JP2002040560A - Hologram display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hologram display device where the deterioration of the quality of a video caused by noise light is restrained to be small. SOLUTION: A screen part 1 is provided with photosensors 31 and 32 constituted to detect the noise light made incident from the front surface side 101 of the screen part 1 and the noise light made incident from the back surface side 102 thereof, respectively, in the angle of view of a transparent hologram screen. Then, the display device has a projection controller constituted to control the quantity of video light 20 projected from a projecting device 2 based on the quantity of the noise light detected by the photosensors.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hologram display device which can be used for a screen mounted on a vehicle, a head-up display, an advertisement installed in a store, an advertisement display, and the like.

[0002]

2. Description of the Related Art In recent years, as a display device used in a vehicle interior, for example, a display device using a liquid crystal panel as typified by, for example, a car navigation device is often used. However, since the liquid crystal panel has a small screen and a low luminance in many cases, there is a problem that a display image is difficult to see in the daytime or a rear seat.

As a display device having a large display area, there is known a hologram display device including a screen portion composed of a transparent member and a transparent hologram screen attached to the transparent member, and a projection device for projecting image light onto the screen portion. ing. This device can be used, for example, as a head-up display for a vehicle or a display device for a front window, or can be used as an in-vehicle screen that does not obstruct the view of a passenger.

[0004]

However, the hologram display device has the following problems. Noise light entering from inside and outside the vehicle may reduce the contrast of the image reproduced on the screen. Conventionally, the following measures have been taken in order to eliminate the adverse effect of unnecessary noise light that degrades the image quality.

Japanese Patent Application Laid-Open No. 4-264487 discloses a light quantity detector and a color detector provided on one side of glass, in addition to performing a diffractive action for forming a virtual image on a hologram combiner in a HUD (head-up display) device. The background light (noise light) is diffracted and detected by the detector, and the brightness of the image light is controlled. However, in this method, noise light from the vehicle interior cannot be detected, and an area with low image quality occurs. Therefore, the contrast of the image is low, and the image sometimes becomes very difficult to view particularly in a bright daytime outside the vehicle.

Japanese Unexamined Patent Application Publication No. 11-59224 discloses a front window display device that utilizes a solar radiation sensor for detecting illuminance and adjusts the brightness of image light according to the output from the solar radiation sensor. However, since the solar radiation sensor is mounted so as to be inserted into the front defroster table, detection of noise light tends to be insufficient. Therefore, the adjustment and control of the luminance are rough and easily insufficient, and the image quality is still low.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a hologram display device in which deterioration of image quality due to noise light is small.

[0008]

According to a first aspect of the present invention, there is provided a screen portion comprising a transparent member and a transparent hologram screen attached to the transparent member, and an image light is projected on the screen portion to form an image. In the hologram display having a projection device configured to be reproduced on the front side of the screen portion, the screen portion includes noise light incident from the front side of the screen portion within the viewing angle of the transparent hologram screen, and incident light from the rear side. An optical sensor configured to respectively detect noise light to be emitted, and a projection control device configured to control the amount of image light projected from the projection device based on the amount of noise light detected by the optical sensor. A hologram display device characterized by having:

What is most notable in the present invention is that noise light incident from the front side and the back side of the screen portion is detected by an optical sensor, and the projection device is controlled using this. Here, when the hologram screen is of a transmission type, the front side of the screen portion is opposite to the side on which the projection device is installed (see FIG. 2). When the hologram screen is of a reflection type, it is on the side where the projection device is installed (see FIG. 10).

The operation and effect according to the present invention will be described. In the hologram display device of the present invention, the screen is transparent, and an image is reproduced on the front side of the screen. Therefore, the noise light entering from the front side and the noise light entering from the back side of the screen portion are captured, and the projection device is controlled based on the noise light amount. As a result, noise light that lowers the contrast of an image can be reliably captured, and the projection device can be accurately controlled to capture a high-quality image.

Also, since the observer of the image views the image mainly from the front side of the screen on which the image is displayed,
Noise light entering from the back side of the screen part is easy to see. Further, noise light entering from the front surface side of the screen portion is reflected on the front surface side of the screen portion and travels toward the observer, so that such noise light is also likely to enter the eyes of the observer. According to the present invention, since such noise light can be detected by the optical sensor, the projector can be controlled in accordance with the amount of the noise light, so that a high quality image can always be provided to the observer. Becomes

As described above, according to the present invention, it is possible to provide a hologram display device in which a decrease in image quality due to noise light is small.

As the transparent member, a transparent plate made of resin or glass can be appropriately used. Further, a hologram display device according to the present invention can be configured by attaching a transparent hologram screen to a window glass or the like. Examples of the transparent hologram screen include a transmission hologram screen that transmits image light and a reflection hologram screen that reflects image light. In the present invention, any screen can be used.

The transmission type hologram screen is a screen used by arranging a projection device on the back side of the screen. The image light projected from the projection device forms an image on the hologram screen to form a real image. The observer can recognize the image by the diffracted light scattered and transmitted from the real image.

On the other hand, a reflection type hologram screen is a screen used by arranging a projection device on the surface side of the screen. The image light projected from the projection device forms an image on the hologram screen to form a real image. The observer can recognize the image by the diffracted light scattered and reflected from the real image.

Further, the hologram screen projects diffused light passing through a light diffuser such as frosted glass as object light and non-diffused light as reference light and projects these lights on a photosensitive member to form interference fringes on the photosensitive member. It can be manufactured by doing.

Next, as the projection device, various devices such as a slide projector, an OHP (over head projector), a projector, a projector, etc., capable of projecting image light such as a still image and a moving image can be used. . Further, an image can be supplied to the projection device from the outside.
In this case, examples of the supply device include various playback devices such as a video tape, an optical disk, and a personal computer.
Of course, the video projector can also incorporate a playback device or the like. Further, it can be supplied from outside using a telephone line, a satellite broadcasting line, a wireless line, or the like. Further, the projection device and the projection control device may be configured as separate devices, or both may be combined into one device.

The bonding of the transparent hologram screen and the transparent member can be performed using an adhesive or the like. In addition, an adhesive tape or various fixing devices may be used. Further, another member such as an anti-reflection material or an anti-glare material may be provided on the transparent member or the hologram screen.

Next, the viewing angle will be described. Hologram screens are manufactured using interference fringes,
The color, brightness, and the like of the displayed image differ depending on the viewing angle, and there are positions where the image is easy to see and positions where the image is difficult to see.
A position at which a particularly excellent image is clearly seen is called a viewing angle.

More specifically, the image on the hologram screen can be viewed only from within a conical space formed by diffracting and diffusing the image light from the projector onto the hologram screen. There is a feature. Therefore, the image light can be seen only in a region where the individual conical spaces formed by irradiating the respective parts of the hologram screen are overlapped. This area is the viewing angle.

Further, as the optical sensor, a photoelectric element such as a photodiode using CdS or the like can be used. In addition, an element using a semiconductor such as GaAs can be used.

Further, the hologram screen according to the present invention can be installed in the interior of an automobile as shown in an embodiment described later (see FIG. 1). Further, the hologram display device can be installed on a mobile body other than an automobile, and the hologram display device can be installed without selecting a particular place such as a general home, a business place, a store, and the like. The present invention is very effective especially when it is installed in a place where strong sunlight or the like is inserted.

Next, as in the second aspect of the present invention, the projection control device calculates an amount of light required as image light based on an output value corresponding to the amount of noise light obtained from the optical sensor. It is preferable to include a light amount detection circuit and a projection device driving circuit that drives the projection device based on the required amount of image light obtained by the light amount detection circuit.

This makes it possible to adjust the required amount of video light emitted from the projection device according to the magnitude of the noise light. Therefore, the observer can always observe a high-quality image in various environments, such as from daytime when sunlight is strongly inserted, to cloudy weather or nighttime without such extra noise light. The light amount detection circuit and the projection device driving circuit will be described later.

Next, as in the third aspect of the present invention, it is preferable that at least one optical sensor is provided on each of the front side and the rear side of the screen section. This makes it possible to reliably detect the noise light inserted from the front side and the noise light inserted from the back side with both optical sensors.

Next, as in the fourth aspect of the present invention, it is preferable that the light receiving directions of the optical sensors installed on the front surface side and the rear surface side of the screen portion are opposite to each other. The light sensor can detect the amount of light that enters from the light receiving direction. Therefore, by turning the light receiving direction of the optical sensor backward, noise light entering from a specific direction can be reliably detected. When the specific direction matches the line of sight of the observer, the control of the projection device by the optical sensor is most effective. This is because the noise light that degrades the image quality the most is the noise light that is incident from a direction that easily enters the eyes of the observer.

Next, it is preferable to dispose the optical sensor such that the light receiving angle of the optical sensor is included in the viewing angle of the transparent hologram screen. As described above, in order to observe a high-quality image from the characteristics of the hologram screen, the observer must enter the viewing angle and look at the screen from there. Therefore, since the light receiving angle of the optical sensor is included in the viewing angle, it is possible to reliably capture noise light that enters the viewing angle that is easy to enter the image of the observer with the image. Therefore, the control of the projection device by the optical sensor is greatly useful for improving the image quality.

Next, as in the sixth aspect of the present invention, the required amount of image light calculated by the light amount detection circuit is a value capable of realizing the required image contrast value obtained based on the following (a). Is preferred. Here, (a) required image contrast value = ｛(image light luminance + total noise light luminance) /
It is the total noise light luminance｝. This allows the projection device to project image light having a sufficiently large light amount with respect to the intensity of the noise light, so that a high-quality image that is hardly deteriorated by the noise light can be displayed on the screen.

Next, as in the present invention, it is preferable that the total noise light luminance in the above (a) is calculated based on the following (b). Here, (b) total noise light luminance = front-side noise light luminance incident from the front side of the screen part × α + back-side noise light luminance incident from the back side of the screen part × β, where α: front side of the screen part And β: transmittance of noise light on the back side of the screen.

A part of the noise light incident from the front side is reflected on the front side and reaches an observer on the front side, but the rest passes through the screen as it is. Part of the noise light incident from the back side is also reflected on the back side, and the remaining transmitted noise light reaches the observer on the front side. That is, since the magnitude and light amount of the noise light that actually lowers the image quality can be obtained by the above (b), the control of the projection device can be performed accurately in terms of further improving the image quality. Here, α and β are numerical values that vary depending on what kind of screen part is used, whether surface treatment is applied, and the like.

Next, as in the eighth aspect of the present invention, it is preferable that the video light luminance in the above (a) is calculated based on the following (c). Here, (c) image light luminance = initial setting image light luminance + γ, where γ: image light correction luminance under the current installation environment of the hologram display device. Thus, the correction according to the installation environment of the hologram display device can be performed, and the control of the projection device can be performed more accurately in terms of further improving the image quality. Here, γ is a numerical value indicating how much the luminance of the image light deviates from the initially set image light luminance of the projection device under the current installation environment.

Next, as in the ninth aspect of the present invention, the projection control device includes a projection device driving circuit between the light intensity detection circuit and the projection device driving circuit based on an output from the light intensity detection circuit. It is preferable to provide a control delay circuit configured to delay the control start time when controlling the control.

The control delay circuit does not control the image light of the projection device immediately after detecting the noise light from the optical sensor, but delays the control of the image light to some extent. This allows
Since flickering of the image reflected on the screen can be prevented, the image quality can be further improved. In particular, this method is very effective in a case where the amount of light in the hologram display installation environment changes suddenly, and even in the above case, it is possible to always provide an excellent image with a constant quality.

Next, it is preferable that the delay amount of the start time in the control delay circuit can be arbitrarily set.

This makes it possible to adapt to the surrounding environment such that the delay amount is small in an environment where the change of the noise light does not fluctuate so much, and the delay amount is large in an environment where the noise light changes greatly. Fine control is possible, and the quality of the image can be improved. It should be noted that the delay amount can be set by the observer of the video so that the observer can obtain a higher quality video.

Next, as in the eleventh aspect of the present invention, the required amount of image light P is set to a control period T which is a fixed time range.
And an average value calculating circuit for calculating an average value obtained by dividing the obtained integrated value by the number of divisions T / Δt determined by the control cycle T and the measurement cycle Δt which is the integration time. It is preferable that the projection device drive circuit be controlled based on the average value obtained by the average value calculation circuit.

By performing control using the average value, it is possible to provide a delay time until the light amount of the projection device is controlled with respect to changes in the surrounding environment. It is possible to eliminate flicker caused by a change in luminance, and it is possible to obtain an effect of further improving image quality.

As a specific method for calculating the average value, the following method can be used. As shown in FIG. 9, a diagram is prepared with the required light quantity P on the vertical axis and the time t on the horizontal axis, and a plurality of rectangles having a width Δt are arranged in the control cycle T, separated by Δt smaller than T. Create an approximate figure. The lower side of this rectangle coincides with the straight line of P = 0, and the upper side is determined based on the smaller of the left side and right side of the rectangle. The total area of the rectangle thus obtained is divided by the number of rectangles, and this value can be used as the average value. The figure shows an example in which there are six rectangles, and calculation may be performed from a larger number of rectangles. It should be noted that another physical quantity corresponding to the required amount of video can be used as P. In the embodiment, a contrast value of an image which is easy to measure is used.

The above-mentioned T and Δt can be selected by selecting T arbitrarily according to the current environment in which the display device is installed rather than Δt, whereby the surrounding light environment which affects the contrast of the display and the preference of the observer can be selected. This is important from the viewpoint of eliminating flicker due to luminance adjustment for maintaining the set contrast by adopting the above-mentioned method. Also T
/ Δt is selected to be an integer. In the example embodiment, T
/ Δt was set to 10.

[0040]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment A hologram display device according to an embodiment of the present invention will be described with reference to FIGS. 1 to 3
As shown in FIG. 1, the hologram display device 3 according to the present embodiment includes a screen unit 1 including a transparent member 10 and a transparent hologram screen 11 attached to the transparent member 10.
And projecting the image light 20 on the screen unit 1,
And a projection device 2 configured to reproduce an image.

As shown in FIG. 3, the screen unit 1 has a front side noise light incident from the front side 101 of the transparent hologram screen 11 within the viewing angle 200 (see FIG. 4) of the transparent hologram screen 11 and a rear side 102 from the back side 102. Front-side and back-side optical sensors 31 and 32 configured to detect incident back-side noise light, respectively, are provided, and the above-described front-side and back-side optical sensors 31 and 32 detect the amount of noise light based on the amount of noise light. There is a projection control device configured to control the amount of image light 20 projected from the projection device 2. It should be noted that the projection control device of this example is incorporated in the projection device and is not shown in the drawing because it is located at a position that cannot be seen in the drawing. Of course, it is also possible to provide as another device.

The above-mentioned projection control device, as shown in FIG.
A light amount detection circuit 51 for calculating a light amount required as the video light 20 based on an output value corresponding to the light amount of the noise light obtained from the front side and back side optical sensors 31 and 32, and a light amount detection circuit 51 When controlling the projection device driving circuit 53 by using the control device, a control delay circuit 52 configured to delay the control start time and the projection device 2 based on the required amount of image light obtained by the light amount detection circuit 51 are driven. And a projection device driving circuit 53 that performs the operation.

The required image light amount calculated by the light amount detection circuit 51 is a value that can realize the required image contrast value obtained based on the following (a). (A) Required image contrast value = {(image light luminance + total noise light luminance) / total noise light luminance} Here, the total noise light luminance is calculated based on the following (b). (B) Total noise light luminance = front-side noise light luminance incident from the front side of the screen section × α + back-side noise light luminance incident from the rear side of the screen section × βα: reflection of noise light on the front side of the screen section Rate β: Transmittance of noise light on the back side of the screen unit The image light luminance is calculated based on the following (c). (C) Image light luminance = initial setting image light luminance + γ γ: Image light correction luminance under the current installation environment of the hologram display device

As shown in FIG. 5, the control delay circuit 52 integrates the required amount of video light P with respect to time in a control period T of a fixed time, and divides the obtained integrated value by the number of divisions T / Δt. And an average value calculation circuit 520 for calculating the average value obtained from the above. The projection device drive circuit 53 is provided based on the average value of the output values obtained by the average value calculation circuit 520.
Control.

The details will be described below. As shown in FIG. 1 and FIG. 2, the screen portion 1 suspended from the ceiling of the vehicle compartment 41 between the front seat 42 and the rear seat 43 in the vehicle compartment 41 has a driver seat 421 of the front seat 42 and a driver seat 421. The image light 20 is projected by the projection device 2 composed of a liquid crystal projector disposed between the passenger seats 422. As a result, an image is displayed on the front side 101 of the screen unit 1, and the image can be provided to the occupant in the rear seat 43.

The screen section 1 will be described. The transparent hologram screen 11 of the present embodiment (hereinafter referred to as hologram screen 11) is formed of a thin-film transparent hologram element and functions as a transmission screen. As shown in FIGS. 1 and 2, the transmission type screen is a projection device 2 for projecting the image light 20 and an observer who observes an image (in this example, a screen in a vehicle interior, and an occupant in a rear seat is connected to the observer). ) Is a screen of a system at a position facing the screen. The image light 20 is on the back side 1 of the screen unit 1.
02, the observer observes the image formed thereby from the front side 101.

As shown in FIGS. 3A and 3B, a film-shaped hologram screen 11 having a thickness of about 0.2 mm.
Was adhered to a transparent member 10 made of a transparent polycarbonate resin having high heat resistance using an adhesive (not shown).

As shown in FIGS. 2 and 3B, the background light 4
91 (light incident from the front seat 42 side) is superimposed on the image to be reproduced, and the deflecting film 12 is adjusted so that the image is not difficult to see.
Was attached to the hologram screen 11 using an adhesive. Also, noise light 492 is displayed on the hologram screen 11.
Is incident and is reflected on the surface side of the screen unit 1,
This reflected light may be superimposed on the image. In order to prevent this, the AR film 13 was attached using an adhesive.

As shown in FIG. 3A, the screen unit 1
At the upper end of the front side, the front side light sensor 31, the back side light sensor 32
Is attached. As shown in FIG. 4, the front side optical sensor 31 and the back side optical sensor 32 are attached to the front side 101 and the back side 102 of the screen unit 1, respectively, and are incident on the hologram screen 11 to lower the image contrast and reduce the image quality. The light receiving direction 31 is received so that the noise light which causes the reduction can be received and the luminance of the noise light can be measured.
It is installed so that the relationship of 9,329 may be reversed. In this example, the light sensor 31, which responds to the brightness of the noise light,
Although the light amount was measured using the light source 32, other sensors for measuring the illuminance may be used.

In addition, the front and back side optical sensors 31 and 32 are attached as shown in FIG. 4 so that the light receiving angles 311 and 321 fall within the viewing angle 200 of the hologram screen 11. In FIG. 3, reference numerals 310 and 320 denote incident ranges of noise light that can be actually detected. In addition, the front and back side optical sensors 3
Reference numerals 1 and 32 denote photoelectric elements each including a photodiode using CdS or the like, and capable of obtaining a voltage output corresponding to the luminance of noise light, as shown in FIG.

Here, the viewing angle 200 will be described.
An image on the hologram screen 11 has a conical space 20 formed by diffracting and diffusing image light 20 from the projection device 2 onto the hologram screen 11.
There is a feature that a video cannot be seen unless the image is inside the image area 1202. Therefore, the image light 20 can be seen only in a region where the individual conical spaces 201 and 202 formed by hitting each part of the hologram screen 11 overlap each other. This area is the viewing angle. FIG. 4 is a view in which the screen unit 1 is viewed from above, and therefore, the viewing angle 2
00 is represented by a triangular area as shown in FIG.

Next, the configuration and operation of the projection control device 5 and the control method will be described in detail. As shown in FIG. 5, the projection control device 5 includes a light amount detection circuit 51, a control delay circuit 5
2, a projection device driving circuit 53; The brightness of the noise light detected by the front side and back side optical sensors 31 and 32;
A correlation diagram with the luminance of the image displayed on the screen unit 1 when this luminance is detected is created from a measurement using a brightness level using a reference light source (JIS C7527) defined by JIS. I do. This correlation diagram is shown in FIG. The light amount detection circuit is manufactured based on the above correlation diagram.

In the light quantity detection circuit, there is provided a microcomputer storing the following contrast calculation formulas (a) to (c) in a ROM. (A) Required image contrast value = {(image light luminance + total noise light luminance) / total noise light luminance} (b) Total noise light luminance = front-side noise light luminance incident from the front side of the screen part × α + screen part Backside noise light luminance incident from the backside of the screen × β α: reflectance of noise light on the front side of the screen section β: transmittance of noise light on the back side of the screen section (c) Image light luminance = initial setting image light Brightness + γ γ: Image light correction brightness under the current installation environment of the hologram display device

In the screen unit 1 of this embodiment, α is 0.02
7, β is 0.05. This value is a numerical value that depends on the AR film 13, the deflection film 12, and the like used. The front-side optical sensor 31 measures the front-side noise light luminance incident from the front-side 101 of the screen unit 1, and the back-side optical sensor 32 measures the rear-side noise light luminance incident from the back-side 102 of the screen unit 1. Also, γ is the video light correction brightness, and this value changes depending on the current installation environment of the hologram display device 3.

Further, in the above-mentioned contrast calculation formula,
Using a monitor test or the like, a numerical value necessary for an observer to observe a high-quality image on the screen unit 1 in an actual vehicle cabin is applied as the initial setting image light luminance. By the above calculation, a contrast value required as the image light projected from the projection device 2 at the present time can be obtained, and the result is input to the next control delay circuit 52.

The control by the control delay circuit 52 will be described with reference to FIG. In FIG. 1, a lamp is a lamp for projecting image light provided in the projection device 2, and the magnitude of the contrast of the image light is determined by the magnitude of the power supplied to the lamp.

A specific method for determining the control delay will be described. Before that, a case where there is no control delay will be briefly described. As described above, the required image contrast value is determined by the light amount detection circuit by the front side and back side optical sensors 31 and 32.
From the output of At this time, at the same time, the contrast value of the actual image currently reflected on the screen unit 1 is measured by a separately provided optical sensor for image contrast measurement.

By comparing the two, if the actual video contrast value is smaller than the required video contrast value, the input power to the lamp is increased, and if the actual video contrast value is larger than the required video contrast value, the input power to the lamp is increased. Make it smaller. It should be noted that the relationship between the luminance and the optical sensor according to FIG. 6 is determined in advance by the optical sensor for measuring the image contrast when the input power should be increased when there is a difference between the two contrast values. Can be prepared in advance and can be determined from the relationship.

In this example, when performing the above control,
At a certain point in time, the required image contrast is obtained, and the input power of the lamp is changed later than that point. Details of the delay time will be described with reference to FIG. FIG. 3 is a diagram in which time fluctuations of three values are described in parallel, and (a) shows a time change of contrast under the current installation environment, that is, an installation environment of a hologram display device in which noise light changes every moment. Below, the contrast value calculated at that time by the initial setting lamp input power is shown.

(B) is a time change of the required power applied to the lamp for maintaining the set contrast, and (c) is a time change of the control power applied to the lamp at each time determined by the control delay circuit. . That is, (b) is
This is a case where a target contrast (for example, 3.5) is secured by continuously changing the power input to the lamp with respect to the contrast value at a certain point in time. Is changed.

The control power amount is obtained by calculating a value obtained by multiplying the sum of the calculated contrast values (10 points) P _{1 to} P ₁₀ for one second by 1/10 as the contrast value for the time interval and calculating the contrast value. is there. This control power amount is the power input to the lamp (that is, the diagram in the middle part of the drawing)
Is correlated with

The delay control of this example was performed with a control cycle T of 1 second and a measurement cycle Δt of 100 ms. For example, as shown in FIG. 7, the width 100m sec rectangular P ₁ to P ₁₀ between 1 second and 2 seconds is 10 form, these total area Delta] t /
Divide by T, that is, 1/10. Assuming that the power input of the lamp is continuously changed from the power calculated at a certain point in the current installation environment, the required power input of the lamp may vary with the contrast as shown in the diagram of FIG. For 200
A delay of m seconds occurs. This value is used as the delay time based on the circuit constant.

In addition to the above-mentioned delay time, the average value of the power input to the lamp required to secure the necessary contrast within a certain time is calculated, and then the calculated value is applied to the lamp. The time is delayed until the control of the electric energy is started. This is the control delay time, and the control delay circuit according to this example requires 300 ms. Therefore, as shown in (c), the actual delay time in this example is 500 ms, which is the sum of the two.

Since the selection of the control cycle T largely depends on the individual difference of the observer, it is preferable to provide the control delay circuit with a function capable of arbitrarily setting the control cycle.

Summarizing the above, the control delay circuit of this example sets the lamp input power amount every 100 ms to 10 points,
That is, the electric energy values from one second after the start of the measurement are integrated, and the average value (P) is calculated. This value is defined as the lamp control power for each second, and the calculation result (P) is expressed as D /
The A-converted data is input to the drive circuit and the power supplied to the lamp of the projection device is controlled. Since these processes are performed by the control delay circuit, a delay time until the control is started is added to the delay time due to the circuit constant, and the control is actually performed after one second of the control cycle, that is, 500 ms. .

By performing the above-described control, the vehicle interior can be used in any of the following situations: daylight where strong direct sunlight is strongly inserted, daytime cloudy weather with little sunlight, and nighttime driving with or without headlights. Also, the image reflected on the screen unit 1 from the rear seat was in a state of good quality.

A specific description will be made with reference to FIG. FIG. 8 shows the relations (a) to (d) between the contrast and the lamp power consumption when there is headlight in the surroundings at the time of fine weather in the daytime, cloudy daytime, and nighttime. The plotted points indicated by black circles in the figure show the results of calculating the contrast value when the outputs of the optical sensors 31 and 32 and the amount of power supplied to the projection device are changed during cloudy weather.

As shown in (a) to (d) of FIG.
In the clear daytime, there is a lot of noise light and the screen unit 1
, The contrast is reduced. To increase the contrast to the set contrast (3.5 in this case), it is necessary to increase the lamp power consumption. On the other hand, at night, the noise light radiated to the screen unit 1 is small,
The contrast of the screen unit 1 increases. for that reason,
In order to maintain the set contrast, it is necessary to reduce the lamp power consumption. The screen in cloudy weather is on par with the set contrast, so there is no need to make any major adjustments. Therefore, by controlling the amount of power supplied to the lamp as described in the present example, as shown by the arrow in the figure, the contrast can be made closer to cloudy weather, and an image that is easy for the observer to see can be provided.

The operation and effect according to this embodiment will be described.
In the present example, noise light entering from the front side 101 and noise light entering from the back side 102 of the screen unit 1 are captured, and the projection device 2 is controlled based on the amount of noise (in this example, luminance is used). Further, the optical sensors 31 and 32
One is installed on each of the front side and the back side 101, 102,
The light receiving directions are facing each other. Further, the light receiving angle 31
1, 321 is the viewing angle 200 of the hologram screen 11
It is installed to be included in.

As a result, noise light that lowers the contrast of the image projected on the screen unit 1 can be reliably captured, and the projection device 2 can be accurately controlled to capture a high-quality image.

In particular, the observer of the display device 3 according to the present embodiment looks at the image from the fixed rear seat 43, and
Even if the image on the screen unit 1 is hard to see, it cannot move. Therefore, noise light entering from the back side 102 of the screen unit 1 and noise light entering from the front surface side of the screen unit 1 and reflected on the front surface particularly enter the eyes, making it difficult to view an image. According to the present example, since such noise light is detected by the optical sensors 31 and 32 and the projection device 2 is controlled, it is possible to always provide an observer with a high-quality image.

As described above, according to the present embodiment, it is possible to provide a hologram display device in which a decrease in image quality due to noise light is small.

Further, the projection control device 5 can easily adjust the image light emitted from the projection device 2 according to the magnitude of the noise light. For this reason, the present invention is also useful in an environment in which the amount of light incident from outside changes greatly from daytime to night, for example. Since the present example is mounted on a car, the above-mentioned advantages are significantly effective.

Further, by providing a control delay circuit and performing control using the average value, the time for calculating the power amount per second, that is, the light amount of the projection device 2 is controlled with respect to changes in the surrounding environment. A delay time can be provided before that, and it is possible to eliminate flickering due to a change in luminance of the screen unit 1 that occurs during continuous control, and it is possible to obtain an effect of further improving video quality.

In this example, a transmission type hologram screen was used. As shown in FIG. 10, a so-called reflection type hologram screen is used in which the image light 20 is projected from the front side 101 and an image formed by the reflected light is observed. Even if the screen unit 1 is configured using the hologram screen described above, the same effect as described above can be obtained.

As shown in FIG. 11, the pop-up type screen unit 1 is installed around the front grille 48, and the image light is projected from the projection device 2 installed between the handle 481 and the window glass. The hologram display device 3 can also be used.

The optical sensors 31 and 3 used in this example
As for the output of No. 2, an output having a linear correlation with the luminance as shown in FIG.
A sensor having a non-linear relationship as shown in (b) or (c) may be used.

Further, as shown in FIG. 13, not only a display device for in-vehicle use but also a window glass 61 of a store.
The hologram display device 3 can be configured such that the screen unit 1 is installed on the ceiling, the projection device 2 is hung on the ceiling surface 62, and the image light 20 for advertising the product is projected. In the figure, reference numeral 63 indicates a floor surface, and reference numeral 64 indicates an observer.

[Brief description of the drawings]

FIG. 1 is a plan view of a vehicle compartment provided with a hologram display device in an embodiment.

FIG. 2 is a perspective view of a vehicle compartment provided with a hologram display device in the embodiment.

3A is a plan view of a screen unit 1 and FIG. 3B is a cross-sectional view taken along line AA in the embodiment.

FIG. 4 shows a view angle of a screen unit in the embodiment.
FIG. 3 is an explanatory diagram showing a light receiving angle of the optical sensor.

FIG. 5 is an explanatory diagram showing a configuration of a projection control device in the embodiment.

FIG. 6 is a diagram showing a relationship between an output of an optical sensor and luminance in the embodiment.

FIG. 7 is an explanatory diagram of delay control in the embodiment.

FIG. 8 is a diagram showing control of contrast by a lamp input power amount with respect to a change in a noise light amount of the hologram display device according to the embodiment in the embodiment.

FIG. 9 is an explanatory diagram when calculating an average value in delay control.

FIG. 10 is an explanatory diagram of a hologram display device having a reflection type screen unit in the embodiment.

FIG. 11 is an explanatory diagram of a hologram display device provided on a front grill in the embodiment.

FIG. 12 is a diagram showing characteristics of an optical sensor in the embodiment.

FIG. 13 is an explanatory diagram of a hologram display device installed on a window glass and a ceiling surface in the embodiment.

[Explanation of symbols]

 1. . . Screen part, 10. . . Transparent member, 101. . . Front side, 102. . . 10. back side, . . Hologram screen, 2. . . Projection device, 20. . . Video light, 200. . . Viewing angle, 3. . . Hologram display device, 31, 32. . . Light sensor,

Claims (11)

[Claims] 1. A screen comprising a transparent member and a transparent hologram screen attached to the transparent member,
A projection device configured to project image light onto the screen portion and reproduce an image on the front side of the screen portion, wherein the screen portion includes a screen portion within a viewing angle of a transparent hologram screen. An optical sensor configured to detect noise light incident from the front side and noise light incident from the back side, respectively, and projecting light from the projection device based on the amount of noise light detected by the optical sensor. A hologram display device comprising a projection control device configured to control the amount of image light. 2. The light amount detection circuit according to claim 1, wherein the projection control device calculates a light amount required as image light based on an output value corresponding to a light amount of the noise light obtained from the optical sensor. A hologram display device comprising: a projection device driving circuit that drives the projection device based on a required amount of image light obtained by a light amount detection circuit. 3. The hologram display device according to claim 1, wherein at least one optical sensor is provided on each of a front side and a rear side of the screen unit. 4. The hologram display device according to claim 3, wherein light receiving directions of the optical sensors installed on the front side and the back side of the screen part are opposite to each other. 5. The method according to claim 1, wherein:
A hologram display device, wherein the optical sensor is installed such that a light receiving angle of the optical sensor is included in a viewing angle of the transparent hologram screen. 6. The method according to claim 2, wherein:
A hologram display device, wherein the required amount of image light calculated by the light amount detection circuit is a value capable of realizing a required image contrast value obtained based on the following (a). Here, (a) required image contrast value = {(image light luminance + total noise light luminance) / total noise light luminance}. 7. The hologram display device according to claim 6, wherein the total noise light luminance in (a) is calculated based on (b) below. Here, (b) total noise light luminance = front-side noise light luminance incident from the front side of the screen part × α + back-side noise light luminance incident from the back side of the screen part × β, where α: front side of the screen part Is the transmittance of noise light on the back side of the screen. 8. The method according to claim 6, wherein (a)
The hologram display device is characterized in that the video light luminance in (1) is calculated based on the following (c). (C) Image light luminance = Initial setting image light luminance + γ where γ: Image light correction luminance under the current installation environment of the hologram display device. 9. The method according to claim 2, wherein:
The projection control device includes a control delay circuit configured to delay a control start time between the light amount detection circuit and the projection device drive circuit when controlling the projection device drive circuit based on the light amount detection circuit. A hologram display device characterized by being provided. 10. The hologram display device according to claim 9, wherein a delay amount of the start time in the control delay circuit can be arbitrarily set. 11. The control delay circuit according to claim 9 or 10, wherein the control delay circuit integrates the required amount of video light P with respect to time in a control cycle T that is a fixed time range, and obtains an integrated value as a control cycle T. An average value calculation circuit for calculating an average value obtained by dividing by a division number T / Δt determined by a measurement period Δt which is an integration time, and an average value obtained by the average value calculation circuit A hologram display device for controlling the projection device driving circuit based on the hologram display device.