JPH0785295B2 - Magnetic tape reading head position recognition method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a head gap position recognition method for position adjustment or inspection of a magnetic tape reading head.

2. Description of the Related Art Conventionally, as a gap position recognition method for a magnetic tape reading head, a method has been often used in which a two-dimensional gray-scale image is line-drawn and a line corresponding to the gap is searched for for position recognition.

Hereinafter, a conventional method for recognizing the gap position of the magnetic tape reading head will be described with reference to the drawings.

FIG. 7 is an enlarged view of the vicinity of the gap on the front surface of the magnetic tape reading head, FIG. 8 is a coefficient of the powder content operator, FIG. 9 is a line drawing of FIG. 1, and FIG. The result of recognizing the position is shown.

Next, the above-described conventional magnetic tape reading head gap recognition method will be specifically described with reference to the drawings.

The image in FIG. 7 is photoelectrically converted by using a solid-state image sensor or an image pickup tube type camera, and further analog / digital converted (hereinafter referred to as A / D conversion) is stored in a storage circuit. In FIG. 7, 1 is a line corresponding to the gap, and 2 is a magnetized portion (hereinafter referred to as a track) of the head. Next, the data stored in the memory circuit is differentiated by a differentiation operator as shown in FIG. The point where the absolute value of the differentiation result is large is the point where the amount of change in brightness is large. FIG. 9 is a line drawing in which the points at which the absolute value of the differential result is locally maximum are connected over the entire screen. Reference numeral 1 in FIG. 9 is a line corresponding to the gap. The intersection of the extended line (hereinafter referred to as the gap extension line) and the line at the end of the track 2 is calculated. 4 in FIG. 10 is the intersection of the gap extension line and the track top line,
5 is the intersection of the gap extension line and the track bottom line, and the position of the gap is obtained by calculating the position of the midpoint 6 of 4 and 5.

Problems to be Solved by the Invention However, the above method has problems that line drawing cannot be performed unless the image has a clear contrast and the recognition time is long, as described above.

In view of the above problems, the present invention provides a method capable of recognizing a gap position of a magnetic tape reading head with high accuracy and high speed even in an image with low contrast.

Means for Solving the Problems In order to solve the above-mentioned problems, a method for recognizing a gap position of a magnetic tape reading head according to the present invention provides an image input device for an image of a recognition target object including a gap of a magnetic tape reading head. Input using, along the running direction of the magnetic tape from the obtained two-dimensional gray-scale image data, the point at which the differential value of the brightness on each of the plurality of parallel lines crossing the gap is maximized is extracted and extracted. It is characterized in that the position of the gap is determined from the position of the diagonal line where the number of points on the parallel lines counted along a plurality of diagonal lines parallel to the inclination of the gap is maximum.

Effect of the Invention With the above configuration, the present invention makes it possible to recognize the gap of the magnetic reading head at high speed and with high accuracy even when the contrast is low, and to prevent erroneous recognition due to dust on the magnetic head or noise on the electric signal. It is possible.

Examples Hereinafter, one example of the present invention will be described with reference to the drawings.

FIG. 1 is an enlarged view of the vicinity of the gap on the front surface of the magnetic tape reading head, and FIG. 2 is a graph showing data of a horizontal line 7 that crosses the gap of FIG. FIG. 3 is a graph in which the data of FIG. 2 is secondarily differentiated. Figure 4 shows
In FIG. 2, the point where the absolute value of the second-order differential in the horizontal direction is maximum is extracted for each horizontal line and is represented by a circle. FIG. 5 is a diagram obtained by dividing FIG. 4 by a set of lines in the same direction as the azimuth angle and at the same intervals. FIG. 6 shows the total number of circles in each area of FIG.

Next, a method of recognizing the gap position of the magnetic tape reading head of this embodiment will be described with reference to the drawings.

The image of FIG. 1 is photoelectrically converted using a solid-state image pickup device or an image pickup tube type camera, and further A / D-converted and stored in a storage circuit. Next, the second-order differentiation of the image in the horizontal direction is performed.
The second derivative is performed by the equation (1).

b _i , _j = -a _i-1 , _j + 2 · a _i , _j -a _{i + i} , _j (1ixs, 1jys) (1) where a _i , _j and b _i , _j are input data And the i-th element from the left of the output data and the j-th element from the top (hereinafter referred to as a pixel). Further, xs and ys are horizontal and vertical sizes of the image (xs is the number of pixels on one horizontal line and ys is the number of pixels on one vertical line).

FIG. 3 shows the result of the second-order differentiation of the data on the horizontal line 7 for the image of FIG.

Next, the minimum value is found for each horizontal line of the output image of the second derivative. Regarding the result of the second derivative of the image in FIG. 1, the result of finding the minimum value of each horizontal line is
Shown in the figure. Here, the minimum value is filled in with a circle.

Next, the coordinates of the minimum value obtained by the above processing are projected in the direction of the azimuth angle. That is, the following processing is performed.

The coordinates of the minimum value are (x, y). x and y are horizontal and vertical coordinates, respectively. For (x, y), the projection p in the azimuth angle direction is obtained by equation (2).

p = x−y · cotan θ (2) where θ is the azimuth angle. On the image, p is (x,
x) is the intersection of a straight line passing through y) parallel to the azimuth angle and the x-axis
Obtained as coordinates.

As described above, a set of projections in the azimuth angle direction having the minimum value of the second derivative is obtained. Calculate the distribution of this set to find the densest part. That is, the x coordinate is divided at equal intervals, and the section containing the largest number of projected points is searched.

The results of this processing for the image of FIG. 1 are shown in FIGS. 5 and 6. FIG. 5 shows a set of equally spaced lines parallel to the azimuth angle. In the direction of this line, the coordinates of the minimum value of the second derivative are projected, and the distribution is calculated for each section divided at equal intervals as shown in FIG. 6, and the section containing the most minimum value is found.

Since the shadow of the gap is emphasized by the second derivative, the probability of being obtained as the minimum value is high, and when the minimum value is projected in the azimuth angle direction, the minimum value corresponding to the gap is added. The false recognition rate due to noise in the image signal or the like is reduced.

After performing the above processing, the average of the set of minimum values included in the section around the found section is calculated and used as the estimated position of the gap.

In this embodiment, the number of screen divisions of the image is about 500 × 500, the visual field range is about 50 μm square, the interval when dividing the minimum azimuth angle projection is 0.1 μm, and the track width is about 50 μm. Recognized as an object, accuracy is about 0.05μ
I'm getting m.

EFFECTS OF THE INVENTION As described above, according to the present invention, along the running direction of the magnetic tape, the points at which the differential value of the brightness is maximized on a plurality of parallel lines that cross the gap are extracted, and these points are set to the slope of the gap. Since the position of the gap is obtained from the position of the diagonal line that maximizes the number counted along a plurality of parallel diagonal lines, it is possible to prevent erroneous recognition due to dust on the magnetic head or noise on the electric signal. In addition, compared with the conventional method of converting a two-dimensional grayscale image into a line drawing and finding the line corresponding to the gap to recognize the position, the gap position of the magnetic tape reading head can be recognized at high speed and with high accuracy even in an image with low contrast. The effect is great.

[Brief description of drawings]

FIG. 1 is an enlarged view of the vicinity of the gap on the front surface of the magnetic tape reading head, and FIG. 2 is a horizontal line 1 crossing the gap of FIG.
Is a graph showing the data of FIG. 3, FIG. 3 is a graph showing the data of FIG. 1 as the second derivative, and FIG. 4 is the maximum absolute value of the second derivative in the horizontal direction in FIG. A diagram in which points are extracted for each horizontal line and represented by circles. Fig. 5 is a diagram of Fig. 4 divided by a set of lines at the same intervals in the same direction as the azimuth angle, and Fig. 6 is Fig. 5. Fig. 7 is a diagram summarizing the number of circles for each area of Fig. 7, Fig. 7 is a diagram similar to Fig. 2,
FIG. 8 is a diagram showing the coefficient of the differential operator, FIG. 9 is a diagram showing the line drawing of FIG. 1, and FIG. 10 is a diagram showing the result of recognizing the positions of both ends of the gap.

Claims (1)

[Claims] 1. An image of an object to be recognized including a gap of a magnetic tape reading head is input using an image input device, and the obtained two-dimensional grayscale image data is traversed through the gap along the running direction of the magnetic tape. The point at which the differential value of the brightness on each of the plurality of parallel lines is maximum is extracted, and the maximum number is obtained by counting each point on the extracted parallel line along a plurality of slopes parallel to the slope of the gap. A method of recognizing a gap position of a magnetic tape reading head, wherein the position of the gap is obtained from the position of the diagonal line.