RU2688904C1 - Optical signal receiver - Google Patents

Abstract

FIELD: optics.SUBSTANCE: invention relates to reception of optical radiation and to a receiver of optical signals. Receiver includes a photosensitive element, a signal processing circuit and an optical gate mounted in front of the photosensitive element. Optical gate is made in the form of a shutter with two working positions. Device incorporates a shutter drive incorporating a flat spring closed in the form of a ring with diametrically opposite sides tightened by tensioning with a force determined by the specified speed of the shutter drive. Shutter is connected to the spring by means of a transfer link so that when changing the stretching length the shutter moves to the specified distance between the initial and working positions. Stretching is a current-conducting thread, to ends of which there is an external source of control electric signal, at supply of which tension is heated, and its length increases due to temperature expansion.EFFECT: providing operability of the device under active and passive laser countermeasures with minimum dimensions and maximum sensitivity at low level of signals.5 cl, 3 dwg

Description

The invention relates to the technique of receiving pulsed optical radiation, mainly to receivers of pulsed laser range finders and other light-emitting devices.

Known receivers of optical signals [1] for systems of pulsed laser location, designed to convert into electrical signals reflected by remote objects of the probe pulses of laser radiation and the timing of electrical pulses to determine their delay τ relative to the moment of radiation of the laser probe pulse. This delay is used to judge the distance R to a reflecting object using the formula R = сτ / 2, where c is the speed of light. Optical signals receivers [2-3] are constructed in a similar way, containing a photosensitive element and a signal processing circuit. These devices have a limited dynamic range that prevents the use of such receivers in range meters and other equipment with increased accuracy requirements. There are a number of technical solutions aimed at expanding the dynamic range and improving the accuracy of temporal fixation of received signals [4-5]. However, these solutions do not ensure the performance of the receiver if the energy of the input radiation exceeds the level of radiation resistance of the photosensitive element.

The closest in technical essence of the present invention is an optical signal receiver containing a photosensitive element, a signal processing circuit, a beam splitter, a photosensor, a delay device and an optical shutter mounted in front of the photosensitive element [6]. In this receiver, the optical shutter does not open if the signal from the photo sensor exceeds the threshold value corresponding to the input radiation level exceeding the radiation resistance threshold of the photosensitive element. Otherwise, the shutter opens and the input radiation enters the photosensitive element. The delay time of the signal in the delay line must exceed the response time of the gate to the control pulse from the photo sensor. Thus, the device ensures functioning not only in the working dynamic range of the reflected signals, but also beyond its limits - in conditions of high-energy input signals.

The disadvantage of the receiver [6] is the radiation losses in the beam splitter, the delay device and the optical shutter, as well as the shutter speed limitations, which increase the signal delay in the delay device. This, in turn, leads to losses in the receiving path, distortion of the shape of the received signal, an increase in the dimensions of the device, especially due to the beam splitter, the delay device and the optical shutter.

The objective of the invention is to ensure the health of the receiver of optical signals for high-energy input signals and the highest sensitivity for weak input signals with minimum dimensions of the device and its maximum performance and reliability.

This problem is solved due to the fact that in a known optical signal receiver containing a photosensitive element, a signal processing circuit and an optical shutter installed in front of the photosensitive element, the optical shutter is designed as a shutter with two working positions, and a curtain drive is inserted into the device, including a flat spring, closed in the form of a ring, the diametrically opposite sides of which are stretched by a stretch with a force F defined by a given shutter speed and the shutter is connected to the springs using the transmission link so that when the length of the stretch changes by Δc, the shutter moves a predetermined distance S between the initial and working positions, in the initial position the shutter overlaps the photosensitive element, and in the working position is outside its field of view, and the stretch is conductive thread, to the ends of which an external source of the control electrical signal is connected, at the supply of which thermal expansion of the stretching from its heating by flowing electric current It leaves the value Δs.

The transmission link may be a fixed fastening element of the shutter to the side of the spring perpendicular to the direction of stretching, while the opposite side of the spring from the shutter is attached to the receiver body.

The transmission link can be a swinging arm, one shoulder of which length L ₁ is connected with a spring, and the second one with length L ₂ - with a shutter, while the stroke of the shutter

The flat spring can be formed in the form of an oval, a larger diameter d _{1 of} which is oriented in the direction of stretching, and a smaller d ₂ in the direction of the curtain stroke, which is attached to the spring on one side of the diameter d ₂ .

где Е_фпу - энергетическая чувствительность приемника; E_min - минимальная энергия высокоэнергетического сигнала поступающего на фоточувствительный элемент; E_max - максимальная энергия высокоэнергетического сигнала; Е_пду - предельно допустимый уровень энергии сигнала, поступающего на фоточувствительный элемент.The shutter can be made translucent with a transmittance τ that meets the condition

where E _fpu - energy sensitivity of the receiver; E _min - the minimum energy of the high-energy signal entering the photosensitive element; E _max - the maximum energy of the high-energy signal; E _{remote control} - the maximum allowable energy level of the signal supplied to the photosensitive element.

In FIG. 1 shows a functional diagram of an optical signal receiver. FIG. 2 shows the drive options with a rigid fastening of the shutter to the side surface of the spring. FIG. 3 shows a variant of the drive of the curtain with a transmission link in the form of a swinging arm.

The receiver of optical signals (Fig. 1) consists of a photosensitive element 1 (for example, a photodiode) and a signal processing circuit 2, which includes a preamplifier 3, an amplifier 4 and a driver of the output signal 5, the output of which is the output of the device. In front of the photosensitive element there is a shutter 6 with a drive in the form of an annular spring 7, tightened by an extension 8 connected to the output of a current pulse shaper 9 connected at the output of the logic module 10, one of the inputs of which is connected to the output of the signal processing circuit 2, and the second is its control by the entrance. The device is placed in a sealed enclosure 11, through the optical window of which the received radiation enters the photosensitive element 1. The shutter drive consists of an oval spring 7 and an extension 8 in the form of a conductive thread, to which a control signal is sent from the former 9. One of its sides is spring 7 and the extension is attached to the housing 11. The opposite side of the spring is rigidly, but without electrical contact, is connected to the second end of the extension, connected to the output of the current pulse shaper 9. In one design variant Tork 6 is attached to the side surface of the spring 7 at equal distances from the ends of extensions (Figs. 1, 2). In another embodiment (Fig. 3), the spring on the side of fastening the free end of the stretch is supported on the short arm of the rocker arm 12, and the shutter 6 is attached to the second arm of the rocker arm. Stretching its fixed end is attached directly to the housing 11, and the spring 7 - through the insulating gasket 13.

The device works as follows.

, создаваемой плоской пружиной, шторка перемещается на расстояние Δs, открывая рабочую площадку фоточувствительного элемента. При отключении управляющего сигнала длина растяжки принимает первоначальное значение с, и шторка возвращается в исходное положение, закрывая рабочую площадку фоточувствительного элемента. Если шторка выполнена полупрозрачной, в ее исходном положении фотоприемное устройство может принимать высокоэнергетические сигналы, превышающие уровень номинальной чувствительности ФПУ в 1/τ раз и более без ущерба для фоточувствительного элемента.In the initial state, the translucent curtain 6 is located in front of the working platform of the photosensitive element 1, attenuating the signals arriving at it by 1 / τ times. When applying a control signal to the stretcher from the shaper 9, the stretch heats up under the action of the current flowing through it, and its initial length increases by Δc = αcΔT, where α is the coefficient of thermal expansion, ΔT is the temperature increment. As a result, by force

created by the flat spring, the shutter moves a distance Δs, opening the working platform of the photosensitive element. When the control signal is turned off, the stretch length takes the initial value with, and the shutter returns to its original position, closing the working platform of the photosensitive element. If the shutter is made translucent, in its initial position the photodetector can receive high-energy signals exceeding the level of the FPU nominal sensitivity by 1 / τ times or more without damage to the photosensitive element.

где d_шт - рабочий диаметр полупрозрачного участка шторки; d_фчэ - диаметр рабочей площадки фоточувствительного элемента; а - расстояние от шторки до поверхности фоточувствительного элемента; α - угол зрения фоточувствительного элемента; Δ - погрешность фиксации поперечного положения шторки при отсутствии управляющего сигнала на входе привода. В величину Δ входят как погрешности юстировки, так и температурный уход в диапазоне окружающих температур.To cover the working platform of the photosensitive element with a shutter, the following condition must be met

where d _pcs - the working diameter of the translucent portion of the curtain; d _FCE - diameter of the working area of the photosensitive element; a is the distance from the shutter to the surface of the photosensitive element; α is the angle of view of the photosensitive element; Δ is the error of fixing the lateral position of the shutter in the absence of a control signal at the input of the drive. The value of Δ includes both the alignment errors and the temperature drift in the ambient temperature range.

The shutter attenuation coefficient τ is determined by the expected level of high-energy laser illumination from an external source. The shutter can be made in the form of a transparent plane-parallel plate with a translucent coating applied, for example, by metallization. The thickness of this coating determines the value of τ while maintaining the overall-connecting parameters. If a signal is formed at the output of processing circuit 2 with the translucent shutter closed, this indicates the presence of a high-energy signal at the input of the photosensitive element 3. Then the logic module 10 prevents the passage of the control signal to the driver 9, and the shutter remains in its original state.

For a flat ring spring loaded by a concentrated tensile force, the formula [7] is valid.

Where

Δx is the amount of deformation (compression of the ring) in the direction perpendicular to the direction of the tensile force, mm;

F - stretched load, N;

- средний радиус кольца, мм;

- average radius of the ring, mm;

d ₁ - internal diameter of the ring, mm;

d ₂ - outer diameter of the ring, mm;

E is the modulus of elasticity of the ring material, Pa;

- момент инерции сечения кольца;

- moment of inertia of the ring section;

b - ring width, mm;

- толщина кольца, мм;

- ring thickness, mm;

The tensile strength of nichrome under tension is σ _B = 0.65-0.70 GPa.

Example 1

Nichrome X20H80 GOST 8803-89 solid alloy.

The tensile strength of 0.77 GPA. Adopted specific load σ _before = 0.1 GPA.

Wire diameter 0.1 mm, length 30 mm. The cross-sectional area S _nichr = 0.00785 mm ² = 7.85⋅10 ^-9 m ² . The workload F = σ _before ⋅S _nichr = 0.1⋅7.85 = 0.8 N.

Ring spring - beryllium bronze BrB2, tape. E = 12000 MPa.

Ширина b = 2 мм.d ₂ = 20.1 mm; d ₁ = 19.9 mm. r = 10 mm.

Width b = 2 mm.

According to the formula (1), the initial transverse narrowing of the ring under the action of a longitudinal force F

(фиг. 2).With temperature expansion of the nichrome filament, the ring tends to restore the former shape with a force F. Then, if the total equivalent mass of the ring and the shutter is m, the acceleration of the shutter

(Fig. 2).

Example 2

The mass of the ring in the above notation m _к = 2πr⋅bh⋅ρ, where ρ is the density of the ring material. The density of bronze BrB2 GOST 1789-70 ρ = 8.8 kg / dm ³ . With these data, m _to = 2πr⋅bh⋅ρ = 2π⋅0.1⋅0.02⋅0.001⋅8.8 = 1.1-10 ^-4 kg. Equivalent accelerated mass, taking into account the shutter and rim m ~ 2⋅10 ^-4 kg. Shear force

The acceleration of the curtain

Moving the curtain S = 0.3 mm.

Travel time

Note: curtain 2 × 2 × 0.2, K8 glass GOST 3514-76 with metallization.

Density ρ = 2.51 g / cm ³ . Mass 0.2⋅0.2⋅0.02⋅2.51 = 2⋅10 ^-2 g = 2⋅10 ^-5 kg.

The working temperature of the stretch must significantly exceed the operating temperature range so that the ambient temperature conditions do not have a noticeable effect on the position of the shutter. On the other hand, the stretching temperature should not be too high so as not to subject the stretching to plastic deformations under working load.

Example 3. Stretching - nichrome wire with length = 20 mm. α = 18⋅10 ^-6 1 / deg. Operating temperature range T _exp = 0 ± ΔT _exp . ΔT _exp = 40 ° C.

Moving the curtain S = 0.3 mm (see Example 2). The corresponding required extension of the stretch Δc depends on the design of the transmission link 12 and the spring 7. It is assumed that Δc = S / 2 = 0.15 mm.

Temperature increment stretching

ΔТ = Δс / αс = 0.15 / (18⋅10 ^-6 ⋅20) ~ 420 ° >> ΔT _exp .

The melting point of the alloy X20H80 - T _pl = 1200 ° C >> ΔT.

The energy required to increase the temperature of the stretch, E _ΔT = βmΔТ, where β is the heat capacity of the stretch material; m is the mass of the heated volume.

Объем V_T ~ 2⋅10^-4 см³.Example 4. Conductive Stretch Dimensions

Volume V _T ~ 2⋅10 ^-4 cm ³ .

The density of the alloy X20H80 ρ _T = 7.94 g / cm ³ ; m = ρ _T V _T = 1,6⋅10 ^-6 kg; the heat capacity of nichrome is β = 0.57 J / kgK.

Е _T = βmΔТ = 0.57⋅1.6⋅10 ^-6 ⋅420 = 0.00038 J = 0.38 mJ.

где ρ_R - удельное сопротивление;Nichrome wire resistance

where ρ _R is the resistivity;

c is the length of the stretch; d - wire diameter.

The current pulse with energy E _T through the stretching may be rectangular with duration t _s or exponential during discharge through the stretching of the storage capacitor C _T charged to the voltage U ₀ .

Example 5

ρ _R = 1.01⋅10 ^-6 Om⋅m (Н20Х80 nichrome); c = 0.02 m; d = 0.1⋅10 ^-3 m.

R _T = 2.6 Ohms.

откуда

Ток через растяжку

Rectangular impulse. R _T = 2.6 Ohm; t _s = 5⋅10 ^-4 s; E _T = 0.38 mJ. Energy

from where

Stretching current

Максимальный ток I_max = U₀/R_T = l,3 А.Exponential momentum. The discharge time constant is τ _C ~ t _s / 3 = 0.17 ms. Energy

Maximum current I _max = U ₀ / R _T = l, 3 A.

The described technical solution ensures the safe use of a photo-receiver device as part of any equipment and in any operating conditions. At the same time, the dimensions and mass of the curtain with a drive, as well as the volume of the logic module, allow these nodes to be embedded into existing miniature receivers without changing their sizes. The placement of the protection elements of the receiver as part of its sealed enclosure ensures their reliability, durability and maximum service life.

Thus, the proposed technical solution ensures the performance of the photodetector for high-energy input signals and the highest sensitivity for weak input signals with the minimum dimensions of the device and its maximum speed and reliability.

Information sources

1. V.A. Volokhatyuk and others. "Questions of optical location." - M .: Soviet Radio, Moscow, 1971. - p. 213.

2. V.G. Vilner et al. Analysis of the input circuit of a photodetector with an avalanche photodiode and noise-reduction correction. "Optical-mechanical industry". No. 9, 1981 - with. 593.

3. V.A. Afanasyev et al. Sensitivity threshold of a pulsed optical radiation receiver with high input impedance. Electronic equipment. Series 11. "Laser technology and optoelectronics." 1988, c. 3. - s. 78-83.

4. V.G. Vilner et al. Receiver of pulsed optical signals. The patent of the Russian Federation №2506547.

5. P.M. Borovkov et al. Peculiarities of circuit design of pulsed threshold FPU with a short sensitivity recovery time after exposure to an overload pulse. Applied Physics, No. 1, 2015 - p. 61-65.

6. Radiation receiver with active optical protection system. US patent No 6,548,807 - prototype.

7. B.B. Danilevsky Laboratory work on mechanical engineering technology. M .: Higher School, 1971 - p. 85.

Claims (5)

1. Receiver of optical signals containing a photosensitive element, a signal processing circuit and an optical shutter installed in front of the photosensitive element, characterized in that the optical shutter is made in the form of a curtain with two working positions, and a curtain actuator including a flat spring closed is inserted into the device in the form of a ring, the diametrically opposite sides of which are stretched by a brace with a force F determined by the given speed of the drive of the shutter, and the curtain is connected to the spring by means of a transmission link so that when you change the length of the stretch by the value of Δc, the shutter moves a predetermined distance S between the initial and working positions, in the initial position the shutter overlaps the photosensitive element, and in the working position is outside its field of view, and the stretch is a conductive thread, the ends of which are supplied by an external source of the control electrical signal, at which the thermal expansion of the stretching from its heating by the flowing electric current is applied is Δc. 2. Receiver of optical signals according to claim 1, characterized in that the transmission link is an element of rigid attachment of the shutter to the lateral side of the spring perpendicular to the direction of stretching, while the opposite side of the curtain of the spring is attached to the receiver body. 3. The receiver of optical signals under item 1, characterized in that the transmission link is a swinging beam, one arm of which length L ₁ is connected with the spring, and the second arm of length L ₂ - with the shutter, while the shutter stroke

4. Receiver of optical signals according to claim 1, characterized in that the flat spring is formed in the form of an oval, the larger diameter d _{1 of} which is oriented in the direction of stretching, and the smaller d ₂ - in the direction of the stroke of the curtain, which is attached to the spring on one of the diameter sides d _2. 5. The receiver of optical signals under item 1, characterized in that the shutter is made translucent with a transmittance t corresponding to the condition

where E _fpu - energy sensitivity of the receiver; E _min - the minimum energy of the high-energy signal entering the photosensitive element; E _max - the maximum energy of the high-energy signal; E _{remote control} - the maximum allowable energy level of the signal supplied to the photosensitive element.

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