光学中的玻璃非球面和塑料非球面是什么意思，求高人指点！

光学中的玻璃非球面和塑料非球面是什么意思，求高人指点！

玻璃非球面指的是玻璃的2个面不可以延展成球型，通俗的讲眼镜的2个面，就不可以延伸成球，这2个面就是非球面，同样塑料非球面一样。

Perpetuating a skewed view of Chinese history
By Antoaneta Bezlova
1 BEIJING - Show-stopping scenes of regal power and wirework martial arts in Chinese period dramas might be all the rage in the West, but the success of these best-selling films has provoked an uneasy debate at home about what Chinese blockbusters should be all about.
2 Described by some critics as feasts for the eyes, these big-budget hits have been slammed for leaving the audiences hungry for substance and deprived of soul. Their artfully scripted scenes of carnage and violence have made some lament that even lowbrow Hollywood films are better at passing judgment and affirming the victory of good over evil.
3 Since Taiwanese director Ang Lee's 2001 film Crouching Tiger, Hidden Dragon drew the curtain on a China of mystery and imagery and went on to win an Oscar, three of mainland China's most -renowned directors have succumbed to the allure of directing opulent period dramas that feature imperial power struggles and captivating kung-fu fights.
4 Zhang Yimou, perhaps the best known of all living Chinese directors, rolled out two big-budget films, Hero in
2002 and the House of Flying Daggers in 2004, both affirming his reputation as maestro of the visual.
5 Hero dazzled the eye with half a dozen hues, breaking the story of an attempted imperial assassination into several cameos of color and retelling it as many times as seen by the film's main characters. Hero became the best-selling Chinese film ever.
6 House of Flying Daggers, for its part, showcased breathtaking martial arts, offset by scenes of willowy bamboo forests and willowy female warriors. While not as grandiose as Hero, House of Flying Daggers firmly established the Chinese industry's potential to compete with Hollywood in artistic talent and audience -drawing sets.
7 Last year saw three new period dramas.
8 Zhang unveiled another court spectacle, the US$45 million Curse of the Golden Flower, said to be the
biggest-budget Chinese film of all time. The new film takes Zhang's talent for staging intricate battle scenes and elaborate ancient rituals to dangerous heights, threatening to smother all intended subtleties under a weight of gold finery.
9 Although it opened in December, Curse became the top-grossing film of 2006. It is projected to rake in more than $32 million in domestic theaters - a record for the Chinese film industry.
10 Zhang's success in the genre of costume drama has not gone unchallenged. His equally famous colleague, Chen Kaige, released earlier last year The Promise - another big-budget film that ventures into ostentatious fight scenes and attempts to rival Zhang's imaginary ancient China with its improbable vistas.
11 The Banquet - a Chinese interpretation of William Shakespeare's Hamlet, directed by the country's most popular commercial film director, Feng Xiaogang - is the last of these mega-productions of imperial grandeur where violence and bloodshed are made controversially esthetic.
12 While these big-budget historical films have proved the commercial viability of China's film industry, they have also drawn critics' ire for establishing a winning formula with foreign audiences while presenting cliched views of ancient China.
13 "China has 5,000 years of history and such a rich cache of classics, but all we see replayed in these
'blockbusters' over and over again is the story of attempts to kill the emperor," complained cultural commentator Chen Danqing.
14 To a certain extent, all these historical firms explore the importance of authoritarian power, personified in
the emperor, and its necessity as a unifying force for China. By making the plot to kill the emperor a centerpiece, critics say, these films intend to be seen as political metaphors but fail in conveying outright condemnation of tyranny.
15 The most famous one perhaps is Zhang Yimou's Hero, where the skillful assassin, or the intended "hero" of the story, wavers at the last moment of striking the fatal blow that would kill the emperor, because he bows to his ruthless authority. Some suggest that the film goes even further, endorsing the ruling authoritarian order by transforming the tyrant into the real "hero" of the film.
16 What anger critics even more are the numerous bloodbaths and pervasive violence that accompany imperial power struggles. In such films as The Banquet and Curse, the ensuing massacres are presented like scene- stealing shows of beautiful and painless deaths. Violent death is only a moment of broken harmony in these imperial courtyards, and the piles of dead bodies are hastily swept away to be replaced with a sea of flowers.
17 "These new productions are not art-house pictures that can easily afford to profess violence and doom," said film critic Zi Yufei. "They aim to be big commercial hits but don't have any bottom line. Which Hollywood blockbuster dares depict so much blood and let the evil triumph over the good?"
18 But others find justification in the fact that to attract foreign audiences, Chinese directors can only make films about ancient China, which, love it or hate it, has a violent history of oppression.
19 "Foreigners don't want to see films about modern China," mused Wang Wu, one of Zhang Yimou's screenwriters. "They don't care about our modern life because there is nothing original in it, it is a copycat of theirs. What is truly and only ours, though, is China's ancient history. Ancient China is the only worthwhile subject for a big commercial film."
20 The pre-eminence of foreign audiences' taste is dictated by the fact that more than half of the financing for these big-budget productions comes from overseas. "When you rely on someone else's money to produce a film, it is inevitable that you have to sacrifice your own original ideas and intentions," said film producer Wang Zhonglei in defense of the new Chinese blockbusters.
21 Ultimately, it is not a question of what these big films got wrong, reflected commentator Chen Danqing. "It is about the lack of thriving and diverse cultural scene in China where only these historical blockbusters get the nod and the money."
(Inter Press Service)

关于非球面，参考楼上的回答。
玻璃和塑料的区别，在于光学玻璃非球面的话，成本很高，因为是要靠非球面打磨机来做，而塑料的，就很简单，可以直接精密压铸，直接就出来镜片。
当然，一般认为光学玻璃的非球面性能好的多，但是成本和价格，也贵很多。