Patent Publication Number: US-2022214227-A1

Title: Temperature detection device, temperature detection system, display device, and head-up display

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of priority from Japanese Patent Application No. 2021-001717 filed on Jan. 7, 2021, the entire contents of which are incorporated herein by reference. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a temperature detection device, a temperature detection system, a display device, and a head-up display. 
     2. Description of the Related Art 
     What-is-called head-up displays (HUD) that project an image onto a member having a light-transmitting property, such as glass, have been known. 
     The technique above describes that sunlight may be incident on a display device through an optical system. When the display device is exposed to the sunlight condensed by the optical system, the temperature of a place thereof exposed to the sunlight becomes high and the display device may be adversely affected. A temperature information acquisition method in which a temperature is specified on the basis of change in an electric resistance value of an electrode provided as a temperature detection element has been known. 
     When a temperature detection function is added to the display device simply, a circuit corresponding to a display output function and a circuit corresponding to the temperature detection function are separately provided and wiring is coupled to each of the circuits. A signal transmission path is also required between the circuit corresponding to the display output function and the circuit corresponding to the temperature detection function in order to control display in response to increase in temperature. Accordingly, the above-mentioned display device causes complication due to increase in the number of circuits and wiring lines and causes increase in cost of a wiring substrate. 
     The present disclosure has been made in view of the above-mentioned problem, and an object thereof is to provide a temperature detection device, a temperature detection system, a display device, and a head-up display capable of preventing increase in cost due to provision of a temperature detection function. 
     SUMMARY 
     A temperature detection device according to an embodiment of the present disclosure includes a plurality of temperature sensors each including a temperature detection resistor element provided in a temperature detection region, and a storage unit configured to store therein unique information for each of a plurality of the temperature detection resistor elements. The temperature detection resistor element is provided for each of a plurality of partial temperature detection regions in the temperature detection region, and an externally provided control device reads out the unique information stored in the storage unit and detects a temperature for each of the partial temperature detection regions in the temperature detection region based on the unique information and an output potential that is output from the temperature sensor. 
     A temperature detection system according to an embodiment of the present disclosure includes a temperature detection device including a plurality of temperature sensors each including a temperature detection resistor element provided in a temperature detection region, and a storage unit configured to store therein unique information for each of a plurality of the temperature detection resistor elements, the temperature detection resistor element being provided in each of a plurality of partial temperature detection regions in the temperature detection region, and a control circuit configured to read out the unique information stored in the storage unit and detect a temperature for each of the partial temperature detection regions in the temperature detection region based on the unique information and an output potential that is output from the temperature sensor. 
     A display device according to an embodiment of the present disclosure includes a display panel configured to display an image, and the temperature detection device above. The temperature detection device is arranged so as to overlap with the display panel. 
     A head-up display according to an embodiment of the present disclosure includes a display panel configured to display an image, and a temperature detection device arranged so as to overlap with a display surface of the display panel. The temperature detection device includes a plurality of temperature sensors each including a temperature detection resistor element provided in a temperature detection region, and a storage unit configured to store therein unique information for each of a plurality of the temperature detection resistor elements, the temperature detection resistor element is provided for each of a plurality of partial temperature detection regions in the temperature detection region, and an externally provided control device reads out the unique information stored in the storage unit and detects a temperature for each of the partial temperature detection regions in the temperature detection region based on the unique information and an output potential that is output from the temperature sensor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a descriptive view for schematically explaining a HUD device; 
         FIG. 2  is a schematic view illustrating the main configuration of a temperature detection device according to a first embodiment and a control device; 
         FIG. 3  is a configuration diagram of a temperature sensor of the temperature detection device according to the first embodiment; 
         FIG. 4  is a block diagram illustrating an example of the configuration of the control device for temperature detection in the temperature detection device according to the first embodiment; 
         FIG. 5  is a flowchart illustrating an example of temperature detection processing in the temperature detection device according to the first embodiment; 
         FIG. 6  is a diagram illustrating an example of pieces of unique information stored in a storage unit of the temperature detection device according to the first embodiment; 
         FIG. 7  is a flowchart illustrating an example of processing of deriving the pieces of unique information; 
         FIG. 8  is a plan view for explaining a positional relation between a display region and a temperature detection region in a display panel; 
         FIG. 9  is a schematic view illustrating the main configuration of a temperature detection device according to a second embodiment and the control device; and 
         FIG. 10  is a schematic view illustrating the main configuration of a temperature detection device according to a modification of the second embodiment and the control device. 
     
    
    
     DETAILED DESCRIPTION 
     Modes for carrying out the present disclosure (embodiments) will be described in detail with reference to the drawings. Contents described in the following embodiments do not limit the present disclosure. Components described below include those that can be easily assumed by those skilled in the art and substantially the same components. Furthermore, the components described below can be appropriately combined. What is disclosed herein is merely an example, and it is needless to say that appropriate modifications within the gist of the disclosure at which those skilled in the art can easily arrive are encompassed in the scope of the present disclosure. In the drawings, widths, thicknesses, shapes, and the like of the components can be schematically illustrated in comparison with actual modes for more clear explanation. They are however merely examples and do not limit interpretation of the present disclosure. In the present specification and the drawings, the same reference numerals denote components similar to those described before with reference to the drawing that has been already referred, and detail explanation thereof can be appropriately omitted. 
     First Embodiment 
       FIG. 1  is a descriptive view for schematically explaining a HUD device  1 . The HUD device  1  includes a light source unit  6 , a diffusion plate  9 , a display panel  2 , and an optical system RM configured to enlarge an image from the display panel  2  and project the image onto a projection plate WS. 
     A housing  4  accommodates therein the light source unit  6  functioning as a light source device, the display panel  2  configured to output the image using light L from the light source unit  6  as a light source, the diffusion plate  9  provided between the display panel  2  and the light source unit  6 , the optical system RM, and a temperature detection device  10 . 
     The light L emitted from the light source unit  6  is diffused by the diffusion plate  9  and reaches the display panel  2 , so that a part or all of the light L passes through the display panel  2  to be light of the image. In the HUD device  1  in the first embodiment, the optical system RM including a mirror member RM 1  and a mirror member RM 2  guides the light L after passing through the display panel  2  to the projection plate WS. The mirror member RM 1  is a plane mirror, and the mirror member RM 2  is a concave mirror. The mirror member RM 1  may be a concave mirror. The mirror member RM 2  may be a plane mirror. The optical system RM is not limited thereto, and the optical system RM may include one mirror member or equal to or more than three mirror members. 
     Light of the image that has passed through the optical system RM is reflected by the projection plate WS and reaches a user H to be recognized as an image VI in a visual field of the user H. That is to say, the HUD device  1  in the first embodiment functions as a display system configured to project the image onto the projection plate WS. It is sufficient that the projection plate WS is a member having a light-transmitting property and located on the visual line of the user H. The projection plate WS is, for example, a windscreen, a windshield, or a light-transmitting plate member called a combiner of a vehicle, the combiner being provided as a separate member from the windscreen. 
     As illustrated in  FIG. 1 , sunlight LL may be incident on an opening  4 S of the housing  4  depending on a relative position of the sun SUN in the HUD device  1 . The sunlight LL is guided by the optical system RM and is condensed toward the display panel  2  in some cases. The condensed sunlight possibly causes abnormality in the display panel  2  during operation. It is therefore desired that a partial temperature state of a display region is detected. 
     In response to the desire, the temperature detection device  10  is provided on the mirror member RM 1  side with respect to the display panel  2  in the first embodiment. As illustrated in  FIG. 1 , the temperature detection device  10  is arranged so as to receive light guided by the optical system RM and condensed toward the display panel  2  on the mirror member RM 1  side of the display panel  2 . The temperature detection device  10  is provided to be capable of detecting a surface temperature of the temperature detection device  10 . Accordingly, in the embodiment, the temperature detection device  10  can detect temperature change caused by the light guided by the optical system RM and condensed toward the display panel  2 . Deterioration in display output quality due to the display panel  2  can be prevented by controlling operations of the display panel  2  and the light source unit  6  on the basis of the temperature change generated in the temperature detection device  10 , such as by preventing a high-temperature portion from being exposed to light from the light source unit  6 , by turning off a display operation in the high-temperature portion, and so on. 
     The temperature detection device  10  may be separated from the display panel  2  or abut against or adhere to the display panel  2 . The temperature detection device  10  may be provided integrally with the display panel  2 . 
       FIG. 2  is a schematic view illustrating the main configuration of the temperature detection device according to the first embodiment and a control device. As illustrated in  FIG. 2 , the temperature detection device  10  includes a sensor base member  20 , a sensor unit  40 , and a storage unit  50 . The temperature detection device  10  is electrically coupled to a control device  100 . 
     The sensor base member  20  has a temperature detection region SA and a peripheral region GA. The temperature detection region SA includes a plurality of partial temperature detection regions PA. The partial temperature detection regions PA are regions in which a plurality of temperature detection resistor elements ER included in the sensor unit  40  are respectively provided.  FIG. 2  illustrates, as an example,  15  partial temperature detection regions PA in total with five partial temperature detection regions PA aligned in a first direction Dx and three partial temperature detection regions PA aligned in a second direction Dy. The number of partial temperature detection regions PA is however not limited thereto. For example, a configuration including  12  partial temperature detection regions PA in total with four partial temperature detection regions PA aligned in the first direction Dx and three partial temperature detection regions PA aligned in the second direction Dy can also be employed. 
     The first direction Dx is one direction in a plane parallel with the sensor base member  20 . The second direction Dy is one direction in the plane parallel with the sensor base member  20  and is a direction orthogonal to the first direction Dx. The second direction Dy may non-orthogonally intersect the first direction Dx. A third direction Dz is a direction orthogonal to the first direction Dx and the second direction Dy, and is a direction normal to the sensor base member  20 . 
     Each temperature detection resistor element ER is an electric resistor using compound (metal compound) containing an alloy or metal, or metal as a material. The resistor element ER may be a multilayered body formed by stacking a plurality of types of materials falling under at least one of the metal, alloy, and metal compound. An expression “alloy or the like” in explanation of the first embodiment indicates a material capable of being employed as a composition of the resistor element ER. In the example illustrated in  FIG. 2 , each of the temperature detection resistor elements ER has such shape that a plurality of L-shaped wiring lines the long sides of which are along the second direction Dy are coupled in the first direction Dx. With such a shape, the mode of each temperature detection resistor element ER is provided by coupling the L-shaped wiring lines such that the short sides of the two L-shaped wiring lines adjacent to each other in the first direction Dx are alternately arranged in the second direction Dy. 
     The peripheral region GA is a region between the outer periphery of the temperature detection region SA and end portions of the sensor base member  20  and is a region in which no temperature detection resistor element ER is provided. A plurality of reference resistor elements  41  and the storage unit  50  are provided in the peripheral region GA. The temperature detection resistor elements ER provided in the respective partial temperature detection regions PA and the reference resistor elements  41  provided in the peripheral region GA configure a temperature sensor, which will be described later. 
     The storage unit  50  is a rewritable non-volatile memory such as a flash memory. The storage unit  50  stores therein pieces of unique information for the respective temperature detection resistor elements ER provided in the partial temperature detection regions PA. The pieces of unique information that are stored in the storage unit  50  are, to be specific, unique values indicating electric characteristics differing for the respective temperature detection resistor elements ER. Resistance values of the temperature detection resistor elements ER under a constant temperature environment may be different due to variations, and change rates of the resistance values thereof for temperature change may be different. Accordingly, when the temperature detection device  10  of the present disclosure detects the temperatures of the partial temperature detection regions PA in the temperature detection region SA, it needs to compensate for variations of the electric characteristics differing for the respective temperature detection resistor elements ER. 
     The control device  100  supplies control signals to the sensor unit  40  and the storage unit  50  to control detection operations of the temperature detection device  10 . The control device  100  may have a mode that supplies control signals to the display panel  2  and the light source unit  6  to control the display operations in the display panel  2  and lighting or non-lighting of the light source unit  6 . 
       FIG. 3  is a configuration diagram of each temperature sensor of the temperature detection device according to the first embodiment.  FIG. 3  exemplifies a temperature sensor SENS(m) corresponding to m (m is an integer of 1 to M) partial temperature detection region PA among M (M=15 in the example illustrated in  FIG. 2 ) partial temperature detection regions PA. 
     As illustrated in  FIG. 3 , the temperature sensor SENS(m) of the temperature detection device  10  according to the first embodiment is configured by electrically coupling the reference resistor element  41  and the temperature detection resistor element ER(m) in series between an input potential Vin input from the control device  100  and a reference potential GND. The temperature sensor SENS(m) outputs an output potential Vout(m) based on a volume resistivity of the temperature detection resistor element ER(m). In other words, a potential at a coupling point between the temperature detection resistor element ER(m) and the reference resistor element  41  is output as the output potential Vout(m) of the temperature sensor SENS(m). 
     In the temperature sensor SENS(m), a current generated on the basis of the input potential Vin tries to flow to the reference potential GND. The flow of the current to the reference potential GND is however inhibited depending on the volume resistivity of the temperature detection resistor element ER(m), so that a current toward the control device  100  is generated. The current flowing toward the control device  100  generates the output potential Vout(m). That is to say, as the volume resistivity of the temperature detection resistor element ER(m) is higher, the output potential Vout(m) is increased. 
     Where a resistance value of the reference resistor element  41  is Rref and a resistance value of the temperature detection resistor element ER(m) is Re(m), the output potential Vout(m) of the temperature sensor SENS(m) is expressed by the following equation ( 1 ). 
         V out( m )=[ Re ( m )/{ Re ( m )+ Rref}]×V in   (1)
 
     In this case, a temperature TPA(m) detected by the temperature sensor SENS(m) is expressed by the following equation (2). 
         TPA ( m )=[ Rref/{V in/ V out( m ))−1)}]× a ( m )+ b ( m )   (2)
 
     In the above-mentioned equation (2), a first coefficient a(m) and a second coefficient b(m) are unique values for compensating for variations of the electric characteristics of the temperature detection resistor element ER(m) and are different for each temperature detection resistor element ER(m). Accordingly, when the control device  100  calculates the temperatures of the respective partial temperature detection regions PA that are detected by the corresponding temperature sensors SENS(m), it needs to apply the first coefficients a(m) and the second coefficients b(m) differing for the respective temperature detection resistor elements ER(m) of the temperature sensors SENS(m), in other words, for the respective output potentials Vout(m) that are output from the partial temperature detection regions PA. 
     In the present disclosure, the storage unit  50  stores therein the first coefficients a(m) and the second coefficients b(m) corresponding to the output potentials Vout(m) that are output from the respective temperature sensors SENS(m) as the pieces of unique information for the respective temperature detection resistor elements ER(m) provided in the corresponding partial temperature detection regions PA. The control device  100  accesses the storage unit  50  to read out the first coefficients a(m) and the second coefficients b(m) corresponding to the output potentials Vout(m) that are output from the respective temperature sensors SENS(m), and calculates the temperatures of the respective partial temperature detection regions PA in the temperature detection region SA. Hereinafter, the configuration for performing processing of calculating the temperatures of the respective partial temperature detection regions PA in the temperature detection region SA and the temperature calculation processing will be described. 
       FIG. 4  is a block diagram illustrating an example of the configuration of the control device for temperature detection in the temperature detection device according to the first embodiment. As illustrated in  FIG. 4 , the control device  100  includes a control circuit  110  and a power supply circuit  120 . The configuration provided by combining the temperature detection device  10  according to the first embodiment and the control circuit  110  corresponds to a “temperature detection system” in the present disclosure. 
     The control circuit  110  is configured by a temperature detection control IC packaged as a what-is-called one-chip integrated circuit (IC), for example. The control circuit  110  may have a mode that is configured by a plurality of ICs, for example. 
     The control circuit  110  includes a temperature detection circuit  80 , a central processing unit (CPU)  84 , a bus  85 , a read only memory (ROM)  86 , an electrically erasable programmable read only memory (EEPROM)  87 , a random access memory (RAM)  88 , and a general purpose input output (GPIO)  89 . The temperature detection circuit  80  includes a filter  81 , an amplification circuit  82 , and an A/D conversion circuit  83 . 
     The filter  81  is a filter circuit configured to remove noise from the output potentials Vout(m) that are output from the partial temperature detection regions PA of the temperature detection device  10 . The amplification circuit  82  amplifies the output potentials provided by noise processing by the filter  81 . The A/D conversion circuit  83  converts analog output potentials provided by amplification by the amplification circuit  82  into digital signals. 
     The CPU  84  of the control circuit  110  performs various pieces of arithmetic processing such as processing based on the digital signals generated by the A/D conversion circuit  83 . 
     The bus  85  functions as a transmission path of various digital signals in the control circuit  110 , and for example, it transmits the digital signals that are output from the A/D conversion circuit  83  to the CPU  84 . The A/D conversion circuit  83 , the CPU  84 , the bus  85 , the ROM  86 , the EEPROM  87 , the RAM  88 , and the GPIO  89  are coupled to the bus  85 . 
     The ROM  86  stores therein a computer program and the like in a non-rewritable manner. The computer program and the like indicate a software computer program that is read out in processing by the CPU  84  and data that is referred in execution of the software computer program. The EEPROM  87  stores therein the computer program and the like in a rewritable manner. The RAM  88  temporarily stores therein various pieces of date and parameters that are generated with execution processing of the computer program and the like by the CPU  84 . 
     The GPIO  89  transmits signals to the outside in response to output from the CPU  84  and the like through the bus  85 . 
     The power supply circuit  120  is a circuit configured to supply the input potential Vin to the sensor unit  40  of the temperature detection device  10 . Potential difference between the input potential Vin and the reference potential GND is thereby applied to the temperature sensor SENS(m) illustrated in  FIG. 3 . The power supply circuit  120  supplies power supply to the storage unit  50  of the temperature detection device  10 . 
     In the above-mentioned configuration, the control circuit  110  performs communication with the storage unit  50  of the temperature detection device  10  and an external high-order control device  200 . The present disclosure is not limited by a protocol, an interface, and the like of communication that is performed with the storage unit  50  of the temperature detection device  10  and the external high-order control device  200 . 
     Hereinafter, the temperature detection processing in the control device  100  using the temperature detection device  10  according to the first embodiment will be described. 
       FIG. 5  is a flowchart illustrating an example of the temperature detection processing in the temperature detection device according to the first embodiment.  FIG. 6  is a diagram illustrating an example of the pieces of unique information stored in the storage unit of the temperature detection device according to the first embodiment. 
     The storage unit  50  of the temperature detection device  10  stores therein the pieces of unique information illustrated in  FIG. 6 , for example, as a precondition of the temperature detection processing illustrated in  FIG. 5 . To be specific, as illustrated in  FIG. 6 , the storage unit  50  stores therein the first coefficients a(m) and the second coefficients b(m) that are used in the above-mentioned equation (2) as the pieces of unique information for the respective temperature detection resistor elements ER(m) provided in the corresponding partial temperature detection regions PA. 
     First, the control device  100  determines whether the temperature detection processing is started (step S 101 ). When the temperature detection processing is not started (No at step S 101 ), the control device  100  repeats the processing at step S 101  until the temperature detection processing is started (Yes at step S 101 ). The start of the temperature detection processing may be in a mode in which a temperature detection start instruction is input from the high-order control device  200  or in a mode in which the control device  100  includes a trigger (for example, a timer) of starting the temperature detection processing, for example. The temperature detection processing illustrated in  FIG. 5  may have a mode that executes as interruption processing into various pieces of processing in the control device  100 . 
     When the temperature detection processing is started (Yes at step S 101 ), the pieces of unique information illustrated in  FIG. 6 , for example, are read out and acquired from the storage unit  50  of the temperature detection device  10  (step S 102 ). The pieces of unique information read out from the storage unit  50  are temporarily stored in the RAM  88  of the control circuit  110 , for example. 
     The power supply circuit  120  of the control device  100  supplies the input potential Vin to the sensor unit  40  of the temperature detection device  10  (step S 103 ). 
     The control device  100  detects the output potential Vout(m) output from the sensor unit  40  of the temperature detection device  10  (step S 104 ), calculates the temperature TPA(m) detected by the temperature sensor SENS(m) with the above-mentioned equation (2) using the pieces of unique information acquired from the storage unit  50  of the temperature detection device  10  for the output potential Vout(m) (step S 105 ), and temporarily stores the calculated temperature TPA(m) in the RAM  88  of the control circuit  110 , for example (step S 106 ). 
     The control device  100  determines whether the temperatures TPA(m) corresponding to all of the partial temperature detection regions PA in the temperature detection region SA are stored (step S 107 ). When the temperatures TPA(m) corresponding to all of the partial temperature detection regions PA in the temperature detection region SA are not stored (No at step S 107 ), the control device  100  repeats the pieces of processing at step S 104  to step S 107  until the temperatures TPA(m) corresponding to all of the partial temperature detection regions PA in the temperature detection region SA are stored (Yes at step S 107 ). 
     When the temperatures TPA(m) corresponding to all of the partial temperature detection regions PA in the temperature detection region SA are stored (Yes at step S 107 ), the control device  100  performs predetermined control on the display panel  2  and the light source unit  6  using the temperatures TPA(m) corresponding to the partial temperature detection regions PA (step S 108 ) and returns to the processing at step S 101 . As the predetermined control on the display panel  2 , a mode in which any of a plurality of display control patterns is applied depending on the temperatures TPA(m) corresponding to the respective partial temperature detection regions PA may be employed. As the predetermined control on the light source unit  6 , a mode in which any of a plurality of light source control patterns is applied depending on the temperatures TPA(m) corresponding to the respective partial temperature detection regions PA may be employed. The present disclosure is not limited by the modes of the control on the display panel  2  and the light source unit  6  depending on the temperatures TPA(m) corresponding to the partial temperature detection regions PA. 
     Next, a method of deriving the pieces of unique information for the respective temperature detection resistor elements ER(m) provided in the corresponding partial temperature detection regions PA, which are illustrated in  FIG. 6 , will be described. The pieces of unique information for the respective temperature detection resistor elements ER(m) provided in the corresponding partial temperature detection regions PA, that is, the first coefficients a(m) and the second coefficients b(m) that are used in the above-mentioned equation (2) are, for example, set in a process before shipping of the temperature detection device  10  according to the first embodiment and stored in the storage unit  50 . 
       FIG. 7  is a flowchart illustrating an example of the processing of deriving the pieces of unique information. 
     A setting tool device is coupled to the temperature detection device  10  according to the first embodiment as a precondition of the processing of deriving the first coefficients a(m) and the second coefficients b(m) for the respective temperature detection resistor elements ER(m) as the pieces of unique information, which is illustrated in  FIG. 7 . The configuration of the setting tool device is similar to the configuration of the control device  100  illustrated in  FIG. 4 . Therefore, in the following description, the setting tool device is replaced with the control device  100 , and a mode in which the control device  100  performs the processing of deriving the pieces of unique information illustrated in  FIG. 6  is described. 
     The processing of deriving the pieces of unique information, which is illustrated in  FIG. 7 , is performed as follows. That is, each first coefficient a(m) and each second coefficient b(m) in the above-mentioned equation (2) are handled as variables, the first coefficient a(m) and the second coefficient b(m) corresponding to each temperature detection resistor element ER(m) are calculated using the following equation (3) and the following equation (4), and the first coefficient a(m) and the second coefficient b(m) that have been calculated are stored in the storage unit  50  as a part of the pieces of unique information illustrated in  FIG. 6 . In the following equation (3), an output potential Vout 1 ( m ) that is output from each partial temperature detection region PA of the temperature detection device  10  under a first temperature TPA 1  environment (to be specific, for example, in an environment of 20° C.) is applied to the above-mentioned equation (2). In the following equation (4), an output potential Vout 2 ( m ) that is output from each partial temperature detection region PA of the temperature detection device  10  under a second temperature TPA 2  environment (to be specific, for example, in an environment of 60° C.) differing from the first temperature TPA 1  is applied to the above-mentioned equation (2). 
         TPA 1( m )=[ Rref /{( V in/ V out1( m ))−1}]× a ( m )+ b ( m )   (3)
 
         TPA 2( m )=[ Rref /{( V in/ V out2( m ))−1)}]× a ( m )+ b ( m )   (4)
 
     First, the control device  100  starts processing of detecting the output potentials Vout 1 ( m ) that are output from the respective partial temperature detection regions PA of the temperature detection device  10  under the first temperature TPA 1  environment (step S 1 ). 
     The power supply circuit  120  of the control device  100  supplies the input potential Vin to the sensor unit  40  of the temperature detection device  10  (step S 201 ). 
     The control device  100  detects the output potential Vout 1 ( m ) output from the sensor unit  40  of the temperature detection device  10  (step  5202 ) and temporarily stores the output potential Vout 1 ( m ) in the RAM  88  of the control circuit  110 , for example (step S 203 ). 
     The control device  100  determines whether the output potentials Vout 1 ( m ) corresponding to all of the partial temperature detection regions PA in the temperature detection region SA are stored (step S 204 ). When the output potentials Vout 1 ( m ) corresponding to all of the partial temperature detection regions PA in the temperature detection region SA are not stored (No at step S 204 ), the control device  100  repeats the pieces of processing at step S 202  to step S 204  until the output potentials Vout 1 ( m ) corresponding to all of the partial temperature detection regions PA in the temperature detection region SA are stored (Yes at step S 204 ). 
     When the output potentials Vout 1 ( m ) corresponding to all of the partial temperature detection regions PA in the temperature detection region SA are stored, the control device  100  subsequently starts processing of detecting the output potentials Vout 2 ( m ) that are output from the respective partial temperature detection regions PA of the temperature detection device  10  under the second temperature TPA 2  environment (step S 2 ). 
     The power supply circuit  120  of the control device  100  supplies the input potential Vin to the sensor unit  40  of the temperature detection device  10  (step S 301 ). 
     The control device  100  detects the output potential Vout 2 ( m ) output from the sensor unit  40  of the temperature detection device  10  (step S 302 ) and temporarily stores the output potential Vout 2 ( m ) in the RAM  88  of the control circuit  110 , for example (step S 303 ). 
     The control device  100  determines whether the output potentials Vout 2 ( m ) corresponding to all of the partial temperature detection regions PA in the temperature detection region SA are stored (step S 304 ). When the output potentials Vout 2 ( m ) corresponding to all of the partial temperature detection regions PA in the temperature detection region SA are not stored (No at step S 304 ), the control device  100  repeats the pieces of processing at step S 302  to step S 304  until the output potentials Vout 2 ( m ) corresponding to all of the partial temperature detection regions PA in the temperature detection region SA are stored (Yes at step S 304 ). 
     When the output potentials Vout 2 ( m ) corresponding to all of the partial temperature detection regions PA in the temperature detection region SA are stored, the control device  100  subsequently starts processing of calculating the first coefficients a(m) and the second coefficients b(m) corresponding to the respective temperature detection resistor elements ER(m) (step S 3 ). 
     The control device  100  reads out the output potential Vout 1 ( m ) and the output potential Vout 2 ( m ) (step S 401 ), calculates the first coefficient a(m) and the second coefficient b(m) corresponding to the temperature detection resistor element ER(m) using the above-mentioned equation (3) and the above-mentioned equation (4) (step S 402 ), and temporarily stores the first coefficient a(m) and the second coefficient b(m) in the RAM  88  of the control circuit  110 , for example (step S 403 ). 
     The control device  100  determines whether the first coefficients a(m) and the second coefficients b(m) corresponding to all of the partial temperature detection regions PA in the temperature detection region SA are stored (step S 404 ). When the first coefficients a(m) and the second coefficients b(m) corresponding to all of the partial temperature detection regions PA in the temperature detection region SA are not stored (No at step S 404 ), the control device  100  repeats the pieces of processing at step S 401  to step S 404  until the first coefficients a(m) and the second coefficients b(m) corresponding to all of the partial temperature detection regions PA in the temperature detection region SA are stored (Yes at step S 404 ). 
     When the first coefficients a(m) and the second coefficients b(m) corresponding to all of the partial temperature detection regions PA in the temperature detection region SA are stored, the control device  100  stores, in the storage unit  50  of the temperature detection device  10 , the first coefficients a(m) and the second coefficients b(m) corresponding to the respective temperature detection regions PA as the pieces of unique information illustrated in  FIG. 6  (step S 405 ). 
     Subsequently, the control device  100  starts processing of checking consistency of the pieces of unique information (step S 4 ). 
     The control device  100  reads out the pieces of unique information stored in the storage unit  50  (step S 501 ) and determines whether the pieces of read unique information are normal (step S 502 ). When the pieces of read unique information are normal (Yes at step S 502 ), the processing of deriving the pieces of unique information is ended. When the pieces of read unique information are not normal (No at step S 502 ), the control device  100  returns to step S 1  and repeats the above-mentioned processing of deriving the pieces of unique information. In the processing of checking the consistency of the pieces of unique information from step S 4 , a mode in which whether pieces of data of the first coefficients a(m) and the second coefficients b(m) temporarily stored in the RAM  88  of the control circuit  110  and pieces of data of the first coefficients a(m) and the second coefficients b(m) as the pieces of unique information stored in the storage unit  50  match with each other is determined may be employed. The present disclosure is not limited by the method of checking the consistency of the pieces of unique information stored in the storage unit  50 . 
     As described above, in the present disclosure, the temperature detection device  10  according to the first embodiment includes the storage unit  50  configured to store therein the first coefficients a(m) and the second coefficients b(m) corresponding to the output potentials Vout(m) that are output from the respective temperature sensors SENS(m) as the pieces of unique information for the respective temperature detection resistor elements ER(m) provided in the corresponding partial temperature detection regions PA, and the external control device  100  reads out the pieces of unique information stored in the storage unit  50  to perform the temperature detection processing for the respective partial temperature detection regions PA in the temperature detection region SA in the temperature detection device  10 . Increase in cost due to provision of the temperature detection function in the HUD device  1  can thereby be prevented. 
     The temperature detection device  10  according to the first embodiment can appropriately change and update the pieces of unique information stored in the storage unit  50  because the storage unit  50  configured by, for example, the non-volatile memory can be rewritten. Flexible approach such as rewriting of the pieces of unique information by the control device  100  can therefore be performed as described above when the pieces of unique information need to be changed or updated after shipping of the temperature detection device  10 . 
     It is sufficient that the temperature detection device  10  according to the first embodiment supplies power supply to the input potential Vin, the non-volatile memory configuring the storage unit  50 , and the like from the control device  100  when the temperature detection processing is performed. Power consumption can thus be reduced in comparison with that when a circuit corresponding to the control circuit  110  is mounted on a temperature detection device. The control circuit  110  can enhance accuracy of the necessary output potentials Vout(m) in the temperature detection processing by understanding the input potential Vin that is supplied from the power supply circuit  120 . 
     The temperature detection device  10  according to the first embodiment includes no circuit corresponding to the control circuit  110  that performs the temperature detection processing. Accordingly, the temperature detection device  10  is not necessarily required when a temperature detection processing computer program is changed or updated, and the temperature detection processing computer program can be changed or updated only by the control device  100 . 
       FIG. 8  is a plan view for explaining a positional relation between the display region and the temperature detection region in the display panel. As illustrated in  FIG. 8 , since the temperature detection device  10  and the display panel  2  overlap with each other in the third direction Dz such that the temperature detection region SA covers the display region AA of an image by the display panel  2 , the temperature detection device  10  can detect temperature change that is possibly caused by light guided by the optical system RM and condensed toward the display region AA of the display panel  2 . Operation control of the display panel  2  in accordance with the temperature change can thereby be performed. When the temperature detection device  10  detects such high temperature that display output quality of the display panel  2  cannot be ensured, operations of the display panel  2  may be stopped. In such a case, display output of an image by the display panel  2  may be stopped only in a range corresponding to a part (partial temperature detection region PA) of the temperature detection device  10  at which the high temperature has been detected. 
     The temperature detection device  10  does not have to be provided in the HUD device  1 . For example, the temperature detection device  10  may be provided so as to overlap with a display device in another mode, the temperature detection device  10  may be combined with a device other than the display device, or the temperature detection device  10  may be provided alone. 
     Second Embodiment 
       FIG. 9  is a schematic view illustrating the main configuration of a temperature detection device according to a second embodiment and a control device. In the following explanation, the same reference numerals denote the same components as those described in the above-mentioned first embodiment and overlapped explanation thereof is omitted. Only different points from the first embodiment will be explained. 
     In a temperature detection device  10   a  according to the second embodiment illustrated in  FIG. 9 , a sensor unit  40   a  includes a multiplexer  42 . 
     The multiplexer  42  is a switch circuit configured to couple any one of the temperature detection resistor elements ER(m) and the control device  100 . The multiplexer  42  selects the temperature detection resistor element ER(m) that is electrically coupled to the control device  100  among the temperature detection resistor elements ER(m). In the present embodiment, the multiplexer  42  is configured by a logic IC provided in the peripheral region GA of a sensor base member  20   a . The multiplexer  42  selects the temperature detection resistor element ER(m) to be coupled to the control device  100  with a control signal that is output from the GPIO  89  of the control circuit  110  provided in the control device  100 , for example. The temperature sensor SENS(m) illustrated in  FIG. 3  is configured by electrically coupling the temperature detection resistor element ER(m) selected by the multiplexer  42  and a reference resistor element  41   a  in series. With this configuration, the number of wiring lines between the temperature detection device  10   a  and the control device  100  can be largely reduced. 
     Modification 
       FIG. 10  is a schematic view illustrating the main configuration of a temperature detection device according to a modification of the second embodiment and a control device. In a temperature detection device  10   b  according to the modification illustrated in  FIG. 10 , a multiplexer  42   a  of a sensor unit  40   b  is configured by a thin film transistor (TFT) switch circuit provided in the peripheral region GA of a sensor base member  20   b  unlike the multiplexer  42  configured by the logic IC in the second embodiment. This configuration can contribute to reduction in cost in comparison with the configuration in the second embodiment. 
     The components in the above-mentioned embodiments can be appropriately combined. Other action effects provided by the modes described in the present embodiments that are obvious from description of the present specification or at which those skilled in the art can appropriately arrive should be interpreted to be provided by the present disclosure.