JP2015169725A - Light source module and projection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light source module capable of properly controlling a light volume even when accuracy of arrangement of a light source element and light reduction component is low.SOLUTION: The light source module has a laser element for emitting light. The light emitted from the laser element enters a first light reduction member. The first light reduction member is configured so that its permeability is reduced at a constant ratio in a first direction in an incidence surface, and transmits light which enters with permeability corresponding to the incidence position. The light transmitted the first light reduction member then enters a second light reduction member. The second light reduction member is configured so that its permeability is increased at the same constant ratio with that of the first light reduction member in the first direction in the incidence surface, and transmits the light entered with permeability corresponding to the incidence position. Driving means drives the first light reduction member and/or second light reduction member along the first direction.

Description

  The present invention relates to a light source module including a laser element.

  Usually, in a display device using a laser element, the amount of light emitted from the laser element is changed according to the image to be displayed. Specifically, the light amount of the laser element is changed by controlling the drive current of the laser element. By the way, depending on the display device, it may be used in such a way as to greatly reduce the light quantity of the laser element. For example, in a display device (in one example, an in-vehicle head-up display) used in an environment where the illuminance changes greatly, the light intensity tends to be set to be much lower during nighttime use than during daytime use. is there. If the drive current of the laser element is lowered in order to realize such a low light quantity, there is a kink that causes the output of the laser element to become unstable (a phenomenon in which the relationship between the drive current and the optical output becomes nonlinear). May occur. When a kink occurs, it becomes difficult to control the low luminance gradation and the image may flicker.

  Such a kink can be suppressed by changing the amount of light by a method different from the method for controlling the drive current and the like. For example, Patent Document 1 discloses that the same polarization beam splitter having a different transmission amount according to the polarization component is symmetrical to a plane orthogonal to the rotation axis of the inner barrel arranged rotatably in the outer barrel and the plane. And the linearly polarized light from the laser light source is made incident so that the optical axis coincides with the rotation axis of the inner lens barrel, and the inner lens barrel is rotated to a desired position, whereby the outgoing optical axis And a technique for adjusting the amount of outgoing light while matching the incident optical axis.

JP 11-258526 A

  However, in the technique described in Patent Document 1 described above, since the internal lens barrel that accommodates the two polarization beam splitters is rotated, the number of parts increases, and the apparatus tends to be large. In addition, in the technique described in Patent Document 1, it is necessary to accurately arrange the polarization beam splitter so that the optical axis of the emitted light does not change in conjunction with the rotation of the inner barrel.

  The present invention has been made to solve the above-described problems, and provides a light source module capable of appropriately controlling the amount of light even if the accuracy of the arrangement of the light source element and the light reducing component is poor. Is the main purpose.

  The invention described in claim is a light source module that emits a set amount of light, and is arranged at a position where the light is incident and a laser element that emits light, and is constant in a first direction on the incident surface of the light A first dimming member having a transmittance that decreases at a rate, and a position where light transmitted through the first dimming member is incident, and the constant rate in the first direction on the incident surface of the light The first dimming member and / or the second dimming member along the first direction so as to change the position where the light is incident and the second dimming member having a transmittance that rises at And driving means for driving.

It is a block diagram which shows schematic structure of the light source module which concerns on 1st Example. The structure of an ND filter part is shown. The top view and transmission characteristic of ND filter are shown. The state of light reduction by the ND filter is shown. It is a graph which shows each transmission characteristic and synthetic | combination transmission characteristic of ND filter. The specific structural example of the light source module which concerns on 1st Example is shown. The structure of the ND filter part by the modification of 1st Example is shown. The schematic structure of the light source module which concerns on 2nd Example is shown.

  In a preferred embodiment of the present invention, the light source module that emits a set amount of light is disposed at a position where the light is incident, a laser element that emits light, and a constant ratio in the first direction on the light incident surface. And a first dimming member having a transmittance that decreases at a position where the light transmitted through the first dimming member is incident, and the light is incident at a certain ratio in the first direction on the incident surface. The first dimming member and / or the second dimming member along the first direction so that the second dimming member having the increasing transmittance and the position where the light is incident are changed. Driving means for driving.

  The light source module includes a laser element that emits light. The light emitted from the laser element enters the first dimming member. The first dimming member is configured such that the transmittance thereof decreases at a constant rate in the first direction on the incident surface, and transmits the incident light at a transmittance corresponding to the incident position of the light. The light transmitted through the first dimming member is incident on the second dimming member. The second dimming member is configured such that the transmittance thereof increases in the first direction on the incident surface at the same constant rate as that of the first dimming member, and the transmission corresponding to the incident position of light. Transmits incident light at a rate. The driving means drives the first dimming member and / or the second dimming member along the first direction. In a preferred example, the dimming member is an ND (dimming) filter.

  The light source module diminishes the light emitted from the laser element to the light amount set by the first and second light reducing members and emits the light. Here, the first dimming member and the second dimming member are configured such that the transmittance changes in the opposite direction with respect to the change in the position in the first direction. Since the change in the transmittance at the first dimming member and the change in the transmittance at the second dimming member due to the above cancel each other, the influence of the shift in the incident position can be suppressed.

  In a preferred example of the light source module, the driving unit moves the dimming member in a direction parallel to the incident surface according to the set light amount. In another preferred example, the driving unit rotates the dimming member within the incident surface according to the set light amount.

  In one aspect of the light source module, the driving unit drives the first dimming member and the second dimming member in opposite directions. Thereby, the light from a laser element can be reduced to the set light quantity.

  In another aspect of the light source module, the laser element is a plurality of laser elements that emit light of different wavelengths, and the dimming member attenuates a combined light from the plurality of laser elements. To do. In this aspect, it is possible to reduce the light while maintaining the color balance by reducing the influence of the positional deviation between the laser beams having a plurality of wavelengths.

  In a preferred example, the above light source module is used as a light source of a projection apparatus.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

[First embodiment]
FIG. 1 is a block diagram showing a schematic configuration of a light source module 10 according to the first embodiment. As shown in FIG. 1, the light source module 10 includes a laser element 1, an ND filter unit 2, an actuator 3, and a control unit 4. The light source module 10 is applied to, for example, a projection device (projector), a head-up display, a head-mounted display, an optical pickup, and the like.

  The laser element 1 includes a laser diode (LD) that emits RGB three-color laser light, and directs the red laser light Lr, the green laser light Lg, and the blue laser light Lb toward an ND (Neutral Density) filter unit 2. Exit. In the following description, when it is not necessary to distinguish the colors of the laser beams, they are simply referred to as “laser beams L”. In addition, laser light is sometimes simply referred to as “light”.

  The ND filter unit 2 includes two rectangular ND (darkening) filters 2A and 2B having the same shape (see FIG. 2). The ND filters 2A and 2B are filters that transmit all wavelengths of visible light with a predetermined transmittance. In the ND filters 2A and 2B, the pattern of the ND film is formed on the incident surface so that the transmittance (optical density) gradually varies depending on the part.

  The actuator 3 drives the ND filters 2A and 2B without changing the direction of the incident surface, and changes the position on the ND filter where the light is incident. The actuator 3 is an example of the “driving means” in the present invention.

  The control unit 4 controls the actuator 3 according to the set light amount, that is, the light amount to be emitted from the light source module 10. The control unit 4 controls the current or voltage input to the laser element 1. In this case, the control unit 4 sets the current or voltage input to the laser element 1 to a current value that does not affect the kink in the laser element 1 (a phenomenon in which the relationship between the current or voltage and the optical output becomes nonlinear) or Hold above voltage. Specifically, a threshold value for a current or voltage that causes the kink in the laser element 1 is obtained in advance, and the control unit 4 inputs a current or voltage that is equal to or greater than the threshold value to the laser element 1.

  Next, the ND filter unit 2 will be described in detail. FIG. 2 shows the configuration of the ND filter unit 2. The ND filters 2 </ b> A and 2 </ b> B are disposed with their incident surfaces directed perpendicular to the optical axis of the light emitted from the laser element 1, and the light of the laser element 1 is incident thereon. The ND filters 2A and 2B are arranged so that the incident surfaces on the respective laser elements 1 side are parallel to each other. The ND filter 2A is disposed at a position where the light L emitted from the laser element 1 is incident, and the ND filter 2B is disposed at a position where the light L transmitted through the ND filter 2A is incident. Thus, the light emitted from the laser element 1 passes through the ND filter 2A and the ND filter 2B in order.

  3A and 3B are front views showing the incident surfaces of the ND filters 2A and 2B, respectively, that is, the incident surfaces viewed from the laser element 1 side. 3C and 3D show the transmission characteristics of the ND filters 2A and 2B, respectively. As shown in FIGS. 3A and 3B, the ND filters 2A and 2B have a rectangular shape, and the transmittance continuously changes along the longitudinal (long side) direction, that is, the X direction in the drawing. Configured as a gradation filter.

  Specifically, as illustrated in FIG. 3C, the ND filter 2A is configured such that the transmittance continuously increases along a predetermined linear direction (X direction) on the incident surface. Note that the transmittance does not change in the direction perpendicular to the X direction (Y direction). Specifically, the ND filter 2A is configured such that the transmittance gradually increases from left to right in FIG. For example, the ND filter 2 is configured such that the transmittance changes within a range of 0% to 100%.

  On the other hand, as shown in FIG. 3D, the ND filter 2B is configured such that the transmittance continuously decreases along a predetermined linear direction (X direction) on the incident surface. Note that the transmittance does not change in the direction perpendicular to the X direction (Y direction). Specifically, the ND filter 2B is configured such that the transmittance gradually decreases from left to right in FIG. For example, the ND filter 2 is configured so that the transmittance changes within a range of 100% to 0%.

  As understood from FIG. 3, the ND filters 2A and 2B have the same rate of change in transmittance, and the direction of the change is reversed. That is, the ND filters 2A and 2B are obtained by inverting the direction in which the transmittance changes. Actually, one of the same two filters may be arranged by rotating 180 degrees about the normal to the incident surface.

  Next, the dimming operation by the ND filters 2A and 2B will be described. The actuator 3 moves the ND filters 2A and 2B in the direction parallel to the incident surfaces of the ND filters 2A and 2B, that is, in the X direction in which the transmittance continuously changes, as indicated by an arrow D1 in FIG. . The control unit 4 controls the actuator 3 so as to move the ND filters 2A and 2B to desired positions based on the amount of light to be emitted from the light source module 10. Specifically, the control unit 4 controls the actuator so that the light on the ND filters 2 </ b> A and 2 </ b> B that can obtain a desired transmittance according to the amount of light to be emitted from the light source module 10 is irradiated with light from the laser element 1. ND filters 2A and 2B are moved through 3 respectively. For example, the control unit 4 combines the control amount of the actuator 3 (for example, drive voltage or drive current, which corresponds to the amount or direction of movement of the ND filters 2A and 2B by the actuator 3) and the ND filters 2A and 2B. The relationship with the transmittance (transmittance corresponding to the location on the ND filters 2A and 2B on which the light of the laser element 1 is incident at the position of the ND filters 2A and 2B arranged by driving the actuator 3) is stored in advance. The actuator 3 is controlled based on the relationship and the amount of light to be emitted from the light source module 10.

  FIG. 4 shows an example of transmittance control by the ND filters 2A and 2B. FIG. 4A shows a case where 100% of the emitted light L (Lr, Lg, Lb) from the laser element 1 is transmitted by the ND filters 2A, 2B. In this case, the control unit 4 moves the ND filters 2A and 2B so that the emitted light L passes through a position where the transmittance of the ND filter 2A is 100% and a position where the transmittance of the ND filter 2B is 100%. . As a result, the combined transmittance of the two ND filters 2A and 2B is 100%.

  FIG. 4B shows a case where 40% of the emitted light from the laser element 1 is transmitted by the ND filters 2A and 2B. In this case, the control unit 4 moves the ND filters 2A and 2B so that the emitted light L passes through the position where the transmittance of the ND filter 2A is 63% and the position where the transmittance of the ND filter 2B is 63%. . As a result, the combined transmittance of the two ND filters 2A and 2B is about 40%.

  FIG. 4C shows a case where 10% of the light emitted from the laser element 1 is transmitted by the ND filters 2A and 2B. In this case, the control unit 4 moves the ND filters 2A and 2B so that the emitted light L passes through the position where the transmittance of the ND filter 2A is 33% and the position where the transmittance of the ND filter 2B is 33%. . As a result, the combined transmittance of the two ND filters 2A and 2B is about 10%.

  Next, the effect of using two stages of ND filters as in this embodiment will be described. In the case where the ND filter has one stage, if there is a deviation in the optical axis of each color laser beam, the transmittance largely changes depending on the position. Thereby, the color balance of each color laser beam will collapse. This problem can be solved by using two stages of ND filters.

  FIG. 5 shows the transmission characteristics of the individual ND filters 2A and 2B and the combined transmission characteristics of the two ND filters 2A and 2B when the ND filter has two stages. By using two stages of ND filters, the combined transmittance can flatten the change in transmittance with respect to the change in the incident position of the laser light near the top of the combined transmittance rather than the transmittance of each ND filter. Therefore, by making the laser light incident at a position where the combined transmittance is substantially flat, the total amount of light reduction by the two-stage ND filters 2A and 2B becomes substantially the same even if there is a deviation in the optical axis of each color laser light. Therefore, it is possible to reduce the light while maintaining the color balance.

  For example, in the example of FIG. 4B, it is assumed that the optical axis of the laser Lr is shifted from the optical axis of the laser light Lg by a predetermined distance d toward the back side in the drawing. In this case, in the first-stage ND filter 2A, the transmittance with respect to the laser light Lr is lower than the transmittance with respect to the laser light Lg by the distance d. However, since the ND filters 2A and 2B are configured so that the transmittance changes in the opposite direction at the same rate, in the second-stage ND filter 2B, the transmittance with respect to the laser light Lr is higher than the transmittance with respect to the laser light Lg. Is also increased by the distance d. That is, the transmittance error generated in the first-stage ND filter 2A due to the deviation of the optical axis of the laser light Lr from the optical axis of the reference laser light Lg is canceled out by the second-stage ND filter 2B. The total light reduction amount of the laser beams Lg and Lr by the two-stage ND filters 2A and 2B is substantially the same. Since such an effect can be obtained for each color of laser light, deviation in color balance can be prevented.

  FIG. 6 shows a specific configuration example of the light source module 10 according to the first embodiment. The light source module 10 is used as a light source of a projector (projection apparatus) including an image signal input unit to which an image signal corresponding to an image to be displayed is input, a MEMS mirror that scans light from the light source module 10, and the like. The

  The light source module 10 includes a red laser element 1R, a green laser element 1G, a blue laser element 1B, ND filters 2A and 2B, and a dichroic prism 5. In addition, illustration of the actuator 3 and the control part 4 is abbreviate | omitted in FIG.

  The laser element 1R emits red laser light Lr, the laser element 1G emits green laser light Lg, and the laser element 1B emits blue laser light Lb. In FIG. 6, the red laser beam Lr is represented by a solid line, the green laser beam Lg is represented by a broken line, and the blue laser beam Lb is represented by a one-dot chain line.

  The dichroic prism 5 is provided with reflecting surfaces 5a and 5b. The reflecting surface 5a reflects the red laser light Lr and transmits the green laser light Lg. The reflection surface 5b reflects the red laser light Lr and the green laser light Lg and transmits the blue laser light Lb. Thereby, each color laser beam is guided by the dichroic prism 5 so that all of the red laser beam Lr, the green laser beam Lg, and the blue laser beam Lb emitted from the laser elements 1R, 1G, and 1B are transmitted to the ND filters 2A and 2B. Incident. That is, the combined light obtained by combining the red laser light Lr, the green laser light Lg, and the blue laser light Lb is incident on the ND filters 2A and 2B.

  The ND filters 2A and 2B are as described above, and are controlled by the actuator 3 and the control unit 4. Specifically, the control unit 4 controls the movement of the ND filters 2A and 2B by the actuator 3 based on the brightness of the image to be projected by the projector, and supplies current to each of the laser elements 1R, 1G, and 1B. Control. As a result, the light source module 10 emits a set amount of light.

(Modification 1)
In the above embodiment, both the ND filters 2A and 2B are moved by the actuator 3. However, when a wide dimming range is not required, either one of the ND filters may be fixed. For example, only the ND filter 2A is movable and the ND filter 2B is fixed. Even in this case, since the change in the combined transmittance is flatter than the change in the transmittance of the ND filter 2A, even if there is a deviation in the optical axis of each color laser beam, it is possible to reduce the light while maintaining the color balance. .

(Modification 2)
In the above embodiment, the ND filters 2A and 2B are rectangular gradation filters, but a circular gradation filter may be used instead. FIG. 7 shows an example using circular ND filters 7A and 7B. As shown in the figure, the ND filters 7A and 7B are configured in a disc shape composed of a circle centered on the center point C.

  The ND filter 7A is configured as a gradation filter whose transmittance continuously changes along a circumferential direction 22 of a circle centered on the center point C on the incident surface. Specifically, the ND filter 7 </ b> A is configured so that the transmittance decreases along the circumferential direction 22. The transmittance does not change in the radial direction 21 of the circle centered on the center point C.

  The ND filter 7B is also configured as a gradation filter whose transmittance continuously changes along the circumferential direction 22 of a circle centered on the center point C on the incident surface. However, the ND filter 7B is configured so that the transmittance increases along the circumferential direction 22 contrary to the ND filter 7A. The transmittance does not change in the radial direction 21 of the circle centered on the center point C.

  In this case, the actuator 3 rotates the ND filters 7A and 7B around the center point C as indicated by an arrow D2 in FIG. The actuator 3 rotates the ND filters 7A and 7B in the reverse direction. Further, the control unit 4 controls the actuator 3 based on the amount of light to be emitted from the light source module 10 so that the ND filters 7A and 7B each have a desired rotation angle. Specifically, the control unit 4 controls the actuator so that the light on the ND filters 7A and 7B from which a desired transmittance corresponding to the amount of light to be emitted from the light source module 10 is obtained is irradiated with light from the laser element 1. 3, the ND filters 7A and 7B are rotated.

(Modification 3)
In the above-described embodiment, the configuration in which the light of the laser element 1 is directly incident on the ND filter 2 is shown. However, an optical element (such as a lens, mirror, or prism) is interposed between the laser element 1 and the ND filters 2A and 2B. The light from the laser element 1 may be incident on the ND filters 2A and 2B via the optical element.

[Second Embodiment]
FIG. 8 shows a configuration of the light source module 20 of the second embodiment. The light source module 20 of the second embodiment includes only the ND filter 2A. In the second embodiment, in place of the ND filter 2B, the color balance at the time of light control is maintained by correcting the light emission amount of each color laser element according to the position of the optical axis of each color laser light L.

  Specifically, as shown in FIG. 8, a half mirror 31 is arranged between the laser element 1 and the ND filter 2 </ b> A, and a part of each color laser beam L is reflected by the half mirror 31 to enter the light receiving unit 32. Let The light receiving unit 32 detects the amount of incident laser light L and sends it to the control unit 4. The control unit 4 detects the positional deviation of each color laser beam L from the reference position based on the light amount of each color laser beam L detected by the light receiving unit 32.

  Then, the control unit 4 calculates a necessary correction amount for each color laser beam according to the direction and amount of deviation of each color laser beam L from the reference position. Specifically, the current or voltage supplied to each color laser element is corrected with reference to a correction table set based on data indicating the transmission characteristics of the ND filter 2A. That is, the light amount of each color laser beam L emitted from the laser element 1 is changed so as to correct the light amount shift due to the positional shift from the reference position. As a result, the second embodiment can also reduce the light while maintaining the color balance.

DESCRIPTION OF SYMBOLS 1 Laser element 2 ND filter part 2A, 2B, 7A, 7B ND filter 3 Actuator 4 Control part 7A, 7B ND filter 10, 20 Light source module 31 Half mirror 32 Light receiving part

Claims (7)

A light source module that emits a set amount of light,
A laser element that emits light;
A first dimming member disposed at a position where the light is incident and having a transmittance that decreases at a constant rate in a first direction on the incident surface of the light;
A second dimming member that is disposed at a position where light transmitted through the first dimming member is incident and has a transmittance that increases in the first direction in the first direction on the light incident surface;
Driving means for driving the first dimming member and / or the second dimming member along the first direction so as to change a position where light is incident;
A light source module comprising:   The light source module according to claim 1, wherein the dimming member is an ND filter.   The light source module according to claim 1, wherein the driving unit moves the dimming member in a direction parallel to the incident surface according to the set light amount.   The light source module according to claim 1, wherein the driving unit rotates the dimming member within the incident surface according to the set light amount.   5. The light source module according to claim 1, wherein the driving unit drives the first dimming member and the second dimming member in directions opposite to each other. 6. The laser elements are a plurality of laser elements that emit light having different wavelengths,
The light source module according to claim 1, wherein the dimming member diminishes combined light of the light from the plurality of laser elements.   A projection apparatus comprising the light source module according to claim 1.