JPH02149089A - Electronic image pickup device - Google Patents

Abstract

PURPOSE:To keep picture quality of images continuously picked up in a consecutive photographing mode at a fixed level and to obtain continuous still pictures stabilizing their color tones by resetting a white balance control value when the change of the value is increased from a fixedly set white balance control value. CONSTITUTION:A white balance sensor (WB sensor) 1 is provided independently of a solid-state image pickup element(CCD) 11. At the time of consecutive photographing operation started by turning on a release switch 9c when a white balance fixed (WBC) mode at the time of consecutive photographing is set up by a mode changing switch 9b, the white balance is controlled while fixedly setting up the white balance. On the other hand, a microprocessor 5 sequentially compares colorimetric data successively found at the time of consecutive photographing mode with colorimetric data stored in storage parts 21a, 21b by comparators 22a, 22b, and when the compared value is sharply changed, updates the colorimetric data stored in the storage parts 21a, 21b by new colorimetric data.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electronic still camera that electronically images and records a subject, and particularly relates to an electronic still camera that can stabilize the image quality of continuously photographed images. It relates to an imaging device.

[Prior Art] In electronic still cameras and video cameras that electronically image and record subjects using solid-state imaging devices such as CCDs,
White balance adjustment is performed on the captured image signal. This white balance adjustment aims to improve image quality by adjusting the sensitivity to each color component of the captured image and controlling the white level to a constant level, and plays an important role in electronic image recording of the subject. .

By the way, since video cameras input continuous images (videos), the state of the incident light is measured with a relatively long time constant and white balance adjustment is performed continuously, but electronic still cameras do not. In order to capture a still image of the subject at the moment when the image is captured, it is necessary to instantaneously measure the state of the incident light and adjust the white balance in synchronization with the imaging operation. For this reason, electronic still cameras use white balance adjustment circuits that have short time constants and excellent responsiveness, unlike those for video cameras described above. Each time the image capturing process is activated by a release operation, the state of the incident light at that time is measured, the measured white balance information is retained, and the white balance adjustment is performed for the captured image. Captured images are recorded on a recording medium such as a floppy disk.

In addition, continuous shooting mode is set for electronic still cameras,
Even when images of a subject are input continuously at predetermined time intervals, each time the image is captured, as shown in the operational sequence shown in Figure 3, white balance information is obtained by photometry of the incident light. is detected, and white balance adjustment for each captured image is performed individually according to the white balance information.

[Problems to be Solved by the Invention] However, when continuous imaging (quick shooting) is performed with an electronic still camera, it is necessary to measure the state of the incident light at each imaging timing and determine the white balance, as shown in Figure 3 above. If these adjustments are made individually, a difference will occur in the white balance of a plurality of continuously captured images due to subtle changes in incident light during the snapshot period. Such subtle differences in white balance between successive captured images directly appear as differences in image quality, resulting in extremely unsightly images. In particular, since the color tone changes individually depending on the white balance adjustment value, there is a problem that the uniformity of continuous still images is lost.

On the other hand, the white balance is fixedly determined during so-called strobe photography using an electronic still camera. However, in this case, since the incident light is uniquely (fixed) determined by the strobe irradiation light, there is no problem even if the first shift of control is fixedly determined in advance.However, when imaging with natural light, the incident light Since the state of the control value changes in various ways, there is no guideline for setting the control value fixedly in advance. Therefore, there is a problem in fixedly determining the white balance control value except during flash photography.

Therefore, the inventors of the present invention previously proposed in Japanese Patent Application No. 83-248872 that the white balance adjustment value obtained at the time of first image capture is stored and retained, and the white balance adjustment value is He proposed using it permanently to perform white balance adjustment for subsequent captured images. According to such a method, it is possible to perform continuous shooting with a constant color tone without worrying about subtle changes in incident light during the snapshot period.

However, there are various situations in which continuous imaging is performed, and the imaging conditions may change rapidly.

For example, the subject to be imaged may change from indoors to outdoors due to camera vanning, and the illumination light conditions may change rapidly. Under such circumstances, if the white balance adjustment value is fixedly used as described above, it will actually cause image quality deterioration. Furthermore, if continuous shooting is once interrupted to avoid such a problem, a problem arises in that a time lag occurs before continuous shooting is resumed.

The present invention has been made in consideration of these circumstances, and its purpose is to maintain constant image quality between images that are continuously captured in continuous shooting mode, and to produce continuous still images with stable color tone. An object of the present invention is to provide an electronic imaging device that can obtain the following.

[Means for Solving the Problems] The present invention has been made to solve these problems, and when recording electronic images of a subject continuously, it is necessary to adjust the settings for the first captured image. Fixedly setting a white balance adjustment value for subsequent captured images, as well as changing the white balance adjustment value for subsequent captured images with respect to this fixedly set white balance adjustment value. The present invention is characterized in that when the white balance adjustment value becomes large, the white balance adjustment value used for the white balance adjustment is reset and used for the subsequent white balance adjustment.

[Operation] By purchasing such a countermeasure, the electronic imaging device according to the present invention has the following features: ,
Basically, even if the state of incident light changes slightly at that time, white balance adjustment is performed on the captured image under certain conditions according to the white balance adjustment value that was adjusted when the image was first captured. Then, when the state of the incident light changes significantly, the adjustment value used for the white balance adjustment is updated with the white balance adjustment value obtained at this time, and is used for the white balance adjustment for the subsequent captured image. As a result, continuous still images with stable (constant) image quality and color tone can be easily obtained without being affected by changes in the state of incident light.

[Embodiment] An electronic still camera, which is an electronic imaging device according to an embodiment of the present invention, will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing a white balance control system of an electronic still camera according to an embodiment. Basically, this electronic still camera inputs an image signal of a subject imaged by a solid-state image sensor 11 such as a COD to an image signal processing circuit section 12, and uses the image signal processing circuit section 12 to perform white balance. It is configured to perform various signal processing such as adjustment, and record image signals on a recording medium 14 such as a floppy disk (SVF) under the control of a recording section 13.

The floppy disk (recording medium) 14 is driven to rotate at a predetermined speed, and approximately 50 recording tracks, for example, are formed concentrically to record captured image signals. One image signal is recorded on each recording track by access control of a head 15 that is moved in the radial direction with respect to the floppy disk 14.

Now, in Figure 1, 1 is a white balance sensor (WB
(sensor), and is provided separately from the solid-state image sensor (CCD) 11. The second WB sensor 1 determines the state of the incident light when the solid-state image sensor 11 captures an image of the object n1.
Constantly detected. Although the state of the incident light may be determined from the output of the solid-state image sensor 11 instead of the WB sensor 1, here, the state of the incident light is detected by external photometry using the WB sensor 1.

Therefore, the WB sensor 1 separates the incident light into color components, performs logarithmic conversion on the 01 light values of each color component of R (red), G (green), and B (blue), and then calculates the ratio ( R/G, B/
The measured value is output as G). nj constant values for these red and blue components (R/G, B/G)
is a preamplifier 2a.

After being amplified to a predetermined signal level via LPF 2b, ripple components such as those caused by flickering of a fluorescent lamp are removed by low pass filters (LPF) 3a and 3b, and then the A/D converter It is input to the microprocessor 5 via 4a and 4b.

As described later, this microprocessor 5 includes data conversion tables 5a and 5b showing the correspondence between colorimetric data and white balance control values, and a white balance corresponding to the colorimetric data from these data conversion tables 5a and 5b. Storage unit 21 as a control function to obtain control values
a, 21b and comparators 22a, 22b. However, the operation of this microprocessor 5 is controlled under the control of a system controller section 6, which will be described later.
By searching the data conversion tables 5a and 5b, a white balance control value corresponding to the embellished color data is determined and output.

The white balance control value thus obtained by the microprocessor 5 is transferred to the D/A converters 7a and 7b.
is provided to the above-mentioned imaging signal processing circuit section 12 via
It is used for white balance adjustment of the captured image inputted from the solid-state image sensor 11.

The control section 8 operates upon receiving the control commands from the system controller section 60, and its synchronization signal generation section 8a generates various synchronization signals, and its COD drive control section 8b generates various synchronization signals from the solid-state image pickup device (CCD) 11. It generates imaging drive pulse signals, etc. Under the control of the control unit 8, the solid-state imaging device (CCD) 11 captures an image of the subject, controls the operation of the image signal processing circuit unit 12, and further controls the rotation of the floppy disk 14, Access control of the head 15 and the like are performed, and recording control of the captured image signal by the recording section 13 is performed.

Refer to FIG. 5 for the conversion of the sensor output (R/G, B/G) indicating the state of incident light measured by the WB sensor 1 into a white balance control value using the data conversion tables 5a and 5b. and explain. The sensor output (R/G, B/G) has a one-to-one relationship with the color temperature (mired) of the incident light. In particular, since the detected color components of the incident light are logarithmically converted and output as described above, the sensor output has a linear relationship with the color temperature.

Specifically, as shown in FIG. 5(a), the lower the color temperature, the stronger the red component, and the higher the color temperature, the stronger the blue component.

With respect to the relationship between the color components of the incident light, the relationship between the control voltage required to adjust the white balance as an image signal for the captured image recorded and reproduced on the floppy disk 14 and the color temperature is, for example, the fifth given as shown in Figure (b). This relationship is determined based on factors such as processing circuit characteristics of the imaging signal and color reproducibility.

The data conversion tables 5a and 5b described above are shown in FIG.
Figure 5 (a) shows the sensor output given with the characteristic
In order to convert the above-mentioned sensor output (R/
G, B/G) and outputs this as a white balance control value. By performing white balance adjustment on the image signal output from the solid-state image sensor 11 in the image signal processing circuit section 12 using the white balance control value obtained in this way, the condition of the incident light (color temperature) can be adjusted. An image signal of constant and stable image quality is obtained and recorded on the floppy disk 14.

The feature of the present invention in the electronic still camera configured as described above is that when the quick shooting mode is set by the continuous shooting/single shooting mode changeover switch 9a, or when the white balance adjustment mode changeover switch 9b is set, When the fixed white balance (WBC) mode is set during quick shooting, the white balance adjustment is fixedly set as shown in the operation sequence shown in Fig. 2 during the quick shooting operation that is started by turning on the release switch 9c. The point is that I tried to do it while doing it. Note that the mode changeover switch 9b may be omitted as it is linked to the mode changeover switch 9a for continuous shooting Φ single shooting.

That is, in this electronic still camera, when the continuous shooting mode is set by the mode changeover switch 9a, the microprocessor 5 is controlled by the system controller section B.
The operation mode of the controller 8 is changed, and an instruction for a snapshot operation is given to the controller 8.

When shooting in the quick shooting mode is started by controlling the operations of the various parts described above by the control unit 8, the color temperature of the incident light is adjusted at each imaging time in the series of continuous shooting operations, as shown in the operation sequence shown in FIG. is detected and the A/D converter 4a
, 4b to the microprocessor 5 sequentially.

In the microprocessor 5, the color temperature of the incident light that is first taken in, that is, the colorimetric data at the time of first imaging, is stored and held in the storage units 21a and 21b.
The data conversion tables 5a and 5b are searched according to the embellishment data stored in the data conversion table 21b. Then, the white balance adjustment value obtained by this table search is
The signal is outputted via the A converters 7a and 7b, and used for white balance adjustment of the first obtained captured image in the image signal processing circuit section 12.

Therefore, the microprocessor 5 stores the colorimetric data obtained one after another during the continuous shooting mode and the storage units 21a and 2.
Comparators 22a and 22
Successive comparison is performed in b. When the input colorimetric data changes significantly compared to the color data stored in the storage units 21a and 21b, that is, when the colorimetric data changes by more than a predetermined threshold value, the storage units 21a and 2Lb
The colorimetric data stored in the camera is updated with new colorimetric data. Then, with the update of the color embellishment data, the data conversion tables 5a, 5 are created using the updated new colorimetric data (colorimetric data stored in the storage units 21a, 21b).
b is searched again and the white balance: A value is determined again. The white balance adjustment value reset in this manner is provided to the image signal processing circuit section 12 via the A/D converters 7a and 7b, and is used for white balance adjustment of the subsequent captured image.

According to the electronic still camera having the white balance control system configured in this manner, the white balance information (111 color data) obtained at the time of first image capture is stored in the storage section 21a.
, 21b, and the white balance control value obtained by searching the data conversion tables 5a, 5b according to this n1 color data is given to the image signal processing circuit section 12 and used for white balance adjustment of the captured image.

As long as the colorimetric data obtained when capturing the second and subsequent images has little change from the colorimetric data stored in the storage units 21a and 21b, that is, if the change in the incident light condition is small, then the first image capturing White balance adjustment is performed by fixedly using the white balance control value determined for the image.

Then, at the time when the continuous shooting is being performed, the incident light conditions change greatly, and for example, the colorimetric data at the time of taking the nth image becomes large compared to the colored data stored in the storage units 21a and 21b. When the color changes, the colorimetric data stored in the storage units 21a and 21b is updated at this point. Then, by re-searching the data conversion tables 5a and 5b, white balance adjustment values for the n-th and subsequent captured images are determined and provided to the image signal processing circuit section 12.

Therefore, the imaging signal processing circuit unit 12 first executes white balance adjustment using the white balance control value obtained at the time of initial imaging, and then the white balance control value is updated in accordance with a large change in the 1TII color data. Until then, the white balance adjustment is continuously performed using the white balance control value obtained at the time of the first imaging. When the white balance control value is updated, this new white balance control value is used to perform white balance adjustment for subsequent captured images.

As a result, if there is only a slight change in the incident light conditions, the white balance adjustment is performed using the initially set white balance adjustment value, but if the incident light conditions change significantly, the white balance adjustment is performed using the initially set white balance adjustment value. Following this, the white balance adjustment value is reset, and thereafter, the white balance adjustment is performed based on the reset white balance adjustment value.

Note that the white balance adjustment value set as described above is canceled by canceling the snapshot mode or by turning off the power.

According to this white balance control mode setting, even if the state of incident light changes slightly during the period in which images are continuously taken at a predetermined time interval due to the snapshot mode setting, the initial image capturing time is Since the white balance is fixedly adjusted in accordance with the obtained white balance control value, the image quality of the multiple captured images is improved regardless of the color temperature change of the incident light during the shooting period in the quick shooting mode. It becomes possible to make the color tone constant and stable. Additionally, if there is a sudden change in the incident light condition during snapshot shooting, the white balance adjustment value will be reset accordingly, so there will be no unintended color tone change due to a drastic change in the incident light condition. It becomes possible to continue imaging without causing any problems. Therefore, there is no variation in image quality or color tone between successive still images as in the prior art, and it is possible to obtain successive still images that are very easy to see.

Note that the present invention is not limited to the embodiments described above. For example, it is of course possible to cancel the constant control of the white balance control value during continuous shooting by operating the mode changeover switch 9b. In this case, it functions in the same way as in the case of single-shot photography, in other words, in the same way as the conventional apparatus, and the white balance is adjusted every time an image is taken. Such switching of the white balance adjustment mode is left to the intention of photographing. In addition, here, the state of the incident light was detected by the WB sensor 1, but C
Of course, it is also possible to use the output of CDII. It goes without saying that the solid-state imaging device 11 is not limited to the CCD shown in the embodiments, and the present invention can be implemented with various modifications without departing from the gist thereof.

[Effects of the Invention] As explained above, according to the present invention, the image quality of a series of continuously captured images (still images) can be adjusted based on subtle changes in the imaging situation (changes in the state of incident light). However, if there is a significant change in the imaging situation, the white balance adjustment value can be reset to follow this change, so that it can be made good. As a result, the reproduced image can be made very easy to view, and the control thereof is also very simple, which brings about great practical effects.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram of a white balance control system of an electronic still camera as an electronic imaging device according to an embodiment of the present invention, and Fig. 2 shows an operation sequence of white balance control in continuous shooting mode in the present invention. 3 is a diagram showing the operation sequence of white balance control in the quick shooting mode in a conventional device, and FIG. 4 is a diagram showing the operation sequence of white balance control in the continuous shooting mode proposed earlier by the present inventors. FIG. 5 is a diagram for explaining the principle operation of white balance control. 1... White balance sensor (WB sensor), 2a
, 2b...Preamplifier, 3a, 3b...Low pass filter (LPF), 4a, 4b-A/D converter, 5-Phycroprocessor, 5a, 5b... Data conversion table, B... system controller section, 7a
, 7b...D/Am converter, 8 ・M a1 part, 9
a, 9 b, 9 c-...switch, 11...
- Solid-state imaging device (CCD), 12... Imaging signal processing circuit unit, 13... Recording unit, 14... Floppy disk (recording medium), 15... Head, 21a, 21b.
...Storage unit, 22a, 22b...Comparator. Applicant's agent Patent attorney Atsushi Tsuboi

Claims (1)

[Claims] an image capturing and recording means for electronically capturing and recording an image of a subject; a continuous shooting means for causing the image capturing and recording means to continuously capture and record images of the subject; When a series of continuous shooting is performed by the white balance adjustment means for adjusting the white balance of the image and the continuous shooting means, the white balance adjustment value adjusted for the first captured image is fixedly set, and the white balance adjustment value adjusted for the first captured image is fixedly set. In addition to providing white balance adjustment for a captured image, when the white balance adjustment value for a subsequent captured image has a large change with respect to this fixedly set white balance adjustment value, the white balance adjustment is used for the white balance adjustment. An electronic imaging device comprising: a control means for resetting a value.