TWI656358B - Optical system of miniaturized head-mounted display - Google Patents

Abstract

The present invention provides an optical system of a miniaturized head-mounted display, which is arranged behind an optical module and in front of a display screen to arrange at least one phase delay element, a partially penetrating and partially reflecting element, and a reflective polarizing element to arrange the display screen. After the incident light is incident, it undergoes multiple polarizations, reflections, and repolarizations to obtain polarized light that can penetrate the last layer of reflective polarizing element. After passing through the reflective polarizing element, the final optical module of the head-mounted display is introduced into the person. Eyes. All the optical elements in the present invention are on the same axis, and through multiple polarizations and reflections, the shortest distance between the display screen and the final optical module is obtained under the approximate optical path of the light, and the miniaturization of the head-mounted display is achieved. .

Description

Optical system of miniaturized head-mounted display

The present invention relates to a head-mounted display technology, and more particularly to an optical system of a miniaturized head-mounted display.

A head-mounted display is a device used to display images and colors. It is usually in the form of an eye mask or helmet. The display screen is close to the user's eyes, and the focal length is adjusted through the light path to project the eyes at a short distance. The screen produces a virtual image magnification effect and increases the sense of presence.

Figure 1 shows a virtual reality head-mounted display. The image projected by the display screen 10 enters the optical module 20 after passing through a light path with an optical path of d. The optical module 20 then introduces the image to the user's eye 22 If the optical path d is 40mm, the length of the head-mounted display must be greater than 40mm after the optical path d plus the optical module and the proper eye distance and the housing. It is slightly bulky for the eye mask and helmet worn on the head, so It is an important issue to reduce the thickness of the head-mounted display and facilitate the user to wear it.

Therefore, the present invention proposes an optical system of a miniaturized head-mounted display, which effectively solves the above problems. The specific architecture and its implementation will be detailed below:

The main object of the present invention is to provide an optical system of a miniaturized head-mounted display, which is provided with a polarizing element, a phase delay element, a partially reflecting part and a penetrating element between the display screen of the head-mounted display and the optical module. The phase delay of the light and multiple reflections are used to achieve an approximate optical path length to shorten the distance between the display screen and the optical module to miniaturize the head-mounted display.

Another object of the present invention is to provide an optical system of a miniaturized head-mounted display. All optical elements are coaxially arranged and adjusted according to the polarization of the display screen to shorten the distance between the display screen and the optical module. Increase the variability and flexibility of the optical system configuration under the premise of distance.

In order to achieve the above object, the present invention provides an optical system of a miniaturized head-mounted display, including: a display screen that outputs an image and emits polarized light; a part of the reflective part penetrates the element and is disposed corresponding to the display screen so that the polarized light part reflects , Partially penetrating the partially reflecting partially penetrating element; a second phase delay element corresponding to the partially reflecting partially penetrating element, phase-delaying the polarized light partially penetrating the partially reflecting partially penetrating element to become a second Polarized light at a polarization angle; a reflective polarizing element is disposed corresponding to the second phase delay element, receives the polarized light at the second polarization angle and performs total reflection, and the polarized light at the second polarization angle passes through the second phase delay element And the partially reflective part penetrates the element, reflects back to the reflective polarizing element and penetrates; and an optical module, corresponding to the reflective polarizing element, receives polarized light penetrating the reflective polarizing element and introduces it In the eyes of at least one person.

According to an embodiment of the present invention, the reflective polarizing element is a polarizer, and the second phase delay element is a phase retarder.

According to an embodiment of the present invention, the reflective polarizing element is a coating provided in the optical module with reflective polarizing function, or a lens with reflective polarizing function in the optical module, and the second phase delay element Is a phase retarder.

According to an embodiment of the present invention, the reflective polarizing element is a coating film having reflective polarizing function provided in the optical module, or a lens having reflective polarizing function in the optical module, and the second phase delay The element is also provided in the optical module, which is a coating with a phase delay function before the reflective polarizing element, or a lens with a phase delay function in the optical module.

According to an embodiment of the present invention, the polarized light sent out by the display screen and entering the partially reflecting partially penetrating element is circularly polarized light.

According to an embodiment of the present invention, the polarized light sent from the display screen is linearly polarized light, and a first phase delay element is further provided between the display screen and the partially reflecting part penetrating element for processing the polarized light. The first phase delay becomes polarized light at a first polarization angle, and linearly polarized light is converted into circularly polarized light after passing through the first phase delay element.

According to an embodiment of the present invention, the reflective polarizing element totally reflects the polarized light of the second polarization angle back to the second phase delay element, so that the polarized light of the second polarization angle penetrates the second phase delay element and becomes The polarized light of the third polarization angle, and the polarized light of the third polarization angle is partially reflected back to the second phase delay element by the partially reflecting part and the penetrating element, and then passes through the second phase delay element and becomes the fourth polarization angle. Polarized light of the fourth polarization angle passes through the reflective polarizing element.

It is assumed that, of the polarized light of the second polarization angle, part of the light that penetrates the second phase delay element is linearly polarized light, and the light that is reflected by the reflective polarization element and penetrates the second phase delay element is circularly polarized light. .

According to an embodiment of the present invention, the polarized light of the second polarization angle reflected by the reflective polarizing element is linearly polarized light, and the polarized light of the fourth polarization angle transmitted by the reflective polarizing element is linearly polarized light.

According to an embodiment of the present invention, the polarized light sent from the display screen has no specific polarization state, and a linear polarizer and a first phase delay element are further provided between the display screen and the partially reflecting part penetrating element. A linear polarizer is disposed between the display screen and the first phase delay element. The polarized light provided by the display screen passes through the linear polarizer and becomes linearly polarized light. The first phase delay element further processes the linearly polarized light. The first phase delay becomes polarized light of a first polarization angle, and the polarized light of the first polarization angle is converted into circularly polarized light.

According to an embodiment of the present invention, the optical module is an aspheric lens, a Fresnel lens or a combination of multiple lenses.

The invention provides an optical system of a miniaturized head-mounted display, which is applied to a head-mounted display, especially a virtual reality system of the head-mounted display. Since it is worn on a user's head, it is difficult to fix it if the volume is too large or too long. The user's head will fall under the influence of gravity. Therefore, the smaller the size of the head-mounted display, the better. The purpose of the present invention is to use a plurality of lenses to reflect light multiple times, and to make the optical mode at an approximate optical path length. The distance between the group and the display screen is shortened to achieve the purpose of miniaturizing the head-mounted display.

Please refer to FIG. 2A and FIG. 2B, which are schematic diagrams of an embodiment of an optical system of a miniaturized head-mounted display according to the present invention, including a display screen 10, a partially reflecting part penetrating element 14, and a second phase delay Element 16, a reflective polarizing element 18, and an optical module 20, please first refer to FIG. 2A. In this embodiment, the display screen 10 outputs an image and emits polarized light, such as the polarized light 1 shown in the figure; The partially reflective partially penetrating element 14 is disposed corresponding to the display screen 10, and partially reflects the incident polarized light 1 back to the display screen 10, and the rest penetrates the partially reflecting partially penetrating element 14, in a preferred embodiment, the The partially-reflecting and partially-transmitting element 14 is half-reflection and half-transmission. In addition, in this embodiment, the second phase delay element 16 is an independent phase retarder, and the reflective polarization element 18 is an independent polarizer. The two-phase retardation element 16 is provided corresponding to the partially reflective partially penetrating element 14, and performs a second phase retardation on the polarized light 1 that has penetrated the partially reflecting partially penetrating element 14 to become the polarized light 2 of the second polarization angle; reflective polarization The element 18 is disposed corresponding to the second phase delay element 16, and will totally reflect the polarized light 2 back to the second phase delay element 16. After the polarized light 2 penetrates the second phase delay element 16, it will be polarized again and become the third polarization. Angle of polarized light 3.

Please refer to FIG. 2B. After the polarized light 3 with the third polarization angle penetrates the second phase delay element 16 and reaches the partially reflective partially transmitting element 14, it is partially reflected back to the second phase delay by the partially reflecting partially transmitting element 14. After the element 16 (partially penetrated part is energy loss), it is polarized after penetrating the second phase delay element 16 and becomes polarized light 4 of the fourth polarization angle. At this time, the fourth polarization angle of the polarized light 4 conforms to the reflection. The polarization condition of the polarizing element 18 is based on the polarization condition. Therefore, the polarized light 4 can pass through the reflective polarizing element 18 and enter the corresponding optical module 20. The optical module 20 guides the polarized light 4 into at least one human eye 22.

In a first embodiment, the light emitted by the display screen 10 is circularly polarized light with a polarization of 45 degrees, so the first polarization angle is 45 degrees (that is, the polarized light 1 is 45 degrees polarized light), and the second phase The retardation element 16 is a 45-degree polarization element, the second polarization angle is 90 degrees (that is, polarized light 2 is 90-degree polarized light), and the third polarization angle is 135 degrees (that is, polarized light 3 is 135-degree polarized light). The four polarization angles are 180 degrees (that is, the polarized light 4 is 180 degrees polarized light). In this embodiment, the reflective polarizing element 18 only provides 180-degree polarized light transmission, so the polarized light 4 can penetrate the reflective polarizing element 18.

In a second embodiment, the display screen 10 has different polarization states. The first polarization angle thereof is 135 degrees (that is, the polarized light 1 is 135 degrees polarized light), but circularly polarized light is also emitted, and the second phase is delayed. Element 16 is also a 45-degree polarizing element, the second polarization angle is 0 or 180 degrees (that is, polarized light 2 is 0 or 180 degrees polarized light), and the third polarization angle is 45 degrees (that is, polarized light 3 is 45 degrees polarized Light), the fourth polarization angle is 90 degrees (that is, polarized light 4 is 90 degrees polarized light). In this embodiment, the reflective polarizing element 18 only provides 90-degree polarized light transmission, so the polarized light 4 can penetrate the reflective polarizing element 18.

In the embodiment shown in FIGS. 2A and 2B, the polarized light 1 emitted by the display screen 10 is circularly polarized light; the polarized light 2 that partially penetrates the second phase delay element 16 is linearly polarized light, and the reflected polarizing element 18 is The reflected polarized light 2 is also linearly polarized light, but the polarized light 3 after passing through the second phase delay element 16 becomes circularly polarized light. This polarized light 3 is originally circularly polarized light, but after being partially reflected by the second phase delay element 16 and after passing through the second phase delay element 16 again, the polarized light 4 becomes linearly polarized light until it penetrates the reflective polarizing element 18 The polarized light 4 is still linearly polarized light.

In the present invention, the optical module 20 is an aspheric lens, a Fresnel lens or a combination of multiple lenses.

FIG. 3A is a schematic diagram of another embodiment of an optical system of a miniaturized head-mounted display according to the present invention. If the display screen 10 emits not circularly polarized light but linearly polarized light, as shown in FIG. 3A, a first phase delay element 12 needs to be added after the display screen 10 to convert the polarized light emitted by the display screen 10 into The circularly polarized light is subjected to the first phase retardation to become the polarized light 1 of the first polarization angle. After the polarized light 1 passes through the partially reflecting partially penetrating element 14, it is partially reflected back to the first phase delay element 12, and the rest passes through the partially reflecting partially penetrating element 14; The polarized light 1 then passes through the second phase delay element 16 and becomes the polarized light 2 of the second polarization angle after the second phase delay; the polarized light 2 is totally reflected back to the second phase delay element 16 by the reflective polarizing element 18 and penetrates The second phase delay element 16 is then polarized again into the polarized light 3 with a third polarization angle. After the polarized light 3 penetrates the second phase delay element 16 and reaches the partially reflective partially transparent element 14, it is partially reflected by the partially reflected partially transparent element 14 back to the second phase delay element 16 (the partially penetrated part is energy loss) ), And is polarized after passing through the second phase delay element 16 and becomes polarized light 4 of the fourth polarization angle. At this time, the fourth polarization angle of the polarized light 4 meets the transmission conditions of the reflective polarizing element 18, so the polarized light 4 can penetrate the reflective polarizing element 18 and enter the corresponding optical module 20, and the optical module 20 guides the polarized light 4 into at least one human eye 22.

In a third embodiment, the polarized light emitted by the display screen 10 is 0-degree linearly polarized light, and the first phase delay element 12 is a 45-degree polarized element, so the first polarization angle is 45 degrees (that is, the polarized light 1 is 45 Polarized light), and the second phase delay element 16 is a 45-degree polarized element, the second polarized angle is 90 degrees (that is, polarized light 2 is 90-degree polarized light), and the third polarized angle is 135 degrees (that is, polarized light 3 is 135-degree polarized light), and the fourth polarization angle is 180 degrees (that is, polarized light 4 is 180-degree polarized light). In this embodiment, the reflective polarizing element 18 only provides 180-degree polarized light transmission, so the polarized light 4 can penetrate the reflective polarizing element 18.

In a fourth embodiment, the display screen emits 90-degree linearly polarized light, and the first phase delay element 12 is a 45-degree polarizer, so the first polarization angle is 135 degrees (that is, the polarized light 1 is 135 degree polarized light), the second phase delay element 16 is also a 45 degree polarized element, the second polarization angle is 0 or 180 degrees (that is, the polarized light 2 is 0 or 180 degrees polarized light), and the third polarization angle is 45 degrees (That is, polarized light 3 is 45-degree polarized light), and the fourth polarization angle is 90 degrees (that is, polarized light 4 is 90-degree polarized light). In this embodiment, the reflective polarizing element 18 only provides 90-degree polarized light transmission, so the polarized light 4 can penetrate the reflective polarizing element 18.

FIG. 3B and FIG. 3C are comparison diagrams of the optical system of the conventional head-mounted display in FIG. 1 and the head-mounted display in FIG. 3A of the present invention. In the present invention, the first phase delay element 12 and the partially reflective partially penetrating element 14 can be set as a group, and the second phase delay element 16 and the reflective polarization element 18 can be set as a group. For example, the second phase delay element 16 and The reflective polarizing element 18 can be the same lens. For example, a reflective polarizing function coating is provided on the side of the second phase retarder 16 near the optical module 20 as the reflective polarizing element 18, or the same lens has a phase using a special material. The functions of retardation and reflective polarization are the same. The first phase delay element 12 and the partially reflective partially penetrating element 14 can also be made on the same lens through coating or material selection. As we all know, the thickness of the lens affects the refractive index and the optical path. When the lens is thicker, the refractive index is higher, so the difference in optical path is higher, but the error is very small and still within the allowable range. Therefore, Figure 3B and Figure 3C can be said to have nearly the same optical path d (the total length of the dashed line in the figure), but the optical system of the present invention has a short back focus distance, which can shorten the back focus distance of the traditional head-mounted display to 0.3 ~ 0.7 It can achieve the same clear image effect as traditional head-mounted displays.

FIG. 4 is a schematic diagram of another embodiment of an optical system of a miniaturized head-mounted display according to the present invention. If the display screen 10 does not have a specific polarization state, as shown in FIG. 4, a linear polarizer 11 needs to be added after the display screen 10 and before the first phase delay element 12 to convert the polarized light emitted from the display screen 10 into Linearly polarized light. Linearly polarized light passes through the first phase delay element 12 and becomes polarized light 1 with a first polarization angle, and polarized light 1 becomes circularly polarized light. After the polarized light 1 passes through the partially reflecting partially penetrating element 14, it is partially reflected back to the first phase delay element 12, and the rest passes through the partially reflecting partially penetrating element 14; The polarized light 1 then passes through the second phase delay element 16 and becomes the polarized light 2 of the second polarization angle after the second phase delay; the polarized light 2 is totally reflected back to the second phase delay element 16 by the reflective polarizing element 18 and penetrates The second phase delay element 16 is then polarized again into the polarized light 3 with a third polarization angle. After the polarized light 3 penetrates the second phase delay element 16 and reaches the partially reflective partially transparent element 14, it is partially reflected by the partially reflected partially transparent element 14 back to the second phase delay element 16 (the partially penetrated part is energy loss) ), And is polarized after passing through the second phase delay element 16 and becomes polarized light 4 of the fourth polarization angle. At this time, the fourth polarization angle of the polarized light 4 meets the transmission conditions of the reflective polarizing element 18, so the polarized light 4 can penetrate the reflective polarizing element 18 and enter the corresponding optical module 20, and the optical module 20 guides the polarized light 4 into at least one human eye 22.

In a fifth embodiment, if the first phase delay element 12 and the second phase delay element 16 are 45-degree polarizing elements, the partially reflecting part and the penetrating element 14 are half reflecting and half penetrating, and the reflective polarizing element 18 only provides 180 Degree of polarized light penetration, in a state where the display screen 10 does not have a specific polarization state, it first becomes linearly polarized light after passing through the linear polarizer 11 and then passes through the first phase delay element 12 to increase a phase delay of 45 degrees. The 45-degree polarized light 1 is passed through the first phase delay element 12, and then the 45-degree polarized light 1 is partially transmitted through the partially-transmissive partial reflection element 14. After passing through the second phase-delay element 16, the polarization is turned to 90 degrees. The phase-delayed polarized light 2 is completely reflected on the reflective polarizing element 18, so that the reflected light passes through the second phase retarding element 16 again, and the phase of the polarized light 3 is adjusted from a 90-degree delay to a 135-degree delay. Then, it partially penetrates the partially reflecting element 14 and reflects it back to the second phase delay element 16. At this time, the phase retardation of the polarized light 3 is adjusted from 135 degrees to the 180 degree polarized light 4 of the original polarization state, and can be incident on Optics Module 20.

In a sixth embodiment, the display screen 10 also has no specific polarization state, but the linearly polarizing plate 11 emits 90-degree linearly polarized light. The first phase delay element 12 is a 45-degree polarizing element, so the first polarization angle is 135 degrees. (That is, polarized light 1 is 135-degree polarized light), and the second phase delay element 16 is also a 45-degree polarized element, and the second polarization angle is 0 or 180 degrees (that is, polarized light 2 is 0 or 180-degree polarized light) , The third polarization angle is 45 degrees (that is, polarized light 3 is 45 degrees polarized light), and the fourth polarization angle is 90 degrees (that is, polarized light 4 is 90 degrees polarized light). In this embodiment, the reflective polarizing element 18 only provides 90-degree polarized light transmission, so the polarized light 4 can penetrate the reflective polarizing element 18.

All the components in the present invention are on the same axis, and according to the polarization state of the display screen of the head-mounted display, the display screen 10 and the linear polarizer 11 in FIG. 3A and FIG. 4 are used to increase or decrease the adjustment. 10 emits circularly polarized light, there is no need to provide a linear polarizer 11 and a first phase delay element 12; if the display 10 emits linearly polarized light, a first phase delay element 12 is required; if the display 10 emits For polarized light without a specific polarization state, a linear polarizer 11 and a first phase delay element 12 need to be provided at the same time.

The invention uses the principle that the approximate optical path can achieve the same image to shorten the length of the head-mounted display. For example, in FIG. 3A, the optical path from the display screen 10 to the optical module 20 undergoes multiple reflections. In the embodiment shown in the figure, the total optical path length of each reflection from the display screen 10 to the optical module 20 is d, which is approximately the same as the optical path d of the display screen 10 to the optical module 20 in the prior art of FIG. 1. It is almost the same, but since the light path from the display screen 10 to the optical module 20 is summed up multiple times in the embodiment of FIG. 3A, the actual length from the display screen 10 to the optical module 20 will be much shorter than that from the display in FIG. 1 The length of the screen 10 to the optical module 20 is to shorten the length of the head-mounted display.

In addition, in the present invention, the reflective polarizing element 18, or the reflective polarizing element 18 and the second phase delay element 16 may be provided in the optical module together. If only the reflective polarizing element is provided in the optical module, It can be a coating with reflective polarization function; if both are set in the optical module, as shown in Figure 5, the reflective polarization element 18 is a coating with reflective polarization function, and the second phase delay element 16 It is a coating with a phase delay function before the reflective polarizer 18. This also makes the back focus distance shorter.

The foregoing are merely preferred embodiments of the present invention, and are not intended to limit the scope of implementation of the present invention. Therefore, all equal changes or modifications made according to the features and spirit described in the scope of the application of the present invention shall be included in the scope of patent application of the present invention.

10‧‧‧ Display

11‧‧‧Linear polarizer

12‧‧‧ the first phase delay element

14‧‧‧ Partially reflective partly penetrating element

16‧‧‧Second Phase Delay Element

18‧‧‧ reflective polarizer

20‧‧‧Optical Module

22‧‧‧ human eye

FIG. 1 is a schematic diagram of an optical path between a display screen of a head-mounted display and a human eye in the prior art. 2A and 2B are schematic diagrams of an embodiment of an optical system of a miniaturized head-mounted display according to the present invention. FIG. 3A is a schematic diagram of another embodiment of an optical system of a miniaturized head-mounted display according to the present invention. FIG. 3B and FIG. 3C are comparison diagrams of the conventional head mounted display and the optical system of the head mounted display in FIG. 3A of the present invention. FIG. 4 is a schematic diagram of another embodiment of an optical system of a miniaturized head-mounted display according to the present invention. FIG. 5 is a schematic diagram of another embodiment of an optical system of a miniaturized head-mounted display according to the present invention.

Claims (6)

An optical system of a miniaturized head-mounted display includes: a display screen that outputs an image and emits polarized light; a part of the reflective part penetrates the element and is arranged corresponding to the display screen to partially reflect the polarized light and partially penetrate the partially reflective part A transmissive element, the polarized light sent from the display screen is linearly polarized light, and a first phase delay element is further provided between the display screen and the partially reflective part of the transmissive element to perform the linearly polarized light for the first time. The secondary phase retardation becomes polarized light at a first polarization angle, and the linearly polarized light is converted into circularly polarized light after passing through the first phase delay element. The first phase delay element and the partially reflective part penetrate the element through the coating or The material is selected and made on the same lens; a second phase delay element is provided corresponding to the partially reflecting part of the penetrating element, and receives the polarized light that partially penetrates the partially reflecting part of the penetrating element, and performs phase retardation to become the second Polarized light at a polarization angle; a reflective polarizing element corresponding to the second phase delay element and receiving polarization at the second polarization angle And perform total reflection back to the second phase delay element, so that the polarized light of the second polarization angle penetrates the second phase delay element and becomes polarized light of the third polarization angle, and the polarized light of the third polarization angle is then After partially reflecting, the partially penetrating element partially reflects back to the second phase delay element, passes through the second phase delay element and becomes polarized light of a fourth polarization angle, and the polarized light of the fourth polarization angle penetrates the reflective polarization element Wherein the polarized light of the second polarization angle reflected by the reflective polarizing element is linearly polarized light, and the polarized light of the fourth polarization angle penetrated by the reflective polarizing element is linearly polarized light; and a set of optical modes The group is arranged corresponding to the reflective polarizing element, receives the polarized light of the fourth polarization angle penetrating the reflective polarizing element, and guides it into at least one human eye. The optical system of the miniaturized head-mounted display according to claim 1, wherein the reflective polarizing element is a polarizer, and the second phase delay element is a phase retarder. The optical system of the miniaturized head-mounted display according to claim 1, wherein the reflective polarizing element is a coating provided in the optical module with a reflective polarizing function, or a reflective polarizing in the optical module Functional lens, the second phase delay element is a phase retarder. The optical system of the miniaturized head-mounted display according to claim 1, wherein the reflective polarizing element is a coating provided in the optical module with a reflective polarizing function, or a reflective polarizing in the optical module Functional lens, and the second phase delay element is also provided in the optical module, which is a coating with a phase delay function before the reflective polarizing element, or a lens with a phase delay function in the optical module. The optical system of the miniaturized head-mounted display according to claim 1, wherein part of the polarized light of the second polarization angle that penetrates the second phase delay element is linearly polarized light and is reflected by the reflective polarizing element Those that penetrate the second phase delay element later are circularly polarized light. The optical system of the miniaturized head-mounted display according to claim 1, wherein the optical module is an aspheric lens, a Fresnel lens, or a combination of multiple lenses.