JP4836591B2 - Endoscope image signal processing apparatus and electronic endoscope system - Google Patents

Description

  The present invention relates to an endoscope image signal processing apparatus that maintains constant brightness of an endoscope image in which an LED is used as a light source.

  In order to observe a subject using an endoscope, it is necessary to illuminate the vicinity of the distal end of the insertion tube of the endoscope. In a conventional endoscope, illumination is performed by transmitting irradiation light from a light source outside the endoscope to a distal end of an insertion tube of the endoscope through a light guide formed by an optical fiber.

  In endoscopes, it is desired to reduce the diameter of the insertion tube. In view of this, there is known an endoscope in which an LED is provided as an illumination light source at the distal end of an insertion tube to reduce the diameter without using a light guide (see Patent Document 1).

However, even if a constant current is supplied to the LED, the problem is that the luminance of the emitted light changes. That is, the brightness of the entire subject image observed due to the change in the luminance of the illumination light is not constant, and it is difficult to observe.
JP-A-11-216111

  Therefore, an object of the present invention is to perform signal processing so that an image captured by an electronic endoscope using an LED as an illumination light source becomes an image having a certain brightness.

  An endoscope image signal processing apparatus according to the present invention receives a forward voltage as an LED voltage signal from a voltage monitor circuit that detects a forward voltage of an LED used as a light source of an electronic endoscope, and takes an image of the electronic endoscope. A reception unit that receives an image as an image signal, and an image signal processing unit that multiplies the image signal by a gain corresponding to the LED voltage signal.

  Furthermore, it is preferable that the image signal processing unit includes a calculation unit that determines a gain for each forward voltage based on the forward voltage versus temperature characteristic and the temperature versus luminance characteristic specific to the LED. Further, in the calculation unit, the gain is a reference brightness predetermined as a reference of the brightness of the light emitted from the LED and the brightness of the LED, which is calculated according to the forward voltage according to the forward voltage vs. temperature characteristic and the temperature vs. brightness characteristic specific to the LED. It is preferable to be determined in accordance with the ratio.

  Moreover, it is preferable that LED is provided in the front-end | tip of the insertion tube of an electronic endoscope.

  The endoscope system of the present invention also includes a voltage monitor circuit that detects a forward voltage of an LED used as a light source of an electronic endoscope, and a subject image that is provided at the tip of the electronic endoscope and is illuminated by the LED. An image pickup device that picks up an image to generate an image signal and an image signal processing unit that multiplies the image signal by a gain corresponding to a forward voltage are provided.

  According to the present invention, it is possible to keep the brightness of an image displayed on a monitor constant regardless of a change in luminance of light emitted due to a temperature change of an LED light source.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is an external view of an endoscope system having an endoscope image signal processing device to which an embodiment of the present invention is applied.

  The endoscope system 10 includes an electronic endoscope 20, an endoscope processor (endoscope image signal processing device) 40, and a monitor 50. The electronic endoscope 20 is connected to the endoscope processor 40 via the connector 21. The monitor 50 is also connected to the endoscope processor 40 via a connector (not shown).

  A subject (not shown) near the distal end of the insertion tube 22 of the electronic endoscope 20 is irradiated with illumination light from a light source (not shown) provided at the distal end of the insertion tube 22. The subject irradiated with the illumination light is imaged by an imaging element (not shown) such as a CCD provided at the distal end of the insertion tube 22.

  The captured image is transmitted to the endoscope processor 40 as an image signal. The image signal transmitted to the endoscope processor 40 is subjected to predetermined processing and then output to the monitor 50 where the subject image is displayed.

  Next, the internal configuration of the electronic endoscope 20 will be described with reference to FIG. FIG. 2 is a block diagram schematically showing the internal configuration of the electronic endoscope 20.

  The electronic endoscope 20 includes an operation unit 23, an insertion tube 22, a cable 24, and a connector 21. The insertion tube 22 is attached to the operation unit 23. The connector 21 is attached to the operation unit 23 via the cable 24.

  The operation unit 23 is provided with an endoscope controller 25, a light source driving circuit 26, an image sensor driving circuit 27, a CDS / AGC 28, an image sensor process circuit 29, and an LED forward voltage monitoring circuit 34. The endoscope controller 25 controls operations of the light source drive circuit 26, the image sensor drive circuit 27, the CDS / AGC 28, and the image sensor process circuit 29.

  A light distribution lens 30, an objective lens 31, an image sensor 32, and an LED light source 33 are provided at the distal end of the insertion tube 22. The LED light source 33 emits light when driven by the light source driving circuit 26, and the emitted light is irradiated to the subject near the tip via the light distribution lens 30. In order to stabilize the amount of light, a constant current is passed through the LED light source 33.

  The objective lens 31 forms an image of the reflected light from the subject irradiated with the illumination light on the light receiving surface of the image sensor 32. The imaging operation is executed by the imaging device 32 driven by the imaging device driving circuit 27. An image signal corresponding to the subject image captured by the image sensor is generated.

  The image signal is sent to the CDS / AGC 28. In the CDS / AGC 28, the image signal is subjected to correlated double sampling, and gain adjustment is performed. The image signal whose gain has been adjusted is transmitted to the image sensor process circuit 29. In the image sensor process circuit 29, predetermined signal processing such as clamping, blanking, and YC separation processing is performed. The image signal subjected to the YC separation process is sent to the endoscope processor 40 as a Y signal and a C signal.

  The input end of the LED light source 33 is connected to the light source driving circuit 26, and the output end is connected to the LED forward voltage monitoring circuit 34. The LED forward voltage monitoring circuit 34 includes a buffer 34a and a differential amplifier circuit 34b.

  The buffer 34a is used for impedance adjustment, and a potential difference between the input end and the output end of the LED light source 33, that is, a forward voltage is detected by the differential amplifier circuit 34b. The detected forward voltage is sent to the endoscope controller 25 as an LED voltage signal. The LED voltage signal is further sent from the endoscope controller 25 to the endoscope processor 40.

  As will be described later, by connecting the electronic endoscope 20 to the endoscope processor 40 via the connector 21, the imaging element process circuit 29 and the endoscope controller 25 are electrically connected to the endoscope processor 40. The

  Next, the configuration of the endoscope processor 40 will be described with reference to FIG. FIG. 3 is a block diagram schematically showing the internal configuration of the endoscope processor 40.

  The endoscope processor 40 includes a front-stage signal processing circuit 41, an A / D converter 42, an image memory 43, a D / A converter 44, a rear-stage signal processing circuit 45, a processor controller 46, and the like.

  When the electronic endoscope 20 is connected to the endoscope processor 40 via the connector 21, the image sensor process circuit 29 and the pre-stage signal processing circuit 41 are connected, and the endoscope controller 25 and the processor controller 46 are connected. .

  The image signal output from the image sensor process circuit 29 is sent to the pre-stage signal processing circuit 41. In the pre-stage signal processing circuit 41, predetermined signal processing such as edge enhancement processing is performed on the image signal. The pre-stage signal processing circuit 41 is connected to an A / D converter 42, and an image signal subjected to predetermined signal processing is A / D converted by the A / D converter 42.

  The A / D converter 42 is connected to the image memory 43. The image signal converted into a digital signal by the A / D converter 42 is stored in the image memory 43. The image memory 43 is further connected to a D / A converter 44, and an image signal stored in the image memory 43 is read out in a timely manner and D / A converted by the D / A converter 44.

  The D / A converter 44 is connected to the subsequent signal processing circuit 45. The image signal D / A converted by the D / A converter 44 is subjected to gain adjustment of the luminance signal component of the image signal in the subsequent signal processing circuit 45 and further subjected to predetermined signal processing. The image signal subjected to the predetermined signal processing is output to the monitor 50 as a video signal having a luminance signal component, a chromaticity signal component, and a synchronization signal component. An image corresponding to the transmitted video signal is displayed on the monitor 50.

  The gain adjustment of the luminance signal performed in the post-stage signal processing circuit 45 will be described in detail. Each time an image signal of one frame is sent to the subsequent signal processing circuit 45, a gain to be multiplied by the luminance signal component of the image signal is sent from the processor controller 46 to the subsequent signal processing circuit 45.

  An LED voltage signal is sent from the endoscope controller 25 to the processor controller 46. In the processor controller 46, a gain corresponding to the LED voltage signal is obtained. The obtained gain is sent from the processor controller 46 to the subsequent signal processing circuit 45 as described above.

  In general, it is known that the luminance conversion efficiency of current varies depending on the temperature of the LED itself. For this reason, it is known that even when the LED is caused to emit light with a constant current, the luminance of the emitted light is reduced in accordance with the temperature change. Further, since the LED generates heat by passing a current through the LED, it is conceivable that the brightness of the LED is reduced by continuous use in a sealed space such as the tip of the insertion tube 22.

  By the way, assuming that the value of the current flowing through the LED is kept constant, the temperature-luminance characteristic is unique for each LED. Further, the forward voltage when a constant current flows through the LED changes according to the ambient temperature at that time, and the forward voltage versus temperature characteristic is also unique for each LED. Therefore, the temperature can be obtained from the forward voltage of the LED light source 33 by the forward voltage versus temperature characteristic, and the luminance of the LED light source 33 can be obtained from the obtained temperature.

  Therefore, it is possible to determine a reference luminance that is a reference for the luminance of the LED light source 33 in advance, and obtain the current luminance corresponding to the temperature obtained from the detected forward voltage. A gain is calculated based on a value obtained by dividing the current luminance by the reference luminance. That is, the gain sent to the subsequent signal processing circuit 45 is decreased or increased in accordance with the rate of increase / decrease of the current luminance with respect to the reference luminance, and as a result, the brightness of the image displayed on the monitor 50 is kept constant.

  The gain obtained in this way is multiplied by the luminance signal component of the image signal in the post-stage signal processing circuit 45. The coefficients of the LED light source 33 for obtaining the brightness of the LED light source 33 at the temperature from the forward voltage vs. temperature characteristic of the LED light source 33 and the temperature of the LED light source 33 are stored in the ROM 47 and necessary. In response, it is sent to the processor controller 46.

  Note that the processor controller 46 controls operations of the front-stage signal processing circuit 41, the A / D converter 42, the image memory 43, the D / A converter 44, and the rear-stage signal processing circuit 45.

  The operation of correcting the display image with respect to the forward voltage of the LED light source 33 performed in the endoscope processor 40 will be described with reference to the flowchart of FIG. In the endoscope system 10, the display image correction process is started by switching to the observation mode in which the captured image of the electronic endoscope 20 is displayed.

  In step S100, an image signal of one frame is received. The received image signal is subjected to predetermined signal processing in step S101. In the next step S102, an LED voltage signal corresponding to the forward voltage of the LED light source 33 when the image signal received in step S100 is generated is received.

  When the LED voltage signal is received, the process proceeds to step S103, and a gain multiplied by the image signal is calculated. That is, the current luminance of the LED light source 33 is obtained based on the LED voltage signal, and the gain is calculated based on the current luminance and the standard luminance.

  In the next step S104, the image signal subjected to the predetermined signal processing in step S101 is multiplied by the gain calculated in step S103. When the gain adjustment is completed, the process proceeds to step S105. Predetermined signal processing is further performed on the image signal whose gain has been adjusted in step S <b> 105, and the image signal is output to the monitor 50.

  In the next step S106, it is determined whether or not there is an input for ending the observation mode. When there is an end input, the display image correction processing in the present embodiment ends. If there is no end input, the process returns to step S100, and the processes in steps S100 to S106 are repeated until there is an end input thereafter.

  According to the endoscope image signal processing apparatus configured as described above, it is possible to keep the brightness of an image displayed on the monitor 50 constant when using an electronic endoscope that uses an LED as an illumination light source. is there.

  In the present embodiment, the gain is calculated by the processor controller 46 based on the forward voltage of the LED light source 33 of the LED light source 33. However, a gain table corresponding to the forward voltage of the LED light source 33 is stored in advance. The gain may be determined according to the detected forward voltage stored in the ROM 47.

  In the present embodiment, the LED light source 33 is provided at the distal end of the insertion tube 22, but may be provided in a light source device outside the endoscope as in a conventional endoscope system. . Moreover, the structure provided in the operation part of an endoscope may be sufficient. However, in the case where the LED light source 33 is provided in the external light source device or the operation unit, it is necessary to transmit the illumination light to the distal end of the insertion tube 22 using a light guide or the like as in a conventional endoscope. .

1 is an external view of an endoscope system having an endoscope image signal processing device to which an embodiment of the present invention is applied. FIG. It is a block diagram which shows roughly the internal structure of an electronic endoscope. It is a block diagram which shows roughly the internal structure of an endoscope processor. It is a flowchart for demonstrating the correction | amendment operation | movement of the display image with respect to the forward voltage of the LED light source performed in an endoscope processor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Endoscope system 20 Electronic endoscope 22 Insertion tube 25 Endoscope controller 29 Image sensor process circuit 32 Image sensor 33 LED light source 34 LED forward voltage monitoring circuit 40 Endoscope processor 45 Subsequent signal processing circuit 46 Processor controller 50 monitor

Claims (4)

A receiving unit that receives the forward voltage as an LED voltage signal from a voltage monitor circuit that detects the forward voltage of an LED used as a light source of the electronic endoscope, and receives an image captured by the electronic endoscope as an image signal When,
An image signal processing unit that multiplies the image signal by a gain corresponding to the LED voltage signal,
The image signal processing unit calculates the gain according to the forward voltage based on the forward voltage vs. temperature characteristic and the temperature vs. luminance characteristic, which are characteristic of the LED that changes according to the temperature of the LED. An endoscopic image signal processing apparatus characterized by comprising a unit.   In the calculation unit, the gain is calculated based on the forward voltage according to the forward voltage vs. temperature characteristic and temperature vs. brightness characteristic specific to the LED, and a reference of the brightness of the LED. The endoscope image signal processing apparatus according to claim 1, wherein the endoscope image signal processing apparatus is determined in accordance with a ratio to a predetermined reference luminance.   The endoscope image signal processing apparatus according to claim 1, wherein the LED is provided at a distal end of an insertion tube of the electronic endoscope. A voltage monitor circuit for detecting a forward voltage of an LED used as a light source of an electronic endoscope;
An image sensor that is provided at a tip of the electronic endoscope and that captures a subject image illuminated by the LED to generate an image signal;
An image signal processing unit that multiplies the image signal by a gain corresponding to the forward voltage,
The image signal processing unit calculates the gain according to the forward voltage based on the forward voltage vs. temperature characteristic and the temperature vs. luminance characteristic, which are characteristic of the LED that changes according to the temperature of the LED. An electronic endoscope system characterized by having a section.

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