JPH046425A - Wave-surface detecting apparatus using phase interference - Google Patents

Abstract

PURPOSE:To make it possible to improve compensation accuracy and to enhance light beam condensing efficiency by leading out reference light from light under observation. CONSTITUTION:The light emitted from a laser oscillator 1 is reflected from a primary reflecting mirror 2. The diameter of the laser beam is expanded. The light is condensed on a target T through a variable-shape mirror 3. The light reflected from the target T is condensed in the reverse path. The reflected light is taken out with a directional half mirror 4. The small part of the reflected light is extracted with a compact mirror 5. After the light is amplified by a laser amplifier 6, the diameter of the beam is expanded with a beam expander (collimator) 7, and the reference light is obtained. The interference pattern between the reference light and light under observation is detected by a detector (interference observing device) 8. The driving amount of the variable mirror 3 is determined with a control device 9 based on the relative phase information. Even if the light under observation is propagated along a long distance, the difference between the reference light and the length of the light path can be kept within the coherent length of the laser oscillator 1. The compensation accurace is largely improved. As a result, the light-beam condensing efficiency can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a wavefront detection device applied to optical compensation for long-distance laser transmission.

[Prior Art] In order to detect the wavefront of coherent light in a long-distance optical communication device or the like, the phenomenon of interference between observation light and reference light is used. Conventionally, reference light has been formed by dividing the output of a laser oscillator using a beam splitter.

[Problems to be Solved by the Invention] In order to observe the interference phenomenon of two laser beams, it is necessary that the phases of the two laser beams are aligned. The output of a real laser oscillator has slight fluctuations in the wavelength (phase) of the laser beam, so in order to actually observe interference, the difference between the optical path length of the observed light and the reference destination must be determined by the coherent length of the laser oscillator. Must be within

In the conventional method, since the reference light is taken out at the output of the laser oscillator, it is difficult to perform long-distance optical transmission and match the optical path length with the light reflected back from the target. Furthermore, in the case of a moving target, interference cannot be observed because the wavelength changes due to the Doppler effect.

[Means and effects for solving the problems] The present invention is characterized in that the reference light is derived from the observed light in order to eliminate the above-mentioned drawbacks.

As a result, even if the observed light is light that has propagated over a long distance,
It becomes possible to keep the difference in optical path length from the reference light within the coherent length of the laser oscillator.

A beam sampling device is used to extract the reference light from the observed light. This can be, for example, a small mirror. A collimator is required to adjust the diameter of the extracted beam and obtain a reference beam with a well-defined wavefront.

A laser amplifier is required to coherently amplify the extracted beam and obtain a reference beam of sufficient intensity.

[Embodiment] To explain the embodiment in FIG. do. The light reflected by the target T is collected in the opposite path, and the reflected light is taken out by the mirror 4.

A small portion of the reflected light is extracted by a small mirror 5, amplified by a laser amplifier 6, and then transferred to a beam expander (collimator) 7.
Expand the beam diameter with and use it as a reference beam. The interference pattern between the reference light and the observed light (reflected light) is detected by the detector 8, and based on this information (relative phase information), the drive amount of the variable shape mirror 3 is determined by the controller 9.

Here, the gain of the laser amplifier is adjusted so that the intensity of the reference light and the intensity of the observed light are as close as possible.

[Effects of the Invention] According to the present invention, it becomes possible to apply an interferometric wavefront detection method to a compensation system of a long-distance spatial optical transmission system, and the compensation accuracy is greatly improved. As a result, beam focusing efficiency increases.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram of a laser transmission system according to an embodiment of the present invention.

Claims (1)

[Claims] Equipped with a beam sampling device, a collimator, a coherent optical amplifier or a coherent optical attenuator, and an interference observation device, a part of the observation light is taken out by the beam sampling device, the beam diameter and wavefront shape are adjusted by the collimator, and the beam is used for reference. A wavefront detection device that forms light, adjusts the light intensities of a reference light and observation light using a coherent optical amplifier or a coherent optical attenuator, and guides the light to an interference observation device to detect the wavefront of the observation light.