JPH04130866A - Electronic image pickup device provided with fluorescent lamp for illumination - Google Patents

Abstract

PURPOSE:To previously prevent the occurrence of flicker by detecting the frequency of a commercial power source lighting a fluorescent lamp irradiating an object and permitting an electronic shutter to control it at shutter speed equal to a period corresponding to the integer multiple frequency of the detected frequency. CONSTITUTION:CPU 10 gives the instruction of the generated timing of a clear pulse to a synchronizing signal generation circuit 11 for controlling signal charge accumulation time (exposure time) in CCD 13 based on the detected commercial power source frequency. The charge accumulation time is set to time equal to the period corresponding to the frequency which is integral multiple (including one-fold) of the detected commercial power source frequency. A signal which is read from CCD 13 passes through a sampling circuit and a color separation circuit, and a variable gain amplifier circuit 16 if necessary, and it is given to a video signal processing circuit 17. It includes a white balance adjustment circuit, a gamma correction circuit, a matrix circuit and an encoder, and it outputs the video signal of NTSC format.

Description

BACKGROUND TECHNICAL FIELD OF THE INVENTION The present invention relates to an electronic imaging device that is equipped with a fluorescent lamp for illumination and that images a subject illuminated by the fluorescent lamp using a solid-state electronic image pickup device with an electronic shutter function. Regarding.

Prior Art and Its Problems In recent years, a new system, which can be called an electronic overhead projector, has been developed to replace the optical so-called overhead projector. This system captures an image of an object such as a manuscript, film, or actual object using a camera equipped with a solid-state electronic imaging device such as a CCD, and uses the obtained video signal to display or project the object image on a large display screen. It is. A fluorescent light is provided near the camera to illuminate the subject. The light from a fluorescent lamp contains a fundamental wave with a frequency twice the power supply frequency and brightness fluctuation components due to its harmonics. When a fluorescent lamp is turned on using a normal commercial power source (50 Hz or 60 Hz), flicker occurs in one displayed image. To prevent this, fluorescent lights are lit at a high frequency of several tens of kilohertz. However, high frequency lighting requires an expensive inverter circuit.

To prevent flicker without an inverter circuit, use a DC-driven incandescent light bulb instead of a fluorescent light, but incandescent light bulbs produce a large amount of heat and are therefore unsafe. Another problem with incandescent light bulbs is that they have a short lifespan.

SUMMARY OF THE INVENTION OBJECTS OF THE INVENTION An object of the present invention is to provide an electronic imaging device that can light a fluorescent lamp at a commercial power frequency without using an inverter circuit and can prevent flicker from occurring.

Structure 9 of the Invention Functions and Effects An electronic imaging device equipped with a fluorescent lamp for illumination according to the present invention includes an illumination device including a fluorescent lamp that illuminates a subject, and a frequency that detects the frequency of a commercial power source that supplies power to the illumination device. a detection means, a solid-state electronic image sensor having an electronic shutter function for imaging a subject illuminated by the illumination device, and controlling charge accumulation time of the solid-state electronic image sensor according to a given shutter speed; a drive circuit that reads out the signal charge at a predetermined period, and an integer multiple (1
The present invention is characterized by comprising a shutter speed control means for controlling the drive circuit to operate at a shutter speed equal to the period corresponding to the frequency (including times).

According to this invention, the frequency of the commercial power source that turns on the fluorescent lamp that illuminates the subject is detected, and the electronic shutter is controlled at a shutter speed equal to a period corresponding to a frequency that is an integral multiple of the detected frequency.

The frequency of commercial power supply in Japan varies depending on the region5.
0 Hz or 60 Hz. If the frequency of the commercial power supply is 50 Hz, the shutter speed is, for example, 1/1.
For example, if it is set to 00 seconds and 80Hz, it is 1/6
Set to 0 seconds or 1/120 seconds.

Therefore, even if the light from a fluorescent lamp contains components that fluctuate at frequencies twice the commercial power supply frequency and integral multiples thereof, the shutter speed is set equal to the period corresponding to the frequency that is an integral multiple of the commercial power supply frequency. Therefore, the charge accumulation time of the solid-state electronic image sensor is exactly an integral multiple of the period of fluctuation of the light of the fluorescent lamp. Therefore, a constant amount of light always enters the solid-state electronic image sensor regardless of fluctuations in the light from the fluorescent lamp.

Always exposed to a constant amount of light. Therefore, flicker caused by fluctuations in the light of the fluorescent lamp does not occur in the reproduced image. Since the fluorescent lamp can be lit using commercial power, there is no need for an expensive inverter circuit for high-frequency lighting, and the cost of the device can be reduced. They are also safer than incandescent bulbs, and fluorescent bulbs have the advantage of longer lifespans than incandescent bulbs.

As mentioned above, since the shutter speed is determined by the frequency of the commercial power supply, the amount of exposure to the solid-state electronic image pickup device is not necessarily performed appropriately. Therefore, it is preferable to further provide means for correcting the exposure amount of the solid-state electronic image sensor.

This correction means includes an iris that directly controls the exposure amount,
There are variable gain amplifier circuits that adjust the level of video signals obtained by imaging.

DESCRIPTION OF THE EMBODIMENTS The drawing shows an embodiment of the present invention, and is a block diagram showing the configuration of an electronic imaging device equipped with a fluorescent lamp for illuminating an object.

One or more fluorescent lamps 7 are provided to illuminate the subject, and the fluorescent lamps 7 are turned on by a lighting circuit 8 using the commercial power supply voltage applied through the outlet plug 1.

The voltage of the commercial power supply input to the device via the outlet plug 1 is stepped down by the transformer 3 and applied to the power supply circuit 4. Power supply circuit 4 is a rectifying and smoothing circuit.

It includes a regulator and the like, and supplies a DC operating power source of a predetermined voltage to each circuit of this imaging device. Further, the stepped-down secondary output of the transformer 3 is given to an attenuator 5, and after being attenuated, only the AC component passes through a capacitor and is input to a waveform shaping circuit 6, where the waveform is shaped into a square wave and input to the CPU10.

The CPU 10 detects the frequency of the commercial power supply by, for example, counting the rise of the input square wave signal over a predetermined period of time or measuring the interval between rises. In our country, the frequency of commercial power supply is 50 Hz or 60 Hz, so it is only necessary to know which of these frequencies it is, so detection of one frequency does not necessarily have to be exact. Based on the detected frequency, the CPU 10 controls the shutter speed of the electronic shutter through the synchronizing signal generating circuit 11 as will be described later, and also performs control for correcting the exposure amount as necessary.

The subject illuminated by the fluorescent lamp 7 is imaged by the CCD 13. The synchronization signal generation circuit 11 generates a horizontal synchronization signal and a vertical synchronization signal based on the reference clock signal, and generates a CCD 13 based on the reference clock signal.
It generates horizontal drive pulses (pixel clocks) and vertical drive pulses for reading out signal charges from the pixel, transfer start (readout start) pulses synchronized with the synchronization signal, clear pulses for storage time control, etc. Output. The CCD drive circuit 12 clears and reads out the CCD based on the above-mentioned various signals, pulses, etc. given from the synchronization signal generation circuit 11. The exposure time by the electronic shutter is controlled by the output timing of the clear pulse.

That is, the signal charges accumulated in the CCD are cleared by the clear pulse (by reverse transfer, forward transfer, sweeping to the substrate, etc.), and thereafter the accumulation of signal charges representing the object image in the CCD begins. The time from the clear pulse to the generation of the next transfer start (read start) pulse is the exposure time. Reading of signal charges from the CCD 13 is repeated at a predetermined period (for example, 1/60 seconds).

The CPU 10 controls the CPU 10 based on the detected commercial power frequency.
In order to control the signal charge accumulation time (exposure time) in the CD 13, the generation timing of a clear pulse is instructed to the synchronization signal generation circuit 11. This charge accumulation time is set to a time equal to a period corresponding to a frequency that is an integral multiple (including one time) of the detected commercial power supply frequency. For example, if the detected commercial power frequency is 50 Hz, this charge accumulation time will be 1/100 second, and if the detected commercial power frequency is 80 Hz, the charge accumulation time will be 1/100 seconds.
z, it is set to 1/60 second or 1/120 second.

The signal read out from the CCD 13 passes through a sampling circuit 1, a color separation circuit, and, if necessary, a variable gain amplifier circuit 1.
6 and is applied to the video signal processing circuit 17. The video signal processing circuit 17 includes a white balance adjustment circuit, a gamma correction circuit,
Including matrix circuits, encoders, etc., such as NTS
Outputs a C format video signal.

As mentioned above, the shutter speed of an electronic shutter is determined by the commercial power frequency.

The amount of exposure to the CCD 13 is not necessarily carried out appropriately. Therefore, if necessary, an iris 14 is provided,
The aperture value of the iris 14 is controlled by the CPU10 via the iris control circuit 15, so that the CCD
The amount of light incident on 13 is adjusted.

Correction is performed so that the exposure amount becomes appropriate. The level of the video signal may be controlled by adjusting the gain of the variable gain amplifier circuit 16 described above.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and are block diagrams showing the electrical configuration of an electronic imaging device. 7... Fluorescent light. 8...Lighting circuit. 10...CPU. 11... Synchronization signal generation circuit. 12...COD drive circuit. 13...CCD0 or more

Claims (2)

[Claims] (1) A lighting device including a fluorescent lamp that illuminates the subject, a frequency detection means that detects the frequency of the commercial power source that supplies power to the lighting device, and an electronic shutter function to image the subject illuminated by the lighting device. A solid-state electronic image sensor having: a drive circuit that controls the charge accumulation time of the solid-state electronic image sensor according to a given shutter speed and reads out the accumulated signal charge at a predetermined period; and a frequency detection means. An electronic imaging device comprising a fluorescent lamp for illumination, comprising: shutter speed control means for controlling the drive circuit to operate at a shutter speed equal to a period corresponding to a frequency that is an integral multiple of a detected power supply frequency. (2) The electronic imaging device equipped with a fluorescent lamp for illumination according to claim (1), further comprising means for correcting the exposure amount of the solid-state electronic imaging device.