Projection-type display system

Abstract

This enables the detection of abnormalities in projection-type display systems caused by factors such as the condition of optical fiber wiring and ambient temperature. [Solution] The light source unit 100 of the projection display system 10 includes a first control unit 110, an abnormality determination unit 113, a laser light source unit 125 equipped with a plurality of optical elements, an optical element driving unit 116, and a first light receiving unit 123 that detects the light intensity of the output light of each optical element. The projection unit 300 includes a second control unit 313, an optical modulation device 322, and a second light receiving unit 324 that detects the light intensity of the light for forming the projection image. The abnormality determination unit 113 determines whether an abnormal condition is caused by at least one of the optical fiber mounting status and ambient temperature, based on the light intensity detected by the second light receiving unit 324 within the timing of a signal obtained by logically ANDing a light source drive value control signal PCR or a processed light source drive value control signal PCR1 obtained therefrom and a light emission enable signal LD_EN.

Description

Technical Field

[0001] The present invention relates to a projection display system, etc. that is mounted on a vehicle such as an automobile and forms a projected image on a road, etc.

Background Art

[0002] A projection display device in which a light source unit and a projection unit are separated is described in, for example, Patent Documents 1 and 2.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] The inventors' studies have revealed the following problems: (1) A projection-type display system, in which the light source and projection unit are separate components, is installed, for example, in an empty space in a vehicle after being shipped from the factory. At this time, it is necessary to connect the light source and projection unit with a communication cable and optical fiber. (2) After this work, it is necessary to determine whether the projection-type display system is operating normally, and if an abnormal condition is detected, appropriate measures such as stopping the light output or notifying the abnormality must be taken. (3) One possible method for determining this abnormality is to provide a light-receiving element (such as a photodiode) on the projection unit side that receives the light for forming the projection image, and to check whether the light for forming the projection image sent from the light source unit via the optical fiber is received by the projection unit with an appropriate amount of light. (4) However, the transmission loss of optical fibers varies considerably depending on the condition of the optical fiber wiring and the fact that the ambient temperature in which the product is actually used differs greatly from the standard temperature (reference temperature) assumed at the time of product shipment. For example, in a wired optical fiber, the transmission loss of the optical fiber tends to increase with the number of bends or the ambient temperature. Therefore, when a projection display system (product) is installed on-site and optical fibers are wired, it is quite possible that, depending on the wiring conditions, a greater transmission loss than the standard transmission loss of the optical fiber assumed at the time of factory shipment will occur, and the amount of light received on the projection side will decrease. In other words, the amount of light transmitted through the optical fiber can vary greatly depending on the wiring conditions of the optical fiber, and under such circumstances, it is not easy to determine normal / abnormal based solely on the light reception intensity of the light receiving element installed on the projection side. (5) If, for example, the amount of light received on the projection side has decreased, and a strict judgment is made based on the light reception intensity of the light receiving element installed on the projection side, it is conceivable that a product that is actually usable may be judged as abnormal. In this case, it will be necessary to reinstall the product, redo the optical fiber wiring, or replace the product, making on-site work inefficient. (6) On the other hand, if the criteria for judgment are appropriately relaxed when determining abnormalities, products that should be judged as abnormal may be judged as normal, which could result in a failure to ensure the reliability and safety of the products.(7) Therefore, while ensuring the reliability and safety of the product, it is necessary to minimize the occurrence of products being judged as abnormal and rendered unusable on-site, thereby preventing inefficiencies in on-site work. (8) Furthermore, if light leaks from the optical fiber during on-site determination of whether a product is normal or abnormal and that light enters the eyes of a worker, it could cause eye damage. Therefore, the method for determining whether a product is normal or abnormal on-site must be able to prevent accidents and ensure the safety of workers. (9) Immediately after switching the display from off to on, the time until light is actually emitted from the light source may vary, and it is conceivable that the light source may be mistakenly judged as abnormal. Patent documents 1 and 2 mentioned above do not describe such problems, nor do they mention any countermeasures.

[0005] These problems were revealed through the inventors' research on this invention.

[0006] One of the objectives of the present invention is to enable the detection of abnormalities in a projection-type display system caused by factors such as the wiring condition of optical fibers and ambient temperature.

[0007] Other objects of the present invention will become apparent to those skilled in the art by referring to the embodiments and best embodiments described below, as well as the accompanying drawings. [Means for solving the problem]

[0008] The following are examples of embodiments of the present invention to facilitate understanding of its outline.

[0009] In a first embodiment, the projection display system is a projection display system in which a light source unit and a projection unit are separated, the light source unit and the projection unit are electrically or optically connected via a communication cable, and light for forming a projection image output by the light source unit is supplied to the projection unit via an optical fiber, and a projection image is formed by the projection unit, wherein the light source unit includes a first control unit having a function to control bidirectional communication with the projection unit, an optical element unit having a plurality of optical elements with different emission colors that generate the light for forming the projection image, an optical element drive unit that drives the plurality of optical elements, and a first light receiving unit that detects the light intensity of each color of light output from the optical element unit, and the projection unit includes a second control unit having a function to control bidirectional communication with the light source unit, and via the optical fiber The optical element drive unit includes an optical element drive unit that drives the optical element based on at least a light source drive value control signal for adjusting the light emission intensity of the optical element and a light emission enable signal for adjusting the light emission timing of the optical element, and an abnormality determination unit that determines whether an abnormal condition is caused by at least one of the mounting status of the optical fiber and the ambient temperature based on the light intensity detected by the second light receiving unit within the timing of a signal obtained by logically ANDing the light source drive value control signal or a light source drive value control processing signal obtained by processing the same and the light emission enable signal.

[0010] In the first embodiment, the light intensity can be reliably detected in accordance with the timing when both the signal for adjusting the light intensity and the signal for adjusting the light emission timing are ON (the timing when the optical element is emitting light), and the normal / abnormal state of the projection display system (product) can be determined.

[0011] In a second embodiment dependent on the first embodiment, the abnormality determination unit adjusts the drive value of the optical element drive unit so that a first condition is met, which is that the received intensity of each of the light for forming the projection image of each color in the second light receiving unit is within a first allowable range. The unit also determines whether a second condition is met, which is that the received intensity of all of the output lights of the plurality of optical elements of different emission colors detected by the first light receiving unit, or a predetermined number of the output lights, is within a second allowable range. If the second condition is not met, the unit performs an abnormality determination process in which it determines that an abnormal state exists.

[0012] Specifically, the drive value of the light source drive unit in the light source unit (in other words, the light emission intensity of each color optical element) is adjusted (calibrated) so that the light received by the second light receiving unit for the light used to form the projected image of each color on the receiving side (projection side) of the optical fiber falls within the first acceptable range (in other words, the first condition is met).

[0013] Here, for example, if the actual transmission loss in the wired optical fiber is within the range of the factory-specified values, then the light emission intensity (adjusted light emission intensity) of each color optical element on the transmitting side (light source side) of the optical fiber should also be within the range of the specifications. If the light emission intensity of all (or a predetermined number of) color optical elements falls outside the range of the specifications, then the optical elements are emitting abnormal light (and are judged to be in an abnormal state). Possible causes of this include problems with the installation of the optical fiber, cracks in the cladding layer of the optical fiber causing light leakage, or a significant difference between the ambient temperature at the site and the pre-specified standard temperature, resulting in an unexpectedly low level of communication reliability. Focusing on this point, in this embodiment, first, the drive value of the light source drive unit in the light source unit (in other words, the light emission intensity of each color optical element) is adjusted (calibrated) so that the light received by the second light receiving unit for forming the projected image of each color on the receiving side (projection side) of the optical fiber is within the first allowable range (in other words, the first condition is met). If the first condition is not met within the allowable dynamic range, it is determined that there is an abnormal condition caused by the wiring condition of the optical fiber, etc. On the other hand, if the first condition is met within the allowable dynamic range, it is determined whether the light emission intensity (adjusted light emission intensity) of all (or a predetermined number of) optical elements of each color detected by the first light receiving unit on the transmitting side (light source side) of the optical fiber is within a predetermined second allowable range (in other words, whether the second condition is met). If the second condition is not met, it is determined that an abnormal condition caused by the wiring condition of the optical fiber, etc. has occurred. By appropriately detecting abnormal conditions, the light output of the light-emitting element can be stopped, or the abnormality can be notified to the user, for example, via a vehicle-side controller, enabling appropriate measures to be taken quickly. In other embodiments dependent on the first embodiment, the abnormality determination unit may perform an abnormality determination process that determines an abnormal condition when the light reception intensity at the second light-receiving unit is outside a preset range (particularly below a preset range).Furthermore, in other embodiments dependent on the first embodiment, the abnormality determination unit determines whether or not an abnormal state exists based on whether the light reception intensity at at least the second light receiving unit falls within a predetermined range, and is not limited to the abnormality determination process described above.

[0014] In a third embodiment dependent on the second embodiment, the abnormality determination unit has a low-luminescence mode in which each of the plurality of optical elements emits light at a luminance lower than the normal luminescence luminance, and a normal-luminescence mode in which each element emits light at the normal luminescence luminance. The abnormality determination process may be performed in the low-luminescence mode to determine whether or not there is an abnormal state in the low-luminescence state, and after it is determined that there is no abnormal state in the low-luminescence state, the abnormality determination process may be performed in the normal-luminescence mode to determine whether or not there is an abnormal state in the normal-luminescence state.

[0015] In the third embodiment, when detecting an anomaly, in addition to the normal emission mode, a low emission mode can be used in which the optical element emits light at a lower brightness than normal emission. For example, when performing the first anomaly detection process after wiring optical fibers on-site, there are workers around the optical fibers, so if, for example, light leaks from the optical fiber and shines into the eyes of the workers, it could cause eye damage. Therefore, it is considered undesirable to suddenly perform an anomaly detection process with high-brightness emission. According to this embodiment, by using the low emission mode, the amount of light propagating through the optical fiber can be sufficiently reduced. Therefore, even if, for example, light leaks from the optical fiber and shines into the eyes of the workers, the light is weak, so the safety of the workers' eyes can be ensured. According to this embodiment, after confirming that the basic performance (minimum performance) of optical transmission via the optical fiber is ensured using the low emission mode, the emission power of the optical element can be returned to the normal level and anomaly detection processing can be performed using the normal emission mode, thereby enabling highly accurate anomaly detection while ensuring the safety of workers.

[0016] In a fourth embodiment dependent on any one of the first to third embodiments, the abnormality determination unit may perform a process to confirm whether communication between the first control unit and the second control unit via the communication cable can be performed correctly by establishing a communication link or by receiving an arbitrary signal changed by the first control unit in the second control unit and returning it to the first control unit.

[0017] In the fourth embodiment, it is possible to confirm whether communication between the first control unit and the second control unit is taking place normally. This ensures that the light intensity received by the second light receiving unit is transmitted normally between the first control unit and the second control unit, thus enabling safe abnormality detection.

[0018] In a fifth embodiment dependent on any one of the first to fourth embodiments, the abnormality determination unit is provided with a first reference light reception value at the first light receiving unit for each color of light, a second reference light reception value at the second light receiving unit for each color of light, and a reference threshold coefficient used to determine the upper and lower limits for defining the second tolerance range for each color of light. The abnormality determination unit has a calibration unit that calibrates the reference threshold coefficient and calculates a calibration threshold coefficient. The calibration unit calibrates the reference threshold coefficient at a magnification determined by comparing a first ratio, which is the ratio of the first and second reference light reception values, with a second ratio, which is the ratio of the first and second measured light reception values ​​at the first and second light receiving units, to calculate the calibration threshold coefficient. If the calculated calibration threshold coefficient is within a predetermined normal range, the calibration threshold coefficient may be used to determine the upper and lower limits for defining the second tolerance range.

[0019] In the fifth aspect, the upper and lower limits for determining the second acceptable range for determining normal / abnormal are determined using a coefficient called the "threshold coefficient." When a product is shipped from the factory, a standard threshold coefficient is provided in advance. However, it is undeniable that immediately after laying optical fibers in the field, transmission loss tends to increase due to bending of the optical fibers, etc., and the quality of optical communication tends to deteriorate. If abnormality is determined using the upper and lower limits set by the standard threshold coefficient provided at the factory, ignoring this situation, it is conceivable that the determination will become too strict, leading to an increase in cases where usable products are judged as abnormal and unusable. In this case, reinstallation of the product, rewiring of the optical fibers, or replacement of the product will be necessary, making on-site work inefficient.

[0020] However, if the judgment criteria are relaxed too much, products that should be judged as abnormal may be judged as normal, which could lead to a situation where the reliability and safety of the product cannot be ensured. Therefore, in this embodiment, the actual measured values ​​of the first and second light receiving units at the site are used to properly calibrate the reference threshold coefficient prepared at the factory. The threshold coefficient obtained as a result is called the "calibration threshold coefficient".

[0021] For this calibration, the reference threshold coefficient is calibrated by a magnification determined by comparing the first ratio of the first and second reference light-receiving values ​​prepared at the factory with the second ratio, which is the ratio of the first and second measured light-receiving values ​​at the first and second light-receiving units, and the calibration threshold coefficient is calculated accordingly. For example, suppose that under standard conditions before product shipment, when each color light element is driven at a reference drive value, the reference light-receiving value at the first light-receiving unit on the light source side becomes a relative value of "1", and the reference light-receiving value at the second light-receiving unit on the projection unit side becomes a relative value of "0.8". If the first ratio is "0.8:1", then the value of that ratio is "0.8 (=0.8 / 1)". On the other hand, suppose that the actual measured values ​​(measured values: expressed here as relative values) at the first light-receiving unit were "1" and "0.4". Here, if we set the second ratio to "0.4:1", the value of that ratio becomes "0.4 (=0.4 / 1)". In the above example, immediately after the optical fiber is wired on site, the amount of light received on the projection side is half of the standard amount of light received at the time of factory shipment, meaning that the optical communication quality is reduced to half.

[0022] Therefore, in this embodiment, the calibration magnification is determined by comparing the first ratio and the second ratio (specifically, by comparing the ratio values). In the example above, the magnification is 2 (=0.8 / 0.4). The reference threshold coefficient is calibrated using this magnification. For example, if the reference threshold coefficient that determines the upper limit of the second tolerance range is γupper and the reference threshold coefficient that determines the lower limit is γunder, then the calibration threshold coefficients obtained by calibration will be "2·γupper" and "2·γunder". The upper limit of the second tolerance range becomes (first light receiving reference value·2·γupper), which is twice the normal value, while the lower limit becomes "first light receiving reference value / (2·γunder)", which is half the normal value. As a result, the second tolerance range is expanded to twice the normal range, making it easier to determine that a product is normal when an abnormality is detected. Therefore, it is possible to minimize the number of times a product is determined to be abnormal and unusable in the field.

[0023] However, if the above calibration is unconditionally permitted, the reliability of the calibration threshold coefficient cannot be ensured when the received light amount on the projection unit side is too low and exceeds the normal range. Therefore, in this aspect, it is determined whether the calibration threshold coefficient obtained by calibration is within a predetermined normal range. As a result of this determination, when the calibration threshold coefficient is normal, the upper limit value and the lower limit value for determining the second allowable range are determined using the calibration threshold coefficient. If the calibration threshold coefficient is outside the normal range, calibration is impossible, and thus, for example, measures are taken to notify the user of this fact.

[0024] As described above, according to this aspect, while ensuring the reliability and safety of the product, it is possible to suppress as much as possible the situation where the product is determined to be abnormal and unusable at the site, thereby suppressing the inefficiency of the work at the site.

[0025] In a sixth embodiment dependent on any one of the first to fourth embodiments, the abnormality determination unit is provided with a first reference light reception value at the first light receiving unit for each color of light, a second reference light reception value at the second light receiving unit for each color of light, and a reference threshold coefficient used to determine the upper and lower limits of the second tolerance range for each color of light. The abnormality determination unit has a calibration unit that calibrates the reference threshold coefficient for abnormality determination and calculates a calibration threshold coefficient. The calibration unit sets the first reference light reception value for each color of light to pd1', the second reference light reception value for each color of light to pd2', the first measured light reception value obtained by measurement at the first light receiving unit for each color of light to pd1'', the second measured light reception value obtained by measurement at the second light receiving unit for each color of light to pd2'', the reference threshold coefficient for the upper limit in the reference threshold coefficient to γupper, and in the reference threshold coefficient Let γunder be the reference threshold coefficient for the lower limit, and it is permissible for γupper and γunder to be the same value, and let γupper(cab) be the calibration threshold coefficient for the upper limit in the calibration threshold coefficient, and let γunder(cab) be the calibration threshold coefficient for the lower limit in the calibration threshold coefficient, then the number represented by γupper·{(pd2' / pd1') / (pd2'' / pd1'')} The γupper(cab) may be calculated using the first calculation formula, and the γunder(cab) may be calculated using the second calculation formula represented by γunder·{(pd2' / pd1') / (pd2'' / pd1'')}. If the calculated γupper(cab) and γunder(cab) are within a predetermined normal range, the upper and lower limits for the second allowable range for each color of light may be determined using the γupper(cab) and γunder(cab).

[0026] In the sixth aspect, the content of the fourth aspect described above is described more specifically. In this aspect, the first reference light reception value for each color of light is designated as "pd1'", the second reference light reception value for each color of light is designated as "pd2'", the first actually measured light reception value obtained by actual measurement in the first light receiving unit for each color of light is designated as "pd1''", the second actually measured light reception value obtained by actual measurement in the second light receiving unit for each color of light is designated as "pd2''", the reference threshold coefficient for the upper limit value in the reference threshold coefficient is designated as "γupper", the reference threshold coefficient for the lower limit value in the reference threshold coefficient is designated as "γunder" (however, γupper = γunder may be satisfied), the calibration threshold coefficient for the upper limit value is designated as "γupper(cab)", the calibration threshold coefficient for the lower limit value is designated as "γunder(cab)", the first arithmetic expression used for calibration is "γupper·{(pd2' / pd1') / (pd2'' / pd1'')}", and the second arithmetic expression is "γunder·{(pd2' / pd1') / (pd2'' / pd1'')}". Also in this aspect, when the obtained calibration threshold coefficients γupper(cab) and γunder(cab) are within a predetermined normal range, the upper limit value and the lower limit value that define the second allowable range for each color of light are determined using these calibration threshold coefficients. When the calibration threshold coefficient is outside the normal range, since calibration is impossible, for example, measures are taken to notify the user of this fact.

[0027] Thus, according to this aspect, while ensuring the reliability and safety of the product, it is possible to suppress as much as possible the situation where the product is determined to be abnormal and unusable at the site, and suppress the inefficiency of the work at the site.

[0028] In a seventh aspect dependent on any one of the first to sixth aspects, the projection display system may be an in-vehicle projection display system mounted on a vehicle.

[0029] When a projection-type display system is installed in a vehicle, the ambient temperature varies considerably depending on the vehicle's driving environment, and can also change rapidly. According to this embodiment, while ensuring the reliability and safety of the product, it is possible to minimize the chances of the product being deemed abnormal and unusable in the field. Therefore, the possibility of using an in-vehicle projection-type display system (for example, a road projector that displays images on the road surface) in various environments is increased.

[0030] Those skilled in the art will readily understand that the embodiments of the present invention illustrated can be further modified without departing from the spirit of the invention. [Brief explanation of the drawing]

[0031] [Figure 1] Figure 1 shows an example of the external appearance of a projection-type display system, as well as an example of the internal configuration of the light source and projection unit. [Figure 2] Figure 2 shows an example of the configuration of the abnormality detection unit, and an example of various reference values ​​and threshold values ​​(including threshold coefficients) that are pre-configured in the abnormality detection unit. [Figure 3] Figure 3 is a flowchart showing an example of the main steps in the low-emission detection process using the low-emission mode. [Figure 4] Figure 4 is a flowchart showing an example of the main steps in the normal emission detection process using the normal emission mode. [Figure 5] Figure 5 shows the timing charts for various signals in this embodiment. [Figure 6] Figure 6 shows the AND circuit in this embodiment. [Modes for carrying out the invention]

[0032] The best embodiments described below are used to facilitate understanding of the present invention. Therefore, those skilled in the art should note that the present invention is not unduly limited by the embodiments described below.

[0033] (First Embodiment) Refer to Figure 1. Figure 1 shows an example of the external appearance of a projection-type display system and an example of the internal configuration of the light source unit and projection unit. In the example of Figure 1, the projection-type display system 10 is an in-vehicle projection-type display system mounted on a vehicle (not shown).

[0034] In recent years, in-vehicle projection display systems (in-vehicle projectors) have been required to be brighter in order to improve visibility. However, in order to make the light source shine brighter, it is necessary to efficiently dissipate the heat generated by the light source, and the size of heat sinks and other heat dissipation devices tends to increase. As a result, in-vehicle projectors may become larger, and it is conceivable that they may not be able to be installed in the limited space of a vehicle. Therefore, in this invention, we have decided to construct a separate projection display system (projector system) 10 by separating the light source unit and the projection unit using optical fiber optical transmission technology.

[0035] By separating the light source unit 100 and the projection unit 300, the light source unit, which generates a large amount of heat, can be installed in available space on a vehicle or the like, while the projection unit, which forms the projected image, can be separated from the heat source and freely installed in an appropriate location, thereby facilitating the installation of the projection display system 10 on a vehicle.

[0036] On the other hand, after installing the light source unit 100 and the projection unit 300 in an empty space in a vehicle or the like, it is necessary to connect the light source unit 100 and the projection unit 300 with a communication cable 210 and an optical fiber 220. After this work, it is necessary to determine whether the projection display system 10 is operating normally, and if an abnormal condition is detected, appropriate measures such as stopping the light output or notifying of the abnormality must be taken. However, the amount of light transmitted through the optical fiber 220 can vary greatly depending on the wiring conditions of the optical fiber 220 and the ambient temperature, and under such circumstances, it is not easy to determine normal / abnormal based solely on the light reception intensity of the first light receiving unit 123 provided on the light source unit 100 side. Therefore, in the first embodiment, a second light receiving unit 324 is also provided on the projection unit 300 side, and information on the measured light intensity obtained from the light receiving unit 123 on the light source side and information on the measured light intensity obtained from the light receiving unit 324 on the projection unit side are acquired, and by using each piece of information to perform an abnormality determination process in a predetermined procedure, it is possible to detect abnormalities in the projection display system 10 caused by the wiring status of the optical fiber 220, ambient temperature, etc. In the second embodiment, the projection display system 10 may detect abnormalities in the laser light source unit 125, abnormalities in the optical fiber 220, or other abnormalities based on the information on the measured light intensity obtained from the second light receiving unit 324 on the projection unit side.

[0037] The following will provide a detailed explanation with reference to the diagrams.

[0038] As shown in Figure 1A-1, the projection display system 10 has a light source unit 100 and a projection unit 300 arranged separately. The light source unit 100 and the projection unit 300 are electrically or optically connected via a communication cable 210, and the light for forming the projection image output by the light source unit 100 is supplied to the projection unit 300 via an optical fiber cable (hereinafter sometimes simply referred to as an optical fiber) 220, and the projection unit 300 forms the projection image. The communication cable 210 may be used for transmitting power, control signals, video signals, etc.

[0039] The light source unit 100 includes a heat sink 101 as a heat dissipation unit, a control board 102, an integrated circuit device (IC) 103 mounted on the control board 102 which includes a microcontroller (MCU: reference numeral 110 in A-2 of Figure 1) as a first control unit, a plurality of mirrors 120-122 as optical elements, a laser light source unit 125 that emits laser light, etc. On the other hand, the projection unit 300 includes an optical modulation element 322 that modulates the light for forming the projected image from the light source unit 100 to generate display light for the image, a projection optical system 323 that projects (emits) the display light for the image to the outside, etc.

[0040] As shown in Figure 1A-2, the light source unit 100 includes an MCU 110 as a first control unit, a serializer (parallel / serial converter) 112, a deserializer (parallel / serial converter) 114, an optical element drive unit (LD driver) 116, multiple optical elements with different emission colors (here, laser diodes corresponding to R (red), G (green), and B (blue)) 117-119, multiple mirrors 120-122, a first light receiving unit (here, a first photodiode PD1 is used) 123 for detecting the light intensity of the light for forming projection images of each color output from the laser light source unit 125, an optical output interface 124, and a power circuit (power supply circuit) 130.

[0041] The first control unit, the MCU (microcontroller) 110, is an integrated circuit device that combines a processor with the function of a main CPU (host CPU) and peripheral circuits such as memory.

[0042] The MCU110 is equipped with a first light intensity measuring unit 111 that measures light intensity based on measured values ​​(pd1(R'' / G'' / B'')) of red (R), green (G), and blue (B) light transmitted from a first light receiving unit (PD1) 123, and an abnormality detection unit 113.

[0043] The laser light source unit 125 is composed of multiple light elements 117-119 with different emission colors, multiple mirrors 120-122, a first light receiving unit (first photodiode PD1) 123, and an optical output interface 124.

[0044] The serializer 112 and the deserializer 114 constitute the first serial interface unit SIF1.

[0045] The projection unit 300 includes a deserializer (serial / parallel converter) 312, a display controller (display control device) 313 as a second control unit, a serializer (parallel / serial converter) 314, an optical input interface 320, an optical modulator (in this case, a DMD (digital mirror device) is used) 322, a second light receiving unit (in this case, a second photodiode PD2 is used) 324 for detecting the light intensity of each color of light for forming the projection image sent via the optical fiber 220, and a power circuit (power supply circuit) 325.

[0046] The second control unit, the display controller 313, is a dedicated integrated circuit device equipped with a sub-CPU (not shown) that performs display control in place of the MCU 110.

[0047] The display controller 313 is equipped with a second light receiving unit 315 that measures light intensity based on the measured values ​​(pd2(R'' / G'' / B'')) of each color of R, G, and B light sent from the second light receiving unit (PD2) 324.

[0048] The deserializer 312 and serializer 314 constitute the second serial interface unit SIF2.

[0049] The optical modulator 322 includes a main body 319 containing an optical modulator element, an input terminal 321 of the optical modulator to which video bitstream data VBSD supplied from the display controller 313 is input, and a projection optical system 323 that projects (emits) display light for the image.

[0050] The optical input interface 320 receives the light for projection image formation transmitted from the light source unit 100 via the optical fiber 220, and supplies the received light (light of each color, R, G, and B) to the main unit 319 of the optical modulator 322.

[0051] Next, we will explain the content of the communication of video signals and control signals via the first serial interface unit SIF1 and the second serial interface unit SIF2.

[0052] The serial communication signals transmitted and received between the first serial interface unit SIF1 and the second serial interface unit SIF2 include, for example, a Communication S1 which includes a communication signal C2 transmitted from the light source unit 100 to the projection unit 300 using the LVDS (Low Voltage Differential Signal) transmission method, a light source drive value control signal PCR (or a processed light source drive value control signal PCR1) that controls the light emission intensity of the optical elements 117-119, and a measurement timing signal STM (R_STM, G_STM, B_STM) generated by performing a logical AND operation on the light emission enable signal LD_EN (R_EN, G_EN, B_EN) that indicates the timing for each of the multiple optical elements 117-119 to emit light, and a Communication S1 which includes a measurement timing signal STM (R_STM, G_STM, B_STM) transmitted from the projection unit 300 to the light source unit 100. Communication S2 includes a signal C4 that performs processing in response to various requests from the control unit 110, a signal indicating the result of the processing (for example, a signal indicating that the processing was successful, or a signal indicating the parameter value obtained as a result of the processing), an emission enable signal LD_EN that permits the emission of light from the optical elements 117 to 119 (specifically, the emission enable signals R_EN, G_EN, and B_EN for each color of LD_R, LD_G, and LD_B), and light intensity information LI which is the measured value (pd2(R'' / G'' / B'')) from the second light receiving unit 315.

[0053] Next, an example of various communication signals will be described. For example, a vehicle-side controller 90 mounted on a vehicle (not shown) can send various request commands C1 based on user settings to the MCU (first control unit) 110 of the light source unit 100.

[0054] Possible request commands include, for example, commands to change the display brightness (dimming level), change the color balance, change the image size, change the image position, correct projection distortion, and turn the display on / off.

[0055] The MCU 110 sends the received request command as a communication signal C2 to the serializer 112. The serializer 112 performs a logical AND operation on the received communication signal C2, a light source drive value control signal PCR (or a processed light source drive value control signal PCR1) which controls the light emission intensity, and a light emission enable signal LD_EN (R_EN, G_EN, B_EN) which indicates the timing for each of the multiple optical elements 117 to 119 to emit light. This measurement timing signal STM (R_STM, G_STM, B_STM) is generated by this AND operation, and the serial video signal (LVDS VideoS) is converted from parallel to serial to generate a communication signal CommunicationS1. The serializer 112 then transmits this communication signal CommunicationS1 to the projection unit 300 via the communication cable 210. The deserializer 312 of the projection unit 300 converts the received communication signal CommunicationS1 from serial to parallel to generate a communication signal C3 and measurement timing signals STM (R_STM, G_STM, B_STM). It sends the communication signal C3 to the display controller (second control unit) 313 and the measurement timing signals STM (R_STM, G_STM, B_STM) to the display controller 313 (light intensity measurement unit 315).

[0056] The display controller (second control unit) 313 performs processing in response to various requests from the MCU (first control unit) 110 of the light source unit 100, and generates signals C4 indicating the result of the processing (for example, a signal indicating that the processing was successful, or a signal indicating the parameter values ​​obtained as a result of the processing), an illumination enable signal LD_EN (R_EN, G_EN, B_EN) indicating the timing for each of the multiple optical elements 117~119 to emit light, and light intensity information LI which is the measured value (pd2(R'' / G'' / B'')) at the second light receiving unit 315, and sends these to the serializer 314. The serializer 314 performs parallel / serial conversion of the communication signal C4, the illumination enable signal LD_EN, and the light intensity information LI to generate a communication signal CommunicationS2, and transmits this communication signal CommunicationS2 to the light source unit 100 via the communication cable 210. The deserializer 114 of the light source unit 100 performs serial / parallel conversion of the received communication signal CommunicationS2 to generate a communication signal C5 and a light emission enable signal LD_EN(R_EN, G_EN, B_EN). It sends the communication signal C5 to the MCU (first control unit) 110 and the light emission enable signal LD_EN(R_EN, G_EN, B_EN) to the MCU (first control unit) 110 and the optical element driving unit 116.

[0057] In this way, the MCU (first control unit) 110 and the display controller (second control unit) 313 can transmit and receive various signals via the first and second serial interface units SF1 and SF2.

[0058] The deserializer 312 of the projection unit 300 converts the received LDVS format video signal LDVS VideoS into a parallel format digital video signal VD, and sends the digital video signal VD to the display controller (second control unit) 313.

[0059] Next, the signal flow related to the abnormality detection process will be explained. The display controller 313 (light intensity measurement unit 315) can transmit the measured value (pd2(R'' / G'' / B'')) from the second light receiving unit 324 to the light source unit 100 as light intensity information LI. Note that the light intensity measurement unit 315 may be provided separately from the display controller 313.

[0060] The light intensity information LI sent from the display controller 313 (light intensity measurement unit 315) is converted from parallel to serial by the serializer 314 and transmitted to the light source unit 100 as serial-formatted light intensity information LI (LightIntensity).

[0061] The deserializer 114 of the light source unit 100 converts the received serial-formatted light intensity information LI from serial to parallel and transmits it as a communication signal C5 to the MCU 110 (more specifically, the abnormality detection unit 113). In parallel with this, it also supplies the light intensity information LI to the optical element driving unit 116.

[0062] Upon receiving the light intensity information LI, the abnormality determination unit 113 performs abnormality determination processing using the measured value (pd2(R'' / G'' / B'')) from the second light receiving unit (PD2) of the projection unit 300. After performing predetermined processing, it generates a light source drive value control signal PCR as needed and sends it to the optical element drive unit 110 to appropriately control the emission intensity of the optical elements 117 to 119 of each color.

[0063] Furthermore, the MCU110 generates a light source drive value control signal PCR to adjust the light emission intensity of each color of photonic elements 117-119 so that it falls within a predetermined set level (a level set by changing the display brightness (changing the dimming level) or changing the color balance). The photonic element drive unit 116 adjusts the light emission intensity of each color of photonic elements 117-119 so that the variation in the transmitted light intensity information LI (measured value (pd2(R'' / G'' / B'')) at the second light receiving unit (PD2) within a predetermined period falls within a predetermined level set by the light source drive value control signal PCR. This enables APC (Automatic Power Control) to stabilize the light output of multiple photonic elements 117-119 with different emission colors.

[0064] The light source drive value control signal PCR adjusts the light output of photonic elements 117-119 by adjusting the duty cycle for each subframe (R subframe, G subframe, B subframe) in which R / G / B are time-division lit within a single frame. This duty cycle is set by changing the display brightness (changing the dimming level) or changing the color balance (it is stored in advance in table data, etc., and read out). Alternatively, the light source drive value control signal PCR may also adjust the light output of photonic elements 117-119 by adjusting the number of on-pulses for each subframe (R subframe, G subframe, B subframe).

[0065] The optical element drive unit 116 smooths the light source drive value control signal PCR using a low-pass filter (not shown), and controls the optical output of optical elements 117-119 (APC) by comparing this smoothed light source drive value control processing signal PCR1 with the light intensity information LI (measured value at the second light receiving unit (PD2) (pd2(R'' / G'' / B''))) using a comparator (not shown). For example, the optical element drive unit 116 controls the optical output of optical elements 117-119 when the light intensity information LI (measured value at the second light receiving unit (PD2) (pd2(R'' / G'' / B''))) is lower than the light source drive value control processing signal PCR1. If the light intensity information LI is exceeded, the optical elements 117, 118, or 119 of the corresponding color are turned on, and if the light intensity information LI is exceeded, the optical elements 117, 118, or 119 of the corresponding color are turned off. If the light intensity information LI is exceeded, the optical elements 117, 118, or 119 of the corresponding color are turned off. If the light intensity information LI is adjusted by the light intensity information LI control signal PCR, the optical element drive unit 116 turns on the optical elements 117, 118, or 119 of the corresponding color for each subframe (subframe R, subframe G, subframe B) by the number of on-pulses indicated by the light intensity information LI control signal PCR.

[0066] The optical element drive unit 116 causes the optical elements 117 to 119 to emit light at a desired light output at predetermined timings (subframes R, G, and B) based on an emission enable signal LD_EN indicating the timing for emitting light from each of the multiple optical elements 117 to 119, and a light source drive value control signal PCR for controlling the light output of each of the multiple optical elements 117 to 119.

[0067] Furthermore, power PS is supplied from the vehicle-side controller 90 to the power circuit 130 of the light source unit 100. The power circuit 130 supplies power voltage to the power circuit 325 of the projection unit 300 via the communication cable 210. The power circuit 325 supplies power voltage to each part within the projection unit 300.

[0068] Next, refer to Figure 2. Figure 2 shows an example of the configuration of the abnormality detection unit, and an example of various reference values ​​and threshold values ​​(including threshold coefficients) that are pre-configured in the abnormality detection unit.

[0069] As shown in Figure 2A-1, the abnormality determination unit 113 includes a reference value storage unit 151 for storing various reference values ​​152, a threshold value storage unit 153 for storing various threshold values ​​154, a low light emission determination processing unit 160, a normal light emission determination processing unit 170, and an abnormality notification unit (including a light output stop unit 181) 180.

[0070] The low light emission determination processing unit 160 includes a light source intensity adjustment unit 162 for low light emission and an abnormality determination unit 164 for low light emission.

[0071] The normal emission determination processing unit 170 includes a light source intensity adjustment unit 172 for normal emission, a calibration unit 174 for a reference threshold for abnormality determination, an abnormality determination unit 176 for normal emission, and a storage processing unit 178 for the adjusted light source intensity and light source drive value.

[0072] Figure 2A-2 shows examples of various reference values ​​152. These various reference values ​​152 are pre-configured at the time of product shipment from the factory.

[0073] For example, with respect to the red (R) light element (laser diode LD(R)), the normal drive value GDR' when the LD(R) emits light alone, the reference light-receiving value pd1R' for the first light-receiving unit (first photodiode PD1: hereinafter sometimes simply referred to as "PD1"), and the reference light-receiving value pd2R' for the second light-receiving unit (second photodiode PD2: hereinafter sometimes simply referred to as "PD2") are predetermined.

[0074] Similarly, for the green (G) light element (laser diode LD(G)), the normal drive value GDG' when the LD(G) emits light alone, the reference light reception value pd1G' for PD1, and the reference light reception value pd2G' for PD2 are pre-defined.

[0075] Similarly, for the blue (B) light element (laser diode LD(B)), the normal drive value GDB' when the LD(B) emits light alone, the reference light reception value pd1B' for PD1, and the reference light reception value pd2B' for PD2 are pre-defined.

[0076] Figure 2A-3 shows examples of various threshold values ​​154. These various threshold values ​​154 are pre-configured at the time of product shipment from the factory.

[0077] For low-light detection processing, the following thresholds are pre-defined: Δpd2 (low power R, G, B), which is the allowable threshold for the variation in the received light value of PD2; βupper, which is the upper limit of the abnormal light value detection threshold for PD1; and βunder, which is the lower limit (however, βupper = βunder = β).

[0078] For normal light emission detection processing, the following thresholds are pre-defined: the allowable threshold Δpd2 (normal power R, G, B) for the variation in the received light value of PD2; the reference threshold coefficient γupper for the upper limit and the reference threshold coefficient γunder for the lower limit as the abnormal detection threshold for the received light value of PD1 (however, γupper=γunder=γ may be set); and the thresholds for determining the normality of each reference threshold coefficient γupper(cab) and γunder(cab) after calibration.

[0079] Next, refer to Figure 3. This flowchart shows an example of the main steps in the low-emission detection process using the low-emission mode.

[0080] In the example shown in Figure 3, a low-luminosity mode is used to make each of the optical elements 117-119 of each color emit light at a lower brightness than normal emission, allowing for preliminary abnormality detection (determination of abnormalities related to basic performance such as faulty optical fiber installation and light leakage from the optical fiber).

[0081] For example, when performing the first abnormality detection process after wiring the optical fiber 220 at a site, there are workers around the optical fiber 220. If, for example, light leaks from the optical fiber 220 and shines into the workers' eyes, it could cause eye damage. Therefore, it is considered undesirable to suddenly perform abnormality detection processing using high-intensity light emission (normal light emission).

[0082] Therefore, in the example shown in Figure 3, by using the low-light-emitting mode to reduce the light emission intensity of each color of light element 117-119, the amount of light propagating through the optical fiber 220 can be sufficiently reduced. Thus, even if, for example, light leaks from the optical fiber 220 and shines into a worker's eyes, the light is weak, ensuring the safety of the worker's eyes.

[0083] In step S1, the MCU 110 sets the drive value (light source drive value control signal PCR) of each color of photonic elements 117 to 119 to 1 / α of the normal drive value (GDR', GDG', GDB' shown in A-2 of Figure 2) (α is an integer greater than 1; in a preferred example, α is set to 5 to 10).

[0084] In step S2, the light elements 117 to 119 of each color are illuminated in sequence, and the measured light intensity (measured value) of PD1 and PD2 is detected. Here, the measured values ​​for red light in PD1 and PD2 are denoted as pd1R'',pd2R'', the measured values ​​for green light are denoted as pd1G'',pd2G'', and the measured values ​​for blue light are denoted as pd1B'',pd2B''.

[0085] In step S3, the drive values ​​of each optical element 117 to 119 are adjusted so as to satisfy equations (1) to (3) below. The drive values ​​are adjusted by sequentially increasing or decreasing the drive current of each optical element 117 to 119 in units of Δi (minimum change in current value), within the maximum allowable dynamic range until equations (1) to (3) below are satisfied. pd2R' / α-pd2R'' ≤ Δpd2(low power R)···(1) pd2G' / α-pd2G'' ≤ Δpd2(low power G)···(2) pd2B' / α-pd2B'' ≤ Δpd2(low power B)···(3). The MCU 110 may also sequentially increase or decrease the duty cycle and on-pulse count of the light source drive value control signal PCR until equations (1) to (3) above are satisfied.

[0086] In equation (1), first, the reference light reception value pd2R' at PD2, shown earlier in Figure 2A-2, is multiplied by (1 / α). This is because, since the drive value of the optical element 117 is 1 / α, it is assumed that the reference light reception value at PD2 will ideally also be 1 / α. Next, it is determined whether the difference between the obtained reference light reception value of PD2 (pd2R' / α) and the measured value at PD2 is less than or equal to the allowable threshold Δpd2 (low power R) for variation in the light reception value of PD2 for red light in low-power mode. If equation (1) is satisfied, it means that light with an amount sufficient for measurement has been detected at PD2. If equation (1) is not satisfied, it means that although the drive value of the red optical element 117 has been adjusted within the maximum dynamic range, the minimum amount of light has not reached through the optical fiber 220, and the subsequent abnormality detection process becomes impossible. Note that the processing steps in equations (2) and (3) are the same as those in equation (1), so their explanations are omitted.

[0087] Next, in step S4, we determine whether the following relationships (4) to (6) are satisfied: (pd1R' / α) / βunder≦pd1R''≦(pd1R' / α)·βupper···(4)(pd1G' / α) / βunder≦pd1G''≦(pd1G' / α)·βupper···(5)(pd1B' / α) / βunder≦pd1B''≦(pd1B' / α)·βupper···(6)

[0088] Equation (4) determines whether the measured value pd1R'' at PD1 for red light is above the lower limit and below the upper limit that defines the tolerance range. The lower limit that defines the tolerance range is calculated by dividing the reference light reception value of PD1 in low light emission mode (pd1R' / α) by the threshold coefficient βunder (an integer greater than 1) for the lower limit of the low light emission mode. Similarly, the upper limit that defines the tolerance range is calculated by multiplying the reference light reception value of PD1 in low light emission mode (pd1R' / α) by the threshold coefficient βupper for the upper limit of the low light emission mode. If equation (4) is satisfied, it means that the measured value at PD1 of the output light of the red light element 117 whose drive value was adjusted in step S2 is within the tolerance range determined based on the reference light reception value and reference threshold coefficient prepared at the factory, and the basic performance (minimum performance) of the product is ensured. If equation (4) is not satisfied, it means that the red light element 117 is emitting light under considerable strain, outside the tolerance range assumed at the time of factory shipment of the product. Note that the processing procedures in equations (5) and (6) are the same as those in equation (4), so their explanation is omitted.

[0089] In step S5, it is determined whether all or at least a predetermined number (at least two in this case) of equations (4) to (6) are satisfied. The reason for specifying at least two is that if two of equations (4) to (6) are satisfied but only one is not, it would be too strict to determine that an abnormality has occurred, so it is treated as being within the normal range. If the result in step S5 is Y, the process proceeds to step S6, where the adjusted drive values ​​of the optical elements 117 to 119 of each color obtained in step S3 are saved, and the low light emission determination process is terminated. If the result in step S5 is N, it can be determined that some kind of abnormality related to basic performance (such as improper installation of the optical fiber 220 or light leakage from the optical fiber 220) has occurred, so in step S7, measures such as stopping the optical output and notifying of the abnormality are taken. After this, the process proceeds to step S10 in Figure 4, where the light emission power of the optical elements is returned to the normal level and abnormality determination processing is performed in normal light emission mode.

[0090] The low-light detection process described above allows for the confirmation, with consideration for worker safety, that the basic performance (minimum performance) of optical communication, for example, via optical fiber, is ensured by using the low-light mode. This enables abnormality detection regarding basic performance while ensuring worker safety.

[0091] Next, refer to Figure 4. This flowchart shows an example of the main steps in the normal emission determination process using the normal emission mode.

[0092] In step S10, the drive values ​​of each colored light element 117-119, which were adjusted and saved in step S6 in Figure 3, are multiplied by α to obtain the normal light emission drive values. In addition, APC (Automactic Power Control) is performed on each colored light element 117-119. This brings the light output of each colored light element 117-119 within the set predetermined level (a level set by changing the display brightness (changing the dimming level) or changing the color balance).

[0093] Next, step S11 is performed. This step S11 corresponds to step S2 in Figure 3, which was explained earlier. In step S11, each color of light element is made to emit light in sequence, and the measured light intensity (measured value) of PD1 and PD2 is detected to obtain the values ​​of pd1R'', pd2R'', pd1G'', pd2G'', pd1B'', pd2B'', respectively.

[0094] Next, step S12 is performed. This step S12 corresponds to step S3 in Figure 3, which was explained earlier. The processing content is essentially the same as step S3, so a detailed explanation is omitted. However, in step S12, since it is the normal emission mode, the reference light received value for PD1 is used as is, without being multiplied by (1 / α), unlike in step S3 in Figure 3. In addition, the tolerance thresholds for normal emission determination processing (Δpd2(normal power R), Δpd2(normal power G), Δpd2(normal power B)) are used as the tolerance thresholds for the variation in the light received value of PD2, and determination is performed according to equations (7) to (9). In this specification, the tolerance range for normal emission determination processing shown in equations (7) to (9) may be referred to as the "first tolerance range," and the conditions defined in equations (7) to (9) may be referred to as the "first conditions."

[0095] Subsequently, the process proceeds through steps S13 and S14 to step S15. Step S15 corresponds to step S4, which was explained earlier in Figure 3. However, in a normal light emission determination process, before step S15 is performed, calibration of the reference threshold coefficient (step S13) and determination of whether the reference threshold coefficient obtained by calibration is within the normal range (step S14) are performed.

[0096] In the normal light emission detection process, similar to the low light emission detection process in Figure 3, an abnormality is determined by whether or not the light received by PD2 for each color light element emitting light with the adjusted drive value falls within a predetermined range; this point is common to both processes.

[0097] However, immediately after wiring the optical fiber 220 on-site, transmission loss tends to increase due to bending of the optical fiber 220 or large changes in ambient temperature, leading to a decrease in the quality of optical communication. If abnormality detection is performed using the upper and lower limits set by the factory-prepared standard threshold coefficients (γupper, γunder) without considering these circumstances, the detection may become too strict, potentially leading to an increase in usable products being incorrectly classified as abnormal and unusable. In such cases, reinstallation of the product, rewiring of the optical fiber, or replacement of the product may be necessary, resulting in inefficient on-site work. On the other hand, if the detection conditions are too relaxed, products that should be classified as abnormal may be classified as normal, potentially compromising product reliability and safety. Therefore, in the example shown in Figure 4, the factory-prepared standard threshold coefficients (γupper, γunder) are properly calibrated using the actual measured values ​​of PD1 and PD2 on-site. The resulting threshold coefficients are called "calibration threshold coefficients" and are denoted as "γupper(cab)" and "γunder(cab)".

[0098] The following describes the calibration of the threshold coefficients. In step S13, the calibration threshold coefficients γupper(cab) and γunder(cab) are calculated using the following formulas: γupper(cab) = {(pd2R' / pd1R') / (pd2R'' / pd1R'')}·γupper γunder(cab) = {(pd2R' / pd1R') / (pd2R'' / pd1R'')}·γunder

[0099] In the above formula, (pd2R' / pd1R') represents the first ratio of the reference light-receiving values ​​for PD1 and PD2, which are provided at the factory. (pd2R'' / pd1R'') represents the second ratio, which is the ratio of the measured light-receiving values ​​for PD1 and PD2. The magnification is determined by comparing the first and second ratios. This magnification is then used to calibrate the reference threshold coefficients γupper and γunder, thereby calculating the calibration threshold coefficients γupper(cab) and γunder(cab).

[0100] For example, suppose that under standard conditions before product shipment, when the optical elements 117-119 of each color are driven at a reference drive value, the reference light reception value of PD1 becomes a relative value of "1", and the reference light reception value of PD2 becomes a relative value of "0.8". If the first ratio is "0.8:1", then the value of that ratio is "0.8 (=0.8 / 1)". On the other hand, suppose that the actual measured values ​​(actual measured values: expressed here as relative values) for PD1 and PD2 are "1" and "0.4". If the second ratio is "0.4:1", then the value of that ratio is "0.4 (=0.4 / 1)". In the above example, immediately after wiring the optical fiber 220 on-site, the amount of light received on the projection unit 300 side is half of the standard amount of light received at the time of factory shipment, meaning that the optical communication quality has decreased by half.

[0101] Taking this into consideration, in step S13 of Figure 4, the first ratio and the second ratio are compared (specifically, the ratio values ​​are compared) to determine the calibration magnification. In the example above, the magnification is 2 (=0.8 / 0.4). The reference threshold coefficients γupper and γunder are calibrated using this magnification. In the example above, the calibration threshold coefficients obtained by this calibration are "2·γupper" and "2·γunder".

[0102] In step S15, this calibration threshold coefficient is used to determine whether each of equations (10) to (12) is satisfied.

[0103] The upper limit used in this determination is (light reception standard value for each color of light · 2 · γupper), which is twice the normal value, while the lower limit is "light reception standard value for each color of light / (2 · under)", which is half the normal value. This expands the acceptable range for determination to twice the normal range, making it easier for abnormalities to be judged as normal. Therefore, it is possible to minimize the number of times a product is judged as abnormal and rendered unusable in the field.

[0104] However, if the above calibration is unconditionally permitted, the reliability of the calculated calibration threshold coefficients γupper(cab) and γunder(cab) cannot be guaranteed, for example, if the amount of light received on the projection unit 300 side is lower than the normal range.

[0105] Therefore, in step S14 of Figure 4, it is determined whether the calibration threshold coefficients γupper(cab) and γunder(cab) obtained by calibration are within a predetermined normal range, using the normal determination threshold shown earlier in Figure 2, A-3. If the calibration threshold coefficients are normal as a result of this determination (Y in step S14), the upper and lower limits used for abnormality determination in step S15 are determined using these calibration threshold coefficients. If the calibration threshold coefficients are outside the normal range (N in step S14), calibration is not possible, and the process proceeds to step S18, where measures are taken, for example, to notify the user of the detected abnormality.

[0106] Step S15 corresponds to Step S4 in Figure 3, which was explained earlier. The processing content is substantially the same. However, in Step S15, since abnormality detection is performed in the normal emission detection process, the reference light reception value of PD1 for each color of light is used as is in equations (10) to (12), without being multiplied by (1 / α). In this respect, it differs from Step S4 in Figure 3. Also, in Step S15, the calibration threshold coefficients γupper(cab) and γunder(cab) obtained by calibration are used. In this respect, it also differs from Step S4 in Figure 3. In this specification, the tolerance range for the normal emission detection process shown in equations (10) to (12) may be referred to as the "second tolerance range," and the conditions defined in equations (10) to (12) may be referred to as the "second conditions."

[0107] Step S16 corresponds to Step S5 in Figure 3, which was explained earlier. The content is essentially the same. If the result in Step S16 is Y, the process proceeds to Step S17. In Step S17, the calibrated drive values ​​of the optical elements 117-119 of each color, obtained in Step S12, are saved as reference drive values ​​after optical fiber installation. In addition, the measured light reception intensities (measured values) pd1R''~pd1B'', pd2R''~pd2B'', corresponding to these drive values ​​for PD1 and PD2 are saved as reference light reception values ​​after optical fiber installation. These saved data can be used in subsequent abnormality detection.

[0108] If the result in step S16 is N, the process proceeds to step S18, where measures such as stopping the optical output or notifying of an anomaly are taken.

[0109] As shown in the example in Figure 4, it is possible to ensure the reliability and safety of the product while minimizing the chances of the product being deemed defective and unusable on-site, thereby preventing inefficiencies in on-site work.

[0110] In the above explanation, the reference light reception values ​​for each color of light in PD1 are described as pd1R', pd1G', and pd1B', but when referring to these collectively as the reference light reception value of PD1, it may simply be written as "pd1'". Similarly, the reference light reception values ​​for each color of light in PD2 are described as pd2R', pd2G', and pd2B', but when referring to these collectively as the reference light reception value of PD2, it may simply be written as "pd2'". Similarly, in the above explanation, the measured light reception intensity (measured value) for each color of light in PD1 is described as pd1R'', pd1G'', and pd1B'', but when referring to the measured light reception intensity (measured value) collectively, it may simply be written as "pd1''. Similarly, in the above explanation, the measured light intensity (measured value) of each color of light in PD2 is described as pd2R'', pd2G'', and pd2B'', but the measured light intensity (measured value) that encompasses these may simply be described as "pd2''".

[0111] Figure 5 shows the timing charts for various signals. The smoothed light source drive value control signal PCR2 (an example of the light source drive value control processing signal PCR1) is obtained by smoothing the light source drive value control signal PCR using a low-pass filter or the like (not shown). The binarized light source drive value control signal PCR3 (an example of the light source drive value control processing signal PCR1) is a signal that is binarized using a comparator or the like (not shown) that shows a low signal when the light source drive value control signal PCR (or the smoothed light source drive value control signal PCR2) is 0, and a high signal when the light source drive value control signal PCR (or the smoothed light source drive value control signal PCR2) is greater than 0.

[0112] Figure 6 shows a logical AND circuit. The logical AND circuit 317 in this embodiment is provided in the light source unit 100 (for example, MCU 110) and generates a measurement timing signal STM (R_STM, G_STM, B_STM) by performing a logical AND operation on the light source drive value control processing signal PCR1, which is obtained by processing the light source drive value control signal PCR that adjusts the light emission intensity of the optical elements 117 to 119, and the light emission enable signal LD_EN (G_EN, R_EN, B_EN) from the deserializer 114. Note that the logical AND circuit 317 in another embodiment may be provided in the projection unit 300. In this case, the AND circuit 317 performs an AND operation on the light emission enable signal LD_EN (G_EN, R_EN, B_EN) from the display controller 313 and the light source drive value control signal PCR (or a modified light source drive value control signal PCR1) which adjusts the light emission intensity and is input from the light source unit 100 (MCU 110) via the communication cable 210, to generate the measurement timing signal STM (R_STM, G_STM, B_STM).

[0113] Immediately after the start of display, it is possible that either the light source drive value control signal PCR, which adjusts the luminescence intensity, or the luminescence enable signal LD_EN, which adjusts the luminescence timing, will be output, while the other will not be output. In Figure 5, from time t1 to t15, the luminescence enable signal LD_EN is output, but the light source drive value control processing signal PCR1 is not output (because the light source drive value control signal PCR is not output). Therefore, in Figure 5, from time t1 to t15, the AND circuit 317 of this embodiment outputs the measurement timing signal STM (R_STM, G_STM, B_STM), which is a low signal, and the measured value in PD2 during this period is not used as the measured value (not used for abnormality detection). In Figure 5, from time t16 to t29, the AND circuit 317 of this embodiment outputs the measurement timing signal STM (R_STM, G_STM, B_STM), which is also a high signal, when both the light source drive value control signal PCR, which adjusts the luminescence intensity, and the luminescence enable signal LD_EN (R_EN, G_EN, B_EN), which adjusts the luminescence timing, are high signals. The abnormality detection unit 117 uses the measured value at PD2 during the period when the measurement timing signal R_STM is a high signal as the measured value of R (red) for abnormality detection, the measured value at PD2 during the period when the measurement timing signal G_STM is a high signal as the measured value of G (green) for abnormality detection, and the measured value at PD2 during the period when the measurement timing signal B_STM is a high signal as the measured value of B (blue) for abnormality detection.

[0114] In some embodiments, the abnormality determination unit 117 determines an abnormality based on the light intensity information LI for the entire period (from the leading edge to the trailing edge) during which the measurement timing signal STM (R_STM, G_STM, B_STM) is a high signal, provided that the measurement timing signal STM is a high signal. In some embodiments, the abnormality determination unit 117 may determine an abnormality based on the light intensity information LI for a portion of the period (from the leading edge to the trailing edge) during which the measurement timing signal STM (R_STM, G_STM, B_STM) is a high signal, provided that the measurement timing signal STM is a high signal. For example, the abnormality determination unit 117 may determine an abnormality based on the light intensity information LI for a portion of the period from when the leading edge is detected until the trailing edge, after a preset delay time has elapsed.

[0115] As described above, according to this embodiment, the light source unit and the projection unit are separated, making it possible to detect abnormalities in the projection-type display system caused by the wiring condition of the optical fibers, ambient temperature, etc.

[0116] Furthermore, while ensuring product reliability and safety, it is possible to minimize the occurrence of products being deemed abnormal and unusable in the field, thereby preventing inefficiencies in on-site work. In addition, by performing a low-emission detection process before the normal emission detection process, it is possible to confirm, for example, that the basic performance (minimum performance) of optical communication via optical fiber is ensured, while considering the safety of the workers. Thus, it becomes possible to determine abnormalities regarding basic performance while ensuring the safety of the workers. Moreover, when a projection-type display system is mounted on a vehicle, the ambient temperature fluctuates in various ways, and the ambient temperature may also change rapidly. According to this embodiment, for example, the reference threshold coefficient can be appropriately calibrated, taking into account changes in transmission loss in optical fiber caused by ambient temperature. In other words, measures are taken to address changes in ambient temperature, and the present invention has high practical value in the field. Furthermore, according to the present invention, accurate abnormality detection can be performed, effectively suppressing a decrease in the quality of the projected image. Thus, it is possible to suppress a decrease in the reliability of on-board projection-type display systems (for example, road projectors that display images on the road surface). Furthermore, using the present invention increases the possibility of using in-vehicle projection display systems (for example, road projectors that display images on the road surface) in various environments.

[0117] The present invention is not limited to the exemplary embodiments described above, and those skilled in the art will be able to easily modify the exemplary embodiments described above to the extent included in the claims. [Explanation of symbols]

[0118] 10... Projection type display system, 90... Vehicle-side controller, 100... Light source unit, 101... Heat sink (heat dissipation unit), 102... Control board, 103... Integrated circuit device (IC), 110... Microcontroller (MCU) as the first control unit, 111... First light intensity measurement unit, 112... Serializer (parallel / serial converter), 113... Anomaly detection unit, 114... Deserializer (parallel / serial converter), 116... Optical element driving unit (LD driver), 117~119... Multiple photoelements with different emission colors 120-122...Laser diodes corresponding to each of the R, G, and B colors, 123...First light receiving unit consisting of a first photodiode PD1, 124...Optical output interface, 125...Optical element unit, SIF1...First serial interface unit, 130...Power circuit (power supply circuit), 151...Reference value storage unit, 152...Various reference values, 153...Threshold storage unit, 154...Various thresholds, 160...Low light emission determination processing unit, 162...Light source intensity adjustment unit for low light emission, 164...Differences for low light emission Normal determination unit, 170...Normal light emission determination processing unit, 172...Light source intensity adjustment unit during normal light emission, 174...Calibration unit for reference threshold for abnormal determination, 176...Abnormal determination unit during normal light emission, 178...Storage processing unit for adjusted light source intensity and light source drive value, 180...Abnormal notification unit, 181...Optical output stop unit, 210...Communication cable, 220...Optical fiber cable (optical fiber), 300...Projection unit, 312...Deserializer (serial / parallel converter), 314...Serializer (parallel / serial converter), 3 13...Display controller as a second control unit, 315...Second light receiving unit, 319...Main unit with built-in optical modulator, 320...Optical input interface, 321...Input terminal of optical modulator, 322...Optical modulator (DMD (Digital Mirror Device)), 323...Projection port (Output port), 324...Second light receiving unit composed of a second photodiode PD2, 325...Power circuit (power supply circuit), SIF2...Second serial interface unit, VideoS...Video signal, LVDSVideoS...Serial video signal transmitted using the LVDS transmission method, VD...Video digital signal, VBSD...Video bitstream data, CommunicationS1, CommunicationS2...Various communication signals, LI...Light intensity information (light intensity signal), pd1(R'' / G'' / B'')...Measured received light intensity of each color of light in PD1 (measured value), pd2(R'' / G'' / B'')...Measured received light intensity of each color of light in PD2 (measured value), PS...Power supply.

Claims

1. A projection display system in which a light source unit and a projection unit are separated, the light source unit and the projection unit are electrically or optically connected via a communication cable, and the light for forming a projected image output by the light source unit is supplied to the projection unit via an optical fiber, and a projected image is formed by the projection unit, The aforementioned light source unit is A first control unit having a function to control bidirectional communication with the projection unit, The optical element section comprises multiple optical elements with different emission colors that generate light for forming the aforementioned projection image, It includes an optical element driving unit that drives the plurality of optical elements, The projection unit is, A second control unit having a function to control bidirectional communication with the light source unit, A light modulation device that modulates the light of each color sent from the light source via the optical fiber to form the projection image and forms the projection image, It has a second light receiving unit that detects the light intensity of each color of light for forming the projected image sent from the light source unit via the optical fiber, The optical element driving unit drives the optical element based on at least a light source driving value control signal for adjusting the light emission intensity of the optical element and a light emission enable signal for adjusting the light emission timing of the optical element. The aforementioned light source drive value control signal or a light source drive value control processing signal obtained therefrom, The system includes an abnormality determination unit that determines whether an abnormal condition is caused by at least one of the mounting status of the optical fiber and the ambient temperature, based on the light intensity detected by the second light receiving unit within the timing of the signal obtained by logically ANDing the light emission enable signal with the optical fiber. Projection-type display system.

2. The abnormality determination unit, The drive value of the optical element drive unit is adjusted so that the first condition is met, which is that the light reception intensity of each color of the light for forming the projected image in the first light receiving unit is within a first allowable range. The second light receiving unit determines whether the second condition is met, which is that the received light intensity for all of the output lights of the plurality of optical elements with different emission colors, or a predetermined number of the output lights, is within a second allowable range. If the second condition is not met, an abnormal condition is determined, and an abnormal condition determination process is performed. The projection display system according to claim 1.

3. The abnormality determination unit, Each of the plurality of optical elements has a low-luminescence mode in which it emits light at a luminance lower than the normal luminescence luminance, and a normal-luminescence mode in which it emits light at the normal luminescence luminance, The abnormality detection process is performed in the low-light emission mode to determine whether or not there is an abnormal condition in the low-light emission state. After it is determined that there are no abnormal conditions in the low-luminescence state, the abnormality detection process is performed in the normal luminescence mode to determine whether or not there are any abnormal conditions in the normal luminescence state. The projection display system according to claim 2.

4. The abnormality determination unit, The system performs a process to confirm whether communication between the first and second control units via the communication cable can be performed correctly by establishing a communication link, or by receiving an arbitrary signal modified by the first control unit in the second control unit and sending it back to the first control unit. The projection display system according to claim 1.

5. The light source unit further comprises a first light receiving unit that detects the light intensity of each color of light output from the optical element unit. The abnormality determination unit includes: The first reference light reception value in the first light receiving unit for each color of light, The second reference light reception value in the second light receiving unit for each color of light, A reference threshold coefficient used to determine the upper and lower limits that define the second tolerance range for each color of light, These are prepared in advance. The abnormality determination unit, The system includes a calibration unit that calibrates the aforementioned reference threshold coefficient and calculates a calibration threshold coefficient. The calibration unit is The calibration threshold coefficient is calculated by calibrating the reference threshold coefficient using a magnification determined by comparing a first ratio, which is the ratio of the first and second reference light-receiving values, with a second ratio, which is the ratio of the first and second measured light-receiving values ​​at the first and second light-receiving sections. If the calculated calibration threshold coefficient is within a predetermined normal range, the upper and lower limits for defining the second tolerance range are determined using the calibration threshold coefficient. The projection display system according to claim 1.

6. The light source unit further comprises a first light receiving unit that detects the light intensity of each color of light output from the optical element unit. The abnormality determination unit includes: The first reference light reception value in the first light receiving unit for each color of light, The second reference light reception value in the second light receiving unit for each color of light, A reference threshold coefficient used to determine the upper and lower limits that define the second tolerance range for each color of light, These are prepared in advance. The abnormality determination unit, The system includes a calibration unit that calibrates the aforementioned reference threshold coefficient for abnormality determination and calculates a calibration threshold coefficient. The calibration unit is Let pd1' be the first reference light reception value for each color of light. Let pd2' be the second reference light reception value for each color of light. Let pd1'' be the first measured light reception value obtained by measurement at the first light receiving unit for each color of light. Let pd2'' be the second measured light reception value obtained by the measurement at the second light receiving unit for each color of light. Let γupper be the reference threshold coefficient for the upper limit in the aforementioned reference threshold coefficient. Let γunder be the reference threshold coefficient for the lower limit in the aforementioned reference threshold coefficient. Furthermore, it is permissible for γupper and γunder to be equivalent in value. Let γupper(cab) be the calibration threshold coefficient for the upper limit in the calibration threshold coefficient. When the calibration threshold coefficient for the lower limit in the calibration threshold coefficient is γunder(cab), The first calculation formula represented by γupper・{(pd2' / pd1') / (pd2'' / pd1'')} is used to calculate γupper(cab), The second calculation formula, represented by γunder・{(pd2' / pd1') / (pd2'' / pd1'')}, is used to calculate γunder(cab). If the calculated γupper(cab) and γunder(cab) are within a predetermined normal range, the upper and lower limits that define the second acceptable range for each color of light are determined using the γupper(cab) and γunder(cab). The projection display system according to claim 1.

7. The aforementioned projection display system is an in-vehicle projection display system mounted on a vehicle. The projection display system according to claim 1.

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