Television – Image signal processing circuitry specific to television – Brightness control
Reexamination Certificate
2000-08-08
2001-12-25
Eisenzopf, Reinhard J. (Department: 2614)
Television
Image signal processing circuitry specific to television
Brightness control
C348S800000, C348S797000, C348S624000, C348S910000, C345S690000, C345S691000, C345S692000
Reexamination Certificate
active
06333766
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a tone display method of a TV image signal and more particularly to a tone display method for displaying the tone of brightness of a luminant element by changing the luminant time width by dividing the inside of the field of a TV signal into several subfields corresponding to the pixel display time and controlling light emission of the subfields and an apparatus therefor.
2. Description of the Prior Art
As a method for displaying the tone of a TV image signal by controlling the brightness of a display element, a method for controlling the luminant time width of a luminant element is conventionally known.
For example, a memory type plasma display is described in T. Kaji et al., “A Proposal of the Drive Method for TV Using AC Type Plasma Display Panel”, Image Engineers Report No. IT72-45, Mar. 12, 1973, The Institute of Electronics and Communication Engineers of Japan. As shown in
FIG. 2
, this is a method for displaying the tone of brightness by dividing the time width of a field of a TV signal into 8 subfields corresponding to the pixel display time, weighting the time width of each of the 8 subfields in binary, and controlling the presence or absence of light emission of each subfield (b0 to b7 are named). In this case, each subfield shown in
FIG. 2
is a time width coded in binary. However, as shown in FIGS.
3
(
a
) and
3
(
b
), for example, it is possible that the luminant time width in the subfields is not almost the entire of the period of the subfields (90% duty ratio in FIG.
3
(
a
)) but as shown in FIG.
3
(
b
) for example, the luminant time width is a half of the time width of the subfields (50% duty ratio).
A TV display example by this intra-field divided subfield system is described in H. Murakami et al., “A Color TV Display Using 8-Inch Pulse Discharge Panel with Internal Memory”,
Journal of the Institute of Television Engineers of Japan
, Vol. 38, No. 9, 1984, pp. 836-842. As shown in
FIG. 4
, this is display of a TV image signal by dividing the period of a field of a TV signal into 8 subfields at even intervals, weighting the luminant time width of each of the subfields in binary, and controlling the presence or absence of light emission of these subfields.
According to the aforementioned prior art, it is known that when a TV image signal is displayed actually, dynamic false contour noise is generated for a moving image. For example, in T. Masuda et al., “New Category Contour Noise Observed in Pulse-Width-Modulated Moving Images”,
Technical Report of IEICE
, Vol. 94, No. 438, EID94-126, January 1995, pp. 61-66, The Institute of Electronics, Information and Communication Engineers of Japan, when in particular, the cheek of the face and skin of a person move by a smooth tone change in the conventional tone display method, contour string noise is generated. It is described that the principle is that the luminant time pattern in several subfields in the field is converted to a spatial pattern on the retina of each eye as the viewing point of an observer moves.
As a method for reducing such dynamic false contour noise for a moving image, a method for displaying by dividing and separating some of the upper bits in a plurality of subfields is disclosed in Japanese Laid-Open Patent Application No. 4-211294 which is a publication of Japanese Patent Application No. 3-30648. However, according to this method, there is a problem imposed that the reduction of dynamic false contour noise is not sufficient and no noticeable improvement effect is produced for a rapidly moving image.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a new tone display method for reducing dynamic false contour noise for a moving image greatly and an apparatus therefor.
To accomplish the above object, the present invention provides a tone display method of a TV image signal in a system having a memory for dividing the time width of a field of a TV signal into a plurality of subfields having a predetermined luminant time width respectively and displaying the tone of a TV image signal by controlling the presence or absence of light emission of the subfields and an apparatus therefor, wherein at least two subfields (most significant subfields) whose luminant time widths are longest and almost equal are generated among the plurality of subfields and when it is assumed that the tones are displayed in the ascending order starting from the lowest level of tone in light emission of the subfields, the tone of a TV image signal is displayed under a rule that two or more light emissions are not started from the aforementioned at least two most significant subfields at the same time.
Furthermore, the present invention provides a tone display method of a TV image signal in a system having a memory for dividing the time width of a field of a TV signal into a plurality of subfields having a predetermined luminant time width respectively and displaying the tone of the TV image signal by controlling the presence or absence of light emission of the subfields and an apparatus therefor, wherein the display device for displaying the tone of a TV image signal converts a TV image signal to a binary-coded signal by converting it from analog to digital and converts the binary-coded signal to a code comprising the aforementioned subfields other than a binary code (bit-subfield conversion).
More concretely, the present invention can be realized by controlling light emission of the subfields according to a TV image signal under a rule that when it is assumed that the light emission of the subfields displays the tones in the ascending order starting from the lowest level of tone, if individual light emission of the most significant subfields is made once, the light emission is continued until the highest level of tone is displayed.
Furthermore, the present invention can be realized if at least one most significant subfield exists in the time position in a field of a TV signal of a subfield other than the most significant subfields (hereinafter called a lower subfield) both before and after the time position of the lower subfield respectively.
Furthermore, the present invention can be realized if when it is assumed that the tones are displayed in the ascending order starting from the lowest level of tone, with respect to the order of individual light emission of the most significant subfields, one of the most significant subfields on both sides of the time of the lower subfield is first and when the display in the ascending order is continued further, the next light emission of the most significant subfield is light emission of the remaining most significant subfield on both sides of the time of the lower subfield.
Furthermore, the present invention can be realized when the number of most significant subfields is 2 and the luminant time width of each of a plurality of subfields is binary coded except one of the most significant subfields.
Furthermore, the present invention can be realized when the number of subfields is 8 and the ratio of luminant time widths of a plurality of subfields is 1:2:4:8:16:32:64:64.
Furthermore, the present invention can be realized when two most significant subfields are positioned at the first and last of a field of a TV signal.
Furthermore, the present invention can be realized when the number of most significant subfields is 3 and the ratio of luminant time widths of subfields is binary coded except two of the most significant subfields.
Furthermore, the present invention can be realized when the number of subfields is 9 and the ratio of luminant time widths of a plurality of subfields is 1:2:4:8:16:32:64:64:64.
Furthermore, in this case, the present invention can be realized when two of the most significant subfields are positioned at the first (or last) of a field of a TV signal and one of the remaining most significant subfields is positioned at the last (or first) of the field of the TV signal.
Furthermore, in this case, the present invention can be realized when the time o
Ishigaki Masaji
Kougami Akihiko
Mikoshiba Shigeo
Toda Kohsaku
Yamaguchi Takahiro
Antonelli Terry Stout & Kraus LLP
Desir Jean W.
Eisenzopf Reinhard J.
Hitachi , Ltd.
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