A method for manufacturing Fresnel lenses that can effectively reduce glare

Abstract

This invention provides a method for manufacturing Fresnel lenses that effectively reduce glare. An additional space is provided at the tip of the recessed groove in the moving or fixed mold corresponding to the Fresnel surface microstructure. This creates an extra space for air trapped at the tip of the recessed groove cavity during injection molding. This improves the filling rate of the plastic within the Fresnel structure mold insertion groove, resulting in a fuller microstructure and thus reducing glare.

Description

Technical Field

[0001] This invention relates to the field of optical technology, and specifically to a method for manufacturing a Fresnel lens that can effectively reduce glare. Background Technology

[0002] Fresnel lenses are widely used in both imaging and non-imaging optics due to their small size and light weight, such as in photovoltaics, automotive lighting, precision imaging systems, solar-pumped lasers, and energy concentrators in vision-correcting ophthalmic lenses. Fresnel lenses offer low cost and good optical performance, and are generally manufactured by injection molding of optical polymers. In recent years, Fresnel lenses have been frequently used in head-mounted displays in the market and research. However, the performance of these lenses does not always satisfy users, as the image perceived by the user's eyes is flawed, primarily manifested as glare and image blur. A halo extends to the center of the Fresnel lens, appearing as the tail of a small bright spot, while image blur means that the expected image is not as sharp as it should be due to reduced resolution.

[0003] Industry insiders are well aware that there are four key parameters for Fresnel structures suitable for Fresnel surfaces: tooth pitch, draft angle, tooth tip radius, and groove radius. Fresnel lenses with smaller tooth pitch produce better images. Simulated ray tracing shows that glare primarily originates from the circular area at the tooth tip, and the draft angle contributes very little to glare. Figure 1 As shown, a smaller draft angle does not necessarily suppress glare better. The groove radius is generated by the tip of the Fresnel structure in the mold, and the precision of the small facet of the Fresnel lens is crucial to image quality. The tooth tip is formed by being shaped in the corresponding groove in the mold. Since there is no perfect cutter to cut a perfect groove in the mold, the groove in the mold is not perfectly sharp. In addition, there is very little air remaining in the mold, and the mold is trapped in the groove, causing the tooth tip to become rounded.

[0004] To clarify the relationship between tooth tips and glare, a bright spot with a radius of 5mm was set as the light source on the monitor, and simulations were performed on Fresnel lenses with different tooth tip radii and draft angles. After the simulation was completed, the bright spot and glare pattern on the illuminance receiver were selected for analysis, and then the selected light rays were displayed, such as... Figure 2 As shown, correct rays are received by the retinal receiver through an effective Fresnel surface, while incorrect rays passing through the circular area of ​​the serration tip directly cause glare. This means that the larger the circular area, the more severe the glare. Therefore, it is known in the industry that glare originates from the circular area of ​​the serration tip, and that the key factor in the image quality of a Fresnel lens is the quality of the serration tip.

[0005] Chinese patent application publication number CN102582034A, authorized on July 18, 2012, discloses a mold for molding a Fresnel condenser lens to produce a Fresnel condenser lens with low light loss. The mold includes a moving mold and a fixed mold. The moving mold or fixed mold is machined with multiple recessed grooves on the exit surface of the Fresnel condenser lens. Each groove includes a second forming surface for forming a second surface of the grooves. The second forming surface is inclined outward from the moving mold along the direction from the tooth root to the tooth tip, so that the second surface of the formed lens is inclined towards the incident surface of the lens. This reduces the light loss through the lens compared to when the second surface is perpendicular to the incident surface. The Fresnel condenser lens molded by this mold adopts a different surface groove structure than existing Fresnel condenser lenses, thereby reducing light loss and improving light energy utilization efficiency. For example, its application in concentrated photovoltaic power generation can improve power generation efficiency. The drawback of this existing technology is that it does not solve the problem of very little residual air in the mold, which causes the mold to be trapped in the groove and the tooth tip to become rounded. Therefore, it cannot directly improve the quality of the tooth tip to reduce glare, and it also reduces the effective surface area of ​​Fresnel.

[0006] To suppress glare, industry experts suggest using absorbing materials. However, this directly affects the lens's appearance, increasing costs and requiring reduced production volume to improve manufacturing precision, posing a significant challenge. In conclusion, the best solution to the glare problem lies in developing better lens tips.

[0007] Given the current state of the technology, how to manufacture Fresnel lenses with fuller tooth tips to reduce glare is a technical problem that industry professionals urgently need to solve. Summary of the Invention

[0008] To address the above problems, this invention provides a method for manufacturing a Fresnel lens that can effectively reduce glare. This method can improve the filling rate of the plastic in the Fresnel structure mold insertion groove, making the microstructure fuller and thus reducing glare.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] A method for manufacturing Fresnel lenses that can effectively reduce glare involves providing an additional space at the tip of the recessed groove of the moving or fixed mold corresponding to the Fresnel surface microstructure in the mold, thereby creating an additional space for air trapped in the tip of the recessed groove cavity during injection molding.

[0011] As a preferred embodiment, the recessed grooves of the moving mold or the fixed mold are cut and shaped using a diamond cutter.

[0012] As a preferred embodiment, the radius of the cutting surface of the diamond cutter used for cutting additional space is set to 2 micrometers.

[0013] As a preferred embodiment, the transition between the recessed toothed cavity and the additional space entrance forms an angle y.

[0014] As a preferred embodiment, the transition between the recessed toothed cavity and the additional space entrance forms a smooth transition surface.

[0015] The beneficial effects of this invention are: air in the Fresnel structure mold insertion groove will prevent the colloidal mold flow from filling the entire cavity. By setting an additional space at the tip of the tooth of the recessed tooth groove of the moving mold or fixed mold corresponding to the Fresnel surface microstructure in the mold, the filling rate in the recessed tooth groove cavity of the moving mold or fixed mold can be increased, making the Fresnel surface microstructure full, thereby achieving the purpose of reducing glare. Attached Figure Description

[0016] Figure 1 A schematic diagram showing that the draft angle contributes little to glare.

[0017] Figure 2 A schematic diagram showing that most of the glare comes from the circular area at the tip of the tooth.

[0018] Figure 3 This is a comparative schematic diagram of conventional mold forming method A and embodiment B of the present invention.

[0019] Figure 4 A comparative measurement diagram of Fresnel structures made using conventional molding methods and Fresnel structures made using the present invention, under the same molding parameter adjustments (showing that the Fresnel structures made using the present invention have higher tooth height and sharper tooth tips; the transcription ratio (TR) is used to quantitatively evaluate the quality of the tooth tips).

[0020] Figure 5 A comparative schematic diagram showing a Fresnel structure-aware pattern made by a conventional molding method and a Fresnel structure-aware pattern made using the present invention.

[0021] Figure 6 for Figure 3 A magnified view at point C.

[0022] Figure 7 This is a schematic diagram of implementation method two.

[0023] Figure 8 for Figure 7 A magnified view at point D.

[0024] The attached figures are labeled as follows: recessed toothed cavity 11, additional space 12, colloidal mold flow 10, and smooth transition surface 13. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0026] Reference Figure 3-6 As shown in Embodiment 1, a method for manufacturing a Fresnel lens that can effectively reduce glare involves providing an additional space 12 at the tip of the recessed groove of the moving or fixed mold corresponding to the Fresnel surface microstructure in the mold. This allows the remaining air trapped in the tip of the recessed groove cavity 11 to create an additional space, thereby reducing competition with the flow of the injected colloidal mold flow 10.

[0027] As a preferred embodiment, the recessed grooves of the moving mold or the fixed mold are cut and shaped using a diamond cutter.

[0028] As a preferred embodiment, the cutting radius of the diamond cutter used to cut additional space is set to 2 micrometers.

[0029] In actual production, during the injection of plastic material, the temperature inside the mold cavity is high, and the remaining air inside the mold cavity is trapped in the valleys of the mold. This results in a low filling ratio or transcription ratio of the injection-molded microstructure, preventing the injected plastic from flowing. This means that the flowing material cannot completely fill the Fresnel structure, and the tooth tips are rounded off by the trapped air. When they cool and solidify, they may even shrink slightly. In this invention, by providing an additional space at the tooth tips of the recessed grooves in the moving or fixed mold corresponding to the Fresnel surface microstructure, the filling rate in the recessed groove cavities of the moving or fixed mold can be increased, making the Fresnel surface microstructure fuller, thereby reducing glare.

[0030] Reference Figure 4 As shown, taking a tooth profile of 20.8mm to 21.0mm as an example, the actual height after fabrication using a conventional mold is 0.128mm, while the height fabricated using the method of this invention is 0.139mm. In this case, the ideal height is 0.145mm, yielding corresponding TR values ​​of 0.88 and 0.96, respectively. TR is the transcription ratio, used to quantitatively evaluate the quality of the tooth tip. These figures demonstrate that the microstructure obtained by this invention is a significant improvement over that fabricated using a conventional mold.

[0031] Reference Figure 5 As shown, a comparison between Fresnel structure-sensing pattern displays made by conventional molding methods and those made using the present invention clearly shows that the lens and sharp microstructures produce less glare.

[0032] In this embodiment, the transition between the recessed toothed cavity 11 and the entrance of the extra space 12 forms an angle y, which is simple and easy to implement.

[0033] Reference Figure 7-8 As shown in Embodiment 2, a smooth transition surface 13 is formed at the transition between the recessed toothed cavity 11 and the inlet of the extra space 12. While Embodiment 1 is simple and easy to implement, it may not be suitable for products with sensitive tip shapes, as the colloidal molded flow may fill the extra space 12, potentially replicating its shape. Embodiment 2 addresses this by forming a smooth transition surface 13 at the transition between the recessed toothed cavity 11 and the inlet of the extra space 12. This smooth transition ensures that even if the colloidal molded flow fills the extra space 12, the smooth transition between the recessed toothed cavity 11 and the extra space 12, considering the influence of fluid surface tension, allows the injection fluid material to enter the extra space 12. Since the extra space 12 is gradually changing, the interaction with surface tension cancels each other out, resulting in more accurate shape replication and a higher transcription / replication ratio (TR), thus leading to a more accurate surface shape.

[0034] The Fresnel lens produced by this method can be used in VR, and may also be used in solar energy, automobiles, and all other applications that utilize Fresnel lenses.

[0035] The above embodiments only illustrate two implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A method for manufacturing a Fresnel lens that can effectively reduce glare, characterized in that, An additional space (12) is provided at the tip of the recessed groove of the moving mold or fixed mold corresponding to the Fresnel surface microstructure in the mold, to create an additional space for the air trapped in the tip of the recessed groove cavity (11) during injection molding; the recessed groove of the moving mold or fixed mold is cut into shape with a diamond cutter; the cutting radius of the diamond cutter used to cut the additional space is set to 2 micrometers; an angle y is formed at the transition between the recessed groove cavity (11) and the entrance of the additional space (12); a smooth transition surface (13) is formed at the transition between the recessed groove cavity (11) and the entrance of the additional space (12).

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