JP2979190B2 - Split metering device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention divides a field of view to be photographed into a plurality of regions, and variously evaluates the average luminance of each of the divided regions to determine the overall exposure amount. The present invention relates to a divided photometric device to be determined.

(Prior Art) A photometric method is known in which outputs of a plurality of divided photometric elements are A / D-converted by a successive comparison method to perform an evaluation photometric operation.

The invention disclosed in Japanese Patent Application Laid-Open No. 62-75323 is such a split photometric device in which the A / D conversion order of the output of the photometric element is determined by using the period of flicker of the object illuminated by the AC light source as one operation period. A method is shown in which A / D conversion is repeatedly performed alternately, an added value or an average value of A / D converted values of each element in one cycle is obtained, and the obtained value is taken out as an output of each element. According to this method, it is necessary to take the A / D conversion values of all the divided photometric elements several times or more for each element in the flicker cycle of the AC light source for illumination.

For example, when the number of divisions increases, a time for switching response of the elements is required, which is not practical.

(Problems to be Solved by the Invention) When the output value of each section of the divided photometric element is obtained and the evaluation photometric calculation is performed by the above-described method, the photographing is usually performed outdoors in daylight.

When it is necessary to consider flicker of the AC light source for illumination, it is often not necessary to perform the evaluative photometry (obtaining data of individual photometric elements individually and determining an exposure amount based on the data).

From the above idea, the whole part is selected first, and in consideration of flicker of the AC light source for lighting, the A / D conversion value of photometry is obtained a plurality of times in one cycle of flicker to determine the variation. Thus, the presence or absence of the illumination AC light source is recognized, and it is determined whether or not the output of each divided element for evaluation photometry is required.

Then, it is better to perform the subsequent processing according to the judgment.

As a result, the A / D converter value of the photometric value of the split element can be obtained in a relatively short time in consideration of the response time of the photometric element switching.

It is to be noted that a circuit may be considered in which it is not necessary to form an amplifier for each of the divided elements and to consider the switching response.

An object of the present invention is to first determine the necessity of evaluation photometry, and to perform the process only when it is necessary, thereby simplifying the circuit and shortening the processing time. It is to provide a device.

(Means for Solving the Problems) In order to achieve the above object, a split photometric device according to the present invention comprises a photometric element comprising a multi-split photometric element, an amplifier, and a switch for individually connecting the multi-split photometric element to the amplifier. , A decoder for driving the switch, and a central processing unit for A / D-converting and evaluating the output of the amplifier and generating a signal for driving the decoder. The central processing unit initially operates the decoder to operate the photometric element. Is selected, and the entire output of the photometric element is sampled and A / D-converted a plurality of times at sampling intervals sufficiently narrower than the expected flicker frequency of the light source, and their outputs have a certain or more variation. In this case, photometric operation is performed using data obtained by selecting the entire photometric element, and when there is no variation exceeding a certain value, individual measurement of the multi-segment photometric element is performed. It is configured to perform a photometric calculation based on the above data.

(Example) Hereinafter, the present invention will be described in more detail with reference to the drawings and the like.

FIG. 1 is a block diagram showing an embodiment of a split photometric device according to the present invention.

The photometric element 2 is composed of four photodiodes A, B, C and D.

The photometric elements 2 are divided and arranged on the same substrate as shown in FIG.

The reflected light from each part of the subject is made incident on the divided areas of A, B, C, and D of the photometric element 2 by the optical system.

Each cathode of the four photodiodes A, B, C, and D of the photometric element 2 is connected to the inverting input terminal of the operational amplifier 5.

The output of the reference voltage generator 1 is connected to the non-inverting input terminal of the operational amplifier 5. The anodes of the four photodiodes A, B, C and D of the photometric element 2 are simultaneously or selectively connected to the non-inverting input terminal of the operational amplifier 5 by a switch driven by the output of the element selecting decoder 3. . The output of the operational amplifier 5 is further amplified by the amplifier 4 and input to the central processing unit (CPU) 6.

The central processing unit (CPU) 6 is a one-chip microcomputer incorporating a successive comparison A / D converter.

The central processing unit (CPU) 6 operates the decoder 3 through the three ports to select a photodiode,
The output of the amplifier 4 is taken into the input section to obtain an A / D conversion value.

Fig. 3 shows the flicker of the subject illuminated by the illumination light source (50Hz) and the timing of A / D conversion,
, Is a graph showing.

The photometry is performed five times every 1.8 msec from any timing.

FIG. 4 is a flowchart for explaining the operation of the central processing unit (CPU) 6 of the split photometric device according to the present invention.

(Step 101) The operating power is turned on.

(Step 102) Select the entire photometry (photodiodes A to D are simultaneously connected to the circuit).

The A / D conversion value is obtained by performing photometry five times every 1.8 msec in consideration of the AC flicker of the illumination light source.

(Step 103) The dispersion of the A / D conversion values of the five photometric values obtained earlier is determined. It is determined whether the difference between the maximum value and the minimum value is 0.5 EV or more. If the difference is 0.5 EV or more, the process proceeds to step 104 on the assumption that the illumination light source is AC and there is flicker.

(Step 105) When the difference between the maximum value and the minimum value in Step 103 is 0.5 EV or less, the light source for illumination is a light source having no flicker component, and the photometric element is switched once.
The photometric value of each of the A, B, C, and D elements is obtained every 1.8 msec (see FIG. 3), and is directly used as the photometric value of each element.

(Step 104) Since there is a large variation of five times in Step 103 and the light source for illumination is like a fluorescent lamp, it is not necessary to perform the photometric calculation by the evaluation photometry. Is used to perform photometric calculation.

(Step 109) A photometric operation is performed using the photometric value obtained through each of the steps 105 and 104.

As described in detail above, the central processing unit of the apparatus according to the present invention initially operates the decoder to select the entire photometric element and is sufficiently narrower than the expected flicker frequency of the light source. The entire output of the photometric element is sampled and A / D converted a plurality of times at a sampling interval, and if the output of the output has a certain or more variation, a photometric operation is performed by using the data obtained by selecting the entire photometric element,
When there is no variation exceeding a certain value, a photometric operation is performed based on individual data of the multi-segment photometric element.

Therefore, only when necessary in consideration of the influence of flicker of the AC light source for illumination, an A / D conversion value necessary for evaluation photometry is obtained from the multi-segment photometry element.

When the A / D conversion value is obtained while taking into account the switching response time of the photometric element in a circuit that uses the photometric element selected by one photometric amplifier, even if the number of divisions of the photometric element increases, the number and the switching response A photometric value can be obtained in a relatively short time with only time taken. The photometric time can be reduced by judging the case where the evaluation photometry becomes unnecessary due to flicker of the illumination AC light source.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a split photometric device according to the present invention. FIG. 2 is a plan view showing a divided form of a photometric element of the photometric device. FIG. 3 shows a light source for lighting with flicker (power frequency 50
Hz) and the brightness of the photometric device
9 is a graph showing the timing of D conversion. FIG. 4 shows a central processing unit (CP) of the split photometric device according to the present invention.
6 is a flowchart for explaining the operation of U). DESCRIPTION OF SYMBOLS 1 ... Reference voltage generator, 2 ... Photometric element 3 ... Decoder, 4 ... Amplifier 5 ... Operational amplifier 6 ... Central processing unit (CPU)

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Claims (1)

(57) [Claims] 1. An A / D converter for evaluating a photometric element comprising a multi-segment photometric element, an amplifier, a switch for individually connecting the multi-segment photometric element to the amplifier, a decoder for driving the switch, and the amplifier. And a central processing unit for generating a signal for driving the decoder, the central processing unit initially operating the decoder to select the entire photometric element, and sampling sufficiently narrower than the expected flicker frequency of the light source. The entire output of the photometric element is sampled and A / D-converted a plurality of times at intervals, and if the output of the entire photometric element has a variation exceeding a certain value, a photometric operation is performed by using data obtained by selecting the entire photometric device, and a constant value is obtained. Wherein the photometric operation is performed by using individual data of the multi-segment photometric element when there is no variation as described above.