JP3925194B2 - Visible light source, optical scanning device, and digital photo processing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a visible light source used in an exposure apparatus of a digital photographic processing apparatus.
[0002]
[Prior art]
2. Description of the Related Art In recent years, digital photographic processing apparatuses that form color images on photographic paper using digital image data taken by a digital camera or the like have been put into practical use. An exposure apparatus of a digital photographic processing apparatus is provided with an R light source, a G light source and a B light source for red (R), green (G) and blue (B) corresponding to the three primary colors, and beams of R, G and B colors. It comprises a scanning mechanism including a polygon mirror and an fθ lens for scanning on photographic paper. In the digital photographic processing apparatus, the photographic paper is conveyed in a predetermined direction at a predetermined constant speed (hereinafter, this direction is referred to as “sub-scanning direction”), and each color beam passes along the photosensitive surface of the photographic paper in the sub-scanning direction. Is scanned in the main scanning direction orthogonal to the. The intensity of each color beam is modulated in accordance with image data obtained by reading a photograph or film with a scanner or image data directly taken in with a digital camera or the like. As a result, latent images of R, G, and B colors are formed on the photographic paper, and a photograph is formed through a predetermined development process.
[0003]
In an exposure apparatus of a conventional digital photographic processing apparatus, a semiconductor laser that outputs a red laser beam with a wavelength of 680 nm is used as an R light source, and a semiconductor laser with a wavelength of 1064 nm, for example, and a laser beam output from the laser are used as a G light source. A light source composed of a wavelength conversion element that converts a green beam having a wavelength of 532 nm is used. Similarly, a light source composed of a laser having a wavelength of 946 nm and a wavelength conversion element for converting a laser beam output from the semiconductor laser into a blue beam having a wavelength of 473 nm is used as the B light source.
[0004]
These G light source and B light source are each called SHG laser (second harmonic generation from laser). In addition, for use as a light source for optical information processing equipment, such SHG lasers are required to be small and low in cost, and a laser beam (infrared light) from a semiconductor laser is directly introduced into a wavelength conversion element. An optical waveguide type SHG laser that outputs visible light has been put into practical use.
[0005]
[Problems to be solved by the invention]
By the way, the fundamental oscillation wavelength of a semiconductor laser varies depending on the temperature. In order to maintain the oscillation wavelength constant, the temperature must be controlled with a high accuracy of about 1/100 ° C.
[0006]
An example of the variation in temperature and the variation in the oscillation wavelength of the semiconductor laser is shown in FIG. Since the relationship between temperature and oscillation wavelength differs depending on the type of semiconductor laser, it is generalized and displayed (T ₁ <T ₂ <T ₃ ). The temperature difference between T ₁ and T _{2 and} the temperature difference between T ₂ and T ₃ are about 0.1 ° C., respectively. As shown in FIG. 6, the fundamental oscillation wavelength of the semiconductor laser changes even with a slight change in temperature (f1 <f2 <f3). The difference between the transmission frequencies f1 and f2 and the difference between f2 and f3 are about 1 nm, respectively.
[0007]
The optical waveguide type wavelength conversion element is designed to modulate a specific wavelength light of the semiconductor laser to, for example, a light having a half wavelength, so that the fundamental oscillation wavelength of the semiconductor laser is the phase of the wavelength conversion element. If it deviates from the matching wavelength (the peak wavelength of the second harmonic conversion efficiency), the wavelength matching cannot be achieved, the second harmonic conversion efficiency is lowered, and the desired power cannot be output. It was. Conversely, in order to output the desired power, it is necessary to prepare an environment capable of temperature control with high accuracy as described above, which is difficult to install in consumer equipment such as a digital photo processing apparatus. It had the problem that.
[0008]
In addition, the semiconductor laser and the optical waveguide type wavelength conversion element can be mass-produced by using a semiconductor manufacturing process, respectively, but there are variations (individual differences) in the characteristics of the individual semiconductor lasers and optical waveguide type wavelength conversion elements that are mass-produced. Arise. When a mass-produced semiconductor laser and an optical waveguide type wavelength conversion element are randomly combined, there is a problem that wavelength matching is not achieved and an SHG laser that cannot output a desired power is generated, and the yield of the SHG laser is deteriorated. Was.
[0009]
The present invention has been made in order to solve the above-described problems of the conventional example. A visible light source capable of outputting a predetermined power even in a relatively moderate temperature control environment and improving the yield, and It is an object of the present invention to provide an optical scanning apparatus and a digital photo processing apparatus using the above.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, a visible light source according to the present invention is a visible light source that introduces output light from a semiconductor laser into an optical waveguide type wavelength conversion element to generate a second harmonic , An optical switch element for branching the output light is provided between the optical waveguide type wavelength conversion element and each of the optical waveguide type wavelength conversion elements has a plurality of optical waveguides having different peak wavelengths of second harmonic conversion efficiency. It has a light switching element is characterized in that it is intended to select a waveguide for introducing the output light in accordance with the temperature of the semiconductor laser.
[0011]
In the above configuration, it is preferable that output light from the semiconductor laser is simultaneously introduced into a plurality of optical waveguides of the optical waveguide type wavelength conversion element, and second harmonics converted by the optical waveguides are simultaneously output.
[0012]
On the other hand, the optical scanning device of the present invention scans a beam in a second direction perpendicular to the first direction with respect to the medium to be exposed conveyed in a predetermined first direction, and exposes the medium to be exposed. In the scanning device, any one of the visible light sources described above is used as the light source of the beam.
[0013]
The digital photographic processing apparatus of the present invention is characterized in that the optical scanning device is an exposure device.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of a visible light source according to the present invention, an optical scanning apparatus and a photo processing apparatus using the same will be described.
[0015]
FIG. 1 shows the appearance of the photographic processing apparatus according to this embodiment. This photographic processing apparatus includes an exposure unit 20 for exposing a photographic paper, a developing unit 30 for performing development, fixing, bleaching and stabilizing processes on the photographic paper, and a drying unit 40 for drying the developed photographic paper. It comprises. In the upper part of the developing unit 30, a first transport belt 42 for stacking developed photographs discharged from the discharge port 41 for each order (for example, the number of frames for one film), and a first transport belt 42. A second conveyor belt 43 is provided for aligning a bundle of photographs for each film transferred from.
[0016]
The inside of the exposure unit 20 is a dark box, and a laser beam scanning unit (optical scanning device) 100, a magazine 21 that stores photographic paper wound in a roll shape, and a cutter that cuts the photographic paper into pieces of photographic paper of a predetermined size. And a transport mechanism that pulls the photographic paper from the magazine 21 to the cutter and transports the cut photographic paper piece to the developing unit 30 through the exposure unit.
[0017]
A detailed configuration of the laser beam scanning unit 100 is shown in FIG. The laser beam scanning unit 100 includes three light sources corresponding to the three primary colors red (R), green (G), and blue (B), that is, an R light source 104R, a G light source 104G, and a B light source 104B.
[0018]
As the R light source 104R, a semiconductor laser that basically outputs a red laser beam having a wavelength of 680 nm is used as it is. On the other hand, as the G light source 104G, for example, an SHG laser composed of a semiconductor laser having a wavelength of 1064 nm and a wavelength conversion element that converts a laser beam output from the semiconductor laser into green SHG light having a wavelength of 532 nm is used. A SHG laser composed of a semiconductor laser having a wavelength of 946 nm and a wavelength conversion element that converts a laser beam output from the semiconductor laser into blue SHG light having a wavelength of 473 nm is used. Details of the G light source 104G and the B light source 104B will be described later.
[0019]
The SHG laser uses a laser as a light source, but is not a laser light source because it does not use optical resonance at the time of wavelength conversion. Further, the green SHG light and the blue SHG light output from the G light source 104G and the B light source 104B, respectively, are not strictly laser beams. However, for convenience, they are referred to as a laser light source and a laser beam in the following description.
[0020]
Three sets of the collimator lens 106 and the acousto-optic modulator 108 are arranged in front of the laser beam emission surfaces of the laser light sources 104R, 104G, and 104B. An adjustable mirror 110 for reflecting the laser beam in the direction of the polygon mirror 120 is provided on the optical path of the laser beam emitted from each of the laser light sources 104R, 104G, and 104B. The polygon mirror 120 is rotated at a predetermined constant speed, for example, in the direction indicated by the arrow A in order to reflect the laser beam in a predetermined direction. In front of the polygon mirror 120, an fθ lens 121, a cylindrical lens 122, and a pair of mirrors 124 and 126 are arranged in this order. The laser beam is deflected in the main scanning direction indicated by the arrow B by the polygon mirror 120, the fθ lens 121 and the cylindrical lens 122, and reflected in the sub-scanning direction indicated by the arrow C by the mirrors 124 and 126.
[0021]
Next, the G light source 104G and the B light source 104B (SHG laser) in the present embodiment will be described. A first configuration example of the SHG laser in the present embodiment is shown in FIG.
[0022]
In the first configuration example, for example, a laser beam introducing element 202 including a DBR (distributed Bragg reflector) semiconductor laser 201 that outputs infrared light, a collimator lens for introducing a laser beam output from the semiconductor laser 201, and the like; According to the temperature of the semiconductor laser 201, an optical switch element 203 for branching the traveling direction of the introduced laser beam and a laser beam branched by the optical switch element 203 are provided corresponding to the phase matching wavelength ( Second harmonic conversion is performed by a plurality of (for example, three) optical waveguide wavelength conversion elements 204A, 204B, and 204C having different second harmonic conversion efficiency peak wavelengths, and the respective optical waveguide wavelength conversion elements 204A, 204B, and 204C. An optical waveguide element 205 having an optical waveguide formed so as to output the generated SHG light in the same direction; A temperature sensor (TS) 206 for detecting the temperature of the semiconductor laser 201 and a control unit (control circuit) for controlling on / off of the electrodes 203A and 203B of the optical switch element 203 in accordance with the temperature of the semiconductor laser 201 207 or the like.
[0023]
For example, when outputting blue SHG light having a wavelength of 470 nm, a DBR semiconductor laser having a fundamental oscillation frequency of 940 nm is used as the semiconductor laser 201. As shown in FIG. 6, since the fundamental oscillation wavelength of a semiconductor laser generally changes within a range of about ± 1 nm, the phase matching wavelengths (second harmonic conversion efficiency) of the optical waveguide type wavelength conversion elements 204A, 204B, and 204C are used. Are set to 939 nm, 940 nm, and 941 nm, respectively. Corresponding to FIG. 6, f1 = 939 nm, f2 = 940 nm, and f3 = 941 nm.
[0024]
The number of branches of the laser beam by the optical switch element 203 is not limited to the above three, and may be two or more. Further, the same number of optical waveguide type wavelength conversion elements 204A... Are prepared according to the number of branches of the optical switch element 203, and the phase matching wavelength (second harmonic conversion efficiency) of each optical waveguide type wavelength conversion element 204A. The peak wavelength of the semiconductor laser 201 may be changed as appropriate. In this case, as the number of branches of the optical switch element 203 is increased, it becomes easier to cope with the change in the fundamental oscillation wavelength of the semiconductor laser 201, and the temperature management (control) condition Can be relaxed.
[0025]
The optical switch element 203 is formed by, for example, forming an optical waveguide with a ferroelectric material such as PLZT on a semiconductor substrate such as LiNbO _3, and changing the refractive index by applying an electric field to a branching portion of the optical waveguide, so that light travels. The direction is switched. In the case of the first configuration example, on / off of the two electrodes 203A and 203B is controlled according to the temperature of the semiconductor laser 201, and the optical waveguide type wavelength conversion element 204A, 204B or 204C for introducing the laser beam is selected. The optical switch element 203 is not limited to this configuration, and may have another configuration.
[0026]
For example, as shown in FIG. 4, the optical waveguide type wavelength conversion element 204A... Is formed by forming a periodically poled region and an optical waveguide in a direction perpendicular to the LiNbO ₃ substrate. The peak wavelength of the second harmonic conversion efficiency can be finely adjusted by changing the width of the optical waveguide. In addition, the peak wavelength of the second harmonic conversion efficiency can be greatly changed by changing the period of the domain-inverted region (see, for example, JP-A-11-160747).
[0027]
The optical waveguide element 205 is obtained by forming an optical waveguide with a ferroelectric material such as PLZT on a semiconductor substrate such as LiNbO ₃ and has no optical switch function. The SHG light subjected to second harmonic conversion by each of the optical waveguide type wavelength conversion elements 204A... Is output from the same place in the same direction by the optical waveguide element 205.
[0028]
Thus, according to the first configuration example, the temperature of the semiconductor laser 201 is detected by the temperature sensor 206, and the optical waveguide type wavelength conversion elements 204A, 204B, and 204C corresponding to the fundamental oscillation wavelength of the semiconductor laser 201 at that temperature are detected. Since the control unit 207 controls on / off of the electrodes 203A and 203B of the optical switch 203 in order to introduce a laser beam to any one of them, the second harmonic is highly efficient regardless of variations in the fundamental oscillation wavelength of the semiconductor laser 201. Wave-converted SHG light can be output. Although the wavelength of the SHG light to be output varies due to variations in the fundamental oscillation wavelength of the semiconductor laser 201, slight variations in the wavelength are not particularly problematic in applications where the photographic paper is exposed in the digital photographic processing apparatus. .
[0029]
Next, a second configuration example of the SHG laser in the present embodiment is shown in FIG. In the second configuration example, the optical waveguide element 208 is used instead of the optical switch element 203, and the laser beam output from the semiconductor laser 201 is divided almost evenly into three optical paths, so that the optical waveguide type wavelength conversion elements 204A, 204B and 204C is introduced simultaneously. According to this second configuration example, even if the fundamental oscillation wavelength of the semiconductor laser 201 varies, any one of the optical waveguide type wavelength conversion elements 204A, 204B, or 204C corresponding to the fundamental oscillation wavelength at that time can achieve high efficiency. Two-harmonic conversion is performed and SHG light is output. In the second configuration example, only about 1/3 of the laser beam output from the semiconductor laser 201 is used for the second harmonic conversion. Therefore, when the power of the semiconductor laser 201 is large or SHG light that is output light is used. This is suitable when the required power is small.
[0030]
In the above embodiment, a plurality of optical waveguide type wavelength conversion elements each having a different phase matching wavelength corresponding to variations in the fundamental oscillation wavelength due to the temperature change of the semiconductor laser are prepared, and the optimum optical waveguide type according to the temperature change. The case where SHG light having a constant power is output by selecting a wavelength conversion element has been described, but the present invention is not limited to this, and individual differences between mass-produced semiconductor lasers and optical waveguide type wavelength conversion elements are explained. The present invention can also be applied when correcting the resulting power drop of SHG light.
[0031]
For example, the fundamental oscillation wavelength of a semiconductor laser at a specific temperature is set to 940 nm. Actually, there is a possibility that the fundamental oscillation wavelength at the specific temperature is 939 nm or 941 nm due to individual differences of semiconductor lasers. In such a case, a plurality of optical waveguide type wavelength conversion elements each having a different phase matching wavelength may be prepared, and a condition that maximizes the power of SHG light may be selected by operating the optical switch element. Alternatively, an SHG laser may be assembled by selecting an optimal combination of a semiconductor laser and an optical waveguide type wavelength conversion element. The same applies to the individual differences of the optical waveguide type wavelength conversion elements.
[0032]
In the above embodiment, a plurality of optical waveguide wavelength conversion elements each having a different phase matching wavelength (peak wavelength of the second harmonic conversion efficiency) are prepared, but a plurality of different phase matching wavelengths are provided on one element. An optical waveguide may be formed. In addition, in claim 1 described above, “the optical waveguide type wavelength conversion element has a plurality of optical waveguides each having a different peak wavelength of the second harmonic conversion efficiency” is described. Needless to say, this includes both a case where a plurality of optical waveguide type wavelength conversion elements having different phase matching wavelengths are prepared and a case where a plurality of optical waveguides having different phase matching wavelengths are formed on one element.
[0033]
Furthermore, in the above-described embodiment, the laser beam scanning unit is used in the photographic processing apparatus. However, the present invention is not limited to this, and can be used as an exposure apparatus such as a color laser processing apparatus.
[0034]
【The invention's effect】
As described above, the visible light source of the present invention, even if variations in the basic oscillation wavelength of the laser beam output from the semiconductor laser by temperature changes, variations and of the optical waveguide type wavelength conversion element corresponding to the basic oscillation wavelength By selecting a waveguide, it is possible to output SHG light that has been subjected to second harmonic conversion with light efficiency.
[0035]
Further, since a certain amount of temperature change can be allowed with respect to the temperature of the semiconductor laser, it is possible to relax, for example, the temperature condition that has conventionally been controlled to about ± 0.1 ° C. to about ± 0.5 ° C. . As a result, the application range of the visible light source can be expanded, and the cost of the apparatus using the visible light source can be reduced.
[0036]
In addition , by selecting an optical waveguide that introduces the output light according to the temperature of the semiconductor laser by an optical switch element , a temperature sensor and a control circuit are required, but the utilization efficiency of the laser beam output from the semiconductor laser is required. SHG light having a constant power can always be output without lowering.
[0037]
On the other hand, the optical scanning device of the present invention scans a beam in a second direction perpendicular to the first direction with respect to the medium to be exposed conveyed in a predetermined first direction, and exposes the medium to be exposed. Since the visible light source according to any one of the above is a light source of the beam, the medium to be exposed (for example, a photographic paper or a photosensitive member) with a certain power while allowing a temperature change of the visible light source to some extent. Drums, etc.) can be exposed.
[0038]
Furthermore, in the digital photographic processing apparatus of the present invention, since the optical scanning device is an exposure device, the visible light source is used as a G light source and a B light source among R, G, and B light sources that are three primary colors. The beam of each color can be output with stable power.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an external configuration of a digital photo processing apparatus according to an embodiment of the present invention.
FIG. 2 is a perspective view showing a configuration of a laser beam scanning unit (optical scanning device) in an embodiment of the present invention.
FIG. 3 is a plan view showing a configuration of a first configuration example of an SHG laser in the embodiment.
FIG. 4 is a perspective view showing a configuration of an optical waveguide type wavelength conversion element in the SHG laser in the embodiment.
FIG. 5 is a plan view showing a configuration of a second configuration example of the SHG laser in the embodiment.
FIG. 6 is a diagram showing an example of a variation in temperature and variation in oscillation wavelength of a semiconductor laser.
[Explanation of symbols]
100: Laser beam scanning unit (optical scanning device)
104R: R light source 104G: G light source 104B: B light source 201: Semiconductor laser 202: Laser beam introducing element 203: Optical switch element 204A: Optical waveguide type wavelength conversion element 204B: Optical waveguide type wavelength conversion element 204C: Optical waveguide type wavelength conversion Element 205: Optical waveguide element 206: Temperature sensor 207: Control unit (control circuit)
208: Optical waveguide device

Claims (3)

A visible light source that introduces output light from a semiconductor laser into an optical waveguide type wavelength conversion element to generate a second harmonic , wherein the output light is transmitted between the semiconductor laser and the optical waveguide type wavelength conversion element. an optical switch element for branching provided, the optical waveguide type wavelength conversion device have a plurality of optical waveguides peak wavelength of the second harmonic conversion efficiency are different, optical switching element, the temperature of the semiconductor laser visible light source, characterized in that it is used to select an optical waveguide for introducing the output light in accordance. 2. An optical scanning device that exposes the medium to be exposed by scanning a beam in a second direction orthogonal to the first direction with respect to the medium to be exposed conveyed in a predetermined first direction. An optical scanning device comprising the visible light source described above as a light source of the beam . A digital photographic processing apparatus, wherein the optical scanning apparatus according to claim 2 is an exposure apparatus .

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