Reference / Paper · 1984
US Patent 4,435,728 — Raven and Annegarn, Field Frequency-Doubling Circuit for a Television Signal (1984)
The 100 Hz field-memory television that breaks raster-timed light guns.
- 100 hz
- field memory
- television
- frame doubling
Reference / Paper · 1984
The 100 Hz field-memory television that breaks raster-timed light guns.
limited States Patent [191 Raven et al. [54] FIELD FREQUENCY-DOUBLING CIRCUIT [56] FOR A TELEVISION SIGNAL [111 ,3s,72 [45] Mar. 6, 1984 References Cited U.S. PATENT DOCUMENTS [75] Inventors: Johannes G. Raven; Marcellinus J. J. C. Annegarn, both of Eindhoven, Netherlands 3,830,971 8/1974 van de Polder .................. .. 358/140 3,832,487 8/1974 de Niet 4,322,750 [73] Assignee: . . .. .. . .. . . . . 4,051,531 9/1977 Baldwin 4,276,565 6/1981 Dalton US. Philips Corporation, New York, 3/1982 . . . . . .. 358/140 358/140 358/140 Lord .................................. .. 358/140 Primary Examiner—Michael A. Masinick Attorney, Agent, or Firm-—Thomas A. Briody; William N. Y. J. Streeter; Edward W. Goodman [21] Appl. No.: 340,545 [22] Filed: [30] [57] Jan. 18, 1982 Foreign Application Priority Data Feb. 9, 1981 [NL] ABSTRACT A ?eld-frequency doubling circuit for a television signal having two ?eld memories (23, 29) may alternatively be employed as a picture memory for the television signal when it is slightly extended by providing a re-write circuit (9, 11) and an adapted output circuit (17, 47) (FIG. 1). This picture memory may be included in, for Netherlands ....................... .. 8100603 example, a noise suppression circuit or a movement [51] detector. Int. (31.3 ............................................. .. H04N 5/02 [52] user ........................................... .. ass/140 [58] Field of Search ...................... .. ass/140, 21 R, 31 ,7 [- 6 Claims, 3 Drawing Figures [CHANGE-OVER DEVICE _ _ _ 1 3 i 1: 7 I9 21 l ' _ _ _ _ _ _ T _ _ _ “"1 l 25 I17 I |----| i: \ V a: 23 : I : V’ \FIELD MEMORY I : 31 i _ {'19 l s ‘H 2] 21g | "T | ,lo'ikFlELD | I '15 :-21~ 4)‘ I 3 ‘3 1.3 12*" N : __ V MEMORY |13 PULSE 7 37 —o' 1.9 1 4,435,728 FIELD FREQUENCY-DOUBLING CIRCUIT FOR A TELEVISION SIGNAL 2 doubled-?eld-frequency output there is a change-over switch switching at half the ?eld frequency from a doubledpicture-frequency output of which a picture frequency-doubled signal may be obtained, then a pic~ BACKGROUND OF THE INVENTION 5 ture frequency doubling can be effected, that is to say The invention relates to a ?eld-frequency doulbing the two consecutive ?elds of an interlaced picture of the circuit for a television signal having an input for the input signal always appear twice in the same sequence television signal whose ?eld frequency must be dou in the output signal. ‘ bled, a ?rst and a second ?eld memory, respectively, a DESCRIPTION OF THE DRAWINGS change-over device switching at half the ?eld fre 10 quency for writing information into the ?rst and the The invention will, now be further described by way second ?eld memory, respectively, at a predetermined of non-limitative example with reference to the accom rate and reading the second and the ?rst ?eld memory, panying drawings. respectively, at a rate of substantially twice the write In the drawings: rate, and an output for the ?eld frequency-doubled 15 FIG. 1 illustrates, by means of a block schematic television signal. Philips Research Reports 1960, pages 30-32 describes a ?eld-frequency doubling circuit of the above-men tioned type. Such a circuit may be used for bandwidth compression in the television transmission channel or for reducing ?icker phenomena in a television picture obtained by means of a television signal which is trans mitted via a conventional broadcasting channel. circuit diagram, a ?eld-frequency doubling circuit in accordance with the invention; FIG. 2 illustrates, by means of a block schematic circuit diagram, a ?eld-frequency doubling circuit in accordance with the invention, which is at the same time a noise suppression circuit and picture-frequency doubling circuit with an automatic change-over from ?eld frequency-doubling to picture frequency-doubling; SUMMARY OF THE INVENTION 25 and FIG. 3 shows the signals at various time periods for The invention has for its object to provide a wider the circuit of FIG. 2. range of applications of such a circuit. According to the invention, a ?eld-frequency dou DESCRIPTION OF THE PREFERRED bling circuit of the type de?ned in the preamble is there fore characterized in that the change-over device com 30 EMBODIMENTS prises a portion for alternately applying a signal which has been delayed by two ?eld periods to a picture mem ory output. plied to an input 1. This television signal comprises picture information and synchronizing information. The measure in accordance withthe invention makes The synchronizing information is processed separately. In FIG. 1 a television signal to be converted is ap the ?eld-frequency doubling circuit also suitable for use 35 The synchronizing signal processing will not be further as a picture memory circuit if it is provided with a described as known techniques may be employed for low-cost extension. this purpose. The picture information of the television In accordance with a further embodiment of the in signal is assumed to be present in digital form, in view of vention, such a ?eld-frequency doubling circuit is also the presently available ?eld memories which are em characterized in that it comprises a combining circuit 40 ployed in this embodiment. coupled to the picture memory output and the input for The input 1 is connected to an input 3 and an input 5 combining an input signal with a signal which has been of a change-over device 7 switching at half the ?eld delayed for two ?eld periods. frequency. The change-over device 7 comprises a num This makes it possible to obtain, for example, a move ber of change-over switches 9, 11, 13, 15, 17 and 19, ment detection circuit or noise suppression circuit by 45 which, during one ?eld period, are of the signal at the means of the combining circuit, while the ?eld-fre input 1, are in the position shown in the drawing and quency doubling function is maintained. during the other ?eld period, are in the position not A still further embodiment in accordance with the shown. invention is characterized in that an output of the com bining circuit is coupled to an input of the changeover 50 A master contact of the changeover switch 9 is con nected to an input 21 of a ?rst ?eld memory 23, a device for alternately writing an output signal of the contact of the change-over switch 9 being connected to combining circuit into the ?rst and the second ?eld an input 25 of the ?rst ?eld memory 23 and a further memory, respectively. contact of the change-over switch 9 being connected to As a result of this measure, a noise suppression may be obtained in the ?eld-frequency doubled signal, pro 55 the input 3 of the change-over device 7. A master contact of the change-over switch 11 is vided the combining circuit is adapted to that function. connected to an input 27 of a second ?eld memory 29, If a ?eld-frequency doubling circuit in accordance with the invention is characterized in that coupled to an a contact of the change-over switch 11 being connected to an output 31 of the second ?eld memory 29 and a output at which the signal having double the ?eld-fre quency appears, this output being designated doubled 60 further contact of the change-over switch 11 being connected to the input 5 of the change~over device 7. ?eld-frequency output in the further course of this de scription, there is a change-over device switching at the A master contact of the change-over switch 13 is ?eld frequency for writing, during half a ?eld period of connected to a clock signal input 33 of the ?rst ?eld the input signal of the ?eld-frequency doubling circuit, memory 23, a contact of the changeover switch 13 the ?eld-frequency-doubled signal into a third ?eld 65 being connected to an output 35 of a pulse generator 37 memory and for writing, during a subsequent half ?eld and a further contact of the change-over switch 13 period its output signal into this third ?eld memory, being connected to an output 39 of the pulse generator while coupled to an output of this ?eld memory and the 37. i 3 4,435,728 A master contact of the change-over switch 15 is connected to a clock signal input 41 of the second ?eld memory 29, a contact of the change-over switch 15 being connected to the output 39 and a further contact 4 the picture memory function. It will be obvious, that instead of serial memories, random access memories may alternatively be used whose write and read address generators are controlled in an adapted manner. When of the change-over switch 15 being connected to the output 35 of the pulse generator 37. no coupling of the outputs to the inputs of the memories is required, the change-over switches 9, 11 may there fore be omitted. In FIG. 2 corresponding components have been The pulse generator 37 produces a pulse signal hav ing a write frequency f at its output 35, a pulse signal having a read frequency 2f which is twice the write frequency at its output 39 and a switching signal, having a switching frequency which is half the ?eld frequency éfv of the input signal, at an output 43, which output 43 is connected to a switching signal input 45 of the given the same reference numerals as in FIG. 1. A combining circuit 51, which acts as a noise suppres sion circuit and an input of_ which is connected to the input 1 of the circuit and an output to the input 3 of the change-over device 7, is arranged between the input 1 change-over device 7, as a result of which all of the of the circuit 51 and the input 3 of the change-over device 7. A further input 53 of said combining circuit is connected to the picture memory output 47 of the change-over device 7 and is supplied with a signal which has been delayed by two ?eld periods, i.e. a picture period, with respect to the signal at the input 1. The two input signals are subtracted from each other in change-over switches 9, 11, 13, 15, 17 and 19 of the change-over device 7 assume a different position ?eld sequentially. A master contact of the change-over switch 17 is connected to a picture memory output 47 of the change over device 7, a contact of the change-over switch 17 being connected to the output 25 of the ?rst ?eld mem a subtracting circuit 55 and applied via an attenuator 57, having an adjustable attenuation, to an adder circuit 59 ory 23 and a further contact of the change-over switch 17 being connected to the output 31 of the second ?eld in which the signal at the input 53 is again added. A memory 29. signal in which the noise has been reduced is then ap A master contact of the change-over switch 19 is 25 plied to the input 3 of the change-over device 7. The connected to a ?eld frequency-doubled output 49 of the attenuation of the attenuator 57 is controlled by an ?eld frequency doubling circuit, a contact of the output signal of a movement detector 61 which in this change-over switch 19 being connected to the output 31 case receives its input signal from the subtracting circuit of the second ?eld memory 29 and a further contact of 5. If so desired, this movement detector 61 may of the change~over switch 19 being connected to the out put 25 of the ?rst ?eld memory 23. In the position shown of the change-over device 7, a television signal is applied during a ?eld period to the input 21 of the ?rst ?eld memory 23 via the input 3 and the change-over switch 9. This television signal is writ ten into the ?rst ?eld memory 23 at a rate which is course be controlled in a manner different from the manner described here and may if so desired comprise ?lters to obtain the desired, properties, such as, for example, insensitivity to noise. In addition, the move ment detector 61 applies a signal to an output 63 of the 35 combining circuit 51. The change-over device 7 is of a somewhat different construction than the device shown in FIG. 1. The functions of the change-over switches 9, 11 and 17 of FIG. 1 are now performed by three change-over determined by the frequency f of the signal at the input 33 of the ?rst ?eld memory 23, which signal is obtained from the output 35 of the pulse generator 37 via the change-over switch 13. Simultaneously, a television swtiches 65, 67, 69, and the functions of change-over signal is read at the same rate from the output 25 of the ?rst ?eld memory 23 and applied to the picture memory change-over switches 71, 73. switches 13 and 15 of FIG. 1 are performed by two output 47 via the change-over switch 17. This read-out The doubled ?eld frequency output 49 is connected television signal is delayed by two ?eld periods with to a contact each of change-over switches 75 and 77, respect to the signal at the input 3, which will be evident 45 respectively. The master contact of the change-over from the following description. switch 75 is connected to an input 81 of a third ?eld During this ?eld period, a television signal which was memory 83, an output 85 of which is connected to the written into the second ?eld memory 41 during the other contact of the change-over switch 75. The master preceding ?eld period is read out via the output 31 and contact 87 of the change-over switch 77 is connected to applied to the doubled ?eld frequency output 49 via the 50 a contact of a change-over switch 79 and the master change-over switch 19. Said reading action is done at a contact 89 of the change-over switch 79 is the output of rate which is determined by the frequency 2f of the the circuit. The other contact of the changeover switch signal applied to the input 41 of the second ?eld mem 79 is connected to the master contact of the change ory via the change-over switch 15. Consequently, this over switch 75. reading rate is twice the write rate of the ?rst ?eld 55 The change-over switch 75 is operated by a signal memory, In addition, the read-out signal is again applied applied to its input 91 and obtained from an output 93 of from the output 31 of the second ?eld memory 29 to the the pulse generator 37, this signal having the frequency input 27 via the change-over switch 11 and again writ fv which is twice the frequency if, which controls the ten into the second ?eld memory 29. This is performed change-over device 7. twice in this ?eld period, so that at the output 49 the The third ?eld memory 83 has a clock signal input 95 television signal of the preceding ?eld is released twice to which the signal having the frequency 2f is applied while at the end of the ?eld period, the signal of said which is received from the output 39 of the pulse gener preceding ?eld is again written into the second ?eld ator 37. As a result thereof, this third ?eld memory 83 memory 29. In the subsequent ?eld period the function of the two ?eld memories 23 and 29 are interchanged, so that the ?rst ?eld memory 23 provides for the ?eld frequency doubling and the second ?eld memory 29 provides for operates as a delay line having a time delay of one ?eld period of the signal of twice the ?eld frequency, i.e. half the ?eld period of the signal at the input 1 of the circuit. The change-over switch 77 is operated by a signal éfv (T/4) having the same frequency as the signal operating 4,435,728 5 change-over device 7 but shifted a quarter of a ?eld 6 interval t5-t7 and the signal B2 in the time interval t9-t11 each at the input signal rate. A signal which is delayed by one picture period with period (T/4) which respect to that signal. This signal 3f, (T/4) is obtained from an output 97 of the pulse generator 37 and applied to an input 99 of the change respect to the signal at the input 3 occurs at the picture over switch 77. memory output 47 of the changeover device 7. This The change-over switch 79 is operated by a signal signal includes plotted along the line 347 and is A1 in the applied to its input 101 and received from the output 63 time interval t3-t5, B1 in the time interval t5-t7, A2111 the of the combining circuit 51. time interval t7-t9, B2 in the time interval t9-t11 and A3 In order to have this signal occur at the correct mo in the time interval t11-t13. ment at the input 101 of the change-over switch 79, it is A signal, which is plotted along the line 349 and passed from the output 63 of the combining circuit 51 which always has twice the rate of the signal at the via a delay circuit, having a change-over switch 103, a input 3, appears at the output 49 of the change-over ?eld memory 105 and a change-over switch 107. This device 7. This signal is A1 from t1 to t2, A1 again from t; ?eld memory 105 may be of a one-bit construction and to t3, B1 from t3 to t4, B1 again from t4 to t5, A2 from t5 is controlled by the same signal as the ?eld memory 29. to t6, A2 again from t6 to t7, B; from t7 to tg, 13; again This signal is applied to an input 109 thereof. from t3 to t9, A3 from t9 to t1o, A3 again from no to m, The operation of the circuit of FIG. 2 will now be B3 from t11 to t12 and B3 again from t12 to t13. So this further described with reference to FIG. 3. signal has twice the ?eld frequency with respect to the FIG. 3 shows a number of time intervals t0—t1, t1-t2, input signal. Also at the input of the third ?eld memory t2—t3, t3—t4, t4—ts, ts—t6, Its-t7, £748, ts—t9, t9—t1o, fro-til, 20 83 there appear only signals with at twice the rate. They t11-t12 and t12-t13 and a number of lines 303, 325, 331, are plotted along the line 381 and are successively A1, 347, 349, 381, 385 and 387, respectively, along which A1, B1, B1, A2, A2, B2, B2, A3, A3 and B3 in the respec the nature of the signals at the points 3 and 25, 31, 47, 49, tive time intervals tz-t3, t3-t4, t4-t5, t5—t6, t6—t7, t7-t3, 49, 81, 85, 87, respectively, of the circuit are indicated. tg-tg, t9—t1(), t1()¢t11, t11—t12 and t12—t13. The signal 381 A1 denotes a signal coming from a ?rst ?eld period of 25 appears with a delay of one ?eld period at the output 85 a ?rst picture of the signal at the input 1 of the circuit, of the third ?eld memory 83. This is plotted along the B1 denotes a signal from the second ?eld period of the line 385. ?rst picture, A; denotes a signal from the ?rst ?eld Finally, along the line 387 the signal at the output 87 period of the second picture, B2 a signal from the second of the change-over switch 77 is plotted which is alter ?eld period of this picture, A3 a signal from the ?rst nately during the periods t2—t4, t6—tg and t10—t12 the ?eld period of the third picture and so forth. signal 349 and during the periods t4—t6, t3-t1() and t12~t13 The following Table shows the positions of the peri the signal 385. This signal is a signal having twice the odically operating switches 7, 75 and 77 for the relevant rate of the input signal but in which the ?elds of each time intervals, s representing the. position shown in picture have the same sequence as in the input signal. FIG. 2 and n the position not shown. The signal 381 is designated the ?eld frequency-dou 35 trli I1—t2 I2—t3 ta-M Ira-ts ts—t6 t6—t7 i742 ts—t9 t9—t1o tic-tn 7 s n n s s n n s s n 75 s n s n s n s n 77 s s n n s s n n li1—t12 £12413 s s s n s s s n bled signal and the signal 387 the picture frequency The following signals are applied to the input 3 of the doubled signal. change-over device 7: the signal A1 in the time interval 45 The signal at the output 89 of the change-over switch t0—t1, the signal B1 in the time interval t1—t3, the signal 79 may therefore, depending on the position of that A; in the time interval t3-t5, the signal B2 in the time switch, be of twice the ?eld frequency or of twice the interval t5-t7, the signal A3 in the time interval t7-t9, the picture frequency. signal B3 in the time interval t9—t11 and the signal A4 in Doubling the ?eld frequency is required if movement the time interval t11—t13, which in FIG. 3 is plotted occurs in the picture and doupling the picture fre along the line 303. quency is required if there is no movement and a con As a result thereof, there appears at the output 25 of the ?rst ?eld memory 23 in the time intervals t1—t2 and tour having a horizontal component is present in the picture; should there be no movement and no contour t2-t3 the signal A1 at twice the rate, in the time interval with a horizontal component then either the ?eld or the t3~t5 the signal A1 at the same rate as in the time interval picture-frequency doubling may be used. The change-over switch 79 is now operated by the to—t1 at the input 3, in the time intervals t5—t6 and t6—t7 the signal A2 at twice the rate, in the time interval t7—-t9 the signal A; at the same rate as at the input 3, in the time intervals t9—t10 and t10—t11 the signal A3 at twice the rate and in the time interval t11—t13 the signal A3 at the same rate as at the input 3. This is plotted in FIG. 3 signal at its input 101 which is received from the move ment detector 61 via the delay circuit 103, 105, 107 and adjusts the change-over switch 79 to the position shown at the occurrence of moving parts of the picture and to the position not shown in the case of stationary parts of along the line 325. Along the line 331 of F IG. 3 there is shown the signal the picture. at the output 31 of the second ?eld memory 29 which action has no effect, as then the two contacts of the In the time intervals t5-t7, t9—t11, . . . a change-over shows the signal B1 in the time intervals t3-t4 and t4-t5, 65 change-over switch 79 carry the same signal (381 and the signal 13;, in the time intervals t7-t3 and tg-t9, the 387). In the time intervals t3~t5, t7-t9, t11—t13, . . . the signal B3 and in the time intervals t11-t12 and t12—t13, change-over must be in correct synchronism with the each at twice the rate and the signal B3 in the time signal at the change-over switch 79. These time inter 4,435,728 7 vals start, when there is no movement, with a B-signal (along the line 387) received from the output 31 of the spectively. second ?eld memory 29. Therefore, the same signal path has been chosen for the movement detection signal as for the B-signal. The synchronization is then correct. When the ?eld frequency is doubled, so at the occur rence of movement, an interpolation may be employed 2. A ?eld frequency-doubling circuit as claimed in claim 1, characterized in that it further comprises a combining circuit coupled to the picture memory out put and the input for combining an input signal with a in the output signal with a signal from the preceding line period of the output signal in order to prevent positional errors on display. ' 8 a signal which has been alternately delayed two ?eld periods by the ?rst and the second ?eld memory, re signal which has been delayed by two ?eld periods. 3. A ?eld frequency-doubling circuit as claimed in claim 2, characterized in that an output of the combin . Instead of being switched only by a signal received from the movement detector 61, the change-over switch 79 may also be switched by, for example, a fur ther signal which is received from a contour detector by ing circuit is coupled to an input of the change-over device for alternately writing an output signal of the combining circuit into the ?rst and the second ?eld memory, respectively. means of which contours with a horizontal component are detected in the picture. At the occurrence of a sta 4. A ?eld frequency-doubling circuit as claimed in any of the preceding claims, characterized in that, cou tionary contour a change-over to picture frequency doubling is then effected. Then the third ?eld memory pled to~the output at which the signal having double the ?eld frequency appears, there is a change-over device 83 may be designed for the transmission of a smaller switching at the ?eld frequency for writing, during half number of bits per video signal sample'as on contours 20 a ?eld period of the input signal of the ?eld-frequency the quantization needs not be very accurate. doubling circuit, the ?eld-frequency doubled signal into It will be obvious that the noise suppression and the a third ?eld memory and, during a subsequent half ?eld operation of the change-over switch 79 may be done period, for writing the third ?eld memory output signal independent of each other, or may be omitted. back into the third ?eld memory, while, coupled to an The signal received from the movement detector 61 25 output of the third ?eld memory and the doubled-?eld for the control of the change-over switch 79 may, if so frequency output, there is a change-over device switch desired, be passed as an additional information bit ing at half the ?eld frequency, from an output of which through a suitably chosen signal path of the video sig a picture-frequency-doubled signal may be obtained. nal. 5. A ?eld frequency-doubling circuit as claimed in What is claimed is: ' 30 1. A ?eld frequency-doubling circuit for a television signal having an input for the television signal whose ?eld frequency must be doubled, a ?rst and a second ?eld memory, respectively, a change-over device switching at half the ?eld frequency for writing infor claim 1, having a combining circuit coupled to the pic ture memory output and the input, characterized in that a change-over switch is coupled to a doubled-?eld fre quency output and the doubled-picture frequency out put, from an output of which a television signal can be 35 obtained whose ?eld-frequency or picture frequency mation into the ?rst and the second ?eld memory, re has been doubled depending on the position of the spectively, at a predetermined rate and reading the second and the ?rst ?eld memory, respectively, at a rate of substantially twice the write rate, and an output for change-over switch. 6. A ?eld frequency-doubling circuit as claimed in claim 5, characterized in that a control signal input of the ?eld frequency-doubled television signal, character 40 the last-mentioned change-over switch is coupled to an ized in that the change-over device comprises a portion output of the combining circuit. # i‘ l * * it for supplying to a picture memory output of the circuit 45 55 60 65