RU2513659C1 - Adaptive protective light filter - Google Patents

Abstract

FIELD: physics, optics.

SUBSTANCE: filter has a light modulator, a measuring photodetector and a processor unit whose output is connected to the control input of the light modulator. The measuring input of the processor unit is connected to the output of the measuring photodetector, the aperture of which is the control input of the device. The entrance aperture of the light modulator is the data input of the device and the exit aperture of the light modulator is the output of the device. The light modulator is binary. The working cycle of the device is broken down into working intervals, the duration of each of which is equal to the sum τ₁+τ₂, where τ₁ and τ₂ denote the time at which the binary light modulator is in the open and closed states, respectively. The ratio τ₁/(τ₁+τ₂) determines average optical transmission over a working interval. The phase during which the binary light modulator is in closed state can vary within the working interval.

EFFECT: improved light protective properties due to that the phase of the closed state coincides with the phase of the emergence of interfering short light pulses while maintaining the average optical transmission of the modulator, which enables to preserve the function of adapting the device to the average light intensity value.

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Description

Technical field

The invention relates to light-protective means for eyes or other light-sensitive sensors and can be used to provide a person with normal vision for observing the surrounding scene and screens of information indicators and displays with sharp changes in scene brightness, for example, for the appropriate protection of the vision of pilots of space, aviation, water, ground transport funds.

State of the art

Known adaptive light protection filter [1], containing an analog optically controlled light modulator (OUMS), including adjacent to each other a layer of semiconductor (FP) and a layer of liquid crystal (LCD), while the first and second electrical inputs of the OUMS are deposited with the first and the second outer side of the layers of the FP and LCD, the first and second layers of the transparent conductor connected to an external voltage source, the input aperture of the FP layer is both information and control inputs of the device, the output of which is The output aperture of the LCD layer is conjugated to the input of the protected photosensitive sensor (with the eyes of the observer).

An analog OUMS is characterized by a half-tone (multi-gradation) optical transmission characteristic. The FP and LC layers are electrically connected in series, and the ratio between their electrical impedances (complex resistances) determines the redistribution of the external source voltage between them. Under the influence of light energy, the impedance of the phase transition layer changes and, accordingly, the voltage on the LC layer changes. Due to the electro-optical properties of the LC layer, the analog OUMS automatically changes its optical transmittance. The higher the average intensity of the incident light from the side of the scene, the lower the optical transmittance of the OUMS, thereby maintaining a constant value of the light intensity at its output (in front of the eyes). A similar reaction of the light protection filter to interfering short intense pulses of light coming from the scene ensures their fast blocking.

A disadvantage of the known device is a violation of the adaptation function to the average value of the light intensity from the scene during a short-term reaction of the device to interfering light pulses. Short-term complete dimming of the entire aperture of the OVMS, necessary for the complete suppression of interfering light pulses, leads to the loss of the ability for the observer to perceive, to observe the scene for the duration of this dimming. In addition, in the known device, it is difficult to accurately adapt to grayscale (multi-gradation) changes in light intensity from the scene in a wide dynamic range. For accurate adaptation, the law of variation of the light intensity at the output of the device must be consistent with the characteristic of the perception by the eyes of various gradations of light intensity. Such coordination to be carried out directly in the OUMS is problematic not only technologically, but also physically due to different materials, the difference in thickness and other parameters of the FP layers and the LC layer. It is also difficult to implement such an OUMS with a sufficiently large and uniform aperture (in terms of optical and electrical properties).

The closest in technical essence (prototype) to the claimed device is an adaptive light protection filter [2] containing an analog light modulator, a measuring photodetector and a processor unit, the input of which is connected to the output of the measuring photodetector, the output of the processor unit is connected to the control input of an analog light modulator, when the input of the measuring photodetector is the control input of the device, the aperture input of the analog light modulator is the information input of the device, the output The aperture of the analog light modulator is connected to the input of the protected photosensitive sensor.

The known device uses an electrically controlled analog (grayscale) light modulator, in which a multi-gradation change in the optical transmittance is carried out under the influence of an external control electric signal with the desired number of gradations of amplitude. The required law of intensity change at the output of the device (at the input of the protected photosensitive sensor) is implemented by setting the corresponding transition characteristic of the processor unit, which can have any physically feasible form in the case of, for example, a digital electronic processor unit. The aperture size of an analog light modulator, for example, made in the form of an LCD modulator with matrix electric addressing, can be any within the limits corresponding to the aperture size limits of standard LCD displays while ensuring a high degree of uniformity of optical properties along the aperture of the light modulator.

A disadvantage of the known device is the impossibility of providing optical protection from interfering short intense light pulses while simultaneously enabling the external scene to be perceived uninterruptedly through the aperture of an analog light modulator, since short-term adaptation to interfering light pulses leads to a temporary loss of the function of adapting the device to the average value of light intensity from the scene.

In addition, the known device cannot provide a correct light-shielding function when the object protected from light is an optical module, consisting, for example, of an information indicator (in particular, a display) and the eyes of an observer perceiving information from the display screen. Short-term sharp dimming of the analog light modulator during adaptation of the device to interfering light pulses leads to a deterioration in the ability of the eyes to correctly perceive information from the display screen, since the light sensitivity of the eyes increases sharply in dark conditions, and the brightness of the display becomes excessive for the correct perception of information during such dimming.

The problem to be solved is the expansion of the device’s functionality by providing protection from interfering intense short light pulses while maintaining the adaptation function of the device to the average light intensity from the scene while expanding the class of objects protected from light.

SUMMARY OF THE INVENTION

The task in an adaptive light-protective filter containing a light modulator, a measuring photodetector and a processor unit, the output of which is connected to the control input of the light modulator, the input of the processor unit is connected to the output of the measuring photodetector, the aperture of which is the control input of the device, the input aperture of the light modulator is the information input of the device and the output aperture of the light modulator is the output of the device optically coupled to the input of the protected optical module, p the light modulator is binary, the operating cycle of the device is divided into operating intervals, the duration of each of which is equal to the sum of times τ ₁ + τ ₂ where τ ₁ and τ ₂ are the residence times of the binary light modulator in open and closed states, respectively, and the ratio τ ₁ / (τ ₁ + τ ₂ ) determines the average optical transmission over the operating interval between the input and output of the device, while the phase of the binary light modulator in the closed state has the possibility of changing within the operating interval.

In the case when the protected optical module is a photosensitive sensor (observer's eyes), the frequency of repetition of the working intervals is selected not less than the critical averaging frequency f _sensor for the protected photosensitive sensor (not less than the lower frequency f _{flicker of} flicker of light for the eyes).

The technical result in the form of improving light-shielding properties by blocking interfering short pulses of light coming from the scene is achieved by implementing a closed state in the binary light modulator during each operating interval, and the phase of implementation of the closed state coincides with the phase of the appearance of interfering short pulses of light from the scene . In this case, the average optical transmittance of the binary optical modulator (between the input and output of the device) is stored, which ensures the preservation of the adaptation function of the device to the average value of the light intensity from the scene.

When the optical module protected from light is a photosensitive sensor (eyes) together with an information indicator (display), then in the corresponding particular embodiment of the device, the lifetime of the closed binary light modulator is chosen no less than the time the information was displayed in the information indicator (display). The advantage of such a private variant of the device is the provision of comfortable conditions for the eyes to read information from the display screen, since at the time the image appears on the screen, all the light from the scene, including interfering light pulses, is blocked by the closed state of the binary light modulator, therefore the same display brightness remains optimal as when blocking interfering pulses of light, and in their absence.

List of figures

Figure 1 - structural diagram of an adaptive filter to protect the photosensitive sensor (eye of the observer).

Figure 2 - diagrams of two states of optical transmission of a binary light modulator during the working interval.

Figure 3 is a structural diagram of an adaptive filter for simultaneously protecting the eyes of the observer and the display screen.

Figure 4 - synchronization phase closed state of the binary light modulator with the arrival phase of the interfering light pulse from the scene.

The implementation of the invention

The adaptive light-protective filter (Fig. 1) contains a binary light modulator 1 (with two possible states of optical transmission, which correspond to the open and closed states of the binary light modulator 1), a measuring photodetector 2 and a processor unit 3, the measuring input of which is connected to the output of the measuring photodetector 2 The output of the processor unit 3 is connected to the control input of the binary light modulator 1, the input aperture of which is the information input of the device, the output aperture of the binary modulator 1 is a light output device optically conjugate with the entrance of the protected optical module, specifically designed as a light-sensitive sensor 4, the control input of the measuring device is a photodetector aperture 2. The working cycle of the device is divided into working intervals, the duration τ _work of each of which is the sum of the time τ ₁ and τ ₂ finding light modulator 1, respectively in the open and closed states _(work τ = τ ₁ + τ _2), wherein the ratio τ ₁ / (τ ₁ + τ ₂₎ determines the average value for the optical operating range a transmission device (determined by the average optical transmittance binary light modulator 1), and repetition frequency of f _work working intervals (f _work = 1 / τ _work) is selected not lower than the critical frequency f _sensor averaging (f _work ≥f _sensor) for the protected photosensitive sensor 4 The _closed phase of the closed state of the binary light modulator 1 has the ability to change within the working interval (figure 2). In the working interval, the reference phase φ _closed state of the binary light modulator 1 corresponds to the reference center of the closed state, presented in angular units (degrees), where the phases corresponding to the beginning and end of the interval are taken equal to 0 ° and 180 °, respectively. The minimum and maximum levels of the binary signal in the diagrams indicate, respectively, the closed state (with minimum optical transmittance) and the open state (with maximum optical transmittance) of the binary light modulator 1. In order to identify the position of the center of the closed state of the binary light modulator 1, the optical transmittance (outside the limits of the working interval of duration τ _work ) of the optical transmittance is indicated on the diagrams, while only the optical transmittance indicated by solid straight lines within the operating interval is physically realized.

In particular, when the eyes of the observer to be protected 4 are the eyes of the observer, the critical averaging frequency f _sensor is the lowest _flicker frequency f _{flicker of} flicker of light for the observer’s vision (f _flicker value is 100-200 Hz depending on the observation conditions).

When the protected optical module is a photosensitive sensor 4 (eyes) together with an information indicator, specifically, a display 6 (Fig. 3), the screen of which is optically coupled to the input of the photosensitive sensor 4, then in the corresponding particular embodiment of the device, the time τ _{closed for the} existence of a closed state binary light modulator 1 is selected not less than the time τ _display information display (τ _display ≤τ _close ) on the display screen 6. The processor unit 3 in a particular embodiment is equipped with an input I _sync external synchronization isations. An alternative information indicator is, in particular, a mnemonic indicator (for example, an LED matrix of information symbols).

Adaptive light filter works as follows. When the protected photosensitive sensor 4 is the eyes (Fig. 1), and light 5 with the intensity J ₀ enters the input aperture of the binary light modulator 1 and the aperture of the measuring photodetector 2, the signal from the output of the measuring photodetector 2 is sent to the measuring input of the processor unit 3, which generates a control signal supplied to the control input of the binary light modulator 1. Binary light modulator 1 is for a time τ ₁ in the open state and for a time τ ₂ in the closed state. This sets the total duration τ ₁ in the general case for a pair of information pulses of light (one passes earlier and the other after the blocking interval of duration τ ₂ , if the latter is not at the ends of the working interval) passing through the binary light modulator 1 in each working interval to the input of the protected photosensitive sensor 4 (for example, into the eyes of the observer of scene 5). Since the frequency f _{work of} following the working intervals is chosen not lower than the critical frequency f _{flicker of the} flicker of light for the eyes, the observer’s vision will perceive the sequence of information light pulses as continuous light with intensity J ₀ times the coefficient τ ₁ / (τ ₁ + τ ₂ ) transmission. The transmission coefficient and the transfer characteristic of the processor unit 3 are selected such that the value of the attenuated intensity J ₀ τ ₁ / (τ ₁ + τ ₂ ) of the light entering the eyes from scene 5 is comfortable for the observer to see. When the light intensity J ₀ changes from scene 5, the duration τ _{1 of the} closed state automatically changes with a constant duration τ _{work of the} working interval (with a constant sum τ ₁ + τ ₂ ), which ensures a constant average level of intensity J ₀ τ ₁ / (τ ₁ + τ ₂ ) of light reaching the eye.

Thus, to protect the photosensitive sensor (eye), adaptive optical pulse-width (PWM) modulation is implemented by the binary light modulator 1.

In the presence of interfering short intense pulses of light coming from scene 5, the phase φ _{closed of a} closed state with a duration of τ ₂ in each working interval is chosen equal to the phase φ _{pulse of the} appearance of interfering light pulses (figure 2). In this case, the closed state of the binary modulator 1 appears synchronously with the appearance of interfering light pulses, ensuring their maximum attenuation without affecting the average optical transmittance of the binary light modulator 1. Thus, when the interfering light pulses are completely blocked, the average value for the working interval, J ₀ τ ₁ (τ ₁ + τ ₂ ) of the light intensity entering the observer’s eyes, is maintained.

Detection of interfering light pulses from scene 5 in order to determine the phase of their arrival is carried out, for example, by differentiating the signal from the measuring photodetector 2, which is performed by the processor unit 3. By choosing the differentiation time constant and the sensitivity threshold to the amplitude of the differentiated signal (to the value of its derivative) selection parameters of the pulsed component of the signal from the measuring photodetector 2.

As a result, a technical result is achieved in the form of improving the light-shielding properties of the device by blocking interfering light pulses (due to synchronization of the phase φ _{closed of the} closed state of the light modulator 1 with the phase φ _{pulse of the} arrival of the light pulse) while maintaining the adaptation of the device to the average value of light intensity from scene 5 (after the expense of maintaining the constant ratio τ ₂ / τ ₁ between the durations of the closed and open states of the light modulator 1 due to the invariability of the duration τ _work = τ ₁ + τ ₂ working intervals).

A feature of the operation of a private embodiment of the device (Fig. 3) is that the protected optical module consists of a photosensitive sensor (eyes) 4 and an information indicator made in the form of a display 6, from the screen of which the eyes perceive the luminous flux of the image under conditions when in the eyes and a display screen 6 receives the adjusted intensity modulator binary 1 luminous flux of light from the scene 5. The phase advance φ _closed closed state binary light modulator 1 corresponds to the phase of formation φ _display depicted I on the display 6. When the duration τ ₃ active state of the information indicator (duration of the picture appears on the display screen 6) selected is no longer than the duration τ _closed closed state binary light modulator 1 (τ ₃ ≤τ _closed), during the existence of the light flux of the image on the display screen 6, the light from scene 5 will not pass to the eyes and to the display screen 6 (it will be completely blocked by the binary light modulator 1). This makes it possible for the observer to successfully read the image from the display screen 6 at a normal level of screen brightness, even when a high-intensity light stream (for example, direct sunlight) arrives from scene 5.

If the electronics of the processor unit 3 and the electronics of the display 6 are not equipped with a single master oscillator, then the required phase synchronization is carried out, for example, by applying an external synchronization of the processor unit 3 to the I _sync input of the corresponding sync pulse (for example, due to the optoelectronic coupling between the external sync input I _sync and display screen 6).

An additional advantage of the private version of the device is its noise immunity from spurious interference of light fluxes in the case of simultaneous independent operation of several adaptive optical filters (ASF). Indeed, since during each working interval the display screen 6 creates the luminous flux of the image only when the binary light modulator 1 is in the closed state (in accordance with the condition τ _close ≥τ _display ), the luminous flux of the image from the screen of this display 6 does not go outside from the ASF (does not appear from the input aperture of the binary modulator 1 of the light that is part of this ASF). When two or more observers equipped with such individual ASFs are facing each other, each of them can see the faces of other observers, but for him they are not visible - blocked - light streams of images from screens of extraneous displays. If the light output of each display were not blocked by the corresponding binary modulator of the corresponding ASF, then each observer would see, for example, interfering flickering glare on the faces of other observers. As a result, each observer has the opportunity to observe both the faces of other observers and the luminous flux of the image from the screen of his display without spurious interference (interference) from the luminous flux of images from the screens of extraneous displays.

Industrial applicability

The binary light modulator 1 can be performed, for example, based on the MEMOMI (MEMory Optical Interference Mode) liquid crystal structure [3], which has two optical states when controlling a pulsed control voltage. Another embodiment of the light modulator is on ferroelectric (ferroelectric) structures [4], characterized by very high speed (tens of microseconds).

An adaptive light-protective filter can be made, for example, as part of a protective glass in helmets, pilot glasses or in the glasses of cabins, portholes in the cabs of vehicles.

Literature

1. Efron U Wu S.T., Hsu T.Y., Schoenmakers W. Liquid crystal light valve goggles for eye protection. - US Patent No. 5,081,542, G02F 1/133, publication date 01/14/1992.

2. Russel J.P., Russel T.J. Controllable, variable transmissivity eyewear. - US Patent No. 4,968,127, G02C 7/10, publication date 11/06/1990 (prototype).

3. Brezhnev V.A., Ezhov V.A., Studentsov S.A., Simonenko G.V. Passive-matrix LCD display and its control method. - RF patent No. 2206914, G02F 1/1337, G09G 3/36, priority 24.04.2001.

4. Andreev AL, Ezhov VA, Kompanets IN, Sobolev AG Fast LC Devices with Lowest Control Voltage. Proc. 17 ^th International Display Workshops (IDW'10), Fukuoka, Japan, 1-3 December 2010, pp. 1811-1812.

Claims (1)

An adaptive light-protective filter containing a light modulator, a measuring photodetector and a processor unit, the output of which is connected to the control input of the light modulator, the measuring input of the processor unit is connected to the output of the measuring photodetector, the aperture of which is the control input of the device, the input aperture of the light modulator is the information input of the device, and the output aperture of the light modulator is the output of the device, characterized in that the light modulator is binary, the duty cycle of oystva divided into working intervals, the duration of each of which is the sum of τ ₁ + τ _2, where τ ₁ and τ ₂ - Times finding binary light modulator, respectively in the open and closed states, and the ratio τ ₁ / (τ ₁ + τ ₂₎ determines the average optical transmission between the input and output of the device over the operating interval, while the phase of the binary light modulator in the closed state has the possibility of changing within the operating interval.

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