JPH0421241B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Commercially manufactured disc records have various mechanical defects. There are also system deficiencies that arise from the mechanical devices used to play records. The present invention relates to some of the deficiencies in disc playback systems, namely unwanted vertical deviations of record grooves, primarily due to record warpage and rumble, including record press noise.
Such defects cause significant deterioration of the reproduced signal.

Sledding A general discussion of record sledding can be found in the following publications: Lari Hutsup and Frank Karloff, “Record Warpage and System Playback Performance,” Journal of the Audio Engineering Society, Vol. 24, No. 8, October 1976, No.
From pages 630 to 638. The authors are approximately 1/2 Hz
(1 degree per revolution at 33-1/3 revolutions per minute)
We found warpage frequencies in the range of 10Hz or higher, but 95% of the warpage was below 8Hz. The peak physical amplitude height of the warpage is approximately
0.64 mm (0.025 inch) and decreased as frequency increased.

Warping of records causes various problems.
The tonearm bounces and sways relative to the surface of the record due to vertical and, to a certain extent, lateral forces introduced as the stylus attempts to track the varying height of the record. This causes not only fluctuations in tracking force, but also cartridge contact with the bottom or loss of needle-to-slot contact. When the tracking force fluctuates from its optimum state in this way, the reproduced signal at the audio frequency is often affected.
In addition to needle and arm tracking issues,
Excessive needle deflection results in geometric distortions and electromechanical nonlinearities of the cartridge. Furthermore, the warpage signal causes distortion due to amplifier overload in electronic equipment that passes such low frequencies, and when applied to a loudspeaker system, it causes external noise and also distortion of high frequency audio signals, including Doppler distortion. This produces woofer motion that causes distortion. moreover,
Due to the geometrical relationship between the stylus and the record groove, as a result of the warping, the stylus tip vibrates back and forth over the recorded note groove, modulating (advancing or delaying) the playback signal at that frequency, producing wah. Wah is also caused by variations in rotational speed as the stylus load on the record groove changes.

The requirement to satisfactorily track warped records has, in the prior art, led to very careful consideration of the geometric relationship between tonearm, cartridge, stylus, and record in pursuit of the best possible combination. , which also often involves the stylus and tonearm mass, tonearm damping, stylus compliance and damping, to provide a controlled tonearm resonance above the normally occurring warpage frequency but below the lowest recorded groove frequency. This results in a compromise between various factors such as and tracking power. A 10Hz arm resonance has been proposed by some designers. Keisuke Ikegami and Susumu Hoshimi, "Advances in Turntable and Tonearm Design," Journal of the
Audio Engineering Society Magazine, No. 24
Volume No. 4, pages 276 to 280, 1976 5
Moon, and Peter Rosa, "Aspects of Low Inertia Tone Arm Design," Journal of the Audio Engineering Society, Vol. 25, No. 9, pp. 550-559, September 1977. See.

Although in principle it is possible to track warped records by appropriately selecting tonearm and cartridge parameters, in practice there are a wide variety of tonearms and cartridges available, and the arm and cartridge matching is often complex. Additionally, even at the design stage, the optimal tonearm and cartridge parameters selected for warp tracking may not be optimal for tracking high frequency groove information. Even when records are properly tracked, the problems of sled-derived geometry and motor wow still remain.

Various passive devices for tracking warped records are known. These devices typically use an element that rides on the surface of the record and is fixed or coupled to a tone arm at or near the pickup cartridge. Such devices include both braked elements and unbraked or fixed elements. Typical prior art braked element devices include Fisher U.S. Pat. No. 2,572,712 (Spring Loaded Plunger);
and Thompson US Pat. No. 2,328,862 (Resiliently Loaded Auxiliary Needle). The fixing element is based on Andreuse et al. US Pat. No. 3,228,700.
(a felt pad at the end of a tone arm with a pivotably supported cartridge), and U.S. Pat. No. 3,830,505 to Rabinoff (air bearing adjacent to the cartridge). It is also known to use a dart pot or brush adjacent the cartridge to dampen vibrations and aid in tracking warpage. Furthermore, proposals for relatively rigid elements for coupling the tonearm to the record surface are known. It has also been suggested that the record be tightened or weighted at the periphery or center to eliminate warping.

Active prior art systems for handling record warpage are described in the following documents: namely, "Overcoming Record Warpage and Low Frequency Turntable Rumble in Records," Kenneth Kranis and Michiel J. Kelly;
Journal of the Audio Engineering Society, July/August 1975, No. 23
Volume No. 6, pages 450 to 458. In this system, the cartridge output is used to servo control the vertical tonearm position to help track record warpage. A similar system is disclosed in U.S. Pat. No. 3,623,734 to Sakamoto et al.
and Rabinoff, US Pat. No. 3,830,505. It is also known to provide a closed loop only around the tonearm movement to improve arm cartridge damping. The present invention significantly improves the performance of these prior art tonearm systems.

Rumble Turntable rumble can come from vibrations in the turntable bearings, electric motor pivot system, and surroundings. Many efforts have been made by turntable manufacturers to eliminate rumble due to these causes.

Other disturbances associated with turntables are caused by acoustic feedback (audible and super-audible) from the loudspeaker. This causes the turntable or record to act as a receptor for vibrations, resulting in coloration or howling. Devices that reduce these effects include the liquid-filled turntable mat disclosed in Kawashima U.S. Pat. No. 3,997,174 and the flexible turntable support cup disclosed in Maeda U.S. Pat. No. 4,054,291. , both of which provide suitable braked support under a warped record.

Despite these efforts, the primary source of problems in the low frequency range is record press rumble or mold surface noise from the disc itself.
The frequency spectrum of record press noise is based on John Argle, “Operating Characteristics of Commercial Stereo Discs”
Journal of the Audio Engineering Society, August 1969, Volume 17, No. 4
Issue, pp. 416-422. Mold surface noise typically reaches several hundred hertz.

Record press rumble and turntable rumble are conventionally reduced by wide area filters in the signal path. Optimal tonearm cartridge resonance characteristics are also useful in reducing low frequency rumble effects.

Prior art approaches to treating warpage are primarily directed to warpage symptoms. For example, passive tonearm-to-record surface contact devices and closed-loop tonearm systems serve primarily as performance enhancement devices that simply track cartridge and tonearm warpage. Therefore, such methods cannot compensate for other effects of warpage, thus reducing tracking performance and signal quality at frequencies other than warpage. Regarding Rumble,
Prior art has focused primarily on electrical filters rather than addressing the rumble mechanism itself.

The method of the present invention is to reduce the effects of warpage and rumble without significantly degrading the bandwidth or other operating characteristics of the signal channel itself.

The invention is based on the observation of the situation shown in FIGS. 1a and 1b. FIG. 1a shows a side sectional view of the upper half of a hypothetical record master in which silent grooves have been recorded. The groove depth "a" is constant and represents an instantaneous vertical signal modulation relative to a complete reference path or plane. The reference surface may be a flat surface of the lacquer master board, but according to the invention shown in FIG. 2, the reference surface is defined during the cutting process. For this purpose, a second flat cutting needle is used which follows the main cutting needle and is arranged to smooth the flat area between the grooves and to limit the dimensions of the flat area. Frequency regions where there is little vertical information recorded on the disc (e.g. 30
(below Hertz), the groove itself may be used as a reference path.

FIG. 1b shows the situation after record pressing on the master. The vertical groove position is no longer constant and contains irregularities. In the case of warpage, the irregularities are dimensionally correlated on both sides of the record, as these irregularities are caused solely by heat and handling distortions during and after the record is removed from the press. (Thickness remains approximately constant). However, high frequency mold roughness noise is uncorrelated on both sides of the record because different dies and stampers are used. That is, the disk includes local thickness variations. Such defects are caused by the transmission of dimensional irregularities from the back side of the stamper to the front side during the pressing operation. Irregularities on the backside include metal crystals from the replication process, patterns from polishing operations to smooth the backside, dirt and debris trapped between the record press stamper and the die, and the die. Contains irregularities.

Since the thickness of the stamper is approximately 0.18 to 0.25 mm (0.007 to 0.01 inch), the shortest wavelength transmitted through the local curvature and strain of the stamper is limited by the stiffness of the material. That is, the shortest wavelength is about 0.50 mm (0.02 inch). Therefore,
Rough surface noise frequency is highest at outer diameter, 30 cm (12 inches)
1kHz on the board [groove speed approximately 50cm (20 inches) per second]
It will be about.

Other sources of low frequency noise in the record itself include:
Geometric distortions due to non-uniformity of the stamping material and operational cooling effects resulting from rapid and non-uniform temperature changes at the tie surface are included. Furthermore, as mentioned above, noise is also introduced by the playback system, i.e., turntable and ambient rumble and acoustically transmitted vibrations of the turntable and disk.

That is, in the conventional reproduction system, the reproduction amount "b" is obtained using the tone arm position as a reference. Quantity "b" therefore contains undesirable low frequency noise components.

A closer look at this problem reveals that the low frequency noise components from all the sources mentioned above are not intricately combined with the original signal modulation. Rather, the recorded signal amount "a" remains unaffected by mechanical defects in the pressing and playback process and playback system. Therefore, if the distorted reference path at the point of needle contact is used as a reference point during regeneration, the quantity "a" can be recovered. Preferably, the playback system operates to remove unwanted fluctuations in the reference point so that the surface of the board becomes virtually flat again (ie virtually unchanged in the vertical direction) in the vicinity of the needle. Wavy reference points are selectively used to determine the true signal amount "a".

According to the teachings of the present invention, the problems of the prior art are solved by a record playback system. That is, by measuring the appropriate amount to reproduce the error signal and using this signal to make appropriate mechanical and electrical corrections, mechanical defects in the disk or reproduction system that cause deviations in the tracking path can be detected. be compensated. The sensing device is
generating a signal responsive to a deviation in the reference path at or near the pick-up or needle position;
The signal is processed to control the system to minimize the effects on the record playback signal caused by deviations.

As used herein, sensing "in the vicinity" means sensing within a fraction (eg, about one-tenth or less) of the shortest wavelength that requires correction. If the wavelength of the mold rough surface noise is approximately 0.5 mm at the disk outer diameter
(0.02 inch), this means approximately
0.05 mm (0.002 inch), meaning sensing at the immediately adjacent flat area. This represents a limitation of the present technique. For low frequency noise and warpage, of course, such close sensing is unnecessary.

The present invention may be conveniently referred to as a vertical noise compensator (VNC).

In an embodiment, the vertical position of the unmodulated portion of the record is sensed at or near the stylus. The information derived in this manner is reference path information, and when sensed relative to the arm or cartridge position, is referred to as reference path arm information. Preferably, the reference path information or reference path arm information is obtained through a sensing device arranged to sense a flat location adjacent to the signal groove and proximate to the signal needle. It is important that the vertical sensor respond substantially only to vertical information. In disc recording technology, the term "vertical" usually refers to perpendicular to the disc surface;
Or it has an axial meaning.

Embodiments of the present invention may be referred to as cartridge VNCs and tonearm VNCs; in the former case,
It is used to obtain reference path arm information and perform corrections within the cartridge or beyond. The reference path arm information is offset electrically or mechanically with the information provided by the signal needle. Reference path arm information may also be selectively retrieved from the cartridge to perform additional corrections according to other embodiments.

The tonearm VNC embodiment is an improvement on prior art closed loop tonearms. In prior art systems, the error signals used include arm cartridge resonance components or other error-inducing information. In the present invention, measurements are made to avoid these deficiencies and are processed to control the tonearm. That is, reference path information is obtained and used to control the tone arm and optionally perform additional corrections in accordance with other embodiments. The high frequency components are also used in cartridge VNC to reduce rumble and mold surface noise. Tone arm VNC, cartridge
Preferably combined with VNC. For example, the effects of warpage and rumble can be reduced by tonearm VNC
can be used to compensate up to 20Hz. Further, frequencies higher than this are processed by the cartridge VNC.

Compatibility characterizes embodiments of the invention. Conventional records can be played with a playback device according to the method of the invention. Conversely, records made with the reference surface of the present invention can be played on conventional playback equipment.

Overcoming noise and tracking problems with the present invention allows the use of lower modulation levels and higher groove densities, thus reaching smaller record diameters with longer playback times.

The fact that the invention eliminates low frequency noise also makes it possible to record high frequency components of the signal to disk with electronic noise reduction encoding, for example by the system known as "Dolby B".
This system, which only processes signals above about 1kHz, produces a compressed signal. This signal has previously been demonstrated to be sufficiently compatible to permit single-piece manufacturing and distribution of cassette tapes. Adopting this in the case of encoded records is even more difficult, if not impossible, to achieve on a commercial basis if low frequency signals also need to be processed. The encoded records are, of course, preferably played using a noise reduction decoder to reduce the high frequency noise and low level crackle caused by the record press.

The invention can therefore make a significant contribution to the current performance and future potential of conventional analog record systems.

The present invention will be explained below with reference to the drawings.

In all the embodiments described below, only essential inventive features are shown or described in detail. Therefore, unless otherwise specified, amplifiers, attenuators, equalizers, differentiators, integrators, feedback loop compensators, gain controllers, etc. that are normally required in electronic technology are used. Similarly, unless specifically indicated, mechanical and electromechanical aspects of the needle, sensor transducer, detailed design of the transducer and disc, cartridge, tone arm, drive motor, etc. are not discussed.

Reference Path In some embodiments, the vertical position of the unmodulated portion of the record (reference path) is sensed at or in close proximity to a signal pickup device, typically a needle. A key element of the invention is the recognition that close-in, high-resolution sensing is useful for reducing mold surface noise. However, it is necessary that the reference path be as free from flaws as possible. For example, there should be no scratches. Additionally, the groove "horn," that is, the protrusion of material that protrudes into the flat at the edge of the groove, is preferably removed during the disk manufacturing process.

Mold polishing is a known method of removing groove horns. Another method is shown in FIG. 2, in which another reference path cutting needle 4 follows the groove cutting needle 6. The substantially flat bottom edge of the reference course not only eliminates the groove horn, but also eliminates any residual rumble modulation on the rack master 2 to compensate for the vertical rumble introduced by the recording platen. This defines a completely silent reference surface for use in the reproduction embodiment of the present invention. In the embodiment of FIG. 6, a pilot groove provides a reference path. In this case, the reference path cutting needle cuts the non-modulated groove adjacent to the signal groove.

Direct Sensing of Reference Track Information Sensing reference track information (ie, sensing a distorted and undulating reference track) is an important element of various embodiments. A typical reference path sensing is shown in FIG. In FIG. 3, reference path information is obtained directly by sensors that follow the signal needle and cartridge in the lateral direction but are independent in the vertical direction. The sensor 8 is attached to the reference surface. In conventional turntables, mounting is usually on the tone arm mounting surface. In theory, the mounting surface may be any suitable reference surface, including a stable surface remote from the turntable itself. Movable member 1 forming part of sensor 8
1 follows the surface undulations of the board. In fact, both record-contacting and non-contacting sensors are available, as will be explained later with respect to FIGS. 4A and 4B.

In a simple embodiment, the reference course needle is placed in a cartridge as shown in FIGS. 6-9 below. In this case, the stylus is relatively tightly coupled to the cartridge body and tonearm, so that the tonearm has a relatively high vertical resonant frequency. The needle may be used alone to reduce rumble and mold roughness noise.

In the embodiment of FIG. 4A, the sensor portion of the arm is vertically fixed, and the vertical displacement sensing transducer is either by ultrasonic or capacitive devices, or by a light beam and detectors (e.g., light emitting diodes and photodiodes). ) etc., it contains a non-mechanical device that senses the board surface 9. a light beam that is focused at the point of contact of the needle and preferably has a beam diameter that includes at least one flat area;
It may also be oriented toward the surface at an angle. This allows the vertical change to be expressed as a lateral change, and 1
Sensed by one or more photodetectors. This technique has the advantage of providing a relatively broadband error signal without mechanical resonance. At least warpage up to several hundred hertz and mold surface noise can be compensated for by this.

In the example of FIG. 4A, a vertically fixed but laterally movable tone arm 10 has a U-shaped end 12 in which a cartridge 14 is attached to a cross-shaped pin 16. is supported by A sensor signal is generated by the arrangement of a light source 18 and detectors 20, 22 similar to the sensor of FIG. 5, which will be described later.

Yet another mechanical reference path sensing, shown in FIG. 4B, uses a separate needle that is laterally coupled to the signal pick-up cartridge but vertically independent. The arm 24, which is supported for movement only laterally (horizontally), has a first lateral support member 26, and a tone arm portion 28 carrying the cartridge 14 has three
0 and is rotatably supported by the member. A second lateral support member and pivot contained within the housing 32 support the shank 3 carrying the second needle 36.
It has 4. A transducer located at a pivot within housing 32 functions as a sensor of vertical movement of second needle 38. The second stylus is arranged so that it is lifted off the record whenever the signal stylus is lifted. Preferably, needle 36 is dimensioned to contact a flat area of cartridge 14 adjacent signal needle 38 .

The second needle may be constructed of a variety of long-life materials that are compatible with the disc surface and resist grooving, such as sapphire or diamond. Sensor transducers include electromagnetic, photoelectric, Hall effect, magnetic diode,
potentiometer, variable resistance, capacitance,
Alternatively, it may be of various types known to those skilled in the art, including an inductance type. The raw output of the transducer corresponds to position, velocity, acceleration, or force (as in pressure-responsive transducers).

The mechanical features of the reference track sensor assembly can be optimized for plumb sensing functionality only. In order to reduce audible rumble and mold surface noise by extending the highest correction frequency upwards, the vertical resonance frequency (sensor deflection and mass) is significantly above the highest warpage frequency and is actually well within the audible range. It should be placed where it enters. The second needle must be placed in close proximity to the first needle. For example, for corrections up to about 50 Hz, it is within 1 mm. To reduce mold surface noise in the middle range, approximately 0.1mm to compensate up to approximately 500 Hz.
Even narrower spacing is preferred.

A second needle or sensor device may be placed slightly in front of the first (signal) needle to generate a leading error signal. This is ideal for reducing the gain and phase requirements of electromechanical servo loops, or alternatively, for optimal error cancellation when a mechanical or electrical phase shift is present, e.g. in low-pass filtering of the reference path information. It is useful to ensure that

Reference Path Arm Information Sensing In another embodiment of the invention, reference path arm information is used. This is a signal obtained by sensing the distance between the reference path and the arm (or cartridge). This signal necessarily includes tonearm motion and arm cartridge resonance effects. The first sensor embodiment simply uses vertical component information from the pick-up cartridge, as is known in the prior art. Although this method provides useful information above the arm cartridge resonant frequency, it is limited to cases and frequency ranges where channel separation is systematically reduced (eg, below 100 hertz) during disk cutting.

To obtain reference path arm information up to higher frequencies, it is necessary to provide a flat sensor independent of the signal needle. A non-mechanical sensing device, such as that described above in connection with FIG. 4A, may be used, but in this case it is fixed to the cartridge holding arm or cartridge rather than to the vertical fixed arm. An example of such a sensor is shown in FIG. Stereo pickup cartridge 40 has a conventional cantilevered shank 42 and stylus 44, shown engaged with record 9. A light source 46, such as a light emitting diode (LED) or a diode laser, generates a light beam that illuminates an area of the record that is 1 mm or less in diameter. The reflected light is received at one or more photoreceptors 40, 50, such as photodiodes, similar to the description of FIG. 4A. The irradiation position and diameter of the light are such that the area where the needle 44 is located and the adjacent flat area are irradiated so that the reflected light is a local change in the flat area where the needle is located or in front of the needle. , is preferably chosen to respond to local changes representing rumble and mold surface noise at that point. The output of the receptors 48, 50 is
It can be sent to a differential amplifier to indicate local plateau changes. With appropriate circuit layout,
It is possible to respond only to changes in the position of the vertical plateau, rather than to the totally reflected light that depends on groove modulation.
Such techniques are used, for example, as automatic slide convergence mechanisms.

Mechanical examples of reference path arm sensors are shown in FIGS. 6 to 9. In each of the embodiments, a dual needle pick-up cartridge is provided in which a native needle tracks groove information content and a second needle senses warp and rumble information. In embodiments of the present invention, such a dual contact combination can improve both warpage and rumble performance within a single, self-contained pickup cartridge. A third contact device, such as the brush or damper of the prior art warpage trackers described above, may optionally be used.

An ideal reference path sensing method is shown in FIG. 6 in which a shallow unmodulated pilot groove 52 is provided adjacent to the main information bearing groove 54 in the record 9a. Point 56 of second needle 58 of cartridge 60
is located within the pilot groove and senses both vertical and lateral warpage and rumble frequencies.
Embodiments of the invention are adapted to use both the vertical and lateral information provided. Fortunately, lateral warpage and rumble are not significant problems, and in practical devices it is sufficient to deal with only the vertical component.

Referring to FIG. 7, in an arrangement suitable for conventional commercial records, the cartridge 62 has a main stylus having a shank 42 and a stylus point 44 that tracks the information-bearing groove 54 of the record 9. The second shank and needle point 66 are located on one or both sides of the main needle and completely or partially surround the main needle. The contact area, if desired, is offset to the outside of the record to minimize pre-echo with reference track information. The second needle tip has a substantially flat bottom with a sufficiently large effective dimension (e.g. a fraction of a millimeter) so that the needle tip rests reliably on at least one flat area and provides lateral information. Accordingly, it does not respond substantially to the information content of the groove, but only to changes in the height of the flat portion, which are indicators of warpage and rumble. The needle tip 66 is guided laterally by the main needle and is also connected to a flexible coupling device 68.
The coupling device 68 generally maintains the relative position of the two needles, but is not involved in their movement.

Another type of needle is shown in FIG. An elongated block-shaped needle tip 70 of a second needle 72 spanning the flats between the several grooves is located in front of and outside the main needle 42. As previously mentioned, the second needle tip is sometimes U-shaped (e.g., element 7 in FIG. 9).
4) or in an O-shape surrounding the main needle. The contact area can be adjusted to reduce pre-echo if desired.
It may also be biased towards the outside of the record. Another important practical consideration is that the needle arrangement must not attract dust and must exclude it.

In most tonearm and cartridge configurations, the design of the reference path arm information sensor is designed to avoid affecting lateral thrust to the cartridge, and to avoid affecting the lateral thrust on the cartridge and to avoid the main needle being used for tracking warpage and large amplitude signals. To avoid force reduction, the main needle tracking force should contain a major portion of the total cartridge tracking force. The tracking force of the second needle is, for example, 1/4, 1/10, or less of the tracking force of the main needle, so that relatively low amplitude and low frequency rumble components are sensed. It is appropriate for Preferably, the second needle is flexibly connected to the cartridge body, and the compliance is preferably significantly greater than that of the main needle. The compliance and tracking forces described above apply primarily to offset tonearm devices where warpage is not compensated. In some devices, the second needle shank is relatively rigidly connected to the cartridge body. Additionally, the effective mass of the second needle and associated moving parts, combined with the nature of the deflection or stiffness of the shank, should produce high frequency resonances above the highest frequency components of mold surface noise. Therefore, a resonant frequency of at least 1 to 2 kilohertz is suitable for the reference path sensor. A suitable mechanical brake may be applied to the second needle, as in conventional signal cartridge designs. If desired, a mechanical reduction filter may be incorporated so that the band of information provided by the second needle is limited to reduce susceptibility to dust and surface scratches.

Information from the reference path arm sensor is used to offset the corresponding vertical information from the signal needle. As explained below, a fully mechanical offset arrangement may be used. In a simple arrangement with a non-flexible second needle, only the vertical movement of the cartridge body is subtracted from the corresponding movement of the first needle. Alternatively, the second needle information may interact within the magnetic or mechanical arrangement of the signal transducer to cancel out the error information. In some configurations,
A separate or matched transducer may be provided for the second needle. Combining the signals can be done within the cartridge itself, such as by interconnected coils. Alternatively, the signals may be brought out for external combination. For example, the high frequency component from the reference path sensor may be used internally or alternatively directed to a preamplifier for mold roughness noise reduction (cartridge VNC or preamplifier VNC).

Sensing reference road information using indirect devices As mentioned above, accurate sensing of reference road information requires
This is achieved directly by a vertically fixed sensor. Approximately, the vertical position of the tonearm is used in a manner known in the prior art. Fourth
A transducer of the type previously described in connection with Figure B is mounted between the arm and the vertical axis to provide an output related to the vertical position or angle of the tonearm and cartridge. This sensing method is useful for providing reference path information below the arm cartridge resonant frequency (eg, 10 Hertz). A relatively rigidly mounted second needle may be used to increase the resonant frequency of the tonearm. The reference path arm sensor described above in connection with FIG. 5 is useful primarily above the resonant frequency. At or near the resonant frequency, both of these methods introduce phase and amplitude errors into the reference path information. Therefore, these methods are useful only at warp or rumble frequencies that differ to some extent from the arm cartridge resonant frequency, ie, typically below about 5 Hertz and above about 20 Hertz.

In the improved method of the present invention, substantially error-free warpage and rumble sensing signals are derived over the entire frequency range of interest (e.g., 0.5
(from hertz to hundreds of hertz). This method uses a combination of the first and second sensing methods described above (i.e., tone arm sensing and reference path arm sensing) as schematically shown in FIG. 3B. This method allows both signals to contain the same error signal (due to arm-cartridge interaction effects), but in complementary form, so that both signals provide a difference signal that accurately indicates warpage and rumble. This is based on the recognition that they can be offset in the same way. The vertical arm position signal x is the distance from the arm 76 to the reference plane,
Further, the reference path arm signal y is the cartridge 78
is the distance from to the disk. The difference z is the amplitude of warpage and rumble. That is, z=x−y. Tone arm sensor 80 and reference path arm sensor 82
The arm cartridge resonant error signal contained in the x and y signals from is canceled in combiner 84 to provide a substantially error-free reference path information signal 86. The y signal is derived by the various devices described above. In other words, if the signal needle 78A is used, approximately 30
Hertz, and with the second needle 78B useful information up to about several hundred hertz can be obtained.

Cartridge VNC FIG. 10 shows a functional block diagram of a cartridge VNC embodiment of the present invention. Warpage and rumble from the main needle (groove arm sensor 220) and mold roughness noise are somehow canceled out from the output signal by arrangement 222. The method uses error information provided by reference path arm sensor 224 to
For example, it can be done mechanically, magnetically or electrically. Preferably, all is accomplished within a unitized dual needle cartridge assembly. Since the operating parameters are fixed and can be preset by the cartridge manufacturer, installation is easy both new and for replacement.

Reference path arm sensor 224 may be of the type shown in FIGS. 5 through 9 described above. A set of two independent transducers 226, 228 (e.g., a magnet and a coil) represents a typical combinational interconnection.
and as shown in FIG. 11B, within the cartridge. The transducer output is split to accommodate left and right signals. A second needle, such as that caused by scratches or rough groove edges, can be removed by providing an electrical or mechanical low-pass filter (e.g. a 300 Hz low-pass filter) whose characteristics can be controlled externally if desired. Components that are neither rumble nor mold surface noise sensed by the mold can be reduced.

In another example shown in FIG. 12, the second needle handle 72 is coupled to the stator component of the signal converter instead of to its own transducer, so that the second needle 70 The oscillation information sensed by the first hand 44 cancels the rumble information sensed by the first hand 44. That is, for rumble frequency, for example, iron or magnet 230 and coil 232
This means that there is no relative movement between the two. Various other analog cancellation arrangements are available, such as using moving coils, moving irons, and moving magnets.
can be used. Two identical armature elements may share the same stator environment, just as two coils, each associated with a needle, share a common magnetic field.

The stator component of the signal converter described above may include the cartridge body itself. However, for optimal noise cancellation, the mass to be displaced by the second hand should be as small as possible.

The signal needle and the second needle therefore preferably have flexible connections 231 and 233 independently of each other to the cartridge body. For optimal tracking, the second needle preferably provides a smaller portion of the total cartridge tracking force and a smaller portion of the total vertical stiffness.

Further mechanically coupled arrangements are possible, in which the movement of the second needle cancels the corresponding movement of the first needle.
An example is shown in the embodiment shown in FIG. In Figure 13,
A U-shaped needle tip 74 partially surrounds the main needle tip 44. The A-shaped handle 234 has a tip 7.
4 are connected to first and second members 274 and 276 which are fixed relative to the cartridge.
The main needle handle 42 is attached to the cross section of the handle 234 at point 278. The end of the handle 42 is connected to the coil 24
4 is connected to a conventional magnet or piece of iron 242 that works together. In operation, the second needle 74, which rests on one or more ground areas adjacent to the groove engaged by the main needle tip 44, responds to the wobbling frequency component, causing movement of the magnet 242 by a corresponding response of the main needle. offset.

Tonearm VNC Tonearm System Improved According to the Present Invention FIG. 14 shows an open loop tonearm VNC. An indirect type reference route information guidance system shown in FIG. 3B is used. The gains of amplifiers 214, 214a are set to follow the situation shown in Figure 3B. Almost pure reference path information is thus obtained that is unaffected by arm cartridge resonance effects. Depending on the gain control settings, under, over, or optimal correction can be obtained. There are no special constraints on the gain or other properties of tonearm actuator servo loop 200. Actuator damping is required only to ensure effective compensation of warping and wobbling, not to avoid vibration. In this way, the gain of loop 200 can be adjusted to provide adequate damping or positive displacement effects of the vertical actuator in the frequency range of interest (e.g., 20 Hz).
) to obtain sufficient warpage and rumble compensation.

For economy, tone arm sensor 80,80
a may be the same sensor. Similarly, amplifiers 202 and 214 may be identical provided that the necessary attenuation is obtained to provide the appropriate level (gain) at the inputs of coupling circuits 216 and 204.

[Brief explanation of drawings]

Figure 1 is a side cross-sectional view of the upper half of a virtual recording master on which silent grooves have been recorded, Figure 1B is a side cross-sectional view of a virtual recording press made from the master disc of Figure 1A, and Figure 2 is a side cross-sectional view of the upper half of a virtual recording press on which silent grooves have been recorded. FIG. 3 is a partial side cross-sectional view of the master disk during the cutting process using a conventional signal cutting needle and a second reference surface cutting needle according to one feature of the present invention; FIG. General representation including line diagrams; Figure 4A is a partially removed perspective view of one type of direct reference path information sensing; Figure 4B is a partially removed perspective view of another type of direct reference path information sensor; 5 is a partially removed side view of one type of reference path arm sensor, FIG. 6 is a partially removed perspective view of one type of reference path arm sensor, and FIG. 7 is a partially removed side view of one type of reference path arm sensor. Fig. 8 is a perspective view of another type of reference path arm sensor with a part removed, and Fig. 9 is a perspective view of another type of reference path arm sensor with a part removed. A perspective view with a part of the needle section removed, Figure 10 is a block diagram showing the general arrangement of the cartridge VNC, and Figure 11A is a diagram showing the cartridge VNC.
A block diagram showing the interconnection of an exemplary combination of converters in a VNC, Figure 11B is a cartridge
A block diagram showing the interconnection of another exemplary combination of converters in a VNC, FIG.
FIG. 13 is a perspective view of a portion of another cartridge VNC, and FIG. 14 is a block diagram showing a tone arm VNC according to the present invention. 2...Ratsuka master, 4...Second cutting needle, 6...
...First cutting needle, 8, 80, 82, 220, 224
...Sensor, 9...Record surface, 11...Movable member.

Claims (1)

[Scope of Claims] 1. By means of a first cutting needle whose vertical position is modulated so as to leave an uncut flat part between the spiral grooves and to leave ridge-like projections protruding into the flat parts at both ends of the groove, A signal groove is carved on the record, and the horn-shaped protrusion and the upper part of the flat part are removed by a second cutting needle that is continuous with the first cutting needle and cuts a flat part that stands upright on the record. Record recording method. 2. A method for playing a record manufactured by the method according to claim 1, comprising: tracing a flat part of the record to determine a vertical reference position; A method for playing a record comprising reading out said signal groove with respect to a reference position.