Microscopic projector optical system and glasses type terminal

Abstract

A microscopic projector optical system for displaying input image light on a display surface includes a first lens, a second lens, and a third lens from the side of the display surface, the paraxial refractive index of the first lens and the third lens being positive, the paraxial refractive index of the second lens being negative, and the paraxial refractive index of the third lens being negative. The focal length of the whole optical system of the microscopic projector is set as ft, the first lens satisfies a specified formula using a focal length f1, the second lens satisfies a specified formula using a focal length f2, and the third lens satisfies a specified formula using a focal length f3.

Description

Technical Field

[0001] This invention relates to an optical system for a micro projector and an eyeglass-type terminal. Background Technology

[0002] Previously, there were known eyeglasses-type devices and head-mounted displays that included display panels that generated images, microscope projector lenses, waveguides, etc., and displayed two-dimensional images for users to observe (for example, see Patent Document 1 and Patent Document 2).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2017-207686

[0006] Patent Document 2: International Publication No. 2023 / 047488 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] Because this type of device incorporates the optical system within a limited space, the optical system can sometimes become complex. Furthermore, if a simple optical system is used, it may sometimes fail to project the image sufficiently onto the necessary display area, or it may lead to image degradation.

[0009] Therefore, the present invention is made in view of these aspects, and aims to enable the realization of a small micro-projector lens in a simple structure in an optical system used to constitute a micro-projector.

[0010] Technical means to solve the problem

[0011] In a first embodiment of the present invention, a microscopic projector optical system is provided for displaying an input image light on a display surface. The microscopic projector optical system includes a first lens, a second lens, and a third lens from the side of the display surface. The paraxial refractive indices of the first lens and the third lens are positive, and the paraxial refractive index of the second lens is negative. If the overall focal length of the microscopic projector optical system is set to ft, and the focal length of the first lens is set to f1, then the first lens satisfies the following formula.

[0012]

[0013] If the focal length of the second lens is set to f2, then the second lens satisfies the following equation:

[0014]

[0015] If the focal length of the third lens is set to f3, then the third lens satisfies the following formula:

[0016] .

[0017] The first lens, the second lens, and the third lens may also satisfy the following formula.

[0018]

[0019] At least one of the first surface on the side of the display surface and the second surface on the side opposite to the first surface of at least one of the first lens, the second lens, and the third lens may also be aspherical.

[0020] The second lens may also be a meniscus lens having a shape that bulges toward the third lens on the optical axis, with the first surface on one side of the display surface and the second surface on the opposite side of the first surface.

[0021] The optical system of the micro projector may also include a brightness aperture between the display surface and the first lens.

[0022] If the distance from the brightness aperture to the imaging surface of the image light is TT, then the overall focal length ft of the micro projector optical system can also satisfy the following formula.

[0023]

[0024] In at least one of the first lens, the second lens, and the third lens, at least one of the first surface on the side of the display surface and the second surface on the side opposite to the first surface may also have a refractive index gradient so that the positive and negative signs of the refractive index on the optical axis are reversed toward the outer edge of the lens.

[0025] In a second embodiment of the present invention, an eyeglass-type terminal is provided for a user to wear. The eyeglass-type terminal includes: a display surface disposed on at least one of the user's right eye lens and left eye lens, and displaying the image light for the user to visually recognize; a frame for fixing the user's right eye lens and left eye lens; an image light emitting section disposed on the frame for emitting the image light; and a micro-projector optical system of the first embodiment disposed on the frame for inputting the image light emitted from the image light emitting section and displaying the input image light on the display surface.

[0026] The effects of the invention

[0027] According to the present invention, it is possible to realize a small-sized micro-projector lens with a simple structure. Attached Figure Description

[0028] [ Figure 1 [] indicates a structural example of the glasses-type terminal 10 in this embodiment.

[0029] [ Figure 2 [] indicates a first structural example of the micro projector optical system 100 of this embodiment.

[0030] [ Figure 3 [This represents an example of the OTF value of the microprojector optical system 100 of the first structural example with respect to the spatial frequency.]

[0031] [ Figure 4 [This represents an example of the OTF value of an optical system being compared with respect to spatial frequency.]

[0032] [ Figure 5 [ ] represents an example of the aberrations of the microprojector optical system 100 of the first structural example.

[0033] [ Figure 6 [This represents an example of the design values ​​for the microprojector optical system 100 of the first structural example.]

[0034] [ Figure 7 [ ] represents an example of the aspherical coefficient of the lens used in the microprojector optical system 100 of the first structural example.

[0035] [ Figure 8 [] indicates a second structural example of the microprojector optical system 100 of this embodiment.

[0036] [ Figure 9 [This represents an example of the OTF value of the microprojector optical system 100 of the second structural example with respect to the spatial frequency.]

[0037] [ Figure 10 [Example of aberration in the optical system 100 of the micro projector of the second structural example]

[0038] [ Figure 11 [This represents an example of the design values ​​for the microprojector optical system 100 of the second structural example.]

[0039] [ Figure 12 [ ] represents an example of the aspherical coefficient of the lens used in the microprojector optical system 100 of the second structural example.

[0040] [ Figure 13 [] indicates a third structural example of the microprojector optical system 100 in this embodiment.

[0041] [ Figure 14[This represents an example of the OTF value of the microprojector optical system 100 of the third structural example with respect to the spatial frequency.]

[0042] [ Figure 15 [Example of aberrations in the optical system 100 of the third structural example of a micro projector]

[0043] [ Figure 16 [This represents an example of the design values ​​for the optical system 100 of the microprojector in the third structural example.]

[0044] [ Figure 17 [ ] represents an example of the aspherical coefficient of the lens used in the microprojector optical system 100 of the third structural example. Detailed Implementation

[0045] <Structural Example of Eyeglasses Terminal 10>

[0046] Figure 1 This illustrates a structural example of the glasses-type terminal 10 according to this embodiment. Figure 1 In this context, three orthogonal axes are designated as the X-axis, Y-axis, and Z-axis. The eyeglasses-type terminal 10 is a device worn by a user, such as a wearable device. The eyeglasses-type terminal 10 has a display surface that allows the user to observe the scenery through their glasses and projects image light onto the lenses of the glasses. The eyeglasses-type terminal 10 includes a display surface 20, a frame 30, an image light emitting unit 40, and a micro-projector optical system 100.

[0047] Display surface 20 is disposed on at least one of the user's right eye lens and left eye lens. Display surface 20 displays image light emitted from the microprojector optical system 100 for the user to visually recognize. Display surface 20 is disposed, for example, on the second surface of the lens, so that at least a portion of the light incident from the first surface of the lens passes through the user's eye and the image light is projected onto the second surface. Here, the first surface of the lens is the surface of the lens facing the side opposite to the user when the user is wearing the eyeglass-type terminal 10. Display surface 20 may be a portion of the second surface of the lens, or it may be approximately the entire area of ​​the second surface of the lens. Alternatively, display surface 20 may also be disposed on the first surface of the lens.

[0048] The frame 30 secures the lenses. For example, the frame 30 secures the user's right and left eye lenses. Alternatively, the frame 30 may also have a single lens serving as both lenses for the user's eyes. In this case, the frame 30 may also have the shape of goggles. The frame 30 has features such as a temple and straps to allow the user to wear the eyeglass-type terminal 10.

[0049] An image light emitting unit 40 is provided on the frame 30 to emit image light and project the image light onto the display surface 20. One or more such image light emitting units 40 are provided on the frame 30. Figure 1 The following example illustrates this: A frame 30 is provided with an image light emitting section 40a for displaying image light L1 on a display surface 20a and an image light emitting section 40b for displaying image light L2 on a display surface 20b.

[0050] The image light emitting unit 40 can be provided at the location of the fixed lens on the frame 30, or on the side support of the frame 30, etc. Ideally, the image light emitting unit 40 is provided as an integral part of the frame 30. For example, the image light emitting unit 40 may also have a display panel such as a liquid crystal, and display the image displayed on the display surface 20 on the liquid crystal.

[0051] A micro-projector optical system 100 is mounted on the frame 30, receives image light emitted from the image light emitting unit 40, and displays the received image light on the display surface 20. The micro-projector optical system 100 has multiple lenses that magnify the field of view of the received image light and output it toward the display surface 20. In addition, the image light output from the micro-projector optical system 100 can also be projected onto the display surface 20 via a reflector or the like. Figure 1 The following example illustrates this: A micro projector optical system 100a corresponding to the image light emitting section 40a and a micro projector optical system 100b corresponding to the image light emitting section 40b are provided on the frame 30.

[0052] As described above, the optical system of the eyeglass-type terminal 10 sometimes becomes complex due to the need to assemble the optical system within a limited space. Furthermore, if a simple optical system is used, image light may not be sufficiently projected onto the display surface 20, or the displayed image may degrade. Therefore, the microprojector optical system 100 of this embodiment is constructed with a simple and compact optical system and, for example, has a large field of view, thus reducing degradation. This microprojector optical system 100 will now be described.

[0053] <First structural example of the optical system 100 for a micro projector>

[0054] Figure 2 This section illustrates a first structural example of the micro-projector optical system 100 according to this embodiment. The micro-projector optical system 100 is an optical system for displaying input image light on the display surface 20. In this embodiment, the axis substantially parallel to the optical axis is designated as the Z-axis. Furthermore, the direction in which image light is input to the micro-projector optical system 100 and the direction in which image light is output from the micro-projector optical system 100 are designated as the -Z direction. Additionally, the surface of the image emitted by the image light emitting unit 40, i.e., the display panel 41, is shown on the input side of the micro-projector optical system 100.

[0055] The optical system 100 of the microprojector includes, from the side of the display surface 20, a brightness aperture 101, a first lens 110, a second lens 120, and a third lens 130. The brightness aperture 101 is disposed between the display surface 20 and the first lens 110, and adjusts the brightness. The brightness aperture 101 has an opening for setting the aperture value. Ideally, the brightness aperture 101 is configured to allow adjustment of the size of the opening.

[0056] The first lens 110, the second lens 120, and the third lens 130 are each a single lens. Figure 2 This example illustrates a microscope projector optical system 100 composed of a total of three lenses. Furthermore, in this embodiment, "display surface 20 side" refers to the viewpoint side of the microscope projector optical system 100, and "input side" or "display panel 41 side" refers to the object side of the microscope projector optical system 100.

[0057] The first lens 110, the second lens 120, and the third lens 130 are formed, for example, of plastic or glass. The paraxial refractive indices of the first lens 110 and the third lens 130 are positive. The paraxial refractive index of the second lens 120 is negative. The first lens 110, the second lens 120, and the third lens 130 are fixed to the main body (not shown) of the microscope projector optical system 100. Ideally, the first lens 110, the second lens 120, and the third lens 130 are configured to be movable along the optical axis.

[0058] For example, the main body of the microprojector optical system 100 may be configured such that the positions of the first lens 110, the second lens 120, and the third lens 130 can be manually adjusted by the user. Alternatively, the microprojector optical system 100 may also include actuators for moving each lens individually.

[0059] exist Figure 2 In this design, the side of the first lens 110 facing the -Z direction on the display surface 20 side is designated as the first lens surface 111, and the side facing the +Z direction on the opposite side of the first lens surface 111 is designated as the second lens surface 112. Similarly, the side of the second lens 120 facing the -Z direction on the display surface 20 side is designated as the third lens surface 121, and the side facing the +Z direction on the opposite side of the third lens surface 121 is designated as the fourth lens surface 122. Furthermore, the side of the third lens 130 facing the -Z direction on the display surface 20 side is designated as the fifth lens surface 131, and the side facing the +Z direction on the opposite side of the fifth lens surface 131 is designated as the sixth lens surface 132.

[0060] At least one of the first surface on the side of the display surface 20 of at least one of the first lens 110, the second lens 120 and the third lens 130, and at least one of the second surface on the side opposite to the first surface, is an aspherical surface. Figure 2 The following examples illustrate that the first lens surface 111, the second lens surface 112, the third lens surface 121, the fourth lens surface 122, the fifth lens surface 131, and the sixth lens surface 132 are all aspherical surfaces.

[0061] If the overall focal length of the micro projector optical system 100 is set to ft and the focal length of the first lens 110 is set to f1, then the first lens 110 satisfies the following formula.

[0062] [Formula 1]

[0063]

[0064] If the focal length of the second lens 120 is set to f2, then the second lens 120 satisfies the following formula. Furthermore, the third lens surface 121 and the fourth lens surface 122 of the second lens 120 have a shape that protrudes along the optical axis toward the third lens 130 on the side opposite to the display surface 20. The second lens 120 is, for example, a meniscus lens.

[0065] [Formula 2]

[0066]

[0067] If the focal length of the third lens 130 is set to f3, then the third lens 130 satisfies the following formula.

[0068] [Formula 3]

[0069]

[0070] In addition, the first lens 110, the second lens 120 and the third lens 130 also satisfy the following formula.

[0071] [Formula 4]

[0072]

[0073] The optical system 100 of the microprojector satisfies equations (1) to (4) through the first lens 110, the second lens 120, and the third lens 130, thereby maintaining a good value of the optical transfer function (OTF) relative to the spatial frequency. The OTF value relative to the spatial frequency is a comprehensive representation of the imaging performance of the optical system 100 of the microprojector, and specifically indicates the degree to which it faithfully reproduces the contrast and phase of the subject in the image. The spatial frequency is the number of black and white lines per millimeter on the image plane, measured in "lines / mm" (lines being the number of line pairs).

[0074] <The OTF value of the optical system 100 of the micro projector relative to the spatial frequency>

[0075] Figure 3 This represents an example of the OTF value of the microprojector optical system 100 of the first structural example with respect to the spatial frequency. Figure 4 This represents an example of the OTF value of an optical system used for comparison with respect to spatial frequency. The optical system used for comparison is an optical system of a microprojector optical system 100 in which the three lenses do not satisfy equations (1) to (4). Figure 3 and Figure 4 The horizontal axis represents spatial frequency, and the vertical axis represents the OTF value. Furthermore, for ease of design, Figure 3 and Figure 4 The results of a simulation obtained by using an inverse tracking optical system that images an infinite number of object points on the side of the display surface 20 onto the display panel 41 are shown.

[0076] exist Figure 3 and Figure 4 In the simulation, straight lines represent the results of light ray simulation in the tangential direction (T direction), and dashed lines represent the results of light ray simulation in the sagittal direction (S direction). Furthermore, the light ray that images at the center of the display panel 41 is designated as the center ray, the light ray incident on the first lens 110 at an angle of 12 degrees is designated as the first ray, the light ray incident at an angle of 21 degrees is designated as the second ray, the light ray incident at an angle of 27 degrees is designated as the third ray, and the light ray incident at an angle of 30 degrees is designated as the fourth ray.

[0077] Furthermore, tangential rays are rays that radiate outwards when the lens is viewed from the Z-axis. For example, in a rotationally symmetric optical system, these rays form concentric pairs of black and white lines centered on the Z-axis. Sagittal rays, on the other hand, are rays that are orthogonal to tangential rays (e.g., rays that radiate outwards with black and white lines centered on the Z-axis).

[0078] Generally speaking, display panels 41, including liquid crystal on silicon (LCOS), organic light-emitting diodes (OLEDs), micro-LEDs, and laser devices with micro-electromechanical systems (MEMS), have pixels of approximately 5 μm. Assuming the spatial frequency is considered to be the linewidth assuming black-and-white line pairs, an OTF value of at least 0.1 and exceeding 0.3 for 100 lines / mm can be considered good performance.

[0079] By Figure 3 and Figure 4 Comparison shows that the optical system 100 of the micro projector satisfies equations (1) to (4) through the first lens 110, the second lens 120 and the third lens 130, and achieves good results in the range from low spatial frequency to high spatial frequency in the light rays with the incident angle calculated from the central ray to the periphery.

[0080] Furthermore, if the total optical path (from the brightness aperture 101 to the imaging surface of the image light (display panel 41) is set as TT, then ideally the overall focal length ft of the micro projector optical system 100 satisfies the following formula.

[0081] [Formula 5]

[0082]

[0083] According to the above formula, TT≦2.5×ft, and the total optical path value TT is less than 2.5 times the overall focal length ft. The overall focal length ft is determined by the size of the display panel 41 and the field of view (FOV) of the microprojector optical system 100. Therefore, satisfying equation (5) means that the length of the microprojector optical system 100 that meets the specified performance is within the specified range. In other words, a microprojector optical system 100 that satisfies equations (1) to (5) can be miniaturized by shortening the overall length of the optical system.

[0084] In the above-described optical system 100 for a microprojector, the refractive index of the paraxial lens has been described, but the system is not limited thereto. The shape of the outer edge of a lens can sometimes affect image distortion. Therefore, in at least one of the first lens 110, the second lens 120, and the third lens 130, at least one of the first surface on the side of the display surface 20 and the second surface on the side opposite to the first surface has a refractive index gradient, so that the sign of the refractive index on the optical axis is reversed toward the outer edge of the lens.

[0085] exist Figure 2 In the example, the first lens surface 111 of the first lens 110, the third lens surface 121 and the fourth lens surface 122 of the second lens 120, and the fifth lens surface 131 of the third lens 130 have a refractive index gradient, so that the sign of the refractive index on the optical axis is reversed towards the outer edge of the lens. As a result, the micro-projector optical system 100 has fewer aberrations in the range from the central image height to the peripheral image height, and can have better imaging performance.

[0086] Figure 5 Examples of aberrations in the first structural example of the microprojector optical system 100. Figure 5 (A) represents the non-point aberration of the optical system 100 of the micro projector. Figure 5(B) represents the distortion aberration of the optical system 100 of the microprojector. According to Figure 5 It can be seen that the optical system 100 for micro projectors can be realized with low distortion.

[0087] <Design values ​​for the optical system of a micro projector>

[0088] Figure 6 This is an example of the design values ​​for the optical system 100 of the microprojector, representing the first structural example. Additionally, Figure 7 This represents an example of the aspherical coefficient of the lens used in the first structural example of the microprojector optical system 100. Furthermore, in Figure 6 and Figure 7 In the design values, the overall focal length ft of the micro projector optical system 100 is 5.497, the total optical path TT is 10.963, and the value of ft / TT is 0.501.

[0089] Furthermore, the (1 / f1) / (1 / ft) ratio of the first lens 110 is 1.141, the (1 / f2) / (1 / ft) ratio of the second lens 120 is -1.587, and the (1 / f3) / (1 / ft) ratio of the third lens 130 is 1.344 (the values ​​on the left side of equations (1) to (3), respectively). Furthermore, the value on the left side of equation (4) is 0.898. By using these design values, the microscope projector optical system 100 can obtain... Figure 3 and Figure 5 The characteristics shown.

[0090] In the above-described microprojector optical system 100, for the microprojector optical system 100 of this embodiment, Figure 2 The optical system of the first structural example shown has been described, but it is not limited to this. The optical system 100 of the micro projector can be any other optical system as long as it satisfies equations (1) to (5). Next, other optical systems will be described.

[0091] <Second structural example of the optical system 100 for a micro projector>

[0092] Figure 8 This illustrates a second structural example of the microprojector optical system 100 according to this embodiment. In the second structural example of the microprojector optical system 100, for... Figure 2 The parts of the microprojector optical system 100 of the first structural example shown that operate in a manner similar to those shown are given the same reference numerals, and repeated descriptions are omitted.

[0093] Figure 9 This represents an example of the OTF value of the microprojector optical system 100 of the second structural example with respect to the spatial frequency. Figure 10Examples of aberrations in the microprojector optical system 100 of the second structural example are shown. Figure 10 (A) represents the non-point aberration of the optical system 100 of the micro projector. Figure 10 (B) represents the distortion aberration of the optical system 100 of the micro projector.

[0094] Figure 11 This is an example of the design values ​​for the optical system 100 of the microprojector, representing the second structural example. Figure 12 This represents an example of the aspherical coefficient of the lens used in the microprojector optical system 100 of the second structural example. Furthermore, in Figure 11 and Figure 12 In the design values, the overall focal length ft of the micro projector optical system 100 is 7.412, the total optical path TT is 13.4, and the value of ft / TT is 0.553.

[0095] Furthermore, the (1 / f1) / (1 / ft) ratio of the first lens 110 is 0.736, the (1 / f2) / (1 / ft) ratio of the second lens 120 is -1.525, and the (1 / f3) / (1 / ft) ratio of the third lens 130 is 1.677. Therefore, the value on the left side of equation (4) is 0.889. By using these design values, the optical system 100 of the microprojector can achieve... Figure 9 and Figure 10 The characteristics shown.

[0096] <Third structural example of the optical system 100 for a micro projector>

[0097] Figure 13 This illustrates a third structural example of the microprojector optical system 100 according to this embodiment. In the microprojector optical system 100 of this third structural example, for... Figure 2 The parts of the microprojector optical system 100 of the first structural example shown that operate in a manner similar to those shown are given the same reference numerals, and repeated descriptions are omitted.

[0098] Figure 14 This is an example of the OTF value of the microprojector optical system 100 of the third structural example with respect to the spatial frequency. Figure 15 Examples of aberrations in the microprojector optical system 100 of the third structural example. Figure 15 (A) represents the non-point aberration of the optical system 100 of the micro projector. Figure 15 (B) represents the distortion aberration of the optical system 100 of the micro projector.

[0099] Figure 16 This is an example of the design values ​​for the optical system 100 of the micro projector, representing the third structural example. Figure 17This represents an example of the aspherical coefficient of the lens used in the third structural example of the microprojector optical system 100. Furthermore, in Figure 16 and Figure 17 In the design values, the overall focal length ft of the micro projector optical system 100 is 7.410, the total optical path TT is 13.55, and the value of ft / TT is 0.547.

[0100] Furthermore, the (1 / f1) / (1 / ft) ratio of the first lens 110 is 0.952, the (1 / f2) / (1 / ft) ratio of the second lens 120 is -1.545, and the (1 / f3) / (1 / ft) ratio of the third lens 130 is 1.481. Therefore, the value on the left side of equation (4) is 0.888. By using these design values, the optical system 100 of the microprojector can achieve... Figure 14 and Figure 15 The characteristics shown.

[0101] As described above, the microprojector optical system 100 according to this embodiment can realize a small microprojector lens with a simple structure. Furthermore, the microprojector optical system 100 can image a bright image by adjusting the size of the brightness aperture 101. In addition, the microprojector optical system 100 can maintain good OTF from low spatial frequency to high spatial wavenumber within the range from the center image height to the peripheral image height, and can reduce various aberrations, thereby exhibiting excellent imaging performance.

[0102] The example described above, in which the eyeglass-type terminal 10 of this embodiment displays an image image formed by the micro-projector optical system 100 on the display surface 20, is not limited to this. The display surface 20 may, for example, be a waveguide that allows image light to propagate and be projected. Such waveguides are described, for example, in Patent Document 2, and the micro-projector optical system 100 may also be applied to this known technology.

[0103] The present invention has been described above using embodiments, but the technical scope of the present invention is not limited to the scope described in the embodiments, and various modifications and alterations can be made within its scope. For example, all or part of the device can be functionally or physically distributed / integrated in any unit. In addition, new embodiments resulting from any combination of multiple embodiments are also included in the embodiments of the present invention. The effects of new embodiments resulting from combinations are the same as the effects of the original embodiments.

[0104] Explanation of icon numbers

[0105] 10: Glasses-type terminal

[0106] 20: Display surface

[0107] 30: Framework

[0108] 40: Image light emission section

[0109] 41: Display panel

[0110] 100: Optical system for micro projectors

[0111] 101: Brightness Aperture

[0112] 110: First lens

[0113] 111: First lens surface

[0114] 112: Second lens surface

[0115] 120: Second lens

[0116] 121: Third lens surface

[0117] 122: Fourth lens surface

[0118] 130: Third Lens

[0119] 131: Fifth lens surface

[0120] 132: Sixth lens surface

Claims

1. A micro-projector optical system for displaying an input image light on a display surface, wherein in the micro-projector optical system, Starting from the side of the display surface, it includes a first lens, a second lens, and a third lens. The paraxial refractive indices of the first lens and the third lens are positive. The second lens has a negative paraxial refractive index. If the overall focal length of the optical system of the micro projector is set to ft, and the focal length of the first lens is set to f1, then the first lens satisfies the following formula: If the focal length of the second lens is set to f2, then the second lens satisfies the following equation: If the focal length of the third lens is set to f3, then the third lens satisfies the following formula: 。 2. The optical system for a microprojector according to claim 1, wherein, The first lens, the second lens, and the third lens also satisfy the following formula. 。 3. The optical system for a microprojector according to claim 1, wherein, At least one of the first surface on the side of the display surface and the second surface on the side opposite to the first surface of at least one of the first lens, the second lens, and the third lens is an aspherical surface.

4. The optical system for a microprojector according to claim 1, wherein, The second lens is a meniscus lens having a shape that bulges toward the third lens on the optical axis, with a first surface on one side of the display surface and a second surface on the opposite side of the first surface.

5. The optical system for a microprojector according to claim 1, wherein, A brightness aperture is also included between the display surface and the first lens.

6. The optical system for a microprojector according to claim 5, wherein, If the distance from the brightness aperture to the imaging surface of the image light is denoted as TT, then the overall focal length ft of the microprojector optical system satisfies the following formula: 。 7. The optical system for a microprojector according to claim 1, wherein, In at least one of the first lens, the second lens, and the third lens, at least one of the first surface on the side of the display surface and the second surface on the side opposite to the first surface has a refractive index gradient such that the sign of the refractive index on the optical axis is reversed toward the outer edge of the lens.

8. A glasses-type terminal for a user to wear, the glasses-type terminal comprising: The display surface is disposed on at least one of the user's right eye lens and left eye lens, and displays the image light so that the user can visually recognize it; The frame is used to fix the user's right eye lens and left eye lens. An image light emitting section is disposed on the frame and emits the image light; as well as The microprojector optical system according to any one of claims 1 to 7 is provided in the frame, the image light emitted from the image light emitting section is input, and the input image light is displayed on the display surface.

Images