Elevator light curtains are now optically synchronized, so synchronization cables are no longer needed.

In the test principle structure for detecting the entry of an object (e.g. a hand) with a light curtain, a number of infrared transmitting tubes are mounted at equal intervals on one side of the light curtain, and infrared receiving tubes are arranged on the other side, with each infrared transmitting tube corresponding to a number of infrared receiving tubes. When the modulated signal (optical signal) from the infrared transmitter tube reaches the infrared receiver tubes without any problem, the modulated signal is received by the infrared receiver tubes. When the modulating signal is received by the infrared receiver tube, the photoelectric conversion is performed. In the case of an obstacle, the modulating signal (light signal) from the infrared transmitter tube does not reach the infrared receiver tube smoothly, and then the infrared receiver tube does not receive the modulating signal, and thus the photoelectric conversion cannot be performed. In this way, information about the presence or absence of an object can be detected by analyzing the state of the internal circuit.

There are a number of basic concepts involved. First is the concept of quantum efficiency. There are 2 technologies to choose from here, COMS and CCD technology. Anyone who has played the camera knows these two terms, the camera in the cell phone are CMOS, digital camera are CCD. CMOS has a disadvantage, under good light conditions, the quantum efficiency of photoelectric conversion is high, but if the light is not good, the conversion rate is low, and the performance of the imaging quality will drop sharply. So the use of CMOS camera cell phone at night imaging quality drops dramatically. Photoelectric conversion efficiency is low how to do? Is to increase the transmitter power ah! The transmitter head is easy to work in a high-power state for a long time damage, and photoelectric conversion efficiency is a direct consequence of the light curtain is prone to misjudgment.

Speaking of light curtains, there are several basic concepts, that is, the number of photoeyes and the number of beams. Now many people simply to the number of beams to distinguish between good and bad light curtains, which is actually a wrong point of view.

Light eyes, generally in the form of a pair, a transmitter, a receiver. Take Cegard Blue, a general-purpose light curtain, for example, why do 16 emitting heads produce 74 beams?

I don't know if you have ever observed the spot of light from a flashlight. The light spot of a flashlight gets bigger and bigger from near to far because light is scattered, and Cegard BLue light curtain utilizes this principle. Due to the scattering of light, the light emitted from one transmitter head can cover 5 receiver heads at a distance, scanning them one by one, which is called 5-way scanning. Of course, the top and bottom of the transmitter head, there will be a few beams of light due to the physical reasons of light scattering can not be accepted. So 16*5-6=74. Of course, we can also do 7-way, 9-way or even 11-way scanning, if 11-way scanning, it is 16*11-6=176-10=160 beams, awesome? And 74 beams of the same component cost, made 170 beams! But this 170 beams is completely meaningless, because this must be in the light curtain transmitter and receiver quite far away to realize.

In fact, the elevator to clip people, are in the last 15~20CM trip. And by that time the vast majority of light curtains are already parallel light.

I do not know if my statement above is clear? If you do not understand, you can look at the following chart.

TX is the transmitting end, RX is the receiving end. The emitting end of the infrared light is scattered. Generally speaking, the design of the lens is a constant angle, so when the RX is at B, the realization of 3-way scanning; when the RX is at C to achieve 5-way scanning. When the RX is at A, only 1-way scanning can be realized, which is the so-called parallel light.

Wrote so much, in fact, I want to express the meaning is that you can not simply look at the number of beams, to determine the cost of the light curtain is the number of light eyes.

Therefore, the general general safety level of light curtains only 16 transmitter and receiver head, so that the last leg of the trip in the car door clamping, retaining the blind spot of more than 10 centimeters, at this time, we just wave the arm, the door will still reopen.

High security level light curtain, there are 32 transmitter and receiver heads, so that the last part of the trip in the car door pinch people, the blind spot is only 5 centimeters, almost the width of a child's palm.

But the existing light curtain technology can not solve two problems, 1 can not detect the dog walking leash, which will cause people to enter the elevator, pets did not enter, the elevator closes; 2 people clamped to the glass into the elevator, the light curtain through the glass, thus closing the door.

It is believed that the light curtain technology version 2.0 can solve this problem.