JPH0733128Y2 - Head posture measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a head posture measuring device using an image processing device.

[Conventional technology]

For example, in a digital audio tape recorder (hereinafter referred to as "DAT"), two magnetic heads are attached to the peripheral surface of a rotating drum, and the two magnetic heads alternately scan the magnetic tape at an angle, The digitally converted audio signal is recorded on a magnetic tape and reproduced.
Such a rotary magnetic head is also used in a video tape recorder. In the rotary magnetic head, the magnetic head must be in a proper posture so that the gap between the magnetic heads can be slidably in contact with the magnetic tape. For example, the position of the gap is attached at the position most protruding from the drum surface.

A head attitude measuring device using an image processing device can be used for measuring the attitude of the magnetic head in the rotary magnetic head. Now, when a microscope with an interference objective lens is used in the image pickup optical system of a television camera and it is moved in the optical axis direction with respect to the magnetic head, the image of the magnetic head and the most protruding position of the magnetic head surface are generated. An image of the generated interference fringes appears. FIG. 10 shows an example of an image signal obtained through a television camera when the magnetic head 27 is mounted in a correct posture. The position where the image of the gap 25 of the magnetic head appears and the position where the interference fringes 17 appear. They match on the image signal. FIG. 11 shows a case where the magnetic head 27 is not properly oriented, and the position where the gap 25 of the magnetic head appears and the position where the interference fringes 17 appear are deviated.

FIG. 12 shows an example of a microscope having an interference objective lens used in a head posture measuring device which the present inventor considered as a premise of the present invention. In FIG. 12, the illumination light from the light source 45 passes through the monochromatic filter 46, is reflected by the half mirror 47, and reaches the interference objective lens 41. A tungsten bulb is used as the light source 45, and white light is emitted. Only a portion of the wavelength of white light passes through the monochromatic filter 46. The interference objective lens 41 is
It has an objective lens 48 with a magnification of m, a half mirror 43 that splits light into reflected light and transmitted light, and a mirror 44 that reflects the reflected light from the half mirror 43 and returns it to the half mirror 43. The light transmitted through the half mirror 43 is applied to the magnetic head 1. The light reflected by the magnetic head 1 is reflected by the half mirror 4
3. It passes through the objective lens 48 and the half mirror 47 and reaches the television camera 5. The image forming point F on the surface of the magnetic head 1 by the objective lens 48 is on the photographing surface of the television camera 5.

One of the two lights split by the half mirror 43 of the interference objective lens 41 is reflected by the surface of the magnetic head 1 and returns to the half mirror 43, where both lights interfere with each other and the objective lens
Interference fringes are generated at 48 image forming points F. The image forming point F is an image forming point that serves as a reference for designing the objective lens 48, and as long as an image is formed at this image forming point, the aberration of the optical meter is corrected.

The center point of the half mirror 43 is C, the center point of the mirror 44 is B,
When the center point of the magnetic head 1 is A, the range in which the interference fringes are generated is determined by the difference between the optical path CAC and the optical path CBC, and the interference fringes in which this difference is too large do not occur.
The range in which interference fringes occur is called the coherence length ε, and is determined by the monochromatic filter 46. This coherence length ε is obtained by ε≈λ ² / Δλ. However, λ is the center wavelength of the monochromatic filter 46, and Δλ is the wavelength band that passes through the monochromatic filter 46.

The image obtained through the microscope having the interference objective lens 41 and the television camera 5 described above is an image in which the image of the interference fringes of the image on the head surface as shown in FIGS. The attitude of the magnetic head can be measured by inputting these image signals into the image processing apparatus and performing image processing.

[Problems to be solved by the invention]

According to the above-described head attitude measuring device, since the image signal of the state in which the image of the head surface and the image of the interference fringe overlap each other is input to the image processing device, the image processing device determines whether the image is the image of the head surface or the interference fringe. It is difficult to accurately determine whether or not the position of the gap 25 is interfered with by interference fringes. Therefore, a mechanism for opening / closing a part of the optical path of the interference optical system to turn on / off the generation of interference fringes has been considered.

However, an interference objective lens having an on / off mechanism for interference fringes is expensive, and a general on / off mechanism for interference fringes is used.
The off mechanism is manually operated, and any attempt to convert it to automatic operation becomes more expensive. Furthermore, even if an automatic on / off mechanism is used, there is a problem that vibration is a problem and the response time is slow because of the mechanical structure.

The present invention has been made in order to solve such a problem, and in a head attitude measuring device using a microscope having an interference objective lens optical system and an image processing device, an interference fringe caused by the interference objective lens is used. It is an object of the present invention to provide an attitude measuring device that can generate and eliminate noise very easily, and can easily automate the measurement, and at low cost, low vibration, and good responsiveness. And

[Means for Solving the Problems]

The present invention relates to a microscope having an interference objective lens, a television camera for obtaining an image signal through the microscope, and an apparatus for processing the head surface image and the interference fringe image obtained by the television camera to measure the posture of the head. The distance between the television camera and the head surface is changeable on the optical axis of the interference objective lens at least in the range from the focus position on the head surface to the focus position on the interference fringes. .

[Action]

By changing the distance between the TV camera and the head surface on the optical axis, it is possible to create a focused state on the head surface and a focused state on the interference fringes generated on the head surface. The stripes can be observed separately. The posture of the head can be measured by performing image processing on the image of the head surface and the image of the interference fringe that can be individually observed.

〔Example〕

An embodiment of a head posture measuring device according to the present invention will be described below with reference to the drawings.

In the illustrated embodiment, since it is configured as a magnetic head position measurement and attitude measurement device in a rotating drum used in a DAT, an outline of the magnetic head position measurement and attitude measurement in the DAT will be described before the description of the embodiment. I'll do it.

FIG. 7 shows an input image of the magnetic head 27 input from the television camera. The magnetic head 27 includes the sendusts 23, 23 arranged with the head gap 25 interposed therebetween, and the sendusts 23, 23.
23 and the ferrite cores 22 and 22 arranged on one side of the head gap 23 and one end of the head gap 25 as one apex.
And glass 24, 24 arranged in a triangular space surrounded by the wellite core 22. The image signal of the magnetic head from the television camera is input to the image processing apparatus, and the position of the head gap 25 is measured as a position on the XX coordinate with reference to a fixed position.

On the rotating drum of the DAT, two magnetic heads are attached to the outer circumference of the drum at intervals of 180 degrees. Therefore, when the drum rotates 180 degrees, the positions of the two magnetic heads must be in the correct positions and match each other. Whether the positions of the two magnetic heads are in the correct positions and whether they match each other is determined by inputting the image signal of one magnetic head with a TV camera and measuring the position, and then moving the drum. It can be judged by rotating 180 degrees and inputting the image signal of the other magnetic head from the television camera and measuring the position. Further, the sliding contact surface of the two magnetic heads with the tape needs to be protruded from the outer peripheral surface of the drum by an appropriate amount in order to obtain a good sliding contact relationship with the tape, and The amount of protrusion of the head must match. further,
The magnetic head 27 is mounted in a correct posture so that the gap 25 can be slidably contacted with the tape. In this embodiment, the position of the gap 25 is attached to the position most protruding from the drum surface.

The attitude of the magnetic head 27 can be measured by using an autofocus device of a television camera having an interference objective lens. 2 to 4 show an example of an autofocus device applicable to the attitude measurement of the magnetic head 27.

By moving the lens of the television camera relative to the magnetic head in the optical axis direction, two peaks a and b appear in the output voltage as shown in FIG.

Peak a is a peak when the magnetic head is focused,
The peak b is a peak due to the generation of interference fringes, but the autofocus device does not know which is the peak when the magnetic head is focused. There is a constant distance D between the peaks a and b, which is determined by the configuration of the interference objective lens optical system. The variation when the magnetic head is inserted into the drum is known in advance, and the scan width S for focusing, which is the range W, is larger than the range W. Which of the output voltage Va at the peak a and the output voltage Vb at the peak b is larger is indefinite, but in the example of FIG. 2, Va> Vb
Has become. Therefore, as shown in FIG. 5, first,
The stage on which the TV camera is attached is moved to a reference point C that is outside the near side of the scan width S, and the reference point C
The voltage Vf obtained by adding α to the output voltage Vc at is stored as a reference voltage. Next, the stage is moved to the far point side of the scan width S, the position at the maximum value of the peak appearing between them is determined, and the position of the maximum value (peak a in the example of FIG.
Position) to the stage. Next, Ve = Vb in the case of FIG. 2 in which the stage is moved to a position away from this position by a distance D toward the far point, and the output Ve after this movement is taken out from the memory. Therefore, we compare Ve and Vf. Since Ve> Vf in FIG. 2, the stage is moved to the position of the maximum value, that is, the position of the peak a and stopped, and this position is set as the target focus position. FIG. 2 shows the movement of the stage.

By the way, in some cases, as shown in FIG. 3, the output voltage Vb of the peak b of the interference fringe may be larger than the output voltage Va of the peak a when the magnetic head is focused. In this case, in the comparison of Ve and Vf in FIG.
Since it can be seen that the position of Ve is not the focal position for the magnetic head but the focal position for the interference fringes, as shown by the chained line frame in FIG. 4, the preset range around Vb, that is, the peak due to the interference fringes. With the data in the range before and after appearing as 0, the process proceeds to the step of obtaining the maximum value and the position of the maximum value again. In the step of obtaining the maximum value and the position of the maximum value, the focus position is obtained in which the position of the peak a appearing by focusing on the magnetic head is obtained, and the stage stops at this position. After that, the operation is performed according to the flow of FIG. 5, and the peak position b with respect to the interference fringe is also detected.

In this way, it is possible to detect the position where the magnetic head is focused and the position where the interference fringes are generated, and by processing the images appearing at the respective focusing positions, the position where the gap of the magnetic head is most protruded from the rotating drum surface is detected. Can be measured, that is, whether the magnetic head is mounted in the correct posture.

Here, the value of the voltage Vc at the reference point C is compared with the voltage at the point a or b because the output line pressure differs depending on the state of the head surface, so if Vc is kept constant from the beginning. Alternatively, the voltage at the point b may become lower than Vc, and the in-focus point may not be detected. Therefore, the voltage Vc at the reference point C is obtained each time and compared. Further, the reason why Vc + a = Vf is set is that the voltage is low only by Vc, and Ve> Vc is established even if Ve is not so high that the focusing position may be wrong.

Next, an example of a device for automatically assembling a magnetic head for DAT using the above-described head attitude measuring device will be described.

In FIG. 1, magnetic heads 1 and 2 are screwed to the outer peripheral portion of a rotating drum 3 of a DAT at 180-degree intervals. Drum 3
Are attached to a jig 12 rotated by a motor 14 with the magnetic heads 1 and 2 side up. When the drum 3 is incorporated in a tape recorder, the drum 3 is rotatably attached to the fixed drum with the magnetic heads 1 and 2 facing down.

A microscope 4 is arranged facing one of the magnetic heads of the drum 3 on the jig 12. The microscope 4 is attached to a precise stage 6 so that the optical axis 42 of the interference objective lens 41 is located substantially at the center of the magnetic head. The magnified sample viewed with the microscope 4 is the magnetic heads 1 and 2 and can be measured with an accuracy on the order of submicrons. A television camera 5 is attached to the stage 6 at the image forming position of the microscope 4. The stage 6 is driven by the motor 13 in the optical axis 42 direction.

The image signal of the magnetic head obtained by the television camera 5 is input to the monitor 8 to display the image of the magnetic head, and is also input to the autofocus device 7. The autofocus device 7 is a buffer 77 for sending an image signal from the television camera 5 to the image processing device 9 efficiently and without interference from other parts, and a portion to be focused on the imaging screen, that is, In this embodiment, a detection area and a scanning line setting unit 73 that sets a portion necessary for extracting only the data of the head surface, and an image signal for passing only the image signal in the range set by the detection and scanning line setting unit 73 A gate 72, a high-pass filter 74 for extracting a high frequency component from the image signal from the gate 72, and an output signal from the high-pass filter 74 by an A / D converter (not shown),
A memory 75 for converting an analog signal into a digital signal and storing the data of this digital signal, and this memory 75
Autofocus control unit 76 which obtains a focus point from the stored data and outputs a signal for moving the stage 6.
And have. The focusing method by the autofocus device 7 is a contrast method.

The autofocus control unit 76 fetches data at each camera position from the memory 75 as the television camera 5 moves. Since this data changes as shown in FIG. 2 or FIG. 3, the in-focus point is detected from this output voltage characteristic, this detection signal is sent to the motor 13, and the motor 13 is driven to move the stage 6 to the objective lens. 41 is moved in the direction of the optical axis 42. Since the microscope 4 and the television camera 5 are attached to the stage 6, the focus position changes as the stage 6 moves.
The autofocus control unit 76 can drive the motor 13 to move the Suge 6 until the microscope 4 reaches the focal point of the magnetic head.

The image processor 9 measures the position of one of the intersections of the head gap 25 intersecting the ferrite core 22, the glass 24 and the sendust 23 from the image signal as shown in FIG. This measurement can be performed, for example, by measuring the intersection point position of the head gap on the XY coordinates when the horizontal axis is X and the vertical axis is Y with the left corner of the surface frame 20 as the origin O. . Further, the image processing apparatus 9 represents the gap position data of one magnetic head 1 by X ₁ and Y ₁ , and the gap position data of the other magnetic head 2 by X ₂ and Y ₂ , which will be described below. It is stored in the memory provided in the control unit 10.

The system control unit 10 includes a jig 12 and an autofocus device 7.
The magnetic head assembly device including the image processing device 9 and the image processing device 9 is controlled, and the gap positions X ₁ , Y ₁ and X ₂ , Y _{2 of} the _two magnetic heads 1, ₂ and the protrusion amount t from the drum 3 are controlled. The positions of the magnetic heads 1 and 2 with respect to ₁ , t ₂ and the drum 3 are measured, and it is determined whether or not these are within the allowable range. Specifically, first, the drum 3 is slightly rotated to obtain the distances Z _D1 and Z _D2 (not shown) to the outer peripheral surface of the drum 3, and then the stage 6 when the magnetic head 1 is focused. Position Z ₁ and the position Z ₂ of the stage 6 when the magnetic head 2 is focused, and the protrusion amount t ₁ of the magnetic head 1 is calculated by t ₁ = (Z _D1 −Z ₁ ). Similarly, the protrusion amount t ₂ of the magnetic head ₂ is t ₂ =
Calculated by (Z _D2- Z ₂ ). Or, instead of the drum 3 to which the magnetic heads 1 and 2 are attached, attach a master work,
The amount of protrusion t, t ₀ of the portion corresponding to the magnetic head is obtained from the position Z, Z ₀ of the stage 6 when the portion corresponding to the magnetic head of the masterwork is focused, Head gap position
Find X, Y, X ₀ and Y ₀ . And the drum 3 as a work
The respective data of the above magnetic heads 1 and 2 are compared with the respective data of the master work, and the respective differences, that is, (t ₁ −t), (t ₂ −t ₀ ), (X ₁ −X ), (X ₂ −
X _0), obtaining the _{(Y 1 -Y), (Y} 2 -Y 0). Further, the attitude of the magnetic head with respect to the drum 3 is measured from the positional shift of the image when the magnetic head surface and the interference fringe generation position are focused by the autofocus device 7. When the value thus obtained is within the preset allowable range, the drum 3 is removed from the jig 12 and the next drum is set to the jig.
Attach to 12. If the obtained value is out of the above allowable range, a signal is sent to the head position correction device 11. When the measurement of one magnetic head is completed, the system control 10 also drives the motor 14 to rotate the jig 12 180 degrees to measure the other magnetic head.

The head position correcting device 11 receives a signal from the system control unit 10 to loosen the mounting screw of the magnetic head 1 or the magnetic head 2 to adjust the position of the magnetic head to be adjusted, and tighten the mounting screw. This is a device for reattaching the magnetic head to the drum 3. The head position correcting device 11 is not directly related to the present invention, and thus its detailed description is omitted.

Next, the operation of the automatic assembling apparatus will be described with reference to the flowchart of FIG.

First, a drum as a master work is installed on the jig 12 manually or by using a drum moving arm or the like not shown. The magnetic head surface of the master work is located on the optical axis 42 of the interference objective lens 41, and the image of the magnetic head of the master work is displayed on the monitor 8. However, since the focus of the microscope 4 is not normally on the magnetic head, the image displayed on the monitor 8 is usually blurred.

Here, one of the two magnetic heads of the master work and the two magnetic heads of the drum 3 is an R channel head, and the other is an L channel head. Therefore, first, the surface of the R channel head of the master work is focused. Therefore, first, a sensor (not shown) detects that a drum as a masterwork is installed, and a signal is sent from the system control unit 10 to the autofocus device 7 based on the detection signal. The autofocus device 7 is a motor 13
Is driven to move the stage 6 over the entire range of its moving stroke, and the memory 75 stores the data of the change in the contrast of the image of the magnetic head accompanying the movement. This stored data is the data shown in FIGS. 2 and 3. The autofocus device 7 also detects the focus position on the head surface and the interference fringe generation position from the data stored in the memory 75, and drives the motor 13 to detect the focus position and the interference fringe generation position. The stage 6, the microscope 4 and the television camera 5 integrated with the stage 6 are moved to the position.

The operation of the autofocus device 7 will be described more specifically. The image signal of the magnetic head as a sample which is magnified by the microscope 4 and is output from the television camera 5 is output from the detection area / scanning line setting unit 73 at the gate 72. A specific scanning line portion is selected from the image signal by the signal of, and the high-pass filter 74 extracts the high-frequency component, and the A / D (not shown)
The converter converts the analog signal into a digital signal and stores the digital signal in the memory 75. This stored data is input to the autofocus control unit 76. The autofocus control unit 76 first drives the motor 13 to move the stage 6 and the microscope 4 and the television camera 5 attached to the stage 6 over the entire range of its movement stroke.
The change in the autofocus signal, which is the output signal from the high-pass filter 74 at this time, is stored in the memory 75.
Next, the autofocus control unit 76 controls the motor 13 based on the data stored in the memory 75 to move the stage 6 so that the magnetic head surface is imaged on the shooting surface of the television camera 5, and , Focus so that interference fringes may occur. The data stored in the memory 75 is
4 is a graph having the characteristics shown in FIG. 2 and FIG. 3, and as described with reference to FIG. 5 among the output characteristics, the motor so that the stage 6 moves to the focal point on the magnetic head surface. Drive 13 Monitor 8 at focus position
The image of the magnetic head shown in FIG. 7 is as shown in FIG.

Returning to FIG. 6, when the focusing operation is completed, the distance from the magnetic head surface at the time of focusing to the stage 6 is set as the position Z of the stage 6 and measured. Since the protrusion amount t of the magnetic head of the master work is set to a predetermined amount, for example, 20 μm in advance, the measured data is stored in the memory in the system control unit 10 with these values as a reference.
The position Z of the stage 6 is measured, for example, by using the motor 13 as a pulse motor, measuring the number of drive pulses from the origin of the motor, and multiplying the number of drive pulses by the known moving distance of the stage 6 for one pulse. Can be obtained by

Next, from the image signal as shown in FIG. 7, the ferrite core 22, the glass 24 and the sendust 23 of the head gap 25 are detected.
Measure one position of the intersection with and by image processing,
Find the gap position of the magnetic head. This can be obtained, for example, by measuring the gap position of the magnetic head on the X and Y coordinates with the origin O at the left corner of the image as shown in FIG. 7, the horizontal axis at X, and the vertical axis at Y. The obtained gap position data is stored in the memory in the system control unit 10.

Further, the posture of the head is measured and stored in the memory according to the procedure described in detail above.

Next, the jig 12 is rotated 180 degrees under the drive of the motor 14 by a signal from the system control unit 10. This allows jig 1
The master work attached to 2 also rotates,
An L channel magnetic head attached to the masterwork is brought onto the optical axis 42 of the microscope 4. With respect to the L channel magnetic head of this masterwork, the position Z ₀ of the stage 6 when focused on the head surface is measured in the same manner as in the case of the R channel magnetic head described above. The amount of protrusion of the L channel magnetic head even Yes set as a reference value t _0, it is stored in the memory location Z ₀ of the stage 6 with respect to the reference value t ₀ as a reference value. Further, the gap position of the L-channel magnetic head is measured by image processing with X and Y values, and the measured data X ₀ and Y ₀ are stored in the memory. The attitude of the L channel head is also measured and stored in the memory.

Next, the master work is removed from the jig 12, and the sample drum 3 is attached to the jig 12 instead. Then, as with the measurement of the masterwork, the stage 6 at that time
Position Z ₁ is measured, and the protrusion amount t ₁ of the R-channel magnetic head is calculated from the measured value and stored in the memory. Also,
Similar to the case of the master work, the position of the gap of the R channel magnetic head of the sample is obtained on the X and Y coordinates, and the measured values X ₁ and Y ₁ are stored in the memory. Further, the posture of the magnetic recording head is measured and stored in the memory.

Next, the protrusion amount t as a reference value stored in the system control unit 10 and the protrusion amount t ₁ of the sample, which is a measured value, are compared to obtain the difference between them. Similarly, for the position of the gap, the reference values X and Y are compared with the measured values X ₁ and Y _1, and the difference between them is calculated. Further, the attitude of the magnetic head is also different from the value of the R channel of the master work. If the difference is within the allowable range, the process proceeds to the measurement step of the L channel magnetic head. The position of the head is adjusted and the measurement is performed again. If the result of measurement is within the allowable range, the process proceeds to measurement of the next L-channel magnetic head.

To measure the L channel magnetic head, first set the jig 12 to 180
The L-channel magnetic head is positioned on the optical axis of the microscope 4 by rotating the optical axis of the microscope 4, focused on the head surface in the same manner as described above, and the position of the stage 6 at that time is measured. Calculate the protrusion t ₂ . In addition, the positions X ₂ and Y ₂ of the gap on the X and Y coordinates are measured, and these values are stored in memory. The attitude of the magnetic head is also measured and the value is stored in memory. Then, these measured values are compared with a reference value which is a measured value of the L channel head of the master work to obtain a difference, and it is judged whether or not the difference is within an allowable value, and the value exceeds the allowable value. For, the position adjustment is performed as described above. If it is within the allowable value, the sample is removed from the jig 12 and the next sample is similarly measured.

According to the above-described embodiment, the distance between the television camera and the head surface is changed in the optical axis direction of the microscope having the interference objective lens, and the head surface image and the interference fringe image generated on the head surface are individually separated. Since the image signal on the head surface can be obtained without being disturbed by the interference fringes, the attitude of the magnetic head can be measured from the deviation between both the image on the head surface and the image of the interference fringes. You can Also,
Since the autofocus device included in the image processing device is used, there is also an effect that the configuration of the device can be prevented from becoming complicated. Furthermore, by using a microscope, it is possible to perform measurement with an accuracy on the order of submicrons, and it is possible to accurately measure even an extremely small object such as a DAT head.

Next, an example of a microscope optical system having an interference objective lens applicable to the autofocus device capable of obtaining the output characteristics shown in FIGS. 2 to 4 will be described.

FIG. 8 shows an example of a microscope optical system applicable to the present invention. However, since the optical parts constituting the microscope are the same as the conventional example shown in FIG. 12, common parts are common. The different components will be mainly described.

In FIG. 8, assuming that the designed image forming point of the objective lens 48 forming the interference objective lens 41 of the microscope 4 is F, it is further displaced from the designed image forming point F by ΔL on the optical axis. The image pickup surface of the image processing device 5 is arranged at the position F ', and the image point distance L'of the objective lens 48 is the designed image point distance L.
ΔL is added to. Designed image point distance L
By adding ΔL to, the object point distance l ′ also changes by Δl with respect to the designed object point distance 1. Here, when the magnification of the objective lens 42 is m, the change amount ΔL is obtained by ΔL = Δl × m ² . The interference objective lens 41 configured by adding the half mirror 43 and the mirror 44 is provided when the surface of the magnetic head 1 as a sample is at a point A separated from the objective lens 48 by the designed object point distance l. , The optical path CAC and the optical path CBC coincidently interfere with each other, and interference fringes generated on the magnetic head surface are imaged on the image surface of the television camera 5 arranged at the position F ′, and the monitor connected to the television camera 5 is formed. Thus, the interference fringe can be observed. That is, since the spatial frequency of the interference fringes is low, the depth of focus on the side of the television camera 5 is deep, so that the image of the interference fringes is formed on the image pickup surface of the television camera 5 arranged at the position F '. .

Now, due to the relative movement of the magnetic head 1 and the microscope 4, the surface of the magnetic head 1 is subject to the objective lens more than the designed image point distance l.
When it is moved to the 48 side by Δl and is at the position A'shown in FIG. 8, the surface of the magnetic head 1 is imaged on the image pickup surface of the television camera 5 arranged at the position F ', and the television camera 5
The surface of the magnetic head 1 is clearly displayed on the monitor connected to. This is a state in which the television camera 5 is focused on the surface of the magnetic head 1. However, at this time, the optical path CA ′
The difference between C and the optical path CBC is outside the coherence length, and no interference fringes occur.

Next, when the magnetic head 1 and the microscope 4 are relatively moved in the optical axis direction by a distance Δl so that the surface of the magnetic head 1 is located on the point A, the difference between the optical path CAC and the optical path CBC is a coherence distance. It falls within the range and interference fringes occur. At this time, the image of the magnetic head 1 on the image pickup surface of the television camera 5 is blurred.

The above occurs because the image-side focal depth of the interference fringes is deep and the image-side focal depth of the sample is shallow.

The microscope optical system can be attached to the television camera as in the above-mentioned embodiment, and the image signal of the head surface and the image signal of the interference fringes can be individually input to the image processing apparatus through the television camera. The posture of the head and other measurements can be performed.

FIG. 9 shows a specific example of the posture measuring operation of the head using the above-mentioned microscope optical system. When the head surface is focused and the gap position data is stored, a signal is next input from the system control section, whereby the stage is moved by Δl and the interference fringes are focused. The focused image data of the interference fringe is stored in the memory, the image data of the head surface is subtracted from the image data of the interference fringe to extract the data of only the interference fringe, and the data is binarized. The barycentric position of the interference fringe is obtained from the binarized data and sent to the system control unit. The system control unit can compare the barycentric position data of the interference fringes with the gap position, and measure the posture of the head by this.

As described above, according to the microscope optical system, in the microscope having the interference objective lens 41, the television camera 5 is arranged at a position displaced from the image forming point F in the design of the interference objective lens 41, and the magnetic head 1 and By moving the microscope 4 relative to each other, it is possible to focus on the surface of the magnetic head 1 and the interference fringes generated on the surface of the magnetic head 1, respectively. There is no need to turn it on and off. Therefore, when automatically switching between the focusing on the surface of the magnetic head 1 and the generation of interference fringes, it is only necessary to relatively move the magnetic head 1 and the microscope in the optical axis direction, so that it is necessary to add a special mechanism. It is possible to obtain a microscope that is excellent in responsiveness without vibration, at low cost, without vibration.

According to the present invention, by moving the head surface and the television camera relative to each other in the optical axis direction, the focus state on the head surface and the focus state on the interference fringes generated on the head surface can be adjusted. Since the head posture is measured by measuring the deviation of both the head surface image and the interference fringe image, the head surface image and the interference fringe image are clearly distinguished. Therefore, it is possible to solve the problem that the interference fringes interfere and the posture of the head cannot be accurately measured. Also, the mechanism for moving the head surface and the television camera relative to each other in the optical axis direction is a relatively simple mechanism, and it is not necessary to add an expensive and complicated mechanism in particular, and in particular, a stage for autofocus is used. It is effective because it can be done. Further, since it is not necessary to add a mechanism for turning on / off the generation of interference fringes, it is possible to provide a head attitude measuring device which is free from vibration and has excellent responsiveness.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of a magnetic head automatic assembling apparatus using a head posture measuring apparatus according to the present invention, and FIG. 2 is a characteristic diagram for explaining an example of an autofocus apparatus applicable to the present invention. FIG. 3 is another characteristic diagram of the above autofocus device, FIG. 4 is a diagram showing that part of the characteristic data is set to 0, and FIG. 5 is a flow chart showing the operation of the above autofocus device. 6 is a flow chart showing the operation of the magnetic head automatic assembling apparatus, FIG. 7 is a front view showing an example of an image of the head surface obtained through a television camera, and FIG. 8 is a microscope optical system applicable to the present invention. FIG. 9 is a flow chart showing an example of head posture measuring operation using the microscope optical system of the same as above, FIG. 10 is an explanatory diagram schematically showing the principle of head posture measurement, and FIG. 11 is F FIG. 12 is an optical layout diagram showing an example of a microscope optical system that can be used for head posture measurement considered as a premise of the present invention. 1,2 head, 4 microscope, 5 TV camera, 1
7 …… Interference fringe, 41 …… Interference objective lens.

Claims (1)

[Scope of utility model registration request] 1. A television camera that obtains an image signal through a microscope having an interference objective lens is used, and an image signal of a head surface on the optical axis of the interference objective lens and interference fringes generated on the head surface by the interference objective lens are displayed. A head posture measuring device for measuring the posture of a head by inputting an image signal and an image signal from the television camera to the image processing device, and image-processing the image signal of the head face and interference fringes. The distance between and can be changed on the optical axis of the interference objective lens at least in the range from the focus position on the head surface to the focus position on the interference fringes, and the image of the head surface input through the television camera. A head posture measuring device characterized by measuring a posture of a head by image-processing a signal and an image signal of an interference fringe.