JPH087382Y2 - Auto focus device - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to an autofocus device for a sample having an image processing apparatus and having a plurality of focus positions.

[Conventional technology]

There is known an autofocus device that captures an image of a sample through an image input device and detects the focus position from the captured image signal by, for example, the contrast method. The contrast method is to detect the focus position by utilizing the fact that the image signal from the image input device has the maximum difference at the in-focus point, that is, the difference between the bright part and the dark part of the image. Now, when the output voltage of the autofocus device is changed while the lens of the image input device is relatively moved in the direction of the optical axis, the curve becomes a mountain curve as shown in FIG. The peak position of this curve is the focus point.

[Problems to be Solved by the Invention] The in-focus point on the sample can be detected by the contrast method. However, some samples have a plurality of focus positions in the optical axis direction of the image input device. For example, in the automatic assembly process of a rotary cylinder head for DAT in which a minute magnetic head is attached to a rotating drum, the image of the magnetic head is input to an image processing apparatus via a microscope optical system having an interference objective lens, and this input is performed. The protrusion amount and posture of the magnetic head are measured based on the image signal. In this measuring device, the output signal of the autofocus device becomes a signal having a plurality of peaks by moving the microscope of the image input device relative to the optical axis direction, as shown in FIG. Among the plurality of peaks, the curved peak is the peak due to the image of the sample, and the sawtooth peak is the peak due to the interference fringes. There is a constant distance D between the peak of the image of the sample and the peak of the interference fringes, which is determined by the configuration of the optical system. In the case of such a sample having a plurality of peak positions, it is uncertain which peak is focused by the conventional autofocus device, and it may not meet the purpose of use.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and it is possible to determine which focus position is in focus even for a sample having a plurality of focus positions. It is an object of the present invention to provide an autofocus device capable of focusing on a predetermined focus position.

[Means for solving the problem]

INDUSTRIAL APPLICABILITY The present invention is used for an image input device, and has a plurality of focus positions in the optical axis direction of the image input device, which are a focus position focused on the sample and a focus position due to generation of interference fringes, and these focus positions are constant. An autofocus device for a sample having a positional relationship of, detecting the peak value of the output appearing corresponding to the plurality of focus positions and the position at that time, and determining each peak value and the reference output as the constant value. By comparing based on the positional relationship of the above, each of the peak values, which is the peak value corresponding to the focus position focused on the sample is identified, and it is focused on a predetermined focus position. .

[Action]

If the distance between the positions where the peak value appears is known in advance, when the condition is satisfied in the comparison between one peak value and the reference value, that position is determined as the predetermined focus position, and the above condition is not satisfied. In this case, the data around the peak position is set to 0, the peak position is detected again, and this peak position is determined to be the predetermined focus position.

〔Example〕

Embodiments of an autofocus 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 rotary drum used for DAT, a brief description of the magnetic head position measurement and attitude measurement in the DAT is given before the description of the embodiment. I will explain.

FIG. 8 shows a magnetic head 27 input from the image input device.
The input image of is shown. The magnetic head 27 has a head gap 25.
Sendusts 23 and 23 arranged with the
Ferrite cores 22, 22 arranged on one side of 3, 23 and one end of head gap 25 as one apex
23 and glasses 24, 24 arranged in a triangular space surrounded by the ferrite core 22. The image signal of the magnetic head from the image input device is input to the image processing device,
XX with the position of head gap 25 as a reference
It is measured as a position on coordinates.

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 or not the positions of the two magnetic heads are in the correct positions and whether they match each other is determined by inputting an image signal of one magnetic head with an image input device and measuring the position of the drum. Can be determined by rotating the position 180 degrees and inputting the image signal of the other magnetic head from the image input device to measure 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. In addition, in order to properly slide the gap 25 on the tape,
The magnetic head 27 must be in the correct posture, and the position of the gap 25 should be the most protruding position from the drum surface.

Now, when a microscope having an interference objective lens is used in the image pickup optical system of the image input device and this is moved in the optical axis direction with respect to the magnetic head as a sample, an image of the magnetic head appears as described above. Interference fringes appear at a position moved from that position in the optical axis direction by a certain distance. Fig. 1 shows a magnetic head
27 shows an example of an image signal obtained by the image input device when 27 is attached in a correct posture, and the position where the image of the gap 25 of the magnetic head appears and the position where the interference fringes 17 appear on the image signal. I am doing it.

In the present embodiment, the position where the image of the gap 25 of the magnetic head appears and the center position of the interference fringe 17 are made to coincide with each other. There is also. FIG. 2 shows a case in which 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 deviate by more than a prescribed amount.
The attitude of the magnetic head 27 can be measured by using the autofocus device of the image input device. 3 to 6 show an example of an autofocus device applicable to the attitude measurement of the magnetic head 27.

By moving the lens of the image input device relative to the magnetic head as a sample in the optical axis direction, two peaks a and b appear in the output voltage as shown in FIG. Peak a
Is the peak when the magnetic head is focused, and the peak b
Is a peak due to generation of interference fringes, but the autofocus device cannot 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 optical system. The variation when the magnetic head as the sample is inserted into the drum is known in advance, and this is referred to as range W. The scan width S for focusing is larger than the range W. It is uncertain which of the output voltage Va at the peak a and the output voltage Vb at the peak b is larger, but in the example of FIG. 3, Va> Vb. Therefore, as shown in FIG. 6, first, the stage to which the image input device is attached is moved to a reference point C that is outside the near point side of the scan width S, and α is set to the output voltage Vc at this reference point C. The added voltage Vf is stored as a reference voltage. Next, the stage is moved to the far point side of the scan width S, the maximum value and the position of the peak appearing therebetween are obtained, and the stage is moved to the position of the maximum value (the position of peak a in the example of FIG. 3). . Next, 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. In the case of FIG. 3, Ve =
It is Vb. Therefore, we compare Ve and Vf. Ve> in Fig. 3
Due to Vf, the stage is at the position of maximum value, that is, peak a
Is moved to and stopped at this position, and this position is set as the target focus position. The movement of the stage is shown in FIG.

By the way, in some cases, as shown in FIG. 4, 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 between Ve and Vf in FIG.
Since it can be seen that the position of Vb is not the focus position for the magnetic head but the focus position for the interference fringes, as shown by the dashed line frame in Fig. 5, a 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 position of the peak a appearing by focusing on the magnetic head becomes the desired focusing position, and the stage stops at this position.

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 voltage differs depending on the state of the head surface. Therefore, if Vc is kept constant from the beginning, a or b This is because the voltage at the point may be lower than Vc and the focus may not be detected. Therefore, the voltage Vc at the reference point C is obtained each time and compared. Further, the reason why Vc + α = 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. The above α is an optimum value obtained by a preliminary experiment.

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

In FIG. 7, 180 is provided on the outer peripheral portion of the rotating drum 3 of the DAT.
Magnetic heads 1 and 2 are screwed at intervals. The drum 3 is attached to a jig 12 which is rotationally driven 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 as an image input device 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 Gate 72,
A high-pass filter 74 for extracting high-frequency components from the image signal from the gate 72, and an output signal from the high-pass filter 74 is converted from an analog signal to a digital signal by an A / D converter (not shown). It has a memory 75 for storing signal data and an autofocus control section 76 for obtaining a focus from the stored data of the memory 75 and outputting a signal for moving the stage 6. 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 microscope 4 and the television camera 5 move on the stage 6. This data is the third
Since it changes as shown in the figure or FIG. 4, the focus point is detected from this output voltage characteristic, and the motor 13 is driven by using this detection signal to move the stage 6 in the optical axis 42 direction of the objective lens 41. Let 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 processing device 9 measures the position of one intersection 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 position of the head gaps on the XY coordinates when the left corner of the screen frame 20 is the origin O, the horizontal axis is X, and the vertical axis is Y. . 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 controls the entire magnetic head assembling apparatus including the jig 12, the autofocus device 7, the image processing device 9, and the like. The gap positions X ₁ and Y _{1 of the} two magnetic heads 1 and 2 are controlled. And X ₂ , Y ₂ , the protrusion amounts t ₁ , t _{2 from the} drum 3 and the attitudes of the magnetic heads 1, 2 with respect to 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 _O of the portion corresponding to the magnetic head is obtained from the position Z, Z _O of the stage 6 when the portion corresponding to the magnetic head of the master work is focused, Head gap position
Find X, Y, X _O , and Y _O. 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 _O ), (X ₁ −X ), (X ₂ −
X _O ), (Y ₁ −Y), (Y ₂ −Y _O ). Further, the attitude of the magnetic head with respect to the drum 3 is measured from the positional deviation between the gap position of the magnetic head and the center position of the interference fringe 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 drum to be the next sample is attached to the jig 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 by 180 degrees in order 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, the microscope 4
Since the focus is not usually 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,
The other is the 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. 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 due to this movement. This stored data is data as shown in FIGS. 3 and 4. The autofocus device 7 also has a memory 75.
The focus position on the head surface and the interference fringe generation position are detected from the data stored in the stage 6, and the motor 13 is driven to move the detected focus position and the interference fringe generation position to the stage 6 and the integrated stage. The microscope 4 and the television camera 5 are moved.

The operation of the autofocus device 7 will be described more specifically. The image signal of the magnetic head as a sample magnified by the microscope 4 and output from the television camera 5 is the gate 72.
In, in the detection area and the signal from the scanning line setting unit 73, a specific scanning line portion is selected from the image signal, the high-pass filter 74 extracts the high-frequency component, and
Converts analog signals to digital signals with the D converter,
This digital signal is stored 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 TV camera 5 attached thereto over the entire range of the movement stroke thereof, and the output signal from the high-pass filter 74 at this time. The change in the autofocus signal, which is, is stored in the memory 75. Next, the autofocus control unit 76
The motor 13 is controlled on the basis of the stored data in 75, and the stage 6 is moved to focus so that the magnetic head surface is imaged on the photographing surface of the television camera 5 and interference fringes are generated. The data stored in the memory 75 is a graph having the characteristics shown in FIGS. 3 and 4, and among these output characteristics, as described in FIG. The motor 13 is driven so that the stage 6 moves to the focal point. The image of the magnetic head displayed on the monitor 8 at the focus position is as shown in FIG.

Returning to FIG. 9, when the focusing operation is completed, the distance from the magnetic head surface at the time of focusing to the stage 6 is measured as the position Z of the stage 6. The protrusion amount t of the magnetic head of the master work is a fixed amount in advance, for example, 20 μm.
Since these values are set, 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 by, for example, the motor 13
Is used as a pulse motor, the number of drive pulses from the origin of the motor is measured, and it can be obtained by multiplying the above-mentioned number of drive pulses by the known moving distance of the stage 6 for one pulse.

Next, from the image signal as shown in FIG. 8, the ferrite core 22, the glass 24 and the sendust of the head gap 25 are detected.
The position of one of the intersections with 23 is measured by image processing to find the gap position of the magnetic head. For example, the left corner of the image as shown in FIG. 8 is the origin O, the horizontal axis is X,
It can be obtained by measuring the gap position of the magnetic head on the X and Y coordinates with the vertical axis as 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 monitor 14 by a signal from the system control unit 10. As a result, the master work attached to the jig 12 also rotates integrally, and the L-channel magnetic head attached to the master work 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 _O of the stage 6 when the head surface is focused is measured in the same manner as in the case of the R channel magnetic head described above. The protrusion amount of the L channel magnetic head is also the reference value t _O
The position Z _{O of the} stage 6 with respect to this reference value t _O is stored in the memory 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 _O and Y _O
Is 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, similarly to the measurement for the master work, the position Z ₁ of the stage 6 at that time is measured, and the projection amount t ₁ of the R channel magnetic head of the sample is calculated from this measurement value and stored in the memory. Further, as in the case of the master work described above, 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 attitude of the magnetic 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 permissible range, the process proceeds to the measurement step of the L channel magnetic head. If the difference exceeds the permissible range, a command signal is sent from the system control unit 10 to the head position correction device 11, and the R channel magnetic head is detected. 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 18
Rotate it by 0 degree to position the L channel magnetic head of the sample on the optical axis of the microscope 4, focus on the head surface as in the case described above, measure the position of the stage 6 at that time, and from the measurement result, Calculate the protrusion amount t ₂ of the magnetic head. Also,
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, it is possible to focus on each focus position of the sample having a plurality of focus positions in the optical axis direction of the image input device, and the predetermined focus position is selected from the plurality of focus positions. Can be detected and focused on. Therefore, as in the illustrated application example, it is possible to focus on the image on the magnetic head surface and the position where the interference fringes occur at the most projecting position of the magnetic head, and measure the attitude of the magnetic head from the displacement of both images. it can. Further, since the autofocus device included in the image processing device is used, there is an effect that it is possible to avoid complication of the configuration of the device. Furthermore, by using the microscope 4, it is possible to perform highly accurate measurement with submicron order accuracy.
It is possible to accurately measure even an extremely small object such as a head.

The position measuring device according to the present invention can be applied not only to an automatic magnetic head assembling machine but also to various other devices.

Further, it is not always necessary to use the master work as a measurement reference.For example, in the case of a rotary drum head, the surface of the drum is focused and used as a reference, and then the head surface is focused. The amount of protrusion may be measured.

[Effect of device]

According to the present invention, it is possible to focus on each focus position of a sample having a plurality of focus positions in the optical axis direction of the image input device, and detect a predetermined focus position from the plurality of focus positions. You can focus on this.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an outline of posture measurement of a magnetic head to which the autofocus device according to the present invention can be applied, and FIG. 2 is an explanatory diagram showing a state of the posture measurement in different postures of the magnetic head. FIG. 4 is a diagram showing an example of output voltage characteristics of the autofocus device according to the present invention, FIG. 4 is a diagram showing different examples of the same output characteristics, and FIG. 5 is the same as above. FIG. 6 is a flow chart showing an operation example of the autofocus device according to the present invention, FIG. 7 is a block diagram showing an example of a magnetic head automatic assembly device which is an application example of the present invention, and FIG. FIG. 9 is a front view showing an example of an image obtained by the image input device, FIG. 9 is a flow chart showing the operation of the magnetic head automatic assembling device, and FIG. 10 is a wave showing an example of a signal obtained by the autofocus device. Figure, FIG. 11 is a diagram showing an example of the output characteristics of the auto-focus device for the sample having a plurality of focus positions. 1,2 ... magnetic head as sample, 5 ... TV camera as image input device, a, b ... focus position, C ... reference point, Va, Vb ... peak value.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location G03B 3/00 A

Claims (1)

[Scope of utility model registration request] 1. A plurality of focus positions used for an image input device and having a focus position focused on a sample and a focus position due to generation of interference fringes in the optical axis direction of the image input device. An autofocus device for a sample having a fixed positional relationship, detecting the peak value of the output that appears corresponding to each of the plurality of focus positions and the position at that time, and measuring each peak value and the reference output. By comparing on the basis of the fixed positional relationship, which of the peak values is the peak value corresponding to the focus position focused on the sample is identified, and the focus position is focused on a predetermined focus position. And auto focus device.