JP2001052301A - Method and apparatus for evaluating running characteristics of recording track, and apparatus for evalusting running characteristics of reference tape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily evaluate a running condition in a short time without relying on linearity measurement of a track pattern by measuring fluctuation of a reproduced output along a time base and calculating a position of a recording track relative to a reproduction head from the thus measured value to evaluate the running condition of the recording track during a special reproduction. SOLUTION: A burst center of a peak of an abacus-ball like shape to obtain a difference from a theoretical value, and an amount of displacement in a width direction of a head locus in a trick play is calculated, in a manner similar to evaluation of a reproduced data by means of ID. Time periods τ1, τ2, τ3, and τ4 measured from a rise of a drum FF in a time base reference are used as units in length. An average value of the four measured values is a burst center, and each of a difference between the time period τ1 and τ2 and a difference between the time periods τ3 and τ4 indicates a fluctuation width. A displacement in a longitudinal direction of the head locus can be obtained by multiplying the amount of fluctuation along the time base with a head speed. By a further conversion into a value in the width direction, the amount of fluctuation to be used as an evaluation value can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for evaluating a tape running characteristic of a recording track for easily evaluating the tape running characteristic of a recording track in a special reproduction for reproducing the data across a recording track.

[0002]

2. Description of the Related Art In magnetic recording / reproducing, an important point is that a recording signal is reproduced without any problem even when a tape recorded by one device is reproduced by another device. That is, compatibility is important. By the way, a certain apparatus checks a recording track recorded on a magnetic tape in a normal state by measuring a track pattern. When the track pattern is developed with a special colloid liquid containing magnetic fine particles, a recorded image appears on the magnetic tape as shown in FIG. The measurement is usually performed using a measuring microscope.

As a specific measuring method, y0 in FIG.
Basically, y1, y2,... yn are obtained and, for example, a pattern deviation from a VHS (registered trademark) standard pattern is calculated. The actual measurement is based on Y, Y on the control signal.
1, Y2... Yn can be used instead. Also in this case, the pattern deviation (D0, D1, D2... D) from the VHS (registered trademark) standard pattern
n) is obtained, which represents the linearity itself of the video track as shown in FIG. In practice, the running state of the tape is estimated by evaluating the linearity of the video track. This calculation requires correction of the tape speed obtained from the pitch of the control signal.

[0004]

By the way, in a normal analog VTR, even if there is a fluctuation in the tape running due to wow / flutter, jitter or vertical movement in the tape width direction during special reproduction, the noise bar is slightly moved up and down. Not a big problem, but digital VTRs, especially D-VHS (registered trademark)
In this case, data for special playback is located only at a predetermined position on the helical track, and an image cannot be composed unless all of the data for special playback is available.Therefore, it is necessary to strictly manage tape fluctuations during special playback. is there. Conventional tape running conditions (REC / PLAY) can be evaluated without problems using conventional technology, but recording in special playback (search / slow / still) conditions is impossible with ordinary equipment and requires modification. Therefore, at present, it can be evaluated only with prototypes. Also,
Even if it is modified so that it can be recorded in the special playback state, in practice, if the tape running fluctuation is large, the entire track running state cannot be grasped unless the track linearity measurement is measured for 10 to 20 data, so it is very difficult take time. Therefore, the emergence of a device for evaluating the running characteristics of a recording track during special reproduction in a digital VTR has been awaited.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and as a first invention, a special recording is performed by performing a special reproduction across a recording track recorded on a recording medium. In a running characteristic evaluation method of a recording track for evaluating a running state of a track, a measuring step A for measuring a time axis variation of a reproduction output, and a measurement value (time) measured in the measuring step A is used to determine a recording track relative to a reproducing head. A second aspect of the present invention relates to a method for evaluating the running characteristics of a recording track, comprising an evaluation step B of calculating a position and evaluating a running state of the recording track during special reproduction. In the tape running characteristic evaluation device that evaluates the running state of the recorded tape by performing special playback across the And a measuring means A for calculating the position of the recording track with respect to the reproducing head from the measured value (time) measured by the measuring means A, and evaluating the tape running state during special reproduction. As a third invention, a tape running characteristic evaluation apparatus which evaluates a running state of a recorded tape by performing special reproduction so as to cross a recording track of a reference tape having a known recording track linearity. In the evaluation device, a measuring means A for measuring a time axis variation of a reproduction output, and a position of a recording track with respect to a reproducing head is calculated from a measurement value (time) measured by the measuring means A, and a reference tape for special reproduction is calculated. And evaluation means B for evaluating the running state of the reference tape.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings with reference to FIGS. FIG.
Is a track pattern for explaining the tape running characteristic evaluation method and apparatus of the present invention. D-VHS (registered trademark)
According to the standard, data is arranged in a certain range around a point of intersection of a head trajectory in trick play (hereinafter referred to as trick play) across a recording track. In order to evaluate the tape fluctuation from the reproduction data ID and the time axis fluctuation amount of the reproduction output, it is necessary to obtain the standard trick play data center (burst center) position. FIG. 3 shows a method of calculating intersection coordinates in trick play in the reverse direction (hereinafter referred to as reverse). FIG. 4 is an explanatory diagram showing a conversion state of recording track displacement, FIG. 5 is an explanatory diagram showing an evaluation result by tape pattern measurement, FIG. 6 is an explanatory diagram showing an evaluation result by a reproduction data ID, and FIG. FIG. 8 is an explanatory view showing one embodiment of the measuring means of the recording track running characteristic evaluation method and apparatus according to the present invention. FIG. 8 is an embodiment of the evaluating means in the recording track running characteristic evaluation method and apparatus according to the present invention. FIG. 9 is an explanatory diagram showing a method of calculating the maximum value and the minimum value, and FIG. 9 is an explanatory diagram showing an evaluation result based on a time-base fluctuation measurement of the output.

<Background of the Invention> It is assumed that the head trajectory of Reverse is tracked at the position of 0 [°] around the drum of the recording track, and this is set as the coordinate origin, and the n-th intersection coordinates are x and y. Here, θ [°] is the recording track angle, θt [°] is the head locus angle of trick play, W
[Mm] is an effective data area (video width). ν [m
m] is the distance that the tape moves while the drum makes a half rotation, and is half the tape speed Vt [mm / s] divided by the drum rotation speed N [s ⁻¹ ].

When x and y are obtained from FIG. 3, (1) and (2)
Expression. However, in Forward, θ <θt, and θ and θt are reversed in the denominator of x and y. y / x = tanθt (1) y / (x−n · ν) = tanθ (2) When x and y are obtained from the equations (1) and (2), (3)
Equation (4) is obtained. x = n · ν · tanθ / tanθ−tanθt (3) y = n · ν · tanθ · tanθt / tanθ−tanθt (4) Since the number of sync blocks (hereinafter referred to as SB) per track is 356, In the above y, 356 / W [SB /
mm] to obtain the SB number of the burst center. By dividing y by 2 NW [mm / s], a time τn [s] from the origin to the n-th intersection can be obtained. XY in the drawing is a tape coordinate system based on the lower edge of the tape. Also, p-δt is the coordinate system of the trick play head trajectory, which is the horizontal axis-vertical axis in the evaluation result diagram.

<Conversion of Data Recording Area and Displacement> In the trick play in the standard mode, eight types of tape speeds are provided, and the number of SBs of the burst center is equal to the number of intersections crossing the recording track at each tape speed. Find the number. Burst centers at different tape speeds may have very close SB numbers or overlap. Therefore, bursts used at each tape speed are allocated in a cycle of 48 tracks, and 112 SB data is extracted between the 48 tracks. Therefore, the minimum required number of SBs that must be reproduced from one burst is the tape speed (the number of intersections).
8 SB to 56 SB. The standard states that
The recording area of the trick play data is set to be three times the required number of SBs in consideration of tape fluctuation and head touch. The product needs to manage the tape fluctuation so that the head trajectory during trick play does not deviate from this data recording area.

The conversion of track displacement due to tape fluctuation will be described with reference to FIG. In tape pattern measurement, Rev
Since the linearity of the track recorded in the erse running state is measured, the displacement amount (δt) of the reverse head trajectory in the width direction is an evaluation value of the tape fluctuation. In a method other than the tape pattern measurement, when the recording track is displaced by δr in the width direction due to the tape fluctuation at the reverse time, the areas A and B are A ′,
Move to B '. At this time, since the reproduced area is not theoretical area A but B 'corresponding to B on the original recording track, it seems that the reproduction area is displaced by Δt in the longitudinal direction on the head trajectory of Reverse. Is measured. On the other hand, when the head trajectory of Reverse is displaced by δt in the width direction, the reproduction area becomes B instead of A, so that the displacement Δt of the reproduction area becomes Reve.
It can be converted to the head locus displacement Δt of rse. The equation for converting Δt obtained from the data ID and the amount of time axis variation of the reproduction output into δt is given by the following equation using the intersection angle Φ [°] formed by the recording track and the trick path of the trick play head. δt = Δt ・ cosΦ ・ sinΦ (5)

<Evaluation by tape pattern measurement> As a method of evaluating tape variation, linearity measurement of a tape pattern is the most common method. In order to detect the state of fluctuation,
The invention of a "recording track running characteristic evaluation apparatus" for measuring the coordinates of a track in the longitudinal direction will be described with reference to FIG.

FIG. 5 shows a measurement result of a tape pattern recorded by forcibly flowing a signal to the head while running the tape in the trick play state. The fluctuation in the center of the track is large as expected at first, and the tape is considered to be in a state like string vibration.

<Evaluation Method Using Reproduced Data ID> Since the track number and the SB number can be obtained from the reproduced data ID, the head trajectory position during trick play can be obtained from the track and SB numbers. The difference Δb [SB] between the SB number b [SB] of the theoretical burst center and the measured SB number is the amount of displacement of the trick play in the longitudinal direction of the head trajectory. Since the unit of b and Δb is [SB], the head trajectory length L of the trick play L [mm or μ]
m] to make a unit of length. The track longitudinal position p [mm] is obtained by equation (4) by multiplying b [SB] by L / 356. Displacement in the width direction (δt) [μm]
Since the value obtained by multiplying the difference Δb [SB] by L / 356 is the longitudinal displacement Δt, Expression (5) is obtained by using Expression (3). p = b · L / 356 (6) δt = Δb · L / 356 · cosΦ · sinΦ (7) FIG. 6 shows the evaluation results obtained from the trick play reproduction data ID. Similar to the measurement result using the tape pattern in FIG. 5, the fluctuation at the center is large.

<Evaluation Method by Measurement of Time Variation of Reproduction Output> The two methods described in the above background require a long time for measurement and data processing. . As a reproduction output in trick play, an abacus-shaped waveform is obtained. As a result of observing this well, it was found that it fluctuated in the time axis direction. When this fluctuating output waveform is stored in a digital oscilloscope, a band-like waveform having a fluctuation width as shown in FIG. 7 is obtained. Since the vertex of the abacus bead is a burst center, if this is measured and the difference from the theoretical value described above is obtained, it is possible to calculate the head trajectory width direction displacement of trick play in the same manner as the evaluation by the ID of the reproduction data. it can. As described above, since the vertex portion of the actual waveform is ambiguous, the point of the present measurement method is to secure the measurement accuracy by the following method.

<Description of Measurement Method and Measuring Means A as Main Parts of the Present Invention> As shown in FIG. 7, a horizontal line as a measurement reference is arbitrarily determined, and a time axis reference drum FF rises (or falls). Time τ1, τ2, τ3, τ4 [m
s] is measured for each abacus bead.

<Explanation of Evaluation Method and Evaluation Means B as Main Parts of the Present Invention> As shown in FIG. 8, the average value τ of the four measured values is the burst center, and the difference δ1, τ3, and τ4 between τ1 and τ2.
The difference δ2 of each means a fluctuation range. Half of the average value δ of δ1 and δ2 is the one-sided variation, and the maximum values τmax and τmin of the burst center are obtained by τ ± δ / 2. These are the average values of τ1 and τ3 and τ2 and τ4 as shown in FIG.
Is the average value.

The difference between the τmax and τmin obtained as described above and the burst center theoretical value τn is the time axis fluctuation amount of the trick play output. Head trajectory longitudinal displacement △ t [μ
m] is the head speed 2NL [mm / s] in the time axis fluctuation amount.
Multiplied by the following equation. Here, τ ′ is τmin or τmax. Δt = 2 · N · L · (τ′−τn) (8)

Here, τn [s] is calculated by (2) as described above.
It is obtained by dividing the equation by 2NW. Furthermore, the displacement amount δt that becomes an evaluation value when reconverted in the width direction using the equation (3)
[Μm] is given by the following equation. However, when τ ′ is τmin, T
= Τ1 + τ3, and when τ ′ is τmax, T = τ2 + τ
4 is assumed. δt = L ・ cosΦ ・ sinΦ × {N ・ Tn ・ ν ・ tanθ ・ tanθt / W ・ │tanθ-t anθt│｝… (9)

FIG. 9 shows the evaluation result obtained from the time axis fluctuation of the trick play reproduction output. Since the result was converted from the maximum value and the minimum value of the time axis fluctuation, it was represented by a line connecting the maximum value and the minimum value of the displacement amount in the width direction. In the above three evaluation results, not only the bending tendency and the fluctuation width but also the absolute value agreed very well.

[0020]

According to the present invention, as described in detail above, the tape running state at the time of special reproduction can be evaluated easily and in a short time without measuring the linearity of the track pattern. Similarly, evaluation of the running characteristics of the reference tape during special reproduction can be performed in a short time. Therefore, it is possible to reduce the time and cost of the process by applying it to the inspection process and the adjustment process of the mass production line.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a conventional track pattern measurement state.

FIG. 2 is an explanatory diagram showing the linearity of a conventional video track.

FIG. 3 is an explanatory diagram for calculating an intersection between a recording track and a reverse track.

FIG. 4 is an explanatory diagram showing a conversion state of a recording track displacement.

FIG. 5 is an explanatory diagram showing an evaluation result by tape pattern measurement.

FIG. 6 is an explanatory diagram showing an evaluation result based on a reproduction data ID.

FIG. 7 is an explanatory diagram showing one embodiment of a method and an apparatus for evaluating running characteristics of a recording track according to the present invention.

FIG. 8 is an explanatory diagram showing a method of calculating a maximum value and a minimum value in the method and apparatus for evaluating the running characteristics of a recording track according to the present invention.

FIG. 9 is an explanatory diagram showing an evaluation result based on a time-base fluctuation measurement of an output.

[Explanation of symbols]

 W Effective data area (video width) SB sync block δt Displacement of head trajectory in width direction θ Recording track angle τ1 to τ4 Time from rising (falling)

Claims (3)

[Claims] 1. A method for evaluating the running characteristics of a recorded track by performing special reproduction across a recording track recorded on a recording medium to evaluate a running state of the recorded track, wherein a time axis fluctuation of a reproduction output is measured. Measurement step and the measured value (time) measured by this measurement step
And calculating the position of the recording track with respect to the reproducing head to evaluate the running state of the recording track during special reproduction. 2. A running characteristic evaluation apparatus for a recording track for evaluating a running state of a recorded track by performing special reproduction across a recording track recorded on a recording medium, and measuring a time axis fluctuation of a reproduction output. Recording means for calculating the position of the recording track with respect to the reproducing head from the measurement value (time) measured by the measuring means, and evaluating the traveling state of the recording track during special reproduction. Truck running characteristics evaluation device. 3. Special reproduction is performed so as to cross a recording track of a reference tape whose recording track linearity is known.
In a tape running characteristic evaluation apparatus for a recording track for evaluating a tape running state of a recording track, a measuring means for measuring a time axis variation of a reproduction output, and a recording track for a reproducing head from a measurement value (time) measured by the measuring means. And a evaluating means for calculating the position of the reference tape and evaluating the running state of the reference tape during special reproduction.