主题：【讨论】在全黑的屋子里，你清醒着，你的眼睛会怎么动？ -- jent

希望指出错误，但愿能不产生误导。还希望专业大牛们不惜举手之劳尽量为我们这些小白们打中文上来，译文如下：

The human eye is very sensitive but can we see a single photon? The answer is that the sensors in the retina can respond to a single photon. However, neural filters only allow a signal to pass to the brain to trigger a conscious response when at least about five to nine arrive within less than 100 ms. If we could consciously see single photons we would experience too much visual "noise" in very low light, so this filter is a necessary adaptation, not a weakness.

人类的眼睛是非常敏感的但我们真能看到单个的光子吗？答案是视网膜上的感知器可以对单个的光子做出反应。但是，只有当短于100毫秒的时间区间内有至少大约五到九个光子到达时，神经上的过滤器才会允许一个信号传往大脑并触发意识层面的反应。如果我们的意识能够觉察单个的光子，我们在低光照环境中就会看到太多的光学“噪声”，所以这个过滤器是必要的适应，并非不够完美。

Some people have said that single photons can be seen and quote the fact that faint flashes from radioactive materials (for example) can be seen. This is an incorrect argument. Such flashes produce a large number of photons. It is also not possible to determine sensitivity from the ability of amateur astronomers to see faint stars with the naked eye. They are limited by background light before the true limits are reached. To test visual sensitivity a more careful experiment must be performed.

有些人引用一些事例，（例如）出自放射性材料的微弱闪光也能被看到，以此证明人可以看到单个光子，但这是一个不正确的证据，上述闪光其实会产生大量的光子。同样的，也不能用业余天文学家以裸眼看到暗弱星体的能力来确定眼睛的灵敏度，因为背景光的强度高于灵敏度的低限。因此必须进行一些更加严密的关于视觉灵敏度的测试。

The retina at the back of the human eye has two types of receptors, known as cones and rods. The cones are responsible for colour vision, but are much less sensitive to low light than the rods. In bright light the cones are active and the iris is stopped down. This is called photopic vision. When we enter a dark room, the eyes first adapt by opening up the iris to allow more light in. Over a period of about 30 minutes, there are other chemical adaptations that make the rods become sensitive to light at about a 10,000th of the level needed for the cones to work. After this time we see much better in the dark, but we have very little colour vision. This is known as scotopic vision.

在人类眼底的视网膜上有两种接收器，所谓锥点和柱点。锥点负责彩色图像，但在低照度下的灵敏度远低于柱点，不过在高照度下，锥点会活跃起来，而瞳孔则会收缩，这称为明视觉。而当我们进入一个黑暗的空间内时，眼睛的第一个适应行为是扩张瞳孔以接收更多的光线，然后经过大约30分钟，眼睛会完成另一个化学方面的适应行为，把锥点变成了对光的灵敏度要高上大约10000倍的柱点。在此之后，我们在黑暗中可以看得更清楚，但对于色彩的感知则大大下降，这称为暗视觉。

The active substance in the rods is rhodopsin. A single photon can be absorbed by a single molecule that changes shape and chemically triggers a signal that is transmitted to the optic nerve. Vitamin A aldehyde also plays an essential role as a light-absorbing pigment. A symptom of vitamin A deficiency is night blindness because of the failure of scotopic vision.

柱点中的活跃物质是视紫红质，单个光子可以被一个这种分子吸收，并改变其形状，并以化学的方式产生一个信号并传导到光感神经。醛化维A作为光吸收染料也在其中扮演了关键角色。维A缺乏引发的夜盲症就是因为暗视觉缺失。

It is possible to test our visual sensitivity by using a very low level light source in a dark room. The experiment was first done successfully by in 1942. They concluded that the rods can respond to a single photon during scotopic vision.

采用非常低照度的光源在黑暗空间中测定我们的视觉灵敏度是有可能实现的，而首先实现这种实验的是Hecht，Schlaer和Pirenne，时间是1942年。他们认为在暗视觉条件下柱点可以对单个的光子产生反应。

In their experiment they allowed human subjects to have 30 minutes to get used to the dark. They positioned a controlled light source 20 degrees to the left of the point on which the subject's eyes were fixed, so that the light would fall on the region of the retina with the highest concentration of rods. The light source was a disk that subtended an angle of 10 minutes of arc and emitted a faint flash of 1 millisecond to avoid too much spatial or temporal spreading of the light. The wavelength used was about 510 nm (green light). The subjects were asked to respond "yes" or "no" to say whether or not they thought they had seen a flash. The light was gradually reduced in intensity until the subjects could only guess the answer.

在他们的实验中，他们首先让受试者用30分钟适应黑暗的环境，然后他们将受试者的双眼固定，在其左侧放置一个20级可控的光源，这样其光线可落入视网膜中柱点密度最大的区域。上述光源是圆盘状的，占据视界10分的弧度，只发射时长1毫秒的微弱闪光，以避免光线在时间和空间上的分散。采用的波长是510纳米（绿光），当闪光过后受试者必须回答是或否以表示他认为他是否看到了闪光。逐步降低光强，直到受试者完全是在瞎猜。

They found that about 90 photons had to enter the eye for a 60% success rate in responding. Since only about 10% of photons arriving at the eye actually reach the retina, this means that about 9 photons were actually required at the receptors. Since the photons would have been spread over about 350 rods, the experimenters were able to conclude statistically that the rods must be responding to single photons, even if the subjects were not able to see such photons when they arrived too infrequently.

他们发现：当进入眼中的光子为90个时，受试者回答的正确率在60%，由于落入眼中的光线只有10%到达视网膜，这就意味着接收器实际要求有大约9个光子才能起作用。由于光子分布在大约350个柱点上，实验者据此认为，即使受试者当光子来得太多时无法看到它们，但从统计上说柱点必然会对单个的光子做出反应。

In 1979 Baylor, Lamb and Yau were able to use toads' rods placed into electrodes to show directly that they respond to single photons.

到1979年，Baylor，Lamb和Yau把蟾蜍的柱点接入电极，直接证明了柱点可以对单个的光子做出反应。

下面是我的一点感想：

虽然可能单个光子能被柱点看到，我觉得除了前面没落到视网膜上，后面被神经过滤器过滤掉了以外，是不是还有没落到柱点上，或没落到柱点上的正确位置的问题？请为咱这样的小白解惑。