JPH089205A - Image monitor - Google Patents

Abstract

(57) [Summary] [Object] To provide an image monitor device capable of eliminating the generation of an unusable and useless space and reducing the size of the device. [Image Constitution] An image generation device 801 for displaying a subject image is incorporated in the image monitor device, and an eyepiece lens 102 and an eyepiece lens 103 are arranged in front of it. At a position near the lower part of the eyepiece 103, a pair of infrared diodes 706a that emit infrared rays toward the eyes of the observer,
706b is arranged. Eyepieces 102, 103
Between the dichroic mirror 101 and the eyepiece 10
It is arranged at an inclination angle larger than 45 degrees with respect to the optical axis of 2,
The dichroic mirror 101 reflects each of the corneal reflection images of the observer. Each corneal reflection image reflected by the dichroic mirror 101 is condensed by the imaging lens 711 and is imaged on the image sensor 712.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image monitor device used for a still camera, a video camera or the like.

[0002]

2. Description of the Related Art Conventionally, various so-called line-of-sight detection methods for detecting a position on the screen where an observer is gazing have been proposed.

Next, the principle of this visual axis detection method will be described with reference to the drawings. 4 and 5 are diagrams for explaining the principle of the visual axis detection method in the conventional visual axis detection device.

As shown in FIG. 4, the line-of-sight detection method uses a pair of infrared diodes 706a and 706b which emit infrared rays toward the eyes of the observer. As shown in FIGS. 4A and 4B, the infrared diodes 706 a and 706 b are substantially symmetrical with respect to the optical axis of the imaging lens 711 in the x direction (horizontal direction) and in the y direction of the imaging lens 711 ( It is located slightly below (vertical direction) and divergently illuminates the eyes of the observer.

A part of the illumination light reflected by the eyeball is imaged on the image sensor 712 by the imaging lens 711. As shown in FIG. 5A, the eyeball image formed on the image sensor is composed of a pupil 701 having a center 703 and an iris 704 defined by an iris end 702.
01, corneal reflection images e and d (virtual images) are formed on a line connecting the iris edge 702b and the iris edge 702a.

As shown in FIG. 5B, the image sensor 712 outputs a high output at a position corresponding to each corneal reflection image e, d (virtual image).

Next, when looking at the horizontal plane, as shown in FIG. 4A, the infrared rays emitted from the infrared diode 706b are applied to the cornea 710 of the observer's eyeball 708, and the infrared rays are reflected by the surface of the cornea 710. To be done. The corneal reflection image d (virtual image) formed by the reflected infrared rays is formed by the imaging lens 7
It is condensed by 11 and forms an image at a position d ′ on the image sensor 712.

Similarly, the infrared rays emitted from the infrared diode 706a are applied to the cornea 710 of the eyeball 708 of the observer, and the infrared rays are reflected by the surface of the cornea 710. The cornea reflection image e (virtual image) formed by the reflected infrared rays is condensed by the imaging lens 711, and the image sensor 7
An image is formed at a position e'on 12 above.

The light beams from the ends a and b of the iris 704 form the images of the ends a and b at the positions a ′ and b ′ on the image sensor 712 via the imaging lens 711.

Eyeball 70 with respect to the optical axis of imaging lens 711
When the rotation angle θ of 8 is small, and the x-coordinates of the ends a and b of the iris 704 are xa and xb, a large number of points xa and x
b is obtained on the image sensor 712 (marked with x in FIG. 5).

Next, the center of the pupil obtained by the method of least squares of the circle is defined as xc, and the x coordinate of the center of curvature o of the cornea 710 is defined as xo.
Then, the rotation angle θx of the eyeball 708 with respect to the optical axis is calculated from the following equation (1).

[0012]

Oc * sin θx = xc−xo (1) Next, when xo is calculated in consideration of a predetermined correction value δ at the midpoint k between the corneal reflection image d and the corneal reflection image e, xo is (2)
Calculated from the formula.

[0013]

## EQU00002 ## xk = (xd + xe) / 2 xo = (xd + xe) /2+.delta.x (2) where .delta.x is a numerical value geometrically determined from the installation method of the device, the eyeball distance, etc. Omit it.

Therefore, θx is obtained by substituting the equation (1) into the equation (2), and the θx is represented by the following equation (3).

[0015]

## EQU00003 ## .theta.x = arcsin [[xc-{(xd + xe) /2+.delta.x}] / oc] (3) Furthermore, the coordinates of each feature point projected on the image sensor 712 are represented by "'" (dash). With (4)
When rewritten as an expression,

[0016]

## EQU00004 ## .theta.x = arcsin [[xc '-{(xd' + xe ') / 2 + .delta.x'}] / oc / .beta.] (4).

Here, β is a magnification determined by the distance sze of the eyeball with respect to the imaging lens 711, and is actually obtained as a function of the interval | xd'-xe '| of corneal reflection images.

Next, looking at the vertical plane, as shown in FIG. 4B, the corneal reflection image generated by the infrared diodes 706a and 706b is generated at the same position, and this corneal reflection image is represented by i. The method of calculating the rotation angle θy of the eyeball is the same as the method of calculating the rotation angle θx in the horizontal plane, but only the above formula (2) is different, and assuming that the y coordinate of the corneal curvature center is yo, the following formula (5) is obtained. Is obtained.

[0019]

## EQU00005 ## yo = yi + .delta.y (5) Here, .delta.y is a numerical value obtained geometrically from the device arrangement method, eyeball distance, etc., and the calculation method is omitted.

Therefore, the rotation angle θy in the vertical direction can be obtained from the following equation (6).

[0021]

[Mathematical formula-see original document] [theta] y = arcsin [{yc '-(yi' + [delta] y ')} / oc / [beta]] (6) Further, the position coordinates (xn, yn) on the screen of the viewfinder of the video camera are the finder optical system. If a constant m determined by is used, it can be obtained from the following equations (7) and (8) on the horizontal plane and the vertical plane respectively.

[0022]

Xn = m * arcsin [[xc '-{(xd' + xe ') / 2 + δx'}] / oc / β] (7)

[0023]

Yn = m * arcsin [{yc ′ − (yi ′ + δy ′)} / oc / β] (6) As is apparent from FIG. 5B, the image sensor 712 is used to detect the pupil edge. Rising of the output waveform of (xb
′) And the falling edge (xa ′) are used, and the sharp rising edge (xe ′, xd ′) is used to detect the coordinates of the corneal reflection image.

By applying the principle of the visual axis detection method described above to a viewfinder of a still camera or a video camera, various functions such as an automatic focus adjustment function can be executed only by directing the visual line to a target subject. .

Next, a viewfinder of a video camera using the above-described visual axis detection method will be described with reference to the drawings. FIG. 6 is a view showing a conventional finder optical system of a video camera using a line-of-sight detection method.

As shown in FIG. 6, the viewfinder of the video camera incorporates an image generation device 801 for displaying the subject image captured by the optical lens on the screen. The image generation device 801 is composed of a liquid crystal display device. In this embodiment, a liquid crystal display device is used as the image generation device 804, but a CRT can be used instead.

An eyepiece lens 802 and an eyepiece lens 803 are arranged in series in front of the screen of the image generator 801 so that their optical axes coincide with each other. Eyepiece 8
02 and the eyepiece lens 803 are spaced from each other. The eyepiece lens 802 and the eyepiece lens 803 cooperate with each other to enlarge the image displayed on the screen of the image generation apparatus 801 by a predetermined enlargement ratio, reduce each aberration, and reduce the influence on the visual axis detection system described later. A lens for the purpose is constructed. The eyepiece lens 803 is a lens for guiding the image formed thereon to the eyes of the observer.

A pair of infrared diodes 706a and 706b are arranged at a distance from each other in the vicinity of the lower portion of the eyepiece lens 803. Each infrared diode 706
Reference numerals a and 706b radiate infrared rays toward the eyes of the observer looking into the eyepiece lens 803. Each infrared diode 706a,
The infrared rays emitted from 706b are applied to the cornea of the eyeball of the observer, and the infrared rays are reflected by the surface of the cornea. A corneal reflection image (virtual image) is formed by each of the reflected infrared rays.

A dichroic mirror 804 is provided between the eyepiece lens 802 and the eyepiece lens 803.
It is arranged so as to be inclined by 45 degrees with respect to the optical axis of 01. The surface of the dichroic mirror 804 is provided with a special coating that reflects only infrared rays.
The dichroic mirror 804 reflects each corneal reflection image (virtual image) from the observer.

An image forming lens 711 is arranged below the dichroic mirror 804, and the respective corneal reflection images reflected by the dichroic mirror 804 by the image forming lens 711 are collected and formed on the image sensor 712, respectively. The image sensor 712 is composed of a CCD (charge coupled device), and the position on the screen of the image generation device 801 that the observer is gazing is detected from the corneal reflection image formed on the CCD.

As described above, it is possible to discriminate the subject to be captured by the observer, and it is possible to execute various functions such as an automatic focusing function for the discriminated subject.

[0032]

However, in the conventional viewfinder, since the dichroic mirror 804 is arranged at an angle of 45 degrees with respect to the optical axis of the image generating device 801, a large space is required for disposing the dichroic mirror 804. In addition, the distance from the eyepiece lens 803 to the screen of the image policing device 801 becomes long. Therefore, a useless and useless space is generated, and the size of the entire apparatus is increased.

An object of the present invention is to provide an image monitor device which can eliminate the useless and useless space and can reduce the size of the device.

[0034]

According to a first aspect of the present invention, in an image monitor device for observing an image captured by an optical lens or the like, display means for displaying the image and the display means for displaying the image. An eyepiece for forming an optical image corresponding to an image on an observer's eye, a detecting means for detecting predetermined information from optical information indicating the movement of the observer's eye, and an image displayed on the display means And an optical separation unit that guides an optical image corresponding to the optical image to the eyepiece lens and separates optical information indicating the movement of the observer's eyes from the optical image from the eyepiece lens to a detection unit. It is characterized in that the detecting means is arranged in the vicinity of the end portion.

According to a second aspect of the present invention, the detection means is
It is characterized in that the image portion gazed at by the observer is detected based on the light information indicating the movement of the observer's eyes.

According to a third aspect of the present invention, the detecting means is
The light source includes a light source for emitting a light beam in a specific wavelength range toward the observer's eye, and a light receiving unit for receiving the light information generated by the light beam from the light source through the light separating unit.

According to a fourth aspect of the present invention, the light receiving means is
It is characterized by comprising a charge coupled device.

The invention according to claim 5 is characterized in that an optical lens for guiding an optical image corresponding to the image to the light separating means is provided between the display means and the light separating means. .

The invention according to claim 6 is characterized in that the light separating means comprises a dichroic mirror.

According to a seventh aspect of the present invention, the light separating means is arranged at an angle of 45 in a direction perpendicular to the optical axis of the eyepiece lens.
It is characterized by being composed of dichroic mirrors arranged at an angle larger than degrees.

The invention according to claim 8 is characterized in that the light splitting means comprises a beam splitter composed of a plurality of prisms.

According to a ninth aspect of the present invention, the light separating means is a semi-transmissive mirror.

[0043]

According to the structure of the image monitor apparatus of claim 1, the display means for displaying the image, the eyepiece for forming the optical image corresponding to the image displayed on the display means in the eyes of the observer, and the observation While detecting the predetermined information from the optical information indicating the movement of the eyes of the person, and guiding the optical image corresponding to the image displayed on the display means to the eyepiece, the optical information indicating the movement of the eyes of the observer. Light separating means for separating the light image and guiding it from the eyepiece to the detecting means is provided, and the detecting means is arranged in the vicinity of the end of the eyepiece.

In the structure of the image monitor apparatus according to the second aspect, the detecting means detects the image portion which the observer is gazing based on the optical information indicating the movement of the observer's eyes.

In the structure of the image monitor apparatus according to the third aspect, the detecting means emits a light ray in a specific wavelength range toward the eyes of the observer, and the light generated by the light ray from the light source. And light receiving means for receiving information via the light separating means.

According to another aspect of the image monitor device of the present invention, the light receiving means is a charge coupled device.

In the structure of the image monitor apparatus according to the fifth aspect, an optical lens for guiding an optical image corresponding to the image to the light separating means is provided between the display means and the light separating means.

In the image monitor apparatus according to the sixth aspect, the light separating means is a dichroic mirror.

In the structure of the image monitor apparatus according to the seventh aspect, the light separating means is a dichroic mirror obliquely arranged at an angle larger than 45 degrees in the vertical direction with respect to the optical axis of the eyepiece lens.

In the structure of the image monitor apparatus according to the eighth aspect, the light separating means is a beam splitter composed of a plurality of prisms.

In the configuration of the image monitor apparatus according to the ninth aspect, the light separating means is a semi-transmissive mirror.

[0052]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a side view showing the configuration of the main part of the first embodiment of the image monitor apparatus of the present invention.

The image monitor device of this embodiment is used as a finder of a video camera. As shown in FIG. 1, the image monitor device incorporates an image generation device 801 that displays a subject image captured by an optical lens (not shown) on a screen. The image generation device 801 is composed of a liquid crystal display device.

In front of the screen of the image generating device 801, an eyepiece lens 102 and an eyepiece lens 103 are arranged in series so that their optical axes coincide with each other. Eyepiece 1
02 and the eyepiece lens 103 are spaced apart from each other. The eyepiece lens 102 and the eyepiece lens 103 cooperate with each other to enlarge the image displayed on the screen of the image generating apparatus 801 by a predetermined enlargement ratio, reduce each aberration, and reduce the influence on a visual axis detection system described later. A lens for the purpose is constructed. The eyepiece lens 103 is a lens for guiding the image formed thereon to the eyes of the observer. Eyepiece 103
A cutout is formed in the lower part of the. The degree of this cutout is determined so that the screen of the image generation device 801 is completely captured within the field of view of the observer and does not affect the optical path to the image sensor 712, which will be described later.

A pair of infrared diodes 706a and 706b are arranged in the vicinity of the lower portion of the eyepiece lens 103 with a space therebetween. Each infrared diode 706
Reference numerals a and 706b radiate infrared rays toward the eyes of the observer looking into the eyepiece lens 103. Each infrared diode 706a,
The infrared rays emitted from 706b are applied to the cornea of the eyeball of the observer, and the infrared rays are reflected by the surface of the cornea. A corneal reflection image (virtual image) is formed by each of the reflected infrared rays.

A dichroic mirror 101 is provided between the eyepiece lens 102 and the eyepiece lens 103.
It is arranged so as to be inclined at an angle larger than 45 degrees with respect to the optical axis of 2. The surface of the dichroic mirror 101 is provided with a special coating that reflects only infrared rays. The dichroic mirror 101 reflects each corneal reflection image (virtual image) from an observer.

An image forming lens 711 is arranged diagonally below the dichroic mirror 101 in the vertical direction, and the image forming lens 7 is formed.
The corneal reflection images reflected by the dichroic mirror 101 by 11 are condensed and formed on the image sensor 712, respectively. The image sensor 712 is composed of a CCD (charge coupled device), and the position on the screen of the image generation device 801 that the observer is gazing is detected from the corneal reflection image formed on the CCD. Therefore, the subject to be captured by the observer is determined, and various functions such as the automatic focus adjustment function for the determined subject are executed.

From the above, the dichroic mirror 101
Since the inclination angle θ of the eyepiece lens 102 with respect to the optical axis is larger than 45 degrees, the eyepiece lens 103 is used to generate the image generation device 8.
The distance x to the screen 01 is shortened, and the vertical dimension y is shortened by the movement of the image sensor 712 and the imaging lens 711 to the eyepiece 103 side, and the device can be downsized.

By moving the image sensor 712 and the imaging lens 711 to the eyepiece 103 side, the eyepiece 10 is provided below the dichroic mirror 101.
2 and the image sensor 712 create a friendly space A in which other components can be incorporated.

Although the dichroic mirror 101 is used as the light separating means in this embodiment, a half mirror may be used instead.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a top view showing the configuration of the main part of the second embodiment of the image monitor device of the present invention.

The image monitor device of this embodiment is used as a finder of a video camera. As shown in FIG. 2, the image monitor device incorporates an image generation device 801 that displays a subject image captured by an optical lens (not shown) on a screen.

An eyepiece lens 102 and an eyepiece lens 103 are arranged in series in front of the screen of the image generator 801 so that their optical axes coincide with each other. Eyepiece 1
02 and the eyepiece lens 103 are spaced apart from each other. The eyepiece lens 102 and the eyepiece lens 103 cooperate with each other to enlarge the image displayed on the screen of the image generation apparatus 801 by a predetermined enlargement ratio, reduce each aberration, and reduce the influence on the visual axis detection system described later. A lens for the purpose is constructed. The eyepiece lens 103 is a lens for guiding the image formed thereon to the eyes of the observer. Eyepiece 103
A cutout portion is formed in a part (the left end portion in the drawing) of the periphery of the. The degree of this cutout is determined by the image generation device 8
The screen No. 01 is determined so as to be completely captured within the field of view of the observer and does not affect the optical path to the image sensor 712 described later.

A pair of infrared diodes 706a, 706b are arranged at a distance from each other in the vicinity of the left and right sides of the eyepiece lens 103. The infrared diodes 706a and 706b emit infrared rays toward the eyes of the observer looking into the eyepiece 103. Each infrared diode 7
Infrared rays emitted from 06a and 706b are applied to the cornea of the eyeball of the observer, and each infrared ray is reflected by the surface of the cornea. A corneal reflection image (virtual image) is formed by each of the reflected infrared rays.

A dichroic mirror 101 is provided between the eyepiece lens 102 and the eyepiece lens 103.
It is arranged so as to be inclined at an angle larger than 45 degrees with respect to the optical axis of 2. The surface of the dichroic mirror 101 is provided with a special coating that reflects only infrared rays. The dichroic mirror 101 reflects each corneal reflection image (virtual image) from an observer.

An imaging lens 711 is arranged diagonally forward of the dichroic mirror 101 (obliquely leftward in the figure), and the dichroic mirror 1 is formed by the imaging lens 711.
The corneal reflection images reflected by 01 are collected and formed on the image sensor 712, respectively.

From the above, the dichroic mirror 101
Since the inclination angle θ of the eyepiece lens 102 with respect to the optical axis is larger than 45 degrees, the eyepiece lens 103 is used to generate the image generation device 8.
The distance to the screen of 01 is shortened, and the lateral dimension of the image sensor 712 and the imaging lens 711 to the eyepiece 103 is shortened, so that the lateral dimension is shortened and the apparatus can be downsized. In addition, it is possible to eliminate unusable waste space.

(Third Embodiment) Next, a third embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a side view showing the configuration of the main part of the first embodiment of the image monitor device of the present invention.

The image monitor device of this embodiment is used as a finder of a video camera. As shown in FIG. 3, the image monitor device incorporates an image generation device 801 that displays a subject image captured by an optical lens (not shown) on a screen.

In front of the screen of the image generating device 801, the eyepieces 102 and 103 are arranged in series so that their optical axes coincide with each other. Eyepiece 1
02 and the eyepiece lens 103 are spaced apart from each other. The eyepiece lens 102 and the eyepiece lens 103 cooperate with each other to enlarge the image displayed on the screen of the image generating apparatus 801 by a predetermined enlargement ratio, reduce each aberration, and reduce the influence on a visual axis detection system described later. A lens for the purpose is constructed. The eyepiece lens 103 is a lens for guiding the image formed thereon to the eyes of the observer. Eyepiece 103
A cutout is formed in the lower part of the. The degree of this cutout is determined so that the screen of the image generation device 801 is completely captured within the field of view of the observer and does not affect the optical path to the image sensor 712, which will be described later.

A pair of infrared diodes 706a and 706b are arranged at a distance from each other in the vicinity of the lower portion of the eyepiece lens 103. Each infrared diode 706
Reference numerals a and 706b radiate infrared rays toward the eyes of the observer looking into the eyepiece lens 103. Each infrared diode 706a,
The infrared rays emitted from 706b are applied to the cornea of the eyeball of the observer, and the infrared rays are reflected by the surface of the cornea. A corneal reflection image (virtual image) is formed by each of the reflected infrared rays.

A beam splitter 301 is arranged between the eyepieces 102 and 103. The beam splitter 301 is composed of two prisms 301a and 301b joined to each other. The surface P of the prism 301a facing the prism 301b is provided with a special coating that reflects only infrared rays, and the prism 301b is formed with a surface Q for receiving the infrared rays reflected by the surface P of the prism 301a. The angle is set to the angle at which the infrared rays incident on it are totally reflected. The beam splitter 301 guides each corneal reflection image (virtual image) from the observer to the imaging lens 711 via the surfaces P and Q.

The imaging lens 711 collects the reflected infrared light from the surface Q, and the collected infrared light is collected by the image sensor 71.
2 is imaged on each. The imaging lens 711 and the image sensor 712 are arranged below the eyepiece lens 103.

As described above, since each of the corneal reflection images (virtual images) from the observer is guided to the imaging lens 711 by the beam splitter 301 via the surfaces P and Q, the distance from the eyepiece 103 to the screen of the image generating device 801. And the image sensor 712 and the imaging lens 711 are moved to the eyepiece 103 side, the vertical dimension is shortened, and the device can be downsized. In addition, it is possible to eliminate a useless space that cannot be used.

In each of the above-described embodiments, the finder is used as a video camera, but it can also be used as a finder for a still camera.

[0077]

As described above, according to the image monitor device of the first aspect, the display means for displaying the image and the optical image corresponding to the image displayed on the display means are formed in the eyes of the observer. An eyepiece for forming an image, a detecting means for detecting predetermined information from optical information indicating the movement of the observer's eyes, and an optical image corresponding to the image displayed on the display means to the eyepiece, and an observer. It is not available because there is a light separating means for separating the optical information indicating the eye movement from the optical image and guiding it from the eyepiece to the detecting means, and the detecting means is arranged in the vicinity of the end of the eyepiece. It is possible to eliminate unnecessary wasteful space and to reduce the size of the device.

According to the image monitor device of the second to ninth aspects, it is possible to eliminate the generation of an unusable and useless space, and to reduce the size of the device.

[Brief description of drawings]

FIG. 1 is a side view showing a configuration of a main part of a first embodiment of an image monitor device of the present invention.

FIG. 2 is a top view showing a configuration of a main part of a second embodiment of the image monitor device of the present invention.

FIG. 3 is a side view showing the configuration of the main part of the first embodiment of the image monitor device of the present invention.

FIG. 4 is a diagram for explaining the principle of a visual line detection method in a conventional visual line detection device.

FIG. 5 is a diagram for explaining the principle of a visual line detection method in a conventional visual line detection device.

FIG. 6 is a diagram showing a conventional finder optical system of a video camera using a visual axis detection method.

[Explanation of symbols]

 101 dichroic mirror (light separation means) 102, 103 eyepiece 301 beam splitters (light separation means) 301a, 301b prisms 706a, 706b infrared diode (light source) 711 imaging lens 712 image sensor (detection means)

Claims (9)

[Claims] 1. In an image monitor device for observing an image captured by an optical lens or the like, display means for displaying the image, and an optical image corresponding to the image displayed on the display means for an observer's eyes. An eyepiece for forming an image on the eye, a detection means for detecting predetermined information from the light information indicating the movement of the observer's eyes, and an optical image corresponding to the image displayed on the display means to the eyepiece. Along with, a light separating means for separating the light information indicating the movement of the observer's eyes from the optical image and guiding it from the eyepiece to the detecting means is provided, and the detecting means is arranged at a position near the end of the eyepiece. An image monitor device characterized by being provided. 2. The image monitor apparatus according to claim 1, wherein the detection unit detects an image portion that the observer is gazing based on light information indicating the movement of the observer's eyes. 3. The light source for radiating a light beam in a specific wavelength range toward the eyes of the observer,
The image monitor device according to claim 1, further comprising a light receiving unit that receives the optical information generated by the light beam from the light source via the light separating unit. 4. The image monitor apparatus according to claim 3, wherein the light receiving unit is a charge coupled device. 5. The image according to claim 1, wherein an optical lens for guiding an optical image corresponding to the image to the light separating means is provided between the display means and the light separating means. Monitor device. 6. The image monitor apparatus according to claim 1, wherein the light separating means is a dichroic mirror. 7. The image monitor according to claim 1, wherein the light separating means is a dichroic mirror obliquely arranged in a direction perpendicular to the optical axis of the eyepiece at an angle larger than 45 degrees. apparatus. 8. The image monitor apparatus according to claim 1, wherein the light splitting means comprises a beam splitter composed of a plurality of prisms. 9. The image monitor apparatus according to claim 1, wherein the light separating means is a semi-transmissive mirror.