JP3118607B2 - Electronic still camera - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electronic still camera.

[Conventional technology]

FIG. 7 is a configuration diagram of a white balance device in a conventional electronic still camera.

In FIG. 7, reference numeral 1 denotes an image sensor that converts an optical image into an electric signal and outputs a plurality of color signals, 2 denotes a luminance signal processing circuit that processes an output signal from the image sensor 1 to generate a luminance signal, 3a, 3b is a color signal processing circuit for each of R (red) and B
(Blue) and Y _L (brightness). 4,5 respectively
These are gain control circuits (R AMP) and (B AMP) for white balance adjustment of the R and B signals.

6a, 6b is the subtraction circuit, the color difference signals R-Y _L, the B-Y _L signal produced.

Reference numeral 13 denotes light source light of each color component (here, red (R) and blue (B)
A colorimetric circuit that divides the output into three primary colors (green (G)) and converts them into electrical signals. The arithmetic controller 7 determines the color temperature of the light source light from each of the outputs R ₁ , G ₁ , and B ₁ , Calculate the control voltage to obtain an appropriate white balance, and calculate R AMP4, B
Controls each gain of AMP5.

[Problems to be solved by the invention]

As described above, in the conventional example, when performing white balance adjustment in an electronic still camera, the colorimetric circuit 13 is necessary to determine the color of the light from the light source, and the colorimetric circuit 13 is expensive. There was a problem that it became a factor of high.

In addition, since the colorimetric circuit 13 and the color filter of the image sensor 1 do not match, an adjustment for the adjustment is necessary, which is troublesome.

The present invention has been made in order to solve the problems of the conventional example as described above, and from the integrated values of Y _L , R-Y _L , and B-Y _L with respect to the white balance control value output at the time of Pre-exposure,
R / B (or R / G, B / G) is calculated, the correction amount of the white balance control value is obtained from this value, and the corrected white balance control value is output at the time of the main exposure, and is always output at the time of the pre-exposure. The color temperature control range can be set similarly on the low color temperature side and the high color temperature side around the color temperature corresponding to the white balance control value of Even if it is changed, it is possible to use the same correction formula or a table of correction values,
White balance control can be performed accurately over a wider color temperature range, and the white balance can be automatically adjusted without the need for a colorimetric circuit for external measurement.
The purpose is to obtain an electronic still camera that leads to significant cost reduction.

[Means for solving the problem]

Therefore, according to the present invention, in an electronic still camera that obtains image information in advance by performing preliminary exposure prior to main exposure for recording a video signal, an imaging device that converts subject light into electrical image information is provided. Acquiring white balance information before the main exposure is performed, based on the image information obtained from the imaging unit during the temporary exposure, and performing the main exposure during the main exposure based on the acquired white balance information. The object is achieved by an electronic still camera having a control unit for controlling a white balance of image information obtained from an imaging unit.

〔Example〕

Hereinafter, two embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a first embodiment of the present invention, FIG. 2 is a time chart showing timing in the first embodiment, FIG. 3 is a flowchart for controlling the operation of the first embodiment, FIG. FIG. 4 is a graph showing a white balance correction amount. FIG. 4 (a) shows a color temperature control range and RwB.
FIG. 4 (b) shows a color temperature control range and a BwB correction value. FIG. 5 is a table showing the white balance correction amount. FIG. 5A shows the correction value of RwB, and FIG.
FIG. 6B shows each of the BwB correction values. Sixth
FIG. 6 is a block diagram showing the configuration of the second embodiment of the present invention.

In the figure, the same or corresponding components as those in the above-mentioned conventional example are denoted by the same reference numerals, and duplicate description will be omitted.

First, a first embodiment of the present invention will be described with reference to FIGS.
This will be described with reference to the drawings.

In FIG. 1, A denotes an image pickup means, which is constituted by an image pickup device 1, and converts an object light into an electric signal and outputs a plurality of color signals. B is a gain control means, which is composed of R AMP4 and B AMP5, and is a means for controlling the gain of the color signal. C denotes an arithmetic control unit, which is configured by the arithmetic control unit 7 and controls the gain control unit based on an output value of an integration circuit (described later). D is a chrominance signal gain control means, which is composed of an arithmetic control unit 7 and which is based on the output signal of the integrator 10 when the gain control value of the chrominance signal is controlled by the arithmetic control means C by the gain control value of the first chrominance signal. The difference between the color temperature at which an appropriate white balance is obtained for the gain control value of the first signal and the color temperature of the subject light is detected, and the gain control value of the first color signal is corrected. This is means for controlling the gain of the color signal with the gain control value of the second color signal. The 8a, 8b, 8c is R-Y _L obtained respectively, B-Y _L, clamp circuit for clamping a predetermined voltage which is determined by Y _L signal reference voltage source 11, 9a, 9b are each in the subject If high-saturation is included, the white balance shifts due to the effect, so the clipping circuit that suppresses the signal of the high-saturation part, 10a, 10b, 10c output 9a, 9b, 8c respectively This is an integration circuit for integrating a signal. Reference numeral 12 denotes a photometric circuit for measuring the brightness of the subject.

Next, the operation of the first embodiment will be described with reference to FIGS. 1 to 3, focusing on the color signal gain control means D. First,
An outline of the operation of this embodiment will be described. In this embodiment, the pre-exposure is performed before the main exposure, the color signals obtained at this time are integrated for one screen, and the R, G, B signals at the time of the pre-exposure are calculated from this signal, and this value (first value) is calculated. The color of the light source light is determined based on the gain control value of the color signal, and a control voltage is calculated to obtain an appropriate white balance. By controlling the gain of the BAMP, appropriate white balance can be automatically adjusted over a wider color temperature range without a colorimetric circuit. The details will be described below.

FIG. 2 is a timing chart for explaining the operation of this embodiment, and FIG. 3 is a flowchart for controlling the operation of this embodiment. In FIG. 3, a switch (Sw)
When 1 (not shown) is turned on (step 101), the magnetic sheet motor servo starts (step 102), and the photometry circuit 12 measures the brightness of the subject (step 103). When the output of the photometric circuit 12 is read by the arithmetic and control unit 7, the timing is not synchronized with the flicker of the fluorescent lamp, for example,
Read at 23 samplings in 50ms. This operation is repeated until Sw2 (not shown) is turned on.
Is ON (step 104), it is determined whether or not the photometry has been completed (step 105).
If 23 samplings have been completed in 0 ms, the white balance (WB) control voltage is set to R AMP4 and B AMP in FIG.
A color temperature known as a gain control value in AMP5, for example, 5000 K
Are output from the arithmetic and control unit 7 in FIG. 1 (step 106).

The fixed values RwBo and BwBo output here are such that white balance can be obtained at a color temperature substantially at the center of the color temperature range in which white balance control is performed as described below.

Next, accumulated in the image pickup device 1 of FIG. 1, performs clear unwanted charges from the timing t ₀ of FIG. 2 during t ₁ (step 107), the shutter is opened at t _2, preceding Pre-exposure is performed for a certain period determined by the result of photometry (step 108). When Pre exposure ends with t _3, 10a from the operation control section 7 of FIG. 1, 10b, of f sending 10c to the respective integrating circuits / the RESET pulse in the High at t _4, starts integration operation, t ₅ from period t _6, it reads the initial value of each integration output to the operation control section 7 (step 109). from t ₇ to the image pickup device 1 of FIG. 1 reads out the signal charges accumulated during Pre exposure (step 110). The read signal is converted into R, G, and B by the color signal processing circuit 3a as in the conventional example, and the R and B signals are respectively output by the white balance adjustment amplifiers 4 and 5,
Previously set to control voltage RwBo, is an amplifier with a gain determined by BwBo, R color signal processing circuit 3b, B, Y _L signal is converted to 6a, 6b R-Y _L by the subtraction circuit, B-Y _L, Three signals of Y _L are obtained. These signals clamp circuit 8a, 8b, is clamped to a predetermined potential that is determined by the reference voltage source 11 in each 8c, for the color difference signals R-Y _L, the B-Y _L except taking the influence of the high saturation portions, In each of the PP clip circuits 9a and 9b, the signal of the high chroma portion is clipped. The clip level of each of the clip circuits 9a and 9b is determined within a color signal level range that varies depending on the light source color in a color temperature range in which white balance is controlled. By doing so, it is possible to prevent overcorrection of the white balance in a portion where the color temperature exceeds the control range.

The outputs of 9a, 9b and 8c are respectively integrated by respective integration circuits of 10a, 10b and 10c, and the respective integrated values ∫R−Y _L , ∫B−Y _L ,
∫Y _L is obtained. Each integration value obtained is t from t ₉ of FIG. 2
_It is read by the arithmetic and control unit 7 during the interval between ₁₀ (step 11).
1). (Step 109) and the value read in (Step 11
The difference from the value read in 1) is the integrated value of each signal.

The arithmetic control unit 7 calculates a white balance control value from the read integral value (step 112).

The method of this calculation will be described below. First (Step 10
Obtained from the difference between the values captured in 9) and (Step 111)
Y _L , R−Y _L , and B−Y _L are integrated values of I _YL , I _R-YL , and I _B-YL , respectively. The value of R / B is calculated by the calculation formula. The color temperature of the light source is determined from the ratio of R and B. That is, at the time of Pre-exposure, if the values of the white balance control voltages RwBo and BwBo output in FIG. 3 (step 106) are appropriate white balance control values, the value of R / B becomes almost 1. When the value of R / B is greater than 1, the color temperature of the light source of the subject is low, when the value of R / B is less than 1, the color temperature is high.
It is determined that it is shifted.

Next, a method for obtaining an appropriate white balance control voltage from the R / B value obtained by this calculation will be described. FIG. 4 is a graph showing a white balance correction amount. FIGS. 4 (a) and 4 (b) are obtained for fixed values RwBo and BwBo output as white balance control voltages at the time of pre-exposure. 9 is a graph showing a value of a white balance correction amount with respect to a value of R / B. That is, when the value of R / B is 1, this is the case where the white balance control is appropriate with the white balance control voltages of RwBo and BwBo as described above, and the correction amount at this time is 0, The control value of the output white balance is set to Rw with respect to RAMP4.
If BwB is set for B and B AMP5, then RwB = RwBo,
BwB = BwBo.

Further, when the value of R / B is, for example, 1.5, RwB = RwBo + 20 and BwB = BwBo-20 corrected as white balance control values are obtained from FIGS. 4 (a) and 4 (b). The value becomes an appropriate white balance control value. That is, the white balance control value at the time of the main exposure is
An appropriate white balance control value is obtained by calculating the amount of correction to obtain an appropriate white balance control value from the R / B value obtained for each of the RwBo and BwBo values output during pre-exposure. Will be done. The correction amount for the R / B may be provided by the calculation control unit 7 having a table, or may be obtained by a calculation formula for calculating the correction amount.

Next, the arithmetic control unit 7 in FIG. 1 compares each of the white balance control values RwB and BwB obtained in step 112 with R A.
Output to MP4 and BAMP5 (step 113). Thereafter is the same as the recording sequence of a general electronic still camera, the imaging device 1 from the timing t ₁₂ of FIG. 2 during the period t ₁₃
Clears unnecessary charges stored in the
114), and accumulating charges in the image pickup device 1 Open time shutter t ₁₅ from Taimiingu t ₁₄ (step 115), at the timing t ₁₆ in the timing of the PG signal, the image pickup device 1
Then, the charge stored in synchronization with the PG is read, the recording gate is opened, and the video signal is recorded on the magnetic sheet (steps 116 and 117).

As described above, in the white balance data calculation (step 112) in FIG. 3, the R / B obtained during the pre-exposure is used.
Of the white balance fixed value RwBo, BwBo output at the time of Pre-exposure for the value of
By adding or subtracting from Bo, a corrected appropriate white balance control value is obtained.However, the method of correction is not limited to addition and subtraction, and RwBo, BwBo Calculate the ratio of correction to
It is also possible to obtain a corrected white balance control value by multiplying wBo and BwBo. The correction amount for R / B may be obtained by using a table (described later), or the correction amount may be obtained by a calculation formula.

In the first embodiment, the integration results of Y _L , R−Y _L , and B−Y _L
R / B ratio is calculated and white balance is controlled only in the color temperature direction, but R / G and B / G are calculated to eliminate the effect of green under fluorescent light, and these two values are calculated. To obtain more white balance control voltage,
If the correction amount for the white balance control value output at the time of exposure is determined from the values of R / G and B / G, and the main exposure is performed using the corrected white balance control value, similarly,
Appropriate white balance control can be performed.

FIGS. 5A and 5B are tables showing correction amounts of white balance control values with respect to R / G and B / G values. White balance control value RwBo output to R AMP4
FIG. 5 (a) shows a table of the correction amounts for BwBo, and FIG. 5 (b) shows a table of the correction amounts for BwBo. Each, a _R ... as a correction value, but have a _B ..., in any case, area correction value 0 is located at the center of the Table.

In FIG. 1, the operator determines in advance whether the color temperature of the light source of the subject is expected, that is, whether the color temperature is low or high with respect to daylight, and this information is used as the color temperature. When a white balance setting switch (not shown) is input to the arithmetic control unit 7 in FIG. 1, the arithmetic control unit 7 outputs a value obtained by shifting the white balance control value output at the time of the pre-exposure by a certain value. Thereafter, in the same manner as described above, a correction value is obtained from the R / B value, an appropriate white balance control value is output, and the video signal is recorded. Also in this case, an appropriate white balance control value can be obtained by using the same calculation method and correction value table as in the case where the white balance control value is not shifted.

Next, a second embodiment of the present invention will be described with reference to FIG.

FIG. 6 is a block diagram of an electronic still camera according to a second embodiment of the present invention, and the configuration is the same as that of the first embodiment. The second embodiment is different from the first embodiment in that, in the first embodiment, R-Y _L and B- are used as information for calculating a control value of white balance.
Although the signals Y _L and Y _L are used, the second embodiment uses the G output of the color signal processing circuit 3a and the R and B signals of the respective outputs of R AMP4 and B AMP5. At this time, in the second embodiment, the control values to be sent to the R AMP4 and B AMP5 at the time of the pre-exposure, respectively, are the same as in the first embodiment. Is set to a value that can be obtained.

The signals of R, G, and B in the second embodiment are clamped by the clamp circuits 8a, 8b, and 8c, respectively.
9a ₁ , 9b ₁ , and 9c ₁ are clipped respectively, and the effect of the high chroma portion is removed. The clip level of each of the clip circuits 9a ₁ , 9b ₁ , 9c ₁ is set to be equal to or higher than the level of the maximum value of the color signal that changes with the light source color in the color temperature range in which the white balance is controlled. Clip circuit 9a ₁ , 9b ₁ , 9c
The outputs of ₁ are integrated by the integration circuits 10a, 10b, and 10c, respectively, and read into the arithmetic control unit 7. Further, the arithmetic control unit 7 calculates a white balance control value from the read integral value in the same manner as in the first embodiment, and performs control.

In the second embodiment, the same operation and effect as those of the first embodiment can be obtained.

〔The invention's effect〕

As described above, the present invention is operational Y _L, R-Y _L for the white balance control value output during Pre exposure, from the integrated value of B-Y _L, R / B or R / G, a B / G Then, the correction amount of the white balance control value is obtained from this value, and the white balance control value corrected at the time of the main exposure is output. Similarly, the color temperature control range can be set on both the temperature side and the high color temperature side, and even if the white balance control value output during Pre-exposure is changed, the same correction formula,
Alternatively, a table of correction values can be used, and there is an effect that the white balance can be accurately controlled over a wider color temperature range. In addition, there is an effect that an electronic still camera can be obtained that does not require a colorimetric circuit for external measurement, can automatically perform white balance, and leads to a significant cost reduction.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment of the present invention, FIG. 2 is a time chart showing timing in the first embodiment, FIG. 3 is a flowchart for controlling the operation of the first embodiment, FIG. FIG. 4A is a graph showing the white balance correction amount. FIG. 4A shows the color temperature control range and the RwB correction value, and FIG. 4B shows the color temperature control range and the BwB correction value. FIG. 5 is a table showing the white balance correction amount. FIG. 5 (a) shows the RwB correction value, and FIG. 5 (b) shows the BwB correction value. FIG. 6 is a block diagram showing the configuration of a second embodiment of the present invention, and FIG.
FIG. 1 is a configuration diagram of a white balance device in a conventional electronic still camera. A: imaging means B: gain control means C: arithmetic control means D: color signal gain control means 1: imaging element 2: luminance signal processing circuit 3a, 3b: color signal processing circuit 4: R AMP 5 BAMP 7 Arithmetic control unit 8a, 8b, 8c CLAMP 9a, 9b P-PCLIP 10 Integrator circuit 12 Photometric circuit Is shown.

Continuation of the front page (56) References JP-A-2-109026 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H04N 9/79-9/898 H04N 9/73 H04N 9 / 04 H04N 5/235

Claims (5)

(57) [Claims] An electronic still camera that obtains image information in advance by performing temporary exposure prior to main exposure for recording a video signal, wherein: an imaging unit that converts subject light into electrical image information; Based on the image information obtained from the imaging unit during exposure, obtain white balance information until the main exposure is performed, and from the imaging unit during the main exposure based on the obtained white balance information. A control means for controlling a white balance of obtained image information. 2. The image processing apparatus according to claim 1, wherein the control unit performs white balance control on image information obtained from the imaging unit during the temporary exposure based on a predetermined white balance control value, and performs the white balance control based on the white balance controlled image information. Acquiring a correction amount for the predetermined white balance control value to control a white balance of image information obtained from the imaging unit during the main exposure.
An electronic still camera as described. 3. The electronic still camera according to claim 2, further comprising setting means for setting said predetermined white balance control value. 4. The apparatus according to claim 1, wherein said control means obtains said white balance control information based on three kinds of signals of R, G and B among image information obtained from said imaging means. Electronic still camera. 5. A clipping means for clipping a high saturation portion of image information obtained from said image pickup means, wherein said control means obtains white balance control information based on the image information clipped by said clipping means. The electronic still camera according to claim 1, wherein: