JP4571808B2 - Light source device and optical communication system using the same - Google Patents

Description

  The present invention relates to a light source device that exhibits a predetermined light emission intensity in a predetermined light emission angle range, and an optical communication system using the same.

  A typical example of conventional optical wireless communication is IrDA (Infrared Data Association). In this IrDA, a light emitting diode (LED) is used as a light source device, and data is exchanged with an optical signal exhibiting a light emission intensity of a predetermined value or more within a predetermined light emission angle area.

  FIG. 14 shows a radiation pattern mask (solid line) used in IrDA1.1 or IrDA1.3, and a radiation intensity-angle distribution (broken line) (hereinafter referred to as a radiation intensity distribution) in an actual light source device. First, the radiation pattern mask will be described with reference to FIG. The communication angle area is standardized to be within ± 15 degrees, and within this range, a radiation intensity of 100 mW / sr or more is required. This 100 mW / sr corresponds to the minimum receiving sensitivity for securing this communication. In addition, when the communication angle area is within ± 30 degrees, the maximum radiation intensity is limited to 500 mW / sr in order to avoid interference with hidden terminals existing on the extension between terminals that are performing communication. On the other hand, in a communication angle area farther than ± 30 degrees, it is necessary to suppress the radiation intensity to be lower than the minimum reception sensitivity in order to avoid interference with the adjacent optical terminal, and is limited to 100 mW / sr or less.

従来、上記指向半値角度θ_Hは、上記通信角度エリアにおける角度１５度程度に設定されている。 The radiation pattern (that is, radiation intensity distribution) of the LED light source used for such IrDA has a shape called a Lambert distribution as shown by a broken line in FIG. The Lambertian distribution will be briefly described below. A radiation intensity distribution of a light source having a light output P and a directivity half-value angle θ _H (a radiation angle at which the radiation intensity is ½ of the maximum radiation intensity) is represented by the following Lambertian distribution L (θ).

Conventionally, the directional half angle theta _H is set at an angle 15 degrees in the communication angle area.

The inventors of the present application have so far proposed to use a so-called eye-safe laser in which a semiconductor laser is made eye-safe by light diffusion, for example, as a light source for IrDA (for example, Patent Document 1 (Japanese Patent Laid-Open No. 2003-258353)). reference). In that case, it has been known that there are a lot of speckles peculiar to the high coherence of the laser light in the radiation intensity distribution, but it has been confirmed that the radiation intensity distribution as a whole is a Lambertian distribution like the LED, the directional half angle theta _H was set to about 15 degrees as in the case of the LED light source. In the Lambertian distribution, to satisfy the radiation pattern mask, the directivity half-value angle θ _H can be set in the range of 12.7 degrees to 30 degrees, but is set to about 15 degrees in consideration of power consumption.

  However, the IrDA light source using the conventional eye-safe laser has the following problems. In other words, even higher speeds are expected in optical wireless communication. At that time, it is expected that the absolute light amount required for communication will increase. On the other hand, it is necessary to ensure a communicable distance that is equal to or greater than before. Also, the receiver size is required to be the same size as before. In order to satisfy these conditions, it is necessary to raise the minimum radiation intensity (In_min) when the radiation angle in the radiation pattern mask shown in FIG. On the other hand, in order to prevent interference with other communication systems, it is difficult to raise the maximum radiation intensity (In_max) when the radiation angle is within ± 2Θ. For the same reason, the value of the maximum radiation intensity (Out_max) when the radiation angle is outside ± 2Θ is also limited to the conventional value.

For example, it is known that when a 100 Mbps optical wireless communication is performed at a distance of 1 m using a receiver having an effective light receiving diameter of 3 mm, the transmitter is required to have a radiation intensity of about 250 mW / sr. In this case, if only In_min is set to 250 mW / sr, (In_max) / (In_min) = 2, and if the directional half-value angle θ _H of the light source is fixed near the radiation angle Θ as before, the optical axis The upper (θ = 0) radiation will exceed In_max. Further, when the directivity half-value angle θ _H is increased, Out_max is exceeded at θ = 2Θ, and it is necessary to change the radiation pattern.

In addition, when an eye-safe laser is used as a light-emitting element, even if the average radiation intensity distribution satisfies the radiation pattern mask, it is locally less than In_min or more than In_max due to the influence of speckles that are present. There is a concern that Such an optimum radiation intensity distribution for a light source including speckle has not been studied at all.
JP 2003-258353 A

  Accordingly, an object of the present invention is to provide a light source device including speckles that can minimize light output while satisfying a required light emission pattern, and an optical communication system using the light source device.

となるようなパターンである
ことを特徴としている。 In order to solve the above problems, the first invention is
A light source device for use in an optical communication system that requires a predetermined light emission intensity in a predetermined light emission angle range,
A light emitting element that produces speckle;
The radiation pattern representing the relationship between the radiation angle and the radiation intensity in the radiated light from the light emitting element is made to satisfy the light radiation intensity in a predetermined light radiation angle range required by the optical communication system. In the light source device including the radiation pattern setting means for setting according to the speckle amount ,
The light emission intensity within a predetermined light emission angle range required by the optical communication system is such that the emission intensity within the emission angle ± Θ is In_min or more and the emission intensity within the emission angle ± 2Θ is In_max or less. And the radiation intensity outside the radiation angle ± 2Θ is not more than Out_max, and In_max / In_min = R and Out_max / In_min = r,
When the speckle amount is s,
Radiation pattern set by the radiation pattern setting means, the light emission intensity is directional half angle theta _H representing the light emission angle which is half of the maximum light emission intensity
θ _H = cos ^-1 (0.5 ^{(1 / n)} )

It is characterized by the following pattern .

  According to the above configuration, when a light emitting element in which the speckle amount exhibits a value larger than that of an LED like a semiconductor laser is set by setting the radiation pattern in the emitted light from the light emitting element by the radiation pattern setting means. Even so, a radiation pattern that satisfies the light radiation intensity in a predetermined light radiation angle range required by the applied optical communication system can be obtained.

At that time, by considering the R, r, and speckle amount s, for example, the above In_min and the Out_max are not changed, and only the In_min is increased and applied to the conventional IrDA radiation pattern mask. It is possible to obtain a radiation pattern that satisfies the light radiation intensity in a predetermined light radiation angle range required by the optical communication system. Therefore, it is possible to obtain a light source device applicable to a new high-speed optical communication system in which interference with IrDA is minimized.

The second invention,
A light source device for use in an optical communication system that requires a predetermined light emission intensity in a predetermined light emission angle range,
A light emitting element that produces speckle;
The radiation pattern representing the relationship between the radiation angle and the radiation intensity in the radiated light from the light emitting element is made to satisfy the light radiation intensity in a predetermined light radiation angle range required by the optical communication system. , Radiation pattern setting means to set according to speckle amount
In the light source apparatus provided with,
The light emission intensity in a predetermined light emission angle range required by the optical communication system is assumed that the emission intensity within the emission angle ± Θ is a predetermined value or more,
When the speckle amount is s,
The radiation pattern set by the radiation pattern setting means has a directivity half-value angle θ _H representing a light radiation angle at which the light radiation intensity is ½ of the maximum light radiation intensity.
θ _H = cos ^-1 (0.5 ^{(1 / n)} )
Where PP (1−s) (n + 1) cos ⁿ Θ ≧ (n ₀ +1) cos ⁿ Θ
PP> 1
n ₀ = −1 / (lncosΘ) −1
It is a pattern that becomes
It is characterized by that .

According to the above configuration, when a light emitting element in which the speckle amount exhibits a value larger than that of an LED like a semiconductor laser is set by setting the radiation pattern in the emitted light from the light emitting element by the radiation pattern setting means. Even so, a radiation pattern that satisfies the light radiation intensity in a predetermined light radiation angle range required by the applied optical communication system can be obtained.

In this case, the PP is a power penalty and represents the ratio between the light output required by the light emitting element and the reference light output. Here, the reference light output is a light output of a radiation pattern that satisfies the light emission intensity in a predetermined light emission angle range required by the applied optical communication system and has a minimum light output. Therefore, by setting the value of the power penalty PP according to the speckle amount s of the light emitting element, a light source device that minimizes the required light output can be obtained.

  In the light source device of one embodiment, the radiation pattern setting means is a lens to which the radiation light is incident, and the radiation pattern is set by setting the shape of the lens.

  According to this embodiment, by setting the shape of the lens, the radiated light from the light emitting element so as to satisfy the light radiation intensity in a predetermined light radiation angle range required by the applied optical communication system. The radiation pattern is set.

  In one embodiment, the light source device includes a lens on which the radiated light is incident, and the radiation pattern setting unit is provided between the light emitting element and the lens so that the radiated light is incident on the lens. It is a light incident position dispersion means for dispersing the position.

  According to this embodiment, the light incident position dispersion means disperses the incident position of the radiated light on the lens, thereby emitting light within a predetermined light radiating angle range required by the applied optical communication system. The radiation pattern of the emitted light from the light emitting element is set so as to satisfy the intensity.

  In one embodiment of the light source device, the light incident position dispersing means is a transparent resin covering the light emitting element and a light diffusing agent mixed in the transparent resin. By setting the concentration of the light diffusing agent, The radiation pattern is set.

  According to this embodiment, by setting the concentration of the light diffusing agent to disperse the incident position of the radiated light on the lens, in a predetermined light radiation angle range required by the applied optical communication system. The radiation pattern of the radiated light from the light emitting element is set so as to satisfy the light radiation intensity.

  In one embodiment, the light incident position dispersing means is a light diffusing plate.

  According to this embodiment, the light diffusing plate disperses the incident position of the radiated light on the lens, so that the light radiation intensity in a predetermined light radiation angle range required by the applied optical communication system is obtained. The radiation pattern of the emitted light from the light emitting element is set so as to satisfy.

  In one embodiment, the light source device includes a lens on which the emitted light is incident, and the radiation pattern setting means disperses the incident angle of the emitted light on the interface between the lens and the air. Dispersion means.

  According to this embodiment, the light incident angle dispersion means disperses the incident angle of the radiated light at the interface between the lens and the air, so that the predetermined light radiating angle required by the applied optical communication system is achieved. The radiation pattern of the emitted light from the light emitting element is set so as to satisfy the light emission intensity in the range.

  In one embodiment, the light incident angle dispersion means is a light diffusing agent mixed in the lens, and the radiation pattern is set by setting the concentration of the light diffusing agent.

  According to this embodiment, the concentration of the light diffusing agent is set to disperse the incident angle of the radiated light to the interface between the lens and the air, so that the predetermined optical communication system to be applied is required. The radiation pattern of the emitted light from the light emitting element is set so as to satisfy the light emission intensity in the light emission angle range.

In one embodiment of the light source device, the radiation pattern setting means further responds to the speckle amount so that the radiation pattern becomes a pattern that exhibits a minimum light output capable of achieving the requirements of the radiation pattern mask. To set.

  According to this embodiment, the function of the radiation pattern setting means requires a predetermined light radiation angle even when a light emitting element having a speckle amount larger than that of an LED is used, such as a semiconductor laser. The light emission intensity in the range can be satisfied. Furthermore, the light output can be minimized.

In the light source device in which In_max / In_min = R and Out_max / In_min = r in one embodiment, the value of R is
2 ≦ R ≦ 3.5
It is.

  In order to minimize interference with conventional IrDA, only In_min should be changed, and In_max and Out_max should not be changed. According to this embodiment, the value of R is set to 2 ≦ R ≦ 3.5, which is smaller than R = 5 in the case of IrDA. Therefore, if the above In_max is made the same as in IrDA, the minimum radiation intensity In_min within the radiation angle ± Θ can be increased to 1.4 to 2.5 times that in IrDA. That is, to provide a light source device for a high-speed optical communication system that minimizes interference with IrDA even when a semiconductor laser (such as the above-mentioned eye-safe laser) having a speckle amount larger than that of an LED is used. Can do.

In the light source device in which In_max / In_min = R and Out_max / In_min = r in one embodiment, the value of r is
0.4 ≦ r ≦ 0.7
It is.

  In order to minimize interference with conventional IrDA, only In_min should be changed, and In_max and Out_max should not be changed. According to this embodiment, the value of r is set to 0.4 ≦ r ≦ 0.7, which is smaller than r = 1 in the case of IrDA. Therefore, if Out_max is made the same as that of IrDA, the minimum radiation intensity In_min within the radiation angle ± Θ can be increased to 1.4 to 2.5 times that of IrDA. That is, to provide a light source device for a high-speed optical communication system that minimizes interference with IrDA even when a semiconductor laser (such as the above-mentioned eye-safe laser) having a speckle amount larger than that of an LED is used. Can do.

である。 In the light source device in which In_max / In_min = R and Out_max / In_min = r in one embodiment, n is

It is.

  According to this embodiment, the power penalty PP can be maximized.

  In the light source device of one embodiment, the value of PP is smaller than 3.

  Generally, the current-light conversion efficiency in a semiconductor laser is about 3 to 4 times higher than that of an LED. According to this embodiment, the value of the power penalty PP is smaller than 3. Therefore, by using a semiconductor laser having a larger speckle amount than that of the LED, even if a penalty for the reference light output occurs, a light output comparable to that of the LED can be obtained.

An optical communication system of a third invention is characterized by using the light source device of the first or second invention.

  According to the above configuration, even when a light emitting element having a speckle amount larger than that of an LED is used as in a semiconductor laser, the light emission intensity in a predetermined light emission angle range required is satisfied. A light source device capable of obtaining a radiation pattern is used. Therefore, for example, a new high-speed optical communication system in which only the In_min is increased without changing the In_max and Out_max with respect to the conventional IrDA radiation pattern mask, and interference with the IrDA is minimized. It becomes possible to provide.

As is clear from the above, the light source device of the first invention sets the radiation pattern of the radiated light from the light emitting element that generates speckle according to the speckle amount by the radiation pattern setting means. Even when a semiconductor laser larger than the LED is used as the light emitting element, a radiation pattern that satisfies the light radiation intensity in a predetermined light radiation angle range required by the applied optical communication system can be obtained.

At that time, by considering the R, r, and speckle amount s, for example, the above In_min and the Out_max are not changed, and only the In_min is increased and applied to the conventional IrDA radiation pattern mask. It is possible to obtain a radiation pattern that satisfies the light radiation intensity in a predetermined light radiation angle range required by the optical communication system. Therefore, it is possible to obtain a light source device applicable to a new high-speed optical communication system in which interference with IrDA is minimized.

In the light source device of the second invention, since the radiation pattern of the radiated light from the light emitting element that generates speckle is set according to the speckle amount by the radiation pattern setting means, the semiconductor having a larger speckle amount than the LED Even when a laser is used as the light-emitting element, it is possible to obtain a radiation pattern that satisfies the light radiation intensity in a predetermined light radiation angle range required by the applied optical communication system.

At that time, by setting the value of the power penalty PP according to the speckle amount s of the light emitting element, a light source device that minimizes the required light output can be obtained. The power penalty PP represents the ratio between the light output required by the light emitting element and the reference light output. Here, the reference light output is a light output of a radiation pattern that satisfies the light emission intensity in a predetermined light emission angle range required by the applied optical communication system and has a minimum light output.

In addition, since the optical communication system of the third invention uses the light source device of the present invention, for example, only the In_min is increased without changing the In_max and Out_max with respect to the conventional IrDA radiation pattern mask. It can also be adapted to the radiation pattern mask. Therefore, interference with the IrDA can be minimized, and a high-speed optical communication system using a semiconductor laser having a speckle amount larger than that of an LED can be provided.

  Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments. FIG. 1 is a cross-sectional view showing an example of the light source device of the present embodiment, FIG. 2 is a diagram showing a radiation pattern mask, and FIG. 3 is a radiation pattern of the light source device shown in FIG. is there. The object of the present invention is to adjust the half-value angle of the light source having speckles. First, speckles and speckle amounts used in the present invention will be described.

  FIG. 3 shows an example of the radiation intensity distribution in the light source device of the present invention. The thin solid line in the figure is the radiation intensity distribution when light is received by a light receiver with an aperture of 2 mmφ at a position 1 m away from the light source (laser element), and laser speckle (random fluctuations in light intensity) can be seen. . Similarly, a thick broken line is a radiation intensity distribution when light is received by a light receiver having an aperture of 20 mm at a position 1 m away from the light source. In this case, speckles are synthesized in the opening, and a distribution with small intensity fluctuation is measured. In the following, the former (thin solid line) is simply referred to as radiation intensity distribution (Intensity), and the latter (thick broken line) is referred to as averaged radiation intensity distribution (Averaged Intensity).

  Since speckles behave stochastically as described above, they appear larger as the aperture diameter is smaller. Therefore, when an optical communication system is determined, the maximum speckle that can appear in the optical communication system is uniquely determined because the maximum communication distance and the minimum light reception size of the optical communication system are determined. For example, as IrDA1.1, the light receiving device having the light receiving area of about 2 mmφ is the smallest, and the communication distance is 1 m at the maximum. Therefore, the speckle obtained by the method of measuring the radiation intensity distribution indicated by the thin solid line in FIG. 3 is the light received by the light receiver when the light source device of the present embodiment is adopted in the optical communication system of IrDA1.1. It means a change in quantity.

FIG. 4 shows the ratio between the radiation intensity and the average radiation intensity in FIG. In this case, the average radiant intensity distribution considers only the range of the radiation angle from the peak value to 1 / e ² of this peak value (e is the base of natural logarithm≈2.718). This is because, according to experience, in the region where the averaged radiant intensity distribution is smaller than 1 / e ^{2 of the} peak value, a phenomenon that speckle is reduced is observed.

In FIG. 4, the speckle amount is determined based on the standard deviation in the distribution of the ratio value of the radiant intensity and the averaged radiant intensity, but the area where the averaged radiant intensity distribution is less than 1 / e ² of the peak value. If the data up to this point is included, the value of the standard deviation becomes small, and the speckle amount in the angular range to be actually considered is not reproduced. Therefore, by eliminating the region where the averaged radiation intensity distribution is less than 1 / e ² of the peak value, it is possible to prevent the apparent speckle from decreasing. In FIG. 4, it is apparent that the radiant intensity is distributed around the averaged radiant intensity, and the manner of distribution is a stochastic event. Actually, the distribution of the ratio value of the radiation intensity and the averaged radiation intensity is represented as a histogram as shown in FIG. According to FIG. 5, the value of the ratio of radiant intensity and averaged radiant intensity is a random probability event and is normally distributed. The standard deviation (σ) at this time is 0.045. In addition, when the ratio of the radiation intensity and the average radiation intensity is measured for some eye-safe lasers proposed by the inventors of the present application, the standard deviation is distributed to about 0.016 to 0.10. Can be confirmed.

  The speckle amount s is determined in the range of 3σ to 6σ with respect to the standard deviation σ. By setting the speckle amount s to 3σ, the probability that a speckle amount greater than the speckle amount s appears is 0.00155 or less. Further, by setting the speckle amount s to 5σ, the probability that speckles greater than the speckle amount s appear can be reduced to 0.00000209 or less. In this way, an amount obtained by multiplying the standard deviation σ by a value of 3 to 6 is referred to as a speckle amount s. Although this value may vary depending on the optical communication system, it is generally considered to be about 5σ. In the present embodiment, the speckle amount s = 5σ is defined and each example will be described below. Hereinafter, the standard deviation σ in the distribution of the ratio value of the radiation intensity and the averaged radiation intensity is referred to as the speckle standard deviation.

First embodiment (Example 1)
FIG. 1 is a cross-sectional view of a light source device for a 100 Mbps optical communication system. In this light source device, a counterbore hole 5 having an inclined surface and a bottom surface at a predetermined angle is formed on a glass epoxy substrate 4, and the semiconductor laser 1 is mounted on the bottom surface inside thereof. A wiring pattern 7 serving as a lower electrode pad of the semiconductor laser 1 is formed from the bottom surface and the inclined surface of the counterbored hole 5 to the upper surface of the glass epoxy substrate 4, and gold plating is applied to form a light reflecting portion. An upper electrode (not shown) of the semiconductor laser 1 and an upper electrode pad 8 formed on the upper surface of the glass epoxy substrate 4 are connected by a gold wire 3. Then, by energizing the wiring pattern 7 from the upper electrode pad 8, the semiconductor laser 1 emits light, and the emitted light 2 is emitted from the end face of the semiconductor laser 1.

The counterbore 5 is filled with a gel-like or rubber-like silicon resin 9 containing a light diffusing agent (acrylic in this embodiment 1) at a weight ratio of about 1%. Therefore, the laser beam 2 is scattered in a random direction in the counterbore hole 5 and becomes a light beam having a spread of about 100 μm when emitted from the silicon resin 9. A lens 6 made of an epoxy resin is formed on the top surface of the sagittal hole 5 and the silicon resin 9 on both sides thereof, and light emitted from the semiconductor laser 1 is reflected by the light reflecting portion and radiated to the space through the lens 6. The At this time, the diameter of the lens 6 is 3.5 mm, which is 30 times larger than the above-described 100 μm spread of the light beam. Therefore, the radiation intensity pattern is well controlled by the lens 6. Indeed, by adjusting the curvature of the lens 6 made hemispherical epoxy resin, a directional half angle theta _H 18.5 degrees (θ _H = 0.32rad), the standard deviation sigma of the speckle sigma = The light source device was 0.09 and the speckle amount s was s = 5 × σ = 0.45. The speckle amount s can be changed according to the degree of diffusion of the emitted light. In the case of the present embodiment, the concentration of the diffusing agent (acrylic) is thin and the speckle is relatively large.

  The case where the light source device having the configuration shown in FIG. 1 and having the above-described characteristics is applied to the IrDA1.1 will be described. In IrDA1.1, as described in the background art, a radiation pattern mask as shown in FIG. 14 is required. In this case, the light output conditions to be satisfied by the light source device are as follows.

が成立することである。また、光軸上における放射強度が５００mＷ/srを超えないための条件は、不等式

が成立することである。 First, the condition for preventing the radiation intensity within a communication angle within ± 15 degrees (± 0.26 rad) from falling below 100 mW / sr is an inequality from the Lambert distribution L (θ) described above.

Is established. The condition for the radiation intensity on the optical axis not to exceed 500 mW / sr is inequality.

Is established.

Therefore, since the light output p required for the light source device is s = 0.45,
128mW ≦ p ≦ 154mW
It becomes. That is, by adjusting the light output p of the light source device within the above range, it is possible to provide a light source device that does not deviate from the IrDA 1.1 radiation pattern mask.

(Comparative Example 1)
While being applied to the case of As in the IrDA1.1 Example 1, a light source device comprising a speckle amount s = 0.45, directional half angle theta _H as curvature of a conventional lens 6 is 15 degrees A comparative example in which the shape is such that will be described.

  In this case, in order to prevent the radiation intensity within the communication angle area of ± 15 degrees from falling below 100 mW / sr, an optical output p of 109 mW or more is required. However, in that case, the maximum radiation intensity on the optical axis is 530 mW / sr, and it cannot be used as a light source for IrDA1.1.

FIG. 6 is a plot of the speckle amount s and the directional half-value angle θ _H in Example 1 and Comparative Example 1. In FIG. 6, the vertical axis represents a value obtained by dividing the directivity half-value angle θ _H by the communication angle (Θ in FIG. 2, 15 degrees in Example 1 and Comparative Example 1). The thick lines in the figure indicate the directional half-value angles defined from the radiation pattern mask when R = 2, R = 3.5, R = 5 and r = 0.4, r = 0.7, r = 1. it is obtained by displaying a range of θ _H. Here, R = (In_max) / (In_min) and r = (Out_max) / (In_min). However, “In_max” is the maximum radiation intensity, “In_min” is the minimum radiation intensity when the radiation angle is within ± Θ, and “Out_max” is the maximum radiation intensity when the radiation angle is outside ± 2Θ.

但し、Ｐは光出力 Here, a relational expression between the directivity half-value angle θ _H and the speckle amount s is derived as follows. That is, the conditions for the above-described Lambert distribution L (θ) (curve indicated by the dotted line in FIG. 2) to be contained in the radiation pattern mask shown in FIG. 2 are expressed by three inequalities of Expressions (1) to (3). .

Where P is the optical output

となる。さらに、式(１)と式(３)とを組み合わせてｎについて解くと、

となる。 Here, combining equations (1) and (2) and solving for n,

It becomes. Furthermore, combining equation (1) and equation (3) and solving for n,

It becomes.

が得られる。これより、
１＝２・cosⁿθ_H …（９）
となるため、式(９)を解いて
θ_H＝cos^-1(０.５^(1/n)) …（１０）
が得られる。また、その場合におけるｎの範囲は、式(５)と式(７)とから、

となる。 Further, since the radiation intensity at the radiation angle 0 is twice the radiation intensity at the directivity half-value angle θ _H , the equation (8) is obtained from the Lambert distribution L (θ).

Is obtained. Than this,
_{^{1 = 2 · cos n θ H}} ... (9)
Therefore, solving equation (9)
θ _H = cos ⁻¹ (0.5 ^{(1 / n)} ) (10)
Is obtained. In addition, the range of n in that case is from Equation (5) and Equation (7),

It becomes.

  By the way, in the case of Example 1, the radiation pattern mask of IrDA1.1 is used. Therefore, the inside of the thick solid line with R = 5 and the thick solid line with r = 1 is the matching range. Accordingly, it can be seen that when the speckle amount s exceeds 0.58, a light source device applicable to IrDA1.1 cannot be obtained.

In a conventional light source device using LEDs, the speckle amount s is 0.05 or less, and the allowable range of the pointing half-value angle θ _H is wide. Therefore, it is no exaggeration to say that the directivity half-value angle θ _H can be set arbitrarily. In doing so, it is desirable that 0.85 <directivity half-value angle / communication angle <1 in order to achieve the requirements of the radiation pattern mask with minimal light output.

On the other hand, in the case of the light source device having the speckle amount s larger than 0.05 as in the first embodiment, the light source of the light source is set so as to have a directivity half-value angle θ _H corresponding to the speckle amount s. It is necessary to set the radiation intensity distribution. Therefore, in the first embodiment, the radiation intensity distribution is controlled so that the directivity half-value angle θ _H according to the speckle amount s is obtained by controlling the shape of the lens 6 as the radiation pattern setting means. is there. For example, as shown in FIG. 7, when the height of the epoxy lens 6 from the surface of the glass epoxy substrate 4 is suppressed as compared with the structure of FIG. 1, the structure of FIG. In addition, it is possible to further widen the pointing half-value angle θ _H. In FIG. 7, members having the same functions as those in FIG. 1 are given the same numbers as in FIG.

As described above, in the first embodiment, when applying the light source device using the semiconductor laser 1 that exhibits a small speckle amount s with a small degree of diffusion of emitted light to the IrDA1.1, as shown in FIG. From the relationship between the speckle amount s determined according to R and r of 1 and the directivity half-value angle θ _H / communication angle, the silicone resin 9 is set so that the directivity half-value angle θ _H corresponds to the speckle amount s. In addition, a light diffusing agent is contained in the glass, and the shape of the epoxy lens 6 is controlled. Therefore, it is possible to obtain a light source device having a radiation intensity distribution adapted to the radiation pattern mask of IrDA1.1 with the minimum light output.

(Example 2)
The present embodiment is an example of a light source device applied to an optical communication module having a communication speed of 100 Mbps different from IrDA used in the first embodiment. Here, the optical communication module used in this embodiment has a radiation pattern mask whose minimum radiation intensity (In_min) is within ± 15 degrees = 250 mW / sr, maximum radiation intensity (In_max) = 500 mW / sr, ± 30 degrees. The maximum radiant intensity (Out_max) = 100 mW / sr, R = (In_max) / (In_min) = 2, and r = (Out_max) / (In_min) = 0.4.

  In the case of 100 Mbps communication, although it depends on the size of the light receiver, 250 mW / sr is required as the radiation intensity on the light source side. In the case of the present embodiment, the effective light receiving diameter of the light receiver (not shown) is 3 mm, and the configuration of the light source device is substantially the same as that of the first embodiment using the hemispherical lens 6 shown in FIG. Therefore, the present embodiment will be described with reference to FIG. 1 as in the case of the first embodiment.

The difference between this example and Example 1 shown in FIG. 1 is that the light scattering agent is contained in a high concentration (weight ratio 5%) in the silicon resin 9 filled in the counterbore hole 5. . Therefore, in this case, the spatial spread of the light beam emitted from the silicon resin 9 reaches 500 μm. At the same time, the amount of speckles can be reduced by increasing the number of scattering in the counterbore hole 5. In this embodiment, the standard deviation of speckle is σ = 0.02, and the speckle amount is s = 0.1. In this case, the spread of the light distribution immediately after the counterbore 5 has the effect of widening the radiation intensity distribution. As a result, a directional half angle theta _H of the light source can be set to 19.5 degrees.

  That is, in the present embodiment, the light incident position dispersing means is constituted by the light diffusing agent contained in the silicon resin 9, and the radiation pattern setting means is constituted by the lens 6.

  The speckle amount s and the directivity half-value angle / communication angle in this embodiment are plotted in FIG. 6 as in the case of the first embodiment. By injecting an optimal current into the light source device, an optical output of 220 mW is obtained. At this time, the minimum radiation intensity within ± 15 degrees> 250 mW / sr, the maximum radiation intensity on the optical axis <500 mW / sr, ± 30 A light source with a radiant intensity distribution with a maximum radiant intensity <100 mW / sr outside the degree was obtained. In this case, R = (In_max) / (In_min) = 2 and r = (Out_max) / (In_min) = 0.4, and as can be seen from FIG. 6, the speckle amount s, the directional half-value angle / communication angle, Is inside the thick dotted line of R = 2 and the thick broken line of r = 0.4, and is within the conforming range of the radiation pattern mask for the optical communication module having the communication speed of 100 Mbps used in the second embodiment. I understand. As a result, high-speed communication of 100 Mbps is ensured in the same communication cover area as before without interfering with optical terminals existing outside the communication area of the light source device (that is, minimizing interference with IrDA). It can be realized.

In the light source device of the second embodiment, the speckle amount s is 0.1. Therefore, when used in an optical communication module for 100 Mbps that is not IrDA, the directivity half-value angle θ _H is equal to the communication angle Θ. It became clear that it was limited to 1.2 times or more. In this case, in the second embodiment, the concentration of the light scattering agent contained in the silicon resin 9 is controlled to enlarge / reduce the spatial spread of the light rays existing inside the lens 6, thereby setting the directivity half-value angle θ _H to the above-described value. It is illustrated that it can be controlled to fall within the range.

When the light source device of the second embodiment is used outdoors such as a base station, the temperature difference is larger than that in the room, and the light output of the light source device fluctuates. As a result, variation in light output becomes a problem. Here, the directivity half-value angle θ _H that can tolerate variations in light output depends on the radiation pattern mask shape, but among them, the directivity half-value angle θ _H (hereinafter referred to as θ _Hmax ) that can tolerate as much variation as possible. It is desirable to manufacture.

FIG. 8 shows the relationship of θ _Hmax with respect to r / R. In the figure, a solid line indicates a case where the communication angle is 10 degrees (Θ = 0.17 rad), a broken line indicates a case where the communication angle is 15 degrees (Θ = 0.26 rad), and a one-dot chain line indicates a communication angle of 30 degrees ( Θ = 0.52 rad). However, θ _Hmax is within the range of the directional half-value angle θ _H represented by the equations (10) and (11) calculated in the first embodiment, depending on the radiation pattern mask required by the applied optical communication system. Only exists.

FIG. 8 shows that the value of θ _Hmax increases as r / R increases at any communication angle. Then, the value of theta _Hmax, if, for example r / R = 0.5, Θ = a 0.17rad (10 degrees) θ _Hmax = 0.35rad (20 degrees), Θ = 0.26rad (15 a in degrees) θ _Hmax = 0.52rad (30 degrees), theta = a 0.52rad (30 degrees) with θ _Hmax = 1.05 (60 °). As can be seen from the above formula, the allowable variation amount depends on the speckle amount s, and the allowable amount (that is, the range of n) decreases as the speckle amount s increases. The second embodiment corresponds to the case where Θ = 0.26 rad (15 degrees), r / R = 0.2 (In_max = 500 mW / sr, Out_max = 100 mW / sr).

FIG. 9 shows the power penalty PP for each pointing half-value angle / communication angle when the speckle amount s = 0.1 in the second embodiment. Here, the power penalty PP is a radiation intensity distribution that conforms to the radiation pattern mask of the applied optical communication system, and the light output of the radiation intensity distribution that minimizes the light output is the reference light output. The ratio between the light output of the light source device and the reference light output. In the figure, the three curves indicate the limits of the light output by the radiation pattern mask, the solid line is the minimum radiation intensity In_min (250 mW / sr) within the radiation angle ± Θ (± 15 degrees), and the broken line is the radiation The maximum radiation intensity In_max (500 mW / sr) within an angle ± 2Θ (± 30 degrees), and the one-dot chain line is the maximum radiation intensity Out_max (100 mW / sr) outside the radiation angle ± 2Θ (± 30 degrees). . 9, the possible range of the pointing half-value angle / communication angle and power penalty PP in the second embodiment is an area surrounded by the above three curves (the pointing half-value angle / communication angle is 1.19 to 1.39). , The power penalty PP is 1.26 to 1.56). In particular, when the directivity half-value angle / communication angle is 1.33 (directivity half-value angle θ _H : about 20 degrees), the margin for variation is the highest, and the power penalty PP is 0.15 from 1.41 to 1.56. Only minutes are acceptable.

Therefore, in the case of the second embodiment in which the speckle amount s is 0.1, it is preferable that the directivity half-value angle θ _H is approximately 20 degrees in consideration of power fluctuation due to temperature change. It can be said. In the present embodiment 2, as previously described, the concentration of the light scattering agent contained in the silicone resin 9 in the weight ratio 5% directional half angle theta _H 19.5 ° (≒ 20 °) Is set. Therefore, it can be seen that the light source device has a desirable directivity half-value angle θ _H with respect to variations in light output.

  Next, the radiation intensity distribution that maximizes the value of the power penalty PP will be described. From FIG. 9, when the light source device is created with the directivity half-value angle / communication angle at the intersection of the curve of the maximum radiation intensity In_max and the curve of the maximum radiation intensity Out_max, the allowable amount of the power penalty PP can be maximized. . The radiation intensity distribution that gives the intersection is the radiation intensity distribution that maximizes the value of the power penalty PP.

この式(１２)と式(１３)とを連立させて解くことによって、上記交点を与える放射強度分布を規定する「ｎ」を求めることができる。つまり、式(１２)から

が得られ、この式(１４)と式(１３)とからｎを求めると、

となる。すなわち、式(１０)と式(１５)とで表される放射強度分布が、放射角度±Θ以内での放射強度がIn_min以上であり、放射角度±Θ内での放射強度がIn_min以上であり、放射角度±２Θ内での放射強度がIn_max以下であり、放射角度±２Θよりも外側での放射強度がOut_max以下であり、In_max/In_min＝ＲおよびOut_max/In_min＝ｒである放射パターンマスクに適合し、且つ、パワーペナルティＰＰの値を最大にする放射強度分布である。 The radiation intensity distribution that gives the intersection is a radiation intensity distribution that touches the radiation pattern mask at a radiation angle of 0 and a radiation angle of 2Θ. Therefore, such a radiation intensity distribution satisfies Expression (12) and Expression (13) from the expression of Lambert distribution L (θ).

By simultaneously solving Equation (12) and Equation (13), “n” that defines the radiation intensity distribution giving the intersection can be obtained. That is, from equation (12)

When n is obtained from the equations (14) and (13),

It becomes. That is, in the radiant intensity distribution represented by the equations (10) and (15), the radiant intensity within the radiation angle ± Θ is In_min or more, and the radiant intensity within the radiation angle ± Θ is In_min or more. A radiation pattern mask in which the radiation intensity within the radiation angle ± 2Θ is less than In_max, the radiation intensity outside the radiation angle ± 2Θ is less than Out_max, and In_max / In_min = R and Out_max / In_min = r It is a radiation intensity distribution that is compatible and maximizes the value of the power penalty PP.

Second embodiment (Example 3)
FIG. 10 is a cross-sectional view of the light source device according to the third embodiment. This light source device is provided as a light source for the IrDA1.1. In FIG. 10, the semiconductor laser 11, the gold wire 13, the glass epoxy substrate 14, the counterbore hole 15, the wiring pattern 17 and the upper electrode pad 18 are the same as the semiconductor laser 1 in the light source device of the first embodiment shown in FIG. This is the same as the gold wire 3, glass epoxy substrate 4, counterbore 5, wiring pattern 7, and upper electrode pad 8.

  The silicon resin 19 in Example 2 does not contain a light diffusing agent such as acrylic. Instead, a light diffusing agent is mixed in the hemispherical lens 16 made of epoxy resin. In this case, since the base material mixed with the light diffusing agent is different, the scattering agent itself is naturally replaced, and light scattering can be optimized by appropriately adding silica particles or the like to the epoxy resin.

  That is, in the third embodiment, the light incident angle dispersion means is configured by the light diffusing agent contained in the lens 16.

The lens 16 in the third embodiment is configured so that the laser light emitted from the lens 16 becomes a light beam substantially parallel to the optical axis when there is no light scattering agent. That is, the directivity half-value angle θ _H when there is no scattering agent is 0 degree. On the other hand, by adding a scattering agent inside the lens 16, the angular distribution of light incident on the interface of the lens 16 (the interface between the epoxy resin and air) can be dispersed with a certain width. Then, this dispersion, the radiation intensity distribution of the light beam emitted from the lens 16 into the air it is possible to Lambert distribution of directional half angle θ _H (≒ 0), directional half angle theta _H is the scattering agent It can be changed by adjusting the density. In Example 3, a scattering agent having a small average scattering angle in one scattering is used. In this case, the value of the scattering factor g represented by the average value of the cosine of the scattering angle is 0.9 or more.

Speckle amount s of the light source apparatus in the third embodiment having the above structure is 0.25, directional half angle theta _H is 12.7 degrees. The speckle amount s and the directivity half-value angle / communication angle in this example are plotted in FIG. 6 as in the case of the first embodiment. As can be seen from FIG. 6, the speckle amount s and the directivity half-value angle / communication angle are compatible with the radiation pattern mask (R = 5, r = 1) for IrDA1.1 used in the third embodiment.

In FIG. 6, the “+” point of PP = 1 shown on the vertical axis indicates the directivity half-value angle θ _H that minimizes the optical output within the communication angle range. That is, when the communication angle is ± 15 degrees, the directivity half-value angle θ _H is 12.7 degrees, and the light use efficiency is maximized. When a semiconductor laser is used, the speckle is generated, and the required power increases according to the speckle amount s. Then, the required light output in the region surrounded by the line of PP = 1.26 is as follows: the light output in the case of PP = 1 is the reference light output, and the required light output <(1.26 × reference light output). Become. Similarly, in the region surrounded by the lines of PP = 2 and PP = 3.16, the necessary light output is a value less than 2 times and 3.16 times the reference light output. At each PP = 1.26, 2, 3.16, the speckle amount s is maximized when the directivity half-value angle θ _H is 12.7 degrees. That is, the allowable range for speckle is maximized.

が得られる。また、パワーペナルティＰＰの定義からＰ/Ｐ₀＝ＰＰ(＞１)である。したがって、式(１６)は式(１７)のごとく変形できる。
ＰＰ(１−ｓ)(ｎ＋１)cosⁿΘ≧(ｎ₀＋１)cosⁿΘ…（１７） Here, an expression representing the relationship among the power penalty PP, the directivity half-value angle θ _H, and the speckle amount s is derived as follows. That is, since the radiation intensity distribution (reference radiation intensity distribution) in contact with the radiation pattern mask at the radiation angle Θ is lower than the radiation intensity distribution in the actual light source device, the light output of the reference radiation intensity distribution is P ₀ , and the above n is When n _0, equation (16)

Is obtained. Further, P / P ₀ = PP (> 1) from the definition of the power penalty PP. Therefore, equation (16) can be transformed as equation (17).
PP (1−s) (n + 1) cos ⁿ Θ ≧ (n ₀ +1) cos ⁿ Θ (17)

となる。したがって、式(１８)において、Ｐ₀を最小にするようなｎ₀を求めればよいことになる。つまり、次式(１９)

＝０ …（１９）
をｎ₀に付いて解けば、式(１８)においてＰ₀を最小にするｎ₀が次式(２０)のごとく求められる。
ｎ₀＝−１/(lncosΘ)−１ …（２０） Further, the n _0, it is necessary to light output P ₀ of the reference radiation intensity distribution is set to be minimized. Therefore, if the radiation intensity at the radiation angle Θ is I ₀ ,

It becomes. Therefore, in Equation (18), n ₀ that minimizes P ₀ may be obtained. That is, the following equation (19)

= 0 (19)
If the melt with the n _0, n ₀ of the P ₀ to a minimum in equation (18) is obtained as the following equation (20).
n ₀ = −1 / (lncos Θ) −1 (20)

That is, the relationship between the power penalty PP and directional half angle theta _H and speckle amount s is represented by the formula (17), "n _0" in this case is of the formula (20).

By the way, from the viewpoint of power consumption, it is desirable that the optical output is as low as possible. In addition, it is desirable that the allowable range for speckle is as large as possible. Based on this concept, in the third embodiment, the concentration of the scattering agent mixed into the lens 16 is adjusted so that the directivity half-value angle θ _H is 12.7 degrees. Therefore, it is possible to obtain a light source device that is compatible with the IrDA 1.1 radiation pattern mask and has a light output that is about 1.3 times the reference light output.

  Generally, the current-light conversion efficiency in a semiconductor laser is about 3 to 4 times higher than that of an LED. Therefore, even if a penalty with respect to the reference light output occurs due to the inclusion of speckles, the advantage of using a semiconductor laser does not fluctuate if the penalty value is about 3 or less.

  11 and 12 show a cross section of a light source device different from those of the first to third embodiments. In the light source device shown in FIG. 11, the gold wire 23, the glass epoxy substrate 24, the counterbore hole 25, the lens 26, the wiring pattern 27, the upper electrode pad 28, and the silicon resin 29 are the same as those in the first embodiment shown in FIG. This is the same as the gold wire 3, glass epoxy substrate 4, counterbore 5, lens 6, wiring pattern 7, upper electrode pad 8 and silicon resin 9 in the light source device. However, the central axis of the lens 26 is coaxial with the central axis of the counterbore hole 25.

  The semiconductor laser 21 emits radiated light 22a and radiated light 22b from both end faces thereof. As a result, the spatial spread of the light beam emitted from the silicon resin 29 can be expanded without increasing the concentration of the light scattering agent mixed into the silicon resin 29 from about 1% by weight in the first embodiment. . Since the addition of a high concentration of the scattering agent to the silicon resin 29 and the lens 26 leads to light absorption, the concentration of the scattering agent is preferably a low concentration as described above. Further, the central axis of the lens 26 and the central axis of the counterbore hole 25 are coaxial. Therefore, the position of the emitted light with respect to the central axis of the lens 26 is the same regardless of which direction the semiconductor laser 21 faces, and the central axes of the lenses 6 and 16 are the same as in the first to third embodiments. There is no problem in manufacturing such as rotating the chips of the semiconductor lasers 1 and 11 in-plane in order to align the position of the emitted light with respect to. Therefore, it is possible to achieve a completely different effect that the yield is improved as compared with the case of the first to third embodiments. In addition, although the light diffusing agent is not included in the lens 26 in FIG. 11, it may be included.

  In the light source device shown in FIG. 12, the gold wire 33, the glass epoxy substrate 34, the counterbore hole 35, the wiring pattern 37, the upper electrode pad 38, and the silicon resin 39 are the same as those in the light source device of the first embodiment shown in FIG. This is the same as the gold wire 3, glass epoxy substrate 4, counterbore 5, wiring pattern 7, upper electrode pad 8, and silicon resin 9. Further, the semiconductor laser 31 emits the radiated light 32a and the radiated light 32b from both end faces, as in the case of the semiconductor laser 21 in FIG. The lens 36 has a central axis that is coaxial with the central axis of the counterbore hole 35, as in the case of the lens 26 in FIG.

In this light source device, a light diffusion plate 40 as the light incident position dispersing means is disposed between the silicon resin 39 and the lens 36. The light diffusing plate 40 has a function of expanding the spatial extent of the light beam, and can be used to adjust the directivity half-value angle θ _{H in} the same manner as in the first to third embodiments. In addition, although the light diffusing agent is not included in the lens 26 and the silicon resin 39 in FIG. 12, the light diffusing agent may be included.

In the first to third embodiments, FIG. 6 shows the relationship between the speckle amount s and the directional half-value angle / communication angle when the communication angle is ± 15 degrees. FIG. 13 shows the relationship between the speckle amount s and the pointing half-value angle / communication angle when the communication angle is ± 30 degrees. 6 and 13, when the communication angle is widened, the radiation pattern mask (the line indicated by r = 1, 0.7, 0.4) in the region outside the communication angle is set to the directivity half-value angle θ _H. It can be seen that it does not affect On the other hand, when the communication angle is ± 15 degrees, it can be confirmed that the allowable range of the directivity half-value angle θ _H is significantly narrowed.

  As described above, according to each of the above embodiments, a semiconductor laser having a speckle amount larger than that of the LED used for IrDA is selected from IrDA in which R = 5 and r = 1, and 2 ≦ R ≦ 3.5 and 0. It can be used for a 100 Mbps high-speed optical communication module in which 0.4 ≦ r ≦ 0.7. Therefore, a semiconductor laser that could not be used in a space where a person exists so far can be applied as a light source of a high-speed optical wireless communication system. As a result, by installing the optical wireless communication system using the light source device of each of the above embodiments in a personal computer or a portable terminal (PDA (personal digital assistant), cellular phone), etc., compared to the case where LEDs are used. In addition, it has low power consumption and can transfer large volumes of data such as moving images in a shorter time and can be carried around.

It is sectional drawing which shows an example in the light source device of this invention. It is a figure which shows a radiation pattern mask. It is a figure which shows the radiation intensity distribution of the light source device shown in FIG. It is a figure which shows ratio of the radiation intensity in FIG. 3, and averaged radiation intensity. It is a histogram of the value of ratio of the radiation intensity shown in FIG. 4, and averaged radiation intensity. It is a figure which shows the relationship between the speckle amount in case a communication angle is +/- 15 degree | times, and a directivity half value angle / communication angle. It is explanatory drawing of the lens shape change in the light source device shown in FIG. It is a figure which shows the relationship between r / R and (theta) _Hmax in the light source device shown in FIG. It is a figure which shows the relationship between the pointing half value angle / communication angle and power penalty in case the speckle amount in the light source device shown in FIG. 1 is 0.1. It is sectional drawing of the light source device different from FIG. It is sectional drawing of the light source device different from FIG. 1 and FIG. It is sectional drawing of the light source device different from FIG.1, FIG10 and FIG.11. It is a figure which shows the relationship between the speckle amount in case a communication angle is +/- 30 degree | times, and a directivity half value angle / communication angle. It is a figure which shows the radiation pattern mask for IrDA1.1 or IrDA1.3, and the radiation intensity distribution of a light source device.

1, 11, 21, 31 ... semiconductor laser,
2, 12, 22a, 22b, 32a, 32b ... synchrotron radiation,
3, 13, 23, 33 ... gold wire,
4, 14, 24, 34 ... Glass epoxy board,
5, 15, 25, 35 ... counterbored holes,
6, 16, 26, 36 ... lens,
7, 17, 27, 37 ... wiring pattern,
8, 18, 28, 38 ... upper electrode pad,
9, 19, 29, 39 ... Silicone resin,
40: Light diffusion plate.

Claims (14)

A light source device for use in an optical communication system that requires a predetermined light emission intensity in a predetermined light emission angle range,
A light emitting element that produces speckle;
The radiation pattern representing the relationship between the radiation angle and the radiation intensity in the radiated light from the light emitting element is made to satisfy the light radiation intensity in a predetermined light radiation angle range required by the optical communication system. in light source device having a radiation pattern setting means for setting in accordance with the speckle amount,
The light emission intensity within a predetermined light emission angle range required by the optical communication system is such that the emission intensity within the emission angle ± Θ is In_min or more and the emission intensity within the emission angle ± 2Θ is In_max or less. And the radiation intensity outside the radiation angle ± 2Θ is not more than Out_max, and In_max / In_min = R and Out_max / In_min = r,
When the speckle amount is s,
Radiation pattern set by the radiation pattern setting means, the light emission intensity is directional half angle theta _H representing the light emission angle which is half of the maximum light emission intensity
θ _H = cos ^-1 (0.5 ^{(1 / n)} )

It is a pattern that becomes
A light source device characterized by that . A light source device for use in an optical communication system that requires a predetermined light emission intensity in a predetermined light emission angle range,
A light emitting element that produces speckle;
The radiation pattern representing the relationship between the radiation angle and the radiation intensity in the radiated light from the light emitting element is made to satisfy the light radiation intensity in a predetermined light radiation angle range required by the optical communication system. , Radiation pattern setting means to set according to speckle amount
In a light source device comprising:
The light emission intensity in a predetermined light emission angle range required by the optical communication system is assumed that the emission intensity within the emission angle ± Θ is a predetermined value or more ,
When the speckle amount is s,
Radiation pattern set by the radiation pattern setting means, the light emission intensity is directional half angle theta _H representing the light emission angle which is half of the maximum light emission intensity
θ _H = cos ^-1 (0.5 ^{(1 / n)} )
Where PP (1−s) (n + 1) cos ⁿ Θ ≧ (n ₀ +1) cos ⁿ Θ
PP> 1
n ₀ = −1 / (lncosΘ) −1
A light source device having a pattern such that In the light source device according to claim 1 or 2 ,
Upper Symbol radiation pattern setting means is a lens in which the emitted light is incident,
A light source device that features Rukoto the radiation pattern is set by setting the shape of the lens. In the light source device according to claim 1 or 2 ,
A lens on which the emitted light is incident;
The radiation pattern setting means is provided between the light emitting element and the lens, the light source device that features light incidence position dispersion means der Rukoto dispersing the incident position to said lens of said emitted light. The light source device according to claim 4 ,
The light incident position dispersing means is a transparent resin covering the light emitting element and a light diffusing agent mixed in the transparent resin,
A light source device that features Rukoto the radiation pattern is set by setting the concentration of the light diffusing agent. The light source device according to claim 4 ,
The light incident position dispersion means, a light source device that features a light diffusing plate der Rukoto. In the light source device according to claim 1 or 2 ,
A lens on which the emitted light is incident;
The light source device according to claim 1, wherein the radiation pattern setting means is a light incident angle dispersion means for dispersing an incident angle of the radiated light on an interface between the lens and air . The light source device according to claim 7 .
Upper Symbol light incident angular dispersion means is a light diffusing agent mixed into the upper Stories lens,
A light source device that features Rukoto the radiation pattern is set by setting the concentration of the light diffusing agent. In the light source device according to claim 1 or 2 ,
The radiation pattern setting means further the radiation pattern, so that the pattern exhibits the lowest light output that can achieve requirements for radiation pattern mask, that you have made to set in accordance with the speckle amount A light source device. The light source device according to claim 1,
The value of R above is
2 ≦ R ≦ 3.5
A light source device according to claim der Rukoto. The light source device according to claim 1 ,
The value of r above is
0.4 ≦ r ≦ 0.7
A light source device characterized by the above. The light source device according to claim 1 ,
N above

A light source device characterized by the above. The light source device according to claim 2,
The light source device characterized in that the value of PP is smaller than 3 . Light communication system characterized by using the light source device according to claim 1 or claim 2.

Images