Frequency fine-adjusting apparatus for a piezo-electric oscillator

Abstract

Piezo-electric oscillators are widely used in reference clocks for various apparatus. Prior to use, the oscillation frequency of the piezo-electric oscillators is generally finely adjusted. For this purpose, a frequency fine-adjusting apparatus includes a laser beam generator for emitting a laser beam having a wavelength of 2 .mu.m or less, a target material having a metallic layer, a set of rollers for feeding the target material in the condition in which the metallic layer confronts the main electrode of the piezo-electric oscillator and is spaced a predetermined length from the main electrode, and an optical system for applying the laser beam to the metallic layer. When the laser beam is applied to the metallic layer, part of the metallic layer is vaporized and adheres to the surface of the main electrode, thereby finely adjusting an oscillation frequency of the piezo-electric oscillator.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a frequency fine-adjusting apparatus for a piezo-electric oscillator to be used in reference clocks for various apparatus.

2. Description of the Prior Art

A piezo-electric oscillator in which a single crystal of a crystal or the like is used has an extremely large Q factor which is sufficient to ensure a highly stable performance. Therefore, a high-level technique is required for the fine adjustments of the oscillation frequency. Although various oscillation modes exist in piezo-electric oscillators, a thickness slip mode is generally used. In this thickness slip mode, the oscillation frequency of the piezo-electric oscillator is inversely proportional to the thickness of an oscillating reed. It is known that the oscillation frequency can be lowered by making use of the mass additional effect with respect to a main electrode. Conventionally, the oscillation frequency has been finely adjusted by the use of the mass additional effect.

FIG. 4 depicts the construction of a crystal oscillator, which is one of the piezo-electric oscillators.

Referring to FIG. 4, an oscillating reed 20 is provided with a main electrode 21, which is supported on a holder 24 of a lead terminal 23 by a conductive bonding agent 22 so that the main electrode 21 and the lead terminal 23 may be electrically connected to each other. The lead terminal 23 is guided out of a case 26 through hermetic sealing glass 25. After the oscillation frequency has been finely adjusted, a secondary electrode 27 is formed on a central portion of the main electrode 21.

FIG. 5 depicts the construction of a conventional frequency fine-adjusting apparatus for a crystal oscillator.

As shown in FIG. 5, an oscillating circuit 32 is initially connected to a crystal oscillator 28, the oscillation frequency of which generally varies before the frequency fine-adjustment is carried out. The crystal oscillator 28 is then accommodated in a vacuum container 29. After the vacuum container 29 has been evacuated, the oscillation frequency is read by a counter 33 while silver particles 31 for finely adjusting the frequency are caused to adhere to the main electrode 21 through a mask 30 so that the secondary electrode 27 may be formed on the main electrode 21. When a comparator 34 detects that the oscillation frequency has been lowered to a preset value due to the mass additional effect, the vacuum evaporation is suspended by a shutter 35. In this way, the oscillation frequency is finely adjusted.

The frequency fine-adjusting apparatus employing such a vacuum evaporation method requires a high vacuum of approximately 10.sup.-5 Torr and the costs of vacuum equipment are excessive. Furthermore, the operation efficiency is relatively low due to the batch processing.

Japanese Patent Laid-open Application No. 59-13412 discloses a method of raising the frequency by removing the main electrode using a laser.

In this method, the main electrode for imparting an electric field to an oscillating reed is partially removed, and the area to be removed becomes larger as the frequency is adjusted more accurately. As a result, the electric field to be imparted to the oscillating reed becomes weaker and the equivalent resistance is increased. Furthermore, the amount of frequency adjustment which exerts no influence upon the equivalent resistance is relatively narrow in the range of adjustment and cannot allow the change of frequency after the evaporation. Accordingly, this kind of method is disadvantageous in that the frequency adjustment cannot be achieved satisfactorily.

SUMMARY OF THE INVENTION

Accordingly, the present invention has been developed to substantially eliminate the above discussed disadvantages inherent in the prior art frequency adjusting apparatus for a piezo-electric oscillator, and has as its essential object to provide an improved frequency adjusting apparatus having a large adjustment range, and causing no increase in the equivalent resistance.

Another object of the present invention is to provide a frequency adjusting apparatus of the above-described type which is capable of effecting a continuous operation using equipment which does not require a high vacuum.

In accomplishing these and other objects, a frequency fine-adjusting apparatus according to the present invention includes a laser beam generator for emitting a laser beam having a wavelength of 2 .mu.m or less, a target material having a metallic layer, means for feeding the target material in the condition in which the metallic layer confronts a main electrode of a piezo-electric oscillator and is spaced a predetermined length from the main electrode, and an optical system for applying the laser beam to the metallic layer.

When the laser beam is applied to the metallic layer, part of the metallic layer is vaporized and adheres to the surface of the main electrode, thereby finely adjusting the oscillation frequency of the piezo-electric oscillator.

In another aspect of the present invention, a frequency fine-adjusting apparatus includes a laser beam generator for emitting a laser beam having a wavelength of 2 .mu.m or less, a metal-containing target material, an optical system for applying the laser beam to the target material, and means for rotating the target material.

When the laser beam is applied to the target material, part of the target material is vaporized, is directed to a main electrode of the piezo-electric oscillator by the rotating means and is adhered to the surface of the main electrode.

In the apparatus according to the present invention, the target material is accommodated in a sealed chamber, which is evacuated prior to frequency fine-adjustment. However, the degree of the vacuum inside the sealed chamber is not relatively high.

As described above, according to the present invention, the laser beam is applied to the metal-containing material through a glass window of the sealed chamber so that vaporized material may adhere to the main electrode of the piezo-electric oscillator for the purpose of finely adjusting the oscillation frequency of the oscillator.

Although the apparatus according to the present invention employs a laser beam generator for emitting the laser beam, the main electrode is not removed by the laser beam, unlike in the conventional case. This fact contributes to less deterioration in the equivalent resistance. Furthermore, the range of adjustment is relatively wide, as compared with the conventional evaporation method, and the degree of the vacuum in the sealed chamber is not high, thus enabling a continuous operation.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and features of the present invention will become apparent from the following description taken in conjunction with the preferred embodiment thereof with reference to the accompanying drawings, throughout which like parts are designated by like reference numerals, and wherein:

FIG. 1 is a block diagram of a frequency fine-adjusting apparatus for a piezo-electric oscillator according to a first embodiment of the present invention;

FIG. 2 is an enlarged view of a processing part in the apparatus of FIG. 1;

FIG. 3 is a block diagram of a frequency fine-adjusting apparatus for a piezo-electric oscillator according to a second embodiment of the present invention;

FIG. 4 is a partially sectioned front view of a conventional crystal oscillator; and

FIG. 5 is a block diagram of a conventional frequency fine-adjusting apparatus for the crystal oscillator of FIG. 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, there is shown in FIG. 1 a block diagram of a frequency fine-adjusting apparatus for a piezo-electric oscillator according to a first embodiment of the present invention. The apparatus is provided with a sealed chamber 6 and two sets of a YAG laser beam generator 1 for emitting a laser beam 2, a reflection mirror 3 for reflecting the laser beam 2, and a converging lens 4 for converging the laser beam 2. The sealed chamber 6 is evacuated prior to frequency fine-adjustment so that the internal pressure thereof may be set to 10.sup.-2 Torr. The sealed chamber 6 is provided with two glass windows 5 through which pass the laser beams 2 emitted from the laser beam generators 1. The sealed chamber 6 accommodates two sets of a feed roll 9 for feeding a film 7 having a metallic layer, a take-up roll 10 for winding the film 7, and a plurality of guide rolls 8 for guiding the film 7.

When the oscillation frequency of a piezo-electric oscillator 12 is finely adjusted, the oscillator 12 is initially accommodated in the sealed chamber 6 so that the metallic layer of the film 7 may confront a main electrode of the oscillator 12 and may be spaced a predetermined length therefrom. A laser beam 2 having a wavelength of 1.06 .mu.m is then emitted from each laser beam generator 1. The laser beam 2 is reflected by the reflection mirror 3 and converged by the converging lens 4. Much of the laser beam 2 passes through the glass window 5 and is focused on the film 7. Since the film 7 is continuously fed from the feed roll 9 towards the take-up roll 10, metal vapor 11 vaporized from the metallic layer of the film 7 continuously adheres to the piezo-electric oscillator 12.

The oscillation frequency of the piezo-electric oscillator 12 is measured by a counter 33 through an oscillating circuit 32 and inputted into a comparator 34, in which the oscillation frequency is compared with a predetermined frequency. When the former has reached the latter, two control devices 36 cause respective laser beam generators 1 to stop emitting the laser beams 2 so that the evaporation may be terminated.

In this embodiment, since opposite surfaces of the piezo-electric oscillator 12 are simultaneously subjected to the evaporation, a well-balanced fine adjustment can be achieved.

FIG. 2 particularly depicts the state of evaporation effected in the above-described embodiment.

As shown in FIG. 2, the film 7 consists of a transparent organic film 13 and a metallic layer 14 bonded to each other. The piezo-electric oscillator 12 is provided with an oscillating reed 15 and two main electrodes 16 securely mounted on opposite surfaces of the oscillating reed 15. A secondary electrode 17 is formed on each main electrode 16 by the evaporation when the frequency of the piezo-electric oscillator 12 is finely adjusted. The YAG laser beam 2 passes through the glass window 5 and is applied to the film 7. The organic film 13 permits much of the YAG laser beam 2 to be transmitted therethrough so that the metallic layer 14 is raised in temperature, melted and vaporized. For example, when a laser beam having a pulse width of 200 ns and a pulse energy of 0.4 mJ is applied as the YAG laser beam 2, the secondary electrode 17 is formed by vaporized metallic particles each having a diameter of approximately 2 .mu.m.

FIG. 3 depicts a frequency fine-adjusting apparatus for the piezo-electric oscillator according to a second embodiment of the present invention.

As shown in FIG. 3, a sealed chamber 6 accommodates a metal-containing target material 18, and a mechanism 19 for rotating the target material 18.

A laser beam 2 having a wavelength of 1.06 .mu.m emitted from a laser beam generator 1 is directed to a converging lens 4 by a reflection mirror 3. A glass window 5 transmits therethrough much of the laser beam 2, which is then focused on the target material 18. The target material on which the laser beam 2 is applied is raised in temperature, melted and vaporized. As a result, vaporized metal 11 is caused to adhere to a main electrode of a piezo-electric oscillator 12. In this embodiment, the laser beam 2 is applied to the target material 18 while the target material 18 is being rotated by the mechanism 19. Accordingly, the amount of vaporized metal 11 and the direction thereof can be desirably controlled.

It is to be noted that the oscillation frequency can be measured using the same system as in the first embodiment.

As is clear from the foregoing description, according to the present invention, the oscillation frequency of a piezo-electric oscillator can be finely adjusted by applying a laser beam to a target material from the outside of relatively low-vacuum equipment so that vaporized material may adhere to the surface of a main electrode. The apparatus according to the present invention can extend the range of adjustment and makes it possible to perform the continuous operation without any deterioration in the equivalent resistance.

Although the present invention has been fully described by way of examples with reference to the accompanying drawings, it is to be noted here that various changes and modifications will be apparent to those skilled in the art. Therefore, unless such changes and modifications otherwise depart from the spirit and scope of the present invention, they should be construed as being included therein.

Claims

1. A frequency fine-adjusting apparatus for a piezo-electric oscillator having at least one main electrode, said apparatus comprising:

at least one laser beam generator for emitting a laser beam having a wavelength of 2 .mu.m or less;

at least one target material having a metallic layer;

a target material feed means for feeding said target material relative to the piezo-electric oscillator in a condition in which said metallic layer confronts the main electrode of the piezo-electric oscillator and is spaced a predetermined length from the main electrode; and

at least one optical system for applying said laser beam to said metallic layer;

whereby, when said laser beam is applied to said metallic layer, part of said metallic layer is vaporized and adheres to a surface of the main electrode, thereby finely adjusting an oscillation frequency of the piezo-electric oscillator.

2. The apparatus according to claim 1 further comprising a sealed chamber for accommodating said target material and said target material feed means, wherein said sealed chamber is evacuated prior to frequency fine-adjustment.

3. The apparatus according to claim 1, wherein said target material includes a transparent film.

4. The apparatus according to claim 1, wherein said target material feed means comprises a feed roller and a take-up roller.

5. The apparatus according to claim 1, wherein the piezo-electric oscillator is provided with two main electrodes on opposite sides thereof and the apparatus includes two sets of said laser beam generator, said target material, said target material feed means, and said optical system so that vaporized material adheres to both said main electrodes.

6. A frequency fine-adjusting apparatus for a piezo-electric oscillator, comprising:

a laser beam generator for emitting a laser beam having a wavelength of 2 .mu.m or less;

a metal-containing target material;

an optical system for applying said laser beam to said target material; and

means for rotating said target material

whereby, when said laser beam is applied to said target material, part of said target material is vaporized and directed to a main electrode of the piezo-electric oscillator by said rotating means and adheres to a surface of the main electrode, thereby finely adjusting an oscillation frequency of the piezo-electric oscillator.