JP6378140B2 - Endoscope system and operating method thereof - Google Patents

Description

  The present invention relates to an endoscope system that displays a normal light image obtained by illuminating an observation target with visible light such as white light, and an operating method thereof.

  In the medical field, diagnosis is generally performed using an endoscope system including a light source device, an endoscope, and a processor device. In the diagnosis using the endoscopic diagnosis, in addition to the normal light observation in which the observation object is illuminated with visible light such as white light, special light with band limitation such as blue narrow band light and green narrow band light is used. Special light observation in which an observation target is illuminated for observation is also being performed.

  In normal light observation, a blue signal, a green signal, and a red signal are acquired by imaging an observation target under illumination with visible light, and the blue signal is used for the monitor B channel, the green signal is used for the monitor G channel, and the red signal is used. Assigned to the R channel of the monitor. As a result, a normal light image realizing a natural color reproduction substantially equivalent to the state observed with the naked eye is displayed on the monitor.

  In special light observation, for example, as shown in Patent Document 1, an observation target is illuminated with special light such as blue narrow band light of 400 to 420 nm and green narrow band light of 530 to 550 nm. Blue narrow-band light and green narrow-band light are closely related to the absorption characteristics of hemoglobin, and use the characteristic that the shorter the wavelength, the shallower the depth of penetration into the living body. By irradiating the living body with these blue narrow-band light and green narrow-band light, the surface blood vessels in the living body can be clearly observed with the blue narrow-band light. Blood vessels can be clearly observed. By clarifying the superficial blood vessels and the middle-deep blood vessels in this way, the blood vessels can be observed from the structural surface such as “atypical”, “nonuniform shape”, “proliferation, dilation” and the like. Furthermore, it is possible to observe a Brownish Area where the boundary with the normal part is clear.

  In special light observation, a blue narrowband signal corresponding to blue narrowband light and a green narrowband corresponding to green narrowband light are captured by imaging the observation target under illumination with blue narrowband light and green narrowband light. Obtain at least a band signal. A blue narrowband signal is assigned to the B channel and G channel of the monitor, and a green narrowband signal is assigned to the R channel of the monitor. As a result, a special light image in which surface blood vessels and middle-deep blood vessels are displayed in pseudo color is displayed on the monitor. In the special light image, the surface of the mucous membrane in the living body, the blood vessel and the fine structure in the middle and deep layers, and the like are reproduced with good contrast. On the special light image, the surface blood vessels are displayed in brown and the deep blood vessels are displayed in cyan. Thus, by displaying blood vessels of different depths in different color tones, it is possible to clarify the visibility and difference of blood vessels.

International Publication 2012/101904 (Japanese Patent No. 5174290)

  As described above, the normal light image can achieve natural color reproduction that is almost the same as the state observed with the naked eye. However, depending on the spectrum and light quantity of the illumination light, the sense of depth is insufficient, It may be difficult to display the observation image clearly throughout. In addition, the unevenness may be difficult to understand even in a distant view far away from the distal end of the endoscope.

  Furthermore, in the normal light image, it is difficult to reproduce the fine structure and the like with a good contrast as well as the superficial blood vessel and the middle-deep blood vessel as in the special light image. Moreover, in the conventional normal light images, it is difficult to display blood vessels clearly and to display an image having a transparent feeling close to a transparent feeling. Therefore, since the normal light image and the special light image are completely different images, when observation is performed focusing on the superficial blood vessels and fine structures, it is necessary to manually switch to the special observation mode for displaying the special light image. there were.

  The present invention provides an endoscope system capable of displaying an image with a sense of depth in the whole body cavity while performing natural color reproduction substantially equivalent to the state observed with the naked eye during normal light observation and its operation It aims to provide a method. It is another object of the present invention to provide an endoscope system capable of displaying a transparent image and a method for operating the same in order to reproduce blood vessel images such as surface blood vessels and middle-deep blood vessels with good contrast.

  An endoscope system according to the present invention includes a light source unit including a first blue semiconductor light source that emits first blue light, a green semiconductor light source that emits green light, and a red semiconductor light source that emits red light, and a first light source for green light and red light. 1 a light source control unit that performs specific light emission control, an imaging unit that images an observation target in a body cavity under illumination with light emitted from the light source unit under the first specific light emission control, and a blue signal and a green signal from the imaging unit And a signal output unit for outputting a red signal, a display unit having a B channel, a G channel, and an R channel, and a blue signal, a green signal, and a red signal for any of the B channel, the G channel, and the R channel. The signal output unit outputs a red signal having at least two peaks in a histogram with the vertical axis representing frequency and the horizontal axis representing pixel value.

  The light source control unit performs the second specific light emission control for the first blue light and the green light, and the signal output unit has a first pixel value difference indicating a difference between the pixel values of the first blood vessel and the mucous membrane as compared with the first blood vessel. Output a blue signal larger than the second pixel value difference indicating the difference between the second blood vessel and the mucous membrane at a deep position, or output a green signal whose first pixel value difference is smaller than the second pixel value difference. Is preferred. The light source control unit performs the third specific light emission control on the first blue light, and the signal output unit performs blue in which the pixel value of the blood vessel in the depth range of the first blue light increases or decreases according to the first blue light. Output a signal.

  The first specific light emission control preferably includes a first light amount control that makes the light amount of red light larger than 1/3 of the light amount of green light. The first blue light has a peak wavelength in the range of 400 nm to 420 nm, and the second specific light emission control preferably includes a second light amount control that makes the light amount of the first blue light larger than 1/3 of the light amount of the green light. The light source unit emits second blue light having a peak wavelength in a range from 430 nm to 480 nm, and the second specific light emission control is a third light amount control that makes the light amount of the first blue light larger than 4/5 of the light amount of the second blue light. It is preferable to contain. The second blue light preferably has a wavelength range of 420 to 480 nm. The light source control unit includes a light amount detection unit that detects a light amount of the first blue light, a light amount of the green light, and a light amount of the red light, and the light source control unit detects the first blue light, the green light, and the red light detected by the light amount detection unit. It is preferable to perform control based on the amount of light.

  Preferably, the first specific light emission control includes a fourth light amount control for controlling the light source unit based on a detection result of the peak detection unit. From the blue signal or the green signal, a first pixel value difference indicating a difference between pixel values of the first blood vessel and the mucous membrane and a second pixel value difference indicating a difference between the second blood vessel located deeper than the first blood vessel and the mucous membrane are obtained. Preferably, the second specific light emission control includes a fifth light amount control for controlling the light source unit based on a calculation result in the pixel value difference calculation unit.

  The first blue light preferably has a wavelength range of 380 to 430 nm, the green light preferably has a wavelength range of 470 to 600 nm, and the red light preferably has a wavelength range of 580 to 700 nm. The display control unit preferably assigns the blue signal to the B channel, the green signal to the G channel, and the red signal to the R channel.

  The operation method of the endoscope system of the present invention includes a step in which a light source unit emits first blue light from a first blue semiconductor light source, emits green light from a green semiconductor light source, and emits red light from a red semiconductor light source; A step in which the light source control unit performs the first specific light emission control for the green light and the red light, and the imaging unit images the observation target in the body cavity under illumination with the light emitted from the light source unit under the first specific light emission control. And a step in which the signal output unit outputs a blue signal, a green signal, and a red signal from the imaging unit, and a red color having at least two peaks in a histogram with the frequency on the vertical axis and the pixel value on the horizontal axis. A step of outputting a signal, and a step of the display control unit controlling the display unit having the B channel, the G channel, and the R channel. The red signal, a B-channel, G channel, and a step of assigning to one of the R channel.

  According to the present invention, during normal light observation, it is possible to display an image with a sense of depth throughout the body cavity while performing natural color reproduction substantially equivalent to the state observed with the naked eye.

It is an external view of an endoscope system. It is a block diagram which shows the function of the endoscope system of 1st Embodiment. It is a graph which shows the spectrum of 1st blue light B1, 2nd blue light B2, green light G, and red light R. It is the image figure which shows the image in the body cavity in R image signal of a normal light image, and the graph which shows the histogram of R image signal. It is an image figure which shows the image in a body cavity in R image signal of a normal light image, and a graph which shows distribution of the pixel value from the A point in a body cavity to B point in R image signal. It is explanatory drawing which shows distribution of the extreme surface blood vessel C1 (alpha) in the submucosa, surface blood vessel C1 (beta), middle layer blood vessel C2, and deep layer blood vessel C3. It is an image figure which shows the image in a body cavity in B image signal of a normal light image, and a graph which shows distribution of the pixel value from the A point in the body cavity in B image signal to B point. It is an image figure which shows the image in a body cavity in G image signal of a normal light image, and a graph which shows distribution of the pixel value from the A point in a body cavity in B image signal to B point. It is a graph which shows the histogram of B image signal. It is a block diagram which shows the function of the endoscope system of 2nd Embodiment. It is a block diagram which shows the function of the endoscope system of 3rd Embodiment. It is explanatory drawing of 3rd specific light emission control. It is a graph which shows the spectrum of 1st blue light B1, 2nd blue light B2, green light G, and red light R different from FIG. It is a graph which shows the spectrum of the purple light and white light which are used by a comparative example.

[First Embodiment]
As shown in FIG. 1, the endoscope system 10 according to the first embodiment includes an endoscope 12, a light source device 14, a processor device 16, a monitor 18, and a console 19. The endoscope 12 is optically connected to the light source device 14 and electrically connected to the processor device 16. The endoscope 12 includes an insertion portion 12a to be inserted into a subject, an operation portion 12b provided at a proximal end portion of the insertion portion 12a, a bending portion 12c and a distal end portion 12d provided at the distal end side of the insertion portion 12a. have. By operating the angle knob 12e of the operation unit 12b, the bending unit 12c performs a bending operation. With this bending operation, the tip 12d is directed in a desired direction. The “display unit” of the present invention corresponds to the monitor 18.

  In addition to the angle knob 12e, the operation unit 12b is provided with a mode switching SW 13a, a freeze button 13b, and a zoom operation unit 13c. The mode switching SW 13a is used for a switching operation between two types of modes, a first normal observation mode and a special observation mode. The first normal observation mode is a mode for displaying a normal light image on the monitor 18. The special observation mode is a mode for displaying a special light image on the monitor 18.

  The freeze button 13b is used when acquiring a still image to be observed. The zoom operation unit 13c is used when performing magnified observation for magnifying and observing an observation target. By operating the zoom operation unit 13c, the zoom lens 47 (see FIG. 2) moves between the tele position and the wide position.

  The processor device 16 is electrically connected to the monitor 18 and the console 19. The monitor 18 outputs and displays image information and the like. The console 19 functions as a UI (User Interface) that receives input operations such as function settings. The processor device 16 may be connected to an external recording unit (not shown) for recording image information and the like.

  As shown in FIG. 2, the light source device 14 includes a B1-LED (B1 Light Emitting Diode) 20a, a B2-LED (B2 Light Emitting Diode) 20b, a G-LED (Green Light Emitting Diode) 20c, and an R-LED (Red). Light Emitting Diode) 20d, a light source control unit 21 that controls driving of the four color LEDs 20a to 20d, and an optical path coupling unit 23 that couples the optical paths of the four color lights emitted from the four color LEDs 20a to 20d. . The light coupled by the optical path coupling unit 23 is irradiated into the subject through the light guide 41 and the illumination lens 45 inserted into the insertion unit 12a.

  An LD (Laser Diode) may be used instead of the LED. The above-mentioned “four-color LEDs 20a to 20d” correspond to the “light source section” of the present invention. The B1-LED 20a corresponds to the “first blue semiconductor light source” of the present invention, the G-LED 20c corresponds to the “green semiconductor light source” of the present invention, and the R-LED 20d corresponds to the “red semiconductor light source” of the present invention.

  As shown in FIG. 3, the B1-LED 20a generates a first blue light B1 having a peak wavelength of 405 nm and a wavelength range of 380 to 425 nm. The B2-LED 20b generates the second blue light B2 having a peak wavelength of 460 nm and a wavelength range of 426 to 475 nm. The G-LED 20c generates green light G having a wavelength range of 476 to 590 nm. The R-LED 20d generates red light R having a peak wavelength included in 620 to 630 nm and a wavelength range of 591 to 700 nm.

  Note that the peak wavelength of the first blue light B1 is not limited to 405 nm but is preferably included in 400 to 420 nm, and the peak wavelength of the second blue light B2 is not limited to 460 nm and may be included in 430 to 480. Further, the upper and lower limits of the wavelength range of the first blue light B1, the second blue light B2, the green light G, and the red light R may be somewhat on the short wavelength side or the long wavelength side. For example, the wavelength range of the first blue light B1 is preferably 380 to 430 nm, the wavelength range of the second blue light B2 is preferably 420 to 480 nm, and the green light G is preferably 470 to 600 nm. The red light R is preferably 580 to 700 nm. Further, in the first blue light B1, the second blue light B2, the green light G, and the red light R, the center wavelength and the peak wavelength may be the same or different.

  As shown in FIG. 2, the light source control unit 21 lights the B1-LED 20a, the B2-LED 20b, the G-LED 20c, and the R-LED 20d in any of the first normal observation mode and the special observation mode. Accordingly, the observation target is irradiated with light in which four colors of light of the first blue light B1, the second blue light B2, the green light G, and the red light R are mixed. In the light source control unit 21, the light quantity ratio among the first blue light B1, the second blue light B2, the green light G, and the red light R is set to be different between the first normal observation mode and the special observation mode. .

  In the first normal observation mode, the LEDs 20a to 20d are controlled so that the amounts of the first blue light B1, the second blue light B2, the green light G, and the red light R are B1cx, B2cx, Gcx, and Rcx, respectively. . In the special observation mode, the LEDs 20a to 20d are controlled so that the light amounts of the first blue light B1, the second blue light B2, the green light G, and the red light R are B1s, B2s, Gs, and Rs, respectively. The amount of light emitted from each of the LEDs 20a to 20d is detected by light amount sensors 24a to 24d (corresponding to the “light amount detection unit” of the present invention) provided at predetermined positions on the light path of the light of each color. Is done. And the light source control part 21 performs control which maintains the light quantity set for every observation mode by controlling light emission of each LED20a-20d based on the result detected with the light quantity sensors 24a-24d.

  Here, in the first normal observation mode, it is preferable that the light source control unit 21 performs the first light amount control that makes Rcx / Gcx larger than 1/3 by adjusting the light amounts of the green light G and the red light R. . By this first light quantity control, it is more preferable that Rcx / Gcx be in the range of 1/3 to 3/5, and it is most preferable that Rcx / Gcx is in the range of 1/2 to 3/5. Thereby, the normal light image becomes an image with a sense of depth. In other words, the observation image can be clearly displayed over the whole body cavity on the normal light image, and the unevenness can be clearly displayed even in a distant view far from the distal end portion 12d of the endoscope. It becomes.

  Further, in the first normal observation mode, the light source control unit 21 performs the second light amount control that makes B1cx / Gcx larger than 1/3 by adjusting the light amounts of the first blue light B1 and the green light G. preferable. By this second light quantity control, B1cx / Gcx is more preferably in the range of 1/3 to 3/5, and B1cx / Gcx is most preferably in the range of 1/2 to 3/5. As a result, the normal light image becomes a transparent image. That is, on the normal light image, it is possible to display the blood vessel clearly, and it is possible to display an image with a transparent feeling close to a clear feeling.

  Note that the light amounts of the first blue light B1, the second blue light B2, the green light G, and the red light R are light amounts obtained at predetermined positions between the LEDs 20a to 20d and the distal end portion 12d of the endoscope. However, in this embodiment, the light amounts of the first blue light B1, the second blue light B2, the green light G, and the red light R at the time when the light is emitted from the distal end portion 12d of the endoscope are used. Here, “light quantity” refers to an integrated value of light intensity in a certain wavelength region. That is, in FIG. 3, the light quantity of the first blue light B1 is an integral value of the light intensity in the wavelength range of 380 to 430 nm, and the light quantity of the second blue light B2 is the light intensity in the wavelength range of 420 to 480 nm. The amount of green light G is the integral value of the light intensity in the wavelength region of 470 to 600 nm, and the amount of light of the red light R is the integral value of the light intensity in the wavelength region of 580 to 700 nm.

  As shown in FIG. 2, the light guide 41 is built in the endoscope 12 and the universal cord (the cord connecting the endoscope 12, the light source device 14, and the processor device 16). The combined light propagates to the distal end portion 12d of the endoscope 12. A multimode fiber can be used as the light guide 41. As an example, a thin fiber cable having a core diameter of 105 μm, a cladding diameter of 125 μm, and a diameter of φ0.3 to 0.5 mm including a protective layer serving as an outer shell can be used. Also, a fiber cable in which small diameter fibers of φ 0.03 mm are bundled can be used.

  The distal end portion 12d of the endoscope 12 is provided with an illumination optical system 30a and an imaging optical system 30b. The illumination optical system 30 a has an illumination lens 45, and light from the light guide 41 is irradiated to the observation target via the illumination lens 45. The imaging optical system 30 b includes an objective lens 46, a zoom lens 47, and an imaging sensor 48. Reflected light from the observation target enters the image sensor 48 through the objective lens 46 and the zoom lens 47. As a result, a reflected image of the observation object is formed on the image sensor 48.

  The imaging sensor 48 (corresponding to the “imaging unit” of the present invention) is a color imaging sensor. The signal output unit 48 a controls the image sensor 48 to output an image signal from the image sensor 48. A still image or a moving image is generated based on the output image signal. The image sensor 48 is preferably a CCD (Charge Coupled Device) image sensor, a CMOS (Complementary Metal-Oxide Semiconductor) image sensor, or the like. The image sensor 48 used in the present invention is a color image sensor for obtaining RGB image signals of three colors of R (red), G (green), and B (blue), that is, an R pixel provided with an R filter. , A so-called RGB imaging sensor including a G pixel provided with a G filter and a B pixel provided with a B filter.

  The image sensor 48 is a so-called complementary color image sensor that includes complementary filters for C (cyan), M (magenta), Y (yellow), and G (green) instead of an RGB color image sensor. May be. When the complementary color imaging sensor is used, CMYG four-color image signals are output. Therefore, it is necessary to convert CMYG four-color image signals into RGB three-color image signals by complementary color-primary color conversion. . Therefore, the configuration including the complementary color imaging sensor and the complementary color-primary color conversion corresponds to the “imaging unit” of the present invention. Further, the image sensor 48 may be a monochrome image sensor not provided with a color filter. In this case, the light source control unit 21 sequentially turns on the first blue light B1, the second blue light B2, the green light G, and the red light R to pick up an image. Generate a frame image.

  The image signal output from the image sensor 48 is transmitted to the CDS / AGCX circuit 50. The CDS / AGCX circuit 50 performs correlated double sampling (CDS (Correlated Double Sampling)) and automatic gain control (AGCX (Auto Gain Control)) on an image signal which is an analog signal. The image signal that has passed through the CDS / AGCX circuit 50 is converted into a digital image signal by an A / D converter (A / D (Analog / Digital) converter) 52. The A / D converted digital image signal is input to the processor device 16.

  The processor device 16 includes a receiving unit 53, a DSP (Digital Signal Processor) 56, a noise removing unit 58, an image processing switching unit 60, a normal light image processing unit 62, a special light image processing unit 64, and display control. Part 68. The receiving unit 53 receives a digital RGB image signal from the endoscope 12. The R image signal (corresponding to the “red signal” of the present invention) corresponds to the signal output from the R pixel of the image sensor 48, and the G image signal (corresponding to the “green signal” of the present invention) is the image sensor 48. The B image signal (corresponding to the “blue signal” of the present invention) corresponds to the signal output from the B pixel of the image sensor 48.

  The DSP 56 performs various signal processing such as defect correction processing, offset processing, gain correction processing, linear matrix processing, gamma conversion processing, and demosaicing processing on the received image signal. In the defect correction process, the signal of the defective pixel of the image sensor 48 is corrected. In the offset process, the dark current component is removed from the RGB image signal subjected to the defect correction process, and an accurate zero level is set. In the gain correction process, the signal level is adjusted by multiplying the RGB image signal after the offset process by a specific gain. The RGB image signal after the gain correction process is subjected to a linear matrix process for improving color reproducibility. After that, brightness and saturation are adjusted by gamma conversion processing. The RGB image signal after the linear matrix processing is subjected to demosaic processing (also referred to as isotropic processing or pixel interpolation processing), and a signal of a color that is insufficient at each pixel is generated by interpolation. By this demosaic processing, all the pixels have RGB signals.

  The noise removing unit 58 removes noise from the RGB image signal by performing noise removal processing (for example, a moving average method, a median filter method, etc.) on the RGB image signal subjected to gamma correction or the like by the DSP 56. The RGB image signal from which noise has been removed is transmitted to the image processing switching unit 60.

  When the first normal observation mode is set by the mode switching SW 13a, the image processing switching unit 60 transmits the RGB image signal to the normal light image processing unit 62 and when the special observation mode is set. Transmits the RGB image signal to the special light image processing unit 64.

  The normal light image processing unit 62 performs color conversion processing, color enhancement processing, and structure enhancement processing on the RGB image signal. In the color conversion process, a 3 × 3 matrix process, a gradation conversion process, a three-dimensional LUT process, and the like are performed on the digital RGB image signal to convert the digital RGB image signal into a color converted RGB image signal. Next, various color enhancement processes are performed on the RGB image signal that has been subjected to the color conversion process. A structure enhancement process such as spatial frequency enhancement is performed on the RGB image signal that has been subjected to the color enhancement process. The RGB image signal subjected to the structure enhancement processing is input from the normal light image processing unit 62 to the display control unit 68 as an RGB image signal of the normal light image.

  As with the normal light image processing unit 62, the special light image processing unit 64 performs color conversion processing, color enhancement processing, and structure enhancement processing on the RGB image signal. These processed RGB image signals are input from the special light image processing unit 64 to the display control unit 68 as RGB image signals of the special light image.

  When the display control unit 68 is set to the first normal observation mode, the B image signal of the normal light image is assigned to the B channel of the monitor 18 and the G image signal of the normal light image is assigned to the G channel of the monitor 18. The R image signal of the normal light image is assigned to the R channel of the monitor 18. As a result, the normal light image is displayed on the monitor 18. On the other hand, when the special observation mode is set, the B image signal of the special light image is assigned to the B channel and the G channel of the monitor 18, and the G image signal of the special light image is assigned to the R channel of the monitor 18. As a result, a special light image is displayed on the monitor 18.

  The normal light image displayed on the monitor 18 is a three-dimensional image having both a sense of depth and a sense of transparency. The reason why the normal light image has a sense of depth is that the R image signal of the normal light image obtained by performing the first light amount control by the light source control unit 21 has the following properties. As shown in FIG. 4, when the pixel value distribution of the R image signal is represented by a histogram in which the vertical axis represents frequency and the horizontal axis represents pixel value, the pixel values are evenly distributed from high pixel values to low pixel values. And peaks PH and PL corresponding to the bright area HA and dark area LA on the R image signal. Thus, if there is at least two peaks in the histogram of the R image signal, a sense of depth can be given to the normal light image.

  When the vertical axis represents the pixel value and the horizontal axis represents the R image signal in the pixel space, as shown in FIG. 5, the pixel value is between A point and B point on the R image signal. While changing gently, the pixel value changes greatly due to the undulations and irregularities of the mucous membrane. Such a change in the pixel value of the R image signal gives a sense of depth in the normal light image.

  Next, in the normal light image, there is a sense of transparency in which a blood vessel of a predetermined depth can be seen through the mucous membrane. The normal light image obtained by performing the second light amount control or the third light amount control in the light source control unit 21. This is because the B image signal or the G image signal has the following properties. Here, as shown in FIG. 6, the blood vessel having a predetermined depth is distributed within the depth range of 50 μm from the mucous membrane M, and is also distributed within the depth range of 50 μm, and the polar surface blood vessel C1α. The surface blood vessel C1β located at a deeper position, the middle blood vessel C2 distributed within a depth range of 50 to 100 μm, and the deep blood vessel C3 distributed within a depth range of 100 to 200 μm are taken up. From the relationship of pixel values, transparency will be described.

  As shown in FIG. 7, in the B image signal of the normal light image, the pixel values of the polar surface blood vessel C1α and the surface blood vessel C1β are extremely lower than the pixel value of the mucous membrane M. In contrast, the pixel values of the middle layer blood vessel C2 and the deep layer blood vessel C3 are lower than the pixel values of the mucous membrane M, but not as low as the pixel values of the extreme surface blood vessel C1α and the surface blood vessel C1β. From the above, in the image based on the B image signal, the superficial blood vessel C1α and the superficial blood vessel C1β appear to be transparent because the difference with respect to the mucous membrane M is large.

  As shown in FIG. 8, in the G image signal of the normal light image, the pixel values of the middle-layer blood vessel C2 and the deep-layer blood vessel C3 are extremely lower than the pixel value of the mucous membrane M. In contrast, the pixel values of the extreme surface blood vessel C1α and the surface blood vessel C1β are lower than the pixel values of the mucous membrane M, but not as low as the pixel values of the middle blood vessel C2 and the deep blood vessel C3. From the above, in the image based on the G image signal, the middle-layer blood vessel C2 and the deep-layer blood vessel C3 appear to be transparent because there is a large difference with respect to the mucous membrane M.

  Further, in the R image signal of the normal light image, the polar surface blood vessel C1α, the surface blood vessel C1β, and the middle layer blood vessel C2 have almost no difference in pixel values from the mucosa M, and only the thick blood vessels such as the deep blood vessel C3 The pixel value is different from M (see FIG. 5). Therefore, in the image based on the R image signal, it seems that there is a sense of transparency regarding the thick deep blood vessel C3.

  As described above, the normal light image includes the B image signal in which the polar surface blood vessel C1α and the surface blood vessel C1β are clearly displayed, the G image signal in which the middle blood vessel C2 and the deep blood vessel C3 are clearly displayed, and the thick deep blood vessel C3. Since it is an image obtained by synthesizing the clearly displayed R image signal, in the normal light image, blood vessels such as the polar surface blood vessel C1α, the surface blood vessel C1β, the middle layer blood vessel C2, and the deep layer blood vessel C3 are displayed very clearly.

  When the pixel value distribution is represented by a histogram in the B image signal of the normal light image, as shown in FIG. 9, the width Wx of the distribution of the pixel value on the histogram of the B image signal is the pixel in the histogram of the R image signal. The width Wy (see FIG. 4) of the value distribution is about ½, and the width Wx is narrower than the width Wy. The width of the pixel value distribution in the histogram of the G image signal is also narrower than the width Wy of the pixel value distribution in the histogram of the R image signal, as in the case of the B image signal. Further, since the R image signal of the normal light image is an image signal obtained based on the red light R having a sufficient amount of light, the gain coefficient for the R image signal can be reduced. By suppressing the gain coefficient low, noise in the R image signal is reduced, and as a result, a sense of transparency can be obtained in the normal light image.

  Further, instead of or in addition to the first normal observation mode, the second normal observation mode in which the light amount ratio among the first blue light B1, the second blue light B2, the green light G, and the red light R is different from the first normal observation mode. May be performed. In the second normal observation mode, the light source control unit 21 sets the light amounts of the first blue light B1, the second blue light B2, the green light G, and the red light R to B1cy, B2cy, Gcy, and Rcy, respectively. The LEDs 20a to 20d are controlled. In the second normal observation mode, similarly to the first normal observation mode, the light source control unit 21 preferably performs the first light amount control that makes Rcy / Gcy larger than 1/3, and sets B1cy / Gcy to 1. It is preferable to perform the second light amount control to be larger than / 3.

  Furthermore, in the second normal observation mode, the light source control unit 21 performs the third light amount control to make B1cy / B2cy larger than 4/5 by adjusting the light amounts of the first blue light B1 and the second blue light B2. It is preferable. By this third light quantity control, B1cy / B2cy is more preferably in the range of 4/5 to 7/5, and B1cy / B2cy is most preferably in the range of 9/10 to 7/5. As a result, the normal light image is an image that is bright overall and has a sense of transparency. The second normal observation mode is the same as the first normal observation mode except that the light amount ratio among the first blue light B1, the second blue light B2, the green light G, and the red light R is different.

[Second Embodiment]
In the first embodiment, as the first specific light emission control, the first light amount control with Rcx / Gcx> 1/3 is performed to output an R image signal having at least two peaks in the histogram. Instead, in the second embodiment, the fourth light amount control is performed in which the LEDs 20a to 20d are feedback-controlled based on the R image signal so that at least two peaks are distributed in the histogram of the R image signal.

  As shown in FIG. 10, the endoscope system 100 of the second embodiment is substantially the same as the endoscope system 10 of the first embodiment, but in the processor device 16, the peak detection unit 70 and the light amount change instruction unit 72. Is added. Further, in the endoscope system 100, unlike the endoscope system 10, the light source devices 14 are not provided with the light amount sensors 24a to 24d.

  The peak detection unit 70 receives an R image signal from the image processing switching unit 60 when the first normal observation mode is set. The peak detector 70 detects from the input R image signal whether there is a bright area HA with a pixel value equal to or greater than a certain value and a dark area LA with a pixel value equal to or smaller than a certain value. When the bright area HA and the dark area LA are detected, the peak detector 70 converts the R image signal into a histogram, and the peak PH corresponding to the bright area HA and the peak PL corresponding to the dark area LA on the histogram. Whether or not exists is detected.

  When at least one of the peak PH and the peak PL is not detected in the peak detection unit 70, the light amount change instruction unit 72 instructs the light source control unit 21 to change the amount of light emitted from each of the LEDs 20a to 20d. . In accordance with this instruction, the light source control unit 21 performs the fourth light amount control for changing the light amount of the light emitted from each of the LEDs 20a to 20d so that both the peak PH and the peak PL appear on the histogram of the R image signal. On the other hand, when the peak PH and the peak PL are detected, the light source control unit 21 does not perform the fourth light amount control.

[Third Embodiment]
In the first embodiment, as the second specific light emission control, the second light amount control for setting B1cx / Gcx> 1/3 or the third light amount control for setting B1cy / B2cy> 4/5 is performed, and the first pixel value difference is determined. A B image signal larger than the second pixel value difference is output, or a G image signal whose first pixel value difference is smaller than the second pixel value difference is output. Instead of this, the third embodiment In the B image signal, the first pixel value difference is larger than the second pixel value difference in the B image signal (or the first pixel value difference is smaller than the second pixel value difference in the G image signal). Based on the G image signal, the fifth light quantity control for feedback control of each of the LEDs 20a to 20d is performed.

  As shown in FIG. 11, the endoscope system 200 according to the third embodiment is substantially the same as the endoscope system 10 according to the first embodiment, but the pixel value difference calculation unit 74 and the light amount change instruction in the processor device 16. Part 72 is added. Further, in the endoscope system 100, unlike the endoscope system 10, the light source devices 14 are not provided with the light amount sensors 24a to 24d.

  The pixel value difference calculation unit 74 receives the B image signal and the G image signal from the image processing switching unit 60 when the first normal observation mode is set. The pixel value difference calculation unit 74 extracts the mucous membrane M based on the B image signal and the G image signal, and extracts the polar surface blood vessel C1α and the surface blood vessel C1β as the first blood vessel, and the middle layer blood vessel C2 and the deep layer blood vessel C3. Is extracted as a second blood vessel. As a method for extracting the first and second blood vessels based on the B image signal and the G image signal, for example, a portion where B / G, which is a ratio of the B image signal to the G image signal, is smaller than a predetermined value is extracted as the first blood vessel. A portion where B / G is larger than a predetermined value can be extracted as a second blood vessel (see, for example, Japanese Patent Application Laid-Open No. 2013-150713 for a blood vessel extraction method).

  Next, the pixel value difference calculation unit 74 calculates the first pixel value difference between the extracted first blood vessel and the mucous membrane M in the B image signal, and calculates the second pixel value difference between the extracted second blood vessel and the mucous membrane M. calculate. Similarly, the pixel value difference calculation unit 74 calculates the first pixel value difference between the extracted first blood vessel and the mucous membrane M in the G image signal, and also extracts the second pixel value difference between the extracted second blood vessel and the mucous membrane M. Is calculated. Then, at least one of a first condition in which the first pixel value difference is larger than the second pixel value difference in the B image signal and a second condition in which the first pixel value difference is smaller than the second pixel value difference in the G image signal If the above condition is not satisfied, the light amount change instruction unit 72 instructs the light source control unit 21 to change the light amount of light emitted from each of the LEDs 20a to 20d.

  In accordance with the instruction from the light amount change instruction unit 72, the light source control unit 21 performs the fifth light amount control for changing the light amount of the light emitted from each of the LEDs 20a to 20d so as to satisfy the first condition and the second condition. Specifically, for example, when the first condition is not satisfied and the first pixel value difference is smaller than the second pixel value difference in the B image signal, the pixel values of the first blood vessel and the mucous membrane are used as the fifth light amount control. In order to increase the difference, control is performed to increase the amount of the first blue light B1. When both the first condition and the second condition are satisfied, the light source control unit 21 does not perform the fifth light amount control.

  In the first to third embodiments, the light source control unit 21 performs the third specific light emission control on the first blue light B1 to obtain the pixel values of the blood vessels in the deep reach range of the first blue light B1. You may make it output the B image signal which increases or decreases according to 1st blue light B1. As shown in FIG. 12, the pixel values of the extreme surface blood vessel C1α and the superficial blood vessel C1β in the deep reach range of the first blue light B1 are decreased, and the pixel value difference between the extreme surface blood vessel C1α and the superficial blood vessel C1β and the mucous membrane M is decreased. Is increased, as the third specific light emission control, control for increasing the light amount of the first blue light B1 is performed. On the other hand, when the pixel values of the polar surface blood vessel C1α and the superficial blood vessel C1β are increased and the pixel value difference between the polar surface blood vessel C1α and the superficial blood vessel C1β and the mucous membrane M is reduced, Control is performed to reduce the amount of one blue light B1. In FIG. 12, the blood vessels in the first blue light penetration range are the polar surface blood vessel C1α and the surface blood vessel C1β, but blood vessels of other depths may be included.

In the first to third embodiments, four colors of light having an emission spectrum as shown in FIG. 3 are used, but the emission spectrum is not limited to this. For example, as shown in FIG. 13, the green light G and the red light R have the same spectrum as that in FIG. 3, while the first blue light B1 has a peak wavelength that is higher than that of the first blue light B1 in FIG. The first blue light B1 ^* on the slightly longer wavelength side may be used instead. Further, the second blue light B2 may be replaced with the second blue light B2 ^* whose peak wavelength is slightly shorter than the second blue light B2 in FIG.

[Examples and Comparative Examples]
Next, in Examples 1 and 2 and the comparative example, as shown in the first embodiment, the first blue light B1, the second blue light B2, the green light G, and the red light R according to the first to third light quantity control. It is obtained when a normal light image obtained when light is emitted and a purple LED (Light Emitting Diode) with a center wavelength of 410 nm and a white LED (Light Emitting Diode) are simultaneously turned on to emit purple light and white light simultaneously. Comparison with a normal light image is performed.

[Example 1]
In the endoscope system 10 of the first embodiment, the first blue light B1, the second blue light B2, the green light G, and the red light R are emitted, and a normal light image is acquired. Here, the light amounts of the first blue light B1, the second blue light B2, the green light G, and the red light R are light amounts at the distal end portion 12d of the endoscope 12. In addition, the measuring method of the light quantity of 1st blue light B1, 2nd blue light B2, green light G, and red light R was performed as follows. First, the first blue light B1, the second blue light B2, the green light G, and the red light R were separately emitted with the cap having the light amount measuring device attached to the distal end portion 12d of the endoscope 12. Each time the light of each color was emitted, the amount of light of each color was measured with a light amount measuring device in the cap. The measurement results are shown in Table 1. In Table 1, the light quantity B2cx of the second blue light B2 is set to 100, the light quantity B1cx of the first blue light B1, the light quantity Gcx of the green light G, and the light quantity Rcx of the red light R are respectively set to the light quantity B2cx of the second blue light B2. It normalizes with. The amount of light of these four colors is the amount of light applied in the first normal observation mode.

[Comparative example]
In the endoscope system 10, purple LEDs (Light Emitting Diodes) and white LEDs (Light Emitting Diodes) are provided in place of the LEDs 20a to 20d. The purple LED and the white LED were turned on at the same time, and purple light and white light having a spectrum as shown in FIG. 14 were emitted simultaneously, and a normal light image was acquired. Further, for the violet light and the white light simultaneously emitted, the light amounts in the same wavelength region as the first blue light B1, the second blue light B2, the green light G, and the red light R of the embodiment are respectively expressed as V components (380). ˜425 nm), B component (426 to 475 nm), G component (476 to 590 nm), and R component (591 to 700 nm). The measurement was performed at the distal end portion 12d of the endoscope 12 as in the example. The measuring method is the same as in the example. The measurement results are shown in Table 2. In Table 2, similarly to Table 1, the light quantity B2cp of the second blue light B2 is set to 100, and the light quantity B1cp of the first blue light B1, the light quantity Gcp of the green light G, and the light quantity Rcp of the red light R are respectively set to the second blue light. Normalization is performed with the light amount B2cp of the light B2.

[Comparison between Example 1 and Comparative Example Regarding Light Ratio]
In Example 1, the light quantity ratio B1cx / Gcx between the first blue light B1 and the green light G, the light quantity ratio Rcx / Gcx between the red light R and the green light G, and the first blue light B1 and the second blue light B2 The light quantity ratio B1cx / B2cx was determined. Also in the comparative example, the light quantity ratio B1cp / Gcp between the first blue light B1 and the green light G, the light quantity ratio Rcp / Gcp between the red light R and the green light G, the first blue light B1 and the second blue light B2 The light quantity ratio B1cp / B2cp was obtained. The results are shown in Table 3.

  Regarding the light quantity ratio between the first blue light B1 and the green light G, B1cx / Gcx (0.368) of the example is B1cx / Gcx (0.368) of the example and B1cp / Gcp (0. 290) is larger than a value 1/3 (≈0.333). On the other hand, B1cp / Gcp (0.290) of the comparative example is smaller than 1/3 (≈0.333). Further, B1cx / Gcx of the example is 20% or more larger than B1cp / Gcp of the comparative example.

  Regarding the light quantity ratio between the red light R and the green light G, Rcx / Gcx (0.547) in the example is Rcp / Gcx (0.547) in the example and Rcp / Gcp (0.308) in the comparative example. ) Is larger than a value 1/3 (≈0.333). On the other hand, Rcp / Gcp (0.308) of the comparative example is smaller than 1/3 (≈0.333).

[Example 2]
As shown in Table 4, the first blue light B1 was emitted with a light amount B1cy, the second blue light B2 was emitted with a light amount B2cy, the green light G was emitted with a light amount Gcy, and the red light R was emitted with a light amount Rcy. The rest is the same as in the first embodiment. Similarly to Table 1, Table 4 assumes that the amount of light B2cy of the second blue light B2 is 100, the amount of light B1cy of the first blue light B1, the amount of light Gcy of green light G, and the amount of light Rcy of red light R, respectively. Normalization is performed with the light amount B2cy of the second blue light B2. The amount of light of these four colors is the amount of light applied in the second normal observation mode.

[Comparison between Example 2 and Comparative Example Regarding Light Ratio]
As shown in Table 5, while obtaining the light quantity ratio B1cy / B2cy of the first blue light B1 and the second blue light B2 in Example 2, the light quantity ratio B1cp of the first blue light B1 and the second blue light B2 in the comparative example. / B2cp was determined. Regarding the light quantity ratio between the first blue light B1 and the second blue light B2, B1cx / B2cx (1.200) in the example is B1cp / B2cx (1.200) in the example and B1cp / B2cp (in the comparative example). 0.35), which is larger than the value 4/5 (0.8). On the other hand, B1cp / B2cp (0.328) of the comparative example is smaller than 4/5 (0.8).

[Comparison between Examples 1 and 2 and Comparative Example for Normal Light Image]
The normal light images (composite images obtained by synthesizing the RGB image signals) obtained in Examples 1 and 2 are images having a sense of transparency and unevenness, as shown in a photograph (reference diagram 1) submitted as a reference material. Yes. In addition, the normal light images of Examples 1 and 2 have smoothness. On the other hand, the normal light image obtained by the comparative example (composite image obtained by synthesizing the RGB image signals) was implemented with respect to the sense of transparency and unevenness as shown in the photograph (reference figure 2) submitted as reference material. It is inferior to the normal light images of Examples 1 and 2. On the other hand, the normal light image of the comparative example is inferior to the normal light images of Examples 1 and 2 in terms of smoothness.

  As for the B image (image based on the B image signal) of the normal light image of Examples 1 and 2, as shown in the photograph (reference diagram 3) submitted as reference material, the amount of image information is large, and the surface layer such as the surface blood vessels The details of the structure are detailed. The blood vessel running pattern is drawn faithfully, and the continuity of blood vessels is also good. On the other hand, as for the B image of the normal light image of the comparative example, the amount of image information is small compared to the cases of Examples 1 and 2, as shown in the photograph (reference FIG. 4) submitted as reference material. The blood vessel running pattern lacks fidelity when compared with Examples 1 and 2, and the continuity of blood vessels also lacks when compared with Examples 1 and 2.

  About the G image (image based on G image signal) of the normal light image of Examples 1 and 2, as shown in the photograph (reference FIG. 5) submitted as reference material, it is generally brighter than the B image. . The contrast of the surface blood capillaries is lowered by the amount brighter than the B image, but the amount of image information is large as in the B image, and the structure of the mid-deep layer such as the mid-deep blood vessel is depicted in detail. The blood vessel running pattern is drawn faithfully like the B image, and the continuity of blood vessels is also good. On the other hand, as for the G image of the normal light image of the comparative example, the amount of image information is small as compared with the case of Examples 1 and 2, as shown in the photograph (reference FIG. 6) submitted as reference material. The blood vessel running pattern lacks fidelity when compared with Examples 1 and 2, and the continuity of blood vessels also lacks when compared with Examples 1 and 2.

  As for the R images (images based on the R image signal) of the normal light images of Examples 1 and 2, as shown in the photograph (reference figure 7) submitted as a reference material, they are excellent in transparency and unevenness. It can be seen that the structure of a deep layer such as a deep blood vessel is clearly displayed regardless of the magnification. Here, the reason why the R images of Examples 1 and 2 are excellent in transparency is as follows. In the first and second embodiments, by setting Rcx / Gcx> 1/3, the amount of red light R is sufficient, so that the gain coefficient for the R image can be reduced. By suppressing the gain coefficient low, noise in the R image is reduced, and as a result, a sense of transparency can be obtained.

  On the other hand, as for the R image of the normal light image of the comparative example, as shown in the photograph (reference figure 8) submitted as a reference material, the sense of transparency and unevenness are inferior to those of Examples 1 and 2. Further, the display of the structure of the deep layer is not clear as compared with Examples 1 and 2. Here, the reason why the transparency of the R image of the comparative example is inferior to that of Examples 1 and 2 is as follows. In the comparative example, since Rcx / Gcx <1/3, the amount of red light R is insufficient, and the gain coefficient for the R image becomes large. When the gain coefficient increases in this way, noise in the R image increases, and as a result, the image lacks transparency.

10, 100, 200 Endoscope system 20a B1-LED
20b B2-LED
20c G-LED
20d R-LED
21 Light source controller 48 Image sensor 68 Display controller 70 Peak detector 74 Pixel value difference calculator

Claims (13)

A light source unit including a first blue semiconductor light source that emits first blue light, a green semiconductor light source that emits green light, and a red semiconductor light source that emits red light;
A light source controller that performs first specific light emission control on the green light and the red light;
An imaging unit that images an observation target in a body cavity under illumination with light emitted from the light source unit under the first specific light emission control;
A signal output unit for outputting a blue signal, a green signal, and a red signal from the imaging unit;
A display unit having a B channel, a G channel, and an R channel;
A display control unit that assigns the blue signal, the green signal, and the red signal to any one of the B channel, the G channel, and the R channel;
The signal output unit is an endoscope system that outputs the red signal having at least two peaks in a histogram in which the vertical axis represents frequency and the horizontal axis represents pixel value. The light source control unit performs second specific light emission control on the first blue light and the green light,
The signal output unit includes a second pixel value indicating a difference between the second blood vessel and the mucous membrane in which a first pixel value difference indicating a pixel value difference between the first blood vessel and the mucous membrane is deeper than the first blood vessel. The endoscope system according to claim 1, wherein the blue signal larger than the difference is output, or the green signal whose first pixel value difference is smaller than the second pixel value difference is output. The light source control unit performs third specific light emission control on the first blue light,
3. The internal vision according to claim 1, wherein the signal output unit outputs the blue signal in which a pixel value of a blood vessel in the depth range of the first blue light increases or decreases according to the first blue light. Mirror system.   2. The endoscope system according to claim 1, wherein the first specific light emission control includes a first light amount control that makes a light amount of the red light larger than ３ of a light amount of the green light. The first blue light has a peak wavelength at 400 nm to 420 nm,
3. The endoscope system according to claim 2, wherein the second specific light emission control includes a second light amount control that makes the light amount of the first blue light larger than ３ of the light amount of the green light. The light source unit emits second blue light having a peak wavelength at 430 nm to 480 nm,
3. The endoscope system according to claim 2, wherein the second specific light emission control includes a third light amount control for making the light amount of the first blue light larger than 4/5 of the light amount of the second blue light.   The endoscope system according to claim 6, wherein the second blue light has a wavelength range of 420 to 480 nm. A light amount detector that detects the light amount of the first blue light, the light amount of the green light, and the light amount of the red light;
The endoscope system according to any one of claims 4 to 7, wherein the light source control unit performs control based on light amounts of the first blue light, the green light, and the red light detected by the light amount detection unit. . A peak detector for detecting a peak in the histogram from the red signal;
The endoscope system according to claim 1, wherein the first specific light emission control includes a fourth light amount control for controlling the light source unit based on a detection result in the peak detection unit. From the blue signal or the green signal, a first pixel value difference indicating a difference between pixel values of the first blood vessel and the mucous membrane and a second blood vessel indicating a difference between the second blood vessel located deeper than the first blood vessel and the mucosa. A pixel value difference calculation unit for calculating a pixel value difference;
3. The endoscope system according to claim 2, wherein the second specific light emission control includes a fifth light amount control for controlling the light source unit based on a calculation result in the pixel value difference calculating unit.   The first blue light has a wavelength range of 380 to 430 nm, the green light has a wavelength range of 470 to 600 nm, and the red light has a wavelength range of 580 to 700 nm. The endoscope system described in the item.   The endoscope system according to claim 1, wherein the display control unit assigns the blue signal to the B channel, the green signal to the G channel, and the red signal to the R channel. A light source unit emitting first blue light from the first blue semiconductor light source, emitting green light from the green semiconductor light source, and emitting red light from the red semiconductor light source;
A light source control unit performing first specific light emission control on the green light and the red light;
An imaging unit imaging an observation target in a body cavity under illumination with light emitted from the light source unit under the first specific light emission control;
The signal output unit is a step of outputting a blue signal, a green signal, and a red signal from the imaging unit, and the red signal having at least two peaks in a histogram in which the vertical axis represents frequency and the horizontal axis represents pixel value. Output step;
The display control unit controls the display unit having the B channel, the G channel, and the R channel, and the display control unit outputs the blue signal, the green signal, and the red signal to the B signal. Assigning to any one of a channel, the G channel, and the R channel.

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