JPH0319756B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an electronic still camera that takes and records still images.

2. Description of the Related Art As shown in FIGS. 3A and 3B, there are two main methods for determining the scanning order for each horizontal pixel column of a general solid-state image sensor used in an electronic still camera. The first method is to transfer the signal charge accumulated in each pixel to the pixel in the first field, as shown in Figure 3A.
The 20 horizontal pixel columns are scanned every other column in the vertical direction (scanning shown by the solid line in Figure 3A), and the remaining horizontal pixel columns that were not scanned first are scanned in the second field ( This is a method in which all signal charges are read out in two fields (=1 frame) (scanning indicated by the broken line in FIG. 3A). The second method, as shown in FIG. 3B, is to scan two adjacent horizontal pixel columns in one horizontal scan and read out all signal charges in one field. The first method has the advantage that frame images can be obtained and is suitable for photographing and recording images with good vertical resolution. The second method has the disadvantage that only field images can be obtained and the vertical resolution deteriorates, but images generally have a strong vertical correlation, and even if the vertical resolution is halved, the overall image quality is not as good as that of a frame image. There is no big difference,
It has the advantage that the number of images that can be recorded on one recording medium is twice that of frame images.

Therefore, it has been considered in the past for electronic still cameras to switch between the first and second scanning methods depending on the situation. (For example, Japanese Unexamined Patent Publication No. 149478/1983) An example of this is shown in FIG. In FIG. 4, 1 is a lens, 2 is an aperture, 3 is a shutter, 4 is a solid-state image pickup device, 5 is a signal processing circuit, 6 is a photometric device, 8 is an exposure control circuit, 9 is a solid-state image pickup device scanning method switching switch, 10 is an element drive circuit, 11 is a recording method changeover switch, 12 is a recording head changeover switch, 1
3 is a recording head switching signal input terminal, 14 is a recording device, 15 is a first recording head, 16 is a second recording head, 17 is a first recording area, 18 is a second recording area, and 19 is a recording mode. It is a changeover switch.
Next, the operation shown in FIG. 4 will be explained. Light from a subject (not shown) is guided through a lens 1 to a photometric element 6, where the brightness of the subject is measured.
Based on the information from the camera, the exposure control circuit 8 determines the appropriate exposure amount, and based on this value, when photographing the subject, the aperture value of the aperture 2 and the shutter speed of the shutter 3 are set to values that provide the appropriate exposure amount to the solid-state image sensor 4. Control. Then, the solid-state image sensor 4 is scanned by the drive signal generated by the element drive circuit 10 by the drive signal switched by the scanning method changeover switch 9, and the signal charge is read out and guided to the signal processing circuit 5. It will be destroyed. With the signal processing circuit 5, the recording device 1
The signal processed into a signal format suitable for recording on 4 is led to a recording method changeover switch 11. On the other hand, when either the frame recording mode or the field recording mode is selected with the recording mode changeover switch 19 and the frame recording mode is selected based on this information, the scanning method changeover switch 9 is switched to the terminal A. The recording method switch 11 is connected to terminal A.
You can switch to Further, when the recording mode changeover switch 19 selects the field recording mode, the scanning method changeover switch 9 is changed over to terminal B, and the recording method changeover switch 11 is changed over to terminal B. Note that a drive signal for carrying out the above-described first scanning method is led to the terminal A of the scanning method changeover switch 9, and a drive signal for carrying out the above-mentioned second scanning method is led to the terminal B. shall be taken as a thing. Therefore, when the frame recording mode is selected, the solid-state image sensor 4 is scanned by the first scanning method, and the signal from the signal processing circuit 5 is guided to the terminal A of the recording method changeover switch 11, and the signal is is guided by the head changeover switch 12 to the first recording head 15 for the first field and to the second recording head 16 for the second field. In area 17,
The signal of the second field is recorded in the second recording area 18. Further, when the field recording mode is selected, the solid-state image sensor 4 is scanned by the second scanning method, and the signal from the signal processing circuit 5 is guided to the terminal B of the recording method changeover switch 11, and the signal is sent to the first recording head. 15 is recorded in the first recording area 17. Note that a field switching pulse is supplied to the terminal 13.

Problems to be Solved by the Invention The conventional electronic still camera configured as described above has the following problems. In other words, the amount of light from the subject guided to the solid-state image sensor 4 (that is, the amount of exposure) is constant between the frame recording mode and the field recording mode, and therefore the amount of signal charge generated on the solid-state image sensor 4 is also constant. . Then, in order to read out the constant signal amount in one frame or two field periods in the frame recording mode, one field period in the field recording mode, and half the period of the frame recording mode, it is read out in a unit time (for example, one field period). The amount of signals read during the frame recording mode and the field recording mode is 1:
2, and the signal level becomes 1:2. Therefore, the dynamic range of the signal charge readout section and signal processing section of the solid-state image sensor 4 needs to be twice as large as, for example, an electronic still camera that is limited to only frame recording mode or only field recording mode. There is a first problem. Furthermore, there is a second problem in that the signal level recorded in the recording device 14 is 1:2 in the frame recording mode and in the field recording mode.

The present invention has been made in view of this point, and has a frame recording mode and a field recording mode.
By keeping the amount of signals read from the solid-state image sensor per unit time constant, the level of the signal passing through the charge reading section and the signal processing section of the solid-state image sensor and the level of the recorded signal are constant.

Means for Solving the Problems The present invention provides a solid-state imaging device whose pixel array is configured to output a frame image, and a scanning state of a horizontal pixel row of the solid-state imaging device, which is configured to output a frame image. Read out the signals simultaneously in one scan,
The first scanning state scans the entire screen in one field period, and the first field sequentially scans the signals of odd or even horizontal pixel columns one column at a time, and the second field scans the signals of the remaining pixel columns one column. a first switching means for switching to a second scanning state in which the entire screen is scanned in one frame period, and a recording mode is changed between field image recording and frame image recording in conjunction with the first switching means; a second switching means for switching, a photometry circuit that calculates an appropriate exposure amount according to subject illuminance, an exposure control unit that applies the appropriate exposure amount to the solid-state image sensor, and a signal processor that processes the output signal of the solid-state image sensor. The amplification factor of the signal processing circuit is kept substantially constant, and the appropriate exposure amount is switched at a ratio of approximately 1:2 between the first scanning state and the second scanning state.

Effects According to the above-described configuration, the amount of exposure to the solid-state image sensor is switched between the frame recording mode and the field recording mode, and the amount of signal charge generated in the solid-state image sensor is changed. In both modes, this changed amount of charge is read out by changing the period, so the amount of charge read out per unit time can be made constant in both modes, so the signal level is constant and the S/
N output signals can be obtained.

Embodiment FIG. 1 is a block diagram showing a first embodiment of the present invention. In FIG. 1, 1 is a lens, 2 is an aperture, 3 is a shutter, 4 is a solid-state image sensor whose scanning method can be switched as shown in FIGS. 3A and B, and 5
1 is a signal processing circuit, 6 is a photometric element, 7 is a variable gain amplifier, 8 is an exposure control circuit, 9 is a scanning method switching switch, 10 is an element driving circuit, 11 is a recording method switching switch, 12 is a recording head switching switch, 13
14 is a recording head switching signal input terminal, 14 is a recording device, 15 is a first recording head, 16 is a second recording head, 17 is a first recording area, 18 is a second recording area, and 19 is a recording mode switch. It's a switch.

When the frame recording mode is selected by the recording mode changeover switch 19, the amplification degree of the variable gain amplifier 7 is switched to G times, and the signal from the photometric element 6 is amplified by G times by the variable gain amplifier 7 and sent to the exposure control circuit 8. be guided. The exposure control circuit 8 controls the aperture value of the diaphragm 2 and the shutter speed of the shutter 3 so as to provide the solid-state image sensor 4 with an appropriate amount of exposure based on this photometric information. Then, the signal charges resulting from this appropriate exposure amount are read out by the first scanning method as shown in FIG. 3A for two field periods as explained in the conventional example in FIG. 5. Recording method selection switch 11, recording head selection switch 12, first recording head 15, second recording head
The first recording area 17 and the second recording area 1 are recorded one field at a time through the recording head 16 of
Recorded in 8.

Next, when the field recording mode is selected by the recording mode changeover switch 19, the gain of the variable gain amplifier 8 is increased by 2G, and the scanning method changeover switch 9 changes the signal for performing the second scanning method shown in FIG. 3B. The recording method changeover switch 11 is switched to the terminal B side where the signal is inputted from the element drive circuit 10. The signal from the photometric element 6 is then amplified by a factor of 2G by a variable gain amplifier 7 and is then amplified by an exposure control circuit 8.
guided by. Therefore, the photometric information guided to the exposure control circuit 8 in the field recording mode, that is, the information regarding the brightness of the subject, will show twice the value as in the frame recording mode even if the brightness of the subject is the same. . Therefore, the appropriate exposure amount calculated by the exposure control circuit 8 is 1/2 that of frame recording (for example, if the lens aperture value is constant, the shutter time value is 1/2). The amount of incident light on the subject is 1/1 in frame recording mode.
2. Therefore, the amount of signal charge generated in the solid-state image sensor 4 is also halved. However, this 1/2 amount of charge can be reduced to 1/2 of that in frame recording mode.
Since reading is performed in one field period of the period , the amount of signal charge read out per one field period is the same as in the frame recording mode, and therefore the signal level is also the same. Then, the signal read out from the solid-state image sensor 4 and having the same signal level as in the frame recording mode is transmitted to the signal processing circuit 5, the recording method changeover switch 11, as in the conventional example shown in FIG. - Recorded in the first recording area 17 via the first recording head 15.

As described above, the amount of signal charge read out from the solid-state image sensor 4 per unit time is the same in the frame recording mode and in the field recording mode.
Therefore, the signal level guided to the signal processing circuit 5 and the recording device 14 is the same in both modes.

In the above embodiment, the degree of amplification of the signal from the photometric element 6 is switched to 1:2 between the frame recording mode and the field recording mode using the variable gain amplifier 7, so that the signal can be recorded as if it were a frame recording. Information such that the brightness of the subject changes 1:2 between mode and field recording mode is sent to the exposure control circuit 8, and the amount of exposure to the solid-state image sensor is configured to be 2:1. However, by any method, the amount of exposure to the solid-state image sensor can be adjusted to 2:1 between frame recording mode and field recording mode.
It is clear that the present invention can be constructed in any case.

FIG. 2 is an example of this, in which even if the photometric element information is the same, the exposure control circuit 21 is changed depending on the information from the recording mode changeover switch 19 in the frame recording mode and in the field recording mode. This is an example in which the exposure control circuit 21 is configured so that the calculated appropriate exposure amount value is 2:1. Other operations are the same as in FIG.

Effects of the Invention As explained above, according to the present invention, even if the scanning method of the solid-state image sensor is switched between frame recording mode and field recording mode, the same level of signal can be output from the solid-state image sensor. This makes it possible to make the recording signal level and the signal level for signal processing in the signal processing circuit the same, which has a great practical effect.

In addition, the S/N of the output signal recorded in the above two recording modes is almost the same, and the field recording mode uses a high-sensitivity electronic still camera, while the frame recording mode uses a high-resolution electronic still camera with no S/N deterioration. It also has the effect of a still camera.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention;
FIG. 2 is a block diagram showing another embodiment of the present invention;
3A and 3B are explanatory diagrams showing a scanning method of a solid-state image sensor, and FIG. 4 is a block diagram of a conventional electronic still camera. 1...Lens, 2...Aperture, 3...Shutter, 4...Solid-state image sensor, 5...Signal processing circuit,
6...Photometric element, 7...Variable gain amplifier, 8...
Exposure control circuit, 9...Scanning method switching switch, 1
0... Element drive circuit, 11... Recording method changeover switch, 14... Recording device, 19... Recording mode changeover switch.

Claims (1)

[Claims] 1. A solid-state image sensor whose pixel array is configured to output a frame image, and the scanning state of a horizontal pixel column of the solid-state image sensor, by simultaneously reading signals of two adjacent horizontal pixel columns in one scan, The first scanning state scans the entire screen in one field period, and the first field sequentially scans the signals of odd or even horizontal pixel columns one column at a time, and the second field scans the signals of the remaining pixel columns one column. sequentially scan 1
a first switching means for switching to a second scanning state in which the entire screen is scanned in a frame period;
a second switching means that switches the recording mode between field image recording and frame image recording in conjunction with the switching means; a photometry circuit that calculates an appropriate exposure amount according to the subject illuminance; It consists of an exposure control section that applies an exposure to the element, and a signal processing circuit that processes the output signal of the solid-state image sensor, and maintains the amplification factor of the signal processing circuit approximately constant and adjusts the appropriate exposure amount to the first scanning state. An electronic still camera characterized in that the electronic still camera is configured to switch approximately 1:2 between a second running state and a second running state.