JP2003334161A - Electronic endoscope system equipped with charge amplification type solid-state imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To display a light image excellent in image quality by making up for the deficiency of the quantity of applied light without an increase in the quantity of light which is applied to a subject. <P>SOLUTION: A videoscope, which is equipped with a charge amplification type solid-state imaging device 54 capable of causing an impact ionization phenomenon so as to amplify an output signal charge, is connected to a processor 10 to which a monitor 39 is connected. The processor 10 is provided with a charge amplifying switch 30A for performing charge amplifying processing. When the switch 30A is operated, the lightness of a subject image is detected according to an image signal which is read out from the imaging device 54. When the detected lightness is a hindrance to observation, the charge amplifying processing is automatically performed. <P>COPYRIGHT: (C)2004,JPO

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 including a videoscope (electronic endoscope) having an image pickup device and a processor for processing an image signal read from the image pickup device, and more particularly, The present invention relates to signal processing for optimizing the brightness of a displayed subject image.

[0002]

2. Description of the Related Art In an electronic endoscope apparatus, in order to maintain a subject image displayed on a monitor at an appropriate brightness, illumination light is automatically dimmed, and based on an image signal read from an image sensor. When the brightness level of the subject image is detected, the light amount is adjusted by controlling the diaphragm. For example, in the case of observing an organ having a wide internal space such as the stomach, when the distance between the distal end of the scope and the observation target increases, the diaphragm opens to increase the irradiation light amount.

Further, in order to prevent the subject image from being blurred due to the movement of the organ itself or camera shake of the videoscope, it is possible to photograph the subject image using the electronic shutter function. When an electronic shutter speed higher than the exposure time during normal observation is set, the diaphragm is driven to increase the amount of light in order to maintain the brightness of the subject image constant. Furthermore, when a bright image cannot be obtained even if the amount of light to the subject is increased, the image signal read from the image sensor is subjected to digital amplification processing, whereby a bright image can be displayed.

[0004]

However, when the amount of light is increased, there is a risk that the observation target will be burned. Further, when the image signal read from the image sensor is amplified, electrical noise is also amplified during the amplification process. It is extremely difficult to maintain the brightness of the displayed subject image while suppressing the risk of burns.

Therefore, an object of the present invention is to provide an electronic endoscope apparatus capable of displaying a bright image with excellent image quality by compensating for the shortage of the irradiation light amount without increasing the light amount to the subject. .

[0006]

An electronic endoscope apparatus according to the present invention is an electronic endoscope apparatus including a videoscope having an image pickup device and a processor to which the videoscope is connected. A charge amplification type solid-state imaging device capable of executing a charge amplification process for amplifying charges generated by photoelectric conversion by causing an impact ionization phenomenon. In the charge amplification type solid-state imaging device, the signal charges extracted from the light receiving surface of the imaging device are impact ionized to generate secondary electrons. By repeatedly performing impact ionization, it is possible to multiply the extracted charges in a multiplying manner. Further, the charge amplification type solid-state image pickup device can also perform signal processing in the same manner as the conventional image pickup device without executing the charge amplification process.

By outputting the amplified charges,
A bright image is displayed on a monitor or the like without driving a diaphragm or the like to increase the light amount. That is, there is no risk of burns. Further, even when the output of the light source lamp for illumination is small or the diameter of the optical fiber bundle is small, a bright image can be displayed without increasing the amount of light to the subject. Furthermore, since the signal read from the image sensor is not amplified, noise is not amplified and a subject image with suppressed noise is displayed. If the charge amplification process is executed only when the irradiation light amount is insufficient, the image pickup device can be efficiently driven. For example, a video scope or the like is preferably provided with a switch operated by an operator to execute the charge amplification process.

In order to maintain the brightness of the subject image at an appropriate level while the moving image is displayed, it is preferable that the automatic light adjustment process is executed. In this case, the electronic endoscope apparatus includes a light amount adjusting unit that adjusts the light amount of the light emitted from the light source to illuminate the subject, and a light amount adjustment so that the displayed subject image is maintained at an appropriate brightness. And an automatic dimming processing means for executing the light amount adjustment by controlling the means. For example, the automatic butterfly light amount processing means calculates the brightness level of the subject image based on the image signal read from the image sensor,
The light amount adjusting means is driven based on the difference between the brightness level and the reference brightness level. The light amount adjusting means may be, for example, a diaphragm or a liquid crystal plate. Alternatively, it may be a light source control circuit that uses a light emitting diode or the like as the light source and controls the amount of light emission by adjusting the current.

In order to automatically execute the charge amplification processing only when necessary, the electronic endoscope apparatus determines whether the brightness of the displayed subject image has reached a predetermined observable brightness. It is preferable to include a brightness determining unit that determines whether the subject image and a charge amplification processing unit that executes a charge amplification process in the charge amplification type solid-state imaging device when the brightness of the subject image does not reach a predetermined brightness. . The predetermined brightness here indicates the brightness near the lower limit in the range of observable brightness, and the setting can be changed as necessary. For example, the brightness is set to the limit of the observable brightness range. Regarding the brightness of the subject image, the brightness level may be calculated based on the image signal read from the charge amplification type solid-state imaging device, and it depends on whether or not the brightness level exceeds the brightness level according to the predetermined brightness. The charge amplification process may be executed. In particular, if the subject image is displayed dark even when the amount of light to the subject is maximized by, for example, fully opening the aperture in the state where the automatic light control process is being performed, the charge amplification process is automatically performed, The subject image is displayed with appropriate brightness. With such automatic charge amplification processing, a sufficiently bright image can be displayed even when the subject is at a long distance (for example, when the distal end of the stomach observation scope is observed in a 180 ° curved state in the stomach). To be done.

When the observed object itself moves, or when the held videoscope has a camera shake, an image blur occurs in the obtained subject image. In order to prevent image blurring, the electronic endoscope apparatus preferably includes an electronic shutter operation unit that executes an electronic shutter operation for taking an image with an exposure time shorter than an exposure time during normal observation. Since the exposure time is shortened, in order to maintain the brightness of the subject image immediately before the electronic shutter operation is performed, the electronic endoscope apparatus uses the charge amplification type solid-state image pickup device when the electronic shutter operation is performed. It is preferable to include charge amplification processing means for executing the amplification processing. A bright subject image can be displayed without driving the diaphragm to increase the amount of light. The gain value at the time of amplification processing may be determined according to the exposure time (image signal read time interval) at the time of normal observation and the electronic shutter speed. In particular, when the automatic light adjustment processing is being executed, it is preferable to set the gain value so that the brightness of the subject image does not change before and after the electronic shutter operation is executed.

A program of the present invention is an electronic endoscope apparatus including a videoscope having an image pickup device and a processor to which the videoscope is connected, wherein the image pickup device causes photoelectric conversion by causing an impact ionization phenomenon. A program for executing a charge amplification process executed in an electronic endoscope apparatus, which is a charge amplification type solid-state imaging device capable of executing a charge amplification process for amplifying generated charges, Brightness determining means for determining whether or not the brightness of the subject image reaches a predetermined observable brightness, and charge amplification type solid-state imaging when the brightness of the subject image does not reach the predetermined brightness. It is characterized in that a charge amplification processing means for executing a charge amplification processing is made to function in the element.

A program of the present invention is an electronic endoscope apparatus including a videoscope having an image pickup device and a processor to which the videoscope is connected, wherein the image pickup device causes an impact ionization phenomenon to perform photoelectric conversion. A program for executing a charge amplification process executed in an electronic endoscope apparatus, which is a charge amplification type solid-state imaging device capable of executing a charge amplification process for amplifying generated charges, and is a normal observation program. Electronic shutter operation means for performing an electronic shutter operation for shooting with an exposure time shorter than the exposure time, and a charge amplification type solid-state imaging device for performing charge amplification processing when the electronic shutter operation is performed. It is characterized by causing the amplification processing means to function.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION An electronic endoscope apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an electronic endoscope apparatus according to the first embodiment. The electronic endoscope device is a device for performing an inspection, an operation, or the like on an organ in the body such as the stomach, and when the inspection or the like is started, a videoscope is inserted into the body for photographing an observation site.

The electronic endoscope apparatus includes a videoscope 50 having a charge amplification type solid-state image pickup element 54 and a processor 10 for processing an image signal sent from the videoscope 50, and a monitor for displaying a subject image. 39 is connected to the processor 10. The video scope 50 is detachably connected to the processor 10, and the keyboard 3
5 and a recorder 40 for recording a still image include a processor 10
Connected to.

The light emitted from the light source lamp 12 is incident on the optical fiber bundle 51 provided inside the videoscope 10 through the diaphragm 34 and a condenser lens (not shown).
It is incident on 1A. The optical fiber bundle 51 is an optical fiber that transmits the light emitted from the lamp 12 toward the distal end portion 50A of the videoscope 50 having the observation site, and the light that has passed through the optical fiber bundle 51 is emitted from the emission end 51B. As a result, the observation site S is irradiated with light.

The light reflected at the observation region S passes through the objective optical system (not shown here) and reaches the light receiving surface of the charge amplification type solid-state image pickup device 54, whereby the image of the observation region S is amplified by the charge amplification. It is formed on the light receiving surface of the solid-state imaging device 54. In the present embodiment, a single-plate simultaneous type is applied as a color image pickup method, and a yellow (Y
A complementary color filter (not shown) in which e), cyan (Cy), magenta (Mg), and green (G) color elements are arranged in a checkered pattern is arranged corresponding to each pixel on the light receiving surface. In the charge amplification type solid-state imaging device 54, an image signal of a subject image corresponding to a color passing through a complementary color filter is generated by photoelectric conversion, and an image signal for one frame or one field is generated at predetermined time intervals according to the color difference line sequential method. Are sequentially read. As the color television system, for example, the NTSC system is applied, and 1/30 (1
The image signals for one frame (one field) are sequentially read out every / 60) second interval and sent to the processor 10. The charge amplification type solid-state image pickup device 54 is driven by an image pickup device drive circuit 56.

The signal processing circuit 20 of the processor 10 includes:
A timing circuit for adjusting the timing (delay time) of reading the image signal, R and B gain circuits for controlling R, G, B gains for white balance adjustment, a gamma correction circuit for performing gamma correction, a luminance signal, A color matrix circuit for generating color difference signals and the like are included (both not shown). Various processes are performed on the image signal input to the signal processing circuit 20 in each circuit, and as a result, a video signal is generated.
The generated video signal is NTSC composite signal, Y /
Video signals such as C separation signals (S video signals) and RGB separation signals are output to the monitor 39, whereby a subject image is displayed on the monitor 39.

A system control circuit 24 including a CPU (Central Processing Unit) controls the entire processor 10 and outputs a control signal to each circuit such as the image pickup device drive circuit 56 and the signal processing circuit 20 and also the entire processor. It has a ROM (not shown) storing a program for executing the operation of. Videoscope 50
A data rewritable EEPROM 57 is provided therein, and data relating to the characteristics of the video scope 50 is stored in the EEPROM 57 in advance. When the videoscope 50 is connected to the processor 10, the EEP
The data stored in the ROM 57 is sent to the processor 10 and stored in the memory (not shown) in the system control circuit 24. Further, a detection circuit (not shown) for detecting attachment and detachment when the videoscope 50 is attached and detached is provided.
When 0 is attached or detached, a detection signal is sent to the system control circuit 24.

A series of panel switches 30 are provided on the front panel of the processor 10, and processing corresponding to the operation on the panel switches 30 is executed. The charge amplification switch 30A is a switch for executing a charge amplification operation regarding the charge amplification type solid-state imaging device 54 described later. The electronic shutter switch 40B is a switch for executing an electronic shutter operation described later. The videoscope 50 is provided with a freeze switch (not shown), and when the freeze switch is operated, the freeze operation is executed. That is, the image signal for one frame is stored in the memory (not shown) in the signal processing circuit 20, and the video signal is sent to the recorder 40 based on the stored image signal. The still image is displayed on the monitor 39 by maintaining the state in which the data of the image signal in the memory is not updated.

Incident end 51A of light guide 51 and light source 1
2 is provided with a diaphragm 34 for adjusting the amount of light irradiated to the subject S, and the diaphragm 34 is a motor 3
It is opened and closed by the drive of 3. The motor 33 is a stepping motor and is driven (rotated) according to the pulse signal sent from the aperture control circuit 32. In the signal processing circuit 20, a luminance signal for one frame is generated based on the input image signal and sent to the system control circuit 24. In the system control circuit 24, a brightness average value indicating the representative brightness of the subject image is calculated based on the sent brightness signal, and the difference between the brightness average value and the reference brightness value indicating the appropriate brightness of the subject image is calculated. Then, a control signal is output to the aperture control circuit 32. Then, the diaphragm 34 is opened and closed by driving the motor 33 so that the subject image is maintained at an appropriate brightness. In the present embodiment, such automatic light control processing is executed as interrupt processing at intervals of 1/60 seconds.

FIG. 2 shows the tip portion 50 of the videoscope 50.
It is the figure which showed the internal structure of A typically.

At the tip portion 50A of the videoscope 50,
A light distribution lens 55 for diffusing the light emitted from the emission end 51B of the optical fiber bundle 51, and an objective optical system 53 for forming a subject image on the light receiving surface of the charge amplification type solid-state imaging device 54 are provided. In addition, on the back surface of the charge amplification type solid-state imaging device 54 (on the side opposite to the objective optical system 53),
A Peltier element 59 for cooling the charge amplification type solid-state imaging device 54 is provided.

The charge amplification type solid-state image pickup device 54 applied in the present embodiment is a solid-state image pickup device capable of amplifying charges by causing an impact ionization phenomenon to generate secondary electrons. Therefore, it is not necessary to amplify the read signal charges with an amplifier as in the case of using a conventional image sensor. Further, since the charge amplification process is executed in the image pickup device, noise when the charges are read from the charge amplification type solid-state image pickup device 54 is not amplified, and the signal output level can be increased without noise superposition. In this embodiment, the operator operates the panel switch 30.
The charge amplification processing is executed by operating the charge amplification switch 30A. When the charge amplification switch 30A is not operated, the signal amplification is not executed and the signal charge is read from the charge amplification type switch 30A.

FIG. 3 is a flowchart showing a charge amplification processing operation according to the operation of the charge amplification switch 30A.

In step S101, the signal level for the charge amplification switch 30A is detected. Step S1
02, whether the signal level of the charge amplification switch 30A is in the ON state or not by the operator's operation,
That is, it is determined whether or not the charge amplification switch 30A is in the ON state. When it is determined that the charge amplification switch 30A is not in the ON state, the process proceeds to step S106.
In step S106, a control signal is output to the image sensor drive circuit 56 so that the charge amplification processing operation is turned off, that is, the signal charge is output without performing the charge multiplication processing operation, and the charge amplification is performed based on this control signal. The solid-state image sensor 54 is driven. When step S106 is executed,
The process moves to step S107.

On the other hand, when it is determined in step S102 that the charge amplification switch 30A is in the ON state, the process proceeds to step S103. In step S103, the charge amplification type solid-state imaging device 5 is used to detect the brightness of the subject image.
The luminance value Y is calculated based on the image signal read out from No. 4. The brightness value here is represented by an integer of 0 to 255 by dividing the brightness level of the subject image into 256 levels. As the brightness value Y, the average brightness of the subject image for one frame is calculated. Then, in step S104, it is determined whether or not the brightness value Y is smaller than the limit brightness value Y0. In the present embodiment, the limit brightness value Y0 represents the minimum brightness within the range in which the brightness of the displayed subject image does not hinder the observation, and the reference brightness set in the automatic light adjustment process. The value is smaller than the value. Luminance value Y
When it is determined that is equal to or higher than the limit luminance value Y0, the process proceeds to step S106, and the charge amplification processing operation is not executed.
On the other hand, when it is determined that the brightness value Y is smaller than the limit brightness value Y0, the process proceeds to step S105, and the charge amplification processing operation is turned on, that is, the charge amplification processing operation is performed in the charge amplification type solid-state imaging device 54. The control signal is sent to the image pickup element drive circuit 56. When step S105 is executed, the process proceeds to step S107.

In step S107, it is determined whether the videoscope 50 has been removed from the processor 10 to terminate the observation. When it is determined that the video scope 50 has not been removed, the process returns to step S101. On the other hand, when it is determined that the videoscope 50 has been removed, this charge amplification processing operation routine ends.

FIG. 4 is a diagram showing a flowchart corresponding to the electronic shutter operation.

In step S201, the panel switch 3
The signal level for the electronic shutter switch 30B of 0 is detected. In step S202, it is determined whether the electronic shutter switch 30B is in the ON state by the operation of the operator, that is, whether the signal level detected in step S201 is the level corresponding to the ON state. If it is determined that the electronic shutter switch 30B is not in the ON state, the process proceeds to step S204. In step S204, a control signal is output to the image sensor drive circuit 56 so that signal charges are output without performing the charge multiplication processing operation, and the charge amplification type solid-state image sensor 54 is driven based on this control signal. . When step S204 is executed, the process proceeds to step S205.

On the other hand, if it is determined in step S202 that the electronic shutter switch 30B is in the ON state, the process proceeds to step S203. In step S203,
The charge amplification type solid-state imaging device 54 is driven so that the signal charge is output according to a predetermined electronic shutter speed. The electronic shutter speed here is 2 of the image signal read time interval (= 1/60 seconds) during normal observation.
It is set to double (= 1/120 seconds). The control signal is supplied to the image pickup element drive circuit 5 so that the charge amplification processing operation is executed.
Sent to 6. The gain value at the time of charge amplification is determined according to the electronic shutter speed, and is doubled here. When step S203 is executed, the process proceeds to step S205.

In step S205, it is determined whether the videoscope 50 has been removed from the processor 10 to end the observation. When it is determined that the video scope 50 has not been removed, the process returns to step S201. On the other hand, if it is determined that the video scope 50 has been removed, the electronic shutter processing operation routine ends.

As described above, according to the present embodiment, the charge amplification type solid-state image pickup device 54 is provided in the video scope 50, and the subject image displayed on the monitor 39 by operating the charge amplification switch 30A is always proper. It is maintained at a bright level. Further, when the electronic shutter switch 30B is operated, the electronic shutter operation is executed, and at this time, the charge amplification process is executed. Therefore, an image without blurring can be displayed without increasing the amount of illumination light, and a clear still image can be recorded by operating the freeze switch.

[0034]

As described above, according to the present invention, it is possible to display a bright image having excellent image quality by compensating for the shortage of the irradiation light amount without increasing the illumination light amount to the subject.

[Brief description of drawings]

FIG. 1 is a block diagram of an electronic endoscope apparatus according to the present embodiment.

FIG. 2 is a diagram schematically showing an internal configuration of a distal end portion of a scope.

FIG. 3 is a diagram showing a flowchart of a charge amplification process according to an operation on a charge amplification switch.

FIG. 4 is a view showing a flowchart of a charge amplification process according to an operation on an electronic shutter switch.

[Explanation of symbols]

10 processors 30A charge amplification switch 30B electronic shutter switch 50 video scope 54 Charge amplification type solid-state imaging device 56 Image sensor drive circuit

Continued front page    F-term (reference) 2H040 BA09 CA03 FA08 FA10 GA02                       GA11                 4C061 CC06 DD03 GG01 JJ18 LL02                       MM05 NN01 PP01 PP15 QQ09                       RR02 RR15 RR18 RR22 SS04                       SS07                 5C054 CC02 CC07 EA01 ED05 ED06                       HA12

Claims (6)

[Claims] 1. An electronic endoscope apparatus comprising a videoscope having an image pickup device and a processor to which the videoscope is connected, wherein the image pickup device is caused by photoelectric conversion by causing an impact ionization phenomenon. An electronic endoscope apparatus characterized by being a charge amplification type solid-state imaging device capable of executing charge amplification processing for amplifying charges. 2. Brightness determining means for determining whether or not the brightness of a captured subject image has reached a predetermined observable brightness, and the brightness of the subject image has reached the predetermined brightness. The electronic endoscope apparatus according to claim 1, further comprising charge amplification processing means for executing the charge amplification processing in the charge amplification type solid-state imaging device. 3. An electronic shutter operation means for performing an electronic shutter operation for taking an exposure time shorter than an exposure time at a normal observation, and the charge amplification type solid-state imaging device when the electronic shutter operation is performed. The electronic endoscope apparatus according to claim 1, further comprising a charge amplification processing unit that causes the element to execute the charge amplification processing. 4. A light amount adjusting means for adjusting a light amount of light emitted from a light source for illuminating an object, and controlling the light amount adjusting means so that an image of an object imaged is maintained at an appropriate brightness. The electronic endoscope apparatus according to any one of claims 1 to 3, further comprising: an automatic light adjustment processing unit that executes light amount adjustment. 5. An electronic endoscope apparatus comprising a videoscope having an image pickup device and a processor to which the videoscope is connected, wherein the image pickup device is caused by photoelectric conversion by causing an impact ionization phenomenon. A program for executing a charge amplification process executed in an electronic endoscope device characterized by being a charge amplification type solid-state image pickup device capable of amplifying charges, and observing the brightness of a subject image to be picked up. Brightness determining means for determining whether or not the brightness has reached a possible predetermined brightness, and when the brightness of the subject image has not reached the predetermined brightness, the charge amplification in the charge amplification type solid-state imaging device is performed. A program that causes a charge amplification processing unit that executes processing to function. 6. An electronic endoscope apparatus comprising a videoscope having an image pickup device and a processor to which the videoscope is connected, wherein the image pickup device is caused by photoelectric conversion by causing an impact ionization phenomenon. A program for executing a charge amplification process executed in an electronic endoscope apparatus characterized by being a charge amplification type solid-state image pickup device capable of executing a charge amplification process for amplifying charges. An electronic shutter operation means for performing an electronic shutter operation for photographing with an exposure time shorter than the exposure time; and when the electronic shutter operation is executed, the charge amplification type solid-state imaging device executes the charge amplification process. A program that causes a charge amplification processing unit to function.