Patent Publication Number: US-2010110395-A1

Title: Image display device and lamp unit

Description:
This application claims priority under 35 U.S.C. Section 119 of Japanese Patent Application No. 2008-284684 filed Nov. 5, 2008, entitled “IMAGE DISPLAY DEVICE AND LAMP UNIT”. The disclosures of the above application is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an image display device and a lamp unit attached to the image display device, and in particular is suitable for use in the case where the lamp unit is replaceable. 
     2. Disclosure of the Related Art 
     Currently, there are commercialized and widespread projection display devices that project a magnified image onto a screen (hereinafter referred to as “projectors”). In such projectors, a lamp is generally used as a light source and light from the lamp is modulated by an imager and is projected onto a screen. 
     In this arrangement, when the lamp has run out in the middle of projecting operation, image display is interrupted. To handle such a situation, the lamp is generally made replaceable in the projector. 
     If lamp replacement can be performed easily, it can be conceived that lamps are replaced as appropriate depending on the scenes of using the projector. For example, when making a presentation with the projector, an old lamp is used for practice and a new high-intensity lamp is used for the real presentation. 
     For frequent lamp replacement, each lamp needs to be managed for lifetime, compatibility with projectors, and others. In general, lamps deteriorate depending on the status of use. Therefore, if lamps are to be often replaced, it is necessary to control the lamps on the basis of usage history. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to allow proper control of lamps on the basis of usage history. 
     A first aspect of the present invention relates to an image display device. The image display device in the first aspect includes a lamp holder that holds a lamp; a lamp-side circuit part that is disposed on the lamp holder side; a holder housing that houses the lamp holder detachably; a main unit-side circuit part that is disposed on a main unit side; and a connector that connects electrically the lamp-side circuit part and the main unit-side circuit part. The lamp-side circuit part has a storage part that stores lamp management information for managing the lamp in a writable and readable manner. The main unit-side circuit part has an information update part that reads the lamp management information from the storage part and updates the lamp management information depending on the status of use of the lamp; and an update storage part that writes the updated lamp management information back into the storage part. 
     According to the image display device in this embodiment, the storage part storing lamp management information is disposed on the lamp side, and the lamp management information held in the storage part is updated depending on the status of use of the lamp. This allows the lamp to hold the lamp management information reflected by the usage history, whereby the lamp can be properly managed on the basis of the information. 
     In the image display device in the first aspect, the lamp management information may contain cumulative time information on cumulative operating time of the lamp. In this case, the information update part updates the cumulative time information depending on the status of use of the lamp. The update storage part writes the updated cumulative time information back into the storage part. This allows the lamp to hold the cumulative operating time of the lamp as a usage history record, whereby it is possible to determine a lifetime of the lamp and the like on the basis of the information. 
     In the first aspect, the “cumulative operating time” refers to a total amount of operating time of a lamp unit after manufacture, which includes the total amount of illuminating time from the first use after manufacture until the present time. 
     A second aspect of the present invention relates to a lamp unit. The lamp unit in the second aspect includes a lamp holder that holds a lamp; a lamp circuit part that is disposed on the lamp holder side; and a connector that connects the lamp circuit part electrically to a circuit part on a main unit side. Here, the lamp circuit part has a storage part that stores lamp management information for managing the lamp in a writable and readable manner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective overview of a projector in an embodiment of the present invention; 
         FIG. 2  is a plane view showing a configuration of an optical engine in the embodiment; 
         FIGS. 3A and 3B  are perspective views of a configuration of a mirror unit in the embodiment; 
         FIG. 4  is an exploded perspective view of a configuration of a lamp unit in the embodiment; 
         FIGS. 5A and 5B  are enlarged perspective views of a part of the lamp unit in the embodiment; 
         FIGS. 6A and 6B  are perspective views of a configuration of a circuit board of the lamp unit in the embodiment; 
         FIG. 7  is a perspective view for describing a method for attachment of the lamp unit in the embodiment; 
         FIGS. 8A ,  8 B, and  8 C are perspective views of the attached lamp unit in the embodiment; and 
         FIG. 9  is a partial cross section view of the attached lamp unit in the embodiment. 
         FIG. 10  is a diagram showing a circuit configuration of a projector in the embodiment; 
         FIG. 11A  is a diagram showing a system configuration of a controller and a circuit part on the lamp unit side in the embodiment;  FIGS. 11B and 11C  are diagrams showing data for use in the configuration shown in  FIG. 11A ; 
         FIG. 12  is a flowchart of an updating process of cumulative operating time in the embodiment; and 
         FIG. 13  is a flowchart of a process performed for the case where lamp information could not be read, in the embodiment. 
     
    
    
     However, the drawings are only for the purpose of illustration and do not limit the scope of the present invention. 
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Hereafter, a configuration of a projector in an embodiment of the present invention will be described with reference to the drawings. The projector in this embodiment has two lamp units as light sources of the illuminating device. 
       FIG. 1  is a perspective overview of the configuration of the projector. The projector includes a cabinet  1 . The cabinet  1  is shaped like an approximately rectangular parallelepiped that is vertically thin and horizontally long, and has an intake port  5  on a side surface to take external air into the cabinet  1 . The cabinet  1  also has on a rear side an openable and closable lamp cover (not shown). The user can open the lamp cover as necessary to replace the lamp units. 
     The cabinet  1  includes an optical engine  2 , a projection lens  3 , and a cooler  4  therein. The optical engine  2  generates light modulated by an image signal (image light). The optical engine  2  has the projection lens  3  attached. A front part of the projection lens  3  is exposed from a front surface of the cabinet  1 . The image light generated by the optical engine  2  is projected by the projection lens  3  onto a surface of a screen in front of the projector. The cooler  4  takes in external air from the intake port  5 , and supplies the external air as cooling winds to the optical engine  2 . 
       FIG. 2  is a diagram showing a configuration of the optical engine. In  FIG. 2 , reference numeral  10  denotes an illuminating device having two lamp units  10   a  and  10   b  and a mirror unit  10   c . The lamp units  10   a  and  10   b  include lamps formed by extra high-pressure mercury lamps, metal halide lamps, xenon lamps, or the like. Light from the lamp units  10   a  and  10   b  is launched as approximately parallel light by the action of a reflector. A configuration of the lamp units  10   a  and  10   b  will be described later in detail. 
     The mirror unit  10   c  has a mirror rotatable in parallel to an X-Z plane shown in  FIG. 2 . The mirror is rotated to guide light from the lamp unit  10   a  to a fly-eye integrator  11  when the lamp unit  10   a  is activated, and to guide light from the lamp unit  10   b  to the fly-eye integrator  11  when the lamp unit  10   b  is activated. A configuration of the mirror unit  10   c  will be described later with reference to  FIGS. 3A ,  3 B,  4 ,  5 A, and  5 B. 
     Light from the illuminating device  10  is entered into a polarized beam splitter (PBS) array  12  and a condenser lens  13  via the fly-eye integrator  11 . The fly-eye integrator  11  includes first and second fly-eye lenses formed by fly-eye lens groups. The fly-eye integrator  11  exerts an optical effect on the incident light from the illuminating device  10  so as to bring a uniform distribution of amounts of incident light on liquid crystal panels  18 ,  24 , and  33 . 
     The PBS array  12  includes an array of a plurality of PBS&#39; s and half-wavelength plates, and unifies polarization directions of incident light from the fly-eye integrator  11 . The condenser lens  13  exerts an effect of gathering the incident light from the PBS array  12 . The light having passed through the condenser lens  13  is entered into a dichroic mirror  14 . 
     Out of the incident light from the condenser lens  13 , the dichroic mirror  14  lets only blue-waveband light (hereinafter referred to as “B light”) pass through and reflects red-waveband light (hereinafter referred to as “R light”) and green-waveband light (hereinafter referred to as “G light”). After having passed through the dichroic mirror  14 , the B light is reflected by a mirror  15  and then is entered into a condenser lens  16 . 
     The condenser lens  16  exerts an optical effect on the B light so that the B light is entered as approximately parallel light into a liquid crystal panel  18 . After having passed through the condenser lens  16 , the B light is entered into the liquid crystal panel  18  via an incident-side polarizer  17 . The crystal panel  18  is driven in accordance with an image signal for blue color to modulate the B light depending on the driven state. After having modulated by the liquid crystal panel  18 , the B light is entered into a dichroic prism  20  via an output-side polarizer  19 . 
     Out of the light reflected by the dichroic mirror  14 , the G light is reflected by a dichroic mirror  21  and then is entered into a condenser lens  22 . The condenser lens  22  exerts an optical effect on the G light so that the G light is entered as approximately parallel light into a liquid crystal panel  24 . After having passed through the condenser lens  22 , the G light is entered into the liquid crystal panel  24  via an incident-side polarizer  23 . The liquid crystal panel  24  is driven in accordance with an image signal for green color to modulate the G light depending on the driven state. After having modulated by the liquid crystal panel  24 , the G light is entered into the dichroic prism  20  via an output-side polarizer  25 . 
     After having passed through the dichroic mirror  21 , the R light is entered into a condenser lens  26 . The condenser lens  26  exerts an optical effect on the R light so that the R light is entered as approximately parallel light into a liquid crystal panel  33 . After having passed through the condenser lens  26 , the R light travels along a light path that is formed by relay lenses  27 ,  29 , and  31  for adjustment of light path length and two mirrors  28  and  30 , and then the R light is entered into a liquid crystal panel  33  via an incident-side polarizer  32 . The liquid crystal panel  33  is driven in accordance with an image signal for red color to modulate the R light depending on the driven state. After having modulated by the liquid crystal panel  33 , the R light is entered into the dichroic prism  20  via an output-side polarizer  34 . 
     The dichroic prism  20  combines the B, G, and R light respectively modulated by the liquid crystal panels  18 ,  24 , and  33 , and enters the same into the projection lens  3 . The projection lens  3  includes a lens group that produces an image of projected light on a projection plane, and an actuator that displaces part of the lens group in a direction of a light axis to thereby adjust zoom and focus states of a projected image. The light combined by the dichroic prism  20  is magnified and projected onto a screen by the projection lens  3 . 
     Next, a configuration of the mirror unit  10   c  will be described with reference to  FIGS. 3A and 3B . 
       FIGS. 3A and 3B  are perspective views of the configuration of the mirror unit  10   c.    
     In  FIGS. 3A and 3B , a base  100  includes an upper plate  101 , a lower plate  102 , a rear plate  103 , and two walls  104 . The upper plate  101 , lower plate  102 , rear plate  103 , and two walls  104  are integrally formed by aluminum die casting. In addition, a hollow  105  is provided between the two walls  104  so as to continue to the upper plate  101 . The lower plate  102  and the upper plate  101  are parallel to each other. A mirror holder  200  is rotatably provided between the lower plate  102  and the upper plate  101 . 
     The two walls  104  and the rear plate  103  have on inner sides a concave contoured to be slightly larger than an adjustment plate  203 . The adjustment plate  203  is fitted and screwed in the concave. The adjustment plate  203  is screwed at a central part on the rear plate  103  and is pressed at parts corresponding to the two walls  104  against the two walls  104  so as to be capable of being elastically displaced. The adjustment plate  203  is formed of a flexible, thin metal film. In addition, the two walls  104  have adjustment screws  204  screwed on outer surfaces, and ends of the adjustment screws  204  are in contact with the adjustment plate  203 . 
     The two walls  104  are formed such that inner surfaces thereof are inclined at an angle of approximately 45 degrees with respect to the respective travel directions of light from the lamp units  10   a  and  10   b  when the mirror unit  10   c  is disposed in the optical engine shown in  FIG. 2 . 
     The mirror holder  200  is provided with a mirror  201 . The mirror holder  200  also has projecting shafts  202  in coaxial positions on upper and lower surfaces. The shaft  202  on the lower surface of the mirror holder  200  is fitted into a shaft hole in the lower plate  102 . The shaft  202  on the upper surface of the mirror holder  200  is attached to a torque limiter  402  via a shaft bearing. 
     The upper plate  101  has on the upper surface a substrate  300  attached via bosses. The substrate  300  has two detection switches  301  and  302  on a lower surface. The detection switches  301  and  302  are pressed and turned on by projections (not shown) on the upper surface of the mirror holder  200  when the mirror holder  200  is brought into a rotation termination position. 
     A drive part  400  includes a gear  401  with a torque limiter  402 , a gear  403 , a motor  404 , a gear (not shown) attached to a drive shaft of the motor  404 , a cover  405 , and a coil spring  406  disposed on the lower plate  102  side. The torque limiter  402  causes the gear  401  to run idle when a specific or higher level of torque is applied. The gear  403  is rotatably attached to the cover  405 . The cover  405  has a shaft hole that engages with a shaft  402   a  of the torque limiter  402 . The cover  405  is screwed into the bosses formed on outer surfaces of the walls  104 . The motor  404  is attached in the hollow  105  between the two walls  104 . 
     A driving force from the motor  404  is transferred to the torque limiter  402  via the gear attached to the drive shaft of the motor  404  and the gears  403  and  401 . The driving force is further transferred to the shaft  202  on the upper surface of the mirror holder  200 , which is attached to the torque limiter  402 . This arrangement allows the mirror  201  to rotate with the mirror holder  200 . 
     The lower plate  102  has a coil spring  406  on a bottom surface. The coil spring  406  is mounted on the mirror unit  10   c  such that both ends thereof are locked between a hook formed on the lower surface of the mirror holder  200  and a hook formed on the bottom surface of the lower plate  102 . The coil spring  406  biases the mirror holder  200  in a direction that presses the mirror holder  200  against the front wall  104  in a state shown in  FIG. 3A , and biases the mirror holder  200  in a direction that presses the mirror holder  200  against the back wall  104  in a state shown in  FIG. 3B . 
     The rotation termination position of the mirror holder  200  can be adjusted by an amount of lifting of the adjustment plate  203  using the adjustment screws  204 . When the mirror unit  10   c  is incorporated into the optical engine shown in  FIG. 2 , the adjustment screws  204  are used to adjust the amount of lifting of the adjustment plate  203  so that light from both the lamp units  10   a  and  10   b  travels properly toward the fly-eye integrator  11 . 
     As shown in  FIG. 3A , light from the lamp unit  10   b  is reflected and guided by the mirror  201  to the fly-eye integrator  11 . To switch to the other lamp unit, the motor  404  is driven to rotate the mirror unit  200  counterclockwise. This rotation is continued until a specific period of time has elapsed after the detection switch  302  is turned on. 
     In the meantime, the mirror unit  200  is pressed against the adjustment plate  203  to position the mirror  201  at a position shown in  FIG. 3B . During the pressing, the gear  401  runs idle by the action of the torque limiter  402 . Accordingly, the mirror unit  200  is situated in a position shown in  FIG. 3B , and light from the lamp unit  10   a  is reflected and guided by the mirror  201  to the fly-eye integrator  11 . If the mirror unit  10   c  is switched from the state of  FIG. 3B  to the state of  FIG. 3A , the same operation as described above is performed except that the direction of driving the motor  404  is reversed. 
     Next, a configuration of a lamp unit and a method of mounting the lamp unit will be described below with reference to  FIGS. 4 to 8A ,  8 B, and  8 C. The following description is given taking one lamp unit as an example, but the described configuration and mounting method are applicable to both of the two lamp units  10   a  and  10   b  shown in  FIG. 2 . 
       FIG. 4  is a diagram showing the configuration of a lamp unit and a mounting portion thereof. The lamp unit includes a lamp  500 , a lamp holder  600  holding the lamp  500 , and a circuit board  700 . Meanwhile, the main unit chassis side has a holder housing  800  housing the lamp holder  600  and a circuit board  900 . The mirror unit  200  is attached to a mirror unit attachment part  830  shown in  FIG. 4 . 
     The lamp holder  600  includes a box  610  to which the lamp  500  is attached. The box  610  has on a front surface an opening  611  for guiding light from the lamp  500  forward. The box  610  also has forward projecting flanges  620  with holes  621  on an upper front surface. The box  610  further has two downward projecting pins  622  on the upper front surface. In addition, the box  610  has on an upper rear surface a backward projecting L-shaped flange  630  with a board holding part  640  extending therefrom. 
       FIG. 5A  is an enlarged view of the board holding part  640 . The board holding part  640  has a vertically penetrating opening  641 . The board holding part  640  also has on an upper surface an L-shaped locking part  642  locking the circuit board  700  in X- and Y-axis directions. The board holding part  640  also has a screw hole  643  into which a screw  710  is screwed. The board holding part  640  further has on the upper surface a placement part  644  on which an outer edge of the circuit board  700  is placed. 
       FIGS. 6A and 6B  are diagrams showing a configuration of the circuit board  700 .  FIG. 6A  is a top view and  FIG. 6B  is a bottom view. The circuit board  700  includes two holes  701  and a notch  702  in a position corresponding to a side screw  710 . The circuit board  700  also has notches  703  and  704  in positions corresponding to the locking part  642  of the board holding part  640 . The circuit board  700  has on the bottom surface a circuit part  705  including an IC and a connector  706  electrically connected to the circuit part  705 . 
     Referring to  FIG. 5A , the circuit board  700  is contoured so as to be displaceable only by a predetermined stroke in the X- and Z-axis directions when the outer edge thereof is placed on the placement part  644  while the notches  703  and  704  are fitted into the locking part  642 . In addition, the placement part  644  is sufficiently widened so that the circuit board  700  does not fall into the opening  641  even if the circuit board  700  is displaced as described above. 
     Returning to  FIG. 4 , the holder housing  800  includes a box attachment part  811  that is open on front and upper sides. The box  610  of the lamp holder  600  is attached to the box attachment part  811 . The box attachment part  811  has, on an upper front side, pins  812  respectively engaging with the two holes  621  of the lamp holder  600 . The box attachment part  811  also has, on a front bottom side, holes  813  (not shown in  FIG. 4 . Refer to  FIG. 7 ) respectively engaging with the two pins  622  of the lamp holder  600 . The box attachment part  811  further has a pair of vertically extending guides  814  that lock the rear surface of the box  610  and guide the lamp holder  600  when the lamp holder  600  is attached. The box attachment part  811  has on two walls a ventilation opening  815  that allows winds to pass through the box attachment part  811 . 
     The holder housing  800  has a board holding part  820  that is opposed to the board holding part  640  of the lamp holder  600  when the lamp holder  600  is attached. 
       FIG. 5B  is an enlarged view of the board holding part  820 . The board holding part  820  has a concave  821 , two pins  822  projecting from the concave  821 , and a screw hole  823 . The board holding part  820  also has a notch  824  near the screw hole  823  on a wall surrounding the concave  821 . 
     The circuit board  900  has a notch  901  and a hole  902 , which engage with the two pins  822  on the board holding part  820 . The circuit board  900  also has on an upper surface a connector  903  that connects with the connector  706  on the circuit board  700  disposed in the lamp holder  600 , and a connector  904  that connects the connector  903  electrically to the main board. The circuit board  900  can be attached to the board holding part  820  by screwing the screw  905  into the screw hole  823 . 
     Returning to  FIG. 4 , for mounting the lamp unit, first the lamp  500  is attached to the box  610  of the lamp holder  600 . Then, the circuit board  700  is attached to the board holding part  640  of the lamp holder  600 . Referring to  FIG. 5A , the circuit board  700  can be attached by placing the circuit board  700  on the placement part  644  while fitting the notches  703  and  704  into the L-shaped locking part  642 , and then screwing the screw  710  into the screw hole  643 . At the time, the screw  710  is screwed into the screw hole  643  in such a manner that a slight clearance is left between the screw head and the upper surface of the circuit board  700 . Accordingly, the circuit board  700  can be attached to the board holding part  640  so as to be displaceable only by a predetermined stroke in the X- and Z-axis directions. 
     Returning to  FIG. 4 , the circuit board  900  is attached to the board holding part  820  in the main unit chassis. Referring to  FIG. 5B , for attachment of the circuit board  900 , the circuit board  900  is placed on the notch  824  and on seats  822   a  at a base of the two pins  822  while the notch  901  and the hole  902  are fitted to the two pins  822 , respectively. An upper surface of the seat  822   a  and an upper surface of the notch  824  are at the same height. Subsequently, the screw  905  is screwed into the screw hole  823 . 
     Here, the notch  901  and the hole  902  are engaged with the pins  822  with almost no play. Accordingly, when being placed on the notch  824  and the seats  822   a  at the base of the pins  822  as stated above, the circuit board  900  is positioned in the X- and Z-axis directions with respect to the board holding part  820 . In addition, the screw  905  is screwed into the screw hole  823  until the screw  905  is pressurized and brought into contact with the upper surface of the circuit board  900 . This allows the circuit board  900  to be incapable of being displaced also in the Y-axis direction and thus be positioned in the Y-axis direction. 
       FIG. 7  is a diagram of the lamp unit in which the two circuit boards  700  and  900  are attached to the board holding parts  640  and  820 , respectively. Subsequently, the lamp holder  600  is mounted to the holder housing  800  by pushing the box  610  into the box attachment part  811  while bringing the rear surface of the box  610  into contact with the guides  814 . 
     A distance from a front inner side of the box attachment part  811  to the guides  814  is made slightly larger than a length of the box  610  in the X-axis direction. Accordingly, the lamp holder  600  can be housed in the holder housing  800  in a predetermined position by pushing the box  610  into the box attachment part  811  while bringing the rear surface of the box  610  into contact with the guides  814 . 
     When the lamp holder  600  is pushed into the box attachment part  811  as stated above, ends of the two pins  812  on the holder housing  800  side are inserted into the two holes  621  of the lamp holder  600  side, and ends of the two pins  622  on the lamp holder  600  side are inserted into the two holes  813  of the holder housing  800 , before the lamp holder  600  reaches the predetermined position in the holder housing  800 . At the same time, ends of the two pins  822  extending from the board holding part  820  are inserted into the two holes  701  of the circuit board  700 . 
     Here, the pins  812  and  622  each have a tapered end, and therefore, when the lamp holder  600  is further pushed into the box attachment part  811 , the lamp holder  600  is guided by the inclined ends of the pins  812  and  622  and then is placed into the predetermined position. Accordingly, the light axis of the lamp  500  attached to the lamp holder  600  is properly set with respect to a subsequent optical system. 
     In addition, the pins  822  have inclines  822   b  at tapered ends (refer to  FIG. 5B ). Therefore, when the lamp holder  600  is further pushed into the box attachment part  811  with the pins  822  inserted into the holes  701 , the circuit board  700  is guided and displaced in the X- and Z-axis directions by the inclines  822   b  at the pin  822  ends. Accordingly, the connector  706  on the circuit board  700  is properly opposed to the connector  903  on the circuit board  900 , and then the lamp holder  600  is further pushed to connect the connectors  706  and  903 . 
       FIG. 8A  is a diagram of the lamp unit in which the lamp holder  600  is pushed completely into the box attachment part  811 .  FIG. 8B  is a perspective view of the vicinities of the board holding  640  and  820 .  FIG. 8C  is a perspective view similar to that in  FIG. 8B  except that the board  700  removed. As shown in  FIGS. 8A to 8C , when the lamp holder  600  is pushed completely into the box attachment part  811 , the lamp  500  is properly positioned, and the connector  706  on the circuit board  700  and the connector  903  on the circuit board  900  are connected to each other. 
       FIG. 9  is a cross section view of the diagram in  FIG. 8B  along a line A-A&#39;. Length of the pins  822  is designed such that portions of the pins  822  further at the base than the ends thereof are fitted into the holes  701  of the circuit board  700 , before the connector  903  on the circuit board  900  are connected to the connector  706  on the circuit board  700 . Accordingly, when starting to connect with each other, the connectors  706  and  903  are completely positioned, thereby allowing smooth connection between the connectors  706  and  903 . 
       FIG. 10  illustrates a circuit configuration of a projector in this embodiment.  FIG. 10  shows only a configuration related to the lamp units  10   a  and  10   b  and the mirror unit  10   c , and other configurations are omitted. 
     A lamp power source  51  supplies power for driving a lamp to a relay circuit  52  in accordance with a control signal from a controller  54 . The lamp power source  51  also monitors a voltage applied to the lamp  500  to thereby determine whether the lamp is on, and provides a result of the determination to the controller  54 . Specifically, the lamp power source  51  provides the controller  54  with a determination that the lamp is on when the applied voltage is below a predetermined threshold, and provides the controller  54  with a determination that the lamp is off when the applied voltage is above the predetermined threshold. 
     The relay circuit  52  supplies the power from the lamp power source  51  to either one of the lamp units  10   a  and  10   b  which is designated by the controller  54 . The relay circuit  52  receives signals from the detection switches  301  and  302  disposed on the mirror unit  10   c . When the mirror  201  in the mirror unit  10   c  is directed toward the lamp unit  10   a , the detection switch  301  is turned on and an ON signal from the detection switch  301  is input to the relay circuit  52 . On the other hand, when the mirror  201  is directed toward the lamp unit  10   b , the detection switch  302  is turned on and an ON signal from the detection switch  302  is input to the relay circuit  52 . 
     The relay circuit  52  is configured so as not to supply the power from the lamp power source  51  to the lamp unit  10   a  if the detection switch  301  has not input an ON signal even though the controller  54  has input a control signal for power supply to the lamp unit  10   a ; and so as not to supply the power from the lamp power source  51  to the lamp unit  10   b  if the detection switch  302  has not input an ON signal even though the controller  54  has input a control signal for power supply to the lamp unit  10   b.    
     A mirror driver  53  drives the mirror unit  10   c  in accordance with a control signal from the controller  54 . At driving of the mirror unit  10   c , the controller  54  monitors signals from the detection switches  301  and  302  disposed in the mirror unit  10   c . Then, after the detection switch located in a driving direction has input an ON signal, the controller  54  provides a control signal to the mirror driver  53  to further drive the mirror  201  in the driving direction for a specific period of time. Accordingly, the mirror  201  can be reliably situated in a desired switch position. 
     When such control has been exercised, the motor  404  is continuously driven even after the rear surface of the mirror holder  200  has contacted the adjustment plate  203 . In this case, however, the torque limiter  402  absorbs a driving force of the motor  404  as stated above, and therefore there arises no problem such as damage to the motor  404  under an overload or an angular shift of the mirror  201  due to a skew in the mirror holder  200 . 
     The controller  54  includes a CPU (not shown) and a switch  54   a , and controls the components according to pre-loaded control programs. The switch  54   a  connects either one of the circuit parts  705  disposed on the lamp units  10   a  and  10   b  to a data bus in the controller  54 . The controller  54  switches the switch  54   a  so as to establish a communication path with either one of the circuit parts  705  disposed on the lamp units  10   a  and  10   b . Then, the controller  54  acquires lamp management information from the circuit part  705  via the communication path, and stores the acquired management information in a memory  55 . 
     A configuration and a control operation relating to communications between the controller  54  and the circuit parts  705  disposed on the lamp units  10   a  and  10   b  will be described later in detail with reference to  FIGS. 11A to 11C , and  12 . 
     In the configuration of  FIG. 10 , when the lamp has burnt out during driving of either one of the lamps, the lamp power source  51  inputs a signal indicative of this event to the controller  54 . In response to this, the controller  54  causes the lamp power source  51  to stop power supply, and then provides a control signal to the mirror driver  53  so as to rotate the mirror  201  into a position where light from the other lamp is reflected. Accordingly, the mirror  201  is rotated. 
     Afterward, when the mirror is rotated into the proper position, either one of the detection switches  301  and  302  provides an ON signal to the controller  54 . After a lapse of the specific period of time since reception of the ON signal, the controller  54  outputs a control signal to the lamp power source  51  so as to start power supply. At the same time, the controller  54  outputs a control signal to the relay circuit  52  to supply power to the other lamp. Accordingly, the other lamp is turned on to resume projection of an image. 
     Next, a configuration relating to communications between the controller  54  and the circuit parts  705  disposed on the lamp units  10   a  and  10   b  will be described below with reference to  FIGS. 11A to 11C . 
       FIG. 11A  is a block diagram of a system including the controller  54  and the circuit parts  705 ;  FIG. 11B  is a diagram showing contents of lamp management information stored in the storage parts  71   a  and  71   b ; and  FIG. 11C  is a diagram showing a configuration of usage history data in the lamp management information.  FIG. 11A  omits the connectors  706  and  903  intervening between the switch  54   a  and the circuit parts  705 , and the intermediate circuit board  900 . 
     As shown in  FIG. 11A , the circuit parts  705  of the lamp units  10   a  and  10   b  include control parts  70   a  and  70   b  and the storage parts  71   a  and  71   b . The control parts  70   a  and  70   b  control writing/reading of data into/from the storage parts  71   a  and  71   b . The storage parts  71   a  and  71   b  store data shown in  FIG. 11B  as lamp management information. 
     Here, lamp identification information refers to data for identifying the lamps  500  attached to the lamp units  10   a  and  10   b , and contains data on manufacturer&#39;s name, model number, and the like of the lamps  500 , for example. Cumulative time data refers to data indicative of cumulative operating time of the lamp  500 . The “cumulative operating time” refers to a total amount of operating time of the lamp  500  after manufacture, which includes the total amount of illuminating time from the first use after manufacture until the present time. 
     Usage history data contains a flag for malfunction and a flag for operability as shown in  FIG. 11C . Here, the flag for malfunction is set at “1” if the lamp  500  has failed to illuminate even once in the past, and is set at “0” if the lamp  500  has never failed to illuminate in the past. The flag for operability is set at “1” if the lamp  500  has become inoperable because the lamp  500  failed to illuminate beyond a predetermined number of times in the past, and is set at “0” if the lamp  500  has never become inoperable. 
     Returning to  FIG. 11A , the controller  54  includes a communication control part  61 ; a storage part  62 ; an on/off detection part  63 ; a time measurement part  64 ; a calculation part  65 ; an operability determination part  66 ; a notification part  67 ; and an operability update part  68 . 
     The communication control part  61  switching-controls the switch  54   a  so as to establish a communication path with either one of the circuit parts  705  disposed on the lamp units  10   a  and  10   b . Then, the communication control part  61  acquires the lamp management information from the storage part  71   a  or  71   b  in the circuit part  705  with which the communication path is established. 
     The storage part  62  stores the lamp management information acquired by the communication control part  61 . The lamp management information stored in the storage part  62  is updated as necessary in processes performed by the calculation part  65  and the operability update part  68  upon the use of the lamp. The storage part  62  sets a storage region for the lamp management information in the memory  55 . 
     The on/off detection part  63  determines on illumination start and illumination end of the lamp  500  as a target of illumination, on the basis of a result of the determination on lamp illumination provided by the lamp power source  51 . Specifically, while the lamp  500  is being driven, the on/off detection part  63  detects that the lamp  500  has started illumination at the instant when the lamp power source  51  has provided a determination that the lamp  500  is on, and then the on/off detection part  63  detects that the lamp  500  has ended illumination at the instant when the lamp power source  51  has provided a determination that the lamp  500  is off. If the lamp  500  has ended illumination at switching of the lamp  500  or at termination of a projection process, the on/off detection part  63  detects that the lamp  500  has turned off at the instant when power supply to the lamp  500  has been stopped. 
     The time measurement part  64  starts time measurement upon reception of an illumination start signal from the on/off detection part  63 , and passes a result of the measurement to the calculation part  65  at specific time intervals. In addition, the time measurement part  64  terminates time measurement upon reception of an illumination end signal from the on/off detection part  63 , and passes a result of the measurement at the time of the termination to the calculation part  65 . 
     The calculation part  65  updates the cumulative time data on the basis of the cumulative time data in the lamp management information stored in the storage part  62  and the result of measurement of elapsed time input from the time measurement part  64 , and writes the updated cumulative time data back into the storage part  62 . 
     The operability determination part  66  determines whether the lamp  500  as a target of illumination is compatible with the device (projector) with reference to the lamp identification data in the lamp management information stored in the storage part  62 , and passes a result of the determination to the notification part  67 . The operability determination part  66  holds in advance the listed lamp identification data for lamps compatible with the device (projector), and determines on compatibility of the lamp  500  depending on whether the lamp identification data stored in the storage part  62  is contained in the list. 
     The operability determination part  66  further determines whether the lamp  500  as a target of illumination is operable with reference to the usage history data in the lamp management information stored in the storage part  62 , and passes a result of the determination to the notification part  67 . Specifically, the operability determination part  66  refers to the operability flag in the usage history data (see  FIG. 11C ) and determines that the lamp  500  is inoperable if the operability flag is set at “1.” 
     If the result of the determination from the operability determination part  66  indicates incompatibility or inoperability, the notification part  67  performs a process to notify the effect to the user. For example, the notification may be displayed on the display part in the projector or may be output as a sound. If the lamp unit as a target of illumination is incompatible with the projector or is inoperable, the lamp unit is not turned on and the foregoing notification is given to the user. 
     The operability update part  68  updates the usage history data in the lamp management information stored in the storage part  62 , depending on the status of use of the lamp  500 . Specifically, the operability update part  68  refers to the usage history data stored in the storage part  62  if the lamp power source  51  has not provided a determination that the lamp  500  has been turned on for a specific period of time at start of illumination of the lamp  500 , or if the power source  51  has provided a determination that the lamp  500  has been turned off during operation of the lamp  500 . If the malfunction flag is set at “0,” the operability update part updates the malfunction flag to “1,” and sets the number of malfunction at 1. If the malfunction flag is already set at “1,” the operability update part increments the number of malfunction (s) by 1, and also sets the operability flag at “1” if the incremented number of malfunction(s) is above a threshold value. 
     Whenever the usage history data is updated as stated above, the communication control part  61  writes the update back into the storage part  71   a  or  71   b  in the corresponding lamp unit  10   a  or  10   b . In addition, if any trouble has occurred in illumination of the lamp  500 , illumination of the lamp  500  is stopped. 
     Next, an updating process of cumulative operating time will be described below with reference to  FIG. 12 . The steps of the flow shown in the diagram are to be carried out when it was possible to read the lamp management information from the lamp unit  10   a  or  10   b . If it was not possible to read the lamp management information from the lamp unit  10   a  or  10   b , the steps shown in  FIG. 13  will be performed instead. 
     When a projecting process is started by input by a user (S 101 : YES), the communication control part  61  establishes a communication path with the circuit part  705  in the lamp unit  10   a  or  10   b  as a target of illumination (S 102 ). Then, the communication control part  61  conducts communications with the circuit part  705  with which the communication path is established (S 103 ), reads the lamp management information from the storage part  71   a  or  71   b  in the circuit part  705  (S 104 ), and initializes the storage part  62  on the basis of the read lamp management information (S 105 ). 
     Afterward, the operability determination part  66  refers to the lamp identification data and the usage history data (the operability flag) in the lamp management information stored in the storage part  62  to thereby determine whether the lamp unit  10   a  or  10   b  as a target of illumination is compatible with the device (projector) and is operable as stated above (S 106 ). Here, if the lamp unit  10   a  or  10   b  is incompatible or inoperable (S 106 : NO), the operability determination part  66  notifies that the lamp unit is inoperable without turning on the lamp unit as stated above (S 107 ). On the other hand, if the lamp unit  10   a  or  10   b  is not incompatible or inoperable (S 106 : YES), the lamp unit  10   a  or  10   b  starts to illuminate (S 108 ). 
     When the lamp unit  10   a  or  10   b  as a target of illumination has started to illuminate in this manner, the time measurement part  64  starts to measure elapsed time. At the same time, the calculation part  65  updates cumulative operating time of the lamp unit  10   a  or  10   b  on the basis of the time measured by the time measurement part  64  and the cumulative time data stored in the storage part  62 . Then, the calculation part  65  writes the updated cumulative operating time as necessary over the previous data in the storage part  62 , and writes the update data back into the storage part  71   a  or  71   b  in the lamp unit  10   a  or  10   b  (S 109 ). Such an update on the cumulative operating time is maintained until the lamp unit  10   a  or  10   b  stops illumination (S 110 : YES), or the lamp unit as a target of illumination is switched by the user or automatically (S 111 : YES). 
     When an illuminating operation of the lamp unit  10   a  or  10   b  has been stopped due to a malfunction of the lamp unit or by the user&#39; s instruction (S 110 : YES), the lamp unit  10   a  or  10   b  ends illumination (S 112 ). Here, an end of illumination due to a malfunction is based on the determination from the lamp power source  51  as stated above. In this case, the operability update part  68  updates the usage history data as stated above, and writes the updated usage history data back into the storage part  71   a  or  71   b  in the lamp unit  10   a  or  10   b.    
     When the lamp unit  10   a  or  10   b  ends illumination at S 112 , the time measurement part  64  and the calculation part  65  terminate the measurement of elapsed time and the calculation of cumulative operating time, and then the cumulative operating time at the time is written back into the storage part  71   a  or  71   b  in the lamp unit  10   a  or  10   b  (S 113 ). Afterward, the communication path is cleared (S 114 ) and the process is terminated. 
     On the other hand, if it is determined at S 111  that the lamp unit as a target of illumination has been switched (S 111 : YES), the lamp unit  10   a  or  10   b  ends illumination (S 115 ). According to this, the time measurement part  64  and the calculation part  65  terminate the measurement of elapsed time and the calculation of cumulative operating time, and then the cumulative operating time at the time is written back into the storage part  71   a  or  71   b  in the lamp unit  10   a  or  10   b  (S 116 ). Then, the communication path is cleared (S 117 ), and the process returns to S 102  to perform S 102  and subsequent steps with respect to the switched lamp unit  10   a  or  10   b.    
     Next, the process performed for the case where it was not possible to read the lamp management information from the lamp unit  10   a  or  10   b , will be described with reference to  FIG. 13 . 
     As in the case of  FIG. 12 , when a projection process is started by input by the user (S 101 : YES), the communication control part  61  establishes a communication path with the circuit part  705  in the lamp unit  10   a  or  10   b  as a target of illumination (S 121 ). Here, if the communication path can be established (S 122 : YES) within a specific period of time (S 123 ), the process moves to S 103  shown in  FIG. 12  to conduct communications with the circuit part  705  with which the communication path is established. In this case, S 104  and subsequent steps shown in  FIG. 12  are carried out. 
     If the communication path cannot be established within the specific period of time (S 122 : N 0 , S 123 : YES), the controller  54  turns on the lamp unit  10   a  or  10   b  as a target of illumination in a low power-consumption and low-illumination mode (S 124 ), and displays on a projection plane a message indicative of no proper lamp unit being attached and an image for the user to decide whether this lamp unit is to be continuously on (S 125 ). In response to this, if the user inputs a decision via a remote control or a main unit key (S 126 : YES) and the decision is to discontinue the illumination (S 127 : YES), the controller  54  turns off the lamp unit, and brings the projector into a standby state (S 128 ). 
     On the other hand, if the decision input by the user is to continue the illumination (S 127 : NO) or if the user has not input any decision within the specific period of time (S 126 : NO, s 129 : YES), the controller  54  displays on the projection plane a message indicating that some functions of the projector will be restricted if this lamp unit is continuously used and an image for the user to make a decision again on whether this lamp unit is to be continuously on (S 130 ). 
     In this case, functional restrictions are imposed on a luminescence mode and an illumination switch mode for the lamp unit. For example, a message is provided to inform the user that the lamp unit will be brought into the low-illumination and low power-consumption mode and that the lamp unit will be incapable of being set in an automatic switch mode in which automatic switching takes place between the lamp units under predetermined control (for example, after each specific period of time), and therefore the lamp unit as a target of illumination is fixed to the currently operational lamp unit. 
     In response to this message, if the user input a decision via the remote control or the main unit key (S 131 : YES) and the decision is to discontinue the illumination (S 132 : YES), the controller  54  turns off the lamp unit, and brings the projector into the standby state (S 128 ). On the other hand, if the decision input by the user is to continue the illumination (S 132 : NO) or if the user has not input any decision within the specific period of time (S 131 : NO, S 133 : YES), the controller  54  continuously illuminates the lamp unit under the functional restrictions stated above (S 134 ). 
     According to this embodiment as described above, the storage parts  71   a  and  71   b  are disposed on the lamp unit  10   a  and  10   b , and the lamp management information stored in the storage parts  71   a  and  71   b  is updated depending on the status of use of the lamp units  10   a  and  10   b , whereby the lamps can hold the lamp management information reflected by the usage histories. Accordingly, when the lamp units  10   a  and  10   b  are used, it is possible to control properly illumination of the lamps on the basis of the lamp management information reflected by the usage histories. 
     In this embodiment, since cumulative operating time of the lamp is held as lamp management information, it is possible to determine a lifetime of the lamp on the basis of the information, for example. In addition, in accordance with the result of the determination, it is possible to notify the user of the coming of the end of the lifetime and the remaining amount of the lifetime, or to exercise control for automatic switching between the lamp units, for example. 
     In addition, since the information on operability of the lamp (usage history data) is held as lamp management information in this embodiment, it is possible to determine whether the lamp unit is operable at a time of use of the lamp unit as stated above. If the lamp unit is inoperable, it is possible to discontinue the illumination of the lamp unit. This avoids unnecessary illumination operations of the lamp. 
     Further in this embodiment, since the lamp identification information for identifying a lamp is held as lamp management information, it is possible to determine whether the lamp unit is compatible with the device (projector) at a time of use of the lamp unit as stated above. If the lamp unit is incompatible, it is possible to discontinue illumination of the lamp unit. This avoids illumination of the incompatible lamp and prevents damage to the lamp and the like. 
     Although an embodiment of the present invention has been described above, the present invention is not limited by the foregoing embodiment. In addition, the embodiment of the present invention can be modified in various manners. 
     For example, although the foregoing embodiment employs a projector on which two lamp units can be mounted, the number of lamp unit (s) may be one, or three or more. In addition, the lamp unit in the present invention is applicable to products other than projectors. 
     In addition, although the foregoing embodiment employs three kinds of data shown in  FIG. 11B  as lamp management information for managing a lamp unit, the lamp management information may contain information other than the foregoing information. For example, the lamp management information may contain information on the lamp&#39;s characteristics, such as intensity of illumination, color variability, and the like. Accordingly, it is possible to correct a projected image as appropriate on the projector side on the basis of the information, thereby improving the quality of the projected image. 
     In addition, the user may include by themselves the name, operation starting date, operational status, or the like of the lamp unit, as necessary in the lamp management information. Such information can be input via the operating part of the projection or can be written from a personal computer via a dedicated interface. This allows the user to check the lamp unit-specific information as necessary, resulting in enhanced convenience for the user. 
     Further in the foregoing embodiment, by every use of the lamp unit, the lamp management information is read from the lamp unit as a target of operation, and the storage part  62  is initialized on the basis of the read management information. Alternatively, if the storage part  62  has a sufficient capacity, lamp management information may be read and stored in the storage part  62  when the two lamp units  10   a  and  10   b  are attached. 
     Besides, the circuit board  900  is provided at the holder housing  800  as a relay to the main board in the foregoing embodiment. Alternatively, if the main board can be disposed in the vicinity of the holder housing  800  at a position corresponding to the board holding part  640  on the lamp holder  600  side, the main board may have a connector that connects with the connector  706  on the lamp holder  600 . In addition to the arrangement in the foregoing embodiment, the two connectors in the present invention may be arranged in such a manner as to be attached to wires routed from the main board side and the lamp holder side and to be connected by hands to each other. 
     The embodiment of the present invention can be modified as appropriate in various manners within the scope of a technical idea shown in the claims.