Electronic still camera with automatic mode setting device

An electronic still camera having a first switch for selecting either a field record mode or a frame record mode, and a second switch for selecting either a normal mode or a high-band mode, further includes a control circuit which sets the frame record mode either when the high-band mode is selected by the second switch, or when the high-band mode is selected by the second switch and the field record mode is selected by the first switch, in the latter case optionally switching to the frame record mode only if no recording operation is performed during a predetermined time period.

BACKGROUND OF THE INVENTION 
This invention relates to an electronic still camera for recording a still 
picture on a magnetic disc. 
A still camera operates in a field record mode or in a frame record mode. 
In the field record mode, for one object, a video signal for one field is 
recorded on the magnetic disc; and in the frame record mode, a video 
signal for one frame (or two fields) is recorded on the magnetic disc. 
When the magnetic disc makes one revolution for the time period 
corresponding to one field, in the field record mode one picture is 
recorded (one track) with one revolution; and in the frame record mode, 
one picture is recorded (on two tracks) with two revolutions. Accordingly, 
in the field record mode, the number of pictures recorded on one magnetic 
disc is twice as many as that recorded in the frame record mode. However, 
in the field record mode, the number of horizontal scanning lines is half 
of that in the frame record mode, and, therefore, the picture recorded in 
the field record mode has lower resolution than one recorded in the frame 
record mode. 
In addition, there are provided a normal mode and a high-band mode for an 
electronic still camera. In the high-band mode, the frequency modulated 
(FM) carrier of the luminance signal has a higher and wider frequency band 
than in the normal mode. Hence, the horizontal resolution is higher. 
The picture quality factor Q (%) with respect to the number of horizontal 
scanning lines and the recording (transmission) bandwidth is, for example, 
shown in FIG. 2. 
In the conventional electronic still camera, the field/frame record mode 
and the normal/high-band mode can be set independently of each other. 
Therefore, a difficulty oftentimes occurs in that even though the 
high-band mode has been selected, the field record mode is not switched 
over to the frame record mode. Consequently, the recording operation is 
performed in both the high-band mode and the field record mode, thus 
resulting in increased horizontal resolution but decreased vertical 
resolution. Therefore, overall resolution is unbalanced, and, accordingly, 
the effect of the high-band mode is reduced. 
In view of the foregoing, an object of this invention is to eliminate 
errors causing a picture to be recorded with poor picture quality, 
resulting from the field record mode not being switched to a frame record 
mode, even though the high-band mode has been selected. 
SUMMARY OF THE INVENTION 
The foregoing and other objects and features of the invention have been 
achieved by the provision of an electronic still camera which, according 
to the present invention, includes: a first switch for selecting a field 
record mode or a frame record mode; a second switch for selecting a normal 
mode or a high-band mode; a timing circuit for controlling the timing of a 
recording signal supplied to a magnetic head so that a video signal of one 
field or one frame is recorded, according to the mode selected by the 
first switch; a modulator circuit for setting a carrier, which is 
frequency-modulated (FM) with a video signal, according to the mode 
selected by the second switch; and a control circuit which sets the frame 
record mode regardless of the mode selected by the first switch when the 
high-band mode is selected by the second switch. 
If the field record mode has been selected by the first switch, and 
subsequently the high-band mode is selected by the second switch, the 
control circuit forcibly switches the field record mode over to the frame 
record mode immediately, or in a predetermined time period. 
Hence, according to the present invention, an image with high resolution 
and picture quality is formed even though the mode (i.e., the field record 
mode) selected by the first switch becomes inappropriate, after the second 
switch selects the high-band mode and subsequent resetting of the 
inappropriate mode to the proper mode has been neglected.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 3 is a block diagram showing the arrangement of an electronic still 
camera according to the present invention in which an image pickup circuit 
1 including a photo-electric conversion element, such as a charge-coupled 
device (CCD), converts the optical image of an object (not shown) into an 
electrical signal which is inputted to amplifier circuit 2. The electrical 
signal is amplified by amplifier circuit 2, and inputted to modulator 
circuit 3. In modulator circuit 3, a carrier having a predetermined 
frequency is frequency-modulated with the output video signal of amplifier 
circuit 2, and inputted to head change-over circuit 4. Head change-over 
circuit 4 selects one of two magnetic heads (only one magnetic head is 
shown for convenience in description), and inputs the signal to the 
magnetic head thus selected. 
Further, in FIG. 3, a magnetic disc 6 is rotated by an electric motor 7, 
and a servo circuit 8 compares a pulse signal which is outputted by a PG 
coil corresponding to the position rotation of the magnetic disc 6 with a 
predetermined reference signal, thereby to control the rotation of the 
motor 7 according to the difference between the pulse signal and the 
predetermined reference signal. Tracking circuit 10 tracks the magnetic 
head 5, and a timing circuit 11 provides a variety of timing signals to 
the above-described circuits. A control circuit 12 comprising, for 
example, a microcomputer, controls the above-described circuits in 
response to instruction signals provided through switches 13, 14, and 15. 
The frame record mode is selected by turning off switch 14, and the field 
record mode is selected by turning on switch 14. The high-band mode is 
selected by turning off switch 15, and the normal mode is selected by 
turning on switch 15. 
When switch 13 is turned on, control circuit 12 controls, via timing 
circuit 11, the image pickup circuit 1. In this operation, the image of 
the object is sent to image pickup circuit 1, which outputs the video 
signal thereof. The outputted video signal is amplified by the amplifier 
circuit 2, and inputted to modulator circuit 3. In modulator circuit 3, 
the carrier having a predetermined frequency is modulated with the video 
signal so as to produce an output signal. In response to a control signal 
from control circuit 12, the carrier of the luminance signal is set to a 
low and narrow frequency band (for example, from 6 MHz to 7.5 MHz) in the 
case of the normal mode being selected, and is set to a high and wide 
frequency band (for example, from 7.7 MHz to 9.7 MHz) in the case of the 
high-band mode being selected. The output of modulator circuit 3 is 
inputted through the head change-over switch 4 to magnetic head 5, so that 
the output is recorded on predetermined tracks on magnetic disc 6 which is 
being rotated by motor 7 at the speed of one revolution per field (i.e., 
3600 rpm in the National Television System Committee (NTSC) system). 
When the field record mode has been selected, the video signal 
corresponding to one field is read-out of image pickup circuit 1, and 
recorded on one of the coaxial tracks on magnetic disc 6. Alternatively, 
when the frame record mode has been selected, the video signal 
corresponding to one frame is read-out from image pickup circuit 1. The 
first magnetic head 5 selected records the video signal of one field on 
one track, whereupon the head change-over switch 4 is activated to select 
the other magnetic head, so that the video signal of the next field is 
recorded on the next track by the other magnetic head thus selected. 
FIG. 1 is a flow chart describing the operation of control circuit 12 
reading switches 14 and 15 and setting the corresponding modes. In 
operation, it is determined first whether or not the high-band mode is 
specified (i.e., whether or not switch 15 is turned off). When it is 
determined that the high-band mode is selected (i.e., switch 15 is turned 
off), control circuit 12 sets the frame record mode regardless of the 
"on/off" state of switch 14. Consequently, even if switch 14 is turned on, 
control circuit 12 forcibly turns off switch 14. 
When the high-band mode is not selected (i.e., switch 15 is turned on), it 
is determined whether or not the field record mode has been selected 
(i.e., whether or not switch 14 is turned on). When it is determined that 
the field record mode has been selected, then the field record mode is 
set. If it is determined that the field record mode has not been selected, 
then the frame record mode is set. 
In the above-described embodiment, when the high-band mode is selected, the 
frame record mode is set automatically. Only when the normal mode has been 
selected is the field record mode, or the frame record mode, set according 
to the operation of switch 14. 
FIG. 4 is a flow chart describing the mode setting operation of a second 
embodiment of the electronic still camera according to the present 
invention. 
In the second embodiment, the operational status of switch 15 first is 
detected. When switch 15 is in the "on" state (i.e., the normal mode is 
selected), the operational status of switch 14 is read, so that the field 
record mode, or the frame record mode, is set according to the "on/off" 
operational state of switch 14. 
When switch 15 is turned off (i.e., the high-band mode is selected), 
control circuit 12 sets the frame record mode once, and reads the state of 
switch 14. When switch 14 is turned off (i.e., the frame record mode is 
selected), control circuit 12 waits until switch 14 is operated, because 
the set mode (i.e., the frame record mode) has been selected. If switch 13 
is turned on during this stand-by period, the recording operation is 
performed. 
When switch 14 is turned on (i.e., the field record mode is selected), 
control circuit 12 changes the set mode over to the field record mode, 
sets the timer built therein, and then starts the timer. During the 
operation of the timer, the timer is monitored regardless of whether or 
not the recording operation is being performed (i.e., whether or not 
switch 13 is turned on). The monitoring operation continues until the 
timer detects the lapse of a predetermined time period. If no recording 
operation is performed during the predetermined time period, the field 
record mode is switched over again to the frame record mode. 
When the recording operation is performed before the predetermined time 
period lapses, the timer is stopped, reset, and then started again. 
In the above-described embodiment, when the normal mode is selected, the 
field record mode or the frame record mode is set according to the 
"on/off" state of switch 14. When the high-band mode is selected, the mode 
is set as described hereinbelow. When switch 14 selects the frame record 
mode, the frame record mode is set as it is. When switch 14 selects the 
field record mode, the field record mode is set for the predetermined time 
period. If no recording operation is performed during the predetermined 
time period, then the frame record mode is set regardless of the "on/off" 
state of switch 14. If a recording operation is performed during the 
predetermined time period, then the field record mode is set for the 
predetermined time period again. This operation is performed repeatedly. 
Hence, if performing a recording operation in both the high-band mode and 
in the field record mode is required, then the recording operation can be 
conducted by selecting both those modes, and by starting the recording 
operation during the predetermined time period. 
As described above, the electronic still camera according to the present 
invention is designed so that when the high-band mode is selected, the 
frame record mode automatically is set, immediately or in a predetermined 
time period. Therefore, the electronic still camera is improved in 
operability, and images having low picture quality and unbalanced 
resolution will not be recorded unintentionally. 
While certain preferred embodiments have been shown and described, many 
changes and modifications within the spirit of the invention will be 
apparent to those of working skill in this technical field. Thus, the 
scope of the invention should be considered as limited only by the 
appended claims.