Description of Related Art Most small and portable printers of the market today, print on small paper surfaces, such as paper rolls having a width of just a few centimetres. These are mainly found in so called receipt printers used in combination with purchases of different kind.

There could be e. g. small printer devices for credit card payment, which print out a receipt as soon the transaction is completed.

There are also larger devices that print on relatively small paper surfaces, such as cashier machines. Different kinds of printing techniques exist in parallel, but the most common would be a thermal printer writing on a specially adapted paper. A drive mechanism feeds the paper, normally by rotating a cylinder on which the paper is wound. The paper passes thereby a fixed print head. Many of such print devices are mobile and therefore powered by batteries and since the driving mechanism consists of power consuming moving mechanical parts, they set the limit for the standby and operating time.

Very common environments for card readers in combination with mobile printers are restaurants. Such an environment is often noisy, crowded and for the personnel also stressful which could lead to accidents where the user drops his printer. Having movable mechanical. parts in your mobile printer will of course increase the risk for serious damage on the device.

Furthermore, the mechanical parts naturally demand higher manufacturing costs.

EP 0942285 Al, EP 0942286 Al and EP 0947833 Al all show a technique called"Optical Translation Measurement-OTM", where light from a collimated optical diode laser source is directed onto a two-dimensional reflexive grating spaced closely to the surface of an object and light reflected by the grating and surface is incident on a spatial filter formed by a lens and a pinhole, before being detected by a sensor. Here the sensor is called encoder. The encoder translates motion into electrical signals. The resulting interference gives rise to a beat signal depending on the motion of the surface. (See also Laser Focus World March 2000 INTERFEROMETRY:"Encoder measures motion through interferometry"by Opher Kinrot and Uri Kinrot. ) This OTM encoder measures the relative motion of surfaces placed adjacent to its aperture at a distance of zero to a few millimeters, using diffusive light reflected by the surface.

Because the only requirement from the surface to be measured is some diffuse reflection, the encoder works equally well on featureless paper and lined wood samples, as well as cloth and most other surfaces, i. e. the encoder can measure full 3-D motion.

According to the inventor and the author of the article, the encoder could be used in a"virtual pen"for digitize text written with it on paper by tracking the pen motion and using OCR software. Another area of use is as a motion detector of the paper in ordinary printing, copying or fax machines instead of what is done hitherto, namely measuring the motion of the drive mechanism for the paper. With the encoder you measure the"actual"movement of the paper instead of the movement of the mechanism feeding the paper, which could be advantageous especially when paper could"slide"due to malfunction of the drive mechanism.

The solution is very handy as it eliminates any malfunction of the drive mechanism, however it does not suggest any elimination of the actual drive mechanism.

According to what is presented above, there exist small printers with a need for less mechanical parts, lower battery consumption and with a construction less exposed to rugged use.

It is therefore an object of the present invention to provide a device which such properties.

Summary It is an object of the present inv to overcome the abovementioned problems by providing a printer without a print medium drive mechanism.

This object is achieved, according to a first aspect of the invention, by feeding the paper manually past the print head and having an optical sensor monitoring the movement of the paper as defined in claim 1 In accordance with one embodiment of the present invention, the printer device comprises means for inputting print data.

In yet another embodiment of the invention, the printer device comprises inertia means for creating a feeling of a counter force as the user pulls out the print medium from the print medium storage means.

In a further embodiment of the invention the printer device comprises print medium storage means in form of a cylinder suitable for paper rolls, whereas another embodiment shows a compartment suitable for loose-leaf system.

The embodiment of the invention comprising a paper roll also shows the printer device with a sharp edge suitable for tearing the paper after printing.

In accordance with another embodiment of the invention, a method for manually operating the print medium past the print head on a printer device as described above is shown where at least one optical sensor detects the motion of the print medium.

The optical sensor/s thereby giving input to a micro controller circuit controlling the print head.

All embodiments of the invention contributes to a low cost printer device with less mechanical parts and thereby also less susceptible to damage. The printer device will also be less power consuming as a user manually accomplishes the feeding of the print medium and not as shown in prior art, a dedicated drive mechanism. Furthermore the printer will be easier to manufacture and naturally more silent without a feeding mechanism.

Brief Description of the Drawings The features of the invention believed to be novel are set forth with particularity in the appended claims. The invention itself however, both as to organisation and method of operation, together with further objects and advantages thereof, may be best understood by reference to the following description with the accompanying drawings, in the several Figures in which: - Fig. 1 shows a top view on a printer device according to a preferred embodiment and - Fig. 2 a side view on the printer device.

Detailed Description of Embodiments Referring now in detail to the drawings and initially to Fig. 1, there is shown a preferred embodiment of the invention where a handheld printer device 1 is depicted.

Such a printer device is suitable for use at e. g. cashier desks, for restaurant personnel, taxi drivers or aiding any kind of"mobile vending"where the geographical location alters from time to time and where a small sized printer is preferable. The technique that will be described below is mostly beneficial to small mobile printers even though larger printers could use the same technique as well.

The printer in Fig 1 has means for inputting data ; in this case both a card reader 2 and a keyboard 3. A printer device of this kind could of course be equipped with only the card reader or only the keyboard. The card reader could be used to perform monetary transactions where the printer subsequent to the transaction prints out a receipt. The printer device could also be used as e. g. a calculator or a cashier machine if the keyboard is used.

The invention should not be limited to what printing data could be entered or in what applications a card reader or keyboard could be used or what applications could be used in combination with a printer, but rather focus on the printing technique per se.

The printer device according to Fig 1 could naturally take on a lot of different forms, shapes and sizes and the figure merely gives an example of one imaginable design. A display 4 showing data to be printed is preferred but not necessary. The display could also indicate other information such as e. g. when the printing could/will be started and when it is terminated, when a refill of printing medium is necessary, time and date and so on.

The printer device also comprises a storage means 5 for the print medium 6. In this embodiment the storage means is cylindrical in order to accommodate a roll of print medium. The print medium is preferably paper 6 but any material suitable for

printing is conceivable. If not using a paper roll the storage means could be a compartment suitable for a loose-leaf system where sheets of paper are stacked. A slit 7 on the storage means functions as an opening for the print medium where the printed parts became visible for the user. In order to tear the paper off the print roll after printing, a sharp edge 8 is arranged on the housing preferably in the vicinity of the slit 7 so to leave a piece of the print medium sticking out from the slit after tearing. A user could then easily pull out a new piece of the print medium at the next printing session. The print medium could alternatively be perforated at suitable distances to facilitate the tearing.

In Fig. 2 the printer device 1 is depicted from a side view with a perspective view on the storage means 5. A cylinder shaped part 9 is included within the storage means 5 on which the print medium 6 is wound. The print medium is here preferably a roll of paper. The storage means should be easily manoeuvrable to open and close in order to load new print medium onto the cylinder 9.

The figure also shows a print head 10 and an optical sensor 11.

Both the print head and the optical sensor should preferably be arranged so the print medium passes them before entering through the slit 7. In that way these sensitive components are enclosed and protected from outer tear within the storage means 5. Their respective placing shown in the figure is merely an example of how they could be placed. Other alternatives are of course conceivable.

The optical sensor could be of any kind known from e. g. optical mice such as e. g. Agilent ADNS-2051 or ADCS-1120. Such sensors take consecutive snapshots of the print medium and compare one picture with the previous so to detect any movement on a pixel level. A micro controller circuit (not shown) is needed to receive positioning data from the optical sensor 11 to give timely printing commands to the print head 10. As the optical

sensor only needs to deal with a vertical movement, there should be enough having just one sensor. If other embodiments employ a different construction an additional sensor could perhaps be needed.

Even though an optical sensor is preferred to detect the movement of the print medium, other components with the ability to detect the movement of the print medium or the velocity. of the cylinder and with the ability to communicate said information to a micro controller circuit, could replace the optical sensor.

The micro controller circuit thereby detects the movement, i. e. the velocity of the print media, in order to adjust the printing commands to the print head accordingly. In that way the image will come out right without any skew, no matter with what speed the print media passes the print head. The upper speed limit will of course depend on either the performance of the sensors, or the micro controller circuit or the print head.

The print head and print medium is preferably of a kind using thermal printing technology, but other printing techniques, such as e. g. ink-jet, bubble jet or laser technology are also conceivable within the scope of the invention.

In a preferred mode of operation a user enters print data, i. e. using the means for inputting data 2 or 3. If the user e. g. uses the card reader 2, a monetary transaction could be performed.

The display 4 could be set to indicate when the transaction is completed. In another embodiment the user enters print data on the keyboard, such as e. g. text or calculations. When the actual printing is wanted on the print medium 6 the user simply pulls the print medium with his hand out of the storage means 5 whereby the optical sensor 11 detects a movement and send input data to the micro controller circuit, which start sending print

commands to the print head. Hence the user manually pulls out the print medium concurrently as the image forms on the paper.

Hence, in this embodiment the micro controller circuit is set to start the print out as soon the optical sensor detects any movement, but in another embodiment the user could choose when to start the print out by first pressing a button on the keyboard and then pull the paper. A memory will be needed to store input/print data before the actual printing.

It would be preferable for a user to experience a resistant force while pulling out the print medium so to avoid a mistake having the entire roll of print medium rolling out at the first pull. A solution with two rollers in contact with each other will create some inertia to a print media passing between them.

In another embodiment, the cylinder 9 could rotate with some inertia around its axis to create the desired resistance.

In another embodiment the printer device could be connected to a host computer to e. g. receive information from a server, such as a bank central or the like. The printer device could either get its power supply from mains connection or alternatively and more convenient from a battery.