JPH01127911A - Speckle pattern interferometer - Google Patents

Abstract

PURPOSE:To obtain an expensive and miniature speckle pattern interferometer which can project uniformly an object by providing a cylindrical lens for enlarging a beam from a semiconductor laser and converting an elliptical beam to a circular beam. CONSTITUTION:An elliptical beam from a semiconductor laser 1 is enlarged only in the rectangular direction by a cylindrical lens 4, becomes a circular beam, split into two by a beam splitter 5, and projects widely a reference rough surface 6 and an object to be measured 7, respectively. Subsequently, each diffused and reflected light from them is synthesized 5 again, and a formed speckle pattern SP is brought to image pickup by a TV camera 8. In that case, in an image processing circuit 9, the SP before deformation of the object 7 is stored in an image memory,and by taking a difference to an image of the SP after deformation, a non-linear conversion is executed and an interference line is emphasized, and based thereon, an out-of-plane displacement is displayed as a contour line of an interference fringe on a monitor 10. Accordingly, since a semiconductor is adopted as a light source so that its beam is enlarged only in a rectangular direction by the lens 4, the title interferometer can be miniaturized and manufactured at a low cost, and also, can project uniformly the object to be measured.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention uses speckle interferometry to measure the displacement of a rough surface,
This invention relates to a speckle pattern interferometer that measures deformation, vibration, etc.

[Conventional technology]

In a speckle pattern interferometer using the conventional speckle interferometry, an optical system as shown in Figure 3 is used to connect the light source to H.
A gas laser such as an e-Ne laser or an argon laser is used, and since these have a small beam diameter, the beam is expanded through a beam expansion lens for measurement. Recently, it has also been proposed to use a semiconductor laser as a light source in order to make the device more compact.

[Problem that the invention seeks to solve]

However, these two conventional techniques each have the following problems. First, when a gas laser such as a He-Ne laser or an argon laser is used as a light source, there are problems in that the apparatus is large-scale, takes up a lot of space, and is inconvenient to move, and gas lasers are very expensive. Furthermore, when a semiconductor laser is used as a light source, inexpensive and compact products can be made, but because the beam spreads out in an elliptical shape, it is impossible to illuminate the entire object without waste, which poses nine problems.

This invention has been made in view of the above problems, and aims to provide a speckle pattern interferometer that is inexpensive, compact, and capable of turning an elliptical beam into a circular shape and uniformly illuminating an object. .

[Means for solving problems]

A specific means for solving the above problems and achieving this objective is to provide a speckle pattern interferometer using speckle interferometry that includes at least a television camera, a light source section, and a beam splitter. A semiconductor laser is used in the invention, and a cylindrical lens is provided to expand the beam from the semiconductor laser.

[For production]

With the above configuration, the ellipsometer beam emitted from the semiconductor laser is expanded by the cylindrical lens only in the direction of small ellipticity (minor axis direction), as shown in Figure 2, and becomes a circular beam that illuminates the entire object without fail. Moreover, since a semiconductor laser is used as a light source, the device can be made cheaper and smaller.

〔Example〕 This invention will be explained in detail below based on one embodiment.

FIG. 1 shows a speckle interferometer as an embodiment of the present invention, in which 1 is a semiconductor laser.

2 is a Peltier element that acts to keep the temperature of the semiconductor laser constant in order to stabilize the oscillation frequency of the semiconductor laser, and 3 is a temperature control circuit, for example, by embedding a thermistor near the semiconductor laser, It works to control the drive current to the Peltier element while monitoring the temperature. 4 is a plano-concave cylindrical lens that expands the beam from the semiconductor laser in only one direction; 5 is a plano-concave cylindrical lens that divides the expanded beam from the semiconductor laser into two; This is a beam splitter that works to illuminate the object to be measured. 6 is a reference rough surface serving as a reference, and 7 is a measurement target in the speckle pattern interferometer. 8 is a television camera that receives interference light of the reflected light from the reference rough surface 6 and the reflected light from the measurement object 7;
This is an image processing circuit that processes video signals from a television camera. 10 is a monitor for displaying the image processed by the image processing circuit 9;

Next, aspects of the invention realized by the above configuration will be described below. First, the elliptical beam from the semiconductor laser 1 is expanded by the plano-concave cylindrical lens 4 only in the direction of small ellipticity, and becomes a circular beam. The expanded semiconductor laser beam is split into two by a beam splitter 5, and the - side irradiates the rough reference surface 6 and the other beam irradiates the measurement object 7. Then, the diffusely reflected light from the measurement object 7 and the diffusely reflected light from the reference rough surface 6 are combined again by the beam splitter 5, and the resulting spare pattern is photographed by the television camera 8. At this time, in the image processing circuit 9, the speckle pattern of the measurement object 7 before deformation is stored in the image memory as a video signal, and the difference with the image of the speckle pattern after deformation is taken to emphasize the interference fringes. A linear transformation is performed. Based on this, out-of-plane displacement (deformation perpendicular to the surface of the object to be measured) is displayed on the monitor 10 as contour lines of interference fringes.

In this embodiment, a plano-concave cylindrical lens is used, but a plano-convex, biconcave, or biconvex cylindrical lens may be used.

〔Effect of the invention〕

As explained above, the speckle pattern interferometer of the present invention employs a semiconductor laser as a light source, and uses a cylindrical lens to expand the beam of the semiconductor laser only in the direction of small ellipticity. It can be manufactured at low cost, and moreover, it can irradiate the object to be measured without fail.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a speckle interferometer according to the present invention, Fig. 2 is a diagram showing the spread of laser light through a cylindrical lens, and Fig. 3 is a block diagram of a conventional speckle pattern interferometer. It is. ■... Semiconductor laser, 2... Peltier element, 3...
... Temperature control circuit, 4... Plano-concave cylindrical lens, 5... Beam splitter, 6... Reference rough surface, 7
... Measurement object, 8 ... Television camera, 9 ... Image processing circuit, 10 ... Monitor, 11 ... Gas laser, 12 ... Beam expansion lens. Patent applicant: KEYENCE CORPORATION Fig. 1A Fig. 2 (a) Short axis direction (b) Long axis direction Fig. 3 A/

Claims (1)

[Claims] (1) In an integrated speckle pattern interferometer using speckle interferometry that includes at least a television camera, a light source section, and a beam splitter, a semiconductor laser is used for the light source section, and a beam from the semiconductor laser is used. A speckle pattern interferometer characterized by being equipped with a cylindrical lens that magnifies.