一、玻璃透鏡的制造方法
1、先前的方法：把熔化好的光學(xué)玻璃在成型過程中制成直徑和需要加工的透鏡直徑略大一點(diǎn)的玻璃棒，然后按照鏡片的厚度切割成片材。拿到專門的機(jī)械加工儀器上，按要求加工成成品。加工的過程主要是：粗磨，中磨，細(xì)磨，精磨，拋光，退火。粗磨至精磨的材料主要是各種不同細(xì)微性的金剛砂。拋光的方法，在要求不高的情況下，可以用火焰拋光。高級鏡片必須用機(jī)械的方法，拋光的材料一般為氧化鈰。
2、現(xiàn)在的方法是先用模具熱壓成型。主要是為了減少原始方法中加工帶來的浪費(fèi)以及提高工作效率。方法是：根據(jù)鏡片品質(zhì)確定好熔融態(tài)玻璃的品質(zhì)，把在一定溫度、粘滯狀態(tài)的玻璃放入模具中，壓制成型，最后退火。結(jié)果有兩種：一是一次到位，成型品即可達(dá)到尺寸精度要求。極微的缺陷可通過鍍膜彌補(bǔ)。對模具的要求非常高，就我所知目前國內(nèi)尚不具備。這種產(chǎn)品可滿足大多數(shù)的需要。鏡片精度主要受模具精度的影響。二是成型品即為精度很高的毛坯，然后再按上述原始的方法進(jìn)行機(jī)械加工，但加工量很少，可明顯地提高生產(chǎn)效率。要求精度極高的產(chǎn)品多采用這種方法。鏡片精度主要受機(jī)械加工儀器精度的影響。二、鍍膜的基本知識
大家知道，任何物體對光線都有反射作用，這也是我們能看到東西的原因。對于鏡片而言，為了使得光線能夠完全透過鏡頭，在底片上完全反映自然的真實(shí)情況，鏡頭最好是各種光線完全穿過。優(yōu)質(zhì)的光學(xué)玻璃，其光線透過率可達(dá)到90%
以上，尚余的光損失就需要在透鏡表面鍍上膜來彌補(bǔ)。所以，在光學(xué)鏡頭上主要是鍍減反射膜也叫增透膜。為了滿足各種要求，往往需要鍍多層膜。為了提高玻璃的抗劃傷能力，最外面的一層往往是高硬度的膜。在實(shí)驗(yàn)室里，現(xiàn)代的工藝技術(shù)幾乎可以達(dá)到光線百分之百通過。之所以這么說，是因?yàn)樵趯?shí)際使用中，鏡頭上會或多或少地受灰塵、臟物等的影響，使得透過鏡頭的光線減少。鍍膜的方法很多，但常規(guī)的方法也就那么幾種。
(一)、化學(xué)方法，包括溶膠—凝膠法、化學(xué)氣相沉積等方法。根據(jù)膜的性質(zhì)配制一定成分的溶液，然后：
1、浸鍍。把潔凈的玻璃加熱到一定溫度，然后放入配置好的化學(xué)溶液里，拿出，烘干。這種膜顯然是雙面膜。
2、噴鍍。把配置好的膜溶液裝在噴槍上，噴到潔凈的、熱的玻璃表面。烘干。玻璃體可以是移動或旋轉(zhuǎn)，以增加膜的均勻性?？慑冸p面或單面。 (以前鏡頭鍍膜有采用所謂的甩膠法，但由于不經(jīng)濟(jì)，現(xiàn)代工藝鍍無機(jī)膜時已將其淘汰，但它仍然是鍍有機(jī)膜的一種常用、成本低廉的方法)。
(二)、物理鍍膜法。有真空蒸鍍、離子鍍膜、濺射鍍膜(均可歸結(jié)為物理氣相沉積)等多種不同的形式。多用于鍍金屬膜、反射膜等。如鏡子。通常，化學(xué)方法的鍍膜強(qiáng)度一般低于物理方法，但隨著鍍膜技術(shù)尤其是近一、二十年的飛速發(fā)展，用化學(xué)或物理的方法達(dá)到的效果已經(jīng)沒有什么分別。只是有成本的區(qū)別罷了。以前，化學(xué)的方法只能鍍一層膜，鍍第二層時，由于溫度的影響常會破壞上層膜，但現(xiàn)代的工藝已基本解決這一難題。
Basic Knowledge of Glass Lens Manufacturing and Coating
I. Methods for Manufacturing Glass Lenses
1. Traditional Method:
o Melted optical glass is formed into glass rods slightly larger in diameter than the required lenses.
o The rods are then sliced into sheets based on the desired lens thickness.
o The sheets are processed on specialized machinery to produce the final lens.
o Key steps in the process include:
? Rough grinding, medium grinding, fine grinding, precision grinding, polishing, and annealing.
o Materials used:
? Grinding: Various grades of diamond abrasives.
? Polishing: For lower precision requirements, flame polishing may suffice. For high-grade lenses, mechanical polishing is mandatory, typically using cerium oxide as the polishing agent.
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2. Modern Method:
o Utilizes hot pressing molds to minimize material waste and improve production efficiency.
o Process:
? Define the quality of molten glass based on lens requirements.
? Heat the glass to a viscous state, place it into a mold, and press it into shape.
? Perform annealing after molding.
o Outcomes of Modern Method:
? Direct precision molding:
? The molded lens meets dimensional accuracy directly.
? Minor defects can be corrected through coating.
? Requires extremely high-precision molds, which are not fully available domestically at present.
? Suitable for most lens applications, with precision largely determined by mold quality.
? Molding as high-precision blanks:
? The molded lens serves as a near-final product with high dimensional accuracy.
? Further mechanical processing (grinding, polishing) is minimal but ensures the highest precision.
? Commonly used for products requiring extremely high precision, with quality dependent on the accuracy of mechanical processing equipment.
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This dual approach enables manufacturers to cater to varying precision and efficiency needs in the production of glass lenses.
II. Basic Knowledge of Coating
It is well known that all objects reflect light, which is why we can see them. For lenses, the goal is to allow light to pass through completely and reflect the true, natural scene onto the film or sensor.
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1. Light Transmission and Coating
? High-quality optical glass can achieve a light transmittance of over 90%.
? However, some light is inevitably lost due to reflection. This loss can be mitigated by applying coatings on the lens surface.
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2. Common Coatings for Lenses
? Anti-Reflective Coatings (AR Coatings):
o Also known as transmission-enhancing coatings, they are primarily used to reduce reflection and improve light transmission.
o To meet various requirements, lenses are often coated with multiple layers.
? Hard Coatings:
o The outermost layer is typically a high-hardness coating to improve scratch resistance.
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3. Laboratory Techniques and Real-World Conditions
? In laboratory settings, modern technology can achieve nearly 100% light transmission through lenses.
? However, in practical use, factors such as dust and dirt on the lens surface reduce light transmission.
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4. Coating Methods
There are many techniques for applying coatings, but only a few are commonly used in practice. These methods are carefully selected to balance performance, durability, and cost.
By applying appropriate coatings, lenses can significantly enhance their performance, reduce reflection, and maintain durability in real-world conditions.
I. Chemical Methods
Chemical methods involve processes like the sol-gel method and chemical vapor deposition (CVD). A solution is prepared based on the properties of the desired coating, and the following techniques are used:
1. Dip Coating:
o The clean glass is heated to a specific temperature and then immersed in the prepared chemical solution.
o The glass is removed and dried.
o This process creates a coating on both sides of the glass.
2. Spray Coating:
o The prepared coating solution is loaded into a spray gun and sprayed onto the clean, heated surface of the glass.
o The glass is dried, and the process can be applied to both single-sided and double-sided coatings.
o The glass can be moved or rotated during the process to improve coating uniformity.
(Note: In the past, a method called "spin coating" was used for lens coatings. Although it has been replaced by modern techniques for inorganic coatings due to inefficiency, it remains a low-cost and commonly used method for organic coatings.)
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II. Physical Coating Methods
Physical methods include techniques like vacuum evaporation, ion plating, and sputter deposition, all of which fall under the category of physical vapor deposition (PVD).
? These methods are commonly used to coat metallic films or reflective coatings (e.g., mirrors).
? Compared to chemical methods, physical methods often produce stronger coatings.
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Comparison Between Chemical and Physical Methods
? Strength:
o Physical coatings tend to have higher strength than chemical coatings.
? Technological Advances:
o With rapid advancements in coating technologies over the past 10–20 years, the performance differences between chemical and physical coatings have become negligible.
? Cost Efficiency:
o The main distinction now lies in the cost, with each method offering its own advantages depending on the application.
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Challenges and Modern Solutions
? Historically, chemical methods could only apply one layer of coating.
? When attempting to add a second layer, temperature changes would often damage the first layer.
? Modern techniques have resolved this issue, enabling multi-layer coatings without compromising quality.
Both chemical and physical methods now provide reliable and high-quality coatings for various optical applications.
