JP4102201B2 - Photometric device, electronic camera - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a metering equipment for performing photometry for exposure more than once with the imaging device when performing photometry.
[0002]
[Prior art]
Conventional silver halide cameras were equipped with a dedicated photometric device because they were exposed to a silver halide film. However, in recent years, electronic cameras that are expanding their market share as cameras have an image sensor that performs photoelectric conversion. Therefore, a device that uses the output of the image sensor to perform photometry has been commercialized.
[0003]
In general, an image pickup element forms an electric potential well by applying an electric signal, and accumulates charges excited by photons from a subject in the well. If the number is too large, the charge overflows from the well, or if the number of photons is too small, it may be greatly affected by thermal noise due to heat-excited charges. Further, when a video signal obtained as analog data is converted into digital data thereafter, signal portions other than the intermediate level are greatly affected by sampling errors and the like. Therefore, it is within the range of the predetermined effective dynamic range that the image sensor can acquire a good electrical signal according to the amount of light.
[0004]
On the other hand, an electronic camera as a device equipped with an image sensor has a wide photometric range in order to shoot subjects with various brightnesses, and one exposure is performed by the image sensor. By itself, it is difficult to cover the entire required photometric range.
[0005]
In view of this, there has been proposed an electronic camera equipped with a photometric device adapted to perform photometry over the entire required photometric range by performing exposure a plurality of times with different exposure conditions during photometry. More specifically, such an electronic camera divides the required photometric range into a plurality of areas corresponding to the amount of light from the subject so that each area falls within the effective dynamic range of the image sensor under the respective exposure conditions. Each of the divided areas is predetermined.
[0006]
The exposure for photometry is basically performed within a period that is a natural number multiple of the vertical scanning period as a unit. When charges are accumulated in a certain vertical scanning period, the next vertical scanning is performed. A signal is read out during a period, and then a photometric value is calculated based on the read video signal.
[0007]
At this time, exposure for photometry that covers a photometric range corresponding to a relatively low luminance within the entire required photometric range is performed over a plurality of vertical scanning periods, for example, several times the vertical scanning period. It may be performed over a period of 10 to 10 times.
[0008]
[Problems to be solved by the invention]
As described above, in order to perform photometric exposure that covers a photometric range corresponding to a relatively low luminance, a long exposure period is required, and it is fixedly predetermined. Conventionally, photometry has taken a long time, and in electronic cameras, the release time lag has become a factor.
[0009]
The present invention has been made in view of the above circumstances, and an object thereof is to provide a photometric device capable of further reducing the photometric time at low luminance.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, a photometric device according to a first invention comprises an imaging device, an imaging device driving means for driving the imaging device based on an exposure time , and an imaging condition driving means for determining an exposure condition. By controlling the image sensor, the image sensor performs exposure for photometry. When the required photometry range deviates from the effective dynamic range of the image sensor, the exposure time is varied and a plurality of exposures for photometry are performed. Before the first exposure for photometry with one exposure time for performing photometry in one photometry range corresponding to a relatively low luminance. The second photometric exposure is performed with another exposure time for performing photometry in another photometric range corresponding to high brightness, and the first photometry is performed using the photometric result of the second photometric exposure. to determine the exposure time of use exposure Comprising a control means for controlling so as to perform photometry for exposure of the first, the said control means, the exposure time of the first photometric exposure, from the photometric result obtained by the second metering exposure The exposure time of the first photometric exposure is determined so as to be the shortest within the estimated necessary range.
[0011]
In the photometric device according to the second invention, in the photometric device according to the first invention, the control means divides a lower limit value of an effective dynamic range of the image sensor by a photometric result obtained by the second photometric exposure. The calculated time obtained by multiplying the exposure time by the exposure time for the second photometric exposure is determined as the exposure time for the first photometric exposure .
[0012]
Further, the photometric device according to the third invention is the photometric device according to the second invention, wherein the control means further includes a calculation result obtained by multiplying the calculation time by a factor of 1 or more and including a margin. It is determined as the exposure time of exposure for photometry.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
1 to 5 show an embodiment of the present invention, and FIG. 1 is a block diagram showing the configuration of an electronic camera equipped with a photometric device.
[0018]
As shown in FIG. 1, the electronic camera includes a lens system 1 for forming a subject image, a lens driving mechanism 2 for driving the lens system 1 for focusing and zooming, and the lens driving. An exposure control mechanism 4 including a lens driver 3 for controlling the mechanism 2, a diaphragm for controlling a passing range of a light beam condensed by the lens system 1, and an illumination light for irradiating a subject. A flash 5 that emits light, an exposure control driver 6 that controls the exposure by controlling the flash 5 and the exposure control mechanism 4 based on exposure information from a system controller 20 described later, and the exposure control mechanism 4. A mechanical shutter 7 for mechanically controlling the time for the passed light beam to reach the CCD 8 described later, and an optical subject image formed through the mechanical shutter 7 A CCD 8 that is an image pickup device that photoelectrically converts and outputs an electrical video signal, a CCD driver 9 that is an image pickup device drive means for controlling an image pickup operation by the CCD 8, and a double correlation with the video signal output from the CCD 8 A CDS (Correlated Double Sampling) 10 that performs sampling and amplification, an A / D converter 11 that converts an analog video signal processed by the CDS 10 into a digital video signal, and the A / D converter 11 A preprocess circuit 12 that performs predetermined preprocessing on the output digital video signal, and various types of processing such as color signal generation processing, matrix conversion processing, enhancement processing, and compression / decompression processing on the video signal processed by the preprocessing circuit 12 A digital process circuit 13 that performs digital signal processing and an image processed by the digital process circuit 13 An LCD 14 such as a color LCD for displaying an image so as to be observable and an image compressed by the digital process circuit 13 are written into a card memory 16 (to be described later) or compressed in the card memory 16 Are set for the electronic camera, a card IF 15 that reads out the image data that has been subjected to the decompression by the digital process circuit 13, the operation switch unit 17 for the photographer to operate the electronic camera, and so on. A process for displaying information such as a shooting mode, a shutter speed, an aperture value, and the like, which is an operation display unit 18 such as a monochrome LCD provided separately from the LCD 14 and a process executed by a system controller 20 described later. Program diagrams and various initial values related to programs and shooting modes And EEPROM19 to store other data and is configured to have a control means serving system controller 20 for integrally controlling the entire electronic camera comprising the elements described above, the.
[0019]
The operation switch unit 17 includes a power switch for turning on the power, a shooting switch including a two-stage switch for inputting a shooting instruction, a mode setting switch for setting a shooting mode, and various settings in the manual mode. It includes a switch for performing.
[0020]
Further, the memory card 13 is detachably attached to the electronic camera via the card IF 12. Therefore, the memory card 13 is not a component unique to the electronic camera.
[0021]
FIG. 2 is a flowchart showing the photographing operation of the electronic camera.
[0022]
After the power switch of the electronic camera is turned on and various initial settings are made, the operation switch unit 17 is put in a standby state. When the photographing switch of the operation switch unit 17 is operated in this state, the photographing operation is started.
[0023]
First, it is determined whether or not the first stage (1st release switch) of the shooting switch consisting of a two-stage switch is on (step S1). If it is off, this shooting process is terminated. If it is turned on, a photometric operation as described later is performed (step S2). This photometric operation is performed by the system controller 20 performing photometric calculation based on the output of the CCD 8 processed by the preprocess circuit 12 and the digital process circuit 13 and controlling the CCD 8 via the CCD driver 9 based on the result. Is called. In addition, the system controller 20 controls the exposure control mechanism 4 via the exposure control driver 6 based on the finally obtained photometric value, or causes the strobe 5 to emit light during the main exposure. ing.
[0024]
Thereafter, an AF operation is performed, and the system controller 20 operates the lens driving mechanism 2 via the lens driver 3 to move the lens system 1 to the in-focus position (step S3).
[0025]
Then, it is determined whether or not the second stage (2nd release switch) of the photographing switch is turned on (step S4). If it is off, the process returns to step S1 to determine whether the first stage is on. Confirmation is made again, and if the second stage is on, exposure for exposure (main exposure) is performed by the CCD 8 via the CCD driver 9 (step S5).
[0026]
Thereafter, the signal processed by the digital process circuit 13 and the like is displayed, and then the captured image is displayed on the LCD 14 (step S6), and the captured image is compressed by the digital process circuit 13 via the card IF 15. The image is stored in the memory card 16 (step S7), and this photographing process is terminated.
[0027]
3 is a flowchart showing the photometric operation of the electronic camera, FIG. 4 is a diagram showing each range of the photometric exposure by the electronic camera, and FIG. 5 is a photometric exposure performed in synchronization with the vertical synchronization signal and its data reading It is a timing chart which shows.
[0028]
When the processing program for performing the photometric operation is called in step S2 of FIG. 2, the photometric operation shown in FIG. 3 is performed.
[0029]
In order to cope with the wide dynamic range of the required metering range (the metering range required according to the subject brightness) when performing the metering, the electronic camera can reduce the necessary metering range to a plurality of narrow dynamic ranges. The photometric operation is performed for each region by dividing the range.
[0030]
Here, as shown in FIG. 4, generally required dynamic range is Bv-4 (for example, corresponding to ISO 400, shutter speed 1 second, aperture value F2.8) to Bv12 (for example, ISO 100, shutter speed). It is assumed that the speed is 1/1000 second and corresponds to the aperture value F11).
[0031]
Further, the output of the CCD 8 via the CDS 10 is converted into, for example, 10-bit (0 to 1023) digital data by the A / D converter 11, and the linearity is within this output range. It is assumed that a region corresponding to four steps from 40 to 640 considered to be relatively good is used as an effective dynamic range in each exposure.
[0032]
At this time, since the generally required exposure range (Bv-4 to Bv12) as described above is for 16 steps and the effective dynamic range is for 4 steps, in order from the smallest Bv value, Divided into four exposure areas: exposure 1 (first photometric exposure), exposure 2 (second photometric exposure), exposure 3 (third photometric exposure), and exposure 4 (fourth photometric exposure) Thus, exposure for photometry is performed.
[0033]
Specifically, the exposure 2 has a range of Bv0 to Bv4 by an effective dynamic range, the exposure 3 has a range of Bv4 to Bv8 by an effective dynamic range, and the exposure 4 has a range of Bv8 to Bv12 by an effective dynamic range. Each range is metered. In addition, for exposure 1, unless any contrivance is applied, the range of Bv-4 to Bv0 is measured by an effective dynamic range as shown by a two-dot chain line in FIG. If a specific photometric range is measured, the photometric time becomes longer. In this embodiment, as will be described later, the range of the Bv value covered by the effective dynamic range is variable (see the one-dot chain line in FIG. 4). Is set to.
[0034]
That is, when the operation is started, exposure 2 that covers the exposure area having the second smallest Bv value among the plurality of exposure areas is performed (step S11). As shown in FIG. 5, this exposure 2 is performed by controlling the exposure time by using a so-called element shutter within one vertical scanning period as a unit.
[0035]
In the next vertical scanning period, exposure 3 is performed and data 2 accumulated by exposure 2 is read (step S12).
[0036]
When data 2 is read, the system controller 20 calculates a photometric value based on the read data 2 within the vertical blanking period between the next vertical scanning periods (step S13), and the calculated photometric value is It is determined whether the exposure is within the effective dynamic range of exposure 2, or above or below (step S14). Here, it is determined whether or not the photometric value calculated based on the data 2 is included in Bv0 to Bv4. If it is included, the photometric value of the data 2 is used (step S15). This photometry process is terminated.
[0037]
In step S14, when it is determined that the photometric value of exposure 2 is below the effective dynamic range, the shortest exposure time T1 that is considered necessary for performing exposure 1 is obtained as the acquired data. Photometric value D2 calculated based on 2, exposure time T2 of exposure 2, and lower limit DL of the effective dynamic range (in the above example in which 40 to 640 of which is digitized by 10 bits becomes the effective dynamic range, 40) in the same vertical blanking period in which the photometric value in step S13 is calculated as shown in the following formula 1 (step S16).
[Expression 1]
T1 = (DL / D2) × T2 × k
Here, the coefficient k is for including a margin, and using a small number α of 0 or more,
[Expression 2]
k = 1 + α
As given. As the number α in Equation 2, a predetermined value stored in advance in the EEPROM 19 at the time of manufacture may be used, or the temperature of the CCD 8 or the like may be detected and dynamically changed according to the result.
[0038]
In step S14, when the photometric value D2 of exposure 2 is lower than the lower limit DL of the effective dynamic range, the calculation of step S16 is performed, so that the relationship of T1> T2 is automatically established. It is like that.
[0039]
Here, an example will be described in detail. When the exposure time T2 of exposure 2 is substantially the same as the vertical scanning period, the exposure time T1 of exposure 1 is determined as the exposure time T1 of exposure by performing conventional fixed exposure. Regardless of the luminance, 16 vertical scanning periods are always required. On the other hand, when T1 calculated by Equation 1 is 3 × T2 according to the luminance of the subject, for example, as shown in FIG. 5, it is sufficient to have three vertical scanning periods as T1. Thus, the photometric time can be greatly shortened.
[0040]
Exposure 1 is performed in one or more vertical scanning periods including the exposure time T1 calculated in this way, and data 3 is read (step S17). Data 3 is read in order to clear the register of the CCD 8 and the like. However, since it is known here that the photometric value is Bv0 or less, the read data 3 may or may not be used. Absent.
[0041]
Then, data 1 by exposure 1 accumulated in the vertical scanning period determined in step S16 is read (step S18), and the system controller 20 calculates a photometric value using the read data 1 (step S19). The photometric value based on the data 1 calculated here is used (step S20), and this photometric process is terminated.
[0042]
On the other hand, if it is determined in step S14 that the photometric value of exposure 2 is above the effective dynamic range, exposure 4 is performed and data 3 is read (step S21).
[0043]
Then, within the vertical blanking period between the next vertical scanning periods, the system controller 20 calculates a photometric value using the read data 3 (step S22), and the calculated photometric value is an effective dynamic range of the exposure 3. It is determined whether it is within or above (step S23). Here, it is determined whether or not the photometric value calculated based on the data 3 is included in Bv4 to Bv8. If it is included, the photometric value of the data 3 is used (step S24). This photometry process is terminated.
[0044]
If it is determined in step S23 that the photometric value of exposure 3 is above the effective dynamic range, the data 4 from the exposure 4 is read (step S25), and the read data 4 is used for the system. The controller 20 calculates a photometric value (step S26), uses the photometric value based on the data 4 calculated here (step S27), and ends this photometric process.
[0045]
Note that FIG. 5 shows an example in which all exposures for exposure 1 to exposure 4 are performed, but in actuality, as described with reference to FIG. Of course not.
[0046]
According to such an embodiment, the exposure condition of the first photometric exposure that covers the lowest photometric range is applied using the photometric result of the second photometric exposure that covers the second lowest photometric range. Therefore, the photometry time at low luminance can be further shortened. In addition to determining the first photometric exposure condition based on the photometric result relating to the photometric range corresponding to the second lowest luminance (Bv) as described above, the photometric range corresponding to the third lowest luminance. The first (and / or second) photometric exposure condition may be determined based on the photometric result.
[0047]
At this time, the exposure time of the first photometric exposure is obtained by multiplying the exposure time of the second photometric exposure by the lower limit of the effective dynamic range divided by the photometric result of the second photometric exposure. Therefore, the exposure time that is the shortest within a necessary range can be easily calculated in a short time.
[0048]
At this time, since the coefficient k including the margin is further multiplied, the photometric result of the first photometric exposure is more surely within the effective dynamic range in the first photometric exposure. be able to.
[0049]
Further, since the calculation of the photometric value and the exposure time of the first photometric exposure are performed within the vertical blanking period, the photometric exposure and data reading in the vertical scanning period can be performed without waste. The time required for photometry can be further shortened.
[0050]
By applying such a photometric device to an electronic camera, the release time lag can be further shortened.
[0051]
It should be noted that the present invention is not limited to the above-described embodiments, and various modifications and applications can be made without departing from the spirit of the invention.
[0052]
【The invention's effect】
According to photometric equipment of the present invention as described above, it is possible to shorten the metering time at the time of low luminance.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of an electronic camera including a photometric device according to an embodiment of the invention.
FIG. 2 is a flowchart showing a photographing operation of the electronic camera in the embodiment.
FIG. 3 is a flowchart showing a photometric operation of the electronic camera in the embodiment.
FIG. 4 is a diagram showing each range of photometric exposure by the electronic camera in the embodiment.
FIG. 5 is a timing chart showing photometric exposure performed in synchronization with a vertical synchronization signal and data reading in the embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Lens system 2 ... Lens drive mechanism 3 ... Lens driver 4 ... Exposure control mechanism 5 ... Strobe 6 ... Exposure control driver 7 ... Mechanical shutter 8 ... CCD (imaging element)
9 ... CCD driver (image sensor driving means)
10 ... CDS
DESCRIPTION OF SYMBOLS 11 ... A / D converter 12 ... Pre-process circuit 13 ... Digital process circuit 14 ... LCD
15 ... Card IF
16 ... Memory card 17 ... Operation switch 18 ... Operation display 19 ... EEPROM
20 ... System controller (control means)

Claims (3)

An image sensor;
An image sensor driving means for driving the image sensor based on an exposure time ;
The exposure condition is determined and the image sensor driving means is controlled to cause the image sensor to perform photometric exposure. When the required photometry range deviates from the effective dynamic range of the image sensor, exposure is performed. by varying the time controlled so as to perform the photometric multiple exposures, when the first metering according to an exposure time for performing photometry of one photometric range corresponding to a relatively low brightness Prior to performing the exposure for the second exposure , the second exposure for the second photometry is performed with another exposure time for performing the photometry in the other photometry range corresponding to the relatively high luminance. Control means for determining an exposure time of the first photometric exposure using the photometric result of the first photometric exposure, and controlling the exposure to the first photometric exposure;
Equipped with,
The control means includes a first photometric exposure so that an exposure time of the first photometric exposure is the shortest within a necessary range estimated from a photometric result of the second photometric exposure. A photometric device for determining the exposure time of the light. The control means is a calculation obtained by multiplying the lower limit of the effective dynamic range of the image sensor by the photometric result of the second photometric exposure and the exposure time of the second photometric exposure. 2. The photometric device according to claim 1, wherein the time is determined as an exposure time of the first photometric exposure . 3. The control unit according to claim 2, wherein the control means determines a value obtained by multiplying the calculation time by a factor of 1 or more as an exposure time of the first photometric exposure including a margin. The photometric device described .

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