JP2698114B2 - Tape amount detection device - Google Patents

Description

The present invention relates to a tape amount detecting device used in a magnetic recording / reproducing device such as a video tape recorder (VTR) for calculating and displaying a tape amount.

(B) Conventional technology In a VTR, the amount of tape travel from the supply reel to the take-up reel is determined by using the reel pulse obtained by magnetically or optically detecting the rotation of the supply and take-up reel during recording or reproduction. A technique of calculating the remaining amount of the tape remaining on the supply reel, displaying the remaining amount, and instructing the user to use it is commonly used.

For example, Japanese Patent Application Laid-Open No. 55-64675 (G11B27 / 14) discloses that a rotation cycle or a rotation angular speed of both reels is detected from a reel pulse, and is substituted into a predetermined arithmetic expression in a microcomputer together with the tape running speed at this time. A method for determining the tape running amount or the remaining tape amount is disclosed.

By the way, there is a fear that noise and chattering may occur in the reel pulse which is the basis of the above-described calculation, and when the tape amount is calculated with the noise and chattering occurring, a large error occurs. Therefore, chattering processing by software is required in a microcomputer. The chattering process has a cycle shorter than the cycle of the reel pulse. For example, several milliseconds
It is a common prize that a reel pulse is sampled at a sampling period of up to several tens of milliseconds so that the H level is recognized only when the H level continues for a predetermined number of times.

(C) Problems to be Solved by the Invention In general, the cycle of the reel pulse during high-speed running of the tape, such as fast-forward or rewind, is at least about 4 msec. The limit is twice reading every tens of microseconds,
Sampling that is coarser than this becomes meaningless, and therefore, a load on software for shortening the sampling period increases. Further, at the time of normal reproduction or recording, the cycle of the reel pulse is about 2 seconds at the maximum, and in this case, even if chattering processing of several tens μsec is performed, it is almost meaningless. For this reason, it is necessary to switch the sampling cycle in accordance with each mode or reel pulse cycle in the tape running and to perform the chattering processing, which further increases the load on software and requires complicated processing.

(D) Means for Solving the Problems According to the present invention, a tape amount calculation result is held for the past several times, and is compared with a past calculation value each time one calculation is completed. In the case where occurs, the new calculation result is not displayed.

(E) Function Since the present invention is configured as described above, even when noise or chattering occurs in the reel pulse, it is possible to eliminate these effects and minimize errors in calculating the tape amount.

(F) Example An example of the present invention will be described below with reference to the drawings.

In the circuit block diagram of FIG. 1, (1) and (2) are supply (S side) and take-up (T side) reels. White and
S-side and T-side rotation detectors (3) comprising optical sensors having light-emitting and light-receiving elements so as to face a reflecting plate in which black patterns are formed radially and at equal intervals and opposed to the reflecting plate. By arranging (4), the rotations of the S-side and T-side reels (1) and (2) are optically detected, and the S-side and T-side reel pulses (Ps) whose period changes according to the rotation speed , (Pt) are output. The pattern of the reflector is formed such that 12 reel pulses are generated each time the reel base makes one rotation.

These S-side reel pulses (Ps) are supplied to an S-side cycle counter (5), and the T-side reel pulses (Pt) are supplied to a T-side cycle counter (6).

The S-side cycle counter (5) is an S-side reel pulse (Ps)
During the input of twelve clock pulses, a clock pulse of a constant period generated from the clock generator (7) is counted, and the rotation period (Ts) of the S-side reel (1) is detected. On the other hand, the T-side cycle counter (6) similarly detects the rotation cycle (Tt) of the T-side reel (2).

The outputs of the S-side and T-side period counters (5) and (6) are input to arithmetic circuits (8) and (9), respectively, and the rotation period (Ts) (Ts)
After squaring t), it is input to the addition circuit (10) and the tape amount calculation circuit (15).

The addition circuit (10) calculates the sum (Ts ² + Tt ² ) of the square values of the rotation periods (Ts) and (Tt), and supplies this value to the tape type determination circuit (11). Here, generally, the tape winding diameter including the reel hubs of the S-side and T-side reels (1) and (2) is represented by (R
s), (Rt), and the total area including the hub area is (S), the following equation holds.

S = πRs ² + πRt ² (a) Assuming that the tape running speed at this time is (V), equation (a)
Is And can be transformed. Here, the total area (S) is a unique value depending on the tape type such as T-120, T-90, T-60, etc. in the case of the NTSC system, so if Ts ² + Tt ² is obtained, the expression ( The total area (S) is obtained from b), and the tape type can be determined from the total area (S) in a determination table prepared in advance. The discrimination result thus determined is supplied to a tape data designating circuit (14), and data relating to the radius (r) of the reel hub and the tape thickness (t) according to each tape type are output to the tape amount calculating circuit (15). . The tape data designating circuit (14) stores in advance a reel hub radius (r), a tape thickness (t), and a total tape length (Q) corresponding to each tape type.

The tape amount calculation circuit (15) calculates the square value of the rotation period (Ts) and (Tt) from the operation circuits (8) and (9), the reel hub radius (r) from the tape data designation circuit (14), and the tape thickness (t). ), Tape length (Q) and tape running speed (V)
Is substituted into an arithmetic expression described later to calculate the remaining tape amount or the running amount of the tape. Here, the remaining tape amount and the running amount are calculated by the following equations (c) and (d).

Equation (c) is Is derived as follows. Equation (d) is Is derived as

The tape running speed (V) is specified by an instruction signal from a servo circuit (17) for controlling the rotation of the capstan for running the tape during reproduction or recording. That is, NTSC
In the case of the system, when an instruction signal indicating the standard (SP) mode is given, V = 33.35 mm / sec, and in the double (LP) mode, V = 16.67 mm / sec, and the triple (SLP) mode. And V = 1
1.12 mm / sec is substituted into equations (c) and (d).

The calculation of the remaining amount of tape or the running amount of the tape in the tape amount calculation circuit (15) is performed by the S-side and T-side period counters (5)
In (6), the rotation cycle (Ts) of the S-side and T-side reels
It is executed every time (Tt) is detected, that is, each time the S-side and T-side reels rotate, and the user can arbitrarily select which of the remaining tape amount and the tape running amount is to be calculated. I have.

In the following, the case where the tape remaining amount is selected to be calculated will be described. The latest tape remaining amount data calculated at the present time calculated by the tape amount calculating circuit (15) is compared with the comparing circuits (19) and (20). Are compared with the data held in the first and second registers (16) and (18), respectively. Here, the first register (holding means) (16) holds the remaining tape data calculated by the previous operation in the tape amount calculation circuit (15) as holding data, and stores the new tape remaining data. When calculated, it is updated. Further, the second register (18) holds the remaining tape data calculated by the two previous calculations in the tape amount calculation circuit (15) as holding data, and every time new tape remaining data is calculated. The first register (1
It is updated with the data stored in 6).

The comparison circuits (19) and (20) compare the remaining tape data at the present time with the data held in the first and second registers (16) and (18), respectively, and determine whether the two are extremely different. A determination is made, and a determination value is set as a reference for this determination. This determination value is set in consideration of the accuracy of the remaining amount calculation such as the standard tolerance of the tape, the error of the reference clock of the microcomputer, the measurement result of the error between the remaining amount calculation result and the actual remaining time, For example, when the tape running speed is in the SP mode, the accuracy of the remaining amount calculation is about ± 3 minutes, so the judgment value is set to ± 5 minutes, which is slightly larger than this ± 3 minutes, and is optimal according to each tape speed. It is configured to switch to a value.

For example, if the data held in the first register (16) is M minutes and the data held in the second register (18) is N minutes, the new tape remaining amount data (L) will be in the condition of M-5 ≦ L ≦ M + 5. When the condition is satisfied, the comparison circuit (19) issues a normality confirmation signal (S1). Similarly, when the condition of N−5 ≦ L ≦ N + 5 is satisfied, the comparison circuit (S2) displays the normality confirmation signal (S2). Departs at (21).

The display control circuit (21) controls the input of the latest tape remaining amount data from the tape amount calculation circuit (15) to the display (22) based on the presence or absence of the normality confirmation signals (S1) (S2). When the normality confirmation signals (S1) and (S2) are both issued, it is determined that the above two conditions are both satisfied and that no large change has occurred in the tape remaining amount data. When the input to the display (22) is permitted and the normality confirmation signal (S1) or (S2) is not issued, that is, when the above two conditions are not satisfied at the same time, the tape It is determined that there is a high possibility that a large error occurs in the remaining amount data, and noise and chattering occur in the reel pulse, and that there is a high possibility of having a large error. Will be blocked.

The display (22) displays only the remaining tape data allowed by the display control circuit (21), and updates the display content each time new data is input. Continue to display the last updated content. Therefore, if the difference between the new tape remaining amount data and the tape remaining amount data obtained by the previous operation and the previous operation is within ± 5 minutes, the new tape remaining amount data is displayed on the display (22). If the difference from any of the remaining tape data obtained by one or two previous calculations exceeds ± 5 minutes, the display of this new tape remaining data is prohibited and the display (22) Will keep the previous data displayed.

In the present embodiment, two registers are used to detect an extreme change in the remaining tape data.
This is to expect higher reliability than performing with one register. Also, the description has been given focusing on the remaining tape data. However, even when the tape running amount is calculated by the tape amount calculating circuit (15) and displayed on the display (22), the first register (16) and the following registers are used. The operation is exactly the same.

Next, it is preferable that a portion surrounded by a dashed line in the circuit block diagram of FIG. FIG. 2 shows a flowchart at this time. In this flowchart, STEP (41) determines the mode of the VTR, and indicates that the following operations are performed in the reproduction and recording modes. Also ST
The EP (42) is processed by the S side and T side cycle counters (5) and (6), and the STEP (43) is processed by the tape type discriminating circuit (11).
(44) in the tape amount calculation circuit (15), STEP (45) (4
6) corresponds to the operation performed by the comparison circuits (19) and (20), and STEPs (48) and (47) correspond to the first and second registers (16).
(18) shows the update of the held data.

(G) Advantageous Effects of the Invention As described above, according to the present invention, the chattering process by software conventionally performed at the time of inputting the reel pulse becomes unnecessary, and the load on the software associated therewith can be reduced. In addition, instead of processing for each reel pulse cycle at the time of input of a reel pulse, processing is performed for each reel rotation cycle by removing the influence of chattering immediately before display, so that time constraints in chattering processing are reduced. The error in the displayed amount of tape is minimized.

[Brief description of the drawings]

1 is a circuit block diagram, and FIG. 2 is a flowchart. (15)… Tape amount calculation circuit, (22)… Display, (1
6) First register (holding means), (19) Comparison circuit.

Claims (1)

(57) [Claims] 1. A tape amount detecting device of a magnetic recording / reproducing apparatus comprising: a tape amount calculating means for calculating a tape running amount or a remaining tape amount as calculation data from a reel pulse; and a display means for displaying the calculated data. Holding means for holding the previous calculated data as held data, and comparing means for comparing the calculated data at the present time with the held data, wherein when the difference between the two data exceeds a predetermined value by the comparing means, And a display unit for prohibiting the display of the calculated data at the present time on the display unit.