Patent Description:
A distance to an object to be observed, the size of the object t be observed, and the like are acquired in an endoscope apparatus. In, for example, <CIT> (<CIT>), a subject is illuminated with illumination light and measurement spotlight and an object to be observed is measured using the position of the spotlight illuminated on the subject. In <CIT> (<CIT>), a saturation peculiar to the color of the spotlight is extracted to detect the position of the spotlight. For example, <CIT> discloses an automatic extracting method for pattern light in a shape measuring endoscope. When an image with halation and rupture is obtained, a black-and-white image is generated. Circumscribed rectangles of regions <NUM>'-<NUM>' are generated, and coordinates of end sections in the pattern direction (Y-coordinate) are obtained. Lengths in the Y-axis direction are obtained. The lengths are compared. When the maximum length is detected, this region is judged as the true pattern light, and this pattern light is extracted. Whether it is overlapped on the Y-coordinate of other region or not is retrieved, and the overlapped region is referred as halation and removed.

In a case where auxiliary measurement light, such as measurement spotlight, is used to measure an object to be observed as in <CIT> (<CIT>), the irradiation position of the auxiliary measurement light on the subject needs to be reliably detected. However, a noise component hindering the detection of the irradiation position of the auxiliary measurement light may be included in a picked-up image that is obtained from the image pickup of the subject illuminated with the auxiliary measurement light and the illumination light. In a case where the noise component is included as described above and, for example, the color of the noise component is substantially the same as the color of the auxiliary measurement light, it may be difficult to detect only the component of the auxiliary measurement light in "the extraction of saturation" disclosed in <CIT> (<CIT>).

An object of the present invention is to provide an endoscope apparatus that can remove noise components hindering the detection of the irradiation position of auxiliary measurement light used to measure a subject.

The present invention relates to an endoscope apparatus with the features of independent claim <NUM>. An endoscope apparatus according to an embodiment of the present invention comprises an illumination light source unit that emits illumination light used to illuminate a subject, an auxiliary measurement light source unit that emits auxiliary measurement light, and a processor. The processor acquires a picked-up image that is obtained from image pickup of the subject illuminated with the illumination light and the auxiliary measurement light and includes at least two first and second spectral images having different wavelength components, obtains a first arithmetic image from which a first noise component hindering detection of an irradiation position of the auxiliary measurement light is removed by first arithmetic processing based on the first and second spectral images, detects the irradiation position of the auxiliary measurement light from the first arithmetic image, and displays a specific image in which a measurement marker set according to the irradiation position of the auxiliary measurement light is superimposed on the picked-up image.

According to the invention, in a case where the processor performs first binarization processing of obtaining a binarized first spectral image by binarizing the first spectral image and second binarization processing of obtaining a binarized second spectral image by binarizing the second spectral image, the processor performs first difference processing of the binarized first spectral image and the binarized second spectral image as the first arithmetic processing. It is preferable that the picked-up image includes a third spectral image having a wavelength component different from the wavelength components of the first and second spectral images and the processor obtains a second arithmetic image from which a second noise component different from the first noise component is removed by second arithmetic processing based on the first arithmetic image and the third spectral image. It is preferable that, in a case where the processor performs third binarization processing of obtaining a binarized third spectral image by binarizing the third spectral image, the processor performs second difference processing of the first arithmetic image and the binarized third spectral image as the second arithmetic processing.

It is preferable that the first spectral image is a red image and the second spectral image is a green image. It is preferable that the third spectral image is a red image. It is preferable that a threshold value condition for the first binarization processing is changed by a histogram of the first spectral image and a threshold value condition for the second binarization processing is changed by a histogram of the second spectral image. It is preferable that a threshold value condition for the third binarization processing is changed by a histogram of the third spectral image. It is preferable that the histogram is a histogram of an image, which corresponds to a specific range other than an illumination position-movable range of the auxiliary measurement light, in the picked-up image.

It is preferable that the measurement marker includes a first measurement marker showing an actual size of the subject or a second measurement marker consisting of a crossing line formed on the subject by the auxiliary measurement light and gradations formed on the crossing line and serving as an index of a size of the subject.

According to the present invention, it is possible to remove noise components hindering the detection of the irradiation position of auxiliary measurement light used to measure a subject.

As shown in <FIG>, an endoscope apparatus <NUM> includes an endoscope <NUM>, a light source device <NUM>, a processor device <NUM>, a monitor <NUM>, and a user interface <NUM>. The endoscope <NUM> is optically connected to the light source device <NUM>, and is electrically connected to the processor device <NUM>. The processor device <NUM> is electrically connected to the monitor <NUM> (display unit) that displays an image. The user interface <NUM> is connected to the processor device <NUM>, and is used for various setting operations and the like for the processor device <NUM>. The user interface <NUM> includes a mouse and the like (not shown) in addition to a keyboard.

The endoscope <NUM> includes an insertion part 12a that is to be inserted into an object to be examined, an operation part 12b that is provided at the proximal end portion of the insertion part 12a, and a bendable part 12c and a distal end part 12d that are provided on the distal end side of the insertion part 12a. The bendable part 12c operates to be bent by the operation of angle knobs 12e of the operation part 12b. The distal end part 12d is made to face in a desired direction by the bending operation of the bendable part 12c.

The endoscope <NUM> has a normal light observation mode and a length measurement mode, and these two modes are switched by a mode changeover switch 13a that is provided on the operation part 12b of the endoscope <NUM>. The normal light observation mode is a mode where an object to be observed is illuminated with illumination light. In the length measurement mode, an object to be observed is illuminated with illumination light and auxiliary measurement light and a measurement marker to be used to measure the size of the object to be observed or the like is displayed in a picked-up image obtained from the image pickup of the object to be observed. Auxiliary measurement light is light that is used to measure a subject.

Further, the operation part 12b of the endoscope <NUM> is provided with a freeze switch 13b that is used to give a static image-acquisition instruction to acquire the static image of a picked-up image. In a case where a user operates the freeze switch 13b, the screen of the monitor <NUM> is frozen and displayed and an alert sound (for example, "beep") informing the acquisition of a static image is generated together. Then, the static images of the picked-up image, which are obtained before and after the operation timing of the freeze switch 13b, are stored in a static image storage unit <NUM> (see <FIG>) provided in the processor device <NUM>. Furthermore, it is preferable that measurement information to be described later is also stored together with the static image of the picked-up image in a case where the endoscope <NUM> is set to the length measurement mode. The static image storage unit <NUM> is a storage unit, such as a hard disk or a universal serial bus (USB) memory. In a case where the processor device <NUM> can be connected to a network, the static image of the picked-up image may be stored in a static image storage server (not shown), which is connected to a network, instead of or in addition to the static image storage unit <NUM>.

A static image-acquisition instruction may be given using an operation device other than the freeze switch 13b. For example, a foot pedal may be connected to the processor device <NUM>, and a static image-acquisition instruction may be given in a case where a user operates the foot pedal (not shown) with a foot. A static image-acquisition instruction may be given by a foot pedal that is used to switch a mode. Further, a gesture recognition unit (not shown), which recognizes the gestures of a user, may be connected to the processor device <NUM>, and a static image-acquisition instruction may be given in a case where the gesture recognition unit recognizes a specific gesture of a user. The gesture recognition unit may also be used to switch a mode.

Furthermore, a sight line input unit (not shown), which is provided close to the monitor <NUM>, may be connected to the processor device <NUM>, and a static image-acquisition instruction may be given in a case where the sight line input unit recognizes that a user's sight line is in a predetermined region of the monitor <NUM> for a predetermined time or longer. Further, a voice recognition unit (not shown) may be connected to the processor device <NUM>, and a static image-acquisition instruction may be given in a case where the voice recognition unit recognizes a specific voice generated by a user. The voice recognition unit may also be used to switch a mode. Furthermore, an operation panel (not shown), such as a touch panel, may be connected to the processor device <NUM>, and a static image-acquisition instruction may be given in a case where a user makes a specific operation on the operation panel. The operation panel may also be used to switch a mode.

As shown in <FIG>, the distal end part of the endoscope <NUM> has a substantially circular shape; and is provided with an objective lens <NUM> that is positioned closest to a subject among optical members of an image pickup optical system of the endoscope <NUM>, an illumination lens <NUM> that is used to irradiate a subject with illumination light, an auxiliary measurement lens <NUM> that is used to illuminate a subject with auxiliary measurement light to be described later, an opening <NUM> that allows a treatment tool to protrude toward a subject, and an air/water supply nozzle <NUM> that is used to supply air and water.

An optical axis Ax of the objective lens <NUM> extends in a direction perpendicular to the plane of paper. A vertical first direction D1 is orthogonal to the optical axis Ax, and a horizontal second direction D2 is orthogonal to the optical axis Ax and the first direction D1. The objective lens <NUM> and the auxiliary measurement lens <NUM> are arranged in the first direction D1.

As shown in <FIG>, the light source device <NUM> comprises an illumination light source unit <NUM> and a light source control unit <NUM>. The illumination light source unit <NUM> generates illumination light that is used to illuminate a subject. Illumination light emitted from the illumination light source unit <NUM> is incident on a light guide <NUM>, and a subject is irradiated with illumination light through the illumination lens <NUM>. In the illumination light source unit <NUM>, a white light source emitting white light, a plurality of light sources, which includes a white light source and a light source emitting another color light (for example, a blue light source emitting blue light), or the like is used as a light source of illumination light. The light source control unit <NUM> is connected to a system control unit <NUM> of the processor device <NUM>. Mixed white light, which is a combination of blue light, green light, and red light, may be used as illumination light. In this case, it is preferable that the illumination lens <NUM> is optically designed to allow the irradiation range of green light to be wider than the irradiation range of red light.

The light source control unit <NUM> controls the illumination light source unit <NUM> on the basis of an instruction given from the system control unit <NUM>. The system control unit <NUM> not only instructs the light source control unit <NUM> to control a light source but also controls a light source 30a (see <FIG>) of an auxiliary measurement light-emitting unit <NUM>. In the normal light observation mode, the system control unit <NUM> performs control to turn on illumination light and to turn off auxiliary measurement light. In the length measurement mode, the system control unit <NUM> performs control to turn on illumination light and to turn on auxiliary measurement light.

An illumination optical system 29a, an image pickup optical system 29b, and an auxiliary measurement light-emitting unit <NUM> are provided in the distal end part 12d of the endoscope <NUM>. The illumination optical system 29a includes the illumination lens <NUM>, and an object to be observed is irradiated with light, which is emitted from the light guide <NUM>, through the illumination lens <NUM>. The image pickup optical system 29b includes the objective lens <NUM> and an image pickup element <NUM>. Light reflected from the object to be observed is incident on the image pickup element <NUM> through the objective lens <NUM>. Accordingly, the reflected image of the object to be observed is formed on the image pickup element <NUM>.

The image pickup element <NUM> is a color image pickup sensor, and picks up the reflected image of an object to be examined and outputs image signals. It is preferable that the image pickup element <NUM> is a charge coupled device (CCD) image pickup sensor, a complementary metal-oxide semiconductor (CMOS) image pickup sensor, or the like. The image pickup element <NUM> used in an embodiment of the present invention is a color image pickup sensor that is used to obtain red images, green images, and blue images having three colors of R (red), G (green), and B (blue). The red images are images that are output from red pixels provided with red color filters in the image pickup element <NUM>. The green images are images that are output from green pixels provided with green color filters in the image pickup element <NUM>. The blue images are images that are output from blue pixels provided with blue color filters in the image pickup element <NUM>. The image pickup element <NUM> is controlled by an image pickup control unit <NUM>.

Image signals output from the image pickup element <NUM> are transmitted to a CDS/AGC circuit <NUM>. The CDS/AGC circuit <NUM> performs correlated double sampling (CDS) or auto gain control (AGC) on the image signals that are analog signals. The image signals, which have been transmitted through the CDS/AGC circuit <NUM>, are converted into digital image signals by an analog/digital converter (A/D converter) <NUM>. The digital image signals, which have been subjected to A/D conversion, are input to the processor device <NUM> through a communication interface (I/F) <NUM>.

In the processor device <NUM>, various programs used to perform various kinds of processing or functions are stored in a program memory. Various programs are operated by the system control unit <NUM> formed of a processor, so that the processor device <NUM> realizes the functions of a communication interface (I/F) <NUM> (image acquisition unit) connected to the communication I/F <NUM> of the endoscope <NUM>, a signal processing unit <NUM>, and a display control unit <NUM>. Accordingly, the functions of a first signal processing section <NUM> and a second signal processing section included in the signal processing unit <NUM> are realized. Further, the functions of a mask processing section <NUM>, a binarization processing section <NUM>, a noise component-removal section <NUM>, and an irradiation position-detection section <NUM> included in the first signal processing section <NUM> are realized.

The communication I/F receives the image signals, which are transmitted from the communication I/F <NUM> of the endoscope <NUM>, and transmits the image signals to the signal processing unit <NUM>. A memory, which temporarily stores the image signals received from the communication I/F <NUM>, is built in the signal processing unit <NUM>, and the signal processing unit <NUM> processes an image signal group, which is a set of the image signals stored in the memory, to generate the picked-up image. In a case where the endoscope <NUM> is set to the length measurement mode, the signal processing unit <NUM> may be adapted to perform structure-emphasis processing of emphasizing structures, such as blood vessels, or color difference-emphasis processing of increasing a color difference between a normal area and a lesion area of the object to be observed on the picked-up image.

The display control unit <NUM> causes the monitor <NUM> to display the picked-up image that is generated by the signal processing unit <NUM>. The system control unit <NUM> performs the control of the image pickup element <NUM> through the image pickup control unit <NUM> provided in the endoscope <NUM>. The image pickup control unit <NUM> also performs the control of the CDS/AGC circuit <NUM> and the A/D converter <NUM> together with the control of the image pickup element <NUM>.

As shown in <FIG>, the auxiliary measurement light-emitting unit <NUM> (auxiliary measurement light source unit) comprises a light source 30a, a diffractive optical element (DOE) 30b, a prism 30c, and the auxiliary measurement lens <NUM>. The light source 30a is to emit light having a color that can be detected by pixels of the image pickup element <NUM> (specifically visible light), and includes a light-emitting element, such as a laser light source LD (laser diode) or a light emitting diode (LED), and a condenser lens that condenses light emitted from the light-emitting element.

Red laser light having a wavelength in the range of, for example, <NUM> to <NUM> is used in this embodiment as light that is emitted from the light source 30a. However, light having a wavelength in other ranges, for example, green light having a wavelength in the range of, for example, <NUM> to <NUM> may be used. It is preferable that the red laser light has high directivity. Further, it is preferable that the central portion of a region irradiated with the red laser light is illuminated with a large amount of light that is enough to cause halation (pixel saturation) in the image pickup element <NUM>. The light source 30a is controlled by the system control unit <NUM> and emits light on the basis of an instruction given from the system control unit <NUM>. The DOE 30b converts the light, which is emitted from the light source, into auxiliary measurement light that is used to obtain measurement information.

A blue laser light source or a green laser light source may be used as the laser light source in addition to a red laser light source, but it is preferable that a red laser light source is used since a blue laser light source or a green laser light source requires high cost for a user at the time of introduction and maintenance. However, red laser light may be mixed with a red color caused by a human body in the case of a red laser light source, but this problem can be solved since the red color caused by a human body can be removed by processing of removing noise components to be described later and only red laser light, which is auxiliary measurement light, can be extracted.

The prism 30c is an optical member that is used to change the travel direction of auxiliary measurement light converted by the DOE 30b. The prism 30c changes the travel direction of auxiliary measurement light so that the auxiliary measurement light crosses the visual field of the image pickup optical system including the objective lens <NUM> and lens groups. The details of the travel direction of auxiliary measurement light will also be described later. A subject is irradiated with auxiliary measurement light Lm, which is emitted from the prism 30c, through the auxiliary measurement lens <NUM>. In a case where the subject is irradiated with the auxiliary measurement light, a spot SP as a circular region is formed on the subject as shown in <FIG>. The position of the spot SP (the irradiation position of the auxiliary measurement light) is detected by the irradiation position-detection section <NUM> (see <FIG>), and a measurement marker showing an actual size is set according to the position of the spot SP. The set measurement marker is displayed in the picked-up image. Plural kinds of measurement markers, such as a first measurement marker and a second measurement marker, are included in the measurement marker as described later, and a measurement marker to be displayed in the picked-up image among the plural kinds of measurement markers can be selected according to a user's instruction. For example, the user interface <NUM> is used for the user's instruction.

An auxiliary measurement slit formed in the distal end part 12d of the endoscope may be used instead of the auxiliary measurement lens <NUM>. Further, it is preferable that an anti-reflection coating (AR coating) (anti-reflection portion) is provided on the auxiliary measurement lens <NUM>. The reason why the anti-reflection coating is provided as described above is that it is difficult for the irradiation position-detection section <NUM> to be described later to recognize the position of the spot SP formed on the subject by auxiliary measurement light in a case where the auxiliary measurement light is reflected without being transmitted through the auxiliary measurement lens <NUM> and a ratio of the auxiliary measurement light with which a subject is irradiated is reduced.

The auxiliary measurement light-emitting unit <NUM> has only to be capable of emitting auxiliary measurement light to the visual field of the image pickup optical system. For example, the light source 30a may be provided in the light source device and light emitted from the light source 30a may be guided to the DOE 30b by optical fibers. Further, the prism 30c may not be used and the directions of the light source 30a and the DOE 30b may be inclined with respect to the optical axis Ax so that auxiliary measurement light Lm is emitted in a direction crossing the visual field of the image pickup optical system.

With regard to the travel direction of auxiliary measurement light, auxiliary measurement light Lm is emitted in a state where an optical axis Lm of the auxiliary measurement light Lm crosses the optical axis Ax of the objective lens <NUM> as shown in <FIG>. In a case where a subject can be observed in a range Rx of an observation distance, it is understood that the positions (points where the respective arrows Qx, Qy, and Qz cross the optical axis Ax) of the spot SP, which is formed on the subject by the auxiliary measurement light Lm, in image pickup ranges (shown by arrows Qx, Qy, and Qz) at a near end Px, an intermediate vicinity Py, and a far end Pz of the range Rx are different from each other. The image pickup angle of view of the image pickup optical system is represented by a region between two solid lines <NUM>, and measurement is performed in a central region (a region between two dotted lines <NUM>), in which an aberration is small, of this image pickup angle of view.

Since the auxiliary measurement light Lm is emitted in a state where the optical axis Lm of the auxiliary measurement light crosses the optical axis Ax as described above, sensitivity to the movement of the position of the spot with respect to a change in the observation distance is high. Accordingly, the size of the subject can be measured with high accuracy. Then, the image of the subject illuminated with the auxiliary measurement light is picked up by the image pickup element <NUM>, so that a picked-up image including the spot SP is obtained. In the picked-up image, the position of the spot SP varies depending on a relationship between the optical axis Ax of the objective lens <NUM> and the optical axis Lm of the auxiliary measurement light Lm and an observation distance. However, the number of pixels showing the same actual size (for example, <NUM>) is increased in the case of a short observation distance, and the number of pixels showing the same actual size (for example, <NUM>) is reduced in the case of a long observation distance.

Accordingly, in a case where information showing a relationship between the position of the spot SP and measurement information (the number of pixels) corresponding to the actual size of a subject is stored in advance as described in detail later, the measurement information can be calculated from the position of the spot SP.

As shown in <FIG>, the signal processing unit <NUM> of the processor device <NUM> comprises a first signal processing section <NUM> and a second signal processing section <NUM> to recognize the position of the spot SP and to set a measurement marker. The first signal processing section <NUM> detects the position of the spot SP in the picked-up image, and the second signal processing section <NUM> sets a measurement marker according to the position of the spot SP. A specific image is caused to be displayed on the monitor <NUM> by the display control unit <NUM>. In a case where the endoscope <NUM> is set to the normal light observation mode, the picked-up image of a subject illuminated with illumination light is input to the signal processing unit <NUM>. In a case where the endoscope <NUM> is set to the length measurement mode, the picked-up image of the subject illuminated with illumination light and auxiliary measurement light is input to the signal processing unit <NUM>. The picked-up image is acquired by the communication I/F <NUM> (image acquisition unit) connected to the endoscope <NUM>.

The first signal processing section <NUM> comprises the mask processing section <NUM>, the binarization processing section <NUM>, the noise component-removal section <NUM>, and the irradiation position-detection section <NUM>. Processing of removing noise components in the first signal processing section <NUM> will be described with reference to <FIG>. The mask processing section <NUM> performs mask processing of extracting a substantially parallelogram-shaped illumination position-movable range Wx, which represents the movable range of the illumination position of the auxiliary measurement light on the subject, on a red image (first spectral image), a green image (second spectral image), and a blue image (third spectral image) of the picked-up image. Accordingly, a red image PRx, a green image PGx, and a blue image PBx from which the illumination position-movable ranges Wx have been extracted and which have been subjected to the mask processing are obtained as shown in <FIG> and <FIG>. Noise components are removed from pixels present in the illumination position-movable ranges, and the irradiation position of the spot SP is detected.

Next, the binarization processing section <NUM> obtains a binarized red image PRy (binarized first spectral image) by performing first binarization processing on pixels present in the illumination position-movable range in the red image PRx having been subjected to the mask processing. In the first binarization processing, as shown in <FIG>, as a threshold value condition for the first binarization processing, pixels having a pixel value of "<NUM>" or more are defined as "<NUM>" and pixels having a pixel value less than "<NUM>" are defined as "<NUM>". The spot SP, which is a component of the auxiliary measurement light, is detected by this first binarization processing. However, in the first binarization processing, a second noise component N2, which is halation (pixel saturation) caused by illumination light, is also detected in addition to a first noise component N1 that is a high-brightness component of a red component of the illumination light. These first and second noise components are factors that hinder the detection of the irradiation position of the spot SP. The threshold value condition refers to a condition that defines the range of the pixel value of a pixel defined as "<NUM>" by binarization and the range of the pixel value of a pixel defined as "<NUM>" by binarization in addition to a condition that is related to a threshold value indicating a boundary between the pixel value of a pixel defined as "<NUM>" by binarization and the pixel value of a pixel defined as "<NUM>" by binarization.

Then, in order to remove the first noise component, the noise component-removal section <NUM> performs first difference processing (first arithmetic processing) of the binarized red image PRy and a binarized green image PGy (binarized second spectral image) that is the green image PGx binarized by second binarization processing. The first noise component N1 has been removed in a first difference image PD1 (first arithmetic image) that is obtained from the first difference processing. However, the second noise component N2 often remains in the first difference image PD1 without being removed. The pixel value of a pixel, which is defined as "<NUM>" or less by the first difference processing, is set to "<NUM>". In the second binarization processing, as a threshold value condition for the second binarization processing, pixels having a pixel value in the range of "<NUM>" to "<NUM>" are defined as "<NUM>" and pixels having a pixel value in other ranges, that is, a pixel value equal to or larger than "<NUM>" and less than "<NUM>" or exceeding "<NUM>" are defined as "<NUM>". The first noise component is removed by the first difference processing of the binarized red image and the binarized green image, but the first noise component may be removed by other first arithmetic processing.

Further, in order to remove the second noise component, as shown in <FIG>, the noise component-removal section <NUM> performs second difference processing (second arithmetic processing) of the first difference image PD1 and a binarized blue image PBy (binarized third spectral image) that is the blue image PBx binarized by third binarization processing. The second noise component, which is difficult to be removed by the first difference processing, has been removed in a second difference image PD2 (second arithmetic image) that is obtained from the second difference processing. The pixel value of a pixel, which is defined as "<NUM>" or less by the second difference processing as in the first difference processing, is set to "<NUM>". In the third binarization processing, as a threshold value condition for the third binarization processing, pixels having a pixel value equal to or larger than "<NUM>" are defined as "<NUM>" and pixels having a pixel value less than "<NUM>" are defined as "<NUM>". The second noise component is removed by the second difference processing of the first difference image and the binarized blue image, but the second noise component may be removed by other second arithmetic processing.

With regard to the threshold value conditions for the first, second, and third binarization processing, there is a case where it is difficult to reliably detect the irradiation position of the spot SP and it is difficult to reliably remove the first and second noise components due to a variation in the sensitivity of the image pickup element <NUM> of each endoscope <NUM>. Accordingly, it is preferable that threshold value change processing of changing the threshold value conditions for the first, second, and third binarization processing is performed using the histogram of an image of a specific range Wy other than the illumination position-movable range Wx. For example, in the case of the threshold value condition for the first binarization processing, as shown in <FIG>, pixels having a pixel value of "<NUM>" or more are defined as "<NUM>" before threshold value change processing based on a histogram but pixels defined as "<NUM>" are changed to pixels having a pixel value, which is equal to or larger than a pixel value smaller than, for example, "<NUM>", by threshold value change processing based on a histogram of the specific range Wy of a red image. The histogram of an image is a graph showing the frequency distribution of pixel values included in the image, and can show a pixel value on a horizontal axis and show the frequency of a pixel value on a vertical axis in the case of a two-dimensional graph. Further, in the length measurement mode, threshold value change processing different from that of the normal light observation mode may be performed in the case of a special light observation mode in which special light, such as light including light of which a specific wavelength range is narrowed is used.

The irradiation position-detection section <NUM> detects the irradiation position of the spot SP from the first difference image or the second difference image. It is preferable that the coordinates of the position of the centroid of the spot SP are acquired in the irradiation position-detection section <NUM> as the irradiation position of the spot SP.

The second signal processing section <NUM> sets a first measurement marker, which shows the actual size of a subject, as a measurement marker on the basis of the position of the spot SP. The second signal processing section <NUM> calculates the size of a marker from the position of the spot with reference to a marker table <NUM> in which a relationship between the position of the spot SP and the first measurement marker showing the actual size of the subject is stored. Then, the second signal processing section <NUM> sets a first measurement marker corresponding to the size of the marker. In a case where the setting of the first measurement marker is completed, the display control unit <NUM> causes the monitor <NUM> to display a specific image in which the first measurement marker is superimposed on a picked-up image obtained from the image pickup of a subject illuminated with illumination light so that the spot SP is positioned at the center of the first measurement marker.

For example, a cruciform measurement marker is used as the first measurement marker. In this case, as shown in <FIG>, a cruciform marker M1, which shows an actual size of <NUM> (a horizontal direction and a vertical direction of the picked-up image), is displayed at the center of a spot SP1 formed on a tumor tm1 of a subject in a case where an observation distance is close to the near end Px. Since the tumor tm1 and a range determined by the cruciform marker M1 substantially coincide with each other, the size of the tumor tm1 can be measured as about <NUM>. The spot is not displayed and only the first measurement marker may be displayed in the picked-up image.

Likewise, as shown in <FIG>, a cruciform marker M2, which shows an actual size of <NUM> (the horizontal direction and the vertical direction of the picked-up image), is displayed at the center of a spot SP2 formed on a tumor tm2 of a subject in a case where an observation distance is close to the intermediate vicinity Py. Further, as shown in <FIG>, a cruciform marker M3, which shows an actual size of <NUM> (the horizontal direction and the vertical direction of the picked-up image), is displayed at the center of a spot SP3 formed on a tumor tm3 of a subject. Since the position of the spot on the image pickup surface of the image pickup element <NUM> varies depending on an observation distance as described above, a position where the marker is displayed also varies. As shown in <FIG> having been described above, the size of the first measurement marker corresponding to the same actual size of <NUM> is reduced with an increase in an observation distance.

In <FIG>, the center of the spot SP and the center of the marker are displayed to coincide with each other. However, the first measurement marker may be displayed at a position away from the spot SP in a case where there is no problem in measurement accuracy. Even in this case, it is preferable that the first measurement marker is displayed near the spot. Furthermore, the distorted first measurement marker is not displayed, and the distortion of the picked-up image may be corrected so that an undistorted first measurement marker may be displayed in a corrected picked-up image.

Further, the first measurement marker corresponding to the actual size of the subject, which is <NUM>, is displayed in <FIG>, but the actual size of the subject may be set to any value (for example, <NUM>, <NUM>, <NUM>, or the like) according to an object to be observed or the purpose of observation. Furthermore, the first measurement marker has a cruciform shape where a vertical line and a horizontal line are orthogonal to each other in <FIG>, but may have a cruciform shape with gradations where gradations Mx are given to at least one of a vertical line or a horizontal line of a cruciform shape as shown in <FIG>. Further, the first measurement marker may have a distorted cruciform shape of which at least one of a vertical line or a horizontal line is inclined. Furthermore, the first measurement marker may have a circular-and-cruciform shape where a cruciform shape and a circle are combined with each other. In addition, the first measurement marker may have the shape of a measurement point group where a plurality of measurement points EP corresponding to an actual size from a spot are combined with each other. Further, one first measurement marker may be displayed or a plurality of first measurement markers may be displayed, and the color of the first measurement marker may be changed according to an actual size.

A method of creating the marker table <NUM> will be described below. A relationship between the position of a spot and the size of a marker can be obtained from image pickup of a chart in which a pattern having an actual size is regularly formed. For example, auxiliary measurement light having the shape of a spot is emitted to a chart, and the image of a graph paper-shaped chart including ruled lines having an interval (<NUM>) equal to an actual size or ruled lines having an interval (for example, <NUM>) smaller than the actual size is picked up while an observation distance is changed to change the position of the spot. As a result, a relationship between the position of the spot (the coordinates of a pixel on the image pickup surface of the image pickup element <NUM>) and the number of pixels corresponding to the actual size (the number of pixels representing an actual size of <NUM>) is acquired.

As shown in <FIG>, (x1,y1) is the position of a pixel of a spot SP4 in the X and Y directions on the image pickup surface of the image pickup element <NUM> (an upper left point is the origin of a coordinate system). The number of pixels in the X direction corresponding to an actual size of <NUM> at the position (x1,y1) of the spot SP4 is denoted by Lx1, and the number of the pixels in the Y direction corresponding to the actual size at the position is denoted by Ly1. Such a measurement is repeated while an observation distance is changed. <FIG> shows a state where the image of a chart including ruled lines having the same interval, which is <NUM>, as that in <FIG> is picked up, but is a state where an observation distance is closer to the far end than in the state shown in <FIG> and an interval between the ruled lines is displayed so as to be narrower. In the state shown in <FIG>, the number of pixels in the X direction corresponding to an actual size of <NUM> at the position (x2,y2) of a spot SP5 on the image pickup surface of the image pickup element <NUM> is denoted by Lx2, and the number of the pixels in the Y direction corresponding to the actual size at the position is denoted by Ly2. Further, measurement shown in <FIG> and <FIG> is repeated while an observation distance is changed; and results thereof are plotted. The chart is shown in <FIG> and <FIG> without the consideration of the distortion of the objective lens <NUM>.

<FIG> shows a relationship between the X-coordinate of the position of a spot and Lx (the number of pixels in the X direction), and <FIG> shows a relationship between the Y-coordinate of the position of a spot and Lx. Lx is expressed as Lx=g1(x) from the relationship shown in <FIG> as the function of a position in the X direction, and Lx is expressed as Lx=g2(y) from the relationship shown in <FIG> as the function of a position in the Y direction. g1 and g2 can be obtained from the above-mentioned plotted results by, for example, a least square method.

Since the X-coordinate and the Y-coordinate of a spot have a one-to-one correspondence, basically the same results (the same number of pixels for the same position of a spot) are obtained even though any one of the function g1 or g2 is used. Accordingly, in a case where the size of the first measurement marker is to be calculated, either function may be used and a function having higher sensitivity of a change in the number of pixels to a change in a position may be selected between g1 and g2. Further, in a case where the values of g1 and g2 are significantly different from each other, it may be determined that "the position of a spot could not be recognized".

<FIG> shows a relationship between the X-coordinate of the position of a spot and Ly (the number of pixels in the Y direction), and <FIG> shows a relationship between the Y-coordinate of the position of a spot and Ly. Ly is expressed as Ly=h1(x) from the relationship shown in <FIG> as the coordinate of a position in the X direction, and Ly is expressed as Ly=h2(y) from the relationship shown in <FIG> as the coordinate of a position in the Y direction. Any one of the function h1 or h2 may be used as Ly as with Lx.

The functions g1, g2, h1, and h2 obtained as described above are stored in the marker table in a look-up table format. The functions g1 and g2 may be stored in the marker table in a function format.

As shown in <FIG>, three concentric circular markers M4A, M4B, and M4C having different sizes (diameters as the sizes are <NUM>, <NUM>, and <NUM>, respectively) may be displayed in the picked-up image as the first measurement marker so that a spot SP4 formed on a tumor tm4 is positioned at the centers of the markers. Since the three concentric circular markers are displayed as a plurality of markers, time and effort required to switch a marker can be saved and measurement can be performed even in a case where a subject has a non-linear shape. In a case where a plurality of concentric circular markers are to be displayed so that a spot is positioned at the centers of the concentric circular markers, a size and a color are not designated for each marker and combinations of a plurality of conditions may be prepared in advance and one can be selected from these combinations.

In <FIG>, all the three concentric circular markers are displayed with the same color (black). However, in a case where a plurality of concentric circular markers are to be displayed, a plurality of color concentric circular markers of which colors are different from each other may be used. As shown in <FIG>, a marker M5A is displayed by a dotted line representing a red color, a marker M5B is displayed by a solid line representing a blue color, and a marker M5C is displayed by a one-dot chain line representing a white color. Since identifiability can be improved in a case where the colors of the markers are different from each other in this way, measurement can be easily performed.

Further, as shown in <FIG>, a plurality of distorted concentric circular markers, which are distorted from the respective concentric circles, may be used as the first measurement marker other than the plurality of concentric circular markers. In this case, distorted concentric circular markers M6A, M6B, and M6C are displayed in the picked-up image so that a spot SP5 formed on a tumor tm5 is positioned at the centers of the distorted concentric circular markers.

Light that forms a spot in a case where a subject is irradiated with the light is used as auxiliary measurement light, but other light may be used. For example, planar auxiliary measurement light that forms a crossing line <NUM> on a subject as shown in <FIG> may be used in a case where the subject is irradiated with light. In this case, a second measurement marker that consists of the crossing line <NUM> and gradations <NUM> formed on the crossing line and serving as an index of the size of the subject (for example, a polyp P) is generated as a measurement marker. In a case where planar auxiliary measurement light is used, the irradiation position-detection section <NUM> detects the position of the crossing line <NUM> (the irradiation position of auxiliary measurement light). An observation distance is shorter as the crossing line <NUM> is positioned closer to the lower side, and an observation distance is longer as the crossing line <NUM> is positioned closer to the upper side. For this reason, an interval between the gradations <NUM> is larger as the crossing line <NUM> is positioned closer to the lower side, and an interval between the gradations <NUM> is smaller as the crossing line <NUM> is positioned closer to the upper side.

In the embodiment, the hardware structures of processing units, which perform various kinds of processing, such as the signal processing unit <NUM>, the display control unit <NUM>, and the system control unit <NUM>, are various processors to be described later. Various processors include: a central processing unit (CPU) that is a general-purpose processor functioning as various processing units by executing software (program); a programmable logic device (PLD) that is a processor of which the circuit configuration can be changed after manufacture, such as a field programmable gate array (FPGA); a dedicated electrical circuit that is a processor having circuit configuration designed exclusively to perform various kinds of processing; and the like.

One processing unit may be formed of one of these various processors, or may be formed of a combination of two or more same kind or different kinds of processors (for example, a plurality of FPGAs, or a combination of a CPU and an FPGA). Further, a plurality of processing units may be formed of one processor. As an example where a plurality of processing units are formed of one processor, first, there is an aspect where one processor is formed of a combination of one or more CPUs and software as typified by a computer, such as a client or a server, and functions as a plurality of processing units. Second, there is an aspect where a processor fulfilling the functions of the entire system, which includes a plurality of processing units, by one integrated circuit (IC) chip as typified by System On Chip (SoC) or the like is used. In this way, various processing units are formed using one or more of the above-mentioned various processors as hardware structures.

Claim 1:
An endoscope apparatus (<NUM>) comprising:
an illumination light source unit (<NUM>) that emits illumination light used to illuminate a subject;
an auxiliary measurement light source unit (<NUM>) that emits auxiliary measurement light;
an image pickup optical system (29b), wherein an optical axis (Lm) of the auxiliary measurement light crosses an optical axis (Ax) of the image pickup optical system (29b); and
a processor (<NUM>),
wherein the processor is configured to acquire a picked-up image that is obtained from image pickup of the subject illuminated with the illumination light and the auxiliary measurement light and includes at least two first and second spectral images having different wavelength components, to obtain a first arithmetic image from which a first noise component hindering detection of an irradiation position of the auxiliary measurement light is removed by first arithmetic processing based on the first and second spectral images, to detect the irradiation position of the auxiliary measurement light from the first arithmetic image, and to display a specific image in which a measurement marker set according to the irradiation position of the auxiliary measurement light is superimposed on the picked-up image,
wherein in a case where the processor (<NUM>) performs first binarization processing of obtaining a binarized first spectral image by binarizing the first spectral image and second binarization processing of obtaining a binarized second spectral image by binarizing the second spectral image, the processor (<NUM>) is configured to perform first difference processing of the binarized first spectral image and the binarized second spectral image as the first arithmetic processing.