Outdoor projector, and outdoor projection display control method

Abstract

To increase the light emission intensity of a light source relative to prior art and suppress deterioration in visibility of a display image caused by ambient illuminance (ambient brightness) or the like, without enlarging an outdoor projector.SOLUTION: An outdoor projector 10 includes a light source 61, a drive part 50, and a control part 44. The control part 44 can switch between a first drive mode for driving the light source 61 with current using a first drive current value, and a second drive mode for driving the light source 61 with current using a second drive current value being larger than the first drive current value, and for intermittently driving the light source using a predetermined duty. In the second drive mode, a first period as a visibility improvement display period of improving the luminance of an image, and a second period as a cooling period of lowering the temperature of the light source having risen according to drive of the light source in the first period, are repeated. The second period is set such that a temperature of the light source does not exceed an allowable upper limit temperature.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an outdoor projector that is mounted on a vehicle such as an automobile and displays an image by projecting light onto an object outside the vehicle, and to an outdoor projection display control method. [Background technology]

[0002] Patent Document 1 (for example, FIGS. 1 and 2) shows an image projection device for a vehicle that projects and displays various types of information onto a road surface, a wall surface, or the like.

[0003] Paragraph

[0006] of Patent Document 2 states that "the projector includes a light source device, an electro-optical device that performs optical modulation by changing the light transmittance or light reflectance of a light beam emitted from the light source device in accordance with the gradation level of image information to form an optical image, and a projection optical device that enlarges and projects the optical image formed by the electro-optical device, and includes a light source drive controller that controls intermittent lighting of the light source device, and a temperature detection unit that is disposed near the light source device and detects the temperature of the light source device. The light source drive controller includes a duty ratio control unit that performs duty ratio control to intermittently light the light source device at a predetermined duty ratio, and a control state switching unit that switches the control state by the duty ratio control unit. The control state switching unit compares the detected temperature detected by the temperature detection unit with a predetermined first temperature threshold, and when the detected temperature exceeds the first temperature threshold, causes the duty ratio control unit to perform duty ratio suppression control to shorten the lighting time per unit time when the light source device is intermittently lighted." [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 7203932 [Patent Document 2] JP 2005-189323 A Summary of the Invention [Problem to be solved by the invention]

[0005] In this specification, a "projector that is mounted on a vehicle (including four-wheeled automobiles as well as three-wheeled and two-wheeled vehicles) and displays an image by projecting light onto an object outside the vehicle (including the road surface, walls, and the outer surfaces of the vehicle's doors and windows)" is referred to as an "outdoor projector (in other words, an exterior projector, a road surface projector, etc.)". However, for ease of explanation, it may be referred to simply as a "projector".

[0006] For example, when a specified image is displayed on the road surface next to the vehicle door, if the illumination around the vehicle is high (for example, when the sun is strong and the surroundings are bright), the visibility of the image will decrease, making it difficult for vehicle occupants to see the image, and it is also possible that the image may not be recognized accurately.

[0007] In addition, the light emission intensity of the projector's light source (such as a laser diode) decreases as the temperature of the light source increases. When the ambient temperature of the vehicle is high (for example, when it is in a sunny summer environment) or when the temperature inside the projector increases due to driving the vehicle for a long period of time, the temperature of the light source also increases, and the light emission intensity of the light source decreases accordingly, which may reduce the visibility of the image, making it difficult for the vehicle occupants to read the image, and may even prevent them from accurately recognizing the image.

[0008] One possible solution to this problem would be to strengthen the cooling function of the light source in order to suppress the temperature rise of the light source. However, in this case, the cooling unit would become larger, which would in turn increase the size of the projector, which may make it difficult to install it in a vehicle.

[0009] On the other hand, in small projectors, the cooling section cannot be enlarged, the ability to suppress the temperature rise of the light source is weakened, and the amount of heat generated by the light source is limited based on the allowable temperature conditions. As a result, for example, in an environment with high illuminance, the brightness of the displayed image is insufficient, reducing visibility or making it difficult to see.

[0010] The above-mentioned Patent Document 2 targets general projectors used indoors, and makes no mention of the unique problem with outdoor projectors, namely, that "the brightness of the displayed image may become insufficient due to the ambient illuminance (surrounding brightness), etc., resulting in problems with image visibility," nor does it mention any measures to address this issue.

[0011] In addition, Patent Document 2 discloses a technique for reducing the light source's lighting duty when the detected temperature exceeds a temperature threshold, but this technique reduces the light emission intensity of the light source when the temperature of the light source is high, which further reduces the brightness of the image. Therefore, Patent Document 2 cannot be a solution to the above problem.

[0012] The present invention aims to increase the emission intensity of a light source compared to conventional methods without increasing the size of an outdoor projector, and to suppress deterioration in visibility of a displayed image caused by ambient illuminance (ambient brightness) and the like.

[0013] Other objects of the present invention will become apparent to those skilled in the art by referring to the following exemplary aspects and best modes, as well as the accompanying drawings. [Means for solving the problem]

[0014] In order to facilitate an understanding of the outline of the present invention, embodiments according to the present invention will be exemplified below.

[0015] In a first aspect, the outdoor projector is mounted on a vehicle and displays an image by projecting light onto an object outside the vehicle, and includes a light source, a drive unit capable of changing an output of the light source by adjusting a drive current value of the light source, and a control unit that controls the drive unit to variably control the output of the light source, wherein the control unit is capable of switching between a first drive mode in which the light source is current-driven with a first drive current value and a second drive mode in which the light source is current-driven with a second drive current value greater than the first drive current value and is driven intermittently with a predetermined duty, and in the second drive mode, a first period as a visibility improvement display period in which the output of the light source is increased by driving with the second drive current value corresponding to the predetermined duty to improve the brightness of the image, and a second period as a cooling period in which the light source is not emitting light to reduce the temperature of the light source that has increased in the first period are repeated, and the second period is set so that the temperature of the light source does not exceed an allowable upper limit temperature.

[0016] In the first aspect, analog dimming is adopted, and a new driving method having first and second driving modes is adopted as a method for driving a light source. In the first drive mode, the light source is driven by a first drive current value, and in the second drive mode, the light source is intermittently driven at a predetermined duty. In the first driving mode, the light source is in principle driven steadily (continuously) at a predetermined driving current value (on current value). However, there may be cases where the light source is driven intermittently at a predetermined duty, for example to adjust the amount of light.

[0017] In this embodiment, when it is necessary to increase the light emission intensity of the light source, a second driving mode is adopted. In the second driving mode, a first period as a visibility improvement display period in which the light source is driven by a second current value larger than the first driving current value to improve the brightness of the image, and a second period as a cooling period in which the light source is not emitting light to lower the temperature of the light source that has increased in the first period are repeated. Here, by setting an appropriate length as the second period, it is possible to prevent the temperature of the light source from exceeding the allowable upper limit temperature.

[0018] In this embodiment, the light emission intensity of the light source is increased in the first period, thereby increasing the brightness of the image displayed by the outdoor projector and improving visibility. On the other hand, the sudden rise in temperature caused by increasing the light emission intensity can be addressed by providing a second period immediately after the first period in which the light source is turned off and cooled. This prevents the temperature of the light source from exceeding the upper allowable temperature limit, thereby reliably suppressing characteristic degradation and failures caused by high temperatures of the light source.

[0019] In this way, according to this aspect, it is possible to achieve both an improvement in the emission intensity of the light source and a prevention of the temperature of the light source from exceeding the allowable upper limit temperature. Therefore, without increasing the size of the outdoor projector (in other words, increasing the size of the cooling unit), it is possible to increase the light emission intensity of the light source more than before and suppress the decrease in visibility of the displayed image caused by ambient illuminance (ambient brightness), etc.

[0020] In a second aspect dependent on the first aspect, the control unit may drive the light source in the first driving mode when it is determined that the vehicle is in a first brightness environment based on illuminance-related information including at least one of illuminance around the vehicle and information capable of estimating the illuminance, and may drive the light source in the second driving mode when it is determined that the vehicle is in a second brightness environment brighter than the first brightness environment.

[0021] In a second aspect, based on the illuminance-related information, it is determined whether the illuminance around the vehicle is in a first brightness environment or a second brightness environment that is brighter than the first brightness environment, and if it is determined that it is in the second brightness environment, intermittent driving of the light source in the second driving mode is performed.

[0022] For example, when a specified image is displayed on the road surface next to the vehicle door, if the illumination around the vehicle is high (for example, when the sun is strong and the surroundings are bright), the visibility of the image will decrease, making it difficult for vehicle occupants to see the image, and it is also possible that the image may not be recognized accurately. Therefore, for example, when the illuminance around the vehicle is equal to or greater than the illuminance judgment threshold, the second driving mode is adopted, and the light emission intensity during the period when the light source is emitting light (the first period) is increased, thereby improving the visibility of the image. Here, the illuminance around the vehicle may be directly measured by an illuminance sensor, or, for example, an external light sensor or the like installed in the vehicle may detect the illuminance and estimate the illuminance (brightness) around the vehicle based on the detected value (in other words, information that allows the illuminance around the vehicle to be estimated), and the above-mentioned drive mode switching may be performed. Also, both a measured value that directly measures the illuminance around the vehicle and information that allows the illuminance around the vehicle to be estimated may be used.

[0023] In a third aspect dependent on the first aspect, the control unit may drive the light source in the first driving mode when it is determined that the temperature environment is a first temperature environment based on temperature-related information including at least one of a temperature of the light source and an ambient temperature of the vehicle, and may drive the light source in the second driving mode when it is determined that the temperature environment is a second temperature environment having a higher temperature than the first temperature environment.

[0024] In a third aspect, based on temperature-related information, it is determined whether the temperature around the vehicle is a first temperature environment or a second temperature environment which is higher than the first temperature environment, and if it is determined to be the second temperature environment, intermittent driving of the light source in the second driving mode is performed.

[0025] When the temperature of the light source rises, the light emission intensity decreases, which may cause insufficient brightness of the displayed image. In addition, the temperature of the light source is also related to the ambient temperature of the vehicle, and if the ambient temperature of the vehicle rises, the temperature of the light source also rises accordingly. In consideration of this point, in this embodiment, it is determined whether the visibility of the image may decrease based on temperature-related information including at least one of the temperature of the light source and the ambient temperature of the vehicle, and the second driving mode is selectively performed based on the result of this determination.

[0026] For example, when the temperature of the light source (or the temperature around the vehicle) is equal to or higher than a predetermined temperature threshold, the second driving mode is adopted and the emission intensity during the period when the light source is emitting light (first period) is increased, thereby making it possible to improve the visibility of the image.

[0027] In a fourth aspect which is dependent on any one of the first to third aspects, when the control unit is controlling the output of the light source in the second driving mode and it is determined that cooling of the light source needs to be strengthened, the control unit may change the second driving current value to a third driving current value which has a lower current value.

[0028] In a fourth aspect, while driving the light source in the second driving mode, for example, if the degree of temperature rise of the light source increases and it becomes necessary to extend the cooling period (second period) of the light source, the second driving current value is changed to a third driving current value having a lower current value, thereby suppressing the temperature rise of the light source. This makes it possible to suppress deterioration of characteristics and breakdowns caused by high temperatures of the light source.

[0029] In a fifth aspect dependent on any one of the first to fourth aspects, the control unit may perform control to switch between the first driving mode and the second driving mode depending on the type of the image.

[0030] In the fifth aspect, the first and second driving modes can be used depending on the type of image. Display images can be roughly divided into, for example, "advertising images and performance images (for example, images for welcome performances)" and "attention-calling images" from the viewpoint of the urgency and importance of the display. As an example, it may be envisaged that advertising images and special images (e.g., images for welcome displays) are displayed in a first driving mode, while warning images are displayed in a second driving mode to increase the likelihood that they will be visible to humans.

[0031] In a sixth aspect dependent on any one of the first to fifth aspects, the control unit may display the image as an image that is highly attention-grabbing to attract the viewer's attention by setting the duty in the second driving mode to 50% or more and blinking the image.

[0032] In a sixth aspect, when an image is displayed, the duty (in other words, the light source light emission / non-light emission duty, display duty, or light source on / off duty) is set to 50% or more and the image is blinked, thereby giving a person (viewer) the impression that the image is highly attention-grabbing, thereby improving visibility.

[0033] When an image is used to draw the attention of a person (a viewer), the image may be made to blink. However, in order to draw attention, the image needs to be displayed in a stable manner so that the person (a viewer) can see it. Here, when the duty is less than 50%, the non-display period (light source off period: second period) per cycle of the display duty becomes longer than the display period (light source on period: first period). In other words, because the display period is short, it becomes difficult for people (the viewer) to understand the meaning of the image, and because the blinking display is unstable and unnatural, it is likely that people (the viewer) will feel uncomfortable and will be less likely to perceive it as a warning display. Therefore, in this embodiment, a duty of 50% or more is ensured so that the display period is longer than the non-display period, providing a person (viewer) with a stable visual sense and making it easier for the person to understand the meaning of the image, while the blinking gives the impression of calling attention, drawing the person's attention to the image, thereby further improving the visibility of the image through psychological factors.

[0034] In a seventh aspect dependent on any one of the first to sixth aspects, a frequency of intermittent driving of the light source in the second driving mode may be 60 Hz or less.

[0035] In the seventh aspect, the frequency of the intermittent drive of the light source in the second drive mode is set to 60 Hz or less. The intermittent drive in the second drive mode is preferably performed quite slowly, for example, like the vibration of a windshield wiper of a car. When the frequency of the intermittent drive is 60 Hz, the period is approximately 0.02 seconds, and when the duty is 50%, a light emission period (first period) of 0.01 seconds can be secured, allowing a person (viewer) to view the image and understand its meaning. On the other hand, a non-display period (second period) of 0.01 seconds can be secured, and during this period, the temperature of the light source can be lowered to a desired level (desired threshold temperature) by dissipating heat from the light source. In this way, by setting the frequency of intermittent drive to 60 Hz or less, it is possible to ensure the visibility of the image while cooling the light source.

[0036] In an eighth aspect which is dependent on any one of the first to seventh aspects, the second drive current value in the second drive mode may be set to 1.2 times or more of the first drive current value in the first drive mode, provided that the temperature of the light source does not exceed an allowable upper limit temperature and the duty in the second drive mode is 50% or more.

[0037] According to the eighth aspect, the second drive current value in the second drive mode is set to be 1.2 times or more the first drive current value in the first drive mode. By increasing the drive current value by at least 1.2 times, the effect of improving the visibility of the image can be obtained, and preferably by increasing the drive current value by 2 times or more. However, it is preferable to set the magnification so that the temperature of the light source does not exceed the upper allowable temperature limit, and since a duty of 50% or more is considered necessary for stable image viewing, as shown in the sixth embodiment, the magnification does not fall below this 50% duty.

[0038] In a ninth aspect dependent on any one of the first to eighth aspects, the vehicle includes a cooling unit that cools the light source, and the control unit drives the light source in the first drive mode when it is determined that the vehicle is in a first brightness environment based on illuminance-related information including at least one of an illuminance around the vehicle and information capable of estimating the illuminance, or when it is determined that the vehicle is in a first temperature environment based on temperature-related information including at least one of a temperature of the light source and an ambient temperature of the vehicle, and determines that the vehicle is in a second brightness environment brighter than the first brightness environment based on the illuminance-related information. or when the determination based on the temperature-related information determines that the environment is a second temperature environment having a temperature higher than the first temperature environment and the cooling unit is operating, the light source may be driven in the second driving mode, and when the determination based on the illuminance-related information determines that the environment is a second brightness environment that is brighter than the first brightness environment or when the determination based on the temperature-related information determines that the environment is a second temperature environment having a temperature higher than the first temperature environment and the cooling unit is not operating, the light source may be driven in the first driving mode.

[0039] In a ninth aspect, the conditions for switching from the first driving mode to the second driving mode include that the cooling unit is operating. In the ninth aspect, it is assumed that the cooling unit does not operate all the time, but operates, for example, when the temperature of the light source approaches the upper allowable temperature limit. It is also assumed here that image formation in the first driving mode in which light is continuously projected is often preferable.

[0040] It is preferable to maintain the first driving mode when transitioning from the first brightness environment to the second brightness environment, but if the cooling unit is operating, which means that the temperature of the light source is close to the upper allowable temperature limit, the second driving mode is selected when the cooling unit is operating.

[0041] Thus, according to the ninth aspect, the first driving mode is generally used to display stable images, while when the first brightness environment is switched to the second brightness environment and the cooling unit is operating and the temperature of the light source is high, the second driving mode is switched to, thereby making it possible to both suppress deterioration of image visibility and prevent deterioration or failure of the light source due to high temperatures.

[0042] In a tenth aspect, an outdoor projection display control method for controlling a display when an image is displayed by projecting light from an outdoor projector mounted on a vehicle onto an object outside the vehicle, includes a first step of determining whether or not visibility of the image will decrease based on at least one of the illuminance around the vehicle, information from which the illuminance can be estimated, a temperature of a light source, and the ambient temperature of the vehicle, and a second step of, when it is determined that the visibility of the image will decrease, setting a second drive current value greater than a first drive current value of the light source when it is determined that the visibility of the image will not decrease, and intermittently driving the light source at a predetermined duty, thereby repeating a first period as a visibility improvement display period for improving the brightness of the image and a second period as a cooling period for lowering the temperature of the light source that has increased due to driving the light source in the first period, thereby intermittently driving the light source so that the temperature of the light source does not exceed an allowable upper limit temperature.

[0043] According to the tenth aspect, it is possible to increase the emission intensity of the light source compared to conventional methods without increasing the size of the outdoor projector, and to suppress deterioration in visibility of a displayed image caused by ambient illuminance (ambient brightness) and the like.

[0044] Those skilled in the art will easily understand that the exemplified embodiments according to the present invention can be further modified without departing from the spirit of the present invention. [Brief description of the drawings]

[0045] [Figure 1] FIG. 1 is a diagram showing an example of a display by an outdoor projector mounted on a vehicle. [Diagram 2] FIG. 2 is a diagram showing an example of image display in each of the first and second periods in the case where the illuminance around the vehicle is high and the second drive mode is adopted. [Diagram 3] FIG. 3A is a diagram showing an example of the configuration of an in-vehicle projection system including an outdoor projector, and FIG. 3B is a diagram showing an example of the configuration of a projection unit in the outdoor projector. [Figure 4] FIG. 4 is a diagram showing an example of the internal configuration of the outdoor projector. [Diagram 5] FIG. 5 is a diagram showing an example of the configuration of a light source drive unit and a control unit in an outdoor projector. [Figure 6] FIG. 6 is a diagram showing an example of the control voltage, the duty of the drive signal of the light source, the optical output of the light source, and the temperature change of the light source in each of the first and second drive modes. [Figure 7] FIG. 7 is a flowchart showing an example of the procedure of a method for driving a light source (a method for controlling outdoor projection display). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0046] The best mode described below is used to easily understand the present invention. Therefore, those skilled in the art should be aware that the present invention is not unduly limited by the mode described below.

[0047] (First embodiment) Please refer to Fig. 1. Fig. 1 is a diagram showing examples of displays by an outdoor projector mounted on a vehicle. Three display examples are shown in Fig. 1. Although each display example is independent, for convenience of explanation, three are shown together in Fig. 1.

[0048] Also, in Figure 1, the sector-shaped area indicated by the dashed line shows an example of each display area of ​​an outdoor projector (here, a road surface projection display device that projects an image onto the road surface) mounted on a vehicle (in other words, fixed integrally to the vehicle).

[0049] In the example of FIG. 1, six outdoor projectors 10a to 10f are mounted on the vehicle 1. The number of outdoor projectors is not limited to this example. The outdoor projectors may be projectors having individual lamps (lamp fixtures), or may be projectors that use, for example, a headlight 2 as a light source. In the example of FIG. 1, each of the six outdoor projectors 10a to 10f is a projector having an individual lamp (lamp fixture).

[0050] In FIG. 1, an outdoor projector 10a mounted on the front right end of a vehicle 1 displays an image 12 of a stop line (e.g., a white line) on the road surface to prompt people 8 to stop temporarily and prevent them from entering the road 4.

[0051] In addition, the outdoor projector 10b attached to the right door of the vehicle 1 displays a so-called welcome image (an image of the letters "Welcome") on the road surface to welcome the arrival of the vehicle 1 at its destination.

[0052] In addition, when the vehicle 1 is reversed onto the road 6, the outdoor projector 10c mounted on the right end at the rear of the vehicle 1 displays an arrow image 16 on the road surface to indicate to occupants of vehicles approaching from behind or cyclists that the vehicle is reversing onto the road.

[0053] Note that the display example in FIG. 1 is merely an example and is not limited thereto. The outdoor projector can display various images on outdoor objects such as the road surface or a wall (or the outer surface of a door or window of the vehicle).

[0054] Please refer to Fig. 2. Fig. 2 is a diagram showing an example of image display in each of the first and second periods when the second driving mode is adopted in a case where the illuminance around the vehicle is high. In Fig. 2, the same reference numerals are used to designate parts common to Fig. 1.

[0055] As shown in A-1 of FIG. 2, in the example of FIG. 2, it is assumed that an image for a welcome effect (an image of the letters "Welcome") is displayed on the road surface next to the right door of the vehicle 1.

[0056] As shown in A-2 of Figure 2, due to strong sunlight and the brightness around vehicle 1 (high ambient illuminance), the text image 14' "Welcome" is lost in the surrounding brightness, significantly reducing its visibility, and in some cases, it is conceivable that the occupants of vehicle 1 may have difficulty viewing (confirming) the image.

[0057] Therefore, in the example of FIG. 2, as shown in A-3 to A-6 in FIG. 2, a new light source driving method (driving mode) is adopted in which the driving current value of the light source is increased and the light source is driven intermittently.

[0058] This new driving mode is called the "second driving mode." The control unit mounted on each of the outdoor projectors 10a to 10f of this embodiment can switch between a "first drive mode" in which the light source is current-driven with a first drive current value, and a second drive mode in which the light source is current-driven with a second drive current value greater than the first drive current value and driven intermittently with a predetermined duty. In the second drive mode, a first period as a visibility improvement display period (in other words, an image display period) in which the output of the light source is increased by driving with the second drive current value corresponding to the predetermined duty, thereby improving the brightness of the image, and a second period as a cooling period (non-display period) in which the light source is not emitting light and the temperature of the light source that has increased in the first period is reduced are repeated, and the second period is set so that the temperature of the light source does not exceed the allowable upper limit temperature.

[0059] The drive frequency of the light source is preferably set to 60 Hz or less, and the displayed image blinks repeatedly at a fairly slow cycle. In the following description, the drive duty of the light source is assumed to be 50%.

[0060] The first half of the driving cycle of the light source is the above-mentioned first period (the visibility-improving display period (in other words, the image display period)), and the second half is the above-mentioned second period (the cooling period for lowering the temperature of the light source (in other words, the non-display period) (see A-2 in FIG. 6 for specific operations).

[0061] In the first period (A-3, A-5 in FIG. 2), the drive current value of the light source (second drive current value) is set to at least 1.2 times, and preferably 2 times, the drive current value of the light source (first drive current value) during normal driving (A-1 in FIG. 2). However, the drive is performed within the range of conditions that the temperature of the light source does not exceed the allowable upper limit temperature and a predetermined duty (here, 50%) can be maintained.

[0062] The specific configuration and operation of the outdoor projector will be described later with reference to FIGS.

[0063] In A-3 of Figure 2, the second driving mode is adopted, so that the output (light emission intensity of the light source) of the light source (e.g., a laser diode (LD)) increases in the first period, which is the first half of the driving cycle of the light source. As a result, although the brightness of the welcome effect image (text image of "Welcome") 14'' is lower than that of the normal text image 14 in A-1 of Figure 2, it is brighter than the text image 14' in A-2 of Figure 2. In other words, visibility is improved, and it is fully possible for the occupants of the vehicle 1 to view (sight) and confirm the image 14''.

[0064] In A-4 of Fig. 2, the light source (here, the LD) is in a non-emitting state in the second period, which is the latter half of the driving cycle of the light source. Accordingly, the image 14'' displayed in A-3 of Fig. 2 is not displayed in A-4 of Fig. 2. During this second period, the light source (LD) is cooled to lower the temperature of the light source that has risen due to the high-output light emission during the first period. During this second period, it is preferable to turn on a cooling unit composed of, for example, a Peltier element to cool the light source and efficiently lower the temperature of the light source.

[0065] Next, in A-5 of FIG. 2, in a first period, the light source is again in a high-output light-emitting state, and the image 14'' shown in A-3 of FIG. 2 is displayed.

[0066] Next, in A-6 of FIG. 2, in a second period, the light source is in a non-emitting state (low output state), and the image 14'' is not displayed. Thereafter, similarly, the light source is intermittently driven at a predetermined duty, whereby the display of the image in the first period and the non-display of the image in the second period are repeated.

[0067] In this way, by increasing the emission intensity of the light source in the first period (A-3 and A-5 in FIG. 2), the brightness of the image (the image for the welcome performance) displayed by the outdoor projector 10b is increased, thereby improving visibility.

[0068] On the other hand, the sudden rise in temperature caused by increasing the light emission intensity can be addressed by providing a second period immediately after the first period in which the light source is turned off (or at low output) to cool the light source. This prevents the temperature of the light source from exceeding the upper allowable temperature limit, thereby reliably suppressing characteristic degradation and failures caused by high temperatures of the light source.

[0069] In this way, by intermittently driving the light source (driving in the second driving mode) shown in A-3 to A-6 in FIG. 2, it is possible to achieve both an improvement in the light emission intensity of the light source and prevention of the temperature of the light source from exceeding the allowable upper limit temperature. Therefore, without increasing the size of the outdoor projector (in other words, increasing the size of the cooling unit), it is possible to increase the light emission intensity of the light source more than before and suppress the decrease in visibility of the displayed image caused by ambient illuminance (ambient brightness), etc.

[0070] Furthermore, by flashing the light source with a duty (in other words, the light emission / non-emission duty of the light source, the display duty, or the on / off duty of the light source) of 50% or more, it is possible to give people (viewers) the impression that the image is highly attention-grabbing, and visibility can also be improved from a psychological perspective (more details on this point will be given later).

[0071] Next, reference will be made to Fig. 3. Fig. 3(A) is a diagram showing an example of the configuration of an in-vehicle projection system including an outdoor projector, and Fig. 3(B) is a diagram showing an example of the configuration of a projection unit in the outdoor projector.

[0072] In FIG. 3(A), an in-vehicle projection system 7 including an outdoor projector has a light distribution control ECU 20, an information acquisition unit 30, a communication unit 32 equipped with an antenna AN, a vehicle control ECU 34, the outdoor projector 10, and a sensor unit 70 (equipped with an illuminance sensor 72 and an ambient temperature sensor 74).

[0073] The light distribution control ECU 20 includes an MPU (microprocessing unit) 21, a RAM 23, a ROM 25, a system bus 26, and a light distribution control unit 27.

[0074] The information acquisition unit 30 acquires various pieces of information about the vehicle (host vehicle) 1 from the vehicle control ECU 34. In addition, the information acquisition unit 30 acquires each piece of detection information (each detection signal) of the illuminance sensor 72 and the ambient temperature sensor 74 from the sensor unit 70.

[0075] The light distribution control unit 27 receives various information from the information acquisition unit 30 (and the communication unit 32) and, based on this information, determines which of the multiple outdoor projectors 10a to 10f (see FIG. 1) mounted on the vehicle 1 is to be used for display. After this determination, the light distribution control unit 27 notifies the outdoor projector 10 (any of 10a to 10f) that has been determined to be used of that fact, and supplies detection information of various sensors (including an illuminance sensor 72 and an ambient temperature sensor 74) obtained from the sensor unit 70 to the outdoor display control device 42 (control unit 44) of that outdoor projector 10 (any of 10a to 10f).

[0076] The outdoor projector 10 has an outdoor display control device 42 (having a control unit 44), a driving unit 50 that drives the light source, a light source 61, a cooling unit 63, a light source temperature sensor (such as a thermistor) 64 that detects the temperature of the light source, and a projection unit (including a projection optical system) 71 that projects the display light of the image onto a road surface, etc.

[0077] The driving section 50 includes an APC circuit (automatic power control circuit) 52. The APC circuit includes a driving current generating section 54 that generates a driving current for the light source 61.

[0078] Furthermore, information on the detected temperature by the light source temperature sensor 64 and information on whether the cooling unit 63 is in operation or not (on / off) are supplied to the control unit 44 of the outdoor display control device 42.

[0079] Here, the control unit 44 may drive the light source in a first driving mode when it is determined that the environment is a first brightness environment based on illuminance-related information including at least one of the illuminance around the vehicle 1 and information that allows estimating the illuminance, and may drive the light source in a second driving mode when it is determined that the environment is a second brightness environment that is brighter than the first brightness environment.

[0080] Here, the illuminance around the vehicle 1 may be directly measured by the illuminance sensor 72, or, for example, an external light sensor (not shown) provided inside the vehicle 1 may detect the illuminance and estimate the illuminance (brightness) around the vehicle 1 based on the detected value (in other words, information that allows the illuminance around the vehicle 1 to be estimated), and the above-mentioned drive mode switching may be performed. Also, both a measured value that directly measures the illuminance around the vehicle 1 and information that allows the illuminance around the vehicle to be estimated may be used.

[0081] In addition, the control unit 44 may drive the light source in a first driving mode when it is determined that the environment is a first temperature environment based on temperature-related information including at least one of the temperature of the light source and the ambient temperature of the vehicle, and may drive the light source in a second driving mode when it is determined that the environment is a second temperature environment having a higher temperature than the first temperature environment.

[0082] When the temperature of the light source rises, the light emission intensity decreases, and this may result in insufficient brightness of the displayed image. The temperature of the light source is also related to the ambient temperature of the vehicle, and if the ambient temperature of the vehicle rises, the temperature of the light source also rises accordingly. In consideration of this, the control unit 44 may determine whether or not a decrease in image visibility may occur based on temperature-related information including at least one of the temperature of the light source and the ambient temperature of the vehicle, and selectively implement the second driving mode based on the result of this determination.

[0083] For example, when the temperature of the light source (or the temperature around the vehicle) is equal to or higher than a predetermined temperature threshold, the second driving mode is adopted and the emission intensity during the period when the light source is emitting light (first period) is increased, thereby making it possible to improve the visibility of the image.

[0084] Next, reference will be made to Fig. 3. In Fig. 3(B), the projection unit 71 has a light collecting optical system 81, a light modulation unit 82 (here, a digital micromirror device in which a large number of minute mirrors (display elements) are formed on a chip is used), a projection optical system 84 that projects display light 88 of an image, and a display element driving unit 86. The operation of the display element driving unit 86 is controlled by the control unit 44.

[0085] Next, reference is made to Fig. 4. Fig. 4 is a diagram showing an example of the internal configuration of an outdoor projector. In Fig. 4, parts common to Fig. 3 are given the same reference numerals.

[0086] The outdoor projector 10 includes an outdoor display control device 42 (including a control unit 44), a drive unit 50, and a projection unit 71.

[0087] The projection unit 71 includes an RGB light generation unit 110 that generates light of each color of RGB, a speckle reduction unit 120 (including a diffuser plate 121) that reduces speckle noise, a focusing optical system 81, an optical path changing unit 140, a light modulation unit (here, a digital micromirror device) 82, a display element driving unit 86 that drives the fine mirrors (display elements) that make up the digital micromirror device, and a projection optical system 84.

[0088] The RGB light generation unit 110 that generates light of each color, RGB, has light sources 61a to 61c corresponding to each color of R (red), G (green), and B (blue), and dichroic mirrors 111 to 113. Here, the light sources 61a to 61c are formed of laser elements (LD).

[0089] Furthermore, the light collecting optical system 81 collects the laser light diffused by the diffusion plate 121 of the speckle reduction section 120. The light collecting optical system 81 includes a collimator lens 131, a fly's eye lens 132, and a condenser lens 133.

[0090] Next, reference is made to Fig. 5. Fig. 5 is a diagram showing an example of the configuration of a light source drive unit and a control unit in an outdoor projector. In Fig. 5, the same reference numerals are used to designate parts common to the previous figures.

[0091] In the following description, the laser diode serving as the light source may be written as "LD." Furthermore, the "light source 61" may be written as "LD 61." Furthermore, the "cooling unit 63" may be written as "Peltier element 63."

[0092] The outdoor projector 10 includes an LD module 100. The LD module 100 includes a driver 50 and an outdoor display control device .

[0093] The drive unit 50 has a duty setting unit 55, a variable voltage source 56, a voltage comparator 57 configured using an operational amplifier, a collector-grounded NPN bipolar transistor (emitter follower) 58 whose base is driven by the output voltage of the voltage comparator 57 and which supplies a drive current (on-current) IL to the LD 61, a light source unit 69 which has the LD 61, a Peltier element 63, and a submount (or stem) 67, a resistor R for monitoring the current of the LD 61 (in other words, the load resistor of the LD 61; hereinafter, sometimes simply referred to as "resistance"), a light source temperature sensor 64, and a Peltier element drive unit (cooling unit drive unit) 65 which drives the Peltier element 63 as a cooling unit.

[0094] Variable voltage source 56 is a voltage source (for example, a variable output voltage regulator) that has two control terminals (output voltage control terminal VC and output enable terminal EN) and can variably control the output voltage. Note that in the figure, the terminal marked as GND is a ground terminal.

[0095] This variable voltage source 56 variably controls the voltage level of the output voltage Vout output from a voltage output terminal VO (hereinafter sometimes referred to as the "VO terminal") by a control voltage V applied to an output voltage control terminal VC (hereinafter sometimes referred to as the "VC terminal").

[0096] In addition, during a period when an active level (e.g., H level) voltage is applied to output enable terminal EN (hereinafter sometimes referred to as "EN terminal") of variable voltage source 56, voltage output from the VO terminal is permitted, while during a period when an inactive level (e.g., L level) voltage is applied, voltage output from the VO terminal is prohibited.

[0097] Therefore, by duty setting unit 55 applying a voltage signal (duty setting voltage) VD of a predetermined period and a predetermined duty to the EN terminal, the duty of the output voltage Vout output from the VO terminal of variable voltage source 56 can be variably controlled.

[0098] In addition, a negative feedback control system is formed by the variable voltage source 56, the voltage comparator 57, the NPN bipolar transistor (emitter follower) 58, the light source unit 69, and the resistor R, and this negative feedback control system forms an APC circuit (automatic power control circuit) 52 (see FIG. 3(A)).

[0099] In other words, the amount of drive current IL is automatically adjusted by negative feedback control so that the output voltage Vout output from the VO terminal of the variable voltage source 56 is the same as the voltage corresponding to the voltage drop in resistor R (determined by the product of the resistance value of resistor R and the drive current IL of the LD).

[0100] Therefore, by adjusting the voltage level of the voltage (control voltage) applied to the VC terminal of the variable voltage source 56, the output voltage Vout output from the VO terminal is set to a predetermined value, and the drive current IL of the LD 61, which is the light source, is uniquely determined in accordance with this predetermined value.

[0101] Moreover, the duty setting section 55, the variable voltage source 56, the voltage comparator 57, the NPN bipolar transistor (emitter follower) 58, and the resistor R constitute a drive current generating section 54 (see FIG. 3A).

[0102] As explained above, the drive unit 50 has a first and second drive modes. In the example of FIG. 5, in the first drive mode, the control voltage V applied to the VC terminal of the variable voltage source 56 is set to V1, and the duty is set to 100%, while in the second drive mode, the control voltage V applied to the VC terminal of the variable voltage source 56 is set to V2 (=2V1), and the duty is set to 50%.

[0103] When duty setting unit 55 sets a duty of 100% (indicated as "Duty 100%" in FIG. 5), a duty setting voltage VD1 of a predetermined voltage value (H level) is applied to the EN terminal of variable voltage source 56. When duty setting unit 55 sets a duty of 50% (indicated as "Duty 50%" in FIG. 5), a duty setting voltage VD2 of which the first half of one cycle is a predetermined voltage value (H level) and the second half is an L level (for example, 0 V) ​​is applied to the EN terminal of variable voltage source 56.

[0104] Correspondingly, an output voltage Vout1 with a duty of 100% and an output voltage Vout2 with a duty of 50% (the voltage value of the H level is twice that of Vout1) are output from the VO terminal of the variable voltage source 56.

[0105] Next, a description will be given of the configuration of the control unit 44 in the outdoor display control device 42. The control unit 44 has a duty determination unit 91, a control voltage generation unit 92, an illuminance determination unit 93, a light source temperature determination unit 95, an ambient temperature determination unit 96, and a cooling unit operation determination unit 97.

[0106] The illuminance determination unit 93 determines the illuminance (degree of brightness, brightness environment, etc.) around the vehicle 1 based on the illuminance detection signal of the illuminance sensor 72. Also, the light source temperature determination unit 95 determines, for example, which temperature category (temperature range) of a plurality of preset temperature categories the temperature of the light source is in based on the light source temperature detection signal of the light source temperature sensor 64. Also, the ambient temperature determination unit 96 determines, for example, which temperature range of a plurality of preset temperature categories the temperature around the vehicle 1 is in based on the ambient temperature detection signal of the ambient temperature sensor 74. Also, the cooling unit operation determination unit 97 determines whether the Peltier element as the cooling unit 63 is operating (cooling) or not based on a signal indicating the operating state supplied from the Peltier element drive unit (cooling unit drive unit) 65.

[0107] The control voltage generating unit 92 determines the voltage level of the control voltage V to be supplied to the VC terminal of the variable voltage source 56 based on at least one of the illuminance around the vehicle 1, the temperature around the vehicle 1, and the light source temperature, or further taking into consideration whether the cooling unit 63 is operating, etc., and generates and outputs the control voltage V.

[0108] Similarly, the duty determination unit 91 determines the duty of the light source drive signal based on at least one of the illuminance around the vehicle 1, the temperature around the vehicle 1, and the light source temperature, or further taking into consideration whether the cooling unit 63 is operating, and notifies the duty setting unit 55 of the determined duty.

[0109] Next, reference is made to Fig. 6. Fig. 6 is a diagram showing an example of the control voltage, the duty of the drive signal, the light output of the light source, and the temperature change of the light source in each of the first and second drive modes.

[0110] As shown in A-1 of Fig. 6, in the first drive mode, the control voltage V that controls the light emission intensity is set to VC1, the duty of the drive signal of the light source (LD 61) is set to 100%, and the light output (light emission intensity) of the light source is P1. In addition, below A-1 of Fig. 6, the change in the light source temperature is shown by a characteristic line Q1.

[0111] In the figure, "Ts1" indicates a first temperature reference value, and "Ts2" indicates a second temperature reference value, which is the upper limit of the allowable temperature. When the temperature of the light source (LD 61) is near the first temperature reference value Ts1, it can be determined that the temperature is low, and when it is near the second temperature reference value (upper limit of the allowable temperature) Ts2, it can be determined that the temperature is high.

[0112] According to the temperature rise indicated by characteristic line Q1, the temperature of the light source (LD61) approaches the second temperature reference value (upper allowable temperature limit) Ts2 around time t6. However, for example, after time t6, by turning on the cooling unit (Peltier element) 63, which had been turned off until then, to enhance the cooling function, the temperature of the light source (LD61) is stabilized after time t6 and does not exceed the second temperature reference value (upper allowable temperature limit) Ts2.

[0113] Next, reference is made to A-2 in Fig. 6. As shown in A-2 in Fig. 6, in the second drive mode, the control voltage V that controls the light emission intensity is set to VC2, the duty of the drive signal of the light source (LD 61) is set to 50% (however, this is just an example and is not limited to this duty), and the light output (light emission intensity) of the light source is increased to P2.

[0114] In A-2 of FIG. 6, "TA" indicates one period of the drive signal of the light source, "TB1" indicates the first period (visibility-enhanced display period), and "TB2" indicates the second period (cooling period).

[0115] By adopting the second driving mode, as previously shown in A-3 and A-5 of Figure 2, the visibility of the displayed image can be improved even in a bright environment with strong sunlight, and the occupants of vehicle 1 can see (visually view) the image.

[0116] In addition, in A-2 of Fig. 6, the change in the light source temperature is shown by characteristic line Q2. Since the light output is changed from P1 to P2, the change in the light source temperature is steeper than in the case of characteristic line Q1 of A-1 of Fig. 6.

[0117] However, by setting the duty to 50%, a second period (light source non-emission period: time t2 to t3, time t4 to t5, time t6 to t7, etc.) is set as a cooling period following a first period (period in which the brightness of an image is increased to improve visibility: time t1 to t2, time t3 to t4, time t5 to t6, time t7 to t8, etc.) as a visibility-improving display period, and thus heat dissipation from the light source (LD61) is promoted during this second period (cooling period) and the temperature of the light source is efficiently reduced. Therefore, even in the second driving mode, the temperature of the light source (LD61) is stabilized and does not exceed the second temperature reference value (allowable upper limit temperature) Ts2.

[0118] However, when the output of the light source (LD61) is being controlled by the second drive mode, if it is determined that cooling of the light source needs to be strengthened, the drive current value of the light source (in A-2 of FIG. 6, it is assumed that the light source is driven at the second drive current value) may be changed to a third drive current value which is a lower current value.

[0119] In other words, when the light source (LD 61) is driven in the second drive mode, for example, when the degree of temperature rise of the light source becomes large and it becomes necessary to make the cooling period (second period TB1) of the light source longer, the second drive current value is changed to a third drive current value having a lower current value, thereby suppressing the temperature rise of the light source. This makes it possible to suppress characteristic deterioration and failure due to high temperature of the light source.

[0120] In addition, the control unit 44 may execute control to switch between the first driving mode and the second driving mode according to the type of image. From the viewpoint of the urgency and importance of the display, the display images can be roughly classified into, for example, "advertising images and performance images (for example, images for welcome performance)" and "attention-calling images".

[0121] As an example, it may be envisaged that advertising images and special images (e.g., images for welcome displays) are displayed in a first driving mode, while warning images are displayed in a second driving mode so that they can be reliably seen by people.

[0122] Furthermore, the control unit 44 may display the image as an image that is highly attention-grabbing to attract the viewer's attention by setting the duty in the second driving mode to 50% or more and blinking the image.

[0123] In other words, when displaying an image, by flashing the image with a duty (in other words, the light source light emission / non-emission duty, or the display duty) of 50% or more, the person (viewer) is given the impression that the image is highly attention-grabbing, thereby improving visibility.

[0124] When an image is used to draw the attention of a person (a viewer), the image may be made to blink. However, in order to draw attention, the image needs to be displayed in a stable manner so that the person (a viewer) can see it.

[0125] Here, when the duty is less than 50%, the non-display period (light source off period: second period) per cycle of the display duty becomes longer than the display period (light source on period: first period). In other words, since the display period is short, it becomes difficult for people (viewers) to understand the meaning of the image, and since it is unstable and unnatural as a blinking display, people (viewers) are likely to feel uncomfortable and are unlikely to be convinced that it is a warning display.

[0126] Therefore, in this embodiment, a duty of 50% or more is ensured so that the display period is longer than the non-display period, providing a person (viewer) with a stable visual sense and making the meaning of the image easier to understand, while the blinking gives the impression of calling attention, drawing the person's attention to the image and thereby further improving the visibility of the image from a psychological aspect.

[0127] In this embodiment, the frequency of the intermittent drive of the light source (LD 61) in the second drive mode is preferably 60 Hz or less. The intermittent drive in the second drive mode is preferably performed quite slowly, as in the case of the wipers of a car vibrating, for example. When the frequency of the intermittent drive is 60 Hz, the period is about 0.02 seconds, and when the duty is 50%, 0.01 seconds can be secured as the light emission period (first period), and a person (viewer) can view the image and understand its meaning.

[0128] On the other hand, a non-display period (second period) of 0.01 seconds can be secured, and during this period, the temperature of the light source can be lowered to a desired level (desired threshold temperature) by dissipating heat from the light source.

[0129] In this way, by setting the frequency of intermittent drive to 60 Hz or less, it is possible to ensure the visibility of the image while cooling the light source.

[0130] In addition, in this embodiment, the second drive current value in the second drive mode may be set to 1.2 times or more, and preferably 2 times or more, the first drive current value in the first drive mode, provided that the temperature of the light source does not exceed the allowable upper limit temperature (Ts2) and the duty in the second drive mode is 50% or more.

[0131] By increasing the driving current value by at least 1.2 times, the effect of improving the visibility of the image can be obtained. It is preferable to increase the driving current value by 2 times or more. However, since the temperature of the light source does not exceed the allowable upper limit temperature and, as described above, a duty of 50% or more is considered to be preferable for stable image visibility, it is preferable to set the magnification so as to satisfy the condition that the duty does not fall below 50%.

[0132] In addition, when it is determined based on illuminance information (illuminance-related information) or temperature information (temperature-related information) that it is better to switch the first driving mode to the second startup mode, the conditions for the switching can include the cooling unit (Peltier element, etc. 63) being operating.

[0133] Here, it is assumed that the cooling unit does not operate all the time, but operates, for example, when the temperature of the light source approaches the upper allowable temperature limit, and that image formation in the first driving mode in which light is continuously projected is often preferable.

[0134] For example, when transitioning from a first brightness environment to a second brightness environment, it is preferable to maintain the first driving mode; however, when the cooling unit 63 is operating, which means that the temperature of the light source 61 is close to the allowable upper limit temperature Ts2, the second driving mode is selected when the cooling unit 63 is operating.

[0135] In this way, a control may be implemented in which a stable image display is performed using the first driving mode in principle, while a transition from the first brightness environment to the second brightness environment occurs, and the cooling unit 63 is operating and the temperature of the light source 61 is high, etc., in which the mode transitions to the second driving mode. This makes it possible to both suppress the deterioration of image visibility and prevent the degradation and failure of the light source due to high temperatures.

[0136] Second Embodiment Please refer to Fig. 7. Fig. 7 is a flowchart showing an example of the procedure of a method for driving a light source (a method for controlling outdoor projection display).

[0137] In step S1, for example, it is determined whether or not the visibility of the image is reduced based on at least one of the illuminance around the vehicle, information that allows the illuminance to be estimated, the temperature of the light source, and the ambient temperature of the vehicle.

[0138] If the answer is N in step S1, the process proceeds to step S2, where normal driving (first driving mode) is adopted.

[0139] If the result in step S1 is Y, the process proceeds to step S3, where the visibility improvement driving (second driving mode) is adopted.

[0140] In step S4, it is determined whether or not the light emission operation of the light source needs to be terminated. If the answer is Y, the operation ends, and if the answer is N, the process returns to step S1.

[0141] As described above, according to the present invention, it is possible to increase the light emission intensity of the light source compared to conventional methods without increasing the size of the outdoor projector, thereby suppressing the decrease in visibility of the displayed image caused by ambient illuminance (ambient brightness), etc.

[0142] The present invention is not limited to the above-described exemplary embodiments, and those skilled in the art could easily modify the above-described exemplary embodiments to the extent that they fall within the scope of the claims. [Explanation of symbols]

[0143] 1 vehicle, 2 headlight, 4, 6 road, 7 in-vehicle projection system, 8 person (passerby, etc.), 10 (10a to 10f) outdoor projector, 12 image of stop line (white line, etc.), 14 image for welcome effect, 16 image of arrow, 20 light distribution control ECU, 21 MPU (microprocessing unit, processor), 23 RAM, 25 ROM, 26 system bus, 27 light distribution control unit, 30 information acquisition unit , AN...antenna, 32...communication unit, 34...vehicle control ECU, 42...outdoor display control device, 44...control unit, 50...drive unit, 52...APC circuit (automatic power control circuit), 54...drive current generation unit, 55...duty setting unit, 56...variable voltage source, 57...voltage comparator, 58...common collector NPN bipolar transistor (emitter follower), 61...light source (laser diode (LD) or the like), 61a to 61c...R (red), Light sources corresponding to the colors G (green) and B (blue), 63...cooling unit (Peltier element, etc.), 64...light source temperature sensor, 65...Peltier element driving unit (cooling unit driving unit), 67...submount (or stem), 69...light source unit, 70...sensor unit, 71...projection unit, 72...illuminance sensor, 74...ambient temperature sensor, 81...light collecting optical system, 82...light modulation unit (digital micromirror device, etc.), 84...projection optical system, 86...display element driving unit, 88... 9...image display light, 91...duty determination section, 92...control voltage generation section, 93...illuminance determination section, 95...light source temperature determination section, 96...ambient temperature determination section, 97...cooling section operation determination section, 110...RGB light generation section, 111-113...dichroic mirror, 120...speckle reduction section, 121...diffusion plate, 140...light path changing section, 131...collimator lens, 132...fly's eye lens, 133...condenser lens, R...resistor.

Claims

1. An outdoor projector that is mounted on a vehicle and displays an image by projecting light onto an object outside the vehicle, A light source; a drive unit capable of changing an output of the light source by adjusting a drive current value of the light source; a control unit that controls the drive unit to variably control the output of the light source; having The control unit is a first driving mode in which the light source is current-driven with a first driving current value; a second drive mode in which the light source is driven with a second drive current value greater than the first drive current value and is driven intermittently with a predetermined duty; It is possible to switch between In the second driving mode, in response to the predetermined duty, a first period as a visibility-enhancing display period in which the output of the light source is increased by driving with the second driving current value, thereby improving the luminance of the image; a second period as a cooling period in which the light source is made not to emit light and the temperature of the light source that has increased in the first period is reduced; and The second period is set so that the temperature of the light source does not exceed an allowable upper limit temperature. Outdoor projector.

2. The control unit is When it is determined that the vehicle is in a first brightness environment based on illuminance-related information including at least one of an illuminance around the vehicle and information capable of estimating the illuminance, the light source is driven in the first drive mode; When it is determined that the environment is a second brightness environment brighter than the first brightness environment, the light source is driven in the second drive mode.

2. The outdoor projector according to claim 1.

3. The control unit is When it is determined that the vehicle is in a first temperature environment based on temperature-related information including at least one of a temperature of the light source and an ambient temperature of the vehicle, the light source is driven in the first drive mode; When it is determined that the temperature environment is a second temperature environment having a higher temperature than the first temperature environment, the light source is driven in the second drive mode.

2. The outdoor projector according to claim 1.

4. The control unit is when it is determined that cooling of the light source needs to be strengthened while the output of the light source is being controlled in the second drive mode, the second drive current value is changed to a third drive current value having a lower current value.

2. The outdoor projector according to claim 1.

5. The control unit is performing control to switch between the first driving mode and the second driving mode according to the type of the image; 2. The outdoor projector according to claim 1.

6. The control unit is by setting the duty in the second driving mode to 50% or more and blinking the image, the image is displayed as an image that is highly attention-grabbing and attracts the attention of a viewer.

2. The outdoor projector according to claim 1.

7. The frequency of the intermittent drive of the light source in the second drive mode is 60 Hz or less.

2. The outdoor projector according to claim 1.

8. The second drive current value in the second drive mode is On the condition that the temperature of the light source does not exceed an allowable upper limit temperature and the duty in the second driving mode is 50% or more, is set to 1.2 times or more the first drive current value in the first drive mode; 2. The outdoor projector according to claim 1.

9. a cooling unit that cools the light source; The control unit is when it is determined that the vehicle is in a first brightness environment based on illuminance-related information including at least one of an illuminance around the vehicle and information capable of estimating the illuminance, or when it is determined that the vehicle is in a first temperature environment based on temperature-related information including at least one of a temperature of the light source and an ambient temperature of the vehicle, driving the light source in the first drive mode; when it is determined based on the illuminance-related information that the environment is a second brightness environment brighter than the first brightness environment, or when it is determined based on the temperature-related information that the environment is a second temperature environment having a higher temperature than the first temperature environment, and when the cooling unit is operating, driving the light source in the second drive mode; when it is determined based on the illuminance-related information that the environment is a second brightness environment brighter than the first brightness environment, or when it is determined based on the temperature-related information that the environment is a second temperature environment having a higher temperature than the first temperature environment, and when the cooling unit is not operating, driving the light source in the first driving mode.

2. The outdoor projector according to claim 1.

10. 1. An outdoor projection display control method for controlling a display in a case where an outdoor projector mounted on a vehicle projects light onto an object outside the vehicle to display an image, comprising: a first step of determining whether or not visibility of the image is reduced based on at least one of an illuminance around the vehicle, information capable of estimating the illuminance, a temperature of a light source, and an ambient temperature around the vehicle; a second step of, when it is determined that the visibility of the image will decrease, setting a second drive current value of the light source that is greater than the first drive current value of the light source when it is determined that the visibility of the image will not decrease, and intermittently driving the light source at a predetermined duty, repeating a first period as a visibility improvement display period for improving the luminance of the image and a second period as a cooling period for lowering the temperature of the light source that has increased due to driving the light source in the first period, thereby intermittently driving the light source so that the temperature of the light source does not exceed an allowable upper limit temperature; An outdoor projection display control method, comprising:

Images