TWI874205B - Optical system and head-mounted device - Google Patents

Abstract

An optical system includes an aperture stop, an image surface, a reflective polarizer, a partial reflector, a first quarter-wave plate, a second quarter-wave plate, a first optical lens element, a second optical lens element and a third optical lens element. The aperture stop is located at a front side of the optical system. The image surface is located at a rear side of the optical system. The reflective polarizer is located between the aperture stop and the image surface. The partial reflector is located between the reflective polarizer and the image surface. The first quarter-wave plate is located between the reflective polarizer and the partial reflector. The second quarter-wave plate is located between the partial reflector and the image surface. The first optical lens element is located between the aperture stop and the first quarter-wave plate. The second optical lens element is located between the first optical lens element and the second quarter-wave plate. The third optical lens element is located between the second optical lens element and the second quarter-wave plate. In addition, the first optical lens element has negative refractive power.

Description

Optical systems and headsets

The present invention relates to an optical system and a head-mounted device, and in particular to an optical system suitable for a head-mounted device.

As semiconductor manufacturing technology becomes more sophisticated, all kinds of electronic components have been miniaturized, making the performance of microelectronic components significantly improved compared to the past. The pixels of photosensitive components can reach a smaller size, and the development of portable devices has become more prosperous, which has led to the rapid progress of lens components, and the rise of head-mounted devices that only existed in science fiction movies in the past. At the same time, the popularity of high-performance microprocessors and microdisplays has led to a rapid improvement in the relevant technology of smart head-mounted devices in recent years. With the rise of artificial intelligence, the application range of electronic devices equipped with optical lenses has become wider, among which the demand for computer vision has grown significantly, and the requirements for optical lenses have also become more diverse.

In addition to being significantly lighter than before, today's head-mounted devices are also beginning to have a variety of intelligent functions, such as virtual reality (VR), augmented reality (AR) and mixed reality (MR), which are rapidly growing in applications. Among them, virtual reality is widely used in medical care, engineering, real estate, education, video games and audio-visual entertainment. However, current head-mounted devices are still in the development stage, and there are still many areas that need to be greatly improved, such as the weight and size of head-mounted devices and the image quality. Most early virtual reality headsets used traditional optical lenses or Fresnel lenses. Although traditional optical lenses can provide excellent imaging quality, they cannot effectively compress the volume. Although Fresnel lenses can achieve the effect of compressing the volume, the imaging quality is often poor. Therefore, current researchers or developers are looking for a lens combination that has both small size and excellent imaging methods.

In view of the above-mentioned problems, the present invention discloses an optical system and a head-mounted device, which can have both small weight and volume and good imaging quality.

The present invention provides an optical system, which includes an aperture, an image plane, a reflective polarizing element, a partial reflective element, a first quarter wave plate, a second quarter wave plate, a first optical lens, a second optical lens and a third optical lens. The aperture is located at the front side of the optical system. The image plane is located at the rear side of the optical system. The reflective polarizing element is located between the aperture and the image plane. The partial reflective element is located between the reflective polarizing element and the image plane. The first quarter wave plate is located between the reflective polarizing element and the partial reflective element. The second quarter wave plate is located between the partial reflective element and the image plane. The first optical lens is located between the aperture and the first quarter wave plate. The second optical lens is located between the first optical lens and the second quarter wave plate. The third optical lens is located between the second optical lens and the second quarter wave plate. The first optical lens has negative refractive power. The focal length of the optical system is f, and the image height presented by the image plane is ImgH, which meets the following conditions:

0 ＜ f/ImgH ＜ 1.20.

The present invention further provides a head mounted device, which comprises the aforementioned optical system.

According to the optical system and head-mounted device disclosed in the present invention, by providing a combination of a wave plate, a reflective polarizing element, a partial reflective element and a lens, the polarization state of the imaging light is converted so that the imaging light can be reflected between the elements, thereby compressing the optical path and reducing the generation of stray light, thereby achieving the compression of the volume of the head-mounted device and reducing the weight.

The above description of the disclosed content and the following description of the implementation methods are used to demonstrate and explain the spirit and principle of the present invention, and provide a further explanation of the scope of the patent application of the present invention.

The detailed features and advantages of the present invention are described in detail in the following embodiments, and the contents are sufficient to enable anyone familiar with the relevant technology to understand the technical content of the present invention and implement it accordingly. According to the contents disclosed in this specification, the scope of the patent application and the drawings, anyone familiar with the relevant technology can easily understand the relevant purposes and advantages of the present invention. The following embodiments further illustrate the viewpoints of the present invention in detail, but do not limit the scope of the present invention by any viewpoint.

The present invention provides an optical system, which includes an aperture, an image plane, a reflective polarizing element, a partial reflective element, a first quarter wave plate, a second quarter wave plate, a first optical lens, a second optical lens, and a third optical lens. The aperture is located at the front side of the optical system, and the image plane is located at the back side of the optical system. The front side of the optical system refers to the side of the optical system close to the user's eyes, for example, and the back side of the optical system refers to the side of the optical system close to a display presenting an image, wherein the image plane can be located on the display, and the position of the aperture can be the position where the user's eyes view the image.

The reflective polarizing element is located between the aperture and the image plane. The partially reflecting element is located between the reflective polarizing element and the image plane. The first quarter wave plate is located between the reflective polarizing element and the partially reflecting element. The second quarter wave plate is located between the partially reflecting element and the image plane. The first optical lens is located between the aperture and the image plane. The second optical lens is located between the first optical lens and the image plane. The third optical lens is located between the second optical lens and the image plane. The third optical lens has a negative refractive power, which helps to adjust the imaging quality. There may be an air gap between the first optical lens and the second optical lens. There may be an air gap between the second optical lens and the third optical lens. The partially reflective element may have, for example, an average light reflectivity of at least 35%, wherein the average light reflectivity may refer to an average value of the reflectivity of the partially reflective element for light of different wavelengths.

The optical system disclosed in the present invention converts the polarization state of imaging light by arranging a combination of a wave plate, a reflective polarizing element, a partial reflective element and a lens, so that the imaging light can be reflected between the elements, thereby compressing the optical path and reducing the generation of stray light, thereby achieving the compression of the volume of the head-mounted device and reducing the weight. Please refer to FIG. 12 , the incident light is incident from the display SC in a longitudinal polarization state, forms a rotated polarization state through the second quarter wave plate QWP2, and then passes through the first quarter wave plate QWP1 to form a transverse polarization state. The reflective polarization element RP only allows the light in the longitudinal polarization state to pass through, so the light in the transverse polarization state is reflected and passes through the first quarter wave plate QWP1 again to form a rotated polarization state. Then, the light in the rotated polarization state is reflected by the partial reflection element BS, and then passes through the first quarter wave plate QWP1 for the third time to form a longitudinal polarization state and can pass through the reflective polarization element RP. In this way, the required optical path can be folded through such a reflection method, effectively shortening the length of the lens set. Among them, the first quarter wave plate, the second quarter wave plate and the partial reflection element can be plated (attached) on the surface of the lens or can be separate elements separated from the lens, but the present invention is not limited thereto. Wherein, the partially reflective element is, for example but not limited to, a reflective mirror having a reflective surface, which can reflect a portion of the light. For example, in some cases, the partially reflective element can be configured to allow a portion of the light to be transmitted and another portion of the light to be reflected when the light passes through.

At least one optical lens in the optical system may have an inflection point. This helps peripheral imaging and aberration correction. Please refer to FIG12, which is a schematic diagram of the inflection point P of the front surface of the first optical lens E1 in the first embodiment of the present invention. FIG12 shows the inflection point P of the front surface of the first optical lens E1 in the first embodiment of the present invention as an exemplary illustration, but in the first embodiment and other embodiments of the present invention, each lens may also have one or more inflection points.

At least one optical lens in the optical system may have a critical point. In this way, peripheral imaging and aberration correction can be further improved. Please refer to FIG. 12, which is a schematic diagram of the critical point C of the front surface of the first optical lens E1 in the first embodiment of the present invention. FIG. 12 shows the critical point C of the front surface of the first optical lens E1 in the first embodiment of the present invention as an exemplary illustration, but in the first embodiment and other embodiments of the present invention, each lens may also have one or more critical points.

The Abbe number of the second optical lens is V2, and the refractive index of the second optical lens is N2, which can meet the following conditions: 18 < V2/N2 < 47. In this way, it can be avoided that the refractive index of the light is too different due to different angles when reflected, which affects the imaging quality. Among them, the following conditions can also be met: 25 < V2/N2 < 40.0. Among them, the following conditions can also be met: 30 < V2/N2 < 38.

The center thickness of the first optical lens on the optical axis is CT1, the center thickness of the second optical lens on the optical axis is CT2, and the center thickness of the third optical lens on the optical axis is CT3, which can meet the following conditions: CT2> CT1; and CT2> CT3. In this way, the use efficiency of the optical lens can be improved. Please refer to Figure 12, which is a schematic diagram of parameters CT1, CT2 and CT3 in the first embodiment of the present invention.

The focal length of the optical system is f, and the focal length of the third optical lens is f3, which can satisfy the following conditions: -10 < f/f3 < 0. Thereby, the imaging quality can be further adjusted. Among them, the following conditions can also be satisfied: -5 < f/f3 < 0. Among them, the following conditions can also be satisfied: -1 < f/f3 < 0.

The focal length of the optical system is f, and the focal length of the second optical lens is f2, which can satisfy the following condition: 0 < f/f2. This helps to shorten the total length of the entire optical system. The following condition can also be satisfied: 0.28 < f/f2 < 1.

The focal length of the first optical lens is f1, the focal length of the second optical lens is f2, and the focal length of the third optical lens is f3, which can meet the following condition: 1.1 < (f2+f3)/f1. This helps to improve the efficiency of the reflective-refractive optical system. Among them, the following condition can also be met: 10 < (f2+f3)/f1. Among them, the following condition can also be met: 100 < (f2+f3)/f1.

The distance from the rear surface of the first optical lens to the front surface of the second optical lens on the optical axis is T12, and the center thickness of the second optical lens on the optical axis is CT2, which can meet the following conditions: 0.55 < T12/CT2 < 1.40. This helps to improve the use efficiency of the second optical lens. Among them, the following conditions can also be met: 0.57 < T12/CT2 < 1.27. Please refer to FIG. 12, which is a schematic diagram of the parameters T12 and CT2 in the first embodiment of the present invention.

The center thickness of the first optical lens on the optical axis is CT1, the center thickness of the second optical lens on the optical axis is CT2, the center thickness of the third optical lens on the optical axis is CT3, the distance from the rear surface of the first optical lens to the front surface of the second optical lens on the optical axis is T12, and the distance from the rear surface of the second optical lens to the front surface of the third optical lens on the optical axis is T23, which can meet the following conditions: 0 < (CT1+CT2+CT3)/(T12+T23) < 1.75. This helps to shorten the length of the optical lens set. Among them, the following conditions can also be met: 0.1 < (CT1+CT2+CT3)/(T12+T23) < 1.7. The following condition may also be satisfied: 0.4 < (CT1+CT2+CT3)/(T12+T23) < 1.4. Please refer to FIG. 12 , which is a schematic diagram showing parameters CT1, CT2, CT3, T12 and T23 according to the first embodiment of the present invention.

The distance from the rear surface of the first optical lens to the front surface of the second optical lens on the optical axis is T12, the distance from the rear surface of the second optical lens to the front surface of the third optical lens on the optical axis is T23, and the distance from the front surface of the first optical lens to the rear surface of the third optical lens on the optical axis is TD, which can meet the following conditions: 0.37 < (T12+T23)/TD < 1. This helps to improve the use efficiency of the optical lens set. Among them, the following conditions can also be met: 0.42 < (T12+T23)/TD < 0.8. Please refer to FIG. 12, which is a schematic diagram of parameters T12, T23 and TD in the first embodiment of the present invention.

The distance from the rear surface of the first optical lens to the front surface of the second optical lens on the optical axis is T12, the distance from the rear surface of the second optical lens to the front surface of the third optical lens on the optical axis is T23, and the distance from the rear surface of the third optical lens to the image plane on the optical axis is BL, which can meet the following conditions: 1.20 < (T12+T23)/BL < 5.20. This helps to shorten the distance between the optical lens assembly and the image. Among them, the following conditions can also be met: 1.50 < (T12+T23)/BL < 4.20. Please refer to Figure 12, which is a schematic diagram of parameters T12, T23 and BL in the first embodiment of the present invention.

The center thickness of the first optical lens on the optical axis is CT1, the center thickness of the second optical lens on the optical axis is CT2, the center thickness of the third optical lens on the optical axis is CT3, and the distance from the aperture to the image plane on the optical axis is SL, which can meet the following conditions: 0.10 < (CT1+CT2+CT3)/SL < 0.35. This helps to shorten the length of the optical system. Among them, the following conditions can also be met: 0.13 < (CT1+CT2+CT3)/SL < 0.27. Please refer to Figure 12, which is a schematic diagram of the parameters CT1, CT2, CT3 and SL in the first embodiment of the present invention.

The radius of curvature of the front surface of the third optical lens is R5, and the radius of curvature of the rear surface of the third optical lens is R6, which can meet the following conditions: 0.01 < |R5/R6| < 1. Thereby, the imaging quality can be further adjusted. Among them, the following conditions can also be met: 0.3 < |R5/R6| < 1. Among them, the following conditions can also be met: 0.55 < |R5/R6| < 1.

The radius of curvature of the front surface of the third optical lens is R5, and the radius of curvature of the rear surface of the third optical lens is R6, which can meet the following condition: 3.85 < |(R5+R6)/(R5-R6)|. This helps to reduce the back focal length. Among them, the following condition can also be met: 4 < |(R5+R6)/(R5-R6)| < 300.

The radius of curvature of the front surface of the third optical lens is R5, and the radius of curvature of the rear surface of the third optical lens is R6, which can meet the following conditions: (R5+R6)/(R5-R6) < 0. This helps to balance the imaging quality and the back focal length. Among them, the following conditions can also be met: -300 < (R5+R6)/(R5-R6) < -3.

The focal length of the optical system is f, and the image height presented by the image plane is ImgH (which can be half of the total diagonal length of the display), which can meet the following conditions: 0 < f/ImgH < 1.20. In this way, a larger image can be provided. Among them, the following conditions can also be met: 0 < f/ImgH < 1.05. Please refer to FIG. 12, which is a schematic diagram of the parameter ImgH in the first embodiment of the present invention.

The distance from the aperture to the image plane on the optical axis is SL, and the image height presented by the image plane is ImgH, which can meet the following conditions: 0.50 < SL/ImgH < 1.17. In this way, the size of the image and the length of the optical system can be balanced.

The distance from the aperture to the image plane on the optical axis is SL, and the focal length of the optical system is f, which can meet the following conditions: 1.08 < SL/f < 1.40. In this way, the image quality and the length of the optical system can be balanced. Among them, the following conditions can also be met: 1.15 < SL/f < 1.25.

The size of the aperture is EPD, and the image height presented by the image plane is ImgH, which can meet the following conditions: 0.380 < EPD/ImgH < 0.476. In this way, a better immersive experience can be provided to the user. Please refer to FIG. 12, which is a schematic diagram of the parameters EPD and ImgH according to the first embodiment of the present invention.

Half of the maximum viewing angle in the optical system is HFOV, and the focal length of the optical system is f, which can meet the following conditions: 0.05 < tan(HFOV)/f < 0.08. In this way, a more three-dimensional image can be provided to the user.

At least one optical lens in the optical system may be a super-thin lens (Metalens), thereby shortening the overall thickness of the head-mounted device.

At least one surface of at least one of the first optical lens, the second optical lens and the third optical lens may have an anti-reflection layer, and the anti-reflection layer is a sub-wavelength structure, thereby preventing stray light from affecting imaging quality.

The optical system may further include a fourth optical lens, wherein the fourth optical lens is located between the aperture and the image plane to further improve the imaging quality.

The present invention provides a head mounted device, which includes a display, a digital signal processor, an inertia measurement unit, a support structure and the aforementioned optical system. The display is used to face the user's eyes to display images, the digital signal processor is communicatively connected to the display and the inertia measurement unit, and the support structure is used to be worn on the user's head. The optical system can be used by the user's eyes. In some embodiments, the head mounted device may include two aforementioned optical systems, and the two sets of optical systems can be used by the user's eyes respectively.

The head mounted device may further include an iris recognition module, wherein the iris recognition module is communicatively connected to the digital signal processor and is used to recognize the user's iris, thereby providing the user with convenience and security in the authentication system.

The optical system may further include a polarizing element, wherein the polarizing element is located between the display and the partially reflective element, and the display may be an organic light-emitting diode (OLED) panel and have a color filter. In this way, the OLED panel can provide a better color image. The OLED panel filters light with a color filter, and the OLED panel may not contain a polarizing element inside, and the light emitted by the display is polarized through the polarizing element located between the display and the partially reflective element. The OLED panel may be, for example, a micro LED panel or a sub-millimeter LED panel.

The head-mounted device may further include a storage mechanism, wherein the storage mechanism is used to compress the volume of the head-mounted device. For example, the storage mechanism provides a user with a method of compressing the volume of the head-mounted device (for example, folding the head-mounted device) when the head-mounted device is not needed.

The head mounted device may further include an autofocus device, wherein the autofocus device is arranged corresponding to the optical system, and the autofocus device is used to move the optical lens of the optical system. Thereby, the autofocus device can provide a focusing function of the optical system, and can adjust the focal length according to the vision of different users. In some implementations, the number of optical systems is two, and the number of autofocus devices is one, wherein the autofocus device can adjust the focal length of the two optical systems at the same time. In addition, in some implementations, the number of optical systems is two, and the number of autofocus devices is two to adjust the focal length of the two optical systems respectively.

The head mounted device may further include a liquid crystal focus module, wherein the liquid crystal focus module is disposed between the aperture and the image plane, and the liquid crystal focus module is used to provide the optical system with a larger focal length adjustment range.

The head mounted device may further include a camera, wherein the camera is communicatively connected to the digital signal processor, and the camera has the function of capturing images of the external environment and presenting them on a display. Thus, the images of the external environment captured by the camera can be presented on the display in real time, so that the user can recognize the environment while wearing the head mounted device.

The head mounted device may further include an eye tracking device, wherein the eye tracking device is used to face the user's eyes to track the position where the user's eyes are looking. This can provide the user with data analysis of usage conditions (e.g., analysis of the user's gaze target or concentration when playing video games or watching movies), and can adjust the clarity of each position of the image according to the eye's gaze range.

The head mounted device may further include a diamond like carbon (DLC) heat dissipation layer, wherein the diamond like carbon heat dissipation layer is used to dissipate heat from a heat generating element (e.g., a display) in the head mounted device. Thus, using the diamond like carbon heat dissipation layer can provide better heat dissipation efficiency. The diamond like carbon heat dissipation layer may be located, for example, on a screen of a display, a heat dissipation module of the head mounted device, and at least one of an inner surface and an outer surface of a housing of the head mounted device.

It should be noted that the communication connection mentioned in this article refers to a connection method in which two components exchange signals with each other, such as by wired or wireless transmission.

The various technical features in the above-mentioned optical system and head-mounted device of the present invention can be configured in combination to achieve corresponding effects.

In the optical system disclosed in the present invention, the material of the optical lens can be glass or plastic. If the material of the optical lens is glass, the freedom of the refractive power configuration of the optical system can be increased, and the influence of the external environmental temperature change on the imaging can be reduced, and the glass lens can be made using grinding or molding techniques. If the material of the optical lens is plastic, the production cost can be effectively reduced. In addition, a spherical surface (SPH) or an aspherical surface (ASP) can be set on the mirror surface, wherein a spherical optical lens can reduce the difficulty of manufacturing, and if an aspherical surface is set on the mirror surface, more control variables can be obtained to eliminate aberrations, reduce the number of lenses, and effectively reduce the total length of the optical system of the present invention. Furthermore, aspheric surfaces can be made by plastic injection molding or molded glass lenses.

In the optical system disclosed in the present invention, if the surface of the optical lens is an aspherical surface, it means that the entire optical effective area of the optical lens surface or a part of it is an aspherical surface.

In the optical system disclosed in the present invention, additives can be selectively added to any (or more) optical lens materials to produce light absorption or light interference effects to change the optical lens's transmittance for light in a specific wavelength band, thereby reducing stray light and color deviation. For example, the additive can have the function of filtering light in the 600-800 nm wavelength band in the system to help reduce excess red light or infrared light; or it can filter light in the 350-450 nm wavelength band to reduce excess blue light or ultraviolet light. Therefore, the additive can prevent light in a specific wavelength band from interfering with imaging. In addition, the additive can be evenly mixed in plastic and made into an optical lens using injection molding technology. In addition, the additive can also be configured as a coating on the surface of the optical lens to provide the above-mentioned effects.

In the optical system disclosed in the present invention, if the optical lens surface is convex and the position of the convex surface is not defined, it means that the convex surface can be located near the optical axis of the optical lens surface; if the optical lens surface is concave and the position of the concave surface is not defined, it means that the concave surface can be located near the optical axis of the optical lens surface. If the refractive power or focal length of the optical lens does not define its regional position, it means that the refractive power or focal length of the optical lens can be the refractive power or focal length of the optical lens near the optical axis.

In the optical system disclosed in the present invention, the inflection point of the optical lens refers to the intersection point of the positive and negative changes in the curvature of the optical lens surface. The critical point of the optical lens refers to the tangent point on the tangent line between the plane perpendicular to the optical axis and the optical lens surface, and the critical point is not located on the optical axis.

In the optical system disclosed in the present invention, the image plane of the optical system can be a plane or a curved surface with any curvature, especially a curved surface with a concave surface facing the forward direction, depending on the corresponding display.

In the optical system disclosed in the present invention, one or more imaging correction elements (flat field elements, etc.) can be selectively arranged between the optical lens closest to the image surface on the imaging light path and the image surface to achieve the effect of correcting the image (such as bending, etc.). The optical properties of the imaging correction element, such as curvature, thickness, refractive index, position, surface shape (convex or concave, spherical or aspherical, diffraction surface and Fresnel surface, etc.) can be adjusted according to the requirements of the head-mounted device. Generally speaking, the preferred imaging correction element configuration is to place a thin flat-concave element with a concave surface facing the front side close to the image surface.

In the optical system disclosed in the present invention, at least one aperture stop may be provided, which may be located before the first optical lens, between each optical lens, or after the last optical lens. The aperture stop may be a glare stop or a field stop, etc., which may be used to reduce stray light and help improve image quality.

The present invention may be appropriately provided with a variable aperture element, which may be a mechanical component or a light regulating component, which can control the size and shape of the aperture by electricity or electrical signals. The mechanical component may include movable parts such as a blade set and a shielding plate; the light regulating component may include shielding materials such as a filter element, an electrochromic material, and a liquid crystal layer. The variable aperture element can enhance the image adjustment capability by controlling the amount of light entering the image or the exposure time. In addition, the variable aperture element may also be the aperture of the present invention, which can adjust the image quality, such as the depth of field or the exposure speed, by changing the aperture value.

The present invention may appropriately place one or more optical elements to limit the form of light passing through the optical system. The optical element may be a filter, a polarizer, etc., but the present invention is not limited thereto. Furthermore, the optical element may be a single-chip element, a composite component, or presented in the form of a film, etc., but the present invention is not limited thereto. The optical element may be placed at the front end, the rear end, or between optical lenses of the optical system to control the passage of a specific form of light, thereby meeting the application requirements.

According to the above implementation, specific embodiments are proposed below and described in detail with reference to the drawings.

<First embodiment>

Please refer to FIG. 1, which is a schematic diagram of an optical system and a display according to the first embodiment of the present invention. The optical system 1 includes an aperture ST, a first optical lens E1, a reflective polarizing element RP, a first quarter wave plate QWP1, a second optical lens E2, a third optical lens E3, a partial reflection element BS, a second quarter wave plate QWP2, and an image plane IMG from the front side to the back side. The display SC is disposed on the image plane IMG. The optical system 1 includes three optical lenses (E1, E2, E3), and there is no other interpolated optical lens between the three optical lenses.

The first optical lens E1 has negative refractive power and is made of plastic material. Its front surface is concave, its rear surface is flat, its front surface is aspherical, its front surface has at least one inflection point, and its front surface has at least one critical point.

The second optical lens E2 has positive refractive power and is made of plastic material. Its front surface is concave, its rear surface is convex, and both surfaces are spherical.

The third optical lens E3 has negative refractive power and is made of plastic material. Its front surface is concave and its rear surface is convex. Both surfaces are aspherical. Its front surface has at least one inflection point and its rear surface has at least one inflection point.

The reflective polarizing element RP is attached to the rear surface of the first optical lens E1, and the first quarter wave plate QWP1 is attached to the reflective polarizing element RP.

The partially reflective element BS is attached to the rear surface of the third optical lens E3.

The second quarter wave plate QWP2 is located between the partial reflection element BS and the image plane IMG.

The curve equations of the aspheric surfaces of the above optical lenses are expressed as follows:

X: The displacement parallel to the optical axis from the intersection of the aspheric surface and the optical axis to the point on the aspheric surface that is Y away from the optical axis;

Y: the vertical distance between the point on the aspheric curve and the optical axis;

R: radius of curvature;

k: cone coefficient; and

Ai: i-th order aspheric coefficient.

In the optical system 1 of the first embodiment, the focal length of the optical system 1 is f, the aperture value (F-number) of the optical system 1 is Fno, and half of the maximum viewing angle of the optical system 1 is HFOV, and its values are as follows: f = 19.09 millimeters (mm), Fno = 2.12, HFOV = 45.0 degrees (deg.).

The Abbe number of the second optical lens E2 is V2, and the refractive index of the second optical lens E2 is N2, which satisfies the following condition: V2/N2 = 36.269.

The center thickness of the first optical lens E1 on the optical axis is CT1, the center thickness of the second optical lens E2 on the optical axis is CT2, and the center thickness of the third optical lens E3 on the optical axis is CT3, which meet the following conditions: CT1 = 1.000 mm; CT2 = 1.606 mm; CT3 = 1.000 mm; CT2 > CT1; and CT2 > CT3.

The focal length of the optical system 1 is f, and the focal length of the third optical lens E3 is f3, which satisfies the following condition: f/f3 = -6.082E-06.

The focal length of the optical system 1 is f, and the focal length of the second optical lens E2 is f2, which satisfies the following condition: f/f2 = 0.051.

The focal length of the first optical lens E1 is f1, the focal length of the second optical lens E2 is f2, and the focal length of the third optical lens E3 is f3, which satisfies the following condition: (f2+f3)/f1 = 41007.129.

The distance from the rear surface of the first optical lens E1 to the front surface of the second optical lens E2 on the optical axis is T12, and the center thickness of the second optical lens E2 on the optical axis is CT2, which satisfies the following condition: T12/CT2 = 0.805.

The center thickness of the first optical lens E1 on the optical axis is CT1, the center thickness of the second optical lens E2 on the optical axis is CT2, the center thickness of the third optical lens E3 on the optical axis is CT3, the distance from the rear surface of the first optical lens E1 to the front surface of the second optical lens E2 on the optical axis is T12, and the distance from the rear surface of the second optical lens E2 to the front surface of the third optical lens E3 on the optical axis is T23, which meets the following condition: (CT1+CT2+CT3)/(T12+T23) = 0.485.

The distance from the rear surface of the first optical lens E1 to the front surface of the second optical lens E2 on the optical axis is T12, the distance from the rear surface of the second optical lens E2 to the front surface of the third optical lens E3 on the optical axis is T23, and the distance from the front surface of the first optical lens E1 to the rear surface of the third optical lens E3 on the optical axis is TD, which satisfies the following condition: (T12+T23)/TD = 0.673.

The distance from the rear surface of the first optical lens E1 to the front surface of the second optical lens E2 on the optical axis is T12, the distance from the rear surface of the second optical lens E2 to the front surface of the third optical lens E3 on the optical axis is T23, and the distance from the rear surface of the third optical lens E3 to the image plane IMG on the optical axis is BL, which meets the following condition: (T12+T23)/BL = 4.175.

The center thickness of the first optical lens E1 on the optical axis is CT1, the center thickness of the second optical lens E2 on the optical axis is CT2, the center thickness of the third optical lens E3 on the optical axis is CT3, and the distance from the aperture ST to the image plane IMG on the optical axis is SL, which satisfies the following condition: (CT1+CT2+CT3)/SL = 0.158.

The radius of curvature of the front surface of the third optical lens E3 is R5, and the radius of curvature of the rear surface of the third optical lens E3 is R6, which meets the following condition: |R5/R6| = 0.990.

The radius of curvature of the front surface of the third optical lens E3 is R5, and the radius of curvature of the rear surface of the third optical lens E3 is R6, which satisfies the following condition: |(R5+R6)/(R5-R6)| = 202.318.

The radius of curvature of the front surface of the third optical lens E3 is R5, and the radius of curvature of the rear surface of the third optical lens E3 is R6, which meets the following condition: (R5+R6)/(R5-R6) = -202.318.

The focal length of the optical system 1 is f, and the image height presented by the image plane IMG is ImgH, which satisfies the following condition: f/ImgH = 1.009.

The distance from the aperture ST to the image plane IMG on the optical axis is SL, and the image height presented by the image plane IMG is ImgH, which satisfies the following condition: SL/ImgH = 1.206.

The distance between the aperture ST and the image plane IMG on the optical axis is SL, and the focal length of the optical system 1 is f, which satisfies the following condition: SL/f = 1.195.

The size of the aperture ST is EPD, and the image height presented by the image plane IMG is ImgH, which satisfies the following condition: EPD/ImgH = 0.476.

Half of the maximum viewing angle of the optical system 1 is HFOV, and the focal length of the optical system 1 is f, which satisfies the following condition: tan(HFOV)/f = 0.052.

The radius of curvature of the front surface of the first optical lens E1 is R1, and the radius of curvature of the rear surface of the third optical lens E3 is R6, which meets the following condition: R1/R6 = 1.160.

The radius of curvature of the front surface of the first optical lens E1 is R1, and the radius of curvature of the rear surface of the first optical lens E1 is R2, which meets the following condition: (R1+R2)/(R1-R2) = -1.000.

The radius of curvature of the front surface of the second optical lens E2 is R3, and the radius of curvature of the rear surface of the second optical lens E2 is R4, which meets the following condition: (R3+R4)/(R3-R4) = 4.039.

The distance from the front surface of the first optical lens E1 to the rear surface of the third optical lens E3 on the optical axis is TD, and the distance from the aperture ST to the image plane IMG on the optical axis is SL, which meets the following condition: TD/SL = 0.484.

The distance from the aperture ST to the front surface of the first optical lens E1 on the optical axis is ER, and the distance from the aperture ST to the image plane IMG on the optical axis is SL, which satisfies the following condition: ER/SL = 0.438. Please refer to FIG12, which is a schematic diagram showing the parameter ER in the first embodiment of the present invention.

Please refer to Table 1A and Table 1B below.

Table 1A, first embodiment f(focal length) = 19.09 mm, Fno(aperture value) = 2.12, HFOV(half viewing angle) = 45.0 degrees Surface Radius of curvature thickness Material Refractive index Abbe number Refraction/Reflection 0 Plane 1E+08 Refraction 1 Plane 2.500 Refraction 2 Aperture Plane 10.000 Refraction 3 First optical lens -41.6288 (ASP) 1.000 Plastic 1.544 56.0 Refraction 4 first quarter wave plate Plane 0.293 Refraction 5 Plane 1.000 Refraction 6 Second optical lens -135.2667 (SPH) 1.606 Plastic 1.544 56.0 Refraction 7 -81.5836 (SPH) 6.138 Refraction 8 Third optical lens -35.5427 (ASP) 1.000 Plastic 1.544 56.0 Refraction 9 Partially reflective elements -35.8958 (ASP) -1.000 Plastic 1.544 56.0 Reflection 10 -35.5427 (ASP) -6.138 Refraction 11 Second optical lens -81.5836 (SPH) -1.606 Plastic 1.544 56.0 Refraction 12 -135.2667 (SPH) -1.000 Refraction 13 first quarter wave plate Plane -0.293 Refraction 14 first quarter wave plate Plane 0.293 Reflection 15 Plane 1.000 Refraction 16 Second optical lens -135.2667 (SPH) 1.606 Plastic 1.544 56.0 Refraction 17 -81.5836 (SPH) 6.138 Refraction 18 Third optical lens -35.5427 (ASP) 1.000 Plastic 1.544 56.0 Refraction 19 -35.8958 (ASP) 0.500 Refraction 20 Second quarter wave plate Plane 0.293 Refraction twenty one Plane 0.807 Refraction twenty two Plane 0.093 Refraction twenty three Image surface Plane 0.100 Refraction The reference wavelength (d-line) is 587.6 nm. The reflective polarizing element RP is located between the first optical lens E1 and the first quarter-wave plate QWP1. The thickness of the reflective polarizer RP is calculated from the thickness of the first quarter-wave plate QWP1 listed in the table.

Table 1B, Aspheric coefficients Surface 3 4 6 7 8 9 k = -80.34579 - - - 1.00000 -10.93496 A4 = 0.43313 - - - -3.80888 -2.85659 A6 = 0.43793 - - - 0.65515 0.48114 A8 = -0.07163 - - - - -0.00690 A10 = - - - - - 0.01995 A12 = - - - - - 0.00526 A14 = - - - - - 0.00112 A16 = - - - - - -0.00001

Table 1A is the detailed structural data of the first embodiment of FIG. 1, wherein the units of the curvature radius and thickness are millimeters (mm), and surfaces 23 to 0 represent the surfaces that the light passes through in sequence from the image plane IMG to the aperture ST. Table 1B is the aspheric surface data of the first embodiment, wherein k is the cone coefficient in the aspheric curve equation, and A4 to A16 represent the 4th to 16th order aspheric surface coefficients of each surface. In addition, the following tables of the embodiments correspond to the schematic diagrams of the embodiments, and the definitions of the data in the tables are the same as those in Tables 1A and 1B of the first embodiment, and are not elaborated here.

<Second embodiment>

Please refer to FIG. 2, which is a schematic diagram of an optical system and a display according to a second embodiment of the present invention. The optical system 2 includes an aperture ST, a first optical lens E1, a reflective polarizing element RP, a first quarter wave plate QWP1, a second optical lens E2, a third optical lens E3, a partial reflection element BS, a second quarter wave plate QWP2, and an image plane IMG from the front side to the back side. The display SC is disposed on the image plane IMG. The optical system 2 includes three optical lenses (E1, E2, E3), and there is no other interpolated optical lens between the three optical lenses.

The first optical lens E1 has negative refractive power and is made of plastic material. Its front surface is concave, its rear surface is flat, its front surface is aspherical, its front surface has at least one inflection point, and its front surface has at least one critical point.

The second optical lens E2 has positive refractive power and is made of plastic material, its front surface is a plane, its rear surface is a convex surface, and its rear surface is a spherical surface.

The third optical lens E3 has negative refractive power and is made of plastic material. Its front surface is concave and its rear surface is convex. Both surfaces are aspherical. Its front surface has at least one inflection point and its rear surface has at least one inflection point.

The reflective polarizing element RP is attached to the rear surface of the first optical lens E1, and the first quarter wave plate QWP1 is attached to the reflective polarizing element RP.

The partially reflective element BS is attached to the rear surface of the third optical lens E3.

The second quarter wave plate QWP2 is located between the partial reflection element BS and the image plane IMG.

Please refer to Table 2A and Table 2B below.

Table 2A, second embodiment f(focal length) = 19.03 mm, Fno(aperture value) = 2.11, HFOV(half viewing angle) = 45.0 degrees Surface Radius of curvature thickness Material Refractive index Abbe number Refraction/Reflection 0 Plane 1E+08 Refraction 1 Plane 2.500 Refraction 2 Aperture Plane 10.000 Refraction 3 First optical lens -24.9117 (ASP) 1.000 Plastic 1.544 56.0 Refraction 4 first quarter wave plate Plane 0.293 Refraction 5 Second optical lens Plane 4.120 Plastic 1.544 56.0 Refraction 6 -35.5817 (SPH) 4.377 Refraction 7 Third optical lens -38.1253 (ASP) 1.000 Plastic 1.544 56.0 Refraction 8 Partially reflective elements -38.4784 (ASP) -1.000 Plastic 1.544 56.0 Reflection 9 -38.1253 (ASP) -4.377 Refraction 10 Second optical lens -35.5817 (SPH) -4.120 Plastic 1.544 56.0 Refraction 11 first quarter wave plate Plane -0.293 Refraction 12 first quarter wave plate Plane 0.293 Reflection 13 Second optical lens Plane 4.120 Plastic 1.544 56.0 Refraction 14 -35.5817 (SPH) 4.377 Refraction 15 Third optical lens -38.1253 (ASP) 1.000 Plastic 1.544 56.0 Refraction 16 -38.4784 (ASP) 0.500 Refraction 17 Second quarter wave plate Plane 0.293 Refraction 18 Plane 0.807 Refraction 19 Plane 0.381 Refraction 20 Image surface Plane 0.100 Refraction The reference wavelength (d-line) is 587.6 nm. The reflective polarizing element RP is located between the first optical lens E1 and the first quarter-wave plate QWP1. The thickness of the reflective polarizer RP is calculated from the thickness of the first quarter-wave plate QWP1 listed in the table.

Table 2B, Aspheric coefficients Surface 3 4 5 6 7 8 k = -25.35240 - - - 0.12735 -20.02253 A4 = -0.23694 - - - -4.50974 -3.16094 A6 = 0.39742 - - - 0.52327 0.53727 A8 = -0.05266 - - - - -0.03480 A10 = - - - - - 0.01634 A12 = - - - - - 0.00225 A14 = - - - - - 0.00038 A16 = - - - - - -0.00014

In the second embodiment, the curve equation of the aspheric surface is expressed in the same form as in the first embodiment. In addition, the definitions described in Table 2C below are the same as those in the first embodiment and are not repeated here.

Table 2C, polynomial data f [mm] 19.03 (CT1+CT2+CT3)/SL 0.262 HFOV [degree] 45.0 |R5/R6| 0.991 Fno 2.11 |(R5+R6)/(R5-R6)| 216.946 V2/N2 36.269 (R5+R6)/(R5-R6) -216.946 CT1 1.000 f/ImgH 1.003 CT2 4.120 SL/ImgH 1.232 CT3 1.000 SL/f 1.228 f/f3 -5.272E-06 EPD/ImgH 0.474 f/f2 0.291 tan(HFOV)/f 0.053 (f2+f3)/f1 78801.084 R1/R6 0.647 T12/CT2 0.071 (R1+R2)/(R1-R2) -1.000 (CT1+CT2+CT3)/(T12+T23) 1.310 (R3+R4)/(R3-R4) 1.000 (T12+T23)/TD 0.433 TD/SL 0.462 (T12+T23)/BL 1.812 ER/SL 0.428

<Third Embodiment>

Please refer to FIG. 3, which is a schematic diagram of an optical system and a display according to a third embodiment of the present invention. The optical system 3 includes an aperture ST, a first optical lens E1, a reflective polarizing element RP, a first quarter wave plate QWP1, a second optical lens E2, a third optical lens E3, a partial reflection element BS, a second quarter wave plate QWP2, and an image plane IMG from the front side to the back side. The display SC is disposed on the image plane IMG. The optical system 3 includes three optical lenses (E1, E2, E3), and there is no other interpolated optical lens between the three optical lenses.

The first optical lens E1 has negative refractive power and is made of plastic material. Its front surface is concave, its rear surface is flat, its front surface is aspherical, its front surface has at least one inflection point, and its front surface has at least one critical point.

The second optical lens E2 has positive refractive power and is made of plastic material. Its front surface is concave and its rear surface is convex. Both surfaces are aspherical. Its front surface has at least one inflection point and its rear surface has at least one inflection point.

The third optical lens E3 has negative refractive power and is made of plastic material. Its front surface is concave, its rear surface is convex, and both surfaces are aspherical.

The reflective polarizing element RP is attached to the rear surface of the first optical lens E1, and the first quarter wave plate QWP1 is attached to the reflective polarizing element RP.

The partially reflective element BS is attached to the rear surface of the third optical lens E3.

The second quarter wave plate QWP2 is located between the partial reflection element BS and the image plane IMG.

Please refer to Table 3A and Table 3B below.

Table 3A, third embodiment f(focal length) = 18.96 mm, Fno(aperture value) = 2.11, HFOV(half viewing angle) = 45.0 degrees Surface Radius of curvature thickness Material Refractive index Abbe number Refraction/Reflection 0 Plane 1E+08 Refraction 1 Plane 2.500 Refraction 2 Aperture Plane 5.294 Refraction 3 First optical lens -1299.3224 (ASP) 2.000 Plastic 1.544 56.0 Refraction 4 first quarter wave plate Plane 0.293 Refraction 5 Plane 2.078 Refraction 6 Second optical lens -90.2411 (ASP) 3.502 Plastic 1.544 56.0 Refraction 7 -22.4511 (ASP) 2.040 Refraction 8 Third optical lens -45.3716 (ASP) 3.186 Plastic 1.544 56.0 Refraction 9 Partially reflective elements -79.5664 (ASP) -3.186 Plastic 1.544 56.0 Reflection 10 -45.3716 (ASP) -2.040 Refraction 11 Second optical lens -22.4511 (ASP) -3.502 Plastic 1.544 56.0 Refraction 12 -90.2411 (ASP) -2.078 Refraction 13 first quarter wave plate Plane -0.293 Refraction 14 first quarter wave plate Plane 0.293 Reflection 15 Plane 2.078 Refraction 16 Second optical lens -90.2411 (ASP) 3.502 Plastic 1.544 56.0 Refraction 17 -22.4511 (ASP) 2.040 Refraction 18 Third optical lens -45.3716 (ASP) 3.186 Plastic 1.544 56.0 Refraction 19 -79.5664 (ASP) 0.500 Refraction 20 Second quarter wave plate Plane 0.293 Refraction twenty one Plane 0.807 Refraction twenty two Plane 1.076 Refraction twenty three Image surface Plane 0.100 Refraction The reference wavelength (d-line) is 587.6 nm. The reflective polarizing element RP is located between the first optical lens E1 and the first quarter-wave plate QWP1. The thickness of the reflective polarizer RP is calculated from the thickness of the first quarter-wave plate QWP1 listed in the table.

Table 3B, Aspheric coefficients Surface 3 4 6 7 8 9 k = 1.00000 - -0.05535 -2.63948 -31.33474 -85.59756 A4 = 0.46364 - 0.01785 -0.05606 -3.56039 -2.56489 A6 = -0.08655 - -0.37062 0.00637 0.01452 0.23593 A8 = -0.04376 - 0.01798 -0.01020 0.05853 -0.05199 A10 = 0.00755 - 0.11511 -0.01095 0.06724 -0.01324 A12 = 0.01548 - -0.03956 0.02718 0.00613 -0.00907 A14 = 0.00285 - 0.03536 -0.00831 -0.04638 0.00530 A16 = -0.00013 - -0.65800 0.00071 0.00992 0.00009 A18 = 0.00102 - -0.72837 -0.00001 0.00267 -0.01070 A20 = -0.00221 - -0.20954 0.00002 -0.00062 -0.00059

In the third embodiment, the curve equation of the aspheric surface is expressed in the same form as in the first embodiment. In addition, the definitions described in Table 3C below are the same as those in the first embodiment and are not repeated here.

Table 3C, polynomial data f [mm] 18.96 (CT1+CT2+CT3)/SL 0.410 HFOV [degree] 45.0 |R5/R6| 0.570 Fno 2.11 |(R5+R6)/(R5-R6)| 3.654 V2/N2 36.269 (R5+R6)/(R5-R6) -3.654 CT1 2.000 f/ImgH 0.994 CT2 3.502 SL/ImgH 1.111 CT3 3.186 SL/f 1.118 f/f3 -9.447E-02 EPD/ImgH 0.472 f/f2 0.351 tan(HFOV)/f 0.053 (f2+f3)/f1 0.061 R1/R6 16.330 T12/CT2 0.677 (R1+R2)/(R1-R2) -1.000 (CT1+CT2+CT3)/(T12+T23) 1.969 (R3+R4)/(R3-R4) 1.662 (T12+T23)/TD 0.337 TD/SL 0.618 (T12+T23)/BL 1.578 ER/SL 0.250

<Fourth embodiment>

Please refer to FIG. 4, which is a schematic diagram of an optical system and a display according to a fourth embodiment of the present invention. The optical system 4 includes an aperture ST, a first optical lens E1, a reflective polarizing element RP, a first quarter wave plate QWP1, a second optical lens E2, a third optical lens E3, a partial reflection element BS, a second quarter wave plate QWP2, and an image plane IMG from the front side to the back side. The display SC is disposed on the image plane IMG. The optical system 4 includes three optical lenses (E1, E2, E3), and there is no other interpolated optical lens between the three optical lenses.

The first optical lens E1 has negative refractive power and is made of plastic material. Its front surface is concave, its rear surface is flat, its front surface is aspherical, its front surface has at least one inflection point, and its front surface has at least one critical point.

The second optical lens E2 has positive refractive power and is made of plastic material. Its front surface is concave and its rear surface is convex. Both surfaces are aspherical. Its front surface has at least one inflection point and its rear surface has at least one inflection point.

The third optical lens E3 has negative refractive power and is made of plastic material. Its front surface is concave and its rear surface is convex. Both surfaces are aspherical. Its front surface has at least one inflection point and its rear surface has at least one inflection point.

The reflective polarizing element RP is attached to the rear surface of the first optical lens E1, and the first quarter wave plate QWP1 is attached to the reflective polarizing element RP.

The partially reflective element BS is attached to the rear surface of the third optical lens E3.

The second quarter wave plate QWP2 is located between the partial reflection element BS and the image plane IMG.

Please refer to Table 4A and Table 4B below.

Table 4A, fourth embodiment f(focal length) = 19.26 mm, Fno(aperture value) = 2.14, HFOV(half viewing angle) = 45.0 degrees Surface Radius of curvature thickness Material Refractive index Abbe number Refraction/Reflection 0 Plane 1E+08 Refraction 1 Plane 2.500 Refraction 2 Aperture Plane 6.762 Refraction 3 First optical lens -369.0739 (ASP) 2.068 Plastic 1.544 56.0 Refraction 4 first quarter wave plate Plane 0.293 Refraction 5 Plane 1.754 Refraction 6 Second optical lens -110.8528 (ASP) 3.591 Plastic 1.544 56.0 Refraction 7 -27.0518 (ASP) 2.871 Refraction 8 Third optical lens -39.0577 (ASP) 3.025 Plastic 1.544 56.0 Refraction 9 Partially reflective elements -62.4807 (ASP) -3.025 Plastic 1.544 56.0 Reflection 10 -39.0577 (ASP) -2.871 Refraction 11 Second optical lens -27.0518 (ASP) -3.591 Plastic 1.544 56.0 Refraction 12 -110.8528 (ASP) -1.754 Refraction 13 first quarter wave plate Plane -0.293 Refraction 14 first quarter wave plate Plane 0.293 Reflection 15 Plane 1.754 Refraction 16 Second optical lens -110.8528 (ASP) 3.591 Plastic 1.544 56.0 Refraction 17 -27.0518 (ASP) 2.871 Refraction 18 Third optical lens -39.0577 (ASP) 3.025 Plastic 1.544 56.0 Refraction 19 -62.4807 (ASP) 0.500 Refraction 20 Second quarter wave plate Plane 0.293 Refraction twenty one Plane 0.807 Refraction twenty two Plane 0.374 Refraction twenty three Image surface Plane 0.100 Refraction The reference wavelength (d-line) is 587.6 nm. The reflective polarizing element RP is located between the first optical lens E1 and the first quarter-wave plate QWP1. The thickness of the reflective polarizer RP is calculated from the thickness of the first quarter-wave plate QWP1 listed in the table.

Table 4B, Aspheric coefficients Surface 3 4 6 7 8 9 k = -6.21810 - -0.64999 -2.51370 -46.14521 -91.88087 A4 = 0.17998 - -0.20099 -0.02191 -4.13732 -2.81443 A6 = -0.08277 - -0.42485 -0.04612 0.16015 0.26839 A8 = -0.00335 - 0.00769 0.00102 0.03907 -0.03789 A10 = 0.00776 - 0.08285 -0.00490 0.04812 0.01225 A12 = 0.00732 - 0.01130 0.01595 0.03745 -0.00928 A14 = 0.00730 - -0.03305 0.00248 -0.05216 -0.00792 A16 = -0.00126 - -0.00021 -0.00548 0.00231 0.01326 A18 = 0.00161 - -0.01997 0.00147 0.00487 -0.00099 A20 = -0.00245 - -0.02403 -0.00012 -0.00055 0.00084

In the fourth embodiment, the curve equation of the aspheric surface is expressed in the same form as in the first embodiment. In addition, the definitions described in Table 4C below are the same as those in the first embodiment and are not repeated here.

Table 4C, polynomial data f [mm] 19.26 (CT1+CT2+CT3)/SL 0.387 HFOV [degree] 45.0 |R5/R6| 0.625 Fno 2.14 |(R5+R6)/(R5-R6)| 4.335 V2/N2 36.269 (R5+R6)/(R5-R6) -4.335 CT1 2.068 f/ImgH 0.985 CT2 3.591 SL/ImgH 1.148 CT3 3.025 SL/f 1.166 f/f3 -9.600E-02 EPD/ImgH 0.460 f/f2 0.297 tan(HFOV)/f 0.052 (f2+f3)/f1 0.200 R1/R6 5.907 T12/CT2 0.570 (R1+R2)/(R1-R2) -1.000 (CT1+CT2+CT3)/(T12+T23) 1.766 (R3+R4)/(R3-R4) 1.646 (T12+T23)/TD 0.362 TD/SL 0.606 (T12+T23)/BL 2.357 ER/SL 0.301

<Fifth Embodiment>

Please refer to FIG. 5, which is a schematic diagram of an optical system and a display according to the fifth embodiment of the present invention. The optical system 5 includes an aperture ST, a first optical lens E1, a reflective polarizing element RP, a first quarter wave plate QWP1, a second optical lens E2, a third optical lens E3, a partial reflection element BS, a second quarter wave plate QWP2, and an image plane IMG from the front side to the back side. The display SC is disposed on the image plane IMG. The optical system 5 includes three optical lenses (E1, E2, E3), and there is no other interpolated optical lens between the three optical lenses.

The first optical lens E1 has negative refractive power and is made of plastic material. Its front surface is concave, its rear surface is convex, its front surface is aspherical, its rear surface is spherical, its front surface has at least one inflection point, and its front surface has at least one critical point.

The second optical lens E2 has negative refractive power and is made of plastic material. Its front surface is concave, its rear surface is convex, and both surfaces are spherical.

The third optical lens E3 has negative refractive power and is made of plastic material. Its front surface is concave and its rear surface is convex. Both surfaces are aspherical. Its front surface has at least one inflection point and its rear surface has at least one inflection point.

The reflective polarizing element RP is attached to the rear surface of the first optical lens E1, and the first quarter wave plate QWP1 is attached to the reflective polarizing element RP.

The partially reflective element BS is attached to the rear surface of the third optical lens E3.

The second quarter wave plate QWP2 is located between the partial reflection element BS and the image plane IMG.

Please refer to Table 5A and Table 5B below.

Table 5A, fifth embodiment f(focal length) = 19.00 mm, Fno(aperture value) = 2.11, HFOV(half viewing angle) = 45.0 degrees Surface Radius of curvature thickness Material Refractive index Abbe number Refraction/Reflection 0 Plane 1E+08 Refraction 1 Plane 2.500 Refraction 2 Aperture Plane 10.000 Refraction 3 First optical lens -32.9019 (ASP) 1.000 Plastic 1.544 56.0 Refraction 4 first quarter wave plate -113.6798 (SPH) 0.293 Refraction 5 -113.6798 (SPH) 1.000 Refraction 6 Second optical lens -60.7410 (SPH) 1.021 Plastic 1.544 56.0 Refraction 7 -63.3644 (SPH) 5.889 Refraction 8 Third optical lens -30.1486 (ASP) 1.031 Plastic 1.544 56.0 Refraction 9 Partially reflective elements -30.5125 (ASP) -1.031 Plastic 1.544 56.0 Reflection 10 -30.1486 (ASP) -5.889 Refraction 11 Second optical lens -63.3644 (SPH) -1.021 Plastic 1.544 56.0 Refraction 12 -60.7410 (SPH) -1.000 Refraction 13 first quarter wave plate -113.6798 (SPH) -0.293 Refraction 14 first quarter wave plate -113.6798 (SPH) 0.293 Reflection 15 -113.6798 (SPH) 1.000 Refraction 16 Second optical lens -60.7410 (SPH) 1.021 Plastic 1.544 56.0 Refraction 17 -63.3644 (SPH) 5.889 Refraction 18 Third optical lens -30.1486 (ASP) 1.031 Plastic 1.544 56.0 Refraction 19 -30.5125 (ASP) 0.500 Refraction 20 Second quarter wave plate Plane 0.293 Refraction twenty one Plane 0.807 Refraction twenty two Plane 0.079 Refraction twenty three Image surface Plane 0.100 Refraction The reference wavelength (d-line) is 587.6 nm. The reflective polarizing element RP is located between the first optical lens E1 and the first quarter-wave plate QWP1. The thickness of the reflective polarizer RP is calculated from the thickness of the first quarter-wave plate QWP1 listed in the table.

Table 5B, Aspheric coefficients Surface 3 4 6 7 8 9 k = -54.97226 - - - 1.00000 -7.00763 A4 = 0.05442 - - - -3.37270 -2.71420 A6 = 0.44055 - - - 0.51626 0.40027 A8 = -0.06039 - - - - 0.00294 A10 = - - - - - 0.01593 A12 = - - - - - 0.00447 A14 = - - - - - 0.00008 A16 = - - - - - -0.00034

In the fifth embodiment, the curve equation of the aspheric surface is expressed in the same form as in the first embodiment. In addition, the definitions described in the following Table 5C are the same as those in the first embodiment and are not repeated here.

Table 5C, polynomial data f [mm] 19.00 (CT1+CT2+CT3)/SL 0.139 HFOV [degree] 45.0 |R5/R6| 0.988 Fno 2.11 |(R5+R6)/(R5-R6)| 166.697 V2/N2 36.269 (R5+R6)/(R5-R6) -166.697 CT1 1.000 f/ImgH 1.004 CT2 1.021 SL/ImgH 1.163 CT3 1.031 SL/f 1.158 f/f3 -8.656E-06 EPD/ImgH 0.476 f/f2 -0.006 tan(HFOV)/f 0.053 (f2+f3)/f1 25716.941 R1/R6 1.078 T12/CT2 1.267 (R1+R2)/(R1-R2) -1.815 (CT1+CT2+CT3)/(T12+T23) 0.425 (R3+R4)/(R3-R4) -47.307 (T12+T23)/TD 0.702 TD/SL 0.465 (T12+T23)/BL 4.070 ER/SL 0.455

<Sixth embodiment>

Please refer to FIG. 6, which is a schematic diagram of an optical system, a display, a liquid crystal focus module and a diamond-like carbon heat dissipation layer according to the sixth embodiment of the present invention. The optical system 6 includes an aperture ST, a first optical lens E1, a reflective polarizing element RP, a first quarter-wave plate QWP1, a second optical lens E2, a third optical lens E3, a partial reflection element BS, a second quarter-wave plate QWP2 and an image plane IMG from the front side to the back side. Among them, the display SC is disposed on the image plane IMG. The optical system 6 includes three optical lenses (E1, E2, E3), and there is no other interpolated optical lens between the three optical lenses. The components of the optical system 6 of the present embodiment described above and the components with the same names and symbols in the optical system 3 of the third embodiment have the same or similar structural features, and thus will not be described in detail.

In this embodiment, a liquid crystal focus module LFM is disposed between the aperture ST and the first optical lens E1, and the liquid crystal focus module LFM is used to provide a larger focal length adjustment range for the optical system 6. In addition, a diamond-like carbon heat sink layer DHL is disposed on the screen of the display SC facing the optical system 6, and the diamond-like carbon heat sink layer DHL is used to dissipate heat from the display SC.

<Seventh Embodiment>

Please refer to FIG. 7 , which is a schematic diagram of an optical system and a display according to the seventh embodiment of the present invention. The optical system 7 includes, from the front side to the back side, an aperture ST, a first optical lens E1, a reflective polarizing element RP, a first quarter-wave plate QWP1, a second optical lens E2, a third optical lens E3, a partial reflection element BS, a second quarter-wave plate QWP2, and an image surface IMG. Among them, the display SC is disposed on the image surface IMG. The optical system 7 includes three optical lenses (E1, E2, E3), and there are no other interpolated optical lenses between the three optical lenses. The elements of the optical system 7 of the above-mentioned embodiment and the elements with the same names and symbols in the optical system 2 of the second embodiment have the same or similar structural features, so they are not repeated here.

In this embodiment, the front surface of the third optical lens E3 has an anti-reflection layer ARL, and the anti-reflection layer ARL is a sub-wavelength structure. In the optical system 7 disclosed in this embodiment, the front surface of the third optical lens E3 is configured with an anti-reflection layer ARL, but the present invention is not limited to this. In other embodiments, the surface of any optical lens in the optical system can be configured with an anti-reflection layer according to actual design requirements.

<Eighth Embodiment>

Please refer to FIG8 , which is a schematic diagram of an optical system and a display according to the eighth embodiment of the present invention. The optical system 8 includes, from the front side to the back side, an aperture ST, a first optical lens E1, a reflective polarizing element RP, a first quarter-wave plate QWP1, a second optical lens E2, a third optical lens E3, a partial reflection element BS, a second quarter-wave plate QWP2, and an image surface IMG. Among them, the display SC is disposed on the image surface IMG. The optical system 8 includes three optical lenses (E1, E2, E3), and there are no other interpolated optical lenses between the three optical lenses. The components of the optical system 8 of the above-mentioned present embodiment and the components with the same names and symbols in the optical system 3 of the third embodiment have the same or similar structural features, so they are not repeated here.

In this embodiment, the optical system 8 further comprises a polarizing element PM, wherein the polarizing element PM is located between the display SC and the partial reflective element BS. In addition, the display SC of this embodiment is an organic light emitting diode panel and has a color filter CF.

<Ninth Embodiment>

Please refer to FIG9 , which is a schematic diagram of an optical system and a display according to the ninth embodiment of the present invention. The optical system 9 includes, from the front side to the back side, an aperture ST, a first optical lens E1, a reflective polarizing element RP, a first quarter-wave plate QWP1, a second optical lens E2, a third optical lens E3, a partial reflection element BS, a second quarter-wave plate QWP2, and an image surface IMG. Among them, the display SC is disposed on the image surface IMG. The optical system 9 includes three optical lenses (E1, E2, E3), and there are no other interpolated optical lenses between the three optical lenses. Except for the first optical lens E1, the components of the optical system 9 of the above-mentioned present embodiment and the components with the same names and symbols in the optical system 4 of the fourth embodiment have the same or similar structural features, so they are not repeated here.

In this embodiment, the first optical lens E1 is a super-smooth lens. In the optical system 9 disclosed in this embodiment, the first optical lens E1 is a super-smooth lens, but the present invention is not limited thereto. In other embodiments, any optical lens in the optical system can be a super-smooth lens according to actual design requirements.

<Tenth Embodiment>

Please refer to Figures 10 and 11, wherein Figure 10 is a schematic diagram of a head-mounted device according to the tenth embodiment of the present invention, and Figure 11 is a schematic diagram of the head-mounted device of Figure 10 viewed from above.

The head mounted device 10 of this embodiment includes a display 101, a digital signal processor 102, an inertia measurement unit 103, a support structure 104, an eye tracking device 105, two optical systems 106, two autofocus devices 107, two cameras 108, a storage mechanism 109 and an iris recognition module 100. The optical system 106 can be any of the optical systems of the aforementioned embodiments, but the present invention is not limited thereto.

The display 101 is used to face the user's eyes to display images. The inertia measurement unit 103 is used to measure the angular velocity and acceleration of the head-mounted device 10 in three-dimensional space to obtain the posture of the head-mounted device 10. The support structure 104 can be at least one strap or at least one structure similar to the temples of glasses, which is used to be worn on the user's head. The eye tracking device 105 is used to face the user's eyes to track the position where the user's eyes are looking, which can provide the user with data analysis of the usage situation and adjust the clarity of each position of the picture according to the eye's gaze range. Two sets of optical systems 106 can be used by the user with both eyes respectively. The two sets of auto-focus devices 107 are respectively arranged corresponding to the two sets of optical systems 106, and the auto-focus devices 107 are used to move the optical lenses of the optical system 106, so as to provide the optical system 106 with a focus function, and can adjust the focal length for different users' vision. The camera 108 and the display 101 are respectively connected to the digital signal processor 102 for communication, and the camera 108 can take an image of the external environment and present it on the display 101 through the digital signal processor 102. The image of the external environment taken by the camera 108 can be presented on the display 101 in real time, so that the user can identify the environment when wearing the head-mounted device 10. Thus, through the camera configuration, the image of the external environment can be captured and presented in real time on the display, providing functions such as VR mode, AR mode, and MR mode of the head-mounted device. The external image real-time presentation function can also be used to view the surrounding environment without taking off the head-mounted device 10. In addition, through the configuration of at least two cameras, optical zoom of a multi-lens configuration can be provided, or recognition function can be provided using computer vision. Among them, the multi-camera configuration can include a type of lidar module configuration, such as structured light or time of flight, to provide more diverse functions. The storage mechanism 109 allows the user to compress the volume of the head-mounted device 10 when the head-mounted device 10 is not needed, for example, the head-mounted device 10 can be folded. The iris recognition module 100 is communicatively connected to the digital signal processor 102, and the iris recognition module 100 is used to recognize the user's iris.

In some implementations, the head mounted device may also have Bluetooth or wireless network functionality to communicate with at least one external device.

In some embodiments, the head-mounted device may also have at least one speaker, at least one earphone or at least one noise reduction earphone to provide the user with sound. In addition, in some embodiments, the head-mounted device may also have at least one microphone to receive the user's sound.

In some implementations, the head-mounted device may also be paired with at least one controller, wherein the controller may be a joystick, a handle, or a handheld device, so as to provide the user with interactive functions such as VR mode, AR mode, and MR mode between the head-mounted device.

Although the present invention is disclosed as above by the aforementioned embodiments, these embodiments are not intended to limit the present invention. Any changes and modifications made within the spirit and scope of the present invention are within the scope of patent protection of the present invention. Please refer to the attached patent application for the scope of protection defined by the present invention.

1,2,3,4,5,6,7,8,9: Optical system 10: Head mounted device 101: Display 102: Digital signal processor 103: Inertia measurement unit 104: Support structure 105: Eye tracking device 106: Optical system 107: Autofocus device 108: Camera 109: Storage mechanism 100: Iris recognition module ARL: Anti-reflection layer BS: Partial reflection element BL: Distance from the rear surface of the third optical lens to the image plane on the optical axis C: Critical point CF: Color filter CT1: Center thickness of the first optical lens on the optical axis CT2: The center thickness of the second optical lens on the optical axis CT3: The center thickness of the third optical lens on the optical axis DHL: Diamond-like carbon heat dissipation layer E1: The first optical lens E2: The second optical lens E3: The third optical lens ER: The distance from the aperture to the front surface of the first optical lens on the optical axis EPD: The size of the aperture f: The focal length of the optical system f1: The focal length of the first optical lens f2: The focal length of the second optical lens f3: The focal length of the third optical lens Fno: The aperture value of the optical system HFOV: Half of the maximum viewing angle in the optical system ImgH: The image height presented by the image plane IMG: Image plane LFM: Liquid crystal focus module N2: The refractive index of the second optical lens P: inflection point PM: polarizing element QWP1: first quarter wave plate QWP2: second quarter wave plate RP: reflective polarizing element R1: radius of curvature of the front surface of the first optical lens R2: radius of curvature of the rear surface of the first optical lens R3: radius of curvature of the front surface of the second optical lens R4: radius of curvature of the rear surface of the second optical lens R5: radius of curvature of the front surface of the third optical lens R6: radius of curvature of the rear surface of the third optical lens ST: aperture SC: display SL: distance from aperture to image plane on the optical axis T12: The distance from the rear surface of the first optical lens to the front surface of the second optical lens on the optical axis T23: The distance from the rear surface of the second optical lens to the front surface of the third optical lens on the optical axis TD: The distance from the front surface of the first optical lens to the rear surface of the third optical lens on the optical axis V2: Abbe number of the second optical lens

FIG. 1 is a schematic diagram of an optical system and a display according to a first embodiment of the present invention. FIG. 2 is a schematic diagram of an optical system and a display according to a second embodiment of the present invention. FIG. 3 is a schematic diagram of an optical system and a display according to a third embodiment of the present invention. FIG. 4 is a schematic diagram of an optical system and a display according to a fourth embodiment of the present invention. FIG. 5 is a schematic diagram of an optical system and a display according to a fifth embodiment of the present invention. FIG. 6 is a schematic diagram of an optical system, a display, a liquid crystal focus module, and a diamond-like carbon heat sink layer according to a sixth embodiment of the present invention. FIG. 7 is a schematic diagram of an optical system and a display according to a seventh embodiment of the present invention. FIG. 8 is a schematic diagram of an optical system and a display according to an eighth embodiment of the present invention. FIG. 9 is a schematic diagram of an optical system and a display according to the ninth embodiment of the present invention. FIG. 10 is a schematic diagram of a head-mounted device according to the tenth embodiment of the present invention. FIG. 11 is a schematic diagram of the head-mounted device of FIG. 10 from above. FIG. 12 is a schematic diagram of the parameters ImgH, CT1, CT2, CT3, T12, T23, ER, EPD, BL, TD, SL and the inflection point and critical point of the first optical lens according to the first embodiment of the present invention.

1:Optical system

BS: Partially reflective element

E1: First optical lens

E2: Second optical lens

E3: Third optical lens

IMG: Image surface

QWP1: First quarter wave plate

QWP2: Second quarter wave plate

RP: reflective polarizing element

ST: aperture

SC:Display

Claims (10)

An optical system comprises: an aperture located at the front side of the optical system; an image plane located at the rear side of the optical system; a reflective polarizing element located between the aperture and the image plane; a partial reflective element located between the reflective polarizing element and the image plane; a first quarter wave plate located between the reflective polarizing element and the partial reflective element; a second quarter wave plate located between the partial reflective element and the image plane; a first optical lens located between the aperture and the first quarter wave plate; a second optical lens located between the first optical lens and the second quarter wave plate; and a third optical lens located between the second optical lens and the second quarter wave plate; The first optical lens has negative refractive power, the focal length of the optical system is f, and the image height presented by the image plane is ImgH, which meets the following conditions: 0 < f/ImgH < 1.20. The optical system as described in claim 1, wherein the center thickness of the first optical lens on the optical axis is CT1, the center thickness of the second optical lens on the optical axis is CT2, the center thickness of the third optical lens on the optical axis is CT3, the distance from the rear surface of the first optical lens to the front surface of the second optical lens on the optical axis is T12, and the distance from the rear surface of the second optical lens to the front surface of the third optical lens on the optical axis is T23, which satisfies the following conditions: 0 < (CT1+CT2+CT3)/(T12+T23) < 1.75. The optical system as described in claim 1, wherein the distance from the rear surface of the first optical lens to the front surface of the second optical lens on the optical axis is T12, the distance from the rear surface of the second optical lens to the front surface of the third optical lens on the optical axis is T23, and the distance from the front surface of the first optical lens to the rear surface of the third optical lens on the optical axis is TD, which satisfies the following conditions: 0.37 < (T12+T23)/TD < 1. The optical system as described in claim 3, wherein the distance from the rear surface of the first optical lens to the front surface of the second optical lens on the optical axis is T12, the distance from the rear surface of the second optical lens to the front surface of the third optical lens on the optical axis is T23, and the distance from the rear surface of the third optical lens to the image plane on the optical axis is BL, which satisfies the following conditions: 1.20 < (T12+T23)/BL < 5.20. The optical system as described in claim 1, wherein the center thickness of the first optical lens on the optical axis is CT1, the center thickness of the second optical lens on the optical axis is CT2, the center thickness of the third optical lens on the optical axis is CT3, and the distance from the aperture to the image plane on the optical axis is SL, which satisfies the following conditions: 0.10 < (CT1+CT2+CT3)/SL < 0.35. The optical system as described in claim 1, wherein the radius of curvature of the front surface of the third optical lens is R5, and the radius of curvature of the rear surface of the third optical lens is R6, which satisfies the following conditions: 0.01 ＜ |R5/R6| ＜ 1. The optical system as described in claim 6, wherein the radius of curvature of the front surface of the third optical lens is R5, and the radius of curvature of the rear surface of the third optical lens is R6, which satisfies the following condition: 3.85 ＜ |(R5+R6)/(R5-R6)|. The optical system as described in claim 6, wherein the radius of curvature of the front surface of the third optical lens is R5, and the radius of curvature of the rear surface of the third optical lens is R6, which satisfies the following condition: (R5+R6)/(R5-R6) ＜ 0. An optical system as described in claim 1, wherein the focal length of the optical system is f, and the focal length of the third optical lens is f3, which satisfies the following condition: -10 ＜ f/f3 ＜ 0. A head mounted device comprising: The optical system as described in claim 1.

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