JPS5952762B2 - Contour moiré fringe measurement method - Google Patents

Description

Detailed Description of the Invention (Technical Field of the Invention) The present invention projects a grid pattern onto an object, converts the deformed grid image reflected from the object into an electrical signal using an imaging device, and then electrically generates a plurality of moiré patterns. The present invention relates to a method of detecting the unevenness of an object from contour moire fringes by coloring and superimposing each of these moire fringes.

(Prior art) Conventionally, in order to obtain contour moiré fringes, a grid image is projected onto an object, and the object on which the grid image is projected is captured by an imaging device such as a camera or a television camera through an imaging grid. A method of photographing is used.

However, just by obtaining contour moire fringes as described above, it is not possible to determine whether the object is concave or convex.

For this reason, in the past, people could judge whether an object is concave or convex by directly viewing the object with their eyes, or by projecting straight lines perpendicular to the grid on the object within the grid plane at the same time as the grid, and superimposing them on the moiré fringes. A method was used to determine whether an object is concave or convex based on the curvature of the captured straight image. However, this is not sufficient, and another method is to slightly move either the projection grating or the imaging grating in the direction perpendicular to the grating, and determine the unevenness from the moving direction of the moiré fringes. It is difficult to automate, the direction of movement of the stripes must be determined by a human, and the grid must be moved every time it is necessary, which is cumbersome.

On the other hand, by projecting a projection grating onto an object with a uniform color pattern at a certain period and using an imaging grating with the opposite color period to obtain color moiré fringes, the irregularities can be determined based on the order in which the colors of the moiré fringes are arranged. A method has also been proposed, but the grid must be colored, an expensive color imaging device is required for imaging, and there are problems when measuring colored objects. (Objective of the Invention) The present invention eliminates these drawbacks, facilitates the determination of unevenness even for colored objects, and eliminates the need for color gratings and imaging devices, thereby simplifying and reducing the cost of the device. It is possible to obtain moiré fringes with good contrast or S/N, and facilitates automatic analysis by an information processing device.The drawings will be described in detail below.

(Principle of the Invention) Figures 1 and 2 are explanatory diagrams for explaining the principle of the present invention. In Figure 1a, Gp is a projection grating, Lp is a projection lens for projecting a grating image onto an object, A is an image-receiving surface of the imaging device, LR is an imaging lens for forming an object image and a deformed lattice image deformed by the object and body shape on the image-receiving surface A, and GR is an imaging grating.

In the present invention, the electrical signal is turned on after imaging. By turning it off, it functions equivalently as an imaging grid. The contour plane group in this case is represented by a group of parallel trigonal lines represented by the middle Pn. In reality, the slits in both gratings have a certain width, so the contour planes are of equal height as shown in Figure b. Next, in order to change the relative position of the projection grating and the imaging grating, for example, move the imaging grating approximately 1/4 in the direction perpendicular to the slit in the grating plane.
If you move it to the position of GR'', the contour plane changes to Pn. In the figure, GR is written above GR, but in reality it is GR moved slightly to the right, so it overlaps in the notation. Because it is difficult to see, it is written in a vertically shifted manner. Figure C shows the same high-rise images based on the imaging gratings GR and GR. Figure 2 shows two Moiré fringe patterns of a certain object obtained in this way, superimposed, with diagonal lines going downward to the left for the pattern created by the imaging grating G8, and diagonal lines going down to the right for the pattern created by the imaging grid GR. Imaging grid GR
Red (R) is attached to the moire fringe pattern according to the imaging grating G.
If we add green (G) to the moire fringe pattern created by R., the moire fringes obtained by superimposing them will be red (R), yellow (Y), green (G), and black (B), as shown in Figure 2. ) will be repeated. If this is applied to equal heights, as shown in Figure C, objects located at equal heights due to the imaging grid GR will appear red, and objects located at equal heights due to the imaging grid GR will appear green. Objects in two overlapping layers (layers with overlapping diagonal lines) appear yellow, which is a combination of two colors, and other points appear black.

That is, in this case, as the moire fringe order increases, the moire fringe hue changes in the order of green, yellow, red, and black. Therefore, the unevenness of an object can be determined by observing the change in hue of the moiré fringes. In addition, the moiré fringes by the imaging grid GR are input to the first bit of the input of the information processing device, and the imaging grid G
When the moire fringes based on R are input as the second bit, the above-mentioned green, yellow, red, and black are input as 10, 11, 01, and 00, respectively, so that the information processing device can easily determine the unevenness.

With this method, green, yellow, red, and black moire stripes are obtained by adding red and green colors to a pair of light and dark moire stripes, respectively.

In other words, if a grid with the same pitch is used, the number of contour lines will be doubled, and therefore twice the precision will be obtained. Conversely, since the grating pitch can be doubled to obtain moire fringes with the same precision, the grating can be manufactured easily, and the contrast can be increased and the S/N ratio can be improved. (Embodiment of the Invention) FIG. 3 shows an embodiment of the present invention, in which a grating image 3 is projected onto an object 1 by a projector 2 containing a black and white grating, and the object 1 on which the grating image 3 is projected is The image is captured by a black and white imaging device 4.

The imaging device 4 has a function of capturing a deformed lattice image and converting it into an electrical signal. 5 is a bandpass filter for removing unnecessary high-order moiré components, and 6 is an amplifier.

7, 8, and 9 turn on the video signal by switching pulses Sl, S2, and S3, which will be described later. This is a video switch that functions as an optical imaging grid when turned off (see Japanese Patent Application No. 16144/1982).

]0, 11, ]2 are low-pass filters that remove grating images and pass only moiré signal components, and their respective outputs are red (R), green (G), and blue (B) of the color monitor 13. ) connected to the three primary color inputs. Reference numeral 14 denotes an oscillator for generating switching pulses, and the oscillation frequency is set to an integral multiple of the horizontal synchronizing frequency of the television camera Nfll (n' integer).

A synchronization signal generator 15 counts down the pulses from the oscillator 14 and supplies a synchronization signal to the imaging device 4 .

This is to synchronize the switching pulse with the synchronization signal of the imaging device and to prevent moiré fringes from moving. ]
6 and 17 are phase shifters for changing the phase of the switching pulse. In such a configuration, video switch 7
, 8, and 9 serve as imaging gratings, the outputs Cl, C2, and C3 of the low-pass filters 10, 11, and 12 are monitored by the monitor 13.
When displayed on top, moiré fringes occur (Patent application 1983)
-16144). The switching pulses Sl, S2, S3 supplied to the video switches 7, 8, 9 have their phase shifted by phase shifters 16, 17, but this is due to changing the relative position of the projection grating. Correspondingly, the output C
l, C2, C3 give contour lines for different isoheights. By inputting the moiré fringe signal outputs Cl, C2, and C3 for different equal layers to the R, G, and B terminals of the monitor, it is possible to simultaneously display the moire fringe signals in different colors, superimposing them on each other. Irregularities can be determined based on changes in hue. (Effects of the Invention) As explained above, since the relative positions of the projection grid and the imaging grid are changed to display a plurality of moiré fringes for different heights in a superimposed manner using different colors, it is easy to determine irregularities. It is.

Further, the imaging device may be monochrome and is not affected by colored objects, and by increasing the number of superimposed moiré fringes, it is possible to detect order jumps within a certain range. Furthermore, since no color grid or color imaging device is used, the device is simple and inexpensive. Furthermore, since the grating pitch to obtain the same precision can be larger than in the conventional case, it is technically simple and moiré fringes with good contrast and S/N can be obtained. Furthermore, by inputting the moire fringe signal to the information processing device instead of inputting it to the monitor, there is an advantage that automatic analysis of the unevenness of the moire fringe can be easily performed.

[Brief explanation of the drawing]

FIG. 1 is an isometric diagram for explaining the principle of the present invention, FIG. 2 is a moire fringe diagram for explaining the principle of the present invention, and FIG. 3 is a configuration diagram showing an embodiment of the present invention. 2... Projector, 3... Grid image on object, 4... Imaging device, 7, 8, 9... Video switch, 13...
・Color monitor or information processing device, 14... oscillator,
16, 17... Phase shifter.

Claims (1)

[Claims] 1. A projector that projects a grating image onto an object, an imaging device that converts the deformed grating image reflected from the object into an electrical signal, an oscillator that generates a switching pulse, and a shifter that changes the phase of the switching pulse. Phase converter, turn on the output of the imaging device,
It consists of two or more video switches that are turned off, and a color monitor that displays the moiré image output from the video switches. A grating image is projected onto an object from one projector, and the deformed grating image reflected by the object is captured by an imaging device. By converting the electrical signal into an electrical signal and turning the electrical signal on and off using switch pulses of different phases in two or more video switches, multiple moiré fringes are obtained, and each of these moiré fringes is given a different color on a color monitor. A method of measuring contour moiré fringes characterized by superimposing and displaying them. 2. A projector that projects a grating image onto an object, an imaging device that converts the deformed grating image reflected from the object into an electrical signal, an oscillator that generates a switching pulse, a phase shifter that changes the phase of the switching pulse, and the imaging device Turn on the output of
It consists of two or more video switches that are turned off, and an information processing device that processes moile images output from the video switches, and a single projector projects a grating image onto an object, and an imaging device captures the deformed grating image reflected by the object. A plurality of moiré fringes are obtained by converting the electrical signal into an electrical signal, turning the electrical signal on and off using switching pulses of different phases in two or more video switches, and attaching a different identification symbol to each of these moiré fringes. A contour moiré fringe measurement method characterized by obtaining combination information of each identification symbol by inputting and processing the information into an information processing device.