Abstract:
The purpose of the present invention is to enable light having a desired light intensity to be outputted in a broad brightness range spanning from low to high brightness, even if light intensity characteristics of light sources have been changed. Light sources emit inspection light of a fixed output and image light of an output based on an image signal. A light-branching unit branches the light from the light sources. A light detection unit detects the light intensity of reflected light branched by the light-branching unit. A signal conversion unit converts a first detection signal from the light detection unit, and outputs the resultant signal as a third detection signal. A main control unit inputs the third detection signal, and controls the output of the image light on the basis of the third detection signal. A refresh unit refreshes the third detection signal inputted to the main control unit.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a light source device outputting light and a display device generating an image by performing spatial light modulation of the light emitted from the light source device. 
       BACKGROUND ART 
       [0002]    Some display devices generate an image by, for example, scanning laser light emitted from a light source device using a scanning unit. In such a light source device, a change in the temperature or the like of a use environment makes a change in the light intensity of light to be emitted, thereby preventing an image generated in the display device to be displayed with desired brightness and color. 
         [0003]    There is a known technique that outputs a desired light intensity by detecting the light intensity of the light source device and controlling the light source device based on the detected light intensity in order to solve such a problem. 
         [0004]    As illustrated in  FIG. 13 , PTL 1 discloses a display device in which a scanning unit has a predetermined scan range  701 , part of the scan range  701  is provided with an effective scan range  702  that can be visually identified by the user, a photo sensor  800  is disposed in a portion outside the effective scan range  702  within the scan range  701 , and a light source device is controlled based on a detection signal detected by the photo sensor  800  when a scanning unit scans light and passes on the photo sensor  800 . 
         [0005]    In addition, as illustrated in  FIG. 14 , PTL 2 discloses a display device including a reflection-light transmission unit  910  that receives light  900  from a light source, reflects part of the light as reflected light  901  to the photo sensor  800 , and transmits part of the light as transmitted light  902  to a scanning unit so as to constantly input the reflected light  901  of the light  900  output from the light source to the photo sensor  800  and control the light source device based on a detection signal by the photo sensor  800 . 
       CITATION LIST 
     Patent Literature 
       [0006]    PTL 1: JP-A-2008-233562 
         [0007]    PTL 2: JP-A-2014-086426 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0008]    When the photo sensor  800  is disposed in the scan range  701  as disclosed in PTL 1, the photo sensor  800  can perform light detection only the time period in which the scanning unit scans the surface of the photo sensor  800 , so the light detection signal may not be input sufficiently. 
         [0009]    In addition, when the photo sensor  800  constantly receives part of the light  900  from the light source as disclosed in PTL 2, if the light source outputs detection light and the photo sensor  800  detects the detection light, the photo sensor  800  may not detect the light intensity accurately because of the effect of the detection signal of the light input to the photo sensor  800  immediately before the detection. 
         [0010]    In the case of installation in a vehicle, an image needs to be displayed in the range from high brightness enabling visual identification in a bright daylight environment to low brightness suppressing glare at nighttime. When the light intensity of light input to the photo sensor  800  is low, an amplifying circuit for amplifying the detection signal or an integration circuit may be disposed between the photo sensor  800  and the control unit. However, when such an amplifying circuit or integration circuit is used as described above, the photo sensor  800  is likely to be affected by the detection signal immediately before the detection as described above and improvement is necessary. 
         [0011]    Accordingly, the invention provides a display device capable of outputting light having a desired light intensity even when the light intensity characteristics of the light source change in a broad brightness range from low brightness to high brightness, and a display device including the light source device. 
       Solution to Problem 
       [0012]    The invention adopts the following means to solve the above problem. 
         [0013]    That is, a light source device according to a first aspect includes a light source capable of emitting at least image light having output power that is based on an image signal, a light branching unit branching light from the light source, a light detection unit detecting a light intensity of the light branched from the light branching unit, a signal conversion unit converting a detection signal from the light detection unit and outputting the converted signal, a control unit controlling output power of the image light based on the input converted signal, and a refresh unit refreshing the converted signal input to the control unit. 
         [0014]    In addition, a display device according to a second aspect includes a light source capable of outputting image light having output power that is based on an image signal and inspection light having fixed output power, a light branching unit branching light from the light source, a light detection unit detecting a light intensity of part of the light branched by the light branching unit, a scanning unit generating an image by receiving part of the light from the light branching unit and scanning the received light, scanning position detection means detecting a scanning position of the scanning unit, a signal conversion unit converting a detection signal from the light detection unit and outputting the converted signal, a control unit receiving the converted signal and controlling output power of the image light based on the converted signal of the inspection light, and a refresh unit refreshing the converted signal input to the control unit at a timing that is based on the scanning position of the scanning unit detected by the scanning position detection means. 
         [0015]    In addition, a display device according to a third aspect includes a light source capable of emitting at least image light having output power that is based on an image signal, a light branching unit branching light from the light source, a light detection unit detecting a light intensity of part of the light branched by the light branching unit, a reflection type image generation unit performing spatial light modulation by receiving the part of light from the light branching unit and reflecting the received light, a signal conversion unit converting a detection signal from the light detection unit and outputting the converted signal, a control unit receiving the converted signal and controlling output power of the image light based on the converted signal of the image light, and a refresh unit capable of refreshing the converted signal input to the control unit. 
       Advantageous Effects of Invention 
       [0016]    The invention can output light having a desired light intensity even when the light intensity characteristics of a light source change in a broad brightness range spanning from low brightness to high brightness. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0017]      FIG. 1  is a diagram illustrating how a HUD device according to an embodiment of the invention is installed. 
           [0018]      FIG. 2  is a cross sectional view schematically illustrating the HUD device according to the above embodiment. 
           [0019]      FIG. 3  is a cross sectional view schematically illustrating a light source device according to the above embodiment. 
           [0020]      FIG. 4  is a diagram illustrating how a screen according to the above embodiment is scanned. 
           [0021]      FIG. 5  indicates temporal changes in the scanning positions of the HUD device according to the above embodiment,  FIG. 5( a )  indicates temporal changes in the sub-scanning position, and  FIG. 5( b )  indicates temporal changes in the main scanning position. 
           [0022]      FIG. 6  is an electric structural diagram illustrating the HUD device according to the above embodiment. 
           [0023]      FIG. 7  is a diagram illustrating a signal conversion unit and a refresh unit according to the above embodiment. 
           [0024]      FIG. 8  is an operational flowchart illustrating the light intensity correction processing of the HUD device according to the above embodiment. 
           [0025]      FIG. 9  is a timing chart illustrating various signals according to the above embodiment. 
           [0026]      FIG. 10  is a diagram illustrating an example of subframes SF obtained by time division of a frame F in a field sequential color system. 
           [0027]      FIG. 11  is a flowchart illustrating an example of the operation of the refresh unit according to the embodiment of the invention and an example of a third detection signal output from the signal conversion unit. 
           [0028]      FIG. 12  is a flowchart illustrating an example of the operation of the refresh unit according to the embodiment of the invention and an example of the third detection signal output from the signal conversion unit. 
           [0029]      FIG. 13  is a diagram illustrating the disposition of a light detection unit in a conventional projection type display device. 
           [0030]      FIG. 14  is a diagram illustrating the disposition of a light detection unit in a conventional projection type display device. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0031]    The following describes an embodiment in which a display device according to the invention is applied to a head-up display device (HUD device) to be installed in a vehicle with reference to the attached drawings. 
         [0032]    As illustrated in  FIG. 1 , a HUD device  1  according to the embodiment of the invention is disposed on the dash board of a vehicle  2  and emits display light K indicating an image M (see  FIG. 2 ) reporting predetermined information toward a windshield  2   a.  The display light K reflected by the windshield  2   a  is visually identified by an observer  3  (mainly the driver of the vehicle  2 ) as a virtual image V formed in front of the windshield  2   a.  In this way, the HUD device  1  causes the observer  3  to visually identify the virtual image V. 
         [0033]    As illustrated in  FIG. 2 , the HUD device  1  includes a light source device  10 , a scanning unit  20 , a screen  30 , a first reflecting unit  40 , a second reflecting unit  50 , a cabinet  60 , and an external light sensor  70 . 
       (Light Source Device  10 ) 
       [0034]    The light source device  10  emits combined laser light C, which will be described later, toward the scanning unit  20  and includes, as illustrated in  FIG. 3 , a light source  11 , a light condensing unit  12 , a light combining unit  13 , a dimming unit  14 , a light branching unit  15 , and a light detection unit  16 . 
         [0035]    The light source  11  emits laser light having predetermined light intensities at predetermined timings under control of a light source control unit  100 , which will be described later. The light source  11  includes a first light source  11   a  emitting blue laser light B, a second light source  11   b  emitting green laser light G, and a third light source  11   c  emitting red laser light R. 
         [0036]    The light condensing unit  12  condenses the laser light B, the laser light G, and the laser light R emitted by the light sources  11   a,    11   b,  and  11   c  to generate converged light with a small spot diameter and includes a first light condensing unit  12   a  condensing the blue laser light B, a second light condensing unit  12   b  condensing the green laser light G, and a third light condensing unit  12   c  condensing the red laser light R. 
         [0037]    The light combining unit  13  combines the laser light B, the laser light G, and the laser light R that have been emitted from the light sources  11   a,    11   b,  and  11   c  and reached the light combining unit  13  via the light condensing unit  12  by aligning their optical axes and outputs them as the combined laser light C. The light combining unit  13  includes a first light combining unit  13   a  for adjusting the optical axis of the blue laser light B, a second light combining unit  13   b  for adjusting the optical axis of the green laser light G, and a third light combining unit  13   c  for adjusting the optical axis of the red laser light R. 
         [0038]    The dimming unit  14  includes a liquid crystal panel (not illustrated) and two polarizing filters (not illustrated) between which the liquid crystal panel is sandwiched. In addition, the dimming unit  14  changes the light transmission ratio of the combined laser light C by driving the liquid crystal panel via a dimming control unit  300 , which will be described later, using a pulse amplitude modulation (PAM) system or pulse width modulation (PWM) system based on a dimming value set by a processing unit  401 , and adjusts (dims) the light intensity of the combined laser light C having input to the dimming unit  14  to a desired light intensity. Note that the dimming unit  14  may be provided in each of the optical paths of the laser light R, the laser light G, and the laser light B before being combined instead of being disposed in the position in which the combined laser light C obtained by combining the laser light R, the laser light G, and the laser light B is received. 
         [0039]    The light branching unit  15  is made of, for example, a transmission member having a reflectivity of approximately 5%, disposed in an optical path of the combined laser light C from the dimming unit  14  to the scanning unit  20 , and transmits most of the combined laser light C from the dimming unit  14  as is while reflecting part of the light to the light detection unit  16 , which will be described later, as reflected light C 1 . 
         [0040]    The light detection unit  16  includes a photodiode or the like, receives the reflected light C 1  reflected by the light branching unit  15 , and detects the light intensities of the laser light B, the laser light G, and the laser light R of the received reflected light C 1 . The light detection unit  16  outputs a first detection signal P 1  to a signal conversion unit  500 , which will be described later, depending on the light intensities of the laser light B, the laser light G, and the laser light R of the received reflected light C 1 . 
         [0041]    The scanning unit  20  receives the combined laser light C emitted from the light source device  10  and scans the received combined laser light C on the screen  30  in a sub-scanning direction Y while scanning it in a main scanning direction X a plurality of times as illustrated in  FIG. 4  under control of a scanning control unit  200  described later, and displays the desired image M on the screen  30 . 
         [0042]    The screen  30  displays the image M on the front surface by receiving the combined laser light C from the scanning unit  20  on the back surface and transmitting and diffusing the combined laser light C, and includes a holographic diffuser, microlens array, diffusion plate, and the like. 
         [0043]    The screen  30  is divided into an effective display area  30   a  surrounded by the bolded frame in  FIG. 4  and non-display areas ( 30   b  and  30   c ) indicated as shaded areas in  FIG. 4 . The effective display area  30   a  can be visually identified by the observer  3  as the virtual image V (that is, the area that is reflected by the first reflecting unit  40  or the like and emitted to the outside as the display light K) and the non-display areas  30   b  and  30   c  cannot be visually identified by the observer  3 . The non-display areas are disposed in the vicinity of turning points in the main scanning of the effective display area  30   a  and includes the intermittent non-display areas  30   b  (the areas to the left and right of the effective display area  30   a  in  FIG. 4 ) to which the effective display area  30   a  is intermittently switched during the main scanning and the continuous non-display areas  30   c  (the areas above and below the effective display area  30   a  in  FIG. 4 ) which are the areas outside the effective display area  30   a  to be scanned continuously during sub scanning. 
         [0044]    As illustrated in  FIG. 4 , the scanning unit  20  scans the combined laser light C from a scanning start position F 1  to a scanning end position F 4  of the screen  30  (see the solid line indicated by symbol C) and, when reaching the scanning end position F 4 , returns to the scanning start position F 1  and performs scanning again. As illustrated in  FIG. 5( a ) , the scanning period of the scanning unit  20  includes an actual scanning period Fa in which the effective display area  30   a  and the non-display areas ( 30   b  and  30   c ) are scanned and a retrace period Fb in which a return from the scanning end position F 4  to the scanning start position F 1  is performed. This frame cycle (one frame F) from when the scanning unit  20  starts scanning at the scanning start position F 1  to when the scanning unit  20  reaches the scanning end position F 4  and returns to the scanning start position F 1  again through a display start position F 2  and a display end position F 3  in which the effective display area  30   a  is scanned is set to a value less than 1/60 second (equal to or more than 60 Hz), which is the critical fusion frequency at which a person can visually identify flicker. 
         [0045]    The first reflecting unit  40  is configured by a plane mirror or the like, receives the display light K representing the image M displayed on the screen  30 , and reflects the display light K to the second reflecting unit  50 . 
         [0046]    The second reflecting unit  50  is configured by a concave mirror or the like and reflects the display light K from the first reflecting unit  40  to the windshield  2   a.  The display light K reflected by the second reflecting unit  50  reaches the windshield  2   a  via a light transmission unit  61 . 
         [0047]    The cabinet  60  houses the light source device  10 , the scanning unit  20 , the screen  30 , the first reflecting unit  40 , the second reflecting unit  50 , and the like and is formed by a light-shielding member. Part of the cabinet  60  is formed as the light transmission unit  61  through which the display light K transmits. 
         [0048]    The light transmission unit  61  is made of translucent resin such as acrylic, allows the transmission of the display light K from the second reflecting unit  50 , and is fitted into the cabinet  60 . The light transmission unit  61  is curved to prevent the received external light from being reflected to the observer  3 . In addition, the external light sensor  70  is provided on an internal surface of the light transmission unit  61  to detect the external illuminance of the HUD device  1  and output illuminance information to a main control unit  400 , which will be described later. 
         [0049]    Next, the electric structure of the HUD device  1  will be described. In addition to the above components, the HUD device  1  includes the light source control unit  100 , the scanning control unit  200 , the dimming control unit  300 , and the main control unit  400  controlling the light source control unit  100 , the scanning control unit  200 , and the dimming control unit  300 , as illustrated in  FIG. 6 . These control units are mounted on, for example, a printed circuit board (not illustrated) provided in the cabinet  60 . These control units may be provided outside the HUD device  1  and may be electrically connected to the light source  11  (the light sources  11   a,    11   b , and  11   c ), the dimming unit  14  (liquid crystal panel), the scanning unit  20 , and the light detection units ( 16 ,  70 , etc.) of the HUD device  1  by wiring. 
         [0050]    The light source control unit  100  drives the light sources  11   a,    11   b , and  11   c  and includes a light source drive unit  101  and a power supply unit  102 . 
         [0051]    The light source drive unit  101  includes a driver IC and the like and drives the light sources  11   a,    11   b,  and  11   c  using a PWM system or PAM system under control of the main control unit  400 . 
         [0052]    The power supply unit  102  supplies electric power to the light sources  11   a,    11   b,  and  11   c  via the light source drive unit  101  and includes a switching circuit having a power supply IC, a transistor, and the like. 
         [0053]    The scanning control unit  200  drives the scanning unit  20  and includes a scanning drive unit  201  and a scanning position detection unit  202 . 
         [0054]    The scanning drive unit  201  includes a driver IC and the like and drives the scanning unit  20  under control of the main control unit  400 . 
         [0055]    The scanning position detection unit  202  calculates feedback data and outputs the feedback data to the main control unit  400 . The feedback data output from the scanning position detection unit  202  is scanning position data such as main scanning switching data indicating the timing at which reciprocating motion of main scanning is switched and frame switching data indicating the timing at which frames are switched. 
         [0056]    A processing unit  401  counts the number of main scanning lines by counting, for example, signals of main scanning switching data of the feedback data input from the scanning drive unit  201 , identifies the sub-scanning position of the scanning unit  20  based on the counted number of main scanning lines, and performs the processing that is based on the sub-scanning position. In addition, the processing unit  401  resets the counted number of main scanning lines according to the signal input of frame switching data, which is feedback data input from the scanning position detection unit  202 , and starts counting the number of main scanning lines of a new frame. 
         [0057]    The dimming control unit  300  includes a driver IC driving the liquid crystal panel and the like and drives the dimming unit  14  based on an instruction signal from the main control unit  400 . 
         [0058]    The main control unit  400  includes the processing unit  401 , a storage unit  402 , and an AD conversion unit (not illustrated). The processing unit  401  includes one or more microprocessors, controllers, microcontrollers, ASICs, FPGAs, other ICs, and the like that are not illustrated and the storage unit  402  includes one or more memories capable of storing programs and data, such as a RAM which is a rewritable memory, a ROM which is a read-only memory, an EEPROM which is an electrically erasable programmable read only memory, a flash memory which is a non-volatile memory that are not illustrated. 
         [0059]    The processing unit  401  controls each unit by reading a program from the storage unit  402  and executing the program. The processing unit  401  causes the light sources  11   a,    11   b,  and  11   c  to emit inspection light, detects the light intensity of the inspection light using the light detection unit  16 , corrects the driving of the light sources  11   a,    11   b , and  11   c  based on the voltage level of a third detection signal P 3  obtained by converting the first detection signal P 1  using the signal conversion unit  500  which will be described later, and causes the light sources  11   a,    11   b,  and  11   c  to output desired light intensities. In addition, the processing unit  401  receives vehicle information and the like from an ECU of the vehicle (not illustrated) and generates image data in sync with scanning by the scanning unit  20  based on the vehicle information output from the ECU of the vehicle and the like. The processing unit  401  outputs the generated image data to the light source drive unit  101  as an image signal and drives the light sources  11   a,    11   b,  and  11   c  with desired output intensities at desired timings. 
         [0060]    The processing unit  401  receives external illuminance from the external light sensor  70 , determines the dimming value based on the external illuminance, and controls the dimming unit  14 . Based on dimming by the dimming unit  14 , the intensity of inspection light received by the light detection unit  16  changes. In addition, the inspection light emitted by the light sources  11   a,    11   b,  and  11   c  is, for example, light that has the maximum brightness set for the light sources  11   a,    11   b , and  11   c.  Since the image M with high brightness is displayed when the external illuminance is high (bright), the dimming value of the dimming unit  14  is set to a high value and the light intensity of inspection light received by the light detection unit  16  increases. Since the image M with low brightness is displayed when the external illuminance is low (dark), the dimming value of the dimming unit  14  is set to a low value and the light intensity of inspection light received by the light detection unit  16  reduces. 
         [0061]    In addition, the processing unit  401  amplifies the first detection signal P 1  from the light detection unit  16  by controlling a gain switching unit  512 , which will be described later. Specifically, when the light detection unit  16  receives the inspection light reduced to low brightness by the dimming unit  14 , since the first detection signal P 1 , which is the detection signal from the light detection unit  16 , becomes small, the processing unit  401  amplifies the first detection signal P 1  by controlling the gain switching unit  512 , which will be described later. That is, the processing unit  401  adjusts the gain of the gain switching unit  512 , which will be described later, based on the dimming state of the dimming unit  14 . 
         [0062]    In addition, the processing unit  401  is connected to a refresh unit  600 , which will be described later, and activates or deactivates the refresh unit  600  according to the scanning position of the scanning unit  20  input from the scanning position detection unit  202 . 
         [0063]    As illustrated in  FIG. 7 , the signal conversion unit  500  includes an amplifying circuit  510  and an integration circuit  520  and outputs the third detection signal P 3  obtained by amplifying and integrating the first detection signal P 1  from the light detection unit  16  to the main control unit  400 . The amplifying circuit  510  is connected to the light detection unit  16  and converts the first detection signal P 1  (electric current) from the light detection unit  16  to a second detection signal P 2  (voltage signal) by amplifying the first detection signal P 1  at a predetermined scaling factor under control of the main control unit  400  and the integration circuit  520  integrates the second detection signal P 2  from the amplifying circuit  510  and outputs the integrated second detection signal P 2  as the third detection signal P 3  to the main control unit  400 . As described later, the refresh unit  600  is connected to the signal conversion unit  500  (integration circuit  520 ). The refresh unit  600  refreshes the third detection signal P 3  to be output to the main control unit  400  at the timing at which the main control unit  400  makes control. 
         [0064]    The amplifying circuit  510  includes a first operational amplifier  511  and the gain switching unit  512  connected in parallel with the first operational amplifier  511  and outputs the second detection signal P 2  obtained by amplifying the first detection signal P 1  from the light branching unit  15  to the integration circuit  520  by switching the gain of the gain switching unit  512  under control of the main control unit  400 . 
         [0065]    When displaying the image M with high brightness (high brightness mode), the main control unit  400  inputs inspection light having high output power to the light detection unit  16  by setting the dimming value of the dimming unit  14  to a high value to increase the transmission ratio. In this case, since the first detection signal P 1  output by the light branching unit  15  becomes large, the main control unit  400  sets the gain of the gain switching unit  512  to a low value. In addition, when displaying the image M with low brightness (low brightness mode), the main control unit  400  outputs inspection light having high output power to the light detection unit  16  by setting the dimming value of the dimming unit  14  to a high value to increase the transmission ratio. In this case, since the first detection signal P 1  output by the light branching unit  15  becomes small, the main control unit  400  sets the gain of the gain switching unit  512  to a high value. 
         [0066]    The integration circuit  520  includes a second operational amplifier  521  integrating the second detection signal P 2  from the amplifying circuit  510  and outputting the third detection signal P 3  to the main control unit  400 , a resistor  522 , a capacitor  523 , and the like. The refresh unit  600  for performing connection or disconnection between the input terminal and the output terminal of the second operational amplifier  521  under control of the main control unit  400  is connected to the second operational amplifier  521 . 
         [0067]    The refresh unit  600  performs connection or disconnection between the input terminal and the output terminal of the second operational amplifier  521  under control of the main control unit  400 . When the main control unit  400  activates the refresh unit  600 , the refresh unit  600  sets the third detection signal P 3  to 0 volts through an imaginary short by connecting the input terminal of the second operational amplifier  521  to the output terminal. In contrast, when the main control unit  400  deactivates the refresh unit  600 , the refresh unit  600  disconnects the input terminal of the second operational amplifier  521  from the output terminal. Then, the second operational amplifier  521  integrates the received second detection signal P 2  and outputs the third detection signal P 3  from the output terminal to the main control unit  400 . That is, when the refresh unit  600  is active, the voltage level of the third detection signal P 3  to be input to the main control unit  400  is forcibly set to 0 volts. When the refresh unit  600  is inactive, the voltage level of the third detection signal P 3  to be input to the main control unit  400  is time-integrated and increased over time. The main control unit  400  detects the peak voltage level of the third detection signal P 3  from the integration circuit  520  and corrects the control of the light source  11 . 
         [0068]    The electric structure of the HUD device  1  according to the embodiment has been described above. The following describes light intensity correction processing for correcting the driving of the light source  11  to cause the light source  11  to output desired light with reference to  FIGS. 8 and 9 .  FIG. 8  is a flowchart of light intensity correction processing for correcting the light intensity of the light source  11  and  FIG. 9  is a timing chart of signals. Signals a to e in  FIG. 9  correspond to voltage levels a to e in  FIG. 7 . 
         [0069]    First, in step S 1 , the processing unit  401  receives external illuminance from the external light sensor  70 , reads the brightness value of the image M appropriate for the received external illuminance from the storage unit  402 , and sets the brightness value. Next, in step S 2 , the processing unit  401  reads the gain based on the determined brightness value and the set light color of the light source  11  from the storage unit  402  and adjusts the gain of the gain switching unit  512 . In addition, in step S 3 , the processing unit  401  activates the refresh unit  600 . This sets the converted signal from the integration circuit  520  to be input to the main control unit  400  to 0 volts. 
         [0070]    Next, in step S 4 , the processing unit  401  detects the scanning position of the scanning unit  20  from the scanning position detection unit  202  to determine whether the scanning position is in the continuous non-display area  30   c.  When the scanning position is not in the continuous non-display area  30   c  (NO in step S 4 ), scanning continues while activating the refresh unit  600 . In contrast, when the scanning position is in the continuous non-display area  30   c  (YES in step S 4 ), the processing unit  401  deactivates the refresh unit  600  in step S 5 . 
         [0071]    In step  56 , the processing unit  401  outputs a driving signal as illustrated in  FIG. 9( a )  to cause the light source  11  of the set color of the light sources  11   a,    11   b,  and  11   c  to output inspection light via the light source control unit  100 . Then, in step S 7 , the light detection unit  16  detects the inspection light and outputs the first detection signal P 1  as illustrated in  FIG. 9( b )  to the signal conversion unit  500  (amplifying circuit  510 ). 
         [0072]    In step S 8 , the signal conversion unit  500  converts the first detection signal P 1  input from the light detection unit  16  to the third detection signal P 3  and outputs the third detection signal P 3  to the main control unit  400 . Specifically, the amplifying circuit  510  converts the first detection signal P 1  input from the light detection unit  16  to the second detection signal P 2  (see  FIG. 9( c ) ) by amplification based on the gain value set in step S 2  and outputs the second detection signal P 2  to the integration circuit  520 . Then, the integration circuit  520  integrates the second detection signal P 2  from the amplifying circuit  510  and outputs the integrated second detection signal P 2  as the third detection signal P 3  (see  FIG. 9( e ) ) to the main control unit  400 . 
         [0073]    In step S 9 , the processing unit  401  causes the light source  11  to output inspection light for a predetermined period (time t 1  to time t 2  in  FIG. 9 ) and then stop the output of the inspection light. This stops the output of the first detection signal P 1  from the light detection unit  16  as illustrated in  FIG. 9( b ) , so the third detection signal P 3  output from the integration circuit  520  gradually reduces over time. The processing unit  401  receives the third detection signal P 3  input from the integration circuit  520  as a digital signal via an AD conversion unit (not illustrated) and temporarily stores the peak voltage level of the third detection signal P 3  in the storage unit  402 . Since the peak voltage level of the third detection signal P 3  appears at the timing (time t 2 ) at which the inspection light is turned off as illustrated in  FIG. 9( e ) , the processing unit  401  desirably stores the voltage level of the third detection signal P 3  at the timing at which the inspection light is turned off in the storage unit  402  temporarily. In this structure, it is possible to easily obtain the peak of the third detection signal (converted signal) P 3  having a low signal-to-noise (SIN) ratio and accurately detect the light intensity of the inspection light. 
         [0074]    In step S 10 , the processing unit  401  determines whether all voltage levels of red light, green light, and blue light have been obtained. When all voltage levels of red light, green light, and blue light have not been obtained (NO instep S 10 ), the processing returns to step S 2  to perform detection for the light source  11  of a different color. In contrast, when all voltage levels of red light, green light, and blue light have been obtained (YES in step S 10 ), the processing unit  401  corrects the driving of the light sources  11   a,    11   b,  and  11   c  so that the image M appropriate for external illuminance can be displayed with desired brightness and desired white balance. 
         [0075]    Light intensity correction processing has been described above. This processing can be described briefly below. 
         [0076]    First, the brightness value for displaying the image M is set based on external illuminance and then the third signal P 3  to be input to the main control unit  400  is refreshed (set to 0 volts) using the refresh unit  600 . 
         [0077]    A determination is made as to whether the scanning position of the scanning unit  20  is in the continuous non-display area  30   c.  When the scanning unit  20  is in the continuous non-display area  30   c,  the refresh unit  600  is deactivated and the first detection signal P 1  of inspection light output from the light source  11  is converted by the signal conversion unit  500  and the converted first detection signal P 1  is input as the third detection signal P 3 . 
         [0078]    The driving of the light sources  11   a,    11   b,  and  11   c  is corrected based on the input third detection signal P 3 . 
         [0079]    In the HUD device  1  described above according to the embodiment, the light detection unit  16  detects the inspection light having light intensity for generating the image M appropriate for external illuminance and corrects the control of the light source  11  based on this, so the brightness and white balance of the image M can be adjusted accurately. 
         [0080]    In addition, since light from the light source  11  can be branched by the light branching unit  15  and part of the branched color light can be input to the light detection unit  16 , enough time can be taken to detect light intensity. 
         [0081]    In addition, since the amplifying circuit  510  can amplify the first detection signal P 1  generated by the light detection unit  16  based on the output power of inspection light, even when receiving inspection light having low light intensity to generate the image M with low brightness, the amplifying circuit  510  can increase the signal strength and the light intensity can be detected accurately. 
         [0082]    In addition, since the integration circuit  520  integrates the detection signal, the detection signal can be averaged and the light intensity can be detected more accurately. 
         [0083]    In addition, even when the light detection unit  16  constantly receives light from the light source  11  as in the embodiment, since the refresh unit  600  refreshes the detection signal before detection of inspection light from the light source  11 , it is possible to prevent the intensity of light other than the inspection light from affecting the detection signal, thereby enabling the accurate detection of light intensity. 
         [0084]    In addition, since the light intensity of the detection light is detected when the scanning position of the scanning unit  20  is in the continuous non-display area  30   c  in which the effective display area  30   a  is not scanned continuously, enough time can be taken to accurately detect the light intensity of the inspection light. 
         [0085]    In addition, since all colors are not detected for each frame, enough time can be taken for each frame F to accurately detect the light intensity of the inspection light. 
       [Modification] 
       [0086]    The invention is not limited by the above embodiments or the above drawings. Changes (including deletion of components) can be made to the embodiments and drawings as appropriate within the spirit of the invention. Examples of modifications will be described below. 
         [0087]    Although the brightness and white balance of the image M are adjusted by correcting the driving of the light sources  11   a,    11   b,  and  11   c  based on the detection signal from the light detection unit  16  in the above embodiment, the brightness and white balance of the image M maybe adjusted by correcting the driving of the dimming unit  14  based on the detection signal from the light detection unit  16  and the driving of the light source  11  and the dimming unit  14  may be corrected based on the detection signal. 
         [0088]    In addition, although the processing unit  401  refreshes the third detection signal P 3  to be input from the signal conversion unit  500  to the processing unit  401  while not driving the light sources  11   a,    11   b,  and  11   c  using the detection signal in the above embodiment, the processing unit  401  only needs to refresh the third detection signal P 3  at least before the processing unit  401  obtains the peak voltage level of the third detection signal P 3 . Specifically, the processing unit  401  only needs to refresh the third detection signal P 3  to be received, for example, before obtaining the peak voltage level of the third detection signal P 3  during driving of the light sources  11   a,    11   b,  and  11   c  using the detection signal when the scanning position of the scanning unit  20  is present between (in the continuous non-display area  30   c ) the display end position F 3  and the next display start position F 2 . 
         [0089]    In addition, the timing at which the processing unit  401  drives the refresh unit  600  may be, for example, the timing that is based on an image signal used by the HUD (display device)  1  to drive the light sources  11   a,    11   b,  and  11   c  for generation of the image M. Specifically, the processing unit  401  only needs to refresh the third detection signal P 3  to be received before, for example, obtaining the peak voltage level of the third detection signal P 3  after driving the light sources  11   a ,  11   b,  and  11   c  using the image signal. 
         [0090]    If the processing unit  401  starts refreshing the third detection signal P 3  to be received when the scanning position of the scanning unit  20  reaches the display end position F 3  or immediately after the light sources  11   a,    11   b,  and  11   c  are driven by the image signal, the third detection signal P 3  can be surely reduced, the light sources  11   a,    11   b,  and  11   c  can be driven by the detection signal, and the peak voltage level of the third detection signal P 3  having low noise can be obtained. 
         [0091]    Although the timing at which the refresh unit  600  is deactivated is the same as the timing at which the light source outputs the inspection light in the embodiment, the invention is not limited to the embodiment and the refresh unit  600  may be deactivated after the light source  11  starts outputting the inspection light. Since this structure prevents the detection signal of unstable light when the light source  11  starts emission from entering the main control unit  400  and the light intensity can be detected more accurately. 
         [0092]    In addition, the dimming unit  14  may be provided in the optical path of each of the laser light B, the laser light G, and the laser light R before being combined, instead of the optical path of the combined laser light C and this structure allows the dimming control of the laser light B, the laser light G, and the laser light R individually. 
         [0093]    In addition, although the main scanning by the scanning unit  20  is counted to determine the timing at which various types of control processing of image adjustment processing are performed in the above embodiment, any other methods of, for example, counting the scanning time may be used to detect the scanning position. 
         [0094]    In addition, although the above embodiment uses an example in which the scanning unit  20  for scanning the combined laser light C from the light source  11  is used as an image generation unit for generating the image M, by replacing the first light source  11   a  emitting blue light, the second light source  11   b  emitting green light, and the third light source  11   c  emitting red light with, for example, light sources such as LEDs having larger spot diameters as the light source  11 , the light source device  10  according to the invention can be used as a light source device for a reflection type image generation unit such as DMD or LCos (registered trademark) or a transmission type image generation unit such as TFT. An example of applying the light source device  10  according to the invention to the light source device of the reflection type image generation unit will be described below. 
         [0095]    The light source device  10  according to the invention applied as the light source device of the reflection type image generation unit or transmission type image generation unit is driven by a field sequential color (FSC) system and illuminates the light sources  11   a,    11   b,  and  11   c  in a time division manner within one frame F. 
         [0096]      FIG. 10  illustrates an example of subframes SF obtained by time-dividing the frame F in a field sequential color system. As illustrated in  FIG. 10 , the light source device  10  to be applied to the reflection type image generation unit has, for example, a display period Fa in which the light sources  11   a ,  11   b,  and  11   c  are illuminated in a time division manner to generate the image M and a non-display period Fb in which the light sources  11   a,    11   b,  and  11   c  are turned off in one frame F. The display period Fa includes, for example, six unequal subframes (SF 5   a  to SF 0   a ) for causing the light source  11   a  to emit blue light, six unequal subframes (SF 5   b  to SF 0   b ) for causing the light source  11   b  to emit green light, and six unequal subframes (SF 5   c  to SF 0   c ) for causing the light source  11   c  to emit red light so as to represent  64  shades of gray for each color. 
         [0097]      FIG. 11  is a flowchart illustrating an example of the operation of the refresh unit  600  in the frame F and an example of the third detection signal P 3  output from the signal conversion unit  500 . In  FIGS. 11 ,( a ), ( b ), and ( c ) indicate the turn-on and turn-off of the light sources  11   a,    11   b,  and  11   c,    FIG. 11( d )  indicates whether the refresh unit  600  is active or inactive, and  FIG. 11( e )  indicates the voltage level of the third detection signal P 3  input to the processing unit  401 . Although subframes SF in the frame F are arranged in descending order of the period in  FIG. 11  to make description easy, the order of arrangement of subframes SF is not limited to this example. 
         [0098]    In the light source device  10  according to the embodiment, as illustrated in  FIG. 11 , the light sources  11   a ,  11   b,  and  11   c  are driven in the subframes SF 5   a,  SF 5   b,  SF 5   c  . . . . Note that the ratio of the periods for driving the light sources  11   a,    11   b,  and  11   c  to the subframes SF 5   a,  SF 5   b,  SF 5   c  . . . depends on the brightness of the virtual image V to be needed. 
         [0099]    In the period from time t 11  to time t 12  in which the light source  11   a  emits blue light, the processing unit  401  deactivates the refresh unit  600 . This outputs the third detection signal P 3  that is based on the intensity of blue light detected by the light detection unit  16  to the processing unit  401  from the signal conversion unit  500 . The processing unit  401  stores the voltage level of the third detection signal P 3  at a predetermined timing in the storage unit  402 . Specifically, for example, the processing unit  401  temporarily stores the peak voltage level immediately before the third detection signal P 3  is refreshed by the refresh unit  600  in the storage unit  402 . 
         [0100]    Next, in the period from time t 12  at which the driving of the light source  11   a  stops to time t 13  at which the light source  11   b  emits green light, the processing unit  401  activates the refresh unit  600 . This refreshes the third detection signal P 3 . 
         [0101]    Next, in the period from time t 13  to time t 14  in which the light source  11   b  emits green light, the processing unit  401  deactivates the refresh unit  600 . This outputs the third detection signal P 3  that is based on the intensity of green light detected by the light detection unit  16  to the processing unit  401  from the signal conversion unit  500 . The processing unit  401  temporarily stores the voltage level of the third detection signal P 3  at a predetermined timing in the storage unit  402 . 
         [0102]    Then, in the period from time t 14  at which the driving of the light source  11   b  stops to time t 15  at which the light source  11   c  emits red light, the processing unit  401  activates the refresh unit  600 . This refreshes the third detection signal P 3 . 
         [0103]    Next, in the period from time t 15  to time t 16  in which the light source  11   c  emits red light, the processing unit  401  deactivates the refresh unit  600 . This outputs the third detection signal P 3  that is based on the intensity of red light detected by the light detection unit  16  to the processing unit  401  from the signal conversion unit  500 . The processing unit  401  temporarily stores the voltage level of the third detection signal P 3  at a predetermined timing in the storage unit  402 . 
         [0104]    Then, until the light source  11   a  in the next frame F emits blue light after the driving of the light source  11   c  stops, the processing unit  401  activates the refresh unit  600 . This refreshes the third detection signal P 3 . 
         [0105]    The processing unit  401  determines whether all voltage levels of red light, green light, and blue light have been obtained. When all voltage levels of red light, green light, and blue light have been obtained, the processing unit  401  corrects the driving of the light sources  11   a,    11   b,  and  11   c  so that the image M appropriate for external illuminance can be displayed with desired brightness and desired white balance. The correction of the driving of the light sources  11   a,    11   b , and  11   c  means the adjustment of the voltage levels for driving the light sources  11   a,    11   b,  and  11   c  and/or the adjustment of the ratio of the periods for driving the light sources  11   a ,  11   b,  and  11   c  to the subframes SF 5   a,  SF 5   b,  SF 5   c . . . .    
         [0106]    As illustrated in  FIG. 11 , the subframes SF for detecting the light intensities of the light sources  11   a,    11   b,  and  11   c  are desirably the longest subframes SF. This lengthens the period for generating a light detection signal and improves the accuracy of the detection of the light intensity. 
         [0107]    Although the voltage level that is based on the light intensity of each color is obtained once for each frame F in the example illustrated in  FIG. 11 , the inventions is not limited to the example and the voltage levels that are based on the light intensities may be obtained in a plurality of subframes SF and the driving of the light sources  11   a,    11   b , and  11   c  maybe corrected by averaging the voltage levels. This further improves the accuracy of the detection of the light intensity. 
         [0108]    In addition, although light detection is performed while the image M is generated by using a transmission film (light branching means) in the above embodiment, a light intensity L may be detected while the light used to generate the image M is transmitted by providing a transmission type light detection unit. However, the dependency of the transmission ratio on the wavelength needs to be considered for each color in the case of a transmission type light detection unit, it is desirable to provide the light branching means as in the above embodiment. 
       INDUSTRIAL APPLICABILITY 
       [0109]    The light source device and the display device according to the invention are applicable particularly to an image display device installed in a movable body or the like in which the illuminance of use environment easily changes or a light source device used in such a display device and, more specifically, to, for example, the meter, head-up display, or head-mount display of the movable body. 
       REFERENCE SIGNS LIST 
       [0110]      1 : HUD device (display device) 
         [0111]      2 : vehicle 
         [0112]      2   a : windshield 
         [0113]      3 : observer 
         [0114]      10 : light source device 
         [0115]      11 : light source 
         [0116]      12 : light condensing unit 
         [0117]      13 : light combining unit 
         [0118]      14 : dimming unit 
         [0119]      15 : light branching unit 
         [0120]      16 : light detection unit 
         [0121]      20 : scanning unit 
         [0122]      30 : screen 
         [0123]      40 : first reflecting unit 
         [0124]      50 : second reflecting unit 
         [0125]      60 : cabinet 
         [0126]      70 : external light sensor 
         [0127]      100 : light source control unit 
         [0128]      200 : scanning control unit 
         [0129]      300 : dimming control unit 
         [0130]      400 : main control unit 
         [0131]      500 : signal conversion unit 
         [0132]      510 : amplifying circuit 
         [0133]      511 : first operational amplifier 
         [0134]      512 : gain switching unit 
         [0135]      520 : integration circuit 
         [0136]      521 : second operational amplifier 
         [0137]      522 : resistor 
         [0138]      523 : capacitor 
         [0139]      600 : refresh unit 
         [0140]    C: combined laser light 
         [0141]    C 1 : first reflected light 
         [0142]    C 2 : second reflected light 
         [0143]    F: frame 
         [0144]    Fa: actual scanning period 
         [0145]    Fb: retrace period 
         [0146]    F 1 : scanning start position 
         [0147]    F 2 : display start position 
         [0148]    F 3 : display end position 
         [0149]    F 4 : scanning end position 
         [0150]    K: display light 
         [0151]    M: image 
         [0152]    P 1 : first detection signal (detection signal) 
         [0153]    P 2 : second detection signal (converted signal) 
         [0154]    P 3 : third detection signal (converted signal) 
         [0155]    V: virtual image