US1951666A - Device maintaining automatically the frequency of an oscillator - Google Patents

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jm m 5R SUBSTTUTE FOR MiSSlNG )1 March 20, 1934. .H. MARTIN 1,951,666

DEVICE MAINTAINING AUTOMATICALLY THE FREQUEJNGY OF AN OSCILLATOR Filed Jan. 27, 1933 I 7V 2Q 9% g a b I c d e v Fig.4 I l In vet: for:

Patented Mar. 20, 1934 Q i i g UNITED STATES PATENT OFFICE Claims.

I have filed an application in Germany, February 2, 1932.

' When deflected successively by two mirror whose planes of vibration are inclined relatively 6 to each other, a pencil of rays describes one of the known Lissajous figures. The form of the figure depends upon the ratio of the amplitudes and the frequency of the vibrations as well as upon the phase-displacement of the two vibral0 tions relative to each other., A permanent figure 1 ,is obtained, however, only when the ratio of the 1 frequencies represents a fraction of two small even numbers. Otherwise, the figure will assume successively and in a definite order a plurality of forms, the result being a consequent variation of the quantity of energy influencing a definite portion of the surface on which the figure is formed. The fact that the repartition of energy on the said surface is varying with respect to time when the ratio of the frequencies of the two mirrors departs from its prescribed value is made use of by the present invention, which aims at maintaining automatically the frequency of an electric or mechanical oscillator, by making the energy of the rays striking a definite portion of the said surface fallon a receiver sensitive to rays, and by using this receiver for so. influencing one of the two oscillators as to decrease the said variation of the frequency and, consequently, to maintain automatically the frequency of this oscillator. In a device according to the invention, a pencil of rays is reflected, on a mirror that is caused to vibrate by an oscillator of a definite frequency (which is assumed to be kept constant either by itself or by other means), and on a mirror that is made to vibrate by the oscillator to be controlled, the consequence being that subsequently to these two reflections (which may take place in either succession) the pencil of 40 rays describes a Lissajous figure. At the locus of this figureis disposed a receiver sensitive to ceives on account of a variation of the Lissajous rays which, according to the ray energy it re-' figure, influences a source of current in such a- DEVICE MAINTAINING AU'roMATIcALLY i THE FREQUENCY OF AN OSCILLATOR 4 Hans Martin, Jena, Germany, assignor to'firm Carl Zeiss, Jena, Germany Application January 27, 1933, Serial No. 653,828 In Germany February 2, 1932 instance, of a bolometer or a thermo-element. When applying a thermo-element, this element represents the receiver sensitive to light as well as the source of current influenced by it.

The variations of energy influencing the receiver will, as a rule, be too small to influence by themselves an electric device suitable for controlling the oscillator, use therefore being made generally of a relay. However, it is convenient not to influence this relay direct, but to connect the element sensitive to rays to the grid of an electron valve whose anode current (eventually after further amplification) actuates the relay.

The electric device controlling the osjlator may be of any type, and this according to what kind of an oscillator is used. If the oscillator to be controlled is a mechanical oscillator, for instance a tuning fork, the electric device may be an electro-nfig'rfetwhlch permits to damp as well as to alter the form of the tuning fork (and, consequently, to alter also the frequency of this fork).

The accompanying drawing. which illustrates the invention, represents in Figure 1 an example of the forms the Lissajous figures will successively assume in certain circumstances, and in Figure 2 a schematical example of the construction of the device. The form a of the Lissajous figures represented in Figure 1 arises when the ratio of the frequencies is 2:3 and the phase displacement, 0. When the phase displacement is 1/4, 1/2, 31/4 and 1, the forms b, c, d, and e, respectively, are obtained. The ratios 51/4, 31/2, and 71/4 correspond to the forms d, c, and b, respectively. When the ratio of the frequencies is not exactly 2:3, the Lissajous figure successively assumes the forms a, b, c, d, e, d, c, b, a and successively repeats taking these forms. When placing at the locus at which the Lissajous figure is formed a receiver sensitive to rays (as is indicated in Figure 1 by small dash-line circles) that covers only a portion of the surface on which the figure is being formed, this receiver will be differently illuminated, and this in accordance with what form the Lissajous figure assumes in each instance. v

In Figure 2, f is a normal tuning fork vibrating in a vertical plane. A tuning fork to be controlled, which vibrates in a horizontal plane, is designated g. Between the two tuning forks is disposed a converging lens h. A selenium cell is designated 2'. The rays of a source of light A are so reflected on the end surface of the prong i of the tuning fork f as to traverse the lens 17.

. is disposed an iron core 1 surrounded by a coil k.

andtobereflected on the end surface of theprong a of the tuning fork a. As a consequence, the lens 7:. projects an image of the source of light at the locus of the selenium cell i. Next to the prong o, in the plane of vibration of the tuning fork g,

This coil is connected by way of the contact 1 l' of a relay 1 and an adjustable resistance m to a battery n. The anode circuit of an electron valve V .o is connected by way of the coil of the relay 1 to a battery p which also heats the incandescent cathode. The selenium cell i is also connected to the battery p and by means of one of its clamps.

to the grid of the valve.

The device works in the following manner. When the two tuning forks vibrate for instance at a ratio of the frequencies of 2:3, there arises one of the forms of the Lissajous figures illustrated in Figure 1 (or an intermediate figure), for instance form b. In this case the selenium cell i is not struck by the figure, it being assumed that the arrangement.is such..that, when the grid tension obtaining when the selenium cell is not struck by the light, the anode current will not suflice to influence the relay 1. When the ratio is not exactly 2:3, the Lissajous figure will gradually depart from the form b and assume the form c. When the figure assumes the form c completely or approximately, the selenium cell is struck by the figure, and its resistance will be reduced. As a consequence, the tension of the grid alters, and the increasing anode current causes the relay l to act. The relay closes the contact 1 l, and the iron core j is magnetized. The iron core consequently damps the vibrations of the prong a and effects at the same time a slight alteration of the form of the prong, this alteration slightly changing the phase displacement of this prong relative to the prong l as well as the frequency of the said prong 0 When choosing the arrangement accordingly, the Lissajous figure changes from form c to form b, and the original condition is arrived at: The selenium cell is not illuminated, the contact 2 P reopens, and the magnetization of the iron core 1' is interrupted. The strength of the influence the iron core exerts upon the prong a when the contact is closedmaybeadjustedbymeansofthere- I claim:

1. In combination, an oscillator, a mirror connected'to, and adapted to be vibrated by, this oscillator, another oscillator, another mirror, this other mirror being connected to, and adapted to be vibrated by, the said other oscillator, a source of rays, a receiver sensitive to the rays emitted by this source of rays, this receiver being so disposed as to be adapted to receive the rays emanating from the source of rays and successively reflected by the said two mirrors, and an electric device connected to the said receiver and adapted to influence one of the two oscillators.

-2. In a combination according to claim 1, an electron valve, 0. battery connected to this valve,

and means connecting this battery to the said electric device, the said receiver being connected to the grid of the said electron valve.

3. In a combination according to claim 1, an electron valve, 0. batery connected to-this valve, and means connecting this battery to the said electric device, these meanscomprising a relay connected to the said device, the said receiver being connected to the grid of the said electron valve.

ror being connected to, and adapted to be vibrated 5 by, the said other oscillator, a source of rays, a receiver sensitive to the rays emitted by this source of rays, this receiverbeing so disposed asw to be adapted to receive the rays emanating from the source of rays and successively reflected by the said two mirrors, and an electro-magnet connected to the said receiver and adapted to influence the said other oscillator.

5. In combination, two tuning forks, a source of rays, a receiver sensitive to the rays emitted by this source of rays, this receiver being so disposed as to be adapted to receive the rays emanating from the source of rays and successively reflected by the two tuning forks, and an electromagnet connected to the said receiver and adapted to influence one of the two tuning forks.

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