Patent Publication Number: US-2007115314-A1

Title: Optical sensor, ink cartridge, and inkjet apparatus

Description:
BACKGROUND  
      1. Technical Field  
      The present invention relates to an optical sensor which can be utilized for identifying ink or the like, and an ink cartridge and an inkjet apparatus which include the optical sensor.  
      2. Related Art  
      In recent years, inkjet printers have become able to realize print qualities equal to of photographs. In addition, durability of printed matters has been improved. It is needless to say that such improvement results from the fact that mechanical performances of printers have been improved. On the other hand, such improvement largely benefits from the fact that performance and qualities of ink have been improved and color tone control technologies based on characteristics of each ink have been developed.  
      As such inkjet printers have become widely used, ink with various characteristics has been developed, and various types of ink have been introduced. To assure print qualities in the circumstances that various types of ink exist, it is necessary to identify ink.  
      As a method of identifying ink, for example, methods disclosed in the following first and second examples of related art have been known. In the first example of related art, light absorption characteristics of ink (color of ink) are identified by sequentially radiating light of R, G, and B toward ink inside the cartridge and comparing reflected light amounts thereof, and thereby whether or not the cartridge is set in the correct position is judged. In the second example of related art, a light receiving device and a light emitting device are arranged in such a manner that a light path traverses an ink flow path of a head, and presence of ink and the ink density are judged from a transmitted light amount of the light.  
      JP-A-2004-66743 and JP-A-2003-63013 are examples of related art.  
      In the optical sensors of the first and the second examples of related art, though rough color difference, rough density change or the like can be identified, it is difficult to assure strict ink qualities (print qualities) such as delicate color tone difference. Further, when other ink of the same color as the original ink with constituents different from of the original ink is used, the ink may be clogged in the nozzle hole or the ink may not be successfully discharged. Such problems are not limited to the case that the ink type is identified., but may commonly occur in the case that various subjects are identified.  
     SUMMARY  
      An advantage of some aspects of the invention is to provide an optical sensor which can precisely identify subjects such as ink, and an ink cartridge and an inkjet apparatus which include such an optical sensor.  
      According to a first aspect of the invention, there is provided an optical sensor for identifying a subject which contains a light absorption member with light absorption characteristics adjusted independently from of the subject, and for identifying the subject by optically identifying the light absorption member. The optical sensor includes a light emitting device for radiating reference light having a peak wavelength in an absorption wavelength region of the light absorption member to the subject, a light receiving device for receiving the reference light transmitted through the subject, and an integrated circuit board provided with the light emitting device and the light receiving device on a substrate face.  
      In the optical sensor according to the first aspect of the invention, the light absorption member (The light absorption member represents a coloring matter, a dye or the like which absorbs reference light in a certain wavelength. In this specification, the light absorption member may be referred to as “identification marker” to differentiate the light absorption member from a coloring matter or the like contained in ink or the like.) as an identification indicator is contained in the subject. The type or the like of the subject is identified by identifying the light absorption member. Here, the light absorption characteristics of the light absorption member are adjusted independently from the light absorption characteristics of the subject. For example, when the subject is ink used for printing, the light absorption characteristics of the light absorption member are adjusted independently from a color material contained in ink. Such light absorption characteristics include a light absorption peak wavelength, light absorbance and the like, which are different from the light absorption peak wavelength, the light absorbance and the like of a color material or the like contained in the subject. The light absorption characteristics of the light absorption member can be voluntarily controlled by the type and the amount (density) of the light absorption member. Therefore, compared to the existing method of identifying the type or the like of a subject by slight difference of light absorption characteristics of the subject itself, more precise identification is enabled.  
      In this case, a light absorption peak wavelength of the light absorption member may exist in the infrared region.  
      According to the above structure, for example, by using a light absorption member which has light absorbance close to 0 in the visible light region and has wavelength absorption characteristics in a state of a peak in the infrared region, the color of the subject may be maintained.  
      In this case, as the light absorption member, a plurality of light absorption members for absorbing light in a wavelength different from each other may be provided. Further, as the light emitting device, a plurality of light emitting devices having each peak wavelength corresponding to a light absorption peak wavelength of the plurality of light absorption members may be provided. Furthermore, the plurality of light absorption members may be identified based on a light absorbance ratio between the plurality of light absorption members in relation to the reference light or a density ratio between the plurality of light absorption members calculated therefrom, and the subject may be identified based on a result of the identification.  
      According to the above structure, compared to the case of identifying a light absorption member by using single reference light, accurate identification may be made. That is, when identification is made by using single reference light, light amount change between the reference light before being transmitted through a subject and after the reference light being transmitted through the subject is detected. In this case, the transmitted light amount could be largely changed due to absorption by a container accommodating the subject or the like, and therefore accurate identification could be difficult. Meanwhile, when identification is made based on the light absorbance ratio between the plurality of reference light (ratio between transmitted light amounts), absorption by a container or the like occurs at a similar ratio for all the reference light, and therefore a detection error as light absorbance ratio is not much large. Therefore, when the light absorbance ratio between each light absorption member (that is, density ratio between the light absorption members) is appropriately adjusted, the type or the like of the subject may be accurately identified with almost no detection error.  
      In this case, the light emitting device may be jointed to the integrated circuit board by a transcription technology.  
      The light emitting device obtained by such a transcription technology is extremely small (for example, an area of several hundred square μm or less, and a thickness of several ten μm or less). Therefore, an integrated circuit board with a compact structure and a high light emitting function can be realized.  
      Further, the light emitting device fabricated by the transcription technology is extremely thin. Therefore, for example, a vertical cavity surface emitting laser or a light emitting diode is fabricated as a light emitting device, not only the light on the top face side radiated as reference light, but also the light on the bottom face side radiated to the compound semiconductor layer side can be extracted outside. That is, when a compound semiconductor substrate formed with a light emitting section is directly utilized as a light emitting device without using the transcription technology, a thick compound semiconductor layer (compound semiconductor substrate) exists under an active layer, and therefore even when light is radiated from the active layer to an integrated circuit board side (compound semiconductor layer side), the light is mostly absorbed by the compound semiconductor layer, and is not able to be extracted outside. Therefore, in this case, when light radiated from the light emitting device is monitored and provided with Auto Power Control (APC), a special light receiving optical system for monitoring which performs, for example, reflecting part of the reference light radiated to the top face side (opposite side of the integrated circuit substrate) becomes necessary.  
      Meanwhile, in the case of the light emitting device fabricated by the transcription technology, the light emitting device is formed by exfoliating the surface section of a compound semiconductor substrate. Therefore, the compound semiconductor layer becomes extremely thin, and the light radiated to the integrated circuit board side is hardly absorbed by the compound semiconductor layer and may be extracted outside. Therefore, when a light receiving device for monitoring such light is provided on the integrated circuit board side, APC may be easily performed without providing a special light receiving optical system. Furthermore, such light is useless light which should be originally absorbed by the compound semiconductor substrate. Therefore, by utilizing such light as monitor light, light may be utilized effectively.  
      Further, the substrate used for forming the light emitting device (a compound semiconductor substrate or the like) can be reutilized repeatedly. Therefore, the cost of the light emitting device itself may be sufficiently reduced.  
      In this case, the light emitting device may be made of a vertical cavity surface emitting laser or a light emitting diode.  
      According to the above structure, since the wavelength width of radiated light is narrow and the wavelength can be selected accurately, reference light which is favorably suitable may be obtained. In addition, such light is suitable as reference light for measuring light absorption and transmission since spread of radiated light is small and directivity thereof is high. Further, compared to the case using an edge emitting laser as a light emitting device, a more compact structure may be realized.  
      In this case, a light receiving device for monitoring which monitors the reference light radiated from the light emitting device to the integrated circuit board side may be provided in a section of the integrated circuit board where the light emitting device is jointed.  
      According to the above structure, light emitted to the integrated circuit board side which does not contribute to a sensor function may be utilized as light for monitoring.  
      In this case, a current control circuit for controlling a light emitting amount of the light emitting device based on a light amount of light received by the light receiving device for monitoring (monitor light) may be provided on the integrated circuit board.  
      According to the above structure, the emitted light amount of the light emitting device may be controlled in a desired range regardless of change of the ambient temperatures, time-series change such as deterioration of the device and the like. Further, since the current control circuit is arranged in the vicinity of the light emitting device or the light receiving device, control may be made speedier and more accurately based on the monitor light.  
      In this case, an amplification circuit for amplifying a signal of light received by the light receiving device for monitoring may be provided on the integrated circuit board.  
      According to the above structure, an emitted light amount of the light emitting device may be controlled more precisely.  
      In this case, the plurality of light emitting devices may radiate the reference light to the subject in the time sharing manner.  
      According to the above structure, the light receiving device may be common to the plurality of light emitting devices. Therefore, the optical sensor may be downsized.  
      In this case, a memory for storing a transmitted light amount of the reference light received by the light receiving device may be provided on the integrated circuit board.  
      According to the above structure, each transmitted light amount of each reference light may be easily compared.  
      In this case, the light receiving device may be directly formed on the integrated circuit board by a semiconductor film forming technology.  
      According to the above structure, compared to the case that the light receiving device is transcription-arranged by using a transcription technology, a light receiving device with larger area may be formed. Therefore, in the case that a light receiving device is common to a plurality of light emitting devices, reference light may be easily received, and the sensitivity may become favorable.  
      in this case, the integrated circuit board may be mounted on a printed wiring insulating substrate.  
      According to the above structure, handling characteristics of the optical sensor may be improved. For example, when the insulating substrate is a flexible film substrate, such film substrate may be wound around a container or the like which accommodates the subject. Thereby, a small optical sensor with a small mounting area may be realized.  
      In this case, the light emitting device or the light receiving device may be sealed by a resin which transmits the reference light.  
      According to the above structure, the light emitting device or the light receiving device may be protected from moisture, oxygen or the like, and mechanical strength of the optical sensor may be improved.  
      According to a second aspect of the invention, an ink cartridge includes the optical sensor according to the first aspect of the invention. In the ink cartridge, the optical sensor identifies ink accommodated in the ink cartridge as the subject.  
      According to the above structure, an ink cartridge in which the type of ink can be accurately identified and mounting wrong ink in an inkjet apparatus main body can be prevented may be provided.  
      In this case, the ink cartridge may be made of a member which transmits the reference light radiated from the light emitting device, and the optical sensor may be mounted on an outer wall of the ink cartridge.  
      According to the above structure, an ink cartridge in which handling the optical sensor is easy and which has a compact structure may be provided.  
      In this case, a resin having a refractive index equal to of the outer wall may be filled between the outer wall of the ink cartridge and the light emitting device or the light receiving device.  
      According to the above structure, light loss due to reflection or refraction on the outer wall interface may be reduced.  
      According to a third aspect of the invention, an inkjet apparatus includes the optical sensor of the first aspect of the invention or the ink cartridge of the second aspect of the invention. In the inkjet apparatus, the optical sensor identifies ink accommodated in the ink cartridge as the subject.  
      According to the above structure, an inkjet apparatus which can prevent lowering of print quality due to mounting a wrong ink cartridge, damage of the inkjet head due to supplying wrong ink or the like may be provided. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements.  
       FIG. 1  is a perspective view showing a schematic structure of an inkjet apparatus according to a first embodiment.  
       FIG. 2  is an exploded perspective view showing a main section structure of an ink cartridge provided in the inkjet apparatus.  
       FIG. 3  is a cross section of an optical sensor provided in the ink cartridge.  
       FIG. 4  is a cross section showing a main section structure of the optical sensor.  
       FIG. 5  is a block diagram showing an APC circuit provided on an integrated circuit board of the optical sensor.  
       FIG. 6  is a block diagram showing a control circuit of the optical sensor.  
       FIGS. 7A, 7B , and  7 C are charts for explaining a method of identifying ink by identification markers.  
       FIG. 8  is a view of a step for explaining a manufacturing method of the optical sensor.  
       FIG. 9  is a view of a step for explaining the manufacturing method of the optical sensor.  
       FIG. 10  is a view of a step for explaining the manufacturing method of the optical sensor.  
       FIG. 11  is a view of a step for explaining the manufacturing method of the optical sensor.  
       FIG. 12  is a view of a step for explaining the manufacturing method of the optical sensor.  
       FIG. 13  is a view of a step for explaining the manufacturing method of the optical sensor.  
       FIG. 14  is a view of a step for explaining the manufacturing method of the optical sensor.  
       FIG. 15  is a view of a step for explaining the manufacturing method of the optical sensor.  
       FIG. 16  is a view of a step for explaining the manufacturing method of the optical sensor.  
       FIG. 17  is a view of a step for explaining the manufacturing method of the optical sensor.  
       FIG. 18  is a cross section showing more preferable mode of the optical sensor.  
       FIG. 19  is a cross section showing other mode of the optical sensor.  
       FIG. 20  is an exploded perspective view showing a main section structure of an ink cartridge according to a second embodiment. 
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS  
      Embodiments of the invention will be described with reference to the drawings.  
      In the following respective drawings, scale sizes of respective layers and respective members are different from each other to show the respective layers and the respective members in proportions recognizable in the drawings.  
     First Embodiment  
      Inkjet Apparatus  
       FIG. 1  is a schematic perspective view of an inkjet apparatus including an ink cartridge according to a first embodiment of the invention.  FIG. 2  is an exploded perspective view showing a main section of a printing unit including the ink cartridge.  
      As shown in  FIG. 1 , an inkjet apparatus  100  includes a carriage  101  mounting an ink cartridge and an inkjet recording head  106 .  
      The carriage  101  supported by a guide member  102  is connected to a step motor  104  through a timing belt  103 , and can be reciprocated in parallel with a platen  105 . The inkjet recording head  106  is mounted on the bottom face of the carriage  101 . A printing unit  107  is removably mounted on the top face of the carriage  101 .  
      As shown in  FIG. 2 , the printing unit  107  includes an ink cartridge  110  and the carriage  101  mounting the ink cartridge  110 .  
      The carriage  101  is formed of an open-top box. The inkjet recording head  106  (hereinafter simply referred to as head) is provided on the bottom face of the carriage  101  which is opposed to a recording sheet  109  (refer to  FIG. 1 ). A plurality of ink supply styluses  108  are provided in the section of the head  106  which is opposed to a supply port  112  on the bottom face of the ink cartridge  110 . The ink supply styluses  108  are inserted in the supply port  112  and receive ink supply from the ink cartridge  110 . The ink supplied to the ink supply styluses  108  is guided to a nozzle (not shown) of the head  106  through an unshown filter.  
      An optical sensor  111  for identifying ink inside the ink cartridge  110  is mounted on an outer wall  1 . 10 a of the ink cartridge  110 .  
      The optical sensor  111  has a light emitting device  113  for radiating reference light to ink  120  inside the ink cartridge  110 , a light receiving device  114  for receiving the reference light transmitted through the ink  120  inside the ink cartridge  110 , an integrated circuit board  115  electrically connected to the light emitting device  113  and the light receiving device  114 , and a printed wiring board  116  electrically connected to the integrated circuit board  115 .  
      The optical sensor  111  identifies the type or the like of the ink  120  by radiating reference light to the ink  120  accommodated in the ink cartridge  110  and measuring light absorbance thereof. In particular, the optical sensor  111  is characterized in that the optical sensor  111  identifies the type or the like of the ink  120  by using light having peak wavelengths corresponding to absorption wavelengths of identification markers  121  and  122  contained in the ink as reference light, and optically identifying the identification markers  121  and  122 .  
      Here, the identification marker means a light absorption member such as a coloring matter and a dye which shows light absorbance for light in a specific wavelength (reference light). The light absorption characteristics of the identification marker is adjusted independently from the light absorption characteristics of the ink  120 , which is a subject, that is, light absorption characteristics of a color material contained in a solvent of the ink or the ink. The light absorption characteristics includes a light absorption peak wavelength, light absorbance and the like, which are different from the light absorption peak wavelength, the light absorbance and the like of the color material or the like contained in the ink  120 . The light absorption characteristics of the identification marker can be voluntarily controlled by the type and the amount (density) of the identification marker.  
      As such an identification marker, a light absorption member with wavelength light absorption characteristics that the light absorbance is close to  0  in the visible light region so that color of the ink  120  is not impaired, and the peak is shown in the infrared region, is suitable. The ink  120  inside the ink cartridge  110  contains a plurality of (2 types in this embodiment) identification markers  121  and  122  with a light absorption peak wavelength different from each other.  
      The light emitting device  113  includes a plurality of light emitting devices  113   a  and  113   b  which radiate reference light in a wavelength different from each other according to multiple types of identification markers contained in the ink. As the light emitting devices  113   a  and  113   b,  a vertical cavity surface emitting laser is suitable. In particular, since in the vertical cavity surface emitting laser, a wavelength width of radiated light is narrow and the wavelength can be selected accurately, the vertical cavity surface emitting laser is highly suitable as reference light. In addition, the vertical cavity surface emitting laser is suitable as reference light for measuring light absorption and transmission since spread of radiated light thereof is small and directivity thereof is high. Further, compared to the case of using an edge emitting laser as a light emitting device, the vertical cavity surface emitting laser can realize a more compact structure. However, it is possible to use a light emitting diode instead of the vertical cavity surface emitting laser.  
      The light emitting devices  113   a  and  113   b  are semiconductor devices formed of a minute tile (minute tile-shaped device). For example, the light emitting devices  113   a  and  113   b  are a quadrangular platy member being 1 μm to 20 μm thick and being several ten μm to several hundred μm long vertically and horizontally. The light emitting devices  113   a  and  113   b  are adhered to the top face of the integrated circuit board  115  made of a silicon substrate or the like, that is, to the face which is a surface of the integrated circuit board  115  opposed to the outer wall of the ink cartridge  110 . The light emitting devices  113   a  and  113   b  are jointed to the integrated circuit board  115  by using a transcription technology called Surface Free Technology by Laser Ablation (SUFTLA, registered trademark).  
      As the light emitting devices  113   a  and  113   b,  a device having a peak wavelength corresponding to a light absorption peak wavelength of each corresponding identification marker is selected. For example, the first light emitting device  113   a  radiates reference light in 814 nm which is a light absorption peak wavelength of a first identification marker mixed in the ink (first wavelength). Meanwhile, the second light emitting device  113   b  radiates reference light in 870 nm which is a light absorption peak wavelength of a second identification marker (second wavelength). Here, the first light emitting device  113   a  which radiates the reference light in  814  nm can be fabricated by using, for example, GaAs quantum well as an active layer of a vertical cavity surface emitting laser. Further, the second light emitting device  113   b  which radiates the reference light in 870 nm can be fabricated by using a GaAs layer as an active layer of a vertical cavity surface emitting laser.  
      As another example, it is possible to use reference light in 850 nm as the first wavelength and reference light in 970 nm as the second wavelength. In this case, the first light emitting device  113   a  which radiates the reference light in 850 nm can be fabricated by using GaAs quantum well as an active layer of a vertical cavity surface emitting laser. Further, the second light emitting device  113   b  which radiates the reference light in  970  nm can be fabricated by using InGaAs quantum well as an active layer of a vertical cavity surface emitting laser.  
      The optical sensor  111  identifies the type or the like of the ink  120  by radiating the plurality of reference light in different peak wavelengths as above to the ink  120  inside the ink cartridge  110  through the outer wall of the ink cartridge  110  and comparing the intensity (that is, light absorbance) of the reference light transmitted through the ink  120  to each other. When such an identification method is adopted, the light absorption characteristics of the identification markers  121  and  122  are voluntarily controlled by the type and the amount of the identification markers  121  and  122 . Therefore, compared to the existing method in which the type or the like of the ink  120  is identified by a slight difference of the light absorption characteristics of the ink itself, more precise identification is enabled. Further, by accurately identifying the type of the ink  120 , that is, the characteristics of the ink  120 , color tone control corresponding to such identification is enabled, and the print quality can be assured. Further, when the ink cartridge  110  is wrongly mounted, users can be notified. Furthermore, the state that ink inside the ink cartridge  110  becomes vacant can be detected by change of the transmitted light amount.  
      The optical sensor  111  is mounted on the outer wall of the ink cartridge  110 . Therefore, as a material for the outer wall of the ink cartridge  110 , a material which sufficiently transmits reference light radiated from the light emitting device  113  is used. A mounting position of the optical sensor  111  can be selected as appropriate according to the shape of the ink cartridge  110  so that detecting ink end can be easily made and the remaining ink amount when detecting ink end is small as much as possible. For example, the mounting position of the optical sensor  111  is preferably in the vicinity of the bottom face of the ink cartridge  110 , in the vicinity of an ink outlet, or in the middle of the final flow path connected to the ink outlet.  
      The light receiving device  114  is a light receiving device common to the light emitting device  113   a  and the light emitting device  113   b.  For example, reference light radiated from the light emitting device  113   a  and the light emitting device  113   b  alternately enters the light receiving device  114  in the time-sharing manner. As the light receiving device  114 , a photodiode is suitable, but a phototransistor can be used as well.  
      Further, the light receiving device  114  is desirably formed directly on the integrated circuit board  115  by a semiconductor film forming technology. In the case of the light receiving device, a light receiving device with a sufficient performance can be formed on the silicon substrate. Therefore, it is not necessary to make transcription-arrangement by using a transcription technology as in the light emitting device. By directly forming the light receiving device on the integrated circuit board  115 , a light receiving device with a larger area than in the case of using a transcription technology such as SUFTIA can be formed. In particular, in this embodiment, the light receiving device is common to the plurality of light emitting devices. Therefore, by forming the light receiving device with a large area, reference light is easily received, and the sensitivity becomes favorable. However, it is possible that the light receiving device is transcription-arranged on the integrated circuit board  115  by a transcription technology.  
      In this embodiment, the light receiving device  114  and the light emitting devices  113   a  and  113   b  are arranged side by side on the same face which is the outer wall  110   a  of the ink cartridge. Therefore, a light reflector  117  which reflects light radiated from the light emitting devices  113   a  and  113   b  to the light receiving device  114  side is provided on an inner wall  110   b  of the ink cartridge  110  which is opposed to the outer wall  110   a.  That is, reference light radiated from the light emitting devices  113   a  and  113   b  is guided to the light receiving device  114  via the outer wall  110   a  of the ink cartridge  110 , the ink  120 , the light reflector  117 , the ink  120 , and the outer wall  110   a.  When the outer wall of the ink cartridge  110  is made of a material which sufficiently transmits the reference light, the light reflector  117  can be arranged on the outer wall of the ink cartridge  110 .  
      The integrated circuit board  115  is a board in which an integrated circuit having at least one function of a light receiving device for detecting ink light absorbance, a current control circuit, an amplification circuit, a judgement circuit, an I/O circuit, a nonvolatile memory and the like is formed on a silicon substrate. The integrated circuit board  115  may be a board in which a Thin Film Transistor (TFT) or the like is formed on a substrate such as a glass substrate and a plastic substrate instead of a silicon substrate. In this embodiment, the integrated circuit board  115  mounts the light receiving device  114  for detecting ink light absorbance, a current control circuit, an amplification circuit, an I/O circuit, a nonvolatile memory, and a controller circuit for comprehensively controlling the above circuits (refer to  FIG. 5  and  FIG. 6 ). Further., by adhering the light emitting devices  113   a  and  113   b  to a desired position of the surface of the integrated circuit board  115 , the light emitting devices  113   a  and  1113   b,  the light receiving device  114 , and the integrated circuit which structure the optical sensor  111  are united.  
      The integrated circuit board  115  is mounted on the printed wiring board  116  which is a printed wiring insulating substrate. As the printed wiring board  116 , a glass epoxy substrate, a Flexible Printed Circuit (FPC), plastic, glass or the like can be used. The glass epoxy substrate is suitably used since the glass epoxy substrate is easily handled and is not expensive. Examples of the FPC include a polyimide film, a glass cloth, and an aramid film, which are all thin and flexible, and thus are easily bent. Therefore, such a FPC can be wound around the outer wall of the ink cartridge  110 .  
      The printed wiring board  116  is mounted on the outer wall of the ink cartridge  110 . The printed wiring board  116  is provided with an electrical contact which is electrically connected to a control circuit  150  (refer to  FIG. 6 ) which is mounted on the inkjet apparatus main body when the ink cartridge  110  is mounted on the inkjet apparatus main body. The printed wiring substrate  116  can be powered from the inkjet apparatus main body or can provide and receive information through the electrical contact.  
       FIG. 3  is a view showing an enlarged joint section between the printed wiring board  116  and the ink cartridge  110 .  
      As shown in  FIG. 3 , the printed wiring board  116  is mounted on the outer wall of the ink cartridge  110  in such a manner that the light emitting device  1 . 13  and the light receiving device  114  are opposed to the ink cartridge  110  side. A resin  119  having a refractive index equal to of the outer wall  110   a  is filled between the outer wall  110   a  of the ink cartridge  110  and the light emitting devices  113   a,    113   b,  and the light receiving device  114 . Thereby, light loss due to reflection and refraction on the outer wall interface can be decreased.  
       FIG. 4  is a view showing an enlarged joint section between the integrated circuit board  115  and the light emitting devices  113   a  and  113   b.    
      As shown in  FIG. 4 , light receiving devices for monitoring  118   a  and  118   b  which monitor light amounts of light radiated from the light emitting devices  113   a  and  113   b  to the integrated circuit board  115  side are provided in the section of the integrated circuit board  115  where the two light emitting devices  113   a  and  113   b  are jointed. As the light receiving devices for monitoring  118   a  and  118   b,  a photodiode, a phototransistor or the like can be used. For example, the light receiving devices for monitoring  118   a  and  118   b  can be formed on the integrated circuit board  115  by, for example, the steps common to of the light receiving device  114  for detecting ink light absorbance (hereinafter referred to as light receiving device for detecting ink light absorbance). In this embodiment, the light emitting devices  113   a  and  113   b  are adhered on the light receiving devices for monitoring  118   a  and  118   b  provided on the integrated circuit board  115 .  
      A vertical cavity surface emitting laser or a light emitting diode as the light emitting devices  113   a  and  113   b  radiates light in the top face direction (in the opposite direction of the integrated circuit board  115 ). The vertical cavity surface emitting laser or the light emitting diode concurrently radiates light with intensity proportional to a light amount of the foregoing light in the bottom face direction (in the direction of the integrated circuit board  115 ). The intensity ratio between light La and Lb radiated in the top face direction and light Ma and Mb radiated in the bottom face direction is constant independently from the intensity, and a value thereof is determined by the structure design of the light emitting devices  113   a  and  113   b.  Therefore, when the intensity of the light Ma and Mb in the bottom face direction is measured at the light receiving devices for monitoring  118   a  and  118   b,  the intensity of the reference light La and Lb radiated in the top face direction can be found. By utilizing such a principle, Auto Power Control (APC) can be performed.  
       FIG. 5  is a block diagram for explaining the APC by a current control circuit  130 .  
      In  FIG. 5 , the light emitting device  113   a  is not particularly differentiated from the light emitting device  113   b,  and the both are referred to as the light emitting device  113 . Similarly, both the light receiving device for monitoring  118   a  and the light receiving device for monitoring  118   b  are referred to as the light receiving device for monitoring  118 . Further, light radiated in the top face direction (reference light) La and Lb is referred to as radiated light on the top face side L, and light radiated in the bottom face direction (monitor light) Ma and Mb is referred to as radiated light on the bottom face side M.  
      As described above, in the light emitting device  113 , the light M is also radiated in the bottom face direction, and the light M enters the light receiving device for monitoring  118 . A current proportional to the light output of the light emitting device  113  flows in the light receiving device for monitoring  118 . A monitor circuit  132  outputs an output control signal corresponding to a size of the current flowing in the light receiving device for monitoring  118  to a driver circuit  131 . Here, the monitor circuit  132  compares a given reference value to the size of the current flowing in the light receiving device for monitoring  118 , and generates the output control signal so that the current becomes a desired certain value, that is, so that the light output of the light emitting device  113  becomes a desired certain value. The driver circuit  131  drives the light emitting device  113  so that light output corresponds to the output control signal. Thereby, the light output of the light emitting device  113  can be kept at a desired certain value regardless of change of the ambient temperatures, time-series change and the like.  
      Next, a method of identifying ink by using the optical sensor  111  will be described with reference to  FIG. 2  and  FIG. 6 .  
       FIG. 6  is a block diagram for explaining the method of identifying ink.  
      In  FIG. 6 , a current control circuit for performing current control for the light emitting device  113   a  (first light emitting device) is referred to as a first current control circuit  130   a,  and a current control circuit for performing current control for the light emitting device  113   b  (second light emitting device) is referred to as a second current control circuit  130   b.    
      In the inkjet apparatus  100 , after the ink cartridge is mounted, or when an apparatus is started, or as a regular operation, a command of sensing is inputted from a CPU  152  of the inkjet apparatus main body to a controller circuit  151 .  
      First, the controller circuit  151  to which the sensing command has been inputted activates an amplification circuit  140  connected to the light receiving device  114  for detecting ink light absorbance.  
      Subsequently, the controller circuit  151  activates the first current control circuit  130   a  to make the first light emitting device  113   a  emit light. Thereby, the reference light La is radiated from the first light emitting device  113   a  to the ink  120  inside the ink cartridge  110  through the outer wall of the ink cartridge  110 .  
      Here, the peak wavelength of the reference light La approximately corresponds with the light absorption peak wavelength of the first identification marker  121  mixed in the ink  120 . The reference light La radiated to the ink  120  is dimmed at a ratio corresponding to the density of the first identification marker  121 , and only reference light Ra at a given ratio is inputted to the light receiving device  114  for detecting ink light absorbance. In the light receiving device  114  for detecting ink light absorbance, a current corresponding to a received light amount (first received light amount) of the reference light Ra is flown, which is detected as a monitor signal (first monitor signal).  
      The first received light amount detected at the light receiving device  114  for detecting ink light absorbance is stored in a nonvolatile memory  141  electrically connected to a judgement circuit  153 .  
      After the foregoing steps are finished, the controller circuit  151  stops the first current control circuit  130   a.    
      Next, the controller circuit  151  activates the second current control circuit  130   b  to make the second light emitting device  113   b  emit light. Thereby, the reference light Lb is radiated from the second light emitting device  113   b  to the ink  120  inside the ink cartridge  110  through the outer wall of the ink cartridge  110 .  
      Here, the peak wavelength of the reference light Lb approximately corresponds with the light absorption peak wavelength of the second identification marker  122  mixed in the ink  120 . The reference light Lb radiated to the ink  120  is dimmed at a ratio corresponding to the density of the second identification marker  122 , and only reference light Rb at a given ratio is inputted to the light receiving device  114  for detecting ink light absorbance. In the light receiving device  114 for detecting ink light absorbance, a current corresponding to a received light amount (second received light amount) of the reference light Rb is flown, which is detected as a monitor signal (second monitor signal).  
      The second received light amount detected at the light receiving device  114  for detecting ink light absorbance is stored in the nonvolatile memory  1 . 41  electrically connected to the judgement circuit  153 .  
      After the foregoing steps are finished, the controller circuit  151  stops the second current control circuit  130   b.    
      After transmitted light amounts of the reference light La and Lb are measured as above, the judgement circuit  153  compares the transmitted light amount of La to the transmitted light amount of Lb (compares the first received light amount to the second received light amount), and detects the type of the ink  120 , the remaining amount of the ink  120  and the like.  
       FIGS. 7A, 7B , and  7 C are charts for explaining a method of detecting a type of ink and a remaining amount of ink.  
      As shown in  FIGS. 7A, 7B , and  7 C, the first identification marker  121  and the second identification marker  122  have a light absorption peak wavelength in the wavelength region different from each other. In the examples of  FIGS. 7A, 7B , and  7 C, the light absorption peak wavelength of the first identification marker  121  is 814 nm which is the peak wavelength of the reference light La, and the light absorption peak wavelength of the second identification marker  122  is 870 nm which is the peak wavelength of the reference light Lb.  
      In the judgement circuit  153 , the light absorbance of the reference light La and the reference light Lb in the light absorption peak wavelengths (814 nm and 870 nm) is measured and the light absorbance ratio or the density ratio therefrom calculated between the first identification marker  121  and the second identification marker  122  is calculated. Calculated results are compared to a lookup table stored in the nonvolatile memory  141  to identify the type of the ink  120 .  
      For example, in the example of  FIG. 7A , the light absorbance ratio between the first identification marker  121  and the second identification marker  122  is approximately 1:2. In the example of  FIG. 7B , the light absorbance ratio between the first identification marker  121  and the second identification marker  122  is approximately 1:10. In the lookup table, the absorbance ratio or the density ratio therefrom calculated between the first identification marker  121  and the second identification marker  122  and the type of the ink  120  are stored in such a manner that such a ratio and the type of the ink  120  are shown correspondingly to each other. By comparing the information of the lookup table to the information of the measured received light amounts, the type of the ink  120  can be accurately identified.  
      The type of ink means a type of ink based on various characteristics of the ink  120  such as a color, a constituent, a manufacturing date, and a sell-by date. For example, the light absorbance ratio between the first identification marker  121  and the second identification marker  122  is specified as 1:2, 1:3, 1:4 and so on according to ink colors, that is, red ink, blue ink, green ink and so on. According to the specified ratio, the identification markers  121  and  122  at a given density are mixed in the ink  120 . Otherwise, the light absorbance ratio between the first identification marker  121  and the second identification marker  122  can be specified as  1 : 2 , 1:3 and so on according to the constituent type of ink, that is, pigment ink, dye ink and so on. In the lookup table, such information on the types of the ink  120  and such information on the light absorbance ratio and the like of the identification markers  121  and  122  are shown correspondingly in relation to one for one. However, in reality, there are other factors such as light absorption characteristics on the outer wall of the ink cartridge  110  and the reflection loss at the light reflector  117  and the like. Therefore, by considering the transmission loss of the reference light La and Lb, the light absorbance ratio and the like are calculated.  
      In this embodiment, one type of information (for example, color of ink) is obtained by using two types of the identification markers  121  and  122 . However, it is possible that three or more types of identification markers are used, and thereby a plurality types of information (for example, color of ink and constitution of ink) are concurrently detected. For example, in the case that three types of identification markers are used, it is possible that the color of the ink  120  is identified from the light absorbance ratio between the first identification marker and the second identification marker, and the constituent of the ink  120  is identified from the light absorbance ratio between the first identification marker and the third identification marker.  
      Next, in the example of  FIG. 7C , the light absorbance ratio between the first identification marker  121  and the second identification marker  122  is approximately 1:1. Each light absorbance is almost 0. It means that the reference light La and Lb is hardly absorbed by the ink  120 , that is, the remaining amount of the ink  120  on the light path of the reference light La and Lb is extremely small. Therefore, by detecting the light absorbance ratio or an absolute value of the light absorbance as above, information on the remaining amount of the ink  120  can be also obtained.  
      Descriptions will be given with reference to  FIG. 6  again. After information such as the type of ink and the remaining amount of ink is detected as above, the judgement circuit  153  outputs a result of the detected information (result of the type of ink, the ink end signal or the like) to the CPU  152  of the inkjet apparatus main body. In the inkjet apparatus  100 , when the ink  120  accommodated in the ink cartridge  110  is ink which does not adapt to the inkjet apparatus  100 , a notice such as a message is issued to users. For example, when the color of the ink  120  set in the cartridge holder is different from the originally planned color of ink, users are prompted to set the ink cartridge  110  in the cartridge holder suitable for the color of the ink cartridge  110 . When the constituent of the ink  120  is different from the originally planned constituent of ink in the inkjet apparatus  100 , users are prompted to set the ink cartridge  110  in which correct ink is accommodated. When the remaining amount of the ink  120  in the ink cartridge becomes small, users are prompted to replace the ink cartridge  110  with a new ink cartridge  110 .  
      Manufacturing Method of the Optical Sensor  
      Next, a manufacturing method of the optical sensor  111  will be described.  
      In the manufacturing method, descriptions will be given of the case that a compound semiconductor device is used as the light emitting devices  113   a  and  113   b,  which is jointed to a silicon LSI chip which is to become the integrated circuit board  115 . However, the type of the semiconductor device and the type of the LSI chip are not necessarily limited thereto. “Semiconductor substrate” in this embodiment means an object made of a semiconductor material. However, the semiconductor substrate is not limited to a platy substrate. “Semiconductor substrate” includes substrates formed of any shape as long as the substrate is made of a semiconductor material. Further, the light emitting devices  113   a  and  113   b  are referred to as the light emitting device (or minute tile-shaped device)  113 , and the light receiving devices for monitoring  118   a  and  118   b  are referred to as the light receiving device for monitoring  118 , except for the case where these elements are particularly distinguished.  
      Step 1  
       FIG. 8  is a schematic cross section showing step 1 of the manufacturing method of the optical sensor  111 .  
      In  FIG. 8 , a substrate  10  is a semiconductor substrate such as a gallium arsenic compound semiconductor substrate. A sacrifice  11  is provided as the lowermost layer in the substrate  10 . The sacrifice layer  11  is made of aluminum arsenic (AlAs), and is, for example, several hundred nm thick.  
      For example, a function layer  12  is provided as an upper layer of the sacrifice layer  11 . The function layer  12  is, for example, about 1 μm to 20 μm thick. A function section  13  is formed in the function layer  12 . The function section  13  structures an operation section of the light emitting devices  113   a  and  113   b.  As the function section  13 , for example, a light emitting diode (LED), a vertical cavity surface emitting laser (VCSEL), a photodiode (PD), a high electron mobility transistor (HEMT), a hetero bipolar transistor (HBT) and the like can be cited. Each function section  13  is a device formed by layering multiple epitaxial layers on the substrate  10 . In each function section  13 , an electrode is formed, and operation test is performed as well.  
      Step 2  
       FIG. 9  is a schematic cross section showing step 2 of the manufacturing method of the optical sensor  111 .  
      In this step, a separating groove  21  is formed to separate each function section  13  from each other. The separating groove  21  shall be a groove with a depth at least reaching the sacrifice layer  11 . For example, both the width and the depth of the separating groove shall be 10 μm to several hundred μm. Further, the separating groove  21  shall be a continuous groove with no dead end so that an after-mentioned selective etching solution flows through the separating groove  21 . Furthermore, the separating groove  21  is preferably formed in a state of a grid.  
      Further, by setting the distance between each separating groove  21  to several ten μm to several hundred μm, each function section  13  which is separated and formed by the separating groove  21  shall have an area of several ten to several hundred square μm. As a method of forming the separating groove  21 , a method by photolithography and wet etching, or a method by dry etching is used. Further, the separating groove  21  may be formed by U-shaped groove dicing in the range where no crack is generated in the substrate.  
      In forming the separating groove  21 , a sulfuric acid etching solution can be used for wet etching, and chlorine gas can be used for dry-etching. Since the separating groove  21  has large pattern dimensions and is not necessarily formed precisely, the etching mask does not have to be a photolithography. For example, as an etching mask, offset lithography can be used. Further, in forming the separating groove  21 , an orientation of the separating groove  21  in relation to a crystal orientation of the substrate  10  is important.  
      Step 3  
       FIG. 10  is a schematic cross section showing step 3 of the manufacturing method of the optical sensor  111 .  
      In this step, an intermediate transcription film  31  is adhered to the surface of the substrate  10  (function section  13  side). The intermediate transcription film  31  is a flexible strip-shaped film with the surface coated with an adhesive.  
      Step 4  
       FIG. 11  is a schematic cross section showing step 4 of the manufacturing method of the optical sensor  111 .  
      In this step, a selective etching solution  41  is injected in the separating groove  21 . In this step, only the sacrifice layer  11  is selectively etched. Therefore, as the selective etching solution  41 , a dilute hydrochloric acid which is highly selective for aluminum arsenic is used. As the selective etching solution  41 , dilute hydrofluoric acid can be also used. However, hydrochloric acid is more desirably used in view of selectivity.  
      Step 5  
       FIG. 12  is a schematic cross section showing step 5 of the manufacturing method of the optical sensor  111 .  
      In this step, after the selective etching solution  41  is injected in the separating groove  21  in step 4 and then a given time lapses, all the sacrifice layer  11  is selectively etched and removed from the substrate  10 . After that, pure water is injected in the separating groove  21  and in the region where the sacrifice layer has existed, which are rinsed with the pure water.  
      Step 6  
       FIG. 13  is a schematic cross section showing step 6 of the manufacturing method of the optical sensor  111 .  
      When the entire sacrifice layer  11  is etched in step 5, the function layer  12  is detached from the substrate  10 . In this step, by secluding the intermediate transcription film  31  from the substrate  10 , the function layer  12  adhered to the intermediate transcription film  31  is secluded from the substrate  10 .  
      Thereby, the function layer  12  formed with the function section  13  is separated by forming the separating groove  21  and etching the sacrifice layer  11 , formed into a semiconductor device in a given shape (for example, minute tile shape) (hereinafter referred to as “minute tile-shaped device  113 ), and held on the intermediate transcription film  31  by being adhered thereto. Here, the thickness of the function layer is preferably, for example, 1 μm to 8 μm, and the size (length and width) thereof is preferably, for example, several ten μm to several hundred μm. The minute tile-shaped device  113  herein formed is applied to the light emitting devices  113   a  and  113   b.    
      Further, the substrate  10  detached from the function layer  12  can be reutilized for forming the function section. When a plurality of sacrifice layers  11  are previously provided, the foregoing steps 1 to 6 can be repeatedly performed. By reutilizing the substrate  10 , the “minute tile-shaped device  113 ” can be repeatedly fabricated.  
      Step 7  
       FIG. 14  is a schematic cross section showing step 7 of the manufacturing method of the optical sensor  111 .  
      In this step, by moving the intermediate transcription film  31  to which the minute tile-shaped device  113  is adhered, the minute tile-shaped device  113  is aligned in a desired position of the final substrate  115 . Here, the final substrate  115  is made of a silicon semiconductor. The surface of the substrate is formed with the light receiving device  114  for detecting ink light absorbance and the light receiving device for monitoring  118 . A desired position of the final substrate  115  is coated with an adhesive  73  for adhering the minute tile-shaped device  113 . A section to which the minute tile-shaped device  113  is to be jointed, that is, a section on which the light receiving device for monitoring  118  is formed is coated with the adhesive  73 . In  FIG. 14 , only one light receiving device for monitoring  118  is shown. However, in reality, the light receiving device  118  is formed in each position on which the light emitting device  113   a  and the light emitting device  113   b  are mounted.  
      Step 8  
       FIG. 15  is a schematic cross section showing step 8 of the manufacturing method of the optical sensor  111 .  
      In this step, the minute tile-shaped device  113  aligned in a desired position of the final substrate  115  is pressed by a rear pressing pin  81  with the intermediate transcription film  31  in between and thereby jointed to the final substrate  115 . Here, the desired position is coated with the adhesive  73 . Therefore, the minute tile-shaped device  113  is adhered to the desired position of the final substrate  115 .  
      In this step, as a method of adhering the minute tile-shaped device  113  to the final substrate  115 , adhesive is used. However, other adhesion method may be used.  
      Step 9  
       FIG. 16  is a schematic cross section showing step 9 of the manufacturing method of the optical sensor  111 .  
      In this step, adhesive force of the intermediate transcription film  31  is diminished to exfoliate the intermediate transcription film  31  from the minute tile-shaped device  113 .  
      The adhesive used for the intermediate transcription film  31  shall be a UV cure adhesive or a heat curable adhesive. When the UV cure adhesive is used, the rear pressing pin  81  is made of a transparent material. By radiating ultraviolet (UV) from the end of the rear pressing pin  81 , the adhesive force of the intermediate transcription film  31  is diminished. When the heat curable adhesive is used, the rear pressing pin  81  is heated. Otherwise, after step 6, for example, by radiating ultraviolet over the intermediate transcription film  31 , the adhesive force of the whole face of the intermediate transcription film  31  may be diminished. Though the adhesive force is diminished, in reality, slight adhesive characteristics remain. In addition, the minute tile-shaped device  113  is extremely thin and light. Therefore, the minute tile-shaped device  113  is held on the intermediate transcription film  31 .  
      Step 10  
      This step is not shown in the figure. In this step, by providing heat treatment or the like, the minute tile-shaped device  113  is definitely jointed to the final substrate  115 . An electrode of the minute tile-shaped device  113  is electrically connected to a circuit on the final substrate  115  by a wiring, and one LSI chip is completed.  
      Step 11  
       FIG. 17  is a schematic cross section showing step 11 of the manufacturing method of the optical sensor  111 .  
      In this step, the final substrate manufactured by the foregoing method, that is, the integrated circuit board  115  is mounted on the printed wiring board  116 . The integrated circuit board  115  is mounted on the printed wiring board  116  in such a manner that the side on which the minute tile-shaped device  113  (light emitting devices  113   a  and  113   b ) is located upward.  
      Next, electrodes  115   a  and  115   b  of the integrated circuit board  115  are electrically connected to printed wirings  116   a  and  116   b  of the printed wiring board  116  through wirings  170   a  and  170   b.  As a connection method thereof, for example, the method described in JP-A-2004-281539 can be used. That is, a slope  160  is formed from an insulating material such as a resin to cover a step on the side face of the mounted integrated circuit board  115 , the wirings  170   a  and  170   b  are provided on the surface of the slope  160 , and thereby the integrated circuit board  115  and the printed wiring substrate  116  can be electrically connected. In this case, the height of the wirings  170   a  and  170   b  becomes smaller than in the case that connection is made by wire bonding, that is, can be almost the same as the height of the integrated circuit board  115 . However, when the height of the wirings  170   a  and  170   b  would not matter, connection may be made by wire bonding.  
      The wirings  170   a  and  170   b  are preferably formed by droplet discharge method for forming a metal pattern by discharging droplets containing a metal from an unshown inkjet head (droplet discharge head). Thereby, compared to the case of forming a metal pattern by photolithography, etching and the like, component materials do not much go to waste and it becomes easy to address design change or the like, and thus the manufacturing cost can be reduced.  
      The surface of the integrated circuit board  115  is desirably protected from mechanical impulse by a resin or the like.  FIG. 18  is a view showing a state that the integrated circuit board  115  is molded by a resin  180 . As the resin  180 , a material having sufficient transmission characteristics for the reference light La, Lb, Ra, and Rb is desirably used. Thereby, the light emitting devices  113   a  and  113   b,  the light receiving device  114  and the like can be protected without affecting light detection.  
      Meanwhile, the printed wiring board  116  is desirably opaque for the reference light La, Lb, Ra, and Rb (for example, transmittance of 10% or less). Otherwise, a light shielding member is desirably provided for the printed wiring board  116  on the opposite face of the integrated circuit board  115 . Thereby, noise due to stray light can be inhibited.  
       FIG. 19  is a schematic cross section showing another example of step 11.  
      In  FIG. 19 , the integrated circuit board  115  is flip-chip mounted on the printed wiring board  116 . That is, the face of the integrated circuit board  115  on which the light emitting devices  113   a  and  115   b,  and the light receiving device  114  are provided is arranged oppositely to the printed wiring board  116 . A bump  190  which is a connection member provided on the integrated circuit board  115  is mounted on the printed wiring of the printed wiring board  116  or a pad thereof. Thereby, the integrated circuit board  115  is electrically connected to the printed wiring board  116 . The method has an advantage that productivity is high, since fixing the integrated circuit board  115  and electrical connection thereof can be performed concurrently.  
      In the foregoing method, the reference light is radiated and is received through the printed wiring board  116 . Therefore, for the printed wiring board  116 , a material with sufficient transmittance (for example, 50% or more) for the reflectance light La, Lb, Ra, and Rb should be used. Otherwise, a through hole for transmitting light may be provided in a radiation section and a receiving section of the reference light (that is, sections opposed to the light emitting devices  113   a  and  113   b,  and the light receiving device  114 ).  
      In the foregoing method, it is desirable that the clearance between the integrated circuit board  115  and the printed wiring board  116  is filled with and coated with the resin  180 , so that the light emitting devices  113   a  and  113   b  and the light receiving device  114  can be protected.  
      Consequently, the optical sensor  111  is completed. The optical sensor  111  is jointed to the outer wall of the ink cartridge  110  with the resin  119  or the like shown in  FIG. 3 . The mounting position of the optical sensor  111  is set to an appropriate position by considering easiness of detecting light, easiness of detecting the remaining amount of ink or the like.  
      As described above, in the optical sensor  111  of this embodiment, the identification markers as an identification indicator are contained in the ink  120 , which is the subject, the identification markers are optically identified, and thereby the type or the like of the ink  120  is identified. The light absorption characteristics of the identification markers can be voluntarily controlled by the type and the amount (density) of the identification markers. Therefore, compared to the existing method of identifying the type or the like of the ink  120  by slight differences of light absorption characteristics of the ink itself, precise identification is enabled.  
      In particular, in this embodiment, as an identification marker, the plurality of identification markers  121  and  122  which absorb light in a wavelength different from each other are contained, and the reference light La and Lb corresponding thereto is radiated to the identification markers  121  and  122 . In addition, the combination of the plurality of identification markers  121  and  122  (that is, the type of the ink  120 ) is identified based on the light absorbance ratio between the plurality of identification markers  121  and  122  in relation to the respectively corresponding reference light La, Lb, or the density ratio between the plurality of identification markers  121  and  122  calculated therefrom. Therefore, compared to the case that the ink  120  is identified by using a single identification marker and single reference light, more accurate identification is enabled. That is, when identification is made by using single reference light, light amount change between the reference light before being transmitted through the ink  120  and the reference light after being transmitted through the ink  120  is detected. In this case, the transmitted light amount may be largely changed due to absorption by the ink cartridge  110  accommodating the ink  120 , and therefore accurate identification may be difficult. Meanwhile, when identification is made based on the light absorbance ratio between the plurality of reference light La and Lb (ratio between transmitted light amounts), absorption by the ink cartridge  110  occurs at the similar ratio for all the reference light, and therefore a detection error as a light absorbance ratio is not much large. Therefore, when the light absorbance ratio between the identification markers  121  and  122  (that is., density ratio between the identification markers  121  and  122 ) is appropriately adjusted, the type or the like of the ink  120  can be accurately identified with almost no detection error.  
      Further, in this embodiment, the light emitting devices  113 a and  113   b  are jointed to the integrated circuit board  115  by the transcription technology. Therefore, the integrated circuit board  115  with a compact structure and a high light emitting function can be realized.  
      Further, the light emitting device fabricated by the transcription technology is extremely thin, being several ten μm or less thick. Therefore, not only the light on the top face side radiated as the reference light La and Lb, but also the light on the bottom face side radiated to the compound semiconductor layer side can be extracted outside. That is, when the compound semiconductor substrate  10  formed with the light emitting section is directly utilized as the light emitting devices  113   a  and  113   b  without using a transcription technology, a thick compound semiconductor layer (compound semiconductor substrate  10 ) exists under the active layer, and therefore even when light is radiated from the active layer to the integrated circuit board  115  side (compound semiconductor layer  10  side), the light is mostly absorbed by the compound semiconductor layer  10 , and is not able to be extracted outside. Therefore, in this case, when light radiated from the light emitting devices  113   a  and  113   b  is monitored and provided with Auto Power Control (APC), a special light receiving optical system for monitoring which performs, for example, reflecting part of the reference light La and Lb radiated to the top face side (opposite side of the integrated circuit board  115 ) becomes necessary.  
      Meanwhile, in the case of the light emitting devices  113   a  and  113   b  fabricated by the transcription technology, the light emitting devices  113   a  and  113   b  are formed by exfoliating the surface section of the compound semiconductor substrate layer  10 . Therefore, the compound semiconductor layer  12  becomes extremely thin, and the light Ma and Mb radiated to the integrated circuit board  115  side is hardly absorbed by the compound semiconductor layer  12  and can be extracted outside. Therefore, when the light receiving devices for monitoring  118   a  and  118   b  which monitor such light are provided on the integrated circuit board  115  side, APC can be easily performed without providing a special light receiving optical system. Furthermore, such light Ma and Mb is useless light which should be originally absorbed by the compound semiconductor substrate  10 . Therefore, by utilizing the light Ma and Mb as monitor light, light can be utilized effectively.  
      Further in this embodiment, the plurality of light emitting devices  113   a  and  113   b  radiate the reference light La and Lb to the ink  120  in the time-sharing manner. Therefore, the light receiving device  114  can be common to the light emitting devices  113   a  and  113   b,  and thus the optical sensor  111  can be downsized.  
      In this embodiment, descriptions have been given of the case that the optical sensor  111  is mounted on the outer wall of the ink cartridge  110 . However, the mounting position of the optical sensor  111  is not limited thereto. For example, the optical sensor  111  can be mounted on the section of the cartridge holder to which the outer wall of the ink cartridge is contacted. The optical sensor  111  can be mounted on the ink cartridge mounting section of the carriage  101  to which the outer wall of the ink cartridge is contacted. The optical sensor  111  can be mounted on the section in the middle of the ink flow path from the ink cartridge  110  to the head  106 . The optical sensor  111  can be built in the head  106 .  
     Second Embodiment  
       FIG. 20  is an exploded perspective view showing a main section of an ink cartridge  210  including an optical sensor  211  according to a second embodiment of the invention. For components similar to in the first embodiment will be affixed with the same referential characters, and detailed descriptions thereof will be omitted.  
      As shown in  FIG. 20 , the optical sensor  211  has the light emitting devices  113   a  and  113   b  for radiating reference light to ink inside the ink cartridge  110 , the light receiving device  114  for receiving the reference light transmitted through the ink inside the ink cartridge  110 , a first integrated circuit board  215  electrically connected to the light emitting devices  113   a  and  113   b,  a second integrated circuit board  214  electrically connected to the light receiving device  114 , and a printed wiring board  216  electrically connected to the first integrated circuit board  215  and the second integrated circuit board  214 .  
      The first integrated circuit board  215  is provided with the first current control circuit  130   a  and the second current control circuit  130   b  shown in  FIG. 6 . The second integrated circuit board  214  is provided with the amplification circuit  140  shown in  FIG. 6 . Functions of the first current control circuit  130   a,  the second current control circuit  130   b,  and the amplification circuit  140  are the same as of the first embodiment.  
      In the optical sensor  211 , the light emitting devices  113   a  and  113   b  and the light receiving device  114  are provided separately on the different integrated circuit boards  215  and  214 . The light emitting devices  113   a  and  113   b  and the light receiving device  114  are respectively arranged on an opposite faces  210   a  and  210   b  of the outer wall of the ink cartridge in such a manner that the light axis of the light emitting devices  113   a  and  113   b  corresponds with the light axis of the light receiving device  114 . The printed wiring substrate  216  mounted with the integrated circuit board  214  and the integrated circuit board  215  is wound around the side face of the ink cartridge  210  in such a manner that the printed wiring board  216  covers an outer wall  210   a  and an outer wall  210   b.    
      In  FIG. 20 , the printed wiring board  216  is one printed wiring board mounted with both the first integrated circuit board  215  and the second integrated circuit board  214 . However, it is possible to provide two printed wiring boards, that is, a first printed wiring board mounted with the first integrated circuit board  215  and a second printed wiring board mounted with the second integrated circuit board  214 .  
      In the optical sensor  211 , a plurality of reference light in a peak wavelength different from each other which is respectively radiated from the light emitting device  113   a  and the light emitting device  113   b  is radiated to the ink  120  inside the ink cartridge  210  through the outer wall of the ink cartridge  210 , each intensity of each reference light transmitted through the ink  120  (that is, light absorbance) is compared, and thereby the type or the like of the ink  120  is identified. In the above structure, the reference light radiated from the light emitting devices  113   a  and  113   b  is guided to the light receiving device  114  via the outer wall  210   a  of the ink cartridge  210 , the ink  120 , and the outer wall  210   b.    
      As above, in the optical sensor  211  of this embodiment, the light emitting devices  113   a  and  113   b  and the light receiving device  114  are arranged oppositely to each other on the opposite faces of the ink cartridge  210 . Therefore, even when the light reflector which is used in the first embodiment is not provided for the ink cartridge  210 , light absorption and transmission of the ink  120  can be measured. It means that the optical sensor of the embodiment of the invention can be applied to an ink cartridge which is not fabricated specially for the optical sensor of the embodiment of the invention. Therefore, for example, when an ink cartridge made by other manufacturer is wrongly mounted and ink with constituents different from of the ink which should be originally used (for example, ink which may cause clogging in the nozzle hole) is used, an alert can be issued to users to note such a state, and users can be prompted to take a measure to use correct ink.  
      While the embodiments according to the invention have been described with reference to the accompanied drawings, it is needless to say that the invention is not limited to the above embodiments. The shapes, combinations and the like of each component member described in the foregoing embodiments are illustrative only, and various modifications may be made based on design requirement and the like within the scope of the invention.  
      For example, in the above embodiments, the case in which the optical sensor of the embodiment of the invention is applied to the ink cartridge for accommodating ink used for printing on the recording sheet  109  has been described. However, the optical sensor of the embodiment of the invention is not limited thereto. For example, the optical sensor of the embodiment of the invention can be widely applied to ink cartridges such as an ink cartridge for accommodating ink for forming a wiring in the case that a metal wiring is manufactured by inkjet method, or an ink cartridge for accommodating ink for forming a device such as an organic EL material and a color filter material. Further, while in the above embodiments, the case that the optical sensor of the embodiment of the invention is applied to a sensor for identifying ink has been described, the optical sensor of the embodiment of the invention is not limited to the purpose for identifying ink but can be widely utilized as a sensor for identifying various subjects.  
      The entire disclosure of Japanese Patent Application No. 2005-333866, filed Nov. 18, 2005 is expressly incorporated by reference herein.