JP5851810B2 - Reference light source - Google Patents

Description

  The present invention relates to a reference light source, and more particularly to a reference light source used for calibration of a photodetector that measures delayed light emission, for example.

  Conventionally, it is known that environmental factors such as chemical substances affect the growth of organisms. As an evaluation method for evaluating the degree of influence of environmental factors, for example, Patent Document 1 below discloses an evaluation method by measuring delayed luminescence emitted from algae. Delayed luminescence is a phenomenon in which when a living organism (photosynthetic sample) having a photosynthetic function such as algae is irradiated with light, fluorescence is emitted from the photosynthetic dye by the energy of the light.

  In this evaluation method, first, a control sample containing no environmental factors and an exposed sample containing environmental factors are prepared using algae samples obtained from the same culture. Subsequently, the amount of delayed luminescence (delayed fluorescence) from the control sample and the amount of delayed luminescence from the exposure material are respectively measured. And the elapsed time of the feature point of a time change is calculated about each measured light quantity, The degree of the influence of an environmental factor is evaluated by calculating | requiring the comparison value of these elapsed time. According to such an evaluation method, it is possible to evaluate the degree of influence of environmental factors in a short time.

  In the evaluation method as described above, the measurement of delayed luminescence from the control sample and the measurement of delayed luminescence from the exposed sample are usually performed with the same time from the culture of the algal sample to the measurement of the delayed luminescence. . For this reason, it is necessary to use a plurality of photodetectors and to measure the delayed light emission simultaneously with different photodetectors. Therefore, if there are differences in the characteristics (sensitivity, spectral characteristics, darkness, uniformity, etc.) of multiple photodetectors, there is a risk that the evaluation cannot be performed accurately. It is necessary to perform calibration in advance so that

  Here, since the algae are dispersed in the water, the delayed luminescence from the control sample and the exposed sample is a luminescence in which the luminescence points are three-dimensionally dispersed and is planar when viewed from the receiver side. It emits light (surface light emission). Therefore, when performing the above calibration, a reference light source that emits surface light is required in the same manner as delayed light emission from the control sample and the exposed sample. In this regard, as a light source that performs surface light emission, for example, a surface light source device (backlight unit) used as a backlight of a liquid crystal display device (liquid crystal panel) is known (for example, see Patent Documents 2 to 6 below). .

International Publication No. 2005/062027 Pamphlet JP-A-2005-91526 JP 2011-102848 A JP 2010-244730 A JP 2009-76329 A JP 2007-115530 A

  By the way, since delayed light emission from algae is weak light, a reference light source used for calibration of a photodetector that measures delayed light emission is required to uniformly emit weak light surface. In addition, in order to perform calibration accurately, the reference light source needs to emit weak light stably over a predetermined period. However, the surface light source device described above emits light that is stronger than delayed light emission from algae, and it is difficult to control the light to stabilize at a weak light level. Therefore, even if the above-described surface light source device is used as a reference light source, weak light cannot be stably emitted, and as a result, calibration may not be performed with high accuracy.

  The present invention has been made to solve such problems, and an object of the present invention is to provide a reference light source that can stably and evenly emit weak light to a surface.

  In order to solve the above-described problems, a reference light source according to the present invention is a reference light source that emits light in a planar direction toward a predetermined direction, and has a light guide surface that has a light emission surface with the predetermined direction as the light emission direction. And a light-emitting portion that is provided on one side of the light guide member in a direction that intersects the predetermined direction, emits light toward the light guide member, and is provided on the other side of the light guide member in a direction that intersects the predetermined direction. A light-receiving unit having a light-receiving surface facing the light-emitting unit through the member, a control unit that controls the amount of light emitted from the light-emitting unit based on the amount of light detected by the light-receiving unit, and light of the light guide member A light emitting part that is provided on the emitting surface and diffuses the light emitted from the light emitting surface of the light guide member and reduces the amount of light so that it is smaller than the amount of light detected by the light receiving part. It is characterized by having provided.

  In the reference light source of the present invention, the light emitted from the light emitting portion toward the light guide member is guided by the light guide member and emitted from the light emitting surface in a predetermined direction, and is also guided by the light guide member. The light is received by the light receiving unit, whereby the amount of light emitted from the light emitting unit is controlled by the control unit. The light emitted from the light emitting surface of the light guide member is diffused by the light emitting unit and dimmed so as to have a light amount smaller than the light amount detected by the light receiving unit. Light is emitted to the outside. Here, since the light emitting unit and the light receiving unit are provided so as to face each other with the light guide member interposed therebetween, the light emitted from the light emitting unit is easily detected by the light receiving unit. Therefore, since the light receiving unit can detect a large amount of light and the control unit can control the light emitting unit based on the large light amount, the light amount of the light emitted from the light emitting unit can be stably controlled. Therefore, according to the present invention, it is possible to stably and evenly emit weak light.

  Further, the light emitting part has a first light attenuating part having a light-reducing effect and having light reflectivity, a first light diffusing part having a light-diffusing action, and a second light-reducing part having a light-reducing action. A second light diffusing portion having a light diffusing action, and the first dimming portion, the first light diffusing portion, the second dimming portion, and the second light diffusing portion are guided along a predetermined direction. It is preferable that they are arranged so as to be laminated in this order in a direction away from the light exit surface of the member. In this case, the light emitted from the light exit surface of the light guide member is attenuated by sequentially passing through the first dimming unit, the first light diffusing unit, the second dimming unit, and the second light diffusing unit. And will be diffused. At this time, since the first dimming portion has light reflectivity, a part of the light emitted from the light emitting surface is reflected into the light guide member by the first dimming member and detected by the light receiving portion. . Therefore, the light receiving unit can detect a larger amount of light.

  In addition, as a configuration that favorably exhibits the above-described effects, specifically, the first dimming portion is provided on a part of the light exit surface of the light guide member, and the first light diffusing portion has directivity. A microlens array for diffusing light, and a diffusion plate in which a light diffusing substance having a light diffusing action is dispersed, and the microlens array and the diffusion plate are arranged along a predetermined direction of the light guide member. The structure arrange | positioned so that it may laminate | stack in this order in the direction away from a light-projection surface is mentioned.

  Further, as a configuration that preferably exhibits the above-described effects, specifically, the first dimming portion is provided on the entire surface of the light emitting surface of the light guide member, and the first light diffusing portion includes a microlens array. The structure which contains is mentioned.

  The first light diffusing unit, the second dimming unit, and the second light diffusing unit each have a light emitting surface whose emitting direction is a predetermined direction. It is preferable that the area of the light emission surface of the part, the area of the light emission surface of the second dimming part, and the area of the light emission surface of the second light diffusion part are increased in this order. In this case, the light emitted from the light exit surface of the light guide member can be preferably used for surface light emission, and the necessity to shield the spread light by providing a light shielding ring or the like can be reduced. It becomes possible.

  Also, at least one location between the light guide member and the first light diffusing portion, between the first light diffusing portion and the second dimming portion, and between the second dimming portion and the second light diffusing portion. It is preferable that a light-shielding part that shields light is provided at the outer edge part of. In this case, when the light emitted from the light emitting surface of the light guide member passes through the first light diffusing unit, the second dimming unit, and the second light diffusing unit, the light leaks between these parts. Can be further suppressed.

  Moreover, it is preferable that the reflective part which has light reflectivity is provided in the surface opposite to the light-projection surface in a light guide member. In this case, the light guided by the light guide member can be reliably reflected into the light guide member by the reflecting portion. As a result, a larger amount of light can be detected by the light receiving unit, and the amount of light emitted from the light emitting unit can be controlled more stably.

  According to the present invention, it is possible to provide a reference light source that can stably and evenly emit faint light.

It is a perspective view which shows the front side of the reference | standard light source which concerns on 1st Embodiment of this invention. It is a perspective view which shows the back side of the reference | standard light source of FIG. It is a disassembled perspective view which shows the reference | standard light source of FIG. It is sectional drawing along the IV-IV line in FIG. It is a conceptual diagram which shows the control part of the reference | standard light source of FIG. It is a flowchart which shows operation | movement of the control part of FIG. It is the schematic which shows the photodetector which performs calibration using the reference | standard light source of FIG. It is a graph which shows the light emission amount of the reference | standard light source of FIG. It is a graph which shows the light-emission quantity of the reference | standard light source which concerns on a comparison form. FIG. 2 is a result showing stability of light emission in the reference light source of FIG. 1 and a result showing stability of light emission in the reference light source according to the comparative example. It is a distribution map which shows light emission by the reference | standard light source of FIG. It is a distribution map which shows light emission by the reference | standard light source which concerns on a comparison form. It is a graph which shows the characteristic of the photodetector which calibrated using the reference | standard light source of FIG. It is sectional drawing which shows the reference | standard light source which concerns on 2nd Embodiment of this invention.

  Hereinafter, preferred embodiments according to a reference light source of the present invention will be described in detail with reference to the drawings. In the following description, the same or equivalent elements will be denoted by the same reference numerals, and redundant description will be omitted.

  1 is a perspective view showing a front side of a reference light source according to the first embodiment of the present invention, FIG. 2 is a perspective view showing a rear side of the reference light source of FIG. 1, and FIG. 3 is an exploded perspective view showing the reference light source of FIG. 4 and 4 are cross-sectional views taken along line IV-IV in FIG. As shown in FIGS. 1-4, 1 A of reference light sources are used for calibration of the photodetector P (refer FIG. 7) which measures the delayed light emission from algae, for example, toward the front (predetermined direction). Emits faint light in a planar shape (surface emission). As shown in FIG. 3, the reference light source 1A includes a housing 2, a substrate 3, a light guide member 4, an LED (Light Emitting Diode) 5, an SPD (Silicon PhotoDiode), a reflector (reflector). ) 7, a light emitting unit 8A, and a control unit 9.

  The housing 2 forms an outer periphery of the reference light source 1A and has a substantially rectangular parallelepiped shape. The case 2 has a size of, for example, about 60 mm × 32 mm × 12 mm. On one side in the longitudinal direction of the housing 2 (the right side in the figure), a through-hole 21A having a circular cross section penetrating in the front-rear direction is provided. The through hole 21A is a hole for accommodating the light guide member 4 and the light emitting portion 8A. As shown in FIG. 4, the diameter changes intermittently along the front-rear direction according to the outer shape of the light emitting portion 8A. It has a stepped shape.

  The rear surface 23 of the housing 2 is provided with a rectangular recess 22 having a slightly narrower area than the rear surface 23 for fitting the substrate 3. On the bottom surface of the recess 22, there are further provided recesses (not shown) for housing electronic components such as the LED 5, the SPD 6, the control unit 9, and the power storage unit 32 (described later). The housing 2 can be formed of, for example, resin or the like, and is formed of black resin in the present embodiment.

  Returning to FIG. 3, the substrate 3 fixes and electrically connects electronic components such as the LED 5, the SPD 6, the control unit 9, and the power storage unit 32. The substrate 3 has a substantially rectangular plate shape that is slightly smaller than the rear surface 23 of the housing 2, and is fitted in the recess 22 of the housing 2. The front surface of the substrate 3 is a substrate surface 31 on which electronic components are fixed. On the other side of the substrate surface 31 in the longitudinal direction, a power storage unit 32 for storing power for driving the reference light source 1A is provided. On the rear surface of the substrate 3, an electrode 33 for taking in electric power from the outside to the power storage unit 32 is provided at a position corresponding to the power storage unit 32 (see FIG. 2). The substrate 3 here is black in order to suppress light from leaking from the substrate surface 31.

  The light guide member 4 guides light emitted from the LED 5 to form planar light. The light guide member 4 has a substantially disk shape and is accommodated in the rear portion of the through hole 21A (see FIG. 4). The front surface as the main surface of the light guide member 4 is a first light exit surface 41. The first light exit surface 41 is a plane whose normal direction is the front-rear direction, and emits light (surface emission) with the front direction as the exit direction.

  The light guide member 4 has a light incident surface 42 and a second light emitting surface 43 on the side surface (circumferential surface). The light incident surface 42 is a surface for taking in the light emitted from the LED 5 into the light guide member 4, and the second light emitting surface 43 emits the light guided by the light guide member 4 toward the SPD 6. It is for the purpose. The light incident surface 42 and the second light emitting surface 43 are opposed to each other in the longitudinal direction of the substrate 3 and constitute two parallel plane portions on the side surface. The light guide member 4 can be formed of a light transmissive material. In the light guide member 4, a reflective material that reflects light from the inside toward the outside is applied to the outer surface except the first light emitting surface 41, the light incident surface 42, and the second light emitting surface 43. .

  In such a light guide member 4, the light incident from the light incident surface 42 is internally reflected and spreads substantially uniformly. A part of the spread light is emitted in a planar shape from the first light emission surface 41 toward the front, and the other part is emitted from the second light emission surface 43 toward the SPD.

As shown in FIG. 4, the LED 5 is provided on one side of the light guide member 4 in the longitudinal direction (that is, the direction crossing the front-rear direction) on the substrate surface 31. The LED 5 is spaced from the light incident surface 42 of the light guide member 4 and emits light toward the light incident surface 42. The LED 5 is connected to the control unit 9 and emits light based on a voltage value applied from the control unit 9. The amount of light emitted from the LED 5 is, for example, about 10 ⁹ to 10 ¹² (S ⁻¹ ) measured by photon counting. Note that the measurement value by photon counting can be obtained as a measurement conversion value when the light emission amount exceeds the detection range of photon counting. For example, if the light passing through a filter that attenuates by 4 digits is 10 ⁵ (S ⁻¹ ) in photon counting, the light is 10 ⁹ (S ⁻¹ ).

  The SPD 6 is provided on the other side of the light guide member 4 in the longitudinal direction on the substrate surface 31 and has a light receiving surface 61. The light receiving surface 61 is provided to face the second light emitting surface 43, that is, to face the LED 5 through the light guide member 4. The SPD 6 is spaced from the second light exit surface 43 of the light guide member 4 and receives the light guided by the light guide member 4 and emitted from the second light exit surface 43.

The SPD 6 is connected to the control unit 9 and outputs a current value corresponding to the amount of received light to the control unit 9. In the SPD 6 here, the light receiving surface 61 is relatively wide in order to increase the amount of light received. The level of the amount of light that can be received by the SPD 6 is, for example, about 10 ⁸ to 10 ¹¹ (S ⁻¹ ) as measured by photon counting.

  The reflection plate 7 reflects light traveling from the inside to the outside of the light guide member 4 toward the inside. The reflection plate 7 has a disk shape substantially the same as the diameter of the light guide member 4, and is disposed on the rear surface (opposite surface of the first light exit surface 41) 44 of the light guide member 4. The light to be emitted from the rear surface 44 in the light guide member 4 is reflected by the reflecting plate 7 toward the first light emitting surface 41 and reflected toward the SPD 6 through the second light emitting surface 43. Is done. The reflection plate 7 can be formed of a material having light reflectivity, which is a property of reflecting light. For example, the reflection plate 7 can be formed by performing plating on the substrate surface 31.

  The light emitting portion 8A diffuses the light emitted from the first light emitting surface 41 of the light guide member 4 and determines the amount of light emitted from the first light emitting surface 41 from the amount of light detected by the SPD 6. It fades out to be smaller. 8 A of light emission parts are accommodated in 21 A of through-holes, and are provided on the said 1st light emission surface 41 (front of the light guide member 4) so that the 1st light emission surface 41 of the light guide member 4 may be opposed. ing.

  The light emitting unit 8A includes a first neutral density filter (first neutral density unit) 10A, a first micro prism sheet 11, a second micro prism sheet 12, a micro lens array 13, a first diffuser plate 14, and a second neutral density filter. A filter (second dimming part) 15 and a second diffusion plate (second light diffusing part) 16 are provided. The first neutral density filter 10A, the first micro prism sheet 11, the second micro prism sheet 12, the micro lens array 13, the first diffuser plate 14, the second neutral density filter 15, and the second diffuser plate 16 are arranged in the front-rear direction. Are arranged in this order in a direction away from the first light exit surface 41.

  The first neutral density filter 10 </ b> A has a function of reducing and transmitting light emitted from the first light exit surface 41 of the light guide member 4, and a function of reflecting the light toward the inside of the light guide member 4. have. The first neutral density filter 10 </ b> A has a substantially crescent shape when viewed from the front (see FIG. 3), and is laminated on a portion of the first light exit surface 41 on the LED 5 side. Thereby, 10 A of 1st neutral density filters reduce and reflect the light radiate | emitted in LED5 vicinity part of the 1st light emission surface 41. FIG. The front surface of the first neutral density filter 10 </ b> A is a surface perpendicular to the front-rear direction, and is a light emitting surface whose front direction is the emitting direction. As the first neutral density filter 10A, a filter having a neutral density effect and light reflectivity can be used. Here, for example, a magic mirror film is used.

  The first microprism sheet 11 collects the light emitted from the first light exit surface 41 and the light that has passed through the first neutral density filter 10A forward, and improves the brightness in the forward direction. The first microprism sheet 11 has a disk shape with a diameter slightly larger than the diameter of the light guide member 4, and is arranged coaxially in front of the first light exit surface 41. The front surface of the first microprism sheet 11 is a surface perpendicular to the front-rear direction, and is a light emitting surface 11 a with the front emitting direction. On the front surface and the rear surface of the first microprism sheet 11, a striped pattern for condensing light and improving the luminance is formed.

  The second microprism sheet 12 condenses the light that has passed through the first microprism sheet 11 forward, and improves the brightness in the forward direction. The second microprism sheet 12 has a disk shape substantially the same as the diameter of the first microprism sheet 11 and is coaxially disposed in front of the first microprism sheet 11. The front surface of the second microprism sheet 12 is a surface perpendicular to the front-rear direction, and is a light emission surface 12a with the front as the emission direction.

  As the second microprism sheet 12, the same one as the first microprism sheet 11 can be used, and a similar striped pattern is formed on the front and rear surfaces thereof. In the present embodiment, the first microprism sheet 11 and the second microprism sheet 12 are arranged so that the striped patterns on the front and rear surfaces thereof are substantially orthogonal to each other, thereby collecting light. The effect of improving brightness by light is further improved.

  The microlens array 13 is an optical element that performs light diffusion with directionality. Here, the microlens array 13 is an optical element that diffuses light that has passed through the second microprism sheet 12 to make it uniform in a planar shape. The microlens array 13 has a disk shape having a diameter substantially the same as that of the second microprism sheet 12 and is coaxially disposed in front of the second microprism sheet 12. The front surface of the microlens array 13 is a surface perpendicular to the front-rear direction, and is a light exit surface 13a with the front being the exit direction.

  A surface relief hologram pattern with fine irregularities is provided on the rear surface (that is, the light incident surface) of the microlens array 13, and the effect of integrating minute lenses in units of μm can be obtained. ing. Thereby, the microlens array 13 has a light diffusing action, which is an action of diffusing light.

  The first diffusing plate 14 has a ground glass shape, and diffuses (internally diffuses) the light in order to make the light passing through the microlens array 13 resemble the delayed light emission of algae. The first diffusion plate 14 has a disk shape with a slightly smaller diameter than the microlens array 13 and is coaxially disposed in front of the microlens array 13. The front surface of the first diffusing plate 14 is a surface perpendicular to the front-rear direction, and is a light emitting surface 14a with the front as the emitting direction.

  The first diffusion plate 14 is formed by dispersing a light diffusing substance in a transmissive material. Thereby, the first diffusion plate 14 internally diffuses the light emitted from the first light emitting surface 41 so that the diffusion points of the light emitted from the first light emitting surface 41 are not aligned in the plane, It is possible to vary the dispersion points themselves. In the present embodiment, the microlens array 13 and the first diffusion plate 14 function as a first light diffusion unit.

  The second neutral density filter 15 attenuates the light so that the light that has passed through the first diffusion plate 14 becomes weak light. The second neutral density filter 15 has a disk shape with a diameter larger than that of the first diffusion plate 14 and the microlens array 13, and is arranged coaxially in front of the first diffusion plate 14. The front surface of the second neutral density filter 15 is a surface perpendicular to the front-rear direction, and is a light emission surface 15a with the front as the emission direction. As the second neutral density filter 15, one having a neutral density action can be used. Here, for example, a gelatin filter is used.

  The second diffusion plate 16 internally diffuses the light passing through the second neutral density filter 15 in order to resemble the delayed light emission of algae. The second diffuser plate 16 has a disk shape with a larger diameter than the second neutral density filter 15 and is disposed in front of the second neutral density filter 15. The front surface of the second diffuser plate 16 is a surface perpendicular to the front-rear direction, and is a light exit surface 16a having the front-rear direction as the exit direction. The light emitting surface 16a is exposed to the outside and constitutes a light emitting surface in the reference light source 1A. As the second diffusion plate 16, the same material as the first diffusion plate 14 can be used.

  The controller 9 controls the light emission amount of the LED 5 based on the amount of light detected by the SPD 6. FIG. 5 is a conceptual diagram illustrating a control unit of the reference light source of FIG. As shown in FIG. 5, the control unit 9 includes an IV converter 91 and a comparator 92. The IV converter 91 converts a current value into a voltage value, and is connected to the SPD 6 and the comparator 92.

  The IV converter 91 converts the current value input from the SPD 6 into a voltage value, and outputs the converted voltage value to the comparator 92 as the output value X. The comparator 92 determines the light emission amount of the LED 5 and is connected to the LED 5. The comparator 92 stores the comparison reference value Y, and determines a voltage value to be applied to the LED 5 based on the output value X input from the IV converter and the comparison reference value Y. The comparator 92 applies the determined voltage value to the LED 5.

  In addition, annular light-shielding rings (light-shielding parts) R1 to R6 are arranged between the members constituting the light emitting part 8A in the reference light source 1A so as to be shielded from light. Specifically, the light shielding ring R <b> 1 is located on the outer peripheral side between the light guide member 4 and the first microprism sheet 11, and a part of the light shielding ring R <b> 1 projects radially outward from the first light emitting surface 41. Is provided.

  The light shielding ring R2 is located on the outer peripheral side between the first microprism sheet 11 and the second microprism sheet 12, and a part thereof is provided so as to protrude outward in the radial direction from the light emitting surface 11a. . The light shielding ring R3 is located on the outer peripheral side between the second microprism sheet 12 and the microlens array 13, and a part thereof is provided so as to protrude outward in the radial direction from the light emitting surface 12a.

  The light shielding ring R4 is located on the outer peripheral side between the microlens array 13 and the first diffusion plate 14, and a part of the light shielding ring R4 is provided so as to protrude radially outward from the light emitting surface 13a. The light shielding ring R5 is located on the outer peripheral side between the first diffusion plate 14 and the second neutral density filter 15, and a part of the light shielding ring R5 is provided so as to protrude outward in the radial direction from the light emitting surface 14a. The light shielding ring R6 is located on the outer peripheral side between the second neutral density filter 15 and the second diffuser plate 16, and a part of the light shielding ring R6 is provided so as to protrude radially outward from the light emitting surface 15a.

  Further, an annular light shielding ring (light shielding portion) R7 is provided on the outer edge portion of the light emitting surface 16a of the second diffusion plate 16 so that a part of the outer surface protrudes radially outward from the light emitting surface 15a. Yes. Thereby, it is suppressed that light leaks from between the through hole 21 </ b> A and the side surface of the second diffusion plate 16. The light shielding rings R1 to R7 can be formed of, for example, a black resin.

  Note that the reference light source 1A can set the light emission amount based on an external input. That is, for example, by connecting a computer to the control unit 9 of the reference light source 1A, the light emission amount of the reference light source 1A can be varied as desired. Incidentally, the comparison reference value Y of the comparator 92 is appropriately changed according to the set light emission amount.

  Next, the operation of the reference light source 1A will be described.

  When the LED 5 emits light toward the light incident surface 42 of the light guide member 4 and light enters the light guide member 4, the incident light is repeatedly guided by surface reflection by the light guide member 4 and guided. Reflected by the reflecting material and the reflecting plate 7 applied to the outer peripheral surface of the member 4, a part of the light is emitted in a planar shape from the first light emitting surface 41 toward the front. And most of the light emitted from the first light emitting surface 41 goes directly to the first microprism sheet 11, and the remaining light emitted from the first light emitting surface 41 passes through the first neutral density filter 10A. After passing and dimmed, it goes to the first microprism sheet 11.

  Subsequently, the light traveling toward the first microprism sheet 11 passes through the first microprism sheet 11 and the second microprism sheet 12 in this order, and is condensed forward to improve the forward luminance. The light that has passed through the first microprism sheet 11 and the second microprism sheet 12 passes through the microlens array 13 and is diffused into a planar shape. The light that has passed through the microlens array 13 passes through the first diffusion plate 14, and its dispersion point varies.

  Subsequently, the light that has passed through the first diffusion plate 14 passes through the second neutral density filter 15 and is attenuated to become weak light. The light that has passed through the second neutral density filter 15 passes through the second diffusion plate 16, and its dispersion point varies. And the light which passed the 2nd diffuser plate 16 is light-emitted planarly toward the front. As described above, finally, faint light is emitted from the reference light source 1A toward the front.

  At this time, the light emitted from the first light emitting surface 41 is between the light guide member 4 and the first microprism sheet 11, between the first microprism sheet 11 and the second microprism sheet 12, and second. Between the micro prism sheet 12 and the micro lens array 13, between the micro lens array 13 and the first diffusion plate 14, between the first diffusion plate 14 and the second neutral density filter 15, and the second neutral density filter 15. When passing between the second diffusion plate 16 and the front surface of the second diffusion plate 16, the light is blocked by the light shielding rings R <b> 1 to R <b> 7, and leakage from the side is suppressed.

  Simultaneously with the surface light emission described above, the light that has entered the light guide member 4 from the LED 5 is guided while repeating the surface reflection by the light guide member 4, and the reflective material applied to the outer peripheral surface of the light guide member 4. Then, the light is reflected by the first neutral density filter 10 </ b> A and the reflecting plate 7 and is emitted from the second light emitting surface 43 toward the SPD 6. Then, the amount of light emitted from the second light exit surface 43 is detected by the SPD 6.

  The SPD 6 outputs the detected light amount to the IV converter 91 of the control unit 9 as a current value. The IV converter 91 converts the current value input from the SPD 6 into a voltage value, and outputs the converted voltage value to the comparator 92 as the output value X. As shown in FIG. 6, when the output value X is input from the IV converter 91 (step S10), the comparator 92 compares the output value X with the comparison reference value Y (step S12).

  When the output value X is larger than the comparison reference value Y in step S12, the comparator 92 determines the power value applied to the LED 5 to be lower than the current power value (step S14). On the other hand, when the output value X and the comparison reference value Y are equal to each other in step S12, the comparator 92 does not change the power value applied to the LED 5 (step S16). On the other hand, when the output value X is smaller than the comparison reference value Y in step S12, the comparator 92 determines the power value applied to the LED 5 to be higher than the current power value (step S18).

  Subsequently, the comparator 92 applies the determined voltage value to the LED 5 to control the light emission amount of the LED 5. As a result, the LED 5 is controlled so that the light emission amount from the LED 5 is stabilized, and the weak light emitted from the reference light source 1A is stabilized.

  Next, a method for calibrating the photodetector using the reference light source 1A will be described. First, a photodetector that performs calibration using the reference light source 1A will be described. FIG. 7 is a schematic diagram illustrating a photodetector that performs calibration using a reference light source according to an embodiment of the present invention.

  As shown in FIG. 7, the photo detector P (multiplier type photo detector: Photo Multiplier Tube) is a device that detects delayed luminescence from a sample (also referred to as a photosynthetic sample) prepared from an algal sample. It is provided in the unit 100. In addition to the photodetector P, the measurement unit 100 includes a sample placement unit 110, a condensing optical system 120, an excitation light source 130, a transmission light source 140, a transmission light detector 150, a first shutter 160, and a second shutter 170. Yes. These components are accommodated in the housing 180.

  The sample placement unit 110 is a part for placing a sample to be measured, and is placed in the sample chamber K. The sample chamber K is a dark box in which a sample can be taken in and out by opening and closing the door, and light from the outside is blocked when the door is closed. The sample placement unit 110 is configured so that a cell containing a photosynthesis sample as a sample can be placed. Note that the sample placement unit 110 may be configured such that the sample can be introduced from the outside of the housing 180 by a liquid feed pump or the like.

  The photodetector P receives delayed light emission generated by the excitation light irradiation to the sample, converts the received delayed light emission into an electric signal corresponding to the light intensity (light emission amount), and an electric signal corresponding to the applied voltage. As an output value to an arithmetic unit (not shown) or the like. The photodetector P is configured using a multiplication type photodetector such as a photomultiplier tube or an avalanche photodiode, for example. The condensing optical system 120 is provided so as to collect the weak delayed light emission generated by the irradiation of the excitation light to the sample and guide the condensed delayed light emission to the photodetector P.

  The excitation light source 130 irradiates the sample installed in the sample installation unit 110 with light (excitation light). The excitation light source 130 only needs to be able to emit a light wavelength (280 to 800 nm) effective for plant photosynthesis. For example, a light emitting diode, a semiconductor laser element, or a light bulb is used. The transmitted light source 140 irradiates the sample with transmitted light, and the transmitted light detector 150 measures transmitted light and scattered light transmitted through the sample.

  The first shutter 160 is provided to be freely opened and closed between the condensing optical system 120 and the sample placement unit 110 in order to optically fractionate the condensing optical system 120, the photodetector P, and the sample chamber K. ing. By closing the first shutter 160, it is possible to prevent light from the excitation light source 130 and the transmission light source 140 from directly entering the condensing optical system 120 and the photodetector P, and light emission of components such as the condensing optical system ( Afterglow) can be prevented.

  The second shutter 170 is provided between the excitation light source 130 and the sample placement unit 110 so as to be openable and closable in order to optically fractionate the excitation light source 130 and the sample chamber K. By closing the second shutter 170, the light irradiated from the excitation light source 130 to the sample setting unit 110 is blocked, and a slight afterglow generated immediately after the excitation light source 130 is turned off is irradiated to the sample setting unit 110. Can be prevented.

  When such a plurality of photodetectors P are used to simultaneously measure delayed emission of a plurality of samples, individual differences in the output characteristics of the photodetectors P become a problem. For example, in the photodetector P, even if the operating conditions such as the applied voltage are the same, individual differences may occur in output characteristics (gain), detection upper limit, detection lower limit, and the like with respect to the optical input. On the other hand, delayed light emission is weak light with extremely low light intensity, and the light intensity of delayed light emission changes over time in the range of 4 to 5 digits, and within a few seconds after stopping the irradiation of excitation light. Since the change is large, if there are individual differences in the output characteristics of the plurality of photodetectors P, the measured values tend to vary. The applied voltage is a voltage adjusted for each photodetector P in order to adjust the range of light intensity of light input that can obtain ideal output characteristics.

  Therefore, before measuring delayed light emission, the following calibration is performed using the reference light source 1A for each of the plurality of photodetectors P in order to reduce the individual difference between the plurality of photodetectors P. That is, first, after the power storage unit 32 is preliminarily charged via the electrode 33, the amount of light emitted from the reference light source 1A is set within the range of the amount of delayed light emitted from the algae. Subsequently, the reference light source 1 </ b> A is immediately set on the sample placement unit 110 in a state where the set amount of light is emitted from the reference light source 1 </ b> A. Note that the amount of light emitted from the reference light source 1A is measured by the light detector P in a state where no light is input (dark), and the error value (dark) output from the light detector P despite the absence of light input. (Value) may be taken into consideration.

  Subsequently, the second shutter 170 is closed, and the light emission amount from the reference light source 1A is measured by the photodetector P in this state. Then, such measurement by the photodetector P is performed a plurality of times while changing the light emission amount from the reference light source 1A. Based on the obtained measurement values, the characteristics of the output (measurement value) with respect to the input (the amount of light emitted from the reference light source 1A) in the photodetector P are obtained.

  If the obtained characteristics do not fall within a predetermined range, the photodetector P is adjusted by the applied voltage, and the above-described measurement by the photodetector P is repeated again. On the other hand, if the obtained characteristics are within a predetermined range, the calibration is terminated. This makes it possible to align the characteristics of the plurality of photodetectors P with predetermined characteristics.

By the way, the amount of delayed luminescence from algae is, for example, about 10 ⁶ (S ⁻¹ ) or less as measured by photon counting, which is very small, while the amount of luminescence from the LED 5 is as described above. For example, it is as large as about 10 ⁹ to 10 ¹² (S ⁻¹ ) as measured by photon counting. For this reason, when the light emitted from the LED 5 is emitted from the first light emitting surface 41 of the light guide member 4 to the outside as it is, the amount of light emitted from the surface is too large compared to the amount of delayed emission from algae. Therefore, in order to resemble delayed light emission from algae, the light emitted from the reference light source 1A to the outside is required to be weak light of about 10 ⁶ (S ⁻¹ ) or less by measurement by photon counting, for example. Therefore, the light emitted from the LED 5 needs to be attenuated to, for example, 1/1000 or less by the light emitting unit 8A.

In this regard, in the reference light source 1A according to the present embodiment, the amount of light emitted from the reference light source 1A to the outside is reduced to 1/1000 or less of the light amount emitted from the LED 5 by adopting the above-described configuration. It is possible to shine. That is, according to the reference light source 1A, for example, measurement by photon counting makes it possible to emit a weak amount of light that is about the same as the amount of delayed light emission from algae (about 10 ³ to 10 ⁶ (S ⁻¹ )). Become.

  Further, in the present embodiment, as described above, the LED 5 and the SPD 6 are provided so as to face each other with the light guide member 4 interposed therebetween. Therefore, the light directly directed from the LED 5 to the SPD 6 increases and the SPD 6 emits from the LED 5. The detected light can be easily detected, and a larger amount of light can be detected. In addition, a large amount of light can be detected by the SPD 6 by reflecting light within the light guide member 4 by the first neutral density filter 10 </ b> A and the reflection plate 7. Therefore, the LED 5 can be controlled by the control unit 9 based on a large amount of light, and the light emission amount of the LED 5 can be stabilized. As a result, according to the present embodiment, weak light can be stably and uniformly surface-emitted.

  8 is a graph showing the amount of light emitted from the reference light source of FIG. 1, FIG. 9 is a graph showing the amount of light emitted from the reference light source according to the comparative example, FIG. 10 is a result showing the stability of light emission of the reference light source of FIG. It is a result which shows stability of light emission of the reference light source concerning a comparison form. Each data in FIG. 8 is obtained by measuring the light amount of the above-described embodiment (reference light source 1A) of three individuals having different light emission amounts using the photodetector P. Similarly, each data in FIG. 9 is obtained by measuring the light amounts of the reference light sources according to the comparison forms of three individuals having different light emission amounts using the photodetector P.

In each measurement, the measurement time is 600 seconds. Moreover, as a light source which concerns on a comparison form, it is set as the light source which does not have 10 A of 1st neutral density filters, and the microlens array 13. FIG. Further, the stability S (%) in FIG. 10 is calculated by the following equation (1) based on the results of FIGS. The stability S indicates that the closer to 100 (%), the higher the stability of light emission.

However,
A _S (S ⁻¹ ): Average value of measured values for 0.1 to 10 seconds after the start of measurement A _E (S ⁻¹ ): Average value of measured values for 590.1 to 600 seconds after the start of measurement

  As shown in FIGS. 8A to 8C, it can be seen that the temporal change (overall inclination and amplitude) of the light emission amount in the reference light source 1A is small in all set values. Moreover, as shown to (a)-(c) of embodiment in FIG. 10, the light emission from 1 A of reference | standard light sources has high stability in all the setting values. On the other hand, as shown in FIGS. 9A to 9C, it can be seen that the change over time in the light emission amount in the comparative embodiment is larger than the light emission amount from the reference light source 1A. Moreover, as shown to (a) and (c) of the comparison form in FIG. 10, the light emission from the light source which concerns on a comparison form does not necessarily become a thing with high stability. As a result, in the present embodiment, it can be confirmed that the weak light is surface-emitted stably and uniformly over a predetermined period.

  11 is a distribution diagram showing light emission from the reference light source of FIG. 1, and FIG. 12 is a distribution diagram showing light emission from the reference light source according to the comparative embodiment. The distribution chart in FIG. 11 is obtained by photo-counting the light surface-emitted from the reference light source 1A with a photo counter (ARGUS-50 manufactured by Hamamatsu Photonics) and integrating the obtained light quantity. Similarly, the distribution chart in FIG. 12 is obtained by photo-counting the light surface-emitted from the light source according to the comparative embodiment and integrating the obtained light quantity. 11 and 12 show three types of distribution diagrams in which the light emission amount is changed, and shows that the light emission amount is larger in the bright part (the light emission amount is smaller in the dark part).

  As shown in FIGS. 11A to 11C, in the reference light source 1A, it is understood that the light emission amount is substantially uniform in the circular light emitting surface 16a (see FIG. 1) through all the set values. . On the other hand, as shown in FIGS. 12B and 12C, in the light source according to the comparative example, the light emission amount is higher in the vicinity of the outer edge than in the central portion in the circular light emission surface, and the light emission amount is uniform. It is not. As a result of the above, it can be confirmed in the present embodiment that weak light is uniformly surface-emitting.

  In the present embodiment, as described above, the first light emitting surface 41 is provided with the first diffusion plate 14 and the second diffusion plate 16 in which the light diffusing substance having a light diffusing action is dispersed. When the light emitted from the first diffusion plate 14 and the second diffusion plate 16 passes through, the dispersion point can be dispersed by the light diffusion material dispersed therein. Therefore, the surface light emitted from the reference light source 1A can be made to resemble the delayed light emission by algae.

  In the present embodiment, as described above, since the reflector 7 is provided on the rear surface 44 of the light guide member 4, a larger amount of light can be detected by the SPD 6, and the weak light can be more stably and uniformly distributed. Can emit surface light. Further, as described above, since the light shielding rings R1 to R7 that shield the light are provided, the light emitted forward from the first light emission surface 41 of the light guide member 4 spreads excessively as it goes forward. Even in this case, leakage of the light to the outside can be reliably suppressed.

  FIG. 13 is a graph showing the characteristics of a photodetector calibrated using the reference light source of FIG. Each data in FIG. 13 is obtained by calibrating three different photodetectors P using the reference light source 1A and measuring delayed light emission from the same sample. As shown in FIGS. 13A to 13C, in this embodiment, it can be seen that the characteristics of the three different photodetectors P can be made substantially the same. Thereby, it is possible to make the characteristics of the plurality of photodetectors substantially the same, and it can be confirmed that good calibration is possible.

  In the first light emitting surface 41 of the light guide member 4, light is likely to reach from the LED 5 in the vicinity of the LED 5, so that a larger amount of light is likely to be emitted than in other parts. In this regard, as described above, in the present embodiment, since the first neutral density filter 10A having the dimming action and the reflective action is provided in the vicinity of the LED 5 on the first light emission surface 41, the first light emission is performed. The light quantity distribution of the light emitted from the surface 41 can be made more uniform.

  Next, a reference light source according to the second embodiment of the present invention will be described. FIG. 14 is a cross-sectional view showing a reference light source according to the second embodiment of the present invention. As shown in FIG. 14, the reference light source 1B according to the present embodiment is different from the reference light source 1A according to the first embodiment (see FIG. 4) in that a light emission part 8B is provided instead of the light emission part 8A. The light guide member 4 includes a light reduction film 10 </ b> C on the rear surface (opposite surface of the first light emission surface 41) 44 side.

  The light emitting portion 8B is accommodated in the through hole 21B and provided on the first light emitting surface 41 so as to face the first light emitting surface 41 of the light guide member 4. The light emitting part 8B includes a light reducing film (first light reducing part) 10B, a microlens array 17 (first light diffusing part), a light reducing filter (second light reducing part) 18, and a diffusion plate (second light). Diffusion part) 19 is provided, and these are arranged so as to be laminated in this order in the direction away from the first light exit surface 41 along the front-rear direction.

  The light reduction film 10 </ b> B attenuates the light emitted from the first light emission surface 41 of the light guide member 4 and reflects the light emitted from the first light emission surface 41 toward the inside of the light guide member 4. To do. This dimming film 10 </ b> B is provided on the entire surface of the first light emitting surface 41. The dimming film 10 </ b> B here is formed, for example, by vapor-depositing a material having a dimming action and a reflecting action on the first light emitting surface 41.

  The microlens array 17 diffuses the light that has passed through the dimming film 10B so as to be uniform in a planar shape, and is disposed in front of the dimming film 10B. The front surface of the microlens array 17 is a surface perpendicular to the front-rear direction, and is a light exit surface 17a having the front-rear direction as the exit direction. The microlens array 17 has a disk shape with a diameter larger than that of the light guide member 4, and the area of the light exit surface 17 a is larger than the area of the first light exit surface 41 of the light guide member 4. Yes. As the microlens array 17, for example, the same one as the microlens array 13 according to the first embodiment can be used.

  The neutral density filter 18 attenuates the light that has passed through the microlens array 17 in order to make the light weak, and is provided on the light exit surface 17 a of the microlens array 17. The front surface of the neutral density filter 18 is a surface perpendicular to the front-rear direction, and is a light exit surface 18 a having the front-rear direction as the exit direction. The neutral density filter 18 has a disk shape larger in diameter than the microlens array 17, and the area of the light exit surface 18 a is larger than the area of the light exit surface 17 a of the microlens array 17. As the neutral density filter 18, for example, the same filter as the second neutral density filter 15 according to the first embodiment can be used, and the neutral density filter 18 is disposed by vapor deposition between the microlens array 17 and the diffusion plate 19. Can do.

  The diffusing plate 19 diffuses the light internally in order to make the light that has passed through the neutral density filter 18 resemble the delayed light emission of algae, and is provided on the light exit surface 18 a of the neutral density filter 18. The front surface of the diffusing plate 19 is a surface perpendicular to the front-rear direction, and is a light exit surface 19 a having the front-rear direction as the exit direction. The diffuser plate 19 has a disk shape with a diameter larger than that of the neutral density filter 18, and the area of the light emission surface 19 a is larger than the area of the light emission surface 18 a of the neutral density filter 18. The light exit surface 19a of the diffuser plate 19 is exposed to the outside and constitutes the light exit surface of the reference light source 1B. As the diffusion plate 19, the same thing as the 1st diffusion plate 14 which concerns on 1st Embodiment can be used.

  The light reduction film 10 </ b> C is provided between the rear surface 44 of the light guide member 4 and the reflection plate 7, and reduces the light reaching the reflection plate 7 and reflects it toward the light guide member 4. The dimming film 10 </ b> C here is formed, for example, by vapor-depositing a material having a dimming action and a reflecting action on the rear surface 44 in the same manner as the dimming film 10 </ b> B described above. In addition, in the light guide member 4, on the outer surface except the first light exit surface 41, the light incident surface 42, the second light exit surface 43, and the rear surface 44, light traveling from the inside to the outside is provided, as in the first embodiment. A reflective material that reflects toward the inside is applied.

  As described above, also in this embodiment, there are substantially the same effects as in the first embodiment. In addition, as described above, since the light reducing film 10B is provided on the entire surface of the first light emitting surface 41 of the light guide member 4, the amount of light reflected in the light guide member 4 by the light reducing film 10B. Since the amount of light received by the SPD 6 can be increased, the LED 5 can be controlled so that the surface emitting light becomes more stable.

  In the present embodiment, as described above, the area of the first light exit surface 41 of the light guide member 4, the area of the light exit surface 17a of the microlens array 17, the area of the light exit surface 18a of the neutral density filter 18, The area of the light exit surface 19a of the diffuser plate 19 is increased in this order. As described above, the light emitting surfaces 41, 17a, 18a, and 19a are configured to expand toward the front, which is the light emitting direction of the reference light source 1B, so that the light is emitted from the first light emitting surface 41 of the light guide member 4. It is possible to cause surface emission by suitably utilizing the spread of the emitted light as it travels forward, and it is possible to reduce the need to shield the spread of the light by providing a light shielding ring or the like. As a result, the number of parts can be reduced.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments. The present invention can be modified without departing from the scope described in the claims or applied to other embodiments. May be.

  For example, in the first embodiment, a sheet (diffusion plate) having a light diffusing action may be further provided between the second neutral density filter 15 and the second diffusion plate 16. In addition, the first embodiment may not include the first microprism sheet 11, the second microprism sheet 12, and the reflection plate 7 depending on circumstances.

  Moreover, in the said embodiment, you may provide the vapor deposition film which has a light reflectivity in the whole surface of the light guide member 4 except the light-incidence surface 42 and the 2nd light-projection surface 43. FIG. In this case, the amount of light received by the SPD 6 can be increased by several tens of percent, for example. Moreover, in the said embodiment, although LED5 was provided as a light emission part, a various optical element can be used as a light emission part, if it emits light. In the above embodiment, the SPD 6 is provided as the light receiving unit, but various optical elements can be used as the light receiving unit as long as they receive light.

In the above embodiment, the light emitted from the LED 5 is reduced to, for example, 1/1000 or less, and the light emitted from the reference light source 1A is measured as weak as about 10 ⁶ (S ⁻¹ ) or less by measurement by photon counting. Although it is light, it is not limited to this. For example, in the above-described embodiment, in order to provide a margin for light emitted from the surface, the upper limit value of the light may be 10 ⁷ (S ⁻¹ ) measured by photon counting. In this case, the light emitted from the LED 5 is reduced to 1/100, for example.

  DESCRIPTION OF SYMBOLS 1A, 1B ... Standard light source, 4 ... Light guide member, 5 ... LED (light emission part), 6 ... SPD (light reception part), 7 ... Reflection plate, 8A, 8B ... Light emission part, 9 ... Control part, 10A ... 1st 1 dimming filter (first dimming part), 10B ... dimming film (first dimming part), 13 ... micro lens array (first light diffusing part), 14 ... first diffusion plate (first light diffusing part) ), 15 ... second attenuating filter (second attenuating part), 16 ... second diffuser plate (second light diffusing part), 17 ... microlens array (first light diffusing part), 17a ... light exit surface, DESCRIPTION OF SYMBOLS 18 ... Light-reducing filter (2nd light reduction part), 18a ... Light emission surface, 19 ... Diffusing plate (2nd light diffusion part), 19a ... Light emission surface, 41 ... 1st light emission surface (light emission surface), 61: light receiving surface, R1 to R8: light shielding ring (light shielding portion).

Claims (8)

A reference light source that emits light in a plane toward a predetermined direction,
A light guide member having a light exit surface in which the predetermined direction is a light exit direction;
A light emitting unit that is provided on one side of the light guide member in a direction intersecting the predetermined direction and emits light toward the light guide member;
A light receiving portion provided on the other side of the light guide member in a direction intersecting with the predetermined direction, and having a light receiving surface facing the light emitting portion via the light guide member;
A control unit that controls the amount of light emitted from the light emitting unit based on the amount of light detected by the light receiving unit;
It is provided on the light emitting surface of the light guide member, diffuses the light emitted from the light emitting surface of the light guide member, and makes the light amount of the light smaller than the light amount detected by the light receiving unit. And a light emitting part for dimming the light. The light emitting part has a first dimming part having a dimming action, a first light diffusing part having a light diffusing action, and a second light diffusing part having a light diffusing action,
The first dimming portion, the first light diffusing portion, and the second light diffusing portion are arranged so as to be stacked in this order along the predetermined direction in a direction away from the light emitting surface of the light guide member. The reference light source according to claim 1, wherein The first dimming part is provided on a part of the light exit surface of the light guide member,
The first light diffusion part includes a microlens array that performs light diffusion with directionality, and a diffusion plate in which a light diffusion material having a light diffusion action is dispersed,
The microlens array and the diffusion plate are arranged so as to be laminated in this order along the predetermined direction in a direction away from the light emitting surface of the light guide member. The reference light source described. The first dimming portion is provided on the entire light emitting surface of the light guide member,
The reference light source according to claim 2, wherein the first light diffusion unit includes a microlens array. The light emitting part is
It has a dimming effect, and said first light attenuating portion having light reflectivity,
Said first light diffusing section having a light diffusing function,
A second dimming part having a dimming effect;
A said second light diffusion portion having a light diffusing function, a,
The first dimming unit, the first light diffusing unit, the second dimming unit, and the second light diffusing unit are arranged in this order in the direction away from the light emitting surface of the light guide member along the predetermined direction. The reference light source according to claim 2, wherein the reference light source is arranged so as to be laminated. The first light diffusing unit, the second dimming unit, and the second light diffusing unit each have a light emitting surface whose emitting direction is the predetermined direction,
The area of the light exit surface of the light guide member, the area of the light exit surface of the first light diffusion portion, the area of the light exit surface of the second dimming portion, and the area of the light exit surface of the second light diffusion portion 6. The reference light source according to claim 5 , wherein the reference light sources are enlarged in this order. Between the light guide member and the first light diffusing unit, between the first light diffusing unit and the second dimming unit, and between the second dimming unit and the second light diffusing unit. The reference light source according to claim 5 , wherein a light shielding portion for shielding light is provided at an outer edge portion in at least one of the reference light source. The reference light source according to any one of claims 1 to 7 , wherein a reflective portion having light reflectivity is provided on a surface opposite to the light emitting surface of the light guide member.