Light source device and endoscope system

Abstract

To make it possible to execute light quantity control quickly in response to a variation in a rolling shutter period (pixel reading period) while avoiding occurrence of distortion and artifact caused by a rolling shutter of an imaging element.SOLUTION: A light source device for generating illumination light with which a subject is to be irradiated comprises: a plurality of semiconductor light-emitting elements for emitting light having wavelength bands differing from each other; and a control unit for controlling light emission profiles of the plurality of semiconductor light-emitting elements to drive the plurality of semiconductor light-emitting elements. The control unit controls the light emission profiles of the plurality of semiconductor light-emitting elements so as to perform main light emission in a pseudo global exposure period of an imaging element and perform preliminary light emission at least in a partial period of a pixel reading period of the imaging element, the preliminary light emission having a light emission level lower than that of the main light emission.SELECTED DRAWING: Figure 12

Description

[Technical field]

[0001] The present disclosure relates to a light source device and an endoscope system. [Background technology]

[0002] In a typical endoscopic device equipped with a rolling shutter type image sensor, the light source is turned off during the effective pixel readout period (rolling shutter period) of the image sensor and turned on (pulse emission control) during the other period (quasi-global exposure period) to perform quasi-global exposure and avoid undesirable phenomena caused by the rolling shutter, such as distortion and artifacts.

[0003] On the other hand, if the light source is completely turned off during the rolling shutter period, the amount of light may be insufficient depending on the subject (site to be observed), and a good image cannot be obtained. For example, Patent Documents 1 to 3 disclose light source control that includes part of the rolling shutter period in the pulse emission period in order to solve this lack of light. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-182580 A [Patent Document 2] Patent No. 5379932 [Patent Document 3] Patent No. 6239220 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when light source control such as that described in Patent Documents 1 to 3 is performed, the difference in exposure time between lines in adjacent frames causes uneven brightness and horizontal stripes on the screen. Then, there is a problem that the uneven brightness and horizontal stripes move up and down on the display screen due to the change in the pulse emission period for each frame, which is an eyesore. In addition, when offset emission is performed during the rolling shutter period to solve the lack of light, if the offset emission becomes strong to a certain extent, an unnatural image is generated that looks like a double exposure of a long exposure image and a high speed exposure image (generation of artifacts and scanning line noise (distortion)).

[0006] Furthermore, in the technologies of Patent Documents 1 to 3, events that change during the off period (rolling shutter period) cannot be observed in the readout during that period, and can only be observed in the next readout frame exposed by the next pulse emission. For this reason, there is a risk that perforation or halation will occur in the image when the tip of the endoscope approaches the subject suddenly. In order to reduce the risk of such perforation or halation occurring, it is necessary to quickly capture the change in brightness of the screen due to the sudden approach and immediately reflect it in the light amount control.

[0007] The present disclosure has been made in consideration of such circumstances, and proposes a technology that enables light quantity control to be performed in rapid response to changes during the rolling shutter period (pixel readout period) while avoiding the occurrence of distortion and artifacts caused by the rolling shutter of the image sensor. [Means for solving the problem]

[0008] In order to solve the above problems, the present embodiment proposes a light source device that generates illumination light to be irradiated onto a subject, the light source device comprising: a plurality of semiconductor light-emitting elements that emit light of different wavelength bands; and a control unit that controls the emission profiles of the plurality of semiconductor light-emitting elements and drives the plurality of semiconductor light-emitting elements, wherein the control unit controls the emission profiles of the plurality of semiconductor light-emitting elements so that main emission is performed during a pseudo-global exposure period of the image sensor, and pre-emission is performed during at least a portion of the pixel readout period of the image sensor, and the emission level of the pre-emission is lower than the emission level of the main emission.

[0009] In addition, the present embodiment proposes an endoscopic system in which an endoscope is inserted into an object to be observed and an image of the object is acquired, the endoscopic system comprising: a plurality of semiconductor light-emitting elements that emit light of different wavelength bands; an image sensor that irradiates the object with illumination light and detects reflected light from the object to generate an image signal; a processor that processes the image signal to generate an image of the object and displays it on a monitor; a main control unit that generates a control signal for controlling an emission profile of the plurality of semiconductor light-emitting elements based on the image signal; and a light source control unit that receives a control signal from the main control unit and drives the plurality of semiconductor light-emitting elements with a drive signal according to the emission profile, wherein the main control unit controls the emission profiles of the plurality of semiconductor light-emitting elements so that main emission is performed during a pseudo-global exposure period of the image sensor and pre-emission is performed during at least a portion of a pixel readout period of the image sensor, and the emission level of the pre-emission is lower than the emission level of the main emission.

[0010] Further features related to the present disclosure will become apparent from the description of the present specification and the accompanying drawings, and the present disclosure may be realized and realized by the elements and combinations of various elements and aspects of the following detailed description and the appended claims. It should be understood that the descriptions in this specification are exemplary and illustrative only and are not intended to limit the scope or application of the claims in any manner. Effect of the Invention

[0011] According to the present disclosure, it becomes possible to execute light amount control in rapid response to changes during a rolling shutter period (pixel readout period) while avoiding the occurrence of distortion and artifacts caused by the rolling shutter of an image sensor. [Brief description of the drawings]

[0012] [Figure 1] 1 is a diagram showing an example of the overall appearance of an endoscope system according to an embodiment of the present invention; [Diagram 2] 1 is a diagram showing an example of a schematic internal configuration of an endoscope system according to an embodiment of the present invention; [Diagram 3] 2 is a diagram showing an example of the internal configuration of a light source device 201 provided inside a processor 200. FIG. [Figure 4] FIG. 13 is a diagram showing the spectra (wavelength characteristics) of the LEDs 2011 to 2015. [Diagram 5] 13 is a diagram showing the characteristics of illumination light (light that illuminates an observation area) generated by transmitting each LED through cross prisms 2017 and 2018. FIG. [Figure 6] FIG. 1 is a diagram showing an example of the configuration of a light source using LEDs with different light distributions. [Figure 7] FIG. 13 is a graph showing the ratio of emitted light intensity to current for each LED. [Figure 8] 1 is a diagram showing an effective pixel area and an ineffective area of ​​a rolling shutter type imaging element, with a CMOS sensor being an example. [Figure 9] 1A to 1C are diagrams showing an example of a typical dimming control process and examples of observed images acquired in each frame. [Figure 10] 1A to 1C are diagrams showing an example of a dimming control process according to Control Example 1 of the present embodiment and examples of observed images acquired in each frame. [Figure 11] 11A to 11C are diagrams showing an example of a dimming control process according to a control example 2 of the present embodiment and examples of observed images acquired in each frame. [Figure 12] 13A to 13C are diagrams showing an example of a dimming control process according to a control example 3 of the present embodiment and examples of observed images acquired in each frame. [Figure 13]13A to 13C are diagrams showing an example of a dimming control process according to a control example 4 of the present embodiment and examples of observed images acquired in each frame. [Figure 14] 10 is a flowchart illustrating a dimming control process according to the above-mentioned control example 1 and control example 2 according to the present embodiment. [Figure 15] 10 is a flowchart illustrating the dimming control process according to the above-mentioned Control Example 3 and Control Example 4 according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. Note that, in the following, an endoscope system will be described as an example of one embodiment of the present disclosure.

[0014] Target sites for observation in an endoscope system include, for example, the respiratory system, digestive system, etc. Examples of the respiratory system include the lungs, bronchi, and ears, nose, and throat. Examples of the digestive system include the large intestine, small intestine, stomach, esophagus, duodenum, uterus, bladder, etc. When observing target sites such as those described above, it is more effective to utilize images that highlight specific biological structures.

[0015] <Endoscope system configuration> Fig. 1 is a diagram showing an example of the overall appearance of an endoscope system of this embodiment, and Fig. 2 is a diagram showing an example of a schematic internal configuration of the endoscope system of this embodiment. The endoscope system 1 includes an endoscope device (electronic scope) 100, a processor 200, and a monitor 300. The processor-side end of the endoscope device 100 is provided with a scope connector (hereinafter, sometimes simply referred to as "connector") 400 including a connector circuit according to this embodiment.

[0016] The endoscope device 100 includes a long and thin tubular insertion section 11 to be inserted into the inside of a subject. The endoscope device 100 includes, for example, an LCB (Light Carrying Bundle) 101 for guiding irradiation light from a light source device 201 described later, a light distribution lens 102 provided at the emission end of the LCB 101, an imaging unit 103 for receiving return light from an irradiated portion (observation site) via an objective lens (not shown), a driver signal processing circuit 105 for driving the imaging unit 103, and a first memory 106.

[0017] Illumination light from the light source device 201 enters the LCB 101 and propagates by repeating total reflection within the LCB 101. The illumination light (illumination light) propagated within the LCB 101 is emitted from the emission end of the LCB 101 disposed within the tip 12 of the insertion section 11, and illuminates the observation site via the light distribution lens 102. Return light from the irradiated area forms an optical image at each pixel on the light receiving surface of the imaging unit 103 via the objective lens.

[0018] The imaging unit 103 is disposed in the tip 12 of the insertion section 11, and may be a CMOS (Complementary Metal Oxide Semiconductor) image sensor, which is a rolling shutter type image sensor. The imaging unit 103 accumulates an optical image (return light from biological tissue) formed at each pixel on the light receiving surface as an electric charge according to the amount of light, and generates and outputs R, G, and B image signals. The imaging unit 103 is not limited to a CMOS image sensor, and may be replaced with other types of imaging devices as long as they are based on the rolling shutter type. The signal output from the imaging unit 103 is processed by a scope connector circuit 401 provided in the scope connector 400, as described later.

[0019] The processor 200 is a device that integrally includes a signal processing device that processes signals from the endoscope device 100, and a light source device that illuminates the inside of a body cavity where natural light does not reach via the endoscope device 100. In another embodiment, the signal processing device and the light source device may be configured as separate devices. The processor 200 includes a light source device 201, a system controller 202, a photometry unit 203, a front-stage signal processing circuit 205, a color conversion circuit 206, a rear-stage signal processing circuit 207, and a second memory 208.

[0020] The processor 200 may include an operation panel (not shown). The operation panel may be configured in various forms. Specific configurations of the operation panel include, for example, hardware keys for each function mounted on the front surface of the processor 200, a touch panel type GUI (Graphical User Interface), a combination of hardware keys and a GUI, etc. The operator (practitioner) can use the operation panel to perform mode switching operations described below.

[0021] The photometry unit 203 acquires luminance information of the image signal obtained by capturing an image from a gain circuit included in the color conversion circuit 206, compares it with a predetermined appropriate luminance value (for example, information on the appropriate luminance value can be stored in advance in an internal memory (not shown) of the photometry unit 203), and notifies the system controller 202 of the comparison result (whether the current luminance value is appropriate, high, or low).

[0022] The system controller 202 executes various programs stored in a memory (not shown) and comprehensively 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 so that processing suitable for the endoscope device 100 connected to the processor 200 is performed. The system controller 202 may be connected to the above-mentioned operation panel.

[0023] In addition, the system controller 202 receives the comparison result with the appropriate brightness value from the photometry unit 203, determines whether the current exposure should be maintained, whether the exposure should be increased (including the level value to increase), or whether the exposure should be decreased (including the level value to decrease), and outputs the result to the light source device 201 as an exposure control signal.

[0024] Furthermore, the system controller 202 changes each operation of the endoscope system 1 and parameters for each operation according to an instruction from an operator inputted from an operation panel. For example, when the operator selects an observation mode through the operation panel (mode switching operation), the system controller 202 outputs a mode selection signal to the light source device 201 for causing a light source corresponding to the observation mode to emit light. As will be described later, the light source device 201 may be, for example, a plurality of LEDs (Light Emitting Diodes) each emitting light of a different wavelength band (see FIG. 3). When the operator selects an observation mode (for example, a normal observation mode, a special light observation mode, a SatO2 mode, etc.) by operating a mode selection switch provided in the processor 200, for example, the system controller 202 generates a mode selection signal corresponding to the selected mode and supplies the signal to a light source control unit 2016 of the light source device 201 (see FIG. 3). The light source control unit 2016 determines the combination of LEDs to be illuminated and their intensity and light amount based on the mode selection signal (for example, the combination of light-emitting LEDs corresponding to the mode selection signal is stored in advance in an internal memory (not shown)), and outputs the required LED control signal to each of the LEDs 2011 to 2015. When each of the LEDs 2011 to 2015 emits light of each wavelength band based on the LED control signal supplied from the light source control unit 2016, the emitted lights are combined by a cross prism to generate irradiation light (combined light).

[0025] Data communication between the endoscope device 100 and the processor 200 may be performed using a wired electrical communication method or a wireless optical communication method.

[0026] 2, the endoscope device 100 and the processor 200 are connected via a scope connector 400. The scope connector 400 includes an LCB that constitutes a part of the LCB 101 that continues from the processor 200 to the endoscope device 100, and a scope connector circuit 401. Note that in this embodiment, the scope connector circuit 401 is provided in the scope connector 400, but it does not necessarily have to be provided inside the scope connector 400. For example, a circuit equivalent to the scope connector circuit 401 may be provided in a connector section on the processor 200 side or inside the processor 200.

[0027] <Example of internal configuration of light source device 201> FIG. 3 is a diagram showing an example of the internal configuration of a light source device 201 provided inside the processor 200, for example. 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 that controls the light emission of each of the LEDs 2011 to 2015, and cross prisms 2017 and 2018.

[0028] When the light source control unit 2016 receives an exposure control signal from the system controller 202, it controls the light emission period and applied current value of each currently emitting LED (the combination of LEDs to emit light is determined depending on the observation mode), thereby changing the light emission profile of each LED to adjust the exposure (adjust the amount of light) (see FIG. 12 described later). For example, after changing the light emission profile by one step, 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 photometry result by the photometry unit 203 (comparison result with the appropriate luminance value).

[0029] Furthermore, the light source control unit 2016 determines the combination of LEDs to emit light based on a mode selection signal indicating an observation mode selected by an operator. At the start of light emission, the light source control unit 2016 controls the light emission of each LED based on, for example, a predetermined light emission profile (default light emission period and drive current value), and thereafter performs exposure adjustment as described above.

[0030] <About each LED light source> Fig. 4 is a diagram showing the spectrum (wavelength characteristics) of each of the LEDs 2011 to 2015. Fig. 5 is a diagram showing the characteristics of illumination light (light that illuminates an observation site) generated by transmitting each of the LEDs through the cross prisms 2017 and 2018.

[0031] The green LED 2011 has a transmission wavelength band of 540 nm to 575 nm, a peak wavelength of 550 nm, and a half width of 30 nm. The green LED 2011 is equipped with a phosphor, which emits light in a transmission wavelength range of about 400 nm to 780 nm, as shown in FIG. 4. In other words, the green LED and the phosphor essentially emit white light, but this white light is an intermediate product, and as described later, the transmission wavelength band is narrowed by the cross prism 2018, and green light is irradiated onto the observation site. The blue LED 2012 has a transmission wavelength band of 460 nm to 490 nm, a peak wavelength of 456 nm, and a half width of 21 nm. The red LED 2013 has a transmission wavelength band of 630 nm to 1000 nm, a peak wavelength of 650 nm, and a half width of 20 nm. The transmission wavelength band of the Amber LED2014 is 600nm to 615nm, with a peak wavelength of 613nm and a half-width of 19nm. The transmission wavelength band of the UV LED2015 is 385nm to 425nm, with a peak wavelength of 405nm and a half-width of 14nm.

[0032] When each light (white light, blue light, red light, amber light, and UV light as intermediate products) emitted from each of the LEDs 2011 to 2015, including the green LED 2011 equipped with a phosphor, passes through the cross prisms 2017 and 2018, it becomes each light with the characteristics shown in FIG. 5 and is irradiated onto the observation area. In detail, the white light emitted from the green LED 2011 + phosphor has its transmission wavelength band limited by the cross prism 2018, and becomes green light of 520 nm to 595 nm. The blue light emitted from the blue LED 2012 becomes blue light of 440 nm to 500 nm by the cross prisms 2017 and 2018. Also, the red light emitted from the red LED 2013 becomes red light of 620 nm to 630 nm by the cross prisms 2017 and 2018. The amber light emitted from the amber LED 2014 becomes amber light of 580 nm to 630 nm through the cross prisms 2017 and 2018. Furthermore, the UV light emitted from the UV LED 2015 becomes UV light of 380 nm to 450 nm through the cross prism 2018.

[0033] <Correction of linearity differences between LEDs> When the light source device 201 is configured with a plurality of LEDs, not only the wavelength of light emitted by each of the LEDs 2011 to 2015 but also the light distribution (luminous intensity distribution in each direction) may differ (see FIG. 6: an example of a light source configuration using LEDs with different light distributions), and this may cause a change in the color and light distribution of the light emitted from each of the LEDs 2011 to 2015. Furthermore, depending on the type of LED, when the forward voltage is lowered to lower the drive current value, the drive current value drops sharply and the LEDs stop emitting light, so that the drive current value cannot be lowered significantly. To deal with such a situation, it becomes necessary to dynamically correct the difference in linearity of the emitted light amount / current ratio of each of the LEDs 2011 to 2015 in accordance with the drive current control of each of the LEDs 2011 to 2015.

[0034] However, since the process of dynamically correcting the difference in linearity is complicated, it is preferable to determine the drive current value in advance so that there is no difference in linearity. Therefore, in this embodiment, a correction table for correcting the linearity of the emitted light amount / current ratio is prepared in advance, and the drive current value of each LED 2011 to 2015 is determined using this correction table. FIG. 7 is a diagram showing a graph of the emitted light amount / current ratio of each LED. In FIG. 7, the relationship of only two LEDs (LED1 and LED2) is shown as an example, but the same applies to the case where five LEDs 2011 to 2015 are used as shown in this embodiment. The relationship of the emitted light amount / current ratio of each LED as shown in FIG. 7 can be obtained by measuring each LED in advance. For this reason, a correction table is prepared in advance (stored in memory) in which the reciprocal of the relationship of the emitted light amount / current ratio is used as a correction parameter as a correction value, and the light source control unit 2016 calculates a corrected drive current value by multiplying the correction parameter corresponding to the desired emitted light amount (target emitted light amount obtained by exposure adjustment) and drives each LED. By doing so, even if the wavelengths or light distributions of the emitted light from each LED are different, it is possible to appropriately control the linearity of the emitted light amount / current ratio.

[0035] <Example of the configuration of the imaging surface of an image sensor> FIG. 8 is a diagram showing the effective pixel area and the invalid area of ​​a rolling shutter type imaging element, taking a CMOS sensor as an example. The CMOS sensor includes an effective pixel area where imaging is possible and an invalid area where imaging is not possible. In addition, a part (periphery) of the effective pixel area is masked, and is an area from which image signals cannot be acquired. When imaging is performed using such an imaging element (in the case of global exposure), various phenomena (characteristics) appear in the captured image. In this embodiment, the period when no image is displayed on the screen is the global exposure period, but the idea of ​​this embodiment is not limited to this case.

[0036] <General dimming control process> FIG. 9 is a diagram showing an example of a typical dimming control process and an example of an observed image acquired in each frame. As shown in FIG. 9, it can be seen that the frames F1 and F2 were observed with the appropriate light intensity (the photometry results are appropriate). During the pseudo-global exposure period between frames F2 and F3, the tip of the endoscope suddenly moved away from the subject, so the amount of light irradiated on the subject was insufficient, and the observed image in frame F3 is dark. The amount of light when acquiring the observed image in frame F3 is dominated by the amount of light emitted during the pseudo-global exposure period between the previous frame (frame F2) and the current frame (frame F3) (strong light emission: can also be called main light emission). Therefore, if the distance to the subject changes after the pseudo-global exposure period, light emission (dimming control) that follows the change in distance is not performed (reflected) until the next frame (frame F4). For this reason, in the pseudo-global period between frames F3 and F4, dimming control is performed in stages based on the photometry results (light emission control (light emission profile is changed) in stages over time (frames F4 → F5 → F6)), the appropriate light amount is determined (light amount increase control), and the appropriate amount of light is irradiated onto the subject. After the tip of the endoscope moves away from the subject (moving away between F2 and F3), an observation image with the appropriate amount of light can be acquired in frame F5.

[0037] During the pseudo-global exposure period between frames F5 and F6, the distance between the endoscope tip and the subject is the same as that of the previous frame F5, so light is emitted with the same profile as that of the pseudo-global exposure period between frames F4 and F5. Therefore, the observation image obtained in frame F6 is the same as that obtained in frame F5. However, in reality, the endoscope tip approaches the subject rapidly during the pixel readout period (rolling shutter period) of frame F6, so the amount of light emitted by the most recent light emission profile is not suitable for the next frame observation, resulting in an excessive amount of light, and halation occurs in the image of frame F7. This is because the amount of light emitted (light emission profile) during the pseudo-global period between frames F6 and F7 is determined based on the photometric result of the image acquired in frame F6 (the photometric result of the observation image of frame F6 is appropriate). Then, only after the photometric result of the observation image of frame F7 due to the excessive amount of light is obtained, the excessive amount of light emitted due to the rapid approach to the subject (including collision) is corrected. That is, the light emission profile is changed for the first time during the pseudo global exposure period between frames F7 and F8 (when the light amount is reduced, the light emission profile is changed in stages, just as when the light amount is increased).

[0038] As described above, with general light control processing, when the tip of the endoscope approaches the subject suddenly, the light control (reduction in light amount) is delayed by one frame. In the case of sudden approach, the amount of light becomes excessive, causing halation in the observed image, making it very difficult for the operator to observe.

[0039] This embodiment discloses a process for correcting the drawback of the general dimming control (delay in changing the light emission profile) described above.

[0040] <Light Adjustment Control Process According to the Present Embodiment> (i) Control example 1 10 is a diagram showing an example of the dimming control process according to control example 1 of this embodiment and an example of an observation image acquired in each frame. In FIG. 10, the distance between the endoscope tip and the subject is assumed to change in the same way as in the general dimming control process (FIG. 9) for comparison.

[0041] Control example 1 is a dimming control process that performs weak pre-emission (continuous light) globally, unlike general dimming control processes. The value (total value) of the light emission time x light emission level of the weak pre-emission (continuous light) in control example 1 is sufficiently smaller than the value of the light emission time x light emission level of the strong light emission in the pseudo global exposure period. In addition, the pre-emission is light emission of such intensity that undesirable events (e.g., distortion and artifacts (scanning line noise, etc.)) caused by the rolling shutter due to the light emission (pre-emission) can be ignored, and the light emission (pre-emission) can be recognized when the tip of the endoscope approaches the subject rapidly. Specifically, the value of the light emission time x light emission level of the pre-emission can be 10% or less, preferably 2% or less, and more preferably 1% or less of the value of the light emission time x light emission level of the strong light emission.

[0042] In the dimming control process according to the control example 1 (continuous preliminary light emission), when the endoscope tip moves away from the subject as shown in FIG. 10, the same process as the general dimming control process (see FIG. 9) described above is performed. That is, for example, frames F1 and F2 can be observed with an appropriate amount of light (the photometry result is appropriate). Then, in the pseudo-global exposure period between frames F2 and F3, the endoscope tip suddenly moves away from the subject, so the amount of light irradiated on the subject is insufficient, and the observation image of frame F3 is dark. The amount of light when acquiring the observation image of frame F3 is dominated by the amount of light from the light emission (strong light emission) during the pseudo-global exposure period between the previous frame (frame F2) and the current frame (frame F3). Therefore, when the distance to the subject changes after the pseudo-global exposure period, the light emission (dimming control) following the change in the distance is performed (reflected) in the next frame (frame F4). Then, in the pseudo-global period between frames F3 and F4, dimming control is performed in stages based on the photometry results (light emission control (light emission profile is changed) in stages over time (frames F4 → F5 → F6)), the appropriate light amount is determined (light amount increase control), and the appropriate amount of light is irradiated onto the subject. After the tip of the endoscope moves away from the subject (moving away between F2 and F3), an observation image with the appropriate light amount is acquired in frame F5. The photometry result may be the photometry value of the center of the observation image, or the average photometry value of all pixels.

[0043] During the pseudo-global exposure period between frames F5 and F6, the distance between the endoscope tip and the subject is the same as that of the immediately preceding frame F5, so light is emitted with the same profile as that of the light emitted during the pseudo-global exposure period between frames F4 and F5. However, during the pixel readout period (rolling shutter period) of frame F6, weak preliminary light is emitted, so that if the endoscope tip approaches the subject rapidly, it is possible to capture the change in brightness of the observed image (detect the approach to the subject). Therefore, the observed image obtained in frame F6 is brighter than the observed image obtained in frame F5. In other words, the influence of the excess light caused by the sudden approach of the endoscope tip to the subject during the pixel readout period (rolling shutter period) of frame F6 is immediately reflected in the observed image. Therefore, when acquiring the observed image in the next frame F7, a dimming control process that reflects this excess light can be executed, and a process of lowering the level of strong light emission during the pseudo-global exposure period between frames F6 and F7 is executed. However, the light emission level is not lowered suddenly, but is lowered stepwise so that the change in brightness becomes more natural for the operator. 10, the amount of light emission in the pseudo global exposure period between frames F6 and F7 can be first reduced to a predetermined value, and then the amount of light emission in the next pseudo global exposure period (between frames F7 and F8) can be further reduced to a predetermined value. The amount of control of the amount of light emission (e.g., the amount of reduction) may be a fixed value, or an emission profile may be determined based on the degree of excess relative to the appropriate value of the photometry result.

[0044] As described above, according to the dimming control process of control example 1, weak pre-emission (continuous light) is performed during the pixel readout period (rolling shutter period). Therefore, in response to a change in the imaging conditions during the pixel readout period (for example, the tip of the endoscope suddenly approaches the subject), dimming control can be performed one frame earlier than with general dimming control process, and the exposure level can be brought closer to an appropriate level (appropriate photometric results can be obtained earlier).

[0045] (ii) Control Example 2 11 is a diagram showing an example of the dimming control process according to control example 2 of this embodiment and an example of an observed image acquired in each frame. In FIG. 11, the distance between the endoscope tip and the subject is assumed to change in the same way as in the general dimming control process (FIG. 9) for comparison.

[0046] Control Example 2 is a dimming control process performed by globally weak pre-emission (pulsed light), unlike general dimming control processes. The value of the light emission time x light emission level of the weak pre-emission (pulsed light) in Control Example 2 is sufficiently smaller than the value of the light emission time x light emission level of the strong light emission in the pseudo global exposure period, as in Control Example 1. The pre-emission is of such intensity that undesirable events (e.g., distortion and artifacts (scanning line noise, etc.)) caused by the rolling shutter due to the light emission (pre-emission) can be ignored, and the light emission (pre-emission) can be recognized when the tip of the endoscope approaches the subject rapidly. Specifically, the value of the light emission time x light emission level of the pre-emission can be set to 10% or less, preferably 2% or less, and more preferably 1% or less of the value of the light emission time x light emission level of the strong light emission. In Control Example 2, pulsed light is used as the weak pre-emission, and the pulse frequency is set to be higher than a predetermined value. For example, the frequency of the pulsed light is set so that the observed image does not become striped when the tip of the endoscope approaches the subject, and the entire image becomes bright (whitish). The contents and effects of the dimming control process according to Control Example 2 are similar to those of the dimming control process according to Control Example 1 described above, and therefore will not be described again.

[0047] (iii) Control Example 3 12 is a diagram showing an example of the dimming control process according to control example 3 of this embodiment and an example of an observation image acquired in each frame. In FIG. 12, the distance between the endoscope tip and the subject is assumed to change in the same way as in the general dimming control process (FIG. 9) for comparison.

[0048] Control example 3 is a dimming control process that performs weak preliminary light emission (continuous light) only for a specific period of the pixel readout period (rolling shutter period) (for example, the last specific period of the rolling shutter period (or the specific period immediately before the next pseudo-global exposure period)).

[0049] In the dimming control process according to control example 3 (which is also the case for control example 4 described later), only a specific area at the bottom of the screen is double-exposed by pre-emission when approaching the subject, compared to control examples 1 and 2 (when pre-emission is performed over the entire pixel readout (rolling shutter) period). Therefore, according to control example 3, it is possible to reduce the discomfort caused by double exposure for the endoscope user, and by adjusting the pre-emission period, it is possible to limit the area in the observation image where the band-like lines caused by double exposure are not noticeable. For example, if the frame rate is 60 Hz (16.6 ms) and the global exposure period (in FIG. 12, the top and bottom second lines in one frame: lines overwritten with electronic mask display and invalid pixel lines) is 2 ms, the remaining 14.6 ms is the readout period of the effective lines. In this case, if pre-emission is performed for 50%=7.33 ms of the effective line readout period, the boundary between the screen area to be double-exposed and the area not to be double-exposed is the line in the center of the screen, which makes the operator feel uncomfortable. So, for example, a) if it is 25%=3.67ms or less, the boundary will be the bottom 1 / 4 of the screen and will be less noticeable than in the center, and b) if it is 10%=1.46ms or less, the boundary will be the bottom 1 / 10 of the screen and will only be slightly reflected on the edge of the screen, so the operator will hardly notice it, and c) if it is only a few lines (e.g., 10 lines or less) in a specified area (e.g., lower area) of the observed image, the boundary will almost coincide with the electronic mask boundary and the operator will not be able to clearly recognize the boundary. At this time, if the total value of the pre-flash period x pre-flash level is not sufficiently smaller than the light emission period x light emission level of strong light emission in the pseudo global exposure period, the above-mentioned boundary will be clearly visible. In the case of conditions such as a) and b) above, although the boundary is not very noticeable, the operator can still recognize it, so it is necessary to make it sufficiently small compared to the strong light emission period x light emission level (for example, an intensity at which undesirable phenomena caused by the rolling shutter due to pre-flash (e.g., distortion and artifacts) can be ignored, and an intensity at which the light emission (pre-flash) can be recognized when the tip of the endoscope suddenly approaches the subject).Specifically, similarly to Control Example 1 and Control Example 2, the value of the light emission time x light emission level of the pre-emission can be 10% or less, preferably 2% or less, and more preferably 1% or less of the value of the light emission time x light emission level of the strong light emission. On the other hand, in the case of the above condition c), since the boundary is not discernible by the operator, it is possible to make the pre-emission intensity equal to (or greater than) the strong light emission intensity. In other words, since the pre-emission period is short, the product with the pre-emission intensity tends to be small as a result, but there is no problem even if the pre-emission is made greater than the strong light emission period x light emission level, for example, by instantaneously making the pre-emission 1000 times stronger than the strong light emission.

[0050] To summarize the amount of light in pre-flash, in the above cases a) and b), the light emission profile is controlled so that the total value (area value) of the pre-flash period x pre-flash level is 10% or less, 2% or less, or 1% of the value (area value) of the light emission period x light emission level of the strong light emission (main light emission). However, in the above case c), such a condition is not imposed, and the pre-flash level can be extremely large in relation to the lines read out in the observed image (it is not bound by the above condition of 10% or less).

[0051] In the dimming control process by the control example 3 (continuous preliminary light emission in a part of the pixel readout period), as shown in FIG. 12, when the endoscope tip moves away from the subject, the same process as the general dimming control process (see FIG. 9) described above is performed. That is, for example, the frames F1 and F2 can be observed with an appropriate amount of light (the light metering result is appropriate). Then, in the pseudo-global exposure period between frames F2 and F3, the endoscope tip suddenly moves away from the subject, so the amount of light irradiated on the subject is insufficient, and the observation image of frame F3 is dark. The amount of light when acquiring the observation image of frame F3 is dominated by the amount of light from the light emission (strong light emission) during the pseudo-global exposure period between the previous frame (frame F2) and the current frame (frame F3). Therefore, when the distance to the subject changes after the pseudo-global exposure period, the light emission (dimming control) following the change in the distance is performed (reflected) in the next frame (frame F4). For this reason, in the pseudo-global period between frames F3 and F4, dimming control is performed in stages based on the photometry results (light emission control (light emission profile is changed) in stages over time (frames F4 → F5 → F6)), the appropriate light amount is determined (light amount increase control), and the appropriate amount of light is irradiated onto the subject. After the tip of the endoscope moves away from the subject (moving away between F2 and F3), an observation image with the appropriate amount of light can be acquired in frame F5.

[0052] During the pseudo global exposure period between frames F5 and F6, the distance between the endoscope tip and the subject is the same as that of the immediately preceding frame F5, so light is emitted with the same profile as that of the light emission during the pseudo global exposure period between frames F4 and F5. However, during the last predetermined period (for example, the period during which the final k lines (k=1 to n: n is an integer (example) obtained by rounding up 1% of the number of effective lines (to the first decimal place)) of the pixel readout period (rolling shutter period) of frame F6 are read out), weak preliminary light emission (continuous light) is performed, so that when the endoscope tip suddenly approaches the subject, it is possible to capture a change in brightness of the observation image (detect the approach to the subject). As shown in FIG. 12, in the observation image of frame F6, a portion (region 1201) formed by pixels read out during the period in which preliminary light emission was performed is whitish (brighter) than other portions. In other words, the effect of excess light caused by the sudden approach of the endoscope tip to the subject during the pixel readout period (rolling shutter period) of frame F6 immediately appears in a part of the observation image. Therefore, when acquiring an observation image in the next frame F7, a dimming control process that reflects this excess light amount can be executed, and a process of lowering the level of strong light emission in the pseudo global exposure period between frames F6 and F7 (adjusting to the appropriate exposure) is performed. However, the light emission level is not lowered suddenly, but is lowered stepwise so that the change in brightness becomes more natural for the operator. For example, as shown in FIG. 12, the light emission amount in the pseudo global exposure period between frames F6 and F7 can be first lowered to a predetermined value, and the light emission amount in the next pseudo global exposure period (between frames F7 and F8) can be further lowered to a predetermined value. The control amount of the light emission amount (for example, the reduction amount) may be a constant value, or the light emission profile may be determined based on the degree of excess relative to the appropriate value of the photometry result.

[0053] As described above, according to the dimming control process of control example 3, weak preliminary light emission (continuous light) is emitted only during a specific period of the pixel readout period (rolling shutter period) (for example, the final specific period of the rolling shutter period (or the specific period immediately prior to the next pseudo-global exposure period)). Therefore, in response to a change in the imaging conditions during the pixel readout period (for example, the tip of the endoscope suddenly approaches the subject), dimming control can be performed one frame earlier than with general dimming control process, and the appropriate exposure level can be approached (appropriate photometric results can be obtained earlier).

[0054] (iv) Control Example 4 13 is a diagram showing an example of the dimming control process according to control example 4 of this embodiment and an example of an observed image acquired in each frame. In FIG. 13, the distance between the endoscope tip and the subject is assumed to change in the same way as in the general dimming control process (FIG. 9) for comparison.

[0055] Control example 4 is a dimming control process that performs weak pre-emission (pulsed light) only during a predetermined period of a pixel readout period (rolling shutter period) (for example, the last predetermined period of the rolling shutter period (or the predetermined period immediately before the next pseudo-global exposure period)). The value of the light emission time x light emission level of the weak pre-emission according to control example 4 is sufficiently smaller than the value of the light emission time x light emission level of the strong light emission during the pseudo-global exposure period, as in control examples 1 to 3. The pre-emission has an intensity such that undesirable events (for example, distortion and artifacts (scanning line noise, etc.)) caused by the rolling shutter due to the light emission (pre-emission) can be ignored, and the light emission (pre-emission) can be recognized when the tip of the endoscope approaches the subject rapidly. Specifically, the value of the light emission time x light emission level of the pre-emission can be set to 10% or less, preferably 2% or less, and more preferably 1% or less of the value of the light emission time x light emission level of the strong light emission. In control example 4, pulsed light is used as the weak pre-emission, and the pulse frequency is set to be higher than a predetermined value. For example, the frequency of the pulsed light is set so that a part of the observation image (region 1301) becomes brighter (whitish) when the tip of the endoscope approaches the subject. The contents and effects of the dimming control process according to Control Example 4 are similar to those of the dimming control process according to Control Example 3 described above, and therefore will not be described again.

[0056] <Flowchart of Dimming Control Process in Control Examples 1 and 2> 14 is a flowchart for explaining the dimming control process according to the above-mentioned control example 1 and control example 2 of this embodiment. The process of each step below is explained with the system controller 202 as the main operating entity, but this is not limited thereto, and a control unit (processor) that performs operation control and arithmetic processing may be separately provided and executed by it. Also, the function of the system controller 202 may be provided in the light source control unit 2016 of the light source device 201. Therefore, the dimming control process can be part of the overall operation of the endoscope system 1, or can be part of the operation of the light source device 201. In this case, the light source control unit 2016 is the main operating entity of the process of each step.

[0057] (i) Step 1401 The light source control unit 2016 receives from the system controller 202 a mode selection signal corresponding to the observation mode selected by the operator, and corrects the linearity of the emission light amount / current ratio of each light source to be emitted (any combination of the green LED 2011 to the UV LED 2015) using the above correction table.

[0058] (ii) Step 1402 The light source control unit 2016 drives each light source by the drive current after linearity correction of the emitted light amount / current ratio to emit light to generate illumination light, and irradiates the subject with the illumination light. The strong light emission profile in the pseudo global exposure period at this time can be a predetermined value (default value), or the light emission profile used in the last operation when the endoscope was used the previous time can be used. In addition, the light emission profile is determined so that the light emission period x light emission level of the weak preliminary light emission (continuous light or pulsed light) in the pixel readout period (rolling shutter period) is 10% or less, 2% or less, or 1% or less of the light emission period (which may be shorter than the pseudo global exposure period) x light emission level of the strong light emission in the pseudo global period (see Figs. 10 and 11).

[0059] (iii) Step 1403 An imaging element (e.g., a CMOS sensor) of the imaging unit 103 detects reflected light from an object (observation site) generated by irradiating the object with illumination light, and transmits a captured image signal to the processor 200 via the scope connector circuit 401. Then, the system controller 202 starts acquiring one frame's worth of image (each pixel) data via the photometry unit 203.

[0060] (iv) Step 1404 The system controller 202 determines whether the acquired pixel (input pixel) is a valid pixel (see FIG. 8: pixel in the valid area of ​​the CMOS sensor). If the acquired pixel is a valid pixel (YES in step 1404), the process proceeds to step 1405. On the other hand, if the acquired pixel is not a valid pixel (invalid pixel or valid but masked pixel: NO in step 1404), the process proceeds to step 1406.

[0061] (v) Step 1405 The system controller 202 accumulates the photometric value (luminance value) of each effective pixel acquired from the photometry unit 203 .

[0062] (vi) Step 1406 The system controller 202 judges whether acquisition of valid pixels for one frame has been completed. If acquisition of valid pixels for one frame has been completed (YES in step 1406), the process proceeds to step 1407. On the other hand, if acquisition of valid pixels for one frame has not yet been completed (NO in step 1406), the process returns to step 1403.

[0063] (vii) Step 1407 The system controller 202 compares the accumulated photometric value for one frame with a predetermined threshold value to determine whether the exposure is appropriate. If the photometric value is determined to be appropriate (YES in step 1407), the light adjustment control process ends. On the other hand, if the photometric value is determined to be inappropriate (for example, excessive light due to rapid approach to the subject or insufficient light due to moving away from the subject) (NO in step 1407), the process proceeds to step 1408.

[0064] (viii) Step 1408 The system controller 202 changes the light emission profile and transmits the changed light emission profile to a light source control unit 2016 of the light source device 201. The change in the light emission profile may be, for example, to reduce or increase a predetermined amount of light, or the profile may be determined based on the degree of excess or deficiency relative to an appropriate value.

[0065] Furthermore, the change patterns of the light emission profile may be stored in advance in a memory (not shown) (e.g., tabulated), and the system controller 202 may determine the light emission profile from the deviation between the measured photometric value and the appropriate photometric value (e.g., 3 dB excess → light emission pattern 1, 6 dB excess → light emission pattern 2, 3 dB shortage → light emission pattern 3, ... etc.).

[0066] Also, as a change in the light emission profile, the light emission level (and / or light emission period) of strong light emission during the pseudo global exposure period may be increased or decreased stepwise for each frame time (for example, 60 Hz=16.6 ms) (see F6→F7→F8 in FIG. 10 and FIG. 11). By doing so, it is possible to avoid a sudden change in brightness, and therefore it is possible to obtain a natural observation image.

[0067] <Flowchart of Dimming Control Process in Control Examples 3 and 4> 15 is a flowchart for explaining the dimming control process according to the above-mentioned control example 3 and control example 4 of this embodiment. The process of each step below is explained with the system controller 202 as the main operating entity, but this is not limited thereto, and a control unit (processor) that performs operation control and arithmetic processing may be separately provided and executed by it. Also, the function of the system controller 202 may be provided in the light source control unit 2016 of the light source device 201. Therefore, the dimming control process can be part of the overall operation of the endoscope system 1, or can be part of the operation of the light source device 201. In this case, the light source control unit 2016 is the main operating entity of the process of each step.

[0068] (i) Step 1501 The light source control unit 2016 receives from the system controller 202 a mode selection signal corresponding to the observation mode selected by the operator, and corrects the linearity of the emission light amount / current ratio of each light source to be emitted (any combination of the green LED 2011 to the UV LED 2015) using the above correction table.

[0069] (ii) Step 1502 The light source control unit 2016 drives each light source by the drive current after linearity correction of the emitted light amount / current ratio to emit light to generate illumination light, and irradiates the subject with the illumination light. The strong light emission profile in the pseudo-global exposure period at this time can be a predetermined value (default value), or the light emission profile used in the last operation when the endoscope was used the previous time can be used. In addition, in control example 3 and control example 4, weak pre-emission (continuous light or pulsed light) is performed in a part of the pixel readout period (rolling shutter period) (the last predetermined period of the pixel readout period). As described above, the light emission profile is determined so that the light emission period of this weak pre-emission x light emission level is 10% or less, 2% or less, or 1% or less of the light emission period of strong light emission in the pseudo-global period (which may be shorter than the pseudo-global exposure period) x light emission level (see Figs. 10 and 11).

[0070] (iii) Step 1503 An imaging element (e.g., a CMOS sensor) of the imaging unit 103 detects reflected light from an object (observation site) generated by irradiating the object with illumination light, and transmits a captured image signal to the processor 200 via the scope connector circuit 401. Then, the system controller 202 starts acquiring one frame's worth of image (each pixel) data via the photometry unit 203.

[0071] (iv) Step 1504 The system controller 202 determines whether the acquired pixel (input pixel) is a valid pixel (see FIG. 8: pixel in the valid area of ​​the CMOS sensor). If the acquired pixel is a valid pixel (YES in step 1504), the process proceeds to step 1505. On the other hand, if the acquired pixel is not a valid pixel (invalid pixel or valid but masked pixel: NO in step 1504), the process proceeds to step 1509.

[0072] (v) Step 1505 The system controller 202 determines whether the acquired (input) effective pixel is a pixel of a pre-emission line. The readout line number in the frame (image) and the irradiation timing of the weak pre-emission are determined in advance. For example, information on the line number and the irradiating object MIG is stored in the internal memory of the system controller 202 or a memory not shown. Therefore, the system controller 202 can determine on which line the weak pre-emission is performed.

[0073] If it is determined that the acquired pixel is a pixel that constitutes a pre-light-emission line (YES in step 1505), the process proceeds to step 1506. On the other hand, if it is determined that the acquired pixel is not related to the pre-light-emission line (NO in step 1505), the process proceeds to step 1507.

[0074] (vi) Step 1506 The system controller 202 obtains a pre-flash photometric value by integrating the luminance values ​​of pixels in a line where weak pre-flash is performed (the pre-flash line is also affected by the strong light emission during the pseudo-global exposure period, so the photometric value is the strong light emission plus the weak pre-flash). In other words, the luminance values ​​of each pixel constituting the line related to the pre-flash are integrated pixel by pixel, and the pre-flash photometric value for one frame is finally calculated. The pre-flash photometric value for one frame is stored in the internal memory of the system controller 202 or in a memory not shown.

[0075] (vii) Step 1507 The system controller 202 integrates the luminance values ​​of the input pixels other than the pre-emission lines to calculate the normal emission photometric value due to strong emission during the pseudo-global exposure period. That is, the luminance values ​​of the pixels constituting the lines other than the pre-emission lines are integrated pixel by pixel, and the normal emission photometric value for one frame is finally calculated. The normal emission photometric value for one frame is stored in the internal memory of the system controller 202 or in a memory not shown.

[0076] (viii) Step 1508 The system controller 202 adds together the preliminary light emission photometric value calculated in step 1506 and the normal light emission photometric value calculated in step 1507 to calculate a photometric value (provisional) for one entire frame.

[0077] (ix) Step 1509 The system controller 202 determines whether acquisition of valid pixels for one frame has been completed. If acquisition of valid pixels for one frame has been completed (YES in step 1509), the process proceeds to step 1510. On the other hand, if acquisition of valid pixels for one frame has not yet been completed (NO in step 1509), the process returns to step 1503. If the answer is YES in step 1509, the photometric value (provisional) of the entire one frame obtained in step 1508 becomes the photometric value (confirmed) of the entire one frame.

[0078] (x) Step 1510 The system controller 202 compares the photometric value (confirmed) of the entire frame with a predetermined threshold (overall photometric threshold) to determine whether the photometric value is appropriate. The overall photometric threshold can also be a value having a predetermined width (range).

[0079] If it is determined that the photometric values ​​(confirmed) of the entire frame are appropriate (YES in step 1510), the process proceeds to step 1511. On the other hand, if it is determined that the photometric values ​​(confirmed) of the entire frame are not appropriate (NO in step 1510), the process proceeds to step 1512.

[0080] (xi) Step 1511 The system controller 202 acquires the pre-flash photometric value for the frame, compares it with a predetermined threshold (pre-flash threshold) and determines whether the photometric value is appropriate. Note that the pre-flash threshold can be a value having a predetermined width (range) like the overall photometric threshold.

[0081] If the pre-flash photometric value is determined to be appropriate (YES in step 1511), the light control process ends. On the other hand, if the pre-flash photometric value is determined to be inappropriate (NO in step 1511), the process proceeds to step 1512.

[0082] (xii) Step 1512 The system controller 202 changes the light emission profile and transmits the changed light emission profile to a light source control unit 2016 of the light source device 201. The change in the light emission profile may be, for example, to reduce or increase a predetermined amount of light, or the profile may be determined based on the degree of excess or deficiency relative to an appropriate value.

[0083] In addition, the change patterns for the light emission profile may be stored in advance in a memory (not shown) (e.g., tabulated), and the system controller 202 may determine the light emission profile from the deviation between the measured photometric value and the appropriate photometric value (e.g., 3 dB excess → light emission pattern 1, 6 dB excess → light emission pattern 2, 3 dB shortage → light emission pattern 3, ... etc.).

[0084] Furthermore, the light emission profile may be changed by increasing or decreasing the light emission level (and / or light emission period) of strong light emission in the pseudo global exposure period stepwise for each frame time (e.g., 1 / 30th of a second) (see F6 → F7 → F8 in Fig. 12 and Fig. 13). By doing so, it is possible to avoid a sudden change in brightness, and therefore it is possible to obtain a natural observation image.

[0085] <Effects of this embodiment> According to this embodiment, the exposure component (luminance component due to weak pre-emission) when the endoscope tip (image sensor) approaches the subject rapidly during the rolling shutter period is added to the photometry result. Considering the light intensity, the luminance component due to strong emission (main emission) during the pseudo global exposure period is overwhelmingly stronger than the luminance component due to weak pre-emission during the rolling shutter period, so the luminance component due to strong emission becomes dominant in the formation of the observation image (however, the emission profile of strong emission was determined when the distance between the image sensor and the subject was greater than that during the rapid approach and was appropriate). On the other hand, when weak pre-emission is performed and the image sensor is rapidly approaching the subject, the entire observation image (control examples 1 and 2) or a part of it (the lower part of the observation image: control examples 3 and 4) becomes whitish, and the photometry result due to the weak pre-emission immediately appears in the observation image, making it possible to immediately detect that there is an excessive amount of light. Therefore, according to the light adjustment control process of this embodiment, it becomes possible to quickly respond to changes during the rolling shutter period (pixel readout period) and perform light amount control. In the above cases of a) and b) in Control Examples 1 and 2, and Control Examples 3 and 4, the weak pre-emission is controlled to 10% or less (preferably 2% or less, more preferably 1% or less) of the main emission in terms of the value of the emission period x emission level. This makes it possible to avoid the occurrence of distortion and artifacts caused by the rolling shutter of the image sensor. Furthermore, in the above case of c) in Control Examples 3 and 4, the pre-emission period is limited to a period in which pixels forming several lines in the lower part of the observation image are read out, so that even if the emission level of the pre-emission is made higher than the emission level of the main emission, it becomes possible to quickly detect the presence or absence of an excessive amount of light in the observation image without giving a sense of discomfort to the operator.

[0086] <Specific matters of this disclosure> (1) Specific matters 1 A light source device that generates illumination light to be irradiated onto a subject, A plurality of semiconductor light emitting elements each emitting light of a different wavelength band; a control unit that controls the light emission profiles of the semiconductor light emitting elements and drives the semiconductor light emitting elements; the control unit controls a light emission profile of the plurality of semiconductor light emitting elements so as to perform main light emission during a pseudo global exposure period of the image sensor and perform preliminary light emission during at least a portion of a pixel readout period of the image sensor; A light source device, wherein a light emission level of the preliminary light emission is lower than a light emission level of the main light emission.

[0087] (2) Specific matters 2 In particular item 1, a total value of the light emission period and the light emission level of the preliminary light emission is sufficiently smaller than a total value of the light emission period and the light emission level of the main light emission to such an extent that noise caused by a rolling shutter of the image sensor can be ignored.

[0088] (3) Specific matters 3 In particular item 1 or 2, The control unit controls a total value of the light emission period x light emission level of the preliminary light emission to be equal to or less than 10% of a total value of the light emission period x light emission level of the main light emission.

[0089] (4) Specific matters 4 In any one of specific matters 1 to 3, The control unit controls the light emission profile so that the preliminary light emission is configured as continuous light or pulsed light over the entire pixel readout period.

[0090] (5) Specific matters 5 In any one of specific matters 1 to 4, The control unit compares a photometric value of one frame of an observed image of the subject with a first threshold value and determines whether or not to change the light emission profile.

[0091] (6) Specific matters 6 In particular item 5, When the photometric value is greater than the first threshold value and an excessive amount of light is present, the control unit changes the light emission profile so as to gradually lower the light emission level of the main emission over a plurality of frames.

[0092] (7) Specific matters 7 In particular item 1 or 2, The control unit controls the light emission profile so as to perform the preliminary emission of continuous light or pulsed light during the pixel readout period of pixels constituting the lower 25% or less of the observed image of the subject.

[0093] (8) Specific matters 8 In particular item 7, The control unit controls a total value of the light emission period x light emission level of the preliminary light emission to be equal to or less than 10% of a total value of the light emission period x light emission level of the main light emission.

[0094] (9) Specific matters 9 In particular item 1 or 2, The control unit controls the light emission profile so as to perform the preliminary emission of continuous light or pulsed light during the pixel readout period of pixels that constitute a predetermined number of lines of the observed image of the subject.

[0095] (10) Specific matters 10 In particular item 9, The control unit controls the light emission profile so as to perform the preliminary emission of the continuous light or the pulsed light during the pixel readout period of pixels that constitute a final predetermined number of lines of the observation image.

[0096] (11) Specific matters 11 In any one of specific matters 7 to 10, The control unit compares a photometric value based on the preliminary light emission in one frame of the observed image of the subject with a second threshold value, and determines whether or not to change the light emission profile.

[0097] (12) Specific matters 12 In particular item 11, When the photometric value is greater than the second threshold value and an excessive amount of light is present, the control unit changes the light emission profile so as to gradually lower the light emission level of the main emission over a plurality of frames.

[0098] (13) Specific matters 13 An endoscope system for inserting an endoscope into an object to be observed and acquiring an image of the object, A plurality of semiconductor light emitting elements each emitting light of a different wavelength band; an image sensor that irradiates the subject with illumination light and detects reflected light from the subject to generate an image signal; a processor for processing the image signals to generate an image of the object for display on a monitor; a main control unit that generates a control signal for controlling a light emission profile of the plurality of semiconductor light emitting elements based on the image signal; a light source control unit that receives the control signal from the main control unit and drives the semiconductor light emitting elements with a drive signal corresponding to the light emission profile, the main control unit controls a light emission profile of the plurality of semiconductor light emitting elements so as to perform main light emission during a pseudo global exposure period of the image sensor and perform preliminary light emission during at least a portion of a pixel readout period of the image sensor; An endoscope system, wherein the light emission level of the preliminary light emission is lower than the light emission level of the main light emission.

[0099] (14) Specific matters 14 In particular item 13, an endoscope system, wherein a total value of the light emission period x light emission level of the preliminary light emission is sufficiently smaller than a total value of the light emission period x light emission level of the main light emission to such an extent that noise caused by a rolling shutter of the image sensor can be ignored.

[0100] (15) Specific matters 15 In particular item 13 or 14, The main control unit controls the total value of the light emission period x light emission level of the preliminary light emission to be 10% or less of the value of the light emission period x light emission level of the main light emission.

[0101] (16) Specific matters 16 In any one of specific matters 13 to 15, An endoscope system, wherein the main control unit controls the light emission profile so that the preliminary light emission is configured as continuous light or pulsed light over the entire pixel readout period.

[0102] (17) Specific matters 17 In any one of specific matters 13 to 16, The main control unit compares a photometric value for one frame of an observation image of the subject with a first threshold value and determines whether or not to change the light emission profile.

[0103] (18) Specific matters 18 In particular item 17, The main control unit changes the light emission profile so as to gradually lower the light emission level of the main emission over multiple frames when the photometric value is greater than the first threshold value and an excessive amount of light is detected.

[0104] (19) Specific matters 19 In particular item 13 or 14, An endoscope system in which the main control unit controls the light emission profile so as to perform the pre-emission of continuous light or pulsed light during the pixel readout period of pixels constituting the lower 25% or less of the observed image of the subject.

[0105] (20) Specific matters 20 In particular item 19, An endoscope system, wherein the main control unit controls the total value of the light emission period x light emission level of the preliminary light emission to be 10% or less of the value of the light emission period x light emission level of the main light emission.

[0106] (21) Specific matters 21 In particular item 13 or 14, An endoscope system, wherein the main control unit controls the light emission profile so as to perform the pre-emission of continuous light or pulsed light during the pixel readout period of pixels that constitute a predetermined number of lines of the observation image of the subject.

[0107] (22) Specific matters 22 In particular item 21, An endoscope system, wherein the main control unit controls the light emission profile so as to perform the preliminary light emission of the continuous light or the pulsed light during the pixel readout period of pixels that constitute a final predetermined number of lines of the observation image.

[0108] (23) Specific matters 23 In any one of specific matters 19 to 22, The main control unit compares a photometric value based on the preliminary emission in one frame of an observation image of the subject with a second threshold value, and determines whether or not to change the emission profile.

[0109] (24) Specific matters 24 In particular item 23, The main control unit, when the photometric value is greater than the second threshold value and an excessive amount of light is present, changes the light emission profile so as to gradually lower the light emission level of the main light emission over multiple frames.

[0110] <Other> The functions of the above-mentioned embodiment can also be realized by software program code. In this case, a storage medium on which the program code is recorded is provided to a system or device, and the computer (or CPU or MPU) of the system or device reads the program code stored in the storage medium. In this case, the program code itself read from the storage medium realizes the functions of the above-mentioned embodiment, and the program code itself and the storage medium storing it constitute the present disclosure. Examples of storage media for supplying such program code include flexible disks, CD-ROMs, DVD-ROMs, hard disks, optical disks, magneto-optical disks, CD-Rs, magnetic tapes, non-volatile memory cards, ROMs, etc.

[0111] Also, an operating system (OS) running on a computer may perform all or a part of the actual processing based on the instructions of the program code, and the functions of the above-mentioned embodiments may be realized by the processing. Furthermore, after the program code read from a storage medium is written into a memory on a computer, a CPU of the computer may perform all or a part of the actual processing based on the instructions of the program code, and the functions of the above-mentioned embodiments may be realized by the processing.

[0112] Furthermore, the program code of the software that realizes the functions of this embodiment may be distributed via a network and stored in a storage means such as a hard disk or memory of the system or device, or in a storage medium such as a CD-RW or CD-R, so that when used, the computer (or CPU or MPU) of the system or device reads out and executes the program code stored in the storage means or storage medium.

[0113] Finally, the processes and techniques described herein are not inherently related to any particular apparatus, but may be implemented by any suitable combination of components. Moreover, various types of general purpose devices may be used in accordance with the teachings described herein. It may prove beneficial to construct specialized apparatus to perform the steps of the methods described herein. Also, various configurations may be formed by suitable combinations of multiple components disclosed in the present embodiment. For example, some components may be omitted from all components shown in the present embodiment. Furthermore, components across different embodiments may be combined as appropriate. Although the present disclosure has been described with reference to specific examples, they should not be construed as limiting in all respects. Those skilled in the art will recognize that there are numerous combinations of hardware, software, and firmware suitable for implementing the techniques of the present disclosure. For example, the described software may be implemented in a wide variety of programming or scripting languages, such as assembler, C / C++, perl, Shell, PHP, Java, and the like.

[0114] Furthermore, in the above-described embodiment, the control lines and information lines are those that are considered necessary for the explanation, and not all of the control lines and information lines in the product are necessarily shown. All of the components may be connected to each other. [Explanation of symbols]

[0115] 1 Endoscope system 100 Endoscopic device 103 Imaging unit 200 processors 201 Light source device 2011 Green LED 2012 Blue LED 2013 Red LED 2014 Amber LED 2015 UV LED 2016 Light source control unit 2017, 2018 Cross Prism 202 System Controller 203 Photometry section 300 Monitors

Claims

1. A light source device that generates illumination light to be irradiated onto a subject, A plurality of semiconductor light emitting elements each emitting light of a different wavelength band; a control unit that controls the light emission profiles of the semiconductor light emitting elements and drives the semiconductor light emitting elements; the control unit controls a light emission profile of the plurality of semiconductor light emitting elements so as to perform main light emission during a pseudo global exposure period of the image sensor and perform preliminary light emission during at least a portion of a pixel readout period of the image sensor; the light emission level of the preliminary light emission is lower than the light emission level of the main light emission, a total value of the light emission period and the light emission level of the preliminary light emission is sufficiently smaller than a total value of the light emission period and the light emission level of the main light emission to such an extent that noise caused by a rolling shutter of the image sensor can be ignored. Light source device.

2. A light source device that generates illumination light to be irradiated onto a subject, A plurality of semiconductor light emitting elements each emitting light of a different wavelength band; a control unit that controls the light emission profiles of the semiconductor light emitting elements and drives the semiconductor light emitting elements; the control unit controls a light emission profile of the plurality of semiconductor light emitting elements so as to perform main light emission during a pseudo global exposure period of the image sensor and perform preliminary light emission during at least a portion of a pixel readout period of the image sensor; the light emission level of the preliminary light emission is lower than the light emission level of the main light emission, the control unit controls a total value of the light emission period x light emission level of the preliminary light emission to be equal to or less than 10% of a value of the light emission period x light emission level of the main light emission. Light source device.

3. In claim 1 or 2, The control unit controls the light emission profile so that the preliminary light emission is configured as continuous light or pulsed light over the entire pixel readout period.

4. In any one of claims 1 to 3, The control unit compares a photometric value of one frame of an observed image of the subject with a first threshold value, and determines whether or not to change the light emission profile.

5. In claim 4, When the photometric value is greater than the first threshold value and an excessive amount of light is present, the control unit changes the light emission profile so as to gradually lower the light emission level of the main emission over a plurality of frames.

6. In claim 1, The control unit controls the light emission profile so as to perform the preliminary emission of continuous light or pulsed light during the pixel readout period of pixels constituting a lower 25% or less of the observed image of the subject.

7. In claim 6, The control unit controls a total value of the light emission period x light emission level of the preliminary light emission to be equal to or less than 10% of a total value of the light emission period x light emission level of the main light emission.

8. In claim 1, The control unit controls the light emission profile so as to perform the preliminary emission of continuous light or pulsed light during the pixel readout period of pixels that constitute a predetermined number of lines of the observed image of the subject.

9. In claim 8, The control unit controls the light emission profile so as to perform the preliminary emission of the continuous light or the pulsed light during the pixel readout period of pixels that constitute a final predetermined number of lines of the observation image.

10. In any one of claims 6 to 9, The control unit compares a photometric value based on the preliminary light emission in one frame of the observed image of the subject with a second threshold value, and determines whether or not to change the light emission profile.

11. In claim 10, When the photometric value is greater than the second threshold value and an excessive amount of light is present, the control unit changes the light emission profile so as to gradually lower the light emission level of the main emission over a plurality of frames.

12. An endoscope system for inserting an endoscope into an object to be observed and acquiring an image of the object, A plurality of semiconductor light emitting elements each emitting light of a different wavelength band; an image sensor that irradiates 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 the image on a monitor; a main control unit that generates a control signal for controlling a light emission profile of the plurality of semiconductor light emitting elements based on the image signal; a light source control unit that receives the control signal from the main control unit and drives the semiconductor light emitting elements with drive signals corresponding to the light emission profile, the main control unit controls a light emission profile of the plurality of semiconductor light emitting elements so as to perform main light emission during a pseudo global exposure period of the image sensor and perform preliminary light emission during at least a portion of a pixel readout period of the image sensor; the light emission level of the preliminary light emission is lower than the light emission level of the main light emission, a total value of the light emission period and the light emission level of the preliminary light emission is sufficiently smaller than a total value of the light emission period and the light emission level of the main light emission to such an extent that noise caused by a rolling shutter of the image sensor can be ignored. Endoscopy system.

13. An endoscope system for inserting an endoscope into an object to be observed and acquiring an image of the object, A plurality of semiconductor light emitting elements each emitting light of a different wavelength band; an image sensor that irradiates 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 the image on a monitor; a main control unit that generates a control signal for controlling a light emission profile of the plurality of semiconductor light emitting elements based on the image signal; a light source control unit that receives the control signal from the main control unit and drives the semiconductor light emitting elements with drive signals corresponding to the light emission profile, the main control unit controls a light emission profile of the plurality of semiconductor light emitting elements so as to perform main light emission during a pseudo global exposure period of the image sensor and perform preliminary light emission during at least a portion of a pixel readout period of the image sensor; the light emission level of the preliminary light emission is lower than the light emission level of the main light emission, the main control unit controls a total value of the light emission period x light emission level of the preliminary light emission to be equal to or less than 10% of a value of the light emission period x light emission level of the main light emission, Endoscopy system.

14. In claim 12 or 13, An endoscope system, wherein the main control unit controls the light emission profile so that the preliminary light emission is configured as continuous light or pulsed light over the entire pixel readout period.

15. In any one of claims 12 to 14, The main control unit compares a photometric value for one frame of an observation image of the subject with a first threshold value and determines whether or not to change the light emission profile.

16. In claim 15, An endoscope system, wherein the main control unit, when the photometric value is greater than the first threshold value and an excessive amount of light is present, changes the light emission profile so as to gradually lower the light emission level of the main emission over multiple frames.

17. In claim 12, An endoscope system, wherein the main control unit controls the light emission profile so as to perform the preliminary light emission of continuous light or pulsed light during the pixel readout period of pixels constituting the lower 25% or less of the observed image of the subject.

18. In claim 17, An endoscope system, wherein the main control unit controls a total value of the light emission period x light emission level of the preliminary light emission to be 10% or less of a value of the light emission period x light emission level of the main light emission.

19. In claim 12, An endoscope system, wherein the main control unit controls the light emission profile so as to perform the pre-emission of continuous light or pulsed light during the pixel readout period of pixels that constitute a predetermined number of lines of the observation image of the subject.

20. 20. In claim 19, An endoscope system, wherein the main control unit controls the light emission profile so as to perform the preliminary light emission of the continuous light or the pulsed light during the pixel readout period of pixels that constitute a final predetermined number of lines of the observation image.

21. In any one of claims 17 to 20, The main control unit compares a photometric value based on the preliminary emission in one frame of an observation image of the subject with a second threshold value, and determines whether or not to change the emission profile.

22. 22. In claim 21, An endoscope system, wherein the main control unit, when the photometric value is greater than the second threshold value and an excessive amount of light is present, changes the light emission profile so as to gradually lower the light emission level of the main light emission over multiple frames.

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