– You forgot to mention one important application of photo cells – in television – Harichkin told.
Larichkin pushed it sideways, however was already late. Filinov quickened and started talking:
– Yes, in television. Now I will explain you what role is played by a photo cell in television.
– We know – Larichkin answered.
– You know? – flew on it Eagle owls. – And I, guilty, not up to the end know. Also I want to understand, explaining to you.
It was its method: “to study, training”. Told about Filinov, as if he complained once: “What pupils, stupid at me! You will explain time – do not understand, you will explain two – do not understand. At last itself you begin to understand, and all of them do not understand yet”. And he liked to explain “known long ago”, assuring that in these explanations always and to itself (himself) you understand something that it seemed unclear and that unexpectedly you will understand more deeply and better.
– I know – Filinov became angry – so can tell only children like you. We, of course, know something, however in the field of radio, as well as in other areas, we still do not know a lot of things. Unless features of a layer of Hevisayd are known to us completely? Unless we are able to explain why the radio transmitter of bad home weak radio station reaches sometimes such distant reception and transfer what you will not always reach at powerful stations? We often grope the way in the dark. If we already “knew everything”, it would be awful. The youth on a share would have one cramming. Fortunately, for an inquisitive, innovative mind there is a work plenty. And for you including, my greyish pupils and assistants! – he added cockily. – The one who knows most, most modest.
By the way, about photo cells and television. Without photo cells also the television, of course, would be impossible. It is still imperfect also now. And therefore before going forward, “we will repeat passed”. I will tell only about the principles.
Larichkin breathed a sigh of relief.
– From your “travel” we learned that light can be turned into electric current. And vice versa: people learned to transform electric current to the public. All television is also based on these two facts. Here beam of light of a certain brightness. I pass it in a photo cell. Light excites current of the corresponding force. I give this current on wires or without wires. In the place of reception I turn electric current again to the public. And on the screen of the reception device there is a light spot, exactly same as though the ray of light from the source fell directly on our screen, without being exposed to transformation and transfer…
– Not exactly – Larichkin corrected. It was evil on this lecture about things, long ago known. – The ray of light loses something in force. Besides…
– Well, of course – Filinov agreed – at any transmission of energy it is necessary to deal with losses. And our purpose – to minimize them. But you do not interrupt me. I set the task to understand to myself… that is to you, the basic. – And it continued: – Thus, the ray of light can be transferred to other place by means of electricity. It would seem, as transfer of images on radio is easy. Put the person facing a photo cell, light more feasibly a face, and light reflected from an appearance will get to a photo cell, will excite current, current will come to other place, there it will turn to the public – and here before you on the screen the image of the person. And actually what we have? Not the image of the person, but light spot, no more. Why? Already and it is not so easy to answer this, apparently, simple question. Here we should think of how we in general see how our sight is arranged.
Why we see? And under what conditions? We see objects only because on them there are treatments of light and shade. In darkness everything is covered by absolute “shadow”, everything is black, and we do not see. However and at bright light we would also see nothing if shadows disappeared. Everything is dazzling would shine, would stick together eyes. And only. Sometimes inexperienced photographers seat photographed against a strong light source. Shadows almost disappear, and on a card instead of the person “pancake” turns out. Features cannot almost be distinguished. And light was more, than it is necessary! If we, as well as on the Moon, had no atmospheres, then all objects standing in a shadow absolutely would disappear from the field of our sight, and the subject lit half would seem to us the photo cut in two. Our sight is adapted for terrestrial conditions where thanks to the atmosphere we have an incalculable set of shadows and penumbras. Let’s take the human face lit sideways. We see this person. However actually we see a huge number of variously lit points – and not therefore only that points are lit unevenly, but also because the person unequally absorbs and reflects rays of light.
The beam which fell on black as if by soot the drawn eyebrow, it is almost entirely absorbed, and the pale cheek will reflect light completely. But also on this cheek there will be many separate points which will unequally reflect light. Each point of the person sends to our eye a separate beam, and beams these different force. Some points do not send beams also at all. All beams meet in our eye “lens” – a pupil, and then, having refracted, again disperse – exactly as in a camera lens! But display arises not on “an opaque plate”, and on an eye retina. The last consists of huge number of separate flasks, and each flask has “wire” – the nerve transferring the image to a brain. Look in a microscope approximately of a fly. There it is visible more distinctly. An eye of a fly is similar to honeycombs. It is not one, but hundreds of six-sided eyes. And on each of them only one beam – strong or weak gets. Our retina represents something like a board for a mosaic with ready dimples into which it is possible to insert stones of the first color. Set of these “multi-colored” rather raznosvetny stones also creates an overall picture, be this person or any other subject.
And the photo cell has no “retina”. The photo cell is only one flask of our retina, it is only one cell of an eye of a fly. If the fly could close all cells of the eye, except one, then either one light point, or an arithmetic average of all beams would get to this cell. And the fly would see only one spot. Here the same arithmetic average of all beams receives also a photo cell from the lit human face. Also it reflects only one spot.
But how in that case to transfer the image of the person? You will not remake a human eye, and a photo cell if on it all beams reflected by a human face fall can transfer only a light spot. It is impossible! But the separate points on a face which are sharply lit can be transferred. If to cover the lit face with the screen and in the screen to make a small hole which, say, passes a light beam only from one point of the person, then this beam, without mixing up with others, gets on a photo cell and causes the corresponding current which can be transferred and again to turn into light point. If we place this hole in the screen against brightly lit point on a nose, then the bright beam will cause also current of the corresponding force, so, and on the accepting screen brighter point will flash. If the hole appears against the shaded point of the person, then and it will be reflected in the screen more dark stain.
Thus, it is possible to transfer only separate “stones” of different coloring for our mosaic portrait. At the same time on our mosaic these “stones” will settle down in the same spatial ratio in what they were on a face. However how to make the finished mosaic portrait? We have an opportunity “to send” only one “stone” for once. Let’s say sent black – eyebrows – and it is necessary to send white “stone” – a forehead. But hardly we will move a screen hole from eyebrows on a forehead, black “stone” will disappear, and we will not receive a mosaic portrait. So it would also be if one feature of our sight did not come to the rescue. From the screen black “stone” disappears, but he still lives in our eye and some time keeps. Our sight is capable to keep what was seen during