RU2216446C2 - Method of master model manufacture for manufacture of multielement spherical fresnel lens - Google Patents

Abstract

FIELD: manufacture of optical elements; applicable in full-scale manufacture of multielement spherical Fresnel lenses in form of built-up construction. SUBSTANCE: master models of single-element spherical Fresnel lenses with contour of shape-forming surface in form of reverse shape of corresponding single-element Fresnel lens serve as assembly units of multi- element lens. Method consists in cutting-out of each assembly unit of master model from separate similar hemispherical semifinished product with contour of shape-forming surface preliminarily applied to it and with radius equaling radius of full shape-forming surface of master model. Method is distinguished by the fact that operation of cutting-out of each assembly unit of master model is executed by using the coordinate of top of hemispherical semifinished product as reference point of coordinate origin with obtaining of volume part of preset geometry whose configuration is restricted by spherical shape-forming surface with preset contour and flat mutually perpendicular surfaces which are combined to assemble single-element master models into single solid hemisphere with high accuracy of assembly. EFFECT: higher efficiency of method due to provision of manufacture of built-up master models suitable for manufacture of all existing types of multielement spherical Fresnel lenses. 2 cl, 18 dwg

Description

 This invention relates to the field of manufacture of optical elements and relates to methods and devices for the manufacture of Fresnel lenses for various purposes in serial production.

 A Fresnel lens is a flat structure with concentric grooves made of optically transparent material (low-pressure polyethylene, polycarbonates, acrylates, etc.), which has the required optical properties and gives the same effect as an optical lens with a spherical surface.

One of the most widely used applications at present is the use of multi-element Fresnel lenses in passive infrared motion detectors designed for burglar alarm systems. In such detectors, the optical unit contains a multi-element Fresnel lens and a pyroelectric detector located in the focal plane of the Fresnel lens, and provides the formation of detection zones of various configurations. In accordance with the configuration features, the detection zones are divided into:
- volumetric detection zones;
- linear detection zones;
- surface detection zones;
- panoramic (circular) detection zones.

 The most common is the volumetric detection zone, covering up to 120-350 sq.m of the protected area indoors.

 Detection zones formed by passive infrared detectors are multi-beam and multi-tiered; in accordance with the detection range, they are formed in several tiers (see "Catalog of security equipment" (Russia, 2001), catalogs of Fresnel Optics (USA) , Combined Optical Industries Ltd. (Great Britain), etc. Accordingly, the Fresnel lens in the optical system of a passive infrared detector with a multipath detection zone is multi-element, in this Fresnel lens each ray of the detection zone corresponds to its own single Fresnel lens, you complete as a single unit together with other single Fresnel lenses of the same Fresnel multi-element lens.Depending on the configuration of the detection zone and the number of rays in it, the number of single lenses and their location as part of a multi-element Fresnel lens are a variable.

 For the manufacture of both single and multi-element Fresnel lenses by injection molding or extrusion in an industrial environment, special technological equipment called the “master model” is used.

 In the strict sense of this concept with respect to the Fresnel lens, the master model is the shape-forming surface, made in the form of the inverse (negative) profile of the working surface of the corresponding, multi-element or single, Fresnel lens. Thus, the master model performs the function of a standard of the forming surface, the receipt of which is provided by technological equipment of this type. Using the master model in some implementations of such technological equipment, for example, working copies of the master model directly used in the manufacturing process of Fresnel lenses are made using the galvanic method.

 In everyday practice, the master model is usually understood as a structure equipped with the shaping surface of the Fresnel lens and having a supporting part for attaching this structure together with the specified surface to the mold for molding or pressing.

 Structurally, the master model of a multi-element Fresnel lens is collapsible. The assembly unit of the collapsible master model is the master model of the corresponding single Fresnel lens as part of a multi-element Fresnel lens. The number of assembly units is equal to the number of single lenses in a multi-element Fresnel lens. The implementation of this collapsible master model provides the ability to replace any one assembly unit with another, if necessary. The connection of the assembly units is carried out in any known manner, for example using screws or pins.

 Recently, spherical multi-element Fresnel lenses have been used more and more widely in the optical system of passive infrared detectors instead of flat multi-element lenses. Spherical Fresnel lenses have improved optical properties, provide a distortion-free detection zone and high collective ability due to the fact that multi-element spherical Fresnel lenses have a larger effective surface area than similar flat lenses.

 Technical solutions regarding methods for manufacturing spherical Fresnel lenses are known. The current level of technology can be estimated by the following analogues of the present invention.

 A known method of manufacturing a master model according to the application EP 0011331, class. B 29 D 11/00, G 02 B, 11/02/1999

 This invention relates to a method for manufacturing a master model having a predetermined inverse profile. According to the method, a plurality of identical Fresnel lenses with a working surface corresponding to the direct profile of said inverse profile can be manufactured.

 This method involves the initial machining of the surface of the workpiece from a solid, non-deformable material in order to obtain an inverse profile. A solid, non-deformable material is a silicon-containing material (ceramic or glass). The material can be processed using diamond turning (ceramic) or by grinding (silicon-containing glass) to obtain a given inverse profile in one pass. Then, a nickel or nickel alloy coating is applied to the surface of the silicon-containing material, followed by mechanical treatment of the nickel surface with a cutting tool, optical polishing to obtain a given profile, and vacuum coating of the surface of the specified profile with a layer of inert non-cracking protective coating (to protect it from scratches). The limitation of this method is that it provides the manufacture of a master model of only a single Fresnel lens.

 The closest analogue of the proposed method is a method of manufacturing a master model for producing a multi-element panoramic Fresnel lens of a spherical shape, where the master model is made in the form of a collapsible multi-sectional design, the assembly units of which are master models of single Fresnel lenses with a profile of the forming surface, obtained in the form the reverse profile of the working surface of the corresponding single Fresnel lens, with each assembly unit of the master model of a multi-element Fresnel lens cutout they are removed from a separate identical hemispherical preform with a profile of the forming surface pre-applied to it and a radius equal to the radius of the full forming surface of the multisection master model, to obtain a volume part of a given geometry, the configuration of which is limited to a spherical forming surface with a given profile and flat mutually perpendicular supporting surfaces providing high precision assembly of a multi-section master model (GB 2332638, 06/30/1999).

 The disadvantage of this method is to obtain one and only one type of lens, namely a panoramic Fresnel lens, intended for use in passive infrared motion detectors installed on the ceiling of a controlled room. From this it follows that the possibility of practical application of the known method-analogue has significant limitations.

 The present invention is free from the limitations inherent in the known method-analogue.

 The technical result achieved by the implementation of this method is the manufacture of a collapsible master model that can be used for the industrial production of all existing types of multi-element spherical Fresnel lenses designed for passive infrared motion detectors with detection zones, namely Fresnel lenses for the formation of volumetric, linear, surface and circular (panoramic) detection zones.

 The specified technical result is achieved by the fact that in the method of manufacturing a master model for producing a multi-element spherical Fresnel lens made in the form of a collapsible design, the assembly units of which are master models of single spherical Fresnel lenses with a profile of the forming surface in the form of an inverse profile corresponding a single Fresnel lens, providing for the cutting of each assembly unit of the master model from a separate identical hemispherical blank with a preliminary According to the invention, the cutting operation of each assembly unit of the master model is carried out using the coordinate of the top of the hemispherical workpiece as the reference point of coordinates, to obtain a volumetric part of a given geometry, the configuration of which is limited by a spherical forming surface with a given profile of mutually perpendicular surfaces, due to the combination of which are assembling single master models into a single dense hemisphere with high precision assembly.

 The operation of cutting each assembly unit of the master model is carried out by electroerosion.

The invention is illustrated by drawings, where figure 1 shows the radiation pattern of a known panoramic Fresnel lens spherical shape of a ceiling type in a vertical plane;
in FIG. 2 is a radiation pattern of a known panoramic Fresnel lens of a spherical shape of a ceiling type in the horizontal plane; figure 3 is a top view of a multi-element Fresnel lens spherical shape with a volumetric detection zone obtained by the method according to this invention; figure 4 is a master model of a multi-element Fresnel lens spherical shape with a three-dimensional detection zone, corresponding to this invention; in FIG. 5 - the same, with the spatial separation of assembly units; Fig.6 is a top view of a multi-element Fresnel lens of a spherical shape with a linear detection zone, obtained by the method according to this invention; Fig.7 is the same with a linear detection zone; in FIG. 8 is a master model of the Fresnel lens of FIG. 7 with a spatial separation of assembly units; figure 9 is a top view of a multi-element Fresnel lens spherical shape with a surface detection zone obtained by the method according to this invention; figure 10 is the same with the surface detection zone; 11 is a master model of the Fresnel lens of FIG. 10 with a spatial separation of assembly units; in Fig.12 is an example of the spatial position of one of the assembly units of a multi-section master model on a hemispherical blank at the time of the cutting operation; 13 and 13a show a detail cut from a workpiece, which is one of the assembly units of a multi-section master model of a spherical Fresnel multi-element lens; on Fig - Assembly unit Mester model of Fig. 4 multi-element Fresnel lenses with a three-dimensional detection zone and its location in the structure of the master model; on Fig - the same, General view; in FIG. 16 is a general view of a master model of a multi-element panoramic Fresnel lens made by the method of this invention; on Fig - the master model of Fig. 15, shown with a spatial separation of the assembly units.

Consider examples of manufacturing collapsible master models for producing multi-element spherical Fresnel lenses with the following widely used detection zones:
a) volumetric detection zone.

 In FIG. 3 shows a top view of a multi-element spherical Fresnel lens with a three-dimensional detection zone. The composition of this Fresnel lens includes 21 single spherical Fresnel lenses, of which 8 lenses (pos. 1, Fig. 3) provide the formation of a far detection zone, 7 lenses (pos. 2, Fig. 3) - the formation of a middle detection zone, 4 lenses (pos. 3, Fig. 3) - formation of the near detection zone and 2 lenses (pos. 4, Fig. 3) - the formation of an anti-tamper zone to protect the space immediately below the passive IR detector.

 FIG. 4 shows a general view of a collapsible master model for producing the Fresnel lens of FIG. 3. The master model of figure 4 is made by the method according to this invention. The number of assembly units 5 in it and their location corresponds to the number and location of single Fresnel lenses in the multi-element Fresnel lens of FIG. 3. Assembly units 5 of the master model of FIG. 4 are assembled by combining all mutually perpendicular supporting surfaces into a single dense hemisphere 6 on the basis of.

 Fig. 5 shows the master model of Fig. 4 with a spatial separation of the assembly units 5 forming it. Figs. 4 and 5 show a smooth spherical surface of both the master model of Fig. 4 and the assembly units of Fig. 4 for simplicity. 5.

b) linear detection zone
In FIG. 6 shows a top view of a multi-element spherical Fresnel lens with a linear detection zone. The structure of this Fresnel lens includes 15 single Fresnel lenses, of which 4 lenses provide the formation of a far detection zone, 5 lenses - the formation of a middle detection zone, 3 lenses - the formation of a near detection zone and 3 lenses - the formation of an anti-tamper zone to protect the space directly below the passive infrared -detector.

 FIG. 7 shows a general view of a collapsible master model for producing the Fresnel lens of FIG. 6 by the method of this invention. The master model of FIG. 7 is made by the method of this invention. The number of assembly units 7 in it and their location correspond to the number and location of single Fresnel lenses in the multi-element Fresnel lens of Fig.7. The assembly units 7 of the master model of FIG. 7 are assembled by combining all mutually perpendicular bearing surfaces into a single dense hemisphere 8. FIG. 8 shows the master model of FIG. 7 with the spatial separation of the assembly units 7 forming it. FIG. 7 and 8 for simplicity, a smooth spherical surface of both the master model of FIG. 7 and the assembly units of FIG. 8 is shown.

c) surface detection zone
In FIG. 9 shows a top view of a multi-element spherical Fresnel lens with a surface detection zone. Lenses of this type provide the formation of a continuous detection zone. The composition of this Fresnel lens includes nine single spherical Fresnel lenses.

 FIG. 10 shows a general view of a collapsible master model for producing a Fresnel lens of FIG. 9: The master model of FIG. 10 is manufactured by the method of this invention. The number of assembly units 9 in it and their location correspond to the number and location of single Fresnel lenses in the multi-element Fresnel line of Fig. 9. Assembly units 9 of the master model of FIG. 10 are assembled by combining all mutually perpendicular supporting surfaces into a single dense hemisphere 10.

 In FIG. 11 shows the master model of FIG. 10 with a spatial separation of the assembly units forming it 9. In FIGS. 10 and 11, for simplicity, the smooth spherical surface of both the master model of FIG. 10 and the assembly units of FIG. 11 is shown.

 As evidence of industrial applicability, we present a specific example of the manufacture of a collapsible master model of FIG. 4 to obtain a multi-element spherical Fresnel lens of FIG. 3 with a volume detection zone.

 The first step of the method is the manufacture of identical blanks with a hemispherical surface, the radius of which is equal to the radius of the full forming surface of the master model. Billets are made, for example, of brass grade LS-59-1. The number of blanks is equal to the number of assembly units in the master model; in this embodiment, 21 billets are made.

 The second operation of the method is the execution on the previously obtained smooth hemispherical surface of the workpiece of the inverse profile of the corresponding single Fresnel lens of a spherical shape. The inverse profile of a single Fresnel lens is performed by a diamond turning method controlled by a computer in one pass, starting from the top of the smooth hemispherical surface of the workpiece, to obtain the specified cutting step, depth and angle of inclination of the grooves.

 The third operation of the method is cutting the assembly unit of the master model from a hemispherical billet by electroerosion.

 The method of electroerosion is as follows: in a bath with a conductive liquid, a brass billet with a profile of the forming surface applied to it is placed and fixed in it, while the billet is oriented in a certain way. A wire of L63 brass with a diameter of 0.2 mm is then fed to the workpiece, to which current is supplied. According to the program, the wire cuts out parts of complex volumetric shape, the configuration of which, taking into account the cut width, corresponds to the spatial position of the assembly unit in the construction of a multi-section master model (Fig. 12). Moreover, when performing the operation of cutting each assembly unit, the coordinate origin coincides with the coordinate of the top of the hemispherical workpiece, which ensures obtaining the profile of the forming surface on each assembly unit with high accuracy (Fig. 13, 13a). The last operation after performing the necessary technical control operations is the assembly using pins or screws of individual assembly units, namely 21 sections of single master models into a single dense multisectional collapsible half-spherical design with high assembly accuracy due to the presence of flat mutually perpendicular surfaces in each assembly unit. This design is a master model of the forming surface for the manufacture of multi-element spherical Fresnel lenses in industrial serial production.

 In FIG. 14, the assembly unit 11 is shown as an integral part of the collapsible master model 12, the assembly units 13 of which are assembled in a single tight hemisphere 14 by combining flat mutually perpendicular supporting surfaces. 14 shows, for simplicity, the smooth spherical surfaces of the master model 12 and assembly unit 11.

 On Fig shows the assembly unit of the master model made by this method.

 The assembly unit 11 has a forming surface 15 on which the inverse profile 16 of a single Fresnel lens is made and the supporting surfaces 17, 18, 19, 20 and 21, which are mutually perpendicular.

 In a similar way, master models with a linear detection zone (Figs. 7 and 8) and a surface detection zone (Figs. 10 and 11) are also made.

 As shown earlier, the method of manufacturing a master model for producing a multi-element spherical Fresnel lens according to this invention provides various types of Fresnel lenses, namely Fresnel lenses with volumetric, linear and surface detection zones.

 Along with this, the method according to this invention without any restrictions ensures the production of a multi-element panoramic Fresnel lens similar to a panoramic Fresnel lens by a known method.

 A master model for producing a multi-element panoramic Fresnel lens manufactured by the method of this invention is shown in Fig. 16.

 In FIG. 17, the master model 22 of FIG. 16 is an exploded view of the assembly units 23 made by the method of the present invention. When assembling the master model 22, all assembly units 23 are assembled into a single dense hemisphere by combining flat mutually perpendicular surfaces with screws or pins.

 The master model according to this invention is universal and provides the ability to produce using its multi-element spherical Fresnel lenses with volumetric, linear and surface detection zones, as well as multi-element panoramic Fresnel lenses of a spherical shape.

 The implementation of the method according to this invention gives almost unlimited possibilities for changing the quantitative composition and spatial structure of the master models of single spherical Fresnel lenses forming the final master model. On this basis, high flexibility of both experimental and mass production of the corresponding high-tech products is ensured.

Claims (2)

 1. A method of manufacturing a master model to obtain a multi-element spherical Fresnel lens made in the form of a collapsible design, the assembly units of which are master models of single spherical Fresnel lenses with a profile of the forming surface in the form of the inverse profile of the corresponding single Fresnel lens, which includes cutting of each assembly unit of the master model from a separate identical billet of a hemispherical shape with a profile of a shaping surface previously applied to it surface and a radius equal to the radius of the full forming surface of the master model, characterized in that the cutting operation of each assembly unit of the master model is carried out using the coordinate of the top of the hemispherical workpiece as a reference point, to obtain a volume part of a given geometry, the configuration of which is limited to spherical a forming surface with a given profile and flat mutually perpendicular surfaces, due to the combination of which the assembly of single ma Ster models into a single dense hemisphere with high precision assembly.  2. The method according to p. 1, characterized in that the cutting operation of each assembly unit of the master model is carried out by electroerosion.

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