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Moiré topography using developed recording methods
Optics and Lasers in Engineering
3
(1982) 59—64
MOIRE TOPOGRAPHY USING DEVELOPED RECORDING METHODS
MASANE SUZUKI and KIY0sHI SUZUKI
Fuji Photo Optical Co., Ltd, 1-324, Uetake-Cho, Omiya, Saitama-Prefecture, Japan (Received: 3 November 1981)
ABSTRACT
Where moire topography is used to record the shape of objects of approximately cylindrical form or that of a series of such objects, a scanning method with a slit camera can be employed. One such method takes photographs by combining conventional shadow type and projection type moire topography with a slit camera. Laser methods of line projection combined with a scanning method developed from the projection type of moire topography are also utilised. The main features of the latter method are that it is not affected by any diffraction effect caused by the grid and that highly accurate recording can be achieved with excellent image quality using the properties of the laser beam. Another distinct advantage is that it is capable of recording the shape of a self-luminous object without contacting by selection of laser wavelengths and matching optical filters. The laser scanning method can therefore be considered to have considerable potential for future applications.
INTRODUCTION
Recording of the shape of three-dimensional objects by means of moire topography has been widely used in various fields. There are a large number of cylindrically shaped objects such as steel bars or tubes as well as a series of sheet material objects such as raw steel plates and pressed steel parts of 3-D form. The conventional moire topography method can be applied to these types of object to record their shapes. However, recording methods can be chosen so as to optically transform cylindrical shapes and to record them 59 Optics and Lasers in Engineering Publishers Ltd, England, 1982 Printed in Northern Ireland
0143-8166/82/0003-0059/$02•75—--©
Applied Science
60
M. SUZUKI, K. SUZUKI
continuously. This technique may also be applied to other shapes such that all the measurement objectives can be achieved by measurement in a plane. Therefore, this method has considerable generality. In this paper, the development of recording methods using the conventional shadow type moire and projection type moire techniques, together with more recent recording methods using laser beam projection methods developed from the classical projection methods are discussed. CONVENTIONAL MOIRE TOPOGRAPHY METHOD
The optical schematic for shadow type moire is shown in Fig. I and that for projection type moire in Fig. 2. Both methods of recording contour moire b
Fig. 1.
s
Optical schematic of shadow type moire. Ob: Object. S: Light source. L: Lens. F: Film. G: Grating. P: Entrance pupil. SL: Slit.
01CLi
SL
9.
Fig. 2. Optical schematic of projection type moire. S: Light source. G1, G2: Gratings. CL1: Condenser lens. L1: Projection lens. L3, L2: Imaging lenses. SL: Slit. CL2: Field lens. F: Film.
61
MOIRE TOPOGRAPHY USING DEVELOPED RECORDING METHODS
fringes are fundamentally the same as the original moire topography method, but there are differences in that they use a slit camera in photographic recording and that they record contour fringes by optically transforming object shapes for simple recording of changes in a flat plane. Shadow moire applied using a peripheral camera As shown in Fig. 1, light from a point light source, S, illuminates an object at a distance, b, from it through a reference grid, G, in front of a surface on a cylindrically shaped object. The image of the grid is deformed according to the shape of the surface onto which it is projected. Now both images of the deformed grids and the reference grid at a position, P, at a distance, b, from the point source and countour moire fringes can be obtained. When a slit camera is placed in a position, P, and a film transport arrangement on either the drum or strip principle within the slit camera is moved in synchronisation with the object which is rotated about an axis perpendicular to the optical axis of the camera, a photograph of the contour moire fringes on the cylindrical object can be observed on the film in the form of a strip. The equation of displacement represented by the contour moire fringes is the same as that of the conventional shadow type moire topography and is given by: h~=bNP0/(1—NP0)
(1)
where: N order number of moire fringe; P0 pitch of the grid; b distance; and 1 distance between the lens and the point source. Figure 3 is a photograph of the cervical vertebrae taken by means of the shadow type version of the developed recording method. All views taken around the subject are incorporated into the strip recording. =
=
=
=
Fig. 3. Typical examples of a moire fringe recording using the peripheral camera to investigate surface contours of an object of approximately cylindrical form: photograph of cervical vertebrae by shadow moire. h = 1 mm.
62
M. SUZUKI, K. SUZUKI
Fig. 4.
As Fig. 3: photograph of a cylindrical surface by projection moire. h = 5 mm.
Projection moire using a peripheral camera In Fig. 2 when light from a point light source, S, collimated by the condenser lens illuminates a reference grid, G1, an image of the grid, G1, is focused on the cylindrically shaped object by projection lens, L1. This image is distorted in accordance with the shape of the object and is focused as a deformed grid on the reference grid, G2, through an imaging lens, L2. The optical images of the reference grid and the deformed grid are superimposed and contour moire fringes are obtained. When these contour moire fringes are focused on a film inside the slit camera through an imaging lens, L3, the film inside the camera is swept in synchronisation with the rotation of the cylindrical object and a photograph containing contour moire fringes can be obtained of the object. The equation of contour moire fringes is the same as that of projection type moire topography and is given by: h~= b(b—f)NP0/{fi—(b—f)NP0}
(2)
where: N=order number of moire fringe; f=focal length of the lens; b = distance and 1 = distance of two optical axes. Figure 4 is a photograph of a record made on. a cylindrical surface by means of the developed projection type recording method. METHOD USING A LASER BEAM
The main feature of this method is its ability to perform highly accurate spread recording without diffraction effects by means of a laser beam with excellent directivity and super-high focusing quality. As shown in Fig. 5, a laser beam is expanded in the first order direction through a cylindrical lens and a projection lens, CL1. It is then projected as a narrow line on to the cylindrical object. The projected laser line is distorted in accordance with the shape of the cylindrical object’s surface and is focused on a reference grid, G1, through an imaging lens, L2, located in a different position. The image of this distorted line and the reference grid are superimposed, and become an image which contains
MOIRE TOPOGRAPHY USING DEVELOPED RECORDING METhODS
63
$j~1~Easer
IIi~2~s:±3~,F Fig. 5.
Optical schematic for method using a single projected line of light from a laser beam. CL 1: Cylindrical lens and projection lens. Ob: Object. L2: Imaging lens. G: Grid. CL: Field lens. FP: Fibre plate. F: Film. L3: Anamorphic lens.
contour positioning data. This image is focused on a film inside a slit camera through a fibre plate, PP. a field lens, CL, and an imaging lens, L3. When the cylindrical object is rotated in synchronisation with a film inside the slit camera being swept, an enlarged image of the object containing contour moire fringes can be obtained on the object. In this case, the equation for the contour moire fringes is: h=P0(b—f)If
(3)
where: P0 pitch of the grid; f focal length of the lens and b distance. Figure 6 is a photograph of a record of the surface of a cylindrical object measured by the laser beam method. This method’s main features are that =
Fig. 6.
=
Photograph of the surface of a cylindrical object using the laser beam technique shown in Fig. 5. h = 1mm.
64
M. SUZUKI. K. SUZUKI
equal separation between each moire fringe can be achieved and that a record of the shape of the surface on a self-illuminated object can be obtained, depending on the type of laser beam.
CONCLUSIONS
The techniques can be applied in cases of continuously rotating components, as may be required for measurement in machine tools or, alternatively, for a single rotation of a component or body on a turntable, giving views around the periphery of the object. The recording method using laser beams gives extremely accurate measurements and, in addition, measurements of shaping on hot working parts and components can be made. It is considered that the method using laser beams will become one of the most useful recording techniques of the future.
REFERENCES
1. 2. 3. 4.
M. SUZUKI and K. SuzuKi, Journal of Japan Society for Technology of Plasticity, 20 (226) (1979) 979. H. TAKASAKI, Appl. Opt., 9 (1970) 1457. M. SUZUKI and K. SUZUKI, Report on the Summer Conference of The Japan Society of Precision Engineering, 1971, 245. M. SUZUKI and K. SUZUKI, Report on the Fall Conference of The Japan Society of Precision Engineering, 1974, 369.
3
(1982) 59—64
MOIRE TOPOGRAPHY USING DEVELOPED RECORDING METHODS
MASANE SUZUKI and KIY0sHI SUZUKI
Fuji Photo Optical Co., Ltd, 1-324, Uetake-Cho, Omiya, Saitama-Prefecture, Japan (Received: 3 November 1981)
ABSTRACT
Where moire topography is used to record the shape of objects of approximately cylindrical form or that of a series of such objects, a scanning method with a slit camera can be employed. One such method takes photographs by combining conventional shadow type and projection type moire topography with a slit camera. Laser methods of line projection combined with a scanning method developed from the projection type of moire topography are also utilised. The main features of the latter method are that it is not affected by any diffraction effect caused by the grid and that highly accurate recording can be achieved with excellent image quality using the properties of the laser beam. Another distinct advantage is that it is capable of recording the shape of a self-luminous object without contacting by selection of laser wavelengths and matching optical filters. The laser scanning method can therefore be considered to have considerable potential for future applications.
INTRODUCTION
Recording of the shape of three-dimensional objects by means of moire topography has been widely used in various fields. There are a large number of cylindrically shaped objects such as steel bars or tubes as well as a series of sheet material objects such as raw steel plates and pressed steel parts of 3-D form. The conventional moire topography method can be applied to these types of object to record their shapes. However, recording methods can be chosen so as to optically transform cylindrical shapes and to record them 59 Optics and Lasers in Engineering Publishers Ltd, England, 1982 Printed in Northern Ireland
0143-8166/82/0003-0059/$02•75—--©
Applied Science
60
M. SUZUKI, K. SUZUKI
continuously. This technique may also be applied to other shapes such that all the measurement objectives can be achieved by measurement in a plane. Therefore, this method has considerable generality. In this paper, the development of recording methods using the conventional shadow type moire and projection type moire techniques, together with more recent recording methods using laser beam projection methods developed from the classical projection methods are discussed. CONVENTIONAL MOIRE TOPOGRAPHY METHOD
The optical schematic for shadow type moire is shown in Fig. I and that for projection type moire in Fig. 2. Both methods of recording contour moire b
Fig. 1.
s
Optical schematic of shadow type moire. Ob: Object. S: Light source. L: Lens. F: Film. G: Grating. P: Entrance pupil. SL: Slit.
01CLi
SL
9.
Fig. 2. Optical schematic of projection type moire. S: Light source. G1, G2: Gratings. CL1: Condenser lens. L1: Projection lens. L3, L2: Imaging lenses. SL: Slit. CL2: Field lens. F: Film.
61
MOIRE TOPOGRAPHY USING DEVELOPED RECORDING METHODS
fringes are fundamentally the same as the original moire topography method, but there are differences in that they use a slit camera in photographic recording and that they record contour fringes by optically transforming object shapes for simple recording of changes in a flat plane. Shadow moire applied using a peripheral camera As shown in Fig. 1, light from a point light source, S, illuminates an object at a distance, b, from it through a reference grid, G, in front of a surface on a cylindrically shaped object. The image of the grid is deformed according to the shape of the surface onto which it is projected. Now both images of the deformed grids and the reference grid at a position, P, at a distance, b, from the point source and countour moire fringes can be obtained. When a slit camera is placed in a position, P, and a film transport arrangement on either the drum or strip principle within the slit camera is moved in synchronisation with the object which is rotated about an axis perpendicular to the optical axis of the camera, a photograph of the contour moire fringes on the cylindrical object can be observed on the film in the form of a strip. The equation of displacement represented by the contour moire fringes is the same as that of the conventional shadow type moire topography and is given by: h~=bNP0/(1—NP0)
(1)
where: N order number of moire fringe; P0 pitch of the grid; b distance; and 1 distance between the lens and the point source. Figure 3 is a photograph of the cervical vertebrae taken by means of the shadow type version of the developed recording method. All views taken around the subject are incorporated into the strip recording. =
=
=
=
Fig. 3. Typical examples of a moire fringe recording using the peripheral camera to investigate surface contours of an object of approximately cylindrical form: photograph of cervical vertebrae by shadow moire. h = 1 mm.
62
M. SUZUKI, K. SUZUKI
Fig. 4.
As Fig. 3: photograph of a cylindrical surface by projection moire. h = 5 mm.
Projection moire using a peripheral camera In Fig. 2 when light from a point light source, S, collimated by the condenser lens illuminates a reference grid, G1, an image of the grid, G1, is focused on the cylindrically shaped object by projection lens, L1. This image is distorted in accordance with the shape of the object and is focused as a deformed grid on the reference grid, G2, through an imaging lens, L2. The optical images of the reference grid and the deformed grid are superimposed and contour moire fringes are obtained. When these contour moire fringes are focused on a film inside the slit camera through an imaging lens, L3, the film inside the camera is swept in synchronisation with the rotation of the cylindrical object and a photograph containing contour moire fringes can be obtained of the object. The equation of contour moire fringes is the same as that of projection type moire topography and is given by: h~= b(b—f)NP0/{fi—(b—f)NP0}
(2)
where: N=order number of moire fringe; f=focal length of the lens; b = distance and 1 = distance of two optical axes. Figure 4 is a photograph of a record made on. a cylindrical surface by means of the developed projection type recording method. METHOD USING A LASER BEAM
The main feature of this method is its ability to perform highly accurate spread recording without diffraction effects by means of a laser beam with excellent directivity and super-high focusing quality. As shown in Fig. 5, a laser beam is expanded in the first order direction through a cylindrical lens and a projection lens, CL1. It is then projected as a narrow line on to the cylindrical object. The projected laser line is distorted in accordance with the shape of the cylindrical object’s surface and is focused on a reference grid, G1, through an imaging lens, L2, located in a different position. The image of this distorted line and the reference grid are superimposed, and become an image which contains
MOIRE TOPOGRAPHY USING DEVELOPED RECORDING METhODS
63
$j~1~Easer
IIi~2~s:±3~,F Fig. 5.
Optical schematic for method using a single projected line of light from a laser beam. CL 1: Cylindrical lens and projection lens. Ob: Object. L2: Imaging lens. G: Grid. CL: Field lens. FP: Fibre plate. F: Film. L3: Anamorphic lens.
contour positioning data. This image is focused on a film inside a slit camera through a fibre plate, PP. a field lens, CL, and an imaging lens, L3. When the cylindrical object is rotated in synchronisation with a film inside the slit camera being swept, an enlarged image of the object containing contour moire fringes can be obtained on the object. In this case, the equation for the contour moire fringes is: h=P0(b—f)If
(3)
where: P0 pitch of the grid; f focal length of the lens and b distance. Figure 6 is a photograph of a record of the surface of a cylindrical object measured by the laser beam method. This method’s main features are that =
Fig. 6.
=
Photograph of the surface of a cylindrical object using the laser beam technique shown in Fig. 5. h = 1mm.
64
M. SUZUKI. K. SUZUKI
equal separation between each moire fringe can be achieved and that a record of the shape of the surface on a self-illuminated object can be obtained, depending on the type of laser beam.
CONCLUSIONS
The techniques can be applied in cases of continuously rotating components, as may be required for measurement in machine tools or, alternatively, for a single rotation of a component or body on a turntable, giving views around the periphery of the object. The recording method using laser beams gives extremely accurate measurements and, in addition, measurements of shaping on hot working parts and components can be made. It is considered that the method using laser beams will become one of the most useful recording techniques of the future.
REFERENCES
1. 2. 3. 4.
M. SUZUKI and K. SuzuKi, Journal of Japan Society for Technology of Plasticity, 20 (226) (1979) 979. H. TAKASAKI, Appl. Opt., 9 (1970) 1457. M. SUZUKI and K. SUZUKI, Report on the Summer Conference of The Japan Society of Precision Engineering, 1971, 245. M. SUZUKI and K. SUZUKI, Report on the Fall Conference of The Japan Society of Precision Engineering, 1974, 369.