各類觀測太陽的儀器介紹及太陽攝影 Solarmax
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文章: 13263
註冊時間: 週一 15 3月, 2004 21:28


文章 Wah!! » 週一 09 1月, 2006 02:22

http://sunearth.gsfc.nasa.gov/eclipse/S ... fety2.html

Unsafe filters(不安全的濾鏡) include:
- all color film 任何彩色負片
- black-and-white film that contains no silver 不含銀的黑白負片
- photographic negatives with images on them (x-rays and snapshots) 有影像的負片 (X光片及攝影)
- smoked glass 燻黑的玻璃
- sunglasses (single or multiple pairs) 太陽眼鏡
- photographic neutral density filters 拍攝用中性減光濾鏡
- polarizing filters 偏光鏡

Most of these transmit high levels of invisible infrared radiation which can cause a thermal retinal burn.
大部份不安全的濾鏡都能使高能量而不可見的紅外線穿透, 能使視網膜灼傷.
The fact that the Sun appears dim, or that you feel no discomfort when looking at the Sun through the filter, is no guarantee that your eyes are safe.
即使透過這些濾鏡看太陽, 眼睛沒有感到不適, 亦不能保證濾鏡是安全的.

Solar filters designed to thread into eyepieces that are often provided with inexpensive telescopes are also unsafe.
These glass filters can crack unexpectedly from overheating when the telescope is pointed at the Sun, and retinal damage can occur faster than the observer can move the eye from the eyepiece.
這些鏡後減光的太陽濾鏡會因陽光聚焦的高熱而隨時爆裂, 觀測者的視網膜會在迅雷不及掩耳的速度下受到傷害.
Density值越低, 安全性越低.
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最後由 Wah!! 於 週一 09 1月, 2006 18:46 編輯,總共編輯了 4 次。

文章: 13263
註冊時間: 週一 15 3月, 2004 21:28

文章 Wah!! » 週一 09 1月, 2006 04:08


Retinal Burns

Solar radiation reaching the surface of the earth ranges from ultraviolet (UV) radiation at wavelengths longer than 290 nm to radio waves in the metre range.
太陽抵達地球表面的幅射的波段範圍, 是由波長290nm的紫外線, 一直到米波長的無線電波.

It is widely accepted that environmental exposure to high levels of solar UV radiation contributes to the accelerated ageing of the outer layers of the eye and skin, and the development of cataracts.
已被公認的, 是處於高劑量的太陽紫外幅射環境, 可使眼睛及皮膚外層加速老化, 並會引致白內障.

However, observing the sun with inadequate or no eye protection results in "eclipse blindness" or retinal burns because the eye transmits most of the optical radiation between 380 nm and 1400 nm to the light-sensitive retina.
但是, 由於眼睛可通過380nm至1400nm的幅射, 沒有保護或不足夠保護地觀測太陽, 可使視網膜灼傷.

Exposure of the retina to high irradiance levels of visible light triggers a series of complex chemical reactions within the light-sensitive rod and cone cells.
強烈的可見光照射視網膜, 可引起視錐和視桿細胞內產生一連串複雜的化學反應.

The resulting photoproducts damage the cells, impairing their ability to respond to light, and in extreme cases can destroy them.
由光化學所產生的化學物質隕害視覺細胞, 減低它們的感光度, 極端的情況可以破壞細胞.

Depending on the severity of the damage, an affected observer experiences either a temporary or permanent loss of visual function.
視乎破壞的程度, 受害者會出現暫時失明或者永久失明的情況.

This photochemical retinal injury mainly occurs when the retina is exposed to blue and green light.
這種光化學的損害, 主要來自藍光和綠光對視網膜的照射.

Longer wavelengths of visible light and near-IR radiation are absorbed by the dark pigment epithelium below the retina, and converted into heat which can literally cook the exposed tissue. This thermal damage also occurs during extended exposure to blue and green light. Photocoagulation destroys the rods and cones, leaving a permanently blind area in the retina.

較長波長的可見光(紅光)及紅外線, 會被視網膜以下的黑色素所吸收, 並轉化成熱量灼傷愛照射的組織. 藍光及綠光也會產生這種熱灼傷. 灼傷可以破壞視錐及視桿, 在視網膜上留下一個永久失明區.

Each wavelength of optical radiation has an associated threshold retinal exposure level that must be exceeded in order for retinal damage to be observed - shorter wavelengths are more effective in that less energy is needed.
對應每種波長的光都有一個極限值, 超過這個極限值才能使視網膜受到損害. 對於較短波長的光幅射, 這個極限值的能量強度較低.

The danger to vision of inadequately protected viewing of the sun is significant because light-induced retinal injuries occur without any feeling of pain (there are no pain receptors in the retina), and the visual effects do not occur for at least several hours after the damage is done.
在不適當的保護下觀測太陽是極度危險的, 因為光照造成的視網膜損傷是不會產生痛楚的 (視網膜上沒有痛覺神經), 以及視網膜會在受損後最少數小時後才會出現徵狀!

Because the threshold exposure levels for photic damage to the retina at each wavelength of the optical spectrum are well known, it is fairly simple to calculate the maximum permissible filter transmittance that will provide adequate retinal protection from sunlight.
由於每種波長光線的極限值都已被測定, 所以要計算出安全太陽濾鏡最高允許透光率是很容易的.

The ratio between the threshold retinal irradiance for light damage to the solar spectral irradiance at each wavelength provides a starting point for this.
每個波長光強度的極限值, 以及對應的太陽光強度, 所得的比例 (估且稱為 "極限比例" ), 可以作為安全係數的計算起點.

The worst case scenario assumes that the sun is at the zenith in a clear sky (air mass of 1).
陽光最猛烈的情況, 是在清朗的天氣下, 太陽位於天頂.

The maximum permissible transmittance level of the filter at a given wavelength can be arbitrarily set at between one per cent and 0.1% of this ratio to provide a "safety" factor.
濾鏡的最高允許透光量, 可設定為 "極限比例" 的百分之1至0.1之間, 以提供一個安全係數.

When this is done for the waveband between 380 and 1400 nm, we find that a filter with a luminous transmittance of 0.0032% in the visible spectrum corresponding to a shade number of 12 provides "adequate" retinal protection during solar viewing.
由波長380nm至1400nm的幅射計算, 我們發現可見光透光率為 0.0032%的濾鏡, 相當於 12號密度, 在觀測太陽時能提供足夠的保護.

However, this does not take into account visual comfort; for comfortable viewing of the sun, a filter with a luminous transmittance of 0.0003% (shade number 14) is often preferable.
然而, 以上的計算並未考慮到觀測時的舒適程度. 在考慮舒適程度後, 建議使用 0.0003%透光率(相當於14號密度) 的濾鏡作太陽觀測.

(以上文字, 一切以英文版本為準, 中文只作參考)
(如有錯漏, 請pm Wah!!)
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