Abstract:
To provide a printer capable of matching arrangement cycles of parallax images and lenses with each other inexpensively and easily. There is provided a printer comprising: a recording head that discharges ink to a predetermined position of a recording medium while being moved in a main scan direction relative to the recording medium on which an image is printed; a recording-head moving unit that moves the recording head in the main scan direction; a recording-medium moving unit that moves the recording medium in a auxiliary scan direction relative to the recording head; and an encoder that measures at least one of the movement of the recording head and the movement of the recording medium, wherein the encoder includes a scale having calibrations of which an interval is varied in one of a direction different from the movement direction of the recording head and the movement direction of the recording medium and a measuring portion that detects the calibrations, and wherein the interval of the calibrations to be detected by the measuring portion is varied by relatively moving the scale and the measuring portion in one of a direction different from the movement direction of the recording head and the movement direction of the recording medium.

Description:
BACKGROUND 
   The present invention relates to a printer. 
   Conventionally, as a three-dimensional image, there have been widely known a three-dimensional image which was obtained by synchronizing a plurality of images taken from plural directions in a stripe shape and which was three-dimensionally visible by observing separately with left and right eyes parallax images, which were recorded on the rear surface of a lenticular sheet having a plurality of pillar-shaped aspherical lenses arranged on the front surface, transmitting through the pillar-shaped aspherical lenses of the lenticular sheet from the front surface side of the lenticular sheet. 
   In addition to the aforementioned three-dimensional image, there have been also known three-dimensional images which were obtained using a technology called an integral photography employing a plurality of two-dimensionally arranged convex lenses, for example, faveolate lenses. 
   The three-dimensional images are obtained by recording parallax images at positions corresponding to a plurality of lenses such as pillar-shaped spherical lenses or faveolate lenses, and have an advantage that it is not necessary to utilize special spectacles such as spectacles in which separate colors are disposed to both eye portions, and the like. 
   As methods of forming the three-dimensional images, there has been suggested, for example, a technology of recording parallax images on the rear surface of a lenticular sheet at the same cycle as an arrangement cycle of the lenses of the lenticular sheet using a printer such as an inkjet printer, etc. (for example, see Patent Documents 1 to 5). 
   [Patent Document 1] Japanese Unexamined Patent Application Publication No. 8-101359 
   [Patent Document 2] Japanese Unexamined Patent Application Publication No. 7-281327 
   [Patent Document 3] Japanese Unexamined Patent Application Publication No. 9-15766 
   [Patent Document 4] Japanese Unexamined Patent Application Publication No. 11-188866 
   [Patent Document 5] Japanese Unexamined Patent Application Publication No. 2001-255606 
   [Patent Document 6] Japanese Unexamined Patent Application Publication No. 2000-103135 
   In Patent Document 1 described above, a technology of absorbing difference in cycle between lenses and parallax images of a lenticular sheet by adjusting the parallax images to be printed is disclosed. However, in the above technology, it is difficult to completely absorb the difference in cycle between the lenses and the parallax images of the lenticular sheet. That is, since the minimum value for adjustment of the parallax images is determined depending upon the maximum resolution of the printer printing the parallax images, finer adjustment cannot be performed. That is, since minute difference in cycle between the lenses and the parallax images of the lenticular sheet remains, it is difficult to realize a three-dimensional image with high quality. 
   In Patent Document 2 and Patent Document 3 described above, a technology of utilizing a lenticular sheet having lenses with a cycle matching a driving cycle of a printer printing parallax images is disclosed. However, in the above technology, since it is necessary to utilize the lenticular sheet having the same cycle as the driving cycle of the printer, there is a problem that the range for selection of the lenticular sheet is restricted and manufacturing cost and running cost are increased due to a special order for lenticular sheets which are an expendable item. 
   In Patent Document 4 and Patent Document 5, a technology that a printer printing parallax images forms lenses on a target to be printed is disclosed. However, in the above technology, since many positions of which specifications should be changed and many elements which should be newly developed exist in a currently used printer, there is a problem that much time is required for realization thereof. 
   In addition to the aforementioned technologies, there has been a technology of matching a driving cycle of a printer with a cycle of lenses of a lenticular sheet. The driving cycle of a printer is determined using parameters such as a driving frequency, a printing speed, a resolution of a linear encoder, etc. The driving frequency and the printing speed can be changed to desired values by changing parameters of the software controlling them. However, since it is difficult to change the resolution of a linear encoder and only one kind of resolution can be expressed as disclosed in Patent Document 6, it is difficult to completely match the cycle of the parallax images with the cycle of the lenses of a lenticular sheet. 
   SUMMARY 
   The present invention is contrived to solve the above problems and it is an object to provide a printer capable of matching arrangement cycles of parallax images and lenses with each other inexpensively and easily. 
   In order to accomplish the above object, according to the present invention, there is provided a printer comprising: a recording head that discharges ink to a predetermined position of a recording medium while being moved in a main scan direction relative to the recording medium on which an image is printed; a recording-head moving unit that moves the recording head in the main scan direction; a recording-medium moving unit that moves the recording medium in a auxiliary scan direction relative to the recording head; and an encoder that measures at least one of the movement of the recording head and the movement of the recording medium, wherein the encoder includes a scale having calibrations of which an interval is varied in one of a direction different from the movement direction of the recording head and the movement direction of the recording medium and a measuring portion that detects the calibrations, and wherein the interval of the calibrations to be detected by the measuring portion is varied by relatively moving the scale and the measuring portion in one of a direction different from the movement direction of the recording head and the movement direction of the recording medium. 
   That is, the encoder of the printer according to the present invention can vary the interval of the calibrations to be detected by the measuring portion, by relatively moving the scale and the measuring portion in one of the direction different from the movement direction of the recording head and the movement direction of the recording medium. As a result, the encoder can have different resolutions, and thus can measure the movement of the recording head with a desired resolution. 
   Accordingly, in the printer according to the present invention, the recording head or the recording medium can be moved with a predetermined cycle, so that it is possible to print images with the predetermined cycle. Therefore, for example, when a lenticular sheet is used as the recording medium, it is possible to easily match the cycle of parallax images with the arrangement cycle of lenses of the lenticular sheet. Since various arrangement cycles of lenses can be coped with, the range for selection of a lenticular sheet can be widened and the lenticular sheets which are a mass-produced item can be used, thereby reducing running cost. 
   In order to embody the above construction, more specifically, the scale may be formed in a rectangular shape and the calibrations may be formed to intersect the lengthwise axis direction of the scale. Further, the scale may be arranged such that the lengthwise axis direction is parallel or substantially parallel to the movement direction of the recording head or the movement direction of the recording-medium. 
   According to this construction, since the lengthwise axis direction of the scale is parallel or substantially parallel to the movement direction of the recording head or the movement direction of the recording-medium, the lengthwise axis direction of the scale is substantially equal to the movement direction of the recording head or the movement direction of the recording medium. Further, since the calibrations are formed to intersect the lengthwise axis direction, it is possible to easily measure the moving distance of the recording head or the moving distance of the recording medium. 
   In order to embody the above construction, more specifically, the interval of the calibrations may be varied in a direction intersecting the main scan direction (including a direction perpendicular to the main scan direction and a direction approximately perpendicular thereto). 
   According to this construction, since the calibration interval is varied in a direction intersecting the main scan direction (including a direction perpendicular to the main scan direction and a direction approximately perpendicular thereto), it is possible to vary the calibration interval used for measurement by moving the relative position between the scale and the measuring portion in the direction intersecting the main scan direction (including a direction perpendicular to the main scan direction and a direction approximately perpendicular thereto). 
   In order to embody the above construction, more specifically, the calibrations may be formed out of a plurality of straight lines extending radially from a predetermined point outside the scale. 
   According to this construction, since the calibrations are formed out of a plurality of straight lines extending radially from a predetermined point outside the scale, the calibration interval is continuously varied in the direction intersecting the main scan direction (including a direction perpendicular to the main scan direction and a direction approximately perpendicular thereto). 
   In order to embody the above construction, more specifically, the measuring portion may be attached to the recording head, the scale may be attached to a belt that is wound around a pair of rollers rotatably disposed and extends in a direction approximately perpendicular to the movement direction of the recording head, and one roller may be provided with a motor that drives the scale in the direction intersecting the movement direction of the recording head (including a direction perpendicular to the movement direction of the recording head and a direction approximately perpendicular thereto) via the roller and the belt. 
   According to this construction, since the scale is attached to the belt that is driven in the direction intersecting the movement direction of the recording head (including a direction perpendicular to the movement direction of the recording head and a direction approximately perpendicular thereto) by the motor, the positional relation of the scale relative to the measuring portion can be changed by driving the scale in the intersecting direction (including a perpendicular direction perpendicular or a approximately-perpendicular direction), thereby varying the calibration interval used for measurement. 
   By attaching the measuring portion to the recording head and driving the scale in the direction intersecting the movement direction of the recording head (including a direction perpendicular to the movement direction of the recording head and a direction approximately perpendicular thereto), the recording head may be formed to be movable only in the main scan direction. Accordingly, the construction can be simplified and it is thus not necessary to drastically change the conventional construction. 
   In order to embody the above construction, more specifically, the scale may be moved in the lengthwise axis direction by the recording-medium moving unit in synchronism with the movement of the recording medium, the measuring portion may be attached to a belt that is wound around a pair of rollers rotatably disposed and extends in a direction intersecting the lengthwise axis direction (including a direction perpendicular to the lengthwise axis direction and a direction approximately perpendicular thereto), and one roller may be provided with a motor that drives the measuring portion in the direction intersecting the lengthwise axis direction (including a direction perpendicular to the lengthwise axis direction and a direction approximately perpendicular thereto) via the roller and the belt. 
   According to this construction, since the measuring portion is attached to the belt that is driven in the direction intersecting the lengthwise axis direction of the scale (including a direction perpendicular to the lengthwise axis direction and a direction approximately perpendicular thereto) by the motor, the positional relation of the measuring portion relative to the scale by driving the measuring portion in the intersecting direction (including the perpendicular direction and the approximately-perpendicular direction) can be changed, thereby varying the calibration interval used for measurement. 
   In order to embody the above construction, more specifically, variation of the calibration interval of the scale may be performed by selecting a calibration interval after variation from a plurality of the calibration intervals of the scale, changing relative positions of the scale and the measuring portion such that the calibration interval measured by the encoder becomes the calibration interval after variation, and changing a driving cycle of the recording head and an imaging speed of an image on the basis of the calibration interval after variation. 
   According to this construction, the interval of the calibrations to be measured by the encoder, the driving cycle of the recording head, and the imaging speed or the printing speed of an image are changed on the basis of the selected calibration interval after variation. As a result, it is possible to print an image at a predetermined cycle, for example, by selecting the calibration interval in accordance with a cycle required for the image to be printed on the recording medium. 
   In order to embody the above construction, more specifically, the recording medium may be one of a lens sheet having a plurality of lenses arranged on one surface thereof and a print medium having convexities and concavities corresponding to lenses, and the calibration interval after variation may be selected on the basis of the number of parallax images and one of an arrangement cycle of the lenses and the convexities and concavities corresponding to the lenses. 
   According to this construction, since the calibration interval after variation is selected on the basis of a predetermined number of parallaxes and one of the arrangement cycle of the lenses of the recording medium and the convexities and concavities corresponding to the lenses, it is possible to print parallax images different by the number of parallax images, for example, in an area of the recording medium where the lenses or the convexities and concavities corresponding to the lenses are arranged, at the cycle equal to the arrangement cycle of the lenses or the convexities and concavities corresponding to the lenses. The number of dots required for forming the respective parallax images can be applied to all the parallax images. 
   In order to embody the above construction, more specifically, the variation of the calibration interval to be measured by the encoder may be performed by moving the scale in the main scan direction through control of driving the motor and thus changing the relative position between the scale and the measuring portion. 
   According to this construction, since the variation of the calibration interval to be measured by the encoder is performed by moving the scale in the main scan direction through control of driving the motor, the relative position between the scale and the measuring portion can be controlled, so that it is possible to change the calibration interval to be measured by the encoder to a predetermined calibration interval. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view illustrating an embodiment of a printer according to the present invention; 
       FIG. 2  is a partially-enlarged cross-sectional view illustrating a periphery of a recording head in the printer according to the present invention; 
       FIG. 3  is a partially-enlarged view illustrating a linear encoder in the printer according to the present invention; 
       FIG. 4  is a diagram illustrating calibrations of a scale of the linear encoder in the printer according to the present invention; 
       FIG. 5  is a partially-enlarged view illustrating the linear encoder in the printer according to the present invention; and 
       FIG. 6  is a flowchart illustrating variation of a calibration interval in the printer according to the present invention. 
   

   DETAILED DESCRIPTION OF EMBODIMENTS 
   Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. 
   The embodiments to be described below is intended to explain a gist of the present invention, but is not intended to limit the present invention as far as specific restrictions do not exist. 
   In the present embodiment, an example where a three-dimensional image sheet is produced using a printer for forming lenses on the same surface as the surface of a recording medium on which parallax images are recorded will be described. 
     FIG. 1  is a perspective view illustrating an example of the printer according to the present invention and  FIG. 2  is a partially-enlarged view illustrating a periphery of a recording head in the printer shown in  FIG. 1 , illustrating a state where a recording medium is inserted into the printer. 
   In  FIG. 1 , a reference numeral  100  denotes a printer. The printer  100  approximately comprises a main body  10  and a sheet feed unit (recording-medium moving unit or recording-medium moving means)  50 . 
   In  FIG. 1 , a reference numeral  60  denotes a lenticular sheet (recording medium). In the lenticular sheet  60 , lenticular lenses (lenses)  60   a  which are a pillar-shaped aspherical lens are disposed approximately at regular intervals on one surface thereof, and a printing surface  60   b  having an ink-absorbing layer for absorbing ink for printing is formed on the other surface. 
   As shown in  FIGS. 1 and 2 , the main body  10  is provided with a carriage  12  as a support member for supporting a cartridge  11  and a carriage moving means (recording-head moving unit or recording-head moving means) to be described later. A recording head  11   a  and the cartridge  11  mounted with an ink envelope (not shown) are fitted to the carriage  12 . 
   As shown in  FIG. 2 , the recording head  11   a  records a parallax image  60   c  on the printing surface  60   b  of the lenticular sheet  60  by discharging the ink of the ink envelope from a nozzle  61  and performs the recording using a liquid crystal discharging method, that is, a so-called inkjet method. 
   The recording head  11   a  is practically used, for example, for an inkjet printer, and a piezo-jet type recording head employing a piezoelectric element, a Bubble Jet (registered trademark) type recording head, etc. employing an electro-thermal conversion member as an energy-generating element. Here, a coloring area and a coloring pattern can be arbitrarily set. 
   As shown in  FIGS. 1 and 2 , a carriage moving means moves the carriage  12  in the main scan direction, and comprises a frame  13 , a guide bar  14 , a motor  15 , gears  17 ,  21 , a driving wheel  18 , a timing belt  19 , and a driven wheel  20 . 
   As shown in  FIG. 1 , the carriage  12  is supported to be movable in the width direction (main scan direction) of the guide bar  14  by a pair of guide bars  14  provided in the frame  13 . For example, a DC motor is provided as the motor  15  which is a driving source for driving the carriage  12  and is rotationally driven in a constant direction. 
   As shown in  FIG. 2 , a first linear encoder (encoder)  40  for measuring the moving distance of the recording head  11   a  and a first resolution variation section  45  are provided between the downside of the carriage  12  and the frame  13 . The moving distance of the recording head  11   a  measured by the first linear encoder  40  is used for positional control correction of the recording head  11   a . A positional control error of the recording head  11   a  is reduced using the first linear encoder  40 , so that it is possible to print parallax images at more accurate positions. 
   The first linear encoder  40  and the first resolution variation section  45  may be disposed between the downside of the carriage  12  and the frame  13  as shown in  FIG. 2 , and may be disposed between one lateral side of the carriage  12  and the frame  13 . The disposal positions thereof are not specifically restricted. 
     FIG. 3A  is a schematic diagram illustrating the first linear encoder and  FIG. 3B  is a diagram illustrating a scale of the first linear encoder. 
   As shown in  FIGS. 3A and 3B , the first linear encoder  40  approximately comprises a scale  41  on which calibrations  42  are formed and a sensor (measuring portion)  43  such as a CCD (Charge Coupled Device) camera for optically detecting the calibrations  42  formed on the scale  41 . The first resolution variation section  45  approximately comprises a belt  47  wound around a pair of rollers  46  and a motor  48  for rotationally driving one of the pair of rollers  46 . 
   As shown in  FIGS. 3A and 3B , the scale  41  is made of a measured member  44  having approximately a rectangular shape and calibrations  42  are formed on the measured member  44 . The calibrations  42  are formed, as shown in  FIG. 4 , out of straight lines L which are expanded radially and at regular intervals toward the measured member  44  from a virtual point (a predetermined point) which is deviated in a minor-axis direction from one end portion of the measured member  44 . The calibration interval  42  of the scale  41  is, for example, about 8.8 μm (corresponding to 1/2880 dpi (dot per inch)) at the side where the interval is narrow (the interval at the upper end of  FIG. 3B ), and about 9.4 μm (corresponding to 1/2700 dpi) at the side where the interval is broad (the interval at the lower end of  FIG. 3B ). The interval of the calibrations  42  therebetween is linearly varied (widened) from the narrow side to the broad side. 
     FIG. 4  is a diagram illustrating a method of forming the calibrations of the scale. 
   The calibrations  42  may have the aforementioned interval, may have an interval broader than the aforementioned interval, and may have an interval narrower than the aforementioned interval. The virtual point P may be placed at the position which is deviated in the minor-axis direction from the end portion of the measured member  44  as shown in  FIG. 4  and may be placed at a position which is deviated in the minor-axis direction from the approximately central portion of the measured member  44 . The first linear encoder  40  may detect the calibrations  42  of the scale  41  with a sensor such as a CCD camera, etc. and may detect the calibrations with a magnetic sensor using the calibrations  42  of the scale  41  as magnetic calibrations. The measured member  44  of the scale  41  may be made of an opaque material which does not transmit light and may be made of a transparent material such as glass, polycarbonate, vinyl chloride, etc. In addition, the measured member  44  may be made of a rigid material (having high rigidity) and may be made of a soft material (having low rigidity). 
   As shown in  FIG. 3A , the first resolution variation section  45  comprises a pair of belts  47  wound around rollers  46  in parallel to each other, and the belts  47  are disposed to extend in a direction approximately perpendicular to the main scan direction. The rollers  46  of the belts  47  are provided with a motor  48 , respectively, and the belts  47  are driven with the motors  48  via the rollers. The motor  48  may be provided in the roller  46  of the respective belts  47  as described above, and the rollers  46  of the respective belts  47  may be supported by a common rotational shaft and driven with only one motor  48 . 
   As shown in  FIG. 1 , control lines  26  for driving the motor  15 , etc. or taking out signals and control lines  27  for inputting control signals for driving the recording head are connected to the main body  10 . 
   As shown in  FIGS. 2 and 3A , the scale  41  is disposed on the belt  47  of the first resolution variation section  45  such that the lengthwise axis direction is parallel or approximately parallel to the main scan direction, and is movable in a direction intersecting the main scan direction (including a direction perpendicular to the main scan direction and a direction approximately perpendicular thereto) together with the belt  47 . the sensor  43  is disposed on the lower surface of the carriage  12  and is movable in the main scan direction together with the carriage  12 . 
   As shown in  FIG. 1 , the sheet feed unit  50  is screw-coupled to a guide surface  13   a  which is formed by bending the frame  13  of the main body  10  upwardly at the right angle, and thus is fixed to the main body  10 . For the purpose of driving the sheet feed unit  50 , the rotation of a gear  21  connected to the driven wheel  20  is supplied via a gear group  51  and a transfer shift (not shown). The gear group  51  is connected to a pair of sheet supply roller and sends out the lenticular sheet  60  inserted into the printer  100  by a predetermined amount. 
     FIG. 5A  is a partial cross-sectional view illustrating a structure of the linear encoder in the auxiliary scan direction, and  FIG. 5B  is a partial plan view illustrating a structure of the linear encoder. 
   The sheet feed unit  50  is provided with a second linear encoder  70  for measuring the moving distance of the lenticular sheet  60  and a second resolution variation section  75 . The moving distance of the lenticular sheet  60  measured by the second linear encoder  70  is used for positional control correction of the lenticular sheet  60 . A positional control error of the lenticular sheet  60  is reduced using the second linear encoder  70 , so that it is possible to print parallax images at more accurate positions. 
   The second linear encoder  70  approximately comprises a scale  41  on which calibrations are formed and a sensor  43  such as a CCD camera for optically detecting the calibrations, similarly to the first linear encoder  40 . The second resolution variation section  75  approximately comprises a belt  47  wound around a pair of rollers  46  and a motor  48  for rotationally driving one of the pair of rollers  46 , similarly to the first resolution variation section  45 . 
   As shown in  FIGS. 5A and 5B , the second resolution variation section  75  comprises a belt  47  wound around rollers  46 , and the belt  47  is disposed to extend in a direction intersecting the auxiliary scan direction (including a direction to perpendicular to the auxiliary scan direction and a direction approximately perpendicular thereto). The roller  46  of the belt  47  is provided with a motor  48 , and the belt  47  is driven with the motor  48  via the rollers. 
   A sensor  43  is disposed on the belt  47  of the second resolution variation section  75  and is movable in the direction intersecting the auxiliary scan direction (including a direction perpendicular to the auxiliary scan direction and a direction approximately perpendicular thereto) together with the belt  47 . 
   The scale  41  is disposed such that the lengthwise axis direction thereof is matching the auxiliary scan direction and such that the opposite surface of the surface on which the calibrations  42  are formed is in contact with gears of the gear group  51 . The opposite surface is formed to engage with the gears of the gear group  51 . 
   For example, when the diameter of the gear driving the scale  41  is equal to the diameter of the sheet supply roller, the moved amount of the scale  41  and the moved amount of the lenticular sheet  60  are equal to each other. Since the ratio between the moved amount of the scale  41  and the moved amount of the lenticular sheet  60  is constant even when the diameter of the gear and the diameter of the sheet supply roller are different from each other, it is possible to measure the moved amount of the lenticular sheet  60 . Although not shown in the figures, the scale  41  may be provided with a structure for winding up the scale and may be provided with a structure for circulating the scale, at the upper side or the lower side in  FIG. 5A . 
   Next, a method of manufacturing the three-dimensional image sheet  6  shown in  FIG. 4  using the printer  100  by recording the parallax images  60   c  on the lenticular sheet  60  and forming the lenticular lenses  60   a  at the positions corresponding to the respective parallax images  60   c  in the lenticular sheet  60  will be described. 
   First, as shown in  FIGS. 1 and 2 , when the control voltage is supplied to the motor  15 , etc. through the control lines  26  and the control signals are supplied to the recording head  11   a  through the control lines  27 , the lenticular sheet  60  is inserted into the printer  100  and is moved in the auxiliary scan direction relative to the recording head  11   a  by the sheet feed unit  50 . Specifically, the gear  21  connected to the driven wheel  20  is rotated through the gear  17 , the driving wheel  18 , and the timing belt  19  by the motor  15 . When the gear  21  is rotationally driven, the gear group  51  is rotationally driven via the transfer shaft (not shown) and a pair of sheet supply rollers is rotationally driven. The lenticular sheet  60  is moved by means of the rotation of the sheet supply roller. 
   The lenticular sheet  60  is placed at the position where the parallax images are recorded in the auxiliary scan direction relative to the recording head  11   a.    
   Next, the recording head  11   a  is moved in the main scan direction with the carriage moving means. Specifically, the gear  17  and the driving wheel  18  are rotationally driven by the motor  15  and the timing belt  19  is rotationally driven by the driving wheel  18 . When the timing belt  19  is rotationally driven, the driven wheel  20  is rotated and thus the gear  21  connected to the driven wheel  20  is rotated. Since the timing belt  19  is provided with a driving pin  30  for allowing the carriage  12  to reciprocate, the carriage  12  reciprocates by means of the rotation of the timing belt  19  in a single direction. The reciprocation of the carriage  12  is basically controlled by means of the rotation of the motor  15  and the moving distance of the carriage  12  measured by the first linear encoder  40  is mainly used for correction. 
   As described above, when it is moved in the main scan direction relatively to the lenticular sheet  60 , the recording head  11   a  records the parallax images  60   c , as shown in  FIG. 3 , by discharging ink of the ink envelope toward the lenticular sheet  60  from the nozzle  61  in synchronism with the movement of the recording head  11   a.    
   Next, a method of allowing the printer  100  to print the parallax images  60   c  in accordance with the arrangement cycle of the lenticular lenses  60   a  of the lenticular sheet  60 . 
   Since the method of printing the parallax images  60   c  in accordance with the arrangement cycle of the lenticular lenses  60   a  using the first linear encoder  40  and the method of printing the parallax images  60   c  in accordance with the arrangement cycle using the second linear encoder  70  have approximately equivalent operation and effects, the method of printing the parallax images  60   c  in accordance with the arrangement cycle using the first linear encoder  40  will be mainly described herein. 
     FIG. 6  is a flowchart illustrating a method of printing the parallax images  60   c  in accordance with the arrangement cycle of the lenticular lenses  60   a.    
   As shown in  FIG. 6 , the method of printing the parallax images  60   c  in accordance with the arrangement cycle of the lenticular lenses  60   a  approximately comprises a cycle selecting process S 10 , a linear encoder setting process S 11 , and a driving parameter setting process S 12 . 
   At the cycle selecting process S 10 , first, one interval of the calibrations  42  is selected from an interval range of the calibrations  42  of the scale  41  in the first linear encoder  40  on the basis of the arrangement cycle of the lenticular lenses  60   a  of the lenticular sheet  60 . In the method of selecting an interval of the calibrations  42 , an interval of the calibrations  42  which is divided by the arrangement cycle of the lenticular lenses  60   a  is first selected sequentially from the side where the interval of the calibrations  42  is narrow (from the side where the resolution is high). When the divided interval of the calibrations  42  exists plurally, the interval of the calibrations  42  which is divided by the number of parallax images is first selected sequentially from a small interval of the calibrations  42 . The number of parallax images means the number of images used for printing a three-dimensional image or printing a motion. For example, supposed that the arrangement cycle of the lenticular lenses  60   a  is 73 dpi (about 347.9 μm), 1/2847 dpi (about 8.9 μm) is selected as the interval of the calibrations  42 . 
   As the arrangement cycle of the lenticular lenses  60   a  used for the cycle selecting process S 10 , a value obtained by allowing a sensor (not shown) provided in the printer  100  to automatically detect the arrangement cycle of the lenticular lenses  60   a  when the lenticular sheet  60  is supplied to the printer  100  may be used and a value obtained by allowing a user to input a predetermined arrangement cycle of the lenticular lenses  60   a  to the printer  100  maybe used. 
   At the linear encoder setting process S 11 , the relative positional relation between the scale  41  and the sensor  43  is adjusted such that the first linear encoder  40  can perform measurement with the interval of the calibrations  42  selected at the cycle selecting process S 10 . The relative positional relation between the scale  41  and the sensor  43  is varied and adjusted by allowing the motor  48  to move the scale  41  in the direction intersecting the main scan direction (including a direction perpendicular to the main scan direction and a direction approximately perpendicular thereto) via the belt  47 . 
   At the driving parameter setting process S 12 , the setting of two driving parameters (a driving frequency and a printing speed) of the carriage  12  is changed on the basis of the interval of the calibrations  42  selected at the cycle selecting process S 10 . For example, when the interval of the calibrations  42  is 1/2847 dpi (about 8.9 μm), the target resolution of an image to be printed is 2847 dpi (which is a resolution where the interval of dots is about 8.9 μm), and the target driving frequency is 14400 Hz, the printing speed of about 5.05 inch/s (about 128.27 mm/s) is obtained from the relational expression of (printing speed)=(driving frequency)/(resolution). Therefore, by controlling the carriage  12  on the basis of the above values, it is possible to print the parallax images  60   c  in accordance with the arrangement cycle of the lenticular lenses  60   a  and also to change the resolution of the parallax images  60   c.    
   As described above, the printing speed may be calculated on the basis of the resolution and the driving frequency, and the driving frequency may be calculated on the basis of the resolution and the printing speed. For example, when the target resolution is 2847 dpi and the target printing speed is 20 inch/s (508 mm/s), the driving frequency is 56940 Hz. 
   According to the above construction, it is possible to vary the interval of the calibrations to be detected by the sensor  43  by relatively moving the scale  41  and the sensor  43  in a direction different from the main scan direction. Accordingly, since the first linear encoder  40  can have different resolutions, it is possible to measure the movement of the recording head  11   a  with a desired resolution. As a result, the printer  100  according to the present invention can precisely move the recording head  11   a  by a desired distance and thus can print an image with a desired resolution. It is also possible to easily allow the arrangement cycle of the lenticular lenses  60   a  of the lenticular sheet  60  and the resolution and the cycle of the parallax images to correspond to each other. 
   Since various arrangement cycles of various lenses  60   a  can be coped with, the range for selection of the lenticular sheet  60  is widened and it is thus possible to reduce the running cost of the printer  100  by utilizing the lenticular sheet  60  which is a mass-produced item. 
   Since the calibrations  42  are formed out of a plurality of straight lines extending radially from a virtual point P located outside the scale  41 , the interval of the calibrations  42  is continuously varied in the direction intersecting the main scan direction (including a direction perpendicular to the main scan direction and a direction approximately perpendicular thereto). As a result, by moving the relative position between the scale  41  and the sensor  43  in the intersecting direction (including the perpendicular direction and the approximately-perpendicular direction), it is possible to continuously vary the interval of the calibrations  42 . 
   Since the scale  41  is attached to the belt  47  which is driven in the direction intersecting the main scan direction (including a direction perpendicular to the main scan direction and a direction approximately perpendicular thereto) by the motor  48 , the relative position to the sensor  43  and can be varied by driving the scale  41  in the intersecting direction (including the perpendicular direction and the approximately-perpendicular direction), thereby varying the interval of the calibrations  42  used for measurement. 
   Further, by attaching the sensor  43  to the recording head  11   a  and driving the scale  41  in the direction intersecting the main scan direction (including a direction perpendicular to the main scan direction and a direction approximately perpendicular thereto), the recording head  11   a  can be moved only in the main scan direction and thus the structure thereof can be simplified, so that it is not necessary to largely change the conventional structure. 
   Since the interval of the calibrations  42  selected at the cycle selecting process S 10  is selected on the basis of the arrangement cycle of the lenticular sheet  60  and a predetermined number of parallaxes, a parallax image  60   c  different by the number of parallax images can be printed, for example, at a position where one lenticular lens  60   a  is disposed, and the number of dots required for forming each parallax image  60   c  can be made constant. That is, the resolutions can be made equal to one another. 
   The technical scope of the present invention is not limited to the above embodiment, but various modifications may be made thereto without departing from the gist of the present invention. 
   For example, although it has been described in the above embodiment that the present invention is applied to the printer for a lenticular sheet on which parallax images of a three-dimensional image can be printed to observe the three-dimensional image, the present invention may be applied to a printer for a lenticular sheet on which parallax images of plural different images can be printed to observe different images depending upon an observation direction, for example, a lenticular sheet which allows a screen to be sequentially varied like a moving picture by varying the observation direction. 
   Although it has been described in the above embodiment that a lenticular sheet having lenticular lenses is used as a recording medium, an integral sheet having faveolate lenses may be used as a recording medium and various other lens sheets may be also used as a recording medium, in addition to the lenticular sheet.