JP2759270B2 - Photometer for electronic imaging camera - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic imaging camera, and more particularly to a photometric device for a still camera using a fixed imaging device.

[Conventional technology]

Conventionally, in an automatic exposure control system of a video camera or an electronic still camera that converts an optical image into a video signal by a solid-state imaging device and records it on a magnetic medium, the incident light is reflected in a light path of an imaging optical system to a finder optical system. A TTL direct photometry system provided with a beam splitter that reflects light reflected from an electronic imaging unit to a photometry system has been proposed.

[Problems to be solved by the invention]

FIG. 4 shows an example of a conventional photometry method. In the figure, when the stop 3 is stopped down and the aperture opening becomes smaller than the half mirror portion of the beam splitter, the reflected light from the aperture blade enters the photometric system and is superimposed on the reflected light from the surface of the image sensor 7 so that proper photometry is performed. There was a problem that a value could not be obtained.

The present invention is an improvement of a TTL direct photometry system of an electronic camera using a solid-state imaging device.In a photometry device that mainly reflects regular reflection light from an imaging device to a photometry system on the back surface of a beam splitter, the reflection light from an aperture blade is used. It is an object of the present invention to provide a photometric device in which the amount of light entering the photometric system is reduced and the photometric accuracy is improved.

[Means for solving the problem]

In order to achieve the above object, it is necessary to make the aperture diameter of the sub-aperture equal to or slightly larger than the aperture diameter of the aperture mechanism arranged behind the beam splitter. According to a first configuration of the present invention (the invention of FIG. 1), an imaging optical system that forms an optical image through light of a subject, an electronic imaging unit that receives the optical image and converts the optical image into an electric signal, and the imaging optical system A beam splitter that is in the optical path of the system and reflects incident light to a finder optical system and reflects light reflected from the electronic imaging unit to a photometric system. An aperture mechanism is provided on the imaging unit side, and a sub-aperture mechanism that enters and exits the imaging optical system is provided on the subject side of the beam splitter.

Next, a second configuration (the invention of FIG. 2) includes an imaging optical system that forms an optical image through light of a subject, an electronic imaging unit that receives the optical image and converts it into an electric signal, and the imaging optical system. A beam splitter that reflects incident light to a finder optical system and reflects reflected light from the electronic imaging unit to a photometric system in the optical path of the electronic imaging camera, wherein the electronic imaging of the beam splitter is performed. An aperture mechanism is provided on the unit side, and a sub-aperture (light flux control) element is fixedly provided on the optical axis on the object side of the beam splitter.

[Action]

According to the above configuration, by reducing the incident light by the sub-aperture mechanism, the reflected light from the blades of the aperture mechanism 3 is reduced,
The light reflected from the surface of the solid-state image sensor can be measured simply and with high accuracy.

〔Example〕

Embodiments will be described with reference to the drawings. FIG. 1 shows an embodiment of a photometer for an electronic camera to which the present invention is applied. A beam splitter 2 for an optical finder is disposed behind the lens system 1 so that a subject (not shown) can be viewed by the finder optical system. An aperture mechanism 3, a master lens 4, and an optical filter 5 are arranged behind the beam splitter 2, and the incident light passes through them and enters the solid-state imaging device 7. Part of the incident light is reflected on the surface of the solid-state imaging device 7, and mainly specular reflection is reflected on the surface of the beam splitter 2, and is guided to the photometric device 9 through the photometric lens 8. The photometric element 9 outputs an electric signal according to the intensity of the incident light as a photometric signal, calculates the photometric circuit 11, and controls the shutter control circuit 12 and the aperture control circuit 13 to obtain an appropriate exposure. Here, if the aperture mechanism 3 is stopped down smaller than the half mirror portion of the beam splitter 2, the light reflected from the aperture blades of the aperture mechanism 3 enters the photometric system. Therefore, the sub-aperture 10 is inserted in front of the beam splitter 2 to reduce the incident light, thereby reducing the reflected light from the aperture blade. Next, in the embodiment shown in FIG. 2, since the mechanism is complicated in the method of taking in and out the sub-aperture 10 shown in FIG. By controlling the aperture, a simple auxiliary aperture function can be achieved.

FIG. 3 is a measurement example showing the relationship between the aperture value of the aperture mechanism 3 and the output of the photometric element in the present embodiment. When there is no sub-aperture, the photometric output increases on the small aperture side, and the linearity is deteriorated. In the case of the present invention, when there is a sub-aperture, good linearity can be obtained even on the small aperture side.

〔The invention's effect〕

As described above, according to the present invention, it is possible to perform TTL direct photometry with high accuracy using a simple structure in which the reflected light from the front surface of the image sensor is reflected by the back surface of the beam splitter and photometry is performed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment of the present invention. FIG. 2 is a block diagram showing a configuration of a second embodiment of the present invention. FIG. 3 shows a measurement example in the case of the embodiment of FIG. FIG. 4 is a block diagram showing a configuration of an example of a conventional photometric device. DESCRIPTION OF SYMBOLS 1 ... Lens system, 2 ... Beam splitter 3 ... Aperture mechanism 4, ... Master lens 5 ... Optical filter, 7 ... Solid-state image sensor 8 ... Photometric lens, 9 ... Photometric element 10 ... Sub-aperture , 10 ': light flux control element, 11: photometry circuit 12: shutter control circuit, 13: aperture control circuit

 ──────────────────────────────────────────────────続 き Continuing from the front page Examiner Keiichi Kato (56) References Jikai Sho 63-141932 (JP, U)

Claims (2)

(57) [Claims] An image pickup optical system for forming a light image through light of a subject, an electronic image pickup unit for receiving the light image and converting the image into an electric signal, and a finder for detecting incident light in an optical path of the image pickup optical system. A beam splitter that reflects light to an optical system and reflects light reflected from the electronic imaging unit to a photometry system, wherein the beam splitter is provided with a diaphragm mechanism on the electronic imaging unit side of the beam splitter; A photometric device for an electronic imaging camera, further comprising a sub-aperture mechanism that enters and exits the imaging optical system on the subject side of the splitter. 2. An imaging optical system for forming a light image by passing light of a subject, an electronic imaging unit for receiving the light image and converting the light image into an electric signal, and a finder for detecting incident light in an optical path of the imaging optical system. A beam splitter that reflects light to an optical system and reflects light reflected from the electronic imaging unit to a photometry system, wherein the beam splitter is provided with a diaphragm mechanism on the electronic imaging unit side of the beam splitter; A photometric device for an electronic imaging camera, wherein a sub-aperture element is fixedly provided on an optical axis on a subject side of a splitter.