Patent Description:
There is known an image projection device that two-dimensionally scans a light beam emitted from a light source to irradiate the retina of a user with the scanned light beam by Maxwellian view to project an image. In addition, there has been proposed an image projection device using Maxwellian view capable of projecting a high-quality image in which distortion, defocus, and the like are reduced (for example, Patent Document <NUM>).

<CIT>, <CIT> and <CIT> disclose image projection devices.

Patent Document <NUM>: International Publication No. <CIT>.

When the image projection device disclosed in Patent Document <NUM> is attached to a frame that is worn on the user's face, such as a spectacle-type frame, the clearance between the image projection device and the user's face tends to be small.

The present invention has been made in view of above problems, and an object of the present invention is to provide an image projection device capable of securing sufficient clearance from the user's face.

The present invention is an image projection device according to claim <NUM>.

In the above configuration, a configuration in which the scanning unit and the first optical member are attached near a temple of the frame, and the light guide member is attached near a rim of the frame and has a shape extending from a front of the eye of the user toward the temple may be employed.

In the above described configuration, a configuration in which the light guide member has an odd number of reflection surfaces as the plurality of reflection surfaces, and the plurality of image light beams that are reflected by the first optical member and travel obliquely forward enter the light guide member may be employed.

In the above configuration, a configuration in which the last reflection surface of the plurality of reflection surfaces is a concave curved surface, and remaining reflection surfaces are substantially flat surfaces may be employed.

In the above configuration, a configuration in which the remaining reflection surfaces are substantially parallel to each other may be employed.

In the above configuration, a configuration in which the light guide member includes a main body portion through which the plurality of image light beams repeatedly reflected by the plurality of reflection surfaces and applied to the retina of the user pass, and a cover portion that covers the last reflection surface and has a refractive index substantially equal to that of the main body portion, the last reflection surface, an emission surface through which the plurality of image light beams reflected by the last reflection surface are emitted from the main body portion, and an opposite surface of the cover portion from the emission surface of the main body portion with respect to the last reflection surface are located in front of the eye of the user, the last reflection surface is a half mirror, and the emission surface of the main body portion and the opposite surface of the cover portion are flatter than the last reflection surface may be employed.

In the above configuration, a configuration in which the emission surface of the main body portion and the opposite surface of the cover portion are substantially parallel to each other and are substantially flat surfaces may be employed.

In the above configuration, a configuration in which a first reflection surface immediately before the last reflection surface among the plurality of reflection surfaces has a region on which both the plurality of image light beams reflected by a second reflection surface immediately before the first reflection surface and the plurality of image light beams reflected by the last reflection surface are incident, and reflects the plurality of image light beams reflected by the second reflection surface to the last reflection surface and transmits the plurality of image light beams reflected by the last reflection surface in the region may be employed.

In the above configuration, a configuration in which the first reflection surface is substantially orthogonal to an optical axis after a central image light beam corresponding to a center of an image projected on the retina of the user among the plurality of image light beams is reflected by the last reflection surface may be employed.

In the above configuration, a configuration in which a convergence angle at which the plurality of image light beams converge at the first convergence point is equal to or greater than a scanning angle of the plurality of image light beams by the scanning unit may be employed.

In the above configuration, a configuration in which the image light beam emitted from the light source travels obliquely forward from a side closer to the face of the user than the scanning unit and enters the scanning unit, and the plurality of image light beams emitted from the scanning unit travel rearward from the scanning unit, are then reflected obliquely forward by the first optical member to enter the light guide member may be employed.

In the above configuration, a configuration in which a housing that is attached to the frame and houses the scanning unit, the first optical member, and the second optical member therein is further provided, and most of the light guide member is not located in the housing may be employed.

In the above configuration, a configuration in which a first optical path length, a second optical path length, a third optical path length, and a fourth optical path length are shorter in this order, where the first optical path length is an optical path length of the image light beam between the second reflection surface and an incident surface through which the image light beam enters the light guide member, the second optical path length is an optical path length of the image light beam between the second reflection surface and the first reflection surface, the third optical path length is an optical path length of the image light beam between the first reflection surface and the last reflection surface, and the fourth optical path length is an optical path length of the image light beam between the last reflection surface and the first reflection surface as an emission surface of the light guide member may be employed.

In the above configuration, a configuration in which an incident angle at which the image light beam enters the first optical member is substantially the same as an incident angle at which the image light beam enters the last reflection surface, and an incident angle at which the image light beam enters the second reflection surface is substantially the same as an incident angle at which the image light beam enters the first reflection surface may be employed.

In the above configuration, a configuration in which some image light beams of the plurality of image light beams pass through the last reflection surface, then enter again an opposite surface of the last reflection surface and pass through the last reflection surface, are reflected by the last reflection surface, and are applied to the retina of the user, and remaining image light beams of the plurality of image light beams are reflected by the last reflection surface without passing through the last reflection surface, and are applied to the retina of the user, and a ratio of luminance of the some image light beams to luminance of the remaining image light beams is <NUM>% or greater when the image light beams enter the eye of the user may be employed.

In the above configuration, a configuration in which some image light beams of the plurality of image light beams pass through the last reflection surface, then enter an opposite surface of the last reflection surface and pass through the last reflection surface, are reflected by the last reflection surface, and are applied to the retina of the user, and remaining image light beams of the plurality of image light beams are reflected by the last reflection surface without passing through the last reflection surface, and are applied to the retina of the user, and the reflectance of the last reflection surface is <NUM>% or less may be employed.

The present invention is an image projection device including: a light source; a control unit configured to generate an image light beam based on image data and control emission of the image light beam from the light source; a scanning unit configured to two-dimensionally scan the image light beam emitted from the light source; and a light guide member that is formed of a glass material through which a plurality of image light beams emitted from the scanning unit at different times pass, has a plurality of reflection surfaces that reflect the plurality of image light beams, converges the plurality of image light beams reflected by a last reflection surface, which reflects the plurality of image light beams last among the plurality of reflection surfaces, at a convergence point in an eye of a user, and then irradiates a retina of the user with the converged image light beams, wherein some image light beams of the plurality of image light beams pass through the last reflection surface, then enter again an opposite side of the last reflection surface and pass through the last reflection surface, are reflected by the last reflection surface, and are applied to the retina of the user, and remaining image light beams of the plurality of image light beams are reflected by the last reflection surface without passing through the last reflection surface, and are applied to the retina of the user, and wherein a ratio of luminance of the some image light beams to luminance of the remaining image light beams is <NUM>% or greater when the image light beams enter the eye of the user.

The present invention is provided an image projection device including: a light source; a control unit configured to generate an image light beam based on image data and control emission of the image light beam from the light source; a scanning unit configured to two-dimensionally scan the image light beam emitted from the light source; and a light guide member that is formed of a glass material through which the plurality of image light beams emitted from the scanning unit at different times pass, has a plurality of reflection surfaces that reflect the plurality of image light beams, converges the plurality of image light beams reflected by a last reflection surface, which reflects the plurality of image light beams last among the plurality of reflection surfaces, at a convergence point in an eye of a user, and then irradiates a retina of the user with the converged image light beams, wherein some image light beams of the plurality of image light beams pass through the last reflection surface, then enter again an opposite side of the last reflection surface and pass through the last reflection surface, are reflected by the last reflection surface, and are applied to the retina of the user, and remaining image light beams of the plurality of image light beams are reflected by the last reflection surface without passing through the last reflection surface, and are applied to the retina of the user, and wherein the last reflection surface has a reflectance of <NUM>% or less.

In the above configuration, a configuration in which the plurality of reflection surfaces have a first reflection surface located closer to the eye of the user, a second reflection surface that is located farther from the eye of the user and on which the plurality of image light beams are incident before entering the last reflection surface, and a third reflection surface on which the plurality of image light beams are incident after passing through the last reflection surface, and a reflectance of the second reflection surface and a reflectance of the third reflection surface are substantially equal to each other may be employed.

In the above configuration, a configuration in which the reflectance of the second reflection surface and the reflectance of the third reflection surface are <NUM>% or greater and <NUM>% or less may be employed.

In the above configuration, a configuration in which a reflectance of the first reflection surface is <NUM>% or greater and <NUM>% or less, the reflectance of the second reflection surface and the reflectance of the third reflection surface are <NUM>% or greater and <NUM>% or less, and the reflectance of the last reflection surface is <NUM>% or greater and <NUM>% or less may be employed.

In the above configuration, a configuration in which the plurality of image light beams are reflected by the plurality of reflection surfaces the same number of times and are applied to the retina of the user may be employed.

The present invention enables to secure sufficient clearance from the face of a user.

First, comparative examples of an optical system used in an image projection device will be described.

<FIG> illustrates an optical system <NUM> in accordance with a comparative example <NUM>. As illustrated in <FIG>, the optical system <NUM> of the comparative example <NUM> includes a light source <NUM>, a scanning unit <NUM>, a lens <NUM>, a reflection mirror <NUM>, a reflection mirror <NUM>, a projection mirror <NUM>, and a lens <NUM>. The light source <NUM> emits a laser beam <NUM>. The lens <NUM> converts the laser beam <NUM> emitted by the light source <NUM> from diffusion light into convergent light. The reflection mirror <NUM> is a plane mirror and reflects the laser beam <NUM> that has passed through the lens <NUM> toward the scanning unit <NUM>. The scanning unit <NUM> two-dimensionally scans the incident laser beam <NUM>. A plurality of the laser beams <NUM> two-dimensionally scanned by the scanning unit <NUM> and emitted from the scanning unit <NUM> at different times enter the reflection mirror <NUM>. The reflection mirror <NUM> is a concave mirror having a curved reflection surface.

Each of the plurality of the scanned laser beams <NUM> enters the reflection mirror <NUM> as diffusion light, and is converted from the diffusion light into substantially parallel light by the reflection mirror <NUM>. The plurality of the laser beams <NUM> scanned and reflected by the reflection mirror <NUM> converge at a convergence point <NUM> before the projection mirror <NUM>. The lens <NUM> is disposed at the convergence point <NUM>. Each of the plurality of the laser beams <NUM> is converted from substantially parallel light into convergent light by the lens <NUM>, is condensed before the projection mirror <NUM>, then becomes diffusion light, and enters the projection mirror <NUM>. The projection mirror <NUM> is a concave mirror having a curved reflection surface, has substantially the same shape as the reflection mirror <NUM>, and has substantially the same radius of curvature as the reflection mirror <NUM>.

Each of the plurality of the laser beams <NUM> is converted from diffusion light into substantially parallel light by the projection mirror <NUM>. The plurality of the laser beams <NUM> reflected by the projection mirror <NUM> are converged at a convergence point <NUM> and then applied to the projection surface <NUM>.

When the optical system <NUM> is used in an image projection device, the convergence point <NUM> is located in the eye of the user (for example, near the pupil), and the laser beam <NUM> is converted from substantially parallel light into convergent light by the crystalline lens and focuses at the vicinity of the retina.

The scanning angle of the laser beam <NUM> by the scanning unit <NUM> and the convergence angle at which the plurality of the laser beams <NUM> converge at the convergence point <NUM> are approximately the same. In the laser beam <NUM>, the optical path length between the scanning unit <NUM> and the reflection mirror <NUM> is approximately equal to the optical path length between the projection mirror <NUM> and the convergence point <NUM>, and the optical path length between the reflection mirror <NUM> and the convergence point <NUM> is approximately equal to the optical path length between the convergence point <NUM> and the projection mirror <NUM>. Therefore, the scanning unit <NUM>, the convergence point <NUM>, and the convergence point <NUM> are in a conjugate relationship of substantially equal magnification.

<FIG> presents a simulation result obtained by evaluating the laser beam <NUM> with which a projection surface <NUM> is irradiated in the optical system <NUM> of <FIG>. The simulation was performed for a case in which the plurality of the laser beams <NUM> emitted from the scanning unit <NUM> each had a substantially circular shape and were substantially uniformly distributed in a substantially rectangular shape as a whole (the same applies to the following similar simulations). As presented in <FIG>, since the scanning unit <NUM> and the convergence point <NUM> are in the conjugate relationship of substantially equal magnification, the plurality of the laser beams <NUM> on the projection surface <NUM> each had a substantially circular shape and were substantially uniformly distributed in a substantially rectangular shape as a whole.

Here, the reason why the lens <NUM> is disposed at the convergence point <NUM> will be described. The lens <NUM> converts the laser beam <NUM> from substantially parallel light to convergent light. The laser beam <NUM> converted into convergent light by the lens <NUM> is condensed before the projection mirror <NUM> and then becomes diffusion light to enter the projection mirror <NUM>. The projection mirror <NUM> has a positive condensing power that causes the plurality of the laser beams <NUM> to converge at the convergence point <NUM>. Therefore, by disposing the lens <NUM> whose focal length is set to an appropriate length at the convergence point <NUM> and setting the NA (numerical aperture) when the laser beam <NUM> enters the projection mirror <NUM> to an appropriate value, the laser beam <NUM> reflected by the projection mirror <NUM> can be made to be substantially parallel light.

<FIG> present simulation results obtained by evaluating the laser beam <NUM> with which the projection surface <NUM> is irradiated when the focal length of the lens <NUM> disposed at the convergence point <NUM> is varied. <FIG> presents a simulation result in a case in which the focal length of the lens <NUM> was inappropriate, and <FIG> presents a simulation result in a case in which the focal length was appropriate. As presented in <FIG>, when the focal length of the lens <NUM> was inappropriate, the sizes of the plurality of the laser beams <NUM> on the projection surface <NUM> varied. This indicates that when the focal length of the lens <NUM> is inappropriate, the laser beam <NUM> that is not substantially parallel light is included in the plurality of the laser beams <NUM> reflected by the projection mirror <NUM>. On the other hand, as illustrated in <FIG>, when the focal length of the lens <NUM> was appropriate, the sizes of the plurality of the laser beams <NUM> on the projection surface <NUM> were substantially uniform. This indicates that when the focal length of the lens <NUM> is appropriate, all of the plurality of the laser beams <NUM> reflected by the projection mirror <NUM> are substantially parallel lights.

As described above, the plurality of the laser beams <NUM> reflected by the projection mirror <NUM> can be made to be substantially parallel lights by disposing the lens <NUM> that converts the laser beam <NUM> from substantially parallel light to convergent light at the convergence point <NUM> and appropriately setting the focal length of the lens <NUM> to appropriately set the NA when the laser beam <NUM> enters the projection mirror <NUM>. As a result, when the optical system <NUM> is used in an image projection device, the plurality of the laser beams <NUM> can be converted from substantially parallel lights to convergent lights by the crystalline lens and focused at the vicinity of the retina, and thereby, a high-quality image can be provided to the user. In addition, since the convergence point <NUM> is a point at which the plurality of the laser beams <NUM> converge, by disposing the lens <NUM> at the convergence point <NUM>, it is possible to easily adjust the degree of convergence of the plurality of the laser beams <NUM> to be appropriate.

Here, in order to secure the viewing angle of the image projected on the retina of the user, it is desirable to increase the size of the shape of the projection mirror disposed in front of the eye of the user. <FIG> illustrates an optical system <NUM> in accordance with a comparative example <NUM>. As illustrated in <FIG>, the optical system <NUM> of the comparative example <NUM> includes a projection mirror 122a having a curvature radius larger than that of the reflection mirror <NUM> instead of the projection mirror <NUM>. Therefore, the optical path length of the laser beam <NUM> between the scanning unit <NUM> and the reflection mirror <NUM> is different from the optical path length of the laser beam <NUM> between the projection mirror 122a and the convergence point <NUM>. The optical path length of the laser beam <NUM> between the reflection mirror <NUM> and the convergence point <NUM> is different from the optical path length of the laser beam <NUM> between the convergence point <NUM> and the projection mirror 122a. On the other hand, the ratio of the optical path length of the laser beam <NUM> between the reflection mirror <NUM> and the convergence point <NUM> to the optical path length of the laser beam <NUM> between the scanning unit <NUM> and the reflection mirror <NUM> is substantially equal to the ratio of the optical path length of the laser beam <NUM> between the convergence point <NUM> and the projection mirror 122a to the optical path length of the laser beam <NUM> between the projection mirror 122a and the convergence point <NUM>. Therefore, the optical system <NUM> has a layout in a similarity relationship of substantially equal magnification, and the scanning angle of the laser beam <NUM> by the scanning unit <NUM> and the convergence angle at which the plurality of the laser beams <NUM> converge at the convergence point <NUM> are substantially the same.

The similarity ratio of the optical system <NUM> may be determined by the distance between the projection mirror 122a and the eye of the user, the shape of the face of the user, and/or the space at the side of the face of the user.

<FIG> presents a simulation result obtained by evaluating the laser beam <NUM> with which the projection surface <NUM> is irradiated in the optical system <NUM> of <FIG>. As presented in <FIG>, since the optical system <NUM> has a layout in a similarity relationship of substantially equal magnification, the plurality of the laser beams <NUM> on the projection surface <NUM> each had a substantially circular shape and were substantially uniformly distributed in a substantially rectangular shape as a whole.

When the optical system <NUM> in accordance with the comparative example <NUM> is used in an image projection device, the optical system <NUM> may be attached to a spectacle-type frame. <FIG> illustrates a state in which the optical system <NUM> in accordance with the comparative example <NUM> is attached to a spectacle-type frame <NUM>. In <FIG>, the path along which the laser beam <NUM> emitted from the light source <NUM> enters the scanning unit <NUM> is different from that in <FIG>. As illustrated in <FIG>, since the projection mirror 122a is disposed in front of the eye of the user, the projection mirror 122a is disposed near a rim <NUM> of the spectacle-type frame <NUM>. Therefore, the reflection mirror <NUM> and the lens <NUM> are disposed near the face of the user, and the laser beam <NUM> passes near the face of the user. In addition, the reflection mirror <NUM>, the projection mirror 122a, the lens <NUM>, and the like are accommodated in a housing <NUM> for protection thereof and protection of the laser beam <NUM>, and the housing <NUM> is attached to a temple <NUM> and the rim <NUM> of the spectacle-type frame <NUM>. Since the reflection mirror <NUM> and the lens <NUM> are disposed near the user's face, the clearance between the housing <NUM> and the user's face is reduced. For example, the distance between an eye <NUM> and the housing <NUM> may be reduced, and the housing <NUM> may interfere with the eyelashes, reducing the quality of the image projected on a retina <NUM>. In addition, since the clearance between the housing <NUM> and the user's face is reduced, the housing <NUM> may interfere with the user's face depending on the shape of the user's face or the like. In addition, the dimension of the housing <NUM> in the front-rear direction cannot be within the clearance between the normal spectacle-type frame and the face, and a design in which the housing <NUM> protrudes forward is unavoidable.

Next, an optical system <NUM> in accordance with a comparative example <NUM> in which the viewing angle of an image is increased compared to the optical system <NUM> of the comparative example <NUM> will be described. <FIG> illustrates the optical system <NUM> in accordance with the comparative example <NUM>. As illustrated in <FIG>, in the optical system <NUM> of the comparative example <NUM>, the position of the convergence point <NUM> is closer to the projection mirror 122a than in the optical system <NUM> of the comparative example <NUM> in order to increase the viewing angle of the image.

In the optical system <NUM> of the comparative example <NUM>, since the position of the convergence point <NUM> is closer to the projection mirror 122a than in the optical system <NUM> of the comparative example <NUM>, as is clear from <FIG>, the clearance between the housing <NUM> and the face of the user is further reduced. Therefore, deterioration in image quality due to interference of the housing <NUM> with the eyelashes and interference of the housing <NUM> with the user's face are more likely to occur.

<FIG> presents a simulation result obtained by evaluating the laser beam <NUM> with which the projection surface <NUM> is irradiated in the optical system <NUM> of <FIG>. As presented in <FIG>, the overall shape of the plurality of the laser beams <NUM> on the projection surface <NUM> was substantially trapezoidal, resulting in generation of trapezoidal distortion. It is considered that the trapezoidal distortion occurred because the convergence point <NUM> was brought close to the projection mirror 122a and the layout was thus deviated from a layout in a similarity relationship of substantially equal magnification. That is, it is considered that the optical power received from the projection mirror 122a when the laser beam <NUM> obliquely entering the projection mirror 122a was reflected by the projection mirror 122a was not canceled by the optical power received from the reflection mirror <NUM> when the laser beam <NUM> was obliquely reflected by the reflection mirror <NUM>, and trapezoidal distortion occurred.

In order to eliminate the trapezoidal distortion presented in <FIG>, there is a method in which the trapezoidal distortion is reduced by performing a process of generating an opposite trapezoidal distortion in the image itself to be projected in advance and canceling out the distortion generated in advance and the distortion generated by the optical system <NUM>, but there is also a method in which the trapezoidal distortion is reduced by adjusting the incident angle of the laser beam <NUM> to the scanning unit <NUM>.

<FIG> and <FIG> illustrate optical systems <NUM> and <NUM> in which the incident angle of the laser beam <NUM> to the scanning unit <NUM> is changed, respectively. As illustrated in <FIG>, in the optical system <NUM>, the laser beam <NUM> obliquely enters the scanning unit <NUM> from the side opposite to the projection mirror 122a with respect to the reflection mirror <NUM>. As illustrated in <FIG>, in the optical system <NUM>, the laser beam <NUM> obliquely enters the scanning unit <NUM> from the same side as the projection mirror 122a with respect to the reflection mirror <NUM>.

<FIG> and <FIG> present simulation results obtained by evaluating the laser beam <NUM> with which the projection surface <NUM> is irradiated in the optical system <NUM> of <FIG> and the optical system <NUM> of <FIG>, respectively. As presented in <FIG>, in the optical system <NUM>, the trapezoidal distortion was larger than that of the simulation result of the optical system <NUM> presented in <FIG>. The reason why the trapezoidal distortion increased in the optical system <NUM> is considered as follows. In the optical system <NUM>, the direction in which the laser beam <NUM> travels toward the scanning unit <NUM> is substantially the same as the direction in which the laser beam <NUM> reflected by the reflection mirror <NUM> travels toward the projection mirror 122a. Therefore, it is considered that the trapezoidal distortion caused by the laser beam <NUM> entering the projection mirror 122a in an oblique direction was combined with the trapezoidal distortion caused by the laser beam <NUM> entering the scanning unit <NUM> in substantially the same oblique direction, and the trapezoidal distortion increased.

On the other hand, as illustrated in <FIG>, in the optical system <NUM>, the trapezoidal distortion was less than that of the simulation result of the optical system <NUM> illustrated in <FIG>. The reason why the trapezoidal distortion was reduced in the optical system <NUM> is considered as follows. In the optical system <NUM>, the direction in which the laser beam <NUM> travels toward the scanning unit <NUM> and the direction in which the laser beam <NUM> reflected by the reflection mirror <NUM> travels toward the projection mirror 122a are different directions (intersecting directions). Therefore, it is considered that the trapezoidal distortion caused by the laser beam <NUM> entering the projection mirror 122a in an oblique direction was weakened by the trapezoidal distortion caused by the laser beam <NUM> entering the scanning unit <NUM> in a different oblique direction, and the trapezoidal distortion was reduced.

As described above, the trapezoidal distortion can be reduced by causing the laser beam <NUM> to enter the scanning unit <NUM> in a direction different from the direction in which the laser beam <NUM> is reflected by the reflection mirror <NUM> and travels toward the projection mirror 122a.

As illustrated in <FIG>, when the optical systems of the comparative examples <NUM> and <NUM> are used in the image projection device, it is difficult to ensure a sufficient clearance between the image projection device and the user's face. In addition, since the image projection device also protrudes in the forward direction, a dedicated frame is required, which impairs the design. Therefore, an example of an image projection device capable of securing a sufficient clearance between the image projection device and the user's face and reducing the amount of protrusion of the image projection device in the forward direction will be described below.

<FIG> illustrates an image projection device <NUM> in accordance with the first embodiment. As illustrated in <FIG>, the image projection device <NUM> includes a light source <NUM>, a scanning unit <NUM>, a lens <NUM>, a reflection mirror <NUM>, a reflection mirror <NUM>, a lens <NUM>, a light guide member <NUM>, a control unit <NUM>, and an image input unit <NUM>. The image input unit <NUM> receives image data from a camera and/or a recording device (not illustrated). The control unit <NUM> controls emission of a laser beam <NUM> from the light source <NUM> on the basis of the input image data. Therefore, the image data is converted by the light source <NUM> into the laser beam <NUM>, which is an image light beam. The control unit <NUM> also controls driving of the scanning unit <NUM>.

Under the control by the control unit <NUM>, the light source <NUM> emits a visible laser beam of, for example, a red laser light (wavelength: about <NUM> to <NUM>), a green laser light (wavelength: about <NUM> to <NUM>), and a blue laser light (wavelength: about <NUM> to <NUM>). Examples of the light source <NUM> that emits red, green, and blue laser lights include a light source in which red, green, and blue (RGB) laser diode chips and a three-color combining device are integrated. The light source <NUM> may emit a laser beam of a single wavelength.

The control unit <NUM> is, for example, a processor such as a central processing unit (CPU). If the camera is installed at an appropriate position so as to face the line-of-sight direction of the user, an image in the line-of-sight direction captured by the camera can be projected onto the retina <NUM>. In addition, an image input from a recording device or the like can be projected, or a camera image and an image from the recording device or the like can be superimposed by the control unit <NUM> to project a so-called augmented reality (AR) image.

The laser beam <NUM> emitted by the light source <NUM> passes through the lens <NUM>. The lens <NUM> is a condensing lens that converts the laser beam <NUM> from diffusion light to convergent light. The laser beam <NUM> that has passed through the lens <NUM> is reflected by the reflection mirror <NUM> toward the scanning unit <NUM>, and enters the scanning unit <NUM> in a state of convergent light. The reflection mirror <NUM> is a plane mirror. The lens <NUM> is provided between the light source <NUM> and the scanning unit <NUM> in order to convert the laser beam <NUM> reflected by the reflection mirror <NUM> into substantially parallel light.

The scanning unit <NUM> (scanner) scans the incident laser beam <NUM> in two-dimensional directions including the horizontal direction and the vertical direction. The scanning unit <NUM> is, for example, a scanning mirror such as a micro electro mechanical system (MEMS) mirror. The scanning unit <NUM> may be of other types such as potassium tantalate niobate (KTN). A plurality of the laser beams <NUM> that are scanned in the two-dimensional directions by the scanning unit <NUM> and are emitted from the scanning unit <NUM> at different times enter the reflection mirror <NUM>. Each of the plurality of the laser beams <NUM> is condensed before the reflection mirror <NUM> and then becomes diffusion light and enters the reflection mirror <NUM>. The reflection mirror <NUM> is a concave mirror having a reflection surface formed of a curved surface such as a free curved surface, and has a positive condensing power. Therefore, each of the plurality of the laser beams <NUM> is converted from diffusion light into substantially parallel light by being reflected by the reflection mirror <NUM>.

The plurality of the laser beams <NUM> reflected by the reflection mirror <NUM> converge at a convergence point <NUM> before the light guide member <NUM>. The lens <NUM> is provided at the convergence point <NUM>. The lens <NUM> is a condensing lens that converts each of the plurality of the laser beams <NUM> from substantially parallel light to convergent light. For the same reason as that described with reference to <FIG>, the lens <NUM> is provided at the convergence point <NUM> in order to make each of the plurality of the laser beams <NUM> emitted from the light guide member <NUM> toward the eye <NUM> of the user substantially parallel light. The plurality of the laser beams <NUM> that have passed through the lens <NUM> enter the light guide member <NUM>.

The light guide member <NUM> is formed of a glass material such as a cycloolefin polymer (COP) resin or an acrylic resin. The laser beam <NUM> passes through the inside of the light guide member <NUM>. The light guide member <NUM> has a plurality of reflection surfaces <NUM>, <NUM>, and <NUM>. The reflection surfaces <NUM>, <NUM>, and <NUM> are formed by, for example, vapor-depositing a reflective material on a glass material. The laser beam <NUM> is reflected by the reflection surface <NUM>, the reflection surface <NUM>, and the reflection surface <NUM> in this order in the light guide member <NUM>, and is then emitted from the light guide member <NUM> to the outside. The reflection surface <NUM> and the reflection surface <NUM> are substantially flat surfaces and are provided substantially parallel to each other. The reflection surface <NUM> and the reflection surface <NUM> are substantially parallel to the face of the user, for example. On the other hand, the reflection surface <NUM> is a concave curved surface such as a free curved surface. The substantially flat surface means a surface that is flat to such an extent that no condensing power is applied to the laser beam <NUM>. The term "substantially parallel" means that the inclination is ±<NUM>° or less, may be ±<NUM>° or less, or may be ±<NUM>° or less.

Each of the plurality of the laser beams <NUM> incident on the light guide member <NUM> travels toward the reflection surface <NUM> while being converged. Each of the plurality of the laser beams <NUM> is condensed near the reflection surface <NUM>. For example, a laser beam 40a corresponding to the center of the image projected onto the retina (which can also be referred to as a laser beam when the deflection angle of the scanning unit <NUM> is <NUM>°) is condensed on the reflection surface <NUM>. Each of the plurality of the laser beams <NUM> reflected by the reflection surface <NUM> travels toward the reflection surface <NUM>. For example, all of the plurality of the laser beams <NUM> are condensed before the reflection surface <NUM> and then become diffusion lights and enter the reflection surface <NUM>. Each of the plurality of the laser beams <NUM> reflected by the reflection surface <NUM> enters the reflection surface <NUM> in a state of diffusion light.

Since the reflection surface <NUM> is a concave curved surface, it has a positive condensing power. Therefore, each of the plurality of the laser beams <NUM> reflected by the reflection surface <NUM> is converted from diffusion light into substantially parallel light, and the plurality of the laser beams <NUM> converge at a convergence point <NUM> in the eye <NUM> of the user. The convergence point <NUM> is located, for example, near a pupil <NUM>. Since the laser beam <NUM> traveling to the eye <NUM> is substantially parallel light, the laser beam <NUM> is converted from substantially parallel light into convergent light by a crystalline lens <NUM> and focuses at the vicinity of the retina <NUM>. Thus, the user can visually recognize the image.

In order to increase the viewing angle of the image projected onto the retina <NUM>, the curvature of the reflection surface <NUM> is set such that the convergence angle α2 at which the plurality of the laser beams <NUM> converge at the convergence point <NUM> is larger than the scanning angle α1 of the scanning unit <NUM>.

The reflection surface <NUM> has a region 34a that reflects the laser beam <NUM> reflected by the reflection surface <NUM> toward the reflection surface <NUM> and a region 34b that allows the laser beam <NUM> reflected by the reflection surface <NUM> to pass therethrough, and the regions 34a and 34b partially overlap each other. In this overlapping region 34c, both a function of reflecting the laser beam <NUM> and a function of transmitting the laser beam <NUM> are required. The incident angle at which the laser beam <NUM> reflected by the reflection surface <NUM> enters the reflection surface <NUM> is larger than the incident angle at which the laser beam <NUM> reflected by the reflection surface <NUM> enters the reflection surface <NUM>. Therefore, by providing at least the region 34c of the reflection surface <NUM> with the angle dependence such that the laser beam <NUM> having a large incident angle is mainly reflected and the laser beam <NUM> having a small incident angle is mainly transmitted, it is possible to both reflect the laser beam <NUM> reflected by the reflection surface <NUM> and transmit the laser beam <NUM> reflected by the reflection surface <NUM>. Further, the laser beam <NUM> reflected by the reflection surface <NUM> is only required to be projected onto the retina <NUM>, and even if the laser beam <NUM> reflected by the reflection surface <NUM> passes through the reflection surface <NUM>, there is substantially no influence. Therefore, by using a half mirror for the reflection surface <NUM>, it is possible to both reflect the laser beam <NUM> reflected by the reflection surface <NUM> and transmit the laser beam <NUM> reflected by the reflection surface <NUM>.

Here, an example of dimensions of the image projection device <NUM> will be described. <FIG> illustrates an example of dimensions of the image projection device <NUM> in accordance with the first embodiment. Note that the following dimension examples are examples in which the refractive index of the light guide member <NUM> is assumed to be about <NUM> to <NUM>. Each of the dimensions indicates the length in the trajectory of the axis of the laser beam 40a corresponding to the center of the image projected onto the retina <NUM>. As illustrated in <FIG>, the length L1 between the scanning unit <NUM> and the reflection mirror <NUM> is <NUM> to <NUM>, and is <NUM>. <NUM> as an example. The length L2 between the reflection mirror <NUM> and an incident surface 31a of the light guide member <NUM> is <NUM>. <NUM> to <NUM>, and is <NUM>. <NUM> as an example. The length L3 of the lens <NUM> is <NUM> to <NUM>, and is <NUM> as an example. The length L4 between the incident surface 31a of the light guide member <NUM> and the reflection surface <NUM> is <NUM> to <NUM>, and is <NUM> as an example. The length L5 between the reflection surfaces <NUM> and <NUM> is <NUM> to <NUM>, and is <NUM> as an example. The length L6 between the reflection surfaces <NUM> and <NUM> is <NUM> to <NUM>, and is <NUM> as an example. The length L7 between the reflection surface <NUM> and an emission surface 31b of the light guide member <NUM> is <NUM> to <NUM>, and is <NUM> as an example. The length L8 between the emission surface 31b of the light guide member <NUM> and a cornea <NUM> of the eye <NUM> is <NUM> to <NUM>, and is <NUM> as an example. The incident angle θ1 of the laser beam 40a to the reflection mirror <NUM> is <NUM>° to <NUM>°, and is <NUM>° as an example. The incident angle θ2 of the laser beam 40a to the reflection surface <NUM> and the incident angle θ3 of the laser beam 40a to the reflection surface <NUM> are <NUM>° to <NUM>°, and are <NUM>° as an example. The incident angle θ4 of the laser beam 40a to the reflection surface <NUM> is <NUM>° to <NUM>°, and is <NUM>° as an example. The dimensions L2 to L7 in <FIG> have the same design result as long as the optical path length, that is, the total sum of the products of the refraction index and the distances is constant. The dimensions may be finely adjusted using this fact.

As described above, for example, the lengths L4, L5, L6, and L7 in the light guide member <NUM> are shorter in this order. For example, the incident angle θ1 of the laser beam 40a to the reflection mirror <NUM> and the incident angle θ4 of the laser beam 40a to the reflection surface <NUM> are substantially the same, the incident angle θ2 of the laser beam 40a to the reflection surface <NUM> and the incident angle θ3 of the laser beam 40a to the reflection surface <NUM> are substantially the same, and the incident angles θ2 and θ3 are substantially twice the incident angles θ1 and θ4. Thus, a high-quality image can be projected onto the retina <NUM>. The term "the incident angles are substantially the same" means that the incident angles are substantially the same to such an extent that a high-quality image can be projected onto the retina <NUM>, and the term "the incident angle is substantially twice another incident angle" means that the incident angle is substantially twice another incident angle to such an extent that a high-quality image can be projected onto the retina <NUM>.

As illustrated in <FIG>, the direction in which the laser beam 40a corresponding to the center of the image projected on the retina <NUM> is reflected by the scanning unit <NUM> and travels toward the reflection mirror <NUM> is substantially parallel to the direction in which the laser beam 40a is reflected by the reflection surface <NUM> of the light guide member <NUM> and travels toward the eye <NUM>. The reflection surface <NUM> is provided so as to be substantially orthogonal to the laser beam 40a when the laser beam 40a is reflected by the reflection surface <NUM> of the light guide member <NUM> and travels toward the eye <NUM>. The reflection surface <NUM> is provided substantially parallel to the reflection surface <NUM>. With such a configuration, a high-quality image can be projected onto the retina <NUM>. The term "substantially parallel" means a case in which the inclination is ±<NUM>° or less, may be a case in which the inclination is ±<NUM>° or less, or may be a case in which the inclination is ±<NUM>° or less. The term "substantially orthogonal" means that the intersecting angle is <NUM>° ± <NUM>°, may be <NUM>° ± <NUM>°, or may be <NUM>° ± <NUM>°.

The laser beam 40a corresponding to the center of the image projected onto the retina <NUM> substantially perpendicularly enters the incident surface 31a of the light guide member <NUM>. The term "substantially perpendicular" refers to <NUM>° ± <NUM>°, and may be <NUM>° ± <NUM>°, or may be <NUM>° ± <NUM>°. The effect of this configuration will be described with reference to <FIG>. <FIG> and <FIG> illustrate optical systems <NUM> and <NUM> for which simulations were performed, respectively, and <FIG> and <FIG> present simulation results obtained by evaluating the laser beam <NUM> with which the projection surface <NUM> is irradiated in the optical system <NUM> of <FIG> and the optical system <NUM> of <FIG>, respectively.

As illustrated in <FIG> and <FIG>, in the optical systems <NUM> and <NUM> used in the simulation, a plurality of the laser beams <NUM> are reflected by the reflection mirror <NUM>, are converged at the convergence point <NUM>, and then enter a light guide member <NUM> from an incident surface 131a. The light guide member <NUM> has a reflection surface <NUM>, and the plurality of the laser beams <NUM> are reflected by the reflection surface <NUM>, converged at the convergence point <NUM>, and then projected onto the projection surface <NUM>. In the optical system <NUM> of <FIG>, the incident surface 131a of the light guide member <NUM> is inclined to one side with respect to the laser beam 140a when the deflection angle of the scanning unit <NUM> is <NUM>°. In the optical system <NUM> of <FIG>, the incident surface 131a of the light guide member <NUM> is inclined to the other side with respect to the laser beam 140a when the deflection angle of the scanning unit <NUM> is <NUM>°.

As presented in <FIG> and <FIG>, when the laser beam 140a entered the light guide member <NUM> at an angle, a deflection and a deflection angle occurred in the plurality of the laser beams <NUM> with which the projection surface <NUM> was irradiated.

The simulation results reveal that the laser beam 40a preferably enters the incident surface 31a of the light guide member <NUM> substantially perpendicularly in order to project a high-quality image on the retina <NUM> in the image projection device <NUM> of the first embodiment.

<FIG> illustrates a state in which the image projection device <NUM> in accordance with the first embodiment is attached to a spectacle-type frame <NUM>. As illustrated in <FIG>, the spectacle-type frame <NUM> has a temple <NUM> and a rim <NUM>. The scanning unit <NUM> and the reflection mirror <NUM> are attached to the spectacle-type frame <NUM> near the temple <NUM>. The light guide member <NUM> is attached to the spectacle-type frame <NUM> near the rim <NUM>. The light source <NUM>, the scanning unit <NUM>, the lens <NUM>, the reflection mirror <NUM>, the reflection mirror <NUM>, and the lens <NUM> are housed in a housing <NUM> for protecting them and the laser beam <NUM>. When the housing <NUM> is attached to the spectacle-type frame <NUM>, the optical components in the housing <NUM> are attached to the spectacle-type frame. Since the light guide member <NUM> is formed of a glass material and the laser beam <NUM> passes through the inside of the light guide member <NUM>, most of the light guide member <NUM> is not located in the housing <NUM>. The term "most of the light guide member <NUM> is not located in the housing <NUM>" means that <NUM>% or more of the light guide member <NUM> is not located in the housing <NUM>, <NUM>% or greater of the light guide member <NUM> may be not located in the housing <NUM>, or <NUM>% or greater of the light guide member <NUM> may be not located in the housing <NUM>.

Since the laser beam <NUM> travels inside the light guide member <NUM> while being reflected by the reflection surfaces <NUM> to <NUM>, the reflection mirror <NUM> and the lens <NUM> can be disposed at positions away from the face of the user. In addition, since the reflection mirror <NUM>, the lens <NUM>, and the like are disposed at positions away from the face of the user, the housing <NUM> that houses the reflection mirror <NUM>, the lens <NUM>, and the like therein is provided away from the face of the user. Therefore, a sufficient clearance can be secured between the housing <NUM> and the user's face, and the housing <NUM> can be prevented from interfering with the user's face.

Since the light guide member <NUM> is formed of a glass material, most of the light guide member <NUM> is not required to be housed in the housing <NUM>. When the viewing angle of the image projected onto the retina <NUM> is increased, the distance between the eye <NUM> and the light guide member <NUM> (the length L8 in <FIG>) decreases. However, since most of the light guide member <NUM> is not housed in the housing <NUM>, the distance between the eye <NUM> and the light guide member <NUM> can be maintained at a length (for example, <NUM> or greater) with which the eyelashes are less likely to interfere with the light guide member <NUM> even when the viewing angle of the image is increased.

In addition, since the light guide member <NUM> formed of a glass material is disposed in front of the eye and the laser beam <NUM> is reflected multiple times inside the light guide member <NUM> and then applied to the retina <NUM>, the light guide member <NUM> has a shape extending along the face of the user. Therefore, compared to the case in which the laser beam is reflected by the projection mirror disposed in front of the eye and applied to the retina <NUM> as in the comparative example <NUM>, the protrusion of the image projection device <NUM> in the forward direction in front of the eye is reduced. Furthermore, since the laser beam <NUM> travels inside the light guide member <NUM>, the light guide member <NUM> does not need to be covered with the housing <NUM>. In this respect, the protrusion of the image projection device <NUM> in the forward direction in front of the eye is reduced. Thus, the design can be improved.

As described above, in the first embodiment, as illustrated in <FIG>, the plurality of the laser beams <NUM> (image light beams) scanned by the scanning unit <NUM> enter the light guide member <NUM> after being converged at the convergence point <NUM> (a second convergence point) before the light guide member <NUM> by the reflection mirror <NUM> (a first optical member). The light guide member <NUM> is formed of a glass material through which the laser beam <NUM> passes, and converges the plurality of the laser beams <NUM> reflected by a plurality of the reflection surfaces <NUM>, <NUM>, and <NUM> at the convergence point <NUM> (the first convergence point) in the eye <NUM> and then irradiates the retina <NUM> with the converged laser beams <NUM>. At the convergence point <NUM>, the lens <NUM> (a second optical member) is provided which causes the laser beam <NUM> to enter the last reflection surface <NUM> of the light guide member <NUM> as diffusion light. By providing the lens <NUM> at the convergence point <NUM>, the NA when the laser beam <NUM> enters the last reflection surface <NUM> of the light guide member <NUM> can be set to an appropriate value, and the plurality of the laser beams <NUM> reflected by the reflection surface <NUM> can be made to be substantially parallel light. Therefore, a high-quality image can be projected. By providing, behind the lens <NUM>, the light guide member <NUM> formed of a glass material through which the laser light <NUM> passes as illustrated in <FIG>, most of the light guide member <NUM> does not need to be housed in the housing <NUM>, and thus it is possible to secure a sufficient clearance between the image projection device <NUM> and the face of the user.

In addition, in the first embodiment, as illustrated in <FIG>, the scanning unit <NUM> and the reflection mirror <NUM> are attached near the temple <NUM> of the spectacle-type frame <NUM>, and the light guide member <NUM> is attached near the rim <NUM> of the spectacle-type frame <NUM>. The light guide member <NUM> has a shape extending from the front of the eye <NUM> of the user toward the temple <NUM> of the spectacle-type frame <NUM>. Therefore, the scanning unit <NUM>, the reflection mirror <NUM>, the lens <NUM>, and the light guide member <NUM> can be disposed along the contour of the face of the user. Therefore, a sufficient clearance can be secured between the image projection device <NUM> and the user's face. In addition, the image projection device <NUM> can be miniaturized.

In addition, in the first embodiment, as illustrated in <FIG>, the light guide member <NUM> has an odd number of the reflection surfaces <NUM>, <NUM>, and <NUM>, and a plurality of the laser beams <NUM> that are reflected by the reflection mirror <NUM> and travel obliquely forward enter the light guide member <NUM>. Therefore, the laser beam <NUM> travels inside the light guide member <NUM> from the temple <NUM> side of the spectacle-type frame <NUM> toward the eye <NUM>, and the scanning unit <NUM>, the reflection mirror <NUM>, the lens <NUM>, and the light guide member <NUM> can be disposed along the contour of the user's face.

In addition, in the first embodiment, as illustrated in <FIG>, the last reflection surface <NUM> of the plurality of the reflection surfaces <NUM>, <NUM>, and <NUM> of the light guide member <NUM> is a concave curved surface, and the remaining reflection surfaces <NUM> and <NUM> are substantially flat surfaces. Therefore, the laser beam <NUM> can be caused to travel inside the light guide member <NUM> from the temple <NUM> side of the spectacle-type frame <NUM> toward the eye <NUM>, and the scanning unit <NUM>, the reflection mirror <NUM>, the lens <NUM>, and the light guide member <NUM> can be disposed along the contour of the user's face. The reflection surfaces <NUM> and <NUM> are preferably substantially parallel to each other.

In the first embodiment, as illustrated in <FIG>, the reflection surface <NUM> (a first reflection surface) immediately before the last reflection surface <NUM> has the region 34c on which both the laser beam <NUM> reflected by the reflection surface <NUM> (a second reflection surface) immediately before the reflection surface <NUM> and the laser beam <NUM> reflected by the last reflection surface <NUM> are incident. The reflection surface <NUM> reflects the laser beam <NUM> reflected by the reflection surface <NUM> to the reflection surface <NUM> and transmits the laser beam <NUM> reflected by the reflection surface <NUM> in the region 34c thereof. As a result, the plurality of the laser beams <NUM> can be converged at the convergence point <NUM> to irradiate the retina <NUM> with the converged laser beams <NUM>. In addition, the light guide member <NUM> can be miniaturized.

In addition, in the first embodiment, the reflection surface <NUM> is substantially orthogonal to the optical axis after the laser beam 40a (central image light beam) corresponding to the center of the image is reflected by the reflection surface <NUM>. Thus, even when the plurality of the laser beams <NUM> reflected by the reflection surface <NUM> are refracted when emitted from the light guide member <NUM>, the plurality of the laser beams <NUM> can be converged at the convergence point <NUM>.

In addition, in the first embodiment, the convergence angle α2 at which the plurality of the laser beams <NUM> converge at the convergence point <NUM> is larger than the scanning angle α1 at which the scanning unit <NUM> scans the plurality of the laser beams <NUM>. Thus, the viewing angle of the image projected on the retina <NUM> can be increased. In addition, since most of the light guide member <NUM> does not need to be housed in the housing <NUM>, it is possible to secure a sufficient clearance between the image projection device <NUM> and the face of the user even when the convergence point <NUM> is brought close to the light guide member <NUM> in order to increase the viewing angle of the image. The convergence angle α2 may be equal to or greater than the scanning angle α1.

In addition, in the first embodiment, as illustrated in <FIG>, the laser beam <NUM> travels obliquely forward from the side closer to the user's face than the scanning unit <NUM> attached near the temple <NUM> of the spectacle-type frame <NUM>, enters the scanning unit <NUM>, travels backward from the scanning unit <NUM>, is then reflected obliquely forward by the reflection mirror <NUM>, and enters the light guide member <NUM> attached near the rim <NUM> of the spectacle-type frame <NUM>. Thus, for the same reason as described with reference to <FIG>, it is possible to project a high-quality image with reduced distortion onto the retina <NUM>.

<FIG> illustrates an image projection device <NUM> in accordance with a second embodiment. In the image projection device <NUM> of the second embodiment, as illustrated in <FIG>, a light guide member 30a includes a main body portion <NUM> in which the plurality of the laser beams <NUM> incident on the incident surface 31a travel while being reflected by the reflection surfaces <NUM> to <NUM> in order to be applied to the eye <NUM> of the user, and a cover portion <NUM> attached to the main body portion <NUM> so as to cover the reflection surfaces <NUM> and <NUM> from the outside. The main body portion <NUM> and the cover portion <NUM> are formed of glass materials having substantially the same refractive index, and are formed of, for example, the same glass material. The emission surface 31b through which the plurality of the laser beams <NUM> reflected by the reflection surface <NUM> are emitted from the main body portion <NUM> is flatter than the reflection surface <NUM>. An opposite surface 39a of the cover portion <NUM> from the emission surface 31b of the main body portion <NUM> with respect to the reflection surface <NUM> is flatter than the reflection surface <NUM>. The opposite surface 39a of the cover portion <NUM> and the emission surface 31b of the main body portion <NUM> are, for example, substantially parallel to each other and substantially flat surfaces. In addition, all of the reflection surfaces <NUM> to <NUM> are half mirrors. Other configurations are the same as those of the first embodiment, and thus description thereof will be omitted.

<FIG> illustrates a case in which the user views the outside world through the light guide member 30a in the second embodiment. As illustrated in <FIG>, the emission surface 31b of the main body portion <NUM>, the reflection surface <NUM>, and the surface 39a of the cover portion <NUM> are located in front of the eye <NUM> of the user. Since the refractive indexes of the main body portion <NUM> and the cover portion <NUM> are substantially the same and the surface 39a of the cover portion <NUM> and the emission surface 31b of the main body portion <NUM> are surfaces having high flatness, the user can visually recognize the outside world through the reflection surface <NUM> that is a half mirror as indicated by a line of sight <NUM> with less discomfort.

In the second embodiment, the light guide member 30a includes the main body portion <NUM> through which the plurality of the laser beams <NUM> that are repeatedly reflected by the plurality of the reflection surfaces <NUM> to <NUM> and applied to the retina <NUM> of the user pass, and the cover portion <NUM> that covers the last reflection surface <NUM> and has substantially the same refraction index as the main body portion <NUM>. The reflection surface <NUM> is a half mirror, and the surface 39a of the cover portion <NUM> and the emission surface 31b of the main body portion <NUM> are flatter than the reflection surface <NUM>. This configuration allows the user to visually recognize the outside world with less discomfort as illustrated in <FIG>. Therefore, it is possible to support augmented reality (AR) in which virtual visual information is superimposed on real scenery and displayed. The term "the refractive indexes of the main body portion <NUM> and the cover portion <NUM> are substantially the same" means that the refractive indexes are the same to such an extent that the user can visually recognize the outside world with less discomfort, and means that the difference between the refractive indexes is <NUM> or less.

In the second embodiment, the surface 39a of the cover portion <NUM> and the emission surface 31b of the main body portion <NUM> are substantially parallel to each other and are substantially flat surfaces. This configuration allows the user to visually recognize the outside world with far less discomfort. Note that the surface 39a of the cover portion <NUM> may be a concave curved surface or a convex curved surface according to the correction power in order to correct the vision of the user. Therefore, the term "the surface 39a of the cover portion <NUM> is a substantially flat surface" includes a case in which the surface 39a is curved to the extent of vision correction, and means that the surface 39a is a flat surface to such an extent that the user can visually recognize the outside world with less discomfort. The term "the surface 39a of the cover portion <NUM> and the emission surface 31b of the main body portion <NUM> are substantially parallel to each other" means that they are parallel to each other to such an extent that the user can visually recognize the outside with less discomfort even when the surface 39a of the cover portion <NUM> is curved to the extent that corrects vision.

Further, as in the second embodiment, the cover portion <NUM> preferably covers both the reflection surfaces <NUM> and <NUM>. This configuration reduces a sense of discomfort at the boundary between the reflection surfaces <NUM> and <NUM> when the user views the outside world.

In the second embodiment, the main body portion <NUM> may be integrally formed as a whole, or a first portion 38a formed of the substantially flat reflection surface and a second portion 38b having the free-curved reflection surface <NUM> may be separately formed and then bonded together. Since the first portion 38a and the second portion 38b are bonded to each other after being molded using separate molds, ease of manufacturing is improved. On the other hand, mass productivity is improved by integrally forming the main body portion <NUM> as a whole.

<FIG> illustrates an image projection device <NUM> in accordance with a third embodiment. In the image projection device <NUM> of the third embodiment, as illustrated in <FIG>, the light guide member 30a includes the main body portion <NUM> and the cover portion <NUM> as in the second embodiment. Similarly to the second embodiment, the main body portion <NUM> includes the reflection surface <NUM> located closer to the eye <NUM> of the user, and the reflection surface <NUM> located farther from the eye <NUM> of the user and on which the plurality of the laser beams <NUM> are incident before entering the last reflection surface <NUM>. The difference from the second embodiment is that the cover portion <NUM> has a reflection surface <NUM> at the opposite side from the emission surface 31b of the main body portion <NUM> with respect to the reflection surface <NUM>. The reflection surface <NUM> is a flat surface similar to the reflection surfaces <NUM> and <NUM>, and is substantially flush with the reflection surface <NUM>. The reflection surfaces <NUM>, <NUM>, <NUM> and <NUM> all reflect a part of the incident laser beam <NUM> and transmit the remainder. The plurality of the laser beams <NUM> are reflected by the plurality of the reflection surfaces <NUM>, <NUM>, <NUM>, and <NUM> the same number of times and are applied to the eye <NUM>.

The number of reflections of the laser beam <NUM> in the light guide member 30a increases when the light guide member 30a is thinned, the light guide member <NUM> protrudes in the lateral direction to reduce interference with the user's face, and/or the viewing angle is secured. In this case, when the plurality of the laser beams <NUM> are converged at the convergence point <NUM>, some laser beams 40c of the plurality of the laser beams <NUM> enter the reflection surface <NUM> from the side of the eye <NUM>, pass through the reflection surface <NUM>, are reflected by the reflection surface <NUM> of the cover portion <NUM>, then enter again the reflection surface <NUM> from the opposite side (opposite surface) from the eye <NUM>, pass through the reflection surface <NUM>, are reflected by the reflection surface <NUM>, and are then reflected by the reflection surface <NUM> to be applied to the eye <NUM>. The remaining laser beams 40a and 40b of the plurality of the laser beams <NUM> are reflected by the reflection surface <NUM> without passing through the reflection surface <NUM>, and are applied to the eye <NUM>. Although not illustrated, some of the laser beams 40a and 40b also pass through the reflection surface <NUM>, but this light is not applied to the retina <NUM> and thus does not need to be considered.

In order to reduce the variation in luminance on the image projected on the retina <NUM>, it is preferable to reduce the difference between the luminance of the laser beams 40a and 40b that do not pass through the reflection surface <NUM> and are reflected by the reflection surface <NUM> and applied to the eye <NUM> and the luminance of the laser beam 40c that is reflected by the reflection surface <NUM> after passing through the reflection surface <NUM> and applied to the eye <NUM> when they enter the eye <NUM>. On the other hand, the light intensity of the laser beams 40a to 40c incident on the eye <NUM> is preferably large to some extent. When the outside world is viewed through the light guide member 30a, the transmittance of the light guide member 30a is preferably about <NUM>% to <NUM>%. A method for achieving the above configurations will be described below.

In the following description, it is assumed that the laser beams 40a to 40c are reflected four times in total by the reflection surfaces <NUM>, <NUM>, and <NUM>, and are applied to the eye <NUM> by the fifth reflection by the last reflection surface <NUM>. Reflectance and the like of each surface are specified as follows. For simplification, it is assumed that the sum of the transmittance and the reflectance of the same surface is <NUM> (transmittance + reflectance = <NUM>).

In this case, the light intensity Pcr when the eye <NUM> is irradiated with the laser beams 40a and 40b that are reflected by the reflection surface <NUM> without passing through the reflection surface <NUM> is calculated as follows.

On the other hand, the light intensity Pct when the eye <NUM> is irradiated with the laser beam 40c that passes through the reflection surface <NUM>, enters the reflection surface <NUM> again, and is reflected by the reflection surface <NUM> is calculated as follows.

Here, for simplification, it is assumed that the transmittance Tp of the incident surface 31a is <NUM>. In this case, the expressions (<NUM>) and (<NUM>) can be modified as follows. <MAT> <MAT>.

In order to reduce variation in luminance on the image projected on the retina <NUM>, expression (<NUM>)/expression (<NUM>) is preferably close to <NUM>. In addition, since the expressions (<NUM>) and (<NUM>) are ratios of the intensity of the light with which the eye <NUM> is irradiated to the intensity of the incident light, the expressions (<NUM>) and (<NUM>) are preferably large.

The fact that expression (<NUM>)/expression (<NUM>) is close to <NUM> is expressed as follows.

Here, since the reflection surface <NUM> and the reflection surface <NUM> are the same continuous surface and the user views the outside world through the reflection surface <NUM> and the reflection surface <NUM>, the reflectances are preferably substantially the same. Therefore, in the following description, it is assumed that Rb = Rd. In this case, the expression (<NUM>) becomes as follows.

Tc = <NUM> means that the reflectance on the reflection surface <NUM> is <NUM> and the laser beams 40a to 40c are not reflected by the reflection surface <NUM> and are not projected onto the retina <NUM>. Therefore, it is preferable to set Tc to a value smaller than <NUM> while considering the balance.

Here, when the user views the outside world through the light guide member 30a for, for example, augmented reality (AR) or the like, light from the outside world reaches the eye <NUM> of the user through the reflection surfaces <NUM> and <NUM>, the reflection surface <NUM>, and the reflection surface <NUM>. In sunglasses, it is generally said that the transmittance of light from the outside world is suitably about <NUM>% to <NUM>%. The transmittance Tar of the reflection surfaces <NUM> and <NUM>, the reflection surface <NUM>, and the reflection surface <NUM> is expressed as follows.

Based on the above, the ranges of Ra, Rb, Rc, Rb, Rc, and Rd are presented below.

It is known that a luminance difference of about <NUM>% to <NUM>% cannot be recognized so much as human visibility. Tc<NUM> in the expression (<NUM>') can be transformed into (<NUM> - Rc)<NUM>, and Pcr/Pct = (<NUM> - Rc)<NUM> can be represented by a graph as illustrated in <FIG>. It can be seen from <FIG> that the range of Rc is preferably as follows in order to reduce the luminance difference to about <NUM>% to <NUM>%.

As described above, from the viewpoint of the intensity of the light with which the eye <NUM> is irradiated, the expression (<NUM>) is preferably large. Rc in the expression (<NUM>) has the above-mentioned restriction, and Rb will be described later, but at least Ta × Ra × Ra × Ta = (<NUM> - Ra)<NUM> × Ra<NUM> included in the expression (<NUM>) is preferably large. In this case, since the maximum value is obtained when Ra = <NUM>, it can be said that the range of Ra is preferably as follows.

<FIG> presents relationships between Rc and Pcr/Pi when Ra is fixed to <NUM>% and Rb is varied to <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, and <NUM>% in the expression (<NUM>). As described above, since the expression (<NUM>) indicates the ratio of the intensity of the light with which the eye <NUM> is irradiated to the intensity of the incident light, the expression (<NUM>) is preferably large. Even when the laser output of the light source <NUM> is several mW and the intensity of the light with which the eye <NUM> is irradiated is attenuated to about <NUM>/<NUM> of several mW, the ratio of the intensity of the light with which the eye <NUM> is irradiated to the intensity of the incident light is preferably about <NUM>%. Therefore, from <FIG>, it can be said that Rb preferably satisfies Rb ≥ <NUM>%.

<FIG> presents relationships between Rc and Tar when Ra is fixed to <NUM>% and Rb is varied to <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, and <NUM>% in the expression (<NUM>). As described above, the transmittance of light from the outside is suitably about <NUM>% to <NUM>%. Therefore, from <FIG>, it can be said that Rb preferably satisfies <NUM>% ≤ Rb ≤ <NUM>%.

Therefore, it can be said from <FIG> that the range of Rb is preferably as follows.

In addition, as described above, since the user views the outside world through the reflection surface <NUM> and the reflection surface <NUM> that are continuous surfaces, Rb and Rd are preferably equal to each other. Therefore, it can be said that the range of Rd is preferably as follows.

Range of the reflectance Ra of the reflection surface <NUM> (a first reflection surface): <MAT>.

Range of the reflectance Rb of the reflection surface <NUM> (a second reflection surface): <MAT>.

Range of the reflectance Rc of the reflection surface <NUM> (a last reflection surface): <NUM>% <MAT>.

Range of the reflectance Rd of the reflection surface <NUM> (a third reflection surface): <MAT> can be said to be preferable.

In the third embodiment, some laser beams 40c of the plurality of the laser beams <NUM> enter the reflection surface <NUM> again after passing through the reflection surface <NUM>, are reflected by the reflection surface <NUM>, and are applied to the retina <NUM>, and the remaining laser beams 40a and 40b are reflected by the reflection surface <NUM> without passing through the reflection surface <NUM>, and are applied to the retina <NUM>. In this case, when the laser beams 40a to 40c enter the eye <NUM>, the ratio of the luminance of the laser beam 40c to the luminance of the laser beams 40a and 40b is set to <NUM>% or greater. This configuration can reduce a variation in luminance on the image projected on the retina <NUM>.

The reflectance Rc of the reflection surface <NUM> is set to <NUM>% or less. By setting the reflectance Rc of the reflection surface <NUM> to <NUM>% or less, as illustrated in <FIG>, the luminance difference between the laser beam 40c that is reflected by the reflection surface <NUM> after passing through the reflection surface <NUM> and the laser beams 40a and 40b that are reflected by the reflection surface <NUM> without passing through the reflection surface <NUM> can be reduced to about <NUM>%. Therefore, it is possible to reduce a variation in luminance on the image projected on the retina <NUM>. In order to reduce the luminance difference, Rc is preferably <NUM>% or less, more preferably <NUM>% or less, and further preferably <NUM>% or less. On the other hand, if Rc becomes too small, the reflection amount of the laser beam <NUM> on the reflection surface <NUM> becomes small, and in order to secure the light intensity of the laser beam <NUM> applied to the eye <NUM>, for example, the output of the light source <NUM> is increased. Therefore, Rc is preferably <NUM>% or greater, more preferably <NUM>% or greater, and further preferably <NUM>% or greater.

The reflectance Rb of the reflection surface <NUM> and the reflectance Rd of the reflection surface <NUM> are adjusted to be substantially the same. This configuration can make luminance difference among the laser beams 40a to 40c depending on presence or absence of reflection by the reflection surface <NUM> small even in a case in which the laser beams 40a and 40b are not reflected by the reflection surface <NUM> and the laser beam 40c is reflected by the reflection surface <NUM>. The term "substantially the same" means that the ratio of the reflectance Rd of the reflection surface <NUM> to the reflectance Rb of the reflection surface <NUM> is <NUM>% to <NUM>%, and may be <NUM>% to <NUM>%.

The reflectance Rb of the reflection surface <NUM> and the reflectance Rd of the reflection surface <NUM> are adjusted to be <NUM>% or greater and <NUM>% or less. This configuration allows the outside world to be viewed with appropriate brightness when the outside world is viewed through the light guide member 30a in AR or the like,.

The reflectance Ra of the reflection surface <NUM> is preferably <NUM>% or greater and <NUM>% or less, the reflectances Rb and Rd of the reflection surfaces <NUM> and <NUM> are preferably <NUM>% or greater and <NUM>% or less, and the reflectance Rc of the reflection surface <NUM> is preferably <NUM>% or greater and <NUM>% or less in order to reduce the luminance difference among the plurality of the laser beams <NUM> applied to the eye <NUM> to be small, ensure a large light intensity of the laser beams <NUM> incident on the eye <NUM>, and ensure visibility of the outside world through the light guide member 30a.

In the first embodiment and the second embodiment, the reflection mirror <NUM> may be another optical member such as a combination of a lens and a mirror or a diffraction element as long as the reflection mirror <NUM> has a positive condensing power and optical characteristics of converging and then diffusing the plurality of the laser beams <NUM>.

In the first and second embodiments, the lens <NUM> may have a function of reducing chromatic aberration. In addition, the lens <NUM> is preferably designed to reduce curvature of image. The lens <NUM> may be another optical member such as a mirror or a diffraction element as long as the lens <NUM> can cause the laser light <NUM> to enter the reflection surface <NUM> of the light guide member <NUM> as diffusion light.

In the first embodiment and the second embodiment, the case in which the image projection device <NUM> is attached to the spectacle-type frame <NUM> has been described as an example. However, as long as the frame can be worn on the user's face and the image projection device <NUM> can be placed in front of the user's eye, the frame is not limited to the spectacle-type frame and may be another type such as a goggle-type frame, an eye-patch-type frame, an ear-hanging frame, or a helmet-mounted frame.

Claim 1:
An image projection device (<NUM>, <NUM>) comprising:
a light source (<NUM>);
a control unit (<NUM>) configured to generate an image light beam (<NUM>) based on image data and control emission of the image light beam from the light source;
a scanning unit (<NUM>) that is attached to a frame (<NUM>) to be worn on a face of a user and two-dimensionally scans the image light beam emitted from the light source;
a light guide member (<NUM>, 30a) that is attached to the frame and disposed in front of an eye (<NUM>) of the user, is formed of a glass material through which a plurality of image light beams (<NUM>) emitted from the scanning unit at different times pass, has a plurality of reflection surfaces (<NUM>, <NUM>, <NUM>) that reflect the plurality of image light beams, converges the plurality of image light beams reflected by the plurality of reflection surfaces at a first convergence point (<NUM>) in the eye of the user, and then irradiates a retina (<NUM>) of the user with the converged image light beams;
a first optical member (<NUM>) that is attached to the frame and converges the plurality of image light beams emitted from the scanning unit at a second convergence point (<NUM>) before the light guide member and then causes the plurality of image light beams to enter the light guide member; and
a second optical member (<NUM>) that is disposed at the second convergence point and causes each of the plurality of image light beams to enter a last reflection surface (<NUM>) of the plurality of reflection surfaces, wherein the last reflection surface reflects the plurality of image light beams last among the plurality of reflection surfaces included in the light guide member, as diffusion light.