JP2017207354A - Light source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce fluctuation in the luminous energy of emitted light in a light source device equipped with a plurality of light-emitting diodes differing in the wavelength range of emitted light.SOLUTION: A light source device 100 according to the present invention comprises: a plurality of light-emitting diodes (LED) 10 mutually differing in the wavelength range of emitted light; a concave diffraction grating 12 for guiding lights emitted from these LEDs 10 to the same synthetic optical path; a semipermeable membrane 16 arranged in the synthetic optical path, for branching the light synthesized by the concave diffraction grating 12 into a measurement light and a monitor light; a spectroscopic element (concave diffraction grating 12) for separating the monitor light into lights that correspond to the wavelength range of light emitted from each of the plurality of LEDs 10; an optical detector 20 having a plurality of optical detection elements for detecting the intensities of a plurality of lights separated by the spectroscopic element; and an output control unit 30 for controlling the outputs of the plurality of LEDs 10 on the basis of detection signals obtained by the plurality of optical detection elements.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a light source device incorporated in an optical measuring device such as a spectrophotometer.

  In an optical measurement device that performs spectroscopic measurement of light generated by the interaction (absorption, reflection, fluorescence, etc.) between the measurement object and light when the measurement object is irradiated with light, the light that interacts with the measurement object Since the wavelengths are different, a light source device that emits light in a wide wavelength range is used. As one of such light source devices, there is a light source device using a plurality of light emitting diodes (hereinafter referred to as LEDs (light emitting diodes)) having different emission wavelength ranges. In this light source device, light emitted from a plurality of LEDs is synthesized by an optical element such as a diffraction grating or a half mirror, thereby realizing light emitted in a wide wavelength range (see Patent Documents 1 and 2).

US2011 / 0132077 A1 JP 2004-286645 A

  In order to perform accurate spectroscopic measurement, it is necessary to stabilize the output of each LED. Therefore, in the light source device described above, a part of the emitted light of each LED is branched, the light intensity is detected by a detector, and the drive current of the LED is feedback-controlled based on the result.

  In a system that synthesizes outgoing light using a diffraction grating, the combined light (synthesized light) is collected by a condenser lens, and an outgoing slit is placed at the condensing position of the condenser lens to achieve the desired diffraction. Only light (for example, first-order diffracted light) is extracted through the exit slit. For this reason, for example, when the condensing position of the synthesized light fluctuates due to expansion or contraction of an optical element such as a diffraction grating or a condensing lens or a frame holding them with a temperature change around the apparatus, the exit slit is changed. The amount of light passing through changes. In such a case, there is a problem that even if the output of each LED is stable, the amount of emitted light actually irradiated onto the measurement object changes, and accurate spectroscopic measurement cannot be performed.

  The problem to be solved by the present invention is to reduce fluctuations in the amount of emitted light in a light source device including a plurality of light emitting diodes having different wavelength ranges of emitted light.

The light source device according to the first aspect of the present invention, which has been made to solve the above problems,
a) a plurality of light emitting diodes having different wavelength ranges of emitted light;
b) a light combining member that guides light emitted from the plurality of light emitting diodes to the same combined light path;
c) a light branching member arranged on the combined light path for branching the light combined by the light combining member into outgoing light and monitor light;
d) a spectroscopic element that splits the monitor light into light corresponding to a wavelength range of light emitted from each of the plurality of light emitting diodes;
e) a photodetector having a plurality of light detecting elements for detecting the intensity of a plurality of lights dispersed by the spectroscopic element;
and f) an output control unit that controls outputs of the plurality of light emitting diodes based on detection signals obtained by the plurality of light detection elements.

  In the light source device according to the first aspect, after the light emitted from the plurality of light emitting diodes is synthesized by the light combining member, it is branched into the emitted light and the monitor light by the light branching member. The emitted light is emitted from the light source device, and is irradiated on, for example, an object for spectroscopic measurement. On the other hand, the monitor light is split into light corresponding to the wavelength range of the light emitted from each of the plurality of light emitting diodes by the spectroscopic element, and is detected by the photodetection element. In this case, the wavelength range of the light split by the spectroscopic element and the wavelength range of the emitted light of each of the plurality of light emitting diodes do not necessarily have to coincide with each other. Further, the spectroscopic element may continuously disperse the monitor light (that is, disperse the light after the separation into a continuous spectrum) or may intermittently disperse the monitor light. The output control unit controls the outputs of the plurality of light emitting diodes based on the detection signals of the respective light detection elements.

  In this case, the output control unit controls the output of the light emitting diode corresponding to the light detection element based on the detection signal obtained from each of the plurality of light detection elements (that is, the light detection element and the light emitting diode are 1: The intensity of the emitted light from each light emitting diode may be determined using detection signals obtained from a plurality of light detection elements and a previously obtained arithmetic expression. May be provided, and the output of each light emitting diode may be controlled based on the intensity of the emitted light of each light emitting diode calculated by the arithmetic processing unit.

In the light source device, the light combining member may be formed of a concave diffraction grating, and a plurality of light emitting diodes may be arranged side by side in the wavelength dispersion direction of the concave diffraction grating.
In this case, by providing a light introducing member for guiding the monitor light to the concave diffraction grating, and by configuring the concave diffraction grating to also serve as the spectroscopic element, the number of component parts of the apparatus can be reduced, Can be miniaturized.

Moreover, the light source device according to the second aspect of the present invention, which has been made to solve the above problems,
a) a plurality of light emitting diodes having different wavelength ranges of emitted light;
b) a concave diffraction grating that guides the diffracted light of the light emitted from the plurality of light emitting diodes to the same combined optical path;
c) a photodetector having a plurality of photodetectors arranged at positions where diffracted light having a different order from the diffracted light emitted from each light-emitting diode guided to the combined optical path by the concave diffraction grating is incident;
d) An output control unit that controls outputs of the plurality of light emitting diodes based on detection signals obtained by the plurality of light detection elements.

  In the light source device of the second aspect, the diffracted light from the concave diffraction grating of the light emitted from the plurality of light emitting diodes is guided to the combined optical path to form the emitted light, which is different from the diffracted light constituting the emitted light. The diffracted light of the order enters the plurality of light detection elements as monitor light.

  In the light source device according to the first aspect of the present invention, since the outputs of the plurality of light emitting diodes are controlled based on the amount of light after being synthesized by the light synthesizing member, the temperature around the device changes, and the light synthesizing member changes from the light emitting diode to the light synthesizing member. Even when there is a change in the arrangement of the optical system up to the above, the change in the amount of emitted light can be reduced.

  Further, in the light source device according to the second aspect of the present invention, the diffracted light by the concave diffraction grating of the light emitted from the plurality of light emitting diodes is guided to the combined optical path to constitute the emitted light, and the diffraction constituting the emitted light Diffracted light of an order different from that of light enters the plurality of light detection elements as monitor light. At this time, when a change occurs in the arrangement of the optical system from the light emitting diode to the concave diffraction grating, the emission direction of the diffracted light from the concave diffraction grating changes. In this case, since the change in the emission direction of the diffracted light becomes the same regardless of the diffraction order, the change in the amount of the emitted light can be reduced by using a part of the diffracted light as the monitor light.

1 is a top view showing a schematic configuration of a light source device according to a first embodiment of the present invention. The side view of the light source device seen from the slit board. The perspective view which shows the positional relationship of monochromatic LED, a photodetector, a diffraction grating, and an output slit. The light intensity distribution figure of monochromatic LED and white LED. The figure for demonstrating the flow of the signal of a light source device. The block diagram centering on the control circuit of the light source device which concerns on 2nd Embodiment of this invention. The top view which shows schematic structure of the light source device which concerns on 3rd Embodiment of this invention.

Hereinafter, specific embodiments of a light source device according to the present invention will be described with reference to the drawings.
[First Embodiment]
As illustrated in FIG. 1, the light source device 100 includes six single-color LEDs 10 (101 to 106), one white LED 11, a concave diffraction grating 12 having a toroidal-shaped incident surface, and a slit plate 13. ing. The slit plate 13 is formed with an exit slit 131 and a monitor light entrance slit 132 made of fine holes arranged vertically (see FIGS. 2 and 3). The six single-color LEDs 101 to 106 are arranged in a line on the flat substrate 14 and have wavelengths centered at 340 nm, 405 nm, 470 nm, 635 nm, 700 nm, and 770 nm in order from one end to the other end. Monochromatic light with a width of about 10 to 20 nm is emitted. The white LED 11 is provided to supplement a wavelength range that is out of the wavelength range of the emitted light of the six single-color LEDs 101 to 106, and emits light in a wavelength range of about 400 nm to 700 nm.

  The concave diffraction grating 12 is formed with a number of grooves parallel to each other at equal intervals in one direction on the concave surface (incident surface) of the optical material. The monochromatic LEDs 101 to 106 are all arranged on the substrate 14 so as to have a positional relationship such that the first-order diffracted light incident on the incident surface of the concave diffraction grating 12 passes through the exit slit 131. The white LED 11 is arranged so that the 0th-order light of the light incident on the incident surface of the concave diffraction grating 12 passes through the exit slit 131.

As shown in FIG. 2, the first-order diffracted light of the emitted light from each of the monochromatic LEDs 101 to 106 and the 0th-order diffracted light of the emitted light from the white LED 11 that has passed through the exit slit 131 are incident on the collimator lens 15 and shaped into parallel light fluxes. Thereafter, the light enters the semipermeable membrane 16. A part of the light incident on the semipermeable membrane 16 passes through the semipermeable membrane 16 and a part thereof is reflected toward the mirror 17. The light that has passed through the semipermeable membrane 16 is emitted from a window portion (not shown).
On the other hand, the light reflected by the semi-transmissive film 16 enters the mirror 17 as monitor light, and after being reflected by the mirror 17, is condensed on the monitor light incident slit 132 by the condenser lens 18. Then, after passing through the monitor light incident slit 132, it enters the incident surface of the concave diffraction grating 12 again. That is, in this embodiment, the semipermeable membrane 16 constitutes a light branching member.

  As shown in FIG. 3, the monitor light re-entered on the concave diffraction grating 12 is wavelength-dispersed by the concave diffraction grating 12 and then enters the seven light detection elements 201 to 207 included in the photodetector 20. Each of the light detection elements 201 to 207 is disposed at a condensing position of each wavelength dispersion light by the concave diffraction grating 12 of the monitor light. In the present embodiment, the light detection elements 201 to 207 are arranged in a line on the substrate 14 as in the case of the single color LEDs 101 to 106, but may be arranged on another substrate. Although not shown, a light shielding member is provided around each of the seven light detection elements 201 to 207 and around each light detection element, and the light (stray light) scattered and reflected in the housing of the light source device 100. Is configured not to enter each of the light detection elements 201 to 207.

  FIG. 4 shows light intensity distributions of the single color LEDs 101 to 106 and the white LED 11 (in FIG. 4, the single color LEDs 101 to 106 are represented as single color LEDs 1 to 6, respectively). The light detection elements 201 to 206 are configured such that light in the peak wavelength region of the single color LEDs 101 to 106 is incident thereon. Further, the detection element 207 is arranged so that light in a wavelength region (region surrounded by a rectangular frame in FIG. 4) that is less affected by the monochromatic LEDs 101 to 106 out of the peak wavelength region of the white LED 11 is incident.

  FIG. 5 is a diagram illustrating a signal flow of the light source device 100. In FIG. 5, as in FIG. 4, the six single-color LEDs 101 to 106 are represented as single-color LEDs 1 to single-color LEDs 6, respectively. Further, seven LED drive circuits 40 including the single-color LED 1 to the single-color LED 6 and the white LED are respectively used as the LED 1 drive circuit to the LED 7 drive circuit, and the light detection elements 201 to detect the intensity of the emitted light from the seven LEDs. Reference numeral 207 denotes a light detection element 1 to a light detection element 7. Hereinafter, description will be made according to this notation.

The control circuit 30 of the light source device 100 includes a storage device 31 and a control calculation unit 32. The storage device 31 uses the signals from the light detection elements 1 to 7 to emit light intensity of the single color LEDs 1 to 6 and the white LED. The following arithmetic expression (1) for calculating (P1 to P7) is stored. The control calculation unit 32 performs a predetermined calculation process using the calculation formula (1) and the signals of the light detection elements 1 to 7 to calculate the intensity of the emitted light from the single color LED 1 to the single color LED 6 and the white LED.

  When driving of the single color LED 1 to single color LED 6 and the white LED is started and signals (I 1 to I 7) from the light detection elements 1 to 7 are input to the control circuit 30, the control circuit 30 outputs the signals (I 1 to I 7 ) And the calculation formula (1) are used to calculate the intensity of the emitted light from each LED. And LED1 drive circuit-LED7 drive circuit is controlled so that this intensity | strength may become the preset target value, and each LED is driven. For the control of the LED1 drive circuit to the LED7 drive circuit, PID control, P control, etc. can be used in addition to feedback control by PI control.

Here, the arithmetic expression (1) will be described. In the arithmetic expression (1), a1 to a7,..., G1 to g7 are conversion coefficients of signals of the light detection elements 1 to 7, respectively. The arithmetic expression (1) is obtained by the following procedure when the light source device 100 is initialized.
First, the drive current is passed through the single color LED 1 to the single color LED 6 and the white LED one by one so that the intensity of the emitted light becomes a constant value (P0). Then, the ratio of the detection signals (I1 to I7) of all the light detection elements 1 to 7 and the emission light intensity (P0) of the light detection elements 1 to 7 is obtained, and this is used as a conversion coefficient. And For example, when the monochrome LED 1 is driven,
a1 = I1 / P0, a2 = I2 / P0 ... a7 = I7 / P0
It becomes.

  With the above configuration, even when light from a plurality of LEDs is incident on each of the light detection elements 1 to 7, the control circuit 30 considers the contribution of each LED to the amount of light detected by each of the light detection elements 1 to 7. Thus, the output of the LED can be controlled. In addition, the emitted light intensity of each single color LED1-6 and white LED at the time of calculating | requiring the conversion coefficient of each photon detection element 1-7 may not be the same. Here, the conversion coefficient is obtained by driving the LEDs one by one. However, for example, when the plurality of LEDs are arranged apart from each other and the influence is small, the plurality of LEDs are driven simultaneously. Thus, the respective conversion coefficients may be obtained.

  As described above, according to the present embodiment, the light after being synthesized by the concave diffraction grating 12 and passing through the exit slit 131 is dispersed, and the light intensity after the spectroscopy is detected by the light detection elements 201 to 207. And the output of single color LED101-106 and white LED11 was controlled based on the detection signal of these photon detection elements 201-207. Therefore, even when the temperature around the light source device 100 changes and the arrangement or the like of the optical system from the single color LEDs 101 to 106 and the white LED 11 to the exit slit 131 changes, the amount of the emitted light can be stabilized.

  Moreover, in the said embodiment, since the concave diffraction grating 12 which is an optical member for synthesize | combining the emitted light of each single color LED101-106 and white LED11 was utilized as a spectroscopic element of monitor light, a number of parts decreased and the apparatus small size. And manufacturing cost can be reduced.

  Furthermore, according to the above embodiment, since the light blocking member is provided around each of the light detection elements 201 to 207 to prevent stray light from entering each of the light detection elements 201 to 207, each of the single color LEDs 101 to 106 and the white LED 11 Output can be controlled stably

[Second Embodiment]
FIG. 6 is a block diagram centering on the control circuit 300 of the light source device according to the second embodiment of the present invention. In this embodiment, a temperature sensor A is provided near each of the plurality of single color LEDs, and the drive current of each single color LED is adjusted based on the detection signal of each temperature sensor A. The emitted light of the plurality of single color LEDs Unlike the first embodiment, the temperature sensor B is provided in the vicinity of the light detecting element for detecting the light and the sensitivity of the light detecting element is corrected based on the detection signal of each temperature sensor B. (Specifically, the configuration of the shielding plate, the shielding member, etc.) is the same as in the first embodiment.

  The temperature sensor A and the temperature sensor B are composed of, for example, a resistance temperature detector or a thermocouple. Both the temperature sensor A and the temperature sensor B may be constituted of a temperature measuring resistor or a thermocouple, and one of the temperature sensor A and the temperature sensor B may be a temperature measuring resistor and the other may be a thermocouple.

  In FIG. 6, the single-color LED 1 and the single-color LED 2 are representatively represented by a plurality of single-color LEDs, and the components corresponding to the single-color LED 1 and the single-color LED 2 are also denoted by numbers 1 and 2 in the same manner.

  In the light source device according to the present embodiment, the detection signals of the light detection elements 1 and 2, the detection signals of the temperature sensors A 1 and A 2, and the detection signals of the temperature sensors B 1 and B 2 are input to the control circuit 300. Based on this, drive circuits such as the LED1 drive circuit and the LED2 drive circuit are controlled.

  That is, when driving of the single color LED 1 and single color LED 2 is started and the intensity of light emitted from the single color LED 1 and single color LED 2 is detected by the light detection elements 1 and 2, the signal is input to the digitizing circuit 1 and digitizing circuit 2. After being digitally converted there, it is input to the sensitivity correction unit 1 and the sensitivity correction unit 2. The sensitivity correction unit 1 and the sensitivity correction unit 2 receive detection signals from the temperature sensor B1 and the temperature sensor B2, and the detection signals from the temperature sensors B1 and B2 and the light detection elements stored in the storage device 301 in advance. Based on each temperature coefficient, the detection signals of the light detection elements 1 and 2 are corrected and sent to the control calculation unit 302. The control calculation unit 302 calculates the intensity of the emitted light from the LEDs 1 and 2 using the correction value of the detection signal of the light detection elements 1 and 2 and the above-described calculation formula (1), and the result is the LED1 output correction unit and LED2. Output to the output correction unit.

  Detection signals are input from the temperature sensor A1 and the temperature sensor A2 provided in the vicinity of the single color LED 1 and the single color LED 2, respectively, to the LED 1 output correction unit and the LED 2 output correction unit. The storage device 301 stores a temperature coefficient for each LED drive circuit in advance. The LED1 output correction unit and the LED2 output correction unit are input from a preset relational expression and the temperature coefficient and control calculation unit 302. The output currents to the LEDs 1 and 2 are determined so as to achieve the target output light intensity using the intensity of the emitted light from the LEDs 1 and 2. The determined output current value is analogized by the analogizing circuits 1 and 2 and then sent to the LED1 driving circuit and the LED2 driving circuit.

  The above-described temperature coefficient for each photodetecting element, temperature coefficient for each LED drive circuit, output current value to the LED, and intensity of emitted light from the LED are calculated, for example, during the adjustment process of the device, and stored in advance in the storage device 301. (See FIG. 6). A value such as a temperature coefficient stored in the storage device 301 is measured every time power is turned on to the light source device, and the influence of aging deterioration of the LED and the light detection element is corrected.

  Although illustration and description are omitted, the white LED is provided with a temperature sensor A in the vicinity of the white LED and a temperature sensor B in the vicinity of the light detection element, as in the case of the single color LED. Based on the detection signal, the output of the white LED is corrected.

[Third Embodiment]
FIG. 7 is a schematic top view of a light source device 400 according to the third embodiment of the present invention. The same parts as those in the first embodiment are denoted by the same reference numerals. In this embodiment, each of the light detection elements 201 to 207 of the light detector 20 is located at a position where the diffracted light of the emitted light from the monochromatic LEDs 101 to 106 and the white light 11 incident on the concave diffraction grating 12 in the normal temperature state is incident. Has been placed. In this case, diffracted light having an order different from that of the diffracted light constituting the emitted light is incident on the light detection elements 201 to 207. For example, the first-order diffracted light of the monochromatic LEDs 101 to 106 and the 0th-order diffracted light of the white LED 11 are made incident on the exit slit 131 as emitted light, and the 0th-order diffracted light of the single-color LEDs 101 to 106 and the first-order diffracted light of the white LED 11 are monitored light. 201-207.

  When the ambient temperature of the light source device 400 changes and a variation occurs in the arrangement of the optical system from each LED to the concave diffraction grating 12, the diffraction angle of the diffracted light by the concave diffraction grating 12 changes and the diffracted light The direction of the optical axis may change. As a result, the amount of light passing through the exit slit 131 varies, but similarly, the amount of light incident on each of the light detection elements 201 to 207 also varies. Therefore, by controlling the outputs of the single-color LEDs 101 to 106 and the white LEDs 11 based on the detection signals of the detection elements 201 to 207, fluctuations in the amount of emitted light can be reduced.

  Further, in this configuration, the light branching member (semipermeable membrane) for branching the emitted light is not necessary, so that the number of parts can be reduced.

In addition, this invention is not limited to above-described embodiment, A change is possible suitably.
For example, in the first and second embodiments, the light that has passed through the semipermeable membrane (light branching member) is incident on the spectroscopic measurement system, and the light reflected by the semipermeable membrane is spectrally analyzed by the concave diffraction grating as monitor light. Then, the light detection element is used for detection, but the reverse is also possible.

In the first and second embodiments, the concave diffraction grating is used as the light combining member. However, a plurality of half mirrors may be used as the light combining member.
Further, the number of white LEDs and the number of single color LEDs may be changed as appropriate, and the light source device can be configured with only single color LEDs.

10, 101-106 ... single color LED
11 ... White LED
12 ... Concave diffraction grating (photosynthesis member)
DESCRIPTION OF SYMBOLS 13 ... Slit board 131 ... Output slit 132 ... Monitor light entrance slit 15 ... Collimator lens 16 ... Semi-permeable membrane (light branching member)
DESCRIPTION OF SYMBOLS 17 ... Mirror 18 ... Condensing lens 20 ... Photo detector 201-207 ... Photo detection element 30, 320 ... Control circuit (output control part)
31, 321, ... Storage devices 32, 322 ... Calculation unit 40 ... Drive circuit 100, 400 ... Light source device

Claims (5)

a) a plurality of light emitting diodes having different wavelength ranges of emitted light;
b) a light combining member that guides light emitted from the plurality of light emitting diodes to the same combined light path;
c) a light branching member arranged on the combined light path for branching the light combined by the light combining member into outgoing light and monitor light;
d) a spectroscopic element that splits the monitor light into light corresponding to a wavelength range of light emitted from each of the plurality of light emitting diodes;
e) a photodetector having a plurality of light detecting elements for detecting the intensity of a plurality of lights dispersed by the spectroscopic element;
f) an output control unit that controls outputs of the plurality of light emitting diodes based on detection signals obtained by the plurality of light detection elements. The photosynthetic member is composed of a concave diffraction grating,
The light source device according to claim 1, wherein the plurality of light emitting diodes are arranged side by side in a wavelength dispersion direction of the concave diffraction grating.   The light source device according to claim 2, further comprising a light introducing member that guides the monitor light to the concave diffraction grating, wherein the concave diffraction grating also serves as the spectroscopic element.   The said light branching member is comprised from the semipermeable membrane which permeate | transmits a part of light synthesize | combined by the said photosynthesis member, and reflects the remaining part. The light source device described. a) a plurality of light emitting diodes having different wavelength ranges of emitted light;
b) a concave diffraction grating that guides the diffracted light of the light emitted from the plurality of light emitting diodes to the same combined optical path;
c) a photodetector having a plurality of photodetectors arranged at positions where diffracted light of a different order from the diffracted light of the light emitted from each light-emitting diode guided to the combined optical path by the concave diffraction grating is incident;
and d) an output control unit that controls outputs of the plurality of light emitting diodes based on detection signals obtained by the plurality of light detection elements.

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