JP6389759B2 - Non-contact edge shape measuring method and apparatus - Google Patents

Description

  The present invention relates to a non-contact edge shape measuring method and apparatus suitable for measuring an acute edge shape of a blade or the like.

  The non-contact shape measurement of sharp edges of workpieces such as tool edges and blades is generally done by measuring the edge shape using a projector or microscope. However, the effect of optical resolution and edge processing accuracy is affected. Therefore, it was impossible to measure the shape with sub-μm resolution.

  As another measurement method, tip edge shape measurement using a confocal microscope etc. has been proposed, but at the edge with a sharp tip, there is little reflected light from the inclined surface and it is accurate due to the influence of the diffraction image of the light etc. Shape measurement cannot be performed.

  A laser probe type non-contact measurement method is expected for such a measurement method. This measurement direction is a structure in which the workpiece is scanned while being auto-focused by a laser probe, and measurement data relating to the edge shape of the workpiece is obtained from the amount of movement in the focus direction of the objective lens of the auto-focus optical system (for example, Patent Document 1).

Japanese Patent No. 3923945

  However, even in such a laser probe type non-contact measurement method, there is a limit that the shape cannot be measured with accuracy less than the laser spot diameter with respect to the edge.

  The present invention has been made paying attention to such a technical problem, and an object thereof is to provide a non-contact edge shape measuring method and apparatus capable of measuring a shape with an accuracy equal to or less than a laser spot diameter.

  In the present invention, in laser probe type non-contact surface shape measurement using laser autofocus, the outputs of the sensor portions of the AF sensor are a and b, and the entire spot is focused on the side surface in the scanning direction (a = b ), The amount of decrease in the total output (a + b) of the AF sensor when the entire spot passes through the edge that is the terminal on each side surface and deviates from the side surface while maintaining the focused state ( 2E), the position when the decrease in the side shape data of each detected side surface is ½ is defined as an edge, and the definition is made in the scanning direction from each of the two detected side surface shape data. A portion beyond the edge is removed, and the shape of the edge is obtained by synthesizing the side shape data after the removal.

  According to the present invention, the output of each sensor portion of the AF sensor is a and b, and the in-focus state is maintained from the state where the entire spot is focused on the side surface (a = b) in the scanning direction. In the detected side surface shape data of each side surface, the decrease in the total output (a + b) of the AF sensor when the entire spot passes through the edge that is the terminal of each side surface and deviates from the side surface is (2E). The position when the decrease is ½ is defined as an edge, and the portions that exceed the defined edge in the scanning direction are removed from the detected two side surface shape data, respectively. Since the edge shape is obtained by combining the side surface shape data, the edge position of the combined side surface shape data is defined with an accuracy equal to or less than the laser spot diameter, so that highly accurate edge shape measurement can be performed.

Schematic which shows a non-contact edge shape measuring apparatus. The flowchart which shows a measuring method. Explanatory drawing which shows the process of a measuring method. The front view which shows AF sensor. The front view which shows the laser spot with respect to a side surface. The side view which shows the laser spot with respect to a side surface. The figure which shows the relationship between a scanning position and the output difference of AF sensor. The figure which shows the relationship of the sum of the output of a scanning position and AF sensor. Explanatory drawing which shows the synthesis | combination of side surface shape data.

  1 to 9 are diagrams showing a preferred embodiment of the present invention.

  FIG. 1 is a view showing a laser probe type non-contact edge shape measuring apparatus according to this embodiment. In FIG. 1, XY is two directions orthogonal to each other on a horizontal plane, X is a focus direction, and Y is a scan direction. Z is the vertical direction.

 The workpiece 1 to be measured is a triangular tool having a sharp edge e at the tip. The workpiece 1 has two side surfaces 2 and 3 forming an acute angle. The side surfaces 2 and 3 are flat, and an acute edge e is formed at the intersection.

  The workpiece 1 is assembled on a rotary stage 4 that is rotatable in the θ direction around the Z axis. The rotary stage 4 is sequentially placed on an X-axis stage 5, a Y-axis stage 6, and a Z-axis stage 7 slidable on the X-axis, Y-axis, and Z-axis, respectively.

  For this work 1, an objective lens 8, a beam splitter 9, an imaging lens 10, and an AF sensor 11 are disposed on an optical axis K that matches the X axis as an autofocus optical system. The laser L from the semiconductor laser irradiation device 12 is reflected by the beam splitter 9 and irradiated onto the workpiece 1 through the objective lens 8. The laser L irradiated to the workpiece 1 is a so-called “laser probe”.

  The laser L is irradiated obliquely from above to the surface of the workpiece 1 from the objective lens 8 along an optical path in a vertical plane including the X axis and the Z axis, and is reflected obliquely downward.

  The return light of the laser L reflected from the surface of the workpiece 1 passes through the beam splitter 9 again from the objective lens 8, then passes through the imaging lens 10 and reaches the AF sensor 11.

  The AF sensor (divided light sensor) 11 is composed of sensor portions 11 a and 11 b that are divided into two parts in the vertical direction around the optical axis K of the objective lens 8. Outputs a and b from the two sensor units 11 a and 11 b are input to the AF controller 14 via the operational amplifier circuit 13. From the operational amplifier circuit 13, the difference (ab) and the sum (a + b) between the outputs a and b from the two sensor units 11a and 11b are calculated and output to the AF controller 14.

  Further, the AF controller 14 feedback-controls the servo mechanism 16 so that the outputs a and b from the two sensor units 11a and 11b are equal to move the objective lens 8 in the focus direction (X direction). Position information in the focus direction of the surface of the workpiece 1 can be detected based on the amount of movement of the objective lens 8 from the reference position at that time. The laser L is reflected by the beam splitter 9 and then passes through a position deviated from the center of the optical axis K of the objective lens 8. Therefore, scattering noise can be reduced and SN can be improved.

  The rotary stage 4, X-axis stage 5, Y-axis stage 6, and Z-axis stage 7 are connected to a stage controller 17. The movement in the scanning direction S is performed by the Y axis stage 6.

  The stage controller 17 outputs a signal for moving in the direction of each stage, and outputs the position of the workpiece 1 in the θ-axis rotation direction, the X-axis direction, the Y-axis direction, and the Z-axis direction to the main controller 15.

  The main controller 15 can acquire the shapes of the two side surfaces 2 and 3 of the workpiece 1, and can measure the edge shape by combining the measured side surface shape data.

 Next, an actual measurement procedure will be described.

  First, an outline of measurement work will be described with reference to FIGS.

  In the state where measurement is started, the workpiece 1 is in a state where the edge e is directed straight toward the objective lens 8 with respect to the optical axis K of the objective lens 8.

(Step S1)
Next, the two side surfaces 2 and 3 of the workpiece 1 are sequentially measured. First, the workpiece 1 is rotated about the θ axis so that the optical axis K of the objective lens 8 is perpendicular to the one side surface 2.

(Step S2)
Then, the spot P of the laser L is scanned on the side surface 2 in the scanning direction S along the Y direction toward the edge e while autofocusing is performed on one side surface 2, and the shape data of the one side surface 2 is acquired.

  In this embodiment, since the side surface 2 is flat, the entire side surface 2 can be perpendicular to the optical axis K. However, when the side surface 2 is not flat but curved or the angle changes stepwise. Uses a range where the angle with respect to the optical axis K is less than ± 30 ° as a unit of measurement, and the portion that exceeds the angle is further divided and measured while rotating the work 1 around the θ axis.

(Step S3)
Next, the workpiece 1 is rotated about the θ axis so that the optical axis K of the objective lens 8 is perpendicular to the other side surface 3.

(Step S4)
Then, the spot P of the laser L is scanned on the side surface 3 in the scanning direction S toward the edge e along the Y direction while autofocusing is performed on the other side surface 3, and the shape data of the other side surface 3 is acquired.

(Step S5)
Finally, the shape data of the two side surfaces 2 and 3 acquired are combined by polar coordinate conversion based on the θ-axis rotation center by the main controller 15 to obtain the shape of the edge e, and the measurement operation is completed.

  Although the above is an outline, in order to obtain an accurate shape of the edge e, it is necessary to accurately acquire the shape data of the two side surfaces 2 and 3 constituting the edge e with high accuracy.

  FIG. 4 is a diagram showing the spot R of the AF sensor 11 and the laser L. Since the laser L is irradiated obliquely from above the workpiece 1 and reflected obliquely downward, the spot R of the laser L on the AF sensor 11 is also displaced vertically. By correcting the displacement and making the optical center of the spot R coincide with the center of the AF sensor 11, autofocus is applied.

  It is essential to match the displacement detection direction (Z direction) of the AF sensor 11 related to the oblique irradiation / reflection direction of the laser L with the longitudinal direction (Z direction) of the edge e. If this directionality is not matched, an error due to a focal shift occurs in the laser probe method, and accurate autofocus cannot be performed.

  Here, a method for measuring one side surface 2 will be described with reference to FIG.

  FIG. 7 shows the relationship between the differential output (ab) of the AF sensor (split light sensor) 11 and the position in the scanning direction S. For convenience of explanation, the spot P is shown enlarged. The irradiation / reflection direction of the laser L is also converted and shown. The thick line is the shape data (profile) of the side surface 2 obtained by autofocus.

  The spot P on the side surface 2 is scanned along the scanning direction S at a constant speed. In the state P (1) where all the spots P are on the side surface 2, all the lasers L are reflected and the surface shape is captured.

  Next, in the state P (2) where the center of the spot P is on the edge e, half of the light beam of the laser L is off the edge e and the reflection component is reduced. However, the light amount distribution of the spot R on the AF sensor 11 only decreases in a half-moon shape in the Y direction. Since the light amount distribution of the spot R is uniform in the Z direction, the side surface 2 can still be measured accurately.

  Then, when the spot P is in a state P (3) where the spot P exceeds the edge e and completely deviates from the edge e, the shape component is reduced because the reflection component disappears. Depending on the shape of the periphery of the edge e, there may be a sudden drop or a rise in some cases, but irregular shape data is detected after passing through the edge e.

  As described above, it is possible to know that the spot P has completely deviated from the edge e by simply acquiring the shape data of the side surface 2 while auto-focusing, but until then, the edge e exists on the way. However, it cannot be known, and eventually it has an error corresponding to the diameter D of the spot P at the maximum.

  Therefore, the addition output (a + b) of the sensor units 11a and 11b of the AF sensor 11 is used to detect the accurate position of the edge e from the acquired shape data of the side surface 2. That is, as shown in FIG. 8, the added output (a + b) is different from the differential output (ab), and when the spot P starts to be applied to the edge e, the value gradually decreases, and the spot P is completely removed from the edge e. 2E decreases at a position deviating from

  Using this characteristic, the position of the edge e is detected by using E which is a half of the decrease 2E of the addition output (a + b) when the spot P completely deviates from the edge e as a threshold, and the side surface obtained by autofocusing is used. The portion beyond the position of the edge e is removed from the shape data 2 as invalid. By doing so, accurate shape data of the side surface 2 can be acquired.

  Then, as shown in FIGS. 9A, 9A, and 9C, the invalid portion removal processing of the shape data of the side surface 2 described above is performed on the other side surface 3 by rotating the workpiece 1, and 2 after the removal. The shape data of the two accurate side surfaces 2 and 3 are synthesized after the polar coordinates are converted and aligned. In this way, the shape of the edge e can be measured with an accuracy equal to or less than the diameter of the spot P of the laser L.

  In the above embodiment, the workpiece 1 in which the edge e exists linearly in the longitudinal direction (up and down direction) is taken as an example. However, for example, when the edge (blade edge) is curved in the longitudinal direction like a knife. The shape of the continuous edge e can be measured by changing the position in the longitudinal direction by a predetermined pitch.

1 Workpiece 2, 3 Side 8 Objective lens 11 AF sensor (split light sensor)
14 AF controller 15 Main controller 17 Stage controller e Edge D Spot diameter K Optical axis L Laser P Spot on workpiece R Spot on AF sensor S Scan direction

Claims (3)

As the three-dimensional coordinate axis XYZ, while performing autofocus control that irradiates the laser along the optical path in the XZ plane with respect to two side surfaces constituting the edge of the X direction end in the cross-sectional shape of the workpiece, The spot is scanned in the direction toward the edge along the Y direction on the side of the workpiece,
In the autofocus optical system, the laser return light from the side surface is controlled so as to be received at the center of the two-split AF sensor in the Z direction at the time of focusing. A non-contact edge shape measuring method for obtaining two side shape data, and combining the two obtained side shape data to obtain an edge shape,
The outputs of the sensor parts of the AF sensor are a and b,
When the entire spot is focused on the side (a = b) in the scanning direction, and the entire spot passes through the edge that is the terminal on each side while maintaining the focused state, The decrease of the AF sensor output (a + b) is 2E,
In the side surface shape data of each detected side surface, the position when the decrease is 1/2 is defined as an edge,
Removing the portion beyond the defined edge in the scanning direction from the detected two side surface shape data,
A non-contact edge shape measuring method characterized in that the shape of an edge is obtained by synthesizing side shape data after removal. Supports the work so that it can rotate in the θ direction around the Z axis.
2. When scanning each side surface of the workpiece, the workpiece is rotated in the θ direction in advance so that the scan range on the side surface is inclined less than ± 30 ° with respect to the optical axis of the objective lens. 2. The non-contact edge shape measuring method according to 1. As the three-dimensional coordinate axis XYZ, while performing autofocus control that irradiates the laser along the optical path in the XZ plane with respect to two side surfaces constituting the edge of the X direction end in the cross-sectional shape of the workpiece, The spot is scanned in the direction toward the edge in the Y direction on the side of the workpiece,
In the autofocus optical system, the laser return light from the side surface is controlled so as to be received at the center of the two-split AF sensor in the Z direction at the time of focusing. A non-contact edge shape measuring device for obtaining two side shape data, and combining the obtained two side shape data to obtain an edge shape;
An AF controller that controls the amount of movement of the objective lens in the X direction so that the laser passes through a position deviated from the optical axis center of the objective lens and the return light of the laser is received at the center of the AF sensor;
A stage controller that relatively scans either the workpiece or the autofocus optical system in the scan direction;
A main controller that determines the shape of the edge by combining the two side surface shape data of the workpiece,
The main controller is
The outputs of the sensor parts of the AF sensor are a and b,
When the entire spot is focused on the side (a = b) in the scanning direction, and the entire spot passes through the edge that is the terminal on each side while maintaining the focused state, The decrease of the AF sensor output (a + b) is 2E,
Define the position at the time of E where the decrease is 1/2 in the side shape data of each detected side as an edge,
Removing the portion beyond the defined edge in the scanning direction from the detected two side surface shape data,
A non-contact edge shape measuring apparatus characterized in that the shape of an edge is obtained by synthesizing side shape data after removal.

Images