Intrareflection telecentric lens

Abstract

The application provides an internal reflection type telecentric lens, which comprises a first lens assembly, a reflecting device and a second lens assembly arranged in sequence along an optical path; the first lens assembly comprises a first lens; the second lens assembly comprises a second lens and a fourth lens arranged in sequence along the optical path; the image side of the first lens is arranged with the reflecting device, the image side of the reflecting device is arranged with the second lens, and the image side of the second lens is arranged with the fourth lens; the first lens assembly is used for receiving a telecentric light beam, converging the telecentric light beam, so that the telecentric light beam converges at the diaphragm position of the second lens assembly after being folded by the reflecting device; the second lens assembly is used for receiving the telecentric light beam reflected by the reflecting device and projecting an image. The application can shorten the optical path length of the whole telecentric lens, reduce the height of the telecentric lens, and thus can apply the telecentric lens to electronic devices such as mobile phones which have requirements on thickness.

Description

TECHNICAL FIELD

[0001] The present application relates to optical lens, in particular to an internal reflection telecentric lens. BACKGROUND

[0002] The projection lens usually adopts the object side telecentric optical path to realize the uniform field of view and the CRA matching. Due to the principle limitation of the telecentric projection lens, there is a large space between the first lens and the subsequent lens group. The conventional design scheme is a direct type structure, the object plane is perpendicular to the optical axis, and the light ray passes through the object plane and the telecentric lens from bottom to top to project the object plane image. Or a reflecting mirror is added at the end of the lens to realize the 90° turning of the light beam, so as to reduce the system height, but the length of the lens is further increased.

[0003] With the development of mobile phones, tablet computers and other portable terminal devices, in a specific application, the device needs to have a projection function. The conventional telecentric projection lens design needs to occupy a large space volume, which limits its application in portable devices. SUMMARY

[0004] In view of the defects in the prior art, the purpose of the present application is to provide an internal reflection telecentric lens, which shortens the optical path length of the entire telecentric lens by setting a reflecting device inside the telecentric lens, so that the lens can be applied to compact devices such as mobile phones.

[0005] The internal reflection telecentric lens provided by the present application comprises a first lens assembly, a reflecting device and a second lens assembly arranged in sequence along the optical path.

[0006] The first lens assembly comprises a first lens; the second lens assembly comprises a second lens and a fourth lens arranged in sequence along the optical path.

[0007] The image side of the first lens is arranged with the reflecting device, the image side of the reflecting device is arranged with the second lens, and the image side of the second lens is arranged with the fourth lens.

[0008] The first lens assembly is used for receiving a telecentric light beam, converging the telecentric light beam, so that the telecentric light beam converges at the stop position of the second lens assembly after being turned by the reflecting device.

[0009] The second lens assembly is used for receiving the telecentric light beam reflected by the reflecting device and projecting an image.

[0010] Preferably, the second lens assembly further comprises a third lens.

[0011] The image side of the second lens is arranged with the third lens, and the image side of the third lens is arranged with the fourth lens.

[0012] Preferably, the first lens has positive refractive power, and the object side surface and the image side surface are convex structures;

[0013] The second lens has positive refractive power, and the object side surface is convex and the image side surface is concave;

[0014] The third lens has positive refractive power, and the object side surface is concave and the image side surface is convex;

[0015] The fourth lens has negative refractive power, and the object side surface is concave and the image side surface is convex.

[0016] Preferably, the chief rays of the telecentric lens at different image heights are parallel to the optical axis of the first lens.

[0017] Preferably, the reflecting surface of the reflecting device is a metal layer, a dielectric film coating, or an internal total reflection surface of a prism.

[0018] Preferably, the reflecting surface of the reflecting device is a plane, which is arranged between the optical paths of the first lens and the second lens, and is inclined by 40° to 50° with respect to the optical axes of the first lens, the second lens, the third lens, and the fourth lens.

[0019] The reflecting device is used to project the telecentric light beam emitted by the first lens to the second lens after being reflected by 90°.

[0020] Preferably, the optical distance between the first lens and the second lens and the size of the reflecting device satisfy the following condition formula:

[0021]

[0022] Preferably, a diaphragm is arranged between the second lens and the third lens, so that the telecentric lens satisfies the following condition formula:

[0023] 73°<FOV<112°

[0024] Wherein, FOV is the field of view of the telecentric lens;

[0025] 0.95<VP<1

[0026] Wherein, VP is the depth of view of the telecentric lens;

[0027] |Distortion|<8%

[0028] Wherein, Distortion is the optical distortion of the optical system formed by the telecentric lens.

[0029] Preferably, the first lens, the second lens, the third lens, and the fourth lens are aspherical plastic lenses.

[0030] The refractive index nd of the first lens, the second lens, the third lens and the fourth lens satisfies the following formula:

[0031] 1.62<nd<1.69

[0032] Wherein, nd is the refractive index of the lens at the wavelength of 587.6nm.

[0033] Preferably, the second lens assembly is capable of moving along the optical axis direction, changing the optical distance of the first lens assembly and the second lens assembly to change the object side focal length of the telecentric lens, and realizing the focusing on different image plane positions.

[0034] Preferably, when the object plane of the telecentric lens is a discrete light spot array, the focusing plane can be changed by adjusting the second lens assembly, and the switching of the projected light spot from a point light array to a surface light array can be realized.

[0035] When the object plane has a multi-layer pattern, the focusing plane can be changed by adjusting the second lens assembly, and the image switching projection of different depths can be realized.

[0036] Compared with the prior art, the present application has the following beneficial effects:

[0037] In the present application, the reflector is arranged between the first lens assembly and the second lens assembly, which shortens the optical path length of the entire telecentric lens, and further reduces the height of the telecentric lens, so that the telecentric lens can be applied to electronic devices such as mobile phones which have requirements for thickness.

[0038] In the present application, when the relative position of the object plane and the first lens assembly changes, the second lens assembly can be correspondingly moved to realize group focusing, so that the focusing of the light projector using the telecentric lens can be facilitated, and different object plane positions can be matched without adjusting the positional relationship between the object plane and the first lens. BRIEF DESCRIPTION OF DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor based on the provided drawings. Other features, objects and advantages of the present application will become more apparent through reading the following detailed description of the non-limiting embodiments with reference to the following drawings:

[0040] Fig. 1(a) is a first kind of structural schematic diagram of the internal reflection type telecentric lens in the embodiment of the present application;

[0041] Fig. 1(b) is a second structure diagram of the internal reflection type telecentric lens in the embodiment of the present application;

[0042] Fig. 1(c) is a third structure diagram of the internal reflection type telecentric lens in the embodiment of the present application;

[0043] Fig. 1(d) is a third structure diagram of the internal reflection type telecentric lens in the embodiment of the present application;

[0044] Figure 2 Fig. 1(e) is a structure diagram of the telecentric lens without the reflecting device in the embodiment of the present application;

[0045] Figure 3 Fig. 1(f) is a structure diagram of the telecentric lens with the reflecting device at the light emitting end in the embodiment of the present application;

[0046] Figure 4 Fig. 1(a) is a side view of the internal reflection type telecentric lens in the embodiment of the present application;

[0047] Figure 4 Fig. 1(b) is another side view of the internal reflection type telecentric lens in the embodiment of the present application;

[0048] Fig. 5(a) is a size diagram of the internal reflection type telecentric lens in the embodiment of the present application;

[0049] Fig. 5(b) is a size diagram of the telecentric lens without the reflecting device in the embodiment of the present application;

[0050] Fig. 5(c) is a size diagram of the telecentric lens with the reflecting device at the light emitting end in the embodiment of the present application;

[0051] Figure 6 Fig. 1(d) is a focusing principle diagram of the first lens assembly and the second lens assembly in the embodiment of the present application;

[0052] Figure 7 Fig. 1(e) is an MTF transfer function curve diagram of the optical system in the embodiment of the present application;

[0053] Figure 8 Fig. 1(f) is a relative luminance curve diagram of the optical system in the embodiment of the present application;

[0054] Figure 9 Fig. 1(g) is a distortion curve diagram of the optical system in the embodiment of the present application.

[0055] In the figures:

[0056] 1 is an object plane; 2 is a first lens; 3 is a reflecting device; 4 is a second lens; 5 is a diaphragm; 6 is a third lens; 7 is a fourth lens; 8 is a lens opening; 9 is a lens assembly; 10 is a first lens assembly; 11 is a second lens assembly. DETAILED DESCRIPTION

[0057] The application will be described in further detail below with reference to the embodiments. The following embodiments will contribute to further understanding of the application by those skilled in the art, but are not intended to limit the application in any form. It should be noted that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the application. These all belong to the protection scope of the application.

[0058] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element. In addition, the connection can be for fixing or for circuit communication.

[0059] It should be understood that the terms "length", "width", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only used to facilitate the description of the embodiments of the application and simplify the description, and therefore cannot be understood as indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the application.

[0060] In addition, the terms "first", "second", "third", "fourth", "fifth", "sixth", "seventh" and "eighth" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined with "first", "second", "third", "fourth", "fifth", "sixth", "seventh" and "eighth" can explicitly or implicitly include one or more of the features. In the description of the embodiments of the application, the meaning of "plurality" is two or more, unless otherwise specifically limited.

[0061] In the embodiments of the application, the internal reflection type telecentric lens provided by the application comprises a first lens assembly, a reflecting device and a second lens assembly arranged in sequence along an optical path;

[0062] The first lens assembly comprises a first lens; the second lens assembly comprises a second lens, a third lens and a fourth lens arranged in sequence along an optical path;

[0063] The image side of the first lens is arranged with the reflecting device, the image side of the reflecting device is arranged with the second lens, the image side of the second lens is arranged with the third lens, and the image side of the third lens is arranged with the fourth lens;

[0064] The first lens assembly is used for receiving a telecentric light beam, converging the telecentric light beam, and making the telecentric light beam converge on a stop position of the second lens assembly after being reflected by the reflecting device; and the second lens assembly is used for receiving the telecentric light beam reflected by the reflecting device and projecting an image.

[0065] In the present application, the reflecting device is arranged in the telecentric lens, the incident discrete collimated light beam is reflected and then emitted from the lens assembly to form a speckle point array on an imaging surface, the optical path length of the entire telecentric lens is shortened, and the height of the optical projector is reduced, so that the depth camera including the optical projector can be applied to electronic devices such as mobile phones which have a requirement for thickness.

[0066] The above is the core idea of the present application. In order to make the above-mentioned purposes, characteristics and advantages of the present application more obvious and easy to understand, the technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0067] Fig. 1(a) is a first structure schematic diagram of an internal reflection type telecentric lens in an embodiment of the present application. As shown in Fig. 1(a), the internal reflection type telecentric lens provided by the present application includes a first lens assembly 10, a reflecting device 3 and a second lens assembly 11 arranged in sequence along an optical path;

[0068] The first lens assembly 10 includes a first lens 2; and the second lens assembly 11 includes a second lens, a third lens 6 and a fourth lens 7 arranged in sequence along an optical path;

[0069] The image side of the first lens 2 is arranged with the reflecting device 3, the image side of the reflecting device 3 is arranged with the second lens 4, the image side of the second lens 4 is arranged with the third lens 6, and the image side of the third lens 6 is arranged with the fourth lens 7;

[0070] The first lens assembly 10 is used for receiving a telecentric light beam, converging the telecentric light beam, and making the telecentric light beam converge on a stop position of the second lens assembly 11 after being reflected by the reflecting device 3; and the second lens assembly 11 is used for receiving the telecentric light beam reflected by the reflecting device 3 and projecting an image.

[0071] Fig. 1(b) is a second structure schematic diagram of the internal reflection type telecentric lens in the embodiment of the present application, as shown in Fig. 1(b), the second lens assembly 11 includes the second lens 4 and the fourth lens 7 arranged in sequence along the optical path, the second lens 4 adopts a meniscus convex lens, used for converging the telecentric light beam to the diaphragm 5; the fourth lens 7 adopts a meniscus concave lens, used for further diverging the telecentric light beam incident through the diaphragm 5 and projecting out, by omitting the third lens in the second lens assembly 11, the size of the internal reflection type telecentric lens system can be further reduced, and the system is more compact.

[0072] Fig. 1(c) is a third structure schematic diagram of the internal reflection type telecentric lens in the embodiment of the present application, as shown in Fig. 1(c), in the embodiment of the present application, the mirror device 3 adopts a right-angle total reflection prism, since the telecentric light beam is totally reflected on the inclined plane reflecting surface of the right-angle reflection prism, since the angle of the light incident on the inclined plane of the right-angle prism exceeds the critical angle of total reflection, therefore, no coating is needed on the inclined plane to achieve 100% reflectivity.

[0073] Fig. 1(d) is a fourth structure schematic diagram of the internal reflection type telecentric lens in the embodiment of the present application, as shown in Fig. 1(d), the second lens assembly 11 includes the second lens 4 and the fourth lens 7 arranged in sequence along the optical path, the second lens 4 adopts a meniscus convex lens, used for converging the telecentric light beam to the diaphragm 5; the fourth lens 7 adopts a meniscus concave lens, used for further diverging the telecentric light beam incident through the diaphragm 5 and projecting out, by omitting the third lens in the second lens assembly 11, the size of the internal reflection type telecentric lens system can be further reduced, and the system is more compact.

[0074] The optical path composition of the internal reflection type telecentric lens includes: an object plane 1, a first lens 2, a mirror device 3, a second lens 4, a diaphragm 5, a third lens 6, and a fourth lens 7.

[0075] The object plane 1 is used for providing a projection pattern, and the object plane 1 can be any light projector, such as a structured light projector or a laser to project a pattern.

[0076] In the embodiment of the present application, the first lens 2 is used for converging the telecentric light beam from the object plane 1, and the focal plane is at the diaphragm 5.

[0077] The mirror device 3 is used for reflecting the telecentric light beam by 90°, which can adopt a plane coated mirror, and the reflectivity of the light on the mirror surface can be improved through the metal layer or the multi-layer dielectric film coating layer on the surface, or a right-angle total reflection prism can be adopted, since the telecentric light beam is totally reflected on the inclined plane reflecting surface of the right-angle reflection prism, since the angle of the light incident on the inclined plane of the right-angle prism exceeds the critical angle of total reflection, therefore, no coating is needed on the inclined plane to achieve 100% reflectivity, but the right-angle surface needs to be coated with an anti-reflection film to improve the transmittance.

[0078] The second lens 4 is a meniscus lens, used to converge the telecentric beam to the aperture 5;

[0079] The aperture 5 is a virtual plane, and the telecentric beam narrows to its narrowest point at the aperture 5;

[0080] The third lens 6 is a meniscus lens, used to diverge and project the telecentric beam incident through the aperture 5.

[0081] The fourth lens 7 is a meniscus lens, used to further diverge and project the telecentric beam incident through the third lens 6.

[0082] In this embodiment of the invention, the first lens 2 has positive optical power, and the object side and image side are convex structures. The principal rays at different image heights on the object side 1 of the telecentric lens are all parallel to the optical axis of the first lens 2.

[0083] The reflective surface of the reflective device 3 is a plane, tilted at 40° to 50° relative to the optical axis of the first lens 2 or the second lens 4, the third lens 6 and the fourth lens 7, wherein the tilt is preferably 45°; the reflector 3 is used to fold the telecentric beam emitted from the first lens 2 by 90° and project it onto the second lens 4.

[0084] The reflective device 3 is designed to take advantage of the large optical distance between the first lens 2 and the second lens 4 in the object-side telecentric optical path and the small optical path tilt angle. By embedding the reflective device 3 in the optical path, the optical path can be folded without increasing the total length of the telecentric lens, which is beneficial to the miniaturization of the lens size.

[0085] The second lens 4 has positive optical power, with a convex object side and a concave image side;

[0086] The third lens 6 has positive optical power, with a concave object side and a convex image side;

[0087] The fourth lens 7 has negative optical power, with a concave object side and a convex image side.

[0088] In this embodiment of the invention, the optical distance between the first lens 2 and the second lens 4 and the size of the reflecting device 3 satisfy the following condition:

[0089]

[0090] In this embodiment of the invention, the optical spacing is the sum of the distance from the vertex of the image side of the first lens along the optical axis to the reflecting device, and the distance from the vertex of the object side of the second lens 2 along the optical axis to the reflecting device.

[0091] In this embodiment of the invention, the length of the reflective device is the length of the reflective device extending between the first lens and the second lens, that is, the length of the reflective device shown in FIG1(a) and FIG1(c).

[0092] In this embodiment of the invention, an aperture stop 5 is provided between the second lens 4 and the third lens 6, such that the telecentric lens satisfies the following condition:

[0093] 73° <FOV<112°

[0094] Wherein, FOV is the field of view of the telecentric lens; FOV is used to limit the range of the lens's field of view to achieve large-angle projection.

[0095] 0.95 <VP<1

[0096] Wherein, VP is the viewpoint depth of the telecentric lens; VP is used to constrain the viewpoint depth of the lens, reduce the aperture size of the lens, and at the same time reduce vignetting, which is beneficial to improving the uniformity of illumination on the image plane.

[0097] |Distortion| <8%

[0098] Distortion refers to the optical distortion of an optical system. Distortion is used to constrain the distortion of wide-angle lenses; for wide-angle lenses, the smaller the distortion, the more realistic the image outline.

[0099] In this embodiment of the invention, the principal rays at different image heights on the object plane 1 of the telecentric lens are all parallel to the optical axis of the first lens 2.

[0100] In one embodiment of the present invention, the first lens 2, the second lens 4, the third lens 6, and the fourth lens 7 are aspherical plastic lenses. The refractive indices nd of the first lens 2, the second lens 4, the third lens 6, and the fourth lens 7 satisfy the following formula:

[0101] 1.62 <nd<1.69

[0102] Where nd is the refractive index of the lens at a wavelength of 587.6 nm.

[0103] The center of the object surface 1 is on the same straight line as the optical axis of the first lens 2;

[0104] The optical axes of the second lens 4, the third lens 6, and the fourth lens 7 are on the same straight line;

[0105] The optical axis of the first lens 2 is perpendicular to the optical axes of the second lens 4, the third lens 6, and the fourth lens 7.

[0106] Figure 2This is a schematic diagram of the telecentric lens structure in an embodiment of the present invention, omitting the reflecting device, as shown below. Figure 2 As shown, the optical axes of object plane 1 and the first lens 2, second lens 4, third lens 6 and fourth lens 7 are all on the same straight line, which can achieve the same projection effect. However, the height of the telecentric lens is significantly increased after omitting the reflector 3.

[0107] Figure 3 This is a schematic diagram of the telecentric lens structure with the reflective device 3 located at the light-emitting end in an embodiment of the present invention, as shown below. Figure 3 As shown, the optical axes of the object plane 1 and the first lens 2, the second lens 4, the third lens 6 and the fourth lens 7 are all on the same straight line. A reflective device 3 is set on the image side of the fourth lens 7, which can achieve the same projection effect, but the length and height of the telecentric lens are significantly increased.

[0108] Figure 4 (a) is a schematic diagram showing the position of one side of the internal reflection telecentric lens assembled in a mobile phone according to an embodiment of the present invention. Figure 4 (b) is a schematic diagram showing the position of one side of the internal reflection telecentric lens assembled in a mobile phone according to an embodiment of the present invention, as shown below. Figure 4 (a) and Figure 4 In (b), there are restrictions on the height and aperture size of the telecentric lens in compact devices such as mobile phones. Therefore, the smaller the aperture size of the telecentric lens, the better, and the height of the telecentric lens needs to be less than the thickness of the mobile phone.

[0109] Figure 5(a) is a schematic diagram of the dimensions of the internal reflection telecentric lens assembled in a mobile phone according to an embodiment of the present invention. Figure 5(b) is a schematic diagram of the dimensions of the telecentric lens without the reflective device in an embodiment of the present invention assembled in a mobile phone. Figure 5(c) is a schematic diagram of the dimensions of the telecentric lens with the reflective device located at the light-emitting end in an embodiment of the present invention assembled in a mobile phone. As shown in Figures 5(a), 5(b), and 5(c), the internal reflection telecentric lens of the present invention has a lower optical height than the telecentric lens without the reflective device 3. The internal reflection telecentric lens has a lower optical height, shorter length, and smaller aperture than the telecentric lens with the reflective device 3 located at the light-emitting end, and can have better compatibility in compact devices.

[0110] Figure 6 This is a schematic diagram illustrating the focusing principle of the first lens assembly and the second lens assembly in an embodiment of the present invention, as shown below. Figure 6 As shown, the second lens assembly 11 can move along the optical axis, thereby enabling focal length adjustment;

[0111] When object plane 1 is located at the dotted line, a relative displacement occurs between the first lens assembly 10 and object plane 1, resulting in loss of focus, i.e., the following occurs: Figure 6 The horizontal displacement shown in the figure can be obtained through...Figure 6 The vertical movement shown in the figure adjusts the position of the second lens assembly 11 to compensate for the refocusing.

[0112] The specific focusing direction is as follows: when the distance between the object surface 1 and the first lens assembly 10 decreases, the second lens assembly 11 is moved closer to the reflecting device 3; when the distance between the object surface 1 and the first lens assembly 10 increases, the second lens assembly 11 is moved further away from the reflecting device 3.

[0113] In this embodiment of the invention, the second lens assembly 11 is disposed in the lens barrel, and the lens barrel is driven to rotate by a micro motor, thereby moving the second lens assembly.

[0114] In this embodiment of the invention, the surface type, radius of curvature, thickness, refractive index nd, and dispersion coefficient vd of the object surface 1, the first lens 2, the reflecting mirror device 3, the second lens 4, the aperture 5, the third lens 6, and the fourth lens 7 are shown in Table 1.

[0115] Table 1

[0116] Surface No. Surface Type Radius of Curvature Thickness Material (nd, vd) 1 Asphere 3.233 0.353 1.65，25.48 2 Asphere 0.664 0.575 3 Asphere 0.866 0.329 1.64，27.56 4 Asphere 0.780 0.145 Stop Plane Infinite 0.110 6 Asphere -3.923 0.644 1.66，20.37 7 Asphere -0.711 1.415 Mirror Plane Infinite 0.802 9 Sphere 2.975 0.462 1.62，33.24 10 Sphere -3.405 0.391 Object Plane Plane Infinite 0.000

[0117] In Table 1, surface number 1 is the light-emitting surface of the fourth lens 7, surface number 2 is the light-receiving surface of the fourth lens 7; surface number 3 is the light-emitting surface of the third lens 6, surface number 4 is the light-receiving surface of the third lens 6; surface number 6 is the light-emitting surface of the second lens 4, surface number 7 is the light-receiving surface of the second lens 4; surface number 9 is the light-emitting surface of the first lens 2, and surface number 10 is the light-receiving surface of the first lens 2.

[0118] Figure 7 This is a graph of the MTF transfer function of the optical system in this embodiment of the invention. The MTF transfer function can comprehensively reflect the imaging quality of the optical system. The higher and smoother the curve is on the Y-axis, the better the imaging quality of the optical system. Figure 7 As shown, the horizontal axis, SPATIAL FREQUENCY IN CYCLES PER MILLIMETER, represents the spatial frequency of line pairs / 1p / mm. The vertical axis represents the MTF value. The higher the curve, the better the image quality. The vertical axis, MODULUS OF THEOTF, where OTF stands for optical transfer function, represents the optical modulation transfer function. In this embodiment, the resolving power of the internal reflection telecentric lens is >110 lp / mm.

[0119] Figure 8 This is a relative illumination curve of the optical system in an embodiment of the present invention, such as... Figure 8As shown, the vertical axis Relative Illumination represents relative illumination, and the horizontal axis Y Field Millimeters represents the height in the Y direction, with units in millimeters.

[0120] Among them, the higher the height of the curve on the Y-axis and the smoother it is, the more uniform the relative illumination of the optical system is. In this embodiment of the invention, the maximum field of view relative illumination of the internal reflection telecentric lens is >70%.

[0121] Figure 9 This is a distortion curve diagram of the optical system in an embodiment of the present invention, such as... Figure 9 As shown, the horizontal axis represents Percentage, and the vertical axis represents Distortion. In this embodiment of the invention, the distortion of the internal reflection telecentric lens is <7% across the entire field of view.

[0122] In this embodiment of the invention, a reflective device is disposed between the first lens assembly and the second lens assembly, which shortens the optical path length of the entire telecentric lens and thus reduces the height of the telecentric lens. This allows the telecentric lens to be used in electronic devices such as mobile phones where thickness is a requirement. In this embodiment of the invention, when the relative position of the object surface and the first lens assembly changes, the second lens assembly can be moved accordingly to achieve group focusing. This facilitates focusing of the light projector using the telecentric lens, thereby enabling matching of different object surface positions without adjusting the positional relationship between the object surface and the first lens.

[0123] The various embodiments described in this specification are presented in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0124] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. An internal reflection telecentric lens, characterized in that, It includes a first lens assembly, a reflective device, and a second lens assembly arranged sequentially along the optical path; The first lens assembly includes a first lens; the second lens assembly includes a second lens and a fourth lens arranged sequentially along the optical path; The first lens has the reflecting device arranged on its image-side surface, the reflecting device has the second lens arranged on its image-side surface, and the second lens has the fourth lens arranged on its image-side surface. The first lens assembly is used to receive the telecentric beam and converge the telecentric beam so that the telecentric beam is refracted by the reflector and converged at the aperture position of the second lens assembly; The second lens assembly is used to receive the telecentric beam reflected by the reflective device and project an image; The second lens assembly also includes a third lens; The third lens is arranged on the image-side surface of the second lens, and the fourth lens is arranged on the image-side surface of the third lens; The first lens has positive optical power, the second lens has positive optical power, the third lens has positive optical power, and the fourth lens has negative optical power.

2. The internal reflection telecentric lens according to claim 1, characterized in that, The object-side and image-side of the first lens are convex structures; The second lens has a convex object-side surface and a concave image-side surface; The object side of the third lens is concave, and the image side is convex. The fourth lens has a concave side and a convex side; The optical axis of the first lens is perpendicular to the optical axes of the second, third, and fourth lenses.

3. The internal reflection telecentric lens according to claim 1, characterized in that, The reflective surface of the reflective device is a metal layer and a dielectric film coating.

4. The internal reflection telecentric lens according to claim 1, characterized in that, The reflecting surface of the reflecting device is the internal total internal reflection surface of a prism.

5. The internal reflection telecentric lens according to claim 1, characterized in that, The reflective surface of the reflective device is a plane, which is disposed between the optical paths of the first lens and the second lens, and is inclined at 40° to 50° relative to the optical axis of the first lens or the second lens, the third lens and the fourth lens; The reflective device is used to refract the telecentric beam emitted from the first lens and project it onto the second lens.

6. The internal reflection telecentric lens according to claim 1, characterized in that, The optical distance between the first lens and the second lens and the size of the reflecting device satisfy the following condition: 。 7. The internal reflection telecentric lens according to claim 1, characterized in that, An aperture stop is provided between the second lens and the third lens, such that the telecentric lens satisfies the following condition: 73° <FOV<112° Wherein, FOV is the field of view of the telecentric lens; 0.95 <VP<1 Wherein, VP is the viewpoint depth of the telecentric lens; |Distortion| <8% Distortion refers to the optical distortion of an optical system.

8. The internal reflection telecentric lens according to claim 1, characterized in that, The first lens, the second lens, the third lens, and the fourth lens are made of aspherical plastic lenses; The refractive indices nd of the first lens, the second lens, the third lens, and the fourth lens satisfy the following formula: 1.62 < nd < 1.69 Where nd is the refractive index of the lens at a wavelength of 587.6 nm.

9. The internal reflection telecentric lens according to claim 1, characterized in that, The second lens assembly can move along the optical axis, changing the optical distance between the first lens assembly and the second lens assembly to change the object-side focal length of the telecentric lens, thereby achieving focusing at different image plane positions; When the distance between the object plane of the telecentric lens and the first lens assembly decreases, the second lens assembly is moved toward the direction of the reflector. When the distance between the object surface and the first lens assembly increases, the second lens assembly is moved away from the reflecting device.

10. The internal reflection telecentric lens according to claim 1, characterized in that, When the object plane of the telecentric lens is a discrete light spot array, the focus plane can be changed by adjusting the second lens assembly, thus switching the projected light spot from a point light array to a surface light array. When the object surface has multiple layers of patterns, the focus plane can be changed by adjusting the second lens assembly to achieve image switching projection at different depths.

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