Abstract:
A tray adapted to be loaded in a recording apparatus which comprises a transport roller transporting a medium in a first direction, a recording head moved in a second direction orthogonal to the first direction to record information on the medium, and a sensor, the tray comprising: a tray body, adapted to be transported in the first direction by the transport roller to a region opposing to the recording head; a set portion, adapted such that the medium is placed thereon; a first boundary line, defining two regions having different reflectivities and orthogonal to the second direction, the first boundary line being adapted to be detected by the sensor to provide a first reference position relative to the second direction; and a second boundary line, defining two regions having different reflectivities and orthogonal to the first direction, the second boundary line being adapted to be detected by the sensor to provide a second reference position relative to the first direction.

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field of the Invention 
     The present invention relates to a tray capable of setting a thin plate-shaped member which is represented by an optical disk. Moreover, the invention relates to a recording apparatus constituted to transport a tray capable of setting a thin plate-shaped member represented by an optical disk. 
     2. Description of the Related Art 
     An ink jet printer according to an example of a recording apparatus has such a structure that an ink droplet is directly discharged to a label surface of an optical disc to be a thin plate-shaped member which is represented by a compact disc or a DVD (Digital Versatile Disc), thereby carrying out recording. In such an ink jet printer, generally, the thin plate-shaped member such as the optical disc is set to a tray having a plate shape and is transported (a secondary scanning feed) through a transport path in the ink jet printer in a setting state to the tray, and recording is thus executed. 
     There has conventionally been proposed a method of detecting a central position of an optical disc (a reference position for printing) in order to carry out the printing over a label surface (printing region) of the optical disc with high precision in such a manner that a shift in a printing position is not caused. As an example, JP-A-2002-127530 has disclosed a method of providing an identification mark on a tray and disposing an optical sensor in a bottom part of a carriage to be reciprocally driven in a primary scanning direction, that is, an opposed portion to the tray to sense the identification mark by means of the sensor, thereby obtaining the central position of the optical disc. 
     In the method described in JP-A-2002-127530, however, the whole optical disc is sensed in the primary scanning direction by means of the optical sensor, and subsequently, the whole optical disc is sensed in the secondary scanning direction in the same manner. For this reason, an amount of a movement of the carriage and an amount of a secondary scanning feed of the tray in the acquirement of the central position are increased. Accordingly, a long time is required for the sensing. 
     Moreover, the tray is apt to generate a slip together with the transport roller in the secondary scanning feed. Accordingly, it is preferable that the amount of the secondary scanning feed of the tray in the sensing should be smaller in order to enhance precision in the detection of the central position. Furthermore, it is preferable that the amount of the movement of the carriage should also be smaller in order to enhance the precision in the detection. 
     SUMMARY OF THE INVENTION 
     Therefore, the invention has been made in consideration of such situations and has an object to shorten a time required for sensing through an optical sensor when obtaining a reference position of a medium which is set to a tray, and furthermore, to enhance precision in the detection of the reference position still more. 
     In order to solve the problems, a first aspect of the invention is directed to a tray comprising a tray body taking a shape of a plate which can be subjected to a secondary scanning feed by means of a transport roller for transporting a medium to an opposed region to a recording head for carrying out recording to the medium, and a set portion formed in the tray body and capable of setting a thin plate-shaped member as the medium, wherein the set portion is provided with a fitting portion for fitting in a fitting hole formed on the medium, and the fitting portion is provided with a first detected line which is formed by a boundary line between regions having different reflectivities and is orthogonal to a primary scanning direction, and a second detected line which is formed by a boundary line between regions having different reflectivities and is orthogonal to the secondary scanning direction. 
     According to the aspect, the first detected line and the second detected line are orthogonal to the primary scanning direction and the secondary scanning direction, respectively. By previously obtaining a distance between a reference position (hereinafter referred to as a “reference position x c ”) in the primary scanning direction in the execution of recording and the first detected line and a distance between a reference position (hereinafter referred to as a “reference position y c ”) in the secondary scanning direction in the execution of the recording and the second detected line, therefore, it is possible to acquire the reference position x c  even if any place in the first detected line is sensed, and to acquire the reference position y c  even if any place in the second detected line is sensed. In other words, the first detected line and the second detected line are orthogonal to the primary scanning direction and the secondary scanning direction, respectively. When the reference position x c  and the reference position y c  are to be obtained, therefore, it is sufficient that the first detected line and the second detected line are detected. Consequently, it is possible to shorten a time required for the sensing. 
     Moreover, it is sufficient that the amount of the secondary scanning feed of the tray in the detection of the second detected line is also small. Therefore, it is possible to reduce or prevent a deterioration in precision of the detection of the reference position y c  due to the generation of a slip between the transport roller for transporting the tray and the tray. 
     In particular, a trace line of the sensor in the detection of the first detected line and the second detected line through the sensor can be prevented from crossing the fitting portion, and furthermore, can consecutively cross the second detected line or the first detected line without getting out of the fitting portion after crossing the first detected line (or the second detected line). Therefore, a very small amount of the secondary scanning feed of the tray is enough when the reference position y c  is to be obtained. Consequently, it is possible to prevent a deterioration in the precision in the detection of the reference position y c  still more reliably, and furthermore, to greatly shorten the time required for the sensing when obtaining the reference position x c  and the reference position y c . 
     A second aspect of the invention is directed to the tray according to the first aspect, wherein the set portion takes a symmetrical shape with respect to the primary scanning direction and the secondary scanning direction and the fitting portion is provided in a central position in the primary scanning direction and the secondary scanning direction of the set portion. 
     According to the aspect, the set portion takes a symmetrical shape with respect to the primary scanning direction and the secondary scanning direction, and furthermore, the fitting portion is provided in the central position in the primary scanning direction and the secondary scanning direction of the set portion. When setting the reference position x c  and the reference position y c  to be the central positions of the medium, therefore, it is possible to obtain the functions and advantages according to the first aspect. 
     A third aspect of the invention is directed to the tray according to the first or second aspect, wherein each of the first detected line and the second detected line is a side constituting one plane figure. 
     According to the aspect, in the first or second aspect, each of the first detected line and the second detected line is the side constituting the plane figure. Therefore, it is possible to easily form the first detected line and the second detected line at a low cost. 
     A fourth aspect of the invention is directed to the tray according to the third aspect, wherein the plane figure is a right triangle. 
     According to the aspect, the plane figure is a right triangle. Therefore, the plane figure can be set to have a necessary minimum area and the degree of freedom of the arrangement of the plane figure in the fitting portion can be enhanced. In the case in which the plane figure is to be formed by a hole, furthermore, it is possible to prevent a reduction in a strength of the fitting portion. 
     A fifth aspect of the invention is directed to the tray according to the third aspect, wherein the plane figure further has a third detected line which is formed by a boundary line between regions having different reflectivities and is orthogonal to the primary scanning direction. 
     According to the aspect, the plane figure further has the third detected line which is formed by the boundary line between the regions having different reflectivities and is orthogonal to the primary scanning direction. When sensing the optical sensor in the primary scanning direction, therefore, it is possible to carry out the sensing by using any of the detected lines which is placed on a closer side (the first detected line or the third detected line) even if the sensor is provided on any side with respect to the fitting portion, to further shorten the time required for the sensing, and furthermore, to enhance the degree of freedom of a control. 
     A sixth aspect of the invention is directed to the tray according to the fifth aspect, further comprising a fourth detected line which is formed by a boundary line between regions having different reflectivities and is orthogonal to the secondary scanning direction. 
     According to the aspect, the plane figure further has the fourth detected line which is formed by the boundary line between the regions having different reflectivities and is orthogonal to the secondary scanning direction. When sensing the optical sensor in the secondary scanning direction, therefore, it is possible to carry out the sensing by using any of the detected lines which is placed on a closer side (the second detected line or the fourth detected line) even if the sensor is provided on any side with respect to the fitting portion, to further shorten the time required for the sensing, and furthermore, to enhance the degree of freedom of a control. 
     A seventh aspect of the invention is directed to the tray according to the fifth or sixth aspect, wherein the plane figure is a square. 
     According to the aspect, the plane figure is the square. Even if any of the detected lines which constitute the square is used, therefore, it is possible to obtain the reference position x c  and the reference position y c , to further shorten the time required for the sensing, and furthermore, to enhance the degree of freedom of a control. 
     An eighth aspect of the invention is directed to a tray comprising a tray body taking a shape of a plate which can be subjected to a secondary scanning feed by means of a transport roller for transporting a medium to an opposed region to a recording head for carrying out recording to the medium, and a set portion formed in the tray body and capable of setting a thin plate-shaped member as the medium, wherein the thin plate-shaped member takes a shape of a disk and the set portion takes a circular shape, the tray body is provided with a first detected line which is formed by a boundary line between regions having different reflectivities and is orthogonal to a primary scanning direction, and a second detected line which is formed by a boundary line between regions having different reflectivities and is orthogonal to a secondary scanning direction, each of the first detected line and the second detected line is a side constituting one plane figure, and the plane figure is disposed on an outside of the set portion, and a position thereof is set away from a central position in the primary scanning direction and a central position in the secondary scanning direction of the set portion within a range of formation of the set portion in the primary scanning direction and/or the range of the formation of the set portion in the secondary scanning direction. 
     According to the aspect, the same functions and advantages as those in the first and third aspects can be obtained. In addition, in the case in which the plane figure is disposed on the outside of the set portion, the residual space which is adjacent to the set portion taking a circular shape is used. In the case in which the plane figure is disposed on the outside of the set portion, therefore, it is not necessary to increase the size of the tray for disposing the plane figure. 
     A ninth aspect of the invention is directed to a tray comprising a tray body taking a shape of a plate which can be subjected to a secondary scanning feed by means of a transport roller for transporting a medium to an opposed region to a recording head for carrying out recording to the medium, and a set portion formed in the tray body and capable of setting a thin plate-shaped member as the medium, wherein the thin plate-shaped member takes a shape of a disk and the set portion takes a circular shape, the tray body is provided with a first detected line which is formed by a boundary line between regions having different reflectivities and is orthogonal to a primary scanning direction, and a second detected line which is formed by a boundary line between regions having different reflectivities and is orthogonal to a secondary scanning direction, each of the first detected line and the second detected line is a side constituting one plane figure, and the plane figure is disposed on an outside of the set portion, and is positioned on a center in the main scanning direction or a center in the secondary scanning direction of the set portion. 
     According to the aspect, the same functions and advantages as those in the first and third aspects can be obtained. In addition, in the case in which the plane figure is disposed on the outside of the set portion, it is provided on the center in the primary scanning direction or the center in the secondary scanning direction of the set portion. In the case in which the reference position x c  and the reference position y c  are set to be the center of the set portion, therefore, a distance between the first detected line and the reference position x c  is reduced if the plane figure is disposed on the center in the primary scanning direction of the set portion or a distance between the second detected line and the reference position y c  is reduced if the plane figure is disposed on the center in the secondary scanning direction of the set portion. Consequently, it is possible to prevent a deterioration in the precision in the detection of the reference position x c  or the reference position y c . 
     A tenth aspect of the invention is directed to a recording apparatus comprising a carriage including a recording head for carrying out recording to a medium, a motor for the carriage which drives the carriage, a sensor provided in an opposed position to the medium in the carriage and serving to detect a difference in a reflectivity of the medium, a transport roller constituted to include a transport driving roller which is rotated and driven to nip and rotate a medium to be transported, thereby transporting the medium to be transported to the recording head, and a transport driven roller driven and rotated in pressure contact with the transport driving roller, a motor for the transport driving roller which serves to rotate and drive the transport driving roller, and a control portion for controlling the motor for the carriage and the motor for the transport driving roller, and having such a structure that a tray constituted to include a tray body taking a shape of a plate and a set portion formed in the tray body and capable of setting a thin plate-shaped member which is the medium can be transported by means of the transport roller, wherein the tray body is provided with a first detected line which is formed by a boundary line between regions having different reflectivities and intersects a primary scanning direction, and a second detected line which is formed by a boundary line between regions having different reflectivities and intersects a secondary scanning direction, each of the first detected line and the second detected line constitutes one plane figure, and the control portion controls the motor for the transport driving roller and the motor for the carriage, thereby forming a trace line in which the sensor crosses the first detected line and a trace line in which the sensor crosses the second detected line. 
     According to the aspect, each of the first detected line and the second detected line constitutes the plane figure, and the control portion controls the motor for the transport driving roller and the motor for the carriage, thereby forming the trace line in which the sensor crosses the first detected line and the trace line in which the sensor crosses the second detected line. Consequently, it is sufficient that the amount of the movement of the carriage and the amount of the secondary scanning feed of the tray in the acquirement of the reference positions x c  and y c  are very small. The deterioration in the precision of the detection of the reference positions x c  and y c  can be prevented still more reliably, and furthermore, the time required for the sensing can be shortened considerably. 
     An eleventh aspect of the invention is directed to a recording apparatus comprising a carriage including a recording head for carrying out recording to a medium, a motor for the carriage which drives the carriage, a sensor provided in an opposed position to the medium in the carriage and serving to detect a difference in a reflectivity of the medium, a transport roller constituted to include a transport driving roller which is rotated and driven to nip and rotate a medium to be transported, thereby transporting the medium to be transported to the recording head, and a transport driven roller driven and rotated in pressure contact with the transport driving roller, a motor for the transport driving roller which serves to rotate and drive the transport driving roller, and a control portion for controlling the motor for the carriage and the motor for the transport driving roller, and having such a structure that a tray constituted to include a tray body taking a shape of a plate and a set portion formed in the tray body and capable of setting a thin plate-shaped member which is the medium can be transported by means of the transport roller, wherein the set portion is provided with a fitting portion for fitting in a fitting hole formed on the medium, the fitting portion is provided with a first detected line which is formed by a boundary line between regions having different reflectivities and is orthogonal to a primary scanning direction, and a second detected line which is formed by a boundary line between regions having different reflectivities and is orthogonal to a secondary scanning direction, and the control portion controls the motor for the transport driving roller and the motor for the carriage in such a manner that a trace line of the sensor in detection of the first detected line through the sensor does not cross the fitting portion but the first detected line in the primary scanning direction and a trace line of the sensor in detection of the second detected line through the sensor does not cross the fitting portion but the second detected line in the secondary scanning direction. 
     According to the aspect, the motor for the transport driving roller and the motor for the carriage are controlled in such a manner that the trace line of the sensor in the detection of the first detected line through the sensor does not cross the fitting portion. Consequently, it is sufficient that the amount of the movement of the carriage and the amount of the secondary scanning feed of the tray in the acquirement of the reference positions x c  and y c  are very small. The deterioration in the precision of the detection of the reference positions x c  and y c  can be prevented still more reliably, and furthermore, the time required for the sensing can be shortened considerably. 
     A twelfth aspect of the invention is directed to a recording apparatus comprising a carriage including a recording head for carrying out recording to a medium, a motor for the carriage which drives the carriage, a sensor provided in an opposed position to the medium in the carriage and serving to detect a difference in a reflectivity of the medium, a transport roller constituted to include a transport driving roller which is rotated and driven to nip and rotate a medium to be transported, thereby transporting the medium to be transported to the recording head, and a transport driven roller driven and rotated in pressure contact with the transport driving roller, a motor for the transport driving roller which serves to rotate and drive the transport driving roller, and a control portion for controlling the motor for the carriage and the motor for the transport driving roller, and having such a structure that a tray constituted to include a tray body taking a shape of a plate and a set portion formed in the tray body and capable of setting a thin plate-shaped member which is the medium can be transported by means of the transport roller, wherein the set portion is provided with a fitting portion for fitting in a fitting hole formed on the medium, the fitting portion is provided with a first detected line which is formed by a boundary line between regions having different reflectivities and is orthogonal to a primary scanning direction, and a second detected line which is formed by a boundary line between regions having different reflectivities and is orthogonal to a secondary scanning direction, and the control portion controls the motor for the transport driving roller and the motor for the carriage in such a manner that a trace line of the sensor in detection of the first detected line and the second detected line through the sensor crosses the first detected line and subsequently crosses the second detected line without getting out of the fitting portion or crosses the second detected line and subsequently crosses the first detected line without getting out of the fitting portion. 
     According to the aspect, the control portion controls the motor for the transport driving roller and the motor for the carriage in such a manner that the trace line of the sensor in the detection of the first detected line and the second detected line through the sensor crosses the first detected line and then crosses the second detected line without getting out of the fitting portion or crosses the second detected line and subsequently crosses the first detected line without getting out of the fitting portion. Consequently, it is sufficient that the amount of the movement of the carriage and the amount of the secondary scanning feed of the tray in the acquirement of the reference positions x c  and y c  are very small. The deterioration in the precision of the detection of the reference positions x c  and y c  can be prevented still more reliably, and furthermore, the time required for the sensing can be shortened considerably. 
     A thirteenth aspect of the invention is directed to the recording apparatus according to any of the tenth to twelfth aspects, wherein the first detected line is orthogonal to the primary scanning direction, the second detected line is orthogonal to the secondary scanning direction, and the sensor detects the first detected line which is orthogonal to the primary scanning direction and the second detected line which is orthogonal to the secondary scanning direction. 
     According to the aspect, the first detected line is orthogonal to the primary scanning direction and the second detected line is orthogonal to the secondary scanning direction. Therefore, the first detected line and the second detected line can be detected easily and reliably. 
     A fourteenth aspect of the invention is directed to the recording apparatus according to any of the tenth to thirteenth aspects, wherein a reference position in execution of recording is calculated based on a result of the detection of the first detected line and the second detected line. 
     According to the aspect, the reference position in the execution of the recording can be obtained accurately in a short time. 
     A fifteenth aspect of the invention is directed to the recording apparatus according to the fourteenth aspect, wherein the medium takes a symmetrical shape in the primary scanning direction and the secondary scanning direction, and the reference position is a central position in the primary scanning direction and the secondary scanning direction of the medium. 
     According to the aspect, in the case in which the reference position in the execution of the recording is set to be the central position of the medium, the central position can be obtained accurately in a short time. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing an appearance of an apparatus body of a printer according to an embodiment of the invention, 
         FIG. 2  is a sectional side view showing the printer according to the embodiment of the invention, 
         FIG. 3  is a block diagram showing a control portion of the printer recording to the embodiment of the invention, 
         FIG. 4  is a plan view showing a tray recording to the embodiment of the invention, 
         FIG. 5  is a perspective view showing a tip of the tray recording to the embodiment of the invention, 
         FIG. 6  is a plan view showing a detected portion (a first embodiment), 
         FIG. 7  is a plan view showing the detected portion (a second embodiment), 
         FIG. 8  is a plan view showing the detected portion (a variant of the second embodiment), 
         FIG. 9  is a plan view showing the detected portion (a third embodiment), 
         FIG. 10  is a plan view showing the detected portion (a variant of the third embodiment), 
         FIG. 11  is a plan view showing the detected portion (a variant of the third embodiment), 
         FIG. 12  is a plan view showing the detected portion (a fourth embodiment), 
         FIG. 13  is a plan view showing the detected portion (a variant of the fourth embodiment), 
         FIG. 14  is a flowchart showing the contents of a sequence for obtaining the central coordinates of a set portion, 
         FIG. 15  is a flowchart showing the contents of the sequence for obtaining the central coordinates of the set portion, 
         FIG. 16  is a flowchart showing the contents of the sequence for obtaining the central coordinates of the set portion, 
         FIG. 17  is a plan view showing a tray recording to the embodiment of the invention, 
         FIG. 18  is a plan view showing the tray recording to the embodiment of the invention, 
         FIG. 19  is a plan view showing the tray recording to the embodiment of the invention, and 
         FIG. 20  is a plan view showing the tray recording to the embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An embodiment of the invention will be described below with reference to the drawings. With reference to  FIGS. 1 and 2 , description will be given to the summary of an ink jet printer (hereinafter referred to as a “printer”)  1  as an example of a recording apparatus according to the invention.  FIG. 1  is a perspective view showing an appearance of an apparatus body of the printer  1  (a state in which an exterior case is removed),  FIG. 2  is a sectional side view showing the same, and  FIG. 3  is a block diagram mainly showing a driving control portion  60 . In the following, a rightward direction (a forward side of the printer) and a leftward direction (a rearward side of the printer) in  FIG. 2  will be referred to as a “downstream side” and an “upstream side” of a transport path for a paper or a tray, respectively. 
     The printer  1  comprises, in a rear part, a feeding device  2  capable of setting a recording paper (mainly, a cut-form paper which will be hereinafter referred to as a “paper P”) according to an example of a “medium to be recorded” and a “medium to be ejected” in an inclination posture, and feeds the paper P from the feeding device  2  toward a transport roller  4  on the downstream side. The paper P thus fed is transported to recording means  3  on the downstream side by means of the transport roller  4  so that recording is executed. The transport roller  4  also transports a tray  100  which will be described below, and the recording means  3  executes the recording to a label surface of an optical disc D to be a thin plate-shaped member (a medium) set to the tray  100 . The paper P or the optical disc D (the tray  100 ) subjected to the recording by the recording means  3  is discharged to a forward part of the apparatus by means of a discharge roller  5  on the downstream side. 
     Components provided on a paper transport path of the printer  1  will be described below in more detail. The feeding device  2  is constituted to include a hopper  11 , a feed roller  12 , a retard roller  13  and a return lever  14 . 
     The hopper  11  is formed by a plate-shaped member and is constituted rotatably around a rotation fulcrum (not shown) in an upper part, and is rotated to cause the paper P supported on the hopper  11  in the inclination posture to come in pressure contact with the feed roller  12  or to separate from the feed roller  12 . The feed roller  12  takes a shape of almost D seen from a side and feeds, to the downstream side, the paper P in an uppermost part which comes in pressure contact through a circular arc portion thereof, while it is controlled in such a manner that a flat portion thereof is opposed to the paper P as shown in order not to generate a transport load during the tranport of the paper P through the transport roller  4  after the paper P is fed. 
     The retard roller  13  is provided to freely come in pressure contact with the circular arc portion of the feed roller  12 . The retard roller  13  is driven and rotated (clockwise in  FIG. 2 ) in contact with the paper P when the overlapping feed of the paper P is not generated but only one paper P is fed, and is brought into a stop state without a rotation because a coefficient of friction between the papers is lower than that between the paper P and the retard roller  13  when a plurality of papers P is present between the feed roller  12  and the retard roller  13 . Accordingly, succeeding papers P to be fed with an overlap together with the uppermost paper P to be fed are not moved from the retard roller  13  toward the downstream side so that the overlapping feed can be prevented. The return lever  14  is provided rotatably and has the function of returning the succeeding papers P to be fed with an overlap onto the hopper  11 . 
     A paper sensor  81  ( FIG. 3 ) for detecting the passage of the paper P and a guide roller  26  for forming a feeding posture of the paper P and preventing the contact of the paper P with the feed roller  12  to relieve the transport load are provided between the feeding device  2  and the transport roller  4 . In the embodiment, the guide roller  26  is supported pivotally so as to be freely rotatable at an end on an upstream side of an upper paper guide  24 . 
     The transport roller  4  provided on the downstream side of the feeding device  2  is constituted to include a transport driving roller  30  to be rotated and driven by means of a motor and a transport driven roller  31  to be driven and rotated in pressure contact with the transport driving roller  30 . The transport driving roller  30  is formed to include a sticking layer obtained by dispersing a wear-resistant particle almost uniformly into an outer peripheral surface of a metal shaft extended in a direction of a width of the paper, and a plurality of transport driven rollers  31  having outer peripheral surfaces formed by a material having a low friction such as elastomer is disposed in an axial direction of the transport driving roller  30 . 
     Moreover, two transport driven rollers  31  are supported pivotally at an end on the downstream side of one upper paper guide  24  so as to be freely rotatable in the embodiment, and three upper paper guides  24  are provided in the direction of the width of the paper as shown in  FIG. 1 . Furthermore, the upper paper guide  24  has a shaft  24   a  supported pivotally on a main frame  23  so that it is provided to be rockable around the shaft  24   a  through the paper transport path seen from a side, and furthermore, is energized by means of a coiled spring  25  in such a direction that the transport driven roller  31  comes in pressure contact with the transport driving roller  30 . 
     Moreover, the transport driving roller  31  is rotated and driven by means of a secondary scan driving portion  59 . More specifically, the secondary scan driving portion  59  executes the secondary scanning feed of the paper P (and the tray  100  which will be described below). 
     The paper P reaching the transport roller  4  is transported in a nipping state between the transport driving roller  30  and the transport driven roller  31  to the recording means  3  on the downstream side by the rotation of the transport driving roller  30 . Moreover, the tray  100  which will be described below is also transported in the nipping state between the transport driving roller  30  and the transport driven roller  31  to the recording means  3  on the downstream side by the rotation of the transport driving roller  30 . 
     The recording means  3  is constituted to include an ink jet recording head (hereinafter referred to as a “recording head”)  36  and a lower paper guide  37  provided opposite to the recording head  36 . The recording head  36  is provided in a bottom part of a carriage  33 , and the carriage  33  is provided to be guided by means of a carriage guide shaft  34  extended in a primary scanning direction (a double-sided direction of a paper in  FIG. 2 ), and furthermore, is reciprocated in the primary scanning direction by means of a primary scan driving portion  57 . More specifically, the primary scan driving portion  57  executes a primary scan for the recording head  36  (and a PW sensor  80  which will be described below). Moreover, a head driving portion  58  drives the recording head  36  in the middle of the primary scan, thereby executing the recording to the paper P (and the optical disc D which will be described below). The carriage  33  mounts an ink cartridge  35  which is independent for each of a plurality of colors, and an ink is supplied from the ink cartridge  35  to the recording head  36 . 
     A rib extended in a secondary scanning direction is formed on an opposed surface to the recording head  36  and a concave portion  37   a  into which the ink is to be thrown away is formed in the lower paper guide  37  for defining a distance between the paper P and the recording head  36 . The ink discharged to a region getting out of the end of the paper P is thrown away into the concave portion  37   a  so that so-called marginless printing for carrying out printing over the end of the paper P without a margin is executed. 
     Successively, a guide roller  43  and the discharge roller  5  are provided on the downstream side of the recording head  36 . The guide roller  43  fulfills the function of preventing a rise in the paper P from the lower paper guide  37  and maintaining the distance between the paper P and the recording head  36  to be constant. The discharge roller  5  is constituted to include a discharge driving roller  41  to be rotated and driven through a PF motor  164  ( FIG. 3 ) and a discharge driven roller  42  to be driven and rotated in contact with the discharge driving roller  41 . In the embodiment, a plurality of discharge driving rollers  41  which is formed by rubber rollers is provided in an axial direction of a shaft member to be rotated and driven. 
     Moreover, the discharge driven roller  42  is formed by a toothed roller having a plurality of teeth on an outer periphery. In addition, a paper discharge frame Assy  45  taking a long shape in the primary scanning direction is provided with a plurality of discharge driven rollers  42  corresponding to a plurality of discharge driving rollers  41 . The paper P subjected to the recording by the recording means  3  is discharged toward the forward part of the apparatus (a stacker which is not shown) by the rotating and driving operation of the discharge driving roller  41  in a nipping state between the discharge driving roller  41  and the discharge driven roller  42 . 
     The paper discharge frame Assy  45  is provided to be freely displaced by release means (not shown) in order to take a contact position in which the discharge driven roller  42  comes in contact with the discharge driving roller  41  and a separating position in which the discharge driven roller  42  separates from the discharge driving roller  41 . 
     The components provided on the paper transport path have been described above. The printer  1  is constituted to freely carry out ink jet recording directly over the label surface of the optical disc (the thin plate-shaped member) such as a CD-R in addition to the cut-form paper acting as the medium. As shown in  FIG. 1 , the optical disc D acting as the medium is set to the tray  100  taking the shape of a plate and is transported through a linear tray transport path in the printer  1  in this condition. The tray  100  is constituted separately from the printer  1  and is supported by a tray guide  7  provided in the forward part of the printer  7 , and at the same time, is manually inserted into the tray transport path toward the rear side (upstream side) of the printer  1  and is then fed in the secondary scanning direction by means of the transport roller  4 . A structure of the tray  100  will be described below in detail. 
     With reference to  FIG. 3 , next, description will be given to a driving control portion  60  for executing a predetermined recording method by controlling each of the primary scan driving portion  57 , the head driving portion  58 , the secondary scan driving portion  59  and peripheral structures thereof. The driving control portion  60  is constituted to freely transmit and receive data together with a host computer  150  for transmitting print information (print data) to the printer  1 , and includes an IF  61  to be an interface with the host computer  150 , an ASIC  62 , an RAM  63 , a PROM  64  and an EEPROM  65 , a CPU  66 , a timer IC  67 , a DC unit  68 , a transporting motor (PF motor) driver  71 , a carriage motor (CR motor) driver  70 , and a head driver  69 . 
     The CPU  66  carries out a calculation processing for executing a control program of the printer  1  and other necessary calculation processings, and the timer IC  67  generates a cyclic interruption signal which is required for various processings with respect to the CPU  66 . The ASIC  62  serves to control a printing resolution and a driving waveform of the ink jet recording head  25  based on print data to be transmitted from the host computer  150  through the IF  61 . The RAM  63  is used as a work area for the ASIC  62  and the CPU  66  and a primary storage area for other data, and the RROM  64  and the EEPROM  65  store various control programs (firmware) required for controlling the printer  1  and necessary data for a processing. 
     The DC unit  68  is a control circuit for controlling the speeds of the DC motors (a CR motor  73  and the PF motor  164 ), and has a PID control portion, an acceleration control portion and a PWM control circuit which are not shown. The DC unit  68  carries out various calculations for controlling the speeds of the DC motors based on a control instruction sent from the CPU  66  or a signal output from detecting means such as a rotary encoder  78 , a linear encoder  79 , the paper sensor  81  for detecting a passage of the recording paper P or the PW sensor  80 , and sends a signal to the CR motor driver  70  and the PF motor driver  71 . 
     The PF motor driver  71  drives and controls the PF motor  164  to be the “motor for a transport driving roller” under the control of the DC unit  68 . The PF motor  164  rotates a plurality of driving targets, that is, the feed roller  13 , the transport driving roller  30  and the discharge driving roller  41  in the embodiment. 
     The CR motor driver  70  drives and controls the CR motor  73  to be the “motor for a carriage” under the control of the DC unit  68 , thereby reciprocating the carriage  33  in the primary scanning direction or stopping and holding the carriage  33 . The head driver  69  drives and controls the recording head  25  in accordance with print data transmitted from the host computer  150  under the control of the CPU  66 . 
     A detection signal sent from the paper sensor  81  for detecting a start end and a termination of the paper P to be transported, a signal output from the rotary encoder  78  for detecting the amount, direction and speed of the rotation of the PF motor  164 , and a signal output from the linear encoder  79  for detecting an absolute position in the primary scanning direction of the carriage  33  are given to the CPU  66  and the DC unit  68 . Moreover, a signal output from the PW sensor  80  is also given to the CPU  66  and the DC unit  68 . 
     The PW sensor  80  is an optical sensor provided in the bottom part of the carriage  33  and is constituted to include a light emitting portion (not shown) for emitting a light toward the paper P or the tray  100 , and a light receiving portion (not shown) for receiving a light reflected from the paper P or the tray  100 , and detects a difference in a reflectance on the recording paper P or a difference in a reflectance on the tray  100 . Consequently, the control portion  60  detects the presence of the paper P and the width of the paper P with the sensing of the PW sensor  80 . 
     When the PW sensor  80  senses a detected portion (which will be described below) provided on the tray  100  as will be described below, moreover, the control portion  60  calculates a central position of a set portion  102  (which will be described below) in the tray  100 . Based on information about the central position thus detected, a position of a recording region with the primary scanning direction and the secondary scanning direction set to be coordinate systems is determined. 
     The rotary encoder  78  includes a disk-shaped scale (not shown) having a large number of light transmitting portions in an outer peripheral part and a detecting portion (not shown) having a light emitting portion for emitting a light to the light transmitting portion and a light receiving portion for receiving a light passing through the light transmitting portion, and the detecting portion outputs a rise signal and a fall signal which are generated by the light passing through the light transmitting portion in accordance with a rotation of the disk-shaped scale and the driving control portion  60  receives the signal output from the rotary encoder  78 , thereby detecting the amount, speed and direction of the rotation of the transport driving roller  30 . Consequently, it is possible to execute a feed control (a secondary scanning feed) of the paper P or the tray  100  which is intended. 
     The linear encoder  79  includes a sign plate  79   b  which is long in the primary scanning direction and a detecting portion  79   a  having a light emitting portion for emitting a light to a plurality of light transmitting portions formed in the primary scanning direction and a light receiving portion for receiving a light passing through the light transmitting portion in the sign plate  79   b . The detecting portion  79   a  outputs a rise signal and a fall signal which are generated by the light passing through the light transmitting portion, and the driving control portion  60  receives the signal output from the detecting portion  79   a , thereby detecting a position in the primary scanning direction of the carriage  33  (that is, the PW sensor  80 ). 
     The PF motor driver  71  and the PF motor  164  constitute the secondary scan driving portion  59  shown in  FIG. 1 , the CR motor driver  70  and the CR motor  73  constitute the primary scan driving portion  57 , and the head driver  69  constitutes the head driving portion  58 . 
     The summary of the printer  1  has been described above, and the structure of the tray  100  will be described below in detail with reference to  FIGS. 4 and 5 .  FIG. 4  is a plan view showing the tray  100  and  FIG. 5  is a perspective view showing an appearance of a tip of the tray  100 . 
     As shown in  FIG. 4 , the tray  100  has a rectangular shape seen on a plane and takes a shape of a plate which can be nipped between the transport driving roller  30  and the transport driven roller  31 , and furthermore, can carry out the secondary scanning feed with the rotation of the transport driving roller  30 . 
     The tray  100  is formed integrally by a resin material in order to include a tray body  101  and the set portion  102 . The set portion  102  is constituted by a concave portion taking a circular shape seen on a plane as shown. A convex portion  103  to be a “fitting portion” is formed on the center of the set portion  102 . When the optical disc D is set to the set portion  102 , a fitting hole (a central hole) Dh ( FIG. 1 ) of the optical disc D is fitted around the convex portion  103 . Consequently, a position of the optical disc D in the set portion  102  (the tray  100 ) is determined. Holes  104  and  104  formed around the set portion  102  are used for taking out (ejecting) the optical disc D. 
     A vertical direction in  FIG. 4  is set to be a direction of transport of the tray  100  (the secondary scanning direction). When the tray  100  is to be inserted (fed) into the transport path of the tray  100  through the tray guide  7  as described above, the tray  100  is inserted with an upper part of  FIG. 4  set to be a tip. More specifically, the reference numeral  106  denotes a tip of the tray  100 . Tongue piece portions  107  and  107  are formed integrally with the tray  100  in the tip of the tray  100  so as to be protruded in the direction of insertion of the tray  100  as shown in  FIG. 5 . 
     The tongue piece portion  107  is tapered toward the tip and has a bottom face to form a flat surface together with the bottom face of the tray body  101  as shown in  FIG. 5 . Moreover, the tip  106  of the tray  100  is also formed to be tapered toward the tip in the same manner as the tongue piece portion  107 . 
     The tongue piece portion  107  has the following functions and advantages. More specifically, when the tray  100  is to be inserted into the transport path for the tray  100 , the tip  106  of the tray  100  is set to be a head and the tray  100  is thus inserted toward the rear side of the printer  1  through the tray guide  7 . 
     In order to feed the tray  100  in the secondary scanning direction by means of the transport driving roller  30  and the transport driven roller  31 , it is necessary to insert the tip  106  of the tray  100  into a portion between the transport driving roller  30  and the transport driven roller  31 . However, the tongue piece portion  107  is formed on the tip  106  of the tray  100 . When the tray  100  is fed toward the transport roller  4  by feeding means which is not shown, therefore, the tongue piece portion  107  enters the portion between the transport driving roller  30  and the transport driven roller  31 . Consequently, the tip  106  of the tray  100  then enters the portion between the transport driving roller  30  and the transport driven roller  31  so that the tray  100  is nipped between both of the rollers soon. 
     More specifically, an area of the tip of the tray  100  (seen on a plane) is reduced very greatly by the tongue piece portion  107 . Therefore, the tip  106  of the tray  100  can easily be caused to enter the portion between the transport driving roller  30  and the transport driven roller  31  by a small force. Accordingly, it is possible to cause the tray  100  to enter the portion between the transport driving roller  30  and the transport driven roller  31  without using means for separating (releasing) the transport driven roller  31  from the transport driving roller  30 . 
     As shown in  FIGS. 4 and 5 , subsequently, a detected portion  105 A to be detected by the PW sensor  80  is formed in the convex portion  103 . The detected portion  105 A (in the same manner as detected portions  105 B,  105 C and  105 D which will be described below) is formed by a hole penetrating through the tray body  101 . Consequently, a difference is made on a reflectivity at the inside and outside (the convex portion  103 ) of the detected portion  105 A. More specifically, the detected portion  105 A takes a shape of a square or a rectangle (one plane figure) constituted by a first detected line  108 A and a third detected line  108 C which are orthogonal to the primary scanning direction (a transverse direction in  FIGS. 4 ,  6  to  13 , and  17  to  20 ) and a second detected line  108 B and a fourth detected line  108 D which are orthogonal to the secondary scanning direction (a vertical direction in  FIGS. 4 ,  6  to  13 , and  17  to  20 ) which are formed by boundary lines between regions (the inside and outside of the hole) having different reflectivities as shown in  FIG. 6 . The “detected line” implies a boundary line between regions having different reflectivities which can be detected by the PW sensor  80 . 
     Moreover, the position in the primary scanning direction of the tray  100  is regulated by means of the tray guide  7 . Therefore, the control portion  60  ( FIG. 3 ) can previously hold information about a position in the primary scanning direction of the detected portion  105 A (the convex portion  103 ), and furthermore, can obtain information about a position in the secondary scanning direction of the detected portion  105 A (the convex portion  103 ) by detecting a change in the reflectance in the passage of the tip  106  of the tray  100  through the PW sensor  80 , for example. The tray  100  may be separately provided with a special detected portion (a reflecting mark) for knowing the position in the secondary scanning direction of the detected portion  105 A. Moreover, the control portion  60  can previously hold the information about the position in the primary scanning direction of the detected portion  105 A (the convex portion  103 ). By placing the PW sensor  80  in that position and then feeding the tray  100  in the secondary scanning direction, therefore, it is possible to directly detect the detected portion  105 A, thereby obtaining the information about the position in the secondary scanning direction of the detected portion  105 A. 
     The role of the detected portion  105 A will be described below in detail with reference to  FIGS. 6 to 16 .  FIGS. 6 ,  7 ,  9 ,  12  and  13  are plan views showing the detected portion  105 A, and  FIGS. 8 ,  10  and  11  are plan views showing the detected portions  105 B,  105 C and  105 D according to a variant of the detected portion  105 A respectively. Moreover,  FIGS. 14 to 16  are flowcharts showing the contents of a sequence for obtaining position coordinates of a center c of the set portion  102 . 
     When the recording is to be executed over the label surface of the optical disc D set to the tray  100 , a region over which the recording is to be executed is set based on the position coordinates of the center (indicated as “c” in  FIGS. 6 to 13 ) of the set portion  102  (the convex portion  103 ). The position coordinates are obtained by driving the carriage  33  (the CR motor  73 ) to trace the detected portion  105 A (or the detected portions  105 B to  105 D which will be described below) in the primary scanning direction through the PW sensor  80  and driving the transport driving roller  30  (the PF motor  164 ) to trace the detected portion  105 A (or the detected portions  105 B to  105 D which will be described below) in the secondary scanning direction through the PW sensor  80 . In the following, coordinates in the primary scanning direction and the secondary scanning direction of the center c (which will be properly referred to as an “x direction” and a “y direction”) are represented by x c  and y c , respectively. 
     In  FIGS. 6 to 13 , arrows indicated as ( 1 ) to ( 4 ) represent a trace line and a direction thereof in the sensing carried out by the PW sensor  80 . 
     In a first embodiment shown in  FIG. 6 , the carriage  33  and the transport driving roller  31  are driven and controlled in such a manner that a trace line obtained in the sensing of the first detected line  108 A through the PW sensor  80  does not cross the convex portion  103  in the x direction as shown in the arrow ( 1 ) and a trace line in the sensing of the second detected line  108 B through the PW sensor  80  does not cross the convex portion  103  in the y direction as shown in the arrow ( 2 ). 
     In a second embodiment shown in  FIG. 7 , the carriage  33  and the transport driving roller  31  are driven and controlled in such a manner that the trace line of the PW sensor  80  does not cross the convex portion  103  in the same manner as in the first embodiment but particularly crosses the first detected line  108 A and then crosses the second detected line  108 B without getting out of the convex portion  103  (and furthermore, the detected portion  105 A) in the embodiment as shown in the arrows ( 1 ) and ( 2 ). 
       FIG. 14  shows a procedure for obtaining the coordinates x c  and y c  through the sensing of the PW sensor  80 . A coordinate x d  in the primary scanning direction of the first detected line  108 A is detected by a sensing ( 1 ) in the x direction (Step S 101 ) and a coordinate y d  in the secondary scanning direction of the second detected line  108 B is detected by a sensing ( 2 ) in the y direction (Step S 102 ). 
     As shown in  FIGS. 6 and 7 , the coordinate x d  and the center c are separated from each other by a distance x 1  in the x direction and the coordinate y d  and the center c are separated from each other by a distance y 1  in the y direction, and the values x 1  and y 1  are previously written to the ROM  64  or the EEPROM  65  ( FIG. 3 ). By detecting the coordinates x d  and y d , accordingly, it is possible to obtain the coordinate x c  in the x direction of the center c with x d −x 1  and to obtain the coordinate y c  in the y direction of the center c with y d −y 1  as shown in Step S 103  of  FIG. 14 . 
     As described above, in the first and second embodiments shown in  FIGS. 6 and 7 , the carriage  33  and the transport driving roller  31  are driven and controlled in such a manner that the trace line of the PW sensor  80  does not cross the convex portion  103 . In the second embodiment shown in  FIG. 7 , moreover, the carriage  33  and the transport driving roller  31  are driven and controlled in such a manner that the trace line crosses the first detected line  108 A and then crosses the second detected line  108 B without getting out of the convex portion  103  (and furthermore, the detected portion  105 A). 
     In any case, therefore, it is sufficient that the amount of the movement of the carriage  33  and the amount of the secondary scanning feed of the tray  100  are small, a deterioration in precision in the detection of the coordinate x c  in the x direction and the coordinate y c  in the y direction of the center c can be prevented still more reliably, and furthermore, it is possible to shorten a time required for the sensing of the PW sensor  80  when obtaining the position of the center c. In particular, it is sufficient that the trace line of the PW sensor  80  is very short in the second embodiment. Therefore, it is possible to shorten the time required for the sensing still more greatly. 
     In the first and second embodiments, the two lines, that is, the first detected line  108 A and the second detected line  108 B are detected. Therefore, it is also possible to form the detected portion  105 A by a right triangle as indicated by  105 B in  FIG. 8 . Consequently, it is sufficient that the area of the detected portion (hole) is small, and a strength of the convex portion  103  can be thus enhanced. 
     In the first and second embodiments, moreover, it is also possible to carry out the same sensing by using two other detected lines, that is, the third detected line  108 C and the fourth detected line  108 D. Thus, the third detected line  108 C and the fourth detected line  108 D are further provided in addition to the first detected line  108 A and the second detected line  108 B. Therefore, it is possible to enhance the degree of freedom of a control. 
     In a third embodiment shown in  FIG. 9 , next, a coordinate x d1  in an x direction of a first detected line  108 A and a coordinate x d2  in the x direction of a third detected line  108 C are used to obtain a coordinate x c  in the x direction of a center c. In more detail, as shown in  FIG. 15 , the coordinate x d1  in the x direction of the first detected line  108 A is detected by a first sensing ( 1 ) in the x direction (Step S 201 ) and the coordinate x d2  in the x direction of the third detected line  108 C is detected by a second sensing ( 2 ) in the x direction (Step S 202 ). Then, a coordinate y d  in a y direction of a second detected line  108 B is detected by a sensing ( 3 ) in the y direction (Step S 203 ). 
     By detecting the coordinates x d1 , x d2  and y d , accordingly, the coordinate x c  in the x direction of the center c can be obtained with (x d1 +x d2 )/2 and a coordinate y c  in the y direction of the center c can be obtained with y d −y 1  as shown in Step S 204  of  FIG. 15 . 
     As described above, the coordinate x c  in the x direction of the center c is obtained by setting two positions, that is, a position of the first detected line  108 A and that of the third detected line  108 C as references. Also in the case in which precision in detection of the first detected line  108 A or the third detected line  108 C is deteriorated, therefore, it is possible to reduce an error (by half). 
     In the embodiment, thus, the center c is assumed to be positioned between the first detected line  108 A and the third detected line  108 C. For this reason, the center c is managed to be positioned between the first detected line  108 A and the third detected line  108 C in respect of the manufacture of the tray  100 . 
     Moreover, the detected portion  105 A can also be caused to take a semielliptical shape indicated as the reference numeral  105 C in  FIG. 10  or a shape of an isosceles triangle indicated as the reference numeral  105 D in  FIG. 11 . Accordingly, the detected line does not need to be orthogonal to the primary scanning direction or the secondary scanning direction. Moreover, the detected line does not need to be a straight line. 
     In a fourth embodiment shown in  FIG. 12 , next, a coordinate x d1  in an x direction of a first detected line  108 A and a coordinate x d2  in the x direction of a third detected line  108 C are used to obtain a coordinate x c  in the x direction of a center c, and a coordinate y d1  in a y direction of a second detected line  108 B and a coordinate y d2  in the y direction of a fourth detected line  108 D are used to obtain a coordinate y c  in the y direction of the center c. In more detail, as shown in  FIG. 16 , the coordinate y d2  in the y direction of the fourth detected line  108 D is detected by a sensing ( 1 ) in the y direction of the PW sensor  80  (Step S 301 ) and the coordinates x d1  in the x direction of the first detected line  108 A and the coordinates x d2  in the x direction of the third detected line  108 C are subsequently detected by sensings ( 2 ) and ( 3 ) in the x direction of the PW sensor  80  (Steps S 302  and S 303 ). Then, the coordinate y d1  in the y direction of the second detected line  108 B is detected by a sensing ( 4 ) in the y direction (Step S 304 ). 
     By detecting the coordinates x d1 , x d2 , y d1  and y d2 , accordingly, the coordinate x c  in the x direction of the center c can be obtained with (x d1 +x d2 )/2 and a coordinate y c  in the y direction of the center c can be obtained with (y d1 +y d2 )/2 as shown in Step S 305  of  FIG. 16 . 
     As described above, the coordinate x c  in the x direction of the center c is obtained by setting two positions, that is, a position of the first detected line  108 A and that of the third detected line  108 C as references, and the coordinate y c  in the y direction of the center c is obtained by setting two positions, that is, a position of the fourth detected line  108 D and that of the second detected line  108 B as references. Also in the case in which precision in detection of the respective detected lines is deteriorated, therefore, it is possible to reduce an error (by half). 
     Moreover, the secondary scanning feed of the tray  100  is set into one direction. Therefore, it is sufficient that the amount of the secondary scanning feed is small, and furthermore, the normal rotation/reverse rotation of the transport driving roller  30  does not need to be switched. Consequently, it is possible to detect the position of the second detected line  108 B or the fourth detected line  108 D more accurately without using a backlash of a gear in a power transmission system. However, this is not restricted but it is a matter of course that the position of the second detected line  108 B or the fourth detected line  108 D can also be detected by the secondary scanning feed in two directions shown in  FIG. 13 . 
     In the embodiment, thus, the center c is positioned between the first detected line  108 A and the third detected line  108 C, and the center c is positioned between the second detected line  108 B and the fourth detected line  108 D. Therefore, the center c is managed to be positioned between the first detected line  108 A and the third detected line  108 C and between the second detected line  108 B and the fourth detected line  108 D in respect of the manufacture of the tray  100 . 
     Also in both of the third and fourth embodiments described above, the carriage  33  and the transport driving roller  31  are driven and controlled in such a manner that the trace line of the PW sensor  80  does not cross the convex portion  103  in the same manner as in the first and second embodiments described above. Therefore, it is sufficient that the amount of the movement of the carriage  33  and the amount of the secondary scanning feed of the tray  100  are small, a deterioration in precision in the detection of the coordinate x c  in the x direction and the coordinate y c  in the y direction of the center c can be prevented still more reliably, and furthermore, it is possible to considerably shorten a time required for the sensing when obtaining the coordinate x c  in the x direction and the coordinate y c  in the y direction of the center c. 
     Although the detected portions  105 A to  105 D are formed in the convex portion  103  in the embodiment, it is also possible to provide them in any place of the tray body  101 . By providing the detected portions  105 A to  105 D in the convex portion  103 , the distance between the center c and the detected portions  105 A to  105 D is reduced. Consequently, it is possible to prevent a positional shift of the center c from being caused by a dimensional error of the tray  100 . 
     Another Embodiment of Tray 
     With reference to  FIGS. 17 to 20 , description will be given to another embodiment of the tray  100 .  FIGS. 17 to 20  are plan views showing a tray according to another embodiment. In  FIGS. 17 to 20 , the same components as those in the tray  100  have the same reference numerals and description thereof will be omitted. 
     In trays  100 A to  100 H shown in  FIGS. 17 to 20 , a detected portion  105 A is not disposed on an inside of a set portion  102  (a fitting portion  103 ) but an outside of the set portion  102 . 
     In the trays  100 A,  100 B,  100 C and  100 D shown in  FIGS. 17(A)  and (B) and  FIGS. 18(A)  and (B), particularly, the position of the detected portion  105 A is placed away from the central position in the primary scanning direction and that in the secondary scanning direction of the set portion  102  within a range of the formation of the set portion  102  in the primary scanning direction (to which the trays  100 B and  100 C correspond), the range of the formation of the set portion  102  in the secondary scanning direction (to which the trays  100 A,  100 B,  100 C and  100 D correspond) or the range of the formation of the set portion  102  in both the primary scanning direction and the secondary scanning direction (to which the trays  100 B and  100 C correspond). 
     More specifically, the tray  100  takes a square shape seen on a plane, and the set portion  102  takes a circular shape seen on the plane. In particular, therefore, the adjacent position to the set portion  102 , that is, the range of the formation of the set portion  102  in the primary scanning direction and the secondary scanning direction becomes a residual space. By utilizing such a residual space to dispose the detected portion  105 A, therefore, it is possible to prevent an increase in the size of the tray in the case in which the detected portion  105 A is disposed on the outside of the set portion  102 . 
     On the other hand, in the trays  100 E,  100 F,  100 G and  100 H shown in  FIGS. 19(A)  and (B) and  FIGS. 20(A)  and (B) respectively, the detected portion  105 A is positioned on the center in the primary scanning direction of the set portion  102  (to which the trays  100 E and  10 OF correspond) or the center in the secondary scanning direction (to which the trays  100 G and  100 H correspond). 
     In case of the trays  100 E and  100 F in which the detected portion  105 A is positioned on the center in the primary scanning direction of the set portion  102 , accordingly, a distance between a coordinate x c  in an x direction of a center c and the first detected line  108 A and third detected line  108 C (see  FIG. 6 ) is reduced. Consequently, it is possible to prevent a deterioration in precision in the detection of the coordinate x c  in the x direction of the center c. 
     In case of the trays  100 G and  100 H in which the detected portion  105 A is positioned on the center in the secondary scanning direction of the set portion  102 , moreover, a distance between a coordinate y c  in a y direction of the center c and the second detected line  108 B and fourth detected line  108 D is reduced. Consequently, it is possible to prevent a deterioration in precision in the detection of the coordinate y c  in the y direction of the center c. 
     While the description has been given to the example in which the invention is applied to the ink jet printer in the embodiments, the invention can also be applied to general liquid ejecting apparatuses. 
     The liquid ejecting apparatus is not restricted to recording apparatuses such as a printer, a copying machine and a facsimile in which a recording head of an ink jet type is used and an ink is discharged from the recording head to carry out recording to a medium but includes an apparatus for ejecting a liquid corresponding to uses from a liquid ejecting head corresponding to the recording head of an ink jet type onto a medium to be ejected corresponding to the medium in place of the ink and sticking the liquid to the medium to be ejected. 
     Examples of the liquid ejecting head include a coloring agent ejecting head to be used for manufacturing a color filter of a liquid crystal display, an electrode material (conducting paste) ejecting head to be used for forming an electrode of an organic EL display or a surface emitting display (FED), and furthermore, a bioorganism ejecting head to be used for manufacturing a biochip and a sample ejecting head to be a precision pipette in addition to the recording head.