JPH04151628A - Photometry device for electronic image pickup device - Google Patents

Abstract

PURPOSE:To reduce an effect of external diffusion and to minimize time delay from trigger-on regardless of the magnification or the sort of a lens by constituting a photometry device so that the photometry of light passed through the lens can be directly executed by the separation of polarized light. CONSTITUTION:An optical low-pass filter means 2 that double refraction for preventing the pseudo resolution of the light is utilized, a photoelectric conversion means which photoelectrically converts the light, a polarized light separation means and a photometry means are provided. That means, a photometry element 10 is arranged on an optical axis polarized by a polarizing beam splitter 11 so that the photometry of the light passed through the lens 1 can be directly executed. Thus, the effect of external diffusion is reduced and the time delay from the trigger-on is minimized regardless of the magnification or the sort of the lens.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a photometry device for an electronic image pickup device, and is capable of directly photometering light passing through a lens.

(Prior Art) FIG. 2 shows a configuration example of a photometric device of a conventional electronic imaging device, and FIG. 3 shows an operation flowchart when using a strobe. Normally, the light passing through the lens J has high spatial frequency components removed by an optical low pass filter (LPF) 2, and is subjected to temporary exposure in advance by a charge coupled device (CCD image sensor) 3. The output of this CCD is the process section 4
The shutter speed (aperture) is input to the microcomputer (CPLJ) 5 via
The shutter drive 11FII6 is controlled at , and the shutter 7 disposed on the optical axis connecting the lens and the CCD is subjected to main exposure.

Next, when using the strobe 8, with the shutter 7 fixed (open) (Sl), the strobe 8 is fired by a signal from the strobe light emitting circuit 9 (S,), and the photometric element IO outside the lens is used to set the horizontal ratio S6. ), and when the CPU 5 reaches the appropriate exposure light amount based on the horizontal ratio signal (YE of S)
S), the strobe 8 is activated by the signal from the strobe light emitting circuit 9.
stops emitting light (S,).

(tlM to be solved by the invention) In the conventional photometering device of the electronic image pickup device shown in FIG. 2, when measuring light using the CCD 3, a time delay always occurs because the trigger (concave path) is pressed and then provisional exposure is performed. do. Further, since the latitude of the CCD itself is narrow, in the case of an extremely high-precision or low-luminance subject, an accurate exposure value cannot be determined with -degree provisional exposure.

Also, when using a strobe, the above CCD exposure cannot be used, so photometry must be done with an external element, but in this case,
It has the following drawbacks:

(a) Since there is a photometric element outside the lens, accurate exposure values cannot be obtained due to changes in the zoom magnification of the lens.

(b) Cannot support lens conversion.

(c) It is not an accurate exposure value of the subject.

(d) Malfunctions are likely to occur if there is a highly reflective object near the subject.

As a means to solve these drawbacks, there is a TTL direct photometry method used in silver halide cameras. this is,
A photometric element measures the reflection of the light that hits the film surface through the lens. If this TTL direct photometry method is applied to an electronic imaging device, the above-mentioned drawbacks will be solved, but in order to save space, an optical low-pass filter (LPF) 2 is usually placed just before the CCD to reduce the reflection of the light that hits the COD. Therefore, there was a problem in that it was difficult to arrange the photometric element.

The present invention solves these problems and provides CC with a simple configuration.
It is an object of the present invention to provide a photometry device for an electronic imaging device that can detect reflected light from the D surface.

(Means for Solving the Problems) In order to solve the above problems and achieve the objects, the present invention provides optical low-pass filter means using birefringence to prevent false resolution of light, and photoelectric conversion of light. photoelectric conversion means;
Polarized light separation means disposed on the optical axis of the optical low-pass filter means and photoelectric conversion means; and the photoelectric conversion means disposed on the polarized optical axis separated from the optical axis by the polarized light separation means. and photometric means for directly photometrically detecting the amount of light incident on the device.

(Function) The present invention is configured so that the light passing through the lens can be directly measured by polarization separation, so there is little influence from external disturbances.
Additionally, the time delay from trigger-on can be minimized, regardless of lens magnification or lens type.

(Embodiment) FIG. 1 shows a configuration diagram of an embodiment of the present invention, and 2 is a CCD
3 is a crystal low-pass filter (LPF) for preventing false resolution; 11 is a polarizing beam splitter (PBS) for light disposed on the optical axis of the LPF 2 and CCD 3;
, ■2 is a l/4 wavelength plate also placed on the optical axis, and the photometric element IO is placed on the optical axis polarized by the PBSII, and is separated from the optical axis connecting lens 1 to CCD 3. has been done.

Next, the operation of the photometric device having the above configuration will be described. The light passing through the lens 1 is filtered with high spatial frequency components by a crystal low-pass filter (LPF) 2 for preventing false resolution by the CCD 3. The light that has passed through the LPF 2 passes through the polarizing beam splitter (P B 5) 11 and enters the CCD 3 via the 174 wavelength plate 12 .

A part of the light incident on the second CCD 3 is reflected on the CCD plate surface or the cover glass and is incident on the PBSll.

Now, the light emitted from the LPF 2 is linearly polarized because this LPF utilizes the birefringence of crystal. This light is then a 174 wavelength plate! Since the light passes through L P j2 twice, the light that is reflected and enters the polarizing beam splitter (P B 5) 11 becomes linearly polarized light with a polarization direction different from that of the light emitted from L P j2. That is, by arranging the direction of PBSll on an appropriate optical axis, the reflected light from the CCD 3 can be taken out off the optical axis without loss.

By detecting this reflected light taken out off the optical axis with the photometric element IO, the CPU 5 can accurately know the amount of light incident on the CCD 3. Then, the CPU 5 determines the exposure amount based on the detected value of the photometric element 10 and controls the shutter drive unit 6.

(Effects of the Invention) As explained above, the present invention provides a polarizing beam splitter.
Since the photometric element is arranged on the optical axis of the polarized light, the problems of the conventional method have been solved.

Since the light passing through the lens can be measured directly, there is little influence from external disturbances, and the time delay from trigger-on can be minimized without being influenced by the magnification of the lens or the type of lens.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a diagram showing an example of the structure of a photometric device of a conventional electronic imaging device, and FIG.
FIG. 2 is a diagram illustrating an operation flow when using a strobe. l...Lens, 2...Low pass filter (L
PF), 3... Charge coupled device (COD), 4...
Process section, 5... microcomputer (CP
U), 6...Shutter drive unit, 7...
Shutter 8... Strobe, 9... Strobe light emitting circuit, 10... Photometric element, 11... Polarizing beam splitter (PBS), 12... 174 wavelength plate. Patent Roganjin Co., Ltd. Riko Figure 7, Figure 1/Z

Claims (1)

[Claims] an optical low-pass filter means using birefringence to prevent false resolution of light; a photoelectric conversion means for photoelectrically converting light; and an optical low-pass filter means disposed on the optical axis of the optical low-pass filter means and the photoelectric conversion means. a polarized light separating means; and a photometric means for directly photometrically detecting the amount of light incident on the photoelectric conversion means disposed on the polarized optical axis separated from the optical axis by the polarized light separating means. A photometric device for an electronic imaging device.