An Electronic Eye

An "electronic eye" is a device that can do hundreds of different things. In electronics and engineering it is called a phototube or a photocell.

Photocells are widely used in food industry. For example, at canning factories an "electronic eye" it is used for counting the finished cans of food which come out of the sealing machinery into the moving conveyor belts.

Its work can be described as follows.

A phototube is placed on one side of the belt and a lamp producing a light beam is put on the other. When a light beam reaches a phototube, the electric current passes from the tube to an electric counting machine. Every time a can comes between the light and the "eye" it cut the beam, and the current is stopped. When the can moves on, the light reaches the tube again, and thus starts the current in the circuit. Each time the electric impulse is started, it moves the counter one digit. The process results in the accurate count of every can that is moved along the conveyor of finished production.

In another part of the canning factory an "electronic eye" is used to inspect labels on the cans. When the labelled cans pass by, the labels do not reflect enough light to start an electric current. But if a can without any label passes near the "electronic eye", the bright metal of the can reflects the light back into the phototube. Now the light is strong enough to start en electric current which flows from the phototube to the controlling device and the controlling rod pushes the unlabelled can off the belt.

An "electronic eye" can not only see things but also distinguish colours. It distinguishes colours of such fruit as oranges, lemons and so on. That's why it can be used to separate the ripe fruits from the green ones. For this purpose at the canning factories, oranges, for example, are sent to the conveyor belt which passes be an electronic sorting device equipped with a phototube. When a green orange passes by the "electronic eye" of the sorting device, the phototube closes the electric contacts of

the device and the rod pushes the orange off the belt.

Other phototubes are used to see whether tomatoes are ripe enough for canning. For this purpose two tubes are used. One of them can "see" only green light, the other "sees" only red light. If the current of the "red" tube is stronger than that of the "green" one, the tomato is ripe enough to be canned. Thus when the device "sees" a red tomato it opens a lid at the end of the conveyor and the tomato continues its way on the production line. If a green tomato is signalled by the device, a rod pushes the tomato off the belt.

Figure 35. "Electronic eye". 84

1. An electronic eye is called a (an) a) photo camera;

b) photocell; c) electric cell;

d) vacuum tube.

2. According to the text

a) the "electronic eye" is used for lighting the canning process; b) the phototube is a device for transporting the vegetables;

c) the phototube is used for counting the cans, inspecting the labels, and distinguishing colours; d) the phototube is used in television sets.

3. Cans counting actually means counting of: a) light beams;

b) electric impulses; c) digits;

d) tubes.

4. Photocells cannot distinguish: a) fruit ripeness;

b) fruit size; c) fruit colour;

d) cans labelling.

5. These fruit or vegetables were not mentioned in the text: a) lemons;

b) tomatoes; c) apples; d) oranges.

Label the diagram of an "electronic eye" (Figure 35) using the information in the text.

Дата добавления: 2015-11-16