JP3330384B2 - Electronic imaging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic image pickup device, and more particularly to an electronic image pickup device for performing photometry with an imager photometer and a sensor photometer.

[0002]

2. Description of the Related Art In recent years, in a video camera or a still camera using an image pickup device, as the performance of a photographic lens and the development of an imager such as an image pickup device have been developed, more responsive photographing and darker lighting have been achieved. It is becoming possible to take pictures. Accordingly, it has been required to determine an appropriate exposure condition of an image as quickly as possible. Conventionally, the exposure condition in the camera is controlled based on photometric data by an imager, that is, an exposure value is calculated by the imager photometry. However, in general, in the image measurement, since the dynamic range of the image is narrow, a photometry value cannot be obtained unless imaging is performed in several fields. That is, the photometric range that must be covered as the photographing subject is 12 to 13 Ev. However, the photometric range of an imager such as a normal CCD is 5 to 6 Ev, and the range that can be used for actual discrimination is about 3 Ev. Therefore, in order to measure the subject's light metering range of 12 to 13 Ev, an appropriate exposure is performed after capturing image signals for some fields while changing the exposure condition of the imager.

FIG. 4 is a diagram showing a field at the time of photometry of the imager.
This indicates a field cycle (VD indicates a vertical synchronizing pulse). When the first test exposure is performed in the first field period T1, the first test exposure is performed in the second field period T2. The exposure reading period is started, and the second test exposure based on the result is performed in the third field period T3. In this way, test exposure is sequentially performed, and finally, appropriate exposure conditions are obtained. Therefore, assuming that photometry in the range of 3 Ev is performed by one test exposure, it is necessary to execute approximately four test exposures in order to perform photometry in the subject photometry range of 12 to 13 Ev. It requires twice the number of fields. If one field is 1/60 SEC,
The above test exposure requires about 130 mmSEC. This is a value obtained when the photometric calculation process is performed in the shortest time using a blanking period or the like in the photometric calculation process,
It actually takes longer. Further, in order to perform a fine test exposure, a longer photometric period is required.

[0006] As a photometry system proposed there, image
An imaging device disclosed in Japanese Patent Publication No. 1-54908 has been proposed as a device capable of quickly performing photometry using both photometric devices by providing a light receiving element separate from the jaw. In other words, this image pickup apparatus is provided with a photoelectric conversion element as a photometry means different from the image pickup means as an imager. The photometric operation of this device first performs coarse photometry by the photoelectric conversion element prior to photometry by the image sensor, and controls exposure of the image sensor based on the output, that is,
Controls the accumulation time of electrical signals. Thereafter, an image sensor performs detailed photometry, and controls the accumulation time of an electric signal corresponding to the subject image based on the photometric output, thereby obtaining subject image photometry information in as short a time as possible. FIG. 7 shows a schematic flowchart of the photometric processing.

[0005]

However, the imaging apparatus disclosed in Japanese Patent Publication No. 1-54908 mentioned above has a possibility that the photometric time is prolonged when the illuminance of the subject is extremely low. That is, a log compression optical sensor circuit as shown in FIG. 5 is used as the photoelectric conversion circuit used as the photometric means. This circuit connects the SPD 21 to the input terminal of the operational amplifier 22, and connects the SPD 21 to the SPD 2 from the output terminal of the operational amplifier 22.
A log compression diode 23 having the characteristics shown in FIG. In this circuit, in a normal operation state, the output voltage Vout is SP
Assuming that the current of D21 is Ip, Vout = (Vref + Vf) + Logk (Ip), and the photometric output can be immediately taken out. However, immediately after the power supply of the camera is turned on, since the charge due to the junction capacitance and the stray capacitance C is accumulated at both ends of the log compression diode 23, the output terminal Vout is equal to Vref +
In some cases, the output value is lower than Vf, and the output value is in an indefinite state without feedback. In particular, when the illuminance of the subject is low, since the current flowing through the SPD 21 is extremely small, the electric charge does not disappear in a short time, and a considerable time is required until normal operation is achieved. Eventually, photometry is delayed. For example, if the capacitance C is several pF, the current Ip of the SPD 21 becomes 10 pF.
In A, the delay time t is about 1 SEC.
Therefore, even if a clamp diode is added to both ends of the diode 23, the degree of improvement is only such that the delay can be reduced by half.

In recent years, the light receiving surface of a CCD, which is an imager, is becoming increasingly smaller. In a camera using such a TTL type sensor photometry system equipped with a CCD, the amount of light incident on the SPD 21 is reduced. So
The rise of the photometry when the power is turned on is further delayed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem. At the start of a photometric operation, photometry of an imager and photometry of a sensor photometric means are appropriately selected in accordance with the illuminance of a subject. It is an object of the present invention to provide an electronic imaging apparatus having a photometric control unit that exhibits a quick start characteristic of a photometric operation even for a low-illuminance subject.

[0008]

According to the present invention, there is provided an electronic imaging apparatus comprising: an imager photometer for performing photometry based on an output signal of an imager; and a photometer sensor different from the imager. A sensor photometer for performing photometry based on the output signal; and a photometer output value of the imager photometer is a predetermined value.
In the case above, the light metering by the sensor
Execute, and if it is less than the predetermined value,
Terminates photometry by using the photometric output value of the means.
And control means configured as described above.

[0009]

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiments. A photometric processing device incorporated in an electronic camera, which is an electronic imaging device according to an embodiment of the present invention, can quickly start up even when the illuminance of a subject is low at the start of a photometric operation. FIG. 1 is a main block diagram of an electronic camera showing the above embodiment. In the present electronic camera, the subject light is captured via the photographing lens 1 and the half mirror 2 and forms an image on the imaging surface of the imager 3. The imaging signal output from the imager 3 is subjected to processing such as amplification and sample hold in a pre-processing circuit 4, further processed by an imaging processing circuit 5, and output to a video signal processing circuit as a video signal. You. Part of the output of the pre-processing circuit 4 is
A luminance signal is extracted from the image pickup signal by the imager photometry circuit 6, and the average value or the weighted average value is taken into a microcomputer (hereinafter referred to as a microcomputer) 7 as a photometry light amount value. On the other hand, the subject light reflected by the half mirror 2 enters the SPD 9 serving as a sensor photometer through the condenser lens 8. The sensor output is taken into the microcomputer 7 after A / D conversion through a photometry circuit 10 equivalent to the log compression photometry circuit shown in FIG.

The photometric processing of the present camera configured as described above will be described with reference to the flowchart of FIG. First, in step S101, a photometric light amount value based on the image pickup signal of the imager 3 is taken into the microcomputer 7 by a predetermined field. The predetermined number of fields is, for example, 1
It may be a field portion. The exposure conditions are as follows:
Therefore, the condition is such that the light amount of the limit capable of photometry can be detected without relatively delay, and the exposure condition is suitable for a subject with relatively low illuminance, that is, a relatively long exposure condition. In step S102, it is determined whether or not the photometric light amount is equal to or more than a predetermined value, for example, 70 IRE. If the light amount is equal to or more than the predetermined value, that is, if the subject is a relatively bright subject, the photometric processing by the SPD 9 is performed. The process proceeds to step S103 assuming that the photometry is completed in a short time, and photometry is performed by the SPD 9 which is a sensor photometry unit.
On the other hand, when the photometric light amount is equal to or less than a predetermined value,
In the case of a relatively dark subject, since the exposure condition of the imager 3 is set to a level suitable for a subject with relatively low illuminance as described above, the approximate exposure is determined by the photometric light amount value of the imager 3. The condition is determined to be required, and the photometric processing ends.

As described above, in the photometric processing in the camera of the present embodiment, even when the illuminance of the subject is low, sensor photometry is performed depending on the degree of the illuminance, or the photometric value of the imager photometry is calculated. Since the selection is made as to whether or not to use, it is possible to prevent the disadvantages such as repeating the photometry for many fields by the imager or continuing the photometry for a long time by the sensor photometry as in the above-mentioned conventional example. can do. The improvement of the rise of the photometric processing is not limited to the effect of only AE (automatic exposure), but also determines the strobe irradiation condition, sets the gain of the process circuit, and sets the auto white balance.
Of course, it is effective also for the imager AF (auto focus).

In the above embodiment, the sensor photometric means using the log compression photometric circuit is used, and particularly, the rise of the photometric processing at power-on is improved. The photometric means is not limited to a sensor photometric means using a log compression photometric circuit, and other photometric means can be used. For example, when an integral type photometer is used as the photometer, the photometric time for each subject with low illuminance is inevitably reduced. It is possible not only at the time of ON, but also at the start of photometry in every photometry process. That is, an integral type photometric device is used as the sensor photometric device. In the photometric process, when it is determined that it takes time to perform photometry with the integral type photometric device when the illuminance of the subject is low, the photometric device is used. In this case, photometry is not performed, and only photometry by an imager is performed, so that the rise of the photometry process can be accelerated as described above.

Next, as a photometric device for a camera according to a modification of the above-described embodiment, after the photometric process of FIG.
Further, a photometric device that performs detailed photometric processing will be described with reference to the flowchart in FIG. In this modification, the configuration of the photometric device is the same as that of the above embodiment, and a part of the photometric processing is different. That is, as shown in the flow chart of the photometry process of FIG. 3, the photometry process of the present modified example is performed by the imager 3 at the initial stage of the photometry process, as in the flow of FIG. Photometry is performed under the conditions, and photometry is performed by the sensor photometry unit only when the photometry light amount is equal to or more than a predetermined value (step S20).
1-23). Then, to get more detailed photometric values,
Photometry based on the output of the imager 3 is performed. This detailed photometric operation is performed after approximate photometric values have been obtained by sensor photometric means for an object having a brightness higher than a predetermined value and by imager photometry for an object having a brightness lower than the predetermined value. Therefore, in the subsequent photometry by the imager, photometry over many fields is unnecessary as described above.

It is to be noted that, in common with the above two examples, a process to which the following judgment is added may be an improved example. That is, step S102 or step S2
In the photometric light amount determination process of 02, when the light amount is equal to or less than a second predetermined light amount set separately, “perform strobe light emission”
May be determined.

[0016]

As described above, in the camera of the present invention, at the start of the photometry operation, first, the image measurement is performed under the low illuminance exposure condition, and the sensor photometry is performed only when the subject at that time is somewhat bright. As a result, according to the present invention, the photometric operation can be started sufficiently quickly even when the illuminance of the subject is low. In addition, depending on the type of sensor photometry means as well as the rise of the photometry operation when the power switch is turned on, it is possible to increase the speed of the rise of the photometry operation itself every time. .

[Brief description of the drawings]

FIG. 1 is a block diagram showing a main configuration of a camera according to an embodiment of the present invention.

FIG. 2 is a flowchart of photometric processing by the camera of FIG. 1;

FIG. 3 is a flowchart of a photometric process of a camera showing a modification of the embodiment of FIG. 1;

FIG. 4 is a view for explaining a photometric processing cycle in an image pickup field period of an image in a conventional camera.

FIG. 5 is a log compression photometry circuit diagram in a conventional camera.

FIG. 6 is a characteristic diagram of a log compression diode used in the circuit of FIG. 5;

FIG. 7 is a flowchart of a photometry process using a sensor photometry unit and an imager photometry unit in a conventional camera.

[Explanation of symbols]

3. Imager 6 Imager photometric circuit (imager photometric means) 7 Microcomputer (imager photometric means, control means) 9 SPD (sensor photometric means) 10 photometric circuit (sensor photometric means)

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Claims (1)

(57) [Claims] 1. An imager photometric means for performing photometry based on an output signal of an imager, and a sensor photometric means for performing photometry based on an output signal of a photometric sensor different from the imager. The photometric output value of the imager photometric means is equal to or greater than a predetermined value.
In the case that the photometry is performed by the sensor photometry means,
If the value is less than the predetermined value, the measurement by the imager
Configured to terminate photometry by using light output value
Electronic imaging apparatus characterized by comprising anda control means which is.