JP2013106692A - Spectrum endoscope device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spectrum endoscope device capable of capturing accurate spectral images by a simple device configuration and with high effective efficiency.SOLUTION: The spectrum endoscope device includes: an electronic endoscope; a light source device for supplying illumination light to the electronic endoscope; a band-pass filter for limiting incident light to the light of a prescribed wavelength range and emitting it; a wavelength filter unit for filtering the light made incident on one of a pair of transmission substrates and emitting a plurality of rays of band limited light having respectively different peak wavelengths within the prescribed wavelength range; and a plurality of color filters for emitting only the light of the transmission wavelength range among the incident light having respectively different transmission wavelength ranges within the prescribed wavelength range. In the wavelength filter unit, an interval between the pair of transmission substrates is changed so that each of the peak wavelengths of the plurality of rays of band limited light is included in at least one transmission wavelength range and the peak wavelengths of the band limited light adjacent to each other are included in the respectively different transmission wavelength ranges.

Description

  The present invention relates to a spectroscopic endoscope apparatus that includes an electronic endoscope and a light source device, and can capture a spectroscopic image.

  In recent years, in order to more effectively diagnose a lesion, an electronic endoscope apparatus that can capture a spectral image has been proposed. A spectral image is an image obtained by irradiating a lesion with light in a narrow wavelength band. For example, the state of a blood vessel in a living tissue can be diagnosed from a spectral image when light having a wavelength band that is absorbed by hemoglobin is irradiated.

  In addition, there is also research that identifies the reflection spectrum of a living tissue by capturing a spectral image while changing the wavelength of light irradiated to the living tissue, and thereby distinguishing between a healthy part and a lesioned part (for example, a tumor part or a cancer part). Has been made. For example, in order to distinguish between a healthy part and a lesioned part (tumor part and cancer part), the reflection spectrum intensity at a wavelength of 540 nm to 580 nm, the inclination of the reflection spectrum at a wavelength of 490 nm to 520 nm, the inclination of the reflection spectrum at 510 nm to 530 nm, It has been proposed to use it as a parameter for distinguishing between a healthy part and a lesioned part (Non-Patent Document 1).

  Such a reflection spectrum of a living tissue is obtained by using an electronic endoscope apparatus that can capture a spectral image by irradiating light of an arbitrary wavelength band as disclosed in Patent Document 1, for example. The electronic endoscope apparatus described in Patent Document 1 is configured to be able to irradiate light in an arbitrary wavelength band by using a Fabry-Perot interference filter as a wavelength filter. A Fabry-Perot interference filter is a parallel arrangement of a pair of transmission substrates having a reflection film formed on one side so that the reflection films face each other. Light incident on the transmission substrate is transmitted between the reflection films. It is a filter that emits light (band-limited light) having a peak in a specific wavelength band by repeatedly reflecting and interfering. The peak wavelength (resonance frequency) and free spectral region (difference between adjacent resonance peak frequencies) of the band-limited light emitted from the Fabry-Perot interference filter are determined by the distance between the reflective films, that is, the distance between the transmissive substrates. Therefore, it is possible to scan the peak wavelength of the band-limited light by configuring one transmissive substrate so as to be separable from the other and moving the one transmissive substrate by a piezoelectric actuator or the like.

Urs Utzinger, Molly Brewer, Elvio Silva, et al. “ReflectanceSpectroscopy for In Vivo Characterization of Ovarian Tissue”, Lasers in Surgeryand Medicine, 28: 56-66, 2001

JP 2008-183350 A

  As described above, it is extremely important to obtain spectral information in the wavelength range of 450 to 600 nm in order to discriminate between a healthy part and a lesion part based on the reflection spectrum of a living tissue. In order to realize this, for example, using an electronic endoscope device described in Patent Document 1, band-limited light having one peak wavelength is scanned at a predetermined scan pitch in a wavelength range of 450 to 600 nm. It is conceivable to have a configuration. However, in this case, in order to obtain one reflection spectrum, it is necessary to capture spectral images as many times as the scan pitch. To obtain an accurate reflection spectrum, at least 16 times (when the scan pitch is 10 nm) ) The above spectral image needs to be captured. For this reason, real-time processing is difficult, and it takes a long time to make a diagnosis based on the reflection spectrum (that is, based on information identifying a healthy part and a lesioned part).

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an accurate spectroscopic image of a specific wavelength band in a spectroscope capable of capturing an accurate spectroscopic image with a simple apparatus configuration and high effective efficiency. An endoscope apparatus is provided.

  In order to achieve the above object, a spectroscopic endoscope apparatus according to the present invention includes an electronic endoscope having an imaging element, a light source that emits white light, and supplies illumination light to the electronic endoscope. And a band-pass filter that is arranged in the optical path of the illumination light from the light source to the imaging device, and that emits light with the incident light limited to light in a predetermined wavelength range, and a reflective film is formed on the surfaces facing each other An optical path of illumination light from the light source to the image sensor, comprising: a pair of transmissive substrates; and a driving unit that changes a wavelength band of light passing through the pair of transmissive substrates by changing an interval between the pair of transmissive substrates. A wavelength filter unit that is disposed inside and filters a light incident on one of a pair of transmission substrates to emit a plurality of band-limited light having different peak wavelengths within a predetermined wavelength range, and from a light source to an image sensor Lighting A plurality of color filters that have different transmission wavelength ranges within a predetermined wavelength range and emit only light in the transmission wavelength range among incident light, and the wavelength filter unit includes: A pair of transmission substrates so that each of the peak wavelengths of the plurality of band-limited lights is included in at least one transmission wavelength range, and the peak wavelengths of the band-limited lights adjacent to each other are included in different transmission wavelength ranges. It is characterized by changing the interval between them.

  With such a configuration, it is possible to simultaneously obtain a plurality of spectral images having different wavelengths through different color filters, thereby reducing the time taken to acquire the spectral image.

  The predetermined wavelength range is 425 to 650 nm, and the wavelength filter unit is preferably configured to change the interval between the pair of transmission substrates within a range of 875 nm to 1250 nm.

  Further, each of the transmission wavelength ranges of the plurality of color filters can be configured to overlap at least part of the other transmission wavelength ranges. In this case, the plurality of color filters include an R filter whose transmission wavelength range is set to transmit red component light, and a G filter whose transmission wavelength range is set to transmit green component light. And a B filter in which a transmission wavelength range is set so as to transmit blue component light. According to such a configuration, it is possible to use a general image sensor for photographing a color image, and therefore it is possible to use the image data processing technique of a conventional spectroscopic endoscope apparatus.

  The band-pass filter includes a low-pass filter that cuts light having a longer wavelength than light in a predetermined wavelength range and a high-pass filter that cuts light having a shorter wavelength than light in the predetermined wavelength range. be able to.

  The reflective film is preferably formed by alternately depositing three or four layers of titanium oxide thin films and silicon oxide thin films from the transmission substrate side. According to such a configuration, it is possible to obtain band-limited light having a uniform intensity within a predetermined wavelength range, so that an accurate spectral image can be obtained.

  The thickness of the titanium oxide thin film is preferably about 54 nm, and the thickness of the silicon oxide thin film is preferably about 84 nm.

  As described above, according to the present invention, a spectroscopic endoscope apparatus that can capture an accurate spectral image in a specific wavelength band with a simple apparatus configuration and high effective efficiency is realized.

FIG. 1 is a block diagram of a spectroscopic endoscope apparatus according to an embodiment of the present invention. FIG. 2 is a spectral characteristic diagram of a color filter built in the spectral endoscope apparatus according to the embodiment of the present invention. FIG. 3 is a side view of a spectral filter and a bandpass filter built in the spectral endoscope apparatus according to the embodiment of the present invention. FIG. 4 is a table showing the relationship between the distance d of the optical thin film of the spectral filter and the peak wavelength of the band-limited light. FIG. 5 is a spectral characteristic diagram of the spectral filter. FIG. 6 is a diagram illustrating the relationship between the spectral characteristics of the spectral filter and the spectral characteristics of the bandpass filter. FIG. 7 is a diagram illustrating the relationship among the spectral characteristics of the spectral filter, the spectral characteristics of the bandpass filter, and the spectral characteristics of the color filter. FIG. 8 is an example of a look-up table showing the relationship between the distance d between the optical thin films, the peak wavelength of the band-limited light, and the R, G, and B filters. FIG. 9 illustrates spectral characteristics of the spectral filter according to the first embodiment. FIG. 10 illustrates spectral characteristics of the spectral filter according to the second embodiment. FIG. 11 shows spectral characteristics of the spectral filter according to the reference example.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram of a spectroscopic endoscope apparatus according to an embodiment of the present invention. The spectroscopic endoscope apparatus 1 of this embodiment includes an electronic endoscope 100, a processor 200, and a monitor 300. Further, the processor 200 includes a light source unit 400 and an image processing unit 500.

  The electronic endoscope 100 includes an insertion tube 110 that is inserted into a body cavity, and an objective optical system 121 is provided at a distal end portion (insertion tube distal end portion) 111 of the insertion tube 110. An image of the living tissue T around the insertion tube tip 111 by the objective optical system 121 is formed on the light receiving surface of the image sensor 141 built in the insertion tube tip 111. The image sensor 141 is an image sensor for color image imaging having a color filter 141a on its light receiving surface, and is, for example, a CCD (Charge Coupled Device). The color filter 141a is a so-called ON filter in which an R filter that transmits light of a red component, a G filter that transmits light of a green component, and a B filter that transmits light of a blue component are arranged in a checkered pattern. Each of the R, G, and B filters, which are chip filters, has spectral characteristics as shown in FIG. As shown in FIG. 2, the R filter of the present embodiment is a filter that transmits light having a wavelength of about 570 nm or more, the G filter is a filter that transmits light having a wavelength of about 470 nm to 620 nm, and the B filter is It is a filter that transmits light having a wavelength of about 530 nm or less.

  The image sensor 141 periodically outputs a video signal corresponding to an image formed on the light receiving surface (for example, every 1/30 seconds). The video signal output from the image sensor 141 is sent to the image processing unit 500 of the processor 200 via the cable 142.

  The image processing unit 500 includes an A / D conversion circuit 510, a temporary storage memory 520, a controller 530, a video memory 540, and a signal processing circuit 550. The A / D conversion circuit 510 performs A / D conversion on a video signal input from the imaging element 141 of the electronic endoscope 100 via the cable 142 and outputs digital image data. Digital image data output from the A / D conversion circuit 510 is sent to and stored in the temporary storage memory 520. The controller 530 processes one or a plurality of image data stored in the temporary storage memory 520 to generate one piece of display image data, and sends this to the video memory 540. For example, the controller 530 calculates display image data generated from a single image data, display image data in which images of a plurality of image data are arranged, or a plurality of image data to calculate a reflection spectrum of living tissue. Thus, display image data for identifying a healthy part and a lesion part, display image data for displaying a graph of a reflection spectrum of a living tissue obtained as a result of image calculation, and the like are generated in the video memory 540. Remember me. The signal processing circuit 550 converts display image data stored in the video memory 540 into a video signal of a predetermined format (for example, NTSC format) and outputs the video signal. The video signal output from the signal processing circuit 550 is input to the monitor 300. As a result, an endoscopic image captured by the electronic endoscope 100 is displayed on the monitor 300.

  The electronic endoscope 100 is provided with a light guide 131. The distal end portion 131 a of the light guide 131 is disposed in the vicinity of the insertion tube distal end portion 111, while the proximal end portion 131 b of the light guide 131 is connected to the processor 200. The processor 200 includes a light source unit 400 (described later) having a light source 430 that generates a large amount of white light WL, such as a xenon lamp, and the light generated by the light source unit 400 is based on the light guide 131. The light enters the end 131b. The light incident on the base end portion 131b of the light guide 131 is guided to the tip end portion 131a through the light guide 131 and is emitted from the tip end portion 131a. A lens 132 is provided in the vicinity of the distal end portion 131a of the light guide 131 at the distal end portion 111 of the insertion tube of the electronic endoscope 100. Light emitted from the distal end portion 131a of the light guide 131 passes through the lens 132. The light passes through and illuminates the living tissue T in the vicinity of the distal end portion 111 of the insertion tube.

  As described above, the processor 200 functions as a video processor that processes a video signal output from the image sensor 141 of the electronic endoscope 100 and illuminates the living tissue T in the vicinity of the insertion tip 111 of the electronic endoscope 100. It also has a function as a light source device that supplies illumination light to the light guide 131 of the electronic endoscope 100.

  The light source unit 400 of the processor 200 includes a light source 430, a collimator lens 440, a spectral filter 410, a filter control unit 420, a condenser lens 450, and a band pass filter 460. The white light WL emitted from the light source 430 becomes parallel light by the collimator lens 440, passes through the spectral filter 410 and the band pass filter 460, and then enters the base end portion 131 b of the light guide 131 by the condenser lens 450.

  FIG. 3 is a side view of the spectral filter 410 and the bandpass filter 460. In the present embodiment, the spectral filter 410 is a Fabry-Perot interference filter. Specifically, the spectral filter 410 includes a pair of transmissive substrates 411 and 412 that are arranged to face each other. As shown in FIG. 3, the transmission substrate 411 is located on the light source 430 side, and the transmission substrate 412 is located on the band pass filter 460 side. Optical thin films 411a and 412a are provided on the surfaces of the transmissive substrates 411 and 412 that face each other. The transmission substrates 411 and 412 are positioned so that their surface portions are perpendicular to the optical axis ax of the collimator lens 440 and the condenser lens 450.

  The optical thin films 411a and 412a are both DBR (Distributed Bragg Reflector) reflecting layers. The DBR reflective layer according to this embodiment is obtained by alternately stacking two types of thin films having different refractive indexes in three layers or four layers (that is, a total of six layers or eight layers), and optical thin films 411a and 412a are predetermined. In the interference condition facing each other at a distance of, a band pass filter having a very high transmittance (90% or more) for a predetermined wavelength can be configured.

  In the interference filter having such a configuration, incident light is repeatedly reflected between the optical thin films 411a and 412a facing each other, and in the process, components other than a plurality of specific wavelength regions are canceled by interference, Band-limited light LL having a wavelength region as a main component (having a plurality of peak wavelengths) is generated. The generated band-limited light LL is emitted toward the band-pass filter 460 through the transmission substrate 412.

It is known that the peak wavelength of the band-limited light LL that passes through the Fabry-Perot interference filter is determined by the distance d between the optical thin films 411a and 412a, and the following equation (Equation 1) holds.

Here, n is the refractive index of the substance between the optical thin films 411a and 412a, θ is the incident angle of light incident on the interference filter (that is, the internal incident angle measured between the optical thin films 411a and 412a), and k is The order of interference (a non-zero positive number) and λ _k indicate a specific resonant transmission wavelength (ie, the peak wavelength of the band-limited light LL). Number 1, also known as single-layer approximation, the combination of degree k and wavelength lambda _k satisfying Equation 1 are numerous and not unambiguous, a plurality of peak wavelengths are observed. The detailed design, the simulation of the optical thin film, a transmission wavelength lambda _k, half-width, the transmittance of the peak top, is performed while grasping the relationship between distance d of the optical thin film 411a and 412a.

As shown in Equation 1, the wavelength lambda _k transmitted through the interference filter is a magnitude proportional to the distance d between the optical thin film 411a and 412a. In the spectral filter 410 of this embodiment, the distance d can be changed by driving the one transmissive substrate 411 to be in contact with and away from the other transmissive substrate 412 by the filter control unit 420. Yes. Specifically, in the present embodiment, the distance d between the optical thin films 411a and 412a is changed in a predetermined step (for example, a step of 10 nm) within a range of 875 nm to 1250 nm. Under this condition, band-limited light LL having 2 to 4 peak wavelengths within a wavelength range of 400 nm to 750 nm is generated.

FIG. 4 is a table showing the relationship between the distance d between the optical thin films 411a and 412a and the peak wavelength of the band-limited light LL. FIG. 5 shows the spectral characteristics of the spectral filter 410 (that is, the peak wavelength of the band-limited light LL). FIG. 5A shows the spectral characteristics when the interval d is set to 875 nm. FIG. 5B shows the spectral characteristics when the interval d is set to 1000 nm, and FIG. 5C shows the spectral characteristics when the interval d is set to 1150 nm. As shown in FIGS. 4 and 5, in the present embodiment, light of interference orders k = 11, 9, 7, and 5 is used, and the distance d between the optical thin films 411a and 412a is set to a predetermined distance. by setting, to obtain a plurality of band-limited light LL having a peak at a wavelength lambda _k which is obtained by the number 1. As can be seen from focusing on the band-limited light LL of “k = 7” in FIG. 5, by increasing the interval d, the peak wavelengths (λ _k ) of the plurality of band-limited lights LL shift to the higher wavelength side. The spectroscopic endoscope apparatus 1 according to the present embodiment uses such characteristics of the spectral characteristics of the spectral filter 410. That is, the spectroscopic endoscope apparatus 1 of the present embodiment is configured to generate a plurality of band-limited light LLs, and further configured to acquire a spectral image efficiently by shifting them. ing.

  The band limited light LL generated by the spectral filter 410 is emitted toward the band pass filter 460 (FIG. 3). The band-pass filter 460 includes a high-pass filter 460 a that transmits light having a wavelength longer than a predetermined wavelength, and a low-pass filter 460 b that transmits light having a wavelength shorter than a predetermined wavelength, and is incident from the spectral filter 410. The band-limited light LL is filtered and emitted to the condenser lens 450. In the present embodiment, the high pass filter 460a is configured to transmit light having a wavelength longer than 425 nm, and the low pass filter 460b is configured to transmit light having a wavelength shorter than 650 nm. Therefore, out of the band limited light LL incident from the spectral filter 410, only the band limited light LL in the wavelength range of 425 nm to 650 nm is extracted and emitted to the condenser lens 450.

  FIG. 6 shows the spectral characteristics of the spectral filter 460 of FIG. 5 added with the spectral characteristics of the bandpass filter 460. As shown in FIG. 6, among the band limited light LL incident from the spectral filter 410, a wavelength shorter than 425 nm and a wavelength longer than 650 nm are cut by the bandpass filter 460 (shown by a dotted line in FIG. 6). Only the band-limited light LL having the characteristic indicated by the solid line in FIG. 6 enters the condenser lens 450 from the bandpass filter 460.

  As described above, the light incident on the condensing lens 450 is condensed on the proximal end portion 131 b of the light guide 131, guided to the distal end portion 131 a by the light guide 131, and enters the living tissue T through the lens 132. Irradiated. Then, the reflected light of the light irradiated to the living tissue T (that is, the image of the living tissue T) forms an image on the light receiving surface of the image sensor 141 through the color filter 141a, and an endoscopic image (video signal). Is obtained. That is, the endoscopic image obtained by the image sensor 141 is obtained by further filtering the light emitted from the bandpass filter 460 with the color filter 141a.

  FIG. 7 shows the spectral characteristic of the spectral filter 460 in FIG. 6 and the spectral characteristic of the bandpass filter 460 in addition to the spectral characteristic of the color filter 141a in FIG. As shown in FIG. 7, in the present embodiment, a plurality of band limited lights LL generated discretely in a wavelength range of 425 nm to 650 nm are transmitted through any of the R, G, and B filters of the color filter 141a. It is configured to belong to a wavelength band. For example, as shown in FIG. 7A, when the distance d between the optical thin films 411a and 412a is set to 875 nm, two band limited lights LL having peaks at wavelengths of 451 nm and 563 nm are incident on the image sensor 141. However, the peak at a wavelength of 451 nm belongs to the transmission wavelength range of the B filter, and the peak at a wavelength of 563 nm belongs to the transmission wavelength band of the G filter. Therefore, by obtaining an endoscope image in this state (by taking an image), a spectral image having a wavelength of 451 nm can be obtained from the pixel of the image sensor 141 corresponding to the B filter, and imaging corresponding to the G filter. A spectral image with a wavelength of 563 nm can be obtained from the pixel of the element 141.

  For example, as shown in FIG. 7B, when the distance d between the optical thin films 411a and 412a is set to 1000 nm, two band-limited lights LL having peaks at wavelengths of 500 nm and 619 nm are generated in the image sensor 141. Although incident, the peak at a wavelength of 500 nm belongs to the transmission wavelength range of the B filter and the G filter, and the peak at a wavelength of 619 nm belongs to the transmission wavelength band of the R filter. Therefore, by imaging in this state, a spectral image having a wavelength of 500 nm can be obtained from the pixels of the image sensor 141 corresponding to the B filter and the G filter, and from the pixels of the image sensor 141 corresponding to the R filter, A spectral image having a wavelength of 619 nm can be obtained.

  For example, as shown in FIG. 7C, when the distance d between the optical thin films 411a and 412a is set to 1150 nm, two band-limited lights LL having peaks at wavelengths of 467 nm and 560 nm are generated in the image sensor 141. Although incident, the peak of wavelength 467 nm belongs to the transmission wavelength range of the B filter, and the peak of wavelength 560 nm belongs to the transmission wavelength band of the G filter. Therefore, by imaging in this state, a spectral image with a wavelength of 467 nm can be obtained from the pixel of the image sensor 141 corresponding to the B filter, and from the pixel of the image sensor 141 corresponding to the G filter, the wavelength of 560 nm. A spectral image can be obtained.

  As described above, in the present embodiment, a plurality of band-limited lights LL are discretely generated in the wavelength range of 425 nm to 650 nm, and each of the band-limited lights LL is selected from any of the R, G, and B filters of the color filter 141a. The image sensor 141 can be detected through the gap. A spectral image is efficiently acquired by simultaneously capturing an image (that is, a plurality of spectral images) obtained by the plurality of band-limited light LL by one imaging operation. As described above, the wavelength of the band-limited light LL can be shifted by changing the distance d between the optical thin films 411a and 412a. In the present embodiment, the controller 530 controls the filter control unit 420 and sequentially acquires a spectral image while gradually changing the distance d between the optical thin films 411a and 412a, thereby obtaining a spectral image in the wavelength range of 450 to 650 nm. For example, it is acquired in 10 nm steps. Specifically, the controller 530 uses a look-up table that shows the relationship between the distance d between the optical thin films 411a and 412a, the peak wavelength of the band-limited light LL, and the R, G, and B filters of the color filter 141a to determine the wavelength 450. Spectral images in the range of ˜650 nm are acquired.

  FIG. 8 is an example of a look-up table showing the relationship between the distance d between the optical thin films 411a and 412a, the peak wavelength of the band-limited light LL, and the R, G, and B filters of the color filter 141a controlled by the controller 530. As shown in FIG. 8, the look-up table of this embodiment includes a bandpass in the table showing the relationship between the distance d between the optical thin films 411a and 412a and the peak wavelength of the band-limited light LL shown in FIG. Information of spectral characteristics of the filter 460 and information of spectral characteristics of the R, G, and B filters of the color filter 141a are added. Here, in FIG. 8, “x” marks indicate wavelengths that are not detected by the image sensor 141 because they are cut by the bandpass filter 460 among the peak wavelengths of the band-limited light LL, and “−” marks indicate image sensors. Although it is detected by 141, the data not used (not stored) is shown. “B” indicates the wavelength of the band limited light LL acquired by the pixel corresponding to the B filter, “G” indicates the wavelength of the band limited light LL acquired by the pixel corresponding to the G filter, and “R” "Indicates the wavelength of the band-limited light LL acquired by the pixel corresponding to the R filter. This look-up table is stored in a non-volatile memory (not shown) in the controller 530. The controller 530 refers to the look-up table when capturing (acquiring) a spectral image, and the interval d between the optical thin films 411a and 412a. The image obtained through the R, G, and B filters is stored in the primary storage memory 520 as a spectroscopic image having a predetermined wavelength.

  As shown in FIG. 8, for example, when the controller 530 controls the filter control unit 420 to set the distance d between the optical thin films 411 a and 412 a to 875 nm, among the images captured by the image sensor 141, the B filter The image obtained by the pixel corresponding to is stored in the primary storage memory 520 as a spectral image of 451 nm, and the image obtained by the pixel corresponding to the G filter is stored in the primary storage memory 520 as a spectral image of 563 nm.

  For example, when the controller 530 controls the filter control unit 420 to set the distance d between the optical thin films 411a and 412a to 1000 nm, the image corresponding to the G filter among the images captured by the image sensor 141 is used. The obtained image is stored in the primary storage memory 520 as a spectral image of 500 nm, and the image obtained by the pixel corresponding to the R filter is stored in the primary storage memory 520 as a spectral image of 619 nm. Here, in this example, the band-limited light LL having a peak at a wavelength of 500 nm enters the pixel corresponding to the B filter (FIG. 7B), but the band-limited light having a peak at a wavelength of 421 nm. Since part of LL is not cut by the bandpass filter 460 and is incident on the image sensor 141 through the B filter, light other than the band limited light LL having a peak at a wavelength of 500 nm is displayed in the image obtained by the pixel corresponding to the B filter. The image obtained by this will also be included. Thus, when two adjacent band-limited lights LL are incident on one of the R, G, and B filters in this way, the spectral characteristics of the R, G, and B filters partially overlap each other. Therefore, the configuration is such that one band-limited light LL is always assigned to one of the R, G, and B filters. It is desirable that the spectral characteristics of the B and G filters and the spectral characteristics of the G and R filters overlap each other by about 50% in the wavelength direction.

  For example, when the controller 530 controls the filter control unit 420 to set the distance d between the optical thin films 411a and 412a to 1025 nm, among the images captured by the image sensor 141, the pixels corresponding to the G filter are used. The obtained image is stored in the primary storage memory 520 as a 511 nm spectral image, and the image obtained by the pixel corresponding to the R filter is stored in the primary storage memory 520 as a 629 nm spectral image. Here, the band-limited light LL having a peak at a wavelength of 428 nm is also incident on the pixel corresponding to the B filter, but there is a high possibility that a part of the band-limited light LL is cut by the band-pass filter 460. Therefore, it is discarded as data. As described above, in the present embodiment, even if the wavelength is not cut by the band-pass filter 460, the band-limited light LL having a peak at a wavelength shorter than 450 nm is a spectral image obtained by the B filter. The data is not used and discarded.

  As described above, the controller 530 changes the distance d between the optical thin films 411a and 412a in the range of 875 nm to 1250 nm with reference to the look-up table shown in FIG. 8, and the image obtained through the R, G, and B filters. Are stored in the primary storage memory 520 as spectral images of predetermined wavelengths, respectively, so that a spectral image can be acquired for each about 10 nm step in the wavelength range of 450 to 650 nm. Then, the controller 530 obtains a reflection spectrum from the acquired spectral image, and outputs display image data identifying the healthy part and the lesion part to the video memory 540. According to the look-up table in FIG. 8, since images (that is, two spectral images) obtained by the two band-limited lights LL can be simultaneously captured by one imaging operation, the spectral image acquisition time is It becomes about half.

  Next, the configuration of the DBR reflection layer of the spectral filter 410 according to the above-described embodiment of the present invention will be described in more detail with reference to some examples and reference examples.

<Method for Manufacturing Spectral Filter 410>
A method of manufacturing the spectral filter 410 according to each example and reference example will be described. First, a borosilicate crown glass (manufactured by HOYA Co., Ltd .: BK7) is processed into a predetermined size to manufacture base materials (transmission substrates 411 and 412). Next, a titanium oxide thin film and a silicon oxide thin film are alternately deposited on the upper surface of the base material by three or four layers (in the reference example, five layers each) by using a vacuum deposition apparatus to form a DBR reflective layer. Form. And a pair of base material is arrange | positioned so that a DBR reflection layer may oppose, and it adjusts so that base materials may become parallel on both sides of an air layer. In addition to titanium oxide, zirconium oxide, niobium pentoxide, or the like can be used, and magnesium fluoride other than silicon oxide can be used.

<Description of Examples and Reference Examples>

The configuration of the DBR reflection layer of the spectral filter 410 of Example 1 is as shown in Table 1. As shown in Table 1, the DBR reflective layer of the spectral filter 410 of Example 1 was formed by alternately depositing three layers of titanium oxide thin films and silicon oxide thin films on the upper surface of the base material (transmission substrates 411 and 412). Is formed. Here, the refractive index of the substrate is 1.519 (λ ₀ = 550 nm), the refractive index of titanium oxide is 2.320 (λ ₀ = 550 nm), and the refractive index of silicon oxide is 1. 486 (λ ₀ = 550 nm). The thickness of each thin film of titanium oxide is 53.89 nm, and the thickness of each thin film of silicon oxide is 84.12 nm.

  FIG. 9 shows the spectral characteristics of the spectral filter 410 according to the first embodiment. As shown in FIG. 9, according to the configuration of the first embodiment, three band-limited lights LL having peaks at wavelengths of 444 nm, 501 nm, and 575 nm are emitted. Here, the transmittance at each peak wavelength was 96.60% (λ = 444 nm), 95.17% (λ = 501 nm), and 96.58% (λ = 575 nm), respectively. That is, an ideal variable wavelength filter having a transmittance of 90% or more at each peak wavelength and a small variation in transmittance (maximum transmittance−minimum transmittance = 1.43%) could be realized.

  The configuration of the DBR reflection layer of the spectral filter 410 of Example 2 is as shown in Table 2. As shown in Table 2, the DBR reflective layer of the spectral filter 410 of Example 2 was formed by alternately depositing four layers of titanium oxide thin films and silicon oxide thin films on the upper surface of the base material (transmission substrates 411 and 412). This is different from the first embodiment in that it is formed.

  FIG. 10 shows the spectral characteristics of the spectral filter 410 of the second embodiment. As shown in FIG. 10, according to the configuration of the second embodiment, three band-limited lights LL having peaks at wavelengths of 445 nm, 501 nm, and 573 nm are emitted. The transmittance at each peak wavelength was 97.18% (λ = 445 nm), 92.31% (λ = 501 nm), and 94.61% (λ = 573 nm), respectively. That is, also in Example 2, the transmittance at each peak wavelength was 90% or more, and the variation in transmittance (4.87%) was also within 10%.

Reference example

  The configuration of the DBR reflection layer of the spectral filter 410 of this reference example is as shown in Table 3. As shown in Table 3, the DBR reflective layer of the spectral filter 410 of this reference example was formed by alternately depositing five layers of titanium oxide thin films and silicon oxide thin films on the upper surface of the base material (transmission substrates 411 and 412). It differs from Example 1 and Example 2 in the point formed.

  FIG. 11 shows the spectral characteristics of the spectral filter 410 of this reference example. As shown in FIG. 11, according to the configuration of this reference example, three band-limited lights LL having peaks at wavelengths of 447 nm, 501 nm, and 570 nm are emitted. The transmittance at each peak wavelength was 94.34% (λ = 447 nm), 69.25% (λ = 501 nm), and 92.46% (λ = 570 nm), respectively. As described above, in this reference example, since the half-value width is narrowed, the transmittance decreases at a specific wavelength (λ = 501 nm in the case of this reference example), but the filter effect (wavelength selection effect) is more wavelength in the gorge band. Can be narrowed down to. To reduce the transmittance at a specific wavelength, the filter characteristics are changed according to the required wavelength information and the sensitivity of the imaging device 141, or the imaging time (integration time) by the imaging device 141 is lengthened. It is possible to cope with it.

  The above is the description of the embodiment of the present invention and specific examples of the embodiment. However, the present invention is not limited to the above-described configuration, and various modifications are possible within the scope of the technical idea of the present invention. Is possible. For example, in the light source unit 400 of the present embodiment, the spectral filter 410 is described as being arranged on the light source 430 side of the bandpass filter 460, but the arrangement of the spectral filter 410 and the bandpass filter 460 may be interchanged. Further, the spectral filter 410 and the bandpass filter 460 only need to be in an optical path until the light emitted from the light source 430 is received by the image sensor 141. For example, the spectral filter 410 and the band pass filter 460 may be configured to be incorporated in the insertion tube distal end portion 111. .

  The image sensor 141 of the present embodiment has been described as an image sensor for color image capturing provided with R, G, and B primary color filters on the front surface thereof, but is not limited to this configuration. For example, an image sensor for capturing a color image including a Y, Cy, Mg, G complementary color filter may be used. In this case, the spectral characteristics of each color of the complementary color filter generally have a wider characteristic (broad characteristics in the wavelength direction) than the spectral characteristics of each color of the primary color filter, and thus a plurality of band limitations. The light LL enters the image sensor through a plurality of color filters. For this reason, in order to obtain a spectral image obtained by one band-limited light LL, it is necessary to perform calculation using image data obtained through each color filter.

  The R filter of the present embodiment is a filter that transmits light with a wavelength of about 570 nm or more, the G filter is a filter that transmits light with a wavelength of about 470 nm to 620 nm, and the B filter is a wavelength of about 530 nm or less. Although described as a filter that transmits light, the configuration is not limited to this configuration as long as it is configured to transmit filters having different peak wavelengths of adjacent band-limited lights LL. It is sufficient if there is a filter having at least two different spectral characteristics in the wavelength range (for example, wavelength 450 to 650 nm). In this case, the look-up table in FIG. 8 is changed according to the peak wavelength of each band-limited light LL and the spectral characteristics of the filter used.

  Moreover, in this embodiment, although comprised so that a spectral image with a wavelength of 450-650 nm could be obtained, in order to distinguish a healthy part and a lesioned part by the reflection spectrum of a biological tissue, a wavelength of 450-600 nm is used. Since it is only necessary to obtain a spectral image of the range, it is also possible to configure using spectral images obtained by the B filter and the G filter. In this case, since it is not necessary to process the spectral image obtained by the R filter, the processing is further speeded up.

  In addition, the image sensor 141 of the present embodiment has been described as an image sensor for color image imaging including the on-chip color filter 141a. However, the image sensor 141 is not limited to this configuration. It is good also as a structure provided with the color filter of what is called a field sequential system using this image pick-up element. In addition, the color filter 141a is not limited to an on-chip configuration, and may be disposed anywhere in the optical path from the light source 430 to the image sensor 141.

DESCRIPTION OF SYMBOLS 1 Diagnostic system 100 Electronic endoscope 110 Insertion tube 111 Insertion tube front-end | tip part 121 Objective optical system 131 Light guide 131a Front-end | tip part 131b Base end part 132 Lens 141 Image pick-up element 141a Color filter 142 Cable 200 Processor for electronic endoscope 300 Monitor 400 Light source unit 410 Spectral filter 420 Filter control unit 430 Light source 440 Collimator lens 450 Condensing lens 460 Band pass filter 500 Image processing unit 510 A / D conversion circuit 520 Temporary storage memory 530 Controller 540 Video memory 550 Signal processing circuit

Claims (7)

An electronic endoscope having an image sensor;
A light source device that emits white light and supplies illumination light to the electronic endoscope;
A band-pass filter that is disposed in the optical path of illumination light from the light source to the imaging device, and that emits light by limiting incident light to light in a predetermined wavelength range;
A pair of transmissive substrates each having a reflective film formed on a surface portion facing each other; and a driving unit that changes a wavelength band of light passing through the pair of transmissive substrates by changing an interval between the pair of transmissive substrates. A plurality of bands that are arranged in an optical path of illumination light from the light source to the imaging device and have different peak wavelengths within the predetermined wavelength range by filtering light incident on one of the pair of transmission substrates A wavelength filter unit that emits limiting light; and
A plurality of light sources arranged in the optical path of illumination light from the light source to the image sensor, each having a different transmission wavelength range within the predetermined wavelength range, and emitting only light in the transmission wavelength range among incident light With color filters,
With
In the wavelength filter unit, each of the peak wavelengths of the plurality of band limited lights is included in at least one of the transmission wavelength ranges, and the peak wavelengths of the band limited lights adjacent to each other are in the different transmission wavelength ranges. The spectroscopic endoscope apparatus characterized in that the interval between the pair of transmission substrates is changed so as to be included. The predetermined wavelength range is 425 to 650 nm,
The spectroscopic endoscope apparatus according to claim 1, wherein the wavelength filter unit changes an interval between the pair of transmission substrates within a range of 875 nm to 1250 nm.   3. The spectroscopic endoscope apparatus according to claim 1, wherein each of the transmission wavelength ranges of the plurality of color filters overlaps with another transmission wavelength range at least in part.   The plurality of color filters include an R filter in which the transmission wavelength range is set to transmit red component light, and a G filter in which the transmission wavelength range is set to transmit green component light. The spectroscopic endoscope apparatus according to claim 3, wherein the spectroscopic endoscope apparatus is a B filter in which the transmission wavelength range is set so as to transmit light of a blue component.   The band-pass filter includes a low-pass filter that cuts light having a longer wavelength than the light having the predetermined wavelength range, and a high-pass filter that cuts light having a shorter wavelength than the light having the predetermined wavelength range. The spectroscopic endoscope apparatus according to any one of claims 1 to 4, wherein the spectroscopic endoscope apparatus is characterized.   6. The reflective film according to claim 1, wherein the reflective film is formed by alternately depositing three or four layers of titanium oxide thin films and silicon oxide thin films from the transmission substrate side. The spectroscopic endoscope apparatus according to one item.   7. The spectroscopic endoscope apparatus according to claim 6, wherein the titanium oxide thin film has a thickness of approximately 54 nm, and the silicon oxide thin film has a thickness of approximately 84 nm.

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