JP2009172077A - Device and method to obtain blood vessel position image - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device and its method to obtain a clear near infrared radiation image of blood vessels in whatever environment the device may be used. <P>SOLUTION: The blood vessel positional imaging device 100 is provided with an imaging condition setting part 101, an imaging part 102 to image reflective or transmission light from an organism after irradiating it with near infrared ray to it in accordance with the imaging conditions, a blood vessel region extraction part 103 to extract a blood vessel region within the irradiating near infrared rays, a blood vessel evaluation value calculator 104 to calculate the evaluation value for evaluating the blood vessel region, and an imaging condition decider 105 to decide the optimum imaging conditions from the blood vessel evaluation value calculated by the evaluation calculator 104. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a technique of an apparatus that acquires biological information using light, and particularly relates to a blood vessel position acquisition apparatus and a blood vessel position acquisition method that acquire a blood vessel position of a living body as an image.

  2. Description of the Related Art Conventionally, there is an apparatus that uses near infrared light as an apparatus for acquiring a blood vessel position of a living body as an image. This utilizes the property that hemoglobin in blood absorbs near infrared light, irradiates the living body with light of near infrared wavelength, and reflects or transmits light from the living body with high near infrared sensitivity. Images are taken with a monochrome CCD camera. In the captured image, reflection or transmission is reduced only in the region where the blood vessel exists, and the image is displayed darkly on the image. Therefore, a blood vessel region can be specified by extracting a darkly projected region by image processing.

  In such a blood vessel position acquisition method using near-infrared light, light other than the near-infrared light for photographing, that is, outside light has a great influence on the quality of the image to be photographed. Since the blood vessel region is not projected darkly, it is necessary to optimize the imaging conditions according to the use environment. In general, a technique is used in which a feature amount is obtained from a specific region in a photographed image and a photographing condition is determined based on the obtained feature amount (see, for example, Patent Document 1).

FIG. 10 shows a process of an imaging method (a process performed on a finger image obtained by capturing a finger) that always captures a vein pattern clearly without being affected by changes in the environment disclosed in Patent Document 1. It is a flowchart which shows the content. First, the contour of the finger is extracted, and the region inside the finger is determined (step S600). Then, the process proceeds to step S616, and in the light amount adjustment mode starting from step S616, the light source output is adjusted so that the captured image is optimized. First, it is checked whether the average luminance of the finger area opposite to the lit light source is within the target range (step S616). If it is lower than the target range (step S618), the amount of light is increased (step S620). If it is higher than the target range, it is checked whether the amount of light can be further reduced (step S622). However, even if the light amount of the light source is the minimum output, whiteout is still observed. More specifically, if saturated luminance pixels are seen in the vicinity of the contour line of the finger, the mode shifts to the sensitivity adjustment mode, and the camera sensitivity is further lowered (step S610). In the camera sensitivity adjustment mode, it is checked whether the average brightness of the finger area opposite to the lit light source is within the target range as in the light amount adjustment mode (step S606), and if it is higher than the target range (step S608), The sensitivity of the camera is lowered (step S610). If it is lower than the target range, it is checked whether the sensitivity can be further increased (step S612), and if it can be increased, it is increased (step S614). If the camera sensitivity is set to the maximum value that can be set and does not reach the target value, there is a limit to imaging in sensitivity adjustment. Therefore, the light amount of the light source is increased (step S620), and the light amount adjustment mode is entered. Here, in the above flow, an upper limit is set in the sensitivity adjustment range of the camera, and when the upper limit is exceeded, transition is made to light amount adjustment. The above is repeated, and when the brightness of the finger is within the target range, the image quality control is terminated (step S626), so that the finger can be imaged with the optimum image quality regardless of the intensity of the external light. .
JP 2006-155575 A

  However, in the above-described conventional blood vessel position acquisition device, the average luminance value of the finger region is used as the evaluation value, and the target blood vessel characteristic, that is, the characteristic in which the blood vessel region in the captured image is darkly reflected is reflected in the evaluation value. Therefore, it is not possible to evaluate how clear the blood vessel region is in the captured image, and it cannot be said that the optimal image that appears most often appears darkly. .

  The present invention solves the above-described conventional problems and provides a blood vessel position acquisition device and a blood vessel position acquisition method capable of acquiring a near-infrared light image in which a blood vessel region is clearly imaged regardless of the use environment. The purpose is to do.

  The blood vessel position acquisition device according to the first invention includes imaging condition setting means, image imaging means, blood vessel region extraction means, blood vessel evaluation value calculation means, and imaging condition determination means. The shooting condition setting means sets shooting conditions when shooting a living body. The image photographing means photographs the reflected light or transmitted light from the living body irradiated with near infrared light based on the photographing conditions, and generates a near infrared light image. The blood vessel region extracting means extracts a blood vessel image in the near-infrared light image as a blood vessel region. The blood vessel evaluation value calculation means determines a blood vessel evaluation pixel and a skin evaluation pixel adjacent to the blood vessel region based on the blood vessel region, and calculates a blood vessel evaluation value for evaluating the blood vessel region. The imaging condition determining unit determines the optimum imaging condition based on the blood vessel evaluation value calculated by the blood vessel evaluation calculating unit.

  Here, for example, the blood vessel evaluation value calculation unit calculates a blood vessel evaluation value for evaluating a blood vessel region that represents a contrast difference with the surrounding region, and the imaging condition determination unit determines the imaging condition based on the blood vessel evaluation value. Has been decided.

  The blood vessel evaluation value is calculated, for example, by subtracting the luminance value of the blood vessel evaluation pixel from the luminance value of the skin evaluation pixel, or obtaining a ratio between the luminance value of the skin evaluation pixel and the luminance value of the blood vessel evaluation pixel. Is done.

  Conventionally, in a device that acquires a blood vessel position using near-infrared light, a finger region average is used as a method for acquiring a blood vessel position without being affected by light other than near-infrared light, that is, outside light. Luminance was calculated, and shooting conditions were adjusted based on this. However, although the entire finger portion in the captured image is adjusted to the optimum image quality, the image is not always captured so that the blood vessel portion to be extracted can be extracted most effectively.

  Therefore, in the blood vessel position acquisition device of the present invention, the blood vessel evaluation value calculation means determines a blood vessel evaluation pixel and a skin evaluation pixel adjacent to the blood vessel region based on the blood vessel region, and the luminance value of the skin evaluation pixel and the blood vessel evaluation are determined. A blood vessel evaluation value for evaluating the blood vessel region is calculated based on the luminance value of the pixel. The imaging condition determining unit determines the imaging condition based on the blood vessel evaluation value calculated by the blood vessel evaluation calculating unit.

Accordingly, it is possible to calculate a blood vessel evaluation value that determines an imaging condition capable of capturing the blood vessel region most clearly in the near-infrared light image from the relationship between the luminance value in the blood vessel evaluation pixel and the luminance value in the skin evaluation pixel. it can.
As a result, since the imaging condition can be determined based on the blood vessel evaluation value, it is possible to acquire a near-infrared light image in which the blood vessel region is clearly imaged regardless of the use environment.

  A blood vessel position acquisition device according to a second invention is the blood vessel position acquisition device according to the first invention, wherein the blood vessel evaluation value calculation means subtracts the luminance value of the blood vessel evaluation pixel from the luminance value of the skin evaluation pixel. The blood vessel evaluation value is calculated by

Here, the blood vessel evaluation value is calculated by subtracting the luminance value of the blood vessel evaluation pixel from the luminance value of the skin evaluation pixel.
This makes it possible to calculate an evaluation value that reflects the degree of contrast difference between the blood vessel region and the peripheral region. As a result, it is possible to determine an imaging condition in which the blood vessel region is projected most darkly compared to the surrounding region.

  A blood vessel position acquisition device according to a third invention is the blood vessel position acquisition device according to the first or second invention, wherein the blood vessel evaluation value calculation means calculates blood vessel evaluation values under a plurality of imaging conditions, The determining means determines the imaging condition when the blood vessel evaluation value is maximum as the optimal imaging condition.

Here, blood vessel evaluation values are calculated under a plurality of imaging conditions, and the imaging conditions at which the blood vessel evaluation value is maximized are determined as the optimum imaging conditions.
As a result, it is possible to determine an imaging condition that allows the blood vessel region to be imaged most clearly.

  A blood vessel position acquisition device according to a fourth invention is the blood vessel position acquisition device according to any one of the first to third inventions, wherein the blood vessel evaluation value calculation means includes a blood vessel evaluation pixel calculation means, and a skin evaluation. It has pixel calculation means and evaluation value calculation means. The blood vessel evaluation pixel calculating means sets the pixel that is the center in the width direction of the blood vessel region as the blood vessel evaluation pixel. The skin evaluation pixel calculating means expands the contour pixels of the blood vessel region by a predetermined pixel outward in the width direction, and sets the expanded pixels as skin evaluation pixels. The evaluation value calculation means calculates the luminance value of the blood vessel evaluation pixel existing in the attention range from the skin representative value obtained using the luminance value of the skin evaluation pixel existing in the attention range centering on one of the blood vessel evaluation pixels. A difference value obtained by subtracting the blood vessel representative value obtained by using is obtained at all blood vessel evaluation pixel positions in the near-infrared light image, and the blood vessel evaluation value is calculated by adding all the difference values.

  Here, the blood vessel evaluation pixel calculating unit extracts a pixel that is centered in the width direction of the blood vessel region as a blood vessel evaluation pixel, and the skin evaluation pixel calculating unit is configured to output a contour pixel of the blood vessel region to a predetermined pixel outside in the width direction, In other words, a predetermined pixel layer is expanded and the expanded pixel is used as a skin evaluation pixel. Then, the evaluation value calculation means calculates the blood vessel evaluation pixel existing in the attention range from the skin representative value obtained using the luminance value of the skin evaluation pixel existing in the attention range centering on one of the blood vessel evaluation pixels. A difference value obtained by subtracting the blood vessel representative value obtained using the luminance value is obtained at each of the blood vessel evaluation pixel positions in the near-infrared light image, and the blood vessel evaluation value is calculated by adding all the calculated difference values. Yes.

The “center” in the “attention range centered on one of the blood vessel evaluation pixels” here includes the case of the center of gravity.
As a result, the blood vessel evaluation value can be calculated for the entire blood vessel region imaged in the near-infrared light image generated by the image photographing means, so that the entire blood vessel region can be imaged more optimally. .

  A blood vessel position acquisition device according to a fifth invention is the blood vessel position acquisition device according to the fourth invention, wherein the skin representative value is an average value of luminance values of the skin evaluation pixels existing in the attention range, and the blood vessel representative value Is the luminance value of the blood vessel evaluation pixel located in the center of the attention range or the average value of the luminance values of the blood vessel evaluation pixels existing in the attention range.

Here, the skin representative value and the blood vessel representative value are calculated using the luminance value of the skin evaluation pixel or blood vessel evaluation pixel existing in the attention range.
Thereby, the representative value of the plurality of pieces of pixel information included in the attention range can be easily calculated.

  A blood vessel position acquisition device according to a sixth invention is the blood vessel position acquisition device according to the fourth or fifth invention, wherein the skin evaluation pixel calculation means expands each expanded skin evaluation pixel. The evaluation value calculating means stores the number of times from the blood vessel region equal to the radius of the thickness of the blood vessel image existing in the attention range among the skin evaluation pixels existing in the attention range. A skin representative value is obtained using only skin evaluation pixels having a distance.

  Here, for example, when the skin evaluation pixel calculating unit expands the contour pixel by one pixel outward in the width direction, when the pixel is expanded by “1” and by two pixels, “2” Is stored as a distance from the blood vessel region. Then, the evaluation value calculating means uses only the skin evaluation pixel having a distance from the blood vessel region equal to the radius of the thickness of the blood vessel image existing in the attention range, for example, the pixel storing the above “1”, and uses the skin representative value. Ask.

  As a result, even if the thickness of the blood vessel image changes in the near-infrared light image, the skin evaluation pixel close to the blood vessel contour is replaced with the blood vessel evaluation pixel and the blood vessel in the thin blood vessel where the blood vessel evaluation pixel and the blood vessel contour are narrow. Since a skin evaluation pixel far from the blood vessel contour can be automatically selected for a thick blood vessel having a wide contour, the evaluation value can be calculated under the same conditions regardless of the thickness of the blood vessel image.

  A blood vessel position acquisition device according to a seventh aspect is the blood vessel position acquisition device according to any one of the fourth to sixth aspects, wherein the skin evaluation pixel calculation means has a maximum diameter in the near-infrared light image. The blood vessel region is expanded by the number of times equal to the radius of the blood vessel image it has.

Here, the skin evaluation pixel calculation means expands the blood vessel region by the number of times equal to the radius of the blood vessel image having the maximum diameter in the near-infrared light image.
Thereby, even if the thickness of the blood vessel image in a near-infrared light image differs, the skin evaluation pixel according to the thickness of the blood vessel image can be selected reliably.

  A blood vessel position acquisition device according to an eighth invention is the blood vessel position acquisition device according to any one of the fourth to seventh inventions, wherein the range of interest is a blood vessel image having a maximum diameter in a near-infrared light image. The shape is a square shape with the number of pixels on one side set based on the diameter of the blood vessel and the number of times the blood vessel region has been expanded by one pixel, and the attention range always includes blood vessel evaluation pixels and skin evaluation pixels It is.

Here, the pixel length of one side of the attention range is calculated as, for example, the maximum blood vessel diameter + the number of expansion times × 2 based on the diameter of the blood vessel image having the maximum diameter in the near-infrared light image and the number of times the blood vessel region is expanded. To do.
Thereby, the blood vessel evaluation pixel and the skin evaluation pixel adjacent to the blood vessel region can be included in the attention range without waste.

  A blood vessel position acquisition device according to a ninth invention is the blood vessel position acquisition device according to the eighth invention, wherein the radius of the blood vessel image in the region of interest focuses on the number of pixels of the blood vessel region existing in the region of interest. Set by dividing by the number of pixels on one side of the range.

Here, the radius of the thickness of the blood vessel image is set by dividing the number of pixels of the blood vessel region existing in the attention range by the number of pixels on one side of the attention range.
Thereby, the radius of the thickness of the blood vessel image can be easily calculated.

  A blood vessel position acquisition device according to a tenth aspect of the present invention is the blood vessel position acquisition device according to any one of the fourth to ninth aspects, wherein the evaluation value calculation means branches the blood vessel image of the range of interest. In this case, the difference value calculated in the attention range is excluded from the elements for calculating the blood vessel evaluation value.

  Here, in the case of the above condition, the evaluation value calculation means excludes the difference value calculated in the attention range from the elements when calculating the blood vessel evaluation value. Further, when the blood vessel image in the attention range is branched, the evaluation value calculation means may not calculate the difference value in the attention range in advance.

Here, there is a problem that an intended skin evaluation pixel cannot be obtained at a portion where the blood vessel is branched because the blood vessel is close.
As a result, the difference value in the problematic range of interest can be excluded, and the accuracy of the blood vessel evaluation value can be increased. Further, if the difference value is not calculated, the blood vessel evaluation value can be calculated efficiently.

  A blood vessel position acquisition device according to an eleventh aspect of the invention is the blood vessel position acquisition device according to any one of the fourth to tenth aspects of the invention, wherein the evaluation value calculation means has the number of pixels of the blood vessel evaluation pixels in the attention range. When it is different from the predetermined value or the number of pixels of the blood vessel evaluation pixel connected to the blood vessel evaluation pixel located at the center of the attention range, the difference value calculated in the attention range is excluded from the elements for calculating the blood vessel evaluation value.

  Here, in the case of the above condition, the evaluation value calculation means excludes the difference value calculated in the attention range from the elements when calculating the blood vessel evaluation value. Further, the evaluation value calculating means may not calculate the difference value in the attention range in advance in the case of the above condition.

  The predetermined value may be set to the pixel length of one side of the attention range when, for example, one blood vessel runs within the attention range. This is because the number of pixels of the blood vessel evaluation value is equal to the pixel length of one side of the attention range, and if it is set in this way, it can be easily determined that it is one blood vessel.

  Here, when the range of interest is set wide, a plurality of thin blood vessels may be included in the range of interest. In this case as well, there is a problem that intended skin evaluation pixels cannot be obtained because the blood vessels are close to each other.

  As a result, the difference value in the problematic range of interest can be excluded, and the accuracy of the blood vessel evaluation value can be increased. Further, if the difference value is not calculated, the blood vessel evaluation value can be calculated efficiently.

  A blood vessel position acquisition device according to a twelfth aspect of the present invention is the blood vessel position acquisition device according to any one of the fourth to eleventh aspects of the present invention, wherein the evaluation value calculation means has the number of pixels of the skin evaluation pixels in the attention range. When the value is smaller than the predetermined value, the difference value calculated in the attention range is excluded from the elements for calculating the blood vessel evaluation value.

  Here, in the case of the above condition, the evaluation value calculation means excludes the difference value calculated in the attention range from the elements when calculating the blood vessel evaluation value. Further, the evaluation value calculating means may not calculate the difference value in the attention range in advance in the case of the above condition.

  Here, when the blood vessel is traveling in an oblique direction or the thickness of the blood vessel is thicker than expected, the skin evaluation pixel corresponding to the blood vessel evaluation pixel may not be included in the attention range. And when there are few skin evaluation pixels, there exists a problem that a skin representative value cannot be calculated | required accurately.

  As a result, the difference value in the problematic range of interest can be excluded, and the accuracy of the blood vessel evaluation value can be increased. Further, if the difference value is not calculated, the blood vessel evaluation value can be calculated efficiently.

  A blood vessel position acquisition device according to a thirteenth aspect of the present invention is the blood vessel position acquisition device according to any one of the fourth to twelfth aspects of the present invention, wherein the evaluation value calculation means has a difference value in the attention range that is greater than a predetermined value. If it is smaller, the difference value is excluded from the elements for calculating the blood vessel evaluation value.

  Here, in the case of the above condition, the evaluation value calculation means excludes the difference value calculated in the attention range from the elements when calculating the blood vessel evaluation value. Further, the evaluation value calculating means may not calculate the difference value in the attention range in advance in the case of the above condition.

Here, the small difference value is treated as noise, and the accuracy of the blood vessel evaluation value can be improved by discarding the difference value. The predetermined value used in this case is, for example, a larger value when the difference is assumed to be large based on the difference in luminance value between the blood vessel region and the surrounding skin region in the assumed near-infrared light image. If the value is assumed to be small, a smaller value can be set.
As a result, the difference value in the problematic range of interest can be excluded, and the accuracy of the blood vessel evaluation value can be increased.

  A blood vessel position acquisition device according to a fourteenth aspect is the blood vessel position acquisition device according to any one of the first to third aspects, wherein the blood vessel evaluation value calculation means is located near the center in the near-infrared light image. A blood vessel evaluation value is calculated for the limited evaluation range.

Here, the blood vessel evaluation value calculation means calculates the blood vessel evaluation value only in the vicinity of the center in the near-infrared light image.
Thereby, since the blood vessel evaluation value can be calculated only in the central pixel region where the near-infrared light strikes well, the accuracy of the blood vessel evaluation value can be increased. In addition, the calculation amount for calculating the blood vessel evaluation value can be reduced by narrowing the target range.

  A blood vessel position acquisition device according to a fifteenth aspect of the present invention is the blood vessel position acquisition device according to any one of the first to third aspects of the present invention, wherein the near-infrared light image captured by the image capturing means is reduced. The image processing apparatus further includes reduced image creation means for creating an infrared light image, the blood vessel region extraction means extracts a blood vessel region from the reduced near infrared light image, and the blood vessel evaluation value calculation means includes reduced near infrared light. A blood vessel evaluation value is calculated for the image.

Here, the reduced image creating means creates a reduced near infrared light image obtained by reducing the near infrared light image, and the blood vessel region extracting means and the blood vessel evaluation value calculating means apply the reduced near infrared light image to the reduced near infrared light image. Perform various processes.
As a result, it is possible to reduce the number of target pixels to be calculated, so that it is possible to greatly reduce the amount of calculation for calculating the blood vessel evaluation value.

  A blood vessel position acquisition device according to a sixteenth invention is the blood vessel position acquisition device according to the fifteenth invention, wherein the reduced image creating means has a diameter of the thickness of the blood vessel image having the maximum diameter in the near-infrared light image. The magnification is determined so as to be constant, and the near-infrared light image is reduced.

Here, the reduced image creating means determines the magnification so that the diameter of the blood vessel image having the maximum diameter in the near infrared light image is constant, and reduces the near infrared light image.
As a result, even if the distance between the camera and the living body changes due to a change in the imaging target, the size of the object in the near infrared light image changes and the blood vessel diameter changes, the reduced near infrared light image Since the blood vessel diameter can be made constant at all times, it is possible to save the trouble of individually correcting various parameters used in calculating the blood vessel evaluation value.

A blood vessel position acquisition device according to a seventeenth aspect is the blood vessel position acquisition device according to any one of the first to sixteenth aspects, wherein an imaging condition set by the imaging condition setting means The amount of infrared light.
Here, the imaging conditions are set by adjusting the amount of near-infrared light irradiated on the living body.
This makes it possible to easily change the imaging conditions based on the blood vessel evaluation value.

  A blood vessel position acquisition device according to an eighteenth aspect of the invention is the blood vessel position acquisition device according to any one of the first to sixteenth aspects of the invention, wherein the imaging condition set by the imaging condition setting means The wavelength of infrared light.

Here, the imaging conditions are set by adjusting the wavelength of light applied to the living body that affects the absorbance to the blood vessels and the transmittance to the living body.
This makes it possible to easily change the imaging conditions based on the blood vessel evaluation value.

  A blood vessel position acquisition device according to a nineteenth aspect is the blood vessel position acquisition device according to any one of the first to sixteenth aspects, wherein the imaging condition set by the imaging condition setting means passes only a specific wavelength. The pass band of the optical filter to be used.

Here, an imaging condition is set by adjusting a pass band of an optical filter that is used to reduce the influence of external light and allows only a specific wavelength to pass therethrough.
This makes it possible to easily change the imaging conditions based on the blood vessel evaluation value.

  A blood vessel position acquisition device according to a twentieth invention is the blood vessel position acquisition device according to any one of the first to sixteenth inventions, wherein the imaging condition set by the imaging condition setting means is an image for imaging a living body. The aperture value of the photographing means is used.

Here, imaging conditions are set by imaging the living body, for example, by adjusting the aperture value of the lens of a CCD camera.
This makes it possible to easily change the imaging conditions based on the blood vessel evaluation value.

  A blood vessel position acquisition device according to a twenty-first aspect is the blood vessel position acquisition device according to the first aspect, wherein the imaging condition setting means is proportional to a small value from a small value or from a large value to a small value. The imaging condition determining means sets a parameter for setting the imaging condition so as to change, and the imaging condition determining means has a predetermined value before and after the blood vessel evaluation value continuous in the time axis direction among the plurality of blood vessel evaluation values obtained by the blood vessel evaluation value calculating means. Except for the case where the above changes are made, the optimum photographing condition is determined.

Here, when the parameters are set in the imaging condition setting means under the above conditions, if the blood vessel evaluation values calculated by the blood vessel evaluation value calculating means are the above conditions, the imaging conditions are not determined.
Here, for example, the blood vessel evaluation value is set in spite of the fact that the light quantity of the near infrared light is sequentially increased from 0 and the photographing conditions are set so that the characteristics of the photographed near infrared light image do not change greatly. Can be determined that the object has moved during shooting or that the outside light has changed significantly.

  Thereby, since the blood vessel evaluation value reflecting the case where elements other than the imaging conditions are changed, such as when the object moves, it is possible to avoid determining inappropriate imaging conditions.

  A blood vessel position acquisition method according to a twenty-second invention includes an imaging condition setting step, an image imaging step, a blood vessel region extraction step, a blood vessel evaluation value calculation step, and an imaging condition determination step. In the photographing condition setting step, photographing conditions for photographing a living body are set. In the image photographing process, reflected light or transmitted light from a living body irradiated with near infrared light is photographed based on photographing conditions to generate a near infrared light image. In the blood vessel region extraction step, a blood vessel image in the near-infrared light image is extracted as a blood vessel region. The blood vessel evaluation value calculation step determines a blood vessel evaluation pixel and a skin evaluation pixel adjacent to the blood vessel region based on the blood vessel region, and calculates a blood vessel evaluation value for evaluating the blood vessel region. The imaging condition determination step determines the optimal imaging condition based on the blood vessel evaluation value calculated in the blood vessel evaluation calculation step.

  Here, in the blood vessel evaluation value calculation step, for example, a blood vessel evaluation value for evaluating a blood vessel region representing a contrast difference with the surrounding region is calculated, and in the imaging condition determination step, the imaging condition is calculated based on the blood vessel evaluation value. Is determined.

  The blood vessel evaluation value is calculated, for example, by subtracting the luminance value of the blood vessel evaluation pixel from the luminance value of the skin evaluation pixel, or obtaining a ratio between the luminance value of the skin evaluation pixel and the luminance value of the blood vessel evaluation pixel. Is done.

  Conventionally, in a method for acquiring a blood vessel position using near infrared light, as a method for acquiring a blood vessel position without being affected by light other than near infrared light, that is, external light, an average of finger regions Luminance was calculated, and shooting conditions were adjusted based on this. However, although the entire finger portion in the captured image is adjusted to the optimum image quality, the image is not always captured so that the blood vessel portion to be extracted can be extracted most effectively.

  Therefore, in the blood vessel position acquisition method of the present invention, in the blood vessel evaluation value calculation step, the blood vessel evaluation pixel and the skin evaluation pixel adjacent to the blood vessel region are determined based on the blood vessel region, and the luminance value of the skin evaluation pixel and the blood vessel evaluation are determined. A blood vessel evaluation value for evaluating the blood vessel region is calculated based on the luminance value of the pixel. In the imaging condition determining step, the imaging condition is determined based on the blood vessel evaluation value calculated in the blood vessel evaluation calculating step.

Accordingly, it is possible to calculate a blood vessel evaluation value that determines an imaging condition capable of capturing the blood vessel region most clearly in the near-infrared light image from the relationship between the luminance value in the blood vessel evaluation pixel and the luminance value in the skin evaluation pixel. it can.
As a result, since the imaging condition can be determined based on the blood vessel evaluation value, it is possible to acquire a near-infrared light image in which the blood vessel region is clearly imaged regardless of the use environment.

  A blood vessel position acquisition method according to a twenty-third invention is the blood vessel position acquisition method according to the twenty-second invention, wherein the blood vessel evaluation value calculating step subtracts the luminance value of the blood vessel evaluation pixel from the luminance value of the skin evaluation pixel. The blood vessel evaluation value is calculated by

Here, the blood vessel evaluation value is calculated by subtracting the luminance value of the blood vessel evaluation pixel from the luminance value of the skin evaluation pixel, and the blood vessel evaluation value is calculated.
This makes it possible to calculate an evaluation value that reflects the degree of contrast difference between the blood vessel region and the peripheral region. As a result, it is possible to determine an imaging condition in which the blood vessel region is projected most darkly compared to the surrounding region.

  A blood vessel position acquisition method according to a twenty-fourth invention is the blood vessel position acquisition method according to the twenty-second and twenty-third inventions, wherein the blood vessel evaluation value calculation step calculates blood vessel evaluation values under a plurality of imaging conditions, In the determining step, the imaging condition when the blood vessel evaluation value is maximum is determined as the optimum imaging condition.

Here, blood vessel evaluation values are calculated under a plurality of imaging conditions, and the imaging conditions at which the blood vessel evaluation value is maximized are determined as the optimum imaging conditions.
As a result, it is possible to determine an imaging condition that allows the blood vessel region to be imaged most clearly.

  A blood vessel position acquisition method according to a twenty-fifth invention is the blood vessel position acquisition method according to any one of the twenty-second to twenty-fourth inventions, wherein the blood vessel evaluation value calculation step includes a blood vessel evaluation pixel calculation step, and a skin evaluation It has a pixel calculation process and an evaluation value calculation process. In the blood vessel evaluation pixel calculation step, a pixel that is the center in the width direction of the blood vessel region is set as a blood vessel evaluation pixel. In the skin evaluation pixel calculation step, the contour pixel of the blood vessel region is expanded by a predetermined pixel outward in the width direction, and the expanded pixel is set as the skin evaluation pixel. In the evaluation value calculation step, the luminance value of the blood vessel evaluation pixel existing in the attention range is obtained from the skin representative value obtained using the luminance value of the skin evaluation pixel existing in the attention range centering on one of the blood vessel evaluation pixels. A difference value obtained by subtracting the blood vessel representative value obtained by using is obtained at all blood vessel evaluation pixel positions in the near-infrared light image, and the blood vessel evaluation value is calculated by adding all the difference values.

  Here, in the blood vessel evaluation pixel calculation step, a pixel that is the center in the width direction of the blood vessel region is extracted as a blood vessel evaluation pixel, and in the skin evaluation pixel calculation step, the contour pixel of the blood vessel region is a predetermined pixel outside in the width direction, In other words, a predetermined pixel layer is expanded and the expanded pixel is used as a skin evaluation pixel. Then, in the evaluation value calculating step, from the skin representative value obtained by using the luminance value of the skin evaluation pixel existing in the attention range centering on one of the blood vessel evaluation pixels, the blood vessel evaluation pixel existing in the attention range is determined. A difference value obtained by subtracting the blood vessel representative value obtained using the luminance value is obtained at each of the blood vessel evaluation pixel positions in the near-infrared light image, and the blood vessel evaluation value is calculated by adding all the calculated difference values. Yes.

The “center” in the “attention range centered on one of the blood vessel evaluation pixels” here includes the case of the center of gravity.
As a result, the blood vessel evaluation value can be calculated for the entire blood vessel region captured in the near-infrared light image generated by the image capturing step and the imaging condition can be determined, so that the entire blood vessel region is imaged more optimally. It becomes possible.

  A blood vessel position acquisition method according to a twenty-sixth aspect of the present invention is the blood vessel position acquisition method according to any one of the twenty-second to twenty-fifth aspects of the present invention, wherein the near-infrared light image captured by the image capturing means is reduced. A reduced image creating step for creating an infrared light image is further provided. The blood vessel region extracting step extracts a blood vessel region from the reduced near infrared light image, and the blood vessel evaluation value calculating step includes a reduced near infrared light. A blood vessel evaluation value is calculated for the image.

  Here, a reduced near-infrared light image obtained by reducing the near-infrared light image is created in the reduced image creation step, and the reduced near-infrared light image is created in the blood vessel region extraction step and the blood vessel evaluation value calculation step. Perform various processes.

  As a result, it is possible to reduce the number of target pixels to be calculated, so that it is possible to greatly reduce the amount of calculation for calculating the blood vessel evaluation value. In addition, even if the distance between the camera and the living body changes due to the change of the imaging target, the size of the object in the near infrared light image changes and the blood vessel diameter changes, in the reduced near infrared light image, The blood vessel diameter can always be constant. For this reason, it is possible to save the trouble of individually correcting various parameters used when calculating the blood vessel evaluation value.

  According to the present invention, it is possible to acquire a near-infrared light image in which a blood vessel region is clearly captured regardless of the use environment.

Embodiments of a blood vessel position acquisition apparatus according to the present invention will be described below in detail with reference to the drawings.
As Embodiment 1 of the present invention, near-infrared light from an LED light source is irradiated from above onto an arm that is a living body, and reflected light from the arm passes through an optical filter that transmits only the near-infrared light wavelength. An example will be described in which a black-and-white CCD camera with high wavelength sensitivity is used to acquire a digitized near-infrared light image. In this near-infrared light image, one pixel is represented by 8 bits, and the pixel value is a grayscale image indicating luminance. In the near-infrared light image captured in this way, hemoglobin in the blood has the property of absorbing near-infrared light, so that the reflected light is reduced only in the region where the blood vessel exists, and the pixels of the blood vessel exist. The luminance value becomes small.

[Embodiment 1]
First, the blood vessel position acquisition device 100 according to Embodiment 1 of the present invention will be described. FIG. 1 is a block diagram showing a schematic configuration of main parts of a blood vessel position acquisition device 100 according to Embodiment 1 of the present invention.

  The blood vessel position acquisition apparatus 100 includes an imaging condition setting unit (imaging condition setting unit) 101, an image imaging unit (image imaging unit) 102, a blood vessel region extraction unit (blood vessel region extraction unit) 103, a blood vessel evaluation value calculation unit (blood vessel evaluation value). Calculation means) 104 and an imaging condition determination unit (imaging condition determination means) 105 are included. Furthermore, the blood vessel evaluation value calculation unit 104 includes a blood vessel evaluation pixel calculation unit (blood vessel evaluation pixel calculation unit) 1041, a skin evaluation pixel calculation unit (skin evaluation pixel calculation unit) 1042, and an evaluation value calculation unit (evaluation value calculation unit). 1043 is configured.

The imaging condition setting unit 101 stores in advance a plurality of adjustment parameter values such as the amount of near infrared light irradiated on the living body, and sequentially outputs the stored adjustment parameter values to the image capturing unit 102.
The image photographing unit 102 includes a CCD camera, a near-infrared LED light source, and an optical filter. The image photographing unit 102 adjusts photographing conditions according to the adjustment parameters output from the photographing condition setting unit 101, and emits near-infrared light to the living body. And the reflected light is captured by a CCD camera through an optical filter to generate a near-infrared light image, and the generated near-infrared light image is output to the blood vessel region extraction unit 103 and the blood vessel evaluation value calculation unit 104. To do. In addition, the blood vessel position acquisition device 100 outputs the output near infrared light image 106.

  The blood vessel region extraction unit 103 extracts, as a blood vessel region, a pixel having a luminance value relatively smaller than that of the surrounding pixels in the near-infrared light image output from the image capturing unit 102, and the position of the extracted blood vessel region A blood vessel region image indicating information is output to the blood vessel evaluation value calculation unit 104.

  The blood vessel evaluation value calculation unit 104 is based on the near-infrared light image output from the image capturing unit 102 and the position information of the blood vessel region indicated in the blood vessel region image output from the blood vessel region extraction unit 103. A blood vessel evaluation value for evaluating the blood vessel region of the near-infrared light image is calculated, and the calculated blood vessel evaluation value is output to the imaging condition determination unit 105.

  Specifically, the blood vessel evaluation pixel calculation unit 1041 included in the blood vessel evaluation value calculation unit 104 is based on the blood vessel region position information indicated in the blood vessel region image output from the blood vessel region extraction unit 103, and is subjected to the blood vessel evaluation value. Is calculated as a blood vessel pixel, and a blood vessel evaluation pixel image indicating the calculated blood vessel evaluation pixel is output to the evaluation value calculation unit 1043.

  The skin evaluation pixel calculation unit 1042 is used as a skin pixel adjacent to the blood vessel region when calculating the blood vessel evaluation value based on the position information of the blood vessel region indicated in the blood vessel region image output from the blood vessel region extraction unit 103. Skin evaluation pixels are calculated, and a skin evaluation pixel image indicating the calculated skin evaluation pixels is output to the evaluation value calculation unit 1043.

  The evaluation value calculation unit 1043 includes a near-infrared light image output from the image capturing unit 102, a blood vessel region image output from the blood vessel region extraction unit 103, a blood vessel evaluation pixel image output from the blood vessel evaluation pixel calculation unit 1041, and skin Using the skin evaluation pixel image output from the evaluation pixel calculation unit 1042, a blood vessel evaluation value is calculated by subtracting the luminance value of the blood vessel evaluation pixel from the luminance value of the skin evaluation pixel in the near-infrared light image.

  The imaging condition determination unit 105 determines the imaging condition that maximizes the blood vessel evaluation value output from the blood vessel evaluation value calculation unit 104 calculated under a plurality of imaging conditions as the optimal imaging condition, and captures the determined imaging condition. Output to the condition setting unit 101. The imaging condition setting unit 101 sets an optimal imaging condition output from the imaging condition determination unit 105, and the image imaging unit 102 captures a near-infrared light image, whereby the blood vessel region is contrasted with the surrounding region. The near-infrared light image that appears darkest due to the difference and appears clearly is output as an output near-infrared light image 106 from the blood vessel position acquisition device 100.

  Next, with respect to the operation of the blood vessel position acquisition device 100 according to Embodiment 1 of the present invention configured as described above, an example in which the adjustment parameter for the amount of near-infrared light irradiated on the living body is used as an imaging condition is illustrated. Details will be described with reference to FIGS.

  FIG. 2 is a flowchart showing processing performed by the blood vessel position acquisition apparatus 100 according to Embodiment 1 of the present invention. 2 includes steps S101 to S107. Step S101 is an example of an imaging condition setting process, step S102 is an example of an image imaging process, step S103 is an example of a blood vessel region extracting process, and steps S1041 to S104 are performed. Step S104 consisting of S1043 is an example of a blood vessel evaluation value calculating step, step S105 is a step of determining whether all imaging conditions have been completed, step S106 is an example of an imaging condition determining step, and step S107 is an imaging condition. The steps of photographing a near-infrared light image under the photographing conditions determined in the determination step are shown respectively.

  First, the imaging condition setting unit 101 sets an initial value of an adjustment parameter for the amount of near-infrared light irradiated on the living body (step S101). The light quantity adjustment parameter is a digital value in which the minimum light quantity is 0 and the maximum light quantity is 255, and 52 adjustment parameters are stored in increments of 5. Also, the initial value is set to 0, and the adjustment parameter is set so that the value becomes larger sequentially. By setting in this way, the captured near-infrared light image gradually changes from a dark image to a bright image. As the adjustment parameter, in addition to the light amount of near-infrared light, the sensitivity of the CCD camera and the aperture amount for light amount adjustment may be used.

  Next, the image photographing unit 102 irradiates the living body with near-infrared light using the light amount adjustment parameter set by the photographing condition setting unit 101, and transmits the reflected light from the living body through only the near-infrared light wavelength. A near-infrared light image captured by the CCD camera is generated through the filter (step S102). Then, the generated near-infrared light image is output to the blood vessel region extraction unit 103 and the blood vessel evaluation value calculation unit 104.

  Next, the blood vessel region extraction unit 103 extracts blood vessel pixels as blood vessel regions from the near-infrared light image output from the image photographing unit 102 (step S103). This is performed by extracting a pixel having a luminance value relatively smaller than that of surrounding pixels as a blood vessel pixel. An image memory having the same size as the near-infrared light image is prepared, and the extracted blood vessel region position information is obtained by setting the pixel value corresponding to the blood vessel region to 1 and the other pixel values to 0. It is stored as data (blood vessel region image).

  Hereinafter, the blood vessel region extraction process will be described. FIG. 3 is a diagram for explaining blood vessel region extraction processing according to Embodiment 1 of the present invention. 3A is a near-infrared light image 300 in which blood vessels output from the image capturing unit 102 are reflected, and FIG. 3B is a broken-line arrow of the near-infrared light image 300 in FIG. 5 is a luminance graph showing luminance values between L1 and L2 on the horizontal line indicated by. Reference numeral 301 denotes a blood vessel, and 302 denotes skin.

  In the blood vessel region extraction processing, the blood vessel region extraction unit 103 extracts pixels between L1 and L2 on the horizontal line of the near-infrared light image 300 as shown in FIG. 3A, and the blood vessels are extracted based on the luminance value of the extracted pixels. A luminance threshold value TH1 used for determining whether the value is 301 is calculated. Then, the blood vessel region extraction unit 103 compares the calculated luminance threshold value TH1 and the luminance value of the target pixel serving as the midpoint between L1 and L2, and if the luminance value of the target pixel is smaller than the luminance threshold value TH1, the target pixel Is extracted as a blood vessel position. In FIG. 3B, since the luminance value of the target pixel C1 is smaller than the luminance threshold value TH1, the target pixel C1 is extracted as the blood vessel 301 by the blood vessel region extraction unit 103.

  In the present embodiment, the distance between L1 and L2 is set, for example, to the number of pixels that is twice the maximum diameter of the blood vessel thickness assumed in the near-infrared light image 300 to be captured. The luminance threshold TH1 is obtained by extracting half of the number of pixels between L1 and L2 from the larger one of the luminance values of the pixels between L1 and L2, calculating the luminance average value of the extracted pixels, and calculating the calculated luminance average. The value is multiplied by 0.8. Thus, by calculating the brightness threshold TH1, it is possible to calculate a threshold for separating the blood vessel position and the skin position.

  Note that the numerical values used here are merely examples, and the distance between L1 and L2 may be set to a pixel distance so that the blood vessel 301 and the skin 302 are necessarily included. In addition, the number of pixels used for the average value is set by the number corresponding to the number of skin 302 pixels from the distance between L1 and L2, and the luminance average value of the skin pixels is obtained. A value smaller than the luminance value of the skin pixel may be set based on the average luminance value.

  The blood vessel region extracting unit 103 extracts pixels between L1 and L2 while shifting this series of processes from the upper part of the near infrared light image 300 for each horizontal line one pixel at a time in order from the left side of the image. By going, blood vessel pixels are sequentially extracted.

The blood vessel region extraction process used here is an example, and a pixel region having a luminance value relatively smaller than that of surrounding pixels may be extracted as a blood vessel position by another method. For example, not only horizontal lines but also vertical line pixels may be extracted and extracted using two lines simultaneously, or similar processing may be performed on a two-dimensional plane.
Then, the extracted blood vessel region image indicating the blood vessel region is output to the blood vessel evaluation value calculation unit 104.

  Next, based on the near-infrared light image output from the image capturing unit 102 and the position information of the blood vessel region indicated in the blood vessel region image output from the blood vessel region extraction unit 103, the blood vessel evaluation value calculation unit 104 calculates a blood vessel evaluation value for evaluating the blood vessel region of the near-infrared light image (step S104). The blood vessel evaluation value calculated here increases as the difference in luminance contrast between the blood vessel region and the skin region in the near-infrared light image increases.

  In this step, based on the position information of the blood vessel region extracted by the blood vessel region extraction unit 103, the blood vessel evaluation pixel calculation unit 1041 calculates the blood vessel pixel used for calculating the blood vessel evaluation value as the blood vessel evaluation pixel (step S1041: Blood vessel evaluation pixel calculation step), and the skin evaluation pixel calculation unit 1042 calculates the skin pixel adjacent to the blood vessel region used for calculation of the blood vessel evaluation value as the skin evaluation pixel (step S1042: skin evaluation pixel calculation step). The value calculation unit 1043 calculates a blood vessel evaluation value by subtracting the luminance value of the blood vessel evaluation pixel from the luminance value of the skin evaluation pixel in the near-infrared light image (step S1043: blood vessel evaluation value calculation step).

  Since the difference in luminance contrast is caused by the difference between the luminance value of the blood vessel region and the luminance value of the surrounding skin adjacent to the blood vessel region, the blood vessel evaluation value is calculated using the blood vessel evaluation pixel and the skin evaluation pixel. Thus, an evaluation value reflecting the degree of contrast difference between the blood vessel region and the surrounding skin region in the near-infrared light image can be calculated.

  Hereinafter, the blood vessel evaluation value calculation process in step S104 will be described more specifically. First, the blood vessel evaluation pixel calculation unit 1041 uses the position information of the blood vessel region indicated in the blood vessel region image output from the blood vessel region extraction unit 103 as a blood vessel evaluation pixel. (Step S1041). An image memory having the same size as the blood vessel region image is prepared, and the calculated blood vessel evaluation pixel information is obtained by setting the pixel value corresponding to the blood vessel evaluation pixel to 1 and setting the other pixel values to 0. Stored as (blood vessel evaluation pixel image). In the subsequent process (step S1043), the blood vessel evaluation pixel can be known by referring to each pixel of the blood vessel evaluation pixel image.

  FIG. 4 is a blood vessel evaluation pixel image 400 showing blood vessel evaluation pixels calculated from the blood vessel region image of the near-infrared light image 300 shown in FIG. 3A, and 401 indicates the blood vessel evaluation pixels. As shown in FIG. 4, the blood vessel evaluation pixel is set to a pixel located on the center line of the blood vessel region.

  A thinning process is used as a method for obtaining the center line of the blood vessel region. The thinning process is a process of adjusting a contour line with uneven thickness to one pixel width, and is performed by cutting the thick contour line from the outside and ending the process when the thickness becomes one pixel. Here, a blood vessel region having a pixel value of 1 in the blood vessel region image is thinned using a Hilditch method that is generally used as a thinning process, and the pixel value is 1 after thinning. Are calculated as blood vessel evaluation pixels.

Note that the method of obtaining the center line used here is an example, and the blood vessel evaluation pixel may be calculated using another method.
Then, a blood vessel evaluation pixel image indicating the blood vessel evaluation pixel calculated in this way is output to the evaluation value calculation unit 1043.

  Next, the skin evaluation pixel calculation unit 1042 uses the position information of the blood vessel region indicated in the blood vessel region image output from the blood vessel region extraction unit 103 to evaluate the skin pixel used for calculating the blood vessel evaluation value. Calculated as a pixel (step S1042). It should be noted that an image memory having the same size as the blood vessel region image is prepared, and the calculated skin evaluation pixel information is obtained by setting the pixel value corresponding to the skin evaluation pixel to 1 or more and the other pixel values to 0. It is stored as data (skin evaluation pixel image). In the subsequent process (step S1043), the skin evaluation pixel can be known by referring to each pixel of the skin evaluation pixel image.

  FIG. 5A is a skin evaluation pixel image 500 showing skin evaluation pixels calculated from the blood vessel region image of the near-infrared light image 300 shown in FIG. 3A, and 501 indicates skin evaluation pixels. As skin evaluation pixels, peripheral pixels adjacent to the blood vessel region are set as shown in FIG.

  Note that dilation processing is used as a method of setting peripheral pixels adjacent to the blood vessel region. The expansion process is a process of increasing the thickness of the connected component outline pixels by a plurality of layers to the outside. Here, in the blood vessel region image, pixels other than the blood vessel region (pixel value is 0) are subjected to the expansion process, and at least one of the eight adjacent pixels centering on the target pixel of interest has a pixel value. When there is a value other than 0, a value of 1 or more is written to the target pixel. By this processing, an image showing a blood vessel region expanded by one pixel in all directions and expanded by one layer with respect to the blood vessel region in the blood vessel region image before processing can be obtained. Then, the pixel value of the corresponding pixel of the blood vessel region image before being inflated is obtained from the blood vessel region image obtained by increasing the blood vessel region for a plurality of layers after repeating the process for expanding the blood vessel region image a plurality of times. By drawing, a skin evaluation pixel image showing a skin evaluation pixel adjacent to the blood vessel region can be obtained.

  In addition, the number of times of performing the expansion process for one layer is the thickness of the blood vessel image having the maximum diameter among the blood vessel images that can be captured in the near-infrared light image captured by the blood vessel position acquisition apparatus 100 of the present embodiment. The pixel width of the radius is set in advance, and the radius of the thickness of the blood vessel image having the maximum diameter is an integer value obtained by (maximum blood vessel diameter + 1) / 2. That is, when the maximum blood vessel diameter is 5 pixels, the radius of the blood vessel thickness is 3, and the number of expansions is 3 times.

  Further, the pixel value of the skin evaluation pixel image indicating the skin evaluation pixel is written with the number of times when the expansion process is performed. By doing so, the pixel value of the skin evaluation pixel becomes the distance from the blood vessel region. This value is used when calculating the blood vessel evaluation value. FIG. 5B is an extracted part of the skin evaluation pixel image 500 of FIG. 5A, and shows the pixel values of the skin evaluation pixels calculated in this way. A blank pixel has a pixel value of 0.

Then, the skin evaluation pixel image indicating the skin evaluation pixel calculated in this way is output to the evaluation value calculation unit 1043.
Next, the evaluation value calculation unit 1043 includes a near-infrared light image output from the image capturing unit 102, a blood vessel extraction image output from the blood vessel region extraction unit 103, and a blood vessel evaluation pixel output from the blood vessel evaluation pixel calculation unit 1041. The blood vessel evaluation value is calculated by subtracting the luminance value of the blood vessel evaluation pixel from the luminance value of the skin evaluation pixel in the near-infrared light image using the image and the skin evaluation pixel image output from the skin evaluation pixel calculation unit 1042. (Step S1043).

  More specifically, at all blood vessel evaluation pixel positions in the near-infrared light image, first, the skin representative value is determined from the luminance value of the skin evaluation pixel existing within the attention range having a predetermined range centered on the blood vessel evaluation pixel. Then, the blood vessel representative value is obtained from the luminance value of the blood vessel evaluation pixel existing in the attention range, and then the blood vessel representative value is subtracted from the obtained skin representative value to obtain a difference value. Then, the blood vessel evaluation value is calculated by adding all the difference values obtained at all the blood vessel evaluation pixel positions. However, the difference value is calculated only at a position where the attention range does not protrude from the near-infrared light image.

  Further, the shape of the attention range used here is a square, and the pixel length of one side is the diameter of the thickness of the blood vessel image having the maximum diameter among the blood vessel images that can be photographed in the near-infrared light image used in step S1042. Using the number of times the blood vessel region is expanded, the maximum blood vessel diameter + the number of expansion times × 2 is obtained and set. That is, since the maximum blood vessel diameter is 5 and the number of expansions is 3, the pixel length of one side of the attention range here is 11. By setting in this way, the blood vessel evaluation pixel and the skin evaluation pixel adjacent to the blood vessel region can be included in the attention range without waste.

  6A and 6B are diagrams for explaining blood vessel evaluation value calculation processing. FIG. 6A shows scanning of a range of interest for the near-infrared light image 300, and FIG. 6B shows blood vessel representative values and skin. It is a figure explaining the calculation method with a representative value.

  As shown in FIG. 6A, first, 0 is substituted for the blood vessel evaluation value, and at the position of the attention range 601 at the upper left of the near-infrared light image 300, it is determined whether the central pixel of the attention range is a blood vessel evaluation pixel. Check. This can be performed by referring to the pixel value of the blood vessel evaluation pixel image. If the center pixel of the attention range is not a blood vessel evaluation pixel, the attention range is shifted to the right by one pixel, checked again, and this is repeated. At the position of the attention range 602, since the central pixel of the attention range is a blood vessel evaluation pixel, a blood vessel representative value is obtained from the blood vessel evaluation pixel in the attention range, and a skin representative value is obtained from the skin evaluation pixel. A difference value obtained by subtracting the blood vessel representative value from the value is obtained, and the obtained difference value is added to the blood vessel evaluation value. By performing this series of processing on the entire near-infrared light image 300 in the order of the arrow 603, the blood vessel evaluation value in the near-infrared light image 300 is calculated.

  In addition, the blood vessel representative value and the skin representative value in the attention range are obtained as follows. FIG. 6B is a diagram in which the position of the blood vessel evaluation pixel image 400 in FIG. 4 is aligned with the skin evaluation pixel image in FIG. Pixels indicated by numerals in FIG. 5B are skin evaluation pixels and their pixel values, hatched pixels and filled pixels represent blood vessel evaluation pixels, and the filled pixels represent the attention range 604. Is the pixel of interest in the center of.

  First, the blood vessel representative value in the attention range 604 is set as the luminance value of the near-infrared light image corresponding to the attention pixel in the center of the attention range 604. Then, the skin representative value in the attention range 604 is obtained by averaging the luminance values of the near-infrared light images corresponding to the skin evaluation pixels having a distance from the blood vessel region equal to the radius of the blood vessel in the attention range 604. Specifically, referring to the blood vessel region image, the radius of the blood vessel in the attention range 604 is obtained, and the luminance values of the near-infrared light images corresponding to the skin evaluation pixels having the obtained blood vessel radius value are averaged. In addition, since the attention range is a square for the radius of the blood vessel, the diameter of the blood vessel is obtained by dividing the number of pixels, which is the area of the blood vessel pixel included in the attention range 604, by the pixel length of one side of the attention range. Area / pixel length of one side) +1) / 2. Accordingly, in FIG. 6B, the radius of the blood vessel is ((55/11) +1) / 2 = 3, and the skin representative value is 3 in the skin evaluation pixels within the attention range 604. It is obtained by averaging the luminance values of the near-infrared light image corresponding to a certain pixel. Then, a difference value obtained by subtracting the blood vessel representative value from the obtained skin representative value is obtained and added to the blood vessel evaluation value.

  By obtaining the blood vessel evaluation value in this way, even if the thickness of the blood vessel image changes in the near-infrared light image, the skin close to the blood vessel contour is obtained in a thin blood vessel where the blood vessel evaluation pixel and the blood vessel contour are narrow. In the case of a thick blood vessel with a wide range from the blood vessel evaluation pixel to the blood vessel contour, the skin evaluation pixel far from the blood vessel contour can be automatically selected, and the evaluation pixel is evaluated under the same conditions regardless of the blood vessel image thickness. A value can be calculated. Further, since the attention range is a square, the blood vessel evaluation value can be obtained by the same processing regardless of the traveling direction of the blood vessel.

  Here, the pixel length of one side of the attention range is obtained by the maximum blood vessel diameter + the number of expansion times × 2. This is because there is no gap when a blood vessel having the maximum blood vessel diameter exists in the horizontal or vertical direction. This is because the evaluation pixel is set so as to fall within the attention range. However, when the blood vessel having the maximum blood vessel diameter is in an oblique direction, there is a problem that the skin evaluation pixels protrude from the attention range and the skin evaluation pixels used for calculating the blood vessel evaluation value within the attention range are reduced. . Therefore, the pixel length of one side of the attention range may be set to the maximum blood vessel diameter + the number of expansions × 2 + α (α is a multiple of 2). However, if the α value is increased, the amount of calculation increases, so it is set to about 2 or 4, and this α value may be set according to the characteristics of the blood vessel in the near-infrared light image.

  In the description, the blood vessel representative value is the luminance value of the near-infrared light image corresponding to the blood vessel evaluation pixel located at the center of the attention range, but the near red corresponding to all the blood vessel evaluation pixels included in the attention range. It is good also as an average value of the luminance value of an outside light image. By calculating in this way, the calculation amount increases to calculate the average value, but it is strong against noise. The skin representative value may be an average value of luminance values of near-infrared light images corresponding to all skin evaluation pixels included in the attention range. In this case, since the skin evaluation pixel used for calculation of the blood vessel evaluation value is not selected, the processing can be performed at high speed, which is effective for rough evaluation.

  Further, the following processing may be performed in order to increase the accuracy of the calculated blood vessel evaluation value. First, when the shape of the blood vessel in the attention range is branched, the blood vessel evaluation value calculation processing at that position is not performed. This is because an intended skin evaluation pixel cannot be obtained at a portion where the blood vessel is branched because the blood vessel is close. For the branching of the blood vessel, the number of connected blood vessel evaluation pixels is counted at all blood vessel evaluation pixel positions within the target range. If the count number is 3 or more, it can be determined that the blood vessel is branched.

  Further, when the number of blood vessel evaluation pixels in the attention range is different from a predetermined value, the blood vessel evaluation value calculation processing at that position may not be performed. This is because when the attention range is set wide, a plurality of thin blood vessels may be included in the attention range, and in this case as well, the intended skin evaluation pixel cannot be obtained because the blood vessels are close to each other. Prevent calculation of blood vessel evaluation values.

  Note that the predetermined value used here is, for example, when one blood vessel is running within the attention range, the number of pixels of the blood vessel evaluation value is equal to the pixel length of one side of the attention range. This can be easily determined by setting the pixel length.

  Moreover, you may compare with the pixel number of the blood vessel evaluation pixel in the attention range connected with the blood vessel evaluation pixel located in the center of the attention range instead of the said predetermined value. If this value is used, the amount of computation increases compared to the case where a predetermined value is used, but there are a plurality of short and thin blood vessels in the range of interest, and the number of pixels of the blood vessel evaluation pixel matches the above-described predetermined value. Even in this case, calculation of the blood vessel evaluation value can be reliably prevented.

  Further, when the number of skin evaluation pixels used for calculating the blood vessel evaluation value in the attention range is smaller than a predetermined number, the blood vessel evaluation value at that position may not be calculated. This occurs because the skin evaluation pixel corresponding to the blood vessel evaluation pixel is out of the attention range when the blood vessel is traveling in an oblique direction or the blood vessel is thicker than expected. If the skin evaluation pixels are small, the skin representative value cannot be obtained with high accuracy. For this reason, the calculation of the blood vessel evaluation value is avoided in such a case. As the predetermined number used here, for example, if the number of blood vessel evaluation pixels within the range of interest is set, the skin representative value can be obtained using skin evaluation pixels on both sides sandwiching a certain amount or more of blood vessels.

  Further, when the difference value between the skin representative value and the blood vessel representative value is obtained at each blood vessel evaluation pixel position, if the obtained difference value is smaller than a predetermined value, the obtained difference value may be discarded and not added. . This is because the accuracy of the blood vessel evaluation value can be improved by treating a small difference value as noise and discarding it. The predetermined value used in this case may be set based on the difference between the luminance values of the blood vessel region and the surrounding skin region in the assumed near-infrared light image. If the difference is assumed to be large, a larger value is used. If the difference is assumed to be small, set a smaller value.

  In addition, each process of step S104 for calculating the blood vessel evaluation value may be performed only in a region included in the limited evaluation range near the center of the near-infrared light image. By doing so, the blood vessel evaluation value can be calculated only in the central pixel region where the near-infrared light shining on the living body is well hit, and the calculation amount can be reduced by narrowing the range. .

  The blood vessel evaluation value reflecting the characteristics of the blood vessel region in the near-infrared light image can be obtained by the processing in step S104 described above. Specifically, the blood vessel evaluation value increases as the contrast difference between the blood vessel region and the surrounding region is larger and clearer, and as the blood vessel region is larger and more blood vessels are projected. Can be requested. Then, the obtained blood vessel evaluation value is output to the imaging condition determination unit 105.

  Next, in step S105, it is determined whether blood vessel evaluation values have been calculated under all imaging conditions. If not completed, the process returns to step S101, the next shooting condition is set, the processing from step S102 to step S104 is performed, and if all shooting conditions are completed, the process proceeds to step S106.

  Next, the imaging condition determination unit 105 determines an optimal imaging condition based on the blood vessel evaluation values in all imaging conditions calculated by the blood vessel evaluation value calculation unit 104 (step S106). FIG. 7 is an example of a graph showing the blood vessel evaluation value calculated for the near-infrared light image captured while sequentially increasing the amount of near-infrared light set in step S101, and the horizontal axis represents the near-infrared light image. This is the imaging condition number used when imaging, and the vertical axis represents the blood vessel evaluation value. In FIG. 7, since the light amount is initially 0, blood vessels are not reflected in the captured near-infrared light image and the blood vessel evaluation value is 0. However, as the light amount increases, the blood vessel evaluation value increases. However, if the amount of light is increased too much, the overall brightness of the image is saturated, and the blood vessel evaluation value decreases. Accordingly, the imaging condition having the maximum value among the blood vessel evaluation values at the peak position 701 in the graph shown in FIG. 7 is determined to be the imaging condition in which the contrast difference between the blood vessel region and the surrounding region appears most. be able to. Then, the determined shooting condition number is output to the shooting condition setting unit 101.

  Then, the shooting condition setting unit 101 sets a light amount corresponding to the shooting condition number output from the shooting condition determination unit 105, and outputs a near-infrared light image obtained by shooting in the image shooting unit 102. The external light image 106 is output from the blood vessel position acquisition device 100 (step S107).

  It should be noted that when the imaging condition is determined in step S106 in the imaging condition determination unit 105, the value changes by a predetermined value or more before and after the calculated blood vessel evaluation value even though the imaging conditions are taken continuously in the time axis direction. In such a case, the shooting conditions may not be determined. This is because, in step S101, the light amount of the near infrared light is sequentially increased from 0, and the imaging conditions are set so that the characteristics of the captured near infrared light image do not change greatly. Since the evaluation value has changed greatly, it can be determined that the object has moved during shooting or that the outside light has changed significantly. When the object moves, elements other than the imaging condition change, and the imaging condition having the maximum blood vessel evaluation value cannot be said to be optimal. Therefore, the imaging condition is not determined.

  Specifically, when the value changes by a predetermined value or more before and after the blood vessel evaluation value, the imaging condition determination unit 105 outputs a value other than the imaging condition number, for example, −1 to the imaging condition setting unit 101. When -1 is input, the imaging condition setting unit 101 sequentially sets the imaging conditions again from the initial value, and repeatedly performs a series of processes for calculating blood vessel evaluation values.

  Further, the predetermined value used here may be set to 20% of the peak value of the blood vessel evaluation value under all imaging conditions, for example. However, when the number of imaging conditions to be set in the imaging condition setting unit 101 is small, or when the adjustment parameters to be set are greatly different, the values change greatly even before and after the continuous blood vessel evaluation value, so that a predetermined value is determined. Set a large percentage.

  By performing the above-described series of processing from step S101 to step S107, the near-infrared light image in which the blood vessel region appears darkest due to the contrast difference with the peripheral region in the near-infrared light image and the visible near-infrared light image is reliably obtained. Can be obtained.

  In the description of the first embodiment, the imaging condition set in step S101 in the imaging condition setting unit 101 has been described by taking the near-infrared light amount irradiated to the living body as an example. Imaging conditions that affect the difference in contrast between blood vessel images in the external light image may be set. For example, the wavelength of light irradiating the living body that affects the absorbance to the blood vessel and the transmittance to the living body, the passband of an optical filter that passes only a specific wavelength used to reduce the influence of external light, It is also possible to use the aperture value of the lens of a CCD camera that captures the image, and it is possible to obtain an optimum near-infrared light image under these photographing conditions by the same processing.

  As for the wavelength of near infrared light, a plurality of types of LEDs having different wavelengths may be prepared as light sources, and lighting may be sequentially switched for each wavelength when setting imaging conditions. As for the passband of the optical filter, a plurality of types of optical filters having different passbands are prepared, and the optical filters may be switched sequentially when setting the photographing conditions. The aperture value of the camera lens is an electric type, and the aperture value adjustment parameter may be changed when setting the shooting conditions. Furthermore, even if these plural imaging conditions are combined, an optimum near-infrared light image can be obtained in the same manner.

[Embodiment 2]
Next, the blood vessel position acquisition device 800 in Embodiment 2 of the present invention will be described. FIG. 8 is a block diagram showing a schematic configuration of a main part of a blood vessel position acquisition device 800 according to Embodiment 2 of the present invention.

  As shown in FIG. 8, the blood vessel position acquisition apparatus 800 includes an imaging condition setting unit (imaging condition setting unit) 101, an image imaging unit (image imaging unit) 102, and a reduced image creation unit (reduced image creation unit) 807. A blood vessel region extracting unit (blood vessel region extracting unit) 803, a blood vessel evaluation value calculating unit (blood vessel evaluation value calculating unit) 804, and an imaging condition determining unit (imaging condition determining unit) 105. In addition, the same code | symbol is attached | subjected about the thing of the same structure as what was demonstrated in Embodiment 1 shown in FIG. 1, and description is abbreviate | omitted. A difference from the configuration of the blood vessel position acquisition apparatus according to the first embodiment shown in FIG. 1 is that a reduced image creation unit 807 is newly added.

  The reduced image creation unit 807 creates a reduced near infrared light image obtained by reducing the near infrared light image output from the image capturing unit 102 and outputs the reduced near infrared light image to the blood vessel region extraction unit 803 and the blood vessel evaluation value calculation unit 804. is there. Then, using the reduced near-infrared light image output from the reduced image creation unit 807, the blood vessel region extraction unit 803 extracts a blood vessel region, and the blood vessel evaluation value calculation unit 804 calculates a blood vessel evaluation value, thereby calculating Since the number of target pixels to be reduced is reduced, the amount of calculation can be greatly reduced. Moreover, even if the size of the object in the near-infrared light image changes and the blood vessel diameter changes because the distance between the camera and the living body changes due to a change in the object to be photographed, etc., the reduced near-infrared light image Since the blood vessel diameter is always constant, the trouble of individually correcting various parameters used when calculating the blood vessel evaluation value can be saved.

  Next, the operation of the blood vessel position acquisition apparatus 800 according to the second embodiment of the present invention will be described in detail with reference to FIG. FIG. 9 is a flowchart for explaining processing performed by the blood vessel position acquisition apparatus 800 according to Embodiment 2 of the present invention. The flowchart in FIG. 9 includes steps S201 to S208, where step S201 is an example of an imaging condition setting step, step S202 is an example of an image shooting step, step S203 is an example of a reduced image creation step, and step S204 is a blood vessel. An example of the region extraction process, step S205 including steps S2051 to S2053 is an example of the blood vessel evaluation value calculation process, step S206 is a process of determining whether all the imaging conditions have been completed, and step S207 is an imaging condition. As an example of the determination process, step S208 indicates a process of capturing a near-infrared light image under the imaging condition determined in the imaging condition determination process.

Hereinafter, as in the first embodiment, the case where the amount of near-infrared light irradiated on a living body is set as an imaging condition will be described in detail according to the flowchart.
First, similarly to step S101 in FIG. 2, the imaging condition setting unit 101 sets an initial value of an adjustment parameter for the amount of near-infrared light irradiated on the living body (step S201).

  Next, similarly to step S102 in FIG. 2, the image photographing unit 102 irradiates the living body with near-infrared light using the light amount adjustment parameter set by the photographing condition setting unit 101, and reflects the reflected light from the living body in the near direction. A near-infrared light image captured by the CCD camera is generated through an optical filter that transmits only the infrared light wavelength (step S202). Then, the generated near-infrared light image is output to the reduced image creation unit 807.

Next, the reduced image creation unit 807 reduces the near-infrared light image output from the image capturing unit 102 at the same vertical and horizontal magnifications, and creates a reduced near-infrared light image (step S203).
Note that a bilinear method that is generally used may be used as a method for reducing the near-infrared light image. However, this is an example, and other methods may be used.

The reduction rate is set based on the maximum blood vessel diameter in the assumed near-infrared light image. Specifically, when the subject is changed, the magnification is set so that the diameter of the blood vessel image having the largest diameter among the blood vessel images that can be taken in the near-infrared light image obtained by photographing each subject becomes constant. And the near-infrared light image is reduced so as to have a blood vessel diameter suitable for the pixel length of one side of the range of interest set in the blood vessel evaluation value calculation unit 804 and the number of expansions of the blood vessel region. Furthermore, the diameter of the blood vessel image having the maximum diameter that becomes the reference when reducing the size is the same as the diameter of the blood vessel having the smallest diameter among the blood vessel images in the pre-captured near-infrared light image. In the infrared light image, after reducing the thickness so as to be 1, the diameter of the thickness of the blood vessel having the maximum diameter in the reduced near-infrared light image may be set.
The reduced near-infrared light image thus created is output to the blood vessel region extraction unit 803 and the blood vessel evaluation value calculation unit 804.

  Next, the blood vessel region extraction unit 803 extracts blood vessel pixels as blood vessel regions from the reduced near-infrared light image output from the reduced image creation unit 807 (step S204). The process of extracting the blood vessel region is the same as step S103 in FIG. For the extracted blood vessel region position information, an image memory having the same size as the reduced near-infrared light image is prepared, and the extracted blood vessel region position information has a pixel value corresponding to the blood vessel region as 1, Is stored as a blood vessel region image with a pixel value of 0, and the blood vessel region image is output to the blood vessel evaluation value calculation unit 804.

  Next, blood vessel evaluation value calculation is performed based on the reduced near infrared light image output from the reduced image creation unit 807 and the position information of the blood vessel region indicated in the blood vessel extraction image output from the blood vessel region extraction unit 803. The unit 804 calculates a blood vessel evaluation value for evaluating the blood vessel region of the near-infrared light image (step S205).

  Specifically, based on the position information of the blood vessel region extracted by the blood vessel region extraction unit 803, the blood vessel evaluation pixel calculation unit 1041 calculates blood vessel evaluation pixels in the same manner as in step S1041 of FIG. 2 (step S2051: blood vessel evaluation). Pixel calculation step), skin evaluation pixel calculation unit 1042 calculates skin evaluation pixels in the same manner as in step S1042 of FIG. 2 (step S2052: skin evaluation pixel calculation step), and evaluation value calculation unit 8043 performs reduced near-infrared light. The luminance value of the blood vessel evaluation pixel is subtracted from the luminance value of the skin evaluation pixel in the image, and the blood vessel evaluation value is calculated in the same manner as in step S1043 in FIG. 2 (step S2053: blood vessel evaluation value calculating step). Then, the calculated blood vessel evaluation value is output to the imaging condition determination unit 105.

  In step S206, as in step S105 of FIG. 2, it is determined whether blood vessel evaluation values have been calculated under all imaging conditions. If not completed, the process returns to step S201, the next shooting condition is set, and the subsequent processing from step S202 to step S205 is performed. If all shooting conditions have been completed, the process proceeds to step S207.

  Next, based on the blood vessel evaluation values in all the imaging conditions calculated by the blood vessel evaluation value calculation unit 804, the imaging condition determination unit 105 determines the optimal imaging conditions in the same manner as in step S106 in FIG. 2 (step S207). ). Then, the determined shooting condition number is output to the shooting condition setting unit 101.

  Then, in the shooting condition setting unit 101, similarly to step S107 in FIG. 2, the light amount corresponding to the shooting condition number output from the shooting condition determination unit 105 is set, and the image shooting unit 102 obtains the image. The near-infrared light image is output from the blood vessel position acquisition device 800 as the output near-infrared light image 106 (step S208).

  By performing the above-described series of processing from step S201 to step S208, the near-infrared light in which the blood vessel region in the near-infrared light image appears darkest due to the contrast difference with the surrounding region and appears clearly with a small amount of calculation. It is possible to reliably obtain an image, and even if the imaging target changes, it is possible to save the trouble of setting various parameters used for calculating the blood vessel evaluation value for each imaging target.

  In the description of the second embodiment, in step S201 in the photographing condition setting unit 101, the amount of near-infrared light that irradiates the living body with the photographing condition has been described as an example. In addition, imaging conditions that affect the difference in contrast between the blood vessels in the near-infrared light image may be set. For example, the light that irradiates the living body that affects the absorbance to the blood vessel or the transmittance to the living body. It is also possible to set the passband of the optical filter that passes only a specific wavelength used to reduce the influence of the wavelength and external light, and the aperture value of the lens of the CCD camera that images the living body. An infrared light image can be obtained. Furthermore, an optimal near-infrared light image can be obtained by the same processing even if these plural imaging conditions are combined.

  The blood vessel position acquisition device and the blood vessel position acquisition method according to the present invention can determine an optimal imaging condition, obtain an image in which a blood vessel region clearly appears, and acquire a blood vessel position of a living body as an image. Useful.

The block diagram of the blood vessel position acquisition apparatus in Embodiment 1 of this invention. The flowchart explaining the blood vessel position acquisition method in Embodiment 1 of this invention. (A), (b) is a figure explaining the blood vessel region extraction process which the blood vessel region extraction part contained in FIG. 1 performs. The figure which shows the blood-vessel evaluation pixel image which the blood-vessel evaluation pixel calculation part contained in FIG. 1 produced. (A), (b) is a figure which shows the skin evaluation pixel image which the skin evaluation pixel calculation part contained in FIG. 1 created. (A), (b) is a figure explaining the blood-vessel evaluation value calculation process which the evaluation value calculation part contained in FIG. 1 performs. The graph which shows the blood-vessel evaluation value input into the imaging condition determination part contained in FIG. The block diagram of the blood vessel position acquisition apparatus in Embodiment 2 of this invention. The flowchart explaining the blood vessel position acquisition method in Embodiment 2 of this invention. The figure which shows the process of the imaging | photography system which image | photographs the conventional vein pattern clearly.

Explanation of symbols

100 Blood vessel position acquisition device 101 Imaging condition setting unit (imaging condition setting means)
102 Image photographing unit (image photographing means)
103 Blood vessel region extraction unit (blood vessel region extraction means)
104 Blood vessel evaluation value calculation unit (blood vessel evaluation value calculation means)
1041 Blood vessel evaluation pixel calculation unit (blood vessel evaluation pixel calculation means)
1042 Skin evaluation pixel calculation unit (skin evaluation pixel calculation means)
1043 Evaluation value calculation unit (evaluation value calculation means)
105 Shooting condition determining unit (shooting condition determining means)
106 Output near-infrared light image 300 Near-infrared light image 301 Blood vessel 302 Skin 400 Blood vessel evaluation pixel image 401 Blood vessel evaluation pixel image 500 Skin evaluation pixel image 501 Skin evaluation pixel 601 First attention range 602 Attention that has a blood vessel evaluation pixel at the center Range 603 Arrow 604 indicating scanning of target range 604 Target range 701 Peak position 800 Blood vessel position acquisition device 803 Blood vessel region extracting unit (blood vessel region extracting means)
804 Blood vessel evaluation value calculation unit (blood vessel evaluation value calculation means)
8043 Evaluation value calculation unit (Evaluation value calculation means)
807 Reduced image creation unit (reduced image creation means)
TH1 brightness threshold

Claims (26)

Shooting condition setting means for setting shooting conditions when shooting a living body;
Image photographing means for photographing reflected light or transmitted light from the living body irradiated with near infrared light based on the photographing conditions and generating a near infrared light image;
A blood vessel region extracting means for extracting a blood vessel image in the near infrared light image as a blood vessel region;
Determining a blood vessel evaluation pixel and a skin evaluation pixel adjacent to the blood vessel region based on the blood vessel region, and calculating a blood vessel evaluation value for evaluating the blood vessel region;
An imaging condition determining unit that determines an optimal imaging condition based on the blood vessel evaluation value calculated by the blood vessel evaluation calculating unit;
A blood vessel position acquisition apparatus comprising: The blood vessel evaluation value calculating means calculates the blood vessel evaluation value by subtracting the luminance value of the blood vessel evaluation pixel from the luminance value of the skin evaluation pixel;
The blood vessel position acquisition device according to claim 1. The blood vessel evaluation value calculating means calculates the blood vessel evaluation value in a plurality of the imaging conditions,
The imaging condition determining means determines the imaging condition when the blood vessel evaluation value is maximum as the optimum imaging condition.
The blood vessel position acquisition device according to claim 1 or 2. The blood vessel evaluation value calculating means includes
A blood vessel evaluation pixel calculating means having the pixel at the center in the width direction of the blood vessel region as the blood vessel evaluation pixel;
A skin evaluation pixel calculating means that expands the contour pixel of the blood vessel region by a predetermined pixel outside in the width direction, and uses the expanded pixel as a skin evaluation pixel;
Using the luminance value of the blood vessel evaluation pixel existing in the attention range from the skin representative value obtained using the luminance value of the skin evaluation pixel existing in the attention range centering on one of the blood vessel evaluation pixels. The difference value obtained by subtracting the blood vessel representative value obtained in this manner is obtained at each of the blood vessel evaluation pixel positions in the near-infrared light image, and the blood vessel evaluation value is calculated by adding all the difference values. Means,
The blood vessel position acquisition device according to any one of claims 1 to 3, further comprising: The skin representative value is an average value of luminance values of the skin evaluation pixels existing in the attention range,
The blood vessel representative value is a luminance value of the blood vessel evaluation pixel located at the center of the attention range, or an average value of luminance values of the blood vessel evaluation pixels existing in the attention range.
The blood vessel position acquisition apparatus according to claim 4. The skin evaluation pixel calculating means stores the number of expansions as a distance from the blood vessel region in association with each of the expanded skin evaluation pixels,
The evaluation value calculation means uses only the skin evaluation pixels having a distance from the blood vessel region equal to the radius of the thickness of the blood vessel image existing in the attention range among the skin evaluation pixels existing in the attention range. To obtain the skin representative value,
The blood vessel position acquisition device according to claim 4 or 5. The skin evaluation pixel calculation means expands the blood vessel region by the number of times equal to the radius of the blood vessel image having the maximum diameter in the near-infrared light image.
The blood vessel position acquisition device according to any one of claims 4 to 6. The attention range is set to the number of pixels on one side based on the diameter of the blood vessel image having the maximum diameter in the near-infrared light image and the number of times the blood vessel region is expanded by one pixel. A square shape,
The attention range always includes the blood vessel evaluation pixel and the skin evaluation pixel.
The blood vessel position acquisition device according to any one of claims 4 to 7. The radius of the thickness of the blood vessel image in the attention range is set by dividing the number of pixels of the blood vessel region existing in the attention range by the number of pixels on one side of the attention range.
The blood vessel position acquisition device according to claim 8. The evaluation value calculation means excludes the difference value calculated in the attention range from the elements for calculating the blood vessel evaluation value when the blood vessel image in the attention range is branched.
The blood vessel position acquisition device according to any one of claims 4 to 9. The evaluation value calculation means, when the number of pixels of the blood vessel evaluation pixel in the attention range is different from a predetermined value or the number of pixels of the blood vessel evaluation pixel connected to the blood vessel evaluation pixel located at the center of the attention range, Excluding the difference value calculated in the attention range from the elements when calculating the blood vessel evaluation value;
The blood vessel position acquisition device according to any one of claims 4 to 10. The evaluation value calculation means excludes the difference value calculated in the attention range from elements when calculating the blood vessel evaluation value when the number of pixels of the skin evaluation pixels in the attention range is smaller than a predetermined value. ,
The blood vessel position acquisition device according to any one of claims 4 to 11. The evaluation value calculating means, when the difference value in the range of interest is smaller than a predetermined value, excludes the difference value from an element when calculating the blood vessel evaluation value;
The blood vessel position acquisition device according to any one of claims 4 to 12. The blood vessel evaluation value calculating means calculates the blood vessel evaluation value for an evaluation range limited to the vicinity of the center in the near-infrared light image.
The blood vessel position acquisition apparatus according to any one of claims 1 to 3. A reduced image creating means for creating a reduced near infrared light image obtained by reducing the near infrared light image photographed by the image photographing means;
The blood vessel region extracting means extracts the blood vessel region with respect to the reduced near infrared light image,
The blood vessel evaluation value calculating means calculates the blood vessel evaluation value for the reduced near-infrared light image;
The blood vessel position acquisition apparatus according to any one of claims 1 to 3. The reduced image creating means determines the magnification so that the diameter of the blood vessel image having the maximum diameter in the near infrared light image is constant, and reduces the near infrared light image.
The blood vessel position acquisition apparatus according to claim 15. The imaging condition set in the imaging condition setting means is a light amount of the near infrared light that irradiates the living body.
The blood vessel position acquisition device according to claim 1. The imaging condition set in the imaging condition setting means is the wavelength of the near infrared light that irradiates the living body.
The blood vessel position acquisition device according to any one of claims 1 to 16. The shooting condition set in the shooting condition setting means is a pass band of an optical filter that passes only a specific wavelength.
The blood vessel position acquisition device according to any one of claims 1 to 16. The photographing condition set in the photographing condition setting means is an aperture value of the image photographing means for photographing the living body.
The blood vessel position acquisition device according to any one of claims 1 to 16. The shooting condition setting means sets a parameter for setting the shooting condition so as to change from a small value to a large value, or in proportion to a small value from a large value,
The imaging condition determining means, except for the case where the value has changed more than a predetermined value before and after the blood vessel evaluation value continuous in the time axis direction among the plurality of blood vessel evaluation values obtained by the blood vessel evaluation value calculating means, Determine optimal shooting conditions,
The blood vessel position acquisition device according to claim 1. A shooting condition setting step for setting shooting conditions when shooting a living body;
An image capturing step for capturing reflected light or transmitted light from the living body irradiated with near-infrared light based on the capturing conditions and generating a near-infrared light image;
A blood vessel region extracting step of extracting a blood vessel image in the near-infrared light image as a blood vessel region;
Determining a blood vessel evaluation pixel and a skin evaluation pixel adjacent to the blood vessel region based on the blood vessel region, and calculating a blood vessel evaluation value for evaluating the blood vessel region;
An imaging condition determining step for determining an optimal imaging condition based on the blood vessel evaluation value calculated in the blood vessel evaluation calculating step;
A blood vessel position acquisition method comprising: The blood vessel evaluation value calculating step calculates the blood vessel evaluation value by subtracting the luminance value of the blood vessel evaluation pixel from the luminance value of the skin evaluation pixel.
The blood vessel position acquisition method according to claim 22. The blood vessel evaluation value calculating step calculates the blood vessel evaluation value in a plurality of the imaging conditions,
The imaging condition determining step determines the imaging condition when the blood vessel evaluation value is maximum as the optimum imaging condition.
The blood vessel position acquisition method according to claim 22 or 23. The blood vessel evaluation value calculation step includes
A blood vessel evaluation pixel calculation step in which the pixel at the center in the width direction of the blood vessel region is the blood vessel evaluation pixel;
A skin evaluation pixel calculation step in which a contour pixel of the blood vessel region is expanded by a predetermined pixel outward in the width direction, and the expanded pixel is a skin evaluation pixel;
Using the luminance value of the blood vessel evaluation pixel existing in the attention range from the skin representative value obtained using the luminance value of the skin evaluation pixel existing in the attention range centering on one of the blood vessel evaluation pixels. The difference value obtained by subtracting the blood vessel representative value obtained in this manner is obtained at each of the blood vessel evaluation pixel positions in the near-infrared light image, and the blood vessel evaluation value is calculated by adding all the difference values. Process,
The blood vessel position acquisition method according to any one of claims 22 to 24, comprising: A reduced image creation step of creating a reduced near infrared light image obtained by reducing the near infrared light image captured in the image photographing step;
The blood vessel region extraction step extracts the blood vessel region with respect to the reduced near-infrared light image,
The blood vessel evaluation value calculating step calculates the blood vessel evaluation value for the reduced near-infrared light image.
The blood vessel position acquisition method according to any one of claims 22 to 25.

Images