JP2013048792A - Endoscopic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an endoscopic device, capable of regularly stably obtaining illuminating light having a desired tone, in generation of illuminating light using a phosphor having temperature-dependent emission characteristics, while reducing change in the intensity of fluorescence generated from the phosphor.SOLUTION: The endoscopic device has a light source unit including a light emitting element LD1 and wavelength conversion members 59A, 59B, the light source unit outputting an illuminating light by composing a transmitted light emitted from the light emitting element and transmitted by the wavelength conversion members with a light emitted from the wavelength conversion members. The endoscopic device includes: a drive signal generation unit 67 which generates a pulse drive signal for driving the light emitting element; a drive signal conversion unit 69 which divides each pulse of the generated pulse drive signal into a plurality of short pulses having a further short pulse width to generate a divided pulse drive signal so that the light quantity change of the illuminating light resulting from the temperature dependency of emission efficiency of the phosphor is an allowable limit value or less; and a light source control unit 61 which drives the light emitting element with the divided pulse drive signal.

Description

  The present invention relates to an endoscope apparatus.

  An endoscope apparatus has been developed that includes a light source having excitation light emitted from a semiconductor light source such as a semiconductor laser or a light emitting diode, and a wavelength conversion member including a phosphor that emits light by the excitation light. For example, in the endoscope apparatus disclosed in Patent Document 1, the light source is driven with a pulsed drive current, and the number of pulses of the drive current, the pulse width, or the pulse amplitude is increased or decreased to always perform appropriate integration. Correction is made so that the amount of light and chromaticity are obtained. This eliminates variations in the integrated light quantity and chromaticity of illumination light caused by individual differences in the light source.

JP 2009-56248 A

However, the emission characteristics of the phosphor of the wavelength conversion member have temperature dependence, and when the phosphor continues to receive excitation light and rises in temperature, the spectral profile of the generated fluorescence changes. FIG. 7 shows the relationship between the drive pulse of excitation light and the output light intensity from the phosphor. The light source outputs excitation light in response to the supplied driving pulse signal having an intensity I ₀ . When this excitation light is applied to the phosphor and the temperature of the phosphor rises, the luminous efficiency of the phosphor changes and causes an increase or decrease from the initial emission intensity. For this reason, the output light intensity according to the drive pulse supplied to the light source cannot be obtained.

In addition, when the wavelength conversion member is configured to include a plurality of types of phosphors, the intensity of the generated fluorescence changes individually with a temperature change. FIG. 8 schematically shows changes in luminous efficiency with respect to temperature of the G-emitting phosphor and the R-emitting phosphor. In general, R-emitting phosphors have lower luminous efficiency than G-emitting phosphors, and the change in luminous efficiency with temperature rise is different for each phosphor. For this reason, when a plurality of types of phosphors are used, the balance of the amount of light emitted from each phosphor may be lost, and the illumination light may change dynamically, resulting in a color that is not designed.
Therefore, the present invention reduces the change in the fluorescence intensity generated from the phosphor when the illumination light is generated using the phosphor having the temperature dependence in the light emission characteristics, and always stabilizes the illumination light of a desired color tone. It is an object of the present invention to provide an endoscopic device obtained in this way.

The present invention has the following configuration.
A wavelength conversion member including a light emitting element and a phosphor that emits light emitted from the light emitted from the light emitting element, transmitted light emitted from the light emitting element and transmitted through the wavelength conversion member, and light emitted from the wavelength conversion member A light source unit that outputs illumination light synthesized with
A drive signal generator for generating a pulse drive signal for driving the light emitting element;
Each pulse of the generated pulse drive signal is further divided into a plurality of short pulses having a shorter pulse width so that the amount of change in the amount of illumination light due to the temperature dependence of the luminous efficiency of the phosphor is not more than an allowable limit value. A drive signal converter for generating a divided pulse drive signal divided into pulses;
A light source controller that drives the light emitting element with the divided pulse drive signal;
An endoscope apparatus comprising:

  According to the endoscope apparatus of the present invention, when the illumination light is generated using the phosphor having the temperature dependency on the light emission characteristic, the change in the fluorescence intensity generated from the phosphor is reduced, and the desired color tone is obtained. Illumination light can always be obtained stably.

It is a figure for describing an embodiment of the present invention, and is a lineblock diagram of an endoscope apparatus showing each apparatus to which an endoscope and an endoscope are connected. It is an external view which shows the specific structural example of an endoscope apparatus. It is explanatory drawing which shows the timing chart of the modulation control of a pulse drive signal. (A) is a pulse drive signal to a laser light source, (B) is explanatory drawing showing the conversion pulse drive signal which divided | segmented one pulse into several short pulses. FIG. 5 is an explanatory diagram schematically showing the light emission intensity of a phosphor that emits light according to the divided pulse drive signal of FIG. (A) is explanatory drawing which shows the intensity | strength change of the output light from the wavelength conversion member with respect to a drive pulse when the idle period Ta is longer than the afterglow period TL, (B) is the case where the idle period Ta is below the afterglow period TL It is explanatory drawing which shows the intensity | strength change of the output light of. It is explanatory drawing which shows the relationship between the drive pulse of the conventional excitation light, and the output light intensity from a fluorescent substance. It is explanatory drawing which shows roughly the mode of the luminous efficiency with respect to the temperature of the conventional G light emission fluorescent substance and R light emission fluorescent substance.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram for explaining an embodiment of the present invention. FIG. 1 is a configuration diagram of an endoscope apparatus representing an endoscope and each apparatus to which the endoscope is connected. FIG. 2 is a specific example of the endoscope apparatus. It is an external view which shows a structural example.
As shown in FIG. 1, the endoscope apparatus 100 inputs information to an endoscope scope (hereinafter referred to as an endoscope) 11, a control device 13, a display unit 15 such as a monitor, and the control device 13. And an input unit 17 such as a keyboard and a mouse. The control device 13 includes a light source device 19 and a processor 21 that performs signal processing of a captured image.

  As shown in FIG. 2, the endoscope 11 includes a main body operation unit 23 and an insertion unit 25 connected to the main body operation unit 23 and inserted into a subject (body cavity). A universal cord 27 is connected to the main body operation unit 23. The distal end of the universal cord 27 is connected to the light source device 19 through a light guide (LG) connector 29A, and is connected to the processor 21 through a video connector 29B.

  The main body operation unit 23 of the endoscope 11 is provided with buttons for performing suction, air supply, and water supply on the distal end side of the insertion unit 25 and various operation buttons 31 such as a shutter button at the time of imaging. A pair of angle knobs 33 is provided.

  The insertion portion 25 is composed of a flexible portion 35, a bending portion 37, and a distal end portion (endoscope distal end portion) 39 in order from the main body operation portion 23 side. The bending portion 37 rotates the angle knob 33 of the main body operation portion 23. The bending operation is performed remotely by moving. Thereby, the front-end | tip part 39 can be turned to a desired direction.

  As shown in FIG. 1, an observation window 41 of an imaging optical system and illumination windows 43A and 43B of an illumination optical system are arranged at the endoscope distal end portion 39. Illumination light is irradiated from each of the illumination windows 43A and 43B, and reflected light from the subject is imaged by the imaging element 45 through the observation window 41. The captured observation image is displayed on the display unit 15 connected to the processor 21.

  The imaging optical system includes an imaging element 45 such as a CCD (Charge Coupled Device) type image sensor or a CMOS (Complementary Metal Oxide Semiconductor) type image sensor, and an optical member 47 such as a lens for forming an observation image on the imaging element 45. Have The observation image formed and captured on the light receiving surface of the image sensor 45 is converted into an electric signal and input to the image signal processing unit 53 of the processor 21 through the signal cable 51, and is converted into a video signal by the image signal processing unit 53. The

  The imaging element 45 may include a primary color system color filter of RGB, or a complementary color system color filter such as CMY or CMYG. In the image sensor 45, an AE signal such as a shutter speed and a diaphragm is set by the image capturing control unit 55.

  The illumination optical system includes a light source device 19, a pair of optical fibers 57A and 57B connected to the light source device 19, and wavelength conversion members 59A and 59B disposed at the light emitting ends of the optical fibers 57A and 57B. The light source device 19 includes laser light sources LD1 and LD2 that are semiconductor light emitting elements, a light source control unit 61 that drives and controls each of the laser light sources LD1 and LD2, a combiner 63 that combines light emitted from the laser light sources LD1 and LD2, And a coupler 65 for branching the combined light into two optical paths by a pair of optical fibers 57A and 57B. The light source device 19 includes a drive signal generation unit 67 that generates a pulse drive signal, which will be described in detail later, a drive signal conversion unit 69 that changes the pulse drive signal, and a characteristic information storage unit 71 that stores phosphor characteristic information.

  The endoscope control unit 73 is connected to an imaging signal processing unit 53, a memory 75 that stores imaging signals and various information, and an image processing unit 77. The endoscope control unit 73 performs appropriate image processing on the image data output from the imaging signal processing unit 53 by the image processing unit 77 and displays the image data on the display unit 15. In addition, the entire endoscope apparatus 100 is controlled such as being connected to a network such as a LAN (not shown) and distributing information including image data.

  The laser light source LD1 is a blue-emitting semiconductor laser having a central wavelength of 445 nm. The laser light source LD1 emits blue laser light whose emission light amount is controlled by the light source control unit 61, and the emitted light is irradiated to the wavelength conversion members 59A and 59B of the endoscope distal end portion 39 through the optical fibers 57A and 57B. . As this laser light source LD1, for example, a broad area type InGaN laser diode can be used.

The wavelength conversion members 59A and 59B absorb a part of the laser light emitted from the laser light source LD1 and excite and emit green to yellow light (for example, YAG phosphor or BAM (BaMgAl ₁₀ O _37). ) And the like. As a result, white light is generated by combining the laser light from the laser light source LD1 and the green to yellow excitation light obtained by wavelength-converting the laser light. A plurality of types of phosphors having different central emission wavelengths used for the wavelength conversion members 59A and 59B are combined by selecting phosphors having the same emission temperature characteristics as much as possible.

  The laser light source LD2 is a violet-emitting semiconductor laser having a central wavelength of 405 nm. The laser light source LD2 is also controlled by the light source controller 61 to emit light, and is emitted from the illumination windows 43A and 43B through the wavelength conversion members 59A and 59B of the endoscope distal end 39.

Next, the emission light quantity ratio of each laser light source when observing the subject with the endoscope apparatus 100 having the above-described configuration will be described.
The light source controller 61 emits white illumination light from the laser light source LD1 (center wavelength 445 nm) and narrowband light from the laser light source LD2 (center wavelength 405 nm) based on instructions from the endoscope controller 73. The amount of light is controlled individually.

  The operator of the endoscope performs an input operation from various operation buttons 31 of the main body operation unit 23 illustrated in FIG. 2 or the input unit 17 on the control device 13 side. The endoscope control unit 73 outputs a control signal to the light source control unit 61 and the imaging control unit 55 based on an operation signal from the operator. At this time, illumination light suitable for the observation target is emitted from the illumination windows 43A and 43B (see FIG. 1) of the endoscope distal end portion 39. The imaging element 45 images the subject under desired imaging conditions.

  At that time, an observation image suitable for diagnosis with high contrast can be acquired by appropriately changing the ratio of the amount of light emitted from the laser light source LD1 and the laser light source LD2 depending on the observation target. When the contrast between the blood vessel (observation object) and the mucous membrane (background image) in the observation image is 1.4 or more, preferably 1.6 or more in the ratio of the observation object / background image, sufficient surface blood vessel extraction ability can be obtained. It becomes like this. Thus, the emission light quantity ratio of the laser light sources LD1 and LD2 causes a clear change in the observation image of the tissue surface layer.

  In order to obtain an appropriately exposed observation image in which the information on the surface of the living tissue is well projected, the emitted light quantity ratio of the laser light sources LD1 and LD2 is adjusted to the desired light quantity ratio with high accuracy, and the laser light sources LD1 and LD2 are used. It is important to match the illumination light generated by the emitted light from the target light amount with high accuracy.

  The light source controller 61 keeps the output light quantity ratio Ra: Rb constant at all times even if the individual emitted light quantity for each target light quantity P1, P2 of each laser light source LD1, LD2 is changed to P1, P2. To control. Thereby, the total of the emitted light amounts of the laser light sources LD1 and LD2 is controlled to the desired target light amount while the emitted light amount ratio of the laser light sources LD1 and LD2 is maintained at the desired emitted light amount ratio.

Next, increase / decrease control of the emission intensity of the laser light sources LD1 and LD2 of the endoscope apparatus 100 will be described.
First, when the operator operates the operation button 31 provided on the main body operation unit 23 of the endoscope 11 shown in FIG. 1, the endoscope control unit 73 performs various observations such as normal observation and narrowband light observation. Control to switch to the mode. That is, in the normal observation mode, the emission light quantity ratio LD1: LD2 of the laser light sources LD1 and LD2 is set to 1: 0, and in the narrowband light observation mode, LD1: LD2 is set to an arbitrary preset ratio.

  In the narrow-band light observation mode, control is performed so that the total emitted light amount of the laser light sources LD1 and LD2 is set to the target light amount while the outputs of both the laser light sources LD1 and LD2 are maintained at the above-described emitted light amount ratio.

  When the surgeon operates the operation button 31 during endoscope observation to switch the observation mode to the narrow-band light observation mode, the endoscope control unit 73 sets a preset emission light amount ratio. A plurality of types of emission light amount ratios Ra: Rb of the laser light sources LD1 and LD2 are prepared in advance so as to be switchable according to the observation mode, and the information is stored in the memory 75. The endoscope control unit 73 reads out the emitted light amount ratio Ra: Rb designated in the switched observation mode from the memory 75 and transmits information on the emitted light amount ratio to the light source control unit 61.

  The light source control unit 61 receives the information on the emitted light amount ratio Ra: Rb transmitted from the endoscope control unit 73. And based on this emitted light quantity ratio, the drive signal production | generation part 67 produces | generates each pulse drive signal which drives laser light source LD1, LD2. Specifically, the current value (amplitude value) of each pulse drive signal of each laser light source LD1, LD2 is increased or decreased from the standard drive current value, and the integrated intensity of each pulse drive signal is the standard drive current value. Is set to be equal to the integrated intensity.

  On the other hand, the target light amount with respect to the total light amount obtained by summing the light amounts emitted from the laser light sources LD1 and LD2 and the fluorescent light amounts from the wavelength conversion members 59A and 59B is the total illumination light amount for the captured image of the previous frame and the captured image. The endoscope control unit 73 is set based on the AE signal.

  The memory 75 stores the total illumination light amount and the target light amount value for the AE signal as table information. The endoscope control unit 73 refers to the memory 75 and obtains a target light amount for the next frame. The endoscope control unit 73 transmits the obtained target light amount to the light source control unit 61.

  Next, based on the set amplitude of the drive signal and the target light amount, the drive signal generation unit 67 generates the pulse drive signals of the laser light sources LD1 and LD2 by common pulse modulation control.

Next, a specific example of generating a pulse drive signal by the common pulse modulation control will be described.
In response to an instruction from the endoscope control unit 73, the light source control unit 61 illustrated in FIG. 1 performs pulse modulation control on the light emission amounts of the laser light sources LD1 and LD2. The drive signal generator 67 generates a pulse drive signal with reference to the memory 75 connected to the endoscope controller 73. There are three types of modulation control of the pulse drive signal: pulse number control (PNM) and pulse density control (PDM: Pulse Density Modulation) and pulse width control (PWM: Pulse Width Modulation). It is implemented using four types of control including pulse amplitude control (PAM).

  FIG. 3 shows a timing chart of modulation control of the pulse drive signal. The drive pulse [1] for lighting at least a part of the exposure period of the electronic shutter is set to the maximum light amount within the period of one frame of the image defined by the vertical synchronization signal VD. Here, one frame period is 33 ms, and the shutter speed is 1/60 s. In addition, the frequency of the drive pulse [1] is 120 kHz, and 2000 pulses are included in the exposure period of the electronic shutter.

  When reducing the light intensity from the maximum light intensity of the drive pulse [1], PNM control in the first pulse modulation area, PDM control in the second pulse modulation area, and PWM control in the third pulse modulation area in descending order of the light intensity And gradually reduce the amount of light.

  First, in the PNM control, the number of pulses is decreased from the entire exposure period Wa of the electronic shutter by the back-alignment on the time axis, and the lighting period is shortened. That is, with respect to the exposure period Wa within one frame by the electronic shutter, as shown in the drive pulse [2], the number of drive pulses is decreased so that the drive start timing is delayed until the predetermined minimum ratio is reached, and the laser light source Reduce the lighting period. Note that the maximum light amount may not be the entire exposure period Wa of the electronic shutter, but may be lit for the entire period of one frame, or may be continuously lit.

  Next, as shown in drive pulse [3], after the lighting period of the laser light source is shortened to a predetermined lighting period Wmin by PNM control, a process of thinning the drive pulse by PDM control is performed. In this PDM control, the pulse density in the lighting period is reduced by thinning out drive pulses at predetermined intervals with respect to the lighting period shortened to the predetermined lighting period Wmin.

  Then, as shown in the drive pulse [4], PDM control is performed until the pulse interval of the drive pulse reaches the thinning limit, that is, until the drive pulse reaches a predetermined minimum pulse density.

  Next, after the drive pulse reaches a predetermined minimum number of pulses, as shown in drive pulse [5], the pulse width of the drive pulse is reduced by PWM control. As shown in drive pulse [6], PWM control is performed in the range until the pulse width of the drive pulse reaches the PWM control limit.

  As described above, when the light amount is controlled to be reduced, the PNM control is first performed from the maximum light amount, so that the lighting period of the laser light source can be shortened and the occurrence of image blurring of the captured image due to blurring can be suppressed. Further, since the non-lighting time of the laser light source becomes longer, the effect of reducing the heat generation of the light source itself and each optical member on the optical path can be obtained as compared with the case of continuous lighting.

  Also, by switching from PNM control to PDM control when the predetermined lighting period is shortened, a reasonably long lighting period is maintained, and flickering during movie observation can be suppressed. The number of pulses, which is the lower limit of PDM control, can prevent the dimming resolution by PDM control from becoming coarse.

  In the PWM control, by changing the duty ratio of each drive pulse, the light quantity in the low light quantity region can be adjusted more finely than the thinning limit, and the dimming resolution is improved.

  By the way, when performing pulse lighting control of the laser light source, the laser light source causes illumination unevenness due to speckle noise. Therefore, in order to obtain a sufficient speckle noise reduction effect, the duty ratio in PWM control has an upper limit.

  Further, the actual laser beam cannot follow the drive rising signal faithfully, and rises with a certain delay component. Similarly, it has a delay component at the time of falling. For this reason, if the drive pulse is an extremely narrow narrow pulse, it is expected that the drive pulse falls before reaching the target value. Therefore, a lower limit of the duty ratio at which PWM control can be accurately performed is set.

  The PNM / PDM control and the PWM control are switched according to the target light amount, and any one of the controls is used exclusively with the other controls. The dynamic range of the controllable light quantity is equal to or greater than the dynamic range of a white lamp such as a xenon lamp by combining each control.

  The number of pulses, pulse density, and pulse width of the pulse drive signal subjected to modulation control are set so that a predetermined amount of illumination light can be obtained. However, when the emission intensity of the phosphor has temperature dependency, the intensity of illumination light as intended may not be obtained. In particular, when a plurality of types of phosphors are used, the luminous efficiency of each phosphor may change individually, resulting in illumination light that deviates from a desired color tone.

FIG. 4A shows a pulse drive signal to the laser light source LD1. Each pulse 83 of the pulse drive signal 81 is a signal having an amplitude intensity of I ₀ , a pulse width of W, and a continuous period T. When the laser light source LD1 is driven by the pulse drive signal 81 to irradiate the wavelength conversion members 59A and 59B with light, fluorescence is generated from the wavelength conversion members 59A and 59B, and the temperatures of the wavelength conversion members 59A and 59B rise. Then, since the light emission characteristics of the phosphors included in the wavelength conversion members 59A and 59B have temperature dependence, the light emission intensity of the phosphors decreases as the temperature rises.

  Therefore, as shown in FIG. 4B, the light source controller 61 divides the single pulse 83 into a plurality of short pulses 87 having a shorter pulse width, and converts the wavelength conversion member 59A. 59B is prevented from being continuously irradiated with light. That is, the drive signal converter 69 (see FIG. 1) has a plurality of short pulses 87 with a pulse width of W1 within a period corresponding to the pulse width W of the pulse 83 of the pulse drive signal 81 before conversion. , 87, 87,... The division into short pulses is performed in the same manner for each pulse of the pulse drive signal 81.

The drive signal conversion unit 69 sets the amplitude intensity I ₁ and the pause period S of each short pulse 87 so that the integrated intensity in the period of the pulse width W is equal to the integrated intensity of the pulse 83. By converting one pulse 83 in the pulse drive signal 81 into a short pulse group 89 composed of a plurality of short pulses 87 having a short pulse width, the continuous light irradiation period to the wavelength conversion members 59A and 59B is shortened, and wavelength conversion is performed. The temperature rise of the members 59A and 59B is suppressed. Thereby, it can prevent that the light quantity and color tone of illumination light change with the intensity | strength of the fluorescence which the wavelength conversion members 59A and 59B generate | occur | produce.

  Specifically, the drive signal converter 69 shown in FIG. 1 first obtains the integrated intensity of one pulse 83 in the pulse drive signal generated by the drive signal generator 67. Then, the drive signal conversion unit 69 determines whether or not the integrated intensity of the one pulse 83 is an intensity that exceeds a predetermined allowable limit value of the change in light amount. The permissible limit value for the change in the amount of light is the minimum amount of light that has a non-negligible effect on the color tone and brightness of the observed image due to changes in the amount of light emitted from the phosphor due to the temperature dependence of the luminous efficiency of the phosphor. It is a change value.

  Here, the phosphor characteristic information indicating the relationship between the permissible limit value of the light amount change and the integrated intensity of one pulse and the light amount change amount is stored in advance in the characteristic information storage unit 71, respectively. The drive signal conversion unit 69 obtains a light amount change amount with respect to the integrated intensity of one pulse 83 with reference to the phosphor characteristic information in the characteristic information storage unit 71, and the obtained light amount change amount and a predetermined light amount change amount. The magnitude of the integrated intensity is determined by comparing with an allowable limit value.

  When the drive signal conversion unit 69 determines that the light intensity change is an integrated intensity exceeding the allowable limit value, each pulse 83 of the pulse drive signal 81 is converted from a plurality of short pulses 87 as shown in FIG. Into short pulse groups 89. For each short pulse 87 in the short pulse group 89, the number of pulses, the pulse width, the pulse period, and the like are set by the drive signal conversion unit 69 according to the integrated intensity value of one pulse 83.

  The light source control unit 61 drives the laser light source LD1 using the converted divided pulse drive signal 85. On the other hand, when it is determined that the integrated intensity is less than or equal to the allowable amount, the laser light source LD1 is driven using the pulse drive signal 81 generated by the drive signal generator 67 as it is.

  FIG. 5 is an explanatory diagram schematically showing the light emission intensity of the phosphor that emits light according to the divided pulse drive signal of FIG. When the laser light source LD1 is driven by the divided pulse drive signal 85, intermittent illumination light corresponding to the short pulse 87 is output from the wavelength conversion members 59A and 59B. The temperature rise period of the wavelength conversion members 59A and 59B by the light emitted from the laser light source LD1 is limited to the period W1 because it is driven by a short pulse having a short pulse width W1. The rest period S after the temperature rise period is a cooling period of the wavelength conversion members 59A and 59B. Therefore, the temperature change of the wavelength conversion members 59A and 59B is slight, and the light emission characteristics of the phosphor do not change greatly. Therefore, the fluorescent light generated corresponding to each short pulse has the same intensity level every time in each short pulse.

  Accordingly, the output light from the wavelength conversion members 59A and 59B when the laser light source LD1 is driven by the divided pulse drive signal has an integrated intensity within the period W, and the ideal output light for one pulse 83 in the pulse drive signal before conversion. This corresponds to an integral intensity of 91. For this reason, it is possible to stably generate a desired amount of illumination light without changing the color tone of the illumination light.

  FIG. 6A is an explanatory diagram showing a change in the intensity of the output light from the wavelength conversion member with respect to the drive pulse. When the laser light source LD1 (see FIG. 1) is driven by a pulse drive signal including the short pulse 87, intermittent output light is obtained from the wavelength conversion members 59A and 59B in accordance with the supply timing of the short pulse 87. However, strictly speaking, the emission response characteristic of the phosphor has a predetermined delay component, so the initial period from when the excitation light is received until the emission starts, and after the excitation light is stopped until the emission stops. The afterglow period is in a transient state.

  On the other hand, as shown in FIG. 6B, when the pause period Ta is set to be less than the afterglow period TL, the wave tail of the intensity waveform in the afterglow period overlaps with the next short pulse. Therefore, the output light by one short pulse does not have a desired integrated intensity, and the set light quantity cannot be obtained. Therefore, as shown in FIG. 6A, the drive signal conversion unit 69 has a pause period between a plurality of short pulses, that is, a pause period Ta from when the laser light source LD1 is turned on to when it is next turned on. After the excitation light is stopped, the divided pulse drive signal is generated so that the emission intensity of the phosphor becomes longer than the afterglow period TL until the emission is stopped. The short pulses of the divided pulse drive signal are set with a pause period Ta longer than the afterglow period TL of the phosphor, so that illumination light according to the integrated intensity of each short pulse can be obtained.

In addition, since the response characteristic of phosphor emission varies depending on the fluorescent material used, the rest period Ta between short pulses is set according to the phosphor material used. Here, the response speed of the phosphor emission with respect to the phosphor material shown as an example below is expressed by the time Te until the emission intensity attenuates and reaches 1 / e, and is as follows.
1) Blue light emitting phosphor: barium magnesium aluminite (BaMg ₂ Al ₁₆ O ₂₇ )
Center emission wavelength 452nm, Te = 2μs
2) Red light emitting phosphor: Y ₂ O ₃ : Eu ²⁺
Center emission wavelength 611nn, Te = 1.1ms
3) Green light emitting phosphor: LaPO ₄ : Ce, Tb
Center emission wavelength 544nm, Te = 2.6ms

  In the phosphor material of the above example, the decay time Te of the blue light emitting phosphor is particularly short. For this reason, the maximum frequency of the short pulse of the divided pulse drive signal may be 500 kHz or less in consideration of the blue light emitting phosphor. Furthermore, in consideration of other general phosphor materials, the frequency is preferably 240 kHz or less.

  The drive signal conversion unit 69 (see FIG. 1) divides one pulse of the pulse drive signal by the drive signal generation unit 67 within a range of the maximum frequency or less. Thereby, illumination light can always be generated with accurate intensity and color tone.

  According to the endoscope apparatus having the above configuration, light source control equivalent to that of an existing configuration such as a xenon lamp is realized, so that an existing processor can be used as it is and a configuration with improved versatility can be achieved. Furthermore, since the light source life of the semiconductor light source is much longer than that of a white lamp such as a xenon lamp, maintenance of the equipment can be reduced.

  Moreover, as a semiconductor light source for narrow-band light illumination, a laser light source having a center wavelength of 360 to 530 nm can be used. With this laser light source, an enhanced image of capillaries and fine structures on the surface of a living tissue can be obtained. The intensity of the white illumination light can be accurately adjusted even when the subject is illuminated by setting the total light amount obtained by mixing the white illumination light and the narrow band light as the target light amount. Therefore, the degree of enhancement can be set with high accuracy, and a good observation image can be obtained.

The present invention is not limited to the above-described embodiments, and those skilled in the art can change or apply the present invention based on the description of the specification and well-known techniques. included. For example, in the present embodiment, an example in which a laser light source is used as a light emitting element has been described, but a light emitting diode may be used. There are various types of light-emitting diodes, such as a bullet-type, surface-mount type, and high-power LED. For any type, the split pulse drive signal is shortened to make the illumination light always accurate. It can be generated with intensity and color tone, and it can save illumination with high brightness.
Moreover, it is good also as a structure which extracts only the specific wavelength by filtering the light from white light sources, such as a xenon lamp.
Further, the light amount control can be controlled by combining the exposure control by the electronic shutter of the imaging means and the light amount control of the light emitting element. In the above description, control of the amount of emitted light with respect to the two laser light sources has been described. However, the number of light sources is not limited to this, and any number of light sources may be used. Furthermore, the emitted light quantity control can be replaced with a drive voltage value control instead of a drive current value control.

As described above, the following items are disclosed in this specification.
(1) A light-emitting element and a wavelength conversion member including a phosphor that emits light by light emitted from the light-emitting element, the transmitted light that is emitted from the light-emitting element and transmitted through the wavelength conversion member, and the wavelength conversion member A light source unit that outputs illumination light synthesized with the emitted light;
A drive signal generator for generating a pulse drive signal for driving the light emitting element;
Each pulse of the generated pulse drive signal is further divided into a plurality of short pulses having a shorter pulse width so that the amount of change in the amount of illumination light due to the temperature dependence of the luminous efficiency of the phosphor is not more than an allowable limit value. A drive signal converter for generating a divided pulse drive signal divided into pulses;
A light source controller that drives the light emitting element with the divided pulse drive signal;
An endoscope apparatus comprising:
According to this endoscope apparatus, the continuous lighting time of the light emitting element is shortened by driving the light emitting element with a divided pulse driving signal obtained by dividing each pulse of the pulse driving signal into a plurality of short pulses having a shorter pulse width. Therefore, it is reduced that the light emitted from the light emitting element is continuously irradiated onto the wavelength conversion member. Therefore, it is possible to efficiently prevent the luminous efficiency of the phosphor from changing due to the temperature rise of the wavelength conversion member and the fluorescence intensity generated from the phosphor from changing. Therefore, it is possible to always stably obtain illumination light having a desired color tone by reducing a change in fluorescence intensity generated from the phosphor.

(2) The endoscope apparatus according to (1),
A characteristic information storage unit that stores phosphor characteristic information representing the relationship between the integrated intensity of one pulse in the pulse drive signal and the amount of light change,
An endoscope apparatus in which the drive signal conversion unit refers to the phosphor characteristic information from the characteristic information storage unit and obtains the light amount change amount with respect to the integrated intensity of the one pulse.
According to this endoscope apparatus, it is possible to easily obtain the amount of light quantity change with respect to the integrated intensity of one pulse by referring to the phosphor characteristic information in the characteristic information storage unit prepared in advance without performing arithmetic processing.

(3) The endoscope apparatus according to (1) or (2),
An endoscope apparatus in which the drive signal conversion unit generates the divided pulse drive signal only when the light amount change amount exceeds the allowable limit value.
According to this endoscope apparatus, the divided pulse drive signal is generated only when the amount of light change exceeds the allowable limit value. Therefore, the divided pulse drive signal is generated only when necessary, and is calculated by the drive signal conversion unit. The burden is reduced.

(4) The endoscope apparatus according to any one of (1) to (3),
The drive signal conversion unit generates the divided pulse drive signal so that a total integrated intensity of the plurality of short pulses obtained by dividing one pulse in the pulse drive signal matches an integrated intensity of the one pulse. Endoscope device.
According to this endoscope apparatus, since the signal intensity after the conversion from the pulse drive signal to the divided pulse drive signal matches, there is no change in the intensity of the illumination light due to the signal conversion, and the desired constant light quantity can be maintained.

(5) The endoscope apparatus according to any one of (1) to (4),
An endoscope apparatus in which the drive signal conversion unit sets a pause period between the plurality of short pulses longer than an afterglow period of emitted light from the wavelength conversion member.
According to this endoscope apparatus, the light emission by the short pulse is not started next within the afterglow period of the light emission from the wavelength conversion member, and the illumination light having the short pulse integrated intensity can be obtained.

(6) The endoscope apparatus according to any one of (1) to (5),
An endoscope apparatus in which the drive signal converter sets a maximum frequency of the short pulse to 500 kHz or less.
According to this endoscope apparatus, the illumination light can be generated with an accurate intensity without being affected by the response delay of the phosphor.

(7) The endoscope apparatus according to any one of (1) to (6),
An endoscope apparatus in which the wavelength conversion member includes a plurality of types of phosphors having different central emission wavelengths.
According to this endoscope apparatus, the intensity of fluorescence generated from a plurality of types of phosphors can be made constant without being affected by the difference in temperature dependence of light emission efficiency. For this reason, the color tone of illumination light can always be made constant.

(8) The endoscope apparatus according to any one of (1) to (7),
An endoscope apparatus in which the light emitting element is a semiconductor light emitting element.
According to this endoscope apparatus, high-intensity illumination light can be obtained with high energy efficiency.

(9) The endoscope apparatus according to any one of (1) to (8),
The light emitting element emits blue light;
An endoscope apparatus that generates white light by combining the fluorescent light generated by the wavelength conversion member and the blue light.
According to this endoscope apparatus, since white light is generated using fluorescent light in a broad wavelength band by a phosphor, illumination light with high color rendering properties can be obtained.

(10) The endoscope apparatus according to any one of (1) to (9),
An endoscope apparatus further comprising narrow band light emitting means for emitting narrow band light having a central wavelength of 360 to 530 nm.
According to this endoscope apparatus, it is possible to emphasize and display capillaries and fine patterns on the surface of a living tissue by irradiating a subject with narrowband light having a visible short wavelength.

(11) The endoscope apparatus according to (10),
An endoscope apparatus in which the drive signal generation unit generates a pulse drive signal so that a total light amount of the illumination light and the narrowband light becomes a target light amount.
According to this endoscope apparatus, the total amount of light obtained by mixing the illumination light and the narrow band light is set as the target light amount, and the subject is illuminated to illuminate the subject. It is possible to accurately adjust the degree of emphasis on capillaries and fine patterns.

<Appendix>
An endoscope apparatus that emits illumination light of a desired light amount from the distal end of an endoscope insertion portion,
A semiconductor light source for generating the illumination light;
An imaging means for adjusting an exposure period by an electronic shutter;
A light source control means for driving the semiconductor light source in a pulsed manner according to the input target light amount,
The light source control means, in order from the highest target light amount,
A first pulse modulation control for shortening the lighting period of the semiconductor light source by reducing the number of pulses of the drive pulse until the predetermined lighting period is reached with respect to the exposure period in one frame by the electronic shutter;
A second pulse modulation control for reducing a pulse density in the lighting period by thinning out the driving pulse at a predetermined interval with respect to a predetermined lighting period in the first pulse modulation region;
A third pulse modulation control for reducing the pulse width for each drive pulse having the minimum number of pulses in the second control range;
An endoscopic device that performs.
According to this endoscope apparatus, the first pulse modulation region in which the number of pulses is decreased and the lighting period is shortened in the descending order of the target light amount, and the second pulse in which the pulse density is decreased by thinning out pulses. By setting the modulation region and the third pulse modulation region for reducing the pulse width, when the target light amount is high, priority is given to control for shortening the lighting time of the light source, and image blur of the captured image is suppressed, Heat generation is reduced. In addition, since a plurality of pulses exist within a predetermined lighting period for a low target light amount, occurrence of flicker can be suppressed. A wide dynamic range and high dimming resolution can be ensured by combining different types of control.

DESCRIPTION OF SYMBOLS 11 Endoscope 13 Control apparatus 19 Light source apparatus 21 Processor 45 Image pick-up element 57A, 57B Optical fiber 59A, 59B Wavelength conversion member 61 Light source control part 67 Drive signal generation part 69 Drive signal conversion part 71 Characteristic information storage part 73 Endoscope control Unit 75 Memory 77 Image processing unit 81 Pulse drive signal 83 Pulse 85 Pulse drive signal after conversion 87 Short pulse 89 Short pulse group 91 Ideal output light 100 Endoscope device LD1, LD2 Laser light source

Claims (11)

A wavelength conversion member including a light emitting element and a phosphor that emits light emitted from the light emitted from the light emitting element, transmitted light emitted from the light emitting element and transmitted through the wavelength conversion member, and light emitted from the wavelength conversion member A light source unit that outputs illumination light synthesized with
A drive signal generator for generating a pulse drive signal for driving the light emitting element;
Each pulse of the generated pulse drive signal is further divided into a plurality of short pulses having a shorter pulse width so that the amount of change in the amount of illumination light due to the temperature dependence of the luminous efficiency of the phosphor is not more than an allowable limit value. A drive signal converter for generating a divided pulse drive signal divided into pulses;
A light source controller that drives the light emitting element with the divided pulse drive signal;
An endoscope apparatus comprising: The endoscope apparatus according to claim 1,
A characteristic information storage unit that stores phosphor characteristic information representing the relationship between the integrated intensity of one pulse in the pulse drive signal and the amount of light change,
An endoscope apparatus in which the drive signal conversion unit refers to the phosphor characteristic information from the characteristic information storage unit and obtains the light amount change amount with respect to the integrated intensity of the one pulse. The endoscope apparatus according to claim 1 or 2,
An endoscope apparatus in which the drive signal conversion unit generates the divided pulse drive signal only when the light amount change amount exceeds the allowable limit value. The endoscope apparatus according to any one of claims 1 to 3,
The drive signal conversion unit generates the divided pulse drive signal so that a total integrated intensity of the plurality of short pulses obtained by dividing one pulse in the pulse drive signal matches an integrated intensity of the one pulse. Endoscope device. The endoscope apparatus according to any one of claims 1 to 4,
An endoscope apparatus in which the drive signal conversion unit sets a pause period between the plurality of short pulses longer than an afterglow period of emitted light from the wavelength conversion member. The endoscope apparatus according to any one of claims 1 to 5,
An endoscope apparatus in which the drive signal converter sets a maximum frequency of the short pulse to 500 kHz or less. The endoscope apparatus according to any one of claims 1 to 6,
An endoscope apparatus in which the wavelength conversion member includes a plurality of types of phosphors having different central emission wavelengths. The endoscope apparatus according to any one of claims 1 to 7,
An endoscope apparatus in which the light emitting element is a semiconductor light emitting element. The endoscope apparatus according to any one of claims 1 to 8,
The light emitting element emits blue light;
An endoscope apparatus that generates white light by combining the fluorescent light generated by the wavelength conversion member and the blue light. The endoscope apparatus according to any one of claims 1 to 9,
An endoscope apparatus further comprising narrow band light emitting means for emitting narrow band light having a central wavelength of 360 to 530 nm. The endoscope apparatus according to claim 10, wherein
An endoscope apparatus in which the drive signal generation unit generates a pulse drive signal so that a total light amount of the illumination light and the narrowband light becomes a target light amount.

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