Television display apparatus with adjustable vertical deflection waveform

In order to display a video signal having an aspect ratio of 4 to 3 on a video display screen having a 16 to 9 aspect ratio a nonlinear vertical deflection signal is used to compress the video image along the top and bottom edges of the 16 to 9 aspect ratio screen. The video image is compressed only along the top and bottom edges of the screen because it has been found that motion of the point of view of the viewer relative to the displayed image is generally horizontal but is infrequently vertical. One approach to providing the non-linear vertical deflection waveform is to detect whether the input video signal for display on a 16 to 9 aspect ratio screen is a 4 to 3 aspect ratio signal and, if so, to read out special, non-linear data from a memory. This special waveform data is used to generate the non-linear vertical deflection waveform. If the input video signal is detected to be a 16 to 9 aspect ratio signal, standard data is read out from the memory to be used to generate the appropriate linear vertical deflection waveform.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to a television receiver having a 
display screen with a wide aspect ratio of 16 to 9 and, more particularly, 
to such a television receiver that can display a video image having a 4 to 
3 aspect ratio. 
2. Description of the Related Art 
A television receiver having a display screen with the wide aspect ratio of 
16 to 9 has been put into practical use. When displaying a video signal 
conformed to a standard aspect ratio of 4 to 3 on a display screen of such 
a television receiver, the conventional approaches have resulted in 
displays such as shown in FIGS. 6A to 6C. That is, in the approach 
resulting in the display of FIG. 6A, portions where no video image is 
displayed are formed at the right and left ends of the display screen. In 
the approach resulting in the display of FIG. 6B, the display of the video 
signal is expanded such that a horizontal width of the 4 to 3 aspect ratio 
video image coincides with the horizontal width of the 16 to 9 aspect 
ratio display screen. 
According to the displaying method corresponding to FIG. 6A, however, the 
portions where no video image is displayed at the right and left ends of 
the display screen are a disadvantage to the viewer. According to the 
displaying method of FIG. 6B, the upper and lower portions of the video 
image based on the video signal to be displayed on the display screen are 
cut off and not seen, so that the viewer is again disadvantaged because he 
can not see all the video image present in the video signal. 
Further, as shown in FIG. 6C, there has been proposed another display 
approach intended as a improvement over the approach of FIG. 6A in which 
the video image based on the 4 to 3 aspect ratio video signal is expanded 
in the horizontal direction, so that the video image based on the 4 to 3 
aspect ratio video signal coincides with the horizontal and vertical 
widths of the 16 to 9 aspect ratio display screen. Nevertheless, according 
to this display method, since the video image on the display screen is 
compressed in the vertical direction, the visual image looks very 
unnatural. This system is described in published EP Patent Application 
0,551,168, for example. 
In contrast to the aforesaid various displaying methods, there has been 
proposed still another displaying method resulting in the screen shown in 
FIG. 7A. In this method, as shown by FIG. 7B representing a conceptual 
drawing of FIG. 7A, only portions in the vicinity of the right and left 
ends of the video image on the screen are expanded in the horizontal 
direction. According to this method, a viewer can see the video image on 
the screen with little unnatural feeling, because the video image can be 
displayed naturally at the center portion of the display screen. In 
addition, the viewer's visual recognition of the video image becomes 
weaker at the vicinity of the right and left ends when the viewer looks at 
the center portion of the display screen. 
When such a display is performed on the screen, however, if the video image 
based on the video signal moves to the right or to the left, the moving 
speed of the video image becomes uneven. As a consequence, a viewer feels 
very unnatural when watching such a moving image. That is, when such a 
display is performed on the screen, a viewer can see the video image with 
little unnatural feeling if the view point of the viewer on the screen is 
fixed, however, the viewer feels very unnatural as the viewer moves his 
view point to the right or left. 
According to an investigation that has been performed as to the number of 
movements of the viewer's view point when the viewer views various kinds 
of programs found in general television broadcasting, it has been proved, 
as shown by the table of FIG. 8, that the number of movements of view 
point in the vertical direction is much less by a factor of two to five 
than the number of movements in the horizontal direction. The present 
invention has been made in view of this disparity between changes in 
horizontal and vertical points of view found in general television program 
material. 
A problem to be solved by the present invention is that, according to each 
of the previously proposed displaying methods as described above, when 
displaying the video image of the video signal with the standard aspect 
ratio of 4 to 3 on the display screen with the wide aspect ratio of 16 to 
9, there is a fear that the viewer will likely feel the displayed visual 
image to be unnatural. 
OBJECT AND SUMMARY OF THE INVENTION 
Therefore, it is an object of the present invention to provide a television 
receiver having a 16 to 9 aspect ratio screen that can display video 
images of 4 to 3 aspect ratio that overcomes the above-noted defects 
inherent in previously proposed systems. 
According to a first aspect of the present invention, there is provided a 
television receiver wherein, when displaying a video image based on the 
video signal conformed to the standard aspect ratio of 4 to 3 on a display 
with the wide aspect ratio of 16 to 9, a horizontal width of the video 
image of the input video signal screen is made substantially coincident 
with the horizontal width of the display screen, and the video image based 
on the input video signal is compressed in the vertical direction at a 
portion in the vicinity of at least one of the upper and lower edges of 
the display screen, so that a vertical height of the video image based on 
the video signal displayed on the display screen is made substantially 
coincident with the vertical height of the display screen. 
According to another aspect of the television receiver of the present 
invention, a vertical linearity of the video image on the display screen 
is changed at the portion in the vicinity of at least one of the upper and 
lower edges of the display screen so as to be smaller, whereby the video 
image based on the video signal is compressed in the vertical direction at 
the portion in the vicinity of at least one of the upper and lower edges 
of the display screen. 
According to another aspect of the television receiver of the present 
invention, there is provided a circuit to change a waveform shape of the 
signal used for correcting vertical linearity of the display screen, so 
that the vertical linearity of the visual image on the display screen is 
changed at the portion in the vicinity of at least one of the upper and 
lower edges of the display screen, so that the image is smaller at those 
locations. 
According to a yet further aspect of the above-described television 
receiver according to the present invention, since the video image based 
on the video signal is compressed in the vertical direction at a portion 
in the vicinity of at least one of the upper and lower edges of the 
display screen, so that a vertical height of the video image based on the 
video signal is made substantially coincident with the vertical height of 
the display screen, a visual image affecting a viewer with little 
unnatural feeling can be displayed on the display screen.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
According to the present invention, as shown in FIG. 1A, a horizontal width 
of the video image based on the video signal to be displayed is made 
substantially coincident with the horizontal width of the display screen. 
Furthermore, the video image based on the video signal is compressed in 
the vertical direction in the vicinity of at least one of the upper and 
lower edges of the display screen, so that a vertical height of the video 
visual image based on the video signal displayed on the display screen is 
made substantially coincident with the vertical height of the display 
screen. In other words, in this case, the video image is compressed only 
at the portions in the vicinity of the upper and lower edges of the 
display screen. FIG. 1B represents a conceptional drawing of FIG. 1A and 
the amount of compression is shown by the extent of difference between the 
rectangles and uniform squares distributed over the face of the screen. 
According to this displaying method, the video image can be displayed 
naturally at the center portion of the display screen, so that the viewer 
can see the visual image on the screen with little unnatural feeling even 
if the video image moves. This is so because the number of movements of 
the viewer's view point in the vertical direction is small compared with 
horizontal view point movements, as described above. 
The circuit of FIG. 2 is employed in order to realize the displaying shown 
in FIGS. 1A and 1B. In FIG. 2, a drive signal generating circuit 1 for 
vertical deflection receives a vertical synchronizing signal Vs derived in 
the known manner from the video signal to be displayed. A mode detecting 
circuit 8 also receives the vertical synchronizing signal V.sub.s, and the 
mode detecting circuit 8 detects whether the supplied video signal is to 
be depressed or not. When the vertical signal is detected to belong to a 
signal to be depressed, that is, when the signal being input is of the 
standard aspect ratio of 4 to 3, the mode detecting circuit 8 outputs a 
signal fed to a waveform memory 2 via a switch 9. The switch 9 can be 
closed by the viewer when the 4 to 3 aspect ratio signal is to be viewed 
or the switch 9 can be actuated by the mode detecting circuit 9, as shown 
by the dashed line in FIG. 2. Alternatively, switch 9 could be eliminated. 
Then, arbitrary waveform data from a waveform memory 2 is supplied to the 
drive signal generating circuit 1, and the drive signal generating circuit 
1 generates a drive signal Vd for vertical deflection. By arbitrary is 
meant that the waveform is selected in keeping with practicing this 
invention. 
The drive signal delivered from the drive signal generating circuit 1 is 
supplied to one end of a vertical deflection yoke 5 through a current 
limiting resistor 3 and an output amplifier 4. The other end of the 
deflection yoke 5 is grounded through another resistor 6. The signal 
appearing at the connection node between the deflection yoke 5 and the 
resistor 6 is fed back to the input of the output amplifier 4 through a 
third resistor 7. 
According to the thus constituted circuit arrangement, when performing a 
normal display on the display screen in accordance with the waveform data 
from the waveform memory 2, there is generated a drive signal Vd, as shown 
in FIG. 3A, from the drive signal generating circuit 1. This is based on 
the standard waveform data from the waveform memory 2. A vertical 
deflection currently as shown by FIG. 3B is caused to flow through the 
vertical deflection yoke 5, so that the normal display having the standard 
vertical linearity characteristic relative to a 16 to 9 aspect ratio is 
performed. Each of the aforesaid displays shown in FIGS. 6A and 7A is 
produced using this standard drive signal Vd. On the other hand, when the 
mode switching signal from the mode detecting circuit 8 is applied through 
closed switch 9 to the waveform memory 2 to change the waveform data 
delivered to the vertical drive signal generating circuit, a drive signal 
Vd shown in FIG. 3C, is generated from the drive signal generating circuit 
1. The non-linearity of this signal is based on the so-called arbitrary 
data from the waveform memory 2. Then, in response to the drive signal Vd 
a deflection currently, as shown by FIG. 3D, is caused to flow through the 
deflection yoke 5. This results in a display as shown in FIG. 1A in which 
the visual image based on the video signal is compressed in the vertical 
direction at the portion in the vicinity of at least one of the upper and 
lower edges of the 16 to 9 aspect ratio display screen. 
According to this circuit arrangement of FIG. 2 there is provided a 
waveform memory 2 that changes the shape of the waveform of the vertical 
drive signal in order to correct the vertical linearity of the image on 
the display screen. When the waveform is changed by using this waveform 
data approach, the vertical linearity of the visual image on the display 
screen can be changed in the vicinity of at least one of the upper and 
lower edges of the screen, so as to be smaller in vertical height than it 
would be otherwise. As a consequence, the video image signal is compressed 
in the vertical direction along at least one of the upper and lower edges 
of the display screen, so that the vertical height of the video image 
based on the video signal displayed on the display screen is made 
substantially coincident with the vertical height of the display screen. 
As described above, according to the aforesaid circuit arrangement, since 
the video image based on the video signal is compressed in the vertical 
direction at the portion in the vicinity of at least one of the upper and 
lower edges of the display screen so that the vertical height of the video 
image based on the video signal displayed on the display screen is made 
substantially coincident with the vertical height of the display screen, a 
visual image affecting a viewer with little unnatural feeling can be 
displayed on the display screen as a whole. 
That is, in the aforesaid circuit arrangement, since the horizontal 
linearity of the video image displayed on the display screen is always 
kept normal, a viewer can see the video image on the screen without any 
unnatural feeling even if the viewer's view point moves in the horizontal 
direction. In contrast; the viewer can see the video image on the screen 
with little unnatural feeling even if the viewer's view point is 
occasionally shifted in the vertical direction, because the number of 
movements of viewer's view point in the vertical direction is small as 
described above. 
Furthermore, since the video image of the 4 to 3 aspect ratio video signal 
is displayed over the entire area of the 16 to 9 aspect ratio display 
screen and is displayed normally at the center portion thereof, the viewer 
can see the visual image with little unnatural feeling. In general, most 
ordinary images are symmetrical with respect to a center line running 
vertically on the screen but few ordinary images are symmetrical with 
respect to a center line running horizontally on the screen. Thus, the 
viewer sees a visual image with less unnatural feeling, even if the video 
image is distorted in linearity in the vertical direction. Further, the 
degree of distortion of the vertical linearity of the video image is about 
10% or slightly more, in order that the vertical height of the 4 to 3 
aspect ratio video image based on the video signal displayed on the 16 to 
9 aspect ratio display screen is made substantially coincident with the 
vertical height of the display screen. This degree of distortion is 
permissible to television receivers at the initial stage of television 
broadcasting. 
Furthermore, in the ordinary cathode ray tube the amount of curvature of 
the face plate in the vertical direction is larger than that in the 
horizontal direction. Moreover, the curvature of the face plate in the 
vertical direction in a cathode ray tube with the aspect ratio of 16 to 9 
is larger than that on a cathode ray tube with the standard aspect ratio 
of 4 to 3. This larger curvature of the face plate in the vertical 
direction is canceled by the aforesaid modification of the linearity of 
the video image in the vertical direction, so that it seems visually as if 
the curvature of the face plate in the vertical direction is made smaller 
by the modification. This means that any visual unnatural feeling of the 
video image is further decreased. 
According to the aforesaid circuit arrangement, the video image can be 
displayed satisfactorily even when the video image based on a video 
software is displayed with the so-called CinemaScope size without 
performing any trimming. That is, in some of the previously proposed 
approaches to displaying such video software, subtitles are displayed at 
the lower portion of the display screen out of the video image as shown in 
FIG. 4A by the several circles in the lower cross-hatched portion. In this 
case, such a display as shown in FIG. 4B can be obtained according to the 
aforesaid circuit arrangement of the present invention. The subtitles are 
represented in FIG. 4B as the larger sized ovals along the bottom of the 
screen below the image. 
Accordingly, in this case, although the subtitles are slightly flattened by 
the vertical compression, such subtitles can be read without any 
difficulty and, hence, the viewer can enjoy the video software 
satisfactorily. In contrast, when such the software is displayed according 
to the conventional enlarging displaying method, both the upper portion of 
the video image and the subtitles are cut off and not fully displayed on 
the screen, as shown in FIG. 4C. 
FIG. 5 shows another embodiment of the circuit arrangement for realizing 
the aforesaid displays according to the present invention, in which a 
sawtooth signal of the vertical period is supplied to one input of an 
error amplifier 12 through a resistor 11. An output signal from the error 
amplifier 12 is supplied to the input of an output amplifier 14 through a 
resistor 13, and an output signal from the output amplifier 14 is supplied 
to one end of the vertical deflection yoke 15. 
The other end of the vertical deflection yoke 15 is grounded through a 
series connected capacitor 16 and resistor 17. Accordingly, a signal 
having parabolic-shaped waveform with the vertical period, as shown in 
FIG. 5, is obtained from the other end of the vertical deflection yoke 15. 
This signal is fed back to the other input of the error amplifier 12 
through a resistor 18, a grounded capacitor 19 and a resistor 20. Further, 
a sawtooth signal having the vertical period, as shown in FIG. 5, is 
obtained at the connection mode between the capacitor 16 and the resistor 
17. This sawtooth signal is fed back to the other input of the error 
amplifier 12 through a resistor 21. 
According to this circuit arrangement, a correction waveform signal having 
the vertical period, as shown in FIG. 5, is supplied to the other input of 
the error amplifier 12 through a resistor 22, so that the linearity of the 
video image on the display screen is changed in the vertical direction 
just like the example shown in FIGS. 3C and 3D. This correction waveform 
is shown connected directly to the other aspect of the error amplifier 12, 
but it is understood that a switch could be provided along with an aspect 
ratio or mode detecting circuit. 
Although in the above-described embodiments the linearity of the video 
image in the vertical direction on the display screen is changed, so that 
a video image is symmetrical about the center line running horizontally on 
the screen, the present invention may be modified in the following manner. 
For example, when the upper half of a person is displayed on the screen, 
the changing ratio of the linearity of the video image corresponding to 
the upper half of the video image which corresponds to the face of the 
person may be made smaller but that corresponding to the lower half of the 
video image may be made larger. Further, in this case, an amount of the 
changing ratio of the linearity may be selected to be an arbitrary value. 
Furthermore, the present invention may be modified in a manner that the 
linearity of the video image in the horizontal direction on the display 
screen is further changed, as in the example shown in FIGS. 7A and 7B, in 
addition to the aforesaid change in the linearity in the vertical 
direction. In this case, the amount of change in the linearity can be 
decreased. The aforesaid change in the linearity of the video image may be 
performed by modifying the video signal through digital signal processing 
techniques, instead of changing the actual deflection signal waveform as 
in the above-described embodiments of the present invention. 
Although the present invention has been described hereinabove with 
reference to the preferred embodiment, it is to be understood that the 
invention is not limited to such illustrative embodiment alone, and 
various modifications may be contrived without departing from the spirit 
or essential characteristics thereof, which are to be determined solely 
from the appended claims.