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

Abstract

The invention provides a Fresnel lens suitable for long-distance detection and an infrared detection device, and the Fresnel lens comprises a central lens which is provided with at least one lens unit and is provided with a central axis, and at most three lens unit groups which are composed of a plurality of lens units and are disposed around the central lens. Wherein the focal length of the lens unit of the central lens is f, the distance between the optical center of the lens unit farthest from the central axis in the lens units of the lens unit group and the central axis is L, and the Fresnel lens is designed in a state that L is less than or equal to 18 mm, f is greater than or equal to 15 mm, and H is less than or equal to 10 mm to meet the condition that L / (f-H) is less than or equal to 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 units of the lens unit group in the direction of the central axis; therefore, the Fresnel lens can give consideration to the miniaturization design of the infrared detection device and the effective detection area in a long-distance detection application scene at the same time.

Description

Technical Field

[0001] The invention 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 Art

[0002] With the development of Internet of Things technology and the popularization of low-carbon and environmental protection concepts, artificial intelligence, smart home, and smart security technology have an increasing demand for environmental detection, especially for human movement detection, so as to control the corresponding electrical equipment based on the detection results of the presence or absence of human body and realize intelligent control of the working status of electrical equipment. For example, the lighting status of lamps is controlled based on the detection results of the presence or absence of human body to realize intelligent low-carbon lighting.

[0003] The existing technologies for detecting the presence of human bodies mainly include: 1. Recognizing the human body and human behavior status based on image acquisition with corresponding algorithms, but it is difficult to be accepted due to the risk of privacy infringement and leakage, and it also has the defects of complex algorithms and high hardware performance requirements and has a high cost. 2. Microwave detection technology based on the principle of Doppler effect, specifically by transmitting a microwave beam and receiving a reflected echo formed by the microwave beam being reflected by the corresponding object, and generating a Doppler intermediate frequency signal corresponding to the frequency difference between the microwave beam and the reflected echo by mixing detection, and the Doppler intermediate frequency signal is the feedback of the movement of the corresponding object. Among them, microwave detection technology based on the principle of Doppler effect has unique advantages in behavior detection and existence detection technology. It can detect moving objects without infringing on human privacy, and therefore has broad application prospects. However, on the one hand, due to the above working principle of microwave detection technology, the current microwave detection device is greatly affected by the environment in the application scenario of long-distance detection and cannot maintain its advantage of being able to detect micro-movements. On the other hand, due to the limitations of civilian-level microwave detection devices in product volume, cost and microwave transmission power, 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 with military phased array radars. 3. Based on the partitioning of the corresponding detection area by Fresnel lens, the cross-area movement of the human body in the detection area is detected by pyroelectric infrared sensor (PIR), which is also the most commonly used and mature human presence detection technology.

[0004] Although the third human presence detection technology is the most commonly used and mature human presence detection technology among the above three human presence detection technologies, the corresponding infrared detection devices currently suitable for long-distance detection of more than 12 meters generally have the defect of being bulky, so that when it is applied to intelligent lighting, the infrared detection device can only be set up in an external manner, and the volume of the external infrared detection device may be larger than the lamp itself. The reason why the volume of the current infrared detection device suitable for long-distance detection is huge is mainly because in the current product design concept of the infrared detection device, the increase in detection distance is achieved by increasing the technical route of increasing the total amount of light entering. Based on this technical route, the corresponding Fresnel lens is generally designed to have a larger light entering angle and light entering surface area, in order to increase the total amount of light entering based on the design of a larger light entering angle and light entering surface area, thereby increasing the amount of infrared light radiated by the pyroelectric infrared sensor to capture the human body at a distance, thereby improving the detection distance of the infrared detection device. The Fresnel lens designed with a larger light-entry angle and light-entry surface area is also designed with a convex light-entry surface shape, and the center of the light-entry surface of the Fresnel lens has a height difference of more than 15mm relative to its periphery based on the convex structural design. In this way, while maintaining the state of the Fresnel lens having a larger light-entry surface area, the peripheral diameter of the Fresnel lens is reduced based on the convex light-entry surface shape design (actually still more than 80mm) to reduce the lateral size of the infrared detection device; and while maintaining the state of the Fresnel lens having a larger light-entry angle, the convex light-entry surface shape design allows each lens unit to be designed with a larger focal length to reduce the overall thickness of the Fresnel lens, correspondingly reducing the loss generated when the infrared light passes through the Fresnel lens, thereby facilitating further increasing the amount of infrared light radiated by the human body at a long distance captured by the pyroelectric infrared sensor to ensure the detection distance of the infrared detection device. Summary of the invention

[0005] One object of the present invention 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 and above, and has a significantly reduced volume compared to the existing Fresnel lens suitable for long-distance detection, and thus has significant commercial value.

[0006] Another object of the present invention is to provide a Fresnel lens and an infrared detection device suitable for long-distance detection, wherein the Fresnel lens, based on the application of long-distance detection, breaks away from the traditional technical route of increasing the total amount of light input in structural design and can avoid the use of a design with a large light input angle and light input surface area, and thus has a significantly reduced volume compared to the existing Fresnel lens suitable for long-distance detection.

[0007] Another object of the present invention is to provide a Fresnel lens and an infrared detection device suitable for long-distance detection, wherein the Fresnel lens achieves an increase in detection distance by a technical route of increasing the proportion of effective light energy in the amount of light input. Based on the characteristic that the effective light energy decreases as the detected target moves away from the infrared detection device, the light input angle of the Fresnel lens is reduced to reduce the range of distance variation between the detected target and the infrared detection device that can be formed by the movement of the detected target in the target detection space, thereby increasing the proportion of effective light energy in the amount of light input. This is completely different from the traditional technical route of increasing the total amount of light input and can avoid the use of designs with large light input angles and light input surface areas.

[0008] Another object of the present invention is to provide a Fresnel lens and an infrared detection device suitable for long-distance detection, wherein taking the vertical detection application scenario of the infrared detection device as an example, although the increase in the light input angle of the Fresnel lens can obtain a larger total amount of light input, the movement of the detected target on the target detection surface (ground) will cause a change in the distance between the detected target and the infrared detection device, and the target will move away from the infrared detection device when moving 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, by reducing the light input angle of the Fresnel lens, the range of distance changes between the detected target and the infrared detection device that can be formed by the movement of the detected target in the target detection space is reduced, thereby being able to increase the proportion of effective light energy in the amount of light input, and completely breaking away from the traditional technical route of increasing the total amount of light input.

[0009] Another object of the present invention is to provide a Fresnel lens and an infrared detection device suitable for long-distance detection, wherein the structural design of the Fresnel lens has a smaller light entrance angle design based on the technical route of increasing the proportion of effective light energy in the amount of light entering, and is suitable for adopting a smaller light entrance surface area design in the state of having a smaller light entrance angle design. Therefore, while being suitable for longer-distance detection, it also has a smaller volume and can reduce costs relative to existing Fresnel lenses suitable for long-distance detection and adapt to the trend of miniaturization of products.

[0010] Another object of the present invention is to provide a Fresnel lens and an infrared detection device suitable for long-distance detection, wherein the structural design of the Fresnel lens is based on a technical route of increasing the proportion of effective light energy in the amount of incoming light, and has a smaller light-incoming angle and a light-incoming surface area design. Therefore, it is not necessary to design the light-incoming surface based on a convex shape, and it is possible to have a smaller peripheral diameter and design each lens unit with a larger focal length to reduce the overall thickness of the Fresnel lens, which is beneficial to increase the amount of infrared light radiated by the long-distance detected target captured by the corresponding pyroelectric infrared sensor, thereby ensuring the detection distance of the infrared detection device.

[0011] Another object of the present invention is to provide a Fresnel lens and an infrared detection device suitable for long-distance detection, wherein the structural design of the Fresnel lens is based on a technical route of increasing the proportion of effective light energy in the amount of incoming light, and has a smaller light input angle and light input surface area design, so that it can have good structural stability without the need for a convex light input surface morphology design, which is correspondingly beneficial to ensuring the working stability of the infrared detection device.

[0012] Another object of the present invention is to provide a Fresnel lens and an infrared detection device suitable for long-distance detection, wherein the Fresnel lens can have a smaller peripheral diameter and each lens unit can be designed with a larger focal length to reduce the overall thickness of the Fresnel lens without being designed based on a convex light-entry surface shape, and the height difference between the center of the light-entry surface of the Fresnel lens and its periphery is allowed to be set in a range of less than 10 mm and can be designed with a flat surface or a slightly convex curved surface, thereby having a more natural and concealed installation effect.

[0013] Another object of the present invention 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 group of lens units arranged around the central lens, and the Fresnel lens forms a light-incoming surface with the smooth surfaces of the central lens and the lens unit group, wherein the central lens is arranged 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, wherein based on the technical route of increasing the proportion of effective light energy in the amount of incoming light, the Fresnel lens of the present invention sets L in a range of less than or equal to 18 mm when having a smaller light-incoming angle, and has a significantly reduced volume compared to the existing Fresnel lens suitable for long-distance detection.

[0014] Another object of the present invention 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, and the Fresnel lens is designed to satisfy L / (fH)≤0.7 under the conditions of L≤18mm, f≥15mm, and H≤10mm, wherein H is the height difference along the central axis 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, so that the Fresnel lens has a light entry angle less than or equal to 70° when applied to the infrared detection device and has a smaller light entry surface area when having a smaller light entry angle.

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

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

[0017] At most three lens unit groups, wherein each lens unit group is composed of a plurality of lens units and is arranged around the central lens, the corresponding Fresnel lens forms a light-entering surface with a smooth surface of each lens unit, and each lens unit of the Fresnel lens is designed with a plurality of concentric circle patterns on a side opposite to the light-entering surface and has a focusing characteristic like a convex lens, wherein the focal length of the lens unit of the central lens is f, and the distance between the optical center of the lens unit farthest from the central axis among the lens units of the at most three lens unit groups and the central axis is L, and the Fresnel lens is designed to satisfy L / (fH)≤0.7 in the state of L≤18mm, f≥15mm, and H≤10mm, wherein H is the height difference along the central axis 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 among the lens units of the lens unit group.

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

[0019] In one embodiment, with the central lens as the center, the lens units in the lens unit group located more peripherally have larger smooth surface areas.

[0020] In one embodiment, the number of the lens unit groups is two, wherein one of the lens unit groups is arranged around the central lens with the outer edge of the central lens as the inner edge, and the other lens unit group is arranged around the central lens with the outer edge of the first lens unit group as the inner edge.

[0021] In one embodiment, the Fresnel lens is designed to satisfy L / (fH)≤0.7 in the state of 11 mm≤L≤13 mm, 21 mm≤f≤25 mm, and H≤5 mm.

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

[0023] In one embodiment, the number of the lens units in the lens unit group with the outer edge of the central lens as the inner edge is four, and the number of the lens units in the other light-transmitting unit group is eight.

[0024] In one embodiment, the central lens in which one of the lens units is arranged has a square outer edge, the lens unit group with the outer edge of the central lens as the inner edge has an outer edge of a regular octagon, and the four lens units are divided by the extension line of the diagonal line of the inner edge of the square, and the other lens unit group has the outer edge of the former lens unit group as the inner edge and has a circular outer edge, and is divided into eight lens units by the extension line of the diagonal line of the inner edge of the regular octagon.

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

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

[0027] Any of the above-mentioned Fresnel lenses suitable for long-distance detection, 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 the side of the Fresnel lens opposite to the light incident surface.

[0029] In one embodiment, the pyroelectric infrared sensor is arranged in a quaternary form and has four sensing surfaces.

[0030] Further objects and advantages of the present invention will be fully apparent from an understanding of the following description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic diagram of the vertical detection application scenario of the existing infrared detection device.

[0032] Figure 2A FIG. 1 is a schematic diagram of the structural principle of an infrared detection device according to an embodiment of the present invention.

[0033] Figure 2B It is a schematic diagram of the refraction principle of the lens unit of the Fresnel lens of the infrared detection device according to the above embodiment of the present invention.

[0034] Figure 3A FIG. 1 is a schematic diagram of the shape of the Fresnel lens on the light incident surface of the infrared detection device according to the above embodiment of the present invention.

[0035] Figure 3B FIG. 1 is a schematic diagram of the morphology of the Fresnel lens of the infrared detection device according to the above embodiment of the present invention on the side opposite to the light incident side.

[0036] Figure 4 The figure is a comparison diagram between the Fresnel lens of the infrared detection device according to the above embodiment of the present invention and the Fresnel lens traditionally used for long-distance detection.

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

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

[0039] Figure 6B This is a diagram showing the effect of installing the infrared detection device of the above embodiment of the present invention on a lamp. DETAILED DESCRIPTION

[0040] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are only examples, and those skilled in the art can think of other obvious variations. The basic principles of the present invention defined in the following description can be applied to other embodiments, variations, improvements, equivalents, and other technical solutions that do not deviate from the spirit and scope of the present invention.

[0041] Those skilled in the art should understand that, in the disclosure of the present invention, the orientation or position relationship indicated by the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. are based on the orientation or position relationship shown in the drawings, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the above terms should not be understood as limiting the present invention.

[0042] It is to 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 an element may be one, while in another embodiment, the number of the element may be multiple, and the term "one" should not be understood as a limitation on the quantity.

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

[0044] Specifically, the present invention achieves an increase in detection distance by a technical route of increasing the proportion of effective light energy in the amount of light entering the Fresnel lens when the Fresnel lens is 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 light entry angle of the Fresnel lens is reduced, thereby reducing the range of distance variation between the detected target and the infrared detection device that can be formed by the movement of the detected target in the target detection space, thereby increasing the proportion of effective light energy in the amount of light entering. Therefore, it is completely different from the traditional technical route of increasing the total amount of light entering and can avoid the use of designs with large light entry angles and light entry surface areas.

[0045] For example, referring to the accompanying drawings of the present invention, Figure 1 As shown, 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 change in the distance between the detected target and the infrared detection device, and will be away from the infrared detection device when it is 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 amount of light can be obtained by increasing the light 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 angle is also farther, that is, the proportion of effective light energy in the light amount increased based on the increase in the light angle is relatively low, thereby reducing the proportion of effective light energy in the total light amount. In view of this, the present invention reduces the light angle of the Fresnel lens, so that the range of distance changes between the detected target and the infrared detection device that can be formed by the movement of the detected target in the target detection space is reduced, thereby increasing the proportion of effective light energy in the light amount, and completely breaks away from the traditional technical route of increasing the total light amount.

[0046] Further reference is made to the accompanying drawings of the present invention. FIG. 2A to FIG. 3BAs shown, the structural principle of the infrared detection device according to an embodiment of the present invention and the structure of the corresponding Fresnel lens are respectively illustrated, wherein the infrared detection device includes a Fresnel lens 10 and a pyroelectric infrared sensor 20, wherein the Fresnel lens 10 has a central lens 11 which is provided with at least one lens unit 100 and has a central axis, and at least one group of lens units 12 which is composed of a plurality of lens units 100 and is provided around the central lens 11, and the Fresnel lens 10 forms a light-incoming surface 101 with a smooth surface of each lens unit 100 , and each lens unit 100 of the Fresnel lens 10 is designed with a plurality of concentric circle patterns on a side opposite to the light incident surface 101 and has a light-gathering property like a convex lens, wherein the focal length of the lens unit 100 of the central 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 with the sensing surface 21 facing the side of the Fresnel lens 10 opposite to the light incident surface 101.

[0047] Corresponds to Figure 2B The refraction principle of the lens unit 100 shown in the figure, the lens unit 100 has the same optical characteristics as a convex lens and has an optical center 1001 and a main optical axis 1002 passing through the optical center 1001, and the light parallel to the main optical axis 1002 of the lens unit 100 is refracted by the lens unit 100 and converged to the focus 1003 of the lens unit 100, wherein the focal plane 1004 of the lens unit 100 is a plane perpendicular to the main optical axis 1002 of the lens unit 100 in the plane where the focus 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 main optical axis 1002 is the secondary optical axis 1005 of the lens unit 100, wherein the light parallel to the secondary optical axis 1005 of the lens unit 100 is refracted by the lens unit 100 and converged to the secondary focus 1006 on the focal plane 1004 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 central lens 11. Corresponding to the state that the number of the lens unit 100 in the central lens 11 is one, the central axis of the central 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 central lens 11 is close to the focal length f of the lens unit 100; and when the number of the lens units 100 in the central lens 11 is multiple, the distance between the optical center 1001 of any lens unit 100 of the central lens 11 and the sensing surface 21 of the pyroelectric infrared sensor 20 along the central axis of the central lens 11 is also close to the focal length f of the lens unit 100. Therefore, in the understanding of the present invention, the light angle θ of the Fresnel lens 10 when applied to the infrared detection device corresponds to Figure 2A It is twice the angle of the angle opposite to the right-angled side with a length of L in a right-angled triangle formed by two right-angled sides with lengths of (fH) and L respectively, wherein H is the height difference along the central axis between the optical center 1001 of the lens unit 100 of the central lens 11 and the optical center 1001 of the lens unit 100 of the lens unit group 12 which is farthest from the central axis. Then the light entry angle θ of the Fresnel lens 10 satisfies tan(θ / 2)=L / (fH).

[0049] It is worth mentioning that, affected by the area and number of the sensing surfaces 21 of the pyroelectric infrared sensor 20 and the errors in the actual installation position and angle of the pyroelectric infrared sensor 20, in the understanding of the present invention, the incident light angle θ defined based on L / (fH) is only used to define the structural characteristics of the Fresnel lens 10, and it neither constitutes a restriction on the specific installation position and angle of the pyroelectric infrared sensor 20, nor constitutes a restriction on the actual effective detection angle of the infrared detection device.

[0050] In particular, the present invention achieves an increase in detection distance by a technical route of increasing the effective light energy ratio in the amount of light entering the Fresnel lens 10 when it is applied to the infrared detection device. In this technical route, on the one hand, the light-entering surface area of ​​the Fresnel lens 10 is not a decisive factor affecting the effective light energy ratio in the amount of light entering. On the other hand, when the structural design of the Fresnel lens 10 is designed with a smaller light-entering angle based on the aforementioned technical route of the present invention, it still corresponds to the traditional technical route based on increasing the total amount of light entering with a larger light-entering surface area. In order to reduce the overall thickness of the Fresnel lens 10 to reduce the loss of infrared light passing through the Fresnel lens 10, and to ensure the detection distance of the infrared detection device, each of the lens units 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 direction of the central axis of the central lens 11 is also very large.

[0051] That is to say, when the structural design of the Fresnel lens 10 is designed with a smaller light input angle based on the aforementioned technical route of the present invention, it still corresponds to the traditional technical route based on increasing the total amount of light input with a larger light input surface area. In order to ensure the detection distance of the infrared detection device, the size of the infrared detection device in the direction of the central axis 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 invention, the structural design of the Fresnel lens 10 has a smaller light entrance angle design based on the aforementioned technical route of the present invention, and the Fresnel lens 10 also has a smaller light entrance surface area design, so that the structural design of the Fresnel lens 10 can take into account the miniaturization design and long-distance detection of the infrared detection device at the same time.

[0053] Specifically, in the structural design of the Fresnel lens 10 of the present invention, the Fresnel lens 10 is designed to satisfy L / (fH)≤0.7 in the state of L≤18mm, f≥15mm, and H≤10mm, so that the light incident angle θ of the Fresnel lens 10 when applied to the infrared detection device is less than or equal to 70° and the light incident surface area is also smaller in the state of having a smaller light incident angle, thereby enabling the structural design of the Fresnel lens 10 to take into account both the miniaturization design and long-distance detection of the infrared detection device.

[0054] In other words, in a state where the structural design of the Fresnel lens 10 has a smaller light entrance angle design based on the aforementioned technical route of the present invention, the Fresnel lens 10 of the present invention can simultaneously take into account the small area design of the light entrance surface 101 and the thin design of the overall thickness in terms of structural design, which correspondingly enables the structural design of the Fresnel lens 10 to simultaneously take into account the miniaturization design and long-distance detection of the infrared detection device.

[0055] It is worth mentioning that, although the structural design of the Fresnel lens 10 has a smaller light-incoming angle design based on the aforementioned technical route of the present invention, the Fresnel lens 10 of the present invention can simultaneously take into account the small-area design of the light-incoming surface 101 and the thinning design of the overall thickness in terms of structural design. However, the small-area design of the light-incoming surface 101 of the Fresnel lens 10 does lead to a reduction in the total amount of light entering and a reduction in the intensity of the total effective light energy. Therefore, in order to ensure the detection distance of the infrared detection device, in the structural design of the Fresnel lens 10 of the present invention, the number of the lens unit groups 12 of the Fresnel lens 10 is at most three groups, and the total number of the lens units 100 of the lens unit group 12 is preferably designed to be less than or equal to 24, so that the light-incoming surface 101 of the Fresnel lens 10 has a smaller area based on the conditions of L≤18mm and H≤10mm, thereby ensuring the light-incoming area of ​​the lens units 100 of each group of the lens unit groups 12, and correspondingly, the intensity of the effective light energy of the lens units 100 passing through each group of the lens unit groups 12 is not reduced due to the small area design of the light-incoming surface 101 of the Fresnel lens 10, thereby ensuring 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 the structural example of the Fresnel lens 10 of this embodiment of the present invention, which is two groups, so as to ensure the light incident area of ​​the lens unit 100 of each group of the lens unit group 12 and the intensity of the effective light energy passing through the lens unit 100 of each group of the lens unit group 12, and at the same time take into account the number of the lens units 100 of the lens unit group 12, corresponding to the state where the Fresnel lens 10 has a smaller light incident angle, based on the characteristic 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, which corresponds to ensuring the effective detection area of ​​the infrared detection device.

[0057] In short, the infrared detection device is based on the partitioning of the corresponding detection area by the lens unit 100 of the Fresnel lens 10 in principle, and uses the pyroelectric infrared sensor 20 to detect the cross-area movement of the human body in the detection area. Therefore, when the Fresnel lens 10 is designed to have a smaller light entrance angle, and the light entrance surface 101 has a smaller area based on the conditions of L≤18mm and H≤10mm, the number of the lens unit groups 12 of the Fresnel lens 10 is designed to be at most three groups. On the one hand, the light entrance area of ​​the lens unit 100 of each group of the lens unit groups 12 can be guaranteed, so that the intensity of the effective light energy of the lens unit 100 passing through each group of the lens unit groups 12 is not reduced due to the small area design of the light entrance surface 101 of the Fresnel lens 10, thereby ensuring the detection distance of the infrared detection device; on the other hand, the characteristic that the target detection surface is far away from the infrared detection device in the long-distance detection application scenario can be utilized, so that the Fresnel lens 10 still has a larger partition coverage area and a reasonable partition arrangement density, thereby ensuring the effective detection area of ​​the infrared detection device.

[0058] In summary, the structural design of the Fresnel lens 10 of the present invention needs to satisfy L≤18mm, f≥15mm, H≤10mm and L / (fH)≤0.7, and at the same time, the number of the lens unit group 12 is designed to be at most three groups, wherein the total number of the lens units 100 of the lens unit group 12 is preferably designed to be less than or equal to 24, so that the light 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-entering surface area at a smaller light-entering angle, and is suitable for long-distance detection of 15 meters and above. Correspondingly, the structural design of the Fresnel lens 10 can take into account both 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 invention, the description of the detection distance range applicable to the Fresnel lens 10 is only to emphasize the maximum detection distance range in which the Fresnel lens 10 can be normally used in terms of performance. That is to say, the maximum detection distance in which the Fresnel lens 10 can be normally used in terms of performance can reach 15 meters and above, 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 invention is recommended for long-distance detection of 15 meters and above, and is not recommended for short-distance detection of less than 8 meters. However, according to actual use requirements, users can still use it for detection in the range of 8 to 15 meters, and the present invention does not limit this.

[0060] The Fresnel lens 10 is structurally designed to meet the requirement that the number of the lens unit groups 12 is designed to be at most three groups, corresponding to the state in which the number of the lens unit groups 12 is one group, the lens unit group 12 is arranged around the center lens 11 with the outer edge of the center lens 11 as the inner edge; and the state in which the number of the lens unit groups 12 is two groups, one group 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 group of the lens unit groups 12 is arranged around the center lens 11 with the outer edge of the first group of the lens unit groups 12 as the inner edge; and so on and so forth, in the state in which the number of the lens unit groups 12 is three groups, one group 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 latter two groups of the lens unit groups 12 are sequentially arranged around the center lens 11 with the outer edge of the first group of the lens unit groups 12 as the inner edge.

[0061] Furthermore, the Fresnel lens 10 is designed to satisfy L≤18mm, f≥15mm, H≤10mm and L / (fH)≤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 be centered on the central lens 11, and the lens units 100 of the lens unit groups 12 that are more peripheral have larger light intake areas (i.e., the area of ​​the aforementioned smooth surface), so as to ensure the intensity and balance of the effective light energy of the lens units 100 passing through each group of the lens unit groups 12, thereby ensuring the stability of the detection sensitivity of the infrared detection device within the effective detection area.

[0062] Specifically, in the structural example of the Fresnel lens 10 of this embodiment of the present invention, the number of the lens units 100 of the central lens 11 is as follows: Figure 3A and Figure 3B The illustrated structural form is one, corresponding to the central lens 11 with the main optical axis 1002 of its lens unit 100 as the central axis, wherein the Fresnel lens 10 is designed to satisfy L / (fH)≤0.7 in the state of 11mm≤L≤13mm, 21mm≤f≤25mm, and H≤5mm. Based on this, the overall thickness of the Fresnel lens 11 is allowed to be designed in a thickness range of less than or equal to 0.6mm, so as to take into account the miniaturized 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 invention, the number of the lens unit groups 12 of the Fresnel lens 10 is two groups, corresponding to a state in which the two groups of lens unit groups 12 are arranged around the central lens 11, wherein one group of the lens unit groups 12 is arranged around the central lens 11 with the outer edge of the central lens 11 as the inner edge, and the other group of the lens unit groups 12 is arranged around the central lens 11 with the outer edge of the first group of the lens unit groups 12 as the inner edge.

[0064] In particular, in the structural example of the Fresnel lens 10 of this embodiment of the present invention, with the central lens 11 as the center, the lens units 100 of the lens unit groups 12 that are closer to the periphery have a larger light-entry area design. In other words, the light-entry area of ​​each lens unit 100 of the lens unit group 12 with the outer edge of the central lens 11 as the inner edge is smaller than the light-entry area of ​​each lens unit 100 of another light-transmitting unit group 12, so as to ensure the balance of the intensity of the effective light energy of the lens units 100 passing through each group 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] Furthermore, in the structural example of the Fresnel lens 10 of this embodiment of the present invention, the number of the lens units 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 units 100 of the other light-transmitting unit group 12 is eight.

[0066] Specifically, in the structural example of the Fresnel lens 10 of this embodiment of the present invention, the central lens 11 in which one lens unit 100 is arranged 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 outer edge of a regular octagon, and the four lens units 100 are divided by the extension line of the diagonal line of the inner edge of the square, and the other lens unit group 12 has the outer edge of the former group of lens unit groups 12 as the inner edge and has a circular outer edge, and is divided into eight lens units 100 by the extension line of the diagonal line of the inner edge of the regular octagon.

[0067] Furthermore, in the structural example of the Fresnel lens 10 of this embodiment of the present invention, the square outer edge of the central 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 central 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 balance of the intensity of the effective light energy of the lens unit 100 passing through each group of the lens unit group 12, thereby ensuring the stability of the detection sensitivity of the infrared detection device within the effective detection area, and when the Fresnel lens 10 has the outer edge of the light incident surface 101 as the peripheral edge, it has a peripheral diameter of only about 35 mm. Figure 4 The diameter shown is much smaller than the peripheral diameter of the Fresnel lens traditionally used for long-distance detection.

[0068] In particular, in the structural example of the Fresnel lens 10 of this embodiment of the present invention, each lens unit 100 of the Fresnel lens 10 is designed with a plurality of concentric circular patterns on a surface opposite to the light-entering surface 101, and the convex lens has a light-gathering property, and the optical center 1001 of the corresponding lens unit 100 can be considered as the center of the concentric circular patterns within a certain error range. Since 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 central lens 11, in order to allow the light passing through the lens unit 100 of the lens unit group 12 to deviate toward the sensing surface 21 of the pyroelectric infrared sensor 20, 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 of deviating toward the central lens 11.

[0069] That is to say, the convex lens that the lens unit 100 of the lens unit group 12 is equivalent to in terms of optical characteristics based on the design of the concentric circle pattern is not limited to a convex lens with the geometric center as the optical center 1001, and it 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 invention, the concentric circle pattern designed in the lens unit 100 corresponds to Figure 5 There is no restriction on having at least one complete circular pattern. The optical center 1001 of the lens unit 100 may not be located on the lens unit 100 body, but the position of the optical center 1001 can still be determined based on the arc pattern formed by the incomplete concentric circle patterns. The present invention does not limit this.

[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 and has four sensing surfaces 21. Based on the arrangement of the multiple sensing surfaces 21, the partitions corresponding to the lens units 100 of the Fresnel lens 10 are further partitioned to improve the resolution of the infrared detection device related to the movement amplitude of the detected target.

[0071] It is worth mentioning that the infrared detection device is usually installed in a lamp to control the lighting state of the lamp based on the detection of the corresponding target to realize intelligent lighting, for example, Fig. 6A The warehouse environment shown in the figure can ensure the advantage of the effective detection area of ​​the infrared detection device in the long-distance detection application scenario by utilizing the structural design of the Fresnel lens 10, and the lamp is installed in a high-mounted manner to realize the intelligent lighting of the warehouse environment. The Fresnel lens 10 is designed to meet the condition of L≤18mm, and the corresponding Fresnel lens 10 has a significantly smaller peripheral diameter than the Fresnel lens traditionally used for long-distance detection, and the Fresnel lens 10 is also designed to meet the condition of H≤10mm, and the light-incoming surface 101 of the Fresnel lens 10 can be designed as a flat surface or a slightly raised curved surface, so that the infrared detection device can correspond to the infrared detection area when it is installed in the lamp. Figure 6B Achieve a more natural and concealed installation effect.

[0072] Those skilled in the art will appreciate that the above embodiments are merely examples, wherein features of different embodiments may be combined with each other to obtain implementation methods that are easily conceivable based on the contents disclosed in the present invention but are not explicitly indicated in the drawings.

[0073] It should be understood by those skilled in the art that the embodiments of the present invention described above and shown in the accompanying drawings are only examples and do not limit the present invention. The purpose of the present invention has been fully and effectively achieved. The functional and structural principles of the present invention have been demonstrated and explained in the embodiments, and the embodiments of the present invention may be deformed or modified in any way without departing from the principles.

Claims

1. A Fresnel lens suitable for long-distance detection, characterized in that: include: a central lens, wherein the central lens is arranged with at least one lens unit and has a central axis; and At most three groups of lens units, wherein each of the lens units is composed of a plurality of lens units and is arranged around the central lens, the corresponding Fresnel lens forms a light-entering surface with a smooth surface of each lens unit, and each lens unit of the Fresnel lens is designed with a plurality of concentric circle patterns on a side opposite to the light-entering surface and has a focusing characteristic like a convex lens, wherein the focal length of the lens unit of the central lens is f, and the distance between the optical center of the lens unit farthest from the central axis among the lens units of the at most three groups of lens units and the central axis is L, and the Fresnel lens is designed to satisfy L / (fH)≤0.7 in the state of L≤18mm, f≥15mm, and H≤10mm, wherein H is the height difference along the central axis 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 among the lens units of the lens unit group. 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 lens unit groups is less than or equal to 24. 3 . The Fresnel lens suitable for long-distance detection according to claim 2 , wherein with the central lens as the center, the lens units in the lens unit group that are closer to the periphery have larger smooth surface areas.

4. A Fresnel lens suitable for long-distance detection according to claim 2 or 3, wherein the number of the lens unit groups is two, one of the lens unit groups is arranged around the central lens with the outer edge of the central lens as the inner edge, and the other lens unit group is arranged around the central lens with the outer edge of the former 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 to satisfy L / (fH)≤0.7 in the state of 11 mm≤L≤13 mm, 21 mm≤f≤25 mm, and H≤5 mm. 6 . The Fresnel lens suitable for long-distance detection according to claim 5 , wherein the number of the lens unit of the central lens is one, and the central lens has a principal optical axis of its lens unit as the central axis.

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

8. A Fresnel lens suitable for long-distance detection according to claim 7, wherein the central lens arranged with one of the lens units has a square outer edge, the lens unit group with the outer edge of the central lens as the inner edge has an outer edge of a regular octagon, and the four lens units are divided by the extension line of the diagonal line of the inner edge of the square, and the other lens unit group has the outer edge of the former lens unit group as the inner edge and has a circular outer edge, and is divided into eight lens units by the diagonal extension line of the inner edge of the regular octagon.

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

10. Infrared detection device, characterized in that, include: A Fresnel lens suitable for long-distance detection as claimed in any one of claims 1 to 9, and A pyroelectric infrared sensor, wherein the pyroelectric infrared sensor has at least one sensing surface and is arranged with the sensing surface facing the side of the Fresnel lens opposite to the light incident surface. 11 . The infrared detection device according to claim 10 , wherein the pyroelectric infrared sensor is arranged in a quaternary form and has four sensing surfaces.

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