JP6158589B2 - Endoscope device - Google Patents

Description

  The present invention relates to an endoscope apparatus that images a subject such as an inner wall of an organ, and more particularly to output processing of pixel signals generated in an image sensor.

  In an electronic endoscope apparatus, an imaging element (image sensor) such as a CMOS or a CCD is provided at the tip of a video scope, an image signal is generated based on a pixel signal read from the image sensor, and a subject image is displayed on a monitor. . The pixel signal output from the image sensor is converted to low impedance by an output buffer (output amplifier) provided at the distal end portion of the scope, and then sent to the scope connector portion or an analog signal processing circuit in the processor via a transmission cable. .

  As the amount of heat generated by the CCD increases, dark current increases and image quality deteriorates. In addition, heat from illumination light emitted from the endoscope distal end affects the CCD output signal and degrades the image quality. In order to prevent such signal degradation due to heat, for example, the power supplied to the output buffer near the CCD is controlled, the power is turned on only when the CCD output signal is being read, and other output signals are read. The supply power is stopped during the period when the power is not used (see Patent Documents 1 and 2).

Japanese Patent No. 2579372 JP 2009-302850 A

  When the power supplied to the output buffer on the CCD side is controlled, the output of the control signal and the ON / OFF operation of the output buffer are frequently performed, which may cause noise in the pixel signal transmitted to the processor side. . In particular, in the case of an endoscope apparatus, since a control signal is transmitted through a signal transmission cable provided in a video scope, a pixel signal is transmitted through a signal cable provided in the endoscope by a switching operation. Noise is likely to occur in the process.

  Therefore, it is required to transmit the pixel signal to the processor side for signal processing while preventing signal degradation due to heat and suppressing noise generation.

  An endoscope apparatus according to the present invention includes an imaging device and an output buffer for current-amplifying a pixel signal output from the imaging device, an imaging unit provided on the endoscope distal end side, and a signal cable By controlling the analog signal processing circuit that processes the analog pixel signal sent from the imaging unit, the brightness adjustment unit that adjusts the amount of illumination light to the subject, and the current supplied to the imaging unit, A pixel signal output adjusting unit that adjusts the output amplitude of the pixel signal.

  Then, the pixel signal output adjusting unit makes the current value when the illumination light amount is a predetermined amount or less larger than the current value when the illumination light amount exceeds the predetermined amount. In other words, the current value is increased when the amount of illumination light is equal to or less than the predetermined amount, and is set to a reference current value otherwise. As the amount of current increases, the output amplitude of the pixel signal increases. Thereby, a pixel signal with little signal deterioration is acquired.

  The pixel signal output adjustment unit can control the current value with various circuit configurations. In consideration of adjusting the current value on the processor side, a constant current circuit is provided in the analog signal processing circuit, and the constant current circuit is controlled so that the amount of current flowing through the current resistor provided in the analog signal processing circuit changes. Is possible.

  When the gain processing circuit is provided in the analog signal processing circuit, the gain value can be suppressed because the output amplitude is large. The pixel signal output adjustment unit can make the gain value when the illumination light amount is a predetermined amount or less smaller than the gain value when the illumination light amount exceeds the predetermined amount. The gain value may be decreased as the current value increases.

  For example, the pixel signal output adjustment unit can set in advance a table indicating the correspondence between the current value and the gain value, and can determine the current value and the gain value based on the table. The gain value may be decreased in proportion to the increase in current amount.

  Even in an observation situation where the amount of illumination light is small, the scope tip is not necessarily close to the subject. In order to compensate that the brightness of the observation image is sufficient, the pixel signal output adjustment unit increases the current value when the illumination light amount is not more than a predetermined amount and the pixel signal luminance value is not less than the predetermined value. It may be.

  As described above, according to the present invention, a high-quality image can be obtained while suppressing signal deterioration and noise generation in an endoscope apparatus.

It is a block diagram of the electronic endoscope apparatus which is this embodiment. It is a block diagram showing an output path of an analog pixel signal and an analog signal processing circuit. It is a flowchart of the current control process performed by a system controller.

  Hereinafter, the electronic endoscope apparatus according to the present embodiment will be described with reference to the drawings.

  FIG. 1 is a block diagram of an electronic endoscope apparatus according to this embodiment. The operation of the electronic endoscope apparatus will be described with reference to FIG.

  The electronic endoscope apparatus includes a video scope 10 whose insertion portion is inserted into the body, and a processor 20, and the video scope 10 is detachably connected to the processor 20. A monitor 60 is connected to the processor 20.

  The processor 20 includes a light source 46 that emits white light, and light emitted from the light source 46 enters a light guide 11 provided in the video scope 10 via a condenser lens 44. The light incident on the light guide 11 exits from the distal end portion of the video scope 10 via the light distribution lens 13 and is irradiated on the subject (observation site).

  The light reflected by the subject is imaged by an objective lens 14 provided at the tip of the video scope 10, and a subject image is formed on the light receiving surface of the image sensor 12. Here, a CCD is used as the image sensor 12. On the light receiving surface of the image sensor 12, a complementary color filter (not shown) is arranged in which color filter elements made of Cy, Ye, G, and Mg are arranged in a mosaic pattern.

  In the image sensor 12, an image signal for one field / frame is read at a predetermined time interval in accordance with the drive signal sent from the CCD drive circuit 32. For example, in the case of the NTSC system, data is read at intervals of 1/60 seconds, and in the case of the PAL system, data is read at intervals of 1/50 seconds. The read pixel signal is subjected to current amplification processing in the output buffer 15 and then sent to the processor 20.

  The analog signal processing circuit 22 of the processor 20 performs amplification processing and gain processing on the analog pixel signal. The pre-stage signal processing circuit 24 performs various signal processing such as digitization processing, white balance processing (gain processing), and gamma correction processing on the analog pixel signal. Thereby, a color image signal is generated. The color image signal is output to the monitor 60 via the memory 26 and the subsequent signal processing circuit 28, and the color image is displayed on the monitor 60.

  A system controller 30 including a CPU, a ROM, etc. outputs control signals to the timing controller 34, the light source power supply 48, the front panel switch 36, etc., and controls the operation of the entire processor 20. The diaphragm 42 is disposed between the incident end of the light guide 11 and the condensing lens 44, and increases or decreases the amount of illumination light by an opening / closing operation by the motor 40. The system controller 30 performs automatic light control processing and sends a control signal to the motor driver 38 based on the luminance signal. The motor driver 38 drives the motor 40 based on the control signal.

  FIG. 2 is a block diagram showing an analog pixel signal output path and an analog signal processing circuit. The adjustment of the current value will be described with reference to FIG.

  The pixel signal output from the image sensor 12 is subjected to analog signal processing in a signal processing range AP from the scope-side output buffer 15 to the processor-side analog signal processing circuit 22. The output buffer 15 includes an emitter follower-connected transistor 16 and amplifies a pixel signal output from the image sensor 12 to convert it into a low impedance. The current-amplified pixel signal is sent to the analog signal processing circuit 22 via the transmission cable CB that is a coaxial cable.

  The analog signal processing circuit 22 includes a constant current circuit 53, resistors 52 and 54, a capacitor 56, an amplifier circuit 57, and a gain processing circuit 58. The input pixel signal is sent to the amplifier circuit 57 via the resistor 52, the capacitor 56, and the resistor 54. A DC bias current flows through the resistor 52 to cause the output buffer 15 to linearly operate.

  Gain processing is performed on the pixel signal input to the gain processing circuit 58 via the amplifier circuit 57. The gain value is determined based on a control signal from the system control circuit 30. The pixel signal for one field / frame that has been sequentially gain processed is output from the analog signal processing circuit 22.

  A predetermined power supply voltage is supplied to the image sensor output terminal and the output buffer 15 from a power supply circuit (not shown) of the processor 20. On the other hand, the output amplitude of the pixel signal output from the image sensor 12 depends on the amount of current flowing to the current resistor 52 side. Since this amount of current corresponds to the amount of current supplied to the image sensor 12 and the output buffer 15, when the amount of current flowing to the resistor 52 side is increased or decreased, the current supplied to the image sensor 12 is also increased accordingly. Increase or decrease.

  The constant current circuit 53 provided between the signal cable CB and the resistor 52 can set and change the constant current value flowing in the signal processing range AP, and the current value supplied to the image sensor 12, that is, the resistor 52 side The amplitude value (output waveform) of the pixel signal output from the image sensor 12 can be increased by increasing the current value of the current flowing through the image sensor 12.

  By increasing the amplitude value of the pixel signal, the gain value in the gain processing circuit 58 can be set relatively small accordingly. This generates the observation image signal by using the information contained in the output pixel signal as much as possible, so that a high-quality observation image can be obtained.

  However, in an observation work situation where the temperature of the image sensor 12 is likely to increase due to a relatively large aperture and a large amount of illumination light, a scope that has been standardized in advance due to the interaction with the heat generated by the increase in the amount of current. There is a risk that the pixel signal will deteriorate due to exceeding the allowable temperature of the tip.

  Therefore, in this embodiment, when the observation situation is less affected by heat, the current value is increased to increase the pixel signal output amplitude, and in other observation situations, the current value is suppressed so as not to be affected by heat generation. .

  FIG. 3 is a flowchart showing a current control process executed by the system controller 30.

  The system controller 30 performs automatic dimming processing at a predetermined time interval (here, 1/60 seconds), and the current control processing is executed as a subroutine at a predetermined time interval (for example, the same time interval) accordingly. Yes.

  In step S101, it is determined whether or not the opening (aperture value) A of the throttle 42 is equal to or smaller than a predetermined allowable maximum opening T0. If the aperture value A is equal to or smaller than T0, the process proceeds to step S102, and it is determined whether or not the luminance value Y of the pixel signal is equal to or larger than the allowable minimum luminance value Y0.

  The allowable maximum opening T0 represents a value at which the heat of the illumination light quantity does not affect the temperature rise of the image sensor 12. The allowable minimum luminance value Y0 represents the minimum luminance value with appropriate brightness for observing the subject image. When the opening A and the luminance value Y satisfy the above conditions, it is determined that the subject is close to the distal end of the scope, and the subject is in an observation state in which a subject image with appropriate brightness can be displayed even with a small amount of illumination light.

  When the opening A is equal to or less than the allowable maximum opening T0 and the luminance level Y of the pixel signal is equal to or higher than the allowable minimum luminance value Y0, the current value is increased by controlling the constant current circuit 53 (S103), The gain value is corrected according to the value (S104).

  The correspondence relationship between the current value and the gain value is set in advance as a look-up table (LUT), and a decrease amount (decrease rate) of the gain value is determined according to an increase amount (increase rate) of the increased current value. . Here, the gain value decreases in proportion to the current increase amount.

  On the other hand, when the opening A is larger than the allowable maximum value T0 or the luminance value Y of the pixel signal is smaller than the allowable minimum luminance value Y0, the amount of illumination light is relatively large, and there is a high possibility that the image quality deteriorates due to the influence of heat. Therefore, it is determined that the current state cannot be increased and the current value and the gain value are set as reference values (S105, S106). The reference value is determined in advance at the time of manufacture, start of use, and the like.

  As described above, according to the present embodiment, the analog pixel signal output from the image sensor 12 is current-amplified in the output buffer 15 and transmitted to the analog signal processing circuit 22 of the processor 20 through the transmission cable CB. When the aperture of the diaphragm 42 is relatively small and the luminance value of the pixel signal is relatively large, it is determined that the influence of heat of the illumination light amount is small and the output amplitude of the pixel signal is increased. 53 is controlled to increase the amount of current supplied to the image sensor 12. As the current amount increases, the gain value in the gain processing circuit 58 is decreased.

  Regarding the determination of the increase in the amount of current, the observation state may be determined only by the aperture opening. Further, a circuit other than the constant current circuit may be provided to control the current value. The image sensor may have a configuration other than a CCD such as a CMOS sensor. In the illumination light quantity adjustment, a configuration other than the diaphragm may be adopted.

10 Videoscope 12 Image sensor (Image sensor)
15 Output Buffer 22 Analog Signal Processing Circuit 30 System Controller (Pixel Signal Output Adjustment Unit)
42 Aperture 53 Constant current circuit (pixel signal output adjustment unit)
CB transmission cable (signal cable)

Claims (5)

An imaging device having an imaging device and an output buffer for current-amplifying a pixel signal output from the imaging device;
An analog signal processing circuit for processing an analog pixel signal sent from the imaging unit via a signal cable;
A brightness adjustment unit that adjusts the amount of illumination light to the subject;
A pixel signal output adjustment unit that adjusts the output amplitude of the pixel signal by controlling the current supplied to the imaging unit;
The pixel signal output adjustment unit has a current value when the illumination light amount is less than or equal to a predetermined amount larger than a current value when the illumination light amount exceeds a predetermined amount ,
The analog signal processing circuit has a gain processing circuit,
An endoscope apparatus, wherein the pixel signal output adjustment unit makes a gain value when the illumination light amount is a predetermined amount or less smaller than a gain value when the illumination light amount exceeds a predetermined amount . The pixel signal output adjustment unit determines whether or not the illumination light amount is a predetermined amount or less at a predetermined time interval, and increases the current value when the illumination light amount is a predetermined amount or less. The endoscope apparatus according to 1. The endoscope apparatus according to claim 1 , wherein the pixel signal output adjustment unit determines a current value and a gain value based on a table indicating a correspondence relationship between a current value and a gain value.   The endoscope apparatus according to any one of claims 1 to 3, wherein the pixel signal output adjustment unit controls a constant current circuit provided in the analog signal processing circuit. An imaging device having an imaging device and an output buffer for current-amplifying a pixel signal output from the imaging device;
An analog signal processing circuit for processing an analog pixel signal sent from the imaging unit via a signal cable;
A brightness adjustment unit that adjusts the amount of illumination light to the subject;
A pixel signal output adjustment unit that adjusts the output amplitude of the pixel signal by controlling the current supplied to the imaging unit;
The pixel signal output adjustment unit has a current value when the illumination light amount is less than or equal to a predetermined amount larger than a current value when the illumination light amount exceeds a predetermined amount ,
The pixel signal output adjusting unit, with a predetermined amount or less of the illumination light amount, when a pixel signal intensity values above a predetermined value, the endoscope apparatus you characterized in that to increase the current value.

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