JPH0679109B2 - Light source for electronic scope - Google Patents

Description

The present invention relates to a light source device for an electronic scope.

[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.

Generally, as a color image pickup method, there is a field sequential method in which red (R), green (G), and blue (B) illumination light is sequentially irradiated to a subject for each screen, and each color component image is picked up for each screen. , There is a mosaic filter method in which a color mosaic filter is applied to a CCD and one image pickup pixel is configured by a plurality of color component light receiving elements. In the case of an electronic scope, since a CCD is built in a narrow space such as the tip of an endoscope, a frame sequential imaging method that can effectively use all pixels is common.

Here, since the light-receiving sensitivity of the CCD differs depending on the color, in such a light source device for a frame-sequential type electronic scope, the light emitted from the lamp is colored into R, G, and B, and the sensitivity depending on the color is changed. It is required to adjust the amount of illumination light of each color to compensate for the difference. There is a xenon lamp as a lamp used in such a light source device, and the xenon lamp is composed of a short arc lamp and a long arc lamp depending on the arc shape.

As a conventional example for flashing a xenon long arc lamp, there is an apparatus described in Japanese Patent Laid-Open No. 60-102082. A rotating color filter is provided on the front surface of the xenon lamp so that R, G, and
The B color filter is located. Xenon lamp
Each time the R, G, B color filters are sequentially positioned on the optical path, the flash is turned on. The flash light amount of the R, G, B illumination light is controlled by adjusting the voltage charged in the discharge capacitor of the xenon lamp.

On the other hand, when using a xenon short arc lamp,
Since the lamp is lit continuously by a constant current,
The amount of R, G, B illumination light is R, G, B on the light path of the light source lamp.
The color filters are adjusted by changing the period in which they are located. Since the rotating color filter is rotated at a constant speed, changing the filter period means changing the length of the filter in the circumferential direction (hereinafter referred to as the aperture ratio).

FIG. 8 shows a conventional example of a light source device for continuously lighting a xenon short arc lamp.

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. Xenon short arc lamp
10 is continuously turned on by a switching regulator 14 including a switching circuit 16 and a constant current circuit 18.

At the start of the period when the rotary color filter 12 is rotated and the R, G, and B color filters are located on the optical path of the xenon short arc lamp 10, a synchronizing pulse is generated as shown in FIG. 9 (a). The illumination light is colored in each color for a certain period after the generation of these synchronization pulses. During this time,
Charges corresponding to each color component image are accumulated in the CCD. After this, the light-shielding period continues until the next sync pulse is generated, and the accumulated charge is read from the CCD. Therefore, as shown in FIG. 9 (b), the light emission amount actually required for the xenon short arc lamp 10 is at a certain level only during the coloring period for a certain period after the sync pulse is generated, and the other light shielding periods are 0 is enough.

However, in the conventional light source device, the lamp current from the constant current circuit 18 is always constant as shown in FIG. 9 (c). Therefore, the power consumption was always constant as shown in FIG. 9 (d), which was far from the required light emission amount.

[Problems to be solved by the invention]

As described above, in the conventional light source device using the xenon short arc lamp, the xenon short arc lamp is continuously turned on regardless of whether the shutter is opened or closed. Therefore, there is a considerable waste of power consumption.

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 having a simple structure that can reduce wasteful power consumption.

[Means for solving problems]

According to the present invention, the xenon short arc lamp 10,
For an electronic scope equipped with a rotary color filter 12 as a shutter provided on the front surface of the xenon short arc lamp 10 as a shutter for opening / blocking the optical path of the xenon short arc lamp 10 and a switching regulator 14 for supplying a constant current to the xenon short arc lamp 10. In the light source device, the switching regulator 14 controls the current value of the stop current supplied to the xenon short arc lamp 10 in conjunction with the shutter opening / closing operation by the rotary color filter 12, and the optical path of the xenon short arc lamp 10 is cut off. The current value during the open period is made lower than the current value during the open optical path.

[Action]

According to the light source device for an electronic scope according to the present invention, since the output constant current value of the switching regulator 14 is lowered during the period when the optical path of the xenon short arc lamp 10 is shielded, the light emission amount of the xenon short arc lamp 10 is reduced, Useless 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. Parts corresponding to those in FIG. 8 are designated by the same reference numerals. In the first embodiment, a synchronizing pulse input terminal 20, a color signal synchronizing circuit 22, and a pulse generating circuit 24 are added to the circuit shown in FIG.

Rotating color filter 12 is a xeno short arc lamp 10
Has a function of sequentially coloring the illumination light from 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. The disk portion between each color filter component works as a shutter for blocking the illumination light from the xenon short arc lamp 10 for reading the signal from the CCD.

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 consists only of the charge storage unit (imaging unit). 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 the first 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 that is incident on the light guide from the xenon short arc lamp 10, and the illumination light is sequentially inserted with a light-shielding period interposed. It is colored R, G, and B.

As shown in FIG. 2 (a), a synchronization pulse is generated at the start of each R, G, B illumination period. Charges corresponding to each color component image information are accumulated in the CCD during a period in which the illumination light is colored R, G, and B for a certain period from the generation of the synchronization pulse. 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 as the same, but in reality, they are 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,
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, and the lamp current can be adjusted as shown in FIG. 4 (c).

In addition to controlling the pulse widths of the switching pulses Ta and Tb, the lamp current can be adjusted by changing the voltage generated on the secondary side of the transistor T1 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, also according to the second embodiment, the lamp current can be increased or decreased in accordance with the rotating operation of the rotating filter with the 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 the light-emission amount of the lamp may be reduced only for a part of the light-shielding transfer (light-shielding) period. 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. 6C, the pulse generation circuit 24 generates a pulse signal after a predetermined period (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. This improves the flicker that is visually perceived by the light pulse-lit by the switching regulator 14.

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. Furthermore, the CCD is not limited to the frame-sequential solid-state imaging device, but may be a line transfer type, an interline transfer type, or a frame transfer type CCD having a color mosaic filter. CC for these CCDs
The amount of light emission is reduced during the period in which the charges accumulated in the D light receiving unit are transferred to the light-shielding transfer unit.

〔The invention's effect〕

As described above, according to the present invention, the current value supplied to the continuously lit xeno short arc lamp is increased or decreased in conjunction with the operation of the shutter that opens / blocks the optical path of the xenon short arc lamp. Provided is a light source device for an electronic scope, which can reduce wasteful power consumption by lowering the current value during the period when the optical path is blocked from the current value during the period when the optical path is opened.

[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. Is a diagram showing an essential part of a fourth embodiment of the present invention, FIG. 8 is a block diagram of a conventional example of a light source device for an electronic scope, and FIG. 9 is a signal waveform for explaining the operation of the conventional example shown in FIG. It is a figure. 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 image pickup device, comprising: a short arc lamp for generating illumination light; and periodically blocking the illumination light generated by the short arc lamp. A light-shielding unit that periodically sets the solid-state image sensor to an exposure period and a light-shielding period, a synchronization signal generation unit that generates a synchronization signal synchronized with the operation of the light-shielding unit, and the solid-state image sensor based on the synchronization signal. Means for driving, in response to the synchronization signal, driving the short arc lamp with a predetermined current during an exposure period to generate illumination light with a predetermined light amount, and during the exposure period with a current lower than the predetermined current. And a control means for driving the short arc lamp to generate illumination light of a smaller light quantity than the predetermined light quantity. -Loop for the light source device.