A near-eye display optical module with a large field of view

Abstract

The present invention discloses a large field-of-view near-eye display optical module, comprising an optical coupling mechanism, a one-dimensional waveguide, and an OLED; the optical coupling mechanism is provided at the light output of the OLED, and the one-dimensional waveguide is provided at the light output of the optical coupling mechanism; the optical coupling mechanism comprises a prism, a first lens, and a second lens; the side of the prism located at the light output of the OLED is defined as the first side, the side of the optical coupling mechanism located at the light output of the OLED is defined as the second side, and the first side is adjacent to the second side; the other side adjacent to the second side is defined as the third side, and the other side adjacent to the first side is defined as the fourth side; the first lens is provided on the third side, and the side of the first lens away from the prism is defined as the first reflector; the second lens is provided on the fourth side, and the side of the second lens away from the prism is defined as the second reflector. In the present invention, the optical coupling mechanism only uses one prism and two lenses, and utilizes a folded optical path to significantly reduce the size, thereby achieving the effects of small size, large field-of-view, and large exit pupil distance.

Description

Technical Field

[0001] The present invention relates to the field of optical imaging technology, and in particular to a large-field-of-view near-eye display optical module. Background Art

[0002] With the continuous advancement of display technology, augmented reality (AR) has become a hot topic. AR projects virtual images into the real world, enabling users to enjoy a richer interactive experience. Comfort and immersion are key attributes of near-eye displays, placing higher demands on device size, field of view, and imaging quality. Currently, there are various optical solutions for AR. Among them, the one-dimensional expanded pupil waveguide solution has become a mainstream solution due to its advantages such as light weight, high ambient light transmittance, and high light efficiency (approximately 8%). The one-dimensional expanded pupil waveguide solution consists of a microdisplay, an optical coupler, and an optical waveguide. Silicon-based OLEDs are a key light-emitting device in microdisplays due to their high contrast and low power consumption. The optical coupler acts as an imaging amplifier, converting the light emitted by the OLED into parallel light and determining the field of view. Existing technologies often use a combination of multiple lenses, resulting in a generally narrow field of view, ranging from 15° to 45°.

[0003] Conventional solutions use a combination of multiple lenses as a coupling optical machine, but it is difficult to resolve the contradiction between small size and large field of view. For example, Chinese patent publication number CN117849912A discloses a folded optical system with a large field of view, including a four-fold reentrant folded optical system and a two-fold reentrant folded optical system; the four-fold reentrant folded optical system and the two-fold reentrant folded optical system include a first metasurface, a second metasurface, and a third metasurface; in the four-fold reentrant folded optical system, the first metasurface, the second metasurface, and the third metasurface are coaxially arranged with the substrate; in the two-fold reentrant folded optical system, the first metasurface and the third metasurface are coaxially arranged with the substrate, and the second metasurface is coaxially arranged in front of the third metasurface. The field of view achieved in this patent is greater than or equal to 40°.

[0004] Existing technologies also employ polarization beam splitters (PBS), on-axis folding (pancake) solutions, and off-axis folding solutions to significantly reduce the size of optical machines. For example, Chinese patent publication number CN118393735A discloses an optical machine system and near-eye display device that utilizes a PBS. PCT international patent publication number WO2023207581A1 discloses an optical polarization device, its manufacturing method, and a near-eye display device that utilizes a pancake solution. However, both PBS and pancake solutions lose more than half of their light efficiency. The off-axis folding solution offers less light efficiency loss and is more suitable for silicon-based OLED screens, but it also suffers from significant stray light issues. Summary of the Invention

[0005] Technical purpose: In response to the defects in the existing technology, the present invention discloses a large field of view near-eye display optical module, which realizes a one-dimensional pupil expansion optical waveguide module solution with a large field of view, small size, low stray light, high brightness and high brightness uniformity.

[0006] Technical solution: In order to achieve the above technical objectives, the present invention adopts the following technical solution.

[0007] A large field-of-view near-eye display optical module includes an optical coupling mechanism, a one-dimensional waveguide, and an OLED; the optical coupling mechanism is provided at the light output of the OLED, and the one-dimensional waveguide is provided at the light output of the optical coupling mechanism;

[0008] The optical coupling mechanism includes a prism, a first lens, and a second lens. The side of the prism located at the OLED light output is defined as the first side, and the side of the optical coupling mechanism located at the light output is defined as the second side. The first side and the second side are adjacent to each other. The other side adjacent to the second side is defined as the third side, and the other side adjacent to the first side is defined as the fourth side. The first lens is provided on the third side, and the side of the first lens away from the prism is defined as the first reflector. The second lens is provided on the fourth side, and the side of the second lens away from the prism is defined as the second reflector. The optical coupling mechanism satisfies the following requirements: ,in, is the curvature radius of the first reflector in the pupil expansion direction, is the curvature radius of the second reflector in the pupil expansion direction, is the curvature radius of the first reflector in the non-pupil expansion direction, is the curvature radius of the second reflector in the non-pupil expansion direction.

[0009] Beneficial effects:

[0010] (1) The present invention proposes a large field of view near-eye display optical module. The coupling optical machine uses only one prism and two lenses, and the folded optical path is used to greatly compress the size, thereby achieving the effects of small size, large field of view, and large exit pupil distance. The size of the optical machine does not exceed 42mm×27mm×25mm, and the field of view angle is ≥50°;

[0011] (2) The present invention reduces the divergence angle of the light source by adding micro lenses to the OLED, so that the light emitted by the OLED has a light intensity less than 10% when the divergence angle β>40, thereby reducing stray light and improving the luminous intensity and the brightness of the light entering the eye;

[0012] (3) The present invention uses microlens offset to make the maximum luminous angle of the corresponding position of the OLED and the main light angle of the optical module composed of the one-dimensional waveguide and the coupling optical machine consistent or not much different, thereby achieving improved brightness uniformity. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1This is a schematic diagram of a large field of view near-eye display optical module according to an embodiment of the present invention. Figure 1 ;

[0014] Figure 2 This is a schematic diagram of a large field of view near-eye display optical module according to an embodiment of the present invention. Figure 2 ;

[0015] Figure 3 This is a schematic diagram showing that the light emitted by OLED has a large divergence angle and obvious stray light;

[0016] Figure 4 is a schematic diagram of the stray light path;

[0017] Figure 5 This is a schematic diagram showing that the light emitted by OLED has a small divergence angle and obviously uneven brightness;

[0018] Figure 6 This is a schematic diagram of the introduction of microlenses and their offset in OLED;

[0019] Figure 7 It is a CRA schematic diagram of the optical module;

[0020] Figure 8 Schematic diagram of the effect after using microlens focusing and offset;

[0021] Among them, 1 is a coupling optical machine, 11 is a prism, 2 is a one-dimensional waveguide, 3 is an OLED; 41 is a first lens, 42 is a second lens, 51 is a first reflector, and 52 is a second reflector. DETAILED DESCRIPTION

[0022] In order to help those skilled in the art better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of this application.

[0023] Example

[0024] As attached Figure 1 As shown, a large field angle near-eye display optical module of this embodiment includes an optical coupling mechanism 1, a one-dimensional waveguide 2, and an OLED 3; the optical coupling mechanism 1 is provided at the light output of the OLED 3, and the one-dimensional waveguide 2 is provided at the light output of the optical coupling mechanism 1;

[0025] The optical coupling mechanism 1 includes a prism 11, a first lens 41, and a second lens 42. The side of the prism 11 located at the light output of the OLED 3 is defined as the first side, and the side of the optical coupling mechanism 1 located at the light output is defined as the second side. The first side and the second side are adjacent to each other. The other side adjacent to the second side is defined as the third side, and the other side adjacent to the first side is defined as the fourth side. The first lens 41 is provided on the third side, and the side of the first lens 41 away from the prism 11 is defined as the first reflector 51. The second lens 42 is provided on the fourth side, and the side of the second lens 42 away from the prism 11 is defined as the second reflector 52.

[0026] The optical path of the optical module in this embodiment is as follows: after the light emitted by the OLED 3 enters the first surface of the prism 11, it first enters the first lens 41 on the third surface, is then reflected by the first reflector 51 and returns to the first lens 41, refracts and enters the prism 11, then enters the second lens 42 on the fourth surface, is reflected by the second reflector 52, returns to the second lens 42, and enters the prism 11 again. After being emitted from the second surface of the prism 11, the light is coupled into the one-dimensional waveguide 2, propagates in the one-dimensional waveguide 2 by total internal reflection, and finally couples out of the one-dimensional waveguide 2 and enters the human eye.

[0027] The third and fourth faces of the prism may be adjacent or not. When the third and fourth faces are adjacent, the prism 11 is a quadrangular prism. Figure 2 When the third and fourth surfaces are not adjacent, the prism 11 has one more surface, that is, the prism 11 is a pentaprism, as shown in the attached Figure 1 That is, the prism can be divided into a pentaprism or a quadrangular prism according to whether the right top corner is cut.

[0028] The refractive index n5 of the material of the prism 11 is greater than 1.8. , is the included angle between the first surface and the second surface of the prism 11 .

[0029] The coupling optical machine 1 meets the following requirements: The dimensions of the coupling optical machine 1 range from 36mm×18mm×18mm to 42mm×27mm×25mm. The non-pupil expansion diaphragm is located at the human eye, and the pupil expansion diaphragm is located at the coupling plane of the one-dimensional waveguide 2. The distance between the two diaphragms is required to be: ;

[0030] The one-dimensional waveguide 2 satisfies: , where L is the distance between the two apertures of the coupling optical machine 1, , ER is the distance from the human eye to the one-dimensional waveguide 2 near the human eye, d is the thickness of the one-dimensional waveguide 2, is the distance from the eye box center of the one-dimensional waveguide 2 to the coupling center of the one-dimensional waveguide 2, and VEB is the eye box size of the one-dimensional waveguide 2 in the pupil expansion direction, which is a numerical value. is the angle between the outcoupling reflection surface of the one-dimensional waveguide 2 and the plane of the one-dimensional waveguide 2, and n is the refractive index of the material of the one-dimensional waveguide 2.

[0031] Maximum chief ray angle in the non-pupil expansion direction of the coupling optical machine 1 satisfy: ,and , where L is the distance between the two apertures of the coupling optical machine 1, f is the focal length of the coupling optical machine 1, and FOV is the diagonal field of view of the coupling optical machine 1.

[0032] In this embodiment, the coupling optical machine only uses one prism and two lenses, and uses the folded optical path to greatly compress the size, achieving the effect of small size, large field of view angle, and large exit pupil distance. The field of view angle is ≥50° and the size does not exceed 42mm×27mm×25mm.

[0033] The optical coupling machine 1 also needs to meet ,in, is the curvature radius of the first reflector 51 in the pupil expansion direction, is the curvature radius of the second reflector 52 in the pupil expansion direction, is the curvature radius of the first reflector 51 in the non-pupil expansion direction, is the curvature radius of the second reflector 52 in the non-pupil expansion direction.

[0034] The material of the first lens 41 is transparent optical plastic. One side of the first lens 41 is a plane coated with an anti-reflection film, which is glued to the prism. The other side is a free-form surface coated with an internal total reflection film, which serves as the first reflector 51. The formula of the first lens 41 is:

[0035] ,

[0036] in, is the z coefficient of the first lens 41, is the curvature of the first lens 41 in the X direction, is the curvature of the first lens 41 in the Y direction, is the cone coefficient of the first lens 41 in the X direction, is the cone coefficient of the first lens 41 in the Y direction, is the high-order coefficient of the first lens 41 in the X direction, is the high-order coefficient of the first lens 41 in the Y direction, Represents x Power, Represents y Power, is the number of high-order terms. In this embodiment, the value is 4 or 5.

[0037] The second lens 42 is made of transparent optical plastic. One side of the second lens 42 is a plane coated with an anti-reflection film, which is glued to the prism. The other side is a free-form surface coated with an internal total reflection film, which serves as the second reflector 52. The formula for the second lens 42 is:

[0038] ,

[0039] in, is the z coefficient of the second lens 42, is the curvature of the second lens 42 in the X direction, is the curvature of the second lens 42 in the Y direction, is the cone coefficient of the second lens 42 in the X direction, is the cone coefficient of the second lens 42 in the Y direction, is the high-order coefficient of the second lens 42 in the X direction, is the high-order coefficient of the second lens 42 in the Y direction, Represents x Power, Represents y Power, is the number of high-order terms. In this embodiment, the value is 4 or 5.

[0040] When the light divergence angle of OLED is large, that is, the divergence angle β>40, and the light intensity is higher than 10%, the light with large divergence angle is incident on the inner wall of the prism and is totally reflected, generating stray light, which seriously affects the viewing effect. Figure 3 The optical path diagram after stray light enters the optical module is shown in the attached figure. Figure 4 As shown in the figure, by analyzing the optical path of stray light, it is found that the light with a large divergence angle emitted by the OLED is incident on the surface of the prism where the one-dimensional waveguide is located, that is, total internal reflection occurs on the second surface, and then enters the one-dimensional waveguide after being reflected by two mirrors, and finally enters the human eye, causing stray light.

[0041] In this embodiment, the OLED3 is provided with a microlens, which is arranged between the light-emitting layer and the optically transparent adhesive layer in the OLED. The optically transparent adhesive layer mainly functions as bonding, optical transparency and moisture-proof, and is located in the OLED encapsulation layer. The microlens is a conventional structure in the prior art. For example, in this embodiment, an H-K9L microlens is used. It should be noted that the material and selection of the microlens are not the focus of this application and will not be elaborated here. The setting of the microlens reduces the divergence angle of the light source, so that the light emitted by the OLED has a light intensity of less than 10% when the divergence angle β>40, thereby reducing stray light and improving the luminous intensity and the brightness entering the eye. That is, narrowing the light emitted by the OLED by the microlens can be used to reduce stray light, but when the divergence angle of the light emitted by the OLED is small, that is, β>40, and the light intensity is less than 10%, the brightness of the edge field of view is seriously lower than that of the center field of view, and the brightness of the edge field of view is less than 50% of that of the center field of view, resulting in uneven brightness of the entire picture, which also affects the viewing experience, as shown in the attached figure. Figure 5 shown.

[0042] As attached Figure 6 As shown, in this embodiment, by shifting the microlens, the maximum light emitting angle at the corresponding position of the OLED 3 and the chief ray angle of the optical module composed of the one-dimensional waveguide and the coupling optical machine are made consistent or have little difference, that is, they meet the following conditions:

[0043] ,

[0044] in, Compatible with OLED3 The maximum luminous angle of the position, The chief ray angle at any position of the optical module is used to achieve improved brightness uniformity, with a brightness uniformity of ≥60%.

[0045] As attached Figure 7 As shown, the optical module also corresponds to the fact that the chief ray angle (CRA) of the coupling machine has different values ​​at different positions. The CRA at the center of the coupling machine is 0, and the CRA at the edge is the largest, as shown in is the maximum principal ray angle in the non-pupil expansion direction of the coupling optical machine 1, which is also the maximum principal ray angle in the X direction. It is the maximum chief ray angle in the pupil expansion direction of the coupling machine, and also the maximum chief ray angle in the Y direction. The CRA change from the center to the edge of the coupling machine is linear. is the chief ray angle at any position of the optical module, and the above relationship must be satisfied between .

[0046] That is to say, in this embodiment, the light is focused by microlenses, so that the light divergence angle β emitted by the OLED is greater than 40, and the light intensity is less than 10%, thereby effectively improving stray light. The brightness uniformity is controlled by microlens offset, and the final effect is shown in the attached figure. Figure 8 shown.

[0047] In other words, in view of the fact that the field of view of current AR optical modules is generally small, basically between 15°-45°, the present invention discloses a one-dimensional pupil-expanding optical waveguide AR module solution with a field of view ≥50 degrees. In order to solve the contradiction between large viewing angle and small size, the present invention adopts a folding solution to make the size of the coupling optical machine ≤42mm×27mm×25mm. In order to solve the stray light problem caused by the folding solution, the present invention adopts micro-lens focusing and micro-lens offset technology to reduce stray light. At the same time, the brightness entering the eye and the brightness uniformity are improved.

[0048] To verify the effect of the optical module of the present invention, the simulation verification process is given below:

[0049] The reverse light path design is adopted, and the field of view is set to a rectangular field of view of 41°×30.2°. The image height is controlled to meet the diagonal field of view ≥50°. The refractive index of the one-dimensional waveguide material is n=1.62, and the angle between the one-dimensional waveguide coupling reflection surface and the one-dimensional waveguide plane is , the distance from the eye box center of the one-dimensional waveguide to the coupling center of the one-dimensional waveguide The geometric waveguide makes the distance from the human eye to the waveguide near the human eye .

[0050] Simulation verification 1:

[0051] set up: , focal length f=16.69mm, the parameters of each surface of the coupling optical machine are shown in Table 1, the parameters of the first reflector are shown in Table 2, and the parameters of the second reflector are shown in Table 3.

[0052] Table 1 Parameters of the optical coupling machine

[0053]

[0054] Table 2 Parameters of the first reflector

[0055]

[0056] Table 3 Parameters of the second reflector

[0057]

[0058] According to the above parameters, the following formula is obtained:

[0059] ,

[0060] ,

[0061] Optical coupling device size: 40mm*24mm*22mm

[0062] n5=1.84>1.8,

[0063] ,

[0064] That is to say, under the above parameter verification, the light divergence angle β of the light emitted by the OLED is made greater than 40 degrees, and the light intensity is less than 10%, thereby effectively reducing the stray light. And by shifting the microlens, the maximum luminous angle at the corresponding position of the screen and the main ray angle of the coupling machine composed of the waveguide and the coupling machine are made consistent or not much different. , achieving high brightness uniformity ≥ 60%.

[0065] Simulation verification 2:

[0066] set up: , focal length f=17.38mm, the parameters of each surface of the coupling optical machine are shown in Table 4, the parameters of the first reflector are shown in Table 5, and the parameters of the second reflector are shown in Table 6.

[0067] Table 4 Parameters of the optical coupling machine

[0068]

[0069] Table 5 Parameters of the first reflector

[0070]

[0071] Table 6 Parameters of the second reflector

[0072]

[0073] According to the above parameters, the following formula is obtained:

[0074] ,

[0075] ,

[0076] ,

[0077] Optical coupling device size: 41mm*26mm*22mm,

[0078] n5=1.84>1.8,

[0079] ,

[0080] That is to say, under the above parameter verification, the light divergence angle β of the light emitted by the OLED is made greater than 40 degrees, and the light intensity is less than 10%, thereby effectively reducing the stray light. And by shifting the microlens, the maximum luminous angle at the corresponding position of the screen and the main ray angle of the coupling machine composed of the waveguide and the coupling machine are made consistent or not much different. , achieving high brightness uniformity ≥ 60%.

[0081] Simulation verification 3:

[0082] set up: , focal length f=17.17mm, the parameters of each surface of the coupling optical machine are shown in Table 7, the parameters of the first reflector are shown in Table 8, and the parameters of the second reflector are shown in Table 9.

[0083] Table 7 Parameters of the optical coupling machine

[0084]

[0085] Table 8 Parameters of the first reflector

[0086]

[0087] Table 9 Parameters of the second reflector

[0088]

[0089] According to the above parameters, the following formula is obtained:

[0090] ,

[0091] ,

[0092] ,

[0093] Optical coupling device size: 38mm*25mm*22mm,

[0094] n5=1.84>1.8,

[0095] ,

[0096] That is to say, under the above parameter verification, the light divergence angle β of the light emitted by the OLED is made greater than 40 degrees, and the light intensity is less than 10%, thereby effectively reducing the stray light. And by shifting the microlens, the maximum luminous angle at the corresponding position of the screen and the main ray angle of the coupling machine composed of the waveguide and the coupling machine are made consistent or not much different. , achieving high brightness uniformity ≥ 60%.

[0097] The above simulation process verifies the effect achieved by the present application. The optical module designed in the present application can also be manufactured, such as by turning.

[0098] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A near-eye display optical module with a large field of view, characterized by: The invention comprises an optical coupling machine (1), a one-dimensional waveguide (2), and an OLED (3); the optical coupling machine (1) is provided at the light output of the OLED (3), and the one-dimensional waveguide (2) is provided at the light output of the optical coupling machine (1); The coupling optical machine (1) comprises a prism (11), a first lens (41), and a second lens (42); a side of the prism (11) located at the light output of the OLED (3) is defined as the first side, a side of the coupling optical machine (1) located at the light output is defined as the second side, and the first side is adjacent to the second side; another side adjacent to the second side is defined as the third side, and another side adjacent to the first side is defined as the fourth side; a first lens (41) is provided on the third side, and a side of the first lens (41) away from the prism (11) is defined as a first reflector (51); a second lens (42) is provided on the fourth side, and a side of the second lens (42) away from the prism (11) is defined as a second reflector (52); Among them, the coupling optical machine (1) satisfies: ,in, is the curvature radius of the first reflector (51) in the pupil expansion direction, is the curvature radius of the second reflector (52) in the pupil expansion direction, is the curvature radius of the first reflector (51) in the non-pupil expansion direction, is the curvature radius of the second reflector (52) in the non-pupil expansion direction; In a one-dimensional waveguide (2), the following conditions are satisfied: , where L is the distance between the two apertures of the coupling optical machine (1), , ER is the distance from the human eye to the one-dimensional waveguide (2) near the human eye, d is the thickness of the one-dimensional waveguide (2), is the distance from the eye box center of the one-dimensional waveguide (2) to the coupling center of the one-dimensional waveguide (2), VEB is the eye box size of the one-dimensional waveguide (2) in the pupil expansion direction, is the angle between the outcoupling reflection surface of the one-dimensional waveguide (2) and the plane of the one-dimensional waveguide (2), and n is the refractive index of the material of the one-dimensional waveguide (2); A microlens is provided in the OLED (3), and the microlens is arranged between the light-emitting layer and the optically transparent adhesive layer in the OLED, so that when the divergence angle β>40, the light intensity is less than 10%.

2. The large field-of-view near-eye display optical module according to claim 1, characterized in that: Maximum chief ray angle in the non-pupil dilation direction of the coupling optical machine (1) satisfy: ,and , where L is the distance between the two apertures of the coupling optical machine (1), f is the focal length of the coupling optical machine (1), and FOV is the diagonal field of view of the coupling optical machine (1).

3. The large field-of-view near-eye display optical module according to claim 1, characterized in that: The material of the first lens (41) is a transparent optical plastic material. One side of the first lens (41) is a plane coated with an anti-reflection film, which is glued to the prism, and the other side is a free-form surface coated with an internal total reflection film, which serves as the first reflector (51).

4. The large field-of-view near-eye display optical module according to claim 1, characterized in that: The formula expression of the first lens (41) is: ， in, is the z coefficient of the first lens (41), is the curvature of the first lens (41) in the X direction, is the curvature of the first lens (41) in the Y direction, is the cone coefficient of the first lens (41) in the X direction, is the cone coefficient of the first lens (41) in the Y direction, is the high-order coefficient of the first lens (41) in the X direction, is the high-order coefficient of the first lens (41) in the Y direction, Represents x Power, Represents y Power, is the number of higher-order terms.

5. The large field-of-view near-eye display optical module according to claim 1, characterized in that: The material of the second lens (42) is a transparent optical plastic material. One side of the second lens (42) is a plane coated with an anti-reflection film, which is glued to the prism, and the other side is a free-form surface coated with an internal total reflection film, which serves as a second reflector (52).

6. The large field-of-view near-eye display optical module according to claim 1, characterized in that: The formula expression of the second lens (42) is: ， in, is the z coefficient of the second lens (42), is the curvature of the second lens (42) in the X direction, is the curvature of the second lens (42) in the Y direction, is the cone coefficient of the second lens (42) in the X direction, is the cone coefficient of the second lens (42) in the Y direction, is the high-order coefficient of the second lens (42) in the X direction, is the high-order coefficient of the second lens (42) in the Y direction, Represents x Power, Represents y Power, is the number of higher-order terms.

7. The large field-of-view near-eye display optical module according to claim 1, characterized in that: After the microlens is shifted, the following conditions are satisfied: ， in, For OLED (3) The maximum luminous angle of the position, is the chief ray angle at any position of the optical module.

8. The large field-of-view near-eye display optical module according to claim 1, characterized in that: The third face and the fourth face of the prism (11) are adjacent or not adjacent.

Images