For a long time, the glare phenomenon during driving at night has always affected the safety of driving and the occurrence of glare. There are many reasons and ways, but the glare phenomenon during driving at night is mostly due to a strong incidence when the background is relatively dark. Light causes the visual inhibition of the human eye, that is, the photoreceptor cells corresponding to the imaging of the strong light source on the retina inhibits the imaging signal of the photoreceptor cells around it.
From the perspective of patent search, foreign research on anti-glare technology has a history of more than half a century, and domestic development of this technology has been more than 20 years. Among the many technical solutions, the technical concept has a method of using the other side lights to open and close the headlights. These technologies seem to be viable, but all have a common flaw, that is, after the user installs/anti-glare device, they actually only provide anti-glare possibilities for the other party, such as the other party not equipped with the same device. However, it is not only beneficial, but it is detrimental. In addition, if the glare is not generated by the headlights of the car, but other light sources, it is more difficult to avoid.
Therefore, at present, there is no ideal practical product at home and abroad. When the car is in use, it still relies on the other party to turn off the high beam and open the low beam to achieve anti-glare.
Most of the night driving accidents are related to glare. In the past, there was less traffic at night, and it was possible to use the alternately closed headlights to meet the car. However, with the increasing number of vehicles in modern society, this method can no longer continue to be used, and the application of technical means to solve the problem of glare is forced to 2 pulses. Lighting anti-glare principle and effect analysis According to the reason of the glare phenomenon described above, in order to prevent glare, it is necessary to reduce the luminance ratio of the glare source in the field of view with respect to the background. We can use the headlights to illuminate the field of view to improve the brightness of the background. However, when the power of the current lamp still does not meet the anti-glare requirements, the brightness of the glare source must be suppressed. Although we cannot adjust the glare source itself, we can Keep away from glare so that it doesn't enter our eyes. The key to the problem is how to block only the glare, but not the light from the headlights. Now we can find this by pulsing the headlights.
2.1 Illumination intermittent flash light source will give the human eye a flickering feeling, but when the flash frequency is higher than 20 times / sec, this flickering sensation will gradually disappear, and finally will be regarded as the ordinary continuous illuminating light source, according to Talbo-Plateau Law, whose brightness is equivalent to the average brightness of a pulsed source. Therefore, the high-speed flash light source can also be used for illumination. For example, we usually use a fluorescent lamp and an energy-saving lamp equipped with an inductive ballast, which is a light source whose illumination changes with a sinusoidal change of 100 times/second.
Compared with other scintillation sources, pulsed xenon lamps have the following two characteristics: one is that its spectrum is closest to the solar spectrum; the other is that its optical pulse width, ie the duration of illumination, can be made very short, but because of the instantaneous power of the illumination Very high, so the average brightness is not low. Therefore, when the pulsed xenon lamp flashes at a high speed, it can also be used as illumination.
2.2 Anti-glare car front lighting pulse can be convenient for anti-glare treatment: use high-frequency strobe headlights with pulsed xenon lamp; use a liquid crystal light switch that can be turned on and off at high speed to make glasses or light barriers. Placed in front of the driver's eyes, control it to open transparent only when the headlights flash, and most of the time to close, so that the effect of the headlight illumination is unchanged, but the glare in front is greatly weakened and eliminated, for example The current lamp is strobed at 128Hz, the period is about 7.8mS, the flash pulse width is 0.3mS, and the liquid crystal switch is operated periodically in synchronization. The original headlight of the other party is 60W, and the glare after passing the liquid crystal switch will also be The stroboscopic light that is cut to the same frequency and pulse width will be visually reduced to 2.3W. The biggest feature of this anti-glare method is that it does not require external coordination, and the system itself can only achieve anti-glare, which is impossible by other methods. Do it. Because the flash of the headlights on both sides may overlap in time, causing glare. This can be solved by the following method: using a light sensor to measure the periodic phase of the flash of the other headlights, and controlling the triggering of the flash of the own headlights between the two flashes of the other headlights. In this case, glare can be completely eliminated rather than weakened.
2.3 How to improve the visibility of lighting anti-glare Our ultimate goal is to provide drivers with a suitable observation.
The pulse illumination anti-glare system realizes anti-glare by flashing illumination of pulse headlights, synchronous opening and closing of optical switches, and working according to small duty cycle mode. The means is to block the external light and retain the light of the illumination effect of the headlights. . In the case of anti-glare, of course, the opening time width of the light barrier is compressed to be equal to the flash pulse width of the headlight, and the width of the flash pulse is as narrow as possible, so that all external light can be blocked. But in reality, the external light is not all glare, and it is more suitable for people to retain some of the background light or even the glare that is no longer dazzling. For example, the sky is not all dark, the background brightness before lighting even exceeds the lighting effect of simple headlights. Just because there is glare in front, we will block all the background light, which will cause additional visual fatigue; In the dark, I saw through the light barrier that a car in front of the car turned to the light and turned to you. What was it? What's more, these external lights even include some signal lights that should not be blocked, such as traffic lights and brake lights. So in fact, how to maximize the observation of these signal lights in the presence of glare is the goal.
4 Preservation of background light criteria and measures, such as no anti-glare, strong glare will make visual disability, unable to observe the scene in the field of view, including signal lighting; but the other extreme situation is anti-glare excessive, when we block When all the external light including the signal light is used, although the signal light can be clearly observed under the illumination of the headlight, it is impossible to judge whether it is emitting light, so the signal light can not be observed. Obviously, the best observation conditions are somewhere in between: it is a state that maximizes the transmission of external light while satisfying the glare-eliminating phenomenon. The specific method is as follows: when the current light flashes, the light blocking plate should be kept in the maximum open state, but in the flashing gap of the headlight, the light blocking plate should not be simply closed, but the light transmittance of the light blocking plate should be adjusted, only closed to The light in the field of view is no longer dazzling. The adjustment method is analyzed below.
* When the other headlights are also pulse headlights, icMblisljg makes people unable to open their eyes. This shows that in a certain place in the airport, a simple example is given. In the sun, a kilowatt of illumination is not dazzling; but at night, a flashlight of less than one watt adjusts G to make the upper formula smaller. The establishment of the number is of course more anti-glare, but the value of the inequality on both sides may cause the aforementioned anti-glare and intensity of the pulsed headlights to flash. Qiu: Will the incident light of the predecessor's eyes be dazzling? Not only depends on the intensity of the person's light, but more importantly, it depends on the ratio of the light intensity to the brightness of the entire field of view. At the same time, there is a critical value, which may be dazzling only after the ratio is greater than the critical value, although for different The threshold and observer, this threshold will vary, but it always exists. For convenience of explanation, the critical value is A, the brightness of the light source of the incident light that may be glare is defined as G, and the brightness of the field of view background is defined as B, the necessary condition for glare should be: therefore, sufficient conditions for glare To: In combination with the night driving environment, the lighting factor of the headlights is introduced, and the illumination of the headlights in the field of view causes the brightness of the background to be added as S, then the above formula becomes: in the anti-glare lighting system, because the light barrier is in In the cycle opening and closing state, the proportion of the opening time of the light barrier is set, that is, the opening duty ratio is because the light blocking plate does not cover the illumination effect of the own headlight, and only the external light is blocked, the upper formula should be modified to: the following formula can be obtained. That is, sufficient conditions for not glare under the pulse illumination anti-glare system.
Because the right side of the inequality is often positive, when the value in parentheses is less than or equal to zero, there is no glare, even if G is 100%, that is, the light barrier does not have to work and stays normally open, even its own headlights Do not need to open, that is, aS is zero, there will be no glare, because the relationship between glare and background brightness does not meet the necessary conditions for glare. If the light is turned on, it is only for lighting, not for anti-glare.
When the value in the brackets is greater than zero, glare may occur. At this time, we should turn on the headlights to improve the background brightness of the field of view and introduce the value of as to suppress the glare; however, when in the field of view The glare source brightness G is too high, the original field of view background B is too dark, even if we turn on the headlights, it will not help, we must make the light barrier work to introduce the duty factor G, and adjust it until the upper equal sign Established. Degree, because it obscures too much of the original background light B, if this happens, you can re-adjust G to the equal sign to make the two values ​​close.
The above is our adjustment method. As long as the opening duty ratio of the light barrier is adjusted so that G is close to the following formula, the state of maximally transmitting external light can be achieved under the premise of satisfying the glare elimination phenomenon.
Where G is the glare brightness, B is the brightness of the background light when there is no illumination, and S is the brightness of the background caused by the illumination of the own headlights, which are provided by the photoelectric sensor which will be mentioned later. The methods provided may be separately provided, and if the signals are superimposed, they may be distinguished and adjusted by a control circuit. And a is a coefficient value that varies from person to person. It is also a function of B. For this reason, there is a knob in the device for the driver to adjust the comfort of observation. It is actually changing the setting parameter a and, if necessary, The signal B can be used to obtain compensation at the same time, so that during driving, the controller will automatically provide a suitable defense for the driver by adjusting the opening duty ratio of the light barrier according to the external background and glare changes. Dizziness and observation.
The light blocking plate is an electronically controlled optical switching device. In order to adjust the light transmittance of the light blocking plate, the time ratio of opening and closing can be changed in the working mode of the switch, and the level of the applied voltage can be changed in the analog working mode. Different light transmittances are obtained. These two methods are equivalent. The above formula is given in terms of switching mode and combined with the duty cycle concept. When the light barrier is operated in the analog mode, the G, which is defined as the on duty ratio, is simply changed to the light transmittance.
When more precise control is required, consider that the light barrier is fully open when the headlights flash, and a correction value is introduced.
We have already given the standard for adjusting the opening duty ratio G of the light barrier, but we should also emphasize the speed of adjustment. In order to avoid the inconvenience caused to the human eye due to external glare or sudden changes in the background light, the adjustment speed should be controlled as follows: when the glare is suddenly present, the opening duty ratio can be reduced faster to avoid glare; However, when the glare disappears or the background suddenly becomes bright, it is not appropriate to adjust G to the standard state immediately and the adjustment process may be 0.5 second to 1 second.
Acceleration analysis of more than 2.5 pulse headlamps According to the design, all pulse headlamps must use the same frequency flash. This frequency is actually derived from a high-frequency-accuracy oscillator when the system passes the light sensor to detect Know that the flash of the light in the opposite glare is adjusted to the moment between the two flashes of the other party, that is, the two sides lock each other and maintain 18 (phase difference. During the car, even if the lock is lost due to bumps, blockage, stray light, etc. The lamp will continue to remain in the phase adjusted before the lock is lost for a long time due to the high frequency stability of the oscillator, and will be strobed with the other headlights until it is re-locked. Once the other lights are locked, the lights are blocked. The light board will be turned off briefly at the moment of flashing of the opponent to block the flash pulse of the other party. For the light barrier, the closing time should be controlled, and the light that is no longer dazzling should be properly transmitted. At this time, the light barrier can be opened as described above. The air ratio G is adjusted, but the glare component that has been blocked is subtracted from the glare sensor signal.
To avoid this situation: two cars that also use pulsed illumination are on the way, they have locked each other's frontlights as glare, and they are staggered and strobed. At this time, we will lock the lights of any one of them as glare. I will feel the glare of another headlight. The avoidance of this situation depends on a sensor that correctly distinguishes between glare and background light. The principle of locking the pulse light is: when there is glare pulse, the strongest pulse in the glare is locked by 180* phase difference; when there is no glare pulse, press 36 (the phase difference locks the strongest pulse in the background light, and the leading lock lags. In this way, when multiple vehicles using pulsed headlights meet, the cars traveling in the same direction should flash at the same time, and the cars that are driving differently will flash at the same time with 180* phase difference. How to deal with them well? The situation where the external pulse glare overlaps with the own light and causes indistinguishable is a problem that needs to be emphasized and should be tested in practice.
3 Automotive pulse headlight illumination anti-glare system A complete automotive pulse headlight illumination anti-glare system should include the following components: pulse headlights under high-speed stroboscopic lighting under controller control. The driver observes through the light barrier, and the light barrier is controlled to open transparent when the headlights flash to ensure that the observation is not affected. The light transmittance in the headlight flash gap is adjusted to block the glare from being dazzled. The photoelectric sensor receives the illumination effect light of the glare, the background light and the headlight for the controller to act as a regulated input signal.
Pulse headlamps are currently made of pulsed xenon lamps and may be replaced by LED products in the future.
The so-called light barrier is actually a large-area electronically controlled optical switch component, which can also be made into glasses, and the anti-glare function is completed together with the headlights. Because it is matched with high-speed strobe, it is required to have a fast switching speed.
Because it is an automotive product, the light barrier, such as liquid crystal material, is expected to meet the working environment temperature requirements, -40C + 50C. If you can use polymer liquid crystal devices will be more suitable.
The photoelectric sensor is composed of a pair of phototransistors, which respectively receive glare and background light, and respectively give corresponding electrical signals reflecting the intensity thereof, and respectively sent to the controller for judging whether anti-glare is needed and how to act, in terms of anti-glare, two Only the photosensitive tube has the same photoelectric characteristics and has a large signal dynamic range and a small drift current.
The key to the requirements of the light sensor is to design a combined lens that can distinguish between glare and background light. In fact, whether the light emitted by a certain light source is used as glare or background light is currently based only on its orientation in the field of view. Light emitted in a flat narrow range within a certain width directly in front of the field of view is generally regarded as glare because light that may cause glare is substantially present in this range. Of course, this can also be solved by an area CCD device that does not have to be too high resolution.
The signals given by the sensors are actually (B+G) and (G+S*), which are the background light illuminated by the headlights, and the glare and illuminating light (S*) sensed by the glare sensor. The sum of the glare and the background light will be overlapped by the sensor structure and the environment. The controller can adjust the light barrier in various ways. At present, the analog method is used, that is, the analog switch plus the op amp circuit is the main method, but considering the production debugging cost and reliability, it is also considered that the controller actually needs to complete the data communication function, and the later adjustment will mainly rely on the dedicated number. The chip is done.
The controller includes a knob for the driver to adjust the viewing comfort. It is actually changing the resistance of a potentiometer that sets a parameter. Of course, the potentiometer can be replaced by other adjustable parameter components, and then compensated by signal B. . When adjusting the light barrier, the controller should also judge whether there is any pulse in the external light, whether the intensity of the glare has reached the level of glare, and the corresponding control. The controller also temporally coordinates the fast-responding pulse headlamps and the relatively slow-resisting light barriers, driving them to accurately synchronize.
4 Basic functional characteristics of automotive pulsed headlight lighting anti-glare system In all current automotive lighting anti-glare solutions, the technology described in this paper is ideal, and can meet the needs of anti-glare without the cooperation of the other party. On both sides of the rendezvous vehicle, the party using the technology will benefit; and the other party will not have additional impact.
It not only prevents glare from the headlights of the other vehicle, but also prevents glare from other roadside or front stray light sources.
Anti-glare does not affect the driver's observation. It is different from the way the rendezvous vehicle closes the headlights, and does not cause the driver to observe the interruption.
Anti-glare is automatic. Once the driver sets the standard for anti-glare according to his own habits, the driving system will automatically adjust for different glare and background environments according to the standard, without manual intervention.
Other advantages of the system are: the lamp type can be made flatter, suitable for the trend of miniaturization of the car; the luminous efficiency is high; the data communication can be performed by using the light to help complete the traffic intelligentization and other special applications.
5 Conclusion As can be seen from the above, the pulse illumination anti-glare technology actually combines two mature technologies: pulse light source and electro-optical switch, according to certain rules, the technology is practical and feasible, and the effect is very significant. Solve the anti-glare problem that has long plagued night driving. The realization of this technology will play a good guarantee role for both the safety of life and property and the improvement of traffic capacity. Compared with the existing automotive lighting technology, pulse headlight illumination, in addition to anti-glare, has more communication functions not mentioned in this article, considering its broader technical application prospects and the society it deserves. And economic benefits, I believe it will become one of the development direction of the headlamps.
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