誘導(dǎo)立體跟隨聚焦自由視覺的分析

1、誘導(dǎo)立體，跟隨聚焦，自由視覺的分析         08-08-23 15:25:00     作者：丁守謙    編輯：studa20【摘要】  本文簡要地回顧立體（3D）成像發(fā)展歷史中的幾個重要事件。對產(chǎn)生立體感覺的所有誘因進行了重新分類。對誘導(dǎo)立體、跟隨聚焦、自由視覺進行了較仔細的分析，并說明了它們的應(yīng)用。最后介紹了一種新型的立體成像器的設(shè)計。使每個具有數(shù)碼相機的人均可自行拍攝立體像對，并用此裝置觀看放大的立體像，其彩色

2、、保真度與彩色照片相當(dāng)。 【關(guān)鍵詞】  誘導(dǎo)立體; 跟隨聚焦; 自由視覺; 立體成像器    In 280 BC, Euclid realized that the sense of spacial object was caused by the dissimilar image between visions in our two eyes. Now it is called binocular parallax. According to this principle, in 1838, C. Wheatstone invented the fir

3、st stereoscope. During the time of renaissance (14001600 AD), L. Da. Vinci and other artists gradually understood the scenography, and they learned to use shadows, luster to stress the stereo perception. In 1948 D. Gabor invented the Hologram. It has recorded not only the wave intensity but also the

4、 phase of it. His new idea was realized by Leith E. N and Upatnieks J. using coherent laser beam in 1962.  The holographic stereo image can be seen from different direction so we can get the lateral information of the object. This was the optimal approach for 3D image and people have placed a g

5、reat hope on it. In 1960, Bela Julesz invented that the depth feeling is priori by means of random dots figure. In 1976  a  Japanese scholar Takanori Okoshi published a book1 where he synthesized the early studies and concluded that ten cues are available for perceiving the depth of an ima

6、ge. These cues are classified further into two major groups: physiological and psychological cues. The former 4 cues can be believed to be more important than the latter 6. However this classification is not so complete since several new discovered cues have not yet been included and the similar per

7、spective can be combined into one. So they are reclassified as following:    1  12 cues of depth perception*2(A) Physiological cues    1. Accommodation    It is the muscular tension of the ciliarys body that adjusts the focal length of the crystallin

8、e lens. It is a monocular depth cue. The cue is effective for a distance less than 2 meter.    2. Convergence    When we turn our two eyeballs and look at a certain point on an object, the angle made by the two viewing axes is called the convergence angle. It gives us a

9、 cue of depth perception. But it will be invalid beyond 10 meters. It will also unify the retinal images of the two eyes. We call this kind of action pattern matching. Experiments showed that an interaction exists between convergence and accommodation.    3. Binocular parallax &#

10、160;  The distance between two eyes is approximately 6.5 cm horizontally, so the image on retinas in both eyes are slightly different. It is called binocular parallax. This difference will be more significant when getting closer. So we could judge how far the object is. It is the most significa

11、nt factor to the depth perception, when objects are within 250 meters.    4. Monocular movement parallax    When we close one of our eyes, and have a relative movement to objects, just like when we are in a train, near object fleet away, distant object move slowly. This

12、 forms the sense of far and near. And it is only valid for several hundred meters.    5. Color Difference    Because of the refraction ratio of our eyes crystalline lens between different colors is different, it may cause the image position on the retina different, too.

13、 The blue objects will stay top on red ones, and green ones stay in the middle.    (B) Psychological cues    1. Retinal image size    Generally speaking, the smaller the image on the retina, the further the object will be. But common sense has already tol

14、d us the size of some objects, so we can distinguish some objects in similar size. Therefore, if we see a man and a similar sized elephant, we will understand that the elephant must be somewhere further than the man.    2. Linear perspective    The scenery will diminish

15、 linearly as the distance grows. For example, it seems to be narrower in the further end of two parallel rails. Painters always use this cue.    3. Areal perspective    Distant landscapes often look hazy due to the scattering by small particles in the air (like smoke, d

16、ust, vapor). So the Chinese painters use less ink to draw mountains and trees far away.    4. Shades and shadows    A three dimensional object exposed to the light will present different shades and shadows in different parts. Western painters use this characteristics to

17、 stress the sense of stereo.    5. Overlapping    Front objects always overlap the things behind them. Generally, an object whose outline pattern looks relatively continuous is felt to be closer, and vice versa.    6. Induced Stereovision2  

18、0; If monocular vision is near the real stereo vision, it would be induced to be “Induced Stereovision”. Its stereo feeling is almost close to the real stereovision. (More details later)    7. Large Screen Stereovision    We have a wide range of visual field, horizontal

19、: 220°and vertical: 130°. It is like a wider angle camera. Generally we can easily see any thing in those ranges: horizontal: 90° and vertical: 70°. When we watch movies on a large or ultra large screen, even a dome screen, we will get stereo perception as well as immerse feelings although the pictures are planar.    In general, ther