TWI714451B - Short distance optical system - Google Patents

Abstract

A short-distance optical system, applied to a miniature head-mounted display, in which a partially penetrating partially reflective element, a first phase retarder, a second phase retarder, and a reflective polarizing element are sequentially arranged in front of the display screen to The emitted light is derived through multiple phase delays and reflections, so that the shortest distance between the display screen and the optical system is obtained under the condition of the approximate optical path, and the miniaturization of the head-mounted display is achieved. The invention uses a combination of a half-wavelength retarder and a quarter-wave retarder as the first retarder and the second retarder to improve the phase retardation conversion efficiency of the retarder for different wavelengths, thereby Improve image clarity.

Description

Short distance optical system

The present invention relates to an optical system, in particular to a short-distance optical system that can be applied to a miniature head-mounted display.

Head-mounted display (Head-mounted display) is a very popular virtual reality (VR) product in the near future. It is usually in the form of an eye mask or a helmet. The display is placed close to the user’s eyes, and the focus is adjusted through the optical path. Projecting images to the eyes at close range creates a virtual image magnification effect and increases the sense of presence.

Figure 1 shows a schematic diagram of the optical system of a head-mounted display in virtual reality. The display screen 10 projects an image, which passes through a light path with an optical path d and then enters the optical module 20. The optical module 20 is a single lens. Or a combination of multiple lenses to guide the image into the user’s eyes 22, assuming that the optical path d is 40mm, and the length of the head-mounted display is the optical path d plus the thickness of the optical module and the eye distance , Shell, etc., the sum of which is slightly cumbersome for eye masks and helmets worn on the head, and burdens the user’s nose, top of the head, and neck. Therefore, the current technology is dedicated to the optical The length of the system is shortened to reduce the thickness of the head-mounted display, which is convenient for users to wear and use.

In addition, in order for the virtual images provided by the head-mounted display to be visually reproduced, high-standard display quality must be obtained. Therefore, the present invention proposes a short-distance optical system, which can not only shorten the distance of the optical system, but also improve the clarity of the displayed image, and effectively solve the above-mentioned problems. The specific structure and implementation methods will be detailed later.

The main purpose of the present invention is to provide a short-distance optical system, which utilizes the first and second phase retarders composed of a half-wavelength retarder and a quarter-wave retarder to extend the phase of the retarder Delay the effective band and improve the conversion efficiency of the phase retarder for different wavelengths to eliminate image chromatic aberration and improve image clarity.

Another object of the present invention is to provide a short-distance optical system, which is provided with optical elements such as partially reflective and partially penetrating elements, first and second phase retarders, and reflective polarizing elements before the display screen of the head-mounted display. Using multiple phase delays and reflections of light to reach an approximate length of optical path, the distance between the display screen and the optical system is shortened, and the head-mounted display is miniaturized.

To achieve the above objective, the present invention provides a short-distance optical system, which is applied to a mini head-mounted display with a display screen. The display screen is used to output images and light. The short-distance optical system includes: a part of reflecting and partly penetrating elements, Corresponding to the display screen setting, receiving light from the display screen, and partially penetrating and partially reflecting the light; a first phase retarder, corresponding to the partially reflecting part of the penetrating element, receiving the partially penetrating part of the reflecting part of the penetrating element , Perform phase retardation to form the first polarized light; a second phase retarder, corresponding to the first phase retarder, receive the first polarized light and perform phase retardation to form the second polarized light; and a reflective polarizing element , Corresponding to the second phase retarder setting, receiving the second polarized light, partially reflecting the second polarized light, so that the second polarized light reflected by the reflective polarizing element passes through the first phase retarder, the second phase retarder and partially reflected After partially penetrating the element, it is reflected back to the reflective polarizing element and passed through; among them, when the first phase retarder is a half-wavelength retarder, the second phase retarder corresponds to a quarter-wave retarder When the first retarder is a quarter-wave retarder, the second retarder is a half-wave retarder.

According to the embodiment of the present invention, it further includes a lens, which is arranged on any one side of the partially reflective and partially penetrating element, the first phase retarder, the second phase retarder and the reflective polarizing element, and the display screen The output image is imported into the eyes of at least one person.

Further, the lens can be selected from spherical lenses, aspheric lenses, Fresnel lenses and a combination of multi-element lenses.

Further, between the human eye and the lens may include one or more pieces of flat glass, and between the lens and the display screen may further include one or more pieces of flat glass.

Furthermore, the partially reflective and partially penetrating element, the first phase retarder, the second phase retarder, and the reflective polarizing element can be thin-film materials or optical coatings, and are arranged on the flat glass in the form of coating, coating or bonding .

According to an embodiment of the present invention, the light emitted from the display screen and entering the partially reflective and partially penetrating element is circularly polarized light.

According to the embodiment of the present invention, it further includes at least one linear polarizer, circular polarizer or phase retarder for adjusting the polarization state of the display screen, and the linear polarizer, circular polarizer and phase retarder are thin film materials or optical coatings, And it is arranged on the display screen or partly reflective partly penetrating element in the form of coating, coating or bonding.

According to an embodiment of the present invention, the light emitted by the display screen is linearly polarized light, and a third phase retarder is further provided between the display screen and the partially reflective and partially penetrating element, so that the linearly polarized light is phased by the third phase retarder After the delay, it is converted into circularly polarized light.

According to an embodiment of the present invention, the light emitted by the display is non-polarized light. A linear polarizer and a third phase retarder are further arranged between the display and the partially reflective and partially transmissive element. The linear polarizer is arranged on the display and Between the third phase retarders, the non-polarized light passes through the linear polarizer to become linearly polarized light, and the linearly polarized light is phase retarded by the third phase retarder and then converted into circularly polarized light.

Further, the above-mentioned third phase retarder may be a quarter-wave retarder.

According to an embodiment of the present invention, the light emitted by the display screen is non-polarized light, and a circular polarizing plate is arranged between the display screen and the partially reflective and partially penetrating element, so that the non-polarized light is converted into circularly polarized light after passing through the circular polarizing plate. .

According to an embodiment of the present invention, the second polarized light reflected by the reflective polarizer passes through the first phase retarder and the second phase retarder for phase retardation to form the third polarized light, and the third polarized light passes through the partial After the reflective part is partially reflected by the penetrating element, the first phase retarder and the second phase retarder undergo phase retardation to form a fourth polarized light, and the fourth polarized light passes through the reflective polarizing element; where the first polarized light , The second polarized light and the fourth polarized light are linearly polarized light, and the third polarized light is circularly polarized light.

Detailed descriptions are given below by specific embodiments, so that it is easier to understand the purpose, technical content, features, and effects of the present invention.

The present invention provides a short-distance optical system, which is applied to a miniature head-mounted display, which uses a plurality of optical elements to reflect light multiple times, and the optical elements are equipped with phase retarders of different angles, which can effectively improve the image quality Sharpness eliminates image chromatic aberration, and can use multiple phase delays and reflections of light to reach an approximate length of optical path, thereby shortening the distance between the display device and the optical system, and miniaturizing the head-mounted display.

Please refer to FIG. 2 and FIG. 3, which are respectively a schematic diagram and an exploded view of the short-distance optical system provided by the first embodiment of the present invention. As shown in Figure 2, the short-distance optical system of this embodiment is arranged in a miniature head-mounted display and is located at the front end of the display screen 10. A part of the reflective and partially penetrating elements 11 are arranged in order from the adjacent display screen 10 sides. , A first phase retarder 12, a second phase retarder 13, a reflective polarizing element 14 and a lens 15. In the present invention, the first phase retarder 12 and the second phase retarder 13 are a combination of a half-wavelength retarder and a quarter-wave retarder; specifically, when the first phase retarder 12 is provided Is a half-wavelength retarder, the second phase retarder 13 is correspondingly set as a quarter-wave retarder, and when the first phase retarder 12 is set as a quarter-wave retarder, the second phase retarder The retarder 13 is correspondingly set as a half-wavelength phase retarder.

As shown in Figure 3, in this embodiment, the display screen 10 outputs an image and emits light 1. The light 1 can be polarized or unpolarized light. When the light 1 is polarized light, the polarized light can be linearly polarized. Light, circularly polarized light or other polarization states. The partially reflective and partially penetrating element 11 is arranged corresponding to the display screen 10, receiving the incident light 1 and partially reflecting the passing light 1 back to the display screen 10, and the remaining partially reflective and partially penetrating element 11; a preferred embodiment Among them, the partially reflective and partially penetrating element 11 is half reflective and half penetrating. The first phase retarder 12 is disposed corresponding to the partially reflective and partially penetrating element 11, receives the light 1 that penetrates the partially reflective and partially penetrating element 11, and performs the first phase retardation to form the first polarized light 2. The second phase retarder 13 is arranged corresponding to the first phase retarder 12, receives the first polarized light 2 of the first phase retarder 12, and performs a second phase retardation to form the second polarized light 3. The reflective polarizing element 14 is arranged corresponding to the second phase retarder 13, receives the second polarized light 3 of the second phase retarder 13, and totally reflects the second polarized light 3. The second polarized light 3 reflected by the reflective polarizing element 14 passes through the second phase retarder 13 and the first phase retarder 12 for the third and fourth phase retardation to form the third polarized light 4. After the third polarized light 4 is partially reflected by the partially reflective and partially penetrating element 11, it passes through the first phase retarder 12 and the second phase retarder 13 for the fifth and sixth phase retardation in order to form the fourth phase. Polarized light 5. At this time, the phase difference of the fourth polarized light 5 meets the transmission condition of the reflective polarizing element 14. Therefore, the reflective polarizing element 14 can pass the fourth polarized light 5 that has undergone six phase delays. The lens 15 can be arranged on any side of any element in the above-mentioned optical system to guide the image output by the display screen 10 into the human eye 22.

The partially penetrating partially reflective element 11, the first phase retarder 12, the second phase retarder 13, and the reflective polarizing element 14 provided in the present invention can be independent elements. As shown in Figure 2, these optical elements The element can also be a thin-film material or an optical coating, and is arranged on one or more pieces of flat glass 16 in the form of coating, coating or bonding. One or more pieces of flat glass 16 can be arranged between the human eye 22 and the lens 15, or It is between the lens 15 and the display screen 10. In the first embodiment, the partially penetrating partially reflective element 11 is an independent partially penetrating partially reflective element, and the first phase retarder 12, the second phase retarder 13 and the reflective polarizing element 14 are pasted or The coating method is set on the same flat glass 16.

The single lens 15 provided in the present invention can be a convex lens. As shown in Figure 2, the lens 15 can be provided on the partially penetrating and partially reflective element 11, the first phase retarder 12, the second phase retarder 13, and Either side of the reflective polarizing element 14 is used to adjust the focal length. No matter it is placed between any two optical elements mentioned above, it can finally achieve the effect of shortening the optical system. In the first embodiment, the lens 15 is placed on the reflective The left side of the polarizing element 14 is close to the human eye 22. In addition, the lens 15 in the present invention may be a spherical lens, an aspheric lens, a Fresnel lens, or a combination of the foregoing multi-element lenses.

Since the first phase retarder 12 and the second phase retarder 13 in the present invention are a combination of a quarter-wave retarder and a half-wave retarder, the light is reflected twice on the transmission optical path. As a result, there will be six phase delays, a total delay of two and a quarter of a wavelength.

Further, taking the first phase retarder 12 and the second phase retarder 13 as a quarter-wave retarder and a half-wave retarder, respectively, as an example, the light 1 emitted by the display screen 10 in the above embodiment will be described in detail. Please refer to Figure 4A to Figure 4C for the transfer process when entering the optical system. First, in Figure 4A, the display screen 10 of this embodiment outputs an image, and the emitted light 1 is operated in the polarization state of circularly polarized light. When the circularly polarized light is received by the partially reflective and partially penetrating element 11, it is partially reflected. The partially penetrating element 11 partially penetrates the circularly polarized light to the first phase retarder 12 and partially reflects back to the display screen 10, while the circularly polarized light penetrating the partially reflective and partially penetrating element 1 passes through the first phase retarder 12, It will increase the phase retardation by a quarter wavelength and transform it into linearly polarized light (first polarized light 2). After the linearly polarized light passes through the second phase retarder 13, the linearly polarized light is delayed by one phase difference, and its phase retardation is four. Then, the linearly polarized light (the second polarized light 3) is totally reflected at the reflective polarizing element 14.

Next, in Figure 4B, the linearly polarized light (second polarized light 3) reflected by the reflective polarizing element 14 returns to the second retarder 13 and the first retarder 12 again, increasing the quarter-wave retardation Then, circularly polarized light (third polarized light 4) is formed, and then, the circularly polarized light is partially penetrated and partially reflected at the partially penetrating partially reflective element 11.

After that, in Figure 4C, the circularly polarized light (third polarized light 4) partially reflected by the partially penetrating partially reflective element 11 passes through the first phase retarder 12 and the second phase retarder 13 in sequence, increasing by four points After one wavelength is retarded, it is converted into linearly polarized light (fourth polarized light 5). Then, the linearly polarized light reaches the reflective polarizing element 14. The reflective polarizing element 14 penetrates the linearly polarized light that has undergone multiple phase delays and enters the lens 15. Finally, the lens 15 guides the transmitted light into at least one human eye 22 .

In an implementation aspect of the above embodiment, the light 1 emitted by the display screen 10 is circularly polarized light with a 45 degree phase difference, and the first phase retarder 12 is a quarter-wave retarder, which can make circularly polarized light The polarization state is delayed by 45 degrees. Therefore, the first polarized light 2 is linearly polarized light with a 90 degree phase difference. The second phase retarder 13 is a half-wavelength phase retarder, which can further retard the polarization state of linearly polarized light by 90 degrees of phase difference, then the second polarized light 3 is linearly polarized light with 180 degrees of phase difference, and the third The polarized light 4 is circularly polarized light with a phase difference of 315 degrees, and the fourth polarized light 5 is linearly polarized light with a phase difference of 90 degrees. In this embodiment, the reflective polarizing element 14 only provides the polarized light with a phase difference of 90 degrees or 270 degrees to penetrate, so the fourth polarized light 5 can penetrate the reflective polarizing element 14.

In another implementation aspect of the above embodiment, the light 1 emitted by the display screen 10 is circularly polarized light with a phase difference of 135 degrees, and the first phase retarder 12 is a quarter-wave retarder, which can make circular polarization The polarization state of the light is delayed by a 45-degree phase difference. Therefore, the first polarized light 2 is a linearly polarized light with a 180-degree phase difference. The second phase retarder 13 is a half-wavelength phase retarder, which can further retard the polarization state of linearly polarized light by 90 degrees of phase difference, then the second polarized light 3 is linearly polarized light with a phase difference of 270 degrees, and the third The polarized light 4 is circularly polarized light with a phase difference of 45 degrees, and the fourth polarized light 5 is linearly polarized light with a phase difference of 180 degrees. In this embodiment, the reflective polarizing element 14 also only provides the penetration of 180-degree phase difference polarized light, so the fourth polarized light 5 can penetrate the reflective polarizing element 14.

In addition, in the present invention, between the display screen 10 and the partially reflective and partially penetrating element 11, one or more linear polarizers, circular polarizers or phase retarders can be added according to the polarization of the display screen 10 to adjust the display screen 10. The material of linear polarizer, circular polarizer and phase retarder can be thin film material or optical coating, which can be set on the display screen 10 or partially reflective and partially penetrating element 11 in the form of coating, coating or bonding on.

Please refer to FIG. 5, which is an exploded view of the short-distance optical system provided by the second embodiment of the present invention. In this embodiment, the first phase retarder 12 and the third phase retarder 17 are quarter-wave retarders, and the second retarder 13 is a half-wave retarder as an example. . If the light 1 emitted by the display screen 10 is not circularly polarized light but linearly polarized light, a third phase retarder 17 needs to be added behind the display screen 10 to make the linearly polarized light emitted by the display screen 10 undergo the first phase delay. Increase the quarter-wavelength phase retardation and convert it into circularly polarized light 1'. Next, the transmission state of the circularly polarized light 1'after entering the partially reflective and partially penetrating element 11 is the same as that of the first embodiment, and the partially reflective and partially penetrating element 11 partially reflects and partially penetrates the circularly polarized 1'light. The penetrating circularly polarized light continues to pass through the first phase retarder 12 for the second phase retardation, increasing the quarter-wavelength phase retardation, and converting it into linearly polarized light (first polarized light 2), and the linearly polarized light passes through the second The phase retarder 13 performs the third phase retardation, and the phase retardation is to one wavelength. Then, the linearly polarized light (the second polarized light 3) is totally reflected by the reflective polarizing element 14 back to the second phase retarder 13 and the first phase retarder 12, and after the fourth and fifth phase retardation, the transition It is circularly polarized light (third polarized light 4). The circularly polarized light penetrates the first phase retarder 12 and reaches the partially reflective and partially penetrating element 11, and then is partially reflected by the partially reflective and partially penetrating element 11 back to the first phase retarder 12 and the second phase retarder 13, and proceed to the sixth After the second and seventh phase delays, it is converted into linearly polarized light (fourth polarized light 5). At this time, the phase difference of the linearly polarized light meets the penetration condition of the reflective polarizing element 14, and can penetrate the reflective polarizing element 14 and enter the lens, and then lead into at least one human eye 22.

In an implementation aspect of the second embodiment, the light 1 emitted by the display screen 10 is linearly polarized light with a phase difference of 0 degrees, and the third retarder 17 is a quarter-wave retarder. Therefore, After the first phase retardation, the polarization state of the linearly polarized light can be delayed by a 45-degree phase difference to form a circularly polarized light with a 45-degree phase difference. The first phase retarder 12 is a quarter-wave retarder. Therefore, after the second phase retardation, the polarization state of the circularly polarized light can be retarded by a 45-degree phase difference and converted into a linear polarization with a 90-degree phase difference. Light (first polarized light 2). The second phase retarder 13 is a half-wavelength phase retarder. Therefore, after the third phase retardation, the polarization state of the linearly polarized light can be retarded by a 90 degree phase difference and transformed into a line with a 180 degree phase difference. Polarized light (second polarized light 3), and after the fourth and fifth phase retardation, it can be converted into circularly polarized light with a phase difference of 315 degrees (third polarized light 4). After the seventh phase retardation, it is converted into linearly polarized light with a phase difference of 90 degrees (fourth polarized light 5). In this embodiment, the reflective polarizing element 14 only provides the polarized light with a phase difference of 90 degrees or 270 degrees to penetrate, so the fourth polarized light 5 can penetrate the reflective polarizing element 14.

In another implementation aspect of the second embodiment, the light 1 emitted by the display screen 10 is linearly polarized light with a phase difference of 90 degrees, and the third phase retarder 17 is a quarter-wave retarder. Therefore, After the first phase retardation, the polarization state of the linearly polarized light can be retarded by a 45-degree phase difference to form a circularly polarized light with a 135-degree phase difference. The first phase retarder 12 is a quarter-wave retarder. Therefore, after the second phase retardation, the polarization state of the circularly polarized light can be retarded by a 45-degree phase difference and converted into a linear polarization with a 180-degree phase difference. Light (first polarized light 2). The second phase retarder 13 is a half-wavelength phase retarder. Therefore, after the third phase retardation, the polarization state of the linearly polarized light can be further delayed by 90 degrees with a phase difference of 90 degrees and converted into a line with a phase difference of 270 degrees. Polarized light (second polarized light 3), and after the fourth and fifth phase retardation, can be converted into circularly polarized light with a 45-degree phase difference (third polarized light 4). After the seventh phase retardation, it is converted into linearly polarized light with a phase difference of 90 degrees (fourth polarized light 5). In this embodiment, the reflective polarizing element 14 only provides transmission of polarized light with a phase difference of 0 degrees or 180 degrees, so the fourth polarized light 5 can penetrate the reflective polarizing element 14.

Please refer to FIG. 6, which is an exploded view of the short distance optical system provided by the second embodiment of the present invention. In this embodiment, the first phase retarder 12 and the third phase retarder 17 are also quarter-wave retarders, and the second phase retarder 13 is a half-wave retarder as an example. Description. If the light 1 emitted by the display screen 10 is non-polarized light without a specific polarization state, a linear polarizer 18 and a third phase retarder 17 need to be added in sequence after the display screen 10. The non-polarized light emitted by the display screen 10 The polarized light passes through the linear polarizer 18 and then is converted into linearly polarized light 1". Then, the linearly polarized light 1" undergoes the first phase retardation through the third phase retarder 17, increasing the quarter-wave retardation to Converted into circularly polarized light 1'. Next, the transmission state of the circularly polarized light 1'after entering the partially reflective and partially penetrating element 11 is the same as in the first and second embodiments described above. The circularly polarized light 1'is partially reflected and partially penetrated by the partially reflecting and partially transmitting element 11. The penetrating circularly polarized light continues to pass through the first phase retarder 12 for the second phase retardation, increasing the quarter-wavelength phase retardation, and converting it into linearly polarized light (first polarized light 2), and the linearly polarized light passes through the second The phase retarder 13 performs the third phase retardation, and the phase retardation is to one wavelength. Then, the linearly polarized light (the second polarized light 3) is totally reflected by the reflective polarizing element 14 back to the second phase retarder 13 and the first phase retarder 12, and after the fourth and fifth phase retardation, the transition It is circularly polarized light (third polarized light 4). The circularly polarized light penetrates the first phase retarder 12 and reaches the partially reflective and partially penetrating element 11, and then is partially reflected by the partially reflective and partially penetrating element 11 back to the first phase retarder 12 and the second phase retarder 13, and proceed to the sixth After the second and seventh phase delays, it is converted into linearly polarized light (fourth polarized light 5). At this time, the phase difference of the linearly polarized light meets the penetration condition of the reflective polarizing element 14, and can penetrate the reflective polarizing element 14 and enter the lens, and then lead to at least one human eye 22.

In an implementation aspect in the third embodiment, the first phase retarder 12 and the third phase retarder 17 are quarter-wave retarders, and the second phase retarder 13 is a half-wave retarder. , The linear polarizer 18 only provides 0 degree polarized light penetration, the partially reflective partially transparent element 11 is half reflected and half transmitted, and the reflective polarizing element 14 only provides 90 degree or 270 degree polarized light penetration. When the display screen 10 does not have a specific polarization state, the non-polarized light first passes through the linear polarizer 11 and then becomes linearly polarized light, and then passes through the third phase retarder 17 for the first phase retardation to convert the linearly polarized light into Circularly polarized light with 45 degree phase difference. Then, as mentioned above, after the second phase retardation, the circularly polarized light is converted into linearly polarized light with a phase difference of 90 degrees (first polarized light 2). After the third phase retardation, it is transformed into a linearly polarized light with a phase difference of 180 degrees (second polarized light 3), and after the fourth and fifth phase delays, it is transformed into a linearly polarized light with a phase difference of 315 degrees. Circularly polarized light (third polarized light 4), after the sixth and seventh phase retardation, is converted into linearly polarized light with a phase difference of 90 degrees (fourth polarized light 5), which can penetrate the reflective type Polarization element 14.

In another implementation aspect of the third embodiment, the first phase retarder 12 and the third phase retarder 17 are quarter-wave retarders, and the second phase retarder 13 is a half-wave retarder. The linear polarizer 18 only provides 90-degree polarized light penetration, the partially reflective partially-transmissive element 11 is half reflective and half penetrating, and the reflective polarizing element 14 only provides polarized light penetration with a phase difference of 0 degrees or 180 degrees. In the state where the display screen 10 does not have a specific polarization state, the non-polarized light first passes through the linear polarizer 18 and then becomes linearly polarized light, and then passes through the third phase retarder 17 for the first phase retardation to make the linearly polarized light It is converted into circularly polarized light with a phase difference of 135 degrees. Then, as mentioned above, after the second phase retardation, the circularly polarized light can be converted into linearly polarized light with a phase difference of 180 degrees (first polarized light 2). After the third phase retardation, it can be transformed into linearly polarized light with a phase difference of 270 degrees (second polarized light 3), and after the fourth and fifth phase delays, it can be transformed into a 45-degree phase. The phase-difference circularly polarized light (third polarized light 4) is transformed into linearly polarized light with a 180 degree phase difference (fourth polarized light 5) after the sixth and seventh phase delays, and can penetrate Reflective polarization element 14.

In the present invention, all the components are on the same axis, and according to the polarization status of the display screen 10 of the head mounted display, the third phase retarder 17 and the linear polarizer 18 of Fig. 4 and Fig. 5 are used to increase or decrease the adjustment. In short, if the display screen 10 emits circularly polarized light, there is no need to provide a linear polarizer 18 and a third phase retarder 17; if the display screen 10 emits linearly polarized light, a third phase retarder 17 is required; If the display screen 10 emits non-polarized light without a specific polarization state, a linear polarizer 18 and a third phase retarder 17 need to be installed at the same time; or, the linear polarizer 18 and the third phase retarder 17 can also use a circular polarizer Tablets to replace.

In summary, the short-distance optical system provided by the present invention utilizes a combination of a quarter-wave retarder and a half-wave retarder to expand the effective wavelength band of the retarder and improve the difference. The wavelength phase delay conversion efficiency can reduce stray light, eliminate image chromatic aberration, and improve contrast to achieve the effect of improving image clarity. At the same time, in the present invention, a partially penetrating and partially reflective element, a first phase retarder, a second phase retarder, and a reflective polarizing element are arranged in front of the display screen, and the optical path of the approximate length is reached by the multiple phase retardation and reflection of light. In order to shorten the distance between the display screen and the optical system, the head-mounted display can be miniaturized. Moreover, all the above-mentioned structures of the present invention can be used for the function of myopia adjustment.

Only the above are merely preferred embodiments of the present invention, and are not used to limit the scope of the present invention. Therefore, all equivalent changes or modifications made in accordance with the characteristics and spirit of the application scope of the present invention shall be included in the patent application scope of the present invention.

1: light 1’: Circular polarization 1’’: Linearly polarized light 2: first polarized light 3: second polarized light 4: third polarized light 5: Fourth polarized light 10: Display 11: Partially reflective and partly penetrating components 12: The first phase retarder 13: The second phase retarder 14: reflective polarizing element 15: lens 16: flat glass 17: The third phase retarder 18: Linear polarizer 20: Optical module 22: Human Eye

Figure 1 is a schematic diagram of the optical path between the display screen of the head mounted display and the human eye in the prior art. Figure 2 is a schematic diagram of the short distance optical system of the first embodiment of the present invention. Figure 3 is an exploded view of the short distance optical system of the first embodiment of the present invention. 4A to 4C are the optical path transmission process of the short-distance optical system according to the first embodiment of the present invention. Figure 5 is an exploded view of the short distance optical system according to the second embodiment of the present invention. Figure 6 is an exploded view of the short-distance optical system of the third embodiment of the present invention.

1: light

2: first polarized light

3: second polarized light

4: third polarized light

5: Fourth polarized light

10: Display

11: Partially reflective and partly penetrating components

12: The first phase retarder

13: The second phase retarder

14: reflective polarizing element

15: lens

22: Human Eye

Claims (10)

A short-distance optical system applied to a miniature head-mounted display with a display screen, the display screen outputs images and its light, and the short-distance optical system includes: a part of reflecting and partly penetrating elements corresponding to the setting of the display screen, Receive the light from the display screen, and make the light partially penetrate and partially reflect; a first phase retarder is provided corresponding to the partially reflective and partially penetrating element, and receives the partially reflective and partially penetrating element. The light undergoes phase retardation to form a first polarized light; a second phase retarder is arranged corresponding to the first phase retarder, receives the first polarized light, and performs phase retardation to form a second polarized light; and A reflective polarizing element is arranged corresponding to the second phase retarder, receives the second polarized light and performs total reflection, so that the second polarized light passes through the first phase retarder, the second phase retarder and the partial reflection After partially penetrating the element, it is reflected back to the reflective polarizing element and penetrated; wherein, when the first phase retarder is a half-wavelength retarder, the second phase retarder corresponds to a quarter-wavelength Phase retarder, and when the first phase retarder is a quarter-wave retarder, the second phase retarder corresponds to a half-wave retarder; wherein the reflective polarizing element reflects the After the second polarized light passes through the first phase retarder and the second phase retarder for phase retardation, a third polarized light is formed. The third polarized light is then partially reflected by the partially reflective and partially penetrating element, and then passes through the The first phase retarder and the second phase retarder perform phase retardation to form a fourth polarized light, the fourth polarized light penetrates the reflective polarizing element, and the first polarized light The light, the second polarized light, and the fourth polarized light are linearly polarized light, and the third polarized light is circularly polarized light. The short-distance optical system according to claim 1, further comprising a lens disposed on any of the partially reflective and partially penetrating element, the first phase retarder, the second phase retarder, and the reflective polarizing element On either side of one, the image output by the display screen is led into the eyes of at least one person. The short-distance optical system according to claim 2, wherein the lens is selected from a spherical lens, an aspheric lens, a Fresnel lens, or a multi-element lens in any combination of the above. The short-distance optical system according to claim 3, wherein between the human eye and the lens can include one or more sheets of flat glass, and between the lens and the display screen can further include one or more flat glasses. . The short-distance optical system according to claim 4, wherein the partially reflective partially penetrating element, the first phase retarder, the second phase retarder, and the reflective polarizing element are thin film materials or optical coatings, and are coated The form of cloth, coating or bonding is arranged on the flat glass. The short-distance optical system according to claim 1, wherein the light emitted from the display screen and entering the partially reflective and partially penetrating element is circularly polarized light. The short-distance optical system according to claim 1, wherein the light emitted by the display screen is linearly polarized light, and a third phase retarder is further provided between the display screen and the partially reflective and partially penetrating element, so that the The linearly polarized light is phase retarded by the third phase retarder, and then converted into circularly polarized light. The short-distance optical system according to claim 1, wherein the light emitted by the display screen is unpolarized light, and a linear polarizer and a third phase are further provided between the display screen and the partially reflective and partially penetrating element Retarder, the linear polarizer is arranged on the display screen and the third phase Between the retarders, the non-polarized light passes through the linear polarizer to become linearly polarized light, and the linearly polarized light is phase retarded by the third phase retarder and then converted into circularly polarized light. The short-distance optical system according to claim 7 or 8, wherein the third phase retarder is a quarter-wave retarder. The short-distance optical system according to claim 1, wherein the light emitted by the display screen is non-polarized light, and a circular polarizer is further provided between the display screen and the partially reflective and partially penetrating element to make the non-polarized light After passing through the circular polarizing plate, it is converted into circularly polarized light.

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