EP4689766A1

EP4689766A1 - Illumination device and image projection apparatus

Info

Publication number: EP4689766A1
Application number: EP24715275.4A
Authority: EP
Inventors: Takashi Sasaki; Kazuhiro Fujita; Kasumi Nakamura; Naoki Nakamura; Sota HIRAHARA
Original assignee: Ricoh Co Ltd
Current assignee: Ricoh Co Ltd
Priority date: 2023-03-27
Filing date: 2024-03-21
Publication date: 2026-02-11
Also published as: CN120858314A; WO2024201217A1

Abstract

An illumination device includes a light source including light-emitting sections arrayed to emit light; a wavelength converter to convert a wavelength of the light emitted from the light source; a condensing optical system between the light source and the wavelength converter in a travel direction of the light, the condensing optical system to converge the light emitted from the light source; and a single light profile adjuster on an optical path of the light converged by the condensing optical system, the single light profile adjuster to homogenize a light intensity distribution of an illumination spot on the wavelength converter.

Description

[DESCRIPTION]

[Title of Invention]

ILLUMINATION DEVICE AND IMAGE PROJECTION APPARATUS

[Technical Field]

[0001]

The present disclosure relates to an illumination device and an image projection apparatus. [Background Art] [0002]

A typical illumination device is known to include a light source with light emission portions arranged in an array; a wavelength converter that converts the wavelength of light emitted from the light source into another wavelength; and a condensing optical system positioned between the light source and the wavelength converter, which converges the light emitted from the light source.

In Patent Literature 1 (PTL 1), the illumination device is described as including two microlens arrays on the light-condensing path where light is converged by the condensing optical system. These arrays function as light profile adjustment elements that homogenize the light intensity distribution of the illumination spot on the phosphor wheel, which acts as the wavelength converter.

The microlens array close to the condensing optical system splits the incident light into multiple beams, and the microlens array close to the wavelength converter then focuses (superimposes) these split beams onto the phosphor wheel, homogenizing the light intensity distribution of the illumination spot on the phosphor wheel.

[Citation List]

[Patent Literature]

[0003]

[PTL 1]

Japanese Patent No. 7165267

[Summary of Invention]

[Technical Problem]

[0004]

However, the technology described in PTL 1 could potentially lead to an increase in the cost of the apparatus. Further, as the converged light enters the upstream microlens in its travel direction, this converged light may cause crosstalk between the lenses in the microlens array, risking reduced uniformity and an expanded illumination spot.

[Solution to Problem]

[0005]

[Advantageous Effects of Invention]

[0006]

According to one aspect of the present disclosure, the device can be made more affordable, and the expansion of the illumination spot diameter can be prevented.

[Brief Description of Drawings]

[0007]

A more complete appreciation of embodiments of the present disclosure and many of the attendant advantages and features thereof can be readily obtained and understood from the following detailed description with reference to the accompanying drawings.

[FIG. 1]

FIG. 1 is a diagram illustrating a configuration of an image projection apparatus incorporating an illumination device according to an embodiment of the present disclosure.

[FIG. 2]

FIG. 2 is a schematic diagram of the illumination device in FIG. 1.

[FIG. 3]

FIG. 3 is a block diagram of a hardware configuration of the image projection apparatus in

FIG. 1.

[FIG. 4]

FIG. 4 is a schematic plan view of an illumination device including one light-source unit.

[FIG. 5A]

FIG. 5A is a schematic diagram of a light-emitting diode (FED) light source and collimator lenses as viewed in the optical-axis direction.

[FIG. 5B]

FIG. 5B is a schematic diagram of a microlens array as viewed in the optical-axis direction.

[FIG. 6A]

FIG. 6A is a diagram illustrating a configuration of an LED light source and its surroundings in a light- source unit with an xLD axis aligned with an xML axis according to a comparative example.

[FIG. 6B]

FIG. 6B is a diagram illustrating a configuration of an LED light source and its surroundings in a light- source unit with an xLD axis tilted at a predetermined angle relative to an xML axis, according to an embodiment of the present disclosure.

[FIG. 7A]

FIG. 7A is a diagram of a profile of light incident on a microlens array with an xLD axis aligned with an xML axis according to a comparative example.

[FIG. 7B] FIG. 7B is a diagram of a profile of light incident on a microlens array with an xLD axis tilted at a predetermined angle relative to an xML axis, according to an embodiment of the present disclosure.

[FIG. 8A]

FIG. 8A is a diagram of a light profile of an illumination spot on a phosphor surface with an xLD axis aligned with an xML axis according to a comparative example.

[FIG. 8B]

FIG. 8B is a diagram of a light profile of an illumination spot on the phosphor surface with an xLD axis tilted at a predetermined angle relative to an xML axis, according to an embodiment of the present disclosure.

[FIGS. 9 A and 9B]

FIGS. 9A and 9B are diagrams each illustrating a mechanism for rotating an LED light source around the optical axis by a predetermined angle.

[FIG. 10A]

FIG. 10A is a diagram of a profile of light incident on a microlens array according to modification 1 of an embodiment of the present disclosure.

[FIG. 10B]

FIG. 10B is a diagram of the microlens array in FIG. 10A used in Modification 1.

[FIG. 11]

FIG. 11 is a cross-sectional view, parallel to a yLD-axis direction, of light beams emitted from light-emitting sections and incident on a microlens array, according to Modification 1. [FIG. 12]

FIG. 12 is a schematic diagram illustrating a configuration of an illumination device with two light-source units, according to Modification 2 of an embodiment of the present disclosure. [FIG. 13]

FIG. 13 is a schematic diagram illustrating a configuration of an illumination device with one light-source unit, according to Modification 2 of an embodiment of the present disclosure. [FIGS. 14A and 14B]

FIGS. 14A and 14B are diagrams each illustrating a light profile of an illumination spot on a phosphor surface of a phosphor wheel in the illumination device of FIG. 4.

[FIGS. 14C and 14D]

FIGS 14C and 14D are diagrams each illustrating a light profile of an illumination spot on a phosphor surface of a phosphor wheel in the illumination device of FIG. 13.

The accompanying drawings are intended to depict embodiments of the present disclosure and should not be interpreted to limit the scope thereof. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted. Also, identical or similar reference numerals designate identical or similar components throughout the several views. [Description of Embodiments] [0008] In describing embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that have a similar function, operate in a similar manner, and achieve a similar result.

Referring now to the drawings, embodiments of the present disclosure are described below. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.

Embodiments of the present disclosure will be described with reference to the drawings. It is easy for a person skilled in the art to make other embodiments by changing and modifying the embodiments of the present disclosure within the scope of the claims, and these changes and modifications are included in the scope of the claims. In the following description, the embodiments of the present disclosure are the best mode of the invention and is not intended to limit the scope of the claims.

[0009]

FIG. 1 is a diagram illustrating a configuration of an image projection apparatus 100 incorporating an illumination device 10 according to an embodiment of the present disclosure. In the following description, X-direction, Y -direction, and Z-direction are perpendicular to each other with the X-direction and the Y-direction being horizontal and the Z-direction being vertical. However, the orientation is not limited to such a configuration.

[0010]

The image projection apparatus 100 includes the illumination device 10 and a digital micromirror device (DMD) 101, which serves as an image generator that modulates the illumination light emitted from the illumination device 10 and generates images. Examples of the image generator may include a liquid crystal panel. The image projection apparatus 100 further includes an illumination optical system 102 that substantially uniformly distributes the light emitted from the illumination device 10 and directs it to the DMD 101, and a projection optical system 103 that enlarges and projects the light, which has been spatially modulated by the DMD 101, onto a projection surface 104.

[0011]

The DMD 101 generates images from the light from the illumination device 10 by reflecting the incident light beams using the micro-mirrors placed on its surface. In the present embodiment, the DMD 101 is used as the image generator. In some examples, a transmissive liquid crystal element, or a reflective liquid crystal element is used.

[0012]

The projection optical system 103 is located downstream from the DMD 101 in the optical path and is designed to project the light beams toward the projection surface 104, which serves as a screen. The illumination optical system 102 guides the illumination light from the illumination device 10 toward the DMD 101. These optical systems include optical elements such as lenses and mirrors and are housed within an enclosure 105 of the image projection apparatus 100.

[0013]

FIG. 2 is a schematic diagram of the illumination device 10. FIG. 2 is a schematic plan view of the illumination device 10, as viewed from above.

As illustrated in FIG. 2, the illumination device 10 includes a first light source unit LSI, a second light source unit LS2, a prism 2 serving as a combining optical element (or a light combiner) light combiner, a color wheel 53, and a rod integrator 3 serving as a light homogenizing element (or a light homogenizer).

[0014]

In the present embodiment, the prism 2, serving as a light combiner, is a polyhedron with four or more faces. Among the multiple faces of the prism 2, the face on which light Fl from the first light source unit LS 1 is incident is a reflective surface 2A, and the face on which light F2 from the second light source unit LS2 is incident is a transmissive surface 2B.

[0015]

For example, the transmissive surface 2B of the prism 2, through which the light F2 from the second light source unit LS2 passes, is preferably a diffusive surface. By using the diffusive surface, unevenness in color and luminance of the light passing through the diffusive surface can be eliminated. In some examples, another diffusion plate is used without incorporating the diffusive surface in the prism 2 to eliminate the unevenness in color and luminance. [0016]

The prism 2 reflects the light Fl from the first light source unit LS 1 with the reflective surface 2A and transmits the light F2 from the second light source unit LS2 through the transmissive surface 2B, combining the light Fl and the light F2 into a light beam that is directed substantially in the same direction toward the rod integrator 3.

In the present embodiment, although the prism 2 is used as the combining optical element, any optical element that combines the light Fl and the light F2 from two or more light source units and directs them substantially in the same direction toward the rod integrator 3 is suitable.

[0017]

If the combining optical element reflects both the light Fl from the first light source unit LSI and the light F2 from the second light source unit LS2 into the rod integrator 3, the device may increase in size for the following reasons. In other words, in this configuration, the optical axis of the light Fl from the first light source unit LSI incident on the combining optical element and the optical axis of the light F2 from the second light source unit LS2 incident on the prism 2 should be arranged to form an angle of approximately 180 degrees. To make such an arrangement, the first light source unit LSI needs to be positioned on one side (e.g., on the -Y-side in FIG. 2) of the rod integrator 3, and the second light source unit LS2 on the opposite side (e.g., on the +Y-side in FIG. 2), leading to an increase in the size of the device. [0018]

In the present embodiment, however, the prism 2 directs the light Fl from the first light source unit LS 1 as reflected light and the light F2 from the second light source unit LS2 as transmitted light into the rod integrator 3. This arrangement allows for the angle between the optical axis of the light Fl from the first light source unit LS 1 incident on the prism 2 and the optical axis of the light F2 from the second light source unit LS2 incident on the prism 2 to be approximately 90 degrees, as illustrated in FIG. 2. This enables a shorter distance between the two light source units LSI and LS2 than the configuration where the combining optical element reflects both the light Fl from the first light source unit LS 1 and the light F2 from the second light source unit LS2 into the rod integrator 3. The configuration of the present embodiment achieves a reduction in the size of the device.

[0019]

The rod integrator 3 is a cylindrical glass optical element that homogenizes incident light through multiple internal reflections. In particular, the rod integrator 3 homogenizes the illuminance and light intensity distribution of the light Fl and the light F2 from the first light source unit LS 1 and the second light source unit LS2, respectively, which are combined by the prism 2, and then outputs them as illumination light L.

[0020]

In the present embodiment, the rod integrator 3 with high efficiency and high output is used as the light homogenizing element. However, other light homogenizing elements such as a prismatic light tunnel created by bonding four mirrors together or a fly-eye lens may also be employed.

[0021]

The rod integrator 3 offers high efficiency and output, but is limited by the angle of incidence of the incoming light. Specifically, the rod integrator 3 achieves uniformity or homogenization by utilizing total internal reflection of light. Considering this mechanism, the angle of incidence of light onto the rod integrator 3 should be within the range where total internal reflection can occur within the rod integrator 3. Thus, the angle at which light enters the rod integrator 3 imposes restrictions on the placement of both the first light source LS 1 and the second light source LS2 to satisfy this condition.

[0022]

However, the prismatic light tunnel, created by bonding four mirrors together as a light homogenizing element, is not constrained by the angle of incident light, unlike the rod integrator 3. Hence, in the case of a prism light tunnel created by bonding four mirrors together as a light homogenizing element, the placement of both the first light source unit LS 1 and the second light source unit LS2 is unrestricted. This enhances the flexibility of their arrangement and achieves the downsizing of the illumination device 10.

[0023]

The first light source unit LSI and the second light source unit LS2 are described below. As both the first light source unit LS 1 and the second light source unit LS2 have a similar configuration, the elements of the first light source unit LS 1 will be described. The elements of the second light source unit LS2 will be denoted by like reference numerals, with descriptions omitted as appropriate.

[0024]

The first light source unit LS 1 includes an LED light source 11 as a source of excitation light, collimator lenses 12 placed facing the LED light source 11, a light-source optical system 13, a condenser 14, a microlens array 19, and a dichroic mirror 15. The first light source unit LSI also includes a disc-shaped phosphor wheel 17 as a wavelength conversion element (or a wavelength converter), a first condensing optical system 16, and a second condensing optical system 18.

[0025]

The LED light source 11 as a light source is a multi-chip laser diode unit in which multiple light-emitting sections are arranged in a one-dimensional or two-dimensional array.

[0026]

The collimator lenses 12 are disposed opposite the light-emitting sections of the LED light source 11 to convert excitation beams emitted from the light-emitting sections into parallel beams. The light-source optical system 13 is a lens designed to converge (or collect and concentrate) the parallel beams converted by the collimator lenses 12. In the present disclosure, the center of the light source typically coincides with the optical axis of the excitation light emitted from the light source. As such, the light-source optical system 13 is positioned to align its optical axis with the center of the light source.

[0027]

The condenser 14 is positioned behind or at a subsequent stage of the light-source optical system 13 (i.e., positioned downstream from the light-source optical system 13 in the direction of light propagation or a travel direction of light), and is a lens with negative power to reduce the focusing power or convergence of the light-source optical system 13. The light beam, whose degree of focus has been mitigated after passing through the condenser 14, enters the microlens array 19 that serves as a light profile adjuster. The microlens array 19 homogenizes the light intensity distribution of the illumination spot that is projected onto a desired position on the phosphor wheel 17.

[0028]

Among the light beam transmitted through the microlens array 19, only light of a specific wavelength is reflected by the dichroic mirror 15, and this reflected light is then converged by the first condensing optical system 16 to form an illumination spot at a desired position on the phosphor wheel 17. In other words, the phosphor wheel 17 is positioned near the illumination spot. In some examples, a reflective diffractive optical element (DOE) is used instead of the dichroic mirror 15.

[0029] The disc-shaped phosphor wheel 17 as a wavelength converter is configured to rotate at high speed driven by a motor (or a drive motor). In the present embodiment, the phosphor wheel 17 has a phosphor area that serves as a wavelength conversion area, which is coated with a phosphor, and an excitation-light reflective area that serves as a non-wavelength conversion area to reflect excitation light. With the rotation of the phosphor wheel 17, the position of the above illumination spot alternates between the excitation-light reflective area and the phosphor area.

[0030]

In the present embodiment, blue light with a central wavelength of 455 nanometers (nm) in its emission intensity distribution is used as the excitation light emitted from the LED light source 11. As such, when the excitation-light reflective area of the phosphor wheel 17 is positioned at the location of the illumination spot, blue light is directly emitted without undergoing wavelength conversion. However, when the phosphor area of the phosphor wheel 17 is positioned at the location of the illumination spot, the light undergoes wavelength conversion and is emitted as yellow or yellow-green fluorescence.

[0031]

In the present embodiment, the phosphor wheel 17 is divided into two areas: the excitationlight reflective area and the phosphor area. However, in some examples, the phosphor wheel 17 includes multiple phosphor areas that convert light into different wavelengths (e.g., a phosphor area that emits yellow light and another phosphor region that emits green light). In some other examples, multiple excitation-light reflective areas 33 may be included.

[0032]

The light beam reflected by the phosphor wheel 17 passes again through the first condensing optical system 16 and is then converged by the second condensing optical system 18, which is composed of a relay lens system. Subsequently, the light Fl from the first light source unit LSI is reflected off the reflective surface 2A of the prism 2, passes through the color wheel 53, and enters the rod integrator 3. The light F2 from the second light source unit LS2 is transmitted through the transmissive surface 2B of the prism 2, and similarly passes through the color wheel 53 to be incident on the rod integrator 3.

[0033]

The color wheel 53 is disposed between the prism 2 and the rod integrator 3, and has a disk shape. The color wheel 53 may be positioned behind the rod integrator 3, or at a position toward which light exits from the rod integrator 3.

[0034]

The color wheel 53 transmits the light Fl and the light F2 from the first light source unit LSI and the second light source unit LS2, respectively while rotating. By doing so, the color wheel 53 time- sequentially divides incident light into red, blue, green, and yellow segments before directing each colored segment to the rod integrator 3. Specifically, the color wheel 53 includes a red area R that outputs red light, a blue area B that outputs blue light, a green area G that outputs green light, and a yellow area Y that outputs yellow light. [0035]

The color wheel 53 is controlled to rotate in synchronization with the phosphor wheel 17 at the same rotation speed as the phosphor wheel 17. For example, when the light time-divided into the blue light and the yellow fluorescence by the phosphor wheel 17 is incident on the color wheel 53 as described above, the rotation of the color wheel 53 is controlled as follows. In other words, the color wheel 53 is controlled to rotate so that the blue area B of the color wheel 53 corresponds to the excitation-light reflective area of the phosphor wheel 17, and the red area R, the green area G, and the yellow area Y correspond to the phosphor areas of the phosphor wheel 17.

[0036]

When the light time-divided into the blue light and the yellow fluorescence by the phosphor wheel 17 is incident on the color wheel 53, the blue area B of the color wheel 53 is formed of a transmissive diffuser panel. By using the transmission diffuser plate for the blue area B, the coherence of the LED light source 11 can be reduced, and the speckle on the projection surface 104 can also be reduced.

[0037]

The yellow area Y of the color wheel 53 is formed of a transmissive plate that allows the wavelength range of yellow fluorescence emitted from the phosphor area to pass through as it is. The red area R of the color wheel 53 includes a dichroic mirror that transmits the red wavelength and reflects the other wavelengths among the yellow fluorescence emitted from the phosphor area of the phosphor wheel 17. The green area G includes a dichroic mirror that transmits the green wavelength and reflects the other wavelengths among the yellow fluorescence.

[0038]

Thus, the red, blue, green, and yellow beams produced sequentially by the phosphor wheel 17 and the color wheel 53 are uniformized or homogenized by the rod integrator 3 before being directed to the DMD 101. Then, based on image data received through an external device connection interface (I/F) 818 (see FIG. 3), images corresponding to the respective colors are formed, and enlarged and projected onto the projection surface 104 by the projection optical system 103.

[0039]

The image projection apparatus 100 according to the present embodiment can be used in various settings including commercial use (e.g. projection displays for business, meetings, and presentations), home use, medical use (e.g., projection displays for monochromatic (grayscale) images such as an X-ray and magnetic resonance imaging (MRI) scans), public use (e.g., a projection display for various information, advertisements, and signage in public places, retail settings, and transportation facilities), or industrial use (e.g., a projection apparatus installed in a factory).

[0040] In the present embodiment, the image projection apparatus 100 features various projection modes for the above applications, such as a color mode, a video mode, a still image mode, a medical mode for projecting medical images, and a public mode for projecting information and signage in outdoor areas or stores. The control of the operation and the amount of drive for the light source, power, cooling, and output can be automatically adjusted depending on the mode change.

[0041]

FIG. 3 is a block diagram of a hardware configuration of an image projection apparatus 100. As illustrated in FIG. 3, the image projection apparatus 100 includes a central processing unit (CPU) 801, a read-only memory (ROM) 802, and a random- access memory (RAM) 803. The image projection apparatus 100 also includes a media PF 807, an operation unit 808, a power switch 809, a bus line 810, a network PF 811, an LED drive circuit 814, an external device connection PF 818, a fan drive circuit 819, and a cooling fan 820.

[0042]

The CPU 801 controls the overall operation of the image projection apparatus 100. The ROM 802 stores a program used to drive the CPU 801. The RAM 803 is used as a work area of the CPU 801.

The media PF 807 controls the media 806 such as a flash memory to read or write (store) data.

[0043]

The operation unit 808 includes various keys, buttons, and LEDs, and is used by the user to perform various operations other than ON/OFF power function of the image projection apparatus 100 by the user. For example, the operation unit 808 receives instructions for various adjustments, such as adjusting the size of the projection image, adjusting the color tone, adjusting the focus, and adjusting the keystone, and then relays these instructions to the CPU 801.

[0044]

The power switch 809 is a switch used to turn the power of the image projection apparatus 100 ON and OFF.

The bus line 810 is, for example, an address bus or a data bus, which electrically connects various components such as the CPU 801 as illustrated in FIG. 3.

The network PF 811 is an interface for performing data communication using a communication network such as the Internet.

The LED drive circuit 814 controls the turning on and off of the LED light source 11 under the control of the CPU 801.

[0045]

The external device connection PF 818 is directly connected to a personal computer (PC) to exchange control signals and image data between the PC and the external device connection PF 818. The fan drive circuit 819 is connected to the CPU 801 and the cooling fan 820, and operates or stops the cooling fan 820 based on a control signal from the CPU 801.

The cooling fan 820 cools the inside of the image projection apparatus 100 by exhausting air from inside the image projection apparatus 100 as the cooling fan 820 rotates.

[0046]

When power is supplied, the CPU 801 boosts up according to a control program stored in advance in the ROM 802. The CPU 801 then sends a control signal to the LED drive circuit 814 to turn on the LED light source 11, and another control signal to the fan drive circuit 819 to rotate the cooling fan 820 at a predetermined speed. In the image projection apparatus 100, when the power supply from the power circuit is initiated, the DMD 101 becomes ready to display an image, and power is also supplied from the power circuit to various other components.

[0047]

In the image projection apparatus 100, when the power switch 809 is turned off, a power OFF signal is sent from the power switch 809 to the CPU 801. Upon detecting the power OFF signal, the CPU 801 sends a control signal to the LED drive circuit 814 to turn off the LED light source 11.

After a predetermined time has elapsed, the CPU 801 sends a control signal to the fan drive circuit 819 to stop the cooling fan 820. The CPU 801 then concludes its own control processing and finally instructs the power circuit to cease power supply.

[0048]

FIG. 4 is a schematic plan view of an illumination device including one light-source unit LS. The light-source unit LS of the illumination apparatus in FIG. 4 has the same configuration as those of the first light source unit LS 1 and the second light source unit LS2 of the illumination apparatus in FIG. 2. Specifically, the light-source unit LS includes the LED light source 11, the collimator lenses 12, the light-source optical system 13, the condenser 14, the microlens array 19, the dichroic mirror 15, the phosphor wheel 17, the first condensing optical system 16, and the second condensing optical system 18.

[0049]

The illumination device 10 in FIG. 4 does not include the prism 2 as the combining optical element, and the light from the light- source unit LS is directly incident on the color wheel 53. [0050]

FIG. 5A is a schematic diagram of the LED light source 11 and the collimator lenses 12 as viewed in the optical-axis direction. FIG. 5B is a schematic diagram of the microlens array 19 as viewed in the optical-axis direction.

In FIG. 5A, the LED light source 11 includes fourteen light-emitting sections I la arranged in a two-dimensional array with 7 rows and 2 columns. Each light-emitting section I la corresponds to one collimator lens 12, and the collimator lenses 12 are arranged in a two- dimensional array of 7 rows and 2 columns, which matches the two-dimensional array of the light-emitting sections I la. [0051]

The microlens array 19 includes rectangular microlenses 19a arranged in a two-dimensional array (or grid pattern), as illustrated in FIG. 5B. The microlenses 19a are single-sided microlenses, each having a curved surface on one side. The microlens 19a is preferably a plano-convex lens having a flat incident surface and a curved exit surface. By forming such a curved exit surface, the diffusion effect is enhanced, and the light intensity distribution of the illumination spot on the phosphor surface is homogenized.

[0052]

In the following description, a row direction (or horizontal direction) of the array of the lightemitting sections 1 la of the LED light source 11 is defined as an xLD axis, and a column direction (or vertical direction) of the array of the light-emitting sections 1 la of the LED light source 11 is defined as a yLD axis. The row direction (or horizontal direction) of the array of the microlenses 19a of the microlens array 19 is defined as an xML-axis, and the column direction (or vertical direction) of the array of the microlenses 19a of the microlens array 19 is defined as a yML-axis.

[0053]

In the present embodiment, the xLD axis is tilted with respect to the xML axis so that the xLD axis is not aligned with the xML axis. In other words, a rectangular plane SLD is rotated around the optical axis by a predetermined angle relative to a rectangular plane SML. The rectangular plane SLD, which is orthogonal to the optical axis, is formed by connecting the centers of the light-emitting sections at the four corners among the multiple light-emitting sections I la. Similarly, the rectangular plane SML, which is orthogonal to the optical axis, is formed by connecting the centers of the microlenses at the four corners among the multiple microlenses 19a. The yLD axis is orthogonal to the xLD axis, and the yML axis is orthogonal to the xML axis. As such, by tilting the xLD axis at a predetermined angle relative to the xML axis, the yLD axis is tilted at a predetermined angle relative to the yML axis. [0054]

FIG. 6A is a diagram illustrating a configuration of an LED light source and its surroundings in a light-source unit LS with the xLD axis aligned with the xML axis. FIG. 6B is a diagram illustrating a configuration of an LED light source and its surroundings in the light-source unit LS with the xLD axis tilted at a predetermined angle relative to the xML axis. FIG. 7A is a diagram of a profile of light incident on the microlens array 19 with the xLD axis aligned with the xML axis. FIG. 7B is a diagram of a profile of light incident on the microlens array 19 with the xLD axis tilted at a predetermined angle with respect to the xML axis. FIG. 8 A is a diagram of a light profile of an illumination spot on the phosphor surface with the xLD axis aligned with the xML axis. FIG. 8B is a diagram of a light profile of an illumination spot on the phosphor surface with the xLD axis tilted at a predetermined angle relative to the xML axis. In the examples of FIGS. 7A, 7B, 8A, and 8B, four light-emitting sections I la are arrayed in the yLD-axis direction within the LED light source.

[0055] In the example of FIGS. 6B and 7B, when the origins of the xLD axis and the yLD axis are on the optical axis, which is defined as a line connecting substantially central points of the lightsource optical system 13 and the condenser 14, the LED light source 11 is rotated around the optical axis by a predetermined angle, which is centered on these origins, so that the xLD axis is tilted by the predetermined angle relative to the xML axis. In FIGS. 6B and 7B, the LED light source 11 is rotated clockwise by a predetermined angle. In some examples, the LED light source 11 may be rotated counterclockwise by a predetermined angle.

[0056]

FIGS. 9A and 9B are diagrams each illustrating a mechanism for rotating the LED light source 11 around the optical axis by a predetermined angle.

FIG. 9A illustrates a holder 110 holding a unit including the LED light source 11 and collimator lenses arranged in a two-dimensional array. The holder 110 is attached to two attachment bosses 111 on the bottom surface 10a of the case of the illumination device 10.

By differentiating the heights of these two attachment bosses 111, the holder 110 is mounted in a tilted position as illustrated in FIG. 9A so that the xLD axis is tilted by a predetermined angle relative to the xML axis.

[0057]

As illustrated in FIG. 9B, a unit including the LED light sources 11 and the collimator lenses 12 arranged in a two-dimensional array is attached to a disc- shaped attachment member 112. The attachment member 112 may be rotatably held in a circular holding hole 110a of the holder 110, so that the tilt angle of the xLD axis with respect to the xML axis can be adjusted. [0058]

The holder 110 may be rotatably supported on the side surface of the case of the illumination device 10, and the holder 110 may be rotated to adjust the tilt angle of the xLD axis with respect to the xML axis.

[0059]

By allowing the adjustment of the tilt angle 9 of the xLD axis relative to the xML axis, the optimal tilt angle 9 for achieving the most uniform light intensity distribution can be determined while measuring the light intensity distribution of the illumination spot on the phosphor surface of the phosphor wheel.

[0060]

The holder for the microlens array 19 is preferably attached to the bottom surface 10a of the case where the holder 110 for holding the unit including the LED light sources 11 and the collimator lenses 12 arranged in a two-dimensional array is attached. The other optical elements, including the light-source optical system 13, the condenser 14, and the first condensing optical system 16, are also preferably attached to the bottom surface 10a of the case via the holder 110. By attaching these components onto the same surface, the relative position can be precisely maintained. In some examples, a base member is used, and these components are attached to it.

[0061] The holder for holding the microlens array 19 may be attached to the bottom surface 10a of the case while being tilted as in FIG. 9A so that the xLD axis is tilted by a predetermined angle relative to the xML axis. Further, as in FIG. 9B, the microlens array 19 may be held by a holder so as to be rotatable about the optical axis, and the microlens array 19 may be rotated to adjust the tilt angle of the xLD axis with respect to the xML axis. However, for the following reasons, it is preferable to rotate the unit including the LED light source 11 and the collimator lenses arranged in a two-dimensional array to set the tilt angle of the xLD axis relative to the xML axis at a predetermined angle. The first condensing optical system 16 employs a rotationally symmetric optical system. As illustrated in FIGS. 8 A and 8B, the illumination spot on the phosphor surface of the phosphor wheel 17 is rectangular, which is substantially similar to the shape of the microlenses 19a. The position of the illumination spot is set so that the illumination spot fits within a phosphor of the phosphor wheel with a fixed width. [0062]

When the microlens array 19 is rotated, the rectangular illumination spot on the phosphor surface of the phosphor wheel 17 is also rotated, which might cause a part of the illumination spot to be deviated from the phosphor. For this reason, with any change in the specification of the tilt angle of the xLD axis relative to the xML axis, for example, the irradiation position on the phosphor wheel should be changed to avoid the deviation of the illumination spot from the phosphor surface. This affects the design specification of the subsequent stage of the microlens array 19. [0063]

However, when the unit including the LED light source 11 and the collimator lenses 12, which are arranged in a two-dimensional array, is rotated to set the tilt angle 9 of the xLD axis relative to the xML axis to a predetermined angle, the rectangular- shaped illumination spot on the phosphor surface of the phosphor wheel 17 does not rotate despite the rotation of this unit. The change in the specification of the tilt angle of the xLD axis relative to the xML axis does not involve changing the design specification of the subsequent stage of the microlens array 19.

This is why it is preferable to rotate the unit including the LED light source 11 and the collimator lenses arranged in a two-dimensional array to set the tilt angle of the xLD axis relative to the xML axis at a predetermined angle. [0064]

As illustrated in FIGS. 7A and 7B, the light beams from the light-emitting sections Ila of the LED light source 11 are incident on the microlens array 19 with little overlap, and a row of light beams, which is similar to the array of the light-emitting sections 1 la, is incident on the microlens array 19. By tilting the xLD axis by a predetermined angle with respect to the xML axis, as illustrated in FIG. 7B, the row of light from the LED light source 11 incident on the microlens array is tilted by a predetermined angle with respect to the array direction of the microlenses. [0065]

When the xLD axis is aligned with the xML axis, as illustrated in FIG. 7A, the row of light from the LED light source 11 incident on the microlens array 19 is parallel to the arrangement direction (i.e., yML axis in this example) of the microlenses 19a. In this arrangement, the light intensity distributions of the light beams incident on the microlenses 19a of the microlens array 19 become similar. The light beams emitted from the microlenses 19a overlap on the phosphor of the phosphor wheel 17 or are superimposed with a slight offset, forming one illumination spot on the phosphor surface of the phosphor wheel. When the light intensity distributions incident on the microlenses 19a are similar, the illumination spot on the phosphor surface of the phosphor wheel 17, which is formed by the overlapping light beams emitted from the microlenses 19a, has the following light intensity distribution. As illustrated in FIG. 8A, non-uniform light intensity distribution with two peaks is obtained.

[0066]

In contrast, when the xLD axis is tilted at a predetermined angle to the xML axis, as illustrated in FIG. 7B, the row of light beams incident on the microlens array 19 is tilted at a predetermined angle relative to the array direction of the microlenses 19a. In a such case, the light intensity distribution of the light beams incident on the microlenses 19a becomes more random. As a result, as illustrated in FIG. 8B, the light intensity distribution of the illumination spot on the phosphor surface of the phosphor wheel 17, which is formed by the overlapping light beams emitted from the microlenses 19a, becomes uniformly enhanced. [0067]

The size and other parameters of the microlenses 19a are set such that a light beam from each light-emitting section 1 la is incident on two or more microlenses in the xML-axis direction and two or more microlenses in the yML-axis direction. Although a light beam from each light-emitting section 1 la is preferably incident on a greater number of microlenses, loss due to scattering at the boundaries of the microlenses might occur. As such, it is not advisable to indiscriminately increase the number of microlenses on which a light beam from each lightemitting section 1 la by reducing the size of the microlenses 19a. Preferably, the number of microlenses on which a light beam from each light-emitting section 1 la is determined in consideration of the loss at the boundaries of the microlenses.

[0068]

In the related art, two microlens arrays are typically used to homogenize or uniformize the light intensity distribution at a specific irradiation position. In this approach, light entering an upstream microlens array in the direction of light propagation is split and individually converged. The concentrated beams are then directed into the other downstream microlens array. Through this process, the beams from the respective microlenses are superimposed at a specific irradiation position, and the light intensity at that particular irradiation position is uniformized. By positioning the downstream microlens array at the positions of the image planes of the microlenses of the upstream microlens array, the system becomes a Koehler illumination system. This arrangement allows the light beams emitted from the microlenses to be precisely overlaid without misalignment on the phosphor surface of the phosphor wheel. However, this approach causes higher device costs. Additionally, if the pitch and alignment of the two microlens arrays are not precisely matched, the illumination spot may be expanded due to crosstalk from adjacent microlenses.

[0069]

In a configuration where two microlens arrays are placed in the light-condensing path to homogenize the light intensity distribution at a specific irradiation position, particularly as described in PTL 1, crosstalk is more likely to occur between microlens arrays, which could compromise uniformity.

[0070]

If a microlens array is placed in a parallel light path between the collimator lenses 12 and the light-source optical system 13, it is not easy to overlap the light beams emitted from the microlenses on the phosphor surface of the phosphor wheel 17 without two microlens arrays. In the present embodiment, however, by placing the microlens array 19 in the lightcondensing path created by the light-source optical system 13 and the condenser 14 between the condenser 14 and the dichroic mirror 15, light entering each microlens converges downstream from the microlenses in the direction of light propagation, forming converging light. Thus, even without the microlens array located upstream in the direction of light propagation, which splits the incoming light into multiple beams and converges each split beam, the light from each microlens can be easily superimposed on the phosphor surface of the phosphor wheel. This results in minimal misalignment of the light beams, which has been emitted from the microlenses, on the phosphor surface of the phosphor wheel, enabling successful overlapping of the light beams. As illustrated in FIG. 8B, the configuration of the present embodiment successfully achieves uniform light intensity distribution for the illumination spot on the phosphor surface of the phosphor wheel 17. Such an approach of the present embodiment addresses the drawbacks of using two microlens arrays, i.e., increased device costs and expanded illumination spot, and achieves successful uniformity in the light intensity distribution for the illumination spot on the phosphor surface of the phosphor wheel 17.

[0071]

Modification 1

A configuration in which 28 light-emitting sections of an LED light source are arranged in a two-dimensional array of seven rows and four columns is described below according to Modification 1 of an embodiment of the present disclosure.

FIG. 10A is a diagram of a profile of light incident on a microlens array 19 according to Modification 1 of an embodiment of the present disclosure. FIG. 10B is a diagram of the microlens array used in Modification 1.

The light-emitting sections 1 la of the LED light source are arranged in two dimensions: horizontally, seven light-emitting sections along the xLD axis (or in the row direction) with a pitch of 2.4 millimeters (mm); and vertically, four light-emitting sections along the yLD axis (or in the column direction) with a pitch of 6.0 mm. The xLD axis in the row direction (or the horizontal direction) of the array of the light-emitting sections 1 la in the LED light source is slightly tilted at an angle relative to the xML axis in the row direction (or the horizontal direction) of the microlens array. [0072]

As illustrated in FIG. 10A, the light beams from the light-emitting sections 1 la of the LED light source 11 are incident on the microlens array 19 with little overlap. Further, an array of light beams arranged in seven columns and four rows, totaling 28, which is similar to the array of the light-emitting sections I la, is incident on the microlens array 19. [0073]

As illustrated in FIG. 10B, the microlens array 19 has a total of 200 microlenses 19a arranged in a two-dimensional array of 10 columns and 20 rows. The number of microlenses 19a in the microlens array 19 can be appropriately determined according to the size of the group of images formed by the source light incident on the microlens array 19. In Modification 1, the microlenses 19a, which are rectangular in shape, have dimensions of 0.45 mm by 0.35 mm. In Modification 1, for the microlenses 19a, sizes such as 0.064 mm by 0.05 mm are suitable, with even the smaller sizes being approximately 0.032 mm by 0.025 mm. If the size of the microlens is made smaller, as described above, the loss due to scattering at the boundaries of the microlenses becomes significant.

[0074]

In Modification 1, the tilt angle 9 of the xLD axis relative to the xML axis is approximately 3 degrees. The tilt angle 9 is preferably between 0 degrees and 5 degrees (0 < 9 < 5 degrees). The uniformity of the light intensity distribution of the illumination spot on the phosphor surface of the phosphor wheel remains satisfactory even when the tilt angle 9 exceeds 5 degrees. As the tilt angle 9 increases, the lengths of the arrayed light beams incident on the microlens array in both the xML-axis direction (i.e., the vertical direction or the Z-direction of the illumination device in the present example) and the yML-axis direction (i.e., the horizontal direction or the Y-direction of the illumination device in the present example) extends, particularly when many light-emitting sections I la are used as illustrated in FIG. 10A. This may lead to an increase in the size of the light-source optical system 13, the condenser 14, and the microlens array 19, potentially resulting in upsizing of the illumination device. However, setting the tilt angle of less than 5 degrees prevents the upsizing of the illumination device when many light-emitting sections I la are used as in Modification 1. [0075]

FIG. 11 is a cross-sectional view, parallel to the yLD-axis direction, of the light beams emitted from a light source (or light-emitting sections) and incident on the microlens array 19 according to Modification 1. The dashed line illustrated in FIG. 11 represents a principal ray, which indicates substantially the central portion of the width of a light beam from the light source or each light-emitting section. In FIG. 11, the light-emitting sections 1 la are referred to as "LD1", "LD2", "LD3", and "LD4" in order from the top. The light beam from each light-emitting section Ila passes through its corresponding collimator lens 12, becoming a parallel light beam before entering the light-source optical system 13. The light beam is then converged by the light-source optical system 13 and the condenser 14.

[0076]

As illustrated in FIG. 11, the width of the light beam emitted from each light-emitting section 1 la after exiting the condenser 14 becomes narrower than immediately after exiting the collimator lens 12. The width of the light beam emitted from each light-emitting section I la decreases progressively with increasing distance from the condenser 14. Upon reaching the microlens array 19, the width of the light beam emitted from each light-emitting section I la becomes smaller than its width immediately after being emitted from the condenser 14. In other words, the light beam from each light-emitting section I la converges as it enters the microlens array 19. After exiting the condenser 14, the principal ray, with the light-beam width, from the light-emitting section LD1 and the principal ray from the light-emitting section LD4 converge toward each other. The microlens array 19 is positioned in the path of their convergence.

[0077]

As illustrated in FIG. 11, after passing through the microlens array 19, the light beams from the light-emitting sections I la converge toward each other, which is caused by the converging action of the light-source optical system 13 and the condenser 14. This arrangement allows for the light beams emitted from the microlenses of the microlens array 19 to converge toward each other, irrespective of the placement of a single microlens array 19 on the lightcondensing path of the condenser 14, which is enabled by the converging action of the lightsource optical system 13 and the condenser 14. Thus, even with the use of a single microlens array 19, the light beams from the microlenses can be effectively overlaid on the phosphor of the phosphor wheel 17, and the light intensity distribution of the illumination spot on the phosphor surface can be successfully uniformized.

[0078]

By positioning the microlens array 19 on the light-condensing path, where the light beams converge towards each other, which is caused by the converging action of the light-source optical system 13 and the condenser 14, the size of the microlens array can be reduced, and thus miniaturization of the device can be achieved.

[0079]

As described above, after passing through the microlens array 19, the light beams from the light-emitting sections I la converge toward each other, which is caused by the converging action of the light-source optical system 13 and the condenser 14. In this scenario, when using two microlens arrays to uniformize the light intensity distribution of the illumination spot, it is challenging to direct the light beams split by the upstream microlens array to the corresponding microlenses of the downstream microlens array in the direction of light propagation. In this configuration, where two microlens arrays are used, crosstalk may occur between the lenses in the microlens array, risking reduced uniformity and an expanded illumination spot. However, in the present embodiment where one microlens array is used, no crosstalk occurs between the lenses of the microlens array, preventing reduced uniformity and expansion of the illumination spot.

[0080]

Modification 2

FIGS. 12 and 13 are schematic diagrams each illustrating a configuration of an illumination device 10 according to Modification 2 of an embodiment of the present disclosure. FIG. 12 is a schematic diagram illustrating a configuration of an illumination device with two lightsource units. FIG. 13 is a schematic diagram illustrating a configuration of an illumination device 10 with one light- source unit.

As illustrated in FIGS. 12 and 13, in Modification 2, the microlens array 19 is disposed between the light-source optical system 13 and the condenser 14, and light that has passed through the light-source optical system 13 directly enters the microlens array 19 without passing through another optical system.

[0081]

In Modification 2, the microlens array 19 is disposed on the light-condensing path of the light-source optical system 13, as in the above embodiment. Using one microlens array 19, the light beams emitted from the microlenses can be overlaid onto the phosphor surface of the phosphor wheel, similar to the embodiment described above.

[0082]

FIGS. 14A and 14B are diagrams each illustrating an illumination spot on the phosphor surface of the phosphor wheel in the illumination device 10 of FIG. 4. FIGS 14C and 14D are diagrams each illustrating an illumination spot on the phosphor surface of the phosphor wheel in the illumination device of FIG. 13.

As illustrated in FIGS. 14C and 14D, it can be observed that, even in Modification 2, where one microlens array 19 is placed in front of the condenser 14 in the direction of light propagation, the light intensity distribution on the phosphor surface becomes uniform. In this way, the light intensity distribution on the phosphor surface can be made uniform by placing the microlens array 19 either in front of or behind the condenser 14 in the direction of the light propagation.

[0083]

Further, when FIGS. 14A and 14B are compared with FIGS. 14C and 14D, in Modification 2, where the microlens array 19 is placed in front of the condenser 14, the illumination spot on the phosphor surface becomes slightly larger. However, the expansion of the illumination spot is reduced to an acceptable level, compared to the expansion of the illumination spot caused by crosstalk that occurs when two microlens arrays are used.

[0084]

In Modification 2, the illumination spot on the phosphor surface can be enlarged, and the light emission efficiency of the phosphor can be increased compared to the embodiment where the microlens array 19 is placed behind the condenser 14. Specifically, the luminous efficiency was improved by 8% as compared with the embodiment. Further, the light concentration density can be reduced, and the temperature increase of the phosphor wheel can also be mitigated.

[0085]

In Modification 2, each microlens 19a is preferably a plano-convex lens having a flat incident surface and a curved exit surface. By forming such a curved exit surface, the diffusion effect is enhanced, and the light intensity distribution of the illumination spot on the phosphor surface is homogenized.

[0086]

Preferably, the microlens array 19 is placed close to the condenser 14, and the distance between the light-source optical system 13 and the microlens array 19 is larger than the distance between the microlens array 19 and the condenser 14. This allows the microlens array 19 to be positioned in the converged portion of the light beam converged by the lightsource optical system 13. Thus, the miniaturization of the microlens array 19 is enabled, achieving the overall downsizing of the illumination device 10.

[0087]

By placing the microlens array 19 close to the condenser 14, even if the microlens array 19 causes slight light divergence, the light can still be incident upon the condenser 14, even when it is of small size.

[0088]

Further, the microlens array 19 and the condenser 14 may be held by the same holding mechanism, and the microlens array 19 may be placed in close contact with the condenser 14. This allows the microlens array 19 to be placed at the point where the light beam is most converged by the light-source optical system 13 between the light-source optical system 13 and the condenser 14, further promoting the miniaturization of the microlens array 19.

[0089]

Although the desirable embodiments and examples of the disclosure have been described above, the disclosure is not particularly limited to such specific embodiments and examples unless otherwise particularly limited in the above description, and various modifications and changes can be made without departing from the spirit and scope of the disclosure as set forth in the appended claims.

[0090]

In the above description, the light-source optical system 13 is composed of one optical lens with positive power. However, the optical system 13 may be composed of multiple optical lenses with power to refract light (either converging or diverging) as long as the light- source optical system converges light passing therethrough, or has positive power as a whole. By placing the microlens array 19 on the light-condensing path of the light-source optical system composed of multiple optical lenses, the light intensity distribution on the phosphor surface can be uniformized or homogenized by using one microlens array 19. In some examples, a mirror (e.g., an optical system that simply reflects light) may be placed between the lightsource optical system 13 and the microlens array 19. Even in such a configuration, the microlens array 19 can be disposed on the light-condensing path created by the light-source optical system 13.

[0091]

The above description is merely one example, and the following aspects yield unique effects. First Aspect

An illumination device 10 includes a light source (e.g., the LED light source 11) including light-emitting sections (Ila) arrayed, the light source to emit light; a wavelength converter (e.g., the phosphor wheel 17) to convert a wavelength of the light emitted from the light source; a condensing optical system (e.g., the light-source optical system 13, the condenser 14) between the light source and the wavelength converter, the condensing optical system to converge the light emitted from the light source; and a single light profile adjuster (e.g., the microlens array 19) on an optical path of the light converged by the condensing optical system, the light profile element to homogenize a light intensity distribution of an illumination spot on the wavelength converter.

In other words, an illumination device includes a light source including light-emitting sections arrayed to emit light; a wavelength converter to convert a wavelength of the light emitted from the light source; a condensing optical system between the light source and the wavelength converter in a travel direction of the light, the condensing optical system to converge the light emitted from the light source; and a single light profile adjuster on an optical path of the light converged by the condensing optical system, the single light profile adjuster to homogenize a light intensity distribution of an illumination spot on the wavelength converter.

It is a common practice to place two light profile adjusters, such as a microlens array, to homogenize or uniformize the light intensity distribution of the illumination spot at a specific irradiation position.

PTL 1 also follows the common practice of using two light profile adjusters to uniformize or homogenize the light intensity distribution of the illumination spot on the phosphor wheel. However, incorporating two light profile adjusters poses the challenge of higher device costs. Additionally, if the pitch and the relative position of the two light profile adjusters are not precisely aligned, crosstalk between adjacent light profile adjusters can cause the illumination spot to expand.

The inventors discovered, through diligent research, that even with a single light profile adjuster placed in the light-condensing path, the light intensity distribution of the illumination spot on the wavelength converter can be sufficiently uniform.

In Aspect 1, a single light profile adjuster was placed on the light-condensing path formed by the condensing optical system to uniformize the light intensity distribution of the illumination spot on the wavelength converter. This allows for sufficient uniformization of the light intensity distribution of the illumination spot on the wavelength converter while reducing device costs, unlike when using two light profile adjusters. Further, using a single light profile adjuster prevents the expansion of the illumination spot diameter, unlike when using two light profile adjusters.

[0092]

Second Aspect

In Aspect 1, the condensing optical system includes a light-source optical system 13 having positive power. The light profile adjuster, such as a microlens array 19, is placed behind the light-source optical system 13 in the direction of light propagation.

In other words, the condensing optical system includes a light-source optical system having positive power, and the single light profile adjuster is downstream from the light-source optical system in the travel direction.

This configuration allows for the placement of a light profile adjuster, such as the microlens array 19, in the light-condensing path created by the light-source optical system 13. [0093]

Third Aspect

In Aspect 2, light passes through the light-source optical system 13 directly enters the single light profile adjuster such as the microlens array 19 without passing through another optical system such as the condensing optical system.

This configuration allows for the placement of a light profile adjuster, such as a microlens array 19, in the light-condensing path created by the light-source optical system 13, as described in Modification 2.

[0094]

Fourth Aspect

In Aspect 2 or 3, the condensing optical system includes a condenser 14 that reduces the convergence of the light-source optical system 13 and converges light at a predetermined position. The single light profile adjuster, such as the microlens array 19, is placed between the light-source optical system 13 and the condenser 14 in the travel direction. The first distance between the light-source optical system 13 and the single light profile adjuster is larger than the second distance between the single light profile adjuster and the condenser 14. This configuration allows for the placement of the light profile adjuster in the narrowest part of the light beam converged by the light-source optical system 13, as described in Modification 2 of the present disclosure. This enables miniaturization of the light profile adjuster.

Additionally, irrespective of the occurrence of slight diffusion from the light emitted from the light profile adjuster, the light emitted from the light profile adjuster can be directed into the condenser without enlarging the condenser.

[0095]

Fifth Aspect

In Aspect 4, the single light profile adjuster, such as the microlens array 19, is displaced at a point where the light beam converged by the light-source optical system 13 becomes the narrowest between the light-source optical system 13 and the condenser 14 in the travel direction.

This configuration allows for the miniaturization of the light profile adjuster, as described in Modification 2 of the present disclosure.

[0096]

Sixth Aspect

In any one of Aspects 1 to 5, the light profile adjuster includes a microlens array 19 including multiple microlenses 19a two-dimensionally arrayed in a plane orthogonal to an optical axis. This configuration allows light beams emitted from the microlenses, respectively, to be superimposed on the wavelength converter such as phosphor wheels, achieving uniform light intensity distribution of the illumination spot on the wavelength converter, as described in the embodiments.

[0097]

Seventh Aspect

In Aspect 6, each of the microlenses 19a of the microlens array 19 (or the single light profile adjuster) has a flat incident surface and a lens-shaped exit surface opposite to the flat incident surface.

This configuration enhances the diffusion effect and can effectively uniformize the light intensity distribution of the illumination spot on wavelength converter such as phosphor wheels, as described in the above embodiment.

[0098]

Eighth Aspect

In Aspect 6 or 7, an array direction of the multiple light-emitting sections 1 la is tilted relative to at least one of a column direction and a row direction of the microlenses two-dimensionally arrayed.

In other words, the light-emitting sections are arrayed tow-dimensionally and tilted by a predetermined tilt angle relative to at least one of a column direction or a row direction of the microlenses two-dimensionally arrayed.

This configuration enables a light intensity distribution with strong randomness for the light beams incident on the microlenses 19a. As a result, the light beams emitted from the microlenses 19a overlap to form an illumination spot on a wavelength converter such as the phosphor wheel 17, effectively homogenizing the light intensity distribution, as described in the above embodiments.

[0099]

Ninth Aspect

In Aspect 8, the light-emitting sections I la has the predetermined tilt angle between 0 degrees and 5 degrees relative to at least one of the column direction or the row direction of the microlenses.

This configuration prevents the enlargement of the condensing optical system, such as microlenses and the condenser 14, when a large number of light-emitting sections are used, and thus prevents the enlargement of the illumination device as described in the above embodiment.

[0100]

Tenth Aspect

In Aspect 8 or 9, the light-emitting sections I la are two-dimensionally arrayed in a plane orthogonal to the optical axis (or the array of the light-emitting sections is arrayed tow- dimensionally in a plane orthogonal to an optical axis). The light-emitting sections have a first rectangular plane SLD orthogonal to the optical axis. The first rectangular plane is formed by connecting centers of light-emitting sections 1 la at four corners of the multiple light-emitting sections I la. The microlenses have a second rectangular plane SML orthogonal to the optical axis. The second rectangular plane is formed by connecting centers of microlenses 19a at four corners of the multiple microlenses 19a. The first rectangular plane is rotated around the optical axis b the predetermined tilt angle relative to the second rectangular plane.

In other words, the light-emitting sections are arrayed two-dimensionally in a first rectangular plane orthogonal to an optical axis formed by connecting centers of light-emitting sections at four comers of the light-emitting sections. The microlenses are arrayed two-dimensionally in a second rectangular plane orthogonal to the optical axis formed by connecting centers of microlenses at four comers of the microlenses. The first rectangular plane is rotated around the optical axis by the predetermined tilt angle relative to the second rectangular plane This configuration allows the array direction (e.g., the xLD axis or the yLD axis) of the lightemitting sections 1 la to be tilted at a predetermined angle relative to the array direction (e.g., the xML axis or the yML axis) of the microlenses 19a, as described in the above embodiment. [0101]

Eleventh Aspect

In any one of Aspects 8 to 10, the illumination device further includes a first holder 110 holding the light source such as an LED light source 11 ; and a second holder holding the microlens array 19. The first holder and the second holder are attached to an attachment surface such as a bottom surface 10a of the case of the illumination device, which is parallel to the optical axis. One of the first holder 110 or the second holder is tilted relative to the attachment surface.

This configuration allows the array direction of the multiple light-emitting sections I la to be tilted relative to at least one of the row or column directions of the microlens array, as illustrated in FIG. 9A.

[0102]

Twelfth Aspect

In any one of Aspects 8 to 11, the light source, such as the LED light source 11, or the microlens array 19 is held to be rotatable about the optical axis.

This configuration allows for the adjustment of the tilt angle of the microlens array 19 relative to the array direction of the microlens, or the array direction of the multiple light-emitting sections 1 la, by rotating the light source such as the LED light source 11, or the microlens array 19, around the optical axis, as illustrated in FIG. 9B.

[0103]

Thirteenth Aspect

In any one of Aspects 1 to 12, the illumination device further includes two light-source units LSI and LS2 each including the light source (e.g., the LED light source 11), the wavelength converter (e.g., the phosphor wheel 17), the condensing optical system (e.g., the condenser 14), and the single light profile adjuster (e.g., the microlens array 19); and a light combiner (e.g., the prism 2) to direct light beams from the two light-source units LSI and LS2 in the same direction toward a light homogenizer (e.g., the rod integrator 3).

This configuration allows for the projection of high-luminance light onto an illumination target such as a DMD.

[0104]

Fourteenth Aspect

In Aspect. 13, the light combiner (e.g., the prism 2) reflects at least one of the light beams from the two light-source units to the light homogenizer.

This configuration enables the light from the two light source units LS 1 and LS2, to be directed in the same direction at a low cost, allowing it to enter a light homogenizer (or a light homogenizing element) such as the rod integrator 3.

[0105]

Fifteenth Aspect

An image projection apparatus includes the illumination device according to any one of Aspects 1 to 14, and an image generator to generate an image with the light emitted from the illumination device.

This configuration allows for the projection of high-quality images.

[0106]

The above-described embodiments are illustrative and do not limit the present invention. Thus, numerous additional modifications and variations are possible in light of the above teachings. For example, elements and/or features of different illustrative embodiments may be combined with each other and/or substituted for each other within the scope of the present invention.

[0107]

This patent application is based on and claims priority to Japanese Patent Application No. 2023-049891, filed on March 27, 2023 and Japanese Patent Application No. 2023-192288, filed on November 10, 2023, in the Japan Patent Office, the entire disclosure of which is hereby incorporated by reference herein.

[Reference Signs List]

[0108]

2: prism (combining optical element)

2A: reflective surface 2B: transmissive surface

3: rod integrator (light homogenizing element)

10: illumination device

10a: bottom surface of the case (attachment surface)

11 : LED light source (light source)

I la: light-emitting section

12: collimator lens

13: light-source optical system

14: condenser (condensing optical system)

15: dichroic mirror

16: first condensing optical system

17: phosphor wheel (wavelength conversion element or wavelength converter)

18: second condensing optical system

19: microlens array (light profile adjuster)

19a: microlenses

53: color wheel

100: image projection apparatus

101: DMD

102: illumination optical system

103: projection optical system

104: projection surface

105: enclosure

110: holder

110a: holding hole

111: attachment boss

112: attachment member

LS 1 : first light source unit

LS2: second light source unit

9: tilt angle

Claims

[CLAIMS]

[Claim 1]

An illumination device comprising: a light source including light-emitting sections arrayed to emit light; a wavelength converter to convert a wavelength of the light emitted from the light source; a condensing optical system between the light source and the wavelength converter in a travel direction of the light, the condensing optical system to converge the light emitted from the light source; and a single light profile adjuster on an optical path of the light converged by the condensing optical system, the single light profile adjuster to homogenize a light intensity distribution of an illumination spot on the wavelength converter.

[Claim 2]

The illumination device according to claim 1, wherein the condensing optical system includes a light-source optical system having positive power, and the single light profile adjuster is downstream from the light-source optical system in the travel direction.

[Claim 3]

The illumination device according to claim 2, wherein the light passed through the light-source optical system directly enters the single light profile adjuster.

[Claim 4]

The illumination device according to claim 2 or 3, wherein the condensing optical system includes a condenser to: reduce convergence of the light-source optical system; and converge the light emitted from the light source, at a predetermined position, the single light profile adjuster is between the light-source optical system and the condenser in the travel direction, and a first distance between the light-source optical system and the single light profile adjuster is larger than a second distance between the single light profile adjuster and the condenser.

[Claim 5]

The illumination device according to claim 4, wherein the single light profile adjuster is disposed at a point, where the light converged by the light-source optical system becomes narrowest, between the light-source optical system and the condenser in the travel direction.

[Claim 6]

The illumination device according to any one of claims 1 to 5, wherein the single light profile adjuster includes a microlens array including multiple microlenses two-dimensionally arrayed in a plane orthogonal to an optical axis.

[Claim 7] The illumination device according to claim 6, wherein each of the multiple microlenses of the single light profile adjuster has: a flat incident surface; and a lens-shaped exit surface opposite to the flat incident surface.

[Claim 8]

The illumination device according to claim 6 or 7, wherein the light-emitting sections are: arrayed two-dimensionally; and tilted by a predetermined tilt angle relative to at least one of a column direction or a row direction of the microlenses arrayed two-dimensionally arrayed.

[Claim 9]

The illumination device according to claim 8, wherein the light-emitting sections has the predetermined tilt angle between 0 degrees and 5 degrees relative to at least one of the column direction or the row direction of the microlenses.

[Claim 10]

The illumination device according to claim 8 or 9, wherein the light-emitting sections are arrayed two-dimensionally in a first rectangular plane orthogonal to an optical axis formed by connecting centers of light-emitting sections at four corners of the light-emitting sections, the microlenses are arrayed two-dimensionally in a second rectangular plane orthogonal to the optical axis formed by connecting centers of microlenses at four corners of the multiple microlenses, and the first rectangular plane is rotated around the optical axis by the predetermined tilt angle relative to the second rectangular plane.

[Claim 11]

The illumination device according to any one of claims 8 to 10, further comprising: a first holder holding the light source; and a second holder holding the microlens array, wherein the first holder and the second holder are attached to an attachment surface of the illumination device parallel to the optical axis, and one of the first holder or the second holder is tilted relative to the attachment surface.

[Claim 12]

The illumination device according to any one of claims 8 to 11, wherein the light source or the microlens array is rotatable about the optical axis.

[Claim 13]

The illumination device according to any one of claims 1 to 12, further comprising: two light-source units each including the light source, the wavelength converter, the condensing optical system, and the single light profile adjuster; and a light combiner to direct light beams from the light-source units in a same direction toward a light homogenizer.

[Claim 14]

The illumination device according to claim 13, wherein the light combiner reflects at least one of the light beams from the light- source units to the light homogenizer.

[Claim 15]

An image projection apparatus comprising: the illumination device according to any one of claims 1 to 14; and an image generator to generate an image with the light emitted from the illumination device.