JPH022293A - Image pickup device - Google Patents

Abstract

PURPOSE:To obtain a picture with a prescribed object field depth independently of the quantity of brightness by providing an exposure adjustment means provided with a liquid crystal panel and varying the orientation of the liquid crystal of the liquid crystal panel so as to adjust the luminous quantity reaching the image pickup means so as to obtain the calculated proper exposure. CONSTITUTION:A TFT liquid crystal panel 5 is arranged in front of a CCD 4, that is, at rear side of a half mirror 2 and has plural picture elements so as to control the orientation of the liquid crystal in the unit of picture elements respectively. When the distance up to the object is matched and the focus adjustment of the lens 1 is finished, a photometric device 3 measures the total amount of the brightness of the object made incident in a photo diode 6 via the lens 1 and the half mirror 2 and the proper exposure corresponding to the total quantity is calculated by a log amplifier 10 and a control signal is outputted to the liquid crystal panel drive circuit 11. The control signal is outputted corresponding to each picture element. The liquid crystal panel drive circuit 11 receiving the control signal applies a drive voltage to each picture element of the TFT liquid crystal panel 5 to adjust the luminous quantity reaching the CCD 4 via the half mirror 2.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to photographing devices such as video cameras and still cameras, and particularly to exposure devices thereof.

(B) Prior Art Conventionally, this type of photographing device basically includes a lens and an aperture ring that is disposed behind the lens and adjusts the amount of light from a subject that enters through the lens. The light passing through the aperture ring forms an image of the subject on the surface of an image sensor, such as a film or a COD image sensor, which is disposed behind the aperture ring.

The aperture ring is constructed of a plurality of blades to form a disc, and has a through hole in its center that can change its area depending on the amount of light. By increasing or decreasing the aperture area of this aperture ring, appropriate exposure can be obtained depending on the subject.

. (C) Problems to be Solved by the Invention However, with the above aperture ring, the light intensity is adjusted by changing the area of the through hole, so it can only be adjusted stepwise in 1/2 EV units. There wasn't. This causes the depth of field to change depending on the area of the aperture, that is, the area of the aperture, and the perspective of the obtained image of the subject may look different depending on the exposure. The effect was particularly large when shooting under high brightness.

This invention has been made in consideration of the above circumstances, and it is an object of the present invention to provide a photographing device capable of linearly adjusting exposure.

(d) Means for Solving Problems According to the present invention, there is provided a photographing means in which an image of a subject incident through a lens is formed on the surface thereof, and a luminance of the subject incident through a lens. a photometric means for measuring the total amount; a calculation means for calculating an appropriate exposure amount corresponding to the total amount measured by the photometry means; There is provided a photographing device characterized by comprising: an exposure adjustment means having a liquid crystal panel that adjusts the amount of light reaching the imaging means.

(e) Operation The photometry means measures the total luminance q of the subject incident through the lens, and outputs a fixed value to the calculation means. The calculation means calculates an appropriate exposure amount from the input measurement value, and the exposure adjustment means including a liquid crystal panel controls the imaging means to obtain the calculated appropriate exposure amount by changing the orientation of the liquid crystal of the liquid crystal panel. Adjust the amount of light that reaches you.

(F) EXAMPLES Hereinafter, examples of the present invention will be described in detail with reference to the drawings, but the present invention is not limited to the following examples.

As an embodiment of the present invention, a video camera using a CCD image sensor as an image pickup device will be described, the configuration of which is shown in FIG. 1.

In FIG. 1, reference numeral 1 denotes a lens, preferably a zoom lens, and the focus can be adjusted manually or automatically if it has a rangefinder. Reference numeral 2 denotes a half mirror, which is disposed behind the lens 1, and allows the light transmitted through the lens 1 to enter the photometer 3, and also connects a CCD image sensor (hereinafter referred to as CCD) 4, which is an imaging means, with a TPT (thin film transistor) liquid crystal display. Avoid reaching through panel 5.

The photometry device 3 is composed of a photodiode 6 that receives light from the half mirror 2, and a log amplifier 10 consisting of an operational amplifier 7, a transistor 8, and a current source 9, the number of which corresponds to the number of pixels of the TPT liquid crystal panel 5. It will be done. In other words, the TFT liquid crystal panel 5 is provided with pixels corresponding to each section obtained by dividing the photographic screen into a plurality of sections, and the photometer 3 corresponds to this, and measures the amount of light in each section. A plurality of them are provided for measurement.

The TPT liquid crystal panel 5 is disposed in front of the CCD 4, that is, behind the half mirror 2, and has one number of pixels as described above. It is sufficient that the alignment of liquid crystal can be controlled for each pixel, and a dot matrix type TPT liquid crystal panel conventionally known in the field may be used. The TFT liquid crystal panel 5 may be a color liquid crystal, in which case it serves as a color conversion filter for correction when the intensities of wavelength components included in light are different.

Reference numeral 11 denotes a liquid crystal panel driving circuit, which applies a voltage to each pixel of the TPT liquid crystal panel 5 in response to a signal from the photometer 3 to drive and control each pixel independently.

I2 is a light shielding plate that prevents light from entering the CCD 4 from sources other than the TPT liquid crystal panel 5.

Next, the operation of this embodiment will be explained. First, adjust the focus of lens I according to the distance to the subject. When the focus adjustment is completed, the photometer 3 measures the total amount of brightness of the subject that is incident on the photodiode 6 via the lens I5 half mirror 2, and calculates the appropriate exposure amount corresponding to the total amount using the log amplifier 10. and outputs a control signal to the liquid crystal panel drive circuit 11. Therefore, the photometric device 3 functions as photometric means and calculation means. As described above, the control signal is output corresponding to each pixel. LCD panel drive circuit that receives control signals! 1 applies a driving voltage to each pixel of the TPT liquid crystal panel 5 corresponding to the section of the photographing screen,
Adjust the amount of light reaching CD4. In other words, the TFT liquid crystal panel 5 and the liquid crystal panel drive circuit 11 function as exposure adjustment means.

Since the TPT liquid crystal panel 5 controls the amount of light to the CCD 4 on a pixel-by-pixel basis, unlike a conventional aperture ring, the area through which light passes does not change, so the depth of field does not change depending on the brightness. On the contrary, the liquid crystal panel drive circuit II
For example, a microprocessor or the like may be used to control the TPT liquid crystal panel 5 by using a signal from a measuring device to change the light passing area in the same way as a conventional aperture ring.

In the above embodiment, an example of a video camera was explained, but C
It goes without saying that it is possible to use a still camera by using ordinary photographic film instead of OD.

(G) Effects of the Invention According to this invention, even if there is a subject with a large brightness difference in one screen, it is possible to adjust the amount of light passing through each pixel of the liquid crystal panel, thereby increasing the COD of the imaging means. It is possible to obtain a photographing device that can prevent charge overflow in the luminance section and can obtain images with a constant depth of field regardless of the magnitude of the luminance.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. 1...Lens, 3...7III7 optical device, 4...COD image sensor, 5...TPT liquid crystal panel, 11...Liquid crystal panel drive circuit. - and -14-・

Claims (1)

[Scope of Claims] 1. Photographing means for forming an image of a subject incident through a lens on its surface; photometry means for measuring the total amount of brightness of the subject incident through the lens; and photometry a calculating means for calculating an appropriate exposure amount corresponding to the total amount measured by the means; and a calculating means arranged in front of the imaging means and adjusting the amount of light reaching the imaging means so as to obtain the appropriate exposure amount calculated by the calculating means. 1. A photographing device comprising: an exposure adjustment means having a liquid crystal panel.