Light source device and endoscope system
By using multiple semiconductor light-emitting elements in the endoscope system to control the light emission profile of light sources in different wavelength bands, the image quality problem caused by rolling shutter is solved, achieving stable image quality and light quantity, and avoiding uneven brightness and horizontal stripes.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HOYA CORPORATION
- Filing Date
- 2021-09-22
- Publication Date
- 2026-07-24
Smart Images
Figure CN116113866B_ABST
Abstract
Description
Technical Field
[0001] This disclosure relates to a light source device and an endoscope system. Background Technology
[0002] In a conventional endoscope device equipped with an image sensor using a rolling shutter method, simulated global exposure is performed by turning off the light source during the effective pixel readout period of the image sensor (during the rolling shutter period) and turning on the light source at other times (during the simulated global exposure period) (pulse emission control), thereby avoiding undesirable phenomena caused by the rolling shutter, such as distortion or artifacts.
[0003] On the other hand, when the light source is completely extinguished during the rolling shutter, the amount of light will be insufficient depending on the subject (the part of the object being observed), making it impossible to obtain a good image. For example, patent documents 1 to 3 show light source control that includes a portion of the rolling shutter period in the pulsed emission period in order to eliminate this insufficient light.
[0004] Existing technical documents
[0005] Patent documents
[0006] Patent Document 1: Japanese Patent Application Publication No. 2018-182580
[0007] Patent Document 2: Japanese Patent No. 5379932
[0008] Patent Document 3: Japanese Patent No. 6239220 Summary of the Invention
[0009] The problem that the invention aims to solve
[0010] However, when the light source control is implemented as described in Patent Documents 1 to 3, uneven brightness or horizontal stripes may occur in adjacent frames due to the exposure time difference between each line. Furthermore, due to the variation in the pulse emission period of each frame, this uneven brightness or horizontal stripes shifts up and down on the displayed screen, becoming glaring. Additionally, when offset emission is performed during rolling shutter speed to eliminate insufficient light, if the offset emission becomes stronger to some extent, an unnatural image may be generated, resulting in a double exposure of a long-exposure image and a high-speed exposure image.
[0011] This disclosure was made in view of the following situation, and its purpose is to provide a technique that ensures sufficient light while avoiding the generation of distortion and artifacts caused by rolling shutter, and that even if changes in the pulse luminescent organ are involved during rolling shutter, uneven brightness and horizontal stripes are not obvious.
[0012] Technical solutions for solving the problem
[0013] To address the aforementioned issues, this embodiment proposes a light source device, specifically a light source device for generating illumination light for illuminating a subject. It comprises: a plurality of semiconductor light-emitting elements for emitting light at different wavelengths; and a control unit for controlling the emission profiles of the plurality of semiconductor light-emitting elements and driving the plurality of semiconductor light-emitting elements. The emission profiles include a strong emission period emitting light at a predetermined light intensity and a weak emission period emitting light at a light intensity weaker than the predetermined light intensity. The control unit performs a restoration control process that maintains the total emission amount during the strong emission period and the weak emission period at a constant value while replacing the emission amount during the weak emission period with the emission amount during the strong emission period.
[0014] Furthermore, this embodiment also proposes an endoscope system, specifically an endoscope system that inserts an endoscope into an object to obtain an image of the subject. The system comprises: multiple semiconductor light-emitting elements that emit light at different wavelengths; an imaging element that illuminates the subject with illumination light and detects reflected light from the subject to generate an image signal; a processor that processes the image signal to generate an image of the subject and displays it on a monitor; a main control unit that generates a control signal based on the image signal to control the light emission profile of the multiple semiconductor light-emitting elements; and a light source control unit that receives the control signal from the main control unit and drives the multiple semiconductor light-emitting elements with a drive signal corresponding to the light emission profile. The light emission profile includes a strong light emission period emitting light at a predetermined light intensity and a weak light emission period emitting light at a light intensity weaker than the predetermined light intensity. The main control unit determines the light emission profile by performing a restoration control process, wherein the restoration control process maintains the total amount of light emission during the strong light emission period and the light emission during the weak light emission period constant while replacing the light emission during the weak light emission period with the light emission during the strong light emission period.
[0015] Further features relating to this disclosure will become apparent from this specification and the accompanying drawings. Furthermore, this disclosure will be realized and obtained by means of elements and combinations thereof, as well as embodiments described below and in the appended claims.
[0016] It should be understood that the description in this specification is exemplary only and is not intended to limit the claims or embodiments in any way.
[0017] Invention Effects
[0018] According to this disclosure, while avoiding the generation of distortion and artifacts caused by rolling shutter, sufficient light is ensured, and even if the changes in the pulse luminescent organ are involved during rolling shutter, uneven brightness and horizontal stripes can be made less noticeable. Attached Figure Description
[0019] Figure 1 This is an example diagram showing the overall appearance of the endoscope system according to this embodiment.
[0020] Figure 2 This is a schematic diagram illustrating the internal structure of the endoscope system according to this embodiment.
[0021] Figure 3 This is a diagram showing an example of the internal configuration of the light source device 201 disposed inside the processor 200.
[0022] Figure 4 This is a graph showing the spectral (wavelength characteristics) of each LED from 2011 to 2015.
[0023] Figure 5 This is a diagram showing the characteristics of the illumination light (light used to illuminate the observation area) generated by passing each LED through orthogonal prisms 2017 and 2018.
[0024] Figure 6 This is a diagram showing an example of the configuration of a light source using LEDs with different light distributions.
[0025] Figure 7 It is a graph showing the ratio of emitted light to current for each LED.
[0026] Figure 8 This is a diagram showing the effective pixel area and ineffective area of a camera element using a rolling shutter mode, with a CMOS sensor as an example.
[0027] Figure 9 This illustrates that when performing general dimming control processing, using a device with... Figure 8 A diagram showing the phenomena (features) that appear in the images captured by the camera element on the camera surface.
[0028] Figure 10 This is a diagram illustrating the operation when extended control (time control only) is performed during pulsed emission and the corresponding state of the acquired image.
[0029] Figure 11 This is a diagram illustrating an outline of the improved dimming control process of this embodiment.
[0030] Figure 12 It is a diagram used to illustrate the effect of the intensity difference between strong and weak light emission.
[0031] Figure 13 To show in more detail Figure 11 The diagram illustrates the dimming control process and serves as an example of an inappropriate dimming control process.
[0032] Figure 14This diagram illustrates the offset luminescence processing (micro-pulse) during periods of no luminescence (or periods of weak luminescence where the luminescence intensity is too weak to be visually discernible).
[0033] Figure 15 It is a diagram used to illustrate the offset luminescence processing (weak continuous light) during periods of no luminescence (or periods of weak luminescence where the luminescence intensity is too weak to be visually discernible).
[0034] Figure 16 This diagram illustrates the differences in the captured image produced when the imaging element rapidly approaches the subject, depending on whether there is offset luminescence.
[0035] Figure 17 This is a flowchart illustrating the dimming control process in this embodiment. Detailed Implementation
[0036] The embodiments of this disclosure will now be described with reference to the accompanying drawings. Furthermore, as one embodiment of this disclosure, an endoscope system will be used as an example for description.
[0037] Examples of sites that can be observed using an endoscope include respiratory organs and digestive organs. Examples of respiratory organs include the lungs, bronchi, and ears, nose, and throat. Examples of digestive organs include the large intestine, small intestine, stomach, esophagus, duodenum, uterus, and bladder. When observing these sites, using images that emphasize specific biological structures is more effective.
[0038] Composition of an Endoscopic System
[0039] Figure 1 This is an example diagram showing the overall appearance of the endoscope system according to this embodiment. Figure 2 This is a schematic diagram illustrating the internal structure of the endoscope system according to this embodiment. The endoscope system 1 includes an endoscope device (electronic observer) 100, a processor 200, and a monitor 300. The processor end of the endoscope device 100 is provided with an endoscope connector (hereinafter referred to as "connector") 400, which includes connector circuitry related to the features of this embodiment.
[0040] The endoscope device 100 includes an elongated tubular insertion portion 11 that is inserted into the body of the patient. For example, the endoscope device 100 includes an LCB (Light Carrying Bundle) 101 for guiding illumination light from the light source device 201 described later; a light distribution lens 102 disposed at the exit end of the LCB 101; an imaging unit 103 that receives reflected light from the irradiated portion (observation area) through an objective lens (not shown); a drive signal processing circuit 105 for driving the imaging unit 103; and a first memory 106.
[0041] Irradiation light from the light source device 201 enters the LCB 101 and propagates through repeated total internal reflection within the LCB 101. The illumination light (light source) propagating within the LCB 101 exits from the exit end of the LCB 101, which is located in the front end portion 12 of the insertion portion 11, and illuminates the observation area via the light distribution lens 102. The return light from the illuminated portion passes through the objective lens and is projected onto the pixels on the light-receiving surface of the imaging unit 103 to form an optical image.
[0042] The imaging unit 103 is disposed within the front end portion 12 of the insertion portion 11, and can be a CMOS (Complementary Metal Oxide Semiconductor) image sensor that is a rolling shutter type image sensor. The imaging unit 103 accumulates the optical image (return light from living tissue) formed by each pixel of the light-receiving surface into a charge corresponding to the amount of light, and generates and outputs R, G, B image signals. In addition, the imaging unit 103 is not limited to a CMOS image sensor, and can be any image sensor based on the rolling shutter type, and can also be replaced with other types of imaging devices. The signals output from the imaging unit 103 are processed by the lens connector circuit 401 provided in the lens connector 400, as described below.
[0043] The processor 200 is an integrated device comprising a signal processing unit for processing signals from the endoscope device 100, and a light source device for illuminating the interior of a body cavity that is inaccessible to natural light via the endoscope device 100. In other embodiments, the signal processing unit and the light source device may be configured separately. The processor 200 includes a light source device 201, a system controller 202, a photometer 203, a pre-processing signal circuit 205, a color conversion circuit 206, a post-processing signal circuit 207, and a second memory 208.
[0044] The processor 200 may also have an operation panel (not shown). The operation panel can take various forms. Specifically, it can be, for example, hardware keys for each function packaged on the front of the processor 200, a touchpad-style GUI (graphical user interface), or a combination of hardware keys and a GUI. The operator (physician) can perform the mode switching operations described later through the operation panel.
[0045] The metering unit 203 obtains the brightness information of the image signal obtained by shooting from the gain circuit included in the color conversion circuit 206, compares it with a predetermined appropriate brightness value (for example, the information of the appropriate brightness value can be stored in advance in the internal memory of the metering unit 203, not shown), and notifies the system controller 202 of the comparison result (whether the current brightness value is appropriate, high or low).
[0046] The system controller 202 executes various programs stored in a memory (not shown) and centrally controls the entire endoscope system 1. The system controller 202 uses control signals to control the operation and timing of various circuits in the processor 200 to properly process the endoscope device 100 connected to the processor 200. Additionally, the system controller 202 can be connected to the aforementioned operation panel.
[0047] In addition, the system controller 202 receives a comparison result from the metering unit 203 after comparing it with an appropriate brightness value, determines whether the current exposure should be maintained, whether the exposure should be increased (including the increased level value), or whether the exposure should be decreased (including the decreased level value), and outputs it to the light source device 201 as an exposure control signal.
[0048] Furthermore, the system controller 202 modifies various actions of the endoscope system 1 and the parameters for each action based on instructions from the operator input from the operation panel. For example, when the operator selects an observation mode (mode switching operation) via the operation panel, the system controller 202 outputs a mode selection signal to the light source device 201, which is used to cause the light source corresponding to the observation mode to emit light. As described later, the light source device 201 can, for example, use multiple LEDs (Light Emitting Diodes) that emit light of different wavelengths (see [reference]). Figure 3 When an operator selects an observation mode (e.g., normal observation mode, special light observation mode, SatO2 mode, etc.) by operating a mode selection switch set on the processor 200, the system controller 202 generates a mode selection signal corresponding to the selected mode and provides it to the light source control unit 2016 of the light source device 201 (see reference). Figure 3 The light source control unit 2016 determines the combination of light-emitting LEDs, their intensity, and light quantity based on the mode selection signal (for example, pre-stores the combination of light-emitting LEDs corresponding to the mode selection signal in an internal memory not shown), and outputs the necessary LED control signals from each LED 2011 to 2015. When each LED 2011 to 2015 emits light of a different wavelength according to the LED control signals provided from the light source control unit 2016, the emitted light is combined by orthogonal prisms to generate illumination light (composite light).
[0049] Data communication between the endoscope device 100 and the processor 200 can be achieved using wired communication or optical wireless communication.
[0050] like Figure 2As shown, the endoscope device 100 and the processor 200 are connected via a scope connector 400. The connector 400 includes an LCB, which is part of an LCB101 extending from the processor 200 to the endoscope device 100, and a scope connector circuit 401. In this embodiment, the scope connector circuit 401 is disposed within the scope connector 400, but this circuit does not necessarily have to be located within the scope connector 400. For example, a circuit equivalent to the scope connector circuit 401 may be disposed in the connector on the processor 200 side or inside the processor 200.
[0051] <Example of the internal structure of the light source device 201>
[0052] Figure 3 This is a diagram illustrating an example of the internal configuration of a light source device 201, for example, disposed inside a processor 200.
[0053] The light source device 201 includes: a green LED 2011 that emits green light, a blue LED 2012 that emits blue light, a red LED 2013 that emits red light, an amber LED 2014 that emits amber light, a UV LED 2015 that emits UV light, a light source control unit 2016 for controlling the emission of light from each of the LEDs 2011 to 2015, and orthogonal prisms 2017 and 2018.
[0054] When the light source control unit 2016 receives an exposure control signal from the system controller 202, it changes the emission profile of each LED by controlling the emission period and applied current value of each currently emitting LED (the combination of emitting LEDs is determined according to the observation mode) and performs exposure adjustment (light intensity adjustment) (see below). Figure 11 and Figure 13 For example, after changing the light emission profile by one level, the light source control unit 2016 determines whether to change the light emission profile again to adjust the exposure based on the exposure control signal determined by the light measurement result of the light metering unit 203 (a comparison result after comparing with an appropriate brightness value).
[0055] Furthermore, the light source control unit 2016 determines the combination of LEDs to emit light based on a mode selection signal, which indicates the observation mode selected by the operator. At the start of the emission phase, the light source control unit 2016 controls the emission of each LED according to, for example, a predetermined emission profile (default emission period and drive current value), and then performs exposure adjustments as described above.
[0056] <About the various LED light sources>
[0057] Figure 4 This is a graph showing the spectral (wavelength characteristics) of each LED from 2011 to 2015. Furthermore, Figure 5 This is a diagram showing the characteristics of the illumination light (light used to illuminate the observation area) generated by passing each LED through orthogonal prisms 2017 and 2018.
[0058] The green LED 2011 has a transmission band of 540nm to 575nm, a peak wavelength of 550nm, and a half-width of 30nm. For example... Figure 4 As shown, a phosphor is mounted on the green LED 2011, through which light with a transmission wavelength of approximately 400nm to 780nm is emitted. That is, white light is essentially emitted through the green LED and phosphor, but this white light is an intermediate product. As described later, the transmission wavelength is narrowed by the orthogonal prism 2018, and the green light is then directed onto the observation area. The blue LED 2012 has a transmission wavelength of 460nm to 490nm, a peak wavelength of 456nm, and a half-width of 21nm. The red LED 2013 has a transmission wavelength of 630nm to 1000nm, a peak wavelength of 650nm, and a half-width of 20nm. The amber LED 2014 has a transmission wavelength of 600nm to 615nm, a peak wavelength of 613nm, and a half-width of 19nm. The UV LED 2015 has a transmission wavelength of 385nm to 425nm, a peak wavelength of 405nm, and a half-width of 14nm. .
[0059] When the light emitted from each of the LEDs 2011 to 2015, including the green LED 2011 equipped with a phosphor (white light, blue light, red light, amber light, and UV light as intermediate products), passes through the orthogonal prisms 2017 and 2018, it will become... Figure 5 The various types of light, exhibiting the characteristics shown, are irradiated onto the observation area. Specifically, the white light emitted from the green LED2011 + phosphor is confined to the transmission band by the orthogonal prism 2018, becoming green light in the range of 520nm to 595nm. The blue light emitted from the blue LED2012 is transformed into blue light in the range of 440nm to 500nm by the orthogonal prisms 2017 and 2018. Furthermore, the red light emitted from the red LED2013 is transformed into red light in the range of 620nm to 630nm by the orthogonal prisms 2017 and 2018. The amber light emitted from the amber LED2014 is transformed into amber light in the range of 580nm to 630nm by the orthogonal prisms 2017 and 2018. Further, the UV light emitted from the UV LED2015 is transformed into UV light in the range of 380nm to 450nm by the orthogonal prism 2018.
[0060] <Correction of linearity difference for each LED>
[0061] In the case where the light source device 201 is composed of multiple LEDs, not only are there differences in the wavelengths of the light emitted by each LED 2011 to 2015, but there are also differences in the light distribution (photometric distribution in each direction) (see reference). Figure 6 (Example of a light source using LEDs with different wavelengths). The color and light distribution of the emitted light from each LED 2011 to 2015 may vary. Furthermore, depending on the type of LED, when the forward voltage is reduced to decrease the drive current, the drive current drops sharply, and the LED stops emitting light; therefore, sometimes the drive current cannot be reduced significantly. To address this situation, the linearity of the emitted light quantity / current ratio of each LED 2011 to 2015 must be dynamically corrected by controlling the drive current of each LED 2011 to 2015.
[0062] However, since the process of dynamically correcting linearity errors is complex, it is preferable to predetermine the drive current value to avoid linearity errors. Therefore, in this embodiment, a calibration table for correcting the linearity of the emitted light quantity / current ratio is prepared in advance, and the drive current value of each LED 2011 to 2015 is determined using this calibration table. Figure 7 This is a graph showing the emitted light quantity / current ratio of each LED. Figure 7 In this example, only the relationship between two LEDs (LED1 and LED2) is shown, but the same applies when using the five LEDs 2011 to 2015 shown in this embodiment. Figure 7 The emitted light intensity / current ratio of each LED can be obtained by pre-measuring each LED. Therefore, as a correction value, a correction table (stored in memory) is prepared in advance, using the reciprocal of the emitted light intensity / current ratio as the correction parameter. The light source control unit 2016 calculates the corrected drive current value by multiplying it by the correction parameter corresponding to the desired emitted light intensity (the target emitted light intensity obtained through exposure adjustment), and drives each LED. In this way, even when the wavelength or light distribution of the emitted light from each LED is different, the linearity of the emitted light intensity / current ratio can be appropriately controlled.
[0063] <Example of the configuration of the imaging surface of an imaging element>
[0064] Figure 8This diagram illustrates the effective pixel area and ineffective area of a rolling shutter imaging element, using a CMOS sensor as an example. The CMOS sensor includes an effective pixel area that can be captured and an ineffective area that cannot. Furthermore, a portion (peripheral area) of the effective pixel area is obscured, effectively becoming an area where an image signal cannot be acquired. When shooting with such an imaging element (in the case of global exposure), various phenomena (features) appear in the captured image. Additionally, in this embodiment, the period not displayed on the screen is defined as the global exposure period, but the technical concept of this embodiment is not limited to this.
[0065] <General dimming control processing>
[0066] Figure 9 This illustrates that when performing general dimming control processing, using a device with... Figure 8 A diagram showing the phenomena (features) appearing in images captured by the imaging element of the camera surface. For example... Figure 9 As shown in Figure a, when pulsed illumination is performed during the readout period of lines not displayed in the image, simulated global exposure can be achieved. Furthermore, as... Figure 9 As shown in b, when pulsed emission is performed, the top row of the effective pixel area receives less exposure than other rows during the period from readout to reset, and the top row appears somewhat darker. However, if the period from readout to reset is sufficiently shorter than the simulated global exposure period (e.g., less than 1%), the darkness is not noticeable. Furthermore, as... Figure 9 As shown in Figure c, during pulsed emission, the upper half of the effective pixel area darkens slightly, but due to the increased total exposure across rows, the darkness in this area becomes less noticeable. This results in the following characteristics: the longer the pulsed emission period, the wider the area with varying exposure, but the brightness difference caused by these exposure differences becomes less pronounced. Furthermore, as... Figure 9 As shown in d, when the pulse emission period is further extended, if the current pulse component increases, the ratio changes smoothly from the bottom to the top of the image. Therefore, artifacts and distortions (undesirable phenomena) become less noticeable.
[0067] Figure 10 This is a diagram illustrating the operation when extended control (time control only) is performed during pulsed emission and the corresponding state of the acquired image. Figure 10 This is a diagram showing in more detail the effect of the extended pulse emission period described above. (See diagram for example.) Figure 10 As shown in Figure A, when the pulse emission period is changed between adjacent frames, the difference in exposure between the lines read before and after the pulse becomes larger, resulting in the horizontal stripes appearing to move up and down on the image. On the other hand, as... Figure 10As shown in B, when the intensity of the weak light emission is changed between adjacent frames, the horizontal stripes on the image become less noticeable.
[0068] However, it is not as described. Figure 9 or Figure 10 Simply extending the exposure time will suffice. This is because, when the exposure is increased, depending on the surrounding environment of the observed area, a whitening effect may occur in the image (bright areas become white). Therefore, it is necessary to maintain an appropriate exposure (the image should not be too dark, nor should it become white) while avoiding distortion and artifacts.
[0069] <Improved dimming control processing>
[0070] Figure 11 This is a diagram illustrating an outline of the improved dimming control process of this embodiment. Furthermore, Figure 12 It is a diagram used to illustrate the effect of the intensity difference between strong and weak light emission.
[0071] When controlling the light source's emission action to ensure that the intensity of light (strong emission) during simulated global exposure is greater than or equal to the intensity of light (weak emission) during rolling shutter, and dimming control is performed by adjusting the weak emission intensity up and down, if the weak emission during rolling shutter is less than or equal to a predetermined threshold, dimming control is generally performed by changing the strong emission intensity or strong emission period within the range of simulated global exposure.
[0072] However, as Figure 12 As shown in Figure A, when the intensity difference between strong and weak light emission increases, and the ratio (integral value ratio) of the product of the intensity and duration of strong light emission (strong light emission integral value) to the product of the intensity and duration of weak light emission (weak light emission integral value) is not large enough, unnatural images are observed, such as double exposure of images with short exposure times and long exposure times. This phenomenon is particularly likely to cause discomfort to the operator when photographing moving subjects. Furthermore, when the light source consists of multiple LEDs with different wavelengths or different light distributions (as in this embodiment), the color or light distribution of the emitted light changes when the emitted light quantity of each LED is not set to a constant ratio. Therefore, as mentioned above, in order to control the drive current value when there is a deviation in the linearity of the light emission quantity / current ratio of each LED, it is necessary to correct the linearity difference of the light emission quantity / current ratio of each LED, which complicates the process.
[0073] Therefore, in order to reduce the complexity of the process, in addition to performing linear correction processing on the emitted light quantity / current ratio of each LED according to the above correction table, any one of the following processes 1 to 3 is performed when the weak luminous intensity is lower than the predetermined threshold.
[0074] Treatment 1: Treatment that reduces weak luminescence intensity while extending the period of strong luminescence.
[0075] Process 2: Processing that shortens the period of weak emission while extending the period of strong emission.
[0076] Treatment 3: Treatment that increases weak emission intensity while shortening the weak emission period.
[0077] In other words, any one of processes 1 to 3 maintains the total luminous integral value (strong luminous integral value + weak luminous integral value) unchanged before and after processing, while spending time sequentially replacing weak luminous emission with strong luminous emission (restoration control processing) to prevent changes in the brightness of the observed image, the phenomenon of horizontal stripes moving up and down in the image, and a decrease in image brightness (brightness reduction). Any one of these processes can eliminate unnatural images such as double exposure that form over time, or undesirable conditions such as changes in the color and distribution of emitted light. For example, it is possible to... Figure 12 Switching from state A (double exposure with horizontal stripes) to... Figure 12 E state (images that have eliminated double exposure or uneven brightness / color and have no horizontal stripes).
[0078] Reference Figure 11 The following details steps 1 through 3. First, the light source control unit 2016 performs dimming control on each LED 2011 through 2015, setting them to strong illumination during the simulated global exposure period and weak illumination during the rolling shutter period, until the exposure reaches an appropriate level. For example... Figure 11 As shown in (1), when reducing the light intensity from a state of uniform light emission throughout the entire period (simulated global exposure period and rolling shutter period), the following dimming control is performed: the light intensity during the rolling shutter period (weak light emission period) is reduced; when there is no light emission during the rolling shutter period, the simulated global exposure period is shortened, or the light intensity during the simulated global exposure period is reduced. On the other hand, as Figure 11 As shown in (2), when the luminous intensity is increased, the following dimming control is performed: the luminous duration during the simulated global exposure period is extended, or the luminous intensity during the simulated global exposure period is increased. When the maximum luminous duration and luminous intensity are reached during the simulated global exposure period, the luminous intensity during the rolling shutter period (weak luminous duration) is increased sequentially.
[0079] For example, assuming by Figure 11 (1) The dimming control achieves an appropriate exposure level in the P1 illumination mode (e.g., a predetermined appropriate level ± α: α is the margin). While continuously shooting in this state, it produces results such as... Figure 12The image shown in Figure A is a double-exposure image. This is because images with different brightness levels can be obtained through a strong illumination image and a weak illumination image, and these images overlap. Therefore, while maintaining the exposure level of illumination mode P1, the dimming control processing is transferred to... Figure 11 Any one of (3-1) to (3-3). Here, Figure 11 (3-1) is equivalent to the above treatment 1. Figure 11 (3-2) is equivalent to treatment 2 above. Figure 11 (3-3) is equivalent to process 3 described above. In processes 1 to 3, when the weak light intensity is less than or equal to a predetermined threshold, a process is performed in each frame to gradually replace the weak light intensity with a strong light intensity period. As a result, the weak light intensity period is eliminated without producing horizontal stripes in the captured image, thereby avoiding the generation of unnatural images and changes in the color / distribution of light from various light sources.
[0080] More specifically, in processing 1 ( Figure 11 In (3-1), the value of luminous intensity × luminous period (weak luminous area) in weak luminous emission is gradually replaced with the value of strong luminous period so that the total area (total luminous integral value) of strong luminous period and weak luminous period is the same, and dimming control (restoration processing) is performed through luminous mode Q1. For example, Figure 11 The light emitted by the restored portions 1001 to 1004 in the frame performing the corresponding restoration processing is compared with the effective pixel area of the imaging element (CMOS sensor) (refer to...) Figure 8 The uppermost and lowermost region of the image is exposed. Therefore, in this frame, the image portion corresponding to the uppermost line is darkened, but the image signal corresponding to that uppermost line can be captured in the next frame.
[0081] Process 2 ( Figure 11 (3-2) and treatment 3 ( Figure 11 (3-3) is a dimming control process based on a different approach (example) from process 1. That is, processes 2 and 3 are the same as process 1, but involve gradually replacing the value of luminous intensity × luminous period (weak luminous area) in the weak luminous period with the value in the strong luminous period (reduction process) to maintain the same total area (total luminous integral value) for both the strong and weak luminous periods. In process 2, while keeping the weak luminous level constant, the weak luminous period is shortened, and the strong luminous period is extended by gradually allocating the luminous integral value corresponding to the reduced weak luminous area due to the shortened period to the strong luminous period. Similarly, in process 3, the weak luminous period is shortened, and the strong luminous period is extended by allocating the luminous integral value corresponding to the reduced weak luminous area due to the shortened period to the weak luminous period and gradually increasing the weak luminous intensity. Emission modes Q1 to Q3 are executed through processes 1 to 3. Furthermore, all emission modes Q1 to Q3 are the same.
[0082] If due to the execution of processes 1 to 3 ( Figure 11 If the change in luminance caused by any of the dimming controls (3-1) to (3-3) is slow enough, it will not cause discomfort to the operator and can avoid the generation of unnatural images such as double exposure. For example, when performing dimming control based on luminance modes Q1 to Q3, the obtained image is as follows: Figure 12 As shown in E, double exposure has been eliminated.
[0083] In illumination modes Q1 to Q3, when the subject is illuminated by light from various light sources, if the exposure level increases and becomes too bright due to subject movement (including camera movement: relative movement) (the exposure level deviates from the appropriate value), then... Figure 11 The process shown in (4-1) is used to explore the appropriate exposure level. For example, when the exposure level is determined to be appropriate at the luminous outline P2 (when the exposure level is too bright, it is appropriate: as above, the exposure level is determined based on the metering result of the metering unit 203), a restoration process (any one of processes 1 to 3) is performed based on the state of the luminous outline P2, and the weak luminous part is restored to strong luminous. On the other hand, when luminous in the state of the luminous outline P2, if the exposure level decreases and becomes too dark due to the movement of the subject (including the movement of the camera: relative movement) (the exposure level deviates from the appropriate value), the process is performed by... Figure 11 The process shown in (4-2) is corrected to an appropriate exposure level (performed sequentially). Figure 11 (As shown in (4-2), the process of increasing the weak luminescence level continues until an appropriate exposure level is achieved. For example, if an appropriate exposure level is achieved in the luminescence profile Q4, such as...) Figure 11 As shown in (5), a restoration process is performed on any one of processes 1 to 3 according to the exposure level of the luminous contour Q4.
[0084] <Detailed explanation of dimming control and how to handle sudden movements of the endoscope>
[0085] Figure 13 To show in more detail Figure 11 The diagram illustrates the dimming control process and serves as an example of an inappropriate dimming control process.
[0086] exist Figure 13For example, when illuminating the subject with light from the luminous contour P11 and taking a picture, if the image is determined to be washed out (the exposure level of P11 is inappropriate), the intensity of the weak light emission during the rolling shutter is sequentially reduced (from contour P11 to the right contour). Here, for example, assuming that an appropriate exposure level (an exposure level that is not washed out and is easy to observe) is achieved in the luminous contour P16, the above-described restoration process (any one of process 1 to process 3) is then performed, and the weak light emission period is replaced with a strong light emission period. Then, the captured image is... Figure 12 State A (when the subject is illuminated in the luminous outline P16, the image becomes an unnatural image, such as a double exposure) becomes Figure 12 The state of E is eliminated, and phenomena such as whitening and double exposure are also eliminated. If the brightness of the captured image does not change (if the change is within a predetermined threshold), light is emitted from each light source 2011 to 2015 in the light emission profile P66.
[0087] Figure 13 In the process, the light-emitting contour P11 moves sequentially to the right to become the light-emitting contour P16, and then dimming control is performed through a restoration process to become the light-emitting contour P66. However, other paths can also be followed (e.g., a tilted forward movement (slowly moving in the vertical direction) such as P11→P12→P13→P24→P25→P36→P46→P56→P66, i.e., a path where dimming control and restoration processes are performed simultaneously). However, dimming control processing cannot be performed according to the path P11→P22→P33→P44→P55→P66. This is because time control is only performed during the period of strong light emission, and... Figure 10 As shown in Figure A, a phenomenon occurs where the bright areas of the image shift vertically (the horizontal stripes shift less). To prevent this phenomenon, it is necessary to spend time slowly restoring the intensity distribution of the weak light emission to strong light emission (restoration processing).
[0088] For example, when it is necessary to obtain from Figure 13 When the luminous outline P66 becomes brighter, extending the intensity distribution of the strong luminescence over time will cause the aforementioned horizontal stripe shifting phenomenon. Therefore, the intensity level of the weak luminescence should be increased first. For example, the luminous outline changes from P66 to P56, and then the dimming control is set to P55. However, when the luminous outline shifts rapidly in the vertical direction, it is synonymous with a rapid shift in the temporal direction. Therefore, for rapid movements of the endoscope (image sensor), it is important to move the outline horizontally and adjust it to an appropriate exposure level before performing restoration processing in the vertical direction.
[0089] On the other hand, when it is necessary to darken from the state of luminous outline P66, it cannot immediately transition to the state of luminous outline P77. Therefore, the following process is performed: the strong luminous level during the rolling shutter is temporarily reduced, and the state of luminous outline P76 is entered during the weak luminous period, and then the state of luminous outline P77 is restored through a restoration process.
[0090] In addition, after determining the appropriate exposure level, dimming control is performed until the luminous outline (Pkk; k = 1, 2, ..., n: n is an integer greater than or equal to 1) is formed when the up and down arrows meet.
[0091] In addition, Figure 13 In this context, the current value Imin represents the linear correction limit of the emitted light quantity / current ratio for each of the aforementioned light sources, or the current value when each LED is off. Therefore, in this embodiment, when performing dimming control to reduce the luminous intensity of weak light emission, the brightness is adjusted by shortening the emission period after the intensity is reduced to Imin, rather than reducing the luminous intensity. Furthermore, in this case, if Imin is sufficiently small relative to strong luminous intensity × time, horizontal stripes will not be observed.
[0092] <Offset Emissive Processing>
[0093] Figure 14 , 15 Figures 1 and 16 are used to illustrate the offset luminescence processing during periods of no luminescence (or periods of weak luminescence where the luminescence intensity is too weak to be visually discernible). Figure 14 The diagram shows offset luminescence caused by a weak pulse. Figure 15 The diagram shows offset luminescence caused by weak continuous light. Figure 16 This diagram illustrates the differences in the captured image produced when the imaging element rapidly approaches the subject, depending on whether there is offset luminescence. Furthermore, here, "weak" refers to a luminescence intensity that is sufficiently low compared to the luminescence intensity during periods of strong luminescence to avoid double exposure, but still allows for visually discernible brightness of the subject when it is close to the endoscope tip.
[0094] Offset light emission processing is different from previous dimming control processing ( Figure 9 (etc.) and the dimming control processing in this embodiment (refer to) Figure 11 and Figure 13 This is performed separately (in the background of the dimming control processing), with a weak offset emission process performed during periods of no emission. This weak offset emission can be considered as pulsed emission (see [reference]). Figure 14 ) and the method of continuous light emission (refer to Figure 15However, other illumination modes are also possible. For example, pulsed and continuous illumination can be combined to form an illumination mode, or an illumination mode with irregular pulse widths can be formed. This weak offset illumination can be considered as 0 (zero) when the illumination intensity is greater than or equal to a predetermined value during dimming control processing (applicable to any dimming control processing). On the other hand, if the illumination intensity is less than the predetermined value (or the illumination intensity is zero) during dimming control processing, the subject is illuminated only by offset illumination. As a result, events that would normally not be captured as images during periods of no illumination can be captured by offset illumination.
[0095] Figure 16 This diagram illustrates the differences in captured images when a camera element rapidly approaches a subject, depending on the presence or absence of weak offset emission (pulsed light, continuous light). In the absence of weak offset emission, the same image as frame Fk-1 is obtained and used as the captured image for frame Fk. On the other hand, in the case of weak offset emission, whether it is pulsed light or continuous light, the captured image for frame Fk is significantly different from that for frame Fk-1, indicating that the event of the camera element rapidly approaching the subject is captured in frame Fk. Furthermore, it is evident that the captured image for frame Fk+1 is not different due to the presence or absence of weak offset emission.
[0096] Dimming Control Process: Flowchart
[0097] Figure 17 This is a flowchart illustrating the dimming control process in this embodiment. Although the following steps are primarily described with the system controller 202 as the main operator, the present invention is not limited thereto; a control unit (processor) for performing action control or computational processing may also be provided and made to perform the operation. Furthermore, the light source control unit 2016 of the light source device 201 may be configured to have the functions of the system controller 202. Therefore, the dimming (restoration) control process may be part of the overall operation of the endoscope system 1 or part of the operation of the light source device 201. In the latter case, the light source control unit 2016 becomes the main operator of each step.
[0098] (i) Step 1701
[0099] The light source control unit 2016 receives a mode selection signal from the system controller corresponding to the observation mode selected by the operator, and uses the above-mentioned calibration table to correct the linearity of the emitted light quantity / current ratio of each light source (any combination of green LED 2011 to UV LED 2015) for each light source to emit light.
[0100] (ii) Step 1702
[0101] The light source control unit 2016 drives each light source to emit light using a drive current that has been linearly corrected for the emitted light quantity / current ratio, generating illumination light and illuminating the subject. Furthermore, the emission profile (strong emission period and weak emission level and period) can be set to a predetermined value (default value), or the emission profile used in the last operation during the last use of the endoscope can be used.
[0102] (iii) Step 1703
[0103] The imaging element (e.g., a CMOS sensor) of the imaging unit 103 detects the reflected light from the subject (observation area) generated by the illumination light generated in step 1702 illuminating the subject, and sends the image signal to the processor 200 via the lens connector circuit 401. The metering unit 203 obtains the brightness information of the current image signal from the gain circuit included in the color conversion circuit 206, compares it with a predetermined appropriate brightness value (e.g., takes the difference), and transmits the comparison result to the system controller 202. Alternatively, in the metering unit 203, the brightness information of the current image signal may only be obtained from the gain circuit, and the comparison with the appropriate brightness value may be performed by other processing units such as the system controller 202.
[0104] (iv) Step 1704
[0105] The system controller 202 compares the comparison result received from the metering unit 203 (or the system controller 202 can calculate the comparison result (difference)) with a predetermined threshold (a threshold used to determine whether the exposure level is appropriate), and determines whether the current exposure level is appropriate. For example, if the comparison result (difference) is less than or equal to the predetermined threshold, it can be determined to be appropriate. If the current exposure level is determined to be inappropriate (No in step 1704), the process proceeds to step 1705. On the other hand, if the current exposure level is determined to be appropriate (Yes in step 1704), the process proceeds to step 1706.
[0106] (v) Step 1705
[0107] The system controller 202 changes the current luminous profile used in the illumination of the subject (indicating information on strong luminous periods, weak luminous periods, and weak luminous levels).
[0108] For example, when the current exposure level is high and the image is too bright (the image appears washed out), the system controller 202 generates an exposure control signal to adjust the exposure level by reducing the weak emission level in the emission profile. Conversely, when the weak emission level in the current emission profile is zero, the system controller 202 generates an exposure control signal to adjust the exposure level by further shortening the strong emission period.
[0109] On the other hand, when the current exposure level is low and the image is too dark, if the strong emission period in the emission contour does not reach the simulated global period width, the system controller 202 extends the strong emission period. Furthermore, if the strong emission period in the current emission contour reaches the simulated global period width, the system controller 202 generates an exposure control signal to adjust the exposure level by further increasing the weak emission level.
[0110] When the luminous profile changes, the process proceeds to step 1702. Here, the luminous profile changes gradually step by step to adjust to an appropriate exposure level. However, for example, information (e.g., a table) showing the relationship between the difference (comparison value) between the brightness value of the captured image and the appropriate brightness value (the brightness value corresponding to the appropriate exposure level) and the magnitude of the change in the luminous profile (information indicating how many steps the luminous profile has changed) can be stored in advance in the internal memory (not shown) of the system controller 202, and the appropriate luminous profile can be directly calculated based on the aforementioned difference (comparison value).
[0111] (vi) Step 1706
[0112] The system controller 202 determines whether restoration control processing is needed for the luminous outline that presents an appropriate exposure level. The determination of whether restoration control processing is needed can be based, for example, on whether the luminous outline has changed since the last restoration control processing. If the luminous outline has not changed, the subject is photographed with the current appropriate exposure level (appropriate brightness) and appropriate dimming (dimming without horizontal stripes), therefore restoration control processing is not required. On the other hand, if the luminous outline has changed, there may be weak luminous components that should be replaced by strong luminous components; therefore, the determination of whether restoration control processing is needed depends on whether there are weak luminous periods in the changed luminous outline.
[0113] If it is determined that restoration control processing needs to be performed (if YES is selected in step 1706), the process proceeds to step 1707. On the other hand, if it is determined that restoration control processing does not need to be performed (if NO is selected in step 1706), the process proceeds to step 1708.
[0114] (vii) Step 1707
[0115] System controller 202 executes Figure 11 Any one of processes 1 to 3 is performed, and while keeping the luminescence integral value (area of the luminescence profile) represented by "strong luminescence period × strong luminescence intensity + weak luminescence period × weak luminescence intensity" constant, the weak luminescence component is gradually replaced with the strong luminescence component. For example, the restoration control process is performed for about 1 second (tens of frames), for example, changing it to be represented by Q1 to Q3. Figure 10 The luminous outline in the image. Therefore, it is possible to obtain the image from a double-exposed image that exhibits horizontal stripes simply by setting the exposure level appropriately. Figure 12 A) obtains an image where these phenomena do not occur. Figure 12 E).
[0116] (viii) Step 1708
[0117] The light source control unit 2016 receives information about the light emission profile to be applied from the system controller 202. Based on the received light emission profile and mode selection signal, it causes any one of the LEDs 2011 to 2015 to emit light, generating illumination light and illuminating the subject. Furthermore, the imaging element (CMOS sensor) of the imaging unit 103 detects reflected light from the illuminated subject, generates an image signal, and sends it to the processor. The processor 200 then performs predetermined image processing on the image signal to generate display image data and displays this image data on the screen of the monitor (display device) 300.
[0118] (ix) Step 1709
[0119] The system controller 202 determines whether the operator has input a command to end the observation, such as ending the recording or turning off the illumination. If the command to end the observation has been input (YES in step 1709), the dimming control process ends. If no command to end the observation has been input (no command detected) (NO in step 1709), the process proceeds to step 1703, continuing the judgment / monitoring of whether the current exposure level is appropriate and dimming control processing, etc. The camera unit 103 is mounted on the front end 12 of the endoscope device 100 and moves within the body cavity of the subject. Therefore, the exposure level may change due to approaching or moving away from the subject (observation area). Therefore, the operation of the light source device 201 is controlled to continuously monitor the brightness level of the recorded image and maintain an appropriate exposure level.
[0120] <Effects of the Implementation Method>
[0121] According to this embodiment, sufficient light can be ensured to capture the subject while avoiding rolling shutter distortion and artifacts. Furthermore, even if changes during pulse emission involve the rolling shutter, the vertical movement of horizontal stripes is not noticeable. Moreover, when using multiple LEDs as light sources simultaneously, if current control is not performed by correcting for linear differences in the emitted light quantity / current ratio of each LED when the luminous intensity changes, the ratio of light quantities of each LED will change, causing variations in pitting or color. However, according to this embodiment, the luminous intensity can be restored to a basic level within a short time, thus solving this problem.
[0122] <Specific matters in this disclosure>
[0123] (1) Specific Item 1
[0124] A light source device is a device for generating illumination light for illuminating a subject, comprising:
[0125] Multiple semiconductor light-emitting elements, each used to emit light in a different wavelength band;
[0126] and a control unit, which controls the light emission profile of the plurality of semiconductor light-emitting elements and drives the plurality of semiconductor light-emitting elements;
[0127] The light emission profile includes a strong light emission period with a predetermined light intensity and a weak light emission period with a light intensity weaker than the predetermined light intensity.
[0128] The control unit performs a restoration control process, which is used to maintain the total amount of light emission during the strong light emission period and the total amount of light emission during the weak light emission period at a constant level, while replacing the amount of light emission during the weak light emission period with the amount of light emission during the strong light emission period.
[0129] (2) Specific Item 2
[0130] A light source device, wherein,
[0131] In Specific Item 1, before the light intensity during the weak light emission period becomes zero, the control unit keeps the length of the weak light emission period constant while reducing the light intensity during the weak light emission period, and replaces the reduced light emission amount with the light emission amount during the strong light emission period, thereby prolonging the strong light emission period.
[0132] (3) Specific Items 3
[0133] A light source device, wherein,
[0134] In Specific Item 1, the control unit shortens the weak emission period while keeping the light intensity constant during the weak emission period, and replaces the amount of light emitted by the shortened period with the amount of light emitted during the strong emission period, thereby extending the strong emission period.
[0135] (4) Specific Items 4
[0136] A light source device, wherein,
[0137] In Specific Item 1, the control unit shortens the length of the weak emission period and increases the light intensity of the weak emission period by the amount of light emitted during the shortened period, thereby replacing the amount of light emitted during the weak emission period with the amount of light emitted during the strong emission period, and thus prolonging the strong emission period.
[0138] (5) Specific Item 5
[0139] A light source device, wherein,
[0140] In any of the specific items 1 to 4, after determining the luminous contour that makes the brightness value of the captured image within a predetermined range, the control unit uses the determined luminous contour as the object to start executing the restoration control process.
[0141] (6) Specific Items 6
[0142] A light source device, wherein,
[0143] In any of the specific items 1 to 5, the control unit also performs a process for correcting the linearity of the emitted light quantity / current ratio of the plurality of semiconductor light-emitting elements.
[0144] (7) Specific Items 7
[0145] A light source device, wherein,
[0146] In any one of specific items 1 to 6, the control unit controls the plurality of semiconductor light-emitting elements such that their light emission intensity during periods of no light emission other than the weak light emission period and the strong light emission period, or during periods of weak light emission where the light emission intensity is too weak to be visually discernible, is sufficiently low compared to the light emission intensity during the strong light emission period, but is able to emit light at a visually discernible level.
[0147] (8) Specific Items
[0148] A light source device, wherein,
[0149] In specific item 7, the control unit performs the offset emission using pulsed light or continuous light.
[0150] (9) Specific Item 9 An endoscope system is an endoscope system in which an endoscope is inserted into an object of observation to obtain an image of the object, and it comprises:
[0151] Multiple semiconductor light-emitting elements, each used to emit light in a different wavelength band;
[0152] An imaging element for illuminating the subject with illumination light and detecting reflected light from the subject to generate an image signal;
[0153] A processor for processing the image signal to generate an image of the subject and displaying it on a monitor; a main control unit for generating control signals based on the image signal to control the light emission profiles of the plurality of semiconductor light-emitting elements;
[0154] And a light source control unit, which is used to receive the control signal from the main control unit and drive the plurality of semiconductor light-emitting elements with a drive signal corresponding to the light emission profile;
[0155] The light emission profile includes a strong light emission period with a predetermined light intensity and a weak light emission period with a light intensity weaker than the predetermined light intensity.
[0156] The main control unit determines the light emission profile by executing a restoration control process, wherein the restoration control process is used to maintain the total amount of light emission during the strong light emission period and the total amount of light emission during the weak light emission period as constant, while replacing the amount of light emission during the weak light emission period with the amount of light emission during the strong light emission period.
[0157] (10) Specific Items 10
[0158] An endoscope system, wherein,
[0159] In specific item 9, the main control unit generates the control signal, which is used to keep the length of the weak emission period constant while reducing the light intensity during the weak emission period before the light intensity during the weak emission period becomes zero, and to replace the light intensity during the weak emission period with the light intensity during the strong emission period, so as to prolong the strong emission period.
[0160] (11) Specific Items 11
[0161] An endoscope system, wherein,
[0162] In specific item 9, the main control unit generates the control signal, which is used to shorten the weak emission period while keeping the light intensity constant during the weak emission period, and replace the amount of light emission by the shortened amount with the amount of light emission during the strong emission period, so as to prolong the strong emission period.
[0163] (12) Specific Items 12
[0164] An endoscope system, wherein,
[0165] In specific item 9, the main control unit generates the control signal, which is used to extend the strong emission period by shortening the length of the weak emission period and increasing the light intensity of the weak emission period by the amount of light emission during the shortened period.
[0166] (13) Specific Items 13
[0167] An endoscope system, wherein,
[0168] In any one of specific items 9 to 12, it further includes a photometer for obtaining brightness value information by using the image signal.
[0169] The main control unit obtains the brightness information from the photometer, and after determining the luminous contour that makes the brightness value of the image signal within a predetermined range, it uses the determined luminous contour as the object to start the restoration control process.
[0170] (14) Specific Items
[0171] An endoscope system, wherein,
[0172] In any one of specific items 9 to 13, the main control unit further generates a control signal for controlling the plurality of semiconductor light-emitting elements such that their light emission intensity during periods of no light emission other than the weak light emission period and the strong light emission period, or during weak light emission periods when the light emission intensity is too weak to be visually discernible, is sufficiently low compared to the light emission intensity during the strong light emission period, but is able to emit light at a visually discernible level, and outputs the signal to the light source control unit.
[0173] Symbol Explanation
[0174] 1. Endoscopic system
[0175] 100 Endoscopic Devices
[0176] 103 camera units
[0177] 200 processors
[0178] 201 Light Source Device
[0179] 2011 Green LED
[0180] 2012 Blue LED
[0181] 2013 Red LED
[0182] 2014 Amber LED
[0183] 2015 UV LED
[0184] 2016 Light Source Control Department
[0185] 2017 and 2018 orthogonal prisms
[0186] 202 System Controller
[0187] 203 Metering Section
[0188] 300 monitor.
Claims
1. A light source device for generating illumination light for illuminating a subject, the light source device comprising: Multiple semiconductor light-emitting elements, each emitting light at a different wavelength; and The control unit is used to control the light emission profile of the plurality of semiconductor light-emitting elements and drive the plurality of semiconductor light-emitting elements. in, The emission profile includes a strong emission period with a predetermined light intensity and a weak emission period with a light intensity weaker than the predetermined light intensity. The control unit performs a restoration control process, which maintains the total amount of light emission during the strong light emission period and the total amount of light emission during the weak light emission period at a constant level, while replacing the amount of light emission during the weak light emission period with the amount of light emission during the strong light emission period. The control unit shortens the length of the weak emission period and increases the light intensity of the weak emission period by the amount of light emitted during that shortened period, thereby replacing the amount of light emitted during the weak emission period with the amount of light emitted during the strong emission period, and thus prolonging the strong emission period.
2. The light source device according to claim 1, wherein, After determining the luminous contour that makes the brightness value of the captured image within a predetermined range, the control unit uses the determined luminous contour as the object to start the restoration control process.
3. The light source device according to claim 1, wherein, The control unit simultaneously performs processing to determine the luminous contour that keeps the brightness value of the captured image within a predetermined range, and the restoration control processing of the luminous contour.
4. The light source device according to any one of claims 1 to 3, wherein, The control unit also performs a process for linearly correcting the emitted light quantity / current ratio of the plurality of semiconductor light-emitting elements.
5. The light source device according to any one of claims 1 to 3, wherein, The control unit controls the plurality of semiconductor light-emitting elements such that their light intensity during periods of no light emission other than the weak light emission period and the strong light emission period, or during periods of weak light emission where the light emission intensity is too weak to be visually discernible, is low enough to avoid creating a double-exposure image, but when the subject is close, they can emit light at a light intensity that allows the subject to be visually discernible.
6. The light source device according to claim 5, wherein, The control unit uses pulsed light or continuous light to perform the offset emission.
7. An endoscope system for inserting an endoscope into an object of observation to obtain an image of the object, the endoscope system comprising: Multiple semiconductor light-emitting elements, each used to emit light in a different wavelength band; An imaging element for illuminating the subject with illumination light and detecting reflected light from the subject to generate an image signal; A processor for processing the image signal to generate an image of the subject and displaying it on a monitor; a main control unit for generating control signals based on the image signal to control the light emission profiles of the plurality of semiconductor light-emitting elements; and A light source control unit is configured to receive the control signal from the main control unit and drive the plurality of semiconductor light-emitting elements with a drive signal corresponding to the light-emitting profile. in, The emission profile includes a strong emission period with a predetermined light intensity and a weak emission period with a light intensity weaker than the predetermined light intensity. The main control unit determines the emission profile by executing a restoration control process, wherein the restoration control process is used to maintain the total emission amount during the strong emission period and the emission amount during the weak emission period at a constant level, while replacing the emission amount during the weak emission period with the emission amount during the strong emission period. The main control unit generates the control signal, which is used to extend the strong emission period by shortening the length of the weak emission period and increasing the light intensity of the weak emission period by the amount of light emission during the shortened period.
8. The endoscope system according to claim 7, wherein, The endoscope system also includes a photometer for obtaining brightness value information by using the image signal. The main control unit obtains the brightness value information from the photometer, and after determining the luminous contour that makes the brightness value of the image signal within a predetermined range, uses the determined luminous contour as the object to start the restoration control process.
9. The endoscope system according to claim 7 or 8, wherein, The main control unit also generates control signals for controlling the plurality of semiconductor light-emitting elements so that their light intensity during periods of no light emission other than the weak light emission period and the strong light emission period, or during weak light emission periods when the light emission intensity is too weak to be visually discernible, is sufficiently low compared to the light intensity during the strong light emission period and will not result in a double exposure image. However, when the subject is close, they can emit light at a light intensity that is visually discernible to the subject and output the light to the light source control unit.