JPH0814882A - Device for measuring three-dimensional surface shape - Google Patents

Abstract

PURPOSE:To provide an inexpensive device for precisely measuring three- dimensional surface shape. CONSTITUTION:A device for measuring three-dimensional surface shape comprising a light source 1 for emitting light, grids arranged at predetermined pitches, a projection lens 4 whose position is slightly deviated so as to project light having passed through the grids onto the surface of an object 2 to be measured in order to obtain a stripe image which is out of focus, an image pick-up lens 6 for picking up the stripe image on the surface of the object to be measured, a CCD camera 7 for inputting the strip image picked by the lens 6, and a computing part 8 for computing a surface shape of the object to be measured from the image given by the CCD camera.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a three-dimensional surface shape measuring apparatus for non-contactly obtaining the surface shape of an object to be measured.

[0002]

2. Description of the Related Art Conventionally, as a method of highly accurately measuring the surfaces of electrical parts such as mechanical parts and contacts in a non-contact manner, an optical contact probe applying the principle of triangulation is used as a measuring head and measured on an XY table. A target object is installed and the surface shape is measured by driving this XY table, or an electron beam is applied to the measurement target object surface using a scanning electron microscope.
There is a method in which the reflected beam is captured by multiple sensors and the shape is calculated by calculation.

However, an application of the principle of triangulation may not be practical because it takes time to scan an XY table, and an application of a scanning electron microscope requires evaporation as a pretreatment of an object to be measured. Because it is necessary
Strictly speaking, it cannot be said to be non-contact, and the object to be measured may become unusable.

Therefore, as disclosed in Japanese Patent Laid-Open No. 4-278406, a grid is projected from a light source located obliquely to the surface of the object to be measured, and the brightness of the striped image formed on the surface of the object is defined as the projection direction of the grid. There is a fringe scanning method that obtains a three-dimensional surface shape of an object by calculating a fringe image by using a modified grid projection method that measures from another angle. As shown in FIG. 4, the measuring device using the modified grid projection method and the fringe scanning method measures a light source 1 that emits light, a grating 3 having a constant pitch, and light that has passed through the grating 3 as a measurement target. Object 2
The projection lens 4 that projects a striped image on the
The taking lens 6 for taking a striped image of the surface of 2, the CCD camera 7 for inputting the striped image taken by the taking lens 6, and the C
It has a control unit 8 which calculates and obtains the surface shape of the measurement target object 2 from the image of the CD camera 7. In this measuring device, when a striped image is projected on a flat plate having no unevenness, a sine waveform image is input to the CCD camera 7, and the deviation from the sine waveform causes the three-dimensional surface shape of an object having unevenness to be determined. Looking for.

[0005]

The three-dimensional surface shape measuring apparatus using the modified grid projection method and the fringe scanning method described above forms a fringe image on a flat plate without unevenness due to the influence of distortion of the projection lens and the photographing lens. Even in the case of projection, the waveform shows a slight deviation from the sine waveform on the CCD camera. Due to this shift,
An error occurs when measuring the surface shape of the object, and the measurement accuracy decreases. For this reason, it is conceivable to install a liquid crystal panel having an intensity distribution that has a sinusoidal waveform on the CCD camera when projecting a striped image on a flat plate without unevenness, instead of a grid. However, this liquid crystal panel is expensive.

Further, a measurement error may occur depending on the color distribution of the object to be measured and how the light hits. For example, a streak generated when the object to be measured is ground causes an error. In this case, when a striped image is projected on a flat plate having no unevenness, the waveform becomes a sinusoidal waveform on which a fine vibration wave is superposed, so that the measurement accuracy decreases when the surface shape of the object is measured.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an inexpensive three-dimensional surface profile measuring apparatus with high measurement accuracy.

[0008]

In order to solve such a problem, the three-dimensional surface profile measuring apparatus according to claim 1 is a light source which emits light, a grating having a pitch of a constant interval, and a grating which passes through the grating. A projection lens that projects light as a striped image on a measurement target object, a shooting lens that captures a striped image on the surface of the measurement target object, and a striped image captured by the shooting lens are input C
In a three-dimensional surface profile measuring device having a CD camera and a control unit for calculating the surface profile of an object to be measured from the image of the CCD camera, a striped image slightly out of focus is input to the CCD camera. It has such a configuration.

According to a second aspect of the present invention, there is provided a three-dimensional surface shape measuring apparatus in which the projection lens according to the first aspect is arranged such that the position of the projection lens is slightly shifted so as to project a fringe image slightly out of focus on the surface of the object to be measured. ing.

According to a third aspect of the surface shape measuring apparatus of the third aspect, the taking lens of the first aspect is constructed such that the position is slightly shifted so that a fringe image with a slight focus shift is input to the CCD camera. .

[0011]

According to the structure described in claim 1, since the fringe image input to the CCD camera is slightly out of focus,
The waveform showing the striped image is rounded, and it becomes difficult to understand the error when measuring the surface shape of the object.

Further, according to the structure of claim 2, in addition to the effect of claim 1, it is only necessary to move the projection lens to shift the focus of the striped image on the surface of the object. Therefore, the structure is simple. is there.

According to the third aspect of the present invention, in addition to the effect of the first aspect, it is only necessary to move the taking lens to input the fringe image with a slight out of focus to the CCD camera. Is easy.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a system configuration diagram of the present invention. The projection system is provided so as to have a constant angle with respect to the normal line of the measurement target object, and the imaging system is provided in the normal direction of the measurement target object.

Reference numeral 1 denotes a light source, which has a lamp 1a, a lens 1b, and a reflector 1c, and emits light. The light passes through a grating and a projection lens, which will be described later, and is applied to the measurement target object 2 at a constant angle.

Reference numeral 3 denotes a grating, which is configured to allow light to pass through a gap having a constant pitch. This grid is formed of metal, resin, wood, liquid crystal, or the like so as to have two patterns of a place where light passes and a place where light does not pass.

Reference numeral 4 denotes a projection lens, which projects the light having passed through the grating 2 onto the surface of the object to be measured 2 to form a striped image having a striped pattern with light and dark. The optical axis of this projection lens 4 is perpendicular to the grating 3 and
It has a certain angle with respect to the normal line. Further, the projection lens 4 is displaced by about 2 mm from the focused position of the focus so that the stripe image projected by the projection lens 4 on the surface of the measurement target object 2 is slightly defocused. 5 is a measuring table on which the object 2 to be measured is placed.

Reference numeral 6 denotes a photographing lens for photographing a fringe image of the surface of the measurement target object 2 and
It is located right above. By the way, light source 1, grating 3,
The projection lens 4, the optical axis consisting of the measurement target object 2
The optical axis consisting of the object to be measured 2 and the taking lens 6 is called the taking system.

Reference numeral 7 denotes a CCD camera, which inputs a striped image taken by the taking lens 6 as a video.

Reference numeral 8 denotes a control unit which calculates the surface shape of the object 2 to be measured from the image of the CCD camera 7. The control unit 8 includes a camera controller 9 and an image input board 1
0, a computer 11 and a table controller 12 are provided, and the striped image input to the CCD camera 7 is input to the computer 11 via the camera controller 9 and the image input board 10. Table controller 12 grid
The position of 3 is moved in the pitch direction, and is controlled by the computer 11.

Next, a surface shape three-dimensional measuring apparatus using the above configuration will be described. By turning on the light source 1,
The light that has passed through the grating 3 and the projection lens 4 is
A fringe image with a slight out-of-focus is formed on the surface of the object at evenly spaced pitches when viewed from the projection system. By observing the fringe image with the photographic lens 6 from the photographic system, it is possible to capture a fringe image composed of a deformed lattice corresponding to the unevenness of the surface of the measurement target object 2. This is the modified grid projection method. The pixel data of the striped image is transferred to the CCD camera 7, camera controller 9,
After inputting to the computer 11 via the image input board 10, the grid 3 is set to the grid 1 by the table controller 12.
Move / 4 pitch in the pitch direction. Then, a striped image is captured in the same manner as above. This is repeated 4 times, and 4 types of striped images (stripe image 1, striped image 2, striped image 3, striped image 4)
Is input to the computer 11 as pixel data.

Assuming that the light intensities of the pixels of each stripe image at any position of the object to be measured 2 are I1, I2, I3 and I4, the phase φ at any position can be calculated by the following equation.

Φ = tan ⁻¹ ((I 2 −I 4) / (I 1 −I 3)) By connecting this data over the entire surface of the measurement target object, the entire shape data can be obtained. In addition,
Performing the above calculation is called a stripe scanning method. Therefore, the three-dimensional surface shape of the measurement target object is obtained from the shape data obtained as described above.

With this structure, a fringe image with a slight deviation in focus is formed on the surface of the object 2 to be measured, so that the influence of distortion of the projection lens 2 is reduced and the fringe image is formed on a flat plate having no irregularities. A more accurate measurement target object because it approaches a sine waveform on the CCD camera 7 when projected.
A surface shape of 2 is required.

Next, a second embodiment of the present invention will be described with reference to FIGS.
Shown in In this embodiment, the taking lens 6 is out of focus, and this point will be mainly described.

The taking lens 6 is used for measuring the object 2 to be photographed.
In order to slightly shift the focus of the striped image on the surface of, the installation position is shifted by about 2 mm from the focus position in focus.

With such a configuration, fine vibration waves generated on the CCD camera 7 due to the color of the surface of the object to be measured 2 and the way the light hits are reduced, and the influence of distortion of the taking lens 6 is also reduced. Therefore, when projecting a striped image on a flat plate having no unevenness, the CCD camera 7 approaches a sinusoidal waveform, and a more accurate three-dimensional surface shape of the measurement target object 2 is required.

FIG. 3 shows the measurement accuracy when the focus of the taking lens 6 is shifted, and the horizontal axis represents the taking lens 6.
From the focus position, and the vertical axis represents the measurement accuracy (smaller values are more accurate). From this figure, it can be seen that the measurement accuracy when the position of the taking lens 6 is shifted by about 2 mm from the focus position of the taking lens 6 is the best.

Although the position of the projection lens 4 or the photographing lens 6 is shifted in order to shift the focus of the striped image, the present invention is not limited to this.
The position of the projection lens 4 or the shooting lens 6
Other configurations are also conceivable, such as having a structure in which is slightly out of focus. The grating 2 has two patterns, that is, a place where light passes and a place where light does not pass. However, it is not limited to this, and it is formed by a liquid crystal pattern in which the amount of passing light gradually changes. Good. Furthermore, the fringe scanning method using four screens has been described, but the present invention is not limited to four screens in particular, and three or more screens can be used. Further, the projection system is provided so as to have a constant angle with respect to the normal line of the measurement target object 2, and the imaging system is provided in the normal direction of the measurement target object 2, but this is not particularly limited.

[0030]

According to the three-dimensional surface shape measuring apparatus of the first aspect, since the fringe image input to the CCD camera is slightly out of focus, the waveform indicating the fringe image is blunted and the surface shape of the object is determined. Since the error when measuring is difficult to understand,
Measurement accuracy is improved.

In addition to the effect of claim 1, the surface shape three-dimensional measuring apparatus according to claim 2 has a structure in which the focus of the striped image on the surface of the object can be shifted only by moving the projection lens. Is simple and cheap.

In addition to the effect of claim 1, the surface shape three-dimensional measuring device according to claim 3 inputs the striped image with a slight defocusing to the CCD camera only by moving the photographing lens. Therefore, the structure is simple and the cost is low.

[Brief description of drawings]

FIG. 1 is a system configuration diagram of a surface shape three-dimensional measuring apparatus showing a first embodiment of the present invention.

FIG. 2 is a system configuration diagram of a surface shape three-dimensional measuring apparatus showing a second embodiment of the present invention.

FIG. 3 is a diagram showing the measurement accuracy.

FIG. 4 is a system configuration diagram of a surface shape three-dimensional measuring apparatus showing a conventional example of the present invention.

[Explanation of symbols]

 1 Light source 2 Object to be measured 3 Lattice 4 Projection lens 5 Measuring table 6 Photographing lens 7 CCD camera 8 Controller 9 Camera controller 10 Image input board 11 Computer 12 Table controller

Claims (3)

[Claims] 1. A light source that emits light, a grating having a constant pitch, a projection lens that projects light passing through the grating as a fringe image on a measurement target object, and a fringe image on the surface of the measurement target object. A surface shape three-dimensional measuring device comprising: a taking lens; a CCD camera for inputting a striped image taken by the taking lens; and a control unit for calculating the surface shape of an object to be measured from an image of the CCD camera. A three-dimensional surface shape measuring apparatus, characterized in that a fringe image slightly out of focus is input to a camera. 2. The surface shape three-dimensional measuring apparatus according to claim 1, wherein the projection lens is slightly displaced in position so as to project a fringe image that is slightly out of focus on the surface of the object to be measured. 3. The surface shape three-dimensional measuring apparatus according to claim 1, wherein the photographing lens is slightly displaced in position so that a fringe image with a slight out-of-focus is input to a CCD camera.