Background of the invention The use of handheld printers greatly facilitates the work of many people who need to make printouts fast and in a convenient and flexible manner. For one thing, a handheld printer excludes the need for a user to go to a stationary printer to retrieve a printout; the user is able to print a printout wherever he or she is.

There are handheld printers previously known, see for example WO 01/94118, assigned to the same applicant as the present application. The handheld printer shown in this document can be manually swept over an optional printout surface by random movements. A microprocessor in the handheld printer can, together with positioning sensors registering where the print head of the handheld printer is located at each instance, calculate when to eject an ink drop. The printer shown in WO 01/94118 can print predetermined printouts stored in the printer or printouts downloaded to the printer.

One advantage with using the handheld printers, for example the printer shown in WO 01/94118, is that a user may select any printout surface, such as a piece of paper, a napkin or even a plastic printout surface. The user simply puts the printer over the selected printout surface and begins to print out a chosen printout pattern. However, when doing this, a user may be uncertain whether there is enough space on a selected printout surface for the desired printout, or possibly if the printout surface is too large for a selected printout.

Further, a user may wish to determine how many copies of a certain printout that can be fitted on a specific printout surface. The user may for example wish to print several copies of his/her business card on a special printout paper, and needs to know how many papers of that special printout paper to buy.

Thus there exists a need to provide a handheld printer device including simple and practicable means for a user to match a selected printout pattern to an available printout surface.

Summary of the invention It is an object of the present invention to provide a handheld printer device that solves the above mentioned problem. In particular, it is an object of the present invention to provide a handheld printer device which allows flexible printouts on available surfaces.

These objects are achieved, according to a first aspect of the invention, by a handheld printer device as claimed in claim 1.

An advantage achieved by the present invention is that the format to be used can be determined after a measuring operation has been performed. This is in contrast to the prior art, where information about the format is sent together with the printout image data. By means of the present invention, printing is greatly facilitated, and intermediate steps, such as cumbersome reformatting of a printout image performed in a separate computer, are eliminated.

By means of the present invention it has been made possible for the handheld printer devices to provide printouts that are adapted to the available printout surface, so that it is possible to ensure that that printout surface is utilised in a

desired and/or optional manner, or to ensure that the surface is large enough.

In accordance with one embodiment of the handheld printer device said means for determining the size comprises determining position information, provided by positioning sensors and a microprocessor, for two points, whereby the microprocessor calculates a width and/or height using this position information. This gives a convenient and easily implemented measuring feature, since a preferred handheld printer device including the present invention already comprises positioning means.

In accordance with another embodiment of the handheld printer device the position information is x-and y-coordinates. These coordinates may be displayed in a display of the handheld printer device, enabling the user to see the coordinates as he/she moves the handheld printer device over a printout surface.

In accordance with another embodiment of the handheld printer device, means are provided for converting a pair of x-and y- coordinates to a length unit in the x-and/or y-direction respectively. The result is preferably displayed on a display of the handheld printer device, giving a convenient digital ruler. The result may be conveyed to the user in some other manner, for example by a digital voice or a printout on a piece of paper, if the handheld printer device has no display.

In accordance with another embodiment, the handheld printer device is arranged to suggest a standard-format lying closest to a measured size of a printout surface. This is a convenient feature for a user, since he or she may just confirm a suggested format. For example, if the result of the measuring operation lies within a predetermined range, e. g. sufficiently

close to an"A4"format, this standard format is suggested. In another embodiment, the standard format lying closest to a performed measurement is automatically chosen by the handheld printer device.

In accordance with another embodiment of the handheld printer device a selected printout image is scaled to match a measured size of a printout surface. The scaling may be performed by software giving a best fit format. A user may thus always obtain a printout size that is best adjusted to a measured size of the printout surface.

The invention also relates to a method for printing using a handheld printer device including a measuring feature.

Brief description of the drawings Fig. 1 shows a handheld printer device which can utilise the present invention.

Fig. 2 shows the handheld printer device of Fig. 2 from beneath.

Fig. 3 shows an example of the measuring procedure in accordance with the present invention.

Detailed description of preferred embodiments With reference to fig. 1, a handheld printer device that may include the present invention is shown. However, it is realised that other handheld printers may utilise the present invention, and the described handheld printer device is only an illustrative example used to describe the present invention. The handheld printer device including the present invention may include additional parts than those shown in Fig. 1, or some parts may be excluded. The handheld printer device shown in Fig. 1 comprises a housing 1, including a print head 2, which could be for example an ordinary ink jet

print head, where several nozzles under the influence of computer controlled electrical signals eject tiny ink drops, which then build up a predetermined pattern. Alternatively, a bubble jet print head could be used or any other suitable print head. The housing 1 has an opening at one end where the print head 2 is situated in order to be able to print on a printout surface 10 chosen by the user.

The handheld printer device further comprises sensors 3 for sensing the position of the print head 2 in relation to a printout surface. If optosensors are used, the characteristics of a printout surface can be sensed and thereby, with the aid of a microprocessor 4, a determination of the position of the print head 2, the speed, acceleration and direction and/or other parameters can be accomplished. In fig. 1 the handheld printer device is shown to include two sensors 3. However, if only linear movements need to be sensed one sensor 3 is enough, and if for example a greater accuracy is needed, more than two sensors 3 may be used. The sensors 3 are situated at the open end of the housing 1, where they are able to determine the current position of the print head 2. An example of sensors that can be used in the handheld printer device 1 is Agilent Sensors ADCS-1120 or ADCA-2120, available from Agilent Technologies.

A microprocessor 4 is also, as mentioned, included within the housing 1. The main task of the microprocessor 4 is to control the functions of the handheld printer device. The microprocessor 4 preferably includes a memory (not shown) for storing information retrieved or stored. The memory could also contain information a priori.

Finally the handheld printer device also includes a power supply 8, e. g. an ordinary battery, for feeding the handheld

printer device with electric power. Alternatively, the handheld printer device is fed from an adjacent device, a mobile unit for example, to which it is connected. The handheld printer device further preferably includes a display 7, one or more command buttons 6, and optionally an aid 13 for facilitating'the positioning of the handheld printer device on a printout surface 10.

The preferred handheld printer device can be used to print on any printout surface 10, a napkin, a piece of paper or even plastic materials. As described above, the user may want to know the size of the printout surface, for example in order to select the size of a selected printout image accordingly. In accordance with the present invention, the handheld printer device includes means for measuring a selected printout surface, which feature will now be described.

As described above, the handheld printer device includes sensors 3 for sensing movements of the print head 2, and thus the movements of the handheld printer device, for enabling the ejection of ink drops when required. The handheld printer device thus includes means for determining at each moment the position of the handheld printer device in relation to the printout surface, which feature is utilised in the present invention. The handheld printer device may for example include means for detecting the movements and showing at each moment of time an x-and y-coordinate. For example, when the user places the handheld printer device on a printout surface 10 and presses a command button 6, this point is marked as the origin of coordinates (that is, x=0, y=0). As the user moves the handheld printer device the coordinates change accordingly.

The handheld printer device may include two different modes of operation, one mode being a"measure mode" (or"format mode") and the other a"print mode". When the user has selected the "measure mode", for example by pressing a command button 6 included in the handheld printer device, the user may then simply place the handheld printer device on one corner of the printout surface 10 and mark this corner in some way, for example by pressing another command button 6 also included in the handheld printer device, or possibly the same as when choosing the measure mode. Thereafter the user moves the handheld printer device over the selected printout surface 10 in one direction, preferably essentially along an x-or y- axis, and presses the command button 6 a second time, indicating that a measuring action along one axis has been completed. This second pressing of the command button 6 may also indicate the starting point for a second measuring action along a second axis, for which the same procedure is performed.

With reference to Fig. 3, an example of the above described procedure is shown. The user places the handheld printer device at one corner 15, in this case the upper left corner, and presses the command button 6 once. Then he/she moves the handheld printer device along the edge of the printout surface 10, as indicated by the arrow 16, in a horizontal direction, to the upper right corner 17, where he/she again presses the command button 6. This completes the measuring operation along an x-axis, giving a measure of the width of the printout surface 10, and the result may now be shown in a display 7, if desired. It is of course not necessary to show the result on a display 7, it is sufficient that the handheld printer device has registered the size of the printout surface. This marked point is also the starting point for the measuring operation

along a y-axis. Thereafter the user moves the handheld printer device along a second edge of the printout surface 10, as indicated by the arrow 18, to the lower right corner 19, where the command button 6 is again pressed indicating the end of the measuring operation. This thus completes the measuring operation along the y-axis, giving a measure of the height of the printout surface 10, which result may again be shown in a display 7. The handheld printer device now has three pairs of coordinates: the coordinates for the first corner 15, the second corner 17 and the third corner 19. These coordinates can now be used to calculate the width and height, respectively, of the printout surface 10.

Naturally, it is difficult for a user to move the handheld printer device perfectly straight along a direction. This is however not necessary with the present invention, since a pair of coordinates are used to calculate the distance. This case is also illustrated in Fig. 3. The user may for example mark a point 20 as the starting point for a measuring operation and another point 21 as the end position. The handheld printer device then has two pairs of coordinates: the coordinates (tao, y20) for point 20 and the coordinates (x21, y2i) for point 21.

Given these coordinates, the microprocessor 4 of the handheld printer device is able to calculate the width of the printout surface by using the x-coordinates X2o and X21. A corresponding measuring operation is then performed along the y-axis, giving the height of the printout surface 10. The user may thus move the handheld printer device in random movements 23 over the printout surface 10, and the width of the printout surface 10 may still be calculated.

In the above description the measuring is performed in two different modes within the measuring mode. The first mode is a mode where the width is determined, i. e. an"measure x-mode"

(or a width measure mode), and the second mode is a mode where the height is determined, i. e. a"measure y-mode" (or a height measure mode). To measure a rectangular printout surface 10 it is conceivable to mark only two diagonally opposite corners, i. e. for example the points 15 and 19, respectively, in Fig.

3, thus performing a measuring in the x-and y-directions simultaneously. The width and the height of the printout surface 10 may then be calculated by means of the coordinates (x15, Yl5) for point 15 and the coordinates (x19, yig) for point 19.

When the size of a selected printout surface 10 is known, the user may conveniently adjust the size of the desired printout image. He or she just switches the handheld printer device to the"print mode"and selects an appropriate scale for the printout image. Given the size of the printout surface 10, the printout image may for example be printed in a"best fit" scale. The bitmap for the printout image may be adjusted to the measured size of the printout surface in any appropriate manner. The printout image may be adjusted or scaled in the handheld printer device or in a separate server, where the printout image is stored. The conversion to a bitmap may also be performed in the handheld printer device or in a separate server. The software used for scaling the printout image may be any commonly known software, for example an image processing program. In general it is desirable to maintain the relationship between the x-and y-directions of an image after scaling, in order to not obtain for example an elongated image. That is, it is desirable to maintain the proportions of the image even after the scaling to the proper size of the printout surface 10. Further, it is realised that the resolution of the image may determine the size of the printout image, as may also the capacity of the print head 2. If the

print head 2 is able to print 100 dpi (dots per inch), this may be a limiting factor for the size of the printout image.

It is further realised that a printout image may be reformatted into different resolutions enabling different sizes of the printout image.

If the results of the measuring operations lie closely to a standard format, for example an ordinary standard paper size, A4, this standard format may be selected automatically.

Alternatively, the handheld printer device may suggest this standard format for example by displaying a question"Use A4?" if the results from the measuring operations lie within a predetermined range, that is, sufficiently close to a standard format. The user may then confirm the use of this format or chose to use the measured values as a special, non-standard format. Alternatively, the handheld printer device always suggests the standard format lying closest to the measuring results.

The printout surface 10 may of course be of other shapes than the shown rectangular shape.

In accordance with the present invention, the handheld printer device includes means for converting a set of x-and y positions respectively into a measure of length, for example cm. The handheld printer device including the measuring feature in accordance with the present invention may thus be used as a convenient way to measure, not only in order to determine the size of a selected printout surface 10, but for measuring operations in general. The handheld printer device including the present invention may in other words be used as a simple and convenient digital ruler, usable in many different situations. The result is suitably displayed in a display 7 included in the handheld printer device.

It is further possible to use some kind of edge detecting means for detecting an edge of a printout surface such as a paper. This edge detecting means could be used in order to detect when the handheld printer device passes over an edge and thereby initiate the measuring operation. When the handheld printer device passes over a second edge, as detected by the edge detection means, the measuring operation is completed. Thus, if a user for example has a commonly used size A4 paper, all he or she has to do is to move the handheld printer device over the paper in one direction, after which the handheld printer device is able to detect that the desired size of the printout surface is A4.

Further, the handheld printer device may include means for selecting a desired printout format. The handheld printer device may for example include a pop-up menu showing different selectable printout formats, e. g. A4, A3 etc.