Electronic flash, electronic camera and light emitting head

R, G and B LEDs are used as a light source of an electronic flash. Electric energy is supplied to a capacitor to the LEDs. A system controller controls light emitting amounts of the LEDs so that a color temperature of the electronic flash light becomes a color temperature that has been manually set with a color temperature setting switch or a color temperature of a light source determined by color temperature sensors.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to an electronic flash, an electronic camera, and a light emitting head. The present invention relates more particularly to an electronic flash using light-emitting devices such as light emitting diodes (LEDs), an electronic camera and a light emitting head.

2. Description of the Related Art

An electronic flash of a camera has a xenon tube as a light source.

There have been high-luminance LEDs that emit red, green, amber, yellow, and milky-white lights, and a high-luminance blue LEDs has been used. These LEDs are mainly used as indicators of various apparatuses.

However, when an electronic flash is used to perform back light correction for the sun light in the morning or evening, the colors of the picture can be unnatural since the spectral characteristics of the xenon tube are close to those of the daylight. Also, the electronic flash with the xenon tube can emit the light for only a few milliseconds, and it can not be used for slow shutter speeds.

SUMMARY OF THE INVENTION

In view of the foregoing, it is an object of the present invention to provide a new electronic flash of a camera using LEDs.

It is an object of the present invention to provide an electronic flash of a camera and an electronic camera that manually or automatically changes a color temperature of an electronic flash light to prevent unnatural colors of a picture.

It is an object of the present invention to provide a light emitting head that can be applied to an electronic flash with light emitting devices such as LEDs.

To achieve the above-mentioned object, the present invention is directed to an electronic flash of a camera, comprising: an electronic flash light source comprising a light emitting diode; and a light emission control device that makes the electronic flash light source emit light by supplying electric energy to the light emitting diode.

The electronic flash light source preferably comprises R, G and B light emitting diodes.

Preferably, the electronic flash further comprises a color temperature setting device that manually sets a color temperature of the light emitted from the electronic flash light source, wherein the light emission control device controls ratios between light emission amounts of the R, G and B light emitting diodes so that a color temperature of the light emitted from the electronic flash light source becomes the color temperature set by the color temperature setting device.

Preferably, the electronic flash further comprises a color temperature determining device that determines a color temperature of subject light, wherein the light emission control device controls ratios between light emission amounts of the R, G and B light emitting diodes so that a color temperature of the light emitted from the electronic flash light source becomes the color temperature determined by the color temperature determining device. Thus, the color temperature of the electronic flash light can be automatically controlled to that of the subject light, and this can prevent unnatural colors of the picture.

Preferably, the electronic flash further comprises a capacitor with a large capacity that is charged by a battery, wherein the light emission control device supplies the electric energy from the capacitor to the light emitting diode. Thus, the electric energy can be obtained with the small battery. In addition, fall of the voltage of the battery can be prevented at the light emission, and misoperation of the other circuits can be prevented.

Preferably, the electronic flash further comprises a temperature sensor that determines a peripheral temperature of the light emitting diode, wherein the light emission control device controls the electric energy to obtain a desired light emission amount according to the peripheral temperature determined by the temperature sensor. Though the light emitting diodes change the light emitting amounts due to their peripheral temperature, the desired light emission amount can still be obtained.

To achieve the above-mentioned object, the present invention is directed to an electronic flash of a camera, comprising: an electronic flash light source that emits electronic flash light; and an adjusting device that adjust a color temperature of the electronic flash light emitted from the electronic flash light source.

Preferably, the adjusting device comprises a color temperature setting device that manually sets a color temperature of the electronic flash light; and a light emission control device that controls a color temperature of the electronic flash light to the color temperature set by the color temperature setting device.

Preferably, the adjusting device comprises a color temperature determining device that determines a color temperature of subject light; and a light emission control device that controls a color temperature of the electronic flash light to the color temperature determined by the color temperature determining device.

Preferably, the color temperature determining device has determining devices that convert color components of the subject light into electric signals and determines the color temperature of the subject light according to a ratio between determination signals of the determining devices. The determining devices may be red and blue determining devices or red, green and blue determining devices.

The color temperature determining device can determine the color temperature of the light source according to color image signals of a subject image captured by imaging devices of the camera. The imaging devices of the camera can be also used as a part of the color temperature determining device.

Preferably, the electronic flash light source is R, G and B light emitting devices and light emitting amounts from the R, G and B light emitting devices can be separately controlled. The R, G and B light emitting devices can be light emitting diodes, organic electroluminescences or plasma light emitting devices.

Preferably, the electronic flash further comprises a capacitor with a large capacity that is charged by a battery, and the adjusting device supplies the electric energy from the capacitor to the light emitting devices.

Preferably, the electronic flash further comprises a temperature sensor that determines a peripheral temperature of the light emitting diodes, and the adjusting device controls the electric energy to obtain a desired light emission amount according to the peripheral temperature determined by the temperature sensor.

Preferably, the adjusting device adjusts the color temperature of the electronic flash light by controlling a ratio between the light emitting amounts from the R, G and B light emitting devices.

The adjusting device can control the ratio between the light emitting amounts from the R, G and B light emitting devices by separately turning on and off the R, G and B light emitting devices.

Preferably, the adjusting device comprises a light adjusting sensor that determines one of an amount of reflected light from a subject emitted from one of the R, G and B light emitting devices of which light emitting amount is smallest among the R, G and B light emitting devices and an amount of reflected light from the subject emitted from the R, G and B light emitting devices; a first light emission controlling device that stops light emission of the one of the R, G and B light emitting devices when the one of the amounts determined by the light adjusting sensor reaches a predetermined reference value according to the ratios between the light emitting amounts from the R, G and B light emitting devices; a measuring device that measures a light emitting time of the one of the R, G and B light emitting devices; a calculating device that calculates light emitting times of others of the R, G and B light emitting devices according to the light emitting time measured by the measuring device and the ratios between the light emitting amounts from the R, G and B light emitting devices; and a second light emission controlling device that stops light emission of the others of the R, G and B light emitting devices according to the light emitting times calculated by the calculating device. The light emitting amount (light emitting time) of the light emitting devices with the smallest light emitting amount is controlled according to the amount determined by the light adjusting sensor. The light emitting times of the other light emitting devices are calculated according to the light emitting time and the ratio between the light emitting amounts from the R, G and B light emitting devices.

Preferably, the adjusting device comprises a device that turns on and off the R, G and B light emitting devices with duty ratios corresponding to the ratios between the light emitting amounts from the R, G and B light emitting devices; a light adjusting sensor that determines an amount of reflected light from a subject emitted from the R, G and B light emitting devices; and a light emission controlling device that stops light emission of the R, G and B light emitting devices when the amount determined by the light adjusting sensor reaches a predetermined reference value.

The adjusting device may comprise a device that turns on and off R, G and B light emitting devices of numbers according to the ratios between the light emitting amounts from the R, G and B light emitting devices; a light adjusting sensor that determines an amount of reflected light from a subject emitted from the R, G and B light emitting devices; and a light emission controlling device that stops light emission of the R, G and B light emitting devices when the amount determined by the light adjusting sensor reaches a predetermined reference value.

Preferably, the electronic flash light source comprises: a white light source that emits white electronic flash light; and color filters that are arranged movably in front of the white light source, wherein the adjusting device adjusts the color temperature of the electronic flash light by moving at least one of the color filters in front of the white light source.

To achieve the above-mentioned object, the present invention is directed to an electronic camera that stores color image signals of a subject image captured with a taking lens and an imaging device, the electronic camera comprising: a color temperature determining device that determines a color temperature of subject light before a shooting; an electronic flash light source that emits electronic flash light; an automatic white balance correcting device that corrects a white balance of the color image signals according to the color temperature determined by the color temperature determining device at the shooting irrespective of light emission of the electronic flash light source; and an adjusting device that adjusts a color temperature of the electronic flash light to the color temperature determined by the color temperature determining device.

The electronic camera emits the light with the color temperature that is the same as the color temperature of the subject light source, and the white balance is corrected according to the color temperature of the subject light source. The conventional electronic camera corrects the white balance no matter what the color temperature of the subject light source is.

To achieve the above-mentioned object, the present invention is directed to an electronic camera that stores color image signals of a subject image captured with a taking lens and an imaging device, the electronic camera comprising: a color temperature determining device that determines a color temperature of subject light; a recording device that records at least one color temperature determined by the color temperature determining device; a designating device that reads the color temperature recorded in the recording device; an automatic white balance correcting device that corrects a white balance of the color image signals according to the color temperature read by the designating device; an electronic flash light source that emits electronic flash light; and an adjusting device that adjusts a color temperature of the electronic flash light to the color temperature read by the designating device. For example, the user records color temperatures of a spotlight of a ceremonial hall, a ceiling light and a studio light, and reads one of the color temperatures so that the electronic flash emits the light with the read color temperature, and the white balance is corrected according to the color temperature.

The color temperature determining device can determine the color temperature of the subject light from the color image signals of the subject image captured with the taking lens and the imaging device.

To achieve the above-mentioned object, the present invention is directed to a an optical member that is one of a polygonal prism and a cylinder; a light emitting device array provided on a side of the optical member; and a reflecting mirror provided on at least a bottom of the optical member, wherein the light emitting device array emits light out of the optical member through a top of the optical member.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This invention will be described in further detail by way of example with reference to the accompanying drawings.

FIG. 1is a perspective view of an electronic flash10for a camera of a first embodiment according to the present invention.

The electronic flash10is composed of a body20with a hot shoe22on its bottom and a light-emitting part30.

Color temperature sensors24(photo sensors24R,24G and24B with R, G and B filters) for measuring a color temperature of subject light are provided on the front of the body20. A switch26for choosing a manual mode or an automatic mode and a color temperature setting switch28are provided on the side of the body20. In the manual mode, a user manually sets a color temperature of an electronic flash light with a color temperature setting switch28. In the automatic mode, the color temperature of the electronic flash light is automatically set.

A reference numeral32denotes a Fresnel lens of the light-emitting part30, and a reference numeral34denotes a light-receiving sensor for adjusting the electronic flash light.

FIG. 2is a back view of the electronic flash10. Color temperature recording switches21(21-1,21-2and21-3), indicators L1, L2and L3and a color temperature reading switch23are provided on the back of the electronic flash10. When one of the color temperature recording switches21is pressed, the current color temperature of the subject light measured by the color temperature sensors24is recorded in a nonvolatile memory (EEPROM)25(seeFIG. 4) of the electronic flash10. The three color temperature recording switches21make it possible to record three color temperatures.

Each time the color temperature reading switch23is pushed, one of the color temperatures recorded with the color temperature recording switches21-1,21-2and21-3is read in order. The indicators L1, L2and L3correspond to the color temperature recording switches21-1,21-2and21-3, respectively, and one of the indicators L1, L2and L3corresponding to the selected color temperature is turned on. The color temperature of the electronic flash light is adjusted to the read color temperature.

FIG. 3(A)is a section of a light source part36of the light-emitting part30, andFIG. 3(B)is a front view of the light source part36.

The light source part36is composed of a reflector37, LEDs38(R, G and B LEDs38R,38G and38B) and a diffusion plate39. The R, G and B LEDs38R,38G and38B are arranged to form an array as shown inFIG. 3(B). The diffusion plate39diffuses high-directivity lights emitted from the LEDs38. The numbers of the LEDs38R,38G and38B does not need to be the same, and they are preferably arranged so that a white light is produced when all the LEDs38emit lights.

FIG. 4is a block diagram of the electronic flash10.

The electronic flash10has a battery40, a step-up transformer42, a large-capacity capacitor44, operational amplifiers46,48and50, a system controller52, a light adjusting circuit54and a temperature sensor56as well as the color temperature recording switches21, the color temperature reading switch23, the color temperature sensors24, the EEPROM25, the switch26, the color temperature setting switch28, the light-receiving sensor34and the LEDs38.

The system controller52controls the electronic flash10, and makes the step-up transformer42output the voltage of 10V from the voltage (for example, 6V) of the battery40in order to charge the capacitor44with the outputted voltage. The capacitor44is charged for two to five seconds, and can discharge to the LEDs38for more than 1/60 sec (approximately 16 ms).

The capacitor44discharges to the LEDs38R,38G and38B through the operational amplifiers46,48and50, and the system controller52controls the operational amplifiers46,48and50to control a light-emitting time and amount of the LEDs38R,38G and38B.

The system controller52receives a light-emitting signal from the camera through the hot shoe22(seeFIG. 1) in synchronization with a shutter release, and receives information (a guide number, etc.) for determining the light-emitting amount in a serial communication. When the switch26is on the manual mode, the system controller52controls the color temperature of the electronic flash light to that set with the color temperature setting switch28. When the switch26is on the automatic mode, the system controller52controls the color temperature of the electronic flash light to that of the subject light determined by the color temperature sensors24. The color temperature sensors24are not limited to those. They determine the color temperature of the subject light according to the ratio between the R, G and B components of the light, but they may do that according to the ratio between the R and B components of the light.

When one of the color temperature recording switches21is pushed, the system controller52records the current color temperature of the subject light determined by the color temperature sensors24in the EEPROM25. When one of the color temperature reading switches23is pushed, the system controller52reads the recorded color temperature, and controls the color temperature of the electronic flash light to the read color temperature. For example, the user records color temperatures of a spotlight of a ceremonial hall, a ceiling light and a studio light with the color temperature sensors24in the EEPROM25, and reads one of the color temperatures with one of the color temperature reading switches23so that the electronic flash emits the light with the read color temperature.

Since the light amounts of the LEDs change according to their peripheral temperature, a temperature sensor56that determines the peripheral temperature of the LEDs38is provided. The system controller52controls the electric current to the LEDs38according to the peripheral temperature determined by the temperature sensor56.

The operation of the system controller52will now be explained with reference to timing charts ofFIGS. 5(A),5(B),5(C),5(D),5(E),5(F) and5(G).

On receiving an electronic flash signal (FIG.5(A)), the system controller52outputs a signal to the step-up transformer42for starting the charging of the capacitor44. When the charging is finished, the system controller52stops the step-up transformer42(FIGS. 5(B) and 5(C)).

When a shutter release button is half pressed, the system controller52gets ready for the discharging (FIG. 5(D)) and receives the information (the guide number, etc.) for determining the light emitting amount. When the switch26is on the automatic mode, the system controller52reads the color temperature of the subject light from one of the color temperature sensors24. When the switch26is on the manual mode, the system controller52reads the manually-set color temperature corresponding to the operated color temperature reading switch23(FIG. 5(E)).

The system controller52determines the light emitting amount according to the received information, outputs a reference value for the light emitting amount to the light adjusting circuit54, determines the ratio between the light emitting amounts of the LEDs38R,38G and38B according to the color temperature of the subject light, and sets R, G and B light emitting levels from the ratio (FIG. 5(F)).

When the shutter release button is fully pressed, the system controller52receives the light emitting signal in synchronization with the shutter release and outputs the R, G and B light emitting levels to positive-sequence input terminals of the operational amplifiers46,48and50. Signals that corresponds to electric currents to be sent to the LEDs38R,38G and38B are inputted to negative-sequence input terminals of the operational amplifiers46,48and50, and the operational amplifiers46,48and50control the electric currents flowing through the LEDs38R,38G and38B according to the R, G and B light emitting levels.

The LEDs38emit the lights with the same color temperature as that of the subject light (FIG. 5(G)).

The light adjusting circuit54determines the light emitting amount with the light-receiving sensor34. When the light emitting amount reaches the reference value, the light adjusting circuit54outputs the light-emission stop signal to the system controller52, which outputs a signal for stopping the light emission of the LEDs38to the operational amplifiers46,48and50. This turns off the electric currents flowing through the LEDs38to stop the light emission of the LEDs38.

FIG. 6is a circuit diagram showing another method of controlling the light emitting amounts of the LEDs38.

The electric currents flow from the capacitor44to the LEDs38through transistors61,62and63and inductors64,65and66.

A step-down transformer60receives signals indicating R, G and B light-emitting levels, the light-emission signal in synchronization with the shutter release, and the light-emission stop signal. After receiving the light-emission signal, the step-down transformer60outputs pulses with a controlled duty ratio to bases of the transistors61,62and63so that the electric currents corresponding to the light-emitting levels flow through the LEDs38until receiving the light-emission stop signal.

The transistors61,62and63turn on and off due to the pulses, and pass the electric currents to the LEDs38R,38G and38B through the inductors64,65and66while they are on. While they are off, electric currents flows to the LEDs38R,38G and38B through diodes67,68and69due to induction electromotive forces of the inductors64,65and66.

The step-down transformer60monitors the electric currents flowing through the LEDs38, and adjusts the duty ratio of the pulses inputted to the transistors61,62and63according to the light emitting levels.

As shown inFIG. 7, light-emitting times of the LEDs38R,38G and38B may be controlled for a desired ratio between the light-emitting amounts of the LEDs38.

When the ratio between the B, R and G light-emitting amounts (the same as the ratio between the light-emitting times, for convenience) is 1:2:4, the LEDs38R,38G and38B start emitting the lights at one time, and the LEDs38B stop emitting the lights a time t later, and the LEDs38R stop emitting the lights a time 2t later, and the LEDs38G stop emitting the lights a time 4t later.

The time t will be explained.

A reference value Vref′ is calculated by the following equation 1,
Vref′={3a/(a+b+c)}×Vref  equation 1,

wherein Vrefis the reference value for adjusting the light-emission amounts and a:b:c (a≦b≦c) is the ratio between the light-emitting amounts.

When the ratio a:b:c is 1:2:4 as shown inFIG. 7, the reference value Vref′ is (3/7) Vref.

The LEDs38R,38G and38B start emitting the lights at one time, and the light adjusting circuit54determines the light emission amount with the light-receiving sensor34. When the light emission amount reaches the reference value Vref′, the LEDs with the lowest light emission amount (the LEDs38B in this case) stop emitting the lights, and the light emission time t is measured. Then, the light emission times of the other LEDs according to the light emission time t and the ratio (a:b:c) are calculated. In case of the ratio 1:2:4, the light emission time of the LEDs38R is 2t, and the light emission time of the LEDs38G is 4t. In the embodiment, the light-receiving sensor34that is sensitive to all the R, G and B lights, but a light-receiving sensor that is sensitive only to the lights with the lowest light emission amount may be used. In this case, the number 3a in the equation 1 is replaced with the number a.

FIG. 8shows a case in which the duty ratios of the LEDs38R,38G and38B are adjusted to control the color temperature of the electronic flash light (the ratio between the R, G and B light-emission amounts).

The duty ratios of the LEDs38R,38G and38B are determined so that the ratio between the total light-emitting times of the LEDs38is the ratio between the R, G and B light emission amounts.

The LEDs38R,38G and38B start emitting the lights at one time, and end it at one time when the light emission amount reaches the desired amount.

If each LED can be turned on and off, the numbers of the LEDs38R,38G and38B to be turned on may be controlled.

FIG. 9is a block diagram showing a second embodiment of an electronic flash70of the camera according to the present invention.

Unlike the electronic flash10of the first embodiment, the electronic flash70does not adjust the color temperature and has only a milky-white LED71. Switches S1and S2turn on and off with an electronic flash switch. When the switches S1and S2are turned on, a step-up transformer73outputs a voltage from that of a battery72to charge a capacitor74. When the switch S1is turned on, an LED75for indicating the charging is turned on. When the voltage of the capacitor74reaches a reference voltage inputted to an operational amplifier76, the charging is finished and the LED75turns off.

A switch S3is a normally open switch, and it is closed for an instant when the shutter release button is pushed.

When the switch S3is open, a capacitor78is charged to more than a predetermined voltage with a light-receiving sensor77for the light adjusting, and an operational amplifier79outputs an L-level signal to turn off a transistor80. Thus, the electric current does not flow through the LED71and it does not emit a light even when the capacitor74for the light emission has been charged.

When the shutter release button is pushed and the switch S3is closed, the capacitor78discharges and the operational amplifier79outputs an H-level signal to turn on the transistor80. This allows the flow of electric current from the capacitor74to the LED71, which emits the light.

Then, the capacitor78is charged with the light-receiving sensor77for the light adjusting. When the voltage of the capacitor78reaches that of a resistor81, the operational amplifier79outputs the L-level signal to turn off the transistor80. This turns off the LED71.

A resistance of an adjustable resistor82can be adjusted according to the guide number, and this changes the voltage of the resistor81to adjust the light emission amount of the LED71. A switch S4that turns on with the shutter release button may be provided instead of an automatic electronic flash circuit (including the light-receiving sensor77for the light adjusting) which is enclosed by a dashed line.

FIG. 10is a block diagram showing a third embodiment of an electronic flash90of the camera according to the present invention.

Unlike the electronic flash10of the first embodiment, the electronic flash90has an organic electroluminescence panel (organic EL panel)91. Parts that are the same as those inFIG. 4are denoted by the same reference numerals, and they will not be explained in detail.

The organic EL panel91is formed in such a manner that R organic ELs whose spectrum peak wavelength is 600–740 nm (red area), G organic ELs whose spectrum peak wavelength is 500–600 nm (green area) and B organic ELs whose spectrum peak wavelength is 380–500 nm (blue area) are arranged in the same way as the LEDs38inFIG. 3(B). Light emitting brightnesses and times of the R, G and B organic ELs are controlled according to control signals inputted from the system controller52.

This enables the organic EL panel91to emit a light with the desired color temperature.

A plasma light-emitting device panel in which plasma light-emitting devices are arranged as an array may be used instead of the organic EL panel91. The plasma light-emitting devices stimulates R, G and B fluorescent materials by emitting ultraviolet rays to make them emit R, G and B lights.

FIG. 11is a block diagram showing a fourth embodiment of an electronic flash92of the camera according to the present invention.

Unlike the electronic flash10of the first embodiment, the electronic flash92has a light source that can change the color temperature of the electronic flash light with color filters94. Parts that are the same as those inFIG. 4are denoted by the same reference numerals, and they will not be explained in detail.

The light source is composed of a light emitting part93that emits a white light, the color filters94(an R filter94R and a B filter94B) and a filter driving motor95.

The color filters94are movably provided in front of the light emitting part93, and a rack94A is connected to one end of the color filters94. A pinion95A engaged with the rack94A is fixed to a driving shaft of the filter driving motor95. Driving the filter driving motor95moves the color filters94vertically inFIG. 11.

The light source emits a light with the color temperature (5500–6000 degrees Kelvin) of the daytime sun when the light emitting part93is not covered as shown inFIG. 11. When the R filter94R covers the light emitting part93, the light source emits a light with the color temperature (2000–3000 degrees Kelvin) of the rising or setting sun. When the B filter94B covers the light emitting part93, the light source emits a light with the color temperature (10000–20000 degrees Kelvin) of the blue sky.

When the color temperature of the electronic flash light is set automatically or manually, the system controller52controls the filter driving motor95to move the color filters94for the light with the color temperature that is the closest to the set color temperature. When the shutter release button is fully pushed and the system controller52receives the light emission signal in synchronization with the shutter release, the system controller52outputs an electronic flash ON signal to the light emitting part93to emit the light.

The light adjusting circuit54determines the light emission amount with the light-receiving sensor34for the light adjusting. When the light emission amount reaches a reference value, the light adjusting circuit54outputs an electronic flash OFF signal to the light emitting part93to stop the light emission.

FIG. 12is a back view of an electronic camera100that can adjust the color temperature of the electronic flash light according to the present invention.

The user rotates a mode dial101to set one of shooting modes including a manual shooting mode, an automatic shooting mode and a person shooting mode. A shutter release button102is provided in the center of the mode dial101, and the shutter release button102can be pushed half and fully.

As shown inFIG. 12, an eyepiece103, a shift key104, a display key105, a record mode/play mode switch106, a cancel key107, an execution key108, a multifunction cross key109and a liquid crystal monitor152are provided on the back of the digital camera.

FIG. 13is a block diagram showing the inner structure of the electronic camera100inFIG. 12.

A subject image formed on a light-receiving surface of a charge coupled device (CCD)114through a taking lens110and a diaphragm112is converted into signal electric charges corresponding to the amount of an incident light by each sensor. The stored signal electric charges are read out to shift registers with read gate pulses applied from a CCD driving circuit116, and sequentially read out as voltage signals corresponding to the signal electric charges with register transfer pulses. The CCD114has an electric shutter function for controlling the exposure time (shutter speed) by outputting the stored signal electric charges with shutter gate pulses.

The voltage signals are outputted from the CCD114to a correlative double sampling circuit (CDS circuit)118, which samples and holds R, G and B signals of each pixel. The CDS circuit118outputs the R, G and B signals to an A/D converter120, which converts the R, G and B signals into digital R, G and B signals and outputs the digital R, G and B signals. The CCD driving circuit116, the CDS circuit118and the A/D converter120are synchronized by timing signals outputted from a timing generator122.

The digital R, G and B signals outputted from the A/D converter120are temporarily stored in a memory124, and then outputted to a digital signal processing circuit126. The digital signal processing circuit126comprises a synchronizing circuit128, a white balance adjusting circuit130, a gamma correcting circuit132, a YC signal producing circuit134and a memory136.

The synchronizing circuit128converts the dot-sequential R, G and B signals read from the memory124into synchronous R, G and B signals, which are outputted to the white balance adjusting circuit130. The white balance adjusting circuit130has multipliers130R,130G and130B that increases or decreases digital values of the R, G and B signals, and the R, G and B signals are inputted to the multipliers130R,130G and130B, respectively. White balance correction values (gains) Rg, Gg and Bg for adjusting the white balance are outputted from a central processing unit (CPU)138to the multipliers130R,130G and130B, respectively. Each of the multipliers130R,130G and130B multiplies the corresponding digital value and gain together, and the multipliers130R,130G and130B get R′, G′ and B′ signals. The white balance adjusting circuit130outputs the R′, G′ and B′ signals to the gamma correcting circuit132. The gains Rg, Gg and Bg will be later explained in detail.

The gamma correcting circuit32corrects the R′, G′ and B′ signals to R, G and B signals with desired gamma characteristic and outputs the R, G and B signals to the YC signal producing circuit134. The YC signal producing circuit134produces luminance signals Y and chroma signals Cr and Cb (YC signals) from the R, G and B signals. The YC signals are stored in the memory136.

The YC signals are read from the memory136and outputted from the liquid crystal monitor152so that a moving image or a still image is displayed on the liquid crystal monitor152.

After the shooting, the YC signals are compressed with a predetermined format by the compressing/decompressing circuit154, and the compressed image data is stored in a storage medium such as a memory card by a storage part156. In the reproducing mode, the image data stored in the memory card or the like is decompressed, and the decompressed image data is outputted to the liquid crystal monitor152so that the image is displayed on the liquid crystal monitor152.

The CPU138controls the circuits according to inputs from a camera control part140including the mode dial101, the shutter release button102and the cross key109. The CPU138also controls automatic focusing, automatic exposure and automatic white balance. For example, the automatic focusing is contrast automatic focusing that moves the taking lens110through a driving part142so that the high-frequency component of the G signal is the maximum when the shutter release button102is half pressed.

In the automatic exposure, the R, G and B signals are read, and the subject brightness (exposure values) is determined according to integrated values of the R, G and B signals. The F-number and the shutter speed are determined from the exposure value. When the shutter release button102is fully pressed, the CPU138drives the diaphragm112through a diaphragm driving part144for the determined F-number, and controls the exposure time for the determined shutter speed. Image data of one frame is captured and processed, and then stored in the storage medium.

The method of correcting the white balance will now be explained.

To manually correct the white balance, the user chooses the record mode with the record mode/play mode switch106and selects the manual shooting mode with the mode dial101. Then, the user pushes the execution key108to display a menu for setting the white balance on the liquid crystal monitor152as shown inFIG. 12, and selects an icon (AUTO, icons showing subject light sources, and M) with the cross key109. When the icon “AUTO” is selected, the color temperature of the subject light (the type of the subject light source) is measured and the white balance is corrected according to the color temperature. When one of the icons showing the light sources is selected, the white balance is corrected according to the subject light source. When the icon “M” is selected, a recorded color temperature is read and the white balance is corrected according to the color temperature.

The measurement of the color temperature of the subject light (the type of the subject light source) in the automatic shooting mode or when the icon “AUTO” is selected in the manual shooting mode will be explained.

The image is divided into multiple areas (8 by 8), and an integrating circuit148inFIG. 13calculates average values of the R, G and B signals in each area stored in the memory124and outputs them to the CPU138. Multipliers150R,150G and150B are provided between the integrating circuit148and the CPU138, and gains are inputted to the multipliers150R,150G and150B.

The CPU138determines the subject light source (daylight, shade-cloudiness, a fluorescent lamp, a tungsten lamp, or the like) according to the average values of the R, G and B signals in each area. Ratios R/G and B/G between the average values of the R, G and B signals in each area are calculated, and determination frames for the subject light sources are set on a co-ordinate system with the ratio R/G as the x coordinate and the ratio B/G as the y coordinate. The number of areas in each determination frame is determined, and the subject light sources is determined according to the brightness level of the subject and the number of areas in each determination frame (see Japanese Patent Provisional Publication No. 2000-224608). The method of determining the subject light source (color temperature) is not limited to this.

After determining the subject light source, the CPU138determines the white balance correction values (gains) Rg, Gg and Bg that are suitable for the subject light source and outputs them to the multipliers130R,130G and130B, respectively. The multipliers130R,130G and130B outputs the white-balanced R′, G′ and B′ signals to the gamma correcting circuit132.

The digital signal processing circuit126corrects the white balance in the embodiment, but an analog signal processing including the CDS circuit118and a gain control amplifier (not shown) may do that. The ratios R/G and B/G are changed in the embodiment, but the chroma signals Cr and Cb may be changed.

The method of controlling the electronic flash146will now be explained.

FIG. 14is a block diagram of the electronic flash146that is built in or attached to the electronic camera100. Parts that are the same as those inFIG. 4are denoted by the same reference numerals, and they will not be explained.

The electronic flash146is different from the electronic flash10of the first embodiment in that it does not have the color temperature sensors24for determining the color temperature of the subject light source. The color temperature is determined according to the R, G and B signals obtained from the CCD114.

The CPU138outputs the light-emission signal in synchronization with the shutter release and serial signals indicating the light emission amount and the color temperature of the electronic flash light to the system controller52of the electronic flash146.

A conventional electronic camera prohibits the light emission in the manual white balance mode, so that the electronic flash light does not affect the manually-corrected white balance. However, the electronic camera100of the present invention does not prohibit the light emission even in the manual white balance mode.

In addition, the conventional electronic camera does not perform either the automatic white balance correction or the manual white balance correction, and adjusts the white balance with the fixed gains according to the electronic flash light (the daylight) to perform a shooting with the electronic flash. However, the electronic camera100of the present invention performs the automatic white balance correction or the manual white balance correction.

The electronic camera100controls the electronic flash146to emit the light with the automatically-measured color temperature of the subject light source in the automatic white balance mode. The electronic camera100controls the electronic flash146to emit the light with the manually-set color temperature in the manual white balance mode.

Therefore, the electronic flash light does not affect the automatically or manually corrected white balance.

FIG. 15is a perspective view of a light emitting head190.

The light emitting head190has a rectangular diffusion plate192, and R, G and B LEDs193R,193G and193B are provided on the four sides of the diffusion plate192, and a dish-shaped reflecting mirror194is arranged on the bottom of the diffusion plate192. Mirrors may be provided on parts of the sides of the diffusion plate192without the LEDs193R,193G and193B to prevent lights from leaking through the sides.

The LEDs193R,193G and193B emit lights out of the diffusion plate192through its top.

The number of the G LEDs193G is larger than those of the R and B LEDs193R and193B to produce a white light. A number of LEDs may be arranged on the sides of the diffusion plate192. The diffusion plate192does not necessarily have to be rectangular, and it may be a polygonal prism or a cylinder. A light guide member may be used instead of the diffusion plate192, and a diffusion plate is provided only on its light emission surface.

According to the present invention, since the LEDs, the organic ELs or the plasma light-emitting devices are used as the electronic flash light source, the light-emission (brightness) level and the light emission time can be easily changed. In addition, since the R, G and B light-emitting devices are used, the color temperature of the electronic flash light can be manually or automatically changed. For example, back light correction for the sun light in the morning or evening can be performed according to the color temperature of the sun light, and this prevents unnatural colors of a picture due to the electronic flash light.

Moreover, since the large-capacity capacitor is charged slowly and it discharges quickly, the electric energy can be obtained with the small battery. Furthermore, fall of the voltage of the battery can be prevented at the light emission, and misoperation of the other circuits can be prevented.

The LEDs or the like can continuously emit the lights for slow shutter speeds, and they can be used as a light source at the auto focus.