Fresnel lens and infrared detection device suitable for long-range detection

Abstract

The application provides a Fresnel lens and an infrared detection device suitable for long-distance detection. The Fresnel lens comprises a center lens provided with at least one lens unit and having a central axis, and at most three groups of lens unit groups composed of a plurality of lens units and arranged around the center lens. The focal length of the lens unit of the center lens is f, the distance between the optical center of the lens unit farthest from the central axis in the lens unit group and the central axis is L, the Fresnel lens is designed in the state of L≤18mm, f≥15mm, and H≤10mm, and L / (f-H)≤0.7 is satisfied, wherein H is the height difference between the optical center of the lens unit of the center lens and the optical center of the lens unit farthest from the central axis in the lens unit group in the direction of the central axis, so that the Fresnel lens can simultaneously consider the miniaturized design of the infrared detection device and the effective detection area in the long-distance detection application scenario.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of infrared detection, and more particularly to a Fresnel lens and an infrared detection device suitable for long-distance detection. BACKGROUND

[0002] With the development of Internet of Things technology and the popularization of low-carbon environmental protection concepts, there is an increasing demand for artificial intelligence, smart home, and smart security technology for environmental detection, especially for human movement detection. The demand for intelligent control of the working state of electrical equipment based on the detection results of the presence or absence of a human body, such as controlling the lighting state of a lamp based on the detection results of the presence or absence of a human body to achieve intelligent low-carbon lighting.

[0003] The existing technologies for detecting the presence of a human body mainly include: 1. Image acquisition based on corresponding algorithms to identify human bodies and human behavior states, but due to the risk of invasion and leakage of privacy, it is difficult to be accepted, and at the same time, it has the defects of complex algorithm and high requirement for hardware performance, resulting in high cost. 2. Microwave detection technology based on the principle of Doppler effect, specifically by emitting a microwave beam and receiving a reflected echo formed by the reflection of the microwave beam on a corresponding object, and generating a Doppler intermediate frequency signal corresponding to the frequency difference between the microwave beam and the reflected echo through a mixing detection method, the Doppler intermediate frequency signal is a feedback to the movement of the corresponding object. The microwave detection technology based on the principle of Doppler effect has unique advantages in behavior detection and presence detection technology, which can detect moving objects without invading privacy, and thus has wide application prospects. However, on the one hand, due to the above working principle of microwave detection technology, the current microwave detection device cannot maintain its advantage of detecting micro-motion in the application scenario of long-distance detection, which is greatly affected by the environment, on the other hand, due to the limitations of product volume, cost and microwave emission power of civilian level microwave detection devices, the beam angle and corresponding detection distance of the microwave beam emitted by the existing microwave detection device are difficult to be accurately designed and controlled as military phased array radar. 3. Based on the zoning of the corresponding detection area by the Fresnel lens, the cross-zone action of the human body in the detection area is detected by the pyroelectric infrared sensor (PIR), which is also the most commonly used and mature human presence detection technology at present.

[0004] Although the third human existence detection technology among the foregoing three human existence detection technologies is the most popular and mature human existence detection technology at present, the current corresponding infrared detection device suitable for long-distance detection of more than 12 meters generally has the defect of a large volume, so that when it is applied to intelligent lighting, the infrared detection device can only be set in an external hanging manner, and the volume of the externally hung infrared detection device can be larger than that of the lamp itself. The reason why the volume of the current infrared detection device suitable for long-distance detection is large is mainly that in the current product design idea of the infrared detection device, the increase of the detection distance is realized by the technical route of increasing the total light amount. Based on this technical route, the corresponding Fresnel lens is generally designed to have a large light incidence angle and a large light incidence surface area, so as to increase the total light amount based on the design of a large light incidence angle and a large light incidence surface area, increase the capture amount of infrared light radiated by a human body at a long distance by the pyroelectric infrared sensor, and further improve the detection distance of the infrared detection device. The Fresnel lens with a large light incidence angle and a large light incidence surface area is also designed to have a convex light incidence surface shape, and the center of the light incidence surface of the Fresnel lens has a height difference of more than 15 mm relative to the periphery based on the convex structure design. In this way, the Fresnel lens has a large light incidence surface area, and the periphery diameter of the Fresnel lens is reduced (actually still more than 80 mm) based on the convex light incidence surface shape design to reduce the lateral size of the infrared detection device; and the Fresnel lens has a large light incidence angle, and each lens unit can be designed with a larger focal length based on the convex light incidence surface shape design to reduce the overall thickness of the Fresnel lens, which corresponds to reducing the loss of infrared light when it passes through the Fresnel lens, thereby facilitating further increase of the capture amount of infrared light radiated by a human body at a long distance by the pyroelectric infrared sensor and ensuring the detection distance of the infrared detection device. SUMMARY

[0005] An object of the present application is to provide a Fresnel lens and an infrared detection device suitable for long-distance detection, wherein the Fresnel lens is suitable for long-distance detection of 15 meters or more, and has a significantly reduced volume compared to existing Fresnel lenses suitable for long-distance detection, thereby having great commercial value.

[0006] Another object of the present application is to provide a Fresnel lens and an infrared detection device suitable for long-distance detection, wherein the Fresnel lens is designed based on long-distance detection application and deviates from the traditional technical route of increasing the total light amount, so as to avoid the design of a large light incidence angle and a large light incidence surface area, thereby having a significantly reduced volume compared to existing Fresnel lenses suitable for long-distance detection.

[0007] Another object of the present application is to provide a Fresnel lens and infrared detection device suitable for long-distance detection, wherein the Fresnel lens increases the detection distance by improving the proportion of effective light energy in the light quantity, and correspondingly, based on the feature that the effective light energy decreases as the detected target moves away from the infrared detection device, the distance variation range between the detected target in the target detection space and the infrared detection device is reduced by reducing the light incidence angle of the Fresnel lens, thereby improving the proportion of effective light energy in the light quantity, which is completely different from the traditional technical route of increasing the total light quantity and avoids the design of large light incidence angle and light incidence area.

[0008] Another object of the present application is to provide a Fresnel lens and infrared detection device suitable for long-distance detection, wherein in the vertical detection application scenario of the infrared detection device, although the increase of the light incidence angle of the Fresnel lens can obtain a larger total light quantity, the movement of the detected target on the target detection surface (ground) will form a distance variation between the detected target and the infrared detection device, and the detected target moves away from the infrared detection device when the projection point on the target detection surface moves away from the infrared detection device, and correspondingly, based on the feature that the effective light energy decreases as the detected target moves away from the infrared detection device, the distance variation range between the detected target in the target detection space and the infrared detection device is reduced by reducing the light incidence angle of the Fresnel lens, thereby improving the proportion of effective light energy in the light quantity, which is completely different from the traditional technical route of increasing the total light quantity.

[0009] Another object of the present application is to provide a Fresnel lens and infrared detection device suitable for long-distance detection, wherein the structural design of the Fresnel lens has a smaller light incidence angle design based on the technical route of improving the proportion of effective light energy in the light quantity, and a smaller light incidence area design is suitable for the state of the smaller light incidence angle design, thereby being suitable for long-distance detection while having a smaller volume, and being able to reduce the cost and adapt to the miniaturization trend of products relative to the existing Fresnel lens suitable for long-distance detection.

[0010] Another object of the present application is to provide a Fresnel lens and infrared detection device suitable for long-distance detection, wherein the structural design of the Fresnel lens has a smaller light incidence angle and light incidence area design based on the technical route of improving the proportion of effective light energy in the light quantity, thereby having a smaller peripheral diameter without the design of a convex light incidence surface, and reducing the overall thickness of the Fresnel lens by designing each lens unit with a larger focal length, which is beneficial to increasing the capture amount of infrared light radiated by a long-distance detected target by the corresponding pyroelectric infrared sensor and ensuring the detection distance of the infrared detection device.

[0011] Another object of the present application is to provide a Fresnel lens and an infrared detection device suitable for long-distance detection, wherein the Fresnel lens has a smaller light inlet angle and a smaller light inlet surface area based on a technical route of improving the proportion of effective light energy in the light inlet amount, and thus has good structural stability without a convex light inlet surface design, which is conducive to ensuring the working stability of the infrared detection device.

[0012] Another object of the present application is to provide a Fresnel lens and an infrared detection device suitable for long-distance detection, wherein the Fresnel lens has a smaller peripheral diameter and each lens unit is designed with a larger focal length to reduce the overall thickness of the Fresnel lens without a convex light inlet surface design, and the height difference between the center of the light inlet surface and the periphery of the Fresnel lens is allowed to be less than 10 mm, so that the Fresnel lens can be designed as a flat or slightly raised arc surface, thus having a more natural and concealed installation effect.

[0013] Another object of the present application is to provide a Fresnel lens and an infrared detection device suitable for long-distance detection, wherein the Fresnel lens has a central lens and at least one lens unit group arranged around the central lens, and the light inlet surface of the Fresnel lens is formed by the smooth surface of the central lens and the lens unit group, wherein the central lens is provided with at least one lens unit and has a central axis, and the distance between the optical center of the lens unit farthest from the central axis in the lens unit group and the central axis is L, and based on the technical route of improving the proportion of effective light energy in the light inlet amount, the Fresnel lens of the present application has a significantly reduced volume compared with the existing Fresnel lens suitable for long-distance detection by setting L in the range of less than or equal to 18 mm in the state of having a smaller light inlet angle.

[0014] Another object of the present application is to provide a Fresnel lens and an infrared detection device suitable for long-distance detection, wherein the focal length of the lens unit of the central lens is f, the Fresnel lens is designed in the state of L≤18 mm, f≥15 mm, and H≤10 mm, and satisfies L / (f-H)≤0.7, wherein H is the height difference between the optical center of the lens unit of the central lens and the optical center of the lens unit farthest from the central axis in the lens unit group in the direction of the central axis, so that the light inlet angle of the Fresnel lens when applied to the infrared detection device is less than or equal to 70°, and the Fresnel lens has a smaller light inlet angle and a smaller light inlet surface area at the same time.

[0015] To achieve at least one of the above objects, the present application provides a Fresnel lens suitable for long-distance detection, the Fresnel lens comprising:

[0016] a center lens, wherein the center lens is disposed with at least one lens unit and has a central axis; and

[0017] at most three groups of lens unit groups, wherein each of the lens unit groups is composed of a plurality of lens units and is disposed around the center lens, each of the lens unit groups corresponds to the Fresnel lens to form a light entrance surface with a smooth surface of each lens unit, and each of the lens units of the Fresnel lens is designed with a plurality of concentric circular patterns on a side opposite to the light entrance surface to have a light converging property of a convex lens, wherein a focal length of the lens unit of the center lens is f, a distance between an optical center of a lens unit farthest from the central axis among the lens units of the at most three groups of lens unit groups and the central axis is L, the Fresnel lens is designed in a state of L≤18mm, f≥15mm, and H≤10mm, and L / (f-H)≤0.7 is satisfied, wherein H is a height difference between the optical center of the lens unit of the center lens and the optical center of the lens unit farthest from the central axis among the lens units of the lens unit groups in a direction along the central axis.

[0018] In an embodiment, wherein a total number of the lens units of the at most three groups of lens unit groups is less than or equal to 24.

[0019] In an embodiment, wherein the lens units of the lens unit groups farther from the center have larger smooth surface areas.

[0020] In an embodiment, wherein the number of the lens unit groups is two, one of the lens unit groups is disposed around the center lens with an outer edge of the center lens as an inner edge, and the other of the lens unit groups is disposed around the center lens with an outer edge of the one of the lens unit groups as an inner edge.

[0021] In an embodiment, wherein the Fresnel lens is designed in a state of 11mm≤L≤13mm, 21mm≤f≤25mm, and H≤5mm, and L / (f-H)≤0.7 is satisfied.

[0022] In an embodiment, wherein the number of the lens units of the center lens is one, and the center lens has a principal optical axis of the lens unit as the central axis.

[0023] In an embodiment, wherein the number of the lens units of the lens unit group with the outer edge of the center lens as an inner edge is four, and the number of the lens units of the other lens unit group is eight.

[0024] In an embodiment, wherein the center lens with a square outer edge of the lens unit arranged with one of the lens units has an octagonal outer edge with the outer edge of the center lens as an inner edge, and the lens unit group is divided into four lens units with diagonal lines of the square inner edge as boundaries, another lens unit group has a circular outer edge with the outer edge of the lens unit group of the previous lens unit group as an inner edge, and is divided into eight lens units with diagonal lines of the octagonal inner edge as boundaries.

[0025] In an embodiment, wherein the square outer edge of the center lens has a side length of 6±0.5mm, the octagonal outer edge of the lens unit group with the outer edge of the center lens as an inner edge has a side length of 7±0.5mm, and the circular outer edge of another lens unit group has a radius of 17.5±0.5mm.

[0026] According to another aspect of the present application, the present application also provides an infrared detection device, the infrared detection device comprising:

[0027] The Fresnel lens suitable for long-distance detection according to any one of the preceding aspects, and

[0028] A pyroelectric infrared sensor, wherein the pyroelectric infrared sensor has at least one sensing surface and is arranged with the sensing surface facing a surface of the Fresnel lens opposite to the light-incident surface.

[0029] In an embodiment, wherein the pyroelectric infrared sensor is arranged in a quadruplet form with four sensing surfaces.

[0030] Further objects and advantages of the present application will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 A schematic diagram of a vertical detection application scenario of an existing infrared detection device.

[0032] Figure 2A A schematic diagram of the structure principle of an infrared detection device according to an embodiment of the present application.

[0033] Figure 2B A schematic diagram of the refraction principle of the lens units of the Fresnel lens of the infrared detection device according to the above embodiment of the present application.

[0034] Figure 3A A schematic diagram of the form of the Fresnel lens of the infrared detection device according to the above embodiment of the present application at the light-incident surface.

[0035] Figure 3B A schematic diagram of the form of the Fresnel lens of the infrared detection device according to the above embodiment of the present application at a surface opposite to the light-incident surface.

[0036] Figure 4 A comparison diagram of the Fresnel lens of the infrared detection device according to the above embodiment of the present application and a conventional Fresnel lens applied to long-distance detection.

[0037] Figure 5 A schematic diagram of a lens unit in which the optical center is not located in the lens unit body.

[0038] Figure 6A A schematic diagram of an application scenario in which the infrared detection device according to the above embodiment of the present application is installed in a lamp and realizes intelligent lighting in a warehouse environment.

[0039] Figure 6B An effect display diagram of installing the infrared detection device according to the above embodiment of the present application in a lamp. DETAILED DESCRIPTION

[0040] The following description is provided so that others skilled in the art can have the best possible understanding of the present application. The preferred embodiments in the following description are only examples and other obvious variations can be thought of by those skilled in the art. The basic principles of the present application defined in the following description can be applied to other embodiments, variations, improvements, equivalents and other technical solutions without departing from the spirit and scope of the present application.

[0041] Those skilled in the art should understand that in the disclosure of the present application, the orientations or positional relationships indicated by the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like are based on the orientations or positional relationships shown in the drawings, which are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore the above terms cannot be understood as a limitation of the present application.

[0042] It can be understood that the term "one" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of one element can be one, and in another embodiment, the number of the element can be multiple, and the term "one" cannot be understood as a limitation on the number.

[0043] The present application provides a Fresnel lens and an infrared detection device suitable for long-distance detection, wherein the Fresnel lens is suitable for long-distance detection of 15 meters and above, and has a significantly reduced volume compared to existing Fresnel lenses suitable for long-distance detection, thus having great commercial value.

[0044] Specifically, the present application increases the detection distance by improving the proportion of effective light energy in the light quantity of the Fresnel lens when applied to the infrared detection device. Based on the characteristic that the effective light energy decreases as the detected target moves away from the infrared detection device, the distance change range between the detected target and the infrared detection device in the target detection space is reduced by reducing the light incidence angle of the Fresnel lens, thereby increasing the proportion of effective light energy in the light quantity and avoiding the design of large light incidence angle and light incidence area.

[0045] For example, referring to the drawings of the present application Figure 1 As shown in the drawings, taking the vertical detection application scenario of the existing infrared detection device as an example, the movement of the detected target on the target detection surface (ground) will form a distance change between the infrared detection device and the detected target, and the detected target will move away from the infrared detection device when it is far away from the projection point of the infrared detection device on the target detection surface. Therefore, based on the characteristic that the effective light energy decreases as the detected target moves away from the infrared detection device, although a larger light quantity can be obtained by increasing the light incidence angle of the Fresnel lens, the distance between the detected target and the infrared detection device in the target detection space formed by the increased light incidence angle is also far away, that is, the proportion of effective light energy in the light quantity increased based on the increase of the light incidence angle is relatively low, and thus the proportion of effective light energy in the total light quantity is lowered. In view of this, the present application reduces the light incidence angle of the Fresnel lens, so that the distance change range between the detected target and the infrared detection device in the target detection space is reduced, thereby increasing the proportion of effective light energy in the light quantity and completely departing from the traditional technical route of increasing the total light quantity.

[0046] Further referring to the drawings of the present application Figures 2A to 3BAs shown, the structural principle of the infrared detecting device and the corresponding structural principle of the Fresnel lens according to an embodiment of the present application are shown respectively, wherein the infrared detecting device comprises a Fresnel lens 10 and a pyroelectric infrared sensor 20, wherein the Fresnel lens 10 has a center lens 11 with at least one lens unit 100 arranged and has a central axis, and at least one lens unit group 12 composed of a plurality of lens units 100 arranged around the center lens 11, the Fresnel lens 10 corresponding to each light-smooth surface of the lens unit 100 forms a light entrance surface 101, and each lens unit 100 of the Fresnel lens 10 is designed with a plurality of concentric circular lines on the side opposite to the light entrance surface 101, so as to have the light converging characteristics of a convex lens, wherein the focal length of the lens unit 100 of the center lens 11 is f, and the distance between the optical center of the lens unit 100 farthest from the central axis in the lens unit group 12 and the central axis is L, wherein the pyroelectric infrared sensor 20 has at least one sensing surface 21 and is arranged such that the sensing surface 21 faces the side of the Fresnel lens 10 opposite to the light entrance surface 101.

[0047] Corresponding to Figure 2B As shown, the refractive principle of the lens unit 100, the lens unit 100 has the same optical characteristics as a convex lens and has an optical center 1001 and a principal axis 1002 passing through the optical center 1001, and the light rays parallel to the principal axis 1002 of the lens unit 100 are converged at the focal point 1003 of the lens unit 100 by refraction of the lens unit 100, wherein the focal plane 1004 of the lens unit 100 is the plane perpendicular to the principal axis 1002 of the lens unit 100 in the plane where the focal point 1003 of the lens unit 100 is located, and the axis passing through the optical center 1001 of the lens unit 100 and inclined to the principal axis 1002 is the secondary principal axis 1005 of the lens unit 100, wherein the light rays parallel to the secondary principal axis 1005 of the lens unit 100 are converged at the secondary focal point 1006 on the focal plane 1004 of the lens unit 100 by refraction of the lens unit 100.

[0048] According to the above-mentioned refraction principle of the lens unit 100, the sensing surface 21 of the pyroelectric infrared sensor 20 is usually arranged near the focal plane 1004 of the lens unit 100 of the center lens 11, corresponding to the state that the number of the lens unit 100 of the center lens 11 is one, the central axis of the center lens 11 is the main optical axis 1002 of the lens unit 100, and the distance between the optical center 1001 of the lens unit 100 and the sensing surface 21 of the pyroelectric infrared sensor 20 along the central axis of the center lens 11 is close to the focal length f of the lens unit 100; and corresponding to the state that the number of the lens unit 100 of the center lens 11 is multiple, the distance between the optical center 1001 of any lens unit 100 of the center lens 11 and the sensing surface 21 of the pyroelectric infrared sensor 20 along the central axis of the center lens 11 is also close to the focal length f of the lens unit 100. Therefore, in the understanding of the present application, the light incidence angle θ of the Fresnel lens 10 when applied to the infrared detection device corresponds to Figure 2A The light incidence angle θ of the Fresnel lens 10 satisfies tan(θ / 2) = L / (f-H), where H is the height difference between the optical center 1001 of the lens unit 100 of the center lens 11 and the optical center 1001 of the lens unit 100 farthest from the central axis in the lens unit group 12 along the central axis, and L is the length of the straight angle opposite the angle of the right-angled triangle formed by the two straight angles of lengths (f-H) and L.

[0049] It is worth mentioning that, due to the area and number of the sensing surface 21 of the pyroelectric infrared sensor 20 and the actual installation position and angle error of the pyroelectric infrared sensor 20, in the understanding of the present application, the light incidence angle θ defined based on L / (f-H) is only used to define the structural characteristics of the Fresnel lens 10, which neither constitutes a limitation on the specific installation position and angle of the pyroelectric infrared sensor 20, nor constitutes a limitation on the actual effective detection angle of the infrared detection device.

[0050] In particular, the present application increases the detection distance by improving the proportion of effective light energy in the light quantity of the Fresnel lens 10 when applied to the infrared detection device, in which the light entrance area of the Fresnel lens 10 is not a decisive factor affecting the proportion of effective light energy in the light quantity. On the other hand, in the state that the structural design of the Fresnel lens 10 has a smaller light entrance angle based on the aforementioned technical route of the present application, and still corresponds to the traditional technical route based on increasing the total light quantity with a larger light entrance area, in order to reduce the overall thickness of the Fresnel lens 10 to reduce the loss generated when infrared light passes through the Fresnel lens 10, and to ensure the detection distance of the infrared detection device, each lens unit 100 of the Fresnel lens 10 must be designed with a larger focal length, so that the size of the infrared detection device in the central axis direction of the central lens 11 is also very large.

[0051] That is, in the state that the structural design of the Fresnel lens 10 has a smaller light entrance angle based on the aforementioned technical route of the present application, and still corresponds to the traditional technical route based on increasing the total light quantity with a larger light entrance area, in order to ensure the detection distance of the infrared detection device, the size of the infrared detection device in the central axis direction of the central lens 11 and the overall thickness of the Fresnel lens 10 cannot be reduced at the same time.

[0052] Therefore, in the structural design of the Fresnel lens 10 of the present application, in the state that the structural design of the Fresnel lens 10 has a smaller light entrance angle based on the aforementioned technical route of the present application, the Fresnel lens 10 also has a smaller light entrance area design, so that the structural design of the Fresnel lens 10 can simultaneously consider the miniaturization design and long-distance detection of the infrared detection device.

[0053] Specifically, in the structural design of the Fresnel lens 10 of the present application, the Fresnel lens 10 is designed in the state of L≤18mm, f≥15mm, and H≤10mm, and satisfies L / (f-H)≤0.7, so that the light entrance angle θ of the Fresnel lens 10 when applied to the infrared detection device is less than or equal to 70°, and has a smaller light entrance area in the state of having a smaller light entrance angle, thereby enabling the structural design of the Fresnel lens 10 to simultaneously consider the miniaturization design and long-distance detection of the infrared detection device.

[0054] In other words, in the state that the structure design of the Fresnel lens 10 has a smaller light incidence angle design based on the aforementioned technical route of the present application, the Fresnel lens 10 of the present application can simultaneously consider the small area design of the light incidence surface 101 and the thinning design of the overall thickness in the structure design, so that the structure design of the Fresnel lens 10 can simultaneously consider the miniaturization design and the long-distance detection of the infrared detection device.

[0055] It is worth mentioning that although in the state that the structure design of the Fresnel lens 10 has a smaller light incidence angle design based on the aforementioned technical route of the present application, the Fresnel lens 10 of the present application can simultaneously consider the small area design of the light incidence surface 101 and the thinning design of the overall thickness in the structure design. However, the small area design of the light incidence surface 101 of the Fresnel lens 10 will indeed result in a decrease in the total light incidence amount and a decrease in the intensity of the total effective light energy. Therefore, in order to guarantee the detection distance of the infrared detection device, in the structure design of the Fresnel lens 10 of the present application, the number of the lens unit groups 12 of the Fresnel lens 10 is at most three, and the total number of the lens units 100 of the lens unit groups 12 is preferably designed to be less than or equal to 24, so that in the state that the light incidence surface 101 of the Fresnel lens 10 has a smaller area based on the conditions of L≤18mm and H≤10mm, the light incidence area of the lens units 100 of each lens unit group 12 is guaranteed, so that the intensity of the effective light energy passing through the lens units 100 of each lens unit group 12 is not reduced due to the small area design of the light incidence surface 101 of the Fresnel lens 10, thereby guaranteeing the detection distance of the infrared detection device.

[0056] Preferably, the number of the lens unit groups 12 of the Fresnel lens 10 corresponds to two groups in the structure example of the Fresnel lens 10 of this embodiment of the present application, so as to guarantee the light incidence area of the lens units 100 of each lens unit group 12 and the intensity of the effective light energy passing through the lens units 100 of each lens unit group 12, while considering the number of the lens units 100 of the lens unit groups 12, so that in the state that the Fresnel lens 10 has a smaller light incidence angle, based on the characteristics that the target detection surface is far away from the infrared detection device in the long-distance detection application scenario, the Fresnel lens 10 still has a larger partition coverage area and a reasonable partition arrangement density, thereby guaranteeing the effective detection area of the infrared detection device.

[0057] In short, the infrared detection device is based on the zoning of the lens unit 100 of the Fresnel lens 10 corresponding to the detection area, and the pyroelectric infrared sensor 20 detects the human body in the detection area. Therefore, in the state that the Fresnel lens 10 has a small light incidence angle design, and the light incidence surface 101 has a small area based on the condition of L≤18mm and H≤10mm, the number of the lens unit group 12 of the Fresnel lens 10 is designed to be at most three groups. On the one hand, it can guarantee the light incidence area of the lens unit 100 of each lens unit group 12, so that the effective light energy intensity of the light passing through the lens unit 100 of each lens unit group 12 is not reduced due to the small area design of the light incidence surface 101 of the Fresnel lens 10, thereby guaranteeing the detection distance of the infrared detection device. On the other hand, it can make use of the characteristics that the target detection surface is far away from the infrared detection device in the long-distance detection application scenario, so that the Fresnel lens 10 still has a large zoning coverage area and a reasonable zoning arrangement density, thereby guaranteeing the effective detection area of the infrared detection device.

[0058] In summary, the Fresnel lens 10 of the present application needs to meet the structural design requirements of L≤18mm, f≥15mm, H≤10mm, and L / (f-H)≤0.7, and at the same time, the number of the lens unit group 12 is designed to be at most three groups, and the total number of the lens unit 100 of the lens unit group 12 is preferably designed to be less than or equal to 24. In this way, the light incidence angle θ of the Fresnel lens 10 applied to the infrared detection device is less than or equal to 70°, and the Fresnel lens 10 has a small light incidence area while having a small light incidence angle, and is suitable for long-distance detection of 15 meters or more. Correspondingly, the structural design of the Fresnel lens 10 can simultaneously consider the miniaturization design of the infrared detection device and the effective detection area in the long-distance detection application scenario.

[0059] It is worth mentioning that in the description of the present application, the description of the detection distance range suitable for the Fresnel lens 10 is only to emphasize the farthest detection distance range in which the Fresnel lens 10 can normally perform. That is, the farthest detection distance in which the Fresnel lens 10 of the present application can normally perform can reach 15 meters or more, which does not constitute a limitation on the actual use state of the Fresnel lens 10. For example, the Fresnel lens 10 of the present application is recommended for long-distance detection of 15 meters or more, and is not recommended for short-distance detection of less than 8 meters, but according to the actual use demand, the user can still use it for detection in the distance range of 8 to 15 meters, and the present application does not limit this.

[0060] The Fresnel lens 10 is designed to satisfy the condition that the number of the lens unit groups 12 is designed to be at most three groups, corresponding to the state that the number of the lens unit groups 12 is one group, the lens unit groups 12 are arranged around the center lens 11 with the outer edge of the center lens 11 as the inner edge; and the state that the number of the lens unit groups 12 is two groups, one of the lens unit groups 12 is arranged around the center lens 11 with the outer edge of the center lens 11 as the inner edge, and the other of the lens unit groups 12 is arranged around the center lens 11 with the outer edge of the former lens unit group 12 as the inner edge; and the state that the number of the lens unit groups 12 is three groups, one of the lens unit groups 12 is arranged around the center lens 11 with the outer edge of the center lens 11 as the inner edge, and the other two of the lens unit groups 12 are arranged around the center lens 11 with the outer edge of the former lens unit group 12 as the inner edge in turn.

[0061] Further, in the case that the Fresnel lens 10 is designed to satisfy the conditions of L≤18mm, f≥15mm, H≤10mm and L / (f-H)≤0.7, and at the same time, the number of the lens unit groups 12 is designed to be at most three groups, the Fresnel lens 10 is preferably designed to satisfy the condition that the lens unit 100 of the lens unit group 12 at the outer periphery has a larger light inlet area (i.e. the area of the aforementioned smooth surface) than the lens unit 100 of the lens unit group 12 at the inner periphery, so as to ensure the intensity and uniformity of the effective light energy of the lens unit 100 of each lens unit group 12, thereby ensuring the stability of the detection sensitivity of the infrared detection device in the effective detection area.

[0062] Specifically, in the structural example of the Fresnel lens 10 of this embodiment of the present application, the number of the lens units 100 of the center lens 11 is one, corresponding to the structural form shown in Figs. 1 and 2, wherein the Fresnel lens 10 is designed to satisfy the conditions of 11mm≤L≤13mm, 21mm≤f≤25mm and H≤5mm, and L / (f-H)≤0.7, based on which, the overall thickness of the Fresnel lens 11 is allowed to be designed in the range of less than or equal to 0.6mm, so as to take into account the miniaturization design and long-distance detection of the infrared detection device. Figure 3A Figure 3B Specifically, in the structural example of the Fresnel lens 10 of this embodiment of the present application, the number of the lens units 100 of the center lens 11 is one, corresponding to the structural form shown in Figs. 1 and 2, wherein the Fresnel lens 10 is designed to satisfy the conditions of 11mm≤L≤13mm, 21mm≤f≤25mm and H≤5mm, and L / (f-H)≤0.7, based on which, the overall thickness of the Fresnel lens 11 is allowed to be designed in the range of less than or equal to 0.6mm, so as to take into account the miniaturization design and long-distance detection of the infrared detection device.

[0063] ​Further, in the structural example of the Fresnel lens 10 of this embodiment of the present application, the number of the lens unit groups 12 of the Fresnel lens 10 is two, corresponding to the state in which the two lens unit groups 12 are disposed around the central lens 11, wherein one of the lens unit groups 12 is disposed around the central lens 11 with the outer edge of the central lens 11 as the inner edge, and the other lens unit group 12 is disposed around the central lens 11 with the outer edge of the former lens unit group 12 as the inner edge.

[0064] In particular, in the structural example of the Fresnel lens 10 of this embodiment of the present application, the lens unit 100 of each of the lens unit groups 12 located further outward has a larger light inlet area design with the central lens 11 as the center. That is, the light inlet area of the lens unit 100 of each of the lens unit groups 12 with the outer edge of the central lens 11 as the inner edge is smaller than the light inlet area of the lens unit 100 of the other lens unit group 12, so as to ensure the uniformity of the intensity of the effective light energy passing through the lens unit 100 of each of the lens unit groups 12, thereby ensuring the stability of the detection sensitivity of the infrared detection device within the effective detection area.

[0065] Further, in the structural example of the Fresnel lens 10 of this embodiment of the present application, the number of the lens unit 100 of the lens unit group 12 with the outer edge of the central lens 11 as the inner edge is four, and the number of the lens unit 100 of the other lens unit group 12 is eight.

[0066] Specifically, in the structural example of the Fresnel lens 10 of this embodiment of the present application, the central lens 11 with one lens unit 100 disposed has a square outer edge, the lens unit group 12 with the outer edge of the central lens 11 as the inner edge has an octagonal outer edge, and the four lens units 100 are divided by the diagonal extension line of the square inner edge, and the other lens unit group 12 with the outer edge of the former lens unit group 12 as the inner edge has a circular outer edge, and the eight lens units 100 are divided by the diagonal extension line of the octagonal inner edge.

[0067] Further, in the structural example of the Fresnel lens 10 of this embodiment of the present application, the square outer edge of the center lens 11 has a side length of 6±0.5 mm, the regular octagonal outer edge of the lens unit group 12 with the outer edge of the center lens 11 as the inner edge has a side length of 7±0.5 mm, and the circular outer edge of the other lens unit group 12 has a radius of 17.5±0.5 mm, so as to ensure the uniformity of the intensity of the effective light energy of the lens unit 100 of each lens unit group 12, thereby ensuring the stability of the detection sensitivity of the infrared detection device within the effective detection area, and the Fresnel lens 10 has a peripheral diameter of only about 35 mm when the outer edge of the light entrance face 101 is the peripheral edge, which is much smaller than the peripheral diameter of the conventional Fresnel lens applied to long-distance detection. Figure 4

[0068] In particular, in the structural example of the Fresnel lens 10 of this embodiment of the present application, each lens unit 100 of the Fresnel lens 10 is designed with a plurality of concentric circular lines on the side opposite to the light entrance face 101, and has a light-converging property like a convex lens, and the optical center 1001 of the lens unit 100 can be considered as the center of the concentric circular lines within a certain error range. Since the sensing face 21 of the pyroelectric infrared sensor 20 is usually arranged near the focal plane 1004 of the lens unit 100 of the center lens 11, the optical center 1001 of the lens unit 100 of the lens unit group 12 is usually designed to deviate from the geometric center of the lens unit 100 in the direction deviating from the center lens 11, so as to enable the light passing through the lens unit 100 of the lens unit group 12 to be deflected to the sensing face 21 of the pyroelectric infrared sensor 20.

[0069] That is, the lens unit 100 of the lens unit group 12 based on the design of the concentric circular lines is equivalent to a convex lens in optical property, which is not limited to a convex lens with the geometric center as the optical center 1001, but can be equivalent to a defective form of a convex lens with the geometric center as the optical center 1001. Therefore, in some embodiments of the present application, the concentric circular lines designed on the lens unit 100 correspond to Figure 5 which is not limited to having at least one complete circular line, and the optical center 1001 of the lens unit 100 can not be located on the lens unit 100 body, but the position of the optical center 1001 can still be determined according to the circular arc line formed by the defective concentric circular lines, and the present application is not limited thereto.

[0070] ​Furthermore, in the infrared detection device of this embodiment of the present invention, the pyroelectric infrared sensor 20 is arranged in a quaternary form with four sensing surfaces 21, thereby further partitioning the partitions corresponding to each lens unit 100 of the Fresnel lens 10 based on the arrangement of the plurality of sensing surfaces 21, thereby improving the resolution of the infrared detection device in relation to the movement amplitude of the detected target.

[0071] It is worth mentioning that the infrared detection device is typically installed in lighting fixtures to achieve intelligent lighting by controlling the lighting state of the fixtures based on the detection of the corresponding target, for example in... Figure 6A The illustrated warehouse environment utilizes the structural design of the Fresnel lens 10 to ensure the effective detection area of ​​the infrared detection device in long-distance detection applications, enabling intelligent lighting of the warehouse environment through high-mount installation of the lamps. Specifically, the Fresnel lens 10 is designed to satisfy L≤18mm, resulting in a significantly smaller peripheral diameter compared to traditional Fresnel lenses used for long-distance detection. Furthermore, the Fresnel lens 10 is designed to satisfy H≤10mm, and its light-gathering surface 101 can be designed as a flat or slightly raised curved surface. This allows the infrared detection device to be positioned within the lamps, corresponding to… Figure 6B Achieve a more natural and discreet installation effect.

[0072] It will be understood by those skilled in the art that the above embodiments are merely examples, and features of different embodiments can be combined with each other to obtain implementation methods that are readily conceivable according to the content disclosed in the present invention but are not explicitly shown in the accompanying drawings.

[0073] Those skilled in the art should understand that the embodiments of the present invention described above and shown in the accompanying drawings are merely examples and do not limit the present invention. The objectives of the present invention have been fully and effectively achieved. The functions and structural principles of the present invention have been demonstrated and explained in the embodiments, and any variations or modifications may be made to the implementation of the present invention without departing from the stated principles.

Claims

1. Fresnel lens suitable for remote detection, characterized in that, The Fresnel lens suitable for long distance detection comprises: a center lens, wherein the center lens is arranged with at least one lens unit and has a central axis; and at most three groups of lens unit groups, wherein each of the lens unit groups is arranged with a plurality of lens units and surrounds the center lens, each of the lens unit groups corresponds to the Fresnel lens to form a light entrance surface with the smooth surface of each lens unit, and each of the lens units of the Fresnel lens is designed with a plurality of concentric circular patterns on the side opposite to the light entrance surface to have the same light converging characteristics as a convex lens, wherein the focal length of the lens unit of the center lens is ƒ, the distance between the optical center of the lens unit farthest from the central axis in the lens unit groups and the central axis is L, the Fresnel lens is designed in the state of L≤18mm, ƒ≥15mm, and H≤10mm, and L / (ƒ-H)≤0.7 is satisfied, wherein H is the height difference between the optical center of the lens unit of the center lens and the optical center of the lens unit farthest from the central axis in the lens unit groups in the direction along the central axis.

2. The Fresnel lens suitable for long distance detection according to claim 1, wherein the total number of lens units in the at most three groups of lens unit groups is less than or equal to 24.

3. The Fresnel lens suitable for long distance detection according to claim 2, wherein the lens units of the lens unit groups farther from the center have larger smooth surface areas.

4. The Fresnel lens suitable for long distance detection according to claim 2 or 3, wherein the number of lens unit groups is two, and one of the lens unit groups is arranged around the center lens with the outer edge of the center lens as the inner edge, and the other lens unit group is arranged around the center lens with the outer edge of the previous lens unit group as the inner edge.

5. The Fresnel lens suitable for long distance detection according to claim 4, wherein the Fresnel lens is designed in the state of 11mm≤L≤13mm, 21mm≤ƒ≤25mm, and H≤5mm, and L / (ƒ-H)≤0.7 is satisfied.

6. The Fresnel lens suitable for long distance detection according to claim 5, wherein the number of lens units of the center lens is one, and the central axis of the center lens is the principal optical axis of the lens unit.

7. The Fresnel lens suitable for long distance detection according to claim 6, wherein the number of lens units of the lens unit group with the outer edge of the center lens as the inner edge is four, and the number of lens units of the other lens unit group is eight.

8. The Fresnel lens suitable for long distance detection according to claim 7, wherein said central lens with one said lens unit arranged thereon has a square outer periphery, said lens unit group with square inner periphery of said central lens has a regular octagonal outer periphery, and another said lens unit group has a circular outer periphery with regular octagonal inner periphery, and is divided into eight said lens units by diagonal extension lines of said regular octagonal inner periphery.

9. The Fresnel lens suitable for long distance detection according to claim 8, wherein said square outer periphery of said central lens has a side length of 6±0.5 mm, said regular octagonal outer periphery of said lens unit group with square inner periphery of said central lens has a side length of 7±0.5 mm, and said circular outer periphery of another said lens unit group has a radius of 17.5±0.5 mm.

10. An infrared detection device, characterized by including: the Fresnel lens suitable for long distance detection according to any one of claims 1 to 9, and a pyroelectric infrared sensor, wherein said pyroelectric infrared sensor has at least one sensing surface and is arranged with said sensing surface facing a surface of said Fresnel lens opposite to said light entrance surface.

11. The infrared detection device according to claim 10, wherein said pyroelectric infrared sensor is arranged in a tetrametric form with four said sensing surfaces.

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