Phosphor member, light source device, projector and chromaticity adjustment method

A phosphor member includes: a phosphor plate that converts a part of excitation light into fluorescent light and emits mixed color light including the fluorescent light and the remaining part of the excitation light; and a reflective layer that is provided on the phosphor plate and that transmits a part of the mixed color light and reflects the remaining part.

TECHNICAL FIELD

The present invention relates to a phosphor member, a light source device, a projector, and a chromaticity adjustment method.

BACKGROUND ART

Some recent projectors include a light source device that combines a phosphor with a solid-state light source such as an LD (Laser Diode) or an LED (Light Emitting Diode) to obtain white light.

Patent Document 1 describes an example of the light source device. The light source device described in Patent Document 1 includes an excitation light source that emits blue excitation light and a phosphor wheel. The phosphor wheel includes a rotatable rotation substrate and a phosphor layer formed on the rotation substrate over the entire periphery. Excitation light is condensed onto the phosphor layer via a condenser lens. The phosphor layer includes a phosphor that is excited by excitation light to emit yellow fluorescent light. Excitation light is irradiated to the phosphor layer in a state in which the rotation substrate is rotated at a constant rotation speed. A part of the excitation light passes through the phosphor layer, and the remaining part is converted into yellow fluorescent light by the phosphor. Blue light (excitation light) that passed through the phosphor layer and yellow fluorescent light that is emitted by the phosphor are synthesized to obtain white light. The white light can be called a mixed light of excitation light and fluorescent light.

LITERATURE OF THE PRIOR ART

Patent Literature

DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention

In the light source device described in Patent Document 1, when the excitation light source is used for a long period of time, the amount of excitation light emitted by the excitation light source may be reduced. This reduction in the amount of excitation light is called deterioration of the excitation light source. In addition, the phosphor has a property in which conversion efficiency of converting excitation energy obtained from excitation light to fluorescent light decreases as the temperature of the phosphor increases. This conversion efficiency of fluorescent light is also called internal quantum efficiency.

When the excitation light source deteriorates, the amount of excitation light decreases, and the amount of blue light included in white light decreases. In addition, since the amount of excitation light irradiated to the phosphor is decreased and the temperature of the phosphor is decreased, the conversion efficiency of fluorescent light is increased and the amount of fluorescent light included in white light is increased. As a result, the hue of white light changes.

As described above, the light source device disclosed in Patent Document 1 has a problem in which the hue of light emitted from the light source device changes due to deterioration of the excitation light source or the like.

In order to adjust the hue of light emitted from the light source device, it is desirable to directly monitor the mixed light of excitation light and fluorescent light to accurately detect the chromaticity of the mixed light.

It is an object of the present invention to provide a phosphor member, a light source device, a projector, and a chromaticity adjustment method which can solve the above-mentioned problems and which can accurately detect the chromaticity of mixed light.

Means for Solving the Problem

In order to achieve the above object, a phosphor member of the present invention includes: a phosphor plate that converts a portion of excitation light into fluorescent light and emits mixed color light that includes the fluorescent light and a remaining part of the excitation light; and a reflective layer that is provided on the phosphor plate and that transmits a part of the mixed color light and reflects a remaining part of the mixed color light.

A first light source device of the present invention includes the above-mentioned phosphor member.

A second light source device of the present invention includes the above-mentioned phosphor member and an optical sensor that measures chromaticity of mixed color light that passed through the reflective layer.

A projector of the present invention includes the above-mentioned light source device, an image forming element in which light that is emitted from the light source device is modulated to form an image and a projection lens that projects the image.

A chromaticity adjustment method of the present invention, which is a method of adjusting chromaticity of a light source device that includes a phosphor member, the phosphor member including: a phosphor plate that converts a portion of excitation light into fluorescent light and emits mixed color light that includes the fluorescent light and a remaining part of the excitation light; and a reflective layer that is provided on the phosphor plate and that transmits a part of the mixed color light and reflects a remaining part of the mixed color light, the method comprising: receiving mixed color light that passed through the reflective layer of the phosphor member to measure chromaticity of the mixed color light; and adjusting the chromaticity of the mixed color light based on a measured result of the chromaticity.

Effects of the Invention

According to the present invention, since a mixed light of excitation light and fluorescent light can be directly monitored, the chromaticity of the mixed light can be accurately detected.

EXAMPLE EMBODIMENTS

Next, example embodiments of the present invention are next described with reference to the accompanying drawings.

First Example Embodiment

FIG. 1AandFIG. 1Bare schematic diagrams for explaining a configuration of a phosphor member according to a first example embodiment of the present invention disclosure.

As shown inFIGS. 1A and 1B, the phosphor member includes phosphor plate10and reflective layer11that is provided on phosphor plate10. Excitation light13enters phosphor plate10(refer toFIG. 1A). Phosphor plate10converts a part of excitation light13into fluorescent light14, and emits mixed light (15a,15b) including fluorescent light14and the remaining part (13a,13b) of the excitation light. Reflective layer11transmits a part of the mixed color light and reflects the remaining part of the mixed color light (refer toFIG. 13).

In the phosphor member of the present example embodiment, the phosphor emits fluorescent light in all directions. Apart of fluorescent light14emitted by the phosphor enters reflective layer11. Reflection layer11reflects a part of the entered fluorescent light and transmits the remaining part. Of excitation light.13, the excitation light, which is not used to excite the phosphor, passes through phosphor plate10to enter reflection layer11. Reflection layer11reflects a part of the entered excitation light and transmits the remaining part.

Mixed color light15athat includes both excitation light13a, which is the reflected light from reflective layer11, and fluorescent light14directed in the opposite direction to reflective layer11is emitted from the first surface of the phosphor member which is the surface on the phosphor plate10side. Mixed color light15bthat includes both fluorescent light14and excitation light13band that passed through reflective layer11is emitted from the second surface which is the surface of the fluorescent member on reflective layer11side. The amount of mixed light15bis sufficiently smaller than the amount of mixed light15a. Since the hue of mixed light15ais the same as the hue of mixed light15b, the chromaticity of mixed light15acan be accurately detected by monitoring mixed light15b.

FIG. 2shows an example of spectral reflection/transmission characteristics of reflective layer11. InFIG. 2, the vertical axis represents reflectance (%) and the horizontal axis represents wavelength (nm). As shown inFIG. 2, in the wavelength range of 420 nm to 700 nm, reflective layer11has a reflectance of 99% or more on average and a transmittance of less than 1% on average. For example, when the wavelength of excitation light is approximately 450 nm, approximately 99% of the excitation light is reflected by reflective layer11, and approximately 1% of the excitation light passes through reflective layer11. When the wavelength of fluorescent light14is 480 nm to 700 nm, approximately 99% of the fluorescent light is reflected by reflective layer11, and approximately 1% of the fluorescent light passes through reflective layer11. In this way, since the amount of mixed light15b, which is monitor light, is sufficiently small compared to the amount of mixed light15a, the ratio of the monitor light can be reduced, and a decrease in brightness can be prevented.

The following modifications can be applied to the phosphor member of the present embodiment.

Phosphor plate10may include a transparent substrate and a phosphor layer that includes a phosphor and that is formed on one surface of the substrate. In this case, reflection layer11may be formed between the substrate and the phosphor layer, or may be formed on a surface of the substrate opposite to the surface on which the phosphor layer is formed.

Phosphor plate10may also include: a plate member that includes first and second segments adjacent to each other in the circumferential direction, wherein the first segment comprises a transmissive substrate and the second segment comprises a metal substrate; and a phosphor layer that includes a phosphor and that is formed circumferentially on the first and second segments. In this case, reflection layer11may be formed between the substrate and the phosphor layer, or may be formed on a surface of the substrate opposite to the surface on which the phosphor layer is formed.

The surface of the substrate opposite to the phosphor layer may be a diffusion surface for diffusing light. The diffusion surface may be, for example, a surface to which surface treatment is applied so that it becomes frosted glass. The substrate may also consist of glass or sapphire or may be a eutectic mixture of glass and sapphire.

Phosphor plate10may be made of a transparent ceramic or a transparent organic material mixed with a phosphor. In this case, reflective layer11may be provided on one surface of the phosphor plate. The transparent ceramic is, for example, transparent alumina or the like. This type of ceramics is also called fine ceramics. The transparent organic material is, for example, a transparent resin or the like.

The phosphor member of the present embodiment can be applied to a light source device. The light source device may include the above-described phosphor member and an optical sensor for measuring the chromaticity of the mixed color light that passed through the reflective layer. The optical sensor may be any sensor capable of measuring the chromaticity of mixed color light. For example, the optical sensor may be a color sensor. Details of the color sensor will be described later.

The light source device may further include a chromaticity adjustment unit that adjusts the chromaticity of mixed color light based on the measurement value of the optical sensor. In this case, the chromaticity adjustment unit may adjust, based on the measurement value of the optical sensor, the rotational frequency of a motor that rotates phosphor plate10. For example, the chromaticity adjustment unit may adjust the rotation speed of phosphor plate10based on the difference between the previous chromaticity measurement value and the current chromaticity measurement value. In addition, the chromaticity adjustment unit may adjust, based on the measurement value of the optical sensor, the gain of the input video signal of the image forming unit in which a plurality of color lights separated from the mixed light are each modulated to form images. For example, the chromaticity adjustment unit may adjust the gain of the input video signal based on the difference between the previous chromaticity measurement value and the current chromaticity measurement value.

The light source device as described above may be applied to a projector. The projector may include the above-mentioned light source device, an image forming element that modulates light emitted from the light source device to form an image, and a projection lens that projects the image.

Second Example Embodiment

FIG. 3A,FIG. 3B, andFIG. 3Care schematic diagrams for explaining a configuration of a phosphor member according to the second example embodiment of the present invention disclosure.FIG. 3Ais a front view.FIG. 3Bis a cross-sectional view of a part indicated by arrow A of a dotted line inFIG. 3A.FIG. 3Cis a cross-sectional view of a part indicated by arrow B of the dotted line inFIG. 3A.

Transparent substrate41and metal substrate42integrally form thin disk-shaped substrate44. Transparent substrate41is formed in a fan shape. A portion obtained by removing fan-shaped transparent substrate41from substrate44is a metal substrate42. Transparent substrate41and metal substrate42may be referred to as first and second circumferentially adjacent segments.

The ratio of metal substrate42to entire substrate44is larger than the ratio of transparent substrate41to entire substrate44. Aluminum which is excellent in heat dissipation and low in cost is preferably used as metal substrate42, for example. Glass or sapphire which is excellent in heat dissipation can be used as transparent substrate41, for example. Transparent substrate41may be made of a eutectic mixture of glass and sapphire.

Phosphor layer43is formed on both transparent substrate41and metal substrate42. As shown inFIG. 3B, reflective layer45is provided between transparent substrate41and phosphor layer43. As shown inFIG. 3C, phosphor layer43is provided on metallic substrates42. Phosphor layer43is provided over the entire circumference. Reflective layer45may be formed on the surface of transparent substrate41opposite to the surface on which the phosphor layer43is formed. The surface of transparent substrate41opposite to phosphor layer43may be a diffusion surface for diffusing light. The diffusion surface may be, for example, a surface to which surface treatment is applied to be a frosted glass.

In the phosphor member of the present embodiment, excitation light is irradiated while phosphor wheel4rotates. The excitation light is sequentially incident on the first segment (a portion of transparent substrate41) and the second segment (a portion of metal substrate42).

In the first segment, a part of fluorescent light emitted by the phosphor in phosphor layer43enters reflective layer45. Reflective layer45reflects a part of the entered fluorescent light and transmits the remaining part. Of excitation light, the excitation light, which is not used to excite the phosphor, passes through phosphor layer43to enter reflective layer45. Reflective layer45reflects a part of the entered excitation light and transmits the remaining part.

First mixed color light that includes both excitation light, which is light reflected by reflective layer45, and fluorescent light directed in a direction opposite to reflective layer45is emitted from the first surface of phosphor wheel4. Second mixed color light that includes both fluorescent light and excitation light that are transmitted through reflective layer45is emitted from the second surface of phosphor wheel4opposite to the first surface. The amount of the second mixed color light is sufficiently smaller than the amount of the first mixed color light. Since the hue of the second mixed color light is the same as the hue of the first mixed color light, the chromaticity of the first mixed color light can be accurately detected by monitoring the second mixed color light. Therefore, the phosphor member of the present embodiment also exhibits the same operation and effect as those of the first example embodiment described above.

In the second segment, a part of fluorescent light emitted by the phosphor in phosphor layer43enters metal substrate42. Metal substrate42reflects the entered fluorescent light toward phosphor layer43. Of excitation light, the excitation light which is not used to excite the phosphor, passes through phosphor layer43to enter metal substrate42. Metal substrate42reflects the entered excitation light toward phosphor layer43. A part of excitation light, which is light reflected by metal substrate42, excites the phosphor, and the remaining part passes through phosphor layer43. As a result, mixed color light that includes both fluorescent light and excitation light is emitted from the surface of phosphor layer43opposite to metal substrate42. The hue of this mixed color light is substantially the same as the hue of the second mixed color light.

Also in the phosphor member of the present example embodiment, the modification of the first example embodiment can be applied.

In phosphor wheel4shown inFIG. 3, substrate44may be composed of only transparent substrate41. In this case, phosphor layer43is formed over the entire circumference of transparent substrate41. Reflective layer45may be formed between phosphor layer43and transparent substrate41, or may be formed on the surface of transparent substrate41opposite to phosphor layer43. The surface of transparent substrate41opposite to phosphor layer43may be a diffusion surface for diffusing light. The diffusion surface may be, for example, a surface to which surface treatment is applied to become frosted glass.

Third Example Embodiment

FIG. 4is a block diagram showing a configuration of a light source device according to a third example embodiment of the present invention.

Referring toFIG. 4, the light source device includes excitation light source101, phosphor member100, optical sensor102, and chromaticity adjustment unit103. Phosphor member100is the phosphor member described in the first or second example embodiment.

Excitation light source101emits excitation light101ato excite the phosphor included in phosphor member100. As excitation light source101, a solid-state light source such as an LED or an LD can be used.

Phosphor member100converts a part of excitation light101ainto fluorescent light, and emits mixed light100a,100bthat include both the fluorescent light and the remaining part of excitation light101a. Mixed color light100ais emitted from the first surface of phosphor member100. Mixed color light100bis emitted from the second surface of phosphor member100which is a surface opposite to the first surface. The amount of mixed color light100ais larger than the amount of mixed color light100b. The hue of mixed light100ais substantially the same as the hue of mixed light100b.

Optical sensor102receives mixed color light100bemitted from the second surface of phosphor member100. Optical sensor102may be any sensor capable of measuring the chromaticity of mixed color light100b. As optical sensor102, a color sensor can be used.

Chromaticity adjustment unit103adjusts the chromaticity of mixed color light100abased on the measurement value of optical sensor102. For example, chromaticity adjustment unit103may adjust the rotational frequency of the motor which rotates the phosphor plate of phosphor member100so that the chromaticity of mixed light100abecomes a predetermined value. In addition, chromaticity adjustment unit103may adjust, based on the measurement value of optical sensor102, the gain of the video signal that is input to the image forming unit that forms an image by modulating a plurality of color lights separated from mixed light100a. For example, chromaticity adjustment unit103may adjust the gain of the input video signal so that the chromaticity of the synthesized light of each color light emitted from the image forming unit becomes a predetermined value.

In the structure shown inFIG. 4, excitation light101aand mixed color light100acan be separated from each other by using polarized light. As an example,FIG. 5shows a configuration in which excitation light101aand mixed color light100aare separated using polarized light.

Referring toFIG. 5, polarizing dichroic mirror104, ¼ wavelength plate105, and condenser lens106are disposed in an optical path between excitation light source101and phosphor member100. Polarizing dichroic mirror104has a property in which, with respect to light in the blue wavelength region, S-polarized light is reflected and P-polarized light is transmitted, and further has a property in which, with respect to non-polarized light, light in at least the yellow wavelength range is transmitted.

S-polarized blue excitation light101areflected by polarizing dichroic mirror104is irradiated onto phosphor member100via ¼ wavelength plate105and condenser lens106. ¼ wavelength plate105can convert linearly polarized light into circularly polarized light or circularly polarized light into linearly polarized light by applying a phase difference of π/2 (=λ/4) to two polarization components that are orthogonal to each other. Blue excitation light101ais converted from S-polarized light to circularly polarized light by passing through ¼ wavelength plate105. Condenser lens106condenses circularly polarized blue excitation light101athat passed through ¼ wavelength plate203on phosphor member100.

Phosphor member100emits mixed color lights100a,100bthat include circularly polarized blue light101band yellow fluorescent light101c. Mixed color light100benters optical sensor102. Mixed color light100apasses through condenser lens106and ¼ wavelength plate105, and then enters polarizing dichroic mirror104. At this time, circularly polarized blue light1bis converted from circularly polarized light to P-polarized light by passing through ¼ wavelength plate105. P-polarized blue light101bpasses through polarizing dichroic mirror104. Non-polarized yellow fluorescent light101calso passes through polarizing dichroic mirror104.

According to the configuration shown inFIG. 5, excitation light101aand mixed color light100acan be separated from each other.

In the configuration shown inFIG. 5, in the portion composed of excitation light source101and polarizing dichroic mirror104, the correspondence relationship between s-polarized light/p-polarized light and reflection/transmission may be reversed.

According to the light source device of the present example embodiment described above, in addition to the effects described in the first example embodiment, it is possible to reduce a change in the hue of the mixed color light when excitation light source101is used for a long period of time.

Moreover, according to the light source device of the present example embodiment, by using the phosphor member100, the following operation and effect can be obtained as compared with the light source device in which the optical sensor is arranged near the optical path of mixed light100a.

Comparative Example

First, the configuration of a comparative example in which the optical sensor is arranged near the optical path of mixed light100aand the problems thereof will be described.

FIG. 6shows a configuration of a light source device of the comparative example. The light source device of this comparative example includes phosphor wheel110, excitation light source101, polarizing dichroic mirror104, ¼ wavelength plate105, condenser lens106, and optical sensor102a. Excitation light source101is composed of, for example, 24 blue LDs in 6 rows and 4 columns. InFIG. 6, the broken line arrow indicates blue laser light emitted from the blue LD at the center. The solid line arrow indicates blue laser light emitted from the blue LD in the peripheral portion.

In phosphor wheel110, a phosphor layer is formed on a metal substrate over the entire circumference. Polarizing dichroic mirror104, ¼ wavelength plate105, and condenser lens106are the same as those shown inFIG. 5. Blue laser light emitted from excitation light source101is irradiated onto the phosphor layer of phosphor wheel110via polarizing dichroic mirror104, ¼ wavelength plate105, and condenser lens106. The phosphor layer converts a portion of blue laser light into fluorescent light. Phosphor wheel110emits mixed color light that includes fluorescent light and blue laser light toward condenser lens106.

Optical sensor102ais arranged near the end of polarizing dichroic mirror104. Optical sensor102areceives the outermost light of the luminous flux of mixed color light that passed through polarizing dichroic mirror104. Here, the mixed color light includes blue laser light emitted by the blue LD in the center portion and blue laser light emitted by the blue LD in the peripheral portion. The blue laser light emitted from the blue LD in the peripheral portion mainly enters optical sensor102a. Therefore, in the chromaticity measurement result of optical sensor102a, the blue LD in the peripheral portion is dominant.

Regarding deterioration of the blue LD, there are individual differences between the blue LDs. Therefore, in the configuration, in which the blue LD in the peripheral portion is dominant, as described above, it is difficult to accurately measure the chromaticity of mixed color light when excitation light source101deteriorates. For example, when only the blue LD in the center portion deteriorates, since the blue LD in the peripheral portion which has been not deteriorated is dominant, the measurement result of optical sensor102ais different from the original chromaticity. On the contrary, when only the blue LD in the peripheral portion deteriorates, since the blue LD in the center portion, which has not been deteriorated, is not sufficiently reflected, the measurement result of optical sensor102ais different from the original chromaticity.

On the other hand, according to the light source device of the present example embodiment, phosphor member100emits mixed color lights100aand100b. Mixed color lights100aand100beach include blue laser light emitted by the blue LD in the center portion and blue laser light emitted by the blue LD in the peripheral portion. The chromaticity of mixed color light100ais the same as the chromaticity of mixed color light100b. Since optical sensor102can receive the entire mixed color light100b, the blue LD in the peripheral portion does not dominate as in the comparative example. Therefore, the chromaticity of mixed color light can be accurately detected.

Fourth Example Embodiment

FIG. 7is a block diagram showing a configuration of a light source device according to a fourth example embodiment of the present invention. Referring toFIG. 7, light source device2includes excitation light source201, polarizing dichroic mirror202, ¼ wavelength plate203, condenser lens204, phosphor wheel205, color sensor207, timer208, motor rotational frequency determination unit209, memory210, motor driving unit211, motor212, and lens213. The portion that includes color sensor207, timer208, motor driving unit211, and motor rotational frequency determination unit209can be referred to as a chromaticity adjustment unit.

Excitation light source201emits s-polarized excitation light toward polarizing dichroic mirror202. As excitation light source201, a solid-state light source such as an LD can be used. Here, excitation light source201includes a blue LD and a collimator lens for collimating the emitted light of the blue LD. When a light source such as an LED which does not have polarized light is used, a polarization conversion element which aligns incident light with s-polarized light is used.

Polarizing dichroic mirror202is disposed so that the blue excitation light (s-polarized light) emitted from excitation light source201is incident at an incident angle of approximately 45°. Polarizing dichroic mirror202has a property in which, with respect to light in the blue wavelength region, s-polarized light is reflected and p-polarized light is transmitted, and further, light in a wavelength region other than the blue wavelength region is transmitted. Polarizing dichroic mirror202reflects the blue excitation light (s-polarized light) from excitation light source201toward ¼ wavelength plate203. In the portion composed of excitation light source201and polarizing dichroic mirror202, the correspondence relationship between s-polarized light/p-polarized light and reflection/transmission may be reversed.

The blue excitation light reflected by polarizing dichroic mirror202is irradiated on phosphor wheel205via ¼ wavelength plate203and condenser lens204. ¼ wavelength plate203can convert linearly polarized light into circularly polarized light or circularly polarized light into linearly polarized light by applying a phase difference of π/2 (=λ/4) to two polarization components that are orthogonal to each other. Condenser lens204condenses the excitation light that passed through ¼ wavelength plate203on phosphor wheel205.

Phosphor wheel205includes a thin disk-shaped transparent substrate. The transparent substrate is rotatable about the center of the disk surface. The transparent substrate is made of sapphire, for example. A reflective layer that has spectral reflection/transmission characteristics as shownFIG. 2is provided on the transparent substrate. A phosphor layer that includes a phosphor that absorbs blue excitation light and emits yellow fluorescent light is provided on the reflective layer. Both the reflective layer and the phosphor layer are formed in an annular shape along the circumferential direction.

In the phosphor layer, the phosphor is excited by the incident blue excitation light. The excited phosphor emits yellow fluorescent light in all directions. Of the yellow fluorescent light emitted in all directions, the yellow fluorescent light directed toward the reflection layer side is reflected toward the condenser lens204side by the reflection layer. Here, since the reflection layer does not constitute the total reflection surface, a part (comma count percent) of the yellow fluorescent light is transmitted through the reflection layer.

A part of blue excitation light that entered the phosphor layer from the condenser lens204side reaches the reflection layer without being absorbed by the phosphor. The reflection layer reflects the arrived blue excitation light toward the phosphor layer. Here, since the reflection layer does not constitute a total reflection surface, a part (comma count percent) of the reached blue excitation light is transmitted through the reflection layer. The blue excitation light reflected by the reflection layer again travels in the phosphor layer toward the condenser lens204side.

In phosphor wheel205, the phosphor layer emits white light, which is mixed color light that includes blue excitation light and yellow fluorescent light, toward condenser lens204. On the other hand, white light, which is mixed color light that includes yellow fluorescent light and blue excitation light that have passed through the reflective layer, is emitted from the back surface of phosphor wheel205, i.e., the back surface of the surface irradiated with the excitation light. The reflective layer is configured to pass a trace amount of white light necessary for color sensor207to measure chromaticity. The chromaticity of white light that passed through the reflection layer substantially matches the chromaticity of white light from the phosphor layer toward the condenser lens204side.

Color sensor207is disposed at the back surface side of phosphor wheel205. Color sensor207has a function of measuring the chromaticity of white light that passed through the reflective layer. As the chromaticity measurement function, the function of an existing chromatometer can be applied. As an example, a configuration for obtaining chromaticity information from the ratio of RGB will be briefly described below.

Color sensor207has a first light receiving surface with a red filter, a second light receiving surface with a green filter, and a third light receiving surface with a blue filter. The red filter transmits light in the red wavelength region of visible light, and absorbs light in other wavelength regions. The green filter transmits light in the green wavelength region of visible light, and absorbs light in other wavelength regions. The blue filter transmits light in the blue wavelength region of visible light, and absorbs light in other wavelength regions. The areas of the first, second and third light receiving surfaces are the same. Color sensor207measures the amount of light (red component) incident on the first light receiving surface, the amount of light (green component) incident on the second light receiving surface, and the amount of light (blue component) incident on the third light receiving surface, respectively. Color sensor207converts the measurement information into chromaticity information. Color sensor207transmits the chromaticity information to motor rotational frequency determination unit209.

Timer208measures the total driving time of light source device2. Here, the total driving time means the total sum of the times during which the phosphor wheel205is irradiated with excitation light.

Motor rotational frequency determination unit209includes memory210. Memory210stores chromaticity data for comparison. In the present example embodiment, as the chromaticity for comparison, memory210stores chromaticity data measured by color sensor207at the time of initial driving, that is, when the driving of light source device2is initially performed. Motor rotational frequency determination unit209performs a chromaticity adjustment process to be described later, determines the rotational frequency of the motor, and sends the information thereof to motor driving unit211.

Motor212rotates phosphor wheel205. Motor driving unit211rotates motor212based on the information of the rotational frequency of the motor transmitted from motor rotational frequency determination unit209.

Next, the operation of light source device2of the present example embodiment for obtaining white light including blue excitation light and yellow fluorescent light will be described in detail.

Excitation light source201emits blue excitation light, which is S-polarized light. Blue excitation light (S-polarized light) emitted from excitation light source201enters polarizing dichroic mirror202. Polarizing dichroic mirror202reflects the blue excitation light (S-polarized light) toward ¼ wavelength plate203. The blue excitation light (S-polarized light) is circularly polarized by passing through ¼ wavelength plate203. The blue excitation light (circularly polarized light) that passed through ¼ wavelength plate203enters condenser lens204. Condenser lens204condenses the blue excitation light (circularly polarized light) on phosphor wheel205.

In phosphor wheel205, a part of the blue excitation light (circularly polarized light) passes through the phosphor layer to reach the reflective layer. The reflection layer reflects the reached blue excitation light (circularly polarized light) toward the condenser lens204side. A part of the blue excitation light (circularly polarized light) reflected by the reflective layer passes through the phosphor layer. The blue excitation light (circularly polarized light) that passed through the phosphor layer enters ¼ wavelength plate203via condenser lens204.

The blue excitation light (circularly polarized light) from the reflection layer passes through ¼ wavelength plate203to become p-polarized light. The blue excitation light (p-polarized light) that passed through ¼ wavelength plate203passes through polarizing dichroic mirror202.

In the phosphor layer, the phosphor is excited by the incident blue excitation light. The excited phosphor emits yellow fluorescent light in all directions. Of the yellow fluorescent light emitted in all directions, the yellow fluorescent light directed toward the reflection layer side is reflected toward the condenser lens204side by the reflection layer. The phosphor layer emits yellow fluorescent light toward the condenser lens204side. The yellow fluorescent light from the phosphor layer passes through condenser lens204, ¼ wavelength plate203, and polarizing dichroic mirror202in this order.

The blue excitation light and the yellow fluorescent light that each passed through polarizing dichroic mirror202enter lens213in the same optical path. Lens213emits white light, which is mixed color light including blue excitation light and yellow fluorescent light. The white light emitted from lens213is light emitted from light source device2.

On the other hand, from the back surface of phosphor wheel205, white light, which is mixed color light that includes blue excitation light and yellow fluorescent light that each passed through the reflective layer, is emitted. The white light emitted from the back surface of phosphor wheel205enters color sensor207.

Next, the chromaticity adjustment operation of light source device2of the present example embodiment will be described in detail.

FIG. 8is a flowchart showing a procedure of the chromaticity adjustment method of light source device2. The chromaticity adjustment method of light source device2will be described with reference toFIGS. 7 and 8.

When the time measured by the timer208reaches a predetermined time, in step S10, color sensor207measures the chromaticity of white light emitted from the back surface of phosphor wheel205. Then, color sensor207outputs chromaticity information based on the measurement result to motor rotational frequency determination unit209. Here, the predetermined time can be arbitrarily set. For example, 100 hours or 200 hours may be set as a predetermined time.

In step S11, motor rotational frequency determination unit209calculates a chromaticity difference, which is the difference between the chromaticity included in the chromaticity information output from color sensor207and the chromaticity for comparison (initial chromaticity) stored in memory210.

In step S12, motor rotational frequency determination unit209determines the rotational frequency of motor212based on the chromaticity difference calculated in step S11. Then, motor rotational frequency determination unit209sends a signal indicating the determined rotational frequency to motor driving unit211. Here, a table, in which the chromaticity difference and the rotational frequency of motor212are stored in association with each other, may be stored in memory210, and motor rotational frequency determination unit209may determine the rotational frequency of motor212with reference to the table.

In step S13, motor driving unit211receives a signal indicating the rotational frequency of the motor from motor rotational frequency determination unit209. Motor driving unit211rotates motor212at the rotational frequency indicated by the received signal (the rotational frequency determined by motor rotational frequency determination unit209).

According to light source device2of the present example embodiment described above, similarly to the third example embodiment, it is possible to reduce a change in the hue of the mixed color light when light source device2is used for a long period of time.

Hereinafter, the operation and effect of light source device2will be described in detail together with the problem in which the color of white light changes.

First, in a light source device that does not have a chromaticity adjustment mechanism, a problem, in which the color of white light changes due to deterioration of an excitation light source because of aging, will be described.

FIG. 9is a chromaticity diagram in which a change in chromaticity of white light emitted from a light source device having no chromaticity adjustment mechanism is plotted on xy chromaticity coordinates. The xy chromaticity coordinates are based on tristimulus values XYZ, which are the three primary colors of a color system. In the xy chromaticity coordinates, the yellow color becomes stronger toward the upper right (in the direction of the arrow in the figure). As can be seen fromFIG. 9, the chromaticity plot position shifts upward and rightward according to the lapse of time. This means that the yellow component of light emitted from the light source device becomes stronger according to the lapse of time.

FIG. 10is a diagram showing a change in the illumination maintenance rate of each of the blue light and the yellow fluorescent light of the light source device that does not have the chromaticity adjustment mechanism. InFIG. 10, the vertical axis represents the illumination maintenance ratio (%), and the horizontal axis represents the driving time of the light source. InFIG. 10, the black diamonds indicate blue light, and the black squares indicate yellow fluorescent light. The illuminance of the blue light and the illuminance of the yellow fluorescence when the driving time is 0 (h) are defined as 100 percent, respectively.

As can be seen fromFIG. 10, the illuminance of each of blue light and yellow fluorescent light decreases according to the lapse of time. The decrease rate of the illuminance differs between blue light and yellow fluorescent light. The decrease rate of the illuminance of the blue light is larger than the decrease rate of the illuminance of the yellow fluorescent light. This means that, with respect to blue light and yellow fluorescent light included in white light emitted by the light source device, the ratio of the yellow fluorescent light to the blue light increases according to the lapse of time. This result is consistent with that ofFIG. 9.

Namely, from the results ofFIGS. 9 and 10, it can be seen that the yellowness of the white light emitted from the light source device increases when the light source device is used for a long period of time.

According to light source device2of the present example embodiment, the problem in which the yellowness of white light becomes strong can be solved as follows.

For example, when timer208reaches a predetermined time, if the yellow component is increased with respect to the blue component due to a change in the ratio of the blue and yellow components included in the white light, motor rotational frequency determination unit209decreases the rotational frequency of motor212. When the rotational frequency of motor212decreases, the rotational speed of phosphor wheel205decreases. When the rotation speed of phosphor wheel205decreases, since the cooling effect accompanying the rotation of the wheel decreases and the irradiation time of excitation light per unit area increases, the temperature of the portion of phosphor wheel205irradiated with the excitation light increases. Thus, the temperature of the phosphor increases, and as a result, the internal quantum efficiency decreases. If the internal quantum efficiency decreases, the amount of yellow fluorescent light emitted by the phosphor decreases. As a result, the yellow component of white light emitted by phosphor wheel205decreases. Therefore, it is possible to prevent a change in chromaticity of white light emitted from light source device2.

In addition, when the phosphor is used for a long period of time, the amount of fluorescent light gradually decreases. Due to deterioration of the phosphor because of aging, the ratio of the blue and yellow components contained in the white light changes. For example, if the degradation rate of the phosphor is higher than the degradation rate of the excitation light source, the ratio of yellow fluorescent light to blue light decreases according to the lapse of time. As a result, in the color component of white light emitted from the light source device, blueness may increase according to the lapse of time.

According to light source device2of the present example embodiment, the problem in which blueness of white light increases can be solved as follows.

For example, when timer208reaches a predetermined time, if the blue component is increased with respect to the yellow component due to a change in the ratio of the blue and yellow components included in white light, motor rotational frequency determination unit209increases the rotational frequency of motor212. When the rotational frequency of motor212increases, the rotational speed of phosphor wheel205increases. When the rotation speed of phosphor wheel205increases, since the cooling effect accompanied by the rotation of the wheel increases and since the irradiation time of the excitation light per unit area decreases, the temperature of the portion of phosphor wheel205irradiated with the excitation light of phosphor wheel205decreases. Thus, the temperature of the phosphor decreases, and as a result, the internal quantum efficiency increases. If the internal quantum efficiency increases, the amount of yellow fluorescent light emitted by the phosphor increases. As a result, the yellow component of white light emitted by phosphor wheel205increases. Therefore, it is possible to prevent a change in chromaticity of white light emitted from light source device2.

Fifth Example Embodiment

The light source device according to the fifth example embodiment of the present invention has the same configuration as the light source device2according to the fourth example embodiment except that the phosphor wheel is different.

In the light source device of the present example embodiment, phosphor wheel4as shown inFIGS. 3A, 3B and 3Cis used. Phosphor wheel4can be used in the same manner as phosphor wheel205described in the fourth example embodiment.

The light source device of the present example embodiment exhibits the same operation and effect as those of light source device2of the fourth example embodiment. However, most of substrate44of phosphor wheel4is made of metal substrate42that has excellent heat radiation properties. Therefore, phosphor wheel4has excellent heat radiation properties as compared with phosphor wheel205. Further, since metal substrate42is inexpensive, the cost can be reduced as compared with phosphor wheel205.

Sixth Example Embodiment

The light source device according to the sixth example embodiment of the present invention has the same configuration as light source device2according to the fourth example embodiment except that the phosphor wheel is different.

In the light source device of the present example embodiment, the phosphor wheel includes a thin disk-shaped substrate and a reflective layer. The substrate is made of a ceramic crystal. The ceramic crystal is made of a transparent material containing a fluorescent material. The transparent material is, for example, an inorganic crystal, glass, or polymer material. The fluorescent material is, for example, a rare earth ion, a transition metal ion, an organic dye molecule, a phosphor, or the like. Inorganic crystals doped with rare earth ions, such as cerium-doped yttrium aluminum garnet (Ce:YAG), or inorganic crystals doped with transition metal ions, such as chromium-doped sapphire or titanium-doped sapphire, can be used as the fluorescent material. In the present example embodiment, for example, a phosphor of Ce:YAG ceramics crystal is used for the substrate. A reflective layer is provided on one surface of the substrate. The reflective layer is the same as that described in the second example embodiment.

The light source device of the present example embodiment also exhibits the same operation and effect as those of light source device2described in the fourth example embodiment.

Seventh Example Embodiment

FIG. 11is a block diagram showing a configuration of a light source device according to a seventh example embodiment of the present invention. The light source apparatus shown inFIG. 11is provided with gain determination unit220instead of timer208and motor rotation speed determination unit209of light source apparatus2of the fourth embodiment. Configurations other than the gain determination unit220are the same as those of the fourth embodiment. InFIG. 11, for convenience, excitation light source201, polarizing dichroic mirror202, ¼ wavelength plate203, condenser lens204, motor driver211, and lens213are omitted.

Display panel222and input signal223constitute a part of a projector to which the light source device of the present example embodiment is applied. Display panel222is, for example, a liquid crystal display panel or a DMD. Display panel222forms an image for each color light separated from mixed color light (white light), which is light emitted from phosphor wheel205. In the case of the single plate type, display panel222forms images of respective colors in a time-division manner. In addition, a plurality of display panels which modulate a plurality of color lights to form an image, respectively, may be provided as display panel222, the plurality of color lights being separated from mixed color light which is light emitted from phosphor wheel205. Input signal223is an input video signal and includes a video signal corresponding to each color light. For example, input signal223includes a video signal corresponding to each color of RGB.

Gain determination unit220includes memory221. Memory221stores chromaticity data for comparison. In the present example embodiment, as the chromaticity for comparison, memory210stores chromaticity data measured by color sensor207at the time of initial driving (that is, when the light source device is firstly driven).

Gain determination unit220adjusts the gain of input signal223of display panel222based on the measurement value of color sensor207. For example, gain determination unit220adjusts the gain of the input video signal so that the chromaticity of synthesized light of each color light emitted from display panel222becomes a predetermined value. This gain adjustment process can be referred to as a chromaticity adjustment process.

As an example,FIG. 12shows a procedure of a RGB gain adjustment process. Hereinafter, the RGB gain adjustment process will be described in detail with reference toFIGS. 11 and 12.

In step S20, color sensor207measures the chromaticity of white light emitted from the back surface of phosphor wheel205. Color sensor207outputs chromaticity information based on the measurement result to gain determination unit220. Here, the measurement start timing of color sensor207can be arbitrarily set.

In step S21, gain determination unit220calculates a chromaticity difference, which is a difference between the chromaticity included in the chromaticity information output from color sensor207and the chromaticity for comparison (initial chromaticity) stored in memory221.

In step S22, gain determination unit220determines RGB gain adjustment values based on the chromaticity difference calculated in step S21. For example, gain determination unit220determines the RGB gain adjustment values based on the chromaticity difference so that the hue of synthesized light (projection light) of each color light emitted from display panel222does not change, in other words, so that the chromaticity of the synthesized light becomes a predetermined value. Here, a table, in which the chromaticity difference and the gain adjustment values of RGB are stored in association with each other, may be stored in memory221, and gain determination unit220may determine the gain adjustment values of RGB with reference to the table.

In step S23, gain determination unit.220performs gain adjustment for each video signal of RGB based on the gain adjustment values of RGB determined in step S22.

The light source device of the present embodiment also exhibits the same operation and effect as those of the fourth example embodiment.

In the light source device of the present embodiment, the configurations of the fifth example embodiment and the sixth example embodiment may be applied.

Eighth Example Embodiment

FIG. 13is a block diagram showing a configuration of DLP (Digital Light Processing) projector5according to an eighth example embodiment of the present invention. As shown inFIG. 13, projector5includes light source device2, color wheel501, light tunnel502, TIR prism (total internal reflection prism)503, DMD (Digital Micromirror Device)504, projection lens505, and lens group506. Light source device2has been described in the fourth example embodiment.

Color wheel501has a thin disk shape and is rotatable about a central axis of the disk surface. Red, green and blue filters are each provided on the surface of color wheel501. The red, green and blue filters are arranged in order in the circumferential direction. The red filter has a characteristic in which light in a red wavelength region is transmitted and light in a wavelength region other than the red wavelength region is absorbed. The green filter has a characteristic in which light in a green wavelength region is transmitted and light in a wavelength region other than the green wavelength region is absorbed. The blue filter has a characteristic in which light in a blue wavelength region is transmitted and light in a wavelength region other than the blue wavelength region is absorbed.

Light tunnel502is disposed at a position where each monochromatic light that passed through color wheel501can enter. Light tunnel502is an element that homogenizes the illuminance distribution of incident light.

TIR prism503is disposed at a position where light emitted from light tunnel502can enter. TIR prism503is a laminate of two triangular prisms, and includes an air layer between the prisms.

DMD504is disposed at a position where light from TIR prism503can enter. DMD504includes an imaging surface comprising a plurality of micromirrors that are arranged in two dimensions. DMD504forms images by modulating incident light in accordance with input video signals. DMD504is an example of an imaging device.

In projector5, light source device2emits white light. The white light emitted from light source device2enters color wheel501. When color wheel501rotates, white light is sequentially irradiated to the red, green, and blue filters of the color wheel501. Color wheel501sequentially emits red light, green light, and blue light.

Red light, green light, and blue light emitted from color wheel501enter light tunnel502. In light tunnel502, the illuminance distributions of the entered red light, green light, and blue light are made uniform. Light tunnel502sequentially emits red light, green light, and blue light.

Red light, green light, and blue light emitted from light tunnels502enter DMD504through TIR prisms503. DMD504modulates the red light to form a red image, modulates the green light to form a green image, and modulates the blue light to form a blue image. DMD504sequentially emits red image light, green image light, and blue image light. The red image light, the green image light, and the blue image light enter projection lens505via TIR prism503. Projection lenses505overlappingly projects the red image, the green image, and the blue image formed by DMD504on a screen (not shown).

In projector5shown inFIG. 13, instead of light source device2, any of the light source devices of the third example embodiment, the fifth example embodiment, the sixth example embodiment, and the seventh example embodiment may be used.

Ninth Example Embodiment

FIG. 14is a block diagram showing a configuration of an LCD (liquid crystal display) projector6according to a ninth example embodiment of the present invention disclosure. As shown inFIG. 14, projector6includes light source device2, fly-eye lens system601, dichroic mirrors602R and602G, lens603, mirror604, lens605, mirror606, mirror607, lenses608R,608G, and608B, liquid crystal displays609R,609G, and609B, cross dichroic prism610, and projection lens611. Light source device2has been described in the fourth example embodiment.

Fly-eye lens system601homogenizes the illuminance distribution of light that entered fly-eye lens system601and emits the light. Fly-eye lens system601is disposed at a position where white light emitted from light source device2can enter.

Dichroic mirror602R has a characteristic in which light in a red wavelength region is reflected and light in a wavelength region other than the red wavelength region is transmitted. Dichroic mirror602G has a characteristic in which light in a green wavelength region is reflected and light in a wavelength region other than the green wavelength region is transmitted.

Dichroic mirror602R is disposed so that white light emitted by fly-eye lens system601is incident at an incident angle of approximately 45°. Red light reflected by dichroic mirror602R enters liquid crystal display609R via mirror607and lens608R.

Dichroic mirror602G is disposed so that light transmitted through dichroic mirror602R (including blue and green components) is incident at an incident angle of approximately 45°. Green light reflected by dichroic mirror602G enters liquid crystal display609G via lens608G.

Liquid crystal display609R forms a red image by modulating incident red light in accordance with an input video signal (R). Liquid crystal display609B forms a blue image by modulating incident blue light in accordance with an input video signal (B). Liquid crystal display609G forms a green image by modulating incident green light in accordance with an input video signal (G).

The red image light emitted from liquid crystal display609R, the blue image light emitted from liquid crystal display609B, and the green image light emitted from liquid crystal display609G enter projection lens611through cross dichroic prism610. Cross dichroic prism610combines the image lights of the respective colors emitted from liquid crystal displays609R,609G, and609B. Here, liquid crystal displays609R,609G, and609B are examples of image forming elements.

Projection lens611projects the red image light, the blue image light, and the green image light that entered from cross dichroic prism610on a screen (not shown).

In projector6shown inFIG. 14, instead of light source device2, any of the light source devices of the third example embodiment, the fifth example embodiment, the sixth example embodiment, and the seventh example embodiment may be used.

Each of the embodiments described above is an example of the present invention, and is not intended to limit the present invention. The configuration of the present invention can be changed within the scope of technical ideas that can be understood by any person of ordinary skill in the art.

Moreover, the present invention may take forms such as, but not limited to, the following Supplementary Notes 1 to 17.

A phosphor member comprising:

a phosphor plate that converts a portion of excitation light into fluorescent light and emits mixed color light that includes the fluorescent light and a remaining part of the excitation light; and

a reflective layer that is provided on the phosphor plate and that transmits a part of the mixed color light and reflects a remaining part of the mixed color light.

The phosphor member according to Supplementary Note 1, wherein the phosphor plate includes:a transparent substrate; and

a phosphor that is formed on one surface of the substrate and contains a phosphor.

The phosphor member according to Supplementary Note 1, wherein the phosphor plate includes:

a plate member that includes first and second segments adjacent to each other in a circumferential direction, wherein the first segment comprises a transmissive substrate and the second segment comprises a metal substrate; and

a phosphor layer that is formed on the phosphor plate along the circumferential direction and contains a phosphor.

The phosphor member according to Supplementary Note 2 or 3, wherein the reflective layer is formed between the substrate and the phosphor layer.

The phosphor member according to Supplementary Note 4, wherein a surface of the substrate opposite to the phosphor layer is a diffusion surface that diffuses light.

The phosphor member according to Supplementary Note 2 or 3, wherein the reflective layer is formed on a surface of the substrate opposite to a surface on which the phosphor layer is formed.

The phosphor member according to any one of Supplementary Notes 2 to 6, wherein the substrate is made of glass or sapphire or a eutectic mixture of glass and sapphire.

The phosphor member according to Supplementary Note 1, wherein the phosphor plate is made of a transmissive ceramic or a transmissive organic material in which a phosphor is mixed, and the reflective layer is provided on a first surface which is one surface of the phosphor plate.

A light source device comprising the phosphor member according to any one of Supplementary Notes 1 to 8.

A light source device comprising:

the phosphor member according to any one of Supplementary Notes 1 to 8; and

an optical sensor that measures chromaticity of mixed color light that passed through the reflective layer.

The light source device according to Supplementary Note 10, further comprising a chromaticity adjustment unit that adjusts the chromaticity of the mixed color light based on a measurement value of the optical sensor.

The light source device according to Supplementary Note 11, wherein the chromaticity adjustment unit adjusts, based on the measurement value of the optical sensor, a rotational frequency of a motor that rotates the phosphor plate.

The light source device according to Supplementary Note 11, wherein the chromaticity adjustment unit adjusts, based on the measurement value of the optical sensor, a gain of an input video signal of an image forming unit in which a plurality of color lights, which are separated from the mixed color light, are respectively modulated to form an image.

A projector comprising:

the light source device according to any one of Supplementary Notes 9 to 13;

an image forming element in which light that is emitted from the light source device is modulated to form an image; and

a projection lens that projects the image.

A method of adjusting chromaticity of a light source device that includes a phosphor member, the phosphor member including: a phosphor plate that converts a portion of excitation light into fluorescent light and emits mixed color light that includes the fluorescent light and a remaining part of the excitation light; and a reflective layer that is provided on the phosphor plate and that transmits a part of the mixed color light and reflects a remaining part of the mixed color light, the method comprising:

receiving mixed color light that passed through the reflective layer of the phosphor member to measure chromaticity of the mixed color light; and

adjusting the chromaticity of the mixed color light based on a measured result of the chromaticity.

The chromaticity adjustment method of Supplementary Note 15, further comprising adjusting a rotation speed of the phosphor plate based on a difference between a previous chromaticity measurement and a current chromaticity measurement.

The chromaticity adjustment method according to Supplementary Note 15, further comprising adjusting, based on a difference between a previous chromaticity measurement and a current chromaticity measurement, a gain of an input video signal of an image forming unit in which a plurality of color lights, which are separated from the mixed color light, are respectively modulated to form an image.

This application claims the benefits of priority based on PCT/JP2017/42264 filed Nov. 24, 2017, the disclosures of which are incorporated herein by reference in their entirety.

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