Light source device and electronic endoscope system

Abstract

One aspect of the present invention is a light source module 30 comprising: a substrate 300; an LED 31 that is disposed on the substrate 300 and emits illumination light toward a subject; a light detection part 34 that is disposed on the substrate 300 and detects the illumination light emitted by the LED 31; and a control unit 21 that, when the light detection part 34 has detected the amount of the illumination light a plurality of times under the same condition, determines the presence or absence of deterioration of the LED 31 on the basis of the difference in the amount of illumination light between a current detection value and a previous detection value. In the substrate 300, a slit 50 is formed as a through groove so as to suppress heat conduction from the LED 31 to the light detection part 34.

Description

Light source device, electronic endoscope system

[0001] The present invention relates to a light source device that generates light to be irradiated onto living tissue.

[0002] In the field of medical devices, an endoscope system is known that can generate images suitable for diagnosing lesions hidden within a body cavity by illuminating biological tissue within the body cavity and capturing an image of the illuminated biological tissue within the body cavity as a subject. While lamp light sources such as xenon lamps and halogen lamps that emit white light have traditionally been used as illumination light, light sources such as light-emitting diodes (LEDs) that emit light within a specific wavelength band have recently been used instead of lamp light sources (see, for example, JP 2022-54011 A).

[0003] Japanese Patent Laid-Open Publication No. 2022-54011 describes an endoscope equipped with an illumination unit including multiple LEDs. This endoscope is equipped with an automatic light control unit that derives a photometric value using a photometric circuit based on imaging data (image signals) obtained by an imaging unit and controls the light intensity of each LED based on the derived photometric value.

[0004] In the conventional illumination unit (i.e., light source device) described in JP 2022-54011 A, automatic dimming control is performed based on the amount of light reflected from the subject that is incident on the imaging unit, and therefore it is not possible to detect a decrease in output due to deterioration of the light source itself over time. In other words, simply observing the light reflected from the subject makes it impossible to determine whether the decrease in the amount of reflected light is due to the characteristics of the subject and / or the distance to the subject, or whether the decrease in the amount of reflected light is due to deterioration of the light source itself.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to enable timely detection of a decrease in output from a light source device that generates light to illuminate a subject.

[0006] According to one aspect of the present disclosure, there is provided a light source device including: a substrate; a light-emitting unit disposed on the substrate and emitting illumination light for a subject; a light-detecting unit disposed on the substrate and detecting the illumination light emitted by the light-emitting unit; and a control unit configured to determine whether the light-emitting unit has deteriorated based on a difference between a current detection value and a previous detection value of the illumination light when the light-detecting unit detects the amount of the illumination light multiple times under the same conditions. The substrate has a through groove formed therein to suppress heat conduction from the light-emitting unit to the light-detecting unit.

[0007] The through groove may extend across an imaginary line between the light emitting section and the light detecting section when the substrate is viewed from above.

[0008] The through groove may be formed in a U-shape so as to surround three sides of the light emitting section and / or the light detecting section when the substrate is viewed from above.

[0009] When the control unit determines that there is no deterioration of the light-emitting unit, the control unit may correct the light-emitting intensity of the light-emitting unit based on the difference between a reference value of the illumination light detected by the light detection unit and the current detection value.

[0010] Another aspect of the present disclosure is an electronic endoscope system including: the light source device; an electronic scope having an imaging device and configured to acquire images of the biological tissue based on illumination light irradiated onto the biological tissue from the light source device; and a processor that processes the images of the biological tissue acquired by the electronic scope.

[0011] According to the above-described light source device, it is possible to detect in a timely manner a decrease in the output of the light source device that generates light for illuminating a subject.

[0012] FIG. 4 is a block diagram showing an example of the configuration of an electronic endoscope system of an embodiment. FIG. 5 is a block diagram focusing on parts related to light source control in the electronic endoscope system of an embodiment. FIG. 6 is a flowchart showing the startup process of the electronic endoscope system of an embodiment. FIG. 7 is a partial plan view of a substrate of a light source module of an embodiment. FIG. 8 is a diagram showing the A-A cross section of FIG. 4. FIG. 9 is a diagram explaining a modified example of the light source module of an embodiment. FIG. 10 is a diagram explaining a modified example of the light source module of an embodiment.

[0013] The electronic endoscope system of this embodiment will be described in detail below with reference to the drawings. Fig. 1 is a block diagram showing an example of the configuration of an electronic endoscope system 1 of this embodiment. As shown in Fig. 1, the electronic endoscope system 1 is a system specialized for medical use, and includes an electronic scope (endoscope) 10, an electronic endoscope processor 20 (hereinafter simply referred to as "processor 20") to which the electronic scope 10 is connected via a connector, and a monitor 40.

[0014] The processor 20 includes a control unit 21. The control unit 21 has a CPU that executes various programs stored in a memory 23 and comprehensively controls the entire electronic endoscope system 1. The control unit 21 is also connected to an operation panel 24. The control unit 21 changes each operation of the electronic endoscope system 1 and parameters for each operation in response to instructions from the surgeon input to the operation panel 24. The control unit 21 supplies clock pulses, which serve as a reference for the timing of each operation of each part in the electronic endoscope system 1, to each part in the system.

[0015] The processor 20 is provided with a light source module 30. The light source module 30 includes a light-emitting device (LED) that emits illumination light for illuminating a subject, such as biological tissue within a body cavity. When a single LED is used, the LED is preferably a white LED. Although not shown, multiple LEDs may be provided. Each of the multiple LEDs emits light with a different wavelength band. For example, the multiple LEDs include a UV LED, a blue LED, a green LED, an amber LED, and a red LED. The illumination light is white light or pseudo-white light obtained by combining the light emitted from the multiple LEDs. White light is light with a flat spectral intensity distribution in the visible light band, while pseudo-white light is light with a non-flat spectral intensity distribution that is a mixture of light from multiple wavelength bands. The illumination light from the light source module 30 is focused on the incident end face of a light carrying bundle (LCB) 11 provided in the electronic endoscope 10 and enters the LCB 11. Furthermore, the illumination light emitted from the exit end face of the LCB 11 is irradiated onto the subject via a light distribution lens 12. Return light from the subject illuminated by the illumination light from the light distribution lens 12 forms an optical image on the light receiving surface of an image sensor 14 via an objective lens 13.

[0016] In one embodiment, the light source module 30 is configured to be installable in a housing (not shown) of the processor 20. Calibration is performed for each LED during manufacturing of the light source module 30, and the calibrated light source module 30 is then installed in the processor 20. Furthermore, if the light source module 30 breaks down or deteriorates over time, a new light source module 30 can be installed in the processor 20 after calibration. Note that while FIG. 1 shows an example in which the light source module is installed in the processor 20, this is not limitative. The light source module may be installed in the electronic scope 10, or may be provided separately from the processor 20 and the electronic scope 10. In this case, the memory 23 and parts of the control unit 21 related to light source control, which will be described later, may be installed in the light source module.

[0017] The image sensor 14 is an image sensor with a Bayer pixel arrangement. The image sensor 14 accumulates and reads an optical image formed by each pixel on the light receiving surface as an electric charge according to the amount of light, and generates and outputs image data. The image sensor 14 may be a CMOS image sensor, a CCD image sensor, or any other type of imaging device. The image sensor 14 may also be equipped with a complementary color filter.

[0018] The electronic scope 10 includes a signal processing unit 15 in a connection with the processor 20. Under the control of the control unit 21, the signal processing unit 15 drives the image sensor 14 and acquires image data from the image sensor 14. In one embodiment, the signal processing unit 15 supplies a one-frame synchronization signal (e.g., a vertical synchronization signal) to the image sensor 14, acquires image data of the subject from the image sensor 14 on a frame-by-frame basis, and transmits the data to the image processing unit 22 of the processor 20. The frame period is, for example, 1 / 30 or 1 / 60 seconds. Note that the signal processing unit 15 is not limited to supplying a one-frame synchronization signal. Some image sensors may transmit image data based on a synchronization signal they create themselves. In such cases, the signal processing unit 15 does not need to supply a one-frame synchronization signal to the image sensor.

[0019] The image processing unit 22 of the processor 20 buffers the imaging data output from the signal processing unit 15 and performs predetermined image processing on the imaging data, and then generates a video format signal and outputs it to the monitor 40. Examples of image processing include demosaic processing, matrix calculation, and edge enhancement processing.

[0020] Next, referring to Fig. 2, a description will be given of the parts related to light source control in the electronic endoscope system 1 of Fig. 1. Fig. 2 is a block diagram showing in more detail the parts related to light source control in the electronic endoscope system 1. In Fig. 2, the light source module 30, the control unit 21, and the memory 23 constitute an example of a light source device.

[0021] 2 , the light source module 30 includes an LED 31, a driver circuit 32, a photodetector 34, ADCs (Analog to Digital Converters) 35 and 37, and a thermistor 36. The control unit 21 includes a CPU 25 and a gain adjustment unit 26. As described above, the light source module 30 includes one or more LEDs, but the configuration for processing each LED is the same, so the following description will focus on one LED system. For example, in FIG. 2 , the light source module 30 is illustrated with one driver circuit 32 and one LED 31 system for the analog dimming signal and the PWM dimming signal supplied from the control unit 21. When multiple LEDs are included, multiple systems corresponding to the number of LEDs actually provided are provided in the light source module 30.

[0022] Generally, PWM dimming and analog dimming are known as LED dimming methods. PWM dimming is a method of adjusting the illuminance of an LED by adjusting the duty ratio of a PWM signal, while analog dimming is a method of adjusting the illuminance of an LED by changing the amount of current supplied to the LED. The following description will be given using an example in which an LED is subjected to analog dimming, but the same method can be applied to PWM dimming as well.

[0023] The memory 23 stores light intensity data of the LEDs 31 measured when the light source module 30 is shipped from the factory or when the system is first started up after the light source module 30 is incorporated into the processor 20 (for example, data indicating the value of the light intensity detected by the photodetector 34 when a current of a reference current value is passed through the LEDs 31 (referred to as the "light intensity reference value"). Furthermore, the memory 23 records the value of the light intensity detected by the photodetector 34 when a current of the reference current value is passed through the LEDs 31 at each system startup, as well as the detection value of the thermistor 36, which will be described later. In one embodiment, instead of the value of the light intensity at each system startup, the value may be the average light intensity from the first system startup after the light source module 30 is incorporated into the processor 20, or the average light intensity at the most recent multiple system startups. The variance of the light intensity at multiple system startups may also be recorded.

[0024] When the processor 20 is started, the CPU 25 generates and outputs an analog dimming signal IL indicating the value of the current to be passed through the LEDs 31 of the light source module 30. The generated signal IL is a required illuminance based on an operation input to the operation panel 24, or a value corresponding to automatic dimming control (not shown). Note that the generation and output of the signal IL may be performed by an ASIC, FPGA, or the like (not shown) instead of the CPU 25.

[0025] The gain adjustment unit 26 amplifies the signal IL supplied from the CPU 25 based on a gain specified by the CPU 25 and outputs the amplified signal IL_OUT. The CPU 25 determines the gain based on the difference between the reference light intensity value stored in the memory 23 and the light intensity of the LED 31 (an example of a currently detected value) detected by the photodetector 34 when a current of the reference current value flows through the LED 31 at system startup. For example, if the currently detected value is 20% lower than the reference light intensity value, the gain is determined to compensate for the 20% decrease. Note that, when determining the difference, an average value of the current light intensity and the detected light intensity values ​​at the most recent system startups may be used instead of the current (current) light intensity of the LED 31 detected by the photodetector 34.

[0026] The driver circuit 32 drives the LED 31 based on the signal IL_OUT supplied from the control unit 21. The driver circuit 32 drives the LED 31 so that the larger the value of the current indicated by the signal IL_OUT, the larger the current that flows through the LED 31.

[0027] Although the above correction shows an example in which the gain is adjusted based on a single reference current value, this is not limitative. Generally, the relationship between the current and the light intensity of an LED is nonlinear, so it is also possible to measure and record the light intensity of the illumination light from the LED 31 when a current of a plurality of different reference current values ​​is passed through it in advance, and when the system is started up, measure the light intensity value of the LED 31 by passing a current of the corresponding plurality of different reference current values ​​through it, and calculate the coefficients of a polynomial model that shows the relationship between the current value passed through the LED 31 and the gain.

[0028] The photodetector 34 is configured by, for example, a photodiode (PD) and outputs an electrical signal (analog signal) corresponding to the amount of light emitted from the LED 31. As will be described later, the photodetector 34 is disposed near the LED 31, and therefore can accurately measure the amount of light emitted from the LED 31. The ADC 35 converts the electrical signal output from the photodetector 34 into a digital signal and sends it to the CPU 25.

[0029] In one embodiment, a thermistor 36 is installed in the light source module 30. The thermistor 36 measures the temperature of the LED 31 and is preferably, but not necessarily, located near the LED 31 on the board on which the LED 31 is mounted. Since it is sufficient to grasp the relative temperature change of the LED 31, the thermistor 36 may be located at any position on the board on which the LED 31 is mounted. Generally, LED characteristics are temperature-dependent (the light output decreases as the temperature increases). Therefore, it is advisable to record the temperature detected by the thermistor 36 when the light intensity reference value is acquired, and perform correction of the LED 31 if the difference between the temperature detected by the thermistor 36 when the light intensity is acquired at system startup (when correcting the LED 31) and the temperature detected by the thermistor 36 when the light intensity is acquired is equal to or less than a predetermined value.

[0030] Next, the startup process of the electronic endoscope system 1 will be described with reference to the flowchart in Figure 3. When the electronic endoscope system 1 is powered on, the control unit 21 applies a reference current to the LED 31 and measures the light intensity and temperature of the LED 31 (step S2). At this time, the CPU 25 generates a signal IL corresponding to the reference current and controls the gain adjustment unit 26 to output a signal IL_OUT without amplifying the signal IL. The output signal IL_OUT is supplied to the driver circuit 32 of the light source module 30. The light intensity of the illumination light emitted from the LED 31 based on the reference current is detected by the photodetector 34, and the resulting digital value is supplied to the CPU 25. The CPU 25 stores (records) the light intensity value of the LED 31 at the reference current in the memory 23 (step S4).

[0031] The CPU 25 determines whether the light intensity value (currently detected value) of the LED 31 at the reference current value is within a range that does not require correction (step S6). Specifically, the CPU 25 compares the current detected value with the reference light intensity value stored in the memory 23, and if the difference between the two is equal to or less than a predetermined threshold, it determines that the current detected value is within a range that does not require correction (step S6: YES), and ends the startup process.

[0032] On the other hand, if the CPU 25 determines that the currently detected value is not within the range not requiring correction, it determines whether the currently detected value is a value that requires correction but is not abnormal, or whether the currently detected value is abnormal (step S8). In step S8, if the difference between the currently detected value and the reference light quantity value stored in the memory 23 is greater than a predetermined second threshold value that is set to a value greater than the threshold value used in step S6, the currently detected value is determined to be abnormal. For example, if the output characteristics of the LED 31 have significantly deteriorated due to aging or damage caused by temperature, the currently detected value of the LED 31 will be abnormal. If the currently detected value is determined to be abnormal (step S8: YES), the CPU 25 outputs a predetermined warning to the monitor 40 (step S10) and terminates the startup process.

[0033] If it is determined that the current detected value is not at an abnormal level (step S8: NO), the CPU 25 determines a gain based on the light intensity reference value so as to correct the output characteristics of the LED 31 (step S12), and ends the startup process. In this case, when the system is operated after the startup process, the CPU 25 operates the gain adjustment unit 26 using the gain determined in step S12.

[0034] Next, the arrangement of the LEDs 31 and the photodetector 34 in the light source module 30 will be described with reference to Figures 4 and 5. Figure 4 shows a partial plan view of the substrate 300 of the light source module 30. Figure 5 shows a cross-sectional view taken along line A-A of the plan view.

[0035] In order to accurately detect the amount of light emitted by the LED 31 even when the amount of light emitted from the LED 31 is small and to improve the accuracy of correction for the LED 31, it is necessary to place the photodetector 34 as close as possible to the LED 31. Furthermore, placing the photodetector 34 as close as possible to the LED 31 also contributes to space-saving of the light source module 30. On the other hand, if the photodetector 34 is placed close to the LED 31, the heat generated by the LED 31 may increase the temperature of the photodetector 34, which may damage the photodetector 34 or may reduce the linearity of the photodetector 34 due to an increase in dark current, etc. Therefore, in the light source module 30, a slit is formed on the substrate 300 as a through groove to suppress heat conduction from the LED 31 to the photodetector 34 while arranging the LED 31 and the photodetector 34 close to each other on the same substrate.

[0036] In one embodiment, as shown in the plan view of FIG. 4 , a slit 50 is provided that includes a portion that extends across the imaginary line IM between the LED 31 and the photodetector 34. Providing a through groove in the portion that extends across the imaginary line IM has the effect of blocking the flow of heat directly from the LED 31 to the photodetector 34. The slit 50 illustrated in FIG. 4 is preferable in that it is formed in a U-shape that surrounds the photodetector 34 on three sides. In this case, it is possible to block not only the heat that flows directly from the LED 31 to the photodetector 34, but also the heat that flows laterally toward the photodetector 34. In other words, it is possible to block the heat that is transmitted from the LED 31 through the substrate 300 on three sides.

[0037] Conductor patterns 41 and 42 are formed on the substrate 300, extending from the two terminals of the photodetector 34 to the connector 38, respectively. The conductor patterns extending from each terminal of the LED 31 are not shown in FIG. 4 . Referring to the cross-sectional view taken along line A-A in FIG. 5 , the LED 31 and the photodetector 34 are surface-mounted on the substrate 300. An insulating layer 43, a solder resist 44 or a conductor pattern 45, a solder paste 46, and a pad 47 are layered on the substrate 300. The terminals (electrodes) of the LED 31 and the photodetector 34 are bonded to the pad 47. These layering and mounting methods can be performed using known techniques and will not be described in detail. The slits 50 are formed before bonding the LED 31 and the photodetector 34 to the pad 47.

[0038] The portion of the slit 50 that crosses the imaginary line IM in the plan view of Fig. 4 penetrates the substrate 300 in the A-A cross-sectional view of Fig. 5. Since the substrate 300 is often made of a conductor with high thermal conductivity such as copper or aluminum, by penetrating the substrate 300 with the slit 50, heat conduction from the LED 31 to the photodetector 34 is significantly suppressed. Note that if the LED 31 and the photodetector 34 were disposed on two different substrates without providing the slit 50, although heat conduction from the LED 31 to the photodetector 34 could be blocked, this is not preferable because variations in the arrangement of the two substrates may impair the detection accuracy of the photodetector 34.

[0039] The shape of the slit 50 shown in Figure 4 is merely one example, and other shapes may be adopted. Figures 6 to 8 show modified examples of the light source module. Figures 6 to 8 each show slits 51 to 53 with shapes different from those shown in Figure 4. The slit 51 shown in Figure 6 is similar to the slit 50 in Figure 4 in that it includes a portion that extends across the imaginary line IM between the LED 31 and the photodetector 34, but differs from the slit 50 in that it is formed in a U-shape that surrounds the LED 31 on three sides. In this case, too, it is possible to block heat from the LED 31 toward the photodetector 34 on three sides.

[0040] The slit 52 shown in FIG. 7 is similar to the slit 50 in FIG. 4 in that it includes a portion extending across the imaginary line IM between the LED 31 and the photodetector 34. However, it differs from the slit 50 in that it is formed in an I-shape rather than a U-shape overall. In this case, too, heat transfer from the LED 31 to the photodetector 34 is suppressed. It is preferable that the slit 52 be sufficiently long. The slit 53 shown in FIG. 8 is similar to the slit 50 in FIG. 4 in that it includes a portion extending across the imaginary line IM between the LED 31 and the photodetector 34. However, it differs from the slit 50 in that it is formed in an H-shape overall so as to surround both the LED 31 and the photodetector 34 on three sides. In this case, too, heat directed from the LED 31 to the photodetector 34 can be blocked on three sides.

[0041] As described above, in the light source module 30, the LED 31 that emits illumination light for a subject and the photodetector 34 that detects the illumination light emitted by the LED 31 are mounted on the same board. When the control unit 21 detects the amount of illumination light multiple times using the photodetector 34 under the same conditions, it determines whether the LED 31 has deteriorated based on the difference between the current and previous detection values ​​of the amount of illumination light. Because the photodetector 34 receives direct light emitted from the LED 31 rather than light reflected from the subject, it can timely detect deterioration over time (e.g., a decrease in light amount) of the LED 31. Furthermore, the board on which the LED 31 and the photodetector 34 are mounted has a through groove formed to suppress heat conduction from the LED 31 to the photodetector 34. This allows the photodetector 34 to be placed sufficiently close to the LED 31 without adversely affecting the photodetector 34 due to heat. This allows the light amount to be accurately detected even when the amount of illumination light from the LED 31 is low, and improves the accuracy of corrections to the LED 31 based on the detection value of the photodetector 34.

[0042] The light source device and electronic endoscope system of the present invention have been described in detail above, but the light source device and electronic endoscope system of the present invention are not limited to the above-described embodiments, and various improvements and modifications may be made without departing from the spirit and scope of the present invention.

[0043] The present invention is related to patent application No. 2023-215481, filed with the Japan Patent Office on December 21, 2023, the entire contents of which are incorporated herein by reference.

Claims

1. A light source device comprising: a substrate; a light-emitting unit arranged on the substrate for emitting illumination light for a subject; a light-detecting unit arranged on the substrate for detecting the illumination light emitted by the light-emitting unit; and a control unit for determining whether or not the light-emitting unit has deteriorated based on a difference between a current detection value and a previous detection value of the amount of illumination light when the amount of illumination light is detected multiple times by the light-detecting unit under the same conditions, wherein a through groove is formed in the substrate to suppress heat conduction from the light-emitting unit to the light-detecting unit.

2. The light source device according to claim 1, wherein the through groove extends across an imaginary line between the light emitting section and the light detecting section when the substrate is viewed in a plan view.

3. The light source device according to claim 2, wherein the through groove is formed in a U-shape so as to surround three sides of the light emitting section and / or the light detecting section when the substrate is viewed in a plan view.

4. A light source device as claimed in any one of claims 1 to 3, wherein when the control unit determines that there is no deterioration of the light-emitting unit, it corrects the light emission intensity of the light-emitting unit based on the difference between a reference value of the illumination light detected by the light detection unit and the current detection value.

5. An electronic endoscope system comprising: a light source device according to any one of claims 1 to 4; an electronic scope having an imaging device and configured to obtain images of the biological tissue based on illumination light irradiated from said light source device onto the biological tissue; and a processor for processing the images of the biological tissue obtained by said electronic scope.

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