JP4415344B2 - How to detect the tip of a drill blade - Google Patents

Description

The present invention relates to a method for detecting the tip of a drill blade that detects the tip of a drill blade that advances and retreats at right angles to the light receiving cell arrangement direction of the line sensor from the output of the line sensor.

  Recently, the printed circuit board has been multi-layered with high density mounting, and through holes are formed in the printed circuit board to electrically connect a plurality of layers. Such a through hole is exclusively formed by using a fine drill blade having a diameter of about 50 to 100 μm, for example, and rotating the drill blade at a high speed to form a hole of a predetermined depth in the printed circuit board. At this time, it is of course possible to select and use a drill blade of a predetermined diameter, attach the drill blade to the drill chuck without any runout, and further accurately grasp the tip position of the drill blade to obtain a predetermined value. It is important to drill holes to the depth of. However, it is generally very difficult to mechanically measure the diameter (drill diameter) of this kind of small-diameter drill blade and to mechanically check for the presence or absence of runout. A typical measuring means is used (see, for example, Patent Documents 1, 2, and 3).

However, the optical measuring method of a drill blade as shown in Patent Documents 1, 2, and 3 only measures the light shielding width by a line sensor or the like using light shielding of the drill blade, and has a diameter. However, it is difficult to accurately measure the diameter of a drill blade having a small diameter of 200 μm or less.
On the other hand, the present inventor uses the approximate expression obtained by approximating the diffraction pattern (intensity distribution) of the light previously generated by Fresnel diffraction using the hyperbolic second function sech (x) to easily and highly increase the edge position. A method for obtaining accuracy was proposed (see, for example, Patent Document 4).
JP 2003-170335 A Japanese Patent Application Laid-Open No. 7-306020 JP 7-260425 A Japanese Patent Application No. 2002-345958

  By the way, when the diameter of the drill blade (drill diameter) or the like is optically measured using the line sensor as described above, it is desirable that the tip position of the drill blade attached to the chuck of the drill can also be detected optically. It is. If the tip position of the drill blade can be measured, the depth of the hole drilled by the drill blade can be accurately controlled by controlling the advance / retreat amount (feed amount) of the drill.

  However, conventionally, a line sensor is provided exclusively along the axial direction of the drill blade, and its tip position is detected from the boundary between the light shielding area and the light receiving area by the drill blade in a plurality of light receiving cells of the line sensor. There are only. For this reason, when measuring the diameter of the drill blade and measuring its tip position, a line sensor for measuring the diameter of the drill provided at a right angle to the axial direction of the drill blade and the axial direction of the drill blade are provided in parallel. In addition, a line sensor for detecting the tip position is required, and it cannot be denied that the configuration of the measuring device becomes large.

The present invention has been made in consideration of such circumstances, and its purpose is to accurately detect the tip of a drill blade using, for example, an output from a line sensor provided at right angles to the axial direction of the drill blade. Another object of the present invention is to provide a method for detecting the tip of a drill blade .

  In the present invention, when the tip of the drill blade is positioned in the optical path of monochromatic parallel light such as laser light, the laser beam (monochromatic parallel light) is diffracted at the tip portion to form a striped diffraction pattern; When the drill blade is displaced in the axial direction so as to cross the longitudinal direction of the line sensor, attention is paid to the fact that the amount of light received at the tip portion is slightly increased due to the striped diffraction pattern. Yes.

In order to achieve the above-described object, a tip detection method for a drill blade according to the present invention includes a line sensor in which a plurality of light receiving cells are arranged at a predetermined pitch in one direction, and a single color toward the plurality of light receiving cells of the line sensor. A light source that projects parallel light, and the tip of a drill blade that enters the optical path of the monochromatic parallel light from the axial direction with the axial direction being substantially perpendicular to the arrangement direction of the light receiving cells from the output of the line sensor When asking
Wherein the drill bit is moved in the axial direction thereof, the tip of the drill bit forward and backward position of the drill bit when the output of the line sensor peaked at a central axial position of the drill bit is positioned in the optical path It is characterized in that it is detected as a state.

Preferably, for the peak detection of the output of the line sensor, the axis of the drill blade is obtained by analyzing the output of the line sensor when the drill blade is positioned in the optical path of the monochromatic parallel light, The output of the light receiving cell at the center position may be monitored. The output becomes the peak position of the line sensor, when to penetrate the drill bit to the optical path from the tip, and the retracting the drill bit to seek respectively when disengaging from the optical path, these peak positions What is necessary is just to obtain | require the tip of a drill blade as an average.

According to the present invention, since the tip of the drill blade can be detected from the output using a line sensor provided at right angles to the axial direction of the drill blade , a line sensor for measuring the drill diameter and the like There is no need to provide a line sensor for detecting the tip position separately, and the configuration of the measuring device can be greatly simplified. In addition, the diameter of the drill blade can be measured by effectively utilizing one line sensor, and further, the position of the tip can be specified from the advance / retreat position of the drill blade when the tip is detected. The information can be effectively used for controlling drilling using, for example, a drill blade.

Hereinafter, a tip detection method for a drill blade according to an embodiment of the present invention will be described with reference to the drawings, taking tip detection of a small-diameter drill blade as an example.
FIG. 1 shows a schematic configuration of a main part of a measuring device used for tip detection. This measuring device has a function of measuring the diameter of a drill blade and detecting the presence or absence of runout during high-speed rotation of the drill blade, and is generally a plurality of arrays arranged at a predetermined pitch w in one direction. A line sensor (light receiving unit) 1 having a plurality of light receiving cells, and monochromatic parallel light having a predetermined light flux width toward a plurality of light receiving cells of the line sensor 1 provided facing the light receiving surface of the line sensor 1 And a light projecting unit 2 that projects 4. The apparatus main body 3 realized by a microcomputer or the like is a shield (rod-like body) positioned in the optical path of the monochromatic parallel light 4 by analyzing the output of the line sensor 1 (the amount of light received by each light receiving cell). 7 plays a role in detecting the edge position in the arrangement direction of the light receiving cells with high accuracy.

  The light projecting unit 2 is a mirror that reflects monochromatic light (laser light) emitted from a light source 2a composed of a laser diode (LD), for example, as schematically shown in FIG. Prism) 2b, an aperture mask (projection window) 2c for defining the light bundle shape of the monochromatic light guided through the mirror 2b as a slit, and the light through the aperture mask 2c into a parallel light bundle. A projection lens (collimator lens) 2d for conversion and projection. Between the projection lens 2d and the light receiving unit 1, a shielding object 7 as a detection target is positioned, and the edge position of the shielding object 7 displaced in the longitudinal direction of the slit of the aperture mask 2c passes through the light receiving unit 1. Detected.

  Specifically, the aperture mask 2c has a rectangular slit, and the light source 2a is provided so as to emit monochromatic light at a predetermined divergence angle toward the slit. In particular, when an LD is used as the light source 2a, laser light emitted from the LD with an elliptical intensity distribution is projected onto the aperture mask 2c as indicated by a broken line in the drawing. In this case, the LD and the aperture mask 2c are optically arranged so that the long axis of the laser beam is in the longitudinal direction of the slit of the aperture mask 2c. preferable. The mirror (prism) 2d forms an optical path that reflects the laser light emitted from the LD at a substantially right angle, thereby maintaining the optical distance between the LD and the aperture mask 2c, and thus the projection lens 2d. It plays the role which makes the whole shape of the optical part 2 compact. Note that such a light projecting unit 2 is incorporated integrally with a U-shaped housing 5 having a predetermined gap L together with the above-described line sensor 1 so as to face each other across the gap. Formed as one sensing unit.

  As shown schematically in FIG. 3 and FIG. 4 by the light projecting unit 2 configured as above, the slit-shaped cross-sectional shape converted into parallel light through the aperture mask 2c and the projection lens 2d, respectively. A parallel light beam (monochromatic parallel light) 4 having a light beam is projected toward a line sensor (light receiving unit) 1. The size of the cross-sectional shape of the parallel light beam is, for example, a long side of 9 mm × a short side of 3 mm. On the other hand, the size of the light receiving surface of the line sensor 1 that receives the parallel light beam is, for example, a long side of 8. 7 mm × short side 0.08 mm. That is, the dimensions of the long sides are substantially equal.

  Incidentally, the dimension of the short side (3 mm) in the cross-sectional shape of the parallel light beam is set to be considerably larger than the short side dimension (0.08 mm) of the light receiving surface of the line sensor 1. This is to facilitate the adjustment of the light source and to avoid the influence of Fresnel diffraction caused by the long side edge 2h of the slit of the aperture mask 2c as shown in FIG. 4 even when the projector or the light receiver is tilted. However, the slit-shaped parallel light bundle (monochromatic parallel light) 4 has an edge on the short side of the slit of the aperture mask 2c as shown in FIG. It cannot be denied that non-parallel light components generated by the influence of Fresnel diffraction in 2e are included. However, the influence of this non-parallel ray component may be corrected by normalizing the output of the line sensor 1 as will be described later.

  The apparatus body 3 includes an input buffer 3a that takes in the output of the line sensor 1 (the amount of light received by each light receiving cell) and obtains the light intensity distribution on the light receiving surface of the line sensor 1. In particular, the apparatus main body 3 receives all of the monochromatic parallel light having a predetermined light bundle width projected from the light projecting unit 2 in advance as the initial setting process by the line sensor 1, and the light intensity distribution at this time is received. Based on this, the diffraction pattern detecting means 3b for obtaining a diffraction pattern of monochromatic parallel light projected by the light projecting unit 2 and for obtaining a normalization parameter for the amount of light received by each light receiving cell according to the reciprocal of the diffraction pattern as will be described later. Prepare. This diffraction pattern is caused by a non-parallel light component generated by the influence of Fresnel diffraction at the short-side edge 2e of the slit formed in the above-described aperture mask 2c.

  Further, the apparatus main body 3 includes a normalizing means 3c for normalizing the output of the line sensor 1 according to the normalization parameter obtained by the diffraction pattern detecting means 3b, and the line sensor normalized by the normalizing means 3c. An edge detection unit 3b for detecting the position of the end (edge) of the shielding object (detection target) 7 according to the output of 1 (normalized output), specifically, the position of the line sensor 1 in the arrangement direction of the light receiving cells; Is provided. Further, in this measuring apparatus, the apparatus body 3 further utilizes the output of the edge detection unit 3d, a drill diameter measurement unit 3e for measuring the drill diameter, and a runout detection unit 3f for detecting the runout of the drill. And a tip position detector 3g for detecting the tip position of the drill blade.

  Incidentally, the edge detection unit 3d is basically configured such that when a part of the monochromatic parallel light is blocked by the blocking object (detection target) 7, Fresnel diffraction occurs at the end (edge). It is noted that the intensity of light that reaches the light receiving surface of the line sensor 1 due to diffraction has a distribution characteristic that rises sharply in the vicinity of the edge position and converges while oscillating as it moves away from the edge position, as described below. And it is comprised so that the position of the edge part (edge) of the said shield 7 may be detected with high precision according to the light intensity distribution on the light-receiving surface of the line sensor 1.

That is, when the shielding object 7 is a plate-shaped object that blocks the optical path of the monochromatic parallel light 4 from one end side of the line sensor 1, the light intensity distribution due to Fresnel diffraction at the edge of the shielding object 7 is shown in FIG. Thus, it rises sharply in the vicinity of the edge position and converges while vibrating as it moves away from the edge position. Such light intensity distribution characteristics are as follows: the wavelength of monochromatic parallel light is λ [nm], the distance from the edge of the inspection object (shield 7) to the light receiving surface is z [mm], and the edge position on the light receiving surface Assuming that x [μm] is [0], ∫ is an operation symbol indicating an integration from [x = 0] to [(2 / λz) ^1/2 · x]. Light intensity = (1/2) {[ 1/2 + S (x)] ² + [1/2 + C (x)] ² }
S (x) = ∫sin (π / 2) · U ² dU
C (x) = ∫cos (π / 2) · U ² dU
Represented as: However, U is a temporary variable.

As for the functions S (x) and C (x) in the above equation, the Fresnel function is used exclusively as shown in the mathematical formulas, and S (x) ′ ≈ (1/2) − where x is large. (1 / πx) cos (πx 2/2)
C (x) '≒ (1/2 ) + (1 / πx) sin (πx 2/2)
Can be approximated respectively. Therefore, basically, by using the approximate expressions S (x) ′ and C (x) ′, the edge position described above can be calculated from the received light intensity of each light receiving cell of the line sensor 1.

  However, when actually calculated, as shown in FIG. 6, the functions S (x), C (x) and the approximate expressions S (x) ′, C (x) ′ are converged after the rise ( Although it approximates very well in the second and subsequent peaks, it cannot be denied that there is a large shift in the first rising portion (first mountain). In particular, the characteristic of the first rising portion plays an important role in edge detection, and the deviation of the characteristic causes a decrease in the detection accuracy of the edge position.

Therefore, the present inventor previously described in Patent Document 4 that the first rising portion of the light intensity distribution on the light receiving surface by Fresnel diffraction of monochromatic parallel light, particularly the distribution characteristics of the first mountain, a, b, c respectively. As coefficient y = a · sech (bx + c)
It is found that the hyperbolic second function sech (x) approximates very well, and the output (light intensity) of the line sensor is analyzed using the hyperbolic second function sech (x) on the light receiving surface by the Fresnel diffraction. It was proposed that the position xo where the light intensity (relative value) is 0.25 in the light intensity distribution is detected as the edge position of the shield 7 in the arrangement direction of the light receiving cells.

Specifically, when the above-described hyperbolic second function is applied to the above-described formula of the light intensity distribution by Fresnel diffraction and approximated to the first rising portion (first mountain) of the light intensity, the hyperbolic second function sech ( x) is the light intensity = 1.37 sech {1.98 (2 / λz) ^1/2 x−2.39}
As shown. This approximate expression agrees with the theoretical expression of the light intensity distribution with an accuracy of about three digits. Where λ is the wavelength of light [nm], z is the distance from the edge to the light receiving surface [mm], and x is the coordinate [μm] where the edge position on the light receiving surface is [0]. The above coefficients are set under various units.

An algorithm for edge position detection processing using such a hyperbolic second function sech (x) will be described below. When calculating the inverse function of the approximated light intensity using the hyperbolic second function sech (x),
Y = (y / 1.37)
X = 1.98 (2 / λz) ^1/2 x
Anyway,
X = 2.39−ln {[1+ (1−Y ² ) ^1/2 ] / Y}
Can be expressed as

  Therefore, in the edge detection unit 3d described above, each of the normalized received light intensities y1, y2,... Obtained from a plurality of (m) light receiving cells in the line sensor 1 is basically performed according to the procedure shown in FIG. From ym, a light receiving cell Cn that is adjacent to each other and obtains a light receiving intensity greater than the above-mentioned reference light intensity [0.25], and a light receiving cell Cn that obtains a light receiving intensity smaller than the above-mentioned reference light intensity [0.25]. −1 is obtained (step S1). That is, two adjacent light receiving cells Cn and Cn-1 having a light receiving intensity of [0.25] in each of the plurality of light receiving cells (C1, C2, to Cm) are obtained. Then, the received light intensity yn, yn-1 of each of the light receiving cells Cn, Cn-1 is divided by the coefficient [1.37] described above to be converted into light intensity Yn, Yn-1 on the XY coordinates ( Step S2).

Thereafter, the positions Xn and Xn-1 on the light receiving surface of the light receiving cells Cn and Cn-1 from which the light receiving intensities Yn and Yn-1 of the light receiving cells Cn and Cn-1 are obtained are expressed by the above-described approximate expression. Xn = 2.39-ln accordance ^{{[1+ (1-Yn 2} ) 1/2] / Yn}
Xn-1 = 2.39-ln {[1+ (1-Yn-1 ² ) ^1/2 ] / Yn-1}
As shown in FIG. 8, the relative position on the X-axis is calculated by inverse transformation (light receiving position calculating means; step S3), and the position of the light receiving cell Cn and the light receiving position are shown in FIG. The difference Δx from the edge position where the intensity is [0.25] is expressed as Δx = W · [Xn / (Xn−Xn−1)]
(Interpolation calculation means; step S4). The difference Δx is the distance from the edge position xo where the light receiving intensity is [0.25] to the position of the light receiving cell Cn, and is thus measured from the first light receiving cell C1 on the entire light receiving surface of the line sensor 1. When the absolute position x of the edge is the cell number of the light receiving cell from which n is obtained and the array pitch of the light receiving cells is W, x = n · W−Δx
Can be obtained as The relative positions Xn and Xn-1 obtained in the inverse transformation are
X = 1.98 (2 / λz) ^1/2 x
As shown below, the value is multiplied by [1.98 (2 / λz) ^1/2 ], but this term is substantially eliminated by obtaining the ratio by the above-described interpolation calculation.

  This interpolation calculation may be executed using the above-described approximate expression. However, if the change in light intensity between the two light receiving cells Cn and Cn-1 can be regarded as linear, it is simple. Simple linear interpolation may be used. Here, a position where the light intensity is [0.25] is found between adjacent light receiving cells, and the two light receiving cells Cn and Cn-1 having the position as the cell boundary are specified. Two or more light receiving cells may be specified. However, in this case, it is only necessary to prevent the calculation accuracy from being lowered by performing the interpolation calculation using the approximate expression described above. Further, the inverse transformation described above can be executed instantaneously, for example, by using a table in which the calculated values are stored in advance, thereby greatly reducing the calculation processing load.

The difference between the relative positions Xn, Xn-1 on the light receiving surface of the light receiving cells Cn, Cn-1 and the position (edge position) xo where the light receiving intensity is [0.25] and the position of the light receiving cell Cn. Paying attention to Δx, the light receiving intensity at the light receiving cell Cn, and the wavelength λ of the monochromatic parallel light, the distance between the edge of the shield 7 and the light receiving surface of the line sensor 1 from the hyperbolic second function sech (x), That is, the distance z in the optical path direction can also be obtained (step S5). Specifically, this distance calculation is basically performed by using the above-described formula approximating the above-mentioned Fresnel diffraction at the first peak. Light intensity A (x) = 1.37 · sech {1.98 (2 / λz) ^1/2 x-2.39}
Solve for the distance z from
z = (2 / λ) {1.98 · x / [arcsech (A (x) /1.37) +2.39]} ²
As described above, the distance z between the edge of the shield 7 and the light receiving surface of the line sensor 1 can be calculated.

In this case, when the edge position in the arrangement direction of the light receiving cells described above is obtained, the position of the light receiving cell Cn where the light intensity is higher than [0.25] is used, and this position and the edge position are determined. From the difference Δx,
z = (2 / λ) {1.98 · Δx / [arcsech (yn / 1.37) +2.39]} ²
As a result, the distance z between the edge of the shield 7 and the light receiving surface of the line sensor 1 can be easily obtained. Especially denominator term in the above equation, the aforementioned Xn = 2.39-ln {[1+ (1-Yn 2) 1/2] / Yn}
Therefore, the above calculation is performed by z = (2 / λ) {1.98 · Δx / Xn} ²
As a result, it becomes possible to calculate more simply.

  By the way, when the shielding object 7 is a small-diameter rod-like body as described above, for example, a drill blade, Fresnel diffraction of the monochromatic parallel light 4 occurs on both sides of the drill blade, so the Fresnel diffraction pattern on the light receiving surface of the line sensor 1 is For example, as shown in FIG. 9 (a), the pattern has a symmetry such that it converges while vibrating on both sides of the center position of the drill blade, and the light receiving intensity at each light receiving cell of the line sensor 1 is as shown in FIG. As shown in b). Moreover, when the drill diameter is 200 μm or less, the received light intensity may not decrease to [0.25]. Therefore, as described above, it is impossible to accurately obtain the position where the light amount is [0.25] using the approximate expression of Fresnel diffraction.

However, the diffraction pattern shown in FIG. 9A is considered to be a combination of Fresnel diffractions generated on both sides of the shield (drilling blade) 7 approximately as shown in FIG. 9C. be able to. Therefore, for example, the light intensity A (x) that has passed through the shield (drilling blade) 7 having the radius r is the light intensity A (x) L of the left diffraction pattern and the light intensity A (x) of the right diffraction pattern. ) R and A (x) = A (x) L + A (x) R
= 1.37 sech {-1.98 (2 / λz) ^1/2 (x + r) -2.39}
+1.37 sech {1.98 (2 / λz) ^1/2 (x−r) −2.39}
Can be understood as However, as the drill diameter becomes smaller, the overlap in the vicinity of [0.25] in the light intensities A (x) L and A (x) R of the left and right diffraction patterns greatly affects the light receiving surface of the line sensor 1. Therefore, the position where the light quantity is [0.25] cannot be directly detected as the edge position as described above.

Therefore, in the measurement apparatus according to the present invention, the light intensity A (x) L, A (x) R of the left and right diffraction patterns described above is almost affected by the other diffraction pattern at the first rising portion. Particular attention is paid to a region where the light intensity (light quantity) is [0.5 to 0.9]. For example, as shown in FIG. 75], the rough edge positions X _R and X _L are obtained (steps S11 and S12). Then, a light shielding width 2a having a light quantity of [0.75] in the diffraction pattern A (x) is obtained from these left and right rough edge positions X _R and X _L (step S13), and the above-described operation is performed according to the light shielding width 2a. The drill diameter (diameter) 2r is obtained by calculating back the radius r of the drill blade (step S14).

Specifically, the edge position X _R where the light intensity is [0.75] is obtained from the right diffraction pattern A (x) _R as follows. That is, the light intensity y
y = 1.37 sech {1.98 (2 / λz) ^1/2 X−1.21}
In
Y = y / 1.37
And put
sech ⁻¹ (Y) = ± ln [{1+ (1−Y ² ) ^1/2 } / Y]
= X'-1.21
However, 0 <y ≦ 1.37, 0 <Y ≦ 1.0, X ′ = 1.98 (2 / λz) ^1/2 X
It becomes.

Therefore, the measured value (normalized data y0, y1, y2,..., Y101) in each light receiving cell of the line sensor 1 composed of 102 cells is between the [n−1] th cell and the nth cell. There is a position where the light intensity is [0.75]. If the light intensity in the [n-1] -th and n-th cells is yn-1, yn,
Yn-1 = yn-1 / 1.37, Yn = yn / 1.37
As in the case shown in FIG. 8, the position where the light intensity is [0.75] is defined as X′n−1 = 1.21−ln [{1+ (1−Yn−1 ² ) ^1/2 } / Yn-1]
X′n = 1.21−ln [{1+ (1−Yn ² ) ^1/2 } / Yn]
Can be mapped respectively. As a result, the edge position X _R is changed from these mapping positions to X _R [μm] = w {n−X′n / (X′n−X′n−1)}.
Can be obtained easily and accurately by interpolation processing. Where w is the width of the cell. As described above, X′n and X′n−1 are not the original cell positions but are values multiplied by 1.98 (2 / λz) ^1/2 , Since this term is substantially eliminated by obtaining, the interpolation process can be performed accurately even if the distance z is unknown.

Similarly, an edge position X _{L at} which the light amount is [0.75] is obtained from the left diffraction pattern A (x) L. Then, according to the edge positions X _R and X _L obtained from these diffraction patterns A (x) R and A (x) L, the light shielding width 2a at the position where the light quantity is [0.75] is set to 2a = X _R − X _L
Asking.

Next, the above light quantity [0.75] and half the value a of the light-shielding width 2a are added to the equation representing the diffraction pattern obtained by combining the light intensities A (x) R and A (x) L of the right and left diffraction patterns. Substituting and calculating the radius r of the drill blade in reverse. For the reverse calculation of r, for example, numerical calculation may be performed using the Newton method.
Specifically, f (r) = 1.37 sech {-1.98 (2 / λz) ^1/2 (a + r) -2.39}
+1.37 sech {1.98 (2 / λz) ^1/2 (ar) -2.39} −0.75
Then, the derivative is f ′ (r) = − 2.71 (2 / λz) ^1/2
Xsech {-1.98 (2 / λz) ^1/2 (a + r) -2.39}
Xtanh {-1.98 (2 / λz) ^1/2 (a + r) -2.39}
-2.71 (2 / λz) ^1/2
× sech {1.98 (2 / λz) ^1/2 (ar) -2.39}
X tanh {1.98 (2 / λz) ^1/2 (ar) -2.39}
It becomes.

Therefore, the initial value r0 of r is set to r0 = {2a−0.845 (λz) ^1/2 } / 2
age,
r _n = r _n−1 −f (r _n−1 ) / f ′ (r _n−1 )
n = 1,2,3, ...
If it is repeatedly calculated until the absolute value of [r _n −r _n−1 ] is, for example, 0.01 or less, the converged r can be obtained as the radius of the drill. For drill diameter is therefore a 2 times the radius r, in particular it is possible to obtain a 2r _n.

  As for the drill diameter (radius r) calculated in this way, when the distance z between the drill blade and the line sensor 1 is known in advance, for example, as shown in FIG. 11, the light shielding width 2a and the diameter 2r. As a relationship, the table may be stored in advance. If such a table 3h is used, since the back-calculation process using the Newton method mentioned above becomes unnecessary each time, it becomes possible to measure a drill diameter easily.

By the way, when the drill blade (shielding object) 7 is rotated, the above-mentioned optical image (image pattern) projected on the light receiving surface of the line sensor 1 is the drill blade 7 because the blade is engraved spirally on the peripheral surface. The camera shakes from side to side as it rotates. However, when the drill blade (shielding object) 7 rotates at a low speed around its axis, the vibration itself is periodically generated according to the rotation angle. When obtaining the light shielding width 2a (= X _R −X _L ) at the position where the amount of received light is [0.75], the central position c at the same time is determined as c = (X _R + X _L ) / 2.
If this is obtained, the runout of the drill blade 7 can be monitored by monitoring the change width of the center position c. If the change width of the center position c exceeds a predetermined threshold value, it can be determined that there is a center shift.

However, when the drill blade 7 is rotating at a high speed, the concave and convex patterns formed by the spirally engraved blades overlap each other at a high speed, so that the above-described optical image projected onto the light receiving surface of the line sensor 1. It cannot be denied that the (image pattern) is totally blurred (so-called defocused state). Accordingly, it is difficult to obtain the light shielding width 2a (= X _R −X _L ) at the position where the received light amount is [0.75].

  Therefore, in order to detect the runout of the drill blade 7 rotated at a high speed, for example, a round bar (shield) is attached to the spindle (drill chuck) to which the drill blade 7 is attached, instead of the drill blade 7. What is necessary is just to detect the runout of the round bar. If a round bar having substantially the same diameter as the drill blade 7 is used, an optical image (image pattern) in which the left and right diffraction patterns diffracted on both sides thereof are combined as described with reference to FIG. 9 is obtained. However, if the round bar (shielding object) 7 rotates at a high speed while causing a runout, the position of the round bar (shielding object) 7 is shaken in the arrangement direction of the light receiving cells of the line sensor 1. 7 are displaced at high speed, and the light that is not blocked by the round bar 7 overlaps with each other at each center position as shown in FIG. 13A, for example. For this reason, the image pattern detected by the line sensor 1 becomes unclear and blurry as a whole like a so-called defocused image as shown in FIG. 13B, for example. Specifically, a diffraction pattern when shifted to the left side and a diffraction pattern when shifted to the right side are combined to form a so-called blurred optical image (image pattern). That is, when the runout occurs, the edge itself is blurred, and the light amount is originally blocked by the round bar 7 to increase the amount of shadow, and the light amount at the peripheral portion decreases. Accordingly, when the diameter of the round bar 7 is measured in this state as described above, the diameter of the round bar 7 is required to be reduced by the amount of light at the original edge boundary.

  On the other hand, in the case where the round bar body (shielding object) 7 is rotating at high speed around its axis (in a state where there is no center deflection), or in the state where the rotation of the round bar body 7 is stopped, the optical image thereof. Since the influence of the above-mentioned center blur does not occur in (image pattern), the diameter of the round bar 7 can be accurately measured by the above-described method. Further, when the total amount of light received by the line sensor 1 when the round bar 7 is positioned in the optical path of the parallel light 4 and when the round bar 7 is removed, the amount of light blocked by the round bar 7 is calculated. Since the amount of light received by the line sensor 1 only decreases, the diameter of the round bar 7 can be determined relatively easily from the ratio of the amounts of received light, even if high measurement accuracy cannot be expected. Further, since the amount of light irradiated per unit time and unit area is constant, the ratio of the amount of received light is constant regardless of whether or not the round bar 7 is misaligned. Accordingly, the diameter of the round bar 7 obtained in this way from the ratio of the amount of received light or in the initial state with no runout, and the round bar 7 obtained in the state where the round bar 7 is rotated at a high speed as described above. This makes it possible to detect whether or not the round bar 7 has run out of core.

Therefore, in the above-described center blur detection unit 3f, first, the total light reception pattern Ai by the line sensor 1 is obtained in a state where the round bar 7 is not placed in the optical path of the monochromatic parallel light 4, and the total value of the light reception amount in each light reception cell. S (= ΣAi) is obtained. Then, the normalization parameter Ni (= 1 / Ai) is obtained so that the amount of light received by each light receiving cell becomes [1].
Thereafter, the round bar 7 is positioned at a distance z from the line sensor 1, the light receiving pattern Yi at that time is obtained, and this light receiving pattern Yi is [yi = Yi × Ni] using the above-described normalization parameter Ni. As normalization. Then, the total amount S1 (= Σyi) of the received light amount when the round bar 7 is inserted is obtained, and the radius R _{OPT of the} round bar 7 is determined from the light quantity ratio between when the round bar 7 is inserted and when it is not. R _OPT = 8670 (S1 / 2S)
It is calculated as The coefficient [8670] indicates the overall length of the line sensor in which 102 light receiving cells having a width w of 85 μm are arranged.

Next, paying attention to the diffraction pattern on the right side of the light receiving pattern in the line sensor 1, as described above, two points yn-1 and yn sandwiching the position where the amount of received light is [0.75] are searched for and described above. Using the inverse Fresnel function, yn-1, yn are inversely mapped to the X axis to obtain positions Xn-1, Xn. Then, the right edge position X _R is converted into X _R = 85 [n−Xn / (Xn−Xn−1)] by interpolation from the inversely mapped positions Xn−1 and Xn.
It is calculated as Similarly focusing on the diffraction pattern of the left of the light receiving pattern, after obtaining the left edge position X _L, the amount of receiving the difference between the right edge position X _R and the left edge position X _L is a [0.75] The diameter (radius) R _CCD of the round bar 7 is obtained from the light shielding width 2a by the reverse calculation described above.

Then, as described above, the difference between the diameter R _{OPT of the} round bar 7 obtained by the light quantity method and the diameter (diameter) 2R _CCD of the round bar 7 obtained by analyzing the output of the line sensor 1 is obtained. It is determined whether or not there is a runout by determining whether or not it is smaller than a predetermined threshold value R _MAX . Specifically, when the difference (R _OPT −2R _CCD ) is smaller than a predetermined threshold value R _MAX , it is determined that there is no center deviation, and the difference (R _OPT −2R _CCD ) sets the predetermined threshold value R _MAX . If it exceeds, it is determined that there is a runout.

  Now, in the measuring apparatus configured with the above-described drill diameter measuring function and run-out detection function, the present invention is characterized in that the drill blade 7 is advanced and retracted at right angles to the longitudinal direction of the line sensor 1. Note that when the tip of the drill blade 7 is positioned in the optical path of the monochromatic parallel light 4, the output of the line sensor 1 changes due to Fresnel diffraction of the monochromatic parallel light 4 at the tip. The point is that the tip of the drill blade 7 is detected by monitoring the output of the sensor 1. Then, the tip position of the drill blade 7 is detected from the forward / backward position when the tip of the drill blade 7 is detected, and the detected information is used for controlling the depth of drilling using the drill blade 7. Yes.

  That is, when diffused light is used as the light source, the transmitted light around the tip of the drill blade 7 has a substantially uniform light amount as illustrated in FIG. 14, and the light amount gradually changes at the edge portion of the drill blade 7. It will be unclear. On the other hand, when monochromatic parallel light (laser light) is used as the light source, stripes around the tip of the drill blade 7 due to Fresnel diffraction generated at the edge portion of the drill blade 7 as illustrated in FIG. A diffraction pattern (diffraction pattern) is generated, and light goes around to the inside of the tip of the drill blade 7. In the tip detection in the present invention, the tip of the drill blade 7 is detected as follows by capturing the change in light intensity due to Fresnel diffraction at the tip of the drill blade 7.

  In order to provide the above-described measurement of the drill diameter or the like, the drill blade 7 is positioned at a right angle with respect to the arrangement direction (longitudinal direction) of the light receiving cells of the line sensor 1, and the drill blade 7 is advanced and retracted in the axial direction. Assuming that the drill blade enters the optical path of the monochromatic parallel light 4 from its tip, the output of the line sensor 1 at that time changes as shown in FIGS. FIG. 16 shows a state in which the tip of the drill blade 7 having a diameter of 1 mm starts to enter the optical path, and the normalized output of the line sensor 1 starts to be slightly disturbed. FIG. 17 shows the normalized output of the line sensor 1 in a state where the drill blade 7 further enters the optical path by 50 μm, and FIG. 18 shows the drill blade 7 further 50 μm (total 100 μm in the optical path). 19) The normalized output of the line sensor 1 in the intruded state, and FIG. 19 shows the normalized output of the line sensor 1 in the state in which the drill blade 7 has further entered the optical path by 50 μm (total 150 μm). Each output is shown.

Therefore, in the present invention, for example, the tip of the drill blade (rod-like body) 7 is detected according to the procedure shown in FIG. Specifically, the shaft portion of the drill blade (rod-like body) 7 is positioned in the optical path of the monochromatic parallel light 4, and the region of the light receiving cell where the shadow of the drill blade 7 is generated is obtained (step S41). At this time, the shading width 2a described above is obtained, and at the same time, the axial center position c of the drill blade 7 is c = (XR + XL) / 2.
It is desirable to identify the light receiving cell corresponding to the axial position c. After that, the amount of light received at the light receiving cell where the shadow is generated (the amount of light received at the position corresponding to the axis of the drill blade 7) is calculated while gradually raising the drill blade (rod-like body) 7, and the amount of received light is calculated. Temporarily store (step S42). Next, the drill blade 7 is further raised by a minute amount, and it is determined whether or not the amount of light received by the light receiving cell at that time increases (step S43). If the amount of received light is increased, the rising position of the drill blade 7 is stored together with the amount of received light at that time (step S44), and the process returns to step S42 to further raise the drill blade 7 by a minute amount.

  The above-described processing is repeatedly executed until the amount of light received by the light receiving cell is lower than the stored amount of received light. When the amount of light received by the light receiving cell is reduced, the drill blade 7 is gradually raised and updated. Further, it is determined that the amount of light received by the light receiving cell indicates the first peak (first peak) (step S46), and the ascending position of the drill blade 7 stored as described above is used as the tip of the drill blade 7. It detects (step S47). That is, as shown in FIG. 17, the tip of the drill blade 7 enters the optical path of the monochromatic parallel light 4, thereby causing Fresnel diffraction, for example, the width of the line sensor 1 having a width of only 85 μm. A state in which the output (output of the light receiving cell) is increased is detected as a state in which the tip of the drill blade 7 is positioned within the range of the light receiving width in the short direction of the line sensor 1.

  Thus, according to the tip detection method for detecting the tip of the drill blade 7 as described above, the peak position at the first rising portion in the Fresnel diffraction pattern is detected as shown in FIG. The tip (edge position) of the blade 7 can be detected with high accuracy. In particular, the tip (edge position) can be detected with high accuracy by using the approximate expression approximating the Fresnel diffraction described above. Moreover, the front end of the drill blade 7 (edge position) is used by directly using the output of the line sensor 1 arranged at right angles to the axial direction of the line sensor 1 without aligning the longitudinal direction of the line sensor 1 parallel to the axial direction of the drill blade 7. ) Can be detected with high accuracy. Therefore, the tip position can be detected using the line sensor 1 used for measuring the drill diameter or the like without using two line sensors having different arrangement directions (longitudinal directions) of the light receiving cells. It is possible to greatly simplify the configuration.

  The present invention is not limited to the embodiment described above. Here, the shaft portion of the drill blade 7 is positioned in the optical path, and the tip is detected while gradually detaching the drill blade 7 from the optical path. Conversely, the drill blade 7 enters the optical path from the tip side. The tip may be detected by detecting the first peak position retroactive from when the drill blade 7 is completely positioned in the optical path. Also, the tip is detected when the drill blade 7 is inserted into the optical path and when the drill blade 7 is pulled out of the optical path, and these detection results are comprehensively determined. The leading end position of the drill blade 7 may be detected.

  In measuring the drill diameter, in this example, the light shielding width 2a at the position where the amount of light is [0.75] is obtained. However, the light shielding width 2a is obtained at the other portion where there is no influence of the diffraction pattern. In practice, for example, it is sufficient to obtain the light-shielding width 2a at an arbitrary position in a range where the light quantity is [0.5 to 0.9]. Further, as the line sensor 1, a sensor other than the specifications described above can be adopted as appropriate. In addition, the present invention can be variously modified and implemented without departing from the scope of the invention.

The figure which shows the principal part schematic structure of the measuring device used for the runout detection method of this invention. The figure which shows the detail of the optical system in the measuring apparatus shown in FIG. The figure which shows typically the state which looked at the optical system shown in FIG. 2 from arrow AA direction. The figure which shows typically the state seen from the arrow BB direction shown in FIG. The figure which shows the intensity | strength pattern of the light which produced the Fresnel diffraction by the edge of the shield. The figure which compares and compares the theoretical value of the light intensity distribution by Fresnel diffraction, and the approximate characteristic using a function. The figure which shows an example of the procedure of the edge detection process from a Fresnel diffraction pattern. The figure which shows the processing concept of the edge detection shown in FIG. The figure for demonstrating the diffraction pattern produced with a micro diameter drill blade, and the measurement principle of this invention. The figure which shows the process sequence of the diameter measuring method which concerns on one Embodiment of this invention. The figure which shows the structural example of the table which shows the relationship between the light-shielding width 2a and the diameter 2r of a drill in the position of light quantity [0.75]. The figure which shows the mode of a runout when rotating a round bar at low speed. The figure which shows the example of the light reception pattern when rotating a round bar at high speed. The figure which shows the image of the front-end | tip part of a drill blade at the time of using a diffused light. The figure which shows the image of the front-end | tip part of a drill blade at the time of using monochromatic parallel light. The figure which shows the output of a line sensor when the front-end | tip part of a 1 mm diameter drill blade begins to penetrate into an optical path. The figure which shows the output of a line sensor when the front-end | tip part of a drill blade is further penetrated by 50 micrometers from the state shown in FIG. The figure which shows the output of a line sensor when the front-end | tip part of a drill blade is further made to penetrate 100 micrometers from the state shown in FIG. The figure which shows the output of a line sensor when the front-end | tip part of a drill blade is further made to penetrate 150 micrometers from the state shown in FIG. The figure which shows the procedure of the front-end | tip detection process which concerns on one Embodiment of this invention. The figure which shows the peak of the diffraction pattern utilized for front-end | tip detection, and the concept of the peak detection.

Explanation of symbols

1 Line sensor 2 Light emitter (light source)
3 apparatus main body 3a diffraction pattern detection unit 3d edge detection unit 3e drill diameter measurement unit 3f runout detection unit 3g tip detection unit 3h table 7 shield (drill blade)

Claims (3)

A line sensor in which a plurality of light receiving cells are arranged at a predetermined pitch in one direction, and a light source that projects monochromatic parallel light toward the plurality of light receiving cells of the line sensor,
When determining the tip of the drill blade that enters the optical path of the monochromatic parallel light from the axial direction with the axial direction being substantially perpendicular to the arrangement direction of the light receiving cells, from the output of the line sensor,
To advance and retract the drill bit in the axial direction, a forward and backward position of the drill bit when the output of the line sensor at a central axial position of the drill bit is peaked tip of the drill bit positioned on the optical path A tip detection method for a drill blade, characterized in that it is detected as a broken state.   The peak detection of the output of the line sensor is performed after the axis of the drill blade is obtained by analyzing the output of the line sensor when the drill blade is positioned in the optical path of the monochromatic parallel light. Item 2. A method for detecting a tip of a drill blade according to Item 1.   The position at which the output of the line sensor reaches a peak is obtained when the drill blade enters the optical path and when the drill blade is detached from the optical path, and the tip position of the drill blade is obtained as an average of these peak positions. The tip detection method of a drill blade according to claim 1, wherein:

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