JP2004053781A - Second harmonic generation device and method for controlling temperature in second harmonic generation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve efficiency of conversion to a second harmonic with an SHG element while avoiding the necessity for highly accurately controlling temperature. <P>SOLUTION: In a second harmonic generation device equipped with the SHG element 55 to generate the second harmonic of an incident laser beam and a temperature controlling means TS to control temperature of the SHG element 55, the temperature controlling means TS is constructed so as to make the degree of heating or cooling on both end parts and on the intermediate part of the SHG element 55 in a light propagating direction different from each other. Thereby even when an optical path length of the SHG element is not so long, the temperature distribution in the light propagating direction is uniformized to the temperature to maintain the efficiency of conversion to the second harmonic at a highly efficient level. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a second harmonic generator including a SHG element that generates a second harmonic of an incident laser beam, and a temperature adjustment unit that adjusts the temperature of the SHG element, and a second harmonic. The present invention relates to a temperature control method in a generator.
[0002]
[Prior art]
Such a second harmonic generation device is a device in which a laser beam is incident on one end side of an SHG element and a laser beam (second harmonic) having a half wavelength of the incident laser beam is extracted.
In the SHG element, it is necessary to control the temperature of the SHG element to a constant temperature with high accuracy in order to maintain the conversion efficiency of the incident laser light into the second harmonic at a high efficiency.
Conventionally, for example, a thermoelectric cooling device that heats or cools an object by using the Peltier effect is provided as a temperature adjusting unit, and the SHG element is controlled to maintain a constant temperature.
[0003]
[Problems to be solved by the invention]
However, in the SHG element, since the light incident end and the light output end are thermally affected from the periphery of the element, both ends of the SHG element are cooled or heated from the periphery, and the temperature distribution in the light propagation direction is shown in FIG. The temperature distribution becomes as shown. FIG. 9 illustrates a case where the temperature is controlled in a state where the SHG element having the optical path length of 10 mm is heated, and the temperature distribution is distributed in the light propagation direction within a temperature difference ΔTmax (about 2 ° C.).
In FIG. 9, assuming that the temperature range for obtaining the required conversion efficiency is ΔTc of about 0.2 ° C., the length of the total optical path length that can efficiently contribute to the generation of the second harmonic is shown in FIG. 9, the length is indicated by "L".
Therefore, the temperature controlled part in the temperature region where the conversion efficiency to the second harmonic can be maintained at a high efficiency is limited to a part in the light propagation direction, and the SHG element converts the second harmonic into the second harmonic. There is a disadvantage that the conversion efficiency is reduced.
To lengthen the flat region in the temperature distribution in the light propagation direction, the length of the SHG element in the light propagation direction may be increased. However, when the length in the light propagation direction is increased, the temperature control of the element is controlled. Is required to be performed with higher precision, which leads to an increase in apparatus cost.
[0004]
That is, as shown in FIG. 10 schematically showing the relationship between the temperature of the SHG element and the conversion efficiency to the second harmonic, the characteristic of the SHG element whose element length in the light propagation direction is relatively short is indicated by a solid line A. When the element length in the light propagation direction is increased, the characteristic becomes as shown by the one-dot chain line B, and the characteristic is equal to or higher than the conversion efficiency indicated by “η” in FIG. The temperature range for obtaining the conversion efficiency is “ΔTc” in the case where the element length is relatively short (solid line A), whereas the temperature range in which the element length is long (dot-dash line). In B), the temperature becomes “ΔTc ′”, and the temperature at which the conversion efficiency to the second harmonic can be kept high is narrower. Therefore, more accurate temperature control is required.
On the other hand, even when the optical path length of the SHG element is extremely shortened, the temperature distribution in the light propagation direction is equalized. However, theoretically, the conversion efficiency is inversely proportional to the square of the optical path length. In addition, even if the temperature distribution becomes uniform, the conversion efficiency is lowered.
The present invention has been made in view of such circumstances, and has as its object to improve the conversion efficiency of the SHG element into the second harmonic as much as possible while avoiding high-precision temperature control. It is in.
[0005]
[Means for Solving the Problems]
2. A second harmonic generation device comprising: an SHG element that generates a second harmonic of the incident laser light; and a temperature adjustment unit that adjusts the temperature of the SHG element. In the apparatus, the temperature adjusting means is configured to change the degree of heating or cooling between both end portions in the light propagation direction of the SHG element and an intermediate portion.
That is, heating or cooling is performed in such a state that the influence of the temperature around the SHG element is compensated by making the degree of heating or cooling different between the both ends in the light propagation direction and the intermediate part in the SHG element. And even if the optical path length of the SHG element is not so long, the temperature distribution in the light propagation direction can be made as uniform as possible to a temperature at which the conversion efficiency to the second harmonic can be maintained at high efficiency. .
Thus, the conversion efficiency of the SHG element into the second harmonic can be improved as much as possible while avoiding the temperature control from being made more precise.
[0006]
In addition, with the configuration according to the second aspect, the temperature adjustment unit separately includes a plurality of heating units or cooling units arranged along the light propagation direction, and the plurality of heating units or cooling units. And temperature control means for controlling the temperature.
That is, in the SHG element, a plurality of heating means or cooling means are arranged in the light propagation direction and individually temperature controlled as means for making the degree of heating or cooling different between both end portions in the light propagation direction and an intermediate portion thereof. By doing so, the conversion efficiency of the SHG element to the second harmonic can be improved while simplifying the device configuration.
[0007]
Further, with the configuration according to the third aspect, the heating means or the cooling means is constituted by a thermoelectric cooling device.
That is, a thermoelectric cooling device provided with a thermoelectric cooling element using the so-called Peltier effect can heat or cool an object with good responsiveness by controlling the current flowing through the thermoelectric cooling element, and improve the accuracy of temperature control. Can be improved.
[0008]
In addition, with the configuration according to the fourth aspect, the temperature adjusting means is configured by a thermoelectric cooling device including a plurality of thermoelectric cooling elements, and a distribution state of the arrangement of the thermoelectric cooling elements in the thermoelectric cooling device. In a portion corresponding to the both end portions and a portion corresponding to the intermediate portion.
That is, a thermoelectric cooling device provided with a thermoelectric cooling element utilizing the so-called Peltier effect can heat or cool an object with good responsiveness by controlling the current flowing through the thermoelectric cooling element. By making the distribution state of the thermoelectric cooling elements in the device different, the degree of heating or cooling can be made different depending on the location even when the same current is applied.
Therefore, by distributing the distribution state of the arrangement of the thermoelectric cooling element between a portion corresponding to both end portions in the light propagation direction and a portion corresponding to an intermediate portion thereof, both end portions in the light propagation direction, and an intermediate portion. And the degree of heating or cooling is varied.
Accordingly, the thermoelectric cooling device itself is provided with a function of correcting the temperature distribution, and the control configuration of the temperature control can be simplified.
[0009]
According to the fifth aspect of the present invention, an SHG element for generating a second harmonic of the incident laser light, and a second harmonic adjusting means for adjusting the temperature of the SHG element are provided. In the temperature control method for the wave generator, the degree of heating or cooling is made different between both ends of the SHG element in the light propagation direction and an intermediate part.
Heating or cooling can be performed in a state where the influence of the temperature around the SHG element is compensated by making the degree of heating or cooling different between the both ends in the light propagation direction and the intermediate part in the SHG element. Thus, even when the optical path length of the SHG element is not so long, the temperature distribution in the light propagation direction can be made as uniform as possible to a temperature at which the conversion efficiency to the second harmonic can be maintained at high efficiency.
Thus, the conversion efficiency of the SHG element into the second harmonic can be improved as much as possible while avoiding the temperature control from being made more precise.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment in which the second harmonic generation device of the present invention is provided in a light source for exposure in a photographic print system will be described with reference to the drawings.
<First embodiment>
The photographic print system DP exemplified in the first embodiment is known as a so-called digital mini lab machine, and as shown in the block diagram of FIG. It comprises an image input device IR for inputting image data for producing a photographic print from a CD-R or the like, and an exposure / development device EP for exposing the image data input by the image input device IR to photographic paper 2. ing.
[0011]
[Schematic Configuration of Image Input Device IR]
As schematically shown in FIG. 4, the image input device IR includes a film scanner 3 for reading a frame image of a photographic film, an external input / output device 4 including a memory reader, an MO drive, a CD-R drive, and the like. A main controller 5 is configured by a general-purpose small computer system, and controls the film scanner 3 and the external input / output device 4 and performs management of the entire photographic print system DP. A monitor 5a for displaying a simulated image simulating a finished print image and various control information, and a console 5b for manually setting exposure conditions and inputting control information are connected.
[0012]
[Overall configuration of exposure / developing apparatus EP]
The exposure / development apparatus EP includes an image exposure apparatus EX, a development processing apparatus PP for developing the photographic paper 2 exposed by the image exposure apparatus EX, and a photographic paper magazine 6 arranged in the enclosure. And a photographic paper transport system PT for transporting the photographic paper 2 drawn out of the printer to the developing device PP by a number of transport rollers 9 and the like.
Although not shown, a sorter is provided outside the housing of the exposure / development device EP to sort the photographic paper 2 developed and dried by the development processing device PP for each order. A conveyor 10 for transporting the printing paper 2 is provided on the upper surface of the housing.
Further, in the middle of the transport path of the photographic paper transport system PT, a cutter 11 for cutting the long photographic paper 2 pulled out from the photographic paper magazine 6 into a set print size, and a plurality of photographic papers 2 transported in a line are provided. And a sorting device 12 for sorting the transfer rows.
[0013]
[Configuration of Image Exposure Apparatus EX]
The image exposure apparatus EX includes an image exposure unit 13 that forms an exposure image on the photographic paper 2 by scanning a light beam on the photographic paper 2, and an exposure control device 14 that controls the image exposure unit 13. It is configured as
[Configuration of Image Exposure Unit 13]
The image exposure unit 13 employs a so-called laser exposure method for exposing an image on the photographic paper 2 using a laser as a light source, and its schematic configuration is shown in a block diagram of FIG.
The image exposure unit 13 includes a red laser light source 20r, a green laser light source 20g, and a blue laser light source 20b that emit red, green, and blue monochromatic lights as collimated light, respectively, and light emitted from each of the laser light sources 20r, 20g, and 20b. An acousto-optic modulator 21 for intensity modulation (hereinafter abbreviated as "AOM element 21") and a beam expander for adjusting the beam diameter of the light beam LB emitted from each of the laser light sources 20r, 20g, and 20b. 22, a cylindrical lens 23, a prism 24 for combining the optical axes of the three red, green and blue light beams LB into one optical axis, a polygon mirror 25 for scanning the light beam LB, and f- An imaging lens group 26 having a θ characteristic and a surface tilt correcting function is provided. In addition, a mirror 27 that bends the optical path of the light beam LB and a pre- Aperture 28 for restricting the light incident on the beam 24 is arranged.
[0014]
[Configuration of Laser Light Sources 20g and 20b]
Each of the laser light sources 20r, 20g, and 20b uses a semiconductor laser element as a light source. The red laser light source 20r uses the light emitted from the semiconductor laser element as it is as a light beam LB, whereas the green laser light source 20g and The blue laser light source 20b emits the light emitted from the semiconductor laser element to the SHG element to generate a second harmonic, and uses the second harmonic as the light beam LB.
Hereinafter, the configurations of the green laser light source 20g and the blue laser light source 20b will be further described. Since these laser light sources 20g and 20b have basically the same configuration, both will be described together.
[0015]
As schematically illustrated in FIG. 2, the green laser light source 20g and the blue laser light source 20b include a semiconductor laser device 41 having a semiconductor laser element housed in a housing, and a laser mounting member 42 for positioning the semiconductor laser device 41. A thermoelectric cooling device 43 mounted on the laser mounting member 42 for maintaining the temperature of the semiconductor laser device 41 at a set temperature, a first collimating lens 44 for converting the light emitted from the semiconductor laser device 41 into parallel light, A condenser lens 45 for condensing the light emitted from the device 41, a second harmonic generator 46 for generating a second harmonic of the laser light condensed by the condenser lens 45, and a second harmonic generator And a second collimating lens 47 for converting the second harmonic light beam emitted from the light into parallel light.
[0016]
[Configuration of Second Harmonic Generator 46]
As shown in FIG. 1, the second harmonic generator 46 includes a base plate 51, first to third thermoelectric cooling devices 52, 53, and 54, and an optical waveguide that is condensed by a condenser lens 45. The SHG element 55 that generates the second harmonic of the laser beam incident on one end of the 55a, the SHG element support 56 that supports the SHG element 55, and the SHG element support 56 that supports the SHG element 55 A cover 57 is provided.
In the first embodiment, an optical waveguide type SHG element is used as the SHG element 55 as described above. Hereinafter, the SHG element 55 is referred to as an “optical waveguide type SHG element 55”.
The SHG element support 56 has a groove 56a for mounting the optical waveguide type SHG element 55, and three fine wires for arranging wiring to a temperature sensor 48a such as a thermistor (not shown in FIG. 1). A groove 56b is formed. Each temperature sensor 48a is attached so as to be in contact with the optical waveguide type SHG element 55.
[0017]
The first to third thermoelectric cooling devices 52, 53, 54 are arranged side by side along the optical waveguide direction of the optical waveguide type SHG element 55 (the direction indicated by arrow C in FIG. 1, that is, the light propagation direction). In order to make the temperature distribution of the optical waveguide type SHG element 55 in the optical waveguide direction into a temperature distribution having a wide flat area as shown by a curve D in FIG. 5, the temperature controller 48 shown in FIG. The sensors 48a are individually controlled so that the detected temperatures are the same.
In the first embodiment, the temperature of the optical waveguide type SHG element 55 is set higher than the room temperature, and the optical waveguide type SHG element 55 is heated by the first to third thermoelectric cooling devices 52, 53, 54. Will be.
[0018]
Since both ends of the optical waveguide type SHG element 55 in the optical waveguide direction are cooled from the surroundings, by performing the above-described temperature control, the optical waveguide type SHG element by the first thermoelectric cooling device 52 and the third thermoelectric cooling device 54 is provided. The degree of heating for 55 is greater than the degree of heating for the second thermoelectric cooling device 53.
In other words, the degree of heating is controlled to be different between both ends of the SHG element 55 in the light propagation direction and the middle part.
Therefore, the temperature adjusting means TS that adjusts the temperature of the SHG element 55 by including the first to third thermoelectric cooling devices 52, 53, and 54 as the plurality of heating means HC and the temperature controller 48 as the temperature controlling means TC. Are configured.
In the first embodiment, since the temperature adjusting means TS configured in this manner sets the temperature of the optical waveguide type SHG element 55 higher than room temperature, the first to third thermoelectric cooling devices 52, 53, 54 functions as the heating means HC, but when the temperature of the optical waveguide type SHG element 55 is set lower than room temperature, the first to third thermoelectric cooling devices 52, 53, 54 function as cooling means CC, and The degree of cooling is different between the both ends of the waveguide type SHG element 55 in the light propagation direction and the middle part thereof.
[0019]
With the green laser light source 20g and the blue laser light source 20b configured as described above, the laser light emitted from the semiconductor laser device 41 emits the first collimating lens 44 and the condensing lens while the temperature is controlled by the temperature controller 48. When the light enters the optical waveguide 55a of the optical waveguide type SHG element 55 through the optical waveguide 45, a part of the laser light propagating through the optical waveguide 55a is converted into a second harmonic having a wavelength of 出 射 and emitted, and the printing paper 2 Light beam LB for exposing the light beam.
[0020]
[Configuration of exposure control device 14]
As shown schematically in FIG. 3, the exposure control device 14 uses image data input from the image input device IR in consideration of the exposure characteristics of the image exposure unit 13 to control the image exposure unit 13 having the above configuration. An image processing circuit 30 for correcting the calculated image data, an image data memory 31 for storing the image data obtained by the image processing circuit 30 for each color of red, green and blue, and for each color of red, green and blue And a D / A converter 32 for D / A converting output data of the image data memory 31 and an AOM for outputting a control signal having an amplitude corresponding to an input signal from each D / A converter 32 to the AOM element 21. A control circuit 33 and a timing control circuit 34 for controlling the transmission timing of an image signal transmitted from each D / A converter 32 are provided.
[0021]
[Exposure operation of image exposure apparatus EX]
Next, the operation of the image exposure unit 13 and the exposure control device 14 having the above configuration will be described.
The image data for exposure input from the image input device IR is corrected and calculated by the image processing circuit 30 and is converted into image data capable of obtaining a good print image when exposed by the image exposure unit 13. 31 are sequentially written.
The data once stored in the image data memory 31 is sent to the D / A converter 32 on a pixel-by-pixel basis in synchronization with a clock signal input from the timing control circuit 34 for each pixel data, and is converted into an analog signal. After that, it is sent to the AOM control circuit 33.
When the timing control circuit 34 detects that the front end of the photographic paper 2 has been transported to the predetermined exposure start position based on the transport information of the photographic paper 2 obtained from the photographic paper transport system PT, the timing control circuit 34 outputs the light beam LB. The clock signal is generated so as to sequentially transmit the image signals to the image exposure unit 13 at a speed corresponding to the exposure processing speed of the image exposure unit 13 while synchronizing with the detection signal of the scanning position.
[0022]
The AOM control circuit 33 outputs a control signal having an amplitude corresponding to the input signal to the AOM element 21. The AOM element 21 emits a laser beam incident from each of the laser light sources 20b, 20g, and 20r with a diffraction index corresponding to the amplitude of the input control signal. Modulates light.
Each light beam LB modulated as described above enters the prism 24 after passing through the beam expander 22 and the like, and the three light beams LB of red, green and blue are combined into one light beam LB. Then, the light is irradiated on the reflection surface of the polygon mirror 25.
[0023]
The light beam LB reflected by the reflection surface of the polygon mirror 25, which is rotationally driven by the drive motor 25a, is scanned in a plane perpendicular to the rotation axis of the polygon mirror 25, and is conveyed onto the photographic paper 2 which is conveyed and moved. The light is converged by the imaging lens group 26. The scanning direction of the light beam LB intersects (more specifically, orthogonally) the transport direction of the photographic paper 2, and the scanning direction of the light beam LB is the main scanning direction, and the transport direction of the photographic paper 2 is the sub-scanning direction. Become. An image to be printed on the photographic paper 2 is formed as a latent image by the scanning of the light beam LB and the transport movement of the photographic paper 2.
[0024]
[Photo print production operation]
Next, an operation of producing a photographic print by the photographic print system DP having the above configuration will be schematically described.
When the operator instructs the production of a photographic print for the frame image of the photographic film, the main controller 5 instructs the film scanner 3 to read the photographic film, and the image data of the photographic film is transmitted from the film scanner 3. Are sequentially received and recorded in a built-in memory.
On the other hand, when the operator instructs the production of a photographic print for image data recorded on a recording medium such as a memory card, MO or CD-R, the main controller 5 sends the corresponding drive of the external input / output device 4 to the corresponding drive. To read the image data, sequentially receive the image data from the drive and record it in the memory.
[0025]
The main control device 5 calculates a simulated image that would be obtained when a print is made with the image data, based on the image data input as described above, using an image processing circuit (not shown). And displays it on the monitor 5a.
The operator observes the simulated image on the monitor 5a and, if an appropriate image has not been obtained, performs an operation for correcting the exposure condition from the console 5b.
The image processing circuit of the main control device 5 generates exposure image data for each of red, green, and blue under predetermined calculation conditions according to the input image data and its correction input.
[0026]
The exposure image data is sent to the exposure control device 14 of the exposure / development device EP, and a latent image of a print image is formed on the photographic paper 2 as described above.
The photographic paper 2 exposed by the image exposure unit 13 is transported to the developing device PP by the photographic paper transport system PT, and is developed by passing through each developing tank sequentially, and the developed photographic paper is processed. 2 is further discharged onto the conveyor 10 after being subjected to a drying treatment, and is sorted by order with a sorter.
[0027]
<Second embodiment>
Next, a second embodiment of the present invention will be described.
The second embodiment is different from the first embodiment only in the configuration of the laser light sources 20r, 20g, and 20b.
More specifically, in the second harmonic generator used for the green laser light source 20g and the blue laser light source 20b, the specific configuration of the temperature adjusting means TS of the optical waveguide type SHG element 55 is different from that of the first embodiment. Only the other parts have the same configuration as the first embodiment.
Hereinafter, the laser light sources 20r, 20g, and 20b of the second embodiment will be described, and the description of the other parts common to the first embodiment will be omitted. Note that portions common to the first embodiment will be described with the same reference numerals as in the first embodiment.
[0028]
[Configuration of Laser Light Sources 20g and 20b]
Also in the second embodiment, similarly to the first embodiment, each of the laser light sources 20r, 20g, and 20b uses a semiconductor laser element as a light source. While the emitted light is directly used as the light beam LB, the green laser light source 20g and the blue laser light source 20b make the light emitted from the semiconductor laser device incident on the optical waveguide type SHG device to generate a second harmonic, and generate the second harmonic. The harmonics are used as the light beam LB.
Hereinafter, the configurations of the green laser light source 20g and the blue laser light source 20b will be further described. In the second embodiment, since these laser light sources 20g and 20b have basically the same configuration, both will be described together. .
[0029]
As schematically illustrated in FIG. 7, the green laser light source 20g and the blue laser light source 20b include a semiconductor laser device 41 having a semiconductor laser element housed in a housing, and a laser mounting member 42 for positioning the semiconductor laser device 41. A thermoelectric cooling device 43 mounted on the laser mounting member 42 for maintaining the temperature of the semiconductor laser device 41 at a set temperature, a first collimating lens 44 for converting the light emitted from the semiconductor laser device 41 into parallel light, A condenser lens 45 for condensing light emitted from the device 41, a second harmonic generator 61 for generating a second harmonic of the laser light condensed by the condenser lens 45, and a second harmonic generator And a second collimating lens 47 for converting the second harmonic light beam emitted from the light into parallel light.
[0030]
[Configuration of Second Harmonic Generator 61]
As shown in FIG. 6, the second harmonic generation device 61 includes a base plate 51, a thermoelectric cooling device 62, and a laser beam collected by the condenser lens 45 and incident on one end of the optical waveguide 55a. An SHG element 55 that generates two harmonics, an SHG element support 56 that supports the SHG element 55, and a cover 57 that covers the SHG element support 56 that supports the SHG element 55 are provided.
Also in the second embodiment, the optical waveguide type SHG element is used as the SHG element 55 as described above, and the SHG element 55 is hereinafter referred to as an “optical waveguide type SHG element 55” as in the first embodiment. Called.
On the SHG element support 56, a groove 56a for mounting the optical waveguide type SHG element 55 and three fine wires for arranging wiring to a temperature sensor 48a such as a thermistor (not shown in FIG. 6). A groove 56b is formed. Each temperature sensor 48a is attached so as to be in contact with the optical waveguide type SHG element 55.
[0031]
As shown in FIG. 8B, the thermoelectric cooling device 62 according to the second embodiment includes a P-type semiconductor block 71 and an N-type semiconductor block 72, each of which forms a current path in series. As shown in FIG. 8 (a), the parts connected alternately by the electrode plates 73 are sandwiched between two heat conductive plates 74 made of a ceramic plate or the like. It has a flat rectangular parallelepiped shape.
In the thermoelectric cooling device 62 configured as described above, when a DC current flows through the P-type semiconductor block 71 and the N-type semiconductor block 72 connected in series, one of the two heat conductive plates 74 generates heat. When the other absorbs heat and reverses the direction of the current, the heat generation and heat absorption are switched.
[0032]
In the thermoelectric cooling device 62 of the second embodiment, the arrangement interval between the P-type semiconductor block 71 and the N-type semiconductor block 72 indicated by “W” in FIG. 8B is set in the optical waveguide direction (FIGS. 6 and 8A ) In the direction indicated by arrow E, that is, in the light propagation direction).
When the control target temperature of the optical waveguide type SHG element 55 is set to a temperature higher than room temperature, the specific value of the interval W is set to the control target temperature of the optical waveguide type SHG element 55 by the temperature controller 48. When heated, the range of the flat portion as shown by the curve D in FIG. 5 is set to have a wide temperature distribution, and can be obtained by a trial experiment or a simulation calculation.
[0033]
Since both ends of the optical waveguide type SHG element 55 in the optical waveguide direction are cooled from the surroundings, by setting the distance W as described above, as shown in FIG. 8A, it is closer to the center in the optical waveguide direction. As the distance W increases, the distance W decreases, and the distance W decreases as the distance to both ends in the optical waveguide direction increases.
By changing the distance W in the direction of the optical waveguide in this way, in other words, the distribution state of the arrangement of the thermoelectric cooling element PC composed of the pair of the P-type semiconductor block 71 and the N-type semiconductor block 72 is changed to the SHG element. By making the portion corresponding to both ends in the light propagation direction in 55 and the portion corresponding to the intermediate portion thereof different, the degree of heating is made different in both ends of the SHG element 55 in the light propagation direction and the intermediate portion. .
[0034]
Therefore, in the second embodiment, a temperature adjusting unit TS that adjusts the temperature of the optical waveguide type SHG element 55 by including the thermoelectric cooling device 62 and the temperature controller 48 is configured.
In the second embodiment, the temperature adjusting means TS configured as described above sets the temperature of the optical waveguide type SHG element 55 higher than room temperature, so that the thermoelectric cooling device 62 acts as a heating means. However, when the temperature of the optical waveguide type SHG element 55 is set lower than the room temperature, the thermoelectric cooling device 62 functions as a cooling means CC, and both ends of the optical waveguide type SHG element 55 in the optical waveguide direction and the middle thereof. The degree of cooling will be different for each part.
[0035]
With the green laser light source 20g and the blue laser light source 20b configured as described above, the laser light emitted from the semiconductor laser device 41 emits the first collimating lens 44 and the condensing lens while the temperature is controlled by the temperature controller 48. When the light enters the optical waveguide 55a of the optical waveguide type SHG element 55 through the optical waveguide 45, a part of the laser light propagating through the optical waveguide 55a is converted into a second harmonic having a wavelength of 出 射 and emitted, and the printing paper 2 Light beam LB for exposing the light beam.
[0036]
<Other embodiments>
Hereinafter, other embodiments of the present invention will be listed.
(1) In the first and second embodiments, the thermoelectric cooling device using the Peltier effect is illustrated as the heating means for the optical waveguide type SHG element 55, but other various heaters may be used. .
(2) In the first embodiment, the temperature controller 48 controls the temperature sensors 48a installed at three locations to have the same temperature. However, the temperature controller 48 controls four or more locations in the optical waveguide direction. The temperature of the optical waveguide may be measured at the locations, and the temperature controller 48 may control the temperature variations at those locations as much as possible.
[0037]
(3) In the first embodiment, three thermoelectric cooling devices of the first to third thermoelectric cooling devices 52, 53, and 54 are provided side by side in the optical waveguide direction as the heating means HC or the cooling means CC. The above-described thermoelectric cooling devices may be arranged side by side and individually controlled in temperature.
(4) In the second embodiment, the interval W between the P-type semiconductor block 71 and the N-type semiconductor block 72 is changed to be wide and narrow in order to make the distribution state of the thermoelectric cooling elements different. The distribution state may be changed by changing the width of the block itself of the semiconductor block 71 or the N-type semiconductor block 72.
[0038]
(5) In the first and second embodiments, the case where the optical waveguide length of the optical waveguide type SHG element 55 is set to 10 mm is illustrated, but other lengths may be used.
(6) In the first and second embodiments, the case where the second harmonic generation device to which the present invention is applied is used as a light source for exposure of a photographic print system DP is illustrated. It can be used for various light sources such as the above light source.
(7) In the first and second embodiments, an optical waveguide type SHG element having an optical waveguide is illustrated as the SHG element 55, but the present invention can be applied to an SHG element having no optical waveguide. .
(8) In the first and second embodiments, the case where the SHG element 55 is used to generate the second harmonic of the green light and the second harmonic of the blue light is exemplified. Light may also be configured to be generated as the second harmonic of the SHG element 55.
[0039]
【The invention's effect】
According to the configuration of the first aspect, in the optical waveguide type SHG element, the temperature around the optical waveguide type SHG element is varied by making the degree of heating or cooling different between the both ends in the optical waveguide direction and the intermediate part thereof. Can be heated or cooled in such a state as to compensate for the influence of the above, and even if the optical waveguide length of the optical waveguide type SHG element is not so long, the temperature distribution in the optical waveguide direction can be converted into the second harmonic. Efficiency can be made as uniform as possible at a temperature at which efficiency can be maintained at high efficiency.
Thus, the conversion efficiency of the optical waveguide type SHG element into the second harmonic can be improved as much as possible while avoiding the temperature control from being made more precise.
[0040]
According to the second aspect of the present invention, in the optical waveguide type SHG element, a plurality of heating means or cooling means are provided as means for changing the degree of heating or cooling between both end portions in the optical waveguide direction and an intermediate portion thereof. By arranging a plurality of means in the direction of the optical waveguide and individually controlling the temperature, the conversion efficiency of the optical waveguide type SHG element into the second harmonic can be improved while simplifying the device configuration.
Further, according to the configuration of the third aspect, the thermoelectric cooling device including the thermoelectric cooling element utilizing the so-called Peltier effect controls the current flowing through the thermoelectric cooling element to heat or heat the object with high responsiveness. It can be cooled and the accuracy of temperature control can be improved.
Further, according to the configuration of the fourth aspect, the thermoelectric cooling device including the thermoelectric cooling element utilizing the so-called Peltier effect controls the current flowing through the thermoelectric cooling element to heat or heat the object with high responsiveness. Although cooling can be performed, the degree of heating or cooling can be varied depending on the location even when the same current flows by making the distribution state of the thermoelectric cooling elements in the thermoelectric cooling device different.
Further, according to the configuration of the fifth aspect, in the optical waveguide type SHG element, the degree of heating or cooling is made different between both end portions in the optical waveguide direction and an intermediate portion thereof, so that the periphery of the optical waveguide type SHG element is improved. Heating or cooling can be performed in such a state as to compensate for the influence of the temperature of the optical waveguide, and even if the optical waveguide length of the optical waveguide type SHG element is not so long, the temperature distribution in the optical waveguide direction is reduced to the second harmonic. Can be made as uniform as possible at a temperature at which the conversion efficiency can be maintained at a high efficiency.
Thus, the conversion efficiency of the optical waveguide type SHG element into the second harmonic can be improved as much as possible while avoiding the temperature control from being made more precise.
[Brief description of the drawings]
FIG. 1 is a perspective view of a second harmonic generation device according to a first embodiment of the present invention.
FIG. 2 is a schematic configuration diagram of a laser light source according to the first embodiment of the present invention.
FIG. 3 is a schematic configuration diagram of an image exposure apparatus according to the first embodiment of the present invention.
FIG. 4 is a block diagram of a photographic print system according to the first embodiment of the present invention.
FIG. 5 is a diagram showing a temperature distribution in an optical waveguide direction according to the first embodiment and the second embodiment of the present invention.
FIG. 6 is a perspective view of a second harmonic generator according to a second embodiment of the present invention.
FIG. 7 is a schematic configuration diagram of a laser light source according to a second embodiment of the present invention.
FIG. 8A is a perspective view of a thermoelectric cooling device according to a second embodiment of the present invention.
(B) An enlarged view of the thermoelectric cooling element according to the second embodiment of the present invention.
FIG. 9 is a diagram showing a temperature distribution in an optical waveguide direction by a conventional temperature control.
FIG. 10 is a diagram showing a relationship between conversion efficiency and temperature of an optical waveguide type SHG element.
[Explanation of symbols]
55 SHG element
52,53,54,62 Thermoelectric cooling device
CC cooling means
HC heating means
PC thermoelectric cooling element
TC temperature control means
TS temperature adjustment means

Claims (5)

A second harmonic generator comprising: an SHG element that generates a second harmonic of the incident laser light; and a temperature adjusting unit that adjusts the temperature of the SHG element.
The second harmonic generator, wherein the temperature adjusting means is configured to change the degree of heating or cooling between both end portions in the light propagation direction of the SHG element and an intermediate portion. The temperature adjustment means, a plurality of heating means or cooling means arranged along the light propagation direction,
The second harmonic generator according to claim 1, further comprising a temperature control unit configured to individually control the plurality of heating units or the cooling units. The second harmonic generator according to claim 2, wherein the heating unit or the cooling unit is configured by a thermoelectric cooling device. The temperature adjusting unit is configured by a thermoelectric cooling device including a plurality of thermoelectric cooling elements,
2. The second harmonic generation according to claim 1, wherein a distribution state of the arrangement of the thermoelectric cooling elements in the thermoelectric cooling device is different between a portion corresponding to the both end portions and a portion corresponding to the intermediate portion. apparatus. A temperature control method for a second harmonic generation device, comprising: an SHG element that generates a second harmonic of an incident laser beam; and a temperature adjustment unit that adjusts the temperature of the SHG element.
A temperature control method in a second harmonic generator in which the degree of heating or cooling is made different between both end portions in the light propagation direction of the SHG element and an intermediate portion.

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