JP2893114B2 - Image recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to image recording in which an optical image incident through a lens by opening and closing a shutter is converted into an electric signal and recorded on a recording medium. Related to the device.

(Prior Art) In an image recording apparatus such as an electronic still camera, white balance control is required, and the color sensor measures the color temperature of external light and controls the white balance according to the color temperature. . In addition, it is conceivable that electronic still cameras perform flash photography, but in this case, white balance control for flash photography that is different from white balance control according to external light is required.

Therefore, for example, a configuration described in Japanese Patent Application Laid-Open No. 58-215885 has been known as one that performs white balance control for flash photography. And this Japanese Patent Application Laid-Open
Japanese Patent No. 215885 describes a method of monitoring the on / off state of a strobe switch and automatically giving a white balance control signal corresponding to a strobe emission spectrum when the strobe switch is turned on.

(Problems to be Solved by the Invention) However, in the method described in Japanese Patent Application Laid-Open No. 58-215885, a white balance control signal corresponding to a strobe emission spectrum is generated in accordance with an on-state of a strobe switch. However, even if the strobe does not emit light because sufficient charge is not accumulated, only the white balance is controlled corresponding to the strobe emission spectrum, and an appropriate color balance cannot be obtained.

Therefore, it is conceivable to adjust the color balance by a white balance control signal corresponding to the strobe emission spectrum only when the strobe actually emits light, although it is not known.

According to this method, an appropriate color balance can be obtained even when the strobe does not emit light. However, in a daytime strobe mode used for backlit shooting or the like, the subject to be shot is located farther than the reach of the strobe light. Even when it is located, white balance control is performed corresponding to the strobe emission spectrum. In this case, since the strobe light is irradiated as auxiliary light of the external light, if the white balance is controlled by the strobe light emission spectrum, an inappropriate image is obtained from the color balance of the external light.

As described above, at the time of flash shooting, there is a problem that white balance control is not properly performed depending on a subject distance (photographing distance), and an image having an inappropriate color balance may be generated.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to provide an image recording apparatus that can always obtain an image having an appropriate color balance during flash photography.

[Configuration of the invention]

(Means for Solving the Problems) The present invention includes an automatic exposure amount control unit that is set so that a shutter speed and an aperture value change in conjunction with each other according to the luminance of external light. In an image recording apparatus that emits a strobe at the time of shooting and converts an optical image incident through a lens by opening and closing a shutter into an electric signal and records the electric signal on a recording medium, an external device is used to control the white balance of the electric signal A white balance circuit that generates either a white balance control signal for external light corresponding to the color temperature of light or a white balance control signal for strobe light corresponding to the strobe light emission spectrum, and the shooting distance to the subject detected by the distance detection circuit Strobe aperture value obtained from the guide number of the strobe used and detected by the photometry circuit A comparing means for comparing the measured brightness with the photometric aperture value determined by the automatic exposure amount control means; and when the flash rate is determined to be larger than the photometric aperture value by the comparing means during photographing using a strobe. White balance switching means for generating a white balance control signal at the time of strobe light emission and generating the white light control signal at the time of external light when it is determined that the strobe aperture value is not larger than the photometric aperture value.

(Operation) In the present invention, a comparison unit compares a flash aperture value obtained from a shooting distance and a guide number of a flash used with a photometric aperture value determined by an automatic exposure amount control unit in accordance with the luminance of external light. If the comparison result indicates that the flash aperture value is larger than the metering aperture value during shooting using the flash, it is determined that the subject is within the flash light reach distance and the appropriate flash light amount has been emitted, If a strobe light is used to generate a white balance control signal, and the comparison result indicates that the strobe aperture value is not greater than the metering aperture value, the subject is located beyond the strobe light reaching distance, and the strobe light that has decreased from the appropriate , Judge that it is irradiated as auxiliary light of external light, generate a white balance control signal at the time of external light, without being affected by the subject distance, The color balance at the time of strobe light emission is always kept in an appropriate state to achieve faithful color reproducibility.

(Embodiment) Hereinafter, an embodiment of the image recording apparatus of the present invention will be described with reference to the drawings.

In FIG. 1, reference numeral 11 denotes a photographing lens.
Numeral 11 is set by the lens drive circuit 31 to a subject distance that provides an appropriate shooting distance. The incident light from the lens 11 is controlled by a shutter 12, and the shutter 12 is controlled to be opened and closed by a shutter drive circuit 32.
The start time of the operation 12 is detected by the home switch 33. The light incident through the lens 11 is incident on a CCD 13 serving as an image sensor, and the CCD 13 converts the incident optical image into an electric signal. Further, the CCD 13 is operated by the camera circuit 14, and the camera circuit 14
The white balance is adjusted based on a white balance control signal which is a voltage signal from the white balance circuit 15. An image signal, which is an electric signal output from the camera circuit 14, is converted by the recording circuit 16 into a video floppy disk 17 as a recording medium.
To record.

Reference numeral 19 denotes a strobe, and the strobe 19 emits light by charges charged in the strobe circuit 21 when the strobe circuit 21 is triggered by a trigger circuit 20. Further, it is detected by the charging voltage detection circuit 22 whether the flash circuit 21 has been charged enough to emit light from the strobe 19, and the guide number (G
_NO , ISO · m) are set by the data setting circuit 23.

Further, reference numeral 25 denotes a distance detection circuit, which may be based on a triangulation method used in an automatic focusing device or the like, and generates an output corresponding to a shooting distance to a subject (not shown). Note that a device that generates an output corresponding to the shooting distance by manual setting may be used. Reference numeral 26 denotes a photometric circuit, which outputs a luminance signal corresponding to the luminance of the external light, and reference numeral 27 denotes a colorimetric circuit, which is a color temperature signal corresponding to the color temperature of the external light. Is output.

Reference numeral 35 denotes a camera release switch, which is a contact S1 for distance measurement, photometry, and colorimetry commands.
And a command contact S2 for shutter release operation,
36 is a strobe mode changeover switch. This strobe mode changeover switch 36 has a contact S11 for strobe off mode,
It has a contact S12 for an auto mode for automatically firing the strobe when the external light has low brightness, and a contact S13 for a flash on mode for forcibly firing the strobe.

Then, based on the designated signals from the camera release switch switch 35 and the strobe mode changeover switch 36, the respective output signals are inputted, a predetermined calculation is performed, and a system control circuit for giving an operation command to each operating section at a predetermined timing. CPU 37 is provided. The CPU 37 has, as a function, an automatic exposure control unit that changes the shutter speed and the aperture value in conjunction with each other based on the luminance signal from the photometry circuit 26. Also, a function for obtaining a flash aperture value FM from the shooting distance signal from the distance detection circuit 25 and the guide number G _NO from the guide number data setting circuit 23 by the following formula, and a function for obtaining the obtained flash aperture value FM There is provided a comparing means for comparing the photometric aperture value AE determined by the automatic exposure control means based on the luminance signal from the photometric circuit 26.

The flash aperture value FM is calculated by the following formula: flash aperture value FM = guide number G _NO / shooting distance [m].

Further, the CPU 37 has white balance switching means for switching the white balance control signal according to the comparison result by the comparing means. In other words, the comparison result is
If FM ≥ metering aperture value AE, that is, if the flash aperture value FM is greater than the metering aperture value AE, a white balance control signal is generated when the flash is fired, and the comparison result is other than the flash aperture value FM ≥ metering aperture value AE If the flash aperture value is not larger than the photometric aperture value, the white balance circuit 15
Control.

Here, the external light white balance control signal includes:
A mode for automatically tracking the color temperature from the colorimetric circuit 27 or a mode fixed to daylight or external light is used.

In addition, the CPU 37 controls the lens drive circuit 31 in accordance with the above-described shooting distance, controls the shutter drive circuit 32 in accordance with the timing, and issues a trigger command to the strobe 19 so that the charge is sufficient for strobe emission. Provided that the battery is charged, the signal is supplied to the trigger circuit 20, and further, in accordance with the recording operation of the image signal by the recording circuit 16, the motor 39 is operated via the motor control circuit 38, and the video floppy Each has the function of rotating 17.

FIG. 2 is a shutter program diagram showing the relationship between the aperture value F _NO (= AE) and the shutter speed T corresponding to the external light luminance EVi (i = 6 to 18). The aperture value _FNO and the shutter time T change on a thick line. The external light brightness EVi is detected by the photometric circuit 26 shown in FIG. 1, and is calculated by the automatic exposure control means by the CPU 37 based on the relationship in FIG. 2, and the result is output to the shutter drive circuit 32. The shutter drive circuit 32
When the command contact S2 of the camera release switch 35 is turned on, the shutter 12 is driven based on the result.

In the example of FIG. 2, when the external light luminance is equal to or less than EV8, the aperture value F _NO = 2.8 (open) and the shutter speed T = 1/30.
Is set so that the shutter time does not become any longer. This is set by the camera shake prevention time and the exposure dark current S / N of the CCD 13. If the auto flash mode is set by the flash mode switch 36 below the brightness EV, the flash 19 automatically emits light during shooting.

Next, the relationship between the shutter opening state and the flash emission timing at the time of flash shooting will be described with reference to FIG.

FIG. 3 shows a shutter opening waveform in the case of the external light luminance EV12. That is, if the brightness is EV12,
From the relationship shown in Fig. 12, the shutter speed T is 1/125 and the aperture value is F _NO
Becomes 5.6. Therefore, when the shutter release is activated,
The shutter 12 shown in FIG. 1 starts the opening operation, and after detecting this time by the hose switch 33, the maximum opening F _NO becomes 5.6 after 8 msec as shown in FIG.

Now, it is assumed that the strobe on mode in which the contact S13 of the strobe mode changeover switch 36 is turned on and the strobe 19 is forcibly emitted is set. In this state, a case where a subject at a shooting distance of 1.25 m is photographed and a case where a subject at a shooting distance of 2.5 m is photographed will be described. Note that the guide number G _NO of the strobe 19 is 10.

In the case of a subject with a shooting distance of 1.25 m, the F _NO of the flash aperture value FM obtained from the shooting distance and the guide number G _{NO of the} flash unit 19 is as follows: flash aperture value FM = 10 / 1.25 [m] = 8.0.

On the other hand, the aperture value determined by the external light brightness EV12
The F _NO of AE is 5.6, and the relationship between the two is that the flash aperture value FM ≧
The aperture value will be AE. In this case, the strobe light 19 is a so-called hillside light emission which emits light synchronously with an aperture value _FNO = 8 in the middle of the opening of the shutter 12, and the subject is irradiated with an appropriate amount of light from the strobe light 19 by the hillside light emission. Also, the subject of the background, F _NO = 5.6, a proper exposure T = 1 / 125sec.

In this case, the main subject at the shooting distance of 1.25 m was given the proper amount of strobe light, so the white balance was
Control is performed based on the color temperature of the flash emission spectrum by a white balance control signal during flash emission.

In the case of a subject with a shooting distance of 2.5 m The flash aperture value F _NO obtained from the shooting distance and the flash guide number G _NO is as follows: Flash aperture value FM = 10 / 2.5 [m] = 4.0.

In contrast, the metering aperture determined by the external light brightness EV12
F _NO is 5.6, and the metering aperture value AE is larger than the flash aperture value FM and the aperture diameter is small.
In the figure, the so-called peak light emission that emits light synchronously with the maximum aperture of _FNO = 5.6. The main subject at a shooting distance of 2.5 m is not irradiated with the appropriate amount of light from the strobe 19, but rather as auxiliary light for external light. . Therefore, the white balance is controlled by the external light white balance control signal corresponding to the color balance of the external light.

 Next, the operation will be described with reference to FIG. 4 and FIG.

First, when the camera release switch 35 shown in FIG. 1 is operated and the contact S1 is turned on, various information is input to the CPU 37. That, is input luminance information EVi, F _NO of the metering aperture AE from the relationship of FIG. 2 is obtained (step a
1, a2). The information is entered regarding the guide number G _NO photographing distance and the strobe 19 (Step a3, a4), obtaining a F _NO metering aperture FM from these (step a5).
Further, information on the color temperature is also input (step a).
6). Further, since a signal is also input from the flash mode changeover switch 36 (step a7), it is determined which mode is set in steps a8 and a9. In the strobe-on mode, which is the forced strobe mode, and in the auto mode, it is determined whether the external light luminance is equal to or less than EV8 (step a).
10) If the external light luminance is EV8 or less, the flash light emission mode (step a11) is set.

In the case of the flash mode, the flash aperture value FM
Is compared with the photometric aperture value AE (step a12). If the flash aperture value FM ≧ the photometric aperture value AE, the hillside emission mode (step a13) is set, so the white balance is set in the flash mode (step a14), and the flash emission is performed. A white balance control signal is output. On the other hand, if the flash aperture value is not equal to or larger than the photometric aperture value AE, the mode is the peak light emission mode (step a15), and the white balance is set to the external light mode (step a16). Is output.

On the other hand, if it is determined in step a8 that the strobe-off mode is set, and if it is determined in step a10 that the external light luminance is higher than EV8 in the auto mode, the strobe non-emission mode (step a17) is set. The light mode (step a16) is set.

Then, when the command contact S2 of the camera release switch 35 is turned on and the shutter 12 starts the release operation,
As shown in FIG. 5, the home switch 33 detects the start time of the operation, and in the case of the strobe light emission mode, the strobe light 19 is triggered after a predetermined time t1 or a predetermined time t2.

The subject image is converted into an electric signal by the CCD 13 by the release, and the white balance circuit 15
The color balance is controlled to an appropriate color by a white balance control signal corresponding to the white balance mode from. After that, it is recorded on the recording medium 17 via the recording circuit 16.

Here, the predetermined time t1, t2 from the shutter release start to flash trigger advance, using the time value up to a predetermined opening degree F _NO stored in the CPU37 for each shutter speed.

According to the above configuration, the balance error between the external light color balance and the strobe light color balance at the time of daytime strobe shooting is adjusted more appropriately, and the color reproducibility of the image can be improved. Also, in the case of low-intensity external light shooting, such as indoor shooting, if the subject is farther than the strobe light reaching distance, the strobe 19 is in the top-emission mode with the aperture open,
Since the white balance is set to the external light mode, color reproduction such as indoor lighting is performed, and more natural color reproduction can be achieved. Further, before and after the exposure timing for obtaining an image, the flash mode and the non-light emission mode are determined for the strobe, and the selection regarding the white balance can be determined before the exposure timing.

In the above embodiment, the strobe mode is set to the switch 36.
Is selected by the user, but an automatic daytime strobe light may be configured using a photometric circuit having an automatic backlight detection function. Further, the recording medium 17 may be anything other than magnetic, such as magneto-optical, optical, or solid-state memory, and can be applied to any device that records an image. Any device or element that converts the signal into an electric signal may be used. Further, the strobe device can be either a built-in type or an external type. Also, if terminals for _GNO output and color temperature setting output are provided depending on the type of strobe, it is possible to control the color temperature of various strobes.

It should be noted that an intermediate color temperature between the strobe light color temperature and the outside light color temperature can be set by performing further calculations on the photometric aperture value AE and the strobe aperture value FM at the time of flash emission.

〔The invention's effect〕

According to the present invention, the white balance at the time of strobe light emission is controlled so as to always maintain a good state in accordance with the position of a subject, so that color reproducibility in an image can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the image recording apparatus of the present invention, FIG. 2 is a program diagram showing a relationship between a shutter speed and an aperture value with respect to external light luminance, and FIG. FIGS. 4 and 5 are a timing chart and a timing chart, respectively, showing the relationship with the flash emission timing. 11 ... lens, 12 ... shutter, 15 ... white balance circuit, 17 ... video floppy as a recording medium,
19 ... Strobe, 25 ... Distance detection circuit, 26 ... Photometry circuit, 37 ... Comparison means and white balance switching means as functions of the system control circuit and CP
U.

Continuation of front page (58) Fields surveyed (Int.Cl. ⁶ , DB name) H04N 9/04 H04N 9/73 H04N 5/235-5/243

Claims (1)

(57) [Claims] An automatic exposure amount control means is set so that a shutter speed and an aperture value are changed in conjunction with each other in accordance with the brightness of external light. An image recording apparatus that converts an optical image incident through a lens by opening and closing a shutter into an electric signal and records the electric signal on a recording medium, wherein an outside corresponding to a color temperature of external light is used to control a white balance of the electric signal. A white balance circuit that generates either a white balance control signal during light emission or a white balance control signal during flash emission corresponding to the flash emission spectrum, the shooting distance to the subject detected by the distance detection circuit, and the strobe guide number used The automatic exposure is obtained from the flash aperture value obtained from A comparing means for comparing the photometric aperture value determined by the quantity control means; and a flash balance white light control signal when the strobe aperture value is determined to be larger than the photometric aperture value during photographing using a strobe. And a white balance switching means for generating the external light white balance control signal when it is determined that the strobe aperture value is not larger than the photometric aperture value.