JPH0679108B2 - Light source for electronic scope - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light source device for an electronic scope having a solid-state image pickup device for performing color image pickup by a color mosaic filter, and more particularly to a light source for an electronic scope using a xenon short arc lamp. Regarding the device.

[Conventional technology]

In recent years, electronic scopes have been developed that incorporate a solid-state imaging device such as a charge-coupled device (CCD) at the tip of an endoscope to color-image a subject.

There is a xenon lamp as a lamp used in such a light source device, and the xenon lamp is classified into a short arc lamp and a long arc lamp according to the arc shape. Here, in the conventional light source device using the xenon short arc lamp, the lamp current is constantly kept constant by the switching rectifier and the lamp is continuously lit. Then, the shutter provided on the front surface of the lamp is closed as necessary to shield the solid-state image sensor from light.

[Problems to be solved by the invention]

Here, if the operation cycle of the solid-state imaging device is roughly classified, it is composed of a storage period in which charges corresponding to the amount of incident light are stored in the light receiving portion, and a period in which the charges stored in the light receiving portion are transferred to the light-shielding transfer portion.
When the electric charge accumulated in the light receiving part has been transferred to the light transfer part,
The next accumulation period begins. Here, since it is necessary to shield the solid-state image sensor during the period in which the electric charges are transferred from the light receiving unit to the light shielding transfer unit, the shutter is closed to block the optical path of the lamp. However, as described above, since the lamp current is always constant and the lamp is continuously lit, the power consumption during the period in which the charges are transferred from the light receiving section to the transfer section is wasted.

This invention has been made to deal with the above-mentioned circumstances,
It is an object of the present invention to provide a light source device for an electronic scope using a xenon short arc lamp with a simple structure that can reduce wasteful power consumption.

[Means for solving problems]

A light source device for an electronic scope according to the present invention includes a xenon short arc lamp 10 and a switching rectifier that reduces the amount of light emitted from the xenon short arc lamp 10 during a period in which charges accumulated in a light receiving portion of a solid-state imaging device are transferred to a light-shielding transfer portion. Equipped with 14.

[Action]

According to the light source device for an electronic scope of the present invention, the light emission amount of the xeno short arc lamp 10 is reduced during the light-shielding period, and unnecessary power consumption is reduced.

〔Example〕

An embodiment of a light source device for an electronic scope according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of the first embodiment. Illumination light from the xenon short arc lamp 10 is incident on a light guide of an electronic scope (not shown) via the rotary color filter 12. The xenon short arc lamp 10 has a switching circuit 16 and a constant current circuit 18
The switching regulator 14 is continuously turned on. The sync pulse input to the sync pulse input terminal 20 is input to the switching circuit 16 via the color signal sync circuit 22 and the pulse generation circuit 24.

Rotating color filter 12 is a xenon short arc lamp
It has a function of sequentially coloring the illumination light from 10 into R, G, and B with a light shielding period interposed. The rotary color filter 12 is a disk in which R, G, and B color filter components are arranged at predetermined intervals on the circumference, and the disk portion between each color filter component is for reading the signal from the CCD. , Xenon short arc lamp 10 works as a shutter to block the illumination light.

Illumination light via the rotating color filter 12 is incident on one end of a light guide of an electronic scope (not shown), and the other end of the light guide is guided to the tip of the electronic scope. A solid-state image sensor (CCD) is provided at the tip of the electronic scope.
Since the tip of the scope is narrow, the CCD has a charge storage unit (imaging unit)
Consists of only. The output signal of the CCD is written into each frame memory for each color component via the multiplexer.
The signals of the three frame memories are simultaneously read and combined.

A through hole for generating a synchronizing pulse is provided outside the foremost portion in the rotating direction of each color filter component of the rotating color filter 10. At the edge of the rotary color filter 12, a photocoupler including a light emitting element and a light receiving element sandwiching the rotary color filter 12 and generating a synchronizing pulse by detecting a through hole is provided. The rotary color filter 12 is rotationally driven at a constant speed by a PLL-controlled motor. The sync pulse is supplied to the sync pulse input terminal 20.

The operation of this embodiment will be described with reference to FIG. With the rotation of the rotary color filter 12, the R, G, and B color filter components are sequentially inserted in the optical path of the illumination light incident on the light guide from the xenon short arc lamp 10.
The illumination light is colored R, G, and B in order with a light blocking period interposed.

As shown in FIG. 2 (a), a synchronization pulse is generated at the start of each R, G, B illumination period. Charges corresponding to image information of each color component are accumulated in the CCD during a period in which the illumination light is colored in R, G, and B for a certain period after the generation of the synchronous pause. After this, the light-shielding period is set until the next illumination period. That is, the CCD is shielded after a certain period of time from the sync pulse generated at the start of each of the R, G, and B illumination periods, and the accumulated charge is read. In this way, the image of the object is picked up by the frame sequential method.

The R, G, and B sync pulses are input from the sync pulse input terminal 20 to the color signal sync circuit 22 and synchronized. The output signal of the color signal synchronizing circuit 22 is supplied to the pulse generating circuit 24, and R,
A pulse is generated according to the amount of light necessary for capturing the G and B color component images. This pulse is supplied to the switching circuit 16 in the switching regulator 14.

The light emission amount of the xenon short arc lamp 10 depends on the pulse width and the switching frequency of the switching pulse inside the switching circuit 16. Therefore, if these are controlled according to the synchronizing pulse of FIG. Can be controlled according to the required amount of light. That is, if the pulse width and the switching frequency of the switching pulse are increased for a certain period according to the sync pulse and then decreased until the next sync pulse is generated, the lamp current output from the constant current circuit 18 becomes It changes as shown in FIG. 2 (c). Therefore, the power consumption of the lamp is
The amount of light can be changed corresponding to the required amount of light shown in FIG. 6B, and wasteful power consumption can be reduced.

Here, in FIG. 2 (b), the light amounts required for image pickup of the respective colors are shown to be the same, but they are actually different.

As described above, according to the first embodiment, the constant current circuit 18 is provided except during the period when the filter is located in front of the lamp and the illumination light is colored.
By reducing the lamp current from the lamp, useless power consumption can be reduced. Further, since the light emission amount of the lamp can be adjusted, it is not necessary to change the aperture ratio of each color of the rotary color filter in order to compensate for the difference in sensitivity depending on the color, and the rotary color filter can be easily manufactured.

FIG. 3 is a block diagram of the second embodiment. In this embodiment, the operation of the switching regulator 14 is simplified. The charges charged in the capacitors C1 and C2 are discharged by the switching operation of the transistors Tr1 and Tr2, and flow to the primary side of the transformer T1. Then, electric power is generated on the secondary side of the transformer T1. This is supplied to the xenon short arc lamp 10 and the xenon short arc lamp 10
Is lit.

The switching operation of the transistors Tr1 and Tr2 will be described with reference to FIG. As shown in FIGS. 4A and 4B, the switching circuit 16 supplies switching pulses Ta and Tb having different phases but constant frequencies to the bases of the transistors Tr1 and Tr2, respectively. The switching pulses Ta and Tb turn on the transistors Tr1 and Tr2, and the discharge currents of the capacitors C1 and C2 flow in the transistor T1.
Therefore, when the pulse widths of the switching pulses Ta and Tb change, the voltage generated on the secondary side of the transformer T1 changes,
The lamp current can be adjusted as shown in FIG.

The lamp current can be adjusted by changing the voltage generated on the secondary side of the transformer T1 not only by controlling the pulse widths of the switching pulses Ta and Tb but also by controlling the frequency.

FIG. 5 shows the operation of the entire second embodiment.

When the synchronizing pulse shown in FIG. 5 (a) is supplied to the pulse generating circuit 24, the pulse generating circuit 24 generates a pulse signal as shown in FIG. 5 (b). The pulse width of this pulse signal is set to the time required to capture the R, G, and B color component images.

This pulse signal is supplied to the switching circuit 16. As shown in FIGS. 5 (c) and 5 (d), the switching circuit 16 has switching pulses Ta and Tb during the period of this pulse signal.
Pulse width is increased, and the pulse width is decreased in other periods. Therefore, as shown in FIG. 5 (e), the lamp current increases during the period of the output pulse of the pulse signal generating circuit 24 and decreases during the other periods.

As described above, according to the second embodiment, the lamp current can be increased / decreased according to the rotating operation of the rotating filter with a control circuit having a simple structure, and wasteful power consumption can be reduced.

In the above-described embodiment, the transfer (light-shielding) period and the period for reducing the light emission amount of the lamp are completely the same, but even if the light-emission amount of the lamp is reduced only for a part of the light-shielding transfer (light-shielding) period. Well, this will be described below as a third embodiment.

FIG. 6 (a) shows the operation of the CCD. In the CCD, the charges corresponding to each color component image accumulated during the light receiving period are read during the transfer (light shielding) period. The rotating color filter 12 has not only the above-mentioned through holes for generating the synchronization pulse but also through holes for generating a timing pulse whose rear end comes at a predetermined timing during the transfer period as shown in FIG. 6 (b). Is also provided. As shown in FIG. 6 (c), the pulse generation circuit 24 generates a pulse signal after a predetermined time (t) from the trailing end of this timing pulse. The trailing edge of the pulse signal coincides with the trailing edge of the timing pulse. Therefore, the lamp current is increased or decreased in the same manner as the waveform of this pulse signal as shown in FIG. 6 (d). That is, the light emission amount of the lamp is reduced during a part of the transfer period.

FIG. 7 is a diagram showing a main part of the fourth embodiment. The feature of this embodiment is that the fluorescent member 32 is provided between the xenon short arc lamp 10 and the electronic scope light guide 34. As a result, the flicker that is visually perceived by the light pulse-lit by the switching reulator 14 is improved.

The present invention can be variously modified without being limited to the above-described embodiments, and the configuration of the lamp lighting control circuit may be other.

Further, the CCD is not limited to the frame-sequential solid-state image sensor, but may be a line transfer type, an interline transfer type, or a frame transfer type CCD having a color mosaic filter. In the case of these CCDs, the amount of light emission is reduced during the period in which the charge accumulated in the light receiving portion of the CCD is transferred to the light shielding transfer portion. In this modified example, the rotary filter 12 is removed from that shown in FIG. 1, and instead of the pulse synchronized with the rotation of the rotary filter 12, a pulse synchronized with the start and end of the light receiving period of the solid-state image pickup device is input to the pulse input terminal 20. And the pulse width of the switching pulse of the switching regulator 14 is shortened or the frequency is lowered from the end of the light receiving period to the start of the next light receiving period.

〔The invention's effect〕

As described above, according to the present invention, the light emission amount of the continuously lit xenon short arc lamp is reduced during the period in which the charge accumulated in the light receiving section of the solid-state image sensor is transferred to the light shielding transfer section. Provided is a light source device for an electronic scope, which can reduce wasteful power consumption.

[Brief description of drawings]

FIG. 1 is a first view of a light source device for an electronic scope according to the present invention.
2 is a block diagram of an embodiment, FIG. 2 is a signal waveform diagram for explaining the operation of the first embodiment, FIG. 3 is a block diagram of the second embodiment of the present invention, and FIG. 4 is a switching circuit of the second embodiment. FIG. 5 is a signal waveform diagram for explaining the operation, FIG. 5 is a signal waveform diagram for explaining the overall operation of the second embodiment, and FIG. 6 is a signal waveform diagram for explaining the operation of the third embodiment of the present invention. FIG. 8 is a diagram showing a main part of a fourth embodiment of the present invention. 10 …… Xenon short arc lamp, 12 …… Rotating color filter, 14 …… Switching regulator, 16 ……
Switching circuit, 18 ... constant current circuit, 22 ... pulse generation circuit, 24 ... color signal synchronization circuit.

Claims (1)

[Claims] 1. A light source device for an electronic scope used in an electronic scope having a solid-state imaging device, comprising: a short arc lamp for generating illumination light for accumulating charges in a light-receiving portion of the solid-state imaging device; and a reference signal at a predetermined cycle. And a unit for periodically transferring the charge accumulated in the light-receiving unit of the solid-state image sensor to the light-shielding transfer unit based on the reference signal, the solid-state imaging device responding to the reference signal. During a period in which electric charge is accumulated in the light receiving portion of the device, the short arc lamp is driven by a predetermined current to generate illumination light of a predetermined light amount, and the electric charge accumulated in the light receiving portion of the solid-state image sensor is transferred to the light-shielding transfer portion. And a control unit for driving the short arc lamp with a current having a level lower than the predetermined current to generate illumination light having a light intensity smaller than the predetermined light intensity during a transfer period. A light source device for an electronic scope, characterized in that