cross section 15 of complete plantar contour 11 ′ crosses the cross section of the sole of the shoe forms the intersection 27 of the blank and the completed plantar contour 11 ′. in the instance of low profile insole supports , smoothing will be required to fit them into higher blanks if they are used . intersection 27 is smoothable by any number of smoothing methods such as , but not limited to , a radius fillet , bspline interpolation , and the like . molded blank 30 is shown in fig1 through 16 . each molded blank is molded to have a predetermined shape and profile . for example , fig1 shows molded blank 30 in the form of a left foot insole . however , molding allows molded blank 30 to be formed into other shapes , such as a right foot insole or a universal insole . shown in fig1 through 15 , molding molded blank 30 allows for a varying thickness 32 and width 34 across its length 33 . thickness 32 of molded blank 30 typically ranges between a minimum of about 10 mm to maximum of about 35 mm , more preferably between 15 mm to 20 mm . for example , fig1 through 18 show various different cross - sections 35 taken along lines 16 - 16 through 18 - 18 , respectively , of fig1 . similar to the discussion above with respect to die cut banks 20 , cross sections 35 of molded blank 30 that correspond to cross sections 15 of partial plantar contour 11 are generated by the scanning system . the scanning system compares each cross section 15 of complete plantar contour 11 ′ to cross section 35 of molded blank 30 and smoothes the intersection of the complete plantar contour and the molded blank . with extrapolation , the foot contour can be cut into insoles with approximately 10 mm in the arch and heal cups , and thereby provide the smoothing with the edges of the blanks . in an alternate embodiment shown in fig2 a and 20 b , block 10 is provided with a plurality of regions having different densities . by way of example , block 10 includes a region 10 - 1 having a first density and a region 10 - 2 having a second lower density . thus , block 10 is adapted to manipulate the foot of the user during the forming of the impression . for instance , region 10 - 1 , being of higher density , ensures improved or better support for the heal and other plantar surfaces . in a preferred embodiment , region 10 - 1 has a density of 5 psi and region 10 - 2 has density of 3 psi . in this embodiment , the higher density of region 10 - 1 ensures that the foot is properly centered within the lower density region 10 - 2 . also shown in fig2 a and 20 b , the inside 21 wall and outside 23 wall of carrier 40 are both shaped having a radius 42 between the sidewall and the bottom wall . radius 42 is adapted to ensure that the heel of the user is properly centered within block 10 . thus , radius 42 further improves the accuracy of the measurement of a person &# 39 ; s foot by more closely approximating the position and shape their foot will assume when properly centered . [ 0076 ] fig2 is a schematic exploded side view of a partial women &# 39 ; s heeled shoe 80 , a dual density cartridge 82 comprising a first lower density layer 84 and second higher density layer 86 , and foot 88 . fig2 is a top view of dual density cartridge 82 . fig2 is a schematic side view of a foot 88 positioned above a carrier filled with dual density foam 82 prior to making a impression . fig2 is a schematic side view of a foot 88 with pressure being applied thereto such that the dual density foam 82 is depressed downward such that both the ball 90 and heel 92 of foot 88 are compressed into higher density foam layer 86 . [ 0077 ] fig2 a through 27 depict another embodiment according to the present invention wherein a foot 96 applies pressure to a shorter or partial ( e . g ., three quarters sized ) dual density foam impression cartridge 98 comprising a first lower density layer 97 and second higher density layer 99 . fig2 a - 26 c demonstrate cartridge 98 deposed within at least a portion of a shoe 100 , wherein shoe 100 acts as a carrier for cartridge 98 . it should be understood that the foregoing description is only illustrative of the invention . various alternatives and modifications can be devised by those skilled in the art without departing from the invention . accordingly , the present invention is intended to embrace all such alternatives , modifications and variances that fall within the scope of the appended claims .
an apparatus for measuring a plantar contour of a foot of a user , the plantar contour having a height . the apparatus comprises an impression block having a thickness sufficient to form an impression of at least a portion of the height of the plantar contour . a method for forming an insole corresponding to a plantar contour of a foot of a user , wherein the plantar contour has a height . the method comprises the steps of placing the foot of the user into an impression block having a thickness wherein the thickness is sufficient to form an impression of at least a portion of the height of the plantar contour ; forming a digitized model of the impression ; extrapolating data from the digitized model of the impression to form a complete digitized model of the full height of the plantar contour ; providing the complete digitized model to a milling machine ; and directing the milling machine to manufacture the insole using the complete digitized model .