JP2007292577A - Light source device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure luminous energy allowing precise detection by an optical sensor, without lowering substantially the luminous energy. <P>SOLUTION: The light source device includes a light source 101 for emitting visible light, a convergence part 102 for converging the light from the light source 101 to a light uniformizing part 103, the light uniformizing part 103 for uniformizing the light, a light acquisition part 104 for taking out one part of the light total-reflected inside the light uniformizing part 103, the optical sensor 105 for receiving the light taken out by the light acquisition part 104, and a light source luminous energy controller 106 for regulating the luminous energy of the light source 101 in response to an output from the optical sensor 105. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a light source device, and more particularly to a technique for monitoring the amount of light and controlling the amount of light.

  In inspection equipment that inspects scratches and coating defects by irradiating light onto the projector and the glass plate or paint application surface to be inspected and observing with a CCD camera etc., the light quantity of the light source is controlled uniformly and uniformly A light source device that emits light is necessary. Therefore, a technique for monitoring the light amount and adjusting the light amount by feedback control is disclosed. (For example, refer to Patent Document 1).

FIG. 6 is a diagram showing a configuration of a conventional light source device. The light from the light source 101 is condensed on the incident surface of the light homogenizing unit 103 via the condensing unit 102, is uniformed by the light uniformizing unit 103, and then exits from the exit surface of the light uniformizing unit 103. Then, the light sensor 105 receives the leaked light irregularly reflected by the defect 601 inside the light uniformizing unit 103 or the scratch on the surface, converts it into an electrical signal, and outputs it. Then, the light source light amount controller 106 adjusts the light amount of the light source 101 according to the output of the optical sensor 105.
JP 2005-233927 A

  However, in the above-described conventional configuration, light leakage light that is irregularly reflected due to a defect or surface scratch on the light uniformizing unit 103 is used, so the amount of light received by the optical sensor 105 is small and the detection accuracy is poor. If the light uniformizing unit 103 has good quality with few defects and scratches on the surface, the amount of leaked light is further reduced, making it difficult to feedback control the light source.

  Accordingly, it is an object of the present invention to provide a light source device that ensures a light amount that can be accurately detected by the optical sensor 105 without substantially reducing the light amount.

  In order to solve the conventional problems, a light source device of the present invention includes a light source that emits visible light, a light collecting unit that collects visible light from the light source and irradiates light, and the light incident on an incident surface. The light from the condensing part is totally reflected on the side surface to be uniformed, and the light uniformizing part that exits from the light exiting surface and the light that is disposed on the side surface of the light uniformizing part to totally reflect the inside of the light uniformizing part. A light acquisition unit that partially extracts, a light sensor that receives light extracted by the light acquisition unit and converts the light into an electric signal, and a light source light amount controller that changes the light amount of the light source according to the electric signal of the light sensor. It is characterized by comprising.

  Further, in the light source device, the light acquisition unit is a prism that includes an exit surface in which an angle formed between the incident light and the perpendicular is less than a critical angle, and the incident light exits from the exit surface to the outside. Is.

  Further, in the light source device, the light acquisition unit has a refractive index equal to or higher than a refractive index of the light uniformizing unit.

  Further, in the light source device, the light acquisition unit is configured to make the incident light having the maximum angle between the perpendicular of the incident surface of the light uniformizing unit and the incident light incident on the incident surface of the light uniformizing unit the light uniformizing unit. It has a refractive index that is larger than the angle formed by the perpendicular to the side surface and smaller than 90 degrees on the side surface.

  Furthermore, in the light source device, one side of the incident surface of the light acquisition unit is located on the same plane as the incident surface of the light uniformizing unit.

  As described above, according to the light source device of the present invention, the light sensor can receive a sufficient amount of light with little influence on the amount of light and uniformity, so that the light amount can be accurately controlled.

  Embodiments of the light source device of the present invention will be described below in detail with reference to the drawings.

  Embodiments of the present invention described in claims 1 to 5 of the present invention will be described below with reference to FIGS.

FIG. 1 is a configuration diagram of a light source device in Embodiment 1 of the present invention.
In FIG. 1, a light source 101 is a light source that emits visible light, such as a mercury lamp, a sodium lamp, a light emitting diode, or a laser, and any light source that emits visible light is applicable. Moreover, what condensed the some light source instead of one light source may be used.

  The condensing part 102 condenses the emitted light of the light source 101 on the light uniformizing part incident surface 103a. The condensing unit 102 is, for example, a condensing lens or an elliptical mirror. The light homogenizer 103 totally reflects the incident light from the light homogenizer entrance surface 103a on the side surface, guides it to the light uniformizer exit surface 103b, and emits it from the light uniformizer exit surface 103b. The light is uniformed by being reflected a plurality of times inside the light uniformizing unit 103, and the light uniformizing unit exit surface 103b has a uniform light quantity distribution. In this embodiment, a prismatic rod prism is used as an example. The light acquisition unit 104 is disposed on the side surface of the light homogenization unit 103 and extracts a part of the light that totally reflects inside the light homogenization unit 103. The optical sensor 105 receives the light emitted from the light acquisition unit 104. The optical sensor 105 is, for example, a photodiode, and converts the amount of received light into an electrical signal and outputs it. The light source light amount controller 106 controls the light amount of the light source 101 according to the output of the optical sensor 105. The light source light quantity controller 106 performs, for example, A / D conversion (conversion from an analog value to a digital value) on the electrical signal from the optical sensor 105. Then, proportional operation and integration with the input as an electrical signal (digital value) from the optical sensor 105 after A / D conversion and the output as the drive signal of each light source so that the light quantity of each light source becomes a predetermined value. PI (Proportional Integral) control combining operations is performed.

Next, the principle by which the light acquisition unit 104 extracts light from the light uniformizing unit 103 will be described in detail with reference to FIG.
FIG. 2 is an enlarged view of the light homogenizing unit 103, the light acquiring unit 104, and the optical sensor 105 of FIG.

  In FIG. 2, the maximum incident angle light beam 201 is the light beam having the maximum incident angle 202 among the light beams incident on the light uniformizing unit incident surface 103a. The incident angle 202 is an angle formed by the normal 206 of the light uniformizing portion incident surface 103 a and the maximum incident light ray 201. The exit angle 203 is an angle formed between the maximum incident angle light beam 201 after passing through the light uniformizing portion incident surface 103 a and the perpendicular 206. The incident angle 204 is an angle formed between the perpendicular line 207 of the light acquisition unit incident surface 104 a on which the light beam enters the light acquisition unit 104 and the maximum incident angle light beam 201. The incident angle 205 is an angle formed by the emission surface of the light acquisition unit 104, the normal 208 of the light acquisition unit emission surface 104 b, and the maximum incident angle light ray 201.

  In this embodiment, when the refractive index of air is 1 and the refractive index of the light uniformizing unit 103 is 1.5, the maximum incident angle light ray 201 is incident on the light uniformizing unit incident surface 103a at an incident angle 202 of 24 degrees. When incident, the exit angle 203 is 16 degrees. Since the incident angle 204 is 74 degrees and the critical angle is about 41.8 degrees, when there is no light acquisition unit 104, all light incident on the light uniformizing unit 103 including the maximum incident angle light ray 201 is totally reflected. . However, when the light acquisition unit 104 is provided and the refractive index thereof is equal to or higher than the refractive index of the light uniformizing unit 103, all light incident on the light uniformizing unit 103 including the maximum incident angle light ray 201 is incident on the light acquisition unit incident surface. 104a is transmitted. Here, the refractive index of the light acquisition unit 104 is 1.5. Then, the light acquisition unit emitting surface 104b having an incident angle 205 less than the critical angle of 41.8 degrees is provided, and all the light incident on the light uniformizing unit 103 including the maximum incident angle light ray 201 is emitted. The optical sensor 105 receives the light emitted from the light acquisition unit emission surface 104b.

  Next, an example of the appearance of the light uniformizing unit 103 and the light acquiring unit 104 will be described. FIG. 3 is an external view of the light homogenization unit 103 and the light acquisition unit 104. As shown in FIG. 3, the light uniformizing unit 103 is a prismatic column of 8.5 mm × 5.2 mm × 50 mm. The light acquisition unit incident surface 104 a is 5 mm × 5 mm, and light incident on this surface is guided into the light acquisition unit 104.

  Next, how the light loss and uniformity on the light uniformizing unit exit surface 103b change when the light acquisition unit 104 of FIG. 3 is moved back and forth in the Z-axis direction will be described. FIG. 4 is a graph showing the amount of light and the degree of uniformity on the light uniformizing unit exit surface 103b with respect to the position of the light acquisition unit 104 in the Z-axis direction.

  In FIG. 4, the horizontal axis represents the Z-axis position, and the vertical axis represents the light amount and the uniformity. Further, 0 in the Z-axis position on the horizontal axis is when the side 301 is arranged at the position of the side 302 in FIG. The light quantity 401 is plotted with the light quantity when the light acquisition unit 104 is not provided as 100%. The reference axis is the left vertical axis. The amount of light lost here is the amount of light incident on the light acquisition unit 104 and thus on the optical sensor. The water average once 402 and the vertical uniformity 403 represent the uniformity of the light amounts of the lines 303, 304, which are drawn in the X-axis direction and the Y-axis direction, respectively, through the center of the light uniformizing part exit surface 103b in FIG. The uniformity when the light acquisition unit 104 is not provided is plotted as 100%. A large value indicates good uniformity and a small value indicates poor uniformity. The reference axis is the right vertical axis.

  Looking at the light quantity 401 in FIG. 4, the light quantity is greatest when the Z-axis position is 0 mm, the light quantity decreases rapidly as the Z-axis position increases, and then converges while undulating around 97%. . This undulation is because the light amount distribution of the light uniformizing portion entrance surface 103a is bright in the center and dark in the periphery depending on the state of the light emitting portion of the light source and the performance of the lens. The bright center light reaches the side surface of the light uniformizing unit 103, where the light acquisition unit 104 is provided. When the light is extracted, the loss of the light amount increases. Therefore, the Z-axis position when the amount of light first reaches the bottom (the part surrounded by the solid line) is the Z-axis position where the light emitted from the center of the light uniformizing part incident surface 103a reaches the side surface, In FIG. 3, since the output angle 203 is 16 degrees, 5.2 / 2 / tan (16 degrees) = 9.1 mm. Slightly different from the calculated value, the bottom is flat because the light uniformizing unit 103 is a prism, and the distance from the center of the light uniformizing unit incident surface 103a to the side surface of the light uniformizing unit 103 is not uniform. Because.

  Here, the amount of light received by the optical sensor 105 is considered. In this embodiment, the optical sensor 105 is assumed to be able to receive light of a maximum of 0.8 mW, for example. That is, it can be said that the amount of light is sufficient if light of 0.8 mW or more can be guided to the optical sensor 105. On the other hand, the amount of light incident on the light acquisition unit 104 is given by the following equation.

  In this embodiment, the light amount of the light source is 800 mW, and the light collection efficiency to the light uniformizing unit 103 is 0.5. The amount of light incident on the light acquisition unit 104 is a loss of the amount of light on the light uniformizing unit exit surface 103b, and the amount of light incident on the light acquisition unit 104 is substantially equivalent to the amount of light received by the optical sensor 105. In FIG. 4, the Z-axis position where the light quantity received by the optical sensor 105 is the smallest is 0 mm, and the light quantity at this time is 99.25%, so the incident light quantity ratio of the light acquisition unit 104 is 0.0075.

  From Equation 1, it can be seen that the amount of light incident on the light acquisition unit 104, that is, the amount of light received by the optical sensor 105 is 3 mW, and a sufficient amount of light reaches the optical sensor 105 wherever the Z-axis position is. In order to prevent the output of the optical sensor 105 from being saturated, an incident light amount may be adjusted by placing a neutral density filter or the like in front of the light receiving portion of the optical sensor 105.

  As described above, in this embodiment, the light acquisition unit 104 having a refractive index equal to or higher than that of the light homogenization unit 103 is disposed on the side surface of the light homogenization unit 103 to totally reflect the inside of the light homogenization unit 103. A part of the light is taken out and a sufficient amount of light can be received by the optical sensor 105.

  Furthermore, by arranging the light acquisition unit 104 at an appropriate Z-axis position, the uniformity of the light uniformizing unit emission surface 103b can be increased without any loss of light quantity.

  In FIG. 4, when the water average once 402 and the vertical uniformity 403 are observed, the uniformity is maintained at the Z-axis position of 18 mm and 12 mm or less, respectively. One time is getting worse with waves. In other words, the light acquisition unit 104 increases the unevenness in the amount of light on the light uniformizing unit exit surface 103b. Therefore, it is preferable to select a range in which the horizontal and vertical uniformity is the same as that when the light acquisition unit 104 is not provided as the Z-axis position. In this embodiment, it is preferably 12 mm or less.

  Furthermore, in order to reduce the loss of light quantity, it is sufficient to select a Z-axis position where the light quantity loss is allowable at 12 mm or less. If there is no other restriction such as a mechanism, it is preferable to select 0 mm with the least amount of light loss.

  Further, the light loss can be further reduced by appropriately selecting the refractive index of the light acquisition unit 104. FIG. 5 is a diagram illustrating the boundary between the light homogenizing unit 103 and the light acquiring unit 104 and the state of incident light on the boundary.

  In FIG. 5, a boundary 501 is a boundary between the light uniformizing unit 103 and the light acquiring unit 104, and the region above the paper upper boundary 501 is the light uniformizing unit 103 and the region below the light acquiring unit 104. Light rays in the angle range 502 are incident on the side surface of the light uniformizing unit 103. The critical line 503 is a line indicating the critical angle of light incident on the boundary 501, and the critical angle is an angle obtained by adding the incident angle 204 and the angle range 505.

  Here, when the refractive index of the light acquisition unit 104 with respect to the light uniformizing unit 103 is selected so that the critical line 503 is between the maximum incident angle light ray 201 and the boundary 501 as shown in FIG. The rays in the range 504 are totally reflected and emitted to the angle range 506, and the rays in the angle range 505 are transmitted through the boundary 501 and emitted to the angle range 507.

  For example, if the refractive index of the light obtaining unit 104 is 1.49 with respect to the refractive index of 1.5 of the light uniformizing unit 103, the critical angle is 83.4 degrees with respect to the incident angle 204 of 74 degrees. The angle range 505 is 9.4 degrees, and the angle range 504 is 6.6 degrees. Since the angle range 506 is a reflection of the angle range 504, the angle range 506 is similarly 6.6 degrees, and the angle range 507 is a transmission of the angle range 505, so it is 14.6 degrees from the calculation. Assuming that the orientation characteristics of the light source are constant at any angle, the amount of light incident on the light acquisition unit 104 is 3 mW multiplied by 9.4 degrees / 16 degrees to be 1.8 mW, which is sufficient for the optical sensor 105 to detect the amount of light. The amount of light. Moreover, the light quantity of the light uniformizing part exit surface 103b is 99.56%, and the loss of the light quantity can be further reduced.

  As described above, by selecting the refractive index of the light acquisition unit 104 so that the critical angle is larger than the incident angle 204 and less than 90 degrees, the light sensor 105 can detect the light amount within a range of light amount sufficient for detecting the light amount. Loss can be reduced. Further, since the loss of light quantity is reduced, the influence on the uniformity is further reduced.

  In addition, a present Example shows an example of this invention and is not restricted to this.

  The light source device according to the present invention is useful for an optical system using a light uniformizing unit, and particularly useful for a device that irradiates light uniformly and uniformly.

1 is a configuration diagram of a light source device according to a first embodiment of the present invention. Enlarged view of the light homogenizer 103, the light acquisition unit 104, and the optical sensor 105 in the first embodiment of the present invention External view of the light uniformizing unit 103 and the light acquiring unit 104 in Embodiment 1 of the present invention The graph which shows the light quantity and uniformity in the light uniformizing part output surface 103b in Example 1 of this invention. The figure showing the mode of the incident light to the boundary of the light equalization part 103 and the light acquisition part 104 in Example 1 of this invention, and a boundary Configuration diagram of conventional light source device

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Light source 102 Condensing part 103 Light homogenization part 103a Light homogenization part entrance surface 103b Light homogenization part exit surface 104 Light acquisition part 104a Light acquisition part entrance surface 104b Light acquisition part exit surface 105 Optical sensor 106 Light source light quantity controller 201 Maximum Incident angle Ray 202 Incident angle 203 Emission angle 204 Incident angle 205 Incident angle 206 Perpendicular 207 Perpendicular 208 Perpendicular 301 Side 302 Side 303 Line 304 Line 401 Light quantity 402 Water average once 403 Vertical uniformity 501 Boundary 502 Angular range 503 Critical line 504 Angular range 505 Angle range 506 Angle range 507 Angle range 601 Defect

Claims (5)

A light source that emits visible light;
A condensing unit for condensing visible light of the light source and irradiating the light;
The light from the condensing part incident on the incident surface is totally reflected by the side surface to be uniformed, and the light uniformizing part that is emitted from the exit surface;
A light acquisition unit that is arranged on a side surface of the light homogenization unit and extracts a part of the light that totally reflects inside the light homogenization unit;
A light sensor that receives the light extracted by the light acquisition unit and converts it into an electrical signal;
A light source light amount controller that changes the light amount of the light source in accordance with an electrical signal of the optical sensor;
A light source device comprising: The said light acquisition part is provided with the output surface from which the angle which the incident light and a perpendicular make is less than a critical angle, It is a prism from which the incident light radiate | emits outside from an output surface. Light source device. The light source device according to claim 1, wherein the light acquisition unit has a refractive index equal to or higher than a refractive index of the light uniformization unit. The light acquisition unit is configured such that incident light having a maximum angle between a perpendicular of an incident surface of the light uniformizing unit and incident light incident on the incident surface of the light uniformizing unit is incident on a side surface of the side surface of the light uniformizing unit. 3. The light source device according to claim 1, wherein the light source device has a refractive index that is larger than an angle formed by the perpendicular and smaller than 90 degrees and has a critical angle. The light source device according to claim 1, wherein one side of the incident surface of the light acquisition unit is located on the same plane as the incident surface of the light uniformizing unit.

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