JPH0276380A - Electronic still camera - Google Patents

Abstract

PURPOSE:To utilize electric charges stored in a sensor effectively and to improve the resolution and sensitivity at field picture recording by adopting one-line readout drive in the case of frame picture recording and frame sensitivity for the changeover of sensitivity and adopting 2-line readout drive in the case of field picture recording and field sensitivity for the changeover of sensitivity. CONSTITUTION:When a field/frame SW is thrown to the position of the field, a control circuit 8 switches the sensitivity of an exposure control circuit 24 to the field sensitivity and a camera circuit 5 also selects a field signal processing. After the end of exposure by the opening/closing of a shutter 21, a drive circuit 4 applies 2-line readout, a field picture is extracted from a sensor 3 and recorded in a recording section 6 through the camera circuit 5. Since signals from two photodiodes of (2n+1) and (2n+2) lines are read out, the signal charges obtained by photoelectric conversion are doubled and then the sensitivity is improved. Since the G component is included in picture element pitches in the horizontal direction, that is, in all columns of m, (m+1), the horizontal resolution is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to exposure control and signal processing during field/frame switching recording suitable for electronic still cameras.

[Conventional technology]

Exposure control of conventional electronic still cameras is described in "Electronic Still Cameras" by Bengami, Nakajiro, Nakazuke et al., Television Science and Technology Report, TEB.
Sloo-4, 8, 35, pp.

17-22 (Dec, 1984), it has been shown that sufficient accuracy can be achieved in exposure control by direct photometry. However, with regard to switching recording between fields and frames, no consideration has been given to the effective use of charges incident through the lens and accumulated in a solid-state image sensor (hereinafter referred to as a sensor).

(Problems to be Solved by the Invention) The above-mentioned conventional technology does not take into consideration the effective use of charges accumulated on the sensor by a sensitive shutter etc. during field recording, and if There is a problem in that when only one first or second field image is recorded, the remaining signals are discarded.

An object of the present invention is to effectively utilize signal charges accumulated in a sensor to improve resolution and sensitivity during field image recording.

[Means to solve the problem]

The above objective is, firstly, to perform so-called one-line readout for frame image recording, and to perform so-called two-line simultaneous readout by selecting a line that increases the resolution during field image recording, a sensor and its drive, and a second signal processing means. It has two sensitivity settings corresponding to each of the above-mentioned readings, field sensitivity when recording a field image and frame sensitivity when recording a frame image, and has an exposure control means to adjust the amount of exposure according to each sensitivity. This is achieved by

[Effect]

The switching between one line and two lines and the readout and the sensitivity of the exposure control means are carried out as follows. First, in the case of frame image recording, the sensor is driven to read out one line, and the sensitivity is switched to capture and record the image with frame sensitivity. In the case of field image recording, the sensor reads two lines, and the sensitivity is switched to field sensitivity. This allows exposure to be controlled in response to changes in sensitivity when reading out one or two lines, thereby improving image quality by using more picture elements when reading out two lines during field recording, and at the same time improving image quality at the time of each switch. Appropriate exposure control is performed, and the charges accumulated in the sensor can be effectively used.

〔Example〕

An embodiment of the present invention will be explained with reference to FIG. In this example, the so-called aperture priority method will be explained as an example of the exposure control method.

In the figure, 1 is a lens, 21 is a shutter, 22 is a photometry circuit, and 23 is a grise 9 for inputting a preset aperture value.
1 to circuits, 231 is a display device, 24 is an exposure control circuit, 3
1 is a sensor, 31 is a variable gain amplifier, 4 is a drive circuit, 5 is a camera circuit, 6 is a recording unit, 71 is a frame/frame SW which is a switch for determining whether to select and record a field image or a frame dual-light image, 72 is the release SW, which is a switch that takes pictures by pressing the shutter button.
, 711 is a sensitivity setting input device, and 8 is a control circuit.

A schematic diagram showing one embodiment of the sensor 3 is shown in FIG. In the figure, 301 indicates a picture element on the sensor.

As shown in the figure, each picture element is equipped with a well-known Bayer array color filter of G (clean), R (red), and B (blue).

When reading a frame image, the sensor 3 reads out 2n, 2n+2, . . . for the first field 1, 2n+1.2n+3, . . . for the second field, etc.
It is assumed that so-called one-row interlaced readout is performed, and G, R, and B signals are output from terminals 311, 312, and 313 as signal charges of color picture elements, respectively. When reading out a field image, it is assumed that so-called two-line simultaneous reading is performed in which two horizontal line pairs are read out. It should be noted that the method of configuring the internal wiring etc. of the sensor 3 can be easily configured by a person skilled in the art if its operational specifications are shown as described above; for example, Masuda et al.
TEBSloo-2, 8, 35゜Pps-10 (Dec
, 1984).

The operation of the first embodiment will be explained in the third section below with reference to the same sensor 3.
This will be explained along the flowchart shown in the figure.

First, after the power is turned on, the setting value of the sensitivity setting input device 711 is taken in. Accordingly, the gain of the variable gain amplifier 31 is changed to change the sensitivity of the sensor. At this time, the exposure control circuit 2
At the same time, the exposure settings for shooting in step 4 are changed. The first feature of the present invention is to change the settings of the exposure control circuit in response to changes in sensor sensitivity due to changes in sensor readout.

This sensitivity switching will be described in detail later in other embodiments.

Next, set the input direction of field/frame SW71 to circuit 8.
(Step 1) For example, when the control circuit 8 detects that the light is being applied to the frame side, the exposure control circuit 24
Set the sensitivity setting to the frame side. This sensitivity setting and control will be explained later. After setting on the frame side, the exposure control circuit 24 displays the shutter speed calculated from the output value of the photometry circuit 22 and the output value of the preset value 23 on the display device 231 (step 2).

Next, when the control circuit 8 detects that the release 5W72 has been pressed (step 3), the circuit sends an exposure start signal to the exposure control circuit 24. At the same time, after noise components such as dark current are removed by driving the drive circuit 4, reading is stopped and a standby state is entered. The camera circuit 5 is set to carry out signal processing for reading one line, which will be explained later. shutter 2
After the exposure is completed by the opening/closing operation of step 1, the drive circuit 4 reads out one line and takes out the frame signal from the sensor 3.
The image is recorded by the recording unit 6 through the camera circuit 5 (Step 4).

In addition, since a loop is created in the flowchart of FIG. 3, when the input of the field/frame SW changes to the field side, the control circuit 8 immediately detects the change and changes the input to the exposure control circuit 24.
Switch the sensitivity of the camera to field, switch the camera circuit 5 to field signal processing (step 5), release 5W.
After 72 is turned on, an exposure start signal is sent to the exposure circuit 24. At the same time, the drive circuit 4 stops the subsequent output after the noise component has been ejected, and the exposure standby state is established. Shark 21
Depends on opening/closing operation. After the exposure is completed, the drive circuit 4 reads out two lines and takes out the field side from the sensor 3.
It is recorded in the recording unit 6 through the camera circuit 5 (step 4).

In this case, the following points have changed with respect to the frame image.

(1) Doubling the signal amount If the exposure time is the same, signals from two photodiodes in the 2n+1 row and 2n+2 row are read out on the field side, so the signal charge obtained by photoelectric conversion is doubled, improving sensitivity. That means you did it.

(2) Improvement in resolution In the pixel array shown in Figure 2, if two rows are read out simultaneously in a pair of rows 2n+1 and 2n+2, the G component will be equal to the pixel pitch in the horizontal direction, that is, m, m+1° in all columns. Since it is included in the horizontal resolution, the horizontal resolution can be improved.

Therefore, for (1), it is necessary to change the sensitivity, that is, the shutter speed (or aperture), and for (2), by increasing the band of signal processing, etc., the resolution of the frame image can be improved. Note that, of course, even if no particular changes are made to the signal processing, the MTF at the time of the signal increases, so a high-quality image with improved sharpness of edges and the like can be obtained.

Now, with the above control, in the case of frame image shooting, a frame image is read out by one line, and in the case of field side shooting, 2 frame images are read out.
It was shown that by taking out the field side of the line readout from the sensor 3 and performing appropriate exposure control by switching the sensor sensitivity during down-down, it is possible to obtain high-sensitivity, high-quality images even in the field. Next, signal processing and exposure control when reading one or two lines will be described in more detail by giving an example.

FIG. 4 shows an embodiment of the signal processing circuit, and FIG. 5 shows its driving pulse.

In Fig. 4, 3 is a sensor, 41 is a drive circuit 1.51
is IHDL with a delay time of one horizontal period.

52, 53 are switches SWI, SW2 .
54 is a camera circuit 1, and 6 is a recording section.

Here, the sensor shown in FIG. 2 is used as an example of the sensor 3 for explaining this embodiment.

When the field/frame SW shown in the figure is applied to the frame side this year, the control circuit 8 sets the drive circuit 41 to the one-line read drive described above, and controls the SWI 52 and SW 2 for signal processing. The signal in Figure 5 (
D) The waveform is shown in (E). Frame read sensor 3
From then on, the G component is output continuously every line, and the RB acid component is output alternately every other line. Therefore, by applying such a control signal, the R or B line sequential signal in the case of one line readout becomes a continuous signal, and the RGB is changed for each horizontal line.
Since the signal can be obtained, it is input to the camera circuit 541, and a video signal can be obtained. The processing of the video signal itself by γ processing etc. in the camera circuit 54 is similar to the signal processing of a general camera.

In the case of a field, the control signals shown in FIGS. 5(b) and 5(c) are input. In this case, the R, G, and H color components are output for each horizontal line because the reading is performed in line pairs of 2n+1 rows and 2n+2 rows. Therefore, it is sufficient to input the signal to the camera circuit 1 without passing through the HDL 51.

Here, the occurrence of blurring due to a decrease in vertical resolution, which tends to be a problem in field images, can be reduced by reading out two lines at the same time, since the aperture ratio is improved and the FMT is reduced. At the same time, the pixel pitch is doubled in the horizontal direction, resulting in high resolution. Therefore, a high-quality screen with improved sharpness and less blurring can be obtained.

Next, taking the so-called direct photometry control method as an example of a control method, one embodiment of the exposure control circuit is shown in FIG.
This will be explained with reference to the waveform diagram in FIG.

In FIG. 6, 251 is a silicon photodiode (SPD) which is an example of a light receiving element, 262 is a reset switch SW3, 261 is an integrating capacitor, 26 is an amplifier forming an integrating circuit, 27 is a comparator, and 273 is a sensitivity This is a changeover switch SW4, and is changed over by a control circuit (not shown) in response to an input to the field/frame changeover SW.

Reference numeral 271 is a frame reference for setting sensitivity during frame imaging, 272 is a voltage source for field use during field imaging, and 252 is a control unit such as a shutter.

This block diagram shows only the basic part of the exposure control circuit using direct photometry, and is a block that controls the operation from the moment the shutter is opened until it is closed. The rest is essentially the same as the configuration shown in FIG. 1 and will not interfere with the explanation, so it will be omitted.

When the release 5W72 is now pressed and the shutter 21 is opened by an opening device (not shown), at the same time the reset switch S
W3 opens and starts integrating the signal from 5PD251. Here, the 5PD 251 is a part of the III'1 optical circuit 22, and the irradiation of light to the 5PD 251 can be easily configured using a half mirror (not shown) or the like.

The integral output is shown in FIG. 7 (H). Now, when the integration is started, at the input position of 5W273 shown in FIG. 6, that is, in the state of exposure to the frame, the integral waveform shown in FIG. 7 (H) is the frame base 4I! 271 voltage (g) of 271
When the reference voltage of the comparator 27 shown in is reached, the waveform (9
) is generated and manually input to the control section 252. The control unit 252 uses the shark 2 as this trigger.
Close 1. As described above, the shutter is opened and closed to perform exposure. Note that in the case of field imaging, the voltage of the power source 272 is set low as shown by V272, so the shutter 21 is closed at a faster shutter speed than for frame imaging.

As mentioned above, two rows of sensors in the field and frame,
It has been shown that it is possible to construct an electronic still camera capable of high resolution and high speed scanning by reading out one line and simultaneously switching the sensitivity of the exposure circuit to obtain appropriate exposure.

I did not mention anything about the sensitivity switching setting level here, but this is because the MO3 type sensor is CCDC.
This cannot be said in part because it varies depending on the top size, etc., and the signal processing. For example, the sensor shown in Figure 2 is a MOS
If you try to oval it with a shape and read it with a field,
The signal amount will be doubled, but the signal line capacitance of the sensor will increase due to the two-line readout, and considering the same S/N, the sensitivity will be reduced by 6d.
B rise is difficult. In the case of the CCD type, there is no increase in signal line capacitance inside the sensor, so an increase of approximately 6 dB is expected. It is desirable to fine-tune the sensitivity setting of the lightning control based on this sensitivity change experimentally since there are other factors such as the shutter.

Next, an embodiment in which the photometry control method can be freely selected is shown in FIG. 8 and will be described below. In this example, the photometric display is performed using so-called open photometry, and the exposure control is performed using direct photometry.
1 is a shutter movement device, 221 is a light receiving unit, 241 is a direct photometry control circuit, 242 is a memory photometry control circuit, 23 is a preset input device for aperture value etc. in the case of the aperture priority method, 3 is a sensor, and 31 is a variable Gain amplifier, 4 is drive circuit,
81 is a control circuit 2. 71 is a field/frame SW,
711 is a sensitivity setting input device, 72 is a release SW, 24
3 is a display device, 811 and 812 are switches swi, and SW2, 311, 242, 2422, and 2423 are terminals.

The operation shown in FIG. 9 will be explained using the flowchart shown in FIG.

It is assumed that the switches 5W811 and 812 are initially turned on in the orientation shown in FIG. The control circuit 81 inputs the sensitivity setting value from the sensitivity setting input device 711, which is a trade-off with the S/N, such as field recording or frame recording and whether the sensitivity is normal, high sensitivity, or low sensitivity. From the value (step 6). Control circuit 81 Based on information input manually, memory photometry control circuit 242
The exposure amount is set for the direct photometry control circuit 241. If the sensitivity is normal and frame readout is OdB, this setting value is approximately 6 dB for field image capture.
Is the dB decrease input from the sensitivity setting input device 711?
For example, in the case of a 6 dB increase in sensitivity, the value is set to a value that is further reduced by 6 dB.

At the same time, in this case, the variable gain amplifier 31 receives a gain of 6d according to the sensitivity setting value from the sensitivity setting input device 711.
Set the B rise. For the drive circuit 4, the drive is switched to two-row readout (step 7).

Next, when performing so-called open photometry, the memory photometry control circuit 242 opens the aperture (not shown), measures the light incident on the lens 1 in that state using the photometer 221, and also uses the preset input device Aperture value from 23 and control circuit 81
The shutter speed is calculated from the sensitivity setting value inputted from and displayed on the display device 243 (step 8). Here, the calculation of the display value has already been performed by the film camera. For example, a calculation method using an Apex value (APEX value) can be easily performed, so a description thereof will be omitted.

In this case, it goes without saying that the sensitivity setting value from the control circuit 81 may be treated in the same manner as the film sensitivity.

The above steps are steps for performing photometry and display when, for example, the power switch (for example, if the shutter button is a two-stage switch, corresponds to the first stage of turning on) is input. Next, it is detected (step 9
), the control circuit 81 turns on the switches SW811 and SW812 in the opposite direction, and prepares the direct photometry control circuit 241 to perform exposure control. At the same time, the diaphragm (not shown) is stopped down to a preset value and the sensor 3 is brought into a reset accumulation state (step 10). Next, the direct photometry circuit 241
controls the shutter 21 by opening and closing it so that the amount of exposure that enters and accumulates in the sensor 3 corresponds to the sensitivity setting value based on the output from the photometer 221 (step 11). After the exposure is completed, the sensor 3 is read out, and the image signal processed by the camera circuit 5 (not shown) is recorded in the recording section 6 through the variable gain amplifier 31 whose gain is adjusted according to the sensitivity setting (step 12). Thereafter, the switches 5W811 and 812 are returned to their initial states again in preparation for the next photographing.

Photography is performed using the shutter through the operations described above, but photography using a strobe is also performed using the direct metering circuit 241.
is the shutter 21 instead of opening/closing control of the shutter 21.
This is easily possible if you use so-called TTL strobe control, which controls the start and stop of strobe light emission with the camera open.Also, in shutter photography as described above, instead of controlling exposure using direct metering, it is possible to use memory metering. Exposure control may be performed using memory photometry, in which the shutter is released at the shutter speed that has been set.

In the example of the sensor shown in FIG. 2, an example of a MOS type sensor in the literature by Masuda et al. is cited, and other examples, such as a CCDC upper type sensor, are not particularly mentioned. Therefore, an example of the case of a CCD type sensor will be explained below. In general, in the MOS type, each picture element and the output terminal are connected via a MOS switch, so it is easy to configure one or two line readout by selecting the switch, but even in the CCD type, if the order of charge transfer is taken into account, it will be explained below. It can be easily realized as follows.

For example, Kochi et al.'s Television Zendaijo pp. 57-58 (1984
) "Two-line readout type CCD image sensor" In the two-line readout type CCD image sensor, two vertical CCD lines are provided for one photodiode column, and two rows are read out simultaneously.

With such a configuration, if each vertical CCD line is used alternately, it is possible to change to one-line reading, but it is not necessary to provide two vertical CCD lines in this way.

FIG. 10 shows one embodiment of a CCD sensor.

310 is an overflow train, 311 is a photodiode, 312 is a transfer gate, 313 is a vertical CC
D, 314 is a horizontal CCD, 315 is an amplifier, 320 is an overflow drain output terminal, 321 is a transfer gate terminal, 322. 323°324.325 is vertical C
CD313 motion pulse input terminal, 326, 327 horizontal CCD31-4 motion pulse input terminal, 328 signal output terminal, 320 distribution SW, 331 distribution pulse input terminal, 332.333. 334 is a signal output terminal. The feature of this embodiment is the vertical CCD 313, and the rest is almost the same as a normal interline CCD. That is, for example, in the first field, the charge of P-1 of the photodiode 311 is converted to V-1 of the vertical CCD 313.
After similarly transferring the charge of P-2 to V-3, etc. by the transformer gate 312, the vertical CCD 313
The water is transferred to the water CCD 314 by the driving pulse, and is output to the distribution circuit 330 through the preamplifier 315.
The signals are distributed and output to terminals 332 to 334. Here, the explanation regarding colorization using pulses, color filters, etc. on the photodiode 311 is that the essence of the present invention is to change the exposure amount according to one line, two lines, or sensitivity switching, and colorization However, once the color filter arrangement and the like are determined, the distribution timing, signal processing, etc. can be easily realized by those skilled in the art, so the explanation will be omitted.

Note that the charge of P-1 of the photodiode 311 is vertical CC.
Although it has been explained that the signal is transferred to V-1 of D313, this is of course closely related to the potential of V-1. This will be explained using FIG. 11, and it will be shown that one or two row read operations are possible. Elements in FIG. 11 with the same numbers as in FIG. 10 are elements that perform the same functions. However, for the transformer gate 312, T-1, T
The gates are marked as -2... to clearly show the transfer of charges (assumed to be electrons in this case) from the photodiode 311 to the vertical CCD 313. Further, the vertical CCD 313 schematically shows charges. Hereinafter, the operation will be explained by explaining the potential waveforms (a) to (e) below. The waveform (A) in FIG. 11 shows the potential distribution under the vertical CCD 313 when the same potential is applied to the terminals 322 to 325. Now, after changing the potentials of terminals 332 and 334 to obtain the potential distribution shown in waveform (b), turn on 1 to 1-312, as shown in waveform diagram (b).
f) The charge on the photodiode 311 shown schematically is
The signal is transferred via the transfer gate 312 to a lower potential portion of the vertical CCD 313 indicated by (g).

Thereafter, driving pulses are applied to the terminals 322 to 325, and the signals are sequentially transferred as shown by waveforms (C) and (D), and signal charges are sent to a horizontal CCD (not shown). The arrow indicated by (nu) in waveform (d) indicates that charge is sent to the next stage by lowering the potential.

On the other hand, in one-row frame readout, by changing the applied voltage only to the terminal 322 and turning on the transfer gate 312 after changing the potential distribution, as shown in the waveform (E), P-L, P-3, P-3 of the photodiode 312,・・・
・The charge shown in (C) above is on the vertical CCD 313 (S)
Transferred as shown in .

In the next field, change the applied voltage only to the terminal 324 and turn on the transfer gate 312.

The charges on P-2, P-4, . . . of the photodiodes 312 are transferred onto the vertical CCD 313. As mentioned above, even a CCD type image sensor can easily read out a single row frame.
Alternatively, it is possible to read two rows of fields at the same time, and since the signal amount changes in response to each readout, the shutter time and the like are changed.

Of course, this is not the only method for implementing one-row and two-row switching readout. For example, a vertical CCD as shown in FIG.
It can also be a configuration. In the figure, 300' is a sensor;
Elements with a dash "1" in the numeral are elements having the same functions as the elements without a dash in FIG.

The operation is similar to that shown in Figure 11 and will not be described in detail, but
In field readout, one non-signal potential well section is sent in the opposite direction to the signal flow.

In frame readout, signals are transmitted to a horizontal CCD (not shown) by sending two out of three no-signal potential wells.
send to

Above, we have explained simultaneous reading of one line or two lines in MOS type and CCD type image sensors, but of course this is not the only option.
ction 'rtransistor) type sensor or C
CD (Charge Priming Devi
The present invention can be applied to a sensor such as a ce) type sensor, in which an active signal processing pond is configured to enable switching between one-line and two-line readout.

Further, although the above description has been made regarding normal shutter photography, it goes without saying that the present invention is also possible under special lighting conditions such as a strobe light. That is, this can be easily implemented by switching the settings of the strobe dimming circuit according to the field and frame readout methods. At this time, for example, if the light is adjusted by direct photometry, the threshold of an integrating circuit for measuring the exposure amount may be changed, and if the light is adjusted by distance measurement or pre-light emission, the amount of light emitted may be changed.

By the way, in shutter photography, shutter 2 in Figure 1
Although the explanation has been given by adding a shutter to the outside of the sensor 3 as shown in 1, it goes without saying that the shutter function may be installed inside the sensor 3. It is only necessary to switch the sensitivity and change the reading method depending on the row reading.

〔Effect of the invention〕

According to the present invention, since the charges accumulated in the sensor can be effectively used, it is possible to obtain an image with high resolution and high sensitivity during field photography.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is an explanatory diagram showing an example of the sensor of the present invention, FIG. 3 is a flowchart showing the embodiment of FIG. 1, and FIGS. 4 and 5. 8 is a circuit diagram of an embodiment of a signal processing circuit and a waveform diagram for explaining the operation of its control waveform, FIG. 8 is a block diagram of an embodiment of exposure control method switching, and FIG. 9 is a diagram illustrating the same embodiment. Flowchart for, No. 10
11 is a schematic diagram for further explaining the embodiment, and FIG. 12 is an explanatory diagram of another embodiment of the CCD sensor. DESCRIPTION OF SYMBOLS 1... Lens, 21... Shutter, 22... Photometry circuit, 23... Preset circuit, 24... Exposure circuit, 71... Field/frame SW, 72... Release SW, 8 ...Control circuit, 3...Sensor, 4.
... Drive circuit, 5... Camera circuit, 6... Recording section,
51...IHDL, 27...Comparator, 241
. . . Direct photometry control circuit, 242 . . . Memory photometry control circuit, 81 . . . Control circuit, 711 . . . Sensitivity setting input device. Masu buryer to substitute Katsoo Ogawa 'M':, I 1st
Collection 3 Xi 8 + times,] +l 57th compilation 6 Figure (b) 8th 23 7! '7// 72 for q Z collection to m compilation 11 page (ha')e e e Gth
12 plane (α) (b)

Claims (1)

[Claims] A 1-row/2-row readout switching type solid-state image sensor that performs interlace readout every other row of a 1- and 2-dimensional photodiode array to obtain a frame image, and reads out 2 rows simultaneously to obtain a field image; In an electronic still camera comprising a drive circuit, a signal circuit, a recording section, and an exposure control means with first and second sensitivity switching according to the first and second line readouts, the drive circuit reads out one line. An electronic still camera characterized in that a control circuit is provided for switching the sensitivity of the exposure control means to a first sensitivity in the case of drive and to a second sensitivity in the case of two-line readout drive.