JP3208273B2 - Surface profile measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light spot scanning speed modulation type surface profile measuring apparatus.

[0002]

2. Description of the Related Art As a conventional light spot scanning speed modulation type surface profile measuring apparatus using a single photodetector, the one shown in FIG. 9 has been proposed.

[0003] As shown in the figure, a scanner 1 scans a surface 2 of a device under test in a fan shape or in parallel while emitting a laser beam toward the surface 2 of the device under test. The laser light reflected at each of the measurement points m <b> 1 to m <b> 5 on the surface 2 of the measured object is imaged by the lens 3. Behind the lens 3, a slit plate 4 having a plurality of openings corresponding to each measurement point is arranged. As shown in FIG. 10, the slit plate 4 is provided with openings E1 to E5 having equal widths at equal intervals, and the laser light passing through the openings E1 to E5
Incident on the photoelectric converter 5 provided behind. The photoelectric converter 5 converts the input laser light into a single measurement pulse signal. The measurement pulse signal is input to the signal processing circuit 6, and reference points M1 to M5 on the reference plane 7 corresponding to a plurality of measurement points m1 to m5 stored in advance with respective input times starting from the measurement start time. Is compared with the input time of the reference pulse signal reflected from the input signal. The signal processing circuit 6
The shape of the surface 2 of the measured object is determined based on the deviation of each of the measurement points m1 to m5 from the reference plane 7 obtained from the result of the comparison.

Here, the principle of determining the shape of the surface 2 of the device under test from the input time of the measurement pulse signal will be described with reference to FIGS. FIG. 11A shows a scanning start pulse detector 8.
10 is a timing chart showing a scanning start pulse signal k output from the signal processing circuit 6 (see FIG. 9). FIG.
(B) shows reference pulse signals R1 to R received by the signal processing circuit 6 when the reference surface 7 (see FIG. 9) serving as a reference when measuring the surface shape is scanned instead of the surface 2 of the object to be measured.
5 is a timing chart of FIG. Reference pulse signals R1 to
R5 is a reference point M1 to M5 (measurement points m1 to
5) correspond to the apertures E1 to E5.
It has been converted after passing through E5. FIG.
(C) is a timing chart of the measurement pulse signals r1 to r5 received by the signal processing circuit 6 when the surface 2 of the device under test is actually scanned.

FIGS. 12 (a) to 12 (c) show FIGS.
FIG. 12 is a timing chart in which one of these pulse signals is extracted.

[0006] The signal processing circuit 6 has a configuration shown in FIG.
As shown in (b), the reference pulse signals R1 to R corresponding to the respective reference points M1 to M5 from the input time of the scanning start pulse signal.
The input times up to the input time of No. 5 are stored, and those input times are stored in the measurement pulse signals r1 to r shown in FIG.
5, the deviation of each of the measurement points m1 to m5 from the reference plane 7 is calculated based on the comparison result, and the shape of the surface 2 of the measured object is determined.

Referring to FIG. 12, the input time Tn of the reference pulse signal Rn to be measured and the input time tn of the corresponding measurement pulse signal rn are compared, and the relative position between the reference plane and the measurement point and the measurement time are measured. The absolute position of each measurement point from the start position is determined, and the shape of the surface 2 of the measured object is determined.

[0008]

However, according to the prior art, due to the difference in the properties of the surface 2 of the object to be measured, for example, a surface having a low reflectivity or a surface having a sharp change in shape. In the case of, the reflected light may not return. If the reflected light is extremely weak, a corresponding pulse signal may not be generated, or it may be difficult to convert the reflected light into a pulse signal. When the pulse signal corresponding to the reflected light disappears, the input time t shown in FIG.
n becomes a different value, and there is a possibility that the surface shape cannot be measured accurately.

SUMMARY OF THE INVENTION An object of the present invention is to provide a surface shape measuring apparatus capable of accurately measuring a surface shape irrespective of the properties and shapes of the surface of an object to be measured.

[0010]

According to a first aspect of the present invention, there is provided a surface shape measuring apparatus for scanning a surface of an object to be measured while emitting a light beam toward the surface of the object to be measured. A lens that forms an image of the light beam reflected from the surface of the object, and a plurality of lenses that are provided corresponding to a plurality of predetermined measurement points on the surface of the object to be measured and have a different number of slits for each measurement point. A slit plate having an opening, photoelectric conversion means for converting the light beam passing through each slit through a lens into a measurement pulse signal, and inputting the measurement pulse signal and setting each input time from the measurement start time as a starting point. ,
The measured time is compared with the input time of the reference pulse signal reflected from the reference plane corresponding to the plurality of measurement points stored in advance, and the measured point is measured based on the deviation of each measurement point from the reference plane obtained from the comparison result. Signal processing means for determining the surface shape of the object.

According to a second aspect of the present invention, there is provided a surface shape measuring apparatus for scanning a surface of an object to be measured while emitting a light beam toward the surface of the object to be measured, and reflecting light from the surface of the object to be measured. A lens for imaging the light beam, and a plurality of apertures provided corresponding to a plurality of predetermined measurement points on the surface of the object to be measured and having one slit having a different width for each measurement point are formed. A slit plate, a photoelectric conversion means for converting the light beam passing through each slit through the lens into a measurement pulse signal, and inputting the measurement pulse signal and pre-stored each input time starting from the measurement start time. The input time of the reference pulse signal reflected from the reference surface corresponding to the plurality of measurement points is compared with the input time, and based on the deviation of each measurement point from the reference surface obtained from the comparison result, the surface of the DUT is measured. form It is obtained by a signal processing means for determining the.

According to a third aspect of the present invention, there is provided a surface shape measuring apparatus for scanning a surface of an object to be measured while emitting a light beam toward the surface of the object to be measured, and reflecting the light from the surface of the object to be measured. A lens for imaging the light beam, and at least one aperture and a measurement point provided corresponding to a plurality of predetermined measurement points on the surface of the object to be measured, each having a different number of slits for each measurement point A slit plate having at least one opening having one slit having a different width for each, a photoelectric conversion unit for converting a light beam passing through each slit through a lens into a measurement pulse signal, and a measurement pulse signal Each input time starting from the measurement start time is compared with the input time of a reference pulse signal reflected from a reference plane corresponding to a plurality of measurement points stored in advance. And, based on the deviation from the reference surface of the measurement points obtained from the comparison result, in which a signal processing means for determining the surface profile of the workpiece.

According to a fourth aspect of the present invention, there is provided a surface shape measuring apparatus for scanning a surface of a device under test while emitting a light beam toward the surface of the device under test, and reflecting light from the surface of the device under test. Between a lens for imaging the light beam, a plurality of openings provided corresponding to a plurality of predetermined measurement points on the surface of the DUT, each having one slit having the same width, and an adjacent opening; A slit plate formed with an index opening having one slit different from the width of each opening, and a photoelectric conversion means for converting the light beam passing through each slit through a lens into a measurement pulse signal;
The measurement pulse signal is input, and each input time starting from the measurement start time is compared with the input time of the reference pulse signal reflected from the reference plane corresponding to a plurality of measurement points stored in advance, respectively. Signal processing means for determining the surface shape of the object to be measured based on the deviation of each measurement point from the reference plane obtained from the comparison result.

According to a fifth aspect of the present invention, there is provided a surface shape measuring apparatus for scanning a surface of an object to be measured while emitting a light beam toward the surface of the object to be measured, and reflecting the light from the surface of the object to be measured. A lens for imaging the light beam, and a slit plate provided corresponding to a plurality of predetermined measurement points on the surface of the object to be measured and having a plurality of openings each having one slit having an equal width. And photoelectric conversion means for converting the light beam passing through each slit through the lens into a measurement pulse signal, and inputting the measurement pulse signal, and invalidating the measurement when the total number of the measurement pulse signals does not match the total number of the measurement points. If they match, the measurement is valid, and each input time starting from the measurement start time is the input time of the reference pulse signal reflected from the reference plane corresponding to a plurality of measurement points stored in advance. Each comparison, based on the deviation from the reference surface of the measurement points obtained from the comparison result, in which a signal processing means for determining the surface profile of the workpiece.

According to a sixth aspect of the present invention, in the surface shape measuring device, the signal processing means according to the fifth aspect compares respective input times of adjacent measurement pulse signals starting from the measurement start time, and calculates a difference between the two. When is larger than a predetermined value, the measurement is invalidated.

According to a seventh aspect of the present invention, in the surface shape measuring apparatus, the scanner according to the fifth aspect scans the same surface of the object to be measured a plurality of times, and the signal processing means obtains the data by performing the plurality of scans. The measured pulse signal is added for each measurement point of the device under test, and a signal exceeding a predetermined value among the added signals is corrected to a correction pulse signal having a certain magnitude, and the measurement start time is defined as a starting point. The input time of each corrected pulse signal is compared with the input time of a reference pulse signal reflected from a reference plane corresponding to a plurality of measurement points stored in advance, and the reference of each measurement point obtained from the comparison result is compared. It is characterized in that the surface shape of the measured object is determined based on the deviation from the surface.

[0017]

The surface shape measuring device according to claim 1 of the present invention is
The number of slits corresponding to the identifier indicating itself is provided for each opening. Thus, the measurement point can be known from the number of measurement pulse signals, and the surface shape can be accurately measured.

In the surface shape measuring device according to a second aspect of the present invention, the width of each opening is set to a size corresponding to an identifier indicating the opening itself. Thereby, the measurement point can be known from the width of the measurement pulse signal, and the surface shape can be accurately measured.

In the surface profile measuring device according to the third aspect of the present invention, slits are provided in a number corresponding to the identifier indicating the opening or the width of the opening is set to the size corresponding to the identifier indicating the opening. Things. Thus, the measurement point can be known from the number and width of the measurement pulse signal, and the surface shape can be accurately measured.

In the surface profile measuring device according to a fourth aspect of the present invention, an index slit is provided between the openings. Thus, each measurement point can be known from the pulse signal from the index slit, and the surface shape can be accurately measured.

The surface profile measuring apparatus according to claim 5 of the present invention uses a conventional slit plate having an opening,
The total number of measurement pulse signals is counted and compared with the total number of measurement points. This allows detection of inaccurate measurements, which can prevent inaccurate surface shape measurements.

The surface profile measuring apparatus according to claim 6 of the present invention uses a conventional slit plate having an opening,
It measures the input time difference between adjacent measurement pulse signals. Thereby, an incorrect measurement can be detected.

A surface profile measuring apparatus according to a seventh aspect of the present invention measures the same surface of an object to be measured a plurality of times, adds a measurement pulse signal for each measurement point, and corrects the added signal. This makes it possible to correct the data of the measurement point where the measurement has failed.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIG.

FIG. 1 is a plan view showing the slit plate 4 of the first embodiment and a timing chart after a laser beam passing through the slit plate 4 is converted into a measurement pulse signal. As shown in the figure, the slit plate 4 is provided with a different number of slits s at each of the openings E1 to E4 through which the laser light from the lens 3 passes, and this number indicates the identifier of the opening. I have. In the slit plate 4 of FIG. 1, one slit s is provided in the first opening E1, two slits s are provided in the second opening E2,..., And the fourth E4 is provided. Four slits s are provided. One laser beam incident on each opening is divided into the number of slits in each opening, and the divided laser light is converted by the photoelectric converter 5 into measurement pulse signals r1 to r4. Each of the measurement pulse signals r1 to r4 is input to the signal processing circuit 6 at a timing as shown in the timing chart of FIG. In the signal processing circuit 6, since the number of slits s provided for each of the openings E1 to E4 is stored in advance, the currently input pulse is counted to determine which of the openings the measurement pulse signal is from. That is, it is possible to know from which measurement point the pulse signal is reflected. As a result, when the pulse signal of the number stored in advance is not input, the signal processing circuit 6 determines that the measurement of the measurement point corresponding to the number has failed, and performs a predetermined abnormal process on the portion, for example, the connection. Processing or measurement value invalidation processing can be performed.

Thus, the surface shape can be accurately measured irrespective of the surface properties and shape.

Next, a second embodiment of the present invention will be described with reference to FIG.

FIG. 2 is a plan view showing the slit plate 4 of the second embodiment and a timing chart after a laser beam passing through the slit plate 4 is converted into a measurement pulse signal. As shown in FIG.
The widths of 1 to E4 are different from each other, and the width is an identifier indicating each of the openings E1 to E4. In the slit plate 4 of FIG. 2, the width of the first opening E1 is w1,
The width of the second opening E2 is w2,.
The width of 4 is w4. One laser beam incident on each of the openings E1 to E4 is converted into measurement pulse signals r1 to r4 by the photoelectric converter 5 after the laser light has passed through each of the openings E1 to E4. Each of the measurement pulse signals r1 to r4 is input to the signal processing circuit 6 at a timing as shown in the timing chart of FIG. In the signal processing circuit 6, since the widths w1 to w4 of the measurement pulse signals corresponding to the widths of the respective openings are stored in advance, by measuring the width of the currently input measurement pulse, the measurement from any opening can be performed. It is possible to know whether the signal is a pulse signal, that is, from which measurement point the pulse signal is reflected. As a result, the signal processing circuit 6
If the measurement pulse signal of the width stored in advance is not input, it is determined that the measurement of the measurement point corresponding to the width has failed, and a predetermined abnormal process for the portion, such as a connection process or invalid measurement value, is performed. Processing and the like can be performed.

Thus, the surface shape can be accurately measured irrespective of the surface properties and shape.

Next, a third embodiment of the present invention will be described with reference to FIG.

FIG. 3 is a plan view showing the slit plate 4 of the third embodiment and a timing chart after a laser beam passing through the slit plate 4 is converted into a measurement pulse signal. As shown, in the slit plate 4, odd-numbered openings E1, E3,..., E5 are provided with a number of slits s indicating the identifier of the opening itself as in the first embodiment. On the other hand, the even-numbered openings E2 and E4 have a width indicating the identifier of the opening itself as in the second embodiment.
As a result, when the signal processing circuit 6 does not input the number of measurement pulse signals stored in advance or does not input a measurement pulse signal having a width stored in advance, the signal processing circuit 6 measures the measurement point. Is determined to be unsuccessful, and a predetermined abnormal process for the portion, such as a connecting process or a measured value invalidating process, can be performed.

This makes it possible to reduce the number and width of the slits in the opening and to perform an abnormal process.

Next, a fourth embodiment of the present invention will be described with reference to FIG.

FIG. 4 is a plan view showing the slit plate 4 of the fourth embodiment and a timing chart after a laser beam passing through the slit plate 4 is converted into a measurement pulse signal. As shown, in the slit plate 4, each opening E
For example, every other opening E1 to E4
Slits I1s, I1s having a width different from the width of
Index openings I1 and I3 each including 3s are provided. As a result, the signal processing circuit 6
1, a measurement pulse signal r1 from the aperture E3, a measurement pulse signal r2 from the aperture E3, a measurement pulse signal r3 from the aperture E3,
A pulse signal i3 from the index slit I3s,
The measurement pulse signal r4 is input from the opening E4. By detecting a deviation from the input pattern, a measurement point at which measurement has failed can be detected.

Thus, the surface shape can be accurately measured irrespective of the surface properties and shape.

Next, a fifth embodiment of the present invention will be described with reference to FIG.

FIG. 5 is a plan view showing the slit plate 4 of the fifth embodiment and a timing chart after a laser beam passing through the slit plate 4 is converted into a measurement pulse signal. As shown, openings E1 to En on slit plate 4 are provided.
Have the same width as in the prior art.

In the signal processing circuit 6 of the fifth embodiment, the number of measurement points stored in advance (in this case, n) is
The total number of actually input measurement pulse signals is compared with each other, and if they do not match, it is determined that the measurement is invalid. For example, FIG.
Shows a case where the (n-1) th measurement pulse signal r (n-1) is not input, and in this case, the measurement is determined to be invalid.

Thus, it is possible to prevent inaccurate surface measurement while using a conventional slit plate having an opening.

Next, a sixth embodiment of the present invention will be described with reference to FIG.

The sixth embodiment uses a conventional slit plate 4 having an opening.

The signal processing circuit 6 of the sixth embodiment calculates the difference T between the input time of the adjacent measurement pulse signals r1 to rn as follows.

T1 = t2-t1 T1 = t3-t2... Tn = t (n + 1) -tn Each variation T corresponds to a distance between adjacent measurement points. Therefore, the change amount T is compared with a predetermined limit value L (set by a measurer using common sense), and if it exceeds, the data is invalidated and a predetermined abnormal process such as a connection process or a measured value is performed on the portion. Perform invalidation processing.

Thus, it is possible to prevent inaccurate surface measurement while using a conventional slit plate.

Next, a seventh embodiment of the present invention will be described with reference to FIGS. 6, 7, and 8. FIG.

In the seventh embodiment, the same portion is scanned a plurality of times while using a conventional slit plate, thereby adding a measurement pulse signal for each measurement point to correct the lack of the pulse signal. . FIG. 6 is a plan view showing the slit plate 4 of the seventh embodiment and a timing chart after the laser light passing through the slit plate 4 is converted into measurement pulse signals r1 to rn. Here, after several measurements,
For example, three times (k times, k + 1 times, k + 2 times) are taken out. The signal processing circuit 6 adds the measurement pulse signals r1 to rn input for each measurement point, adds the measurement pulse signals r1 to rn for each measurement point, and obtains added pulse signals ar1 to arn (see the timing chart of FIG. 7). . The magnitude of each of the added pulse signals ar1 to arn is compared with a predetermined value, here, the threshold 13, which is a level slightly lower than the magnitude of one pulse signal. Signal processing circuit 6
In the sum signal pulse signals ar1 to arn, those exceeding the threshold 13 are determined to be valid measurement values, and are converted into pulse trains of a certain size to generate correction pulse signals hr1 to hrn (FIG. 8). The input time of the correction pulse signals hr1 to hrn is treated as the input time of the measurement pulse signal, and the surface shape is determined. In FIG. 6, at the time of the (k + 1) th measurement, 2
FIG. 7 shows a case in which the measurement pulse of the first time cannot be detected. However, as shown in FIG. ing.

As a result, it is possible to correct a missing measurement pulse signal at an arbitrary measurement point.

[0048]

According to the first aspect of the present invention, the measurement point can be known from the number of measurement pulse signals, and the surface shape can be measured accurately.

According to the second aspect of the present invention, the measurement point can be known from the width of the measurement pulse signal, and the surface shape can be accurately measured.

According to the third aspect of the present invention, the measurement point can be known from the number and width of the measurement pulse signal, and the surface shape can be accurately measured.

According to the fourth aspect of the invention, the measurement point can be known from the index slit, and the surface shape can be accurately measured.

According to the fifth aspect of the present invention, since the total number of measurement pulse signals is counted while using a conventional slit plate having an opening, inaccurate measurement can be prevented.

According to the invention of claim 6, since the input time difference between adjacent measurement pulse signals is measured while using the conventional slit plate having an opening, an inaccurate measurement can be detected.

According to the seventh aspect of the present invention, since the same location is measured a plurality of times, it is possible to correct the data at the measurement point where the measurement failed.

[Brief description of the drawings]

FIG. 1 is a plan view showing a slit plate and a timing chart showing measurement pulse signals of a first embodiment of a surface profile measuring apparatus according to the present invention.

FIG. 2 is a plan view showing a slit plate according to a second embodiment of the present invention and a timing chart showing measurement pulse signals.

FIG. 3 is a plan view showing a slit plate of a third embodiment according to the present invention and a timing chart showing measurement pulse signals.

FIG. 4 is a plan view showing a slit plate according to a fourth embodiment of the present invention and a timing chart showing measurement pulse signals.

FIG. 5 is a plan view showing a slit plate of a fifth embodiment and a sixth embodiment according to the present invention, and a timing chart showing a measurement pulse signal.

FIG. 6 is a plan view showing a slit plate of a seventh embodiment according to the present invention, and a timing chart showing measurement pulse signals.

FIG. 7 is a timing chart showing an addition pulse signal.

FIG. 8 is a timing chart showing a corrected pulse signal after correcting an added pulse signal.

FIG. 9 is a diagram for explaining the operation principle of the surface shape measuring device.

FIG. 10 is a plan view showing an opening included in a slit plate of a surface profile measuring device according to a conventional technique.

FIG. 11 is a timing chart showing a scanning start pulse signal, a reference pulse signal, and a measurement pulse signal.

FIG. 12 is a timing chart showing a pulse signal corresponding to one measurement point in FIG. 11;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Scanner 2 Surface of an object to be measured 3 Lens 4 Slit plate 5 Photoelectric converter 6 Signal processing circuit 7 Reference plane 8 Scan start pulse detector E1 to E5 Opening s Slit m1 to m5 Measurement points M1 to M5 Reference points r1 to r5 Measurement pulse signal R1 to R5 Reference pulse signal k Measurement start signal

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-207821 (JP, A) JP-A-2-268207 (JP, A) JP-A-7-318325 (JP, A) JP-A 8- 201521 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01B 11/00-11/30 102 G01C 3/00-3/32 G01S 17/00-17/88

Claims (7)

(57) [Claims] 1. A scanner for scanning a surface of an object to be measured while emitting a light beam toward the surface of the object to be measured;
A lens for imaging the light beam reflected from the surface of the device to be measured, and a plurality of predetermined measurement points on the surface of the device to be measured that are different from each other for each of the measurement points A slit plate formed with a plurality of openings having a number of slits, photoelectric conversion means for converting the light beam passing through each slit through the lens into a measurement pulse signal, and inputting the measurement pulse signal and measuring Each input time starting from the start time is compared with a previously stored input time of a reference pulse signal reflected from a reference plane corresponding to the plurality of measurement points, and each measurement obtained from the comparison result is performed. A signal processing means for determining a surface shape of the object to be measured based on a deviation of a point from the reference plane. 2. A scanner for scanning a surface of a device under test while emitting a light beam toward the surface of the device under test.
A lens for imaging the light beam reflected from the surface of the device under test, and a lens provided corresponding to a plurality of predetermined measurement points on the surface of the device to be measured, each of which has a width. A slit plate formed with a plurality of openings having one different slit, photoelectric conversion means for converting the light beam passing through each of the slits through the lens into a measurement pulse signal, and inputting the measurement pulse signal. Each input time starting from the measurement start time is compared with the input time of the reference pulse signal reflected from the reference plane corresponding to the plurality of measurement points stored in advance, and the input time is obtained from the comparison result. A surface shape measuring device comprising: signal processing means for determining a surface shape of the object to be measured based on a deviation of each measurement point from the reference plane. 3. A scanner that scans the surface of the device under test while emitting a light beam toward the surface of the device under test.
A lens for imaging the light beam reflected from the surface of the device to be measured, and a plurality of predetermined measurement points on the surface of the device to be measured that are different from each other for each of the measurement points A slit plate having at least one opening having a number of slits and at least one opening having one slit having a different width for each of the measurement points, and a light beam passing through each slit via the lens Photoelectric conversion means for converting the measurement pulse signal into a measurement pulse signal, and inputting the measurement pulse signal and reflecting each input time from the measurement start time from a reference plane corresponding to the plurality of measurement points stored in advance. A signal for determining the surface shape of the object to be measured based on the deviation of each measurement point from the reference plane obtained from the comparison result with the input time of the reference pulse signal to be measured. Surface shape measuring apparatus and a processing unit. 4. A scanner that scans the surface of the device under test while emitting a light beam toward the surface of the device under test.
A lens that forms an image of the light beam reflected from the surface of the device under test, and a lens that is provided in correspondence with a plurality of predetermined measurement points on the surface of the device and has the same width.
A slit plate formed with a plurality of openings having one slit and an index opening having one slit having a width different from the width of each opening between adjacent openings, and passing through each of the slits via the lens; Photoelectric conversion means for converting the obtained light beam into a measurement pulse signal, and inputting the measurement pulse signal and setting each input time starting from the measurement start time as a reference corresponding to the plurality of measurement points stored in advance. Signal processing means for comparing the input time of the reference pulse signal reflected from the surface with each other, and determining the surface shape of the object to be measured based on the deviation of each measurement point from the reference surface obtained from the comparison result. Surface profile measuring device provided. 5. A scanner for scanning a surface of an object to be measured while emitting a light beam toward the surface of the object to be measured;
A lens that forms an image of the light beam reflected from the surface of the device under test, and one slit that is provided corresponding to a plurality of predetermined measurement points on the surface of the device under test and has the same width. A slit plate formed with a plurality of openings having a photoelectric conversion unit that converts a light beam that has passed through each of the slits through the lens into a measurement pulse signal,
The measurement pulse signal is input, the measurement is invalidated when the total number of the measurement pulse signals does not match the total number of the measurement points, the measurement is enabled when the measurement pulse signals match, and each input time from the measurement start time as a starting point. The input time of the reference pulse signal reflected from the reference plane corresponding to the plurality of measurement points stored in advance is compared with each other, and based on the deviation of each measurement point from the reference plane obtained from the comparison result. And a signal processing means for determining a surface shape of the object to be measured. 6. The signal processing means compares input times of adjacent measurement pulse signals starting from a measurement start time, and invalidates the measurement when the difference between the two is greater than a predetermined value. The surface shape measuring device according to claim 5, wherein 7. The apparatus according to claim 1, wherein the scanner scans the same surface of the device under test a plurality of times, and the signal processing unit converts a measurement pulse signal obtained by the plurality of scans into a measurement point of the device under test. Each time, a signal exceeding a predetermined value among the added signals is corrected to a correction pulse signal having a fixed magnitude, and each correction pulse signal input time starting from the measurement start time is stored in advance. The input time of the reference pulse signal reflected from the reference plane corresponding to the plurality of measurement points is compared with each other, and based on the deviation of each measurement point from the reference plane obtained from the comparison result, The surface shape measuring apparatus according to claim 5, wherein the surface shape of the object is determined.