The instruments that make distant object appear as if they were right in front of us. But how do they do it? The far away objects don’t take up much space on our eyes’ retina. But in telescopes, the light is reflected by the mirrors and then magnified. But how do telescopes do that? There are more than one kind of telescopes. The one you see here is a reflector telescope. The light, when passing from a lens to another, either refracts or reflects. Just like the image of a pencil in a glass half full of water. It appears to be broken but in reality it isn’t. What creates this illusion is actually the light which refract when passing from air to water. The light that enters the telescope refracts twice.
Once in the lens in front, and again in the lens located just behind it. Different lenses force the light to travel in different paths. This objective lens gathers the light and bend it to a focus near the back of the tube. The light then reflects on the diagonal mirror and an upside down image appears on the focus point. This image is magnified by the lenses in the ocular. And the eye piece brings the image to our eye. Most telescopes use two lenses. Light consists of a combination of different colors. And the use of two lenses is for preventing chromatic aberration. Because colors have a separate focal points for each of them a single lens cannot create a common focal point. A second lens solves the problem and corrects the aberrations.
Some high quality lenses can do this on their own, but using more than one lens is another option. Cementing lenses together eliminates two surface reflecting losses and the light travel from one lens to the other directly without traveling in air. The objective lens gathers the light and the image and the ocular magnifies it. This 25 mm ocular has 3 lenses and magnifies the image 24 times. This magnifying process isn’t really important in terms of the quality of the instrument. What’s really important is how much light is gathered by the objective, which is determined by the size of the objective lens. Bigger objective lenses gather more light and this means better and sharper images. Larger objectives gather more light and make the objects too far away to be seen by naked eye visible. Telescope, a brilliant invention that makes invisible visible.
Now let’s take a look at the barcode. Without barcode readers, all this black and white bars mean nothing. These bars contain a 12 digit code and each bar represents a digit. The laser beam of the scanner hits the bars and reflects back to the reader this information is then sent to a computer and compared to the inventory to reach the relevant information. But in order to understand the technology behind all this, we need to dismantle it. The laser beam is fired from this cylinder and reflects from some points before it reaches its final destination.
The first reflecting surface is a mirror. The second one is another mirror that vibrates 75 times per minute. This vibrating mirror divides the light and send it to an angled mirror creating many reflections. A single beam turns into 150 scan lines. Beams are reflected in a grid pattern allowing the scanner to see many angles to analyze the barcode. But for all these the light is needed. Not the ordinary light, but a laser beam.
Now, let’s see how it is generated. This cylinder houses the diode that generates the laser beam. The diode consists of two special layers of semiconductors that cause the electrons charged by the electrodes beneath the diode to be jump from one into the other. As these charged electrons enter the other layer they lose energy in the form of photons. This is the light carrying particle. All the light produced is restricted in a narrow tunnel with mirrors at the ends.
As the photons bounce back and forth, it is amplified as it collides with the other charged electrons. The result is a brilliant chain reaction. Photons keep on bouncing back and forth and colliding with the electrons and it further amplifies the light. This magnificent amplification of light goes on. The laser diode has a converging lens at the end that bends or focuses the beam turning it into a fine column of light. This is a laser beam and it can read the barcodes. So, semiconductors, mirrors, all these cooperate to read the barcode.