JPH032529A - Method and device for correcting leak current for photometry element in ttl division photometry - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application of the Invention) The present invention is directed to a TTL split photometry device that prevents leakage current from entering some photometry elements of a divided subject screen from other photometry elements and causing erroneous photometry. 11 and relates to a method and apparatus for obtaining correct photometric values.

(Prior art and problems to be solved by the invention) When using an SFD as a photometric element in TTL split photometry, considering the split photometry on the subject screen as shown in Figures 2 and 3, leakage current from each part of the multi-segment SFD occurs and correct photometric values cannot be obtained. As a correction method, there is a method of reducing the influence of leakage current by widening the isolation between each SFD, but this method results in a large dead zone. In addition, as described in Japanese Patent Application Laid-open No. 59-46521, there is a method to prevent leakage current by shorting the seven nodes of the SPD that are unnecessary during photometry and the cathode, but this requires an extra switch. A circuit is required. Also, each SP
There is also a way to prevent leakage current by installing an amplifier in parallel to D.
The number of amplifiers required is equal to the number of SPDs, and the circuit becomes complicated.

(Means for Solving the Problems) In view of the dual vehicle circumstances, the present invention incorporates the influence of leakage current between adjacent part of photometry means and other part of photometry means that performs TTL division photometry into a correction coefficient. The photometric output (EVa), which is not affected by leakage current from other photometric surfaces, is determined by the following formula.

(FV!E "υ8)" EV a=EVA-K -2 (However, when receiving the luminous flux from the photometric surface with no brightness difference while allowing the leakage current of the other photometric means, (Example) The present invention will be described below with reference to the drawings. This will be explained in detail accordingly.

FIG. 1 is a diagram showing an embodiment of the apparatus of the present invention, FIG. 2 is a diagram showing an example of dividing a subject screen, and FIG. 3 is a diagram showing another example of dividing a subject screen.

In FIG. 1, 5PDI, 2.3.4, and 5 correspond to A, B, C, D, and E in FIG. 3, respectively, and the photocurrents generated from these SPDs are It is logarithmically compressed and A-D converted by the A-D converter 7, and the arithmetic unit 8 calculates the correction formula described later for the photometric optical system using the leakage current between each part as a parameter, and calculates the true photometric value. An action to obtain is performed. 9 to 13 are switches, and 14 is a regulator.

Next, the correction formula will be explained. To simplify the explanation,
The two-part method shown in FIG. 2 will be explained. EVa is the true EV value (exposure value) that is not affected by the leakage current of other photometric elements, and EVA is the EV value that includes the influence of the leakage current of other photometric elements.
, when the correction coefficient is set to K and light is measured by receiving a luminous flux from a photometric surface with uniform brightness in the center area A and the peripheral area B, the center area A
The true EV value of EVa=EVA- can be determined by the equation (1).

Therefore, both the central area A and the peripheral area B are irradiated with the light flux of the photometric surface toward a surface light source with uniform brightness, and the SP of the B area is
Measure the EV value E V A of the central part A when the oven is in the anode and cathode state of D, and irradiate both the central part A and the peripheral part B with a luminous flux of the same brightness as the first order, and calculate the SPD of the B part. If we measure the EV value EVa at the center A when the anode and cathode are shorted, the correction coefficient will be = EVA - EVa * * Meeting #6
It can be obtained using equation (2).

If this correction coefficient K is stored in the arithmetic unit 8, the central part A
When the peripheral part B and the peripheral part B have the same brightness, it is possible to obtain the true EVa value of the central part A which is not affected by the leakage current of the peripheral part B.

However, it is natural that the brightness of the central part A and the peripheral part B may be different. For example, if the brightness is doubled, the correction coefficient must also be doubled.

Therefore, if the EV value of the peripheral part B including the influence of the leakage current of the central part A is EVB, then the true EV is
The a value can be determined.

” EV affected by leakage current as shown in the double series.
The correction coefficient K can be determined by taking the difference between the EV value and the EV value that is not affected by the leakage current as the influence. This can also be applied to the case of multiple divisions as shown in Figure 3. It is. In this case, the correction formula is as follows.

(EVB-Eυ^) EVa=EVA-Kb ・ 2 (EVC-Eυ^) Kc ・ 2 -Kd ・ 2 As explained in detail above, according to the present invention, highly accurate TTL division photometry can be achieved with a simple configuration. It can be carried out.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the apparatus of the present invention, FIG. 2 is a diagram showing an example of dividing a subject screen, and FIG. 3 is a diagram showing another example of dividing a subject screen. 1-5II・-3PD, 6..Conflict logarithm compressor, 7..
A-D converter, 8... life calculator, 9-13... switch, 14-- regulator (however, the EV value of the 0 part, D part, and E part, which includes the influence of leakage current, is Evc, EVD, and EVE, respectively, and the correction coefficients are Kb, Kc, Kd, and Ke.) Note that this correction may cause some errors, but the corrected values can be calculated using Equation 3 or 4. Use it for the exponent part of 2,
Accurate correction can be achieved by performing the correction twice or many times. (Effect) Patent applicant Kyocera Corporation

Claims (2)

[Claims] (1) Partial photometry means responsible for photometry of a part of the subject screen subjected to TTL division photometry, other part photometry means responsible for photometry of other parts of the screen, and photometry output of these photometry means calculation storage means for calculating and storing the data, irradiating both the photometry means with a uniform light beam from the photometering surface, and irradiating the light beam from the photometering surface with the leakage current of the other photometering means cut off. The output (EVa) of the partial photometric means when receiving the light flux from the photometric surface while allowing the leakage current of the other photometric means (EVA) Then, the output (EVB) of the other part of the photometry means when receiving the light flux from the photometry surface is measured while allowing the leakage current of the part of the photometry means, EVa=EVA-K・2^(^E ^V^B^-^E^V
A photometric element in TTL split photometry characterized by obtaining a correction coefficient using the formula ^A^) and subtracting the coefficient K from the photometry output to obtain a photometry output that does not affect leakage current from other photometry means. Leakage current correction method. (2) A partial photometry means that takes charge of the photometry of a part of the subject screen to be subjected to TTL division photometry, another part photometry means that takes charge of the photometry of the other part of the screen, and The output (EVa) of the partial photometric means when receiving the luminous flux from the photometric surface with a uniform light beam irradiated and the leakage current of the other photometric means cut off, and the output (EVa) of the other photometric means. The output (EV
A) and the output (EVB) of the other part of the photometry means when receiving the light flux from the photometering surface while allowing the leakage current of the part of the photometry means, EVa=EVA-K・2^
(＾E＾V＾B＾-＾E＾V＾A＾) The correction coefficient obtained by the formula is stored, and the output of both photometric means and the coefficient K
1. A leakage current correction device for a photometric element in TTL division photometry, comprising: calculation storage means for calculating a photometry output that is not affected by leakage current of other photometry means.