Image reading apparatus and image reading method

An image reading apparatus includes: a pointer having an axis extending along an axis line, that indicates a position on a medium; N (N≧3) irradiating units that respectively irradiate light toward an area that includes the position; and a signal generator that generates, from the irradiated light reflected by the medium, a signal representing an image on the medium.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 U.S.C. 119 from Japanese Patent Application Nos. 2009-69702 and 2009-73774, which were filed on Mar. 23, 2009 and Mar. 25, 2009, respectively.

TECHNICAL FIELD

The present invention relates to an image reading apparatus.

RELATED ART

In recent years, technologies for converting content written on paper to electronic data, transferring this data to a personal computer, mobile telephone or the like, and displaying the written content on a monitor, or transferring/saving the written content as data have been attracting interest. These technologies use special paper having tiny dots formed in various different patterns printed on the surface thereof, and a digital pen that digitizes the written content by reading these dots. This digital pen reads the dot pattern in the vicinity of the pen point with an imaging device when writing is performed on the special paper, and specifies the position of the pen point on the special paper based on the read dot pattern.

SUMMARY

In an aspect of the invention, there is provided an image reading apparatus including: a pointer having an axis extending along an axis line, that indicates a position on a medium; N (N≧3) irradiating units that respectively irradiate light toward an area that includes the position; and a signal generator that generates, from the irradiated light reflected by the medium, a signal representing an image on the medium.

DETAILED DESCRIPTION

FIRST EXAMPLE

FIG. 1shows an exemplary configuration of a system according to an embodiment of the present invention. InFIG. 1, a digital pen60is an exemplary reading apparatus provided with a function of writing characters, graphics and the like on a medium50such as paper, and a function of reading a code pattern image (image to be read) formed on the medium50. An information processing apparatus10is an exemplary writing information generating apparatus that is a personal computer, for example, and generates writing information representing written content according to signals output from the digital pen60.

The code pattern image formed on the medium50is obtained by encoding identification information identifying the medium50and position information representing coordinate positions on the medium50to create an image.

Here, an exemplary code pattern image formed on the medium50will be described with reference toFIG. 2.FIG. 2shows an exemplary code pattern image formed on the medium50. The code pattern image represents the abovementioned identification information and position information by the mutual positional relation of multiple dot images, and areas A1to A9are predetermined as areas in which these dot images can be disposed. In the example shown inFIG. 2, the black areas A1and A2show areas in which dot images are disposed, and the shaded areas A3to A9show areas in which dot images are not disposed. The identification information and the position information are expressed by which areas the dot images are disposed in. This code pattern image is formed over the entire medium50by an electrophotographic image forming apparatus (not shown) such as a printer, for example. The digital pen60reads the code pattern image, and detects the position of a pen point69A (seeFIG. 3) of the digital pen60by analyzing the read code pattern image. The digital pen60then transmits the position information indicating the detected position to the information processing apparatus10. The information processing apparatus10generates writing information representing an image obtained by disposing pixels in positions corresponding to the position information, displays an image according to the writing information on a display or the like, thereby presenting the written content to the user.

Apart from the abovementioned code pattern image, an image such as a document, graphics or the like aimed at conveying information to a person may be formed on the medium50. Hereinafter, this image will be called a “document image”, but includes images such as pictures, photographs and graphics, as well as other images, rather than being limited to an image representing a document that includes text. The image forming apparatus performs image forming using K (black) toner when forming a code pattern image, and performs image forming using C (cyan), M (magenta) and Y (yellow) toner when forming a document image. The document image and the code pattern image are formed one on top of the other on the medium50. The code pattern image and the document image are formed using materials with different spectral reflection characteristics, and the digital pen60is set so as to read only the code pattern image making use of the different spectral reflection characteristics.

Note that the “medium” in the present example may be a plastic sheet such as an OHP sheet, for example, or a sheet of another material, rather than being limited to so-called paper. The “medium” may also be so-called digital paper whose display content is electrically rewritable. In short, the medium50need only have at least a code pattern image formed thereon.

Next, a basic configuration of the digital pen60will be described with reference to the drawings.FIG. 3is a functional block diagram schematically showing the functions of the digital pen60. InFIG. 3, a controller61is a controller that controls the operation of the entire digital pen60. Various parts of the digital pen60are connected to the controller61. A pressure sensor62is a detecting unit that detects a writing operation by the digital pen60, by pressure applied to a pen tip69.

An optics unit70is equipped with an irradiating unit80, an image forming unit81, and an imaging unit82. The irradiating unit80is an exemplary irradiating unit that is a near-infrared LED (light emitting diode), for example, and irradiates near-infrared light onto the medium50along an irradiation axis a. The image forming unit81is an exemplary image forming unit that collects reflected light reflected by the medium50along a light-receiving axis b, and forms an image of the image on the medium50on the imaging unit82according to the reflected light, the image forming unit81being configured by a convex lens, for example. The imaging unit82is an exemplary signal generating unit that converts the image of the image on the medium50formed by the image forming unit81according to the reflected light to electrical signals, and includes a CMOS (Complementary Metal Oxide Semiconductor) image sensor, a CCD (Charge Coupled Device) image sensor, or the like.

A first memory65is a memory that stores identification information and position information. A communication unit66is a communication unit that controls communication with an external device. A battery67is a rechargeable power supply unit that supplies power for driving the digital pen60to the various parts. A second memory68is a memory that stores identification information (pen ID) of the digital pen60. The pen tip69has a penholder that extends along the axis line, and the front end portion (tip) thereof forms the pen point69A. This pen tip69is an exemplary indicating unit that indicates a position on the medium50having the code pattern image (image to be read) formed thereon with the pen point69A, when a writing operation is performed by a user. The irradiating unit80irradiates light having the irradiation axis a as the axis thereof in a predetermined irradiation range, toward a medium area that includes the position on the medium50indicated by the pen point69A, when a writing operation is performed by the user. Beams of light irradiated from the irradiating unit80respectively have different directivities, and travel toward the medium50in a diffused state.

A switch75is operated by the user, and various settings of the digital pen60are switched according to the operation.

Next, the functional configuration of the controller61will be described with reference toFIG. 4.FIG. 4is a functional block diagram of the controller61. InFIG. 4, a code detecting unit612detects the code pattern image from the signals output from the imaging unit82(signals representing imaged images). A data processing unit613extracts the identification information and the position information from the code pattern image detected by the code detecting unit612. An illumination controller614transmits illumination control signals for causing the irradiating unit80to pulse to the irradiating unit80, and causes the irradiating unit80to pulse. An imaging controller616supplies image capture signals that are synchronized with the illumination control signals transmitted to the irradiating unit80to the imaging unit82.

Further, a schematic of the operation of the controller61in the digital pen60will be described.FIG. 5is a timing chart showing output timing of the illumination control signals controlling the pulsing of the irradiating unit80, the image capture signals to the imaging unit82, and output image signals. When the user starts writing by the digital pen60, the pressure sensor62connected to the pen tip69detects the writing operation. The controller61thereby starts the process of reading identification information and position information.

Firstly, the illumination controller614of the controller61transmits illumination control signals ((A) inFIG. 5) for causing the irradiating unit80to pulse to the irradiating unit80, and causes the irradiating unit80to pulse.

The imaging unit82images the image on the medium50in synchronization with the image capture signals ((B) inFIG. 5). At this time, the imaging unit82images the image on the medium50illuminated by the pulsing irradiating unit80. Thus, in the imaging unit82, image signals (output image signals: (C) inFIG. 5) relating to the image on the medium50illuminated by the irradiating unit80are generated in order.

The output image signals sequentially generated by the imaging unit82are sent to the code detecting unit612. The code detecting unit612, having received the output image signals, processes the output image signals, and detects the code pattern image from the images imaged by the imaging unit82. The code pattern image acquired by the code detecting unit612is sent to the data processing unit613. The data processing unit613, having received the code pattern image, decodes the code pattern image, and acquires the identification information and the position information embedded in the code pattern image.

The above is the basic configuration of the digital pen60.

Next, the structure of the digital pen60according to the present example will be described with reference to the drawings. In the digital pen60, three irradiating parts80A,80B and80C and three image forming parts81A,81B and81C are respectively disposed in predetermined positions to constitute an optics unit70A. Note that, hereinafter, the three irradiating parts80A,80B and80C and the three image forming parts81A,81B and81C will be respectively referred to as irradiating parts80and image forming parts81, if there is no need to distinguish between them.

FIG. 7is a perspective view schematically showing a front end portion of the digital pen60,FIG. 8Ais a cross-sectional view as seen from an arrow VIIIa-VIIIa direction inFIG. 7, andFIG. 8Bshows the ranges of the irradiating parts80and the image forming parts81as seen from an arrow VIIIb-VIIIb direction inFIG. 7.

The pen tip69extending along the axis line O-O is provided in a pen body60A that forms a casing of the digital pen60. The pen tip69is for performing writing on a paper surface (medium50). In a vicinity of the pen tip69forming a front end portion of the pen body60A, a detecting unit60B formed using a material that blocks visible light and transmits infrared light is provided, and backward of that is provided the optics unit70A. Note that inFIG. 7, the case is illustrated where the periphery of the pen body60A is circler, but the periphery may be a polygonal shape such as a triangle. The direction in which the user holds the digital pen60can be regulated, by making the digital pen60into a shape that is easy for the user to hold.

The irradiating parts80A,80B and80C and the image forming parts81A,81B and81C of the optics unit70A are, as shown inFIG. 7, disposed around the pen tip69which extends in the axis line O-O direction. The irradiating parts80A,80B and80C are, as shown inFIG. 8A, disposed at the vertices of an equilateral triangle Ta whose centroid is the intersection with the axis line O-O on a plane orthogonal to the axis line. In the example inFIG. 8A, the irradiating parts80A,80B and80C are shown as being disposed on the upper side, the lower left side, and the lower right side, respectively. The three irradiating parts80A to80C are thereby disposed equidistant from the pen tip69.

The image forming parts81A,81B and81C are, similarly to the irradiating parts80, disposed around the pen tip69which extends in the axis line O-O direction, along the axis line O-O direction. The image forming parts81A,81B and81C are, as shown inFIG. 8A, disposed at the vertices of an equilateral triangle Tb whose centroid is the intersection with the axis line O-O of the pen tip69on a plane orthogonal to the axis line. In the example inFIG. 8A, the image forming parts81A,81B and81C are shown as being disposed on the lower side, the upper right side, and the upper left side, respectively. The three image forming parts81A to81C are thereby disposed equidistant from the pen tip69.

Since the image forming parts81are disposed in positions closer to the pen tip69than the irradiating parts80, the equilateral triangle Tb is smaller than the equilateral triangle Ta.

Here, an irradiation range Aa of the irradiating unit80A on the medium50will be described with reference toFIGS. 8A and 8B,FIG. 9andFIG. 10. Here, the case where the digital pen60is placed against the surface of the medium50such that the axis line O-O of the pen tip69is orthogonal to the surface of the medium50will be illustrated. Note thatFIG. 9schematizes the spreading out of light irradiated from the irradiating parts80and the irradiation ranges thereof, in a state where the digital pen60is seen from the right side (arrow R direction ofFIG. 8B).FIG. 10shows the irradiation ranges at this time as seen from the medium50side.

The light irradiated from the irradiating parts80A,80B and80C diffuses according to the directional characteristics of the irradiating parts80A,80B and80C, and illuminates the irradiation ranges Aa, Ab and Ac on the medium50. At this time, as shown inFIG. 10, the irradiation ranges Aa to Ac of the three irradiating parts80A to80C intersect one another in an area S that includes the position of the pen point69A. The positions of the irradiating parts80A,80B and80C, particularly the distances from the irradiating parts80A,80B and80C to the pen point69A and the pen tip69are designed in advance such that the irradiation ranges Aa to Ac of the irradiating parts80A to80C thus intersect in an area S of appropriate size. Further, since the irradiating parts80A,80B and80C are disposed centered on the pen tip69, an area that would be in the shadow of the pen tip69with respect to light from one of the irradiating parts (e.g.,80A) will be illuminated by light from the other irradiating parts80B and80C, so a shadow does not readily arise around the pen point69A at this time.

Next, imaging ranges Ba, Bb and Bc of the image forming parts81A,81B and81C will be described.

The image forming parts81are configured by a convex lens, for example, and form an image of the image in a prescribed imaging range B on the medium50. The positions of the image forming parts81, particularly the distances from the image forming parts81A,81B and81C to the pen point69A and the pen tip69are designed in advance such that the imaging ranges Ba, Bb and Bc of the image forming parts81intersect one another at the pen point69A.

The image forming parts81send light to the imaging parts82(not shown) after having formed an image from the light reflected from the medium50, and output image signals are supplied from the imaging parts82to the controller61. The controller61combines the signals from the imaging parts82, and generates a signal that depends on the image around the pen point69A.

In this way, by using the three image forming parts81(imaging parts82A to82C), the imaging range thereof is expanded, in comparison with the imaging range of a single image forming unit81(imaging unit82). Further, the area on the far side of the pen tip69as seen from the single image forming unit81A (imaging unit82A) can be read with the other image forming parts81B and81C (imaging parts82B and82C).

InFIGS. 8 to 10, the case where the digital pen60is placed against the medium50such that the axis line O-O of the pen tip69is orthogonal to the medium50is shown, but in actual fact, the digital pen60is normally used in a state of being tilted with respect to the medium50. In order to make the user use the digital pen60tilted in a set direction, a mark may be added to the pen body60A, or the portion that is held may be formed into a polygonal shape.

FIG. 11schematizes the spreading out of light irradiated from the irradiating parts80and the irradiation ranges thereof, in a state where the digital pen60is seen from the right side (arrow R direction inFIG. 8B).FIG. 12shows the irradiation ranges at this time as seen from the medium50side. Note that the irradiation ranges shown inFIG. 12are expressed elliptically, but strictly speaking, the irradiation ranges are circular with the arc on the upper side of the irradiation ranges becoming larger, and the arc on the lower side of the irradiation ranges becoming smaller. Even in this case, the shadow of the pen tip69that would occur due to the light of the single irradiating unit80A is erased by the light from the other irradiating parts80B and80C, so a shadow does not readily arise around the pen point69A.

Next, the operation of the digital pen60according to the present embodiment will be described. When the user starts writing with the digital pen60, the pressure sensor62connected to the pen tip69detects the writing operation. The controller61thereby starts the process of reading identification information and position information. Firstly, the illumination controller614transmits illumination control signals for causing the irradiating unit80to pulse to the irradiating unit80, and causes the irradiating unit80to pulse. Also, the imaging controller616supplies image capture signals that are synchronized with the illumination control signals transmitted to the irradiating unit80to the imaging unit82. The imaging unit82images the code pattern image based on the reflected light whose image is formed by the image forming unit81, in response to the image capture signals supplied from the imaging controller616, and outputs output image signals representing the imaged code pattern image to the code detecting unit612.

Next, the operations of the code detecting unit612and the data processing unit613will be described with reference to the flowchart shown inFIG. 6. The output image signals representing the image on the medium50are input to the code detecting unit612from the imaging unit82(step S601). The code detecting unit612performs a process for removing noise included in the output image signals (step S602). Here, examples of noise include noise generated by electronic circuitry and variation in CMOS sensitivity. The process performed in order to remove noise is determined according to the characteristics of the imaging system of the digital pen60. For example, a gradation process or a sharpening process such as unsharp masking can be applied. Next, the code detecting unit612detects the dot pattern (position of the dot images) from the image (step S603). Also, the code detecting unit612converts the detected dot pattern to digital data on a two-dimensional array (step S604). For example, the code detecting unit612converts the detected dot pattern such that positions with a dot image are “1” and positions without a dot image are “0” on the two-dimensional array. This digital data on a two-dimensional array (code pattern image) is then transferred from the code detecting unit612to the data processing unit613.

The data processing unit613detects the dot pattern composed of the combination of two dot images shown inFIG. 2, from the transferred code pattern image (step S605). For example, the data processing unit613is able to detect the dot pattern, by moving the boundary positions of a block corresponding to the dot pattern over the two-dimensional array, and detecting the boundary positions at which the number of dot images included in the block is two. When a dot pattern is thus detected, the data processing unit613detects an identification code and a position code, based on the type of dot pattern (step S606). Subsequently, the data processing unit613decodes the identification code to acquire identification information, and decodes the position code to acquire position information (step S607). In the process shownFIG. 6, the case where a dot pattern is not detected from an imaged image and the digital pen60is unable to acquire identification information and position information (i.e., a reading error) arises, in the case where the amount of light received by the imaging unit82is too little or conversely in the case where the amount of received light is too much. In the case where identification information and position information cannot thus be acquired, the data processing unit613acquires reading failure information showing reading failure, instead of identification information and position information.

The digital pen60transmits the identification information and the position information acquired by the process ofFIG. 6to the information processing apparatus10. At this time, the digital pen60transmits the information showing reading failure to the information processing apparatus10, in the case where the reading of identification information and position information fails. The information processing apparatus10receives the identification information and the position information from the digital pen60, and generates writing information based on the received position information. The information processing apparatus10, in the case where information showing a reading error is received from the digital pen60, generates writing information by interpolating or the like using identification information and position information received previously or subsequently.

As aforementioned, because the three irradiating parts80A,80B and80C disposed centered on the pen tip69respectively illuminate around the pen point69A, a shadow does not readily arise around the pen point69A. Also, the area on the far side of the pen tip69as seen from the single image forming unit81A can be read with the other image forming parts81B and81C.

Also, an irradiation range A of light irradiated onto the medium50by the three irradiating parts80is widened in comparison with a single irradiating unit80, and the imaging range B in which image forming is performed on the medium50by the three image forming parts81is widened in comparison with a single image forming unit81, with an image being read by combining the images obtained by the three image forming parts81.

2. SECOND EXAMPLE

A second embodiment will now be described. Hereinafter, description of portions that are common with the first embodiment will be omitted, and only portions that differ from the first embodiment will be described.

In the second embodiment, a controller61A is used instead of the controller61. The functional configuration of the controller61A will be described with reference toFIG. 13. InFIG. 13, the code detecting unit612detects a code pattern image from the signals output from the imaging parts82(signals representing an imaged image). The data processing unit613extracts identification information and position information from the code pattern image detected by the code detecting unit612. The illumination controller614transmits illumination control signals for causing the irradiating parts80to pulse to the irradiating parts80via a light amount adjusting unit615, and causes the irradiating parts80(irradiating parts80A to80C) to pulse. The light amount adjusting unit615adjusts the light amount (luminance) of the irradiating parts80(irradiating parts80A to80C) according to the tilt of the digital pen60or the like. The imaging controller616supplies image capture signals synchronized with the illumination control signals transmitted to the irradiating parts80to the imaging parts82.

Here, since the irradiation range Aa of the irradiating unit80A positioned on the upper side becomes wider, and the irradiation ranges Ab and Ac of the irradiating parts80B and80C positioned on the lower side become narrower in the case where the digital pen60is used at an angle, as shown inFIG. 11andFIG. 14, it is evident that illuminance with respect to the medium50(brightness on the medium50) will be less on the upper side of the pen point69A than on the lower side. In the case where light of the same luminance is irradiated from the irradiating parts80A to80C, the illuminance on the lower side will be too much, and the illuminance on the upper side will be too little, as a result of which it may not be possible to detect the dot pattern from the image imaged in the imaging parts82, and a reading error may arise.

In order to solve this problem, the digital pen60of the present embodiment is provided with a light amount adjusting unit615that adjusts the light amount (luminance) of the irradiating parts80A to80C. Also, the light amount adjusting unit615is incorporated in the controller61A, together with the code detecting unit612, the data processing unit613, the illumination controller614and the imaging controller616. This light amount adjusting unit615is provided with a specifying unit that specifies an irradiating unit80that is far from the medium50, out of the irradiating parts80A to80C, and a light amount adjusting unit that adjusts the luminances of the irradiating parts80, such that the luminance of light irradiated from the specified irradiating unit80is larger than the luminances of light irradiated from the other irradiating parts80.

Here, the operation of the light amount adjusting unit615will be described with reference to the flowchart ofFIG. 15.

Firstly, the light amount adjusting unit615reads the signals output from the imaging parts82(step Sa1), and detects the illuminance (intensity of reflected light) in prescribed portions (detection areas Ca, Cb, Cc) of the imaged image (imaging range B) (step Sa2). The detection areas Ca, Cb, and Cc are, as shown inFIG. 14, for example, set in positions closer to the pen point69A than the positions at which the irradiation axes a of the irradiating parts80A to80C reach the medium50. Further, the detection area Ca is for monitoring the illuminance of light irradiated from the irradiating unit80A, the detection area Cb is for monitoring the illuminance of light irradiated from the irradiating unit80B, and the detection area Cc is for monitoring the illuminance of light irradiated from the irradiating unit80C.

Next, the light amount adjusting unit615compares the illuminances in the three detection areas Ca, Cb, and Cc. With the state inFIG. 11andFIG. 14, the detection areas Cb and Cc have the same degree of brightness, and the detection area Ca is darker than the other detection areas Cb and Cc. Therefore, the light amount adjusting unit615specifies the irradiating unit80A corresponding to the dark detection area Ca as the irradiating unit that is far from the medium50, out of the irradiating parts80A to80C (step Sa3). Also, the light amount adjusting unit615computes the tilt direction by the size of the illuminances of the detection areas Ca, Cb and Cc, and calculates the tilt amount by digitizing the illuminances of the detection areas Ca, Cb and Cc and computing the ratios thereof.

Further, the light amount adjusting unit615adjusts the luminance of the specified irradiating unit80A, in order to approximate the illuminance of light reaching the medium50from the irradiating unit80A and the illuminances of light reaching the medium50from the irradiating parts80B and80C to one another (step Sa4). In the case of this example, the crest value of the illumination control signals output to the irradiating unit80A is increased, in order to increase the luminance of the irradiating unit80A.

Note that with this example, the luminance of the specified irradiating unit80A is adjusted so as to be larger than the luminances of the other irradiating parts80B and80C, but the luminances of the other irradiating parts80B and80C may be made smaller than the luminance of the irradiating unit80A. Also, by computing the tilt direction and the tilt amount, the luminances of the irradiating parts80A to80C may be adjusted individually, based on the computed tilt direction and tilt amount. Further, correction amounts for the irradiating parts80A,80B and80C with respect to differences in the luminances of the detection areas Ca, Cb, and Cc may be mapped and prestored on ROM, and the luminance may be adjusted after determining the correction amount with reference to this map.

The light amount adjusting unit615performs feedback control whereby the operations of the above steps Sa1to Sa4are repeated. The light amount adjusting unit615thereby constantly monitors the illuminance of light reaching the medium50, and realizes light amount adjustment of the irradiating parts80A to80C. As a result, with the digital pen60, differences in illuminance on the medium50are eliminated, and reading errors are reduced.

Steps Sa1to Sa3in the present embodiment constitute a specific example of a specifying unit according to an aspect of the invention, and step Sa4constitutes a specific example of a light amount adjusting unit according to an aspect of the invention.

3. OTHER EXAMPLES

The above exemplary embodiments may be modified as follows. Also, the following variations may be combined.

The second embodiment was described in terms of adjusting the luminance of the irradiating parts80, in order to adjust the illuminance (intensity of reflected light) in prescribed portions (detection areas Ca, Cb, Cc) of an image imaged by the imaging parts82, but the present invention is not limited to this, and control may be performed such that the illuminance in the brightest portion and the illuminance in the darkest portion are approximated to one another, by extracting the portion with the brightest luminance and the portion with the darkest luminance from the imaged image, and appropriately adjusting the light amounts of the irradiating parts80A to80C.

Also, the irradiating unit80that is far from the medium50may be specified by dividing the imaged image into partition detection areas, and detecting and comparing the illuminances in the partition detection areas.

The light amount adjustment of the irradiating parts80in the light amount adjusting unit615can be performed by other methods, rather than only being performed based on an image imaged by the imaging parts82.

For example, as shown in the functional block diagram ofFIG. 16, a tilt detection sensor617that detects the tilt direction and tilt amount of the digital pen60is provided in the pen body60A. This tilt detection sensor617is a gyrosensor, a 2-axis velocity sensor that detects tilt with respect to two axes that are orthogonal to the axis line O-O, an acceleration sensor, or the like. It is preferable that detections by the 2-axis velocity and acceleration sensor is performed in the arrangement that the medium50is faced vertically.

Also, the light amount adjusting unit615specifies the irradiating unit80positioned on the upper side as the irradiating unit80that is far from the medium, by the tilt detection sensor617detecting the tilt direction of the digital pen60. Further, the light amount adjusting unit615adjusts the luminance of the irradiating unit80that is far from the medium, by the tilt detection sensor617detecting the tilt amount of the digital pen60. For example, the light amount adjusting unit615prestores correction amounts for the irradiating parts80corresponding to tilt amounts of the digital pen60on ROM, and reads out the corresponding correction amount based on the detected tilt amount and adjusts the luminance of the irradiating parts80.

The installation positions of the irradiating parts80may also be adjusted, such that the distances along the axis line O-O direction from the irradiating parts80A,80B and80C to the medium50are equal (more precisely, such that the difference in distances falls within a given value range), instead of electrically adjusting the luminances of the irradiating parts80A to80C in order to approximate the illuminances in the irradiation ranges Aa, Ab and Ac on the medium50to one another.

In the first embodiment and the second embodiment (hereinafter, the above exemplary embodiments), the irradiating parts80and the image forming parts81are fixed with respect to the pen body60A, but the irradiating parts80A,80B and80C and the image forming parts81A,81B and81C may be provided rotatably around the pen tip69, while maintaining their relative positions to one another.

Specifically, the irradiating parts80A,80B and80C and the image forming parts81A,81B and81C are fixed to a ring member that serves as a circular conductive member, and this ring member is rotatably supported by a supporting member around the rotation center of the pen tip69. The ring member and the controller61are electrically connected with a so-called slip ring. Further, a weight is provided on the ring member. The weight is added, such that the irradiating parts80A,80B and80C and the image forming parts81A,81B and81C are in a fixed configuration, in a state where the digital pen60is tilted.

The ring member rotates under the influence of the weight, such that the irradiating parts80A,80B and80C take a prescribed configuration (the most mechanically stable configuration) with respect to the medium50, whichever direction the user tilts the digital pen60. This means that the user no longer needs to tilt the digital pen60in a set direction. Note that the part connecting the ring member and the controller61is not limited to a slip ring, and may electrically connect the ring member and the controller61by a lead wire, and, in short, need only have a structure that is unlikely to cause mechanical resistance when the ring member rotates. It is preferable that the medium50is arranged horizontally during the digital pen60reads an image on the medium50. In the case where a light amount adjusting unit is employed with respect to a digital pen having this configuration, the tilt detection sensor may be a sensor that detects the tilt amount of only one axis.

In the above exemplary embodiments, the irradiating parts80A,80B and80C are disposed at the vertices of the equilateral triangle Ta, but the irradiating parts80A,80B and80C need not necessarily be disposed at the vertices of an equilateral triangle, and need only be disposed around the pen tip69with a suitable space opened up between one another, such that a shadow does not readily arise around the pen point69A. Specifically, as shown inFIG. 17, irradiating parts80A′,80B′ and80C′ need only be disposed in every other equally divided area (e.g., D1, D3, D5), where a circle centered on the axis line O-O is equally divided by six into six wedge-shaped equally divided areas D1to D6. At this time, the configuration position of the irradiating parts80A′,80B′ and80C′ in the equally divided areas is determined according to illuminance or the like.

Also, the number of irradiating parts80is not limited to three, and four or more. For example, when there are four, the four irradiating parts80are respectively disposed in every other equally divided area, where a circle centered on the axis line O-O is equally divided by eight into eight wedge-shaped areas. That is, in the case of N irradiating parts, the N irradiating parts need only be respectively disposed in every other non-adjacent equally divided area, where a circle centered on the axis line O-O is equally divided by 2N into 2N wedge-shaped equally divided areas. Also, the circular area composing the equally divided areas is not limited to being formed on a surface that is orthogonal to the axis line O-O, and may be formed on an angled surface centered on the axis line O-O.

Further, the number of the image forming parts81is not limited to three, and may be one, two, or four or more. In short, it need only be possible to form an image of the reflected light of light irradiated around the pen point69A.

In the above exemplary embodiments, a digital pen for writing characters, graphics and the like on a medium50was described, but the digital pen may, for example, be provided with a pointing device (mouse) function, or a stylus function of reading information (e.g., command information) recorded in correspondence with areas on a medium.

Note that in the above exemplary embodiments, the operation in the case of writing characters and the like on a medium50was described, but the present invention is not limited to this, and the digital pen60can also be used, for example, in the case where a position on a display surface is merely designated, such as where a soft button provided on a medium50that functions as a display apparatus is selected.

In the above exemplary embodiments, near-infrared LEDs that irradiate near-infrared light are used as the irradiating parts80, but the irradiating parts80are not limited to this, and LEDs having other light emitting properties may be used. In short, the irradiating parts80need only irradiate light that enables the code pattern image formed on the medium50to be read with the reflected light thereof.

In the above exemplary embodiments, information that uniquely identifies the medium is used as identification information, but the identification information is not limited to this, and information that uniquely identifies the electronic document may be used as identification information, for example. In the case where information that uniquely identifies the medium is used, different identification information is assigned to different media when multiple copies of the same electronic document are formed. In contrast, in the case where information that uniquely identifies the electronic document is used as identification information, the same identification information is assigned even to different media when the same electronic document is formed.

Also, in the above exemplary embodiments, a code pattern image representing position information and identification information is read, but the information represented by the code pattern image is not limited to position information or identification information, and may, for example, be information representing text data or a command, or an image representing only position information. In short, an image representing information of some sort need only be formed on the medium50.

With the above image forming apparatus, the code pattern image is formed using K toner. This is because K toner absorbs more infrared light than C, M or Y toner, and the code pattern image is read in high contrast with the digital pen60. However, the code pattern image can also be formed using a specialty toner. As a specialty toner, an invisible toner with a maximum absorption rate in a visible light region (400 nm to 700 nm inclusive) of 7% or less, and an absorption rate in a near-infrared region (800 nm to 1000 nm inclusive) of 30% or more can, for example, be used. Note that “visible” and “invisible” are distinguished not by whether the toner is visually perceivable, but by whether an image formed on a medium can be perceived due to whether the toner has color developing properties attributed to the absorption of specific wavelengths in the visible light region. Also, a toner that has some color developing properties attributed to the absorption of specific wavelengths in the visible light region but is difficult to perceive with the human eye is also included as “invisible”. Also, this invisible toner desirably has an average dispersion diameter in a range of 100 nm to 600 nm inclusive, in order to enhance the near-infrared light absorption capability necessary for mechanical reading of images.

Also, the image forming apparatus is not limited to an electrophotographic system, and may use any other system, such as an inkjet system.

A computer program that is executed by the controller61of the digital pen60can be provided in a state of being stored on a computer-readable recording medium such as a magnetic recording medium (magnetic tape, magnetic disk, etc.), an optical recording medium (optical disk, etc.), a magneto-optical recording medium, or a semiconductor memory. Also, the computer program can be downloaded to the digital pen60via a network such as the Internet. Note that various devices other than a CPU can be applied as a controller that performs the abovementioned control, and a dedicated processor may be used, for example.