JP7626586B2 - Image display device - Google Patents

Description

The present invention relates to an image display device, and in particular to an image display device that displays image information in front of the user's eyes, such as a head mounted display (HMD, also known as a helmet mounted display) or a head-up display (HUD).

Rotary-wing aircraft and airplanes use HMDs that display image information in front of the pilot's eyes by projecting an image onto a projection object such as a visor attached to a helmet worn by the pilot (user) on the head, or onto goggles or glasses worn by the pilot in front of the eyes. Examples of such HMDs include those that have a light source, a display element made of a transmissive liquid crystal panel fixed to the helmet, and an optical fiber arranged to receive light emitted from the light source at one end and irradiate the light from the other end onto the back of the display element. With this configuration, the light emitted from the light source is irradiated onto the back of the display element through the optical fiber, and the light that passes through the display element is projected onto the projection object, thereby displaying image information. By using optical fiber in this way, the light source can be provided outside the wearable object such as a helmet worn by the pilot, and the weight of the head-mounted portion of the image display device can be reduced.

Laser light sources are generally used as the light source. Laser light sources are superior to other light sources such as LEDs (light-emitting diodes) in that the wavelength deviation of the light (laser light) they generate is small, and light can be efficiently introduced from the light source into the optical fiber.

However, when a laser light source and optical fiber are used, the light that passes through the optical fiber interferes with one another to produce a spot-like interference pattern (speckle), which is then irradiated onto the display element, causing the speckle to be superimposed on the image projected onto the target object. Such speckle is caused by the interference of multiple propagation modes of light that pass through the optical fiber due to their phase differences (see Patent Document 1).

Patent Document 1 describes providing an image display device with a vibration generator that applies vibrations to the optical fiber. This causes the position of the optical fiber to fluctuate, which in turn changes the weighting of each propagation mode, causing fluctuations in the speckles. If the speckles fluctuate at a frequency too high for humans to perceive, the HMD user will not be able to perceive the speckles in the image projected onto the object after the laser light has passed through the optical fiber and the display element, and problems caused by speckles can be avoided.

U.S. Patent Publication No. 2010/0053729

When using a vibration generating device such as that described in Patent Document 1, power is required to operate the vibration generating device, which increases running costs.

So far, we have taken the example of a rotorcraft or aircraft pilot using an image display device, but similar problems arise when an image display device is used by a pilot of a moving body other than a rotorcraft or aircraft that carries people on board, such as an automobile or railroad vehicle, or by a person other than the pilot (such as a passenger) on a moving body (including rotorcraft and aircraft, as well as other things). In addition, in the above example, we have taken the example of an HMD that projects an image onto an attachment such as a helmet worn by the pilot, but similar problems arise with image display devices such as HUDs that display image information in front of the user's eyes by projecting an image onto an object other than such attachment, such as the windshield of a rotorcraft or aircraft or the windshield of an automobile.

The problem that this invention aims to solve is to provide an image display device that can reduce the impact of laser light interference on image degradation while keeping running costs low.

In order to solve the above problems, the present invention provides an image display device mounted on a moving body, comprising:
A laser light source installed at a first portion of the moving object;
an optical fiber having one end disposed at a position where the laser light emitted from the laser light source is incident;
an image display element disposed between the other end of the optical fiber and a display surface;
The movable body includes a second portion different from the first portion, and a fixing portion for fixing an intermediate portion of the optical fiber.

In the image display device mounted on a moving body according to the present invention , the optical fiber vibrates in the same manner as the first part of the moving body at the end (the one end) on the light source side, and vibrates in the same manner as the second part at the middle part. Since the first part and the second part are different parts of the moving body, they vibrate differently when the moving body moves. In this way, since the optical fiber vibrates differently at the end and the middle part, its shape (curvature) fluctuates, and the weighting of each propagation mode of the laser light propagating through the optical fiber changes. This causes fluctuations in the speckles, and the user of the image display device mounted on a moving body cannot see the speckles. According to the image display device mounted on a moving body according to the present invention , since no power is required to impart vibration to the middle part, it is possible to suppress the influence of the interference of the laser light on image deterioration while suppressing running costs.

1 is a schematic configuration diagram showing a first embodiment of an image display device to be mounted on a moving body according to the present invention; A photograph of the image of laser light emitted from an optical fiber when no vibration is being generated in the optical fiber. A photograph of the image of laser light emitted from an optical fiber when vibrations are being generated in the optical fiber. FIG. 5 is a schematic configuration diagram showing a second embodiment of the image display device to be mounted on a moving body according to the present invention. FIG. 13 is a schematic configuration diagram showing a modified example of the image display device to be mounted on a moving body according to the second embodiment. FIG. 11 is a schematic configuration diagram showing a third embodiment of the image display device to be mounted on a moving body according to the present invention.

1 to 5, an embodiment of an image display device to be mounted on a moving body (hereinafter, abbreviated as "image display device") according to the present invention will be described.

(1) First embodiment
1 shows a schematic configuration of an image display device 10 according to the first embodiment. The image display device 10 includes a laser light source 11, an optical fiber 12, an intermediate excitation unit 13, an image display element 14, and a half mirror 15.

The laser light source 11 is housed in a housing 111, which is placed on the floor 91 (corresponding to the first portion) of the moving body. In addition to the laser light source 11, the housing 111 also contains two lenses 112 and 113 that introduce the laser light from the laser light source 11 to one end (referred to as the "first end 121") of the optical fiber 12. The housing 111 is provided with a hole into which a portion of the optical fiber 12 near the first end 121 is inserted, and the optical fiber 12 inserted into the hole is fixed to the housing 111 so that the first end 121 is positioned opposite the lens 113.

In this embodiment, a multimode fiber is used for the optical fiber 12. In addition to multimode fiber, there is also single mode fiber, but multimode fiber has a larger core diameter and is superior in that it can pass a larger amount of light. On the other hand, multimode fiber propagates light of multiple propagation modes, which was the main cause of speckle in conventional image display devices.

The fixed portion 123 in the middle of the optical fiber 12 is fixed to the side wall 92 (corresponding to the second portion) of the moving body by affixing it with an adhesive. When this adhesive has solidified, it becomes the intermediate excitation portion 13. The intermediate excitation portion 13 transmits the vibrations generated in the side wall 92 to the fixed portion 123 of the optical fiber 12, and vibrates the fixed portion 123. Note that a fixing member other than the solidified adhesive, such as a metal fitting, may also be used as the intermediate excitation portion 13.

The image display element 14 is made of a transmissive liquid crystal panel and is provided on the optical path of the light emitted from the other end (hereinafter referred to as the "second end 122") of the optical fiber 12. Between the second end 122 and the image display element 14, there are disposed a lens 141 that collimates the light emitted from the optical fiber 12, and a diffuser plate 142 that diffuses (scatters) the light that passes through the lens 141. A signal line 143 is connected to the image display element 14 for receiving an image signal for displaying an image from an image display processing device (not shown).

The half mirror 15 allows the user to view the image displayed on the image display element 14 as a virtual image by projecting light that has passed through the transmissive liquid crystal panel of the image display element 14. In this embodiment, the half mirror 15 is a substantially transparent visor provided on a helmet worn by the user (operator of the moving body). The user views an image obtained by superimposing the image displayed on the image display element 14 as a virtual image on an image seen in the normal field of view through the half mirror 15. It is also possible to use an opaque mirror instead of the half mirror 15, and further provide a camera that captures an image corresponding to the user's normal field of view in the image display device 10, and display an image obtained by superimposing an image captured by the camera and an image based on an image signal supplied from the image display processing device on the image display element 14, and project the image on the mirror to allow the user to view the superimposed image as a virtual image. A display optical system 151 that introduces light from the image display element 14 to the half mirror 15 is provided between the image display element 14 and the half mirror 15.

The second end 122 of the optical fiber 12, the lens 141, the diffuser 142, the image display element 14, the display optical system 151, and the half mirror 15 (each of the components shown surrounded by a dashed line in FIG. 1) are fixed to the helmet.

Of the optical fiber 12, the parts other than the first end 121, the fixed part 123, and the second end 122 described above are not fixed to other objects, and when vibrations are applied from the outside, these parts vibrate and deform in response to the vibrations.

(1-2) Operation of the image display device of the first embodiment The operation of the image display device 10 of the first embodiment will be described. Before operating the image display device 10, the user puts the helmet on the head. The user views the outside through the visor (half mirror 15).

The image display device 10 is used when the moving object is moving. The image display element 14 displays an image on the transmissive liquid crystal panel based on an image signal transmitted from the image display processing device through the signal line 143. At the same time, the laser light source 11 emits laser light. The laser light passes through the lenses 112 and 113, enters the optical fiber 12 from the first end 121, propagates through the optical fiber 12, and then exits from the second end 122, passes through the lens 141 and the diffuser plate 142, and enters the image display element 14. The laser light then passes through the transmissive liquid crystal panel of the image display element 14 and is reflected by the half mirror 15. This allows the user to view the image displayed on the image display element 14 as a virtual image.

When the moving body is moving, vibrations are generated in the floor 91 and side wall 92 of the moving body due to vibrations generated by the power source (engine, etc.) of the moving body, vibrations due to air resistance from the outside that the moving body receives, or vibrations from the road surface in the case of an automobile. The vibrations of the floor 91 are transmitted to the first end 121 of the optical fiber 12 via the housing 111. On the other hand, the vibrations of the side wall 92 are transmitted to the fixed part 123 in the middle part of the optical fiber 12 by the intermediate vibration part 13. Here, since the floor 91 and the side wall 92 are made of different materials and have different thicknesses, they vibrate with different amplitudes, periods, and/or phases. Therefore, the first end 121 and the fixed part 123 vibrate with different amplitudes, periods, and/or phases. This causes the shape (curvature) of the optical fiber 12 to fluctuate, and the weighting of each propagation mode of the laser light propagating through the optical fiber 12 to change. This causes fluctuations in the speckles, making it impossible for the user of the image display device 10 to see the speckles in the image.

According to the image display device 10 of the first embodiment, the vibrations generated in the moving body are transmitted to the middle part of the optical fiber 12 by the intermediate vibration unit 13, thereby vibrating the optical fiber 12. This eliminates the need for power to vibrate the optical fiber 12, and reduces the impact of laser light interference on image degradation while keeping running costs down.

Next, the results of observing the laser light emitted from the optical fiber 12 are shown for the cases where vibration is not generated in the optical fiber 12 and where vibration is generated. In this experiment, the image of the laser light emitted from the second end 122 projected onto a screen (not a component of the image display device 10, but provided opposite the second end 122 for this experiment) was photographed by a camera. Instead of vibration actually generated on the side wall 92 of the moving body, the optical fiber 12 was given a vibration by fixing both ends of the optical fiber 12 and slightly loosening it, and rotating the entire optical fiber 12 so that the middle part of the optical fiber 12 rotates around the straight line connecting the two ends (like a jump rope). The rotation radius of the optical fiber 12 was 6 mm at the maximum position, and the rotation frequency was 2 Hz or less. The exposure time of the camera was 0.033 seconds (60 Hz period), which corresponds to the period at which a person can recognize a change. Note that the floor 91 of a moving body usually requires strength to support a heavy object, so it is made of a material that is less likely to vibrate than the side wall 92. Therefore, in this experiment, the vibration of the first end 121 caused by the vibration of the floor 91 was ignored as being sufficiently smaller than the vibration of the fixed part 123 caused by the vibration of the side wall 92, and was not applied to the first end 121.

Photographs of the image projected onto the screen are shown in FIG. 2A when no vibration is applied to the optical fiber 12, and in FIG. 2B when vibration is applied to the optical fiber 12. When no vibration is applied to the optical fiber 12, black spots are seen in the image, whereas when vibration is applied to the optical fiber 12, such spots are hardly seen. Therefore, according to the image display device 10 of the first embodiment, vibration is generated in the fixed part 123 based on the vibration of the side wall 92 of the moving body having the same frequency and amplitude as the vibration applied to the optical fiber 12 in this experiment, and an image without the influence of speckles can be displayed.

(2) Image display device according to the second embodiment
(2-1) Configuration of the image display device of the second embodiment Fig. 3 shows a schematic configuration of the image display device 20 of the second embodiment. This image display device 20 has a laser light source 11, an optical fiber 12, a power generation unit 231, an intermediate vibration unit 232, a rechargeable battery 233, an image display element 14, and a half mirror 15. The configurations of the laser light source 11, the optical fiber 12, the image display element 14, and the half mirror 15 are similar to those in the image display device 10 of the first embodiment, and therefore detailed description thereof will be omitted.

The power generation unit 231 and the rechargeable battery 233, and the rechargeable battery 233 and the intermediate vibration unit 232 are electrically connected to each other. The power generation unit 231 is fixed to the side wall 92 of the moving body, and has a piezoelectric conversion element that converts the mechanical vibration received from the side wall 92 into AC power. The rechargeable battery 233 is charged with the power generated by the power generation unit 231. The intermediate vibration unit 232 is fixed to the fixed part 223 in the middle part of the optical fiber 12, and has a power conversion unit that converts the DC power supplied from the rechargeable battery 233 into AC power having a predetermined frequency, and a piezoelectric conversion element that converts the AC power into mechanical vibration. This predetermined frequency is set to a high value such that when vibration of the same frequency is applied to the optical fiber 12, a person cannot see the speckles. The fixed part 223 of the optical fiber 12 is vibrated by the mechanical vibration of the piezoelectric conversion element of the intermediate vibration unit 232.

The rechargeable battery 233 may be omitted, and the power generation unit 231 and the intermediate vibration unit 232 may be directly electrically connected. In this case, the piezoelectric conversion element of the intermediate vibration unit 232 is mechanically vibrated by the power generated by the power generation unit 231.

(2-2) Operation of the image display device of the second embodiment The operation of the image display device 20 of the second embodiment will be described. The image display device 20 is used when a moving object is moving. As with the image display device 10 of the first embodiment, an image is displayed on the transmissive liquid crystal panel of the image display element 14, and laser light is emitted from the laser light source 11, so that the image displayed on the transmissive liquid crystal panel is reflected by the screen 15. This allows the image displayed on the image display element 14 to be viewed by the user as a virtual image.

Vibrations occurring on the floor 91 when the moving body moves are transmitted to the first end 121 of the optical fiber 12 via the housing 111. On the other hand, the vibrations of the side wall 92 are converted into electricity by the power generating unit 231, and then vibrations are applied to the fixed part 223 at the middle part of the optical fiber 12 by the intermediate vibration unit 232 that operates with the electricity (which is charged in the rechargeable battery 233 and supplied from the rechargeable battery 233 in this embodiment). As a result, the first end 121 and the fixed part 223 vibrate with different amplitudes, periods, and/or phases, so that the shape (curvature) of the optical fiber 12 fluctuates, and the weighting of each propagation mode of the laser light propagating through the optical fiber 12 changes. As a result, the speckles also fluctuate, and the user of the image display device 20 cannot see the speckles.

According to the image display device 20 of the second embodiment, like the image display device 10 of the first embodiment, no power is required to vibrate the optical fiber 12, and the impact of laser light interference on image degradation can be suppressed while keeping running costs low.

Furthermore, when a rechargeable battery 233 is provided, the power converted by the power generating unit 231 is first charged in the rechargeable battery 233 and then supplied to the intermediate vibration unit 232, so that stable power can be supplied to the intermediate vibration unit 232, and the intermediate portion of the optical fiber 12 can be vibrated with stable amplitude and frequency. This makes it possible to more reliably suppress the effect of laser light interference on image degradation.

(3) Image display device according to a modification of the second embodiment Fig. 4 shows a schematic configuration of an image display device 30 according to a modification of the second embodiment. This image display device 30 has an intermediate vibration unit (torsional vibration unit) 332 as described below, instead of the intermediate vibration unit 232 in the image display device 20 according to the second embodiment. This intermediate vibration unit 332 has a gripping unit that grips a gripped portion 323 that is a part of the intermediate portion of the optical fiber 12, a motor that rotates the optical fiber 12 around an axis corresponding to the direction in which the optical fiber 12 extends in the gripping unit, and a control unit that controls the rotation of the motor. The motor and control unit are operated by power supplied from a rechargeable battery 233. The control unit controls the motor so that the rotation direction is reversed every time the motor rotates by a predetermined angle.

In the image display device 30 of this modification, the power generated by the power generating unit 231 due to the vibration of the side wall 92 is charged in the rechargeable battery 233, and the motor of the intermediate vibration unit 332 operates in such a way that the rotation direction is reversed every time it rotates by a predetermined angle according to the control of the control unit by the power supplied from the rechargeable battery 233. As a result, the optical fiber 12 rotates about the axis of the direction in which the optical fiber 12 extends in the gripping unit, relative to the first end 121 fixed to the housing 111 and the second end 122 fixed to the helmet. This rotation causes a twist in the optical fiber 12, and the rotation direction is reversed every time it rotates by a predetermined angle, causing a torsional vibration in the optical fiber 12. This torsional vibration causes the shape (curvature) of the optical fiber 12 to fluctuate, and the weighting of each propagation mode of the laser light propagating through the optical fiber 12 to change. This also causes a fluctuation in the speckle, making it impossible for the user of the image display device 30 to see the speckle.

According to the image display device 30 of this modified example, as with the image display device 20 of the second embodiment, no power is required to vibrate the optical fiber 12, and the impact of laser light interference on image degradation can be suppressed while keeping running costs low. Furthermore, the occurrence of torsional vibration in the optical fiber 12 causes a greater change in the shape of the optical fiber 12 than when reciprocating vibration is generated, so that it is possible to more reliably prevent the user from seeing the interference pattern of the laser light.

In the image display device 30 of this modified example, a torsional vibration separate from the reciprocating vibration of the moving body occurs in the intermediate portion of the optical fiber 12 .

(4) Third embodiment
(4-1) Configuration of the image display device of the third embodiment Fig. 5 shows a schematic configuration of an image display device 40 of the third embodiment. This image display device 40 has a laser light source 11, an optical fiber 12, a vibration damping material 43, an image display element 14, and a half mirror 15. The configurations of the laser light source 11, the optical fiber 12, the image display element 14, and the half mirror 15 are similar to those in the image display device 10 of the first embodiment, and therefore detailed description thereof will be omitted.

The vibration-damping material 43 is made of a spring, one end of which is fixed to the floor 91 of the moving body, and the other end of which is fixed to a fixed point 423 in the middle of the optical fiber 12. Note that the vibration-damping material 43 is not limited to a spring, and may be an elastic body such as rubber or urethane foam.

(4-2) Operation of the image display device of the third embodiment The operation of the image display device 40 of the third embodiment will be described. The image display device 40 is used when a moving object is moving. As with the image display device 10 of the first embodiment, an image is displayed on the transmissive liquid crystal panel of the image display element 14, and laser light is emitted from the laser light source 11, so that the image displayed on the transmissive liquid crystal panel is reflected by the half mirror 15. This allows the image displayed on the image display element 14 to be viewed by the user as a virtual image.

Vibrations occurring on the floor 91 when the moving object moves are transmitted to the first end 121 of the optical fiber 12 via the housing 111. On the other hand, since the fixed point 423 in the middle part of the optical fiber 12 is connected to the floor 91 by the vibration-damping material 43, the fixed point 423 of the optical fiber 12 and its surroundings are a free vibration part that can vibrate separately from the floor 91. As a result, the first end 121 and the free vibration part vibrate differently, so the shape (curvature) of the optical fiber 12 fluctuates, and the weighting of each propagation mode of the laser light propagating through the optical fiber 12 changes. This also causes fluctuations in the speckles, making it impossible for the user of the image display device 40 to notice the speckles.

The image display device 40 of the third embodiment does not require power to apply vibration, so it is possible to reduce running costs while suppressing the impact of laser light interference on image degradation.

(5) Other Modifications The present invention is not limited to the above-described embodiment, and various modifications are possible within the scope of the present invention.

For example, in the image display device 10 of the first embodiment, the fixed portion 123 of the middle portion of the optical fiber 12 is fixed to the side wall 92 of the moving body, but instead, it may be fixed to the ceiling of the moving body or to a position on the floor 91 away from the housing 111. Similarly, in the image display devices 20 and 30 of the second embodiment and its modified example, the power generation unit 231 may be fixed to the ceiling of the moving body or to a position on the floor 91 away from the housing 111.

In the image display device 40 of the third embodiment, one end of the spring, which is the vibration-damping material 43, is fixed to the floor 91 of the moving body, but it may be fixed to a part of the moving body other than the floor 91, such as a side wall or ceiling. Alternatively, instead of the vibration-damping material 43, a string may be tied to the middle part of the optical fiber 12, and the end of the string may be fixed to the ceiling of the moving body.

As a modification of the third embodiment, instead of the vibration-damping material 43, a combination of a pendulum that receives vibrations from a moving body and performs a pendulum motion at a predetermined natural frequency, and a mechanism that transmits the pendulum motion of the pendulum to the optical fiber as a torsional vibration, can be used. With this configuration, as with the image display device 30 of the modification of the second embodiment, no power is required to vibrate the optical fiber 12, and the impact of laser light interference on image degradation can be suppressed while keeping running costs low. In addition, the torsional vibration of the optical fiber 12 causes a greater change in the shape of the optical fiber 12 than when reciprocating vibration occurs, so it is possible to more reliably prevent the user from seeing the interference pattern of the laser light.

In each of the above embodiments, an HMD has been described as using a visor attached to a helmet worn by the user as a half mirror, but something other than a visor, such as goggles, may be used as the half mirror, and the present invention may be applied to a HUD that uses a half mirror installed inside a moving body.

[Aspects]
It will be appreciated by those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

(Section 1)
An image display device to be mounted on a moving body according to one embodiment includes:
A laser light source installed at a first portion of the moving object;
an optical fiber having one end disposed at a position where the laser light emitted from the laser light source is incident;
an image display element disposed between the other end of the optical fiber and a display surface;
The movable body includes a second portion different from the first portion, and a fixing portion for fixing an intermediate portion of the optical fiber.

In the mobile body mounted image display device described in paragraph 1, the optical fiber vibrates in the same manner as a first portion of the mobile body at the end portion on the light source side, and in the middle portion vibrates in the same manner as a second portion different from the first portion, so that the end portion and the middle portion vibrate differently, and the shape (curvature) of the optical fiber fluctuates, and the weighting of each propagation mode of the laser light propagating through the optical fiber changes. This causes fluctuations in the speckles, making it impossible for the user of the mobile body mounted image display device to notice the speckles.

According to the image display device to be mounted on a moving body described in paragraph 1, since no power is required to impart vibration to the intermediate portion, it is possible to reduce running costs while suppressing the effects of image degradation due to interference of laser light.

(Section 2)
Another aspect of the image display device to be mounted on a moving body includes:
A laser light source installed at a first position of the moving body;
an optical fiber having one end disposed at a position where the laser light emitted from the laser light source is incident;
an image display element disposed between the other end of the optical fiber and a display surface;
A power generation unit that converts the vibration of the moving body into electric power;
and an intermediate vibration unit that vibrates an intermediate portion of the optical fiber by electric power from the power generation unit.

In the mobile body mounted image display device described in the second paragraph, the optical fiber vibrates differently at the end and the middle part for the same reason as in the mobile body mounted image display device described in the first paragraph, so that the shape (curvature) of the optical fiber fluctuates and the weighting of each propagation mode of the laser light propagating in the optical fiber changes. This causes fluctuations in the speckle, so that the user of the mobile body mounted image display device cannot see the speckle.

According to the image display device to be mounted on a moving body described in paragraph 2, since no power is required to impart vibration to the intermediate portion, it is possible to reduce running costs while suppressing the effects of image degradation due to interference of laser light.

(Section 3)
The moving body mounted image display device described in Item 2 further comprises a rechargeable battery that is charged with the electric power converted by the power generating unit and supplies the charged electric power to the intermediate vibration unit.

According to the mobile object mounted image display device described in the third aspect, the power converted by the power generating unit is temporarily charged in a rechargeable battery and then supplied to the intermediate excitation unit, so that stable power can be supplied to the intermediate excitation unit and the intermediate portion of the optical fiber can be excited with stable amplitude and frequency. This makes it possible to more reliably suppress the effect of laser light interference on image degradation.

(Section 4)
In the moving body mounted image display device described in Item 2 or 3, the intermediate vibration exciting unit is a torsional vibration exciting unit that applies a torsional vibration to an intermediate portion of the optical fiber.

According to the image display device to be mounted on a moving body described in paragraph 4, the occurrence of torsional vibration in the optical fiber causes a greater change in the shape of the optical fiber than when vibration due to reciprocating motion occurs, so that it is possible to more reliably prevent the user from seeing the interference pattern of the laser light.

(Section 5)
A further aspect of the image display device to be mounted on a moving body includes:
A laser light source installed at a first position of the moving body;
an optical fiber having one end disposed at a position where the laser light emitted from the laser light source is incident;
an image display element disposed between the other end of the optical fiber and a display surface;
In a moving body mounted image display device comprising:
A free vibration portion is provided in the middle portion of the optical fiber.

In the mobile- mounted image display device described in paragraph 5, the optical fiber vibrates differently at the end on the laser light source side and the free vibration portion, so that the shape (curvature) of the optical fiber fluctuates, and the weighting of each propagation mode of the laser light propagating through the optical fiber changes. This causes fluctuations in the speckle, making it impossible for the user of the mobile- mounted image display device to notice the speckle.

According to the image display device to be mounted on a moving body described in paragraph 5, since no power is required to impart vibration to the free vibration part, it is possible to reduce running costs while suppressing the effects of image degradation due to interference of laser light.

(Section 6)
The moving body mounted image display device described in item 5 further comprises a torsional vibration excitation section which converts vibration of the moving body into torsional vibration and applies the torsional vibration to the free vibration portion.

According to the image display device to be mounted on a moving body described in paragraph 6, the occurrence of torsional vibration in the optical fiber causes a greater change in the shape of the optical fiber than when vibration due to reciprocating motion occurs, so that it is possible to more reliably prevent the user from seeing the interference pattern of the laser light.

DESCRIPTION OF SYMBOLS 10, 20, 30, 40...Image display device 11...Laser light source 111...Housing 112, 113, 141...Lens 12...Optical fiber 121...First end 122...Second end 123, 223...Fixed portion 13, 232, 332...Intermediate vibration excitation portion 14...Image display element 142...Diffusion plate 143...Signal line 15...Half mirror 151...Display optical system 231...Power generation portion 233...Rechargeable battery 323...Holded portion 423...Fixed point 43...Vibration damping material 91...Floor 92...Side wall

Claims (1)

A laser light source installed at a first portion of the moving object;
an optical fiber having one end disposed at a position where the laser light emitted from the laser light source is incident;
an image display element disposed between the other end of the optical fiber and a display surface;
a fixing unit that fixes a second portion of the optical fiber to a second portion that is different in material or thickness from the first portion of the moving body and vibrates differently from the first portion when the moving body moves, so that a user cannot perceive speckles in an image as a result of the vibration of the second portion being transmitted to the intermediate portion of the optical fiber;
The image display device is characterized in that the image display element is a transmissive liquid crystal panel, and the laser light that propagates within the optical fiber and is emitted from the optical fiber is passed through the image display element, and an image displayed on the image display element is projected onto the display surface as a virtual image.

Images