JPH04364213A - Head gap position detection device - Google Patents

Abstract

PURPOSE:To highly precisely measure head fitting positions against a reference based on the image output of a one-dimensional sensor having a prescribed angle relation for a head gap. CONSTITUTION:The one-dimensional sensor 18 which inclines by a prescribed angle against the gap 36 of the magnetic heads 3A and 3B image-picks up the tape sliding surface of the magnetic heads. Moving means (X-Y tables 10A and 10B) which move the one-dimensional sensor 18 in a tape sliding direction are provided. A head gap position signal is detected by discriminating it from a pseudo signal such as noise based on image output in first and second different cross positions where the one-dimensional sensor 18 and the head gap cross, and angle information of the head gap against the one-dimensional sensor. Then, head position information against a reference position is obtained based on level information or position information on the detected gap position signal.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic head gap position detection device, and is particularly suitable for use in a device for automatically attaching an azimuth gap head of a video tape recorder to a rotating drum.

0002

2. Description of the Related Art A VTR magnetic head has three directions relative to a rotating drum (disc): rotational direction, height direction, and protrusion direction.
The elements must be mounted with extremely high precision. Various jigs have been developed as rotary head assembly devices, but they are basically auxiliary jigs for adjustment and assembly by humans.

0003

[Problems to be Solved by the Invention] Attempts have been made to image the tape sliding surface of a magnetic head with a video camera or the like and measure the gap position by image analysis, but the device is not large-scale and requires a lot of time. There is a problem that detection accuracy cannot be obtained.

The present invention aims to automatically assemble a rotary head, and provides a head gap position detecting device for this purpose. According to the present invention, the relative position between the magnetic head and the rotating drum can be measured with extremely high precision using a device with a relatively simple configuration, and the magnetic head can be positioned and automatically assembled based on the measured value. becomes possible.

[0005]

[Means for Solving the Problems] A magnetic head gap position detecting device of the present invention includes a one-dimensional sensor that is tilted at a predetermined angle with respect to the head gap of the magnetic head and captures an image of the tape sliding surface of the magnetic head; a moving means for moving the one-dimensional sensor in the tape sliding direction; an image detecting means for detecting an image of the tape sliding surface of the magnetic head on the one-dimensional sensor; a first image output and a second image output of the image detection means at a first position and a second position where the one-dimensional sensor and the head gap intersect when moving in the sliding direction; and detecting means for detecting the head gap position based on information on the inclination of the head gap with respect to the one-dimensional sensor.

[0006]

[Operation] The head gap and the one-dimensional sensor have a predetermined angular relationship, and calculation is performed based on the angular relationship to determine whether the gap information of each image output at the first and second different intersection positions is a pseudo signal such as noise. It can be determined by Therefore, the gap position signal can be extracted separately from other pseudo signals, and two-dimensional position information of the head relative to the reference can be obtained with high precision based on the level information and phase (position) information of the extracted gap position signal. It will be done.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic perspective view of a rotary head assembly apparatus using a head gap position detection device according to the present invention, and FIG. 2 is a perspective view of the rotary head assembly.

As shown in FIG. 2, the rotating head assembly (1) has A-channel and B-channel magnetic heads (3A) (3B) mounted at 180° intervals on a rotating disk (2). be. Each magnetic head (3A) (3
B) consists of a head chip (4) and a mounting piece (5), and the mounting piece (5) is fixed to the disk (2) with screws (6).

In the head assembly (1) of FIG. 2, the magnetic heads (3A) and (3B) are temporarily fixed, and as shown in FIG. Clamped by arm (9). X for disk
-Y table (8) is the main coordinate of this assembly device, and the disk (2) is set at the origin of this main coordinate XY. Note that the disks (2) are processed with high precision, and all disks are fixed at the same origin position. Each mounting piece of the magnetic head (3A) (3B) (
5) is chucked by a chuck device (not shown) which is fixed independently of the movement of the disk X-Y table (8).

A channel and B channel heads (
The positions of 3A) and 3B with respect to the disk (2) (origin of principal coordinates) are determined using the A channel X-Y table (10
It is read by optical reading devices (11A) (11B) provided on the X-Y table (10B) for A) and B channels. These X-Y tables (10A) (
10B) respectively the X-Y table (8) for the disk;
It can be freely moved in the X-Y directions independently of the coordinates, and forms a sub-coordinate system with respect to the main coordinates.

The optical reading device (11A) (11B) can read the position (center of the gap) of the heads (3A) (3B) with an accuracy of, for example, 0.5 μ. The read sub-coordinate values (X, Y) are compared with the sub-coordinate data (X0, Y0) obtained by measuring a standard head assembly (master work) assembled in advance with high precision. Ru. The difference from this master work measurement value is the relative positional relationship between the disk (2) and the head (3A) or (3B) for the head assembly (1) currently being measured.

When the measurement is completed, the disk XY table (8) is moved so that the difference between the master work and the measured data becomes zero, and thereby the disk (2) of the magnetic head (3A) (3B) is moved. ) is achieved. In this positioning work, the disk (2
) is moved, and the head mounting piece (5) remains fixed by the chuck and does not move. After positioning, the screw tightening device (12) is operated and the heads (3A) (3B)
is fixed to the disk (2).

[0014] The optical reading devices (11A) (11B) also read information about the height (Z axis) of the head;
This is to confirm whether the head height is within the specified tolerance. The assembly device in Figure 1 is a disk (2)
There is no function to automatically adjust the height of the head, so the shape of the mounting piece (5) on which the head chip (4) is attached must be mechanically measured with a micrometer etc. in order to obtain the desired head height. Then, as shown in Figure 2, head (3A) (
3B) is temporarily fixed to the disk, the height is adjusted using a spacer of, for example, 5 μm.

FIG. 3 shows a schematic perspective view of one optical reading device (11A). The other reading device also has the same configuration. This reading device includes a light source (14), a half mirror (15) that provides light from the light source to an objective lens system (16), and a head (3B) that forms an image of reflected light from the objective lens system (16). and a line sensor (18) provided on the screen (17) in the Z-axis direction.

The line sensor (18) is shown in the plan view of FIG.
As shown in A), 256 photodiodes and the like are arranged in a row, and one pitch is 25.4μ. If the magnification of the objective lens system (16) in FIG. 3 is increased to 40 times, a resolution of 25.4/40=0.635μ can be obtained. From each light-receiving element (19) of the line sensor (18), an image (20) of the tape sliding surface of the head is transmitted along the Z-axis, as shown in the waveform diagram (B) in FIG. A video signal scanned along a line along (the longitudinal direction of the line sensor) is obtained. The output of each element (pixel) (19) forming such a video signal is A/D converted for each pixel and sent to the data processing device shown in FIG. 5 for specifying the head position.

The data processing device is composed of a microprocessor including a CPU (23), memory (24) (ROM and RAM), and a data bus (25) connecting these. The output of each pixel of the A channel and B channel line sensors (18A) (18B) is passed through a changeover switch (26) to an 8-bit A/D converter (27).
and converted into a digital signal. Note that the changeover switch (26) can be switched to process data channel by channel in order to simplify the hardware. A
The output of the /D converter (27) is differentiated by a differentiation circuit (28) in order to perform waveform recognition (gradient detection) of the head image signal detected by the line sensor, and further to perform figure recognition of the head surface image. CPU (23) and memory (2
4) is used to process the data. The differential circuit (28) is
It may be a circuit that calculates the difference between the outputs of adjacent pixels,
Of course, this can be realized by software using an arithmetic program using the CPU (23).

[0018] Selector switch (26), A/D converter (2
7), the differential circuit (28) is connected to the control logic (2
9). X-Y table (10A) (10B) for moving the optical reading device (11A) (11B) for measuring head position, rotating disk (RD) (2)
The X-Y table (8) and screw tightening device (12) for
They are each driven by pulse motors (30A) to (30E). The drive signals for these pulse motors are sent by the CPU (
Based on the operation command generated from the data output port (31), the pulse motor driver (32A) to (3)
2E). Each X-Y table (10A)
(10B) The coordinate data of (8) is held in the memory of the microprocessor.

Furthermore, in order to monitor the measurement data,
Serial interface (33) to data bus (25)
A CRT terminal (34) is connected through it.

Next, the operation of the rotary head assembly apparatus of this embodiment will be explained. FIG. 6 is a schematic diagram showing a head surface image (projection image (20) of the tape sliding head surface on the screen (17) in FIG. 3) and line scanning by the line sensor (18). Further, FIG. 7 is a partial plan view of the rotating magnetic head and the reading optical system.

According to the present invention, the gap between the line sensor and the head is inclined by a predetermined angle. This arrangement is extremely convenient for data processing, as will be described later, for the purpose of recognizing the head gap based on the output of the line sensor and measuring the position of the head center (X and Y directions), and has many advantages. has.

The magnetic head of this embodiment is an azimuth head in which the gap (36) is inclined at a predetermined angle (for example, 7 degrees) with respect to the direction (Z-axis) perpendicular to the scanning direction (direction of arrow a in FIG. 6). be. Therefore, the line sensor in the Z-axis direction (18
), the gap (36) is inclined at a predetermined angle. Note that when implementing the present invention with a head having a gap without azimuth, the line sensor is tilted from the Z axis.

The position of the head (3A) or (3B) in the rotational direction with respect to the disk (2) is as shown in A, B, and C of FIG.
It is measured by moving the line sensor (18) (reading device) in the Y-axis direction as shown in FIG. Further, the amount of protrusion of the head relative to the circumferential surface of the disk is measured by moving the reading device in the X-axis direction (optical axis direction of the optical system) as shown in A', B', and C' in FIG.

FIG. 8 shows a reading device (1) as shown in FIGS. 6 and 7.
Line sensor (18) when moving 1) in the X-Y direction
) is shown as a CRT sweep waveform. When the head surface is located at the focal point of the objective lens (16) of the optical system, signals shown in FIGS. 8A, B, and C are obtained at positions A, B, and C in FIG. 6 by movement in the Y direction. At position C, a gap signal g indicating a steep rise and fall corresponding to the boundary of the track width T of the head and a head gap (36) is generated.
A waveform having each of the following is generated. On the other hand, when the reading device (11) is moved in the X direction at the position shown in FIG. 6C,
Signals shown in FIG. 8A', B', and C' are obtained at positions ' and C'. That is, the focus is aligned in the direction of A'→B', and a waveform in a focused state is obtained at the position C'. The amount of head protrusion can be determined from the X coordinate of the reading optical system during focus alignment.

The head position measuring system is an X-Y system as shown in FIG.
Position data is calculated by data processing the output waveform of the line sensor (18) due to movement in the axial direction. The waveform changes in the specific measurement procedure are as shown in (■) to (■) in FIG. That is, at the position of the start point S in Fig. 6, perform focus coarse adjustment as shown in ■→■ in Fig. 9, then coarse feed in the Y direction as shown in ■ to position A, and here as shown in ■ Fine tune your focus. Next, as shown in ■, feed the track width to position B in Figure 6.
is detected, and a gap signal is further detected at the position C in FIG. At position C, the focus is aligned by detecting the peak of the gap signal.

Next, data processing at each stage in FIG. 9 will be explained. ■For fine focus adjustment, the line sensor (18
) until the absolute value of the differential value (differential or difference in the pixel column direction) of the output reaches the maximum as shown in FIG. 10A'→B'→C'. Move it in the X direction as shown in '. In other words, at the focus alignment position, the contrast between light and shade of the image becomes extremely clear, and the absolute value of the gradient of the image signal on the head surface detected by the line sensor is at its maximum, which is used to automatically control fine focus adjustment. . For this reason, data processing is performed using the differential circuit (28) in FIG.
This is achieved by, for example, observing the time change of the maximum absolute value of the differential value using the PU (23) and detecting the point where the maximum value changes from increasing to decreasing.

In the track width detection at stage (■) in FIG.
As shown by the black circles P1 to P3 and N1 to N3 in FIG.
It is determined that there are two locations (P and N) and that the signs of the differential values at these two locations (P and N) are reversed. The track width T can be measured as the difference between the pixel numbers of the line sensors corresponding to the two locations.

In the detection of the gap signal at stage (3) in FIG. 9, a signal that satisfies the following conditions is determined to be a true gap signal, and other pseudo gap signals are excluded. That is, FIG.
A diagonal area W is set within the already detected track width T as shown in FIG.

(I) For the signal existing in this region, (II) the ascending slope (differential value) in the left half and the descending gradient in the right half are constant values (for example, ±6 bits/10 pixels). ), (III) As shown in FIG. 13A, when the measurement optical system is moved a certain distance ΔY in the Y direction,
As shown in 3B, the peak of the gap signal is the line sensor (18
) and the gap (36), corresponding to the tangent tan θ of the inclination angle θ (azimuth)
θ) (for example, moving the optical system by 1 in the Y direction
When sending a pulse (0.5 μm), the peak is 3 bits (pixel)
or more).

A true gap signal and a pseudo gap signal caused by dust, disturbance noise, etc. are discriminated under the following conditions.

Furthermore, in the focus matching at stage (■) in FIG.
As shown in g→g′→g″→ in FIG. 14, the reading optical system is This gap signal level change is extremely critical, and is approximately 2μ
It is possible to detect the focus alignment position with an accuracy of 100 mL, and thereby measure the amount of head protrusion.

Furthermore, the center of the head gap (36) in the Y direction (disk rotation direction) can be calculated based on the position data of the gap signal discriminated as described above and the data of the track width T. . In other words, how many steps should the detection optical system be moved in the Y direction to make the pixel number of the line sensor (18) at the detected gap position match the pixel number at the midpoint of the track width T? , can be obtained by calculation, and thereby the data of the center of the gap in the Y direction can be detected. Note that the detection optical system may actually be moved to the center of the gap in the Y direction and the Y coordinate at that time may be read.

The sub-coordinate data (Y', X'
) is the master work measurement data (Y0
, X0 ), and the difference (Y0 - Y', X0
-X') for the disk in Figure 1
-Y table (8) (principal coordinates) is moved. As a result, the head is positioned at the same position as the master work.

[0034]

As described above, according to the present invention, the output of the image detecting means at two intersecting positions shifted in the tape sliding direction and the inclination information between the head gap and the one-dimensional sensor (azimuth angle in the embodiment) ), it is possible to extract the gap position signal from the output of the image detection means, distinguishing it from other pseudo signals. Information on the head position relative to the reference can be obtained with extremely high accuracy from the information (level or phase) of the extracted gap position signal. Therefore, it is possible to automatically assemble the rotary head with high precision based on this head position information.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view of a rotary head assembly device using a head position measuring device according to the present invention.

FIG. 2 is a perspective view of the rotating head assembly.

3 is a schematic perspective view of the principle of the optical reading device of FIG. 1 for measuring head position; FIG.

FIG. 4 is a front view of a line sensor in the optical system of FIG. 3 and a diagram of its output waveform.

FIG. 5 is a block diagram of a data processing device that controls the head mounting device of FIG. 1;

FIG. 6 is an enlarged partial plan view of a head surface image and a measurement optical system using a line sensor.

FIG. 7 is an enlarged partial plan view of the head and the measurement optical system.

8 is a sweep waveform diagram of the output of the line sensor when the measurement optical system moves as shown in FIGS. 6 and 7. FIG.

FIG. 9 is a sweep waveform diagram of line sensor output in a specific measurement procedure.

FIG. 10 is a waveform diagram of a differential signal output from a line sensor during focusing of the optical system.

FIG. 11 is a diagram of a sweep waveform output from a line sensor when measuring track width data.

FIG. 12 is a sweep waveform diagram of a line sensor output when detecting a gap signal.

FIG. 13(A) is a schematic diagram showing a head surface image and the position of a line sensor when detecting a gap signal. (B) is a sweep waveform diagram of the line sensor output corresponding to FIG. 13(A).

FIG. 14 is a waveform diagram showing changes in a gap signal during focus adjustment of the measurement optical system.

[Explanation of symbols]

2 Rotating disk 3A Magnetic head 3B Magnetic head 4 Head chip 5 Mounting piece 8 X-Y table for disk 10A A
Channel X-Y table 10B B channel X-
Y table 11A Optical reader 11B Optical reader 18A Line sensor 18B Line sensor

Claims (1)

[Claims] 1. A one-dimensional sensor that is tilted at a predetermined angle with respect to a head gap of a magnetic head and captures an image of a tape sliding surface of the magnetic head; and a moving means that moves the one-dimensional sensor in the tape sliding direction. image detection means for detecting an image of the tape sliding surface of the magnetic head on a one-dimensional sensor;
When the one-dimensional sensor is moved in the sliding direction of the tape by the moving means, the first position of the image detecting means at a first position and a second position where the one-dimensional sensor and the head gap intersect. Gap position detection of a magnetic head, comprising a detection means for detecting the head gap position based on an image output, a second image output, and information on the inclination of the head gap with respect to the one-dimensional sensor. Device.