JPS6219824A - Range finding and photometry device - Google Patents

Abstract

PURPOSE:To obtain a photometry output in which the influence of a flicker is eliminated by providing an averaging circuit which finds the mean value of memory time information on plural light memory operations of a sensor and outputting the mean value as a light measured value. CONSTITUTION:The memory 103 and counter 101 of the averaging circuit 7 are reset by the 1st operation of a release button and the AF sensor 3 begins to integrate the quantity of incident light with an integration start signal from an integration control circuit 2. The AGC output of the sensor 3 increases with the integrated quantity of light and the output of a comparator 4 is inverted. The sensor 3 finished the integration in response to it and a counter 5 is inhibited from counting. The contents of the counter 5 are added to the contents of the memory circuit 103 by an adding circuit 102 and the sum is transmitted to a dividing circuit 104. The counter 101 counts the output of the comparator 4 to generate and output frequency information to the circuit 104. A mean value generated by the circuit 104 is transferred to the memory of an exposure control circuit 8 on every integrating operation to control exposure control by using the light measurement output in which the influence of a flicker is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention is used in a distance measurement/photometering device that performs photometry using a lower AF sensor (referred to as a lower AF sensor).

(Prior Art) Various distance-measuring photometers have been proposed in the past, in which a light amount accumulating type AF sensor for distance measurement is also used as a sensor for photometry.

In order to prevent the above AF sensor output from being affected by brightness when obtaining ranging information, it is necessary to make the accumulation time by the above sensor variable.On the other hand, when using the above sensor for photometry, the light amount accumulation Assuming the time is constant,
A possible method is to obtain the brightness information based on the sensor output within that time, or to obtain the brightness information based on the accumulation time until the sensor output becomes constant.

As mentioned above, since it is necessary to make the M integration time variable in order to obtain distance measurement information, the latter method is used instead of the former method to perform photometry using the sensor.

However, this method has the disadvantage that accurate photometric values cannot be obtained due to the influence of flicker that occurs when the light source illuminating the subject fluctuates due to commercial power supply.

In other words, even if the above-mentioned flicker exists in the light source as shown in Fig. 3(b), when the light level is small, that is, under low luminance, the accumulation time E1 until the output of the sensor becomes constant depends on the flicker period. As the length increases, the flicker is averaged out, so the effect of flicker is not much of a problem.On the other hand, when the light level is large as shown in Figure 3(a), even if the brightness is constant, The accumulation time is different, and brightness information cannot be obtained from this time information.

To explain in detail, even if the brightness is constant, the slope in FIG. 3(a)!
Even if the area, that is, the integrated amount of light by the sensor is constant as in the Jij section, the accumulation time t1 until it reaches a constant value is influenced by flicker and fluctuates, and brightness information cannot be obtained from this time information. That will happen.

(Purpose) The present invention has been made in view of the above-mentioned matters, and has a structure that detects information related to the accumulation time until the AF sensor output reaches a predetermined value multiple times, and calculates the average value of the multiple times of information. It is an object of the present invention to provide a distance measuring/photometering device which prevents the influence of flicker by employing this as luminance information.

(Embodiment) FIG. 1 and FIG. 7iIJ2 are circuit diagrams showing an embodiment of the distance measuring/photometering device according to the present invention. In fig.

l is a known FLL11 distance circuit that performs distance measurement (focus detection) operation based on the output of the AF sensor 3, 3 is a storage type AF sensor that integrates an incident light image, and 2 is the output of a comparator 4, which will be described later. This is an integration control circuit that repeatedly outputs an integration start signal in response to (high) until a release operation is performed.

4 is a comparator, and the AGC output of the AF sensor 3 (a signal representing brightness information such as the peak value or average value of the image signal integrated by the sensor) is input to this comparator, and this AGC output is constant. When the bell V is reached, the comparator output changes from low to high.

A counter 5 is cleared in response to the integration start signal and moves to an initial state, counts pulses from the clock generator 6, and inhibits counting in response to the output (high) of the comparator 4. Also, the sensor Comparator 3 transfers the sensor output to the distance measuring circuit in response to the comparator output (high) and shifts the integration state to the initial state.Therefore, comparator 4 shifts its output from high to low after the integration is completed, and the counter The prohibition letter IE of 5 will be lifted.

Therefore, the optical ffi 11-minute operation of the image signal by the sensor 3 is executed over and over, and the counter 5 forms a digital value corresponding to each integral operation time for each integral operation.

7 is an average circuit, and the configuration of the average circuit is shown in FIG. In the averaging circuit shown in the second diagram, 102 is an adder that adds the count value of the counter 5 and the contents of the memory circuit 103, and transfers the addition result to the memory circuit in response to the comparator output (high).

101 is a counter that counts the comparator output (high); 104 is a division circuit that divides the addition output by the count value of the counter 101 at the comparator output (high); the output of this division circuit is Every time the above division operation is performed, it is transferred to the memory of the exposure control circuit.

Further, the memory circuit 103 and the counter lot are cleared by an exposure end signal from an exposure control circuit and a power-on signal from a burry-up clear circuit (not shown). 9 is a logarithmic compression circuit for logarithmically compressing the output of the division circuit 104 and transmitting the compressed signal to the memory of the exposure control circuit.

Next, the operation of the present invention with the above configuration will be explained.

By performing the first step operation of a release button (not shown), power is supplied to the circuit and the memory circuit 103 and counter 101 are reset.

Further, the integral control circuit 2 starts operating, and the AF sensor 3 starts integrating the amount of incident light in response to an integration start signal from the integral control circuit 2. Further, the integration start signal is input to the manual clearer of the counter 5, the counter 5 is cleared, and the counting of pulses from the clock generator 6 is started from the initial state. As the light intensity integration by the sensor 3 is started in this way, the AGC output of the sensor 3 increases according to the integrated light intensity, and when the output level exceeds the inversion input V of the comparator 4, the output of the comparator 4 is Flips from low to high. The AF sensor 3 responds to this comparator output (high) and ends its integration. Further, in response to this cooperator signal, a read clock (not shown) is applied to the sensor 3, and the integrated image output of the sensor is sent to a distance measuring circuit for distance measurement calculation.

On the other hand, when the output of comparator 4 becomes high, counter 5 prohibits counting. Therefore, the counter 5 counts the time from the start of the integration to the end of the integration as a clock pulse generated by the clock generator 6.

Therefore, a digital value corresponding to the luminance is formed in the counter 5 every time the above integration operation is performed. The contents of the counter 5 are added together with the contents of the memory circuit 103 in an adder circuit 102 and input to the memory circuit 103. Therefore, the digital values formed in the counter 5 are summed up in the memory circuit each time each integral operation is performed.

The total value is transmitted to the division circuit 104. Further, since the counter 101 counts the output of the cone parator 4, it forms information on the number of times the above-mentioned integral operation has been performed, and the above-mentioned total value is divided by this number of times information, and each integral operation is calculated. The average value of the digital values formed when the integration operation is performed is transferred to the memory of the exposure control circuit each time the integration operation is performed.

Thereafter, by performing a second step operation of a release button (not shown), exposure control is performed based on data transferred to the memory of the exposure control circuit.

In the embodiment, the average of the digital values formed in each integral operation until the release operation is performed is calculated. The division circuit 104 may divide the count value and transmit the result to the memory of the exposure control circuit.

In this case, a first detection circuit is provided to detect the count value of the counter 101 and generate an output when the count value reaches a predetermined value to operate the division circuit 104 and reset the memory circuit 103° counter 101. That's fine.

In this case, a second detection circuit is provided which detects the count value of the counter 5 and generates an output when the count value is less than a predetermined value, and the first detection circuit is connected to the first detection circuit when the value of the counter 101 is equal to The content of the counter 5 is divided into a first detection section that generates an output when the value is reached, and a second detection section that generates an output when the second value is larger than the first value. is provided with selection means for selecting the second detection section when is below a predetermined value at the end of the integration operation, and selecting the first detection section when it is above a predetermined value, and selects the above average value according to the contents of the counter 5. It is also possible to adjust the number of times information used to obtain .

(Effects) As described above, in the distance measurement/photometering device according to the present invention, the AF
Since luminance information is obtained from the average value for each integration time of the sensor, it is possible to prevent the influence of flicker and obtain accurate photometric output from the AF sensor.
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[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the distance measuring/photometering device according to the present invention, FIG. 2 is a circuit diagram showing an embodiment of the averaging circuit 7 shown in FIG. 1, and FIG. ) is a waveform diagram for explaining the operation of the conventional device. 3--AF sensor, 4-m-comparator, 5-
m-counter, 7--average circuit. Figure 2

Claims (1)

[Scope of Claims] A distance measuring/photometering device that controls the accumulation time of a light accumulation type AF sensor so that the output is at a constant level in order to obtain distance measurement information, and obtains a photometry value from the accumulation time information, comprising: A distance measuring/photometering device comprising: an averaging circuit for calculating an average value of accumulated time information in a plurality of light accumulation operations by a sensor; and outputting the average value as a photometric value.