JPH0378733A - Photometry device - Google Patents

Abstract

PURPOSE:To lessen the influence of the drop of the peripheral light quantity by a lens system and to allow the setting of a diaphragm value beta and shutter speed always meeting the actuality by multiplying the photometric output subjected to the influence of the drop of the peripheral light quantity by the coefft. predetermined according to the diaphragm set in the actual photographing, and thereby correcting the output. CONSTITUTION:The respectively discrete photometric outputs by the plural photometric regions of a transducer means 30 for photometry are read out in the state in which the diaphragm of the optical system relating to an image pickup plane 5 is desired to be set at the open diaphragm or the 1st diaphragm value a approximate to the open diaphragm. At least one of photometric outputs from 1st and 2nd photometric means 31, 32 among the respective discrete photometric outputs read out so as to adapt the diaphragm of the optical system relating to the image pickup plane 5 to the 2nd diaphragm value state set to execute the actual photographing is multiplied by the predetermined prescribed coefft., by which the photometric value corresponding to the 2nd diaphragm value is calculated. The influence of the drop of the peripheral light quantity by the lens system 1 is lessened in this way and the photometric value of the high accuracy is obtd. The always optimum photographing is thus executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a photometric device used in ordinary cameras, electronic still cameras, etc. that use silver halide film.

[Conventional technology]

Heretofore, there is one that employs a TTL photometry method as one of this type of photometry devices. For example, as shown in FIG. 5, this device transmits light transmitted through a photographic lens system 1 to a half mirror 2.
etc., and guide it to the photometric sensor 3, and the photometric value is determined from the received light output. Note that 4 is an aperture mechanism built into the photographic lens 1, and the aperture is generally set to be open during photometry. In other words, open metering is performed. 5 is film or CCD
This is the imaging surface of a sensor, etc. This type of photometering device has the advantage that even if the photographing range changes due to lens exchange, for example, the photometry range changes accordingly, so that it can always perform optimal photometry according to the photographing conditions.

[Problem to be solved by the invention]

However, such conventional devices have the following problems. That is, when performing open photometry as described above, the amount of light received at the light-receiving surface of the photometry sensor 3 is lower in the peripheral portion than in the central portion due to the light transmission characteristics of the photographing lens system 1. In other words, a phenomenon called peripheral light falloff occurs, and the photometric distribution in the photometric sensor 3 tends to be more center-weighted. Therefore, if you set the aperture value and shutter speed by directly using the photometric values affected by peripheral illumination, as with conventional devices, the brightness of the subject will change depending on the aperture value set in the actual shooting condition. Depending on the distribution of images, it may not be possible to perform appropriate exposure compensation, and therefore optimal photography may not be possible.

Therefore, the present invention has focused on the above-mentioned circumstances, and an object of the present invention is to provide a photometry device that can obtain highly accurate photometry values by reducing the influence of peripheral light falloff caused by the lens system, and thereby can always perform optimal photography. shall be.

[Means to solve the problem]

The present invention has taken the following measures to achieve the above object. That is, the fixed photometry area includes at least a first photometry area set corresponding to a relatively peripheral part of the imaging surface and a second photometry area set corresponding to a relatively central part of the imaging surface. a photometric transducer means having a plurality of photometric areas, a first means, and a second means; In a state where the aperture value is set to a first aperture value that is wide open or relatively close to wide open, the photometric outputs of each of the plurality of photometric regions of the photometric transducer means are read out, and the second means reads out the photometric outputs of the plurality of photometric regions of the photometric transducer means, and the second means performs the imaging operation. In order to adapt the aperture of the optical system related to the surface to the second aperture value state set for actual photography, at least the first At least one of the photometric output from the photometric area and the second photometric area should be multiplied by a predetermined coefficient determined in advance corresponding to the second aperture value to correspond to the second aperture value. The photometric value is now calculated.

[For production]

By taking such measures, the following effects are achieved. In other words, the first means yields a photometric output that is affected by peripheral illumination due to the lens system, but the second means yields a photometric output that is affected by peripheral illumination. This is corrected by multiplying by a predetermined coefficient determined in advance according to the aperture set for snoring. Therefore, the influence of the peripheral light falloff caused by the lens system is reduced, and as a result, it is possible to always set an appropriate aperture value and shutter speed in accordance with the actual situation.

〔Example〕

FIG. 1 is a functional configuration diagram of a photometric device in an embodiment of the present invention. In this embodiment, an example in which the present invention is applied to an electronic still camera will be explained.

In the figure, an optical image of a subject divided by a half mirror 2 is guided to a photometric sensor 30. This photometric sensor 30
As shown in FIG. 2(a), the photometric surface corresponding to the imaging surface is divided into two parts, a central part 31 and a peripheral part 32.
Similar to the normal photometric distribution during aperture photometry described above, due to the characteristics of the optical system, it inevitably tends to become a center-weighted photometric distribution as shown in FIG. 2(b). These central parts 3
The light reception outputs SP and AV of the light receiving unit 1 and the peripheral portion 32 are selectively selected by the changeover switch 33 and then introduced into the logarithmic amplifier circuit 40 . This logarithmic amplifier circuit 40 includes an amplifier main body 41
and a diode 42, and each of the above-mentioned light receiving outputs SP, A
After amplifying V according to a predetermined logarithmic function, it is supplied to the correction amplification circuit 50. This correction amplifier circuit 50 is for correcting the level difference between the received light outputs SP and AV caused by the difference in area between the central part 31 and the peripheral part 32 of the photometric sensor 30 to an appropriate range. Feedback resistor 52
and a gain switching circuit 53. The switch 54 of the gain switching circuit 53, together with the changeover switch 33 of the photometric sensor 30, is switched by a switching control signal output from a control circuit 70, which will be described later. Then, the received light output SP whose level has been corrected by the correction amplification circuit 50,
The AV is converted into a digital signal by an analog-to-digital (A/D) converter 60 and then introduced into a control circuit 70 .

By the way, the control circuit 70 has, for example, a microcomputer as a main control unit, and in addition to various functions as a system controller that controls the entire system such as a video circuit system and a video recording/playback system (not shown), it also performs the following functions related to photometry. It is equipped with various control means such as. That is, the control means are a photometry control means 71, an aperture value setting means 72, a photometry value correction means 73, and a shutter speed setting means 74.

The photometry control means 71 controls the changeover switch 3 of the photometry sensor 30 by outputting a switching control signal SS during photometry.
3 and the switch 54 of the correction amplifier circuit 50 are switched at a predetermined timing, whereby the central part 3 of the photometric sensor 30
1 and the peripheral portion 32, respectively.

The aperture value setting means calculates a rough photometric value BV by adding together the levels of the light receiving outputs SP and AV detected by the photometry control means 71, that is, BV=AV+SP, and calculates the approximate photometry value BV. The aperture value corresponding to the value is determined based on a predetermined program diagram.

The photometric value correction means 73 obtains a correction coefficient Kn corresponding to the aperture value obtained by the aperture value setting means 72, and multiplies this correction coefficient Kn by the value of the received light output AV of the peripheral portion 32, that is, BV'. =Kn AV+SP The following calculation is performed to obtain a photometric value BV' in which the influence of peripheral light falloff due to the lens system is corrected. still,
The above correction coefficient Kn is calculated for each aperture value (for example, F2.8,
The optimum value is determined for each F5.8, Fil) through theoretical calculations, experiments, etc., and is stored in advance in the ROM in the control circuit 70.

The shutter speed setting means 74 includes the photometric value correction means 73.
The optimum shutter speed corresponding to the photometric value BV' corrected by is calculated by apex calculation.

Next, the control circuit 7 controls the operation of the device configured as described above.
This will be explained according to the control procedure of No. 0. In the steady state, the control circuit 70 monitors the operation of the shutter button (not shown) in step 3a, as shown in FIG. When the shutter button is pressed a certain amount in this state, the control circuit 7
0 first outputs an aperture control signal to the aperture mechanism 4 in step 3b to set the aperture to open, and then in step 3c.

3d, a switching control signal SS is output at a predetermined timing. Then, first, the peripheral part 32 of the photometric sensor 30
The light reception signal AV received at
The data is digitized, input to the control circuit 70, and stored in the RAM within the control circuit 70. When the input of the received light signal AV is completed, the received light signal SP received by the central portion 32 of the photometric sensor 30 is digitalized by the A/D converter 60 after passing through the logarithmic amplifier circuit 40 and the correction amplifier circuit 50, respectively. is input into the control circuit 70 and stored in the internal RAM.

After each of the light reception signals AV and SP is obtained, the control circuit 70 proceeds to step 3e and performs the calculation BV=AV+SP, thereby calculating an approximate photometric value BV. Then, in step 3f, the aperture value corresponding to the photometric value BV is selected based on the program chart stored in the ROM in the control circuit 70, and this aperture value is temporarily stored in the internal RAM.

Now, when the above aperture value selection is completed, the control circuit 70
In step 3g, a correction coefficient Kn corresponding to the aperture value set above is selected from data of correction coefficients for the aperture value previously stored in the internal ROM. For example, if the aperture value is set to F5.6 (0), the imaging output waveform at this time is, for example, as shown in Figure 4 (b).
), the level corresponding to the periphery of the imaging surface is somewhat lower than that at the center.

Therefore, in this case, the correction coefficient Kl is selected according to the amount of decrease in the level. On the other hand, suppose now that the aperture value is set to F2.8. In this case, since this aperture value of F2.8 is close to open, the influence of peripheral light falloff due to lens system 1 is large, and the imaging output waveform is, for example, 4th.
As shown in Figure (a), the level drop corresponding to the peripheral area of the imaging plane becomes large. Therefore, in this case, a larger correction coefficient KO is selected than in the case of F5.6. Further, when the aperture value is set to Fil, the effect of peripheral light falloff due to the lens system 1 is relatively small, and the level of the imaging output waveform becomes approximately flat as shown in FIG. 4(C). Therefore, in this case, the above aperture value F
2 is selected as a smaller correction factor than in the case of 5.8.

When the correction coefficient Kn corresponding to the aperture value is selected, the control circuit 70 performs a photometric value correction calculation of BV'=Kn AV+SP based on the correction coefficient Kn in step 3h. And step 31
Apex calculation is performed, thereby calculating the optimum shutter speed corresponding to the photometric value corrected for the peripheral light falloff. Thus, the series of controls related to photometry is completed.

When the series of controls described above is completed, the control circuit 70 moves to step 3j and monitors whether the shutter button has been further pressed, for example, into a half-pressed state. When the half-press state is detected, the process moves to step 3k, where the aperture mechanism 4 is driven and controlled according to the aperture value selected in step 3f, thereby setting the exposure.

As described above, in this embodiment, the peripheral part 3 of the photometric sensor 30
Since the photometric value is corrected by multiplying the received light output AV obtained in step 2 by a predetermined correction coefficient Kn according to each aperture value, the peripheral light falloff due to lens system 1 is adjusted to each aperture value. Each will be appropriately corrected. Therefore, by setting the shutter speed and photographing based on such photometric values, it is possible to obtain a high-quality image signal from which the influence of the peripheral light falloff is removed.

For example, when the aperture value is set to F2.8, the imaging output waveform becomes approximately flat with the signal level corresponding to the peripheral area sufficiently raised, as shown in ■ in Figure 4(a). . Similarly, when the aperture value is set to F5, 6, and Fil, the imaging output waveform is as shown by @ in Figure 4 (b) and O in Figure 4 (c), respectively. The waveform is flatter (as shown by the chain line) than in the case of (as shown by the solid line). Note that if the correction as in this embodiment is performed, the level at the center of the imaging surface will theoretically increase by the same amount as the level corresponding to the peripheral area of the imaging plane.

However, in electronic still cameras using solid-state image sensors,
Due to the latitude of the solid-state imaging device, the level corresponding to the center of the imaging plane is saturated and does not increase above a certain level.

Therefore, problems such as the level corresponding to the central portion of the imaging surface becoming too high and warping resulting in deterioration of the quality of the imaging signal do not occur.

3 In addition, the following effects can be obtained with this embodiment. That is, the peripheral light falloff in the image pickup signal occurs not only due to the photographing lens system 1, but also when the aperture diameter of the photometric optical system from the nof mirror 2 to the photometric sensor 30 is not sufficient. However, with the configuration of this embodiment,
By setting a correction coefficient in advance in consideration of the influence of the photometric optical system, it is possible to effectively correct the influence of peripheral light falloff due to the photometric optical system.

Note that the present invention is not limited to the above embodiments. For example, in the above embodiment, the light reception output AV of the peripheral part 32 of the photometric sensor 30 is multiplied by a correction coefficient to correct the peripheral light falloff caused by the lens system 1. It may be corrected by multiplying the received light output SP of the peripheral part 32 by a negative correction coefficient, or by multiplying the received light output AV of the peripheral part 32 by a positive correction coefficient, and also by multiplying the received light output SP of the central part 32 by a negative correction coefficient. The correction may be performed by multiplying by a coefficient. Even with such a configuration, it is possible to prevent the center-weighted tendency on the photometric surface from becoming too strong. others,
The division configuration of the photometric area of the photometric sensor, the photometric distribution, the configuration of the photometric optical system, the circuit configuration for obtaining the photometric signal, the control procedure and content of the control circuit, the type of camera, etc.
Various modifications can be made without departing from the spirit of the invention.

〔Effect of the invention〕

As detailed above, according to the present invention, the first photometric area is set corresponding to at least a relatively peripheral part of the imaging surface, and the second photometric area is set corresponding to a relatively central part of the imaging surface. a photometric transducer means having a plurality of fixedly set photometric areas including a photometric area; a first means; and a second means; In a state where the aperture of the optical system related to the imaging surface is set to a first aperture value that is wide open or relatively close to wide open, reading out each photometric output from the plurality of photometric regions of the photometric transducer means; The second means adjusts the aperture 5 of the optical system related to the imaging surface to the second aperture value state set for actual photography. Among the other photometric outputs, at least one of the photometric outputs from the first photometric area and the second photometric area is multiplied by a predetermined coefficient that is predetermined corresponding to the second aperture value. By calculating the photometric value corresponding to the second aperture value using A photometric device capable of photographing can be provided.

[Brief explanation of drawings]

1 to 4 are for explaining one embodiment of the present invention. FIG. 1 is a functional configuration diagram of a photometric device, FIG. 2 is a diagram showing a division configuration of a photometric sensor and a photometric distribution, and FIG. Fig. 3 is a flowchart showing the control procedure and control contents of the control circuit, Fig. 4 is a signal waveform diagram showing an example of the imaging output waveform corresponding to two different aperture values, and Fig. 5 is an example of a conventional photometry device. FIG. 6 1...Photography lens system, 2...Half mirror 4...
・Aperture mechanism, 5...imaging surface, 30...photometering sensor,
31... Central part, 32... Peripheral part, 33... Changeover switch, 40... Logarithmic amplifier circuit, 50... Correction amplifier circuit, 60... A/D converter, 70... Control circuit, 71... Photometry control means, 72... Aperture value setting control means, 73... Photometry value correction means, 74... Shutter speed setting means.

Claims (1)

[Scope of Claims] At least a first photometric area set corresponding to a relatively peripheral part of the imaging surface and a second photometric area set corresponding to a relatively central part of the imaging surface a photometric transducer means having a plurality of fixedly set photometric areas; a first means for reading out photometric outputs from each of the plurality of photometric regions of the transducer means; and a second aperture value state that adapts the aperture of the optical system related to the imaging surface to a state of a second aperture value set for actual photographing. The first thing to do is
of the respective photometric outputs read from the means, at least one of the photometric outputs from the first photometric area and the second photometric area is predetermined in correspondence with the second aperture value. and second means for calculating a photometric value corresponding to the second aperture value by multiplying the second aperture value by a predetermined coefficient.