JPH03289505A - Three-dimensional shape measuring apparatus - Google Patents

Abstract

PURPOSE:To measure the shape and the position of a body to be measured highly accurately by emitting slit light on the surface of the material to be measured, froming the fringe image on the surface, picking up the image, and correcting the obtained distribution data of luminance with the distribution data of luminance at the time of the total emission. CONSTITUTION:The light from a lamp 11 becomes the fringe light through a condenser lens 12, a liquid-crystal shutter 13 and a projecting lens, and the surface of a body to be measured M is irradiated. The image of the surface of the body M is focused on an image sensing element 24 of a camera 20. The output is inputted into a CPU 30a through an A/D converter 31 and an interface 30d. Thus the luminance distribution data of the body M are obtained. Then, a pattern control part 32 switches the shutter 13 based on the command from the CPU 30a, and the body M is irradiated with the total light. The image is picked up with the camera 20. The image signal is received in the CPU 30a, and the luminance distribution data are obtained. The fringe-shaped luminance distribution data are corrected, and the shape of the body M is determined and displayed on a surface-shape displaying device 40.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a three-dimensional shape measuring device, and more specifically, the present invention relates to a three-dimensional shape measuring device, and more specifically, the present invention relates to a three-dimensional shape measuring device, and more specifically, the present invention relates to a three-dimensional shape measuring device. The present invention relates to a three-dimensional shape measuring device that measures the shape and position of an object to be measured based on the state of an image.

[Prior Art] Conventionally, this type of three-dimensional shape measuring device is known, for example, as disclosed in Japanese Patent Application Laid-Open No. 64-54206. This device measures the shape of the object to be measured based on brightness distribution data that represents the fringe image on the surface of the object by the intensity of brightness and darkness. In order to prevent the brightness distribution data from being distorted and the measurement accuracy from decreasing due to the influence of the above, the following configuration was adopted.

First, an image of the surface of the object to be measured is taken in a non-irradiation state in which no light is irradiated, and luminance distribution data is created that shows the surface in the non-irradiation state by the intensity of brightness and darkness. The brightness distribution data at the time of no irradiation is data indicating the change that background light has on the brightness distribution data of the striped image. Next, the brightness distribution data of the striped image is corrected using the brightness distribution data in the non-irradiation state, that is, the image in the non-irradiation state is constructed from the illuminance level value Sa of each pixel constituting the image of the striped image. A process of subtracting the illuminance level value sb of each pixel is performed to create brightness distribution data of a striped image (illuminance difference data D=Sa-5b) without distortion caused by background light. The accuracy of this type of measurement was improved by detecting the phase and shape of each line from the brightness distribution data of the fringe image created in this way.

[Problems to be Solved by the Invention] However, although the above-mentioned conventional device was able to eliminate the influence of background light, the brightness of the fringe image caused by variations in the reflectance distribution on the surface of the object to be measured, bias in the illuminance distribution of the light source, etc. There is a problem in that distortion of the distribution data cannot be removed and improvement in measurement accuracy is hindered.

The three-dimensional shape measuring device of the present invention solves the above problems and makes it possible to remove distortions in brightness distribution data caused by variations in the reflectance distribution on the surface of the object to be measured and bias in the illuminance distribution of the light source,
The purpose is to achieve high-precision measurements.

K Skin Ω Configuration ``Means for Solving the Problems'' The three-dimensional shape measuring device of the present invention, as illustrated in FIG. A three-dimensional method in which a fringe image is formed on the surface of the object to be measured, and the condition of each line is detected from the brightness distribution data of the fringe image obtained by imaging the fringe image with an imaging means to determine the shape or position of the object to be measured. In the shape measuring device, a total irradiation means for irradiating the entire surface of the object to be measured with light having the same illuminance distribution as that of the light source; A brightness distribution data correction means for correcting the brightness distribution data of the fringe image using brightness distribution data.

"Operation" In the three-dimensional shape measuring device of the present invention having the above configuration, the brightness distribution data of the striped image is corrected as follows. First, the light having the same illuminance distribution as the light source that irradiates the striped light is completely The entire surface of the object to be measured is irradiated by the irradiation means and imaged to obtain brightness distribution data at the time of full irradiation.The brightness distribution data at the time of full irradiation is based on variations in the reflectance distribution on the surface of the object to be measured and the illuminance distribution of the light source. This data indicates the change that the bias, etc. of the stripe image has on the brightness distribution data of the fringe image.
The brightness distribution data of the fringe image is corrected using the brightness distribution data at the time of full irradiation, and distortions caused by variations in the reflectance distribution on the surface of the object to be measured and bias in the illuminance distribution of the light source are corrected. Remove from data. From the brightness distribution data of the fringe image corrected in this way, the phase of each line can be accurately detected, and the shape or position of the object to be measured can be measured with high precision.

[Example] A three-dimensional shape measuring device as an example of the present invention will be described below with reference to the drawings.

As shown in FIG. 2, the three-dimensional shape measuring device includes a projector 0, a camera 20, a signal processing device 30, and a surface shape display device 40.

The projector [O] includes a lamp [1], a condensing lens [2], a liquid crystal shutter [3], and a projection lens 14.

The liquid crystal shutter 13 includes a polarizing plate 15 as shown in FIG.
Transparent electrodes 17 are formed in stripes at predetermined intervals on the inner surface of the polarizing plate 16, transparent electrodes 8 are formed in a planar shape on the inner surface of the opposing polarizing plate 16, and liquid crystal 19 is filled between the picture electrodes 17 and 18. This is what I did.

Transparent electrode] 7 includes a pattern control section 32 as described later.
Electric power is applied individually to create various projection patterns consisting of transparent portions and light-shielding portions of the liquid crystal 9. The transparent electrode 8 is a common electrode that corresponds to all of the transparent electrodes 7. The liquid crystal shutter 13 of the embodiment is arranged such that the polarization directions of the two polarizing plates 15 and 16 are perpendicular to each other.
It becomes light-shielding when an electric field is applied. Note that the liquid crystal shutter 13 may be made transparent by application of an electric field.

Therefore, as shown in FIG. 2, the light from the lamp passes through the condenser lens 12 and then becomes, for example, striped light through the liquid crystal shutter [3], and is projected onto the surface of the object to be measured through the projection lens [4]. irradiated.

As the camera 20, as shown in FIG. 2, a CCD camera having an objective lens 22 and an image sensor 24 is used in the embodiment. An image of the surface of the object to be measured M is formed on the image sensor 24 .

The signal processing device 30 is configured as a computer f5
It includes a CPU 30a, a ROM 30b, a RAM 30C, and an interface 30d, and is configured to be able to mutually transmit signals via a bus 30e.

Furthermore, the interface 30d includes an A/D converter 3]
, a pattern control section 32, a camera control section 33, and a surface shape display device 40 are connected.

The A/D converter 3] converts an analog signal from the camera 20 into a digital signal according to a command from the CPU 30a, and outputs the digital signal to the interface 30d.

The pattern control unit 32 supplies power to predetermined transparent electrodes 17 of the liquid crystal shirt octopus 3 according to commands from the CPU 30a, and creates various projection patterns composed of transparent parts and opaque parts.

In this example, as shown in FIG. 4, three kinds of patterns are created: a completely light-shielding pattern shown in FIG. 4 (A), a fully transparent pattern shown in FIG. 4 (B), and a striped pattern shown in FIG. Note that in the figures, the light-shielding portions are indicated by hatching for convenience.

The camera control unit 33 controls the electronic shutter of the camera 20 based on instructions from the CPU 30a. The control will be detailed later.

The surface shape display device 40 displays the finally determined shape of the object to be measured M as a three-dimensional image or the like.

Next, the shape measurement process executed in the hidden signal processing device 30 will be explained based on the flowcharts of FIGS. 5 and 6.

The shape measurement processing routine (FIG. 5) is executed every time a measurement start command is issued after starting up the three-dimensional shape measuring device.

When this routine is started, first, a pattern image capturing process (step 100) is performed in which the surface of the object to be measured M is imaged while switching between the three types of projection patterns.

The details of the pattern image capture process (step 100) are shown in the flowchart of FIG. When you start the import process,
First, as an initial process, set a value to a variable that specifies the projection pattern (Step 10), wait for the vertical synchronization signal of the camera 20 to be input (Step 120), and close the electronic shutter of the camera 20 (Step 10). ]30
).

After these initial processes, a process (step 140) is performed in which the pattern formed by the liquid crystal shutter 13 is changed to a pattern specified by a variable value.

First, set the total light-shielding pattern (Figure 4 (A)
). In the embodiment, a value of 2 switches the variable to a completely transparent pattern (FIG. 4(B)), and a value of 3 switches to a striped pattern (FIG. 4(C)).

Next, open the electronic shutter of the camera (step 150).
, exposure is started in a state where the light of the lamp is blocked by the total light-blocking pattern.

When a vertical synchronization signal is input from the camera 20 after a predetermined period of time has passed (step 160), the electronic shutter of the camera 20 is closed (step 70), and the captured video signal is then read out and converted by the A/D converter 31. After digital conversion, the signal is stored in a predetermined area of the RAM 30c as brightness distribution data during non-irradiation (step 80).

When the storage of the brightness distribution data during non-irradiation is completed, the value 1 is then added to the variable (step) 90.

Since the variable value is 2 and the projection pattern number is less than or equal to 3 (step 195), the process returns to step 40 and the pattern of the liquid crystal shutter 13 is changed to a pattern corresponding to the variable value of 2, that is, a fully transparent pattern. Switch. After this,
The process from step 150 onwards is executed to image the state in which the light from the lamp 11 passes through the fully transparent pattern and illuminates the entire surface of the object to be measured M, and converts the video signal digitally to obtain the brightness when the entire surface is illuminated. The data is stored in a predetermined area of the RAM 30c as distribution data (step 180).

Finally, the variable is added to the value 3 (step] 90), and the projection pattern of the liquid crystal shutter 13 is switched to a striped pattern (step) 40). Then, an image is taken of the state in which the light from the lamp] passes through the striped pattern and illuminates the surface of the object to be measured M in a striped pattern, and the video signal is digitally converted and stored in the RAM 30c as brightness distribution data of the striped image. The information is stored in a predetermined area (step 180).

In this way, imaging using the three types of projection patterns is completed, and when the value 1 is added to the variable RI (step 190), the value 4 of the variable RI becomes thicker than the predetermined value 3 (step 195), and this processing ends. do.

The timing chart in FIG. 7 shows how the liquid crystal shutter] 3 and camera 20 are controlled by executing the pattern image capture process (FIG. 6).

As shown in the figure, during one cycle of the imaging period of the camera 20 (while outputting the vertical synchronization signal), the liquid crystal shutter] 3
Pattern switching (step 40) and exposure of the camera 20 (step 150) are performed. therefore,
Imaging of the completely light-shielding pattern, the completely transparent pattern, and the striped pattern is completed within three imaging cycles.

After completing the pattern image capture process (FIG. 6) described above, next, a process (FIG. 5) is performed in which the brightness distribution data of the striped image is corrected for each pixel.

First, as shown in FIG. 5, in step 20, both variables i and J, which specify the coordinates of pixels to be corrected, are reset to the value O.
0), then a process (step 210) is performed to correct the brightness distribution data of the fringe image for the pixel specified by the variables i and j.

In the correction process (step 210), as shown in FIG. The brightness distribution data 5Aij and the brightness distribution data 5Bij at the time of full irradiation are used to correct according to the following equation.

5ij= (SCij-8Aij) / (SBij-
3Aij) ...■ However, Sij is the brightness distribution data of the fringe image after correction, = 0 to 511. j=0 to 511 (
The screen of the embodiment is composed of 512×512 pixels).

This equation 0 was derived as follows.

As exemplified in the graph of FIG. (corresponding to the brightness distribution data 5Bij) and the video signal b(Xc) at the time of no irradiation (corresponding to the brightness distribution data SAJ at the time of no irradiation). In other words, the video signal f (Xc) during full irradiation is a signal that reflects variations in the reflectance distribution on the surface of the object to be measured M and the bias in the illuminance distribution of the lamp 1, and the video signal b when no irradiation is performed. It is shown that (Xc) is a signal in which background light is reflected.

Here, assuming that the surface of the object M to be measured is in an optically ideal state (a state in which light is completely diffused) and the illuminance distribution of the lamp 11 is uniform, the mapping of the fringe image to the camera 20 is G(Xc
) (corresponding to the corrected brightness distribution data SU). Similarly, the mapping of the lamp light to the camera 20 during full irradiation and the mapping of the background light to the camera during no irradiation are respectively F (X
c), B (Xc). In addition, when considering actual measurements, the mapping of the uneven reflected light of the lamp light and background light onto the camera caused by variations in the reflectance distribution on the surface of the object to be measured M, as well as the bias in the illuminance distribution of the lamp light, The mapping of the resulting non-uniform reflected light onto the camera is defined as Rf (Xc) for the lamp light and Rb (Xc) for the background light.

At this time, each video signal f (Xc), g (Xc),
b (Xc) C can be expressed by the following formulas.

g(Xc)=F(Xc)G(Xc)・Rf(Xc)10B
(Xc)-Rb(Xc)-■f(Xc) =F(
Xc) Rf(Xc)+B(Xc)Rb(Xc) --
−■b (Xc) = B (Xc) ・Rb(Xc)
・Substituting the 00 formula into the ■ Mr. ■ formula, the following two formulas are obtained.

g(Xc)=F(Xc)G(Xc)Rf(Xc)+b(
Xc) −■f (Xc) = F (Xc) Rf
(Xc)+b(Xc)-00 The following equation is obtained.

G(Xc)=(g(Xc)-b(Xc))/(F
(Xc)-Rf(Xc))...■ From equation 0, the following equation is obtained.

F (Xc) Rf (Xc) = f (Xc) - b (
Xc) --- When the 00 formula is substituted into the 0 formula, the following 0 formula is obtained.

G (Xc)” (g (XC)-b (Xc)) /
(f (Xc)-b(Xc))...■ The above formula 0 does not include the terms Rf(Xc) and Rb(Xc). Formula 200 is equivalent to formula 0. In other words, the brightness distribution data 5Cij of the fringe image and the brightness distribution data 5A during no irradiation.
iJ and the brightness distribution data 5Bij at the time of full irradiation,
It is possible to describe the brightness distribution data Sij of the fringe image, which removes variations in the reflectance distribution on the surface of the object to be measured M, deviations in the illuminance distribution of the lamp, and the influence of background light.

Correction processing based on the 0 formula explained above (step 210)
When the brightness distribution data of the fringe image of one pixel specified by the variables i and j is corrected, the value of the variable i that specifies the row is changed to the value indicating the last row in the column j (here, the value 5
11), and if it is not the last value, add the value 1 to the variable i (step 230).
, the above process is repeated to complete the correction of all pixels in column j (initially value O). After completing the correction of the pixels in column j, it is then determined whether variable j is the last column (here, the value 51) (step 240), and if it is not the last column, the value 1 is added to variable j. However, the variable i is reset to the value O (step 250).

When the above process is repeated to complete the correction of all the pixels in the column where the variable j has the value 51 (step 240), the correction of the brightness distribution data of the fringe image has been completed. Reset again to value O (step 2
6o) Shape measurement calculations from step 270 onward are performed for each column.

Shape measurement calculations are performed as follows.

First, the 5
Twelve luminance data groups are read (step 270).

In the embodiment, the luminance data is expressed in 256 gradations. Subsequently, a fundamental wave f is calculated by interpolation from a set of points of which this luminance data group consists of 256 gradations, and the peak position of each wave in the fundamental wave f is detected (step 280). Since interpolation is a well-known process, details will be omitted.

Next, detect the phase of each peak position (step 290
). Once the peak position and its phase are obtained in this way, the shape of the portion corresponding to the j column is calculated based on trigonometry (step 300). Since the calculation for calculating the shape is well known, details thereof will be omitted.

After this, it is determined whether the value of variable j is the last value 511 or not (step 3); if it is not the last value, the value is added to variable j (step 320); From the luminance data group of the column specified in (), the shape of the portion corresponding to that column is calculated as described above.

In this way, each time the value 1 is added to the variable, the shape of the part corresponding to that column is calculated, and when the calculation of the shape of the column where the variable has the value 5] is completed, this processing is terminated.

The shape of the object M to be measured thus calculated is displayed on the surface shape display device 40 as necessary.

According to the three-dimensional shape measuring device of the embodiment described above, the brightness distribution data of the fringe image is corrected using the brightness distribution data during full irradiation and the brightness distribution data during no irradiation, and the reflectance of the surface of the object to be measured is Since variations in the distribution, bias in the illuminance distribution of the lamp, and the influence of background light can be removed from the brightness distribution data of the fringe image, this has the excellent effect of significantly improving measurement accuracy.

In addition, in this embodiment, since the switching of the liquid crystal shutter [3] pattern and exposure are performed in one imaging cycle of the camera, the pattern image can be captured in a short time, and the measurement time can be shortened compared to the conventional method. There are advantages. In addition,
Since the time required to capture the pattern image is short, there is less possibility of deviations in the imaging position or changes in background light, etc., and even if changes occur, they are minute, so shape measurements can be performed with higher precision. . It is also possible to use general control as shown in FIG. 10, that is, control in which the liquid crystal shutter pattern is switched between the camera's imaging cycle and the camera is exposed in the next imaging cycle. can. However, according to the control of the above-described embodiment, the time to capture the pattern image can be reduced by half.

In addition, as another configuration that aims to shorten the time to capture such pattern images, for example, a camera that can freely set the imaging cycle is used, and the first imaging cycle is set to the time required for switching the pattern of [LCD shutter] 3. , the next imaging cycle may be set to the required exposure time of the camera and the idle time may be omitted.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments in any way, and it goes without saying that it can be implemented in various forms without departing from the gist of the present invention. For example, in addition to the LCD shutter, PL
A ZT electro-optical shutter array or a CRT as a projector may be used to project various patterns.

The order in which the three types of patterns are projected does not matter. The non-irradiation pattern may be realized by turning off the lamp 11.

Effects of the Invention As detailed above, according to the three-dimensional shape measuring device of the present invention, distortions caused by variations in the reflectance distribution on the surface of the object to be measured, bias in the illuminance distribution of the light source, etc. Since it can be removed from the distribution data, it has the excellent effect of significantly improving the accuracy of measuring the shape and position of the object to be measured.

[Brief explanation of drawings]

FIG. 1 is a block diagram illustrating the basic configuration of the present invention, FIG. 2 is a block diagram of a three-dimensional shape measuring device as an embodiment of the present invention, and FIG. 3 (A) is a front view of a liquid crystal shutter. Figure 3 (B) is a cross-sectional view of the liquid crystal shutter, Figure 4 (A),
(B) and (C) are front views showing three types of projection patterns created by the liquid crystal shutter, and FIG. 5 is a flowchart showing an example of shape measurement processing executed in the signal processing device. A flowchart showing the process,
Fig. 7 is a timing chart showing control of capturing the pattern image, Fig. 8 is a perspective view of the image to explain the correction process, Fig. 9 is a graph of the video signal to explain the correction process, and Fig. 10 is a graph of the pattern image. FIG. 2 is a timing chart when acquisition control is performed using conventional control. FIG. 10... Projector 13... Liquid crystal shutter 13a... Fully shielding pattern 13b... Fully transparent pattern 13c... Striped image pattern

Claims (1)

[Claims] 1. The object to be measured is irradiated with light from a light source in a striped manner through a slit to form a striped image on its surface, and the striped image is captured by an imaging means. The condition of each stripe is determined from the brightness distribution data of the striped image obtained. The three-dimensional shape measuring device detects the shape or position of the object to be measured, the total irradiation means for irradiating the entire surface of the object to be measured with light having the same illuminance distribution as that of the light source; and brightness distribution data correction means for correcting the brightness distribution data of the striped image using brightness distribution data at the time of full irradiation obtained by imaging with full irradiation of light. measuring device.