JPH0510732A - Underwater object inspection apparatus by laser light - Google Patents

Abstract

PURPOSE:To provide an underwater object inspection apparatus, which is able to measure an underwater object without being affected by scattering of laser light under water while using laser light. CONSTITUTION:An underwater object inspection apparatus by laser light radiates laser light to the underwater object diagonally to receive reflected light from the underwater object through a light route different from the light route of the incoming light. Or, the radiated laser light is made to be a line-beam gradually spreading in vertical direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for inspecting an underwater object using a laser beam.

[0002]

2. Description of the Related Art An inspection apparatus as shown in FIG. 3 is conceivable for inspecting the shape of a structure existing in water with a laser beam.

In FIG. 3, 1 is a laser light source, 2 is an optical fiber, 3 is a beam collimator, 4 is a mirror for reflecting the laser light from the beam collimator 3, 5 is the seabed, and laser light reflected from an object such as the seabed. The mirror 4
The light is collected by the condenser lens 6, condensed by the condenser lens 6, and detected by the detector 7.
In this device, the field of view of the mirror 4 in a stationary state is, for example, about 15 cm in diameter. Therefore, in practice, the mirror 4 is rotated and tilted to scan the laser light in the X and Y directions. It is possible to inspect the seabed topography of the area of.

[0004]

However, when a laser beam is emitted, it is scattered in the entry path of the laser beam due to the fine turbidity in the water when the laser beam is emitted, and the reflection from the seabed is hidden under the influence. This is the same as in a movie theater, where the light from the projector shines white due to dust in the air, so when you look at the screen from the projector lens position, the white brilliance in the middle makes the screen invisible. However, when the screen is viewed from a customer who is far from the projector, the scattered light does not enter the field of view, so that the screen can be seen well.

When the laser light is incident on the water, there is a phenomenon that the above-mentioned influence of scattering greatly occurs up to a certain distance below the surface of the water and thereafter decreases (short-range effect due to backscattering). FIG. 4 is an explanatory diagram of the water depth and the reception level.
That is, when the apparatus shown in FIG. 3 is used, the influence of scattering due to the laser light incidence is largely shown in the portion near the mirror 4,
In any case, the laser reflected light from the object reaches the mirror 4 through the portion greatly affected by the scattering, so that inspection becomes impossible or an error occurs.

The present invention eliminates the above drawbacks.

[0007]

A device for inspecting an underwater object using a laser beam according to the present invention comprises means for emitting a laser beam obliquely to an underwater object, and a laser beam reflected by the underwater object. And a means for giving a scanning motion to the laser light emitting means, the means for detecting the incident light through an optical path different from the incident light path of

[0008]

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

In the present invention, as shown in FIG. 1, the underwater object is irradiated with a laser beam through the beam collimator 3 from a portion horizontally displaced from the optical axis connecting the mirror 4 and the underwater object. To do. In this way, even if the laser light is scattered, it is generated only on the upper surface of the water due to the proximity effect, and this portion is outside the passage of the laser reflected light from the object as is clear from FIG. 1, which hinders the inspection. It won't come. In this embodiment, the beam collimator 3 is also caused to perform scanning movement in synchronization with the scanning movement of the mirror 4.

However, in the case of the apparatus shown in FIG. 1, the water depth of the object is measured in advance by an arbitrary means, and the beam collimator 3 is oriented so that the laser beam hits the area of the inspection field of view of the object having a diameter of approximately 15 cm. It is necessary to adjust, and when the water depth of the object is different, even a slight difference causes the laser beam to deviate from the inspection field of view, so it is necessary to change the launch angle of the laser beam according to the water depth each time the water depth changes. is there.

Therefore, in another embodiment of the present invention, FIG.
As shown in FIG. 3, the laser beam emitted from the beam collimator 3 is formed into an elongated or elliptical linear beam that gradually expands in the vertical direction. Various techniques for extracting such a linear beam from laser light are known, and description thereof will be omitted.

In this embodiment of the present invention, for example, the measurable range extends to a range from 1 m to 6 m in water depth, and even if the object 8 moves in this range, the line-shaped beam does not change in the firing angle of the laser beam without changing the emission angle of the laser beam. It is possible to irradiate a part of the laser beam, and it is possible to measure, for example, the unevenness of the sea bottom with high accuracy and at high speed without changing the emission angle of the laser beam each time.

[0013]

As described above, according to the apparatus for inspecting an underwater object using laser light of the present invention, it is possible to measure an underwater object without being affected by backscattering of the laser light. The use of a linear beam that gradually expands in the vertical direction has a great advantage that it can directly respond to changes in the water depth of the object.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an inspection device for an underwater object using a laser beam according to the present invention.

FIG. 2 is an explanatory view of another embodiment of the inspecting apparatus for an underwater object using laser light according to the present invention.

FIG. 3 is a diagram illustrating the principle of a device for inspecting an underwater object using laser light.

FIG. 4 is an explanatory diagram of water depth and reception level.

[Explanation of symbols] 1 laser light source 2 optical fiber 3 beam collimator 4 mirror 5 seabed 6 Condensing lens 7 detector 8 objects

Claims (2)

[Claims] 1. A means for emitting a laser beam obliquely to an underwater object, a means for detecting reflected laser light from the underwater object via an optical path different from the incident optical path of the laser light, and A device for inspecting an underwater object using laser light, which comprises means for giving a scanning motion to the laser light emitting means. 2. The laser beam emitted into the water is a linear beam which is gradually diffused in the vertical direction.
The device for inspecting an underwater object using the laser light described.