JP3225538B2 - Electronic endoscope device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic endoscope apparatus and, more particularly, to an electronic endoscope imaging system suitably used for medical purposes.

[0002]

2. Description of the Related Art An electronic endoscope apparatus generally includes an endoscope main body, a processor, a monitor device, and a light source device, and an insertion portion of the endoscope main body is inserted into a body cavity or the like to form a light source device. The illumination light from the illumination lamp built into the optical fiber for light guide, that is, guided into the body through the light guide,
Irradiation light is emitted toward the observation target portion, and a reflected image from the observation target portion is imaged by photoelectric conversion by solid-state imaging means having a solid-state imaging device such as a CCD, and this image signal is output from the solid-state imaging means. The data is read out, transmitted to a processor, and subjected to signal processing by the processor before displaying an image of the subject on a monitor device.

[0003] Here, the image quality of an image obtained by the solid-state imaging means largely depends on the amount of illumination light. That is, when the amount of illumination light is small, the image becomes dark and unclear. On the other hand, if the amount of illumination light is too large, the solid-state imaging device easily saturates, causing a so-called overexposure phenomenon. Therefore, the image quality of the color image displayed on the monitor screen is reduced. In order to avoid such inconveniences and to improve the image quality, it is necessary to always illuminate with an appropriate amount of light. However, when observing a position near the distal end of the insertion section, the amount of reflected light from the subject is large, and when observing a position far away, the reflected light from the subject is reduced. The optimal amount of illumination varies depending on the distance between the means and the subject. Also, the light level of the reflected light varies depending on the light reflectance of the subject. For this reason, it is necessary to appropriately adjust the amount of illumination light according to the observation site and the like.

[0004] From the above demands, it has been known that a stop member is interposed between an illumination lamp in a light source device and an entrance end of a light guide, and the amount of illumination is adjusted by the stop member. Have been. An automatic light amount adjusting means (ALC) is provided for automatically controlling the aperture member so as to obtain an optimum illumination light amount in accordance with a positional relationship with an object which is currently being photographed. The output video signal is taken into this automatic light amount adjusting means, and the optimum light amount is calculated based on the luminance component.
A control signal is input to a servo mechanism that controls the operation of a driving unit for a diaphragm member such as a motor, and the driving unit is operated to adjust the aperture amount of illumination light by the diaphragm member.

[0005]

In an endoscope used for medical purposes, the safety of a patient must be protected. For this purpose, the members constituting the imaging system are divided into a patient circuit and a secondary circuit.
Signals are transmitted and received between the next circuit and an isolation means including a transformer, a photocoupler, and the like, so that both circuits are insulated. Here, the automatic light amount adjusting means must be provided on the secondary circuit side because of the connection with the servo mechanism connected to the aperture driving means such as a motor. However, in some cases, the automatic light amount adjusting means must be connected to the patient circuit side in order to capture the video signal output from the solid-state imaging means. Therefore, it is necessary to interpose the isolation means also at the connection to the automatic light quantity adjustment means, and the configuration of the apparatus becomes large and complicated. Moreover, for example, a diaphragm plate or the like is used as the light amount diaphragm member, and the diaphragm amount is changed by displacing the diaphragm plate in a direction orthogonal to the illumination optical path. There is also the disadvantage of not being able to control it.

Meanwhile, in a television camera using a solid-state image pickup device, in order to adjust the exposure amount,
It has a so-called electronic shutter mechanism. The electronic shutter mechanism applies a sweeping pulse during the accumulation of signal charges in the solid-state imaging device, thereby sweeping out the accumulated charges to the drain, newly accumulating charges after the sweeping transfer time, and reusing the accumulated charges. It is extracted as a color image signal, and is for adjusting the exposure transfer amount by adjusting the sweep-out transfer time point, thereby preventing the solid-state imaging device from being saturated and causing a whiteout phenomenon. This electronic shutter mechanism
Since the sweep pulse is applied to the solid-state imaging device, this pulse can be output from the driving circuit of the solid-state imaging device, and an exposure amount adjusting unit having a mechanism similar to the automatic light amount adjusting unit described above is provided. Since the application timing of the sweep-out pulse may be set by a signal from the exposure amount adjusting means, the entire exposure amount adjusting mechanism can be provided on the patient circuit side, and the circuit configuration is extremely simplified. In addition to the above, there are advantages such as fine control.

However, it may be difficult to completely adjust the exposure amount only by adjusting the exposure amount by the electronic shutter mechanism. For example, in an esophagus endoscope, it is necessary to irradiate strong illumination light in order to spread the illumination light to a deep part of the esophagus. On the other hand, for example, in the case of examining the stomach wall with a stomach endoscope, since an object at a close distance is photographed, the illumination light for the object must be significantly reduced. However, since the light source device is commonly used for these various endoscopes, if the light amount of the light source device is constant, it may not be possible to perform sufficient exposure adjustment depending on the electronic shutter mechanism. In the case of the gastric endoscope described above, even if the exposure time is minimized, the solid-state imaging device may become saturated, and in the case of an esophageal endoscope, the exposure time may be maximized. Even so, there is a problem that the obtained image is dark and unclear, and as a result, an electronic endoscope device that performs exposure adjustment using an electronic shutter mechanism has not yet been put to practical use. It is.

The present invention has been made to solve the above-mentioned drawbacks and problems of the prior art, and it is an object of the present invention to sufficiently protect a patient with a simple configuration. Another object of the present invention is to provide an electronic endoscope apparatus capable of capturing a very clear image of a subject.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention provides an illumination means for irradiating an object with illumination light by R, G, and B sequential illumination, and a solid-state device for imaging an object. An electronic endoscope device including an imaging unit,
Among the output signals from the solid-state imaging means, a luminance signal is obtained from any of the R, G, and B image signals, and a proper exposure time is calculated based on the luminance signal to obtain a signal charge in the solid-state imaging device. Exposure amount control means having an electronic shutter mechanism for controlling the exposure time by applying a sweep pulse at a predetermined timing during the accumulation of
This exposure amount control means is provided for each of the entire illumination periods of R, G, and B.
The maximum exposure time during which the solid-state imaging device is not saturated
Set as Rmax, Gmax, Bmax respectively
R, G, and B are sequentially illuminated, and Rmax:
The electronic shutter mechanism is controlled so as to determine the application timing of the sweeping pulse so that the ratio of Gmax: Bmax is maintained .

[0010]

As described above, depending on the type and use of the endoscope, there is a difference in the appropriate amount of illumination that cannot be corrected even by using the electronic shutter mechanism. Therefore, the illumination light amount is adjusted in advance by the aperture member, and the electronic shutter mechanism is operated to adjust the exposure time within the range of the illumination light amount level adjusted in this manner, whereby the exposure amount of the solid-state imaging device is adjusted. Can be finely controlled. For example,
In the case of using a gastric endoscope, the amount of illumination light sent from the light source device is reduced by a diaphragm member,
When an esophageal endoscope is used, the illuminating member is opened to emit strong illumination light. Thus, the exposure adjustment function of the electronic shutter mechanism can be sufficiently exhibited, and the state of the positional relationship between the solid-state imaging device and the subject, the reflectance of the subject, the sensitivity of the solid-state imaging device, and the like are determined. Even if it is, by the sequential illumination of R, G, B
When acquiring each color image signal according to the illumination light
Set the application timing of the sweep pulse individually
This makes it possible to always obtain a clear image.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 1 shows the basic configuration of the entire electronic endoscope apparatus of the present invention. In FIG. 1, reference numeral 1 denotes an endoscope main body, 2 denotes a processor, and 3 denotes a light source device. The endoscope main body 1 has an insertion portion 1a inserted into a body cavity. It is configured to be detachably connected to the processor 2 and the light source device 3 by the cord 1b.

The light source device 3 has a built-in illumination lamp 31. Illumination light from the illumination lamp 31 is transmitted through a rotary color filter 34 through a light quantity stop member 32 and a condenser lens 33 in order. R
Illumination is sequentially output by light of wavelengths (red), G (green), and B (blue). Reference numeral 11 denotes a light guide made of an optical fiber bundle. The light guide 11 is inserted from the end of the flexible cord 1b in the endoscope body 1 to a position facing an illumination window provided at the tip of the insertion portion 1a. When the flexible cord 1b is connected to the light source device 3, the incident end of the light guide 11 faces the illumination optical path, and the illumination light of R, G, and B is sequentially incident. The illumination light transmitted by the light guide 11 is emitted toward the subject from an illumination window at the tip of the insertion section 1a.

An objective lens 12 is mounted on the distal end of the insertion portion 1a, and a solid-state image sensor 13 such as a CCD is mounted at an image forming position on the objective lens 12. The image is formed and photoelectrically converted. Then, the video signal acquired by the solid-state imaging device 13 is transmitted to the processor 2 via the signal cable 14, and the processor 2 performs signal processing. For this purpose, the processor 2 is provided with a video signal processing circuit 21 for performing predetermined signal processing.
Image signals of each color of R, G, and B are generated. Then, the image signals of these colors are stored in a field memory 23 via an A / D converter 22, and then these three color image signals are simultaneously read out and converted into analog signals by a D / A converter 24. Then, they are combined by the color encoder 25 and output to the monitor device 26 as a composite video signal, so that an image of the subject is displayed on the monitor device 26.

In order to read out the signal charges stored in the solid-state imaging device 13, a solid-state imaging device driving circuit 27 is provided in the processor 2 (or the endoscope main body 1 side). The signal charge accumulated in the light receiving area of the solid-state imaging device 13 is transferred to a storage unit (or a transfer unit) by a drive pulse signal from the solid-state imaging device drive circuit 27, and is sent out to the signal cable 14 from the storage unit. A synchronization circuit 28 is connected to the solid-state imaging device driving circuit 27, and a pulse signal required to drive the solid-state imaging device 13 is generated based on a synchronization signal sent from the synchronization circuit 28. The synchronization circuit 28
Is also connected to a video signal processing circuit 21, an A / D converter 22, a field memory 23, and a D / A converter 24. The reference clock signal, the horizontal synchronizing signal, and the vertical synchronizing signal necessary for the operation of these circuits are provided. You can get it.

Here, the solid-state image pickup device 13 has an electronic shutter mechanism. Therefore, an electronic shutter mechanism in the case where a frame transfer type CCD is used will be described below. In order to drive the solid-state imaging device 13 by the frame transfer method, as is well known, the light receiving area is made to receive light while sequentially illuminating with the wavelength light of each color of R, G, and B. Accumulates a signal charge, and when a certain time of the charge accumulation time has elapsed, a reverse transfer pulse is applied to the solid-state imaging device 13 as a sweeping pulse from the solid-state imaging device driving circuit 27, and during this time, the light receiving area is The electric charge accumulated in the drain is swept to the drain as unnecessary electric charge. Next, the signal charge newly accumulated in the light receiving area is transferred to the transfer unit as an image signal by applying a positive transfer pulse to the solid-state imaging device 13 during the vertical blanking period, and is extracted.

In order to set the application timing of the reverse transfer pulse, the processor 2 is provided with an exposure control circuit 29. The exposure amount control circuit 29 includes an encoder 25
Of the output video signals from the luminance signal Y (or R,
One of the G and B images, for example, an output signal of the G image) is taken in, and the output timing of the reverse transfer pulse is set according to the luminance level. By the way, from the light transmission characteristics of the rotating color filter 34 and the light guide 11 and the sensitivity characteristics of the solid-state imaging device 13, R, R
The output levels of the G and B color image signals are not the same.
As shown in the above, the level of the R color image signal is the highest,
Next, the level of the G signal is high, and the B color image signal is R,
The level tends to be extremely lower than that of G. Therefore, it is necessary to individually set the application timing of the reverse transfer pulse for each of the R, G, and B color images. However, the ratio of the output levels in the R, G, and B color image signals is determined in advance from the sensitivity characteristics described above. Therefore, the maximum exposure time of all the illumination periods of R, G, and B is preset, and the application timing of the reverse transfer pulse is determined according to the luminance signal Y within the range of the maximum exposure time. It is composed.

As shown in FIG. 3A, the illumination light from the illumination lamp 31 is supplied to the rotating color filter 34.
, The illumination is sequentially performed with the R, G, and B wavelength lights, and this is illuminated to the observation target portion through the light guide 11. The subject is illuminated with the R, G, and B wavelength region lights, The light-shielding period S between the illumination periods by the R, G, and B wavelength lights is sequentially repeated. Therefore, as shown in FIG.
When irradiating light of each wavelength of G and B, R, G, and
The signal charges are accumulated in each of the field periods RF, GF, and BF of B, and the signal charges accumulated in the light receiving area are accumulated by applying the transfer pulse TP during the vertical blanking period VB during the light shielding period S. Transferred to the department.

Here, all field periods RF, GF, B
By setting a part of F to be the invalid accumulation periods RD, GD, and BD, the effective charge accumulation periods RE, GE, and BE are limited, and the exposure amount of the solid-state imaging device 13 is adjusted. That is,
For example, the R field period RF starts after the light shielding period S, the exposure of the light receiving area in the solid-state imaging device 13 starts, and signal charges are accumulated. When the reverse transfer pulse RP is applied from the circuit 27 to the solid-state imaging device 13, as shown in (c), the charges accumulated so far are swept out to the drain as unnecessary charges. Then, since the R field period RF continues even after the application of the reverse transfer pulse RP, the accumulation of electric charges is restarted thereafter. When the R field period RF ends and the light shielding period S starts, the solid-state imaging device 1
3, the transfer pulse TP is applied, and the invalid charge accumulation period R
Only the charge accumulated during the effective charge accumulation period RE after D has elapsed is transferred. Moreover, as described above, the maximum exposure time of all the R, G, and B illumination periods , that is, the maximum exposure time during which the solid-state imaging device 13 is not saturated.
Large exposure Exposure time Rmax, Gmax, B
By presetting the luminance signal Y as a maximum value, the exposure amount control circuit 29 takes in the luminance signal Y from the video signals output from the encoder 25 and outputs the luminance signal Y.
, The exposure time is controlled so that the ratio of Rmax: Gmax: Bmax is maintained, that is, the application timing of the reverse transfer pulse RP is set.

As described above, by limiting the effective charge accumulation period for the entire field period according to the positional relationship between the solid-state imaging device 13 and the subject, the light reflectance of the subject, etc. By limiting the exposure time of the image sensor 13, the exposure amount is adjusted to be in an optimal state. Therefore, the exposure amount control circuit 29 for calculating the application timing of the reverse transfer pulse RP and the solid-state image sensor driving circuit 2
7 constitute an electronic shutter mechanism.

With this electronic shutter mechanism, when the amount of light received by the solid-state imaging device 13 is large, the ineffective charge accumulation period is lengthened. When the amount of received light is small, the ineffective charge accumulation period is shortened. By eliminating the above, it is possible to prevent the solid-state image sensor 13 from saturating and causing a whiteout phenomenon, and prevent the image stored in the solid-state image sensor 13 from being too small to be unclear.

By the way, various endoscopes are connected to the light source device 3. As described above, the esophageal endoscope and the stomach endoscope have a required amount of illumination light. Significantly different. Therefore, simply adjusting the exposure time by the electronic shutter mechanism is not enough. When the subject is photographed by connecting the esophageal endoscope, the image becomes too dark even if the electronic shutter mechanism is fully opened. hand,
When the image becomes unclear or when a gastric endoscope is connected, the solid-state imaging device may be saturated even if the exposure time is minimized by the electronic shutter mechanism. In view of this, the light source itself can be adjusted in parallel with the electronic shutter mechanism. This adjustment of the light source light amount
This is performed by a light amount stop member 32 built in the light source device 3. The light amount diaphragm member 32 can adjust the light amount of the illumination light manually or automatically.

Therefore, after adjusting the light amount level of the illumination light irradiated toward the subject by the light amount stop member 32, the exposure time of the solid-state imaging device 13 is determined by the electronic shutter mechanism based on the image signal actually acquired. Is adjusted, the illumination light level itself does not become too low or too high, so that exposure adjustment can be performed reliably.

[0023]

The present invention is constructed as described above.
Fine adjustment of the exposure amount of the solid-state imaging means with a simple configuration
It can shoot very clear subject images
And so on.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of an electronic endoscope apparatus according to a first embodiment of the present invention.

FIG. 2 shows R, R when the electronic shutter mechanism is not operated.
FIG. 3 is a diagram illustrating output levels of G and B color image signals.

FIG. 3 is an operation explanatory view of an electronic shutter mechanism.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, Endoscope main body 2 Processor 3 Light source device 13 Solid-state image sensor 21 Video signal processing circuit 27 Solid-state image sensor drive circuit 29 Exposure amount control circuit 31 Illumination lamp 32 Light intensity stop member

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) A61B 1/04-1/06 G02B 23/24-23/26

Claims (2)

(57) [Claims] 1. An electronic endoscope apparatus comprising: illuminating means for illuminating a subject with illumination light by sequential illumination of R, G, and B; and solid-state imaging means for imaging a subject. Of the R, G, and B image signals among the output signals from the image sensor, calculate an appropriate exposure time based on the luminance signal, and calculate the appropriate exposure time during the accumulation of signal charges in the solid-state imaging device. having an exposure amount control means having an electronic shutter mechanism for controlling the exposure time by applying a pulse sweeping at a predetermined timing, the exposure amount control means, R, G, total illumination period of each of B
The maximum exposure time during which the solid-state imaging device is not saturated
Set as Rmax, Gmax, Bmax respectively
R, G, and B are sequentially illuminated, and Rmax:
An electronic endoscope apparatus, which controls so as to determine the application timing of a sweeping pulse in the electronic shutter mechanism so that a ratio of Gmax: Bmax is maintained . 2. The application timing of the sweep pulse for each of R, G, and B illuminations set by the exposure amount control means is controlled so that the output level of each of the image signals is substantially constant. 2. The electronic endoscope apparatus according to claim 1, wherein: