The invention relates to a method of selling personalized products and to a process of applying a decoration to an object such as a housing of a domestic appliance.

A consumer product like a household appliance or shaver is usually mass-manufactured, and as a result the product is offered for sale as one of series of uniform products. However, it is expected that buyers want to buy unique, personal products, different from products bought by other people. For example, when buying a shaver or a household appliance, the buyer would like to obtain a personal product. The buyer wants the product to say something about him-or herself and that distinguishes him-or herself from others.

The design and manufacture of unique products conflicts with the needs of mass-manufacture and its benefits like low-cost and consistent quality control. As a result, a product is usually offered for sale either as one from a series of uniform products at a reasonably low price or the buyer has to order that a unique, personal product be made for him or her individually at a considerably higher price. A significant demand could be satisfied if it could be made possible to offer the buyer the power to order manufacture his or her unique, personal product, while retaining the essential advantages of mass-manufacture.

Products can be made unique and personal by applying unique decorations to their surface. A known manufacturing technique for decorating three-dimensional products involves pasting two-dimensional decorations onto the surface of the products (the products themselves being rigid non-flat three-dimensional objects). For example, a method of applying a decoration to ceramics is disclosed in an article by C. K. Chua, W. Hoheisel, G. Keller and E. Werling, titled "Adapting decorative patterns for ceramic tableware"and published in the Computing & Control Engineering Journal, October 1993 pages 209 to 217. This article discusses the design and production of so-called"decals" : printed transfers with decorative patterns that are pasted onto objects like dishes etc. The decorative patterns are made up of a repetition of a basic pattern. The article focuses on the generation of the repetition and the adaptations needed to conform to the shape of the object. These adaptations include scaling the basic pattern so that an integer number of basic patterns occurs along a rim of the object, adaptation to achieve a circular disposition of the basic pattern on a surface of the object etc.

As can be seen, application of the decoration requires familiarity with the shape of the object and some expertise to adapt the flat decoration to the shape of the object. In the known method this has to be done by an expert who is familiar with the design process and the shape of the object. Offering the service of such an expert to the buyer who wants to order a unique, personal product is inconsistent with the need to design and manufacture the product at low cost.

Moreover, the known method is limited to application of decorations to surfaces that are essentially planar, so that they can be unfolded to a flat surface. Decorations cannot easily be applied (at low cost) to other surfaces that have a more complex curvature. Adaptation to the curvature of the objects is limited to bending the decoration plane around the object surface.

This presents problems if the surface of the object is curved in more than one direction at a location on the surface where the decoration is applied, such as on a saddle shaped surface for example. In that case, the pattern cannot follow the surface without deformations like changes in the angles between lines in the decoration. Adaptation to such a surface with curvature in two directions could be realized by projecting the decoration onto the surface, as it where through a slide, pattern locations on the surface being defined by the intersection between the surface and rays through the pattern on the slide. However, this also leads to undesirable deformations in case of a surface with curvature in two directions, for example in the neighborhood of singular points where the rays intersect the surface at a large angle to its normal.

What is needed is a method of offering personalized products to buyers of individual products, in a way that allows a price consistent with mass-manufacture.

Amongst others, it is an object of the invention to make it economically feasible to deliver object with a personalized decoration on demand by buyer.

Amongst others, it is an object of the invention to provide for a process of applying decorations with fewer distortions to a surface that is curved in more than one direction.

It is another object of the invention to simplify the application of different decorative patterns onto surfaces with the same shape.

It is another object of the invention to make it possible to deliver objects decorated to order, for orders received after definition of surface, while production of objects is already running.

A method of selling the object according to the invention comprises

-designing a shape of a rigid three-dimensional curved surface of the product; -manufacturing the product as part of a series of products, all with the designed shape; -offering the product for sale via a public switching network; -setting up a computer to receive an order for the product via the public switching network, the order comprising a pattern of decoration as a function of two dimensional coordinates specified by a buyer; -receiving the order in combination with the pattern with the computer; -mapping the two dimensional coordinates to corresponding positions on the curved surface, according to a mapping function determined as a function of the designed shape of the object; -applying the pattern to the product as mapped by the mapping function; -delivering the product to the buyer in response to the order.

Thus, the buyer is given the opportunity to specify the decoration using a switching network, such as the internet. By using the definition of the shape of the product, the decoration is automatically mapped and applied to the surface of the object. The shape is designed in common for a series of objects and mapping is performed automatically by computer, which allows manufacture and design at costs near that of mass-production.

Preferably, the shape of the surface is defined using the parameters of a mapping function from two-dimensions to a three dimensional surface, such as a NURBS function. Thus points on the surface lie at the same relative positions as the points to which different point in the two dimensions are mapped. The use of parameters makes it easy to determine the mapping of positions in the pattern to points on the surface.

The map which is used to shape the surface is reused for assigning points of a pattern to locations on the surface, so as to control the operation of applying the decoration. This also avoids problems with singular points. It has been found that this reduces unattractive deformations. Preferably a NURBS function (Non Uniform Rational B Spline function) is used to define the shape of the object. Such a function defines the coordinate vectors R of locations on the surface as a function of two-dimensional surface coordinates (u, v). The pattern values assigned to surface coordinates (u, v) are then mapped to locations with coordinate vector R.

Preferably the map that is used to shape the surface is reused to compute both locations and normals for positioning object and surface modifying tools relative to one another.

Movement of the object relative to a surface modifying tool may be along scan lines independent of the object, the modification of the surface being modulated according to the pattern. In this way, the movement may be computed once for all locations. Alternatively, the

movement may be along lines that make up the pattern. This minimizes the required amount of movement, be it at the expense of computing relative positions for each different pattern.

With the invention, the manufacture of a series objects can start before the pattern that is to be applied to an object of the series is known. The pattern can be received independent of the shape of the object. This makes it economically possible to sell objects such as domestic appliances or personal care products with a personalized design. The buyer orders such a product and submits his or her personal decoration as a description of an image. This description is sent to a factory, where the pattern is applied to the product by holding the object relative to a decoration applying tool so that the relative positions can be controlled in terms of design coordinates.

These and other advantageous aspects of the invention will be described by means of illustrative, but not exhaustive embodiments of the invention, using the following figures.

Figure 1 shows an object and a tool for modifying the properties of a surface of the object Figure 2 shows a diagram of a system for controlling modification of the properties of the surface Figure 3 shows a flow-chart of a method of modifying the properties of the surface.

Figure 1 shows an object 10 that has a surface which is curved in two directions. For example, the location L on the surface is a saddlepoint, where the surface has a convex curvature in first direction and a concave curvature in a second direction perpendicular to the first direction.

Figure 1 also schematically shows a tool 12 positioned relative to the object 10 so as to modify the properties of the surface of the object 10. The tool 12 is for example a laser, positioned along the normal to the surface of the object 10 at the location L at a predetermined distance of the location L. Other examples of tools could be drill-head, a spark- erosion head, an inkjet printer head etc. These tools are preferably brought to a predetermined position and orientation to the surface point L where the object is to be modified. The laser is used for example to remove matter from the surface at the point L or to induce a reaction in a photosensitive layer on the surface at the point L.

Figure 2 shows a diagram of a system for controlling modification of the properties of the surface of the object 10. The system contains a design station 20, an object shaping station 22, a surface modifying station 24, a pattern input station 28 and a surface modifying control station 26.

A designer uses the design station to design the shape of the surface of the object. The shape of the surface is defined by a function that assigns coordinates R of the surface to two-dimensional surface coordinate pairs (u, v). A preferred example of such a function is the function used to define a NURBS surface A NURBSS defines the coordinates R of points on the surface by means of functions of two dimensional surface coordinates (u, v):

R= Sum Pi*Fi (u, v) Here the Pi, are the coordinates of so called control points which serve as parameters for defining the shape of the surface. The expression for R assigns an R-value to each value of the surface coordinates (u, v) and the R-values assigned to a continuous set of surface coordinates (u, v) defines a surface in three-dimensional space.

The designed shape of the surface is transferred to the object shaping station, where it is used to manufacture a series of objects with a surface that has the designed shape.

Although the object shaping station is shown as a single station, it will usually be realized by a complex of equipment operating at different times, such as an NC controlled lathe that manufactures a mold for the object using the parameters of the designed shape and a molding machine for molding a series of objects in the mold.

Independent of the actual shaping process, the pattern input station 28 receives a pattern input. This is information describing a two-dimensional image, for example in terms of a bit-map with color and/or intensity values for a set of pixels (points) in the image, or in terms of the parameters of a number of lines in a two-dimensional plane that together make up the image. Any one of a number of formats can be used to represent this information, for example a postscript (TM) format or JPEG etc.

The pattern input is transferred from the pattern input station 28 to the surface modifying control station 26.

Various kinds of stations can be used as pattern input station 28. For example the pattern input station 28 may be a PC (personal computer) where the pattern is generated by scanning an image with a scanner, or with a drawing program. The pattern may be transmitted to the surface modifying control station 26 via the internet.

The surface modifying control station 26 may contain a complex of devices such as a world wide web server, with a WWW page that allows a customer to order a domestic appliance or a device for personal care (e. g. an electric shaver) with a personalized decoration. The WWW page provides for setting up transactions where the customer entitles the manufacturer to payment for the object and submits the pattern that should be applied to the object. At the end of the transaction, the surface modifying control station contains the pattern.

Alternatively, the surface modifying control station 26 may contain a terminal located in a retail shop, where a customer can submit the pattern and order his/or her object. In

this case, the retailer handles the transaction and sends the pattern to the surface modifying control station, for example also via the internet but one may also use a point to point modem line or even a physical delivery service.

The surface modifying control station 26 receives the pattern and uses it to control the surface modifying station 24. In this process, positions in the pattern are mapped to locations on the object. For this purpose, information describing the function used to define the shape of the object for the object shaping station 22 is reused. Coordinates (xp, yp) of points P in the pattern are assigned to two dimensional surface coordinates (up, vp) (e. g. using a linear relation: (up, vp) = (uO+a*x+b*y, vO+c*x+d*y) and the point P in the pattern is associated with the coordinates R of the location L that is assigned to the surface coordinates (up, vp).

The object 10 is held in a movable holder (not shown) so that the position of the object 10 relative to the tool 12 can be varied under control of the surface modifying control station, so that the coordinates R of the location of interaction between the tool 12 and the surface of the object 10 are known. Alternatively, the tool 10 may be moved relative to the object 10 or both may be moved relative to one another.

The tool 12 is positioned relative to the location L on the surface of the object 10 that corresponds to the coordinates R, so that the location L becomes the point of interaction between the object 10 and the tool 12. This is done for example using the vector components of the normal to the surface at the point L. These vector components are computed by means of the derivatives of the function that assigns three dimensional coordinates to two-dimensional surface coordinates (u, v). In this example, the object is moved so that the normal is aligned with the axis of the tool (e. g. the beam in case of a laser tool) with the location L at that axis at a predetermined distance from the tool (e. g. in the focus of optics of the laser). The surface is then modified at the location L by activating the tool (e. g. by irradiating the surface).

It has been found that this way of mapping the pattern onto the surface provides a natural way of mapping without disturbing distortions, especially when NURBS surfaces are used to define the shape of the object.

The tool 12 and the object 10 are positioned relative to one another sequentially at a series of relative positions, so that the locations L corresponding to a series of points in the pattern are successively brought to the point of interaction of the tool 12 and the object 10. At each location L the surface is modified according to the pattern.

In case the pattern is made up of a number of lines, the object and the tool may be positioned successively so that the locations L (t) corresponding to successive points P (t) on a line become to the point of interaction successively. Thus, the surface modifying station 24 traces the line along the surface of the object 10. Again, the coordinates (x (t), y (t)) of points P (t) are mapped to surface coordinates (u (t), v (t)) and the function that was used to shape the surface is reused to compute the coordinates R=F (u (t), v (t)) of the successive points of interaction.

Alternatively the surface modifying control station 26 moves the object 10 and the tool 12 to relative positions in a succession independent of the content of the pattern, along a series of locations L that correspond to a series of surface coordinate pairs (ui, vi) (i=O....).

For example by scanning over the surface. The successive coordinate pairs are then used to retrieve the content of the pattern I (u, v) for the positions (ui, vi) and the content I (u, v) is used to modulate the interaction between the tool and the surface of the object 10 at the time that the location L assigned to the coordinates (ui, vi) is at the point of interaction.

Figure 3 summarizes the steps of the method according to the invention. In a first step 31, the parameters of the function that relates two dimensional surface coordinates to three dimensional coordinates. In a second step 32, the object is manufactured with a surface shaped according to the function. In a third step 33, a pattern is received. In a fourth step 34, points in the pattern are associated with locations on the object, by mapping the points in the pattern to two-dimensional (u, v) surface coordinates and assigning three dimensional coordinates R to the these (u, v) coordinates according to the function according to which the surface of the object has been shaped. In a fifth step 35, the properties of the surface of the object are modified according to the pattern at the locations determined from the function according to which the surface of the object was shaped.