Title: Tuning indicator for a radio frequency receiver

Description: BACKGROUND OF THE INVENTION

The invention relates to radio and television receivers and in particular to indicators for displaying the radio frequency of a station to which the receivers are tuned.

Numerous popular entertainment devices, such as television and AM and FM radios, utilize radio frequency receivers to detect and reproduce in audible form radio frequency signals transmitted by distant broadcast stations. These receivers are generally tuned to select one of a number of stations by setting the resonant frequency of an oscillator in the receiver to a frequency which differs from the frequency of the signal transmitted from the station by a predetermined fixed amount. In conventional receivers, the resonant frequency of the oscillator can be continually varied for detection of all stations in a band of frequencies, for example, by varying the capacitance of a capacitor in the oscillator circuit. Coupled to the capacitor is a tuning indicator, which moves as the capacitance is changed, to identify the frequency of the station to which the receiver is tuned.

Many types of tuning indicators have been used in the past. In one type of indicator, the frequencies are imprinted on a disc rotatably coupled to the capacitor. As the capacitance is changed, the disc moves relative to a window positioned in the receiver through which the frequencies of the stations can be observed. In a second type of indicator, the frequencies are imprinted on a fixed scale and a pointer is arranged to move relative to the fixed scale as the receiver is tuned. These indicators, however, are often difficult to read and do not always provide an accurate indication of the frequency of the station being received.

Recently, digital displays have been introduced for a variety of applications. An example is an "Optical Display Digital Watch" disclosed in U.S. Pat. No. 3,566,602 to Bergey et al, of Mar. 2, 1971 wherein the time is displayed in digital form in a display window. Fiber optic bundles are interposed between the display window and minute and hour wheels, having indicia representative of the time which are driven by the watch movement, and provide light transmission paths for displaying the time indicia, from the minute and hour wheels, in the display window. While this type of display is relatively easy to read, the watch disclosed in the above-referenced patent provides a continuous display and has no provisions for accurately aligning the time information with the fiber optic bundle.

In accordance with the present invention, a tuning indicator for a radio frequency receiver produces a digital display of the frequencies of received broadcast stations which is accurate and relatively easy to read and is displayed only when the receiver is tuned to a station.

SUMMARY OF THE INVENTION

In accordance with the invention, a tuning indicator for a radio frequency receiver, tunable to one of a plurality of stations in a frequency band, has a display panel, a first light source, a fiber optic bundle having its distal end terminating in the display board and its proximal end positioned to receive light from the first light source, and a station frequency encoder, having at least one set of indicia representative of the frequency of one of the plurality of stations, mounted for movement between the first light source and the proximal end of the fiber optic bundle to orient the set of indicia in a reading position between the first light source and the proximal end of the fiber bundle. The tuning means for indicating the alignment of the set of indicia between the first light source and the proximal end of the optical fiber bundle in the reading position including a second light source and means responsive to light from the second light source for producing a control signal indicative of the alignment of the set of indicia for controlling the first light source in accordance with the alignment of the set of indicia at the reading position.

In the preferred embodiment of the invention, the station frequency encoder includes an alignment index positioned proximate each set of indicia for cooperation with aligning means. Further, the means responsive to light from the second light source includes a light sensitive device, a first optical fiber having its distal end coupled to the second light source and its proximal end positioned for alignment with the alignment index and a second optic fiber having its proximal end positioned for alignment with the alighment index and its distal end coupled to the light sensitive device.

In operation, as the receiver is tuned, the station frequency encoder carrying the sets of indicia moves between the fiber optic bundle and the first light source. When a set of indicia corresponding to the frequency of a station is aligned between the fiber optic bundle and the first light source at the reading position, light from the second light source is transmitted via the first and second optical fibers and the alignment index to the light sensitive device producing a control signal which actuates the first light source. Light from the first light source is then transmitted to the proximal end of the fiber optic bundle and through the individual optic fibers aligned with the indicia to illuminate the display panel and form a digital display of the frequency of the station. When the set of indicia is not aligned with the fiber optic bundle at the reading position, no light is received by the light sensitive device. Thus the control signal is not present and the first light source is deactuated to prevent light from the first light source from reaching the proximal end of the fiber optic bundle. In this manner, the display is formed on the display panel only when a set of indicia are aligned between the first light source and the proximal end of the fiber optic bundle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan and schematic representation of a tuning indicator according to the present invention;

FIG. 2 is a sectional view taken along the line 2--2 of FIG. 1 and looking in the direction of the arrow;

FIG. 3 is an enlarged plan view taken along the line 3--3 of FIG. 2 looking in the direction of the arrow and partially in section showing a typical set of indicia aligned with the fiber optic bundle;

FIG. 4 is an enlarged view taken along the line 4--4 of FIG. 1 and looking in the direction of the arrow and partially broken away showing the optical fibers arranged in a seven-bar squared eight configuration;

FIG. 5 is a sectional view taken along the line 5--5 of FIG. 4 and looking in the direction of the arrow showing typical terminations of optic fibers on the display panel; and

FIG. 6 is a diagramatic and schematic representation of a circuit for insuring alignment between the station frequency encoder and fiber optic bundle.

DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference to the figures, there is shown a portion of a radio frequency receiver for receiving an information modulated radio frequency carrier signal transmitted from a television or radio broadcast station. The receiver has a conventional input circuit, generally designated by reference numeral 10, which is tunable to select one of the transmitted radio frequency signals. The input circuit conventionally contains a variable frequency oscillator whose resonant frequency is changed by varying the capacitance of a variable capacitor in the tank circuit of the oscillator. As shown schematically, the capacitor is coupled through gears 12 and 14 to shaft 16 which is connected to a tuning knob. In tuning the radio frequency receiver to select a broadcast station, shaft 16 is rotated thereby changing the capacitance and resonant frequency of the oscillator. A broadcast station having a carrier frequency which is a fixed frequency difference from the resonant frequency of the oscillator causes a signal to be produced which is coupled to a demodulator which separates the information from the radio frequency carrier signal. The information signal is then amplified and an output signal produced.

In accordance with the invention, the receiver has a tuning indicator for accurately displaying, in an easy to read format, the carrier frequency of a selected station. The tuning indicator includes a station frequency encoder 22, in the form of an elongated closed loop paper tape or photographic film, supported for movement around drums 24 and 26 which are mounted on the receiver. Drum 24, fixed to shaft 16 has sprockets 28 projecting from the surface thereof arranged to engage perforations 30 extending at space intervals along the opposite edges of station frequency encoder 22.

Rather than provide a graduated numerical scale, the frequencies of the stations are encoded on the station frequency encoder as sets of indicia, 32, which can, for example, be elongated perforations in a paper tape or undeveloped spots on a developed photographic film. As shown, by way of example, each set of perforations on a paper tape consists of three columns, 32A, 32B, 32C, for encoding each of three numbers, with seven positions in each column. As will be described, by placing perforations at appropriate positions in each column, digits can be formed for identifying a received broadcast station.

Arranged on one side of the tape at reading position, 34, is light source 36 having a reflector 38 positioned to concentrate and direct the light toward the reading position. Mounted on the opposite side of tape 22, and positioned at reading position 34, is a fiber optic bundle, generally designated by reference numeral 40, having its proximal end terminating at the reading position. The individual optic fibers, 40a, comprising the fiber optic bundle are arranged in three rows of seven fibers for alignment with the sets of indicia on the tape. The distal ends of the optical fibers are mounted on display panel 42 and arranged to illuminate individual segments of a seven-bar numeral in the form of a squared figure eight. In one form of the invention, the distal ends of the optic fibers are widened in order that each fiber forms of the numerals.

As the receiver is tuned by rotation of shaft 16, the sprockets in drum 28 engage perforations 30 to move the station frequency encoder carrying the sets of indicia past reading station 34. When a set of indicia is aligned at reading station 34, light from light source 36 is transmitted through the indicia and the optic fibers aligned with the indicia to illuminate bars of the seven-bar numeral. For example, if there are three indicia in one column of the tape, light transmitted through the three optic fibers aligned with the indicia illuminates three bars of the numeral. By proper selection of the positions of the indicia, various combinations of bars can be illuminated to form the digits between 0 and 9 and the set of indicia, as shown, can encode a three digit number to represent the frequency of a received broadcast station. Of course, a greater or lesser number of digits can be used.

To insure that the number displayed on display panel 42 accurately represents the frequency of a received station, the tuning indicator further includes an alignment indicator, designated by reference numeral 50, which prevents light from light source 36 from being transmitted to the reading station until a set of indicia is properly aligned with the fiber optic bundle. The alignment indicator includes a light source 52 surrounded by light shield 54 and positioned on one side of tape 22. Coupled between shield 54 and the reading position is optic fiber 56. Positioned on the other side of the tape, at reading position 34 is optic fiber 58, having one end aligned to receive light from optic fiber 56 and its opposite end coupled to a light sensitive device, such as photocell 60 (FIG. 6). The output of photocell 60 is coupled to switch circuit 62, which is preferably an AND gate whose other input signal is derived from an appropriate circuit in the receiver to indicate that the receiver is receiving a broadcast signal, as represented by reference numeral 64. The output of the switch circuit actuates light source 36 to allow the light source to transmit light to reading station 34 by, for example, turning the light "on", or opening a shutter between the light source and the reading position. Positioned on the tape for alignment between optic fibers 56 and 58, is an alignment index 70, associated with each set of indicia, which cooperates with the alignment indicator to insure that the indicia corresponding to the frequency of a received station are aligned at the reading position before a number is displayed on the display panel.

The operation of the alignment indicator will now be described. When a set of indicia becomes aligned with fiber optic bundle during the tuning of the receiver, alignment index 70 is positioned between optic fibers 56 and 58 permitting light to be transmitted from light source 52 to photocell 60. Light incident to the photocell produces an output signal which is coupled to switch circuit 62. If the receiver is simultaneously tuned to a station, the receiver provides a second input to the switch circuit which actuates light source 36. Light is transmitted to the reading position to selectively illuminate segments of the numbers on the display panel, thereby forming a display of the frequency of the received station, as described above. As a set of indicia moves out of alignment with the fiber optic bundle, the tape becomes interposed between optic fibers 56 and 58 thereby preventing light, transmitted by light source 52, from reaching photocell 60. Since one input signal to switch circuit 62 is not present, the output signal is reduced to zero and light source 40 is deactivated. Thus, as the receiver is tuned, numbers corresponding to the frequency of broadcast stations are consecutively displayed in an easy to read manner to allow an operator to accurately and quickly select a desired broadcast station.

While an illustrative embodiment of the invention has been described in detail, it is to be expressly understood that the invention is not limited thereto. Various changes may also be made in the design and arrangement of the parts without departing from the spirit and scope of the invention as the same is understood by those skilled in the art. For example, the station frequency encoder can be in the form of a disc rather than an elongated tape.
Other info:


Inventors: Nakamura, Tadao (Flushing, NY, US)
Detwiler, Barry C. (New Milford, NJ, US)
Marchetti, John A. (Staten Island, NY, US)

Application Number: 409940
Filing Date: 1973-10-26
Publication_date: 1976-04-27
Assignee: Matsushita Electric Industrial Co., Ltd. (Kadoma, JA)
Primary Class(es): 455/157.2 116/244, 334/86, 340/815.42, 345/44
Other Classes:
US Patent Ref:

3222666	Dec, 1965	Hallden	340/324.
3555539	Jan, 1971	Richards	340/324.
3639747	Feb, 1972	Schmidt	350/96.
3701951	Oct, 1972	Krausser	325/455.
3753119	Aug, 1973	Close	325/455.
3820096	Jun, 1974	Himmelsbach	350/96.
3836911	Sep, 1974	Gibson et al.	340/380.

Other Refs:
Primary Examiner: Griffin, Robert L.
Assistant Examiner: Psitos, Aristotelis M.
Attorney: