JPS59222711A - Plane-shape displaying device - Google Patents

Abstract

PURPOSE:To obtain flatness readily, by holding a medium having a high refractive index with a medium having the refractive index lower than said medium, using an interference film device having a pair of interfaces, and judging the sequence of the change in lightneess in three stages. CONSTITUTION:A device comprises a first dielectric layer 28 having a relatively high refractive index and a second dielectric layer 30 and a third dielectric layer 32, which hold the layer 28 and have a refractive index lower than that of the layer 28. There are a first interface 34 and a second interface 36. The reflected light beams from the first interface 34 and the second interface 36 reach a half mirror 14 through a collimator lens 16 together with the reflected light beam from a material to be checked 20. The light beams are reflected by the half mirror 14 and received by an industrial TV camera 24 through a condenser lens 22. Interference fringes constituting an interference image 38 comprise the bright fringes, whose lightness is large, the intermediate fringes, whose lightness is medium, and the dark fringes, whose lightness is small. The sequence of the lightness corresponds to the slant direction of the surface of the material to be checked.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a planar shape display device that visually displays the planar edge of a mirror-finished surface of an object to be sandwiched.

・Background of the invention The planar shape of the surface of mirror-finished objects such as mirrors, IC wafers, and lenses in optical order such as micron order or submicron order cannot be visually inspected. It is generally recognized visually by using an interference device. In other words, by irradiating the surface of the specimen with monochromatic light through an interference film device,
An interference image consisting of interference fringes based on the mutual interference between the reflected light from the surface of the object and the light reflected from the interference film device is generated, and the plane of the surface of the object ( This is to understand the shape (irregularities and convexities).

However, in conventional devices, the inclination direction of the object surface is unknown only from the multiple interference fringes in the interference image. It was necessary to move the fringes and determine the planar shape (concave or convex) of the surface of the object according to the moving direction of the interference fringes. For this reason, the conventional apparatus requires a device for relatively moving the object to be inspected and the interference film device, and a relative movement operation thereof, making the apparatus complicated and difficult to operate.

・Purpose of the Invention With the above circumstances as a background, the present inventor has devised a method for easily changing the planar shape of the surface of an object to be inspected without requiring a device for relatively moving the object to be inspected and an interference film device and an operation therefor. With the aim of providing a planar display device for displaying images, we conducted various inspections on optical interference devices, and found that a medium with a relatively high refractive index is sandwiched between a medium with a lower refractive index and a medium with a lower refractive index. By using an interference film device having a pair of interfaces formed between each, interference fringes with three levels of brightness can be obtained.
Furthermore, we have discovered that the order of change in brightness for each interference fringe is related to the direction of inclination of the surface of the object.

The present invention has been made based on the above findings.

・Structure of the invention, that is, the gist of the present invention is as follows: (1) A first medium having a high refractive index, and second and third media sandwiching the first medium and having a lower refractive index than the first medium. , between the first medium and the second medium, and between the first medium and the third medium, the mutual spacing is (2n+1) λ/4 (where λ is the wavelength and n is an integer starting from zero). an interference film device in which a parallel first boundary surface and a second boundary surface are formed; (2) through the interference film device, the surface of the object to be inspected is irradiated with monochromatic light having a wavelength of λ and having a uniform phase; a light source; (3) an imaging device that captures an interference image consisting of a plurality of interference fringes based on mutual interference of respective reflected lights from the surface of the test object, the first boundary surface, and the second boundary surface;
(4) a storage device that stores the interference image captured by the image pickup device; (5) an output device; , a central processing unit having a display control means for determining the inclination direction of the object surface and visually displaying the planar shape of the object surface along the cutting line on the output device according to the inclination direction and the number of interference fringes; and a device.

・Effects of the Invention In this way, when the surface of the object to be measured is irradiated with monochromatic light through the interference film device, interference fringes with three levels of brightness can be obtained, and the order of change in brightness for each interference fringe can be changed. Since this corresponds to the direction of inclination of the surface of the object to be pinched, the oblique direction of the surface of the object to be pinched is determined based on the order of change in brightness. Therefore, without moving the object and the interference film device relative to each other, the planar shape (irregularity) of the surface of the object along the tangential line can be easily displayed visually on the output device according to the inclination direction and the number of interference fringes. It is. The flatness of the surface of the sandwiched object can be easily calculated based on the planar shape of the surface of the sandwiched object visually displayed on such a display device or the data for visually displaying the planar shape on the output device. be.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below based on the drawings.

・Configuration of the Embodiment FIG. 1 shows a so-called Fizeau interferometer to which the present invention is applied, in which monochromatic laser light with a wavelength λ emitted from a laser light source of 1° passes through a half mirror I4 to a collimator. After reaching the lens 16 and being made into parallel light by the collimator lens 16, the light is irradiated onto the surface of the object 20 through the interference film device 18. The reflected light from the surface of the test object 20 passes through the interference film device 18 and the collimator lens 16 and reaches the half mirror 14. After being reflected by the half mirror 14, the light is condensed by the condenser lens 22 and sent to the industrial television camera 24. I can be accepted. The interference film device 18 consists of an optically flat reference plate 26 and a multilayer film coated on the surface of the reference plate 26 facing the object 2o. The multilayer film includes a first dielectric RF428 as a first medium with a relatively high refractive index, and a second dielectric layer 30 as a second medium with a lower refractive index sandwiching the first dielectric layer 28. and a third dielectric layer 32 as a third medium, and these first dielectric layer 28 and second dielectric layer 30
and between the first dielectric layer 28 and the third dielectric jftf3
2, a first boundary surface 34 and a second boundary surface 3G are formed. The reflected light from the I-th boundary surface 34 and the second boundary surface 36 also reaches the half mirror 14 through the collimating lens 16, and after being reflected by the half mirror 14, is received by the industrial television camera 24 through the condenser lens 22. .

Therefore, in the industrial television camera 24, there are multiple An interference image 38 consisting of interference fringes is received as shown in FIG. 2Fal.

Here, the interference fringes constituting the interference image 38 consist of a bright line 4o with high brightness, an intermediate line 42 with intermediate brightness, and a dark line 44 with low brightness, and the order of brightness is determined by the slope of the surface of the object to be sandwiched. Corresponds to the direction. For example, in Figure 2 (al
and (as shown in bl, bright lines 40, dark stripes 44, and intermediate lines 42 appear in this order in the part where the inclination direction is positive, and bright lines 40, intermediate stripes 42.nl appear in the part where the inclination is negative) stripes 4
They appear in the order of 4.

The fact that such stripes having three levels of brightness can be obtained has been confirmed by simulations performed by the present inventor. In other words, in a conventional interferometer using an interference film device having a single boundary surface, the combined intensity (brightness) of the reflected light from the surface of the object 200 and the reflected light from the interface of the interference film device is calculated. As a result, the brightness of the combined reflected light (interference fringes) with respect to the phase difference could only be obtained in two stages, as shown in FIG.
6 and their interface 34
．． When the combined reflected light of the reflected light from 36 and the reflected light from the surface of the test object 20 is calculated, three different interference fringes are obtained as shown in FIGS. 4 to 7.

Note that the distance between the first boundary surface 34 and the second boundary surface 36 at this time is λ/4 (λ is the wavelength of the laser beam), and the second dielectric layer 3
The refractive index n(2) of 0 is 1.5, the refractive index n(3) of the third dielectric N31) is 1.5, and the amplitude reflectance r of the surface of the test object 20
m is −0.95, and the refractive index n(
1) is 3.0 in Figure 4, 4.0 in Figure 5,
It is 5.0 in FIG. 6 and 6.0 in FIG.

Here, the above-mentioned interference fringes with three levels of brightness can be obtained even if the distance between the first boundary surface 34 and the second boundary surface 36 is changed; for example, if the distance is set to 3λ/4. Also, interference fringes with three levels of brightness as shown in FIG. 8 can be obtained.

In other words, the distance between the first boundary surface 34 and the second boundary surface 36 is (2n+1)λ/4 (where n is an integer starting from 0)
That's fine. Note that the first dielectric material Jiif28
If the refractive index n (1) of is 2.0, it becomes difficult to obtain interference fringes with three levels of brightness as shown in FIG. Therefore, the refractive index n(1) of the first dielectric layer 28 may be twice or more the refractive index n(2) of the second dielectric layer 3o or the refractive index n(3) of the third dielectric layer N32. preferable.

In addition, as mentioned above, interference fringes with three levels of brightness 40.42
．． 44 has been experimentally confirmed as shown in FIG. At this time, an industrial television camera 2 is placed at the position where the interference image is formed in the apparatus shown in FIG.
A phototransistor is provided in place of 4, and the phototransistor is moved in a direction perpendicular to the optical axis (scanning).
This is the data obtained by

On the other hand, the interferometer shown in FIG. 1 is equipped with a control device shown in FIG. 11. That is, the industrial television camera 24
A video signal representing the interference image received is provided via an A/D converter 46 to a video signal storage device 48 where it is stored. Some or all of the video signals stored in video signal storage 48 are provided to I10 port 50 according to command signals from the I10 port. I10
The board 50 is connected to a CPU 52 . as a central processing unit via a data bus line. ROM54. The CPU 52 uses the primary storage function of the RAM 56 according to programs stored in advance in the ROM 54 and operation signals from the keyboard 58, and processes signals from the video signal storage device 48 to display the display device 60. The display signal is supplied to the The display device 60 is constituted by a cathode ray tube or printer capable of displaying images, a plotter capable of displaying graphs, or the like.

Operation of the Embodiment The operation of this embodiment will be explained below with reference to the flowcharts of FIGS. 12 to 16.

First, the object 20 to be examined is centered, and the laser beam from the laser light source 10 is applied to the half mirror 14, collimator lens 16, . When the light is irradiated through the interference film device 18, the reflected light from the object 20 and the interference film device 18 is received by the industrial television camera 24 via the half mirror 14. 2
The interference image 38 shown in FIG. , the video signal stored in the video signal storage device 48 is classified into three predetermined gradations according to its brightness. Depending on which gradation it belongs to, it represents, for example, a dark level, a middle level, and a bright level, respectively. By assigning codes rOj, rlj, and r2J, it is processed into three gradations and read into the RAM 56. Then, step S2 is executed, and the flatness acceptance criteria for the surface of the test object 20 are read.

The acceptance criteria are set and input from the keyboard 58. In step S3, it is determined whether or not the setting input of the acceptance criteria has been completed. If it has not been completed, step S2 is executed again, but in the completed state, step S4 is executed and the specified input is completed. The positions of one or more tangent lines are read. The cutting line position is input by operating the keyboard 58. Next, step S
In step 5, it is determined whether or not the input of the cutting line position has been completed, and if it has not been completed, step S4 is executed again, but if it has been completed, step S6 is executed,
Interference fringe width on pre-specified cutting line position, e.g. dark line 4
It is determined whether the number of pixels of 4 is less than a predetermined maximum number, for example, 30 pixels, and if it is not, step S7 is executed and an error 1 message is output. That is, the number of pixels is a measure of the sharpness of the interference image 38, and if the width of the dark line 44 is large (the number of pixels is large) and the number of fringes in the interference image 38 is small, the image will become unclear. A message is displayed on the error indicator or screen indicating that the installation of the test object 20 is inappropriate and is out of scope for measurement. If it is determined in step S6 that the number of pixels of the dark line 44 is 30 pixels or less, that is, it is determined that the installation is appropriate, step s8 is executed, and the number Nm of interference fringes on the cut line position read in step S4 is It is memorized for each cut line.

For example, if the m-th tangent position specified in step S4 is m in Fig. 2 (al), then Fig. 2 tar
In the interference image 38, the number of dark lines 44 is 19.

Step S9 is then executed, and it is determined whether the number Nm of stripes on the designated tangent line is greater than 3 and less than 20. If the number of stripes Nm is not within that range, step 31
0 is executed and an error message is generated. In other words, if the number Nm of stripes is less than 3, the flatness is extremely good, and if there are more than 20 stripes even after adjusting the sandwiched object, the flatness is extremely poor and is not suitable for measurement. is displayed on the display device 60. Next, step Sll is executed, and it is determined whether or not the designation input of all cutting line positions has been completed. If not, step SI2 is executed, and 1 is added to the contents of register m-. After that, steps 84 and subsequent steps are executed again. By repeating the above operations, a total of n cutting lines are designated and input.

Here, the number Nm of fringes indicates the number N of interference fringes (dark lines 44 in this embodiment) on the cutting line of m book openings.

When the cut line specification completion key is operated on the keyboard 58, step 313 is executed, and the contents of register M are set to be the same as the contents of register m representing the total number n of specified cut lines, and step S14 is executed. , the contents of register m are set to 1 in preparation for the next designation.

When the acceptance criteria for flatness and the position of the cut line are inputted as described above, the surface shape and flatness of the surface of the test object along each cut line are calculated in the following steps, and the test object 2 It is determined whether the test passes or not and is displayed.

First, in step 515, the cross-section processing routine shown in FIG. 13 is executed, and each X-coordinate value for drawing the planar shape (cross-sectional shape) of the surface of the test object 20 along the specified cutting line is determined. That is, step SDI is executed to perform scanning along a predetermined cut line, and step SD2 is executed to determine whether the brightness is at the lowest level "0" among the three gradations, in other words, whether or not the dark line is detected. 44 exists. Such scanning is continued until the dark line 44 is detected, and at the same time the dark line 44 is detected, step SD
3 is executed and the coordinates Xmk are stored.

For example, if scanning is performed from the left end along the tangential line m in the interference image 38 shown in FIG.
This is the position indicated by the dot.

After that, step SD4 is executed to further continue the scan, and in step SD5 it is determined whether the scan has ended, in other words, whether the right end of the interference image 38 has been reached, and if it has ended, then The cross section processing routine is terminated, but since it is not generally terminated, step S is performed.
D6 is executed, and it is determined whether the brightness is the lowest level "0". If the brightness is still at the lowest level, steps 84 and subsequent steps are executed again, but when the scanning position reaches the right end of the dark line 44, the brightness is at the intermediate level rlJ or the highest level "2". Therefore, step SD7 is executed and the brightness is set to the intermediate level "1".
”, but whether or not it is determined is determined. That is, it is determined whether the right side of the dark line 44 is the intermediate line 42 or the bright line 4o.

If it is the intermediate line 42, step SD8 is executed;
The content of (SGNXmk), which is information corresponding to the coordinate Xmk and indicates whether the slope of the surface of the test object 20 is positive or negative, is set to a predetermined constant positive value, for example, 1/2. Then, step SD9 is executed, and the content of k is set to 1.
Add. This k is the X coordinate Xmk and (SGN
Since 1 is added each time mk) is determined, it corresponds to the number of dark lines 44.

On the other hand, if the bright line 4o with the highest level of brightness "2" is detected on the right side of the dark line 44 in step SD7, step 5DIO is executed and the content of (SGN Xmk) is set to a predetermined constant negative value. The value is, for example, 1/2. Then, step 5DII is executed, and 1 is added to the contents of k by 1λ similarly to step SD9. For example, point B in Fig. 2 fa) is such a case.

After the step SD9 is completed, the steering knob 5
DI2 is executed and further scanning is executed, and step S D 1.3 is executed to determine whether the scanning has ended or not. If not, step 5D14 is further executed and if the brightness is still intermediate. Level "1"
However, it is decided whether or not it is. If the intermediate level is still "1", steps 5D12 and subsequent steps are executed again, but if interference fringes adjacent to the right side of the intermediate line 42 are detected and the brightness is not the intermediate level "1", step S I )
15 is executed, and it is determined whether the brightness is at the lowest level rOJ. If the brightness is at the lowest level rOJ, the steps from step 84 described above are executed, but if the brightness is not at the lowest level rOJ, that is, the brightness is at the highest level.
2'', step 5D16 is executed and scanning is continued. Point C in FIG. 2 (al) shows this state. When the scan in step 5D16 is executed, step 5D17 is executed to determine whether the scan is finished, and if it is not finished, step 5DI8 is executed. Then, it is determined whether the brightness is still at the highest level "2". If the brightness is still at the highest level "2", steps 5DI6 and subsequent steps are repeated, but the brightness is still at the highest level "2".
If not, step 5D19 is executed, and it is determined whether the brightness is at the intermediate level "1". That is,
It is determined whether the interference fringes to the right of the bright line 4° are the dark line 44 or the intermediate line 42. If the brightness is not at the intermediate level "l", that is, if the brightness is at the lowest level "0", steps SD3 and subsequent steps are executed again, but when the brightness is at the intermediate level "1"
If so, the steps from step 5DI2 described above are executed.

The above steps are repeatedly executed until the scan is completed, that is, until the right end of the tangent line is reached, and the coordinate Xmk of the left end of the dark line 44 on the tangent line m and the inclination direction of the surface of the object 20 at that coordinate position are shown (SGN Xmk ) are stored respectively.

This information is used in the flatness subtraction routine and display routine described below.

When the execution of the cross-section processing routine is completed as described above, the flatness subtraction routine of Ste.knob S16 in FIG. The flatness Dm of the surface of the test object 20 along a predetermined cutting line is calculated as follows.

As shown in FIG. 14, first, Ste Knob SH1 and Step SH2 are executed, and it is determined whether the slope falling at each X coordinate point determined by the cross section processing routine is 0, and whether it is positive or negative. be judged. That is, in step SHI, (SGN Xmk) + (S
It is determined whether the calculated value of GN Xmk++) is 0 or not, and it is also determined whether the calculated value of Ste Knob SH2 is +1 or -1. If it is determined in step SHI that the slope is 0, step SH3 is executed and a new Z coordinate Zik
After the content of +1 is made the same as the content of the Z coordinate Zmk adjacent to the left, step SH4 is executed and the content of k is set to 1.
is added. Furthermore, if it is determined that the slope is positive in step SH2, then in step SH5 the contents of the new Z coordinate Zmk++ are added by 1/2 to the contents of the Z coordinate value Zmk of the coordinate point adjacent to the left side. value, and if it is determined that the slope is negative, the contents of the new X coordinate Zmk++ are changed to Zmk' (1/2 is subtracted from the D contents in step SH6. After H6 is executed, the above-mentioned SH4 is executed, and then step SH7 is executed to judge whether k is larger than the number Nm of interference fringes on the m-th tangential line, and if it is not larger, then Steps SHI and subsequent steps are executed again, but if it is larger, step SH8 is executed and the content of k is set to 2. That is, according to the execution of steps SH1 to SH7, the X coordinate Xn+k on the m-th cutting line is The corresponding Z coordinate Zmk is determined respectively.Before executing step SHI, an initialization routine (not shown) is executed, and the Z coordinate corresponding to the leftmost X coordinate Xm+ is determined.
The content of the coordinate Zm+ is O. Therefore, since the coordinates (Xm+, Zm+) are taken as the origin, step SH8 is provided.

Next, the first flatness calculation routine in step SH9 is executed to calculate each coordinate point (Xmk, Zm
k) to the virtual plane (perpendicular distance) Dmk
is calculated, and the second flatness calculation routine of step 5H10 is executed to determine whether the distance Dmk calculated in step SH9 is above or below the reference line G (SGN Dmk). Ru. Here, the reference line G is the origin (Xm+, Zm+) and the rightmost coordinate point (
Xmn, Zmn), and indicates a virtual plane.If the content of (SGN Dmk) is 1, it indicates the upper side of the virtual plane, and if it is -1, it indicates the upper side of the virtual plane. Showing the bottom side.

In the first flatness calculation routine, the so-called Cramer's equation is used to calculate the coordinate points (Nmk, Z
mk) to the virtual plane is calculated. That is, as shown in FIG. 15, by executing steps SEI to SE3, the following equation (11, (
Drno, Dmx, Dmz based on 21 and (3)
is calculated, and the following equations (4) and (5) are calculated in steps SE4 and SE5, so that
Dmo and Dm obtained in steps SEI to SE3
Based on x, Dmz, the seating point (Xmk, Zmk)
Coordinates (X'mk, Z'mk) of the intersection of the perpendicular line drawn from to the virtual plane and that virtual plane (reference line G)
are required respectively. Then, in step SE6, the calculation of the following equation (6) is executed, and the coordinate point (Xmk,
Zmk) and the intersection (X'mk.

The distance Dmk of the straight line connecting Z'mk) is determined as shown in FIG.

Z' mk=Dmz/Dmo
---(51 And the second flatness calculation
The routine is executed according to each step shown in FIG. 17, and as shown in FIG. 18, the position vector of each coordinate point is on the upper side or the lower side with respect to the virtual plane according to the vector calculation. will be judged. That is, in step SFI, the following equation (7) is calculated to calculate the virtual plane vector Y = (XllIL Zmi), and in step SF2, the following equation (8) is calculated.
is calculated, and the position vector of each coordinate point Q=(Xmr.

Xmr) is calculated.

Trap x completion=Xmr -Zmi -Xmi -Zmr
----191 Then, in step SF3, it is determined whether or not the position vector prize is below the virtual plane hector end. That is, as shown in equation (9), it is determined whether the cross product of the virtual plane vector trap and the position vector is positive, and if it is positive, step SF4
is executed, and the content of <SGN Dmk) is set to the value indicating the upper side +1. On the other hand, if it is negative, step S
F5 is executed, and the contents of (SGN Dmk) are set to -1 indicating the lower side.

As described above, the first flatness calculation routine and the second
When the routine is executed, step 5HII in FIG. 4 is executed, 1 is added to the contents of k, and step 5H12 is executed, where k does not indicate the number of dark lines 44 on the tangent line m, and 1 is subtracted from Nm. It is determined whether or not it is larger than the subtracted value, and if it is not larger, steps SH9 and subsequent steps are executed again, but if it is larger, the next step S Hl 3 is executed.
is executed. That is, the dark line 44 at the predetermined cutting line
The distance Dmk of the coordinate point (Xn+, Z+nk) to the virtual plane is calculated for each time, and the distance (SGN Dmk) indicating whether the distance or the coordinate point (Xmk, Zmk) is above or below the virtual plane is calculated. It is decided.

Then, steps 5H13 and 5H14 are executed,
The maximum value Dmkmax and the minimum value Dmkmi of the distance Dmk determined in steps SH9 to 5H12
While n is determined, step 5HI5 is executed based on the result, and the flatness Dm is calculated. Here, the maximum value Dmkmax is the maximum value of the distance Dmk above the virtual plane, as shown in FIG. 19, and the minimum value Dmkmin is the distance lD below the virtual plane.
This is the maximum value of mkl.

In addition, flatness is as shown in JISBO621,
It refers to the minimum interval when a curved part is sandwiched between two parallel geometric planes (straight lines), and in this example, when the geometric planes are sandwiched parallel to the reference line G representing a virtual plane. corresponds to

Returning to FIG. 12, when the flatness calculation routine of step S16 is executed as described above, step S17 is executed and 1 is added to the contents of register m, and step 818 is executed and the contents of register m is register M
It is determined whether or not the content is larger than the content of . If it is not large, steps SL5 and subsequent steps are executed again, but if it is large, the next step S19 is executed. That is,
The above-described cross section processing routine and flatness calculation routine are executed for each preset cutting line, and the coordinate points (Xmk, Zmk) and flatness Dm of the dark line 44 for each cutting line are determined.

Then, step S19 is executed, and it is determined whether or not the flatness Dm obtained in step 316 is smaller than the set flatness, which is the acceptance criterion set in step S2. If it is smaller, step S20 is executed. Then, the non-defective message is displayed on the display device 60, but if the flatness Dm is equal to or higher than the set flatness, step S21 is executed, and the defective message is displayed on the display device 60.
Displayed in . At the same time, the display routine of step S22 is executed, and each coordinate point (Xmk
. As shown in the figure, a three-dimensional display is made in which two-dimensional data representing such a planar shape are superimposed in a predetermined Y direction.

In this way, according to this embodiment, the interference fringes 40, 42 . j4 is obtained, and the unevenness in the interference image 38 can be easily determined based on the change order of brightness without relatively moving the test object 20 and the interference film device 18, and the test object is detected in the display word W60. The planar shape of the 20 surface can be easily displayed visually.

Further, according to this embodiment, not only the uneven shape of the surface of the test object 20 is visually displayed, but also the flatness of the surface of the test object 20 is automatically calculated, and the flatness is calculated according to the preset acceptance criteria. It has the advantage of being able to judge the quality and indicate whether it is a good product or a defective product.

Although the embodiment of the present invention has been described above based on the drawings, the present invention can also be applied to other aspects.

For example, in the embodiments described above, the interference film device 18 is
There is no problem even if the dielectric N30 is removed. That is, this is because the reference plate 26 is generally made of glass having the same refractive index as the third dielectric N32. Further, an air layer may be used instead of the second dielectric layer 30 and/or the third dielectric layer 32. In short, the interference film device has a spacing of (2
n+1) a pair of first and second interface surfaces 34 and λ/4;
It is sufficient that the medium provided with the boundary surface 36 and sandwiched between the first boundary surface 34 and the second boundary surface 36 has a higher refractive index than the other medium.

Further, in the above embodiment, each coordinate point is determined based on the dark line 44, and the intermediate line 42 is next to the dark line 44.
The test object 2 depends on which of the bright lines 40 and 40 is present.
0 The slope of the surface is determined, but dark line 4
4, the inclination of each coordinate point or the surface of the object 20 may be determined based on the intermediate line 42 or the bright line 40.

Furthermore, although laser light is used in the above-described embodiments, other monochromatic light having known wavelengths and uniform phases may also be used.

It should be noted that the above-mentioned bending is merely one embodiment of the present invention, and various changes may be made to the present invention without departing from the spirit thereof.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating the mechanical configuration of an embodiment of the present invention. Figure 2 (al is a diagram showing an example of an interference image received by the apparatus in Figure 1, and Figure 2 (bl is a diagram showing the planar (uneven) shape of the object displayed based on the interference image. FIG. 3 is a diagram showing the brightness of interference fringes obtained by a conventional interferometer. FIGS. 4 to 9 are diagrams showing the brightness of interference fringes obtained by the apparatus of FIG. FIGS. 4 to 7 are diagrams showing the first
The refractive index of the dielectric layer (first medium) is changed, and FIG. A diagram corresponding to the diagram,
FIG. 9 is a diagram in which the refractive index of the first dielectric layer is less than twice the refractive index of the second dielectric layer and the third dielectric layer. FIG. 10 is an actual measurement diagram showing three levels of brightness of interference fringes obtained by the apparatus shown in FIG. FIG. 11 is a block diagram showing the electrical configuration in one embodiment of the present invention. Figures 12, 13, 14, 15 and 17
The figure shows the main program, cross-section processing routine, and
3 is a flowchart showing a flatness calculation routine, a first flatness calculation routine, and a second flatness calculation routine, respectively. FIG. 16, FIG. 18, and FIG. 19 are diagrams explaining the calculation processing of the first flatness calculation routine, the second flatness calculation routine, and the flatness calculation routine, respectively. FIG. 20 is a diagram showing an example of three-dimensionally displaying the planar shape of the surface of the object to be sandwiched. 10: Laser light source (light source) 181 Interference film device 20: Test object 24; Industrial television camera (imaging device) 28: First dielectric N (first medium) 30; Second dielectric layer (second medium) 32: Third dielectric N (third medium) 34: First boundary surface 36: Second boundary surface 38: Interference image 48: Video signal storage device (storage device) Applicant Brother Industries, Ltd. No. 2o Figure 7 Procedural amendment Blind acting type) % type % Indication of the case 1982 Patent application No. 98202 Name of the invention Person who corrects flat shape display device Relationship to the case Patent applicant name (526) Agent for Brother Industries, Ltd. ■
450 7. Contents of amendment (11 Specification, page 8, line 3, page 12, line 5, page 14, line 6, page 14, lines 6 to 7, page 16, line 9, 18 "1-Figure 2 (a)" in seven locations on the second line of the page and the 20th line of the same page is corrected to "Figure 2 upper row." (2) "2 (Figures 81 and (b)" are corrected to 1, upper row and upper row of Figure 2.) (3) "Figure 2 (b)" in line 1 of page 29 of the specification is corrected to "upper row of Figure 2." (4) Page 31, lines 7 to 10 [Figure 2 (al.
This is a diagram showing... [Figure 2 shows an example of an interference image received by the apparatus in Figure 1 in the upper row, and an example of the plane (unevenness) shape of the object displayed based on the interference image is shown in the above interference image. It is a comparison diagram shown in the upper row in correspondence with the above. ” is corrected. (5) Figure number “Figure 2 (a)” in the drawing is “Figure 2”
and delete figure number 1, figure 2 (b). Above 59

Claims (1)

[Claims] A first medium with a high refractive index, and second and third media sandwiching the first medium and having a lower refractive index than the first medium, and between the first medium and the second medium. and a first boundary surface and a second boundary that are parallel to each other and have a mutual spacing of (2n+1>・λ/4 (where λ is a wavelength and n is an integer starting from zero) between the first medium and the third medium). an interference film device in which a surface is formed; a light source that irradiates the surface of a test object with monochromatic light having a wavelength λ and a uniform phase through the interference film device; and a surface of the test object and a first boundary surface. , an imaging device that captures an interference image made up of a plurality of interference fringes based on mutual interference of the respective reflected lights from the second boundary surface, a storage device that stores the interference image captured by the imaging device, and an output device. and determining the inclination direction of the surface of the object based on the order of change in brightness for each interference fringe on a predetermined tangential line of the interference image,
a central processing unit having a display control means for causing the output device to visually display the planar shape of the surface of the sandwiched object along the cutting line according to the inclination direction and the number of interference fringes; Device.