The present application is based on, and claims priority from JP Application Serial Number 2018-135018, filed Jul. 18, 2018, the present disclosure of which is hereby incorporated by reference herein in its entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to an image display module and an image display device.

2. Related Art

In image display devices such as head-mounted displays or projectors, there has been known a color combining element that combines blue light, green light, and red light to emit the combined light. JP-A-2012-230151 described below discloses a projection-type display device including a first display unit configured to emit blue light, a second display unit configured to emit green light, a third display unit configured to emit red light, and a cross dichroic prism configured to combine light rays emitted from each of the display units. In the projection-type display device, each of the display units includes two organic electroluminescence (EL) panels that exhibit different emission peak wavelengths in the wavelength region of the same color, and combines the color light rays emitted from the two organic EL panels by a dichroic mirror.

Traditionally, a dichroic prism that includes a dichroic mirror having polarization separation characteristics has been used as a color combining element for combining light rays from liquid crystal panels. A dichroic prism for liquid crystal panels is designed to meet wavelength separation characteristics in either the P-polarized light or the S-polarized light. While the light emitted from the organic EL panel used in JP-A-2012-230151 contains both the P-polarized light and the S-polarized light and has no polarization characteristics, unlike the case of liquid crystal panels. Accordingly, only one of the S-polarized light and the P-polarized light contained in the light from the organic EL panel is available when the light rays emitted from the organic EL panel are combined by a dichroic prism for liquid crystal panels. That is, in the above combination, there is a drawback that only up to 50% light utilization efficiency can be achieved at the maximum.

In order to resolve the above-described drawback, studies have been conducted to investigate a dichroic mirror for combining light rays that do not have polarization characteristics, like the light emitted from an organic EL panel. However, since such a type of dichroic mirror is practically produced to combine blue light, green light, and red light, there is a drawback in that the light utilization efficiency of red light is particularly low among the three color light rays. Moreover, there is a drawback in that stray light is generated in the dichroic prism.

SUMMARY

To resolve the above-described drawbacks, an image display module according to one aspect of the present disclosure includes a first panel configured to emit first imaging light of a red wavelength region, the first imaging light having no polarization characteristics, a second panel configured to emit second imaging light in a blue wavelength region, the second imaging light having no polarization characteristics, a third panel configured to emit third imaging light of a green wavelength region, the third imaging light having no polarization characteristics, and a color combined prism configured to emit combined light combined from the first imaging light, the second imaging light, and the third light, wherein the color combined prism includes a first dichroic mirror having no polarization separation characteristics, and a second dichroic mirror having no polarization separation characteristics, and a peak wavelength in the red wavelength region is in a range of from 630 nm to 680 nm.

In the image display module according to one aspect of the present disclosure, a utilization efficiency of the first imaging light in the first dichroic mirror and the second dichroic mirror may be equal to or greater than 50%.

In the image display module according to one aspect of the present disclosure, the first dichroic mirror has characteristics of transmitting the third imaging light and reflecting the first imaging light, the second dichroic mirror has characteristics of transmitting the third imaging light and reflecting the second imaging light, and a transmission bandwidth of the third imaging light in the first and second dichroic mirrors may be equal to or greater than 130 nm.

In the image display module according to one aspect of the present disclosure, each of the first panel, the second panel, and the third panel may include a light-emitting element including an organic electroluminescence element.

In the image display module according to one aspect of the present disclosure, the organic electroluminescence element may include an optical resonator.

An image display device according to one aspect of the present disclosure includes the image display module according to one aspect of the present disclosure.

