Method and apparatus for displaying effective keys

The present invention relates to a method and apparatus for displaying information corresponding to effective keys for changing the operation mode of a camcorder on the screen of the camcorder. The apparatus of the present invention includes a control circuit which checks present key signals input to the camcorder, determines whether the key signal can be operated to change operation from a present operating mode to a next operating mode, and displays information representing all of the effective keys which may be operated to change the operation mode of the camcorder from the present play mode on an electronic viewfinder and/or a monitor when the input key signal corresponds to a function which cannot proceed the present operating mode. Accordingly, the present invention provides the convenience of user's operation by displaying effective keys capable of proceeding from a present operating mode to a next operating mode.

BACKGROUND OF THE INVENTION 
The present invention relates to a method and apparatus for displaying 
information corresponding to effective function keys of a camcorder so 
that the camcorder may be easily manipulated, and more particularly to a 
method and apparatus for displaying information indicating which function 
keys of the camcorder are effective function keys for changing the 
operating mode from the present operating mode when an input key signal is 
not effective. 
Generally, since a photographer should view both an electronic viewfinder 
(hereinafter referred to as "EVF") showing a picture of what is to be 
photographed and the area in front of the EVF when photographing objects 
with a camcorder, the user cannot directly view the function keys provided 
on the camcorder. Therefore, the user cannot recognize which function keys 
correspond to effective keys for altering the present operating mode 
because the camcorder only displays information indicating the present 
operating mode on a monitor. Japanese patent laid-open publication No. 
04096580, published on Mar. 27, 1992, solves the above problems. The prior 
art provides an operating mode display and a gazing point detecting device 
enabling a user to easily change the operating mode of the camcorder by 
looking through a finder. 
SUMMARY OF THE INVENTION 
In order to overcome the above-mentioned problem differently from the above 
prior art, it is an object of the present invention to provide a method 
for displaying information corresponding to all of the effective keys 
which may be operated during the present operating mode when other key 
signals corresponding to function keys which are not effective for 
altering the present operating mode are detected as input signals. 
It is another object of the present invention to provide an apparatus for 
performing the above method of displaying information corresponding to 
effective keys. 
Thus, to accomplish objects of the present invention, there is provided a 
method for displaying information corresponding to effective keys 
comprising the steps of: 
receiving a key signal; checking a present operating mode; determining 
whether the checked key signal corresponds to an effective key for the 
present operating mode; generating character data corresponding to 
information representing effective keys which are operable when the 
determined key signal is not an effective key; and overlapping the 
character data onto the video signal and displaying the overlapped data. 
There is provided an apparatus for displaying information corresponding to 
effective keys in accordance with the present invention, the apparatus 
comprising: 
input means for inputting a key signal; controlling means for detecting the 
key signal supplied from the input means, determining whether the key 
signal is functionable or effective in a present operating mode, 
controlling operation of the apparatus when the key signal is effective, 
and for outputting effective signal data when the input key signal is not 
effective; sync separating means for detecting a sync signal from the 
input video signal; an on screen display (OSD) unit for synchronizing 
character data, output in response to the data signal supplied from the 
controlling means, with the sync signal supplied from the sync separator; 
mixing means for overlapping the character data supplied from the OSD unit 
onto the video signal; and a display unit for displaying a signal supplied 
from the mixing means.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
Hereinbelow, a preferred embodiment of the present invention will be 
described with reference to the attached drawings. 
FIG. 1 illustrates an effective key display apparatus in accordance with 
the present invention. In FIG. 1, a control panel 11 provided with a 
key-matrix manipulates a plurality of functions. An output terminal of the 
control panel 11 is connected to a controller 12 having a timer 
incorporated therein. A switch SW selectively outputs any one of a video 
signal S.sub.1 to be recorded by the camcorder in a camera mode and a 
video signal S.sub.2 to be reproduced by the camcorder in a VTR mode. The 
switch SW performs switchover operations according to a selection signal 
SEL supplied from the controller 12. A sync separator 13, connected to an 
output terminal of the switch SW, detects a sync signal from the selected 
video signal. An OSD unit 14 having character data is connected between 
the output terminals of the controller 12 and the sync separator 13. Two 
mixers 15, 16 are connected to the OSD unit 14. The first mixer 15 is 
coupled to receive both a video signal from the sync separator 13 and 
character data CHAR from the OSD unit 14. The second mixer 16 is coupled 
to receive a video signal from the sync separator 13 and character data 
NCHAR from the OSD unit 14 which represents effective keys capable of 
being applied to a present operating mode. A recorder 17, connected to an 
output terminal of the first mixer 15, records the output signal from the 
first mixer 15. The output terminal of the second mixer 16 is connected to 
a monitor 18 and to an electronic viewfinder 19 which display the output 
signal from the second mixer 16. 
The operation of the effective key display apparatus in accordance with the 
present invention will be described in detail. 
First, the controller 12 detects a key signal Skey, supplied from the 
control panel, which selects either the camera mode or the VTR mode of the 
camcorder. The controller 12 then outputs a selection signal SEL which 
controls the switchover operation of the switch SW. The switch SW includes 
a first node `a` which receives the video signal S.sub.1 to be recorded at 
present, and a second node `b` which receives the video signal S.sub.2 to 
be reproduced from a recording medium. Accordingly, the video signal 
S.sub.1 is supplied to the sync separator 13 via the first node `a`, and 
the video signed S.sub.2 is supplied to the sync separator 13 via the 
second node `b`. 
A photographer should operate a corresponding key among various keys of the 
control panel 11 when proceeding from the present operating mode into the 
next operating mode of the camcorder. The controller 12 performs the 
operation as shown in FIG. 2 when the function key signal Skey is supplied 
from the control panel 11. 
FIG. 2 is a flow chart illustrating the operation of the controller 12. 
First, the controller 12 determines whether the function key signal Skey 
is supplied from the control panel 11 (step 210). When the function key 
signal Skey is not detected, the controller 12 determines whether the 
display time T.sub.DISP of the timer, for displaying character data is "0" 
(step 270). When the display time T.sub.DISP is "0", the controller 12 
clears the character data from a display status (step 280), thereby ending 
the character display operation. When the display time T.sub.DISP not "0", 
the controller 12 continues operation of the timer (step 260). The timer 
functions to count time during display of the character data, which will 
be described in FIG. 3. Step 270 is repeated by the controller 12 until 
the display time T.sub.DISP is "0". 
When a function key signal Skey is detected, the controller 12 checks the 
present operating mode (step 220), and judges whether the input function 
key signal Skey is effective for changing the present operating mode (step 
230). For example, in the case that the input function key signal Skey 
corresponds to a stop mode under the present operating mode, the input key 
signal is determined to be an effective key and the controller 12 controls 
each part of the system so that operation is accomplished from the present 
operating mode to the stop mode. In the case that the input function key 
signal Skey corresponds to a record mode when the camcorder is presently 
operating under the play mode, the input key signal is determined to 
correspond to a non-effective key and the controller 12 controls each part 
of the system so that character data which represents the effective keys 
in the present operating mode is displayed (step 240). The display time is 
set at step 250, and the timer is actuated at step 260. 
FIG. 3 is a flow chart illustrating the operation of the timer incorporated 
in the controller 12. The timer pushes the display time on the monitor 
and/or the EVF of character data stored in storing means (not shown) (step 
310). The timer judges if the pushed time is "0" (step 320), and pops the 
time itself at the storing means when the pushed time is "0", and then 
ends the operation. The timer value is decremented by one each second (in 
the case of a second-timer) when the pushed time is not "0" (330). The 
reduced time is popped at the storing means at step 340 and the operation 
is completed. 
Referring to FIG. 2, along with the operation of the timer as shown in FIG. 
3, the controller 12 checks the present operating mode and the display 
time T.sub.DISP of character data which indicates the effective keys 
corresponding to the present operating mode (step 270). The controller 12 
controls the operation so that step 270 and step 260 are repeated when the 
character data is not displayed for a preset time. When the character data 
is displayed for the preset time, the data under a display status is 
cleared (step 280) and the operation is completed. Table 1 shows whether 
mode keys in the present operating mode are effective keys for altering 
the operation of the camcorder from the present operating mode. In 
addition, the left side modes are first performed when a plurality of key 
signals are input. 
TABLE 1 
__________________________________________________________________________ 
Conversion Mode 
REC 
DUB REC 
DUB REC 
+ + + + F/ + 
Present Mode 
STOP 
EJT 
REW FWD FPS 
RPS 
STILL 
NPB 
NPB NPB 
SPB 
FPB 
PAU 
PAU ADV DUB 
__________________________________________________________________________ 
STOP .largecircle. 
.largecircle. 
.largecircle. 
X X X .largecircle. 
.largecircle. 
.largecircle. 
X X X X X X 
EJECT .largecircle. 
X X X X X X X X X X X X X X 
REW .largecircle. 
.largecircle. 
.largecircle. 
X X X .largecircle. 
.largecircle. 
.largecircle. 
X X X X X X 
FWD .largecircle. 
.largecircle. 
.largecircle. 
X X X .largecircle. 
.largecircle. 
.largecircle. 
X X X X X X 
STILL .largecircle. 
.largecircle. 
X .largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
X X .largecircle. 
.largecircle. 
REC + .largecircle. 
X X X X X X X X X X .largecircle. 
X X X 
NPB 
DUB + .largecircle. 
X X X X X X X X X X .largecircle. 
X X X 
NPB 
NPB .largecircle. 
.largecircle. 
X X .largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
X X X X 
SPB .largecircle. 
.largecircle. 
X X .largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
X X X X 
FPB .largecircle. 
.largecircle. 
X X .largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
.largecircle. 
X X X X 
REC + .largecircle. 
X X X X X X .largecircle. 
X X X X .largecircle. 
X X 
PAU 
DUB + .largecircle. 
X X X X X X .largecircle. 
.largecircle. 
X X X .largecircle. 
X X 
PAU 
REC + .largecircle. 
X X X X X X X X X X X X X X 
DUB 
__________________________________________________________________________ 
.largecircle.: possible mode 
X: impossible mode 
Referring to FIG. 1, the sync separator 13 detects a sync signal Sync from 
the selected video signal supplied from the switch SW and simultaneously 
supplies it to the OSD unit 14 as well as to the first and second mixers 
15 and 16, respectively. The OSD unit 14 receives information representing 
a present operating mode from the controller 12 and determines character 
data corresponding to effective keys of the present operating mode, 
synchronizes the character data with the sync signal Sync supplied from 
the sync separator 13, and outputs both record character data CHAR for 
recording character data and non-record character data NCHAR for 
displaying on the monitor and/or EVF. The first mixer 15 outputs data by 
overlapping the character data CHAR from the OSD unit 14 onto the video 
signal input via the sync separator 13 where the camcorder is set to a 
camera mode. The video signal, to which the record character data CHAR is 
inserted, is supplied to the recorder 17 so that it can be recorded on the 
recording medium. 
The second mixer 16 outputs data by overlapping the non-record character 
data NCHAR from the OSD unit 14 onto the video signal input via the sync 
separator 13 when the camcorder is set to a camera mode or a VTR mode. The 
video signal, into which the non-record character data NCHAR is inserted, 
is supplied to the monitor 18 and the EVF 19, which are coupled to the 
camcorder, respectively. The monitor 18 and/or the EVF 19 display the 
signal supplied from the second mixer 16 so that an operator can easily 
recognize the operating modes which are available in the present operating 
mode of the camcorder. 
As described above, a method and apparatus for displaying information 
corresponding to effective keys according to the present invention 
provides for easy operation of the camcorder by informing a user of 
effective keys capable of being operated to change the operation from the 
present operating mode to next operating mode.