DISPLAY DEVICE AND DISPLAY SYSTEM

A display device is provided with an input unit for inputting a detection signal from a detection unit capable of detecting the brightness of ambient light around a dimming member. The display device is also provided with a control unit which, on the basis of the detection signal input by the input unit, controls at least one of the optical transmittance of the dimming member and the operation of a projector to adjust an image projected onto the dimming member to a display state corresponding to the brightness of the ambient light.

TECHNICAL FIELD

The present invention relates to a display device and a display system.

BACKGROUND ART

A known display system shows an image by projecting the image with a projector onto a light control member having a variable light transmittance. Patent Document1describes a display system that controls the light transmittance of the light control member. The light control member is controlled to become opaque when showing projected images and transparent when not showing projected images.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

The projected image gives a user different impressions depending on the brightness of the environment surrounding the light control member. Accordingly, there may be a need to display an image that is easily recognizable in accordance with the brightness of the surrounding environment.

An objective of the present invention is to provide a display device and a display system that improve visual recognition.

A display device that solves the above problem shows an image by projecting the image from a projector onto a light control member having a variable light transmittance and arranged on an optical material. The display device includes an input unit and a controller. The input unit receives a detection signal from a detector configured to detect a brightness of ambient light around the light control member. The controller controls at least one of the light transmittance of the light control member and operation of the projector based on the detection signal received by the input unit to adjust a display state of the image projected onto the light control member in accordance with the brightness of the ambient light.

A display system that solves the above problem shows an image on a light control member and includes the light control member and a projector. The light control member has a variable light transmittance and is arranged on an optical material. The projector projects the image onto the light control member. The display system also includes a detector and a display device. The detector is configured to detect a brightness of ambient light around the light control member. The display device receives a detection signal from the detector and controls at least one of the light transmittance of the light control member and operation of the projector based on the received detection signal to adjust a display state of the image projected onto the light control member in accordance with the brightness of the ambient light.

Advantageous Effects of Invention

The display device and the display system according to the present invention improve visual recognition.

DESCRIPTION OF EMBODIMENT

An embodiment of a display device and a display system will now be described with reference to the drawings.

As shown inFIG.1, a display system1includes a display screen2, a projector3, and a display device4. The projector3projects an image onto the display screen2. The display device4controls the shown image. The projector3is, for example, a laser projector. The display device4outputs image data D of the image that will be projected to the projector3. The projector3projects the image that corresponds to the received image data D onto the display screen2. In the present embodiment, the display screen2is arranged in a vehicle and shows the image to a user in the vehicle. The image includes a picture, a still image, a video, character information, and/or the like indicating various types of information.

As shown inFIG.2, the display screen2includes an optical material5and a light control member6. The optical material5is formed by a transparent member such as a light-transmissive glass. The light control member6has a variable light transmittance. The light control member6is bonded to the optical material5. In the present embodiment, the optical material5is a glass material of a vehicle such as a window glass of side door for a rear seat. The light control member6is a liquid crystal material of which the light transmittance decreases in accordance with, for example, the voltage applied. For example, as the light transmittance decreases and the light control member6becomes opaque, the shown image projected from the projector3becomes clearer. The display device4outputs a control voltage V to the light control member6to control the light transmittance.

The projector3is arranged on a ceiling or the like inside the passenger compartment to project an image onto the display screen2from inside the passenger compartment. That is, the projector3is of a front projection type in which the projector3and the user are at the same side of the display screen2. The projector3emits image light L1toward the display screen2based on the image data D. The image light L1is divided into reflected light L2and transmitted light L3in accordance with the light transmittance of the light control member6of the display screen2. The reflected light L2is diffusely reflected on the light control member6. The transmitted light L3is transmitted through the display screen2. When the user views the display screen2, the user visually perceives the reflected light L2and recognizes the image shown on the display screen2. Further, the projector3intermittently displays the image on the light control member6. During the intermittent display, the time during which no image is shown, that is, the time during which the projector3does not emit the image light L1, is controlled in fixed or non-fixed time intervals.

In addition to the image light L1, ambient light E is emitted to and around the light control member6by light sources located inside and outside the vehicle. Examples of the ambient light E include sunlight from outside the vehicle and external light produced by lighting outside the vehicle. The ambient light E from outside the vehicle enters the passenger compartment through the display screen2. Further, the brightness A of the ambient light E affects the brightness of the image visually perceived by the user. For example, if the brightness A of the ambient light E is brighter than the reflected light L2, the projected image will appear to be dark, and if the brightness A of the ambient light E is darker than the reflected light L2, the projected image will appear to be bright. Accordingly, the display system1of the present embodiment has a functionality to control a display state of the image in accordance with the brightness A of the ambient light E.

The display system1includes a detector7configured to detect the brightness A of the ambient light E around the light control member6. The detector7is, for example, an illuminometer that detects the intensity of illumination inside the passenger compartment as the brightness A around the light control member6. The illuminometer is arranged to detect, for example, the intensity of the light emitted to the display screen2or the intensity of the light emitted to the user. The detector7outputs a detection signal S to the display device4as a detection result.

As shown inFIG.1, the display device4includes an input unit11and a controller12. The input unit11receives the detection signal S from the detector7. The controller12adjusts the display state of the image based on the detection signal S received by the input unit11. The controller12controls at least one of the light transmittance of the light control member6and operation of the projector3based on the detection signal S so that the display state is controlled in accordance with the brightness A of the ambient light E. In the present embodiment, the controller12controls the light transmittance of the light control member6with the control voltage V and controls the operation of the projector3with the image data D.

The display device4includes a memory13that allows for the writing and reading of various types of data. The memory13stores in advance a control map used for adjusting the display state of the image.

As shown inFIG.3, the control map indicates the relationship of the brightness A of the ambient light E, a voltage value of the control voltage V output to the light control member6, and an image brightness Db of the image projected from the projector3. The voltage value of the control voltage V corresponds to “the first instruction value” for controlling the light control member6. Further, the image brightness Db corresponds to “the second instruction value” for controlling the projector3. The image brightness Db is, for example, the brightness value of the pixels in the image data D input to the projector3. The brightness value may be a statistical value such as a maximum value, a minimum value, an average value, or the like of the pixels.

When the controller12acquires the brightness A of the ambient light E from a detection signal S, the controller12uses the control map to obtain the control voltage V and the image brightness Db corresponding to the brightness A of the ambient light E. Then, the controller12adjusts the display state of the image with the obtained control voltage V and the obtained image brightness Db.

The controller12readjusts the display state of the image based on a detection signal S obtained at a time during which the image is not shown during the intermittent display performed by the projector3. The controller12may control the time during which no image is shown in fixed time intervals by, for example, inserting black image data D between sets of the image data D. The controller12may control the time during which no image is shown in non-fixed time intervals by, for example, switching the screen. Further, the controller12repeats the readjustment at specified times. For example, the controller12performs the readjustment whenever no image is shown during the intermittent display. The memory13of the display device4stores in advance a conversion map used for the readjustment.

As shown inFIG.4, the conversion map indicates the relationship of a detection value Sa of the detection signal S, the present value that has been set as the control voltage V when the detection occurred, and a conversion value Sc of the detection signal S. When the controller12receives a detection signal S while controlling the light control member6with the control voltage V, the controller12uses the conversion map to convert the detection value Sa into the conversion value Sc so that the conversion value Sc corresponds to the brightness A of the ambient light E. Then, the controller12obtains from the control map a new control voltage V and a new image brightness Db corresponding to the brightness A of the ambient light E, which was acquired from the conversion value Sc, to readjust the display state of the image in accordance with the new control voltage V and the new image brightness Db.

The operation of the present embodiment will now be described. It is assumed here that the control voltage V and the image data D are not being output by the display device4, that is, the display device4is in an uncontrolled state. Further, it is assumed that in the uncontrolled state, image light L1is not emitted from the projector3.

As shown inFIG.5, in S101(“S” stands for step), the display device4performs an image projection initiation process. The image projection initiation process is performed when, for example, the user carries out an operation. In the image projection initiation process, for example, the display device4acquires the image data D that is to be projected or reads the image data D stored in advance in the memory13.

In S102, the detector7detects the brightness A of the ambient light E around the light control member6. The detector7of the present embodiment detects the intensity of illumination inside the passenger compartment and outputs a detection signal S including the detection value Sa to the display device4.

In S103, the controller12of the display device4adjusts the display state of the image based on the detection signal S received by the input unit11. In the present embodiment, when the detection signal S is received, the controller12uses the control map to obtain the control voltage V and the image brightness Db and adjusts the display state of the image with the control voltage V and the image brightness Db.

The concept of the display state of an image will now be described.

The light transmittance of the light control member6affects the display state of an image. If the brightness of the ambient light E and the brightness of the image light L1were to be constant, an increase in the light transmittance of the light control member6would decrease the reflected light L2and increase the transmitted light L. Thus, the image would be shown on the display screen2in a dark display state. Further, a decrease in the light transmittance of the light control member6would increase the reflected light L2and decrease the transmitted light L3. Thus, the image would be shown on the display screen2in a bright display state.

Therefore, in the control map, the control voltage V is associated with the brightness A of the ambient light E such that the light transmittance of the light control member6decreases as the brightness A of the ambient light E increases. Accordingly, the controller12controls the light control member6such that the light transmittance of the light control member6increases as the brightness A of the ambient light E decreases. Further, the controller12controls the light control member6such that the light transmittance of the light control member6decreases as the brightness A of the ambient light E increases.

The image brightness Db also affects the display state of an image. If the brightness A of the ambient light E and the light transmittance of the light control member6were to be constant, an increase in the image brightness Db would show the image in a bright display state. Further, a decrease in the image brightness Db would show the image in a dark display state.

Therefore, in the control map, the image brightness Db is associated with the brightness A of the ambient light E such that the image brightness Db increases as the brightness A of the ambient light E increases. Accordingly, the controller12controls the projector3such that the image brightness Db of the image projected from the projector3decreases as the brightness A of the ambient light E decreases. Further, the controller12controls the projector3such that the image brightness Db increases as the brightness A of the ambient light E increases.

As shown inFIG.3, as described above, the control map indicates the relationship of the brightness A of the ambient light E, the control voltage V, and the image brightness Db. When the controller12receives a detection signal S in an uncontrolled state, the controller12acquires the detection value Sa included in the detection signal S as the brightness A of the ambient light E. The controller12uses the control map to obtain the control voltage V and the image brightness Db corresponding to the brightness A of the ambient light E. For example, when the brightness A of the ambient light E is “A1”, the controller12obtains “V1” and “Db1” as the control voltage V and the image brightness Db, respectively. The controller12outputs the control voltage V to the light control member6so that the control voltage V becomes “V1” to control the light transmittance. In other words, the controller12supplies the light control member6with the control voltage V having the voltage value “V1”. Also, the controller12processes the image data D so that the image brightness Db becomes “Db1” and outputs the processed image data D to the projector3.

Returning toFIG.5, in S104, the projector3projects the processed image data D onto the light control member6of the display screen2to show the image. The brightness of the projected image corresponds to the light transmittance of the light control member6, which is controlled with the control voltage V, and the image brightness Db of the image data D. In this manner, the display state of the image is adjusted with the control voltage V and the image brightness Db, which are associated with the brightness A of the ambient light E, using the control map. Thus, the display state of the image is controlled in accordance with the brightness A of the ambient light E.

As shown inFIG.2, the ambient light E includes, for example, light from outside the passenger compartment. The brightness of the outside light changes depending on where and when the vehicle travels. Accordingly, the brightness A of the ambient light E also changes during use of the display device4. The display device4of the present embodiment readjusts the display state in accordance with such changes in the brightness A of the ambient light E.

As shown inFIG.6, in S201, during a period in which an image is shown, the projector3intermittently displays the image. The intermittent display shows no image at certain times. The projector3performs the intermittent display by, for example, having the controller12insert a black image between sets of image data D in fixed time intervals. Preferably, the display time during intermittent display is extremely short and cannot be recognized by the user.

In S202, the detector7detects the brightness A of the ambient light E at a time during which the image is not shown and outputs the detection value Sa on a detection signal S to the display device4. For example, the controller12controls the detector7to detect the brightness A of the ambient light E at a time during which the image is not shown. In this manner, the controller12receives the detection signal S obtained at a time during which the image is not shown.

In S203, the controller12checks the present value of the control voltage V that has been set when the detection of the detection signal S occurred. For example, the controller12re-reads the voltage value of the control voltage V that was obtained from the control map in the preceding cycle and acknowledges this voltage value as the present value.

In S204, the controller12uses the conversion map to perform conversion on the detection value Sa. The controller12uses the conversion map to obtain the conversion value Sc corresponding to the detection value Sa, which is included in the detection signal S, and the present value of the control voltage V. The controller12acquires the conversion value Sc as the brightness A of the ambient light E.

The concept of the conversion value Sc will now be described.

When detecting the brightness A of the ambient light E, the light transmittance of the light control member6affects the detection value Sa of the brightness A of the ambient light E. For example, if the light transmittance of the light control member6is increased when the image light L1is not being emitted, the ambient light E entering the passenger compartment through the display screen2will increase and the brightness A of the ambient light E will increase. Further, if the light transmittance of the light control member6is decreased, the ambient light E entering the passenger compartment through the display screen2will decrease and the brightness A of the ambient light E will decrease.

As shown inFIG.4, the conversion map indicates the relationship of the detection value Sa, the present value of the control voltage V, and the conversion value Sc. In the present embodiment, in the conversion map, the detection value Sa is associated with the conversion value Sc such that the conversion value Sc corresponds to a brighter state when the detection value Sa corresponds to a brighter state. Further, when the detection value Sa is the same, the present value of the control voltage V is associated with the conversion value Sc such that the conversion value Sc corresponds to a brighter state as the present value of the control voltage V changes in a direction in which the light transmittance decreases.

The controller12uses the conversion map to obtain the conversion value Sc from the detection value Sa and the present value of the control voltage V. For example, when the detection value Sa is “Sa1” and the present value of the control voltage V is “V1”, the controller12obtains “Sc11” as the conversion value Sc. Further, for example, when the detection value Sa is “Sa1” and the present value of the control voltage V is “V2”, the controller12obtains “Sc12” as the conversion value Sc. The controller12acquires the conversion value Sc as the brightness A of the ambient light E in the control map.

Returning ofFIG.6, in S205, the controller12obtains a new control voltage V and a new image brightness Db corresponding to the brightness A of the ambient light E, which was acquired from the conversion value Sc, and readjusts the display state of the image in accordance with the new control voltage V and the new image brightness Db.

In S206, the projector3projects the image light corresponding to the image data D, which was processed by the readjustment, onto the light control member6of the display screen2. The brightness of the projected image corresponds to the light transmittance of the light control member6controlled by the control voltage V and the image brightness Db of the image data D.

The controller12repeats the readjustment process of S201to S206at specified times. For example, the controller12performs the readjustment each time no image is shown during the intermittent display. In this manner, the readjustment is performed according to changes in the brightness A of the ambient light E during image display. This controls the display state of the image in accordance with the brightness A of the ambient light E.

As described above, the controller12uses the control map to adjust the display state of the image projected onto the light control member6in accordance with the brightness A of the ambient light E. This adjusts the brightness of the image perceived by the user in accordance with the brightness A of the ambient light E around the light control member6. Further, the display state is readjusted when the brightness A of the ambient light E changes.

When showing an image, the controller12uses a detection signal S obtained at a time at which no image is shown during the intermittent display to readjust the image. Thus, the image light L1emitted from the projector3does not affect the detection result of the detector7and allows the brightness A of the ambient light E to be detected correctly.

The controller12uses the control map to control both the light transmittance of the light control member6and the operation of the projector3. This allows the brightness of an image to be controlled over a wider range than when controlling only one of the light transmittance of the light control member6and the operation of the projector3.

The controller12uses the conversion map to obtain the conversion value Sc of the detection signal S from the detection value of the detection signal S and the present value of the control voltage V. Then, the controller12uses the conversion value Sc as the brightness A of the ambient light E to obtain a new control voltage V and a new image brightness Db from the control map and readjusts the display state of the image with the new control voltage V and the new image brightness Db. In this manner, when controlling the light control member6, the controller12converts the detection value Sa of the detector7, which changes with the light transmittance of the light control member6, with the conversion map and performs the readjustment in accordance with the obtained conversion value Sc with the control map. This readjusts the display state of the image in a preferred manner.

The controller12processes the image data D of the image projected onto the light control member6to control the operation of the projector3. Thus, the projector3only needs to project the received image data D. This simplifies the process performed by the projector3.

The present embodiment has the following advantages.

(1) The display device4includes the input unit11that receives a detection signal S from the detector7configured to detect the brightness A of the ambient light E around the light control member6. Further, the display device4includes the controller12that controls at least one of the light transmittance of the light control member6and the operation of the projector3based on the detection signal S received by the input unit11to adjust the display state of an image projected onto the light control member6in accordance with the brightness A of the ambient light E. This configuration adjusts the brightness of the image perceived by a user in accordance with the brightness A of the ambient light E around the light control member6. Thus, visual recognition is improved.

(2) The projector3intermittently displays an image onto the light control member6. Further, the controller12performs readjustment of the display state based on a detection signal S obtained at a time during which no image is shown and repeats the readjustment at specified times. This configuration performs the readjustment in accordance with changes in the brightness A of the ambient light E when the display device4is in use. Thus, the display state of the image is controlled in accordance with changes in the brightness A of the ambient light E. Furthermore, the image is readjusted based on the detection signal S obtained at a time during which no image is shown so that the image light L1projected from the projector3does not affect the detection result of the detector7. This correctly detects the brightness A of the ambient light E and properly readjusts the display state of the image. Thus, visual recognition is improved.

(3) When controlling the light control member6with the control voltage V, the controller12uses the conversion map to obtain the conversion value Sc from the detection value Sa and the present value of the control voltage V. Further, when using the obtained conversion value Sc as the brightness A of the ambient light E, the controller12obtains a new control voltage V and a new image brightness Db corresponding to the brightness A of the ambient light E from the control map and readjusts the display state with the new control voltage V and the new image brightness Db. With this configuration, when controlling the light control member6, the controller12converts the detection value Sa of the detector7, which changes with the light transmittance of the light control member6, with the conversion map and performs readjustment in accordance with the obtained conversion value Sc with the control map. This readjusts the display state of the image in a preferred manner and improves visual recognition.

(4) The controller12executes control such that the light transmittance of the light control member6increases as the brightness A of the ambient light E decreases and the light transmittance of the light control member6decreases as the brightness A of the ambient light E increases. With this configuration, when the brightness A of the ambient light E decreases, the light transmittance is increased to show the image in a dark display state so that the image will not be too bright and difficult to view. Further, when the brightness A of the ambient light E increases, the light transmittance is decreased to show the image in a bright display state so that the image will not be too dark and difficult to view. This improves visual recognition.

(5) The controller12executes control such that the image brightness Db of the image projected from the projector3decreases as the brightness A of the ambient light E decreases and the image brightness Db of the image projected from the projector3increases as the brightness A of the ambient light E increases. With this configuration, when the brightness A of the ambient light E decreases, the image brightness Db is decreased to show the image in a dark display state so that the image will not be too bright and difficult to view. Further, when the brightness A of the ambient light E increases, the image brightness Db is increased to show the image in a bright display state so that the image will not be too dark and difficult to view. This improves visual recognition.

(6) The controller12processes the image data D of the image projected onto the light control member6to control the operation of the projector3. With this configuration, the projector3only needs to project the received image data D. This simplifies the process performed by the projector3and the configuration of the projector3.

(7) The light control member6is arranged on a glass of a vehicle. This configuration improves visual recognition of the image shown on the glass of the vehicle.

The present embodiment may be modified as follows. The present embodiment and the following modifications can be combined as long as the combined modifications remain technically consistent with each other.

The controller12does not have to process the image data D to control the operation of the projector3. The controller12may control the irradiation intensity of the light source of the projector3.

The controller12may show an image in a dark display state when the brightness A of the ambient light E increases and show an image in a bright display state when the brightness A of the ambient light E decreases.

The image brightness Db may be any value related to the brightness of the projected image. For example, the image brightness Db may be a brightness value of the pixels in the image data D, the irradiation intensity of the light source of the projector3, or the intensity of the brightness filter.

The first instruction value for controlling the light transmittance of the light control member6is not limited to that in the description of the present embodiment.

The second instruction value for controlling the operation of the projector3is not limited to that in the description of the present embodiment.

The controller12may check the present value of the control voltage V by detecting the output voltage value of the control voltage V.

In an uncontrolled state, the controller12may check the present value of the control voltage V and obtain the conversion value Sc. In other words, the controller12may check the present value of the control voltage V and obtain the conversion value Sc each time the controller12controls the display state of an image.

The control map may include a range in which the control is executed with only one of the control voltage V and the image brightness Db in accordance with the brightness A of the ambient light E and the other one of the control voltage V and the image brightness Db is not changed. In other words, when the brightness A of the ambient light E is in a certain range, the control map can associate brightness A of the ambient light E with the control voltage V and the image brightness Db, with one of the control voltage V and the image brightness Db having various values and the other one of the control voltage and the image brightness Db not having various values.

In the conversion map, the relationship of the control voltage V and the conversion value Sc is not limited to that in the description of the present embodiment. For example, the control voltage V and the conversion value Sc may be associated so that the conversion value Sc corresponds to a darker state as the control voltage V changes in a direction in which the light transmittance decreases.

In the conversion map, the detection value Sa prior to the conversion may be the same as the conversion value Sc subsequent to the conversion.

In the control map, the relationship of the brightness A of the ambient light E, the control voltage V, and the image brightness Db is not limited and may be changed as required.

In the conversion map, the relationship of the detection value Sa, the present value of the control voltage V, and the conversion value Sc is not limited and may be changed as required.

The controller12does not have to use the control map and the conversion map to execute control and may, for example, increment or decrement the control voltage V or the image brightness Db in accordance with the brightness of the ambient light E.

When the light control member6is being controlled with the control voltage V, the controller12may check the time when a detection signal S is obtained to determine a detection signal S that is obtained at a time during which no image is shown. In other words, as long as the brightness A of the ambient light E is detected at a time during which an image is not shown, there is no limit to the detection method.

When an image is being projected, the controller12does not have to execute control based on the detection signal S obtained at a time during which no image is shown. The controller12may execute control based on the detection signal S obtained when the image light is being emitted.

The controller12may control only one of the light transmittance of the light control member6and the operation of the projector. In other words, the controller12only needs to control at least one of the light transmittance of the light control member6and the operation of the projector.

The ambient light E is not limited to the light entering the inside of the vehicle from outside the vehicle through the display screen2and may include the light from a light source located inside the passenger compartment and/or the outside light entering the inside of the vehicle through a glass other than the display screen2.

The detector7does not have to detect the brightness of the ambient light inside passenger compartment as the brightness around the light control member6. The detector7may detect the brightness of the ambient light around the light control member6at the outer side of the passenger compartment as the brightness around the light control member6.

The detector7does not have to detect the intensity of illumination inside the passenger compartment as described in the embodiment above. For example, the detector7may detect the brightness of the light emitted toward the user from the side of the display screen2.

The detector7may be applied to any of various types of devices configured to detect brightness, such as an illuminometer arranged inside the passenger compartment or a camera directed toward the user.

The optical material5of the display screen2is not limited to a transparent member and may be, for example, a mirror. For example, the display screen2may be a sideview mirror, a rearview mirror, or the like.

The display system1may include an operation unit configured to change the brightness of the projected image in accordance with a user operation. Further, the operation unit may be a physical switch, a touch-operation unit that is touched and operated, a camera that detects a gesture, or the like.

The light control member6may be transparent when no voltage is applied and have a light transmittance that is decreased in accordance with the applied voltage. Alternatively, the light control member6may be opaque when no voltage is applied and have a light transmittance that is increased in accordance with the applied voltage.

The light control member6may be a liquid crystal material, an electrochromic material, a photochromic material, or the like.

The projector3may be of a front projection type in which the projector3, which projects an image, and the user are at the same side of the display screen2or a rear projection type in which the projector3, which projects an image, and the user are at opposite sides of the display screen2.

The projector3is not limited to a laser projector and may be applied to any of various types of projectors.

The installation position of the projector3is not limited, and the projector3may be arranged, for example, inside or outside the passenger compartment of a vehicle. The projector3may be arranged on a ceiling inside the passenger compartment or a sideview mirror outside the passenger compartment.

Image projection may be initiated by any event such as a user operation, power source transition of the vehicle, or communication with another device.

There is no limit to the content of the projected image. For example, the contents projected by an image may indicate various types of information or pictures in cooperation with an on-board device such as a navigation system and an audio device. Further, the contents projected by an image may indicate road information and/or information and advertisement of nearby facilities.

The projected image may include a picture, a still image, a video, character information, and the like.

The display system1does not have to be applied to a vehicle and may be arranged on various types of equipment and apparatus or in a building or facility.

The display device4can be circuitry including one or more processors that run on a computer program (software) to execute various processes, one or more exclusive hardware circuits such as an application specific integrated circuit (ASIC) that execute at least part of various processes, or a combination of the above. A processor includes a central processing unit (CPU) and a memory, such as a random-access memory (RAM) or a read-only memory (ROM). The memory stores program codes or commands that are configured to have the CPU execute processes. The memory, which is a computer readable medium, may be any available medium that is accessible by a versatile or dedicated computer.

Technical concepts that can be understood from the above embodiment and the modified examples will now be described.

(a) A display device in which the optical material is a transparent material. This configuration improves visual recognition of the image shown on the transparent member such as a light-transmissive glass.

(b) A display device that shows an image by projecting the image from a projector onto a light control member having a variable light transmittance and arranged on an optical material, the display device including circuitry configured to receive a detection signal from a detector configured to detect a brightness of ambient light around the light control member and control at least one of the light transmittance of the light control member and operation of the projector based on the received detection signal to adjust a display state of the image projected onto the light control member in accordance with the brightness of the ambient light.

REFERENCE SIGNS LIST