WO2016031890A1

WO2016031890A1 - Tomography apparatus

Info

Publication number: WO2016031890A1
Application number: PCT/JP2015/074131
Authority: WO
Inventors: 小林　直樹
Original assignee: 興和株式会社
Priority date: 2014-08-28
Filing date: 2015-08-27
Publication date: 2016-03-03
Also published as: JPWO2016031890A1; JP6599876B2

Abstract

　Light from a low-coherence light source 10 is divided into measurement light and reference light, and the measurement light enters an eye 21 to be examined. A tomographic image of the fundus 21a is formed on the basis of interfering light produced by the overlapping of measurement light reflected by the fundus and reference light reflected by a reference mirror 33. Light from the low-coherence light source enters an optical coupler 12, and a light quantity monitor 50 is connected, via an optical fiber 12d, to the light-exit-side port of the optical coupler 12. The light quantity value measured by the light quantity monitor and a prescribed light quantity value (light quantity range) are compared by a control circuit 51, and the light quantity value measured by the light quantity monitor is adjusted to the prescribed light quantity value (light quantity range) by a light quantity adjustment unit 11.

Description

Tomography system

The present invention relates to a tomographic imaging apparatus that forms a tomographic image of a target object based on interference light generated by superimposing measurement light reflected by the target object and reference light reflected by the reference object.

There is a tomographic imaging apparatus using optical interference called OCT (Optical Coherence Tomography), which is one of the ophthalmologic diagnosis machines and takes a tomographic image of the fundus. Such a tomographic imaging apparatus can irradiate the fundus with broadband low-coherent light as measurement light, and can capture a tomographic image of the fundus with high sensitivity by causing the reflected light from the fundus to interfere with the reference light.

Measured light quantity used for tomographic imaging must be strictly controlled in order to capture stable and good quality tomographic images. However, in the tomographic imaging apparatus, precise parts such as optical fibers are used as constituent parts, which are easily affected by the use environment such as temperature and may fluctuate. In addition, the amount of measurement light is expected to change over time due to deterioration of the devices and light sources used.

When the measurement light quantity increases, there is a problem that a light hazard due to excessive irradiation light quantity on the object to be measured occurs. On the other hand, when the measurement light quantity decreases, there is a problem that the image quality of the tomographic image to be taken deteriorates.

Therefore, in order to obtain appropriate measurement light, in Patent Document 1 below, a light amount measuring means for measuring the light amount of the laser light is disposed outside the optical path of the laser light irradiated to the object to be measured, and the light amount measurement is performed. Control is performed so that the amount of light measured by the means becomes an appropriate amount of light.

JP 2010-243280 A

However, in the configuration described in Patent Document 1, since the light quantity measuring unit is arranged outside the optical path of the measurement light, the light quantity measuring unit measures not only the measurement light incident on the object to be measured but also other light. There is a problem that it is impossible to perform high-quality tomographic imaging.

Also, since the image quality of the tomographic image to be photographed is affected not only by the amount of light irradiated to the object to be measured but also by the intensity of the return light from the reference optical system, control of the reference light amount is also important.

Also, when the light amount is adjusted by controlling the output of the light source, there is a problem that the shape of the emission spectrum changes, the depth resolution is affected, and a tomographic image with good image quality cannot be obtained.

Furthermore, when the object to be measured is a living body such as an eye to be examined, excessive light quantity may be temporarily generated during the light quantity adjustment, and the living body may be damaged.

The present invention has been made in view of the above points, and provides a tomographic imaging apparatus capable of acquiring tomographic images with appropriate measurement light incident on a target object to obtain a high-quality tomographic image. The task is to do.

The present invention
The light from the light source is incident on the demultiplexing / combining optical system, the light emitted from the demultiplexing / multiplexing optical system is divided into measurement light and reference light, and incident on the target object and the reference object. A tomography apparatus for forming a tomographic image of a target object based on interference light generated by superimposing reflected measurement light and reference light reflected by a reference object,
A light amount monitor for measuring the amount of light emitted from the demultiplexing / multiplexing optical system;
A light amount adjustment unit that adjusts the light amount from the light source so that the light amount value measured by the light amount monitor is within a light amount range determined by a predetermined light amount value or a predetermined upper limit value and lower limit value;
It is characterized by providing.

In the present invention, the light amount adjustment unit adjusts the light amount while maintaining the spectral shape of the light from the light source.

In the present invention, a variable aperture stop is disposed in the optical path through which the reference light reflected by the reference object passes, and the variable aperture stop is adjusted according to the light amount of the reference light reflected by the reference object when adjusting the light amount by the light amount monitor. The opening diameter is controlled.

In the present invention, a light shielding mechanism is provided in the optical path through which the reference light reflected by the reference object passes, and the reference light is shielded by the light shielding mechanism when adjusting the light amount by the light amount monitor.

In the present invention, the light amount monitor is the first light amount monitor, the second light amount monitor is disposed at a position off the optical path through which the measurement light passes, and the measurement light is incident on the second light amount monitor. The light amount adjustment by the first light amount monitor is performed without entering the object.

In the present invention, when the light quantity measured by the second light quantity monitor shows an abnormal value, the measurement light is controlled so as not to enter the target object.

In the present invention, a light amount monitor that measures the amount of light emitted from the demultiplexing / combining optical system is provided, and the light amount value measured by the light amount monitor is determined by a predetermined light amount value or a predetermined upper limit value and lower limit value. Since the amount of light from the light source is adjusted so as to be within the light amount range, it is possible to obtain a tomographic image with good image quality by performing tomographic imaging by making appropriate measurement light incident on the target object.

It is an optical diagram which shows the whole structure of a tomographic imaging apparatus. It is the block diagram which showed the detailed structure of one Example of the light quantity adjustment unit. It is the block diagram which showed the detailed structure of the other Example of the light quantity adjustment unit. It is the optical figure which showed the Example which provides another light quantity monitor in the vicinity of an objective lens, and performs light quantity control. It is the optical figure which showed the Example which provides another light quantity monitor in the vicinity of an objective lens, and performs abnormality detection.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 1 shows an optical system of the entire tomographic imaging apparatus (OCT apparatus). Reference numeral 10 denotes a broadband low-coherence light source, which is composed of, for example, a superluminescent diode (SLD), and emits light having a wavelength of 700 nm to 1100 nm and a temporal coherence length of about several μm to several tens of μm.

The low coherence light generated by the low coherence light source 10 enters the light amount adjustment unit 11 through the optical fiber 11a, and the light amount is adjusted. The low-coherence light whose light amount has been adjusted is incident on the optical coupler 12 via the optical fiber 12a, and is then guided to the beam splitter 14 as a splitting optical element via the optical fiber 12b and the collimator lens 13. The optical coupler 12 demultiplexes / combines the light incident thereon and emits the light to constitute a demultiplexing / multiplexing optical system.

The light incident on the beam splitter 14 is divided into reference light and measurement light. The measurement light is focused on the fundus by the focus lens 15 and then scanned in an arbitrary direction by an x-axis scanning mirror (galvano mirror) 17 and a y-axis scanning mirror (galvano mirror) 18 driven by a galvano mirror driver 16. . The measurement light scanned by the x-axis and y-

axis scanning mirrors

17 and 18 passes through the scan lens 19 and the objective lens 20 and is incident on the fundus 21a of the eye 21 to be examined as a target object. , Scanned in the y direction.

The measurement light reflected by the fundus 21a returns to the beam splitter 14 following the above path. Here, the optical system from the beam splitter 14 to the objective lens 20 constitutes a measurement optical system. In addition to the illustrated optical components, the measurement optical system is appropriately provided with optical components such as a mirror and a lens. Are omitted to avoid complications.

On the other hand, the reference light split by the beam splitter 14 is reflected by the mirror 30, passes through the lens 31, passes through the variable aperture stop 32 having a variable aperture diameter for adjusting the reference light quantity, and is used as a reference object. The mirror 33 is reached. The reference mirror is movable in the direction of the optical axis in order to adjust the optical path length, and the reference light reflected by the reference mirror 33 returns to the beam splitter 14 following the optical path in the reverse direction. Here, the optical system from the beam splitter 14 to the reference mirror 33 constitutes a reference optical system. In addition to the optical components shown in the figure, the reference optical system appropriately compensates for a mirror, a lens, or an optical path length and dispersion. An optical component or the like is provided, but is omitted to avoid complication.

The measurement light and the reference light that have returned to the beam splitter 14 are superimposed and become interference light, which enters the spectroscope 40 through the collimating lens 13, the optical fiber 12b, and the optical coupler 12 through the optical fiber 12c. The spectroscope 40 includes a diffraction grating 40a, an imaging lens 40b, a line sensor 40c, and the like. The interference light is split into a spectrum corresponding to the wavelength of the low coherence light by the diffraction grating 40a and is lined by the imaging lens 40b. An image is formed on the sensor 40c.

The signal from the line sensor 40c is subjected to signal processing including Fourier transformation by a tomographic image forming means realized by a CPU of the computer 41, and the like, and a depth signal indicating information in the depth direction (z direction) of the fundus 21a to be examined. Is generated. Since the depth signal (A scan image) at the sampling time is obtained by the interference light at each sampling time of the fundus scan, when one scan is completed, the z direction image (A scan image) along the scan direction is used. A two-dimensional tomographic image (B-scan image) can be formed.

The measurement light used for tomographic imaging is likely to fluctuate because precision components such as optical fibers are easily affected by the usage environment such as temperature, and the device being used and the low-coherence light source 10 There is a possibility that it may change over time due to deterioration of the material. When the amount of measurement light increases, a light hazard is generated on the subject's eye due to an excessive amount of light applied to the subject's eye, and when the amount of light decreases, the image quality of the tomographic image to be captured decreases.

In the present embodiment, in order to solve such a problem, a light amount monitor 50 is provided, and the interference optical system (collimating lens 13, beam splitter 14, and subsequent measurement optical system and reference optical system are provided from the low coherence light source 10. In the process of reaching the optical system), a part of the low coherence light is taken out and monitored by the light quantity monitor 50.

The light quantity monitor 50 is composed of a light detection element such as a photodiode, and is connected via an optical fiber 12d to an outgoing side port different from the outgoing side port of the optical coupler 12 to which the optical fiber 12b is connected. The light quantity measured by the light quantity monitor 50 is input to the control circuit 51. The control circuit 51 stores a predetermined light amount value or a light amount range determined by a predetermined upper limit value and a lower limit value, compares the light amount value from the light amount monitor 50 with a predetermined light amount value (light amount range), and a deviation signal thereof. Is output to the light quantity adjustment unit 11 as a control signal, and feedback control is performed so that there is no deviation, that is, the light quantity value measured by the light quantity monitor 50 becomes a predetermined light quantity value (light quantity range).

FIG. 2 shows a detailed configuration of the light amount adjustment unit 11. The light amount adjustment unit 11 includes a cylindrical split sleeve 111. In the hollow portion of the sleeve 111, the ferrule 112 having the other end of the optical fiber 11a connected to the low coherence light source 10 fixed and the optical coupler 12 are incident. A ferrule 113 with the other end of the optical fiber 12a connected to the side port fixed inside is housed. The

ferrules

112 and 113 are supported by

support plates

114 and 115, and the

optical fibers

11 a and 12 a penetrate the

support plates

114 and 115 and are guided to the outside of the light amount adjustment unit 11. A feed screw 117 rotated by a motor 116 is fixed to the support plate 115, and the feed screw 117 is attached so as to be screwed with the supported 114. When the feed screw 117 is rotated by the motor 116, the support plate 114 and the ferrule 112 are moved in the optical axis direction with respect to the ferrule 113. The

optical fibers

11a and 12a are connected to the

ferrules

112 and 113 so that the axis of the optical fiber 11a and the axis of the optical fiber 12a always coincide even when the ferrule 112 moves relative to the ferrule 113 by driving the motor 116. It is attached.

The motor 116 of the light amount adjustment unit 11 receives the control signal from the control circuit 51 in FIG. 1 and moves the support plate 114 and the ferrule 112 supported by the support plate 114 in the optical axis direction. As the distance between the

ferrules

112 and 113 increases, the coupling efficiency of the

optical fibers

11a and 12a deteriorates, and the amount of light from the low coherence light source 10 input to the optical coupler 12 via the optical fiber 12a decreases. On the other hand, when the distance between the

ferrules

112 and 113 decreases, the coupling efficiency increases and the amount of light input to the optical coupler 12 increases.

Note that the end face of the optical fiber 11a in the ferrule 112 and the end face of the optical fiber 12a in the ferrule 113 are slightly inclined rather than perpendicular to the optical axis direction in order to prevent interference due to light reflection at the end face. It is better to leave it.

With such a configuration, when the light amount value measured by the light amount monitor 50 is larger than the predetermined light amount value or exceeds the predetermined light amount range, the control circuit 51 increases the distance between the

optical fibers

11a and 12a. Thus, the support plate 114 and the ferrule 112 are moved. As a result, the amount of light passing through the optical fiber 12a is reduced and adjusted so that the light amount value measured by the light amount monitor 50 becomes a predetermined light amount value or within a predetermined light amount range.

On the other hand, when the light amount value measured by the light amount monitor 50 is smaller than the predetermined light amount value or below the predetermined light amount range, the control circuit 51 supports the distance between the

optical fibers

11a and 12a so as to decrease. The plate 114 and the ferrule 112 are moved. As a result, the amount of light passing through the optical fiber 12a increases, the amount of measurement light that is split by the beam splitter 14 and incident on the eye 21 is kept at a predetermined light amount value (light amount range), and good tomographic imaging can be performed. It becomes possible.

The light quantity adjustment unit may be a light quantity adjustment unit 11 'composed of a variable optical attenuator (Variable Optical Attenuator) as shown in FIG. The light amount adjustment unit 11 ′ reflects the low coherence light emitted from the optical fiber 11 a connected to the low coherence light source 10 by the mirror 121 through the lens 120, and the low coherence light reflected by the mirror 121 through the lens 120. Then, the light is incident on the end of the optical fiber 12 a connected to the incident side port of the optical coupler 12. Since the low-coherence light incident on the optical fiber 12a can be changed by rotating the mirror 121, the reflection angle of the mirror 121 is controlled by the control signal of the control circuit 51.

When the light amount value measured by the light amount monitor 50 is larger than the predetermined light amount value or exceeds the predetermined light amount range, the control circuit 51 reduces the reflection angle of the mirror 121 and the light amount incident on the optical fiber 12a. To change. On the other hand, when the light amount value measured by the light amount monitor 50 is smaller than the predetermined light amount value or below the predetermined light amount range, the reflection angle of the mirror 121 is set so that the amount of light incident on the optical fiber 12a increases. , Change. Thereby, the light quantity of the measurement light split by the beam splitter 14 and incident on the eye 21 to be examined can be adjusted to be a predetermined light quantity value (light quantity range).

Usually, the low-coherence light source 10 is controlled so that a constant output can be obtained by a built-in APC (Automatic Power Control) circuit. In this embodiment, the light amount adjustment unit is not directly controlled by the control signal of the control circuit 51 but connected between the low coherence light source 10 and the optical coupler 12 via optical fibers 11a and 12a. 11 (11 ′) adjusts the amount of light. Since the light amount adjustment unit 11 (11 ′) changes the light amount by changing the coupling efficiency of the optical fiber through which the light from the low coherence light source 10 passes, the spectral shape (distribution) of the light from the low coherence light source 10 ) Can be maintained and only the amount of light can be changed. Therefore, even if the amount of light is adjusted, the spectral shape of the light incident on the measurement optical system and the reference optical system does not change, and the tomographic image in the depth direction is not affected, and a tomographic image with good image quality is formed The effect that it can be obtained.

In the case of the OCT apparatus, since the reference light is formed by demultiplexing the light from the light source, a part of the return light from the reference optical system also returns to the light source side. May fluctuate.

Therefore, the reference light amount is adjusted by the variable aperture stop 32 disposed in the optical path of the reference optical system. The reference light amount is measured by evaluating the average luminance value of only the reference light or the spectrum of the reference light and the measurement light with the spectroscope 40. Alternatively, the spectrum on the spectroscope 40 is Fourier-transformed by the computer 41 to calculate an autocorrelation signal, and the intensity is used as a measured value of the reference light amount. Alternatively, the cross-correlation signal constituting the tomographic image is calculated by the computer 41, and the intensity is used as the measured value of the reference light amount. Or it is good also as a measured value of reference light quantity with light shot noise amount (background noise of a tomographic image).

In accordance with the reference light amount thus measured, the computer 41 reduces the aperture diameter of the variable aperture stop 32 if the reference light amount is large, and increases the aperture diameter if the reference light amount is small. The aperture diameter of the variable aperture stop 32 is controlled so as to be within a light amount range determined by a light amount value or a predetermined upper limit value and lower limit value.

Further, in a situation where it is unknown whether the reference light amount can be controlled to an appropriate value, a light shielding mechanism 34 is provided in the reference optical system in order to cut the return light from the reference optical system. 34a is inserted into the reference light path so as to block the reference light.

As described above, when the light amount is adjusted by the light amount monitor 50, the return light from the reference optical system is controlled to a predetermined light amount value (light amount range) or shielded, so that the light source output fluctuation due to the return light is suppressed, and the measured light amount It is possible to perform favorable tomographic imaging by appropriately adjusting the angle.

Although the light amount adjustment by the light amount monitor 50 can be performed even during tomographic imaging, an excessive amount of light temporarily exceeding an appropriate amount of light is emitted from the objective lens 20 and enters the eye 21 to be examined due to a control defect. Hazard risk may occur. Therefore, as shown in FIG. 4, the light amount monitor 50 is used as the first light amount monitor, and a light amount monitor 60 as the second light amount monitor is disposed in the vicinity of the outside of the objective lens 20, and the measurement light is transmitted through the light amount monitor 60. When it is confirmed that the light does not enter the lens 20 and therefore does not enter the eye 21, the light amount adjustment by the light amount monitor 50 is performed.

The light quantity monitoring mechanism by the light quantity monitor 60 is shown in FIG. 4 corresponds to the portion indicated by the alternate long and short dash line in FIG.

As shown in FIG. 4, the light amount monitor 60 is disposed in the vicinity of the objective lens 20 at a position deviated from the optical path through which the measurement light passes in the measurement optical system. Similar to the light quantity monitor 50, the light quantity monitor 60 is composed of a light detection element such as a photodiode.

The light quantity monitor 60 is connected to a detection circuit 61. The detection circuit 61 outputs a detection signal when the light quantity measured by the light quantity monitor 60 is equal to or greater than a predetermined threshold value. The detection signal of the detection circuit 61 is input to the control circuit 51 in FIG. 1. When the detection signal is input to the control circuit 51, the control circuit 51 is activated, and when there is no detection signal, the control circuit is disabled. Activated.

With such a configuration, when the light amount is adjusted by the light amount monitor 50, the galvano mirror driver 16 drives the x-axis scanning mirror 17 and the y-axis scanning mirror 18 so that the measurement light enters the light amount monitor 60. When the measurement light split by the beam splitter 14 due to the low-coherence light source 10 is turned on, the light quantity measured by the light quantity monitor 60 exceeds a predetermined threshold value, and a detection signal is output from the detection circuit 61. The control circuit 51 is activated. The control circuit 51 outputs a control signal to the light amount adjustment unit 11 and performs feedback control so that the light amount value measured by the light amount monitor 50 becomes a predetermined light amount value (light amount range).

In this way, when the measurement light does not enter the objective lens 20 and therefore does not enter the eye 21, the light amount of the measurement light is adjusted. Therefore, an excessive amount of light is incident on the eye to be inspected due to a control failure. Risk can be prevented from occurring.

Note that if the predetermined threshold value of the light amount set in the detection circuit 61 is set to a high value, the control circuit 51 is not triggered and the light amount adjustment may not be performed smoothly. Set it to about half of the light intensity. Although the amount of light measured by the light amount monitor 60 fluctuates due to the light amount adjustment by the light amount monitor 50, the control circuit 51 becomes inoperable during the light amount adjustment by setting the threshold value to a lower value. It is possible to prevent and perform smooth light quantity adjustment.

As described above, when the light amount monitor 50 performs light amount monitoring, there is a high correlation between the light amount measured by the light amount monitor 50 and the light amount of the measurement light emitted from the objective lens 20 (hereinafter referred to as the objective emission light amount). That is the premise. Here, since there is a high correlation between the amount of light measured by the light amount monitor 60 and the amount of light emitted from the objective, the light amount measured by the light amount monitor 50 is measured with the light amount monitor 50. A high correlation is provided between the amount of light to be emitted and the amount of light emitted from the objective.

However, the correlation between the light amounts measured by the light amount monitors 50 and 60 depends on the optical characteristics of the optical system before reaching the light amount monitor 60, and may change over time. Long-term factors such as changes in the propagation characteristics due to contamination and modification of the optical system can be considered as factors causing changes in the characteristics of the optical system in the middle. Particularly, the adhesion of dirt to the fiber end face has a great influence. Further, the propagation of optical fiber components due to a medium-term factor such as a change in the propagation characteristic of the optical fiber of the optical coupler 12 due to a change in the environmental temperature, or a stress change to the optical fiber caused by an external force applied to the tomographic imaging apparatus. Short-term factors such as changes in characteristics will change the characteristics of the optical system.

Therefore, in order to investigate the correlation variation between the light amounts measured by the light amount monitors 50 and 60, the ratio (B / A) of the light amount value B measured by the light amount monitor 50 to the light amount value A measured by the light amount monitor 60 is calculated. The correlation coefficient is obtained and registered, and after starting the tomographic imaging apparatus, the fluctuation is always checked at a constant time interval or before the start of measurement, and the fluctuation of the ratio is monitored to adjust the light amount.

When the fluctuation with respect to the registered correlation coefficient is within 10%, the ratio of the current correlation coefficient to the registered correlation coefficient is calculated, and the ratio is set as a control parameter (proportional component) of the control circuit 51. ) Is output to the motor 116 of the light amount adjustment unit 11 to adjust the light amount.

On the other hand, if a fluctuation of 10% or more occurs, it is determined that the optical system needs to be cleaned halfway, a message is output to the user to request maintenance, and the objective emission newly measured with the optical power meter The correlation coefficient between the light quantity, the light quantity monitor 50, and the light quantity monitor 60 is calculated, and the correlation coefficient after fluctuation is registered instead of the already registered correlation coefficient to calibrate the correlation coefficient. The calibrated correlation coefficient is used as an initial correlation coefficient when examining subsequent fluctuations of the correlation coefficient.

Also, if there is a short-term fluctuation that causes a fluctuation of 10% or more from the correlation coefficient at the previous correction, it is determined that the optical system is in the middle, and a message prompting the user to readjust the light amount is output.

As described above, since the light quantity measured by the light quantity monitor 50 and the objective outgoing light quantity can be highly correlated, the objective outgoing light quantity can be adjusted to the target light quantity.

Further, in the present invention, since the light amount monitoring is performed by the light amount monitor 50 connected to the emission side of the optical coupler 12, the light amount monitoring can be performed in real time even during the measurement in which the measurement light is incident on the target object.

As described above, when the light amount is adjusted by the light amount monitor 50, the appropriate measurement light is incident on the fundus of the eye to be examined, so that it is possible to start tomographic imaging. Further, since the fluctuation of the measurement light is expected during the tomographic image capturing, the light amount adjustment by the light amount monitor 50 can be continued. When the light amount is adjusted by the light amount monitor 50 during tomographic image capturing, the measurement light is incident on the objective lens 20 and is not incident on the light amount monitor 60. Therefore, a detection signal from the detection circuit 61 is input to the control circuit 51. As a result, the control circuit 51 becomes inoperative and the light amount adjustment by the light amount monitor 50 becomes impossible. Therefore, in such a case, the connection between the detection circuit 61 and the control circuit 51 is cut off.

According to the present invention, the low light coherence light source 10, the control circuit 51, and the like fail to prevent the measurement light from becoming an abnormal light amount, and tomography is in a dangerous state by monitoring with the light amount monitor 60. Can do.

This embodiment is shown in FIG. 5, and the same parts and devices as those in FIG. 4 are given the same numbers, and detailed description thereof is omitted.

In FIG. 5, the light amount monitor 60 is connected to the abnormality detection circuit 70, and the abnormality detection circuit 70 is dangerous for the eye to be examined, for example, the light amount measured by the light amount monitor 60 may damage the eye to be examined. When the amount of light exceeds the threshold, an abnormality detection signal is generated. The abnormality detection signal is input to the galvanometer mirror driver 16, the computer 41, and the display device 80.

This abnormality detection is performed once, for example, before the start of tomographic imaging. The eye to be examined is retracted so that the measurement light does not enter the eye to be examined 21, and the low coherence light source 10 is turned on. Thereafter, the galvano mirror driver 16 drives the x-axis scanning mirror 17 and the y-axis scanning mirror 18 so that the measurement light enters the light amount monitor 60. When the amount of light measured by the light amount monitor 60 exceeds a threshold value that is dangerous for the eye to be examined, the abnormality detection circuit 70 outputs an abnormality detection signal to the galvanometer mirror driver 16. At this time, the galvanometer mirror driver 16 controls the x-axis scanning mirror 17 and the y-axis scanning mirror 18 so that the measurement light does not move to a position other than the light amount monitor 60, or the x-axis scanning mirror 17 and the y-axis. The scanning mirror 18 is driven to deflect the measurement light so that the measurement light is incident on the light-absorbing scatterer 71 disposed at a position symmetrical to the objective lens 20 with respect to the optical axis of the measurement optical system. Thereby, for example, it is possible to prevent the measurement light having an abnormal light amount due to a failure of the low-coherence light source 10 or the control circuit 41 from passing through the objective lens 20. Further, the abnormality detection signal is also input to the computer 41, whereby the photographing process is stopped. Further, an abnormality detection signal is input to the display device 80, and the display device 80 displays that the measurement light has an abnormal value.

If no abnormality is detected, the fact is displayed on the display device 80. Therefore, the light amount is adjusted by the light amount monitor 50, the fundus of the eye to be examined is scanned with the measurement light, and a tomographic image of the fundus is taken.

By performing such an abnormality detection before the start of tomographic imaging or periodically withdrawing the eye to be examined, it is possible to detect a failure of the low-coherence light source 10 or the control circuit 41, so that safe tomographic imaging is performed. be able to.

In the above-described embodiments, the target object has been described as the eye to be examined. However, the present invention is not limited to this and may be another target object. In the present invention, since the appropriate measurement light is incident on the target object, if excessive measurement light is incident on the target object, the target object is damaged or is in a dangerous state. Suitable for tomography.

DESCRIPTION OF SYMBOLS 10 Low coherence light source 11, 11 'Light quantity adjustment unit 12 Optical coupler 14 Beam splitter 15 Focus lens 16 Galvanometer mirror driver 17 X axis scanning mirror 18 Y axis scanning mirror 19 Scan lens 20 Objective lens 21 Eye to be examined 32 Variable aperture stop 33 Reference mirror 34 light shielding mechanism 40 spectroscope 41 computer 50 light quantity monitor 51 control circuit 60 light quantity monitor 61 detection circuit 70 abnormality detection circuit 71 light absorption scatterer 80 display

Claims

The light from the light source is incident on the demultiplexing / combining optical system, the light emitted from the demultiplexing / multiplexing optical system is divided into measurement light and reference light, and incident on the target object and the reference object. A tomography apparatus for forming a tomographic image of a target object based on interference light generated by superimposing reflected measurement light and reference light reflected by a reference object,
A light amount monitor for measuring the amount of light emitted from the demultiplexing / multiplexing optical system;
A light amount adjustment unit that adjusts the light amount from the light source so that the light amount value measured by the light amount monitor is within a light amount range determined by a predetermined light amount value or a predetermined upper limit value and lower limit value;
A tomographic imaging apparatus comprising:
The tomography apparatus according to claim 1, wherein the demultiplexing / combining optical system is an optical coupler that couples optical fibers.
The tomograph according to claim 2, wherein the light quantity monitor is connected to an outgoing side port different from an outgoing side port of an optical coupler through which light divided into measurement light and reference light is emitted via an optical fiber. Image taking device.
The tomography apparatus according to claim 2 or 3, wherein the light amount adjustment unit is connected to the light source and the optical coupler via an optical fiber between the light source and the optical coupler, respectively.
5. The tomographic imaging apparatus according to claim 1, wherein the light amount adjustment unit is a light amount adjustment unit that adjusts a light amount while maintaining a spectral shape of light from a light source. .
6. The tomographic imaging apparatus according to claim 5, wherein the light amount adjusting unit adjusts the light amount by changing a distance between the optical fiber connected to the optical coupler and the optical fiber connected to the light source.
The light quantity adjusting unit adjusts the light quantity by causing low-coherence light emitted from an optical fiber connected to a light source to enter an optical fiber connected to an optical coupler at a different angle. The tomographic imaging apparatus described.
8. The tomographic imaging apparatus according to claim 1, further comprising a light shielding mechanism that shields the reference light reflected by the reference object so as not to enter a light source.
The variable aperture stop is disposed in an optical path through which the reference light reflected by the reference object passes, and the aperture diameter of the variable aperture stop is controlled according to the reference light reflected by the reference object. 8. A tomographic imaging apparatus according to any one of items 1 to 7.
A state in which the second light amount monitor is disposed at a position off the optical path through which the measurement light passes, and the measurement light is incident on the second light amount monitor, and the measurement light does not enter the target object. The tomographic imaging apparatus according to claim 1, wherein the light amount is adjusted by a first light amount monitor.
11. The tomographic imaging apparatus according to claim 10, wherein the second light quantity monitor is disposed in the vicinity of the objective lens.
Before starting tomographic imaging of the target object or periodically, the measurement light is incident on the second light quantity monitor to measure the light quantity by the second light quantity monitor, and the light quantity measured by the second light quantity monitor is abnormal. The tomography apparatus according to claim 10 or 11, wherein when the value is indicated, the measurement light is deflected to a position where the measurement light does not enter the target object.
13. The tomographic imaging apparatus according to claim 10, wherein a ratio of light quantity values respectively measured by the first and second light quantity monitors is obtained, and a light quantity adjustment is performed by monitoring a change in the ratio. Image taking device.
The tomographic imaging apparatus according to any one of claims 1 to 13, wherein the target object is an eye to be examined.