CN108506743A - A kind of free form surface Fresnel lighting system of high degree of focus - Google Patents

Abstract

The present invention provides a kind of free form surface Fresnel lighting system of high degree of focus, it is related to optical devices technologies field, it is disposed with a point light source by the light direction of propagation, one includes the Fresnel Lenses and a receiving plane of free form surface, the Fresnel Lenses is arranged in parallel with the receiving plane, the point light source is arranged on the perpendicular bisector of the Fresnel Lenses and the receiving plane, the Fresnel Lenses include into optical plane and with it is described enter the multistage compound curved surface that is oppositely arranged of optical plane, dry free form surface sawtooth of N is provided on the multistage compound curved surface, the point light source be arranged it is described enter optical plane side, the receiving plane is arranged in the side of the multistage compound curved surface；The point light source has shooting angleThe shooting angleN parts are divided into correspond with the free form surface sawtooth.Usefulness of the present invention is that the uniformity is high, simple in structure and optical energy loss is few, to adapt to actual illumination needs.

Description

A Freeform Fresnel Illumination System with High Focus

technical field

The invention relates to the technical field of optical equipment, in particular to a high-focus free-form surface Fresnel lighting system.

Background technique

Fresnel lens has the advantages of low price, large area, light weight and portability. It is a widely used optical element, and its design and manufacture involve many fields. The main uses of the Fresnel lens are as follows: one is to focus on lighting, this lens is widely used in solar energy, projector lighting, SLR cameras, naked-eye 3D displays and other fields; the other is to combine passive infrared detectors (Passive Infrared Detection, referred to as : PIR detector) to detect pyro-infrared signals.

The Fresnel lens is usually composed of many small sawtooths. By controlling the angle of the working surface of these sawtooths, it can reflect or refract the light energy in the specified spectral range. The sawtooth working surface of a conventional Fresnel lens is usually a plane, or a straight line in the radial direction (annular Fresnel lens). The focusing efficiency of this type of lens depends on the sawtooth density. The greater the sawtooth density, the Fresnel The better the focusing efficiency of the lens, and vice versa. In practice, the smaller the tooth width or tooth depth of the sawtooth, the higher the corresponding mold processing accuracy requirements, resulting in higher cost. In addition, the Fresnel lens with each sawtooth plane cannot properly correct parameters such as spherical aberration, which affects the uniformity of light source illumination.

Contents of the invention

The invention overcomes the shortcomings in the prior art and provides a high-focus free-form Fresnel lighting system with high uniformity, simple structure and less loss of light energy, so as to meet the needs of actual lighting.

In order to solve the above technical problems, the present invention is achieved through the following technical solutions:

A high-focus free-form surface Fresnel lighting system, which is provided with a point light source, a Fresnel lens containing a free-form surface, and a receiving surface in sequence according to the direction of light propagation, and the Fresnel lens is parallel to the receiving surface It is set that the point light source is arranged on the perpendicular line between the Fresnel lens and the receiving surface, and the Fresnel lens includes a light-incident plane and a multi-segment mixed curved surface opposite to the light-incident plane, so N dry free-form surface sawtooths are arranged on the multi-segment mixed curved surface, the point light source is set on one side of the light-incident plane, and the receiving surface is set on one side of the multi-segment mixed curved surface; the point light source has an output angle The exit angle The division into N parts corresponds to the sawtooth of the free-form surface one by one, and the light emitted from the irradiation area passes through the corresponding sawtooth of the free-form surface to form a linear light spot on the receiving surface.

Further, the radius of the Fresnel lens is 30mm.

Further, the distance between the point light source and the light incident plane of the Fresnel lens is 50 mm, and the distance between the receiving surface and the Fresnel multi-segment blended curved surface is 500 mm.

Further, the point light source is an LED point light source.

Compared with prior art, the beneficial effect of the present invention is:

The present invention proposes a ring-shaped Fresnel free-form surface hybrid sawtooth structure and a many-to-one mapping method. By dividing LED point light sources with different light-emitting angle areas, each light-emitting area is identical to each free-form surface sawtooth of Fresnel. One-to-one correspondence, the light rays of different ranges of angles pass through the corresponding sawtooth area to independently form a seamlessly connected linear spot, which can not only achieve uniform illumination on the receiving surface, but also allow all points on the receiving surface to receive corresponding light Light energy, thus improving the uniformity of illumination. In addition, the free-form surface Fresnel lens provided by the present invention can also be made into corresponding variants, which can be applied to solar energy focusing to improve the focusing efficiency of light energy.

Description of drawings

Accompanying drawing is used for providing further understanding to the present invention, is used for explaining the present invention together with the embodiment of the present invention, does not constitute limitation of the present invention, in accompanying drawing:

Fig. 1 is a working principle diagram of the present invention;

Fig. 2 is the surface data diagram of the free-form surface sawtooth obtained by surface fitting;

Fig. 3 is the lens entity figure that adopts curved surface fitting to contain free-form surface;

Figure 4 is a simulation effect diagram of the simulation software tracePro;

Fig. 5 is a simulation diagram without adding a lens and keeping the same optical element parameters.

In the figure: 100-point light source, 110-light incident plane, 120-multi-segment mixed curved surface, 121, 122, 123, 124, 125, 126-free curved surface sawtooth, 130-receiving surface.

Detailed ways

The preferred embodiments of the present invention will be described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described here are only used to illustrate and explain the present invention, and are not intended to limit the present invention.

As shown in Figure 1, a high-focus free-form surface Fresnel lighting system is provided with a point light source 100, a Fresnel lens containing a free-form surface, and a receiving surface 130 in sequence according to the direction of light propagation, and the Fresnel lens Arranged in parallel with the receiving surface 130, the point light source 100 is arranged on the mid-perpendicular line between the Fresnel lens and the receiving surface 130, the Fresnel lens includes a light-incident plane 110 and a multi-segment blended curved surface 120 arranged opposite to the light-incident plane 100, the multi-segment The mixed curved surface 120 is provided with N dry free-form surface serrations. In this embodiment, as shown in FIG. Sawtooth curved surface, the point light source 100 is set on one side of the light incident plane 110, and the receiving surface 130 is set on one side of the multi-segment mixed curved surface 120; the point light source 100 has an exit angle exit angle Divided into N parts corresponding to the free-form surface sawtooth 121, 122, 123, 124, 125, 126, N is 6, the light emitted by the irradiation area passes through its corresponding free-form surface sawtooth 121, 122, 123, 124, 125, After 126, a linear light spot is formed on the receiving surface 130; preferably, the point light source 100 is an LED point light source, which has the characteristics of energy saving and high brightness; preferably, the radius of the Fresnel lens is 30mm, and the point light source 100 is away from the Fresnel The distance between the light incident plane 110 of the lens is 50 mm, and the distance between the receiving surface 130 and the Fresnel multi-segment blended curved surface 120 is 500 mm.

As shown in Figure 1, the point light source 100 is set at the origin (0,0) of the yz coordinates, and the light energy emitted by it passes through the light incident plane 110 of the Fresnel lens and the multi-segment mixed curved surface 120 along the direction of light propagation, and finally reaches the receiving surface 130, the point light source 100 is an LED point light source, and its maximum luminous angle is set to be The number of serrations of the Fresnel lens is set to 2N, and the light emitting angle of the point light source 100 is divided into 2N parts according to the number of saw teeth. Each part of light energy is transmitted to the receiving surface 130 by the corresponding saw teeth through refraction, and is responsible for the corresponding area illumination. The half-width of the receiving surface 130 is y _m , which is divided into N parts according to the number of serrations of the Fresnel lens, and the line shape interval of each part is y _m /N. In order to achieve uniform illumination on the receiving surface 130, the illuminance of each divided area is set to E. The maximum light intensity of the point light source 100 is I _o , and its distribution according to the angle is expressed as:

P is a point on the free-form surface sawtooth 123, and the vector P can be expressed as:

is a point on the receiving surface 130, then the unit vector of the outgoing light is

in, for the surface point on the target surface distance between points.

Let the unit normal vector on point P be N, after derivation, the expression of normal vector N is:

in represents the function p opposite angle Find partial derivatives.

The refraction formula of light passing through a Fresnel lens is:

Where n _I is the refractive index of the medium where the incident light is located, and no is the refractive index of the medium where the outgoing light is located.

From formulas (1)-(5), the position equation of point p on the free surface can be obtained as:

The above formula is a first-order ordinary differential equation, which can be solved numerically.

According to the law of conservation of energy, there are:

Combining formulas (6) and (7), the function p can be obtained by using the quasi-Newton method The numerical solution of the method can calculate the coordinate data of each point of the sawtooth mixed surface of the free-form surface through matlab programming.

According to the surface data, non-uniform rational B-spline (Non uniform rational B-spline, NURBS) is used for surface fitting, so as to obtain a multi-segment mixed surface 120 as shown in FIG. 2 . In this embodiment, Rhinoceros modeling software based on the principle of NURBS is used for surface fitting, so as to obtain a lens entity including the multi-segment mixed curved surface 120 .

The embodiment of the present invention further provides a free-form surface Fresnel lens lighting system obtained based on the above-mentioned design method, including an LED point light source 100 , a light incident plane 110 , a multi-segment mixed curved surface 120 and a receiving surface 130 . Without loss of generality, assume that the radius of the Fresnel lens is 30 mm, the preset illumination area is a circular spot of 20 mm, the distance between the LED point light source 100 and the incident plane 110 of the Fresnel lens is 50 mm, and the distance between the receiving surface 130 and the The distance of the multi-segment mixed curved surface 120 of the Fresnel lens is 500 mm, and the number of serrations of the Fresnel lens is 10 for the convenience of expressing the characteristics of the present invention. The thickness of the lens is 4mm, the material is PMMA, and the refractive index is 1.49. According to the parameters, the calculated surface data of the multi-segment mixed curved surface 120 is shown in Figure 2. From the calculation results, it can be seen that as the number of saw teeth increases, the arrangement of the saw teeth will collapse downwards in order to achieve uniform illumination. , which is very different from the sawtooth arrangement of conventional Fresnel lenses.

According to the surface data, non-uniform rational B-splines (Non uniform rational B-spline, NURBS) are used to perform surface fitting, thereby obtaining a multi-segment mixed surface 120. In this embodiment, the Rhinoceros construction based on the principle of NURBS is used. Surface fitting is performed by the modeling software, so as to obtain the lens entity containing the multi-segment mixed curved surface 120, as shown in FIG. 3 .

After the entity is established according to the surface shape, the model is imported into the simulation software tracePro for simulation. The simulation effect is shown in FIG. 4. It can be seen from FIG. The illumination uniformity on the receiving surface 130 can reach more than 80%. As a comparison, when the lens is not added, the same optical element parameters are kept for simulation, and the obtained effect diagram is shown in Figure 5. Comparing FIG. 4 and FIG. 5 , it can be found that the free-form surface lens can more effectively realize the focused illumination of the LED point light source 100 , so that the light energy is more concentrated and the utilization efficiency is higher.

Finally, it should be noted that the above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art can still understand the foregoing The technical solutions recorded in each embodiment are modified, or some of the technical features are equivalently replaced, but within the spirit and principles of the present invention, any modifications, equivalent replacements, improvements, etc., shall be included in the present invention within the scope of protection.

Claims (4)

1. a high-focus free-form surface Fresnel lighting system is characterized in that, a point light source, a Fresnel lens comprising a free-form surface and a receiving surface are arranged successively by the direction of light propagation, and the Fresnel lens Arranged in parallel with the receiving surface, the point light source is arranged on the mid-perpendicular line between the Fresnel lens and the receiving surface, the Fresnel lens includes a light incident plane and is arranged opposite to the light incident plane A multi-segment mixed curved surface, where N dry free-form surface serrations are arranged on the multi-segment mixed curved surface, the point light source is arranged on one side of the light incident plane, and the receiving surface is arranged on one side of the multi-segment mixed curved surface; The point light source has an exit angle The exit angle Divide into N parts of irradiation areas corresponding to the sawtooth of the free-form surface one by one, and the light emitted from the irradiation area passes through the corresponding sawtooth of the free-form surface to form a linear light spot on the receiving surface. 2. A high-focus free-form surface Fresnel lighting system according to claim 1, wherein the radius of the Fresnel lens is 30 mm. 3. a kind of free-form surface Fresnel lighting system of high focusing degree according to claim 2, is characterized in that, the distance of described point light source from the incident light plane of described Fresnel lens is 50mm, and described receiving The distance from the surface to the Fresnel blended surface is 500mm. 4. A high-focus free-form surface Fresnel lighting system according to claim 1, wherein the point light source is an LED point light source.