JPS63206684A - Apparatus for measuring speed of projectile - Google Patents

Abstract

PURPOSE:To measure the flying speed of a projectile with high accuracy without receiving restriction of the Radio Law, by measuring the flying speed of the projectile by applying optical Doppler effect. CONSTITUTION:A beam expander 9 magnifies the laser beam emitted from a laser oscillator 8 in required magnifying power and a semipermeable mirror 10 splits said laser beam into reference beam R and sample beam S. Two total reflection mirrors 11a irradiate a projectile 2 with both beams R, S so as to cross said beams on the surface of the projectile 2. The total reflection mirror 11b is allowed to coincide with a reference axis at the center thereof and receives the scattering beams generated when both beams R, S are reflected from the projectile 2 at a required effective caliber to send the same to a beam detector 14. Subsequently, the output signal of the beam detector 14 is amplified by an amplifier 15 and a frequency memory device 16 instantaneously stores the frequency thereof. A frequency tracking device 17 calculates the flying speed of the projectile 2 on the basis of the signal from the frequency memory device 16. A voltage control oscillator 18 attains to shorten a searching time by manually setting the Doppler frequency corresponding to the preliminarily estimated speed of the projectile 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for measuring the velocity of a bullet fired from an anti-aircraft gun or the like. In general, in order to increase the accuracy of shots fired by anti-aircraft guns, the initial velocity of a bullet fired from an anti-aircraft gun is often measured and fed back to a fire control device. To achieve this purpose, a device for determining the velocity of a bullet using the Doppler effect of microwaves was developed.
It is put into practical use.

[Conventional technology]

Figure 2 shows a schematic diagram of a conventional bullet velocity measuring device that utilizes the Doppler effect of microwaves.
1) is the other part, (2) is the bullet, (3I is the parabolic antenna, (41 is the transceiver, (51 is the frequency measuring device).

161 is a firing control device. The Doppler frequency fd obtained in FIG. 2 is expressed by the well-known equation.

v fd ==-7-CO8θ fl+here λ: microwave growth θ: Center axis of parabolic antenna and bullet The angle formed by the central axis of V2 bullet speed It is.

As is clear from equation (1), the Doppler frequency fd is determined by the constant λ and the angle θ, so in order to improve measurement accuracy, it is necessary to accurately know the value of θ.

In order to set θ accurately, it is desirable to select θ = θ° or θ = 90°, but θ = 0° cannot be selected in practice, and θ = 90° will result in COS θ = 0. Therefore, this cannot be selected either. Therefore, in practice, θ is.

Although θ is often set to a value as close as possible to 0°, it is difficult to set the above value of θ accurately in actual battlefields, etc., and this is a major factor that reduces the measurement accuracy of this method. It has become.

[The balance that the invention attempts to solve]

The conventional bullet velocity measuring device is constructed as shown above, but the cross section of the bullet y (
Cross 5ection) is generally small and therefore requires a high antenna gain, which also has the disadvantage of increasing the size of the device. Furthermore, since electromagnetic waves such as microwaves are subject to restrictions under the Radio Law, there is a problem that even if there is a desirable wavelength range from the viewpoint of improving accuracy and reducing size and weight, it is not possible to arbitrarily select it.

[Means for solving problems]

This invention was made to solve the above-mentioned problems, and uses a laser device that generates coherent light instead of microwaves.

[Effect]

The bullet velocity measuring device according to the present invention uses a laser device and applies the optical Doppler effect to measure the bullet velocity.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, (7) is a laser device, (81 is a laser oscillator, (91 is a beam expander, and an is a semi-transparent mirror.

(11a) and (11b) are total reflection mirrors, aZ is an optical glass window, 3 is an aperture, (141 is a photodetector, t
tS is an amplifier, ae is an 8-wavenumber memory, an is a frequency tracker, aFj is a voltage controlled oscillator, and +19 is a collimator. Laser light has excellent coherent properties, so
Split the laser beam from laser oscillator +81 into two [
Here, one is called the reference light (hereinafter referred to as R light) and the other is referred to as sample light (hereinafter referred to as 8 elements)], and when the above S light and R light are crossed by an appropriate means, light interference occurs. It is known that fringes occur at the intersection. The distance g between the fringes can be calculated from the following equation based on the interference of the two beams at equal inclination angles.

Here.

λ: wavelength of laser light y: Angle between R light and S light It is.

If the object to be measured is located at the intersection, the scattered light will be strong when the object is in the bright part of the fringe.

Furthermore, the scattered light is weak when it is in the dark part of the fringe.

Therefore, for the sake of simplicity, if the object to be measured vertically crosses the fringe at a velocity V, the scattered light becomes a signal with a frequency fd expressed by the ninth order equation, and this is the Doppler frequency fd of the light.
It is.

fd=ヱ= ”'s in L131 g λ 2 (As is clear from equation 31, fd is determined by the constant λ and the optical arrangement. It is determined only by the intersection angle y of the R light and the S light. In addition, since λ is very short compared to the microwave wavelength, the Doppler frequency fd/d becomes large, which is advantageous in terms of product 1) accuracy.Laser oscillator +
81 is, for example, a He-Ne gas laser with λ==0.6328 mμ. The beam expander +91 is, for example, an inverted telescope with a magnification of n, and the diameter Dd generated from the laser oscillator (8)
The laser beam is expanded into a parallel beam with a diameter of nDd. The semi-transparent mirror shaft is parallel to the reference axis indicated by the dashed line Vc1, and divides the expanded laser beam into R light and S light. 2
The total reflection mirrors (11a) are placed in axially symmetrical positions with respect to the reference axis, and the center of the intersection of the R light and the S light is 2 on the reference axis.
Distance from the center of the total reflection mirrors (Ha)! It is set to appear at

In other words, the distance between the centers of the two total reflection mirrors (11a) is a
As.

ヱ = tan-1(-) (41).

Total reflection d (11b) has its center aligned with the reference axis, and each scattered light when the R light and S light are reflected by the bullet (21) is received with a required effective aperture and sent to the photodetector a4. The aperture αJ is inserted into the front surface of the photodetector (141) so that the output signal fdO8/N of the photodetector I is optimized, but its diameter is generally selected experimentally. A4 converts the received light into an electrical signal using, for example, a photomultiplier tube.The optical glass window side is pushed in perpendicularly to the reference axis, and the S/N and Q values of the signal are the required values, and the distance is as described above. Even if l fluctuates by a prescribed ±Δ!, the frequency deviation 1±Δfd of the above-mentioned signal has a relationship such that the S/N and Q values maintain the required values.Amplifier a9 is a photodetector. The output signal of the device a4 is amplified by the required amplification degree.The frequency storage device We instantly stores the above frequency.The frequency tracker ([71 is the above 8 wave number storage device + 161
The velocity V of one bullet (2) is calculated by tracking the fd of formula 31 using the signal.The voltage controlled oscillator is 6 seconds long.

Although it is a component of the frequency tracker +171, it has a primary function in this invention. In other words, in general, when trying to track (search) the Doppler frequency from the part corresponding to zero velocity, the system response time requires a time on the order of 101] ms.
By manually setting the Doppler frequency fdo corresponding to the speed of 1, the above-mentioned tracking (search) time is reduced. The collimator a9 is used to set the central axis of the bullet (21) and the above-mentioned reference axis at a required angle 9, for example 90°.

〔Effect of the invention〕

As described above, according to the present invention, when measuring the velocity of one bullet (2), it is possible to use a compact and weighing device, and it is not subject to restrictions under the Radio Law, and it is possible to measure with high accuracy, and its effects are as follows. big.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an embodiment of the present invention. FIG. 2 shows a schematic diagram of a conventional bullet velocity measuring device that utilizes the Doppler effect of microwaves. 0) is i item, (21 is bullet, (3) is parabolic antenna, 14) is transceiver, (5) is frequency measuring device, (6) is fire control device, 17) is laser device, (8I is laser Oscillator, (9) is beam expander, no is semi-transparent mirror e (1
1a), (11b), the total reflection mirror a3 is an optical glass window,
α3 is an aperture, aa is a photodetector, (Is is an amplifier, tte is a frequency storage device, αD is a frequency tracker, ``Gate'' is a voltage controlled oscillator, +19 is a collimator. In the figures, the same symbols are the same or A considerable portion is shown.

Claims (1)

[Claims] a laser oscillator that generates coherent light; an enlarging means for enlarging the laser beam irradiated from the laser oscillator by a required magnification; and a dividing means for dividing the laser beam enlarged by the enlarging means into a reference beam and a sample beam. , an irradiation means for irradiating the reference light and the sample light so as to intersect on the surface of the object to be measured; a variable setting means for variably setting the angle; a light receiving means for receiving each scattered light when the reference light and the sample light are reflected by the object to be measured with a required aperture diameter on the reference axis; a setting means for setting an effective light-receiving solid angle or an effective light-receiving area in a rear optical path; an optical glass window arranged perpendicular to the reference axis to isolate the optical system from outside air; and a frequency proportional to the speed of the object to be measured. A laser having a calculation means for processing a signal to calculate the speed, a storage means for instantly storing the frequency signal, and a setting means for setting a frequency signal corresponding to the predicted speed of the object to be measured. 1. A bullet velocity measuring device comprising: a device; and a collimator that collimates a reference axis of the laser device to a central axis in the traveling direction of the object to be measured at a predetermined angle.